Merge illumos-gate

[unleashed.git] / kernel / os / streamio.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */


/*
 * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2017 Joyent, Inc.
 * Copyright 2018 OmniOS Community Edition (OmniOSce) Association.
 */

#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/signal.h>
#include <sys/stat.h>
#include <sys/proc.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/stream.h>
#include <sys/strsubr.h>
#include <sys/stropts.h>
#include <sys/tihdr.h>
#include <sys/var.h>
#include <sys/poll.h>
#include <sys/termio.h>
#include <sys/ttold.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/cmn_err.h>
#include <sys/sad.h>
#include <sys/netstack.h>
#include <sys/priocntl.h>
#include <sys/jioctl.h>
#include <sys/procset.h>
#include <sys/session.h>
#include <sys/kmem.h>
#include <sys/filio.h>
#include <sys/vtrace.h>
#include <sys/debug.h>
#include <sys/strredir.h>
#include <sys/fs/fifonode.h>
#include <sys/fs/snode.h>
#include <sys/strlog.h>
#include <sys/strsun.h>
#include <sys/project.h>
#include <sys/kbio.h>
#include <sys/msio.h>
#include <sys/tty.h>
#include <sys/ptyvar.h>
#include <sys/vuid_event.h>
#include <sys/modctl.h>
#include <sys/sunddi.h>
#include <sys/sunldi_impl.h>
#include <sys/autoconf.h>
#include <sys/policy.h>
#include <sys/dld.h>
#include <sys/zone.h>
#include <sys/limits.h>

/*
 * This define helps improve the readability of streams code while
 * still maintaining a very old streams performance enhancement.  The
 * performance enhancement basically involved having all callers
 * of straccess() perform the first check that straccess() will do
 * locally before actually calling straccess().  (There by reducing
 * the number of unnecessary calls to straccess().)
 */
#define i_straccess(x, y)       ((stp->sd_sidp == NULL) ? 0 : \
                                    (stp->sd_vnode->v_type == VFIFO) ? 0 : \
                                    straccess((x), (y)))

/*
 * what is mblk_pull_len?
 *
 * If a streams message consists of many short messages,
 * a performance degradation occurs from copyout overhead.
 * To decrease the per mblk overhead, messages that are
 * likely to consist of many small mblks are pulled up into
 * one continuous chunk of memory.
 *
 * To avoid the processing overhead of examining every
 * mblk, a quick heuristic is used. If the first mblk in
 * the message is shorter than mblk_pull_len, it is likely
 * that the rest of the mblk will be short.
 *
 * This heuristic was decided upon after performance tests
 * indicated that anything more complex slowed down the main
 * code path.
 */
#define MBLK_PULL_LEN 64
uint32_t mblk_pull_len = MBLK_PULL_LEN;

/*
 * The sgttyb_handling flag controls the handling of the old BSD
 * TIOCGETP, TIOCSETP, and TIOCSETN ioctls as follows:
 *
 * 0 - Emit no warnings at all and retain old, broken behavior.
 * 1 - Emit no warnings and silently handle new semantics.
 * 2 - Send cmn_err(CE_NOTE) when either TIOCSETP or TIOCSETN is used
 *     (once per system invocation).  Handle with new semantics.
 * 3 - Send SIGSYS when any TIOCGETP, TIOCSETP, or TIOCSETN call is
 *     made (so that offenders drop core and are easy to debug).
 *
 * The "new semantics" are that TIOCGETP returns B38400 for
 * sg_[io]speed if the corresponding value is over B38400, and that
 * TIOCSET[PN] accept B38400 in these cases to mean "retain current
 * bit rate."
 */
int sgttyb_handling = 1;
static boolean_t sgttyb_complaint;

/* don't push drcompat module by default on Style-2 streams */
static int push_drcompat = 0;

/*
 * id value used to distinguish between different ioctl messages
 */
static uint32_t ioc_id;

static void putback(struct stdata *, queue_t *, mblk_t *, int);
static void strcleanall(struct vnode *);
static int strwsrv(queue_t *);
static int strdocmd(struct stdata *, struct strcmd *, cred_t *);

/*
 * qinit and module_info structures for stream head read and write queues
 */
struct module_info strm_info = { 0, "strrhead", 0, INFPSZ, STRHIGH, STRLOW };
struct module_info stwm_info = { 0, "strwhead", 0, 0, 0, 0 };
struct qinit strdata = { strrput, NULL, NULL, NULL, NULL, &strm_info };
struct qinit stwdata = { NULL, strwsrv, NULL, NULL, NULL, &stwm_info };
struct module_info fiform_info = { 0, "fifostrrhead", 0, PIPE_BUF, FIFOHIWAT,
    FIFOLOWAT };
struct module_info fifowm_info = { 0, "fifostrwhead", 0, 0, 0, 0 };
struct qinit fifo_strdata = { strrput, NULL, NULL, NULL, NULL, &fiform_info };
struct qinit fifo_stwdata = { NULL, strwsrv, NULL, NULL, NULL, &fifowm_info };

extern kmutex_t strresources;   /* protects global resources */
extern kmutex_t muxifier;       /* single-threads multiplexor creation */

static boolean_t msghasdata(mblk_t *bp);
#define msgnodata(bp) (!msghasdata(bp))

/*
 * Stream head locking notes:
 *      There are four monitors associated with the stream head:
 *      1. v_stream monitor: in stropen() and strclose() v_lock
 *              is held while the association of vnode and stream
 *              head is established or tested for.
 *      2. open/close/push/pop monitor: sd_lock is held while each
 *              thread bids for exclusive access to this monitor
 *              for opening or closing a stream.  In addition, this
 *              monitor is entered during pushes and pops.  This
 *              guarantees that during plumbing operations there
 *              is only one thread trying to change the plumbing.
 *              Any other threads present in the stream are only
 *              using the plumbing.
 *      3. read/write monitor: in the case of read, a thread holds
 *              sd_lock while trying to get data from the stream
 *              head queue.  if there is none to fulfill a read
 *              request, it sets RSLEEP and calls cv_wait_sig() down
 *              in strwaitq() to await the arrival of new data.
 *              when new data arrives in strrput(), sd_lock is acquired
 *              before testing for RSLEEP and calling cv_broadcast().
 *              the behavior of strwrite(), strwsrv(), and WSLEEP
 *              mirror this.
 *      4. ioctl monitor: sd_lock is gotten to ensure that only one
 *              thread is doing an ioctl at a time.
 */

static int
push_mod(queue_t *qp, dev_t *devp, struct stdata *stp, const char *name,
    int anchor, cred_t *crp, uint_t anchor_zoneid)
{
        int error;
        fmodsw_impl_t *fp;

        if (stp->sd_flag & (STRHUP|STRDERR|STWRERR)) {
                error = (stp->sd_flag & STRHUP) ? ENXIO : EIO;
                return (error);
        }
        if (stp->sd_pushcnt >= nstrpush) {
                return (EINVAL);
        }

        if ((fp = fmodsw_find(name, FMODSW_HOLD | FMODSW_LOAD)) == NULL) {
                stp->sd_flag |= STREOPENFAIL;
                return (EINVAL);
        }

        /*
         * push new module and call its open routine via qattach
         */
        if ((error = qattach(qp, devp, 0, crp, fp, B_FALSE)) != 0)
                return (error);

        /*
         * Check to see if caller wants a STREAMS anchor
         * put at this place in the stream, and add if so.
         */
        mutex_enter(&stp->sd_lock);
        if (anchor == stp->sd_pushcnt) {
                stp->sd_anchor = stp->sd_pushcnt;
                stp->sd_anchorzone = anchor_zoneid;
        }
        mutex_exit(&stp->sd_lock);

        return (0);
}

/*
 * Open a stream device.
 */
int
stropen(vnode_t *vp, dev_t *devp, int flag, cred_t *crp)
{
        struct stdata *stp;
        queue_t *qp;
        int s;
        dev_t dummydev, savedev;
        struct autopush *ap;
        struct dlautopush dlap;
        int error = 0;
        ssize_t rmin, rmax;
        int cloneopen;
        queue_t *brq;
        major_t major;
        str_stack_t *ss;
        zoneid_t zoneid;
        uint_t anchor;

        /*
         * If the stream already exists, wait for any open in progress
         * to complete, then call the open function of each module and
         * driver in the stream.  Otherwise create the stream.
         */
        TRACE_1(TR_FAC_STREAMS_FR, TR_STROPEN, "stropen:%p", vp);
retry:
        mutex_enter(&vp->v_lock);
        if ((stp = vp->v_stream) != NULL) {

                /*
                 * Waiting for stream to be created to device
                 * due to another open.
                 */
                mutex_exit(&vp->v_lock);

                if (STRMATED(stp)) {
                        struct stdata *strmatep = stp->sd_mate;

                        STRLOCKMATES(stp);
                        if (strmatep->sd_flag & (STWOPEN|STRCLOSE|STRPLUMB)) {
                                if (flag & (FNDELAY|FNONBLOCK)) {
                                        error = EAGAIN;
                                        mutex_exit(&strmatep->sd_lock);
                                        goto ckreturn;
                                }
                                mutex_exit(&stp->sd_lock);
                                if (!cv_wait_sig(&strmatep->sd_monitor,
                                    &strmatep->sd_lock)) {
                                        error = EINTR;
                                        mutex_exit(&strmatep->sd_lock);
                                        mutex_enter(&stp->sd_lock);
                                        goto ckreturn;
                                }
                                mutex_exit(&strmatep->sd_lock);
                                goto retry;
                        }
                        if (stp->sd_flag & (STWOPEN|STRCLOSE|STRPLUMB)) {
                                if (flag & (FNDELAY|FNONBLOCK)) {
                                        error = EAGAIN;
                                        mutex_exit(&strmatep->sd_lock);
                                        goto ckreturn;
                                }
                                mutex_exit(&strmatep->sd_lock);
                                if (!cv_wait_sig(&stp->sd_monitor,
                                    &stp->sd_lock)) {
                                        error = EINTR;
                                        goto ckreturn;
                                }
                                mutex_exit(&stp->sd_lock);
                                goto retry;
                        }

                        if (stp->sd_flag & (STRDERR|STWRERR)) {
                                error = EIO;
                                mutex_exit(&strmatep->sd_lock);
                                goto ckreturn;
                        }

                        stp->sd_flag |= STWOPEN;
                        STRUNLOCKMATES(stp);
                } else {
                        mutex_enter(&stp->sd_lock);
                        if (stp->sd_flag & (STWOPEN|STRCLOSE|STRPLUMB)) {
                                if (flag & (FNDELAY|FNONBLOCK)) {
                                        error = EAGAIN;
                                        goto ckreturn;
                                }
                                if (!cv_wait_sig(&stp->sd_monitor,
                                    &stp->sd_lock)) {
                                        error = EINTR;
                                        goto ckreturn;
                                }
                                mutex_exit(&stp->sd_lock);
                                goto retry;  /* could be clone! */
                        }

                        if (stp->sd_flag & (STRDERR|STWRERR)) {
                                error = EIO;
                                goto ckreturn;
                        }

                        stp->sd_flag |= STWOPEN;
                        mutex_exit(&stp->sd_lock);
                }

                /*
                 * Open all modules and devices down stream to notify
                 * that another user is streaming.  For modules, set the
                 * last argument to MODOPEN and do not pass any open flags.
                 * Ignore dummydev since this is not the first open.
                 */
                claimstr(stp->sd_wrq);
                qp = stp->sd_wrq;
                while (_SAMESTR(qp)) {
                        qp = qp->q_next;
                        if ((error = qreopen(_RD(qp), devp, flag, crp)) != 0)
                                break;
                }
                releasestr(stp->sd_wrq);
                mutex_enter(&stp->sd_lock);
                stp->sd_flag &= ~(STRHUP|STWOPEN|STRDERR|STWRERR);
                stp->sd_rerror = 0;
                stp->sd_werror = 0;
ckreturn:
                cv_broadcast(&stp->sd_monitor);
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        /*
         * This vnode isn't streaming.  SPECFS already
         * checked for multiple vnodes pointing to the
         * same stream, so create a stream to the driver.
         */
        qp = allocq();
        stp = shalloc(qp);

        /*
         * Initialize stream head.  shalloc() has given us
         * exclusive access, and we have the vnode locked;
         * we can do whatever we want with stp.
         */
        stp->sd_flag = STWOPEN;
        stp->sd_siglist = NULL;
        stp->sd_pollist.ph_list = NULL;
        stp->sd_sigflags = 0;
        stp->sd_mark = NULL;
        stp->sd_closetime = STRTIMOUT;
        stp->sd_sidp = NULL;
        stp->sd_pgidp = NULL;
        stp->sd_vnode = vp;
        stp->sd_rerror = 0;
        stp->sd_werror = 0;
        stp->sd_wroff = 0;
        stp->sd_tail = 0;
        stp->sd_iocblk = NULL;
        stp->sd_cmdblk = NULL;
        stp->sd_pushcnt = 0;
        stp->sd_qn_minpsz = 0;
        stp->sd_qn_maxpsz = INFPSZ - 1; /* used to check for initialization */
        stp->sd_maxblk = INFPSZ;
        qp->q_ptr = _WR(qp)->q_ptr = stp;
        STREAM(qp) = STREAM(_WR(qp)) = stp;
        vp->v_stream = stp;
        mutex_exit(&vp->v_lock);
        if (vp->v_type == VFIFO) {
                stp->sd_flag |= OLDNDELAY;
                /*
                 * This means, both for pipes and fifos
                 * strwrite will send SIGPIPE if the other
                 * end is closed. For putmsg it depends
                 * on whether it is a XPG4_2 application
                 * or not
                 */
                stp->sd_wput_opt = SW_SIGPIPE;

                /* setq might sleep in kmem_alloc - avoid holding locks. */
                setq(qp, &fifo_strdata, &fifo_stwdata, NULL, QMTSAFE,
                    SQ_CI|SQ_CO, B_FALSE);

                set_qend(qp);
                stp->sd_strtab = fifo_getinfo();
                _WR(qp)->q_nfsrv = _WR(qp);
                qp->q_nfsrv = qp;
                /*
                 * Wake up others that are waiting for stream to be created.
                 */
                mutex_enter(&stp->sd_lock);
                /*
                 * nothing is be pushed on stream yet, so
                 * optimized stream head packetsizes are just that
                 * of the read queue
                 */
                stp->sd_qn_minpsz = qp->q_minpsz;
                stp->sd_qn_maxpsz = qp->q_maxpsz;
                stp->sd_flag &= ~STWOPEN;
                goto fifo_opendone;
        }
        /* setq might sleep in kmem_alloc - avoid holding locks. */
        setq(qp, &strdata, &stwdata, NULL, QMTSAFE, SQ_CI|SQ_CO, B_FALSE);

        set_qend(qp);

        /*
         * Open driver and create stream to it (via qattach).
         */
        savedev = *devp;
        cloneopen = (getmajor(*devp) == clone_major);
        if ((error = qattach(qp, devp, flag, crp, NULL, B_FALSE)) != 0) {
                mutex_enter(&vp->v_lock);
                vp->v_stream = NULL;
                mutex_exit(&vp->v_lock);
                mutex_enter(&stp->sd_lock);
                cv_broadcast(&stp->sd_monitor);
                mutex_exit(&stp->sd_lock);
                freeq(_RD(qp));
                shfree(stp);
                return (error);
        }
        /*
         * Set sd_strtab after open in order to handle clonable drivers
         */
        stp->sd_strtab = STREAMSTAB(getmajor(*devp));

        /*
         * Historical note: dummydev used to be be prior to the initial
         * open (via qattach above), which made the value seen
         * inconsistent between an I_PUSH and an autopush of a module.
         */
        dummydev = *devp;

        /*
         * For clone open of old style (Q not associated) network driver,
         * push DRMODNAME module to handle DL_ATTACH/DL_DETACH
         */
        brq = _RD(_WR(qp)->q_next);
        major = getmajor(*devp);
        if (push_drcompat && cloneopen && NETWORK_DRV(major) &&
            ((brq->q_flag & _QASSOCIATED) == 0)) {
                if (push_mod(qp, &dummydev, stp, DRMODNAME, 0, crp, 0) != 0)
                        cmn_err(CE_WARN, "cannot push " DRMODNAME
                            " streams module");
        }

        if (!NETWORK_DRV(major)) {
                savedev = *devp;
        } else {
                /*
                 * For network devices, process differently based on the
                 * return value from dld_autopush():
                 *
                 *   0: the passed-in device points to a GLDv3 datalink with
                 *   per-link autopush configuration; use that configuration
                 *   and ignore any per-driver autopush configuration.
                 *
                 *   1: the passed-in device points to a physical GLDv3
                 *   datalink without per-link autopush configuration.  The
                 *   passed in device was changed to refer to the actual
                 *   physical device (if it's not already); we use that new
                 *   device to look up any per-driver autopush configuration.
                 *
                 *   -1: neither of the above cases applied; use the initial
                 *   device to look up any per-driver autopush configuration.
                 */
                switch (dld_autopush(&savedev, &dlap)) {
                case 0:
                        zoneid = crgetzoneid(crp);
                        for (s = 0; s < dlap.dap_npush; s++) {
                                error = push_mod(qp, &dummydev, stp,
                                    dlap.dap_aplist[s], dlap.dap_anchor, crp,
                                    zoneid);
                                if (error != 0)
                                        break;
                        }
                        goto opendone;
                case 1:
                        break;
                case -1:
                        savedev = *devp;
                        break;
                }
        }
        /*
         * Find the autopush configuration based on "savedev". Start with the
         * global zone. If not found check in the local zone.
         */
        zoneid = GLOBAL_ZONEID;
retryap:
        ss = netstack_find_by_stackid(zoneid_to_netstackid(zoneid))->
            netstack_str;
        if ((ap = sad_ap_find_by_dev(savedev, ss)) == NULL) {
                netstack_rele(ss->ss_netstack);
                if (zoneid == GLOBAL_ZONEID) {
                        /*
                         * None found. Also look in the zone's autopush table.
                         */
                        zoneid = crgetzoneid(crp);
                        if (zoneid != GLOBAL_ZONEID)
                                goto retryap;
                }
                goto opendone;
        }
        anchor = ap->ap_anchor;
        zoneid = crgetzoneid(crp);
        for (s = 0; s < ap->ap_npush; s++) {
                error = push_mod(qp, &dummydev, stp, ap->ap_list[s],
                    anchor, crp, zoneid);
                if (error != 0)
                        break;
        }
        sad_ap_rele(ap, ss);
        netstack_rele(ss->ss_netstack);

opendone:

        /*
         * let specfs know that open failed part way through
         */
        if (error) {
                mutex_enter(&stp->sd_lock);
                stp->sd_flag |= STREOPENFAIL;
                mutex_exit(&stp->sd_lock);
        }

        /*
         * Wake up others that are waiting for stream to be created.
         */
        mutex_enter(&stp->sd_lock);
        stp->sd_flag &= ~STWOPEN;

        /*
         * As a performance concern we are caching the values of
         * q_minpsz and q_maxpsz of the module below the stream
         * head in the stream head.
         */
        mutex_enter(QLOCK(stp->sd_wrq->q_next));
        rmin = stp->sd_wrq->q_next->q_minpsz;
        rmax = stp->sd_wrq->q_next->q_maxpsz;
        mutex_exit(QLOCK(stp->sd_wrq->q_next));

        /* do this processing here as a performance concern */
        if (strmsgsz != 0) {
                if (rmax == INFPSZ)
                        rmax = strmsgsz;
                else
                        rmax = MIN(strmsgsz, rmax);
        }

        mutex_enter(QLOCK(stp->sd_wrq));
        stp->sd_qn_minpsz = rmin;
        stp->sd_qn_maxpsz = rmax;
        mutex_exit(QLOCK(stp->sd_wrq));

fifo_opendone:
        cv_broadcast(&stp->sd_monitor);
        mutex_exit(&stp->sd_lock);
        return (error);
}

static int strsink(queue_t *, mblk_t *);
static struct qinit deadrend = {
        strsink, NULL, NULL, NULL, NULL, &strm_info, NULL
};
static struct qinit deadwend = {
        NULL, NULL, NULL, NULL, NULL, &stwm_info, NULL
};

/*
 * Close a stream.
 * This is called from closef() on the last close of an open stream.
 * Strclean() will already have removed the siglist and pollist
 * information, so all that remains is to remove all multiplexor links
 * for the stream, pop all the modules (and the driver), and free the
 * stream structure.
 */

int
strclose(struct vnode *vp, int flag, cred_t *crp)
{
        struct stdata *stp;
        queue_t *qp;
        int rval;
        int freestp = 1;
        queue_t *rmq;

        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRCLOSE, "strclose:%p", vp);
        ASSERT(vp->v_stream);

        stp = vp->v_stream;
        ASSERT(!(stp->sd_flag & STPLEX));
        qp = stp->sd_wrq;

        /*
         * Needed so that strpoll will return non-zero for this fd.
         * Note that with POLLNOERR STRHUP does still cause POLLHUP.
         */
        mutex_enter(&stp->sd_lock);
        stp->sd_flag |= STRHUP;
        mutex_exit(&stp->sd_lock);

        /*
         * If the registered process or process group did not have an
         * open instance of this stream then strclean would not be
         * called. Thus at the time of closing all remaining siglist entries
         * are removed.
         */
        if (stp->sd_siglist != NULL)
                strcleanall(vp);

        ASSERT(stp->sd_siglist == NULL);
        ASSERT(stp->sd_sigflags == 0);

        if (STRMATED(stp)) {
                struct stdata *strmatep = stp->sd_mate;
                int waited = 1;

                STRLOCKMATES(stp);
                while (waited) {
                        waited = 0;
                        while (stp->sd_flag & (STWOPEN|STRCLOSE|STRPLUMB)) {
                                mutex_exit(&strmatep->sd_lock);
                                cv_wait(&stp->sd_monitor, &stp->sd_lock);
                                mutex_exit(&stp->sd_lock);
                                STRLOCKMATES(stp);
                                waited = 1;
                        }
                        while (strmatep->sd_flag &
                            (STWOPEN|STRCLOSE|STRPLUMB)) {
                                mutex_exit(&stp->sd_lock);
                                cv_wait(&strmatep->sd_monitor,
                                    &strmatep->sd_lock);
                                mutex_exit(&strmatep->sd_lock);
                                STRLOCKMATES(stp);
                                waited = 1;
                        }
                }
                stp->sd_flag |= STRCLOSE;
                STRUNLOCKMATES(stp);
        } else {
                mutex_enter(&stp->sd_lock);
                stp->sd_flag |= STRCLOSE;
                mutex_exit(&stp->sd_lock);
        }

        ASSERT(qp->q_first == NULL);    /* No more delayed write */

        /* Check if an I_LINK was ever done on this stream */
        if (stp->sd_flag & STRHASLINKS) {
                netstack_t *ns;
                str_stack_t *ss;

                ns = netstack_find_by_cred(crp);
                ASSERT(ns != NULL);
                ss = ns->netstack_str;
                ASSERT(ss != NULL);

                (void) munlinkall(stp, LINKCLOSE|LINKNORMAL, crp, &rval, ss);
                netstack_rele(ss->ss_netstack);
        }

        while (_SAMESTR(qp)) {
                /*
                 * Holding sd_lock prevents q_next from changing in
                 * this stream.
                 */
                mutex_enter(&stp->sd_lock);
                if (!(flag & (FNDELAY|FNONBLOCK)) && (stp->sd_closetime > 0)) {

                        /*
                         * sleep until awakened by strwsrv() or timeout
                         */
                        for (;;) {
                                mutex_enter(QLOCK(qp->q_next));
                                if (!(qp->q_next->q_mblkcnt)) {
                                        mutex_exit(QLOCK(qp->q_next));
                                        break;
                                }
                                stp->sd_flag |= WSLEEP;

                                /* ensure strwsrv gets enabled */
                                qp->q_next->q_flag |= QWANTW;
                                mutex_exit(QLOCK(qp->q_next));
                                /* get out if we timed out or recv'd a signal */
                                if (str_cv_wait(&qp->q_wait, &stp->sd_lock,
                                    stp->sd_closetime, 0) <= 0) {
                                        break;
                                }
                        }
                        stp->sd_flag &= ~WSLEEP;
                }
                mutex_exit(&stp->sd_lock);

                rmq = qp->q_next;
                if (rmq->q_flag & QISDRV) {
                        ASSERT(!_SAMESTR(rmq));
                        wait_sq_svc(_RD(qp)->q_syncq);
                }

                qdetach(_RD(rmq), 1, flag, crp, B_FALSE);
        }

        /*
         * Since we call pollwakeup in close() now, the poll list should
         * be empty in most cases. The only exception is the layered devices
         * (e.g. the console drivers with redirection modules pushed on top
         * of it).  We have to do this after calling qdetach() because
         * the redirection module won't have torn down the console
         * redirection until after qdetach() has been invoked.
         */
        if (stp->sd_pollist.ph_list != NULL) {
                pollwakeup(&stp->sd_pollist, POLLERR);
                pollhead_clean(&stp->sd_pollist);
        }
        ASSERT(stp->sd_pollist.ph_list == NULL);
        ASSERT(stp->sd_sidp == NULL);
        ASSERT(stp->sd_pgidp == NULL);

        /* Prevent qenable from re-enabling the stream head queue */
        disable_svc(_RD(qp));

        /*
         * Wait until service procedure of each queue is
         * run, if QINSERVICE is set.
         */
        wait_svc(_RD(qp));

        /*
         * Now, flush both queues.
         */
        flushq(_RD(qp), FLUSHALL);
        flushq(qp, FLUSHALL);

        /*
         * If the write queue of the stream head is pointing to a
         * read queue, we have a twisted stream.  If the read queue
         * is alive, convert the stream head queues into a dead end.
         * If the read queue is dead, free the dead pair.
         */
        if (qp->q_next && !_SAMESTR(qp)) {
                if (qp->q_next->q_qinfo == &deadrend) { /* half-closed pipe */
                        flushq(qp->q_next, FLUSHALL); /* ensure no message */
                        shfree(qp->q_next->q_stream);
                        freeq(qp->q_next);
                        freeq(_RD(qp));
                } else if (qp->q_next == _RD(qp)) {     /* fifo */
                        freeq(_RD(qp));
                } else {                                /* pipe */
                        freestp = 0;
                        /*
                         * The q_info pointers are never accessed when
                         * SQLOCK is held.
                         */
                        ASSERT(qp->q_syncq == _RD(qp)->q_syncq);
                        mutex_enter(SQLOCK(qp->q_syncq));
                        qp->q_qinfo = &deadwend;
                        _RD(qp)->q_qinfo = &deadrend;
                        mutex_exit(SQLOCK(qp->q_syncq));
                }
        } else {
                freeq(_RD(qp)); /* free stream head queue pair */
        }

        mutex_enter(&vp->v_lock);
        if (stp->sd_iocblk) {
                if (stp->sd_iocblk != (mblk_t *)-1) {
                        freemsg(stp->sd_iocblk);
                }
                stp->sd_iocblk = NULL;
        }
        stp->sd_vnode = NULL;
        vp->v_stream = NULL;
        mutex_exit(&vp->v_lock);
        mutex_enter(&stp->sd_lock);
        freemsg(stp->sd_cmdblk);
        stp->sd_cmdblk = NULL;
        stp->sd_flag &= ~STRCLOSE;
        cv_broadcast(&stp->sd_monitor);
        mutex_exit(&stp->sd_lock);

        if (freestp)
                shfree(stp);
        return (0);
}

static int
strsink(queue_t *q, mblk_t *bp)
{
        struct copyresp *resp;

        switch (bp->b_datap->db_type) {
        case M_FLUSH:
                if ((*bp->b_rptr & FLUSHW) && !(bp->b_flag & MSGNOLOOP)) {
                        *bp->b_rptr &= ~FLUSHR;
                        bp->b_flag |= MSGNOLOOP;
                        /*
                         * Protect against the driver passing up
                         * messages after it has done a qprocsoff.
                         */
                        if (_OTHERQ(q)->q_next == NULL)
                                freemsg(bp);
                        else
                                qreply(q, bp);
                } else {
                        freemsg(bp);
                }
                break;

        case M_COPYIN:
        case M_COPYOUT:
                if (bp->b_cont) {
                        freemsg(bp->b_cont);
                        bp->b_cont = NULL;
                }
                bp->b_datap->db_type = M_IOCDATA;
                bp->b_wptr = bp->b_rptr + sizeof (struct copyresp);
                resp = (struct copyresp *)bp->b_rptr;
                resp->cp_rval = (caddr_t)1;     /* failure */
                /*
                 * Protect against the driver passing up
                 * messages after it has done a qprocsoff.
                 */
                if (_OTHERQ(q)->q_next == NULL)
                        freemsg(bp);
                else
                        qreply(q, bp);
                break;

        case M_IOCTL:
                if (bp->b_cont) {
                        freemsg(bp->b_cont);
                        bp->b_cont = NULL;
                }
                bp->b_datap->db_type = M_IOCNAK;
                /*
                 * Protect against the driver passing up
                 * messages after it has done a qprocsoff.
                 */
                if (_OTHERQ(q)->q_next == NULL)
                        freemsg(bp);
                else
                        qreply(q, bp);
                break;

        default:
                freemsg(bp);
                break;
        }

        return (0);
}

/*
 * Clean up after a process when it closes a stream.  This is called
 * from closef for all closes, whereas strclose is called only for the
 * last close on a stream.  The siglist is scanned for entries for the
 * current process, and these are removed.
 */
void
strclean(struct vnode *vp)
{
        strsig_t *ssp, *pssp, *tssp;
        stdata_t *stp;
        int update = 0;

        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRCLEAN, "strclean:%p", vp);
        stp = vp->v_stream;
        pssp = NULL;
        mutex_enter(&stp->sd_lock);
        ssp = stp->sd_siglist;
        while (ssp) {
                if (ssp->ss_pidp == curproc->p_pidp) {
                        tssp = ssp->ss_next;
                        if (pssp)
                                pssp->ss_next = tssp;
                        else
                                stp->sd_siglist = tssp;
                        mutex_enter(&pidlock);
                        PID_RELE(ssp->ss_pidp);
                        mutex_exit(&pidlock);
                        kmem_free(ssp, sizeof (strsig_t));
                        update = 1;
                        ssp = tssp;
                } else {
                        pssp = ssp;
                        ssp = ssp->ss_next;
                }
        }
        if (update) {
                stp->sd_sigflags = 0;
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        stp->sd_sigflags |= ssp->ss_events;
        }
        mutex_exit(&stp->sd_lock);
}

/*
 * Used on the last close to remove any remaining items on the siglist.
 * These could be present on the siglist due to I_ESETSIG calls that
 * use process groups or processed that do not have an open file descriptor
 * for this stream (Such entries would not be removed by strclean).
 */
static void
strcleanall(struct vnode *vp)
{
        strsig_t *ssp, *nssp;
        stdata_t *stp;

        stp = vp->v_stream;
        mutex_enter(&stp->sd_lock);
        ssp = stp->sd_siglist;
        stp->sd_siglist = NULL;
        while (ssp) {
                nssp = ssp->ss_next;
                mutex_enter(&pidlock);
                PID_RELE(ssp->ss_pidp);
                mutex_exit(&pidlock);
                kmem_free(ssp, sizeof (strsig_t));
                ssp = nssp;
        }
        stp->sd_sigflags = 0;
        mutex_exit(&stp->sd_lock);
}

/*
 * Retrieve the next message from the logical stream head read queue
 * using either rwnext (if sync stream) or getq_noenab.
 * It is the callers responsibility to call qbackenable after
 * it is finished with the message. The caller should not call
 * qbackenable until after any putback calls to avoid spurious backenabling.
 */
mblk_t *
strget(struct stdata *stp, queue_t *q, struct uio *uiop, int first,
    int *errorp)
{
        mblk_t *bp;
        int error;
        ssize_t rbytes = 0;

        /* Holding sd_lock prevents the read queue from changing  */
        ASSERT(MUTEX_HELD(&stp->sd_lock));

        if (uiop != NULL && stp->sd_struiordq != NULL &&
            q->q_first == NULL &&
            (!first || (stp->sd_wakeq & RSLEEP))) {
                /*
                 * Stream supports rwnext() for the read side.
                 * If this is the first time we're called by e.g. strread
                 * only do the downcall if there is a deferred wakeup
                 * (registered in sd_wakeq).
                 */
                struiod_t uiod;
                struct iovec buf[IOV_MAX_STACK];
                int iovlen = 0;

                if (first)
                        stp->sd_wakeq &= ~RSLEEP;

                if (uiop->uio_iovcnt > IOV_MAX_STACK) {
                        iovlen = uiop->uio_iovcnt * sizeof (iovec_t);
                        uiod.d_iov = kmem_alloc(iovlen, KM_SLEEP);
                } else {
                        uiod.d_iov = buf;
                }

                (void) uiodup(uiop, &uiod.d_uio, uiod.d_iov, uiop->uio_iovcnt);
                uiod.d_mp = 0;
                /*
                 * Mark that a thread is in rwnext on the read side
                 * to prevent strrput from nacking ioctls immediately.
                 * When the last concurrent rwnext returns
                 * the ioctls are nack'ed.
                 */
                ASSERT(MUTEX_HELD(&stp->sd_lock));
                stp->sd_struiodnak++;
                /*
                 * Note: rwnext will drop sd_lock.
                 */
                error = rwnext(q, &uiod);
                ASSERT(MUTEX_NOT_HELD(&stp->sd_lock));
                mutex_enter(&stp->sd_lock);
                stp->sd_struiodnak--;
                while (stp->sd_struiodnak == 0 &&
                    ((bp = stp->sd_struionak) != NULL)) {
                        stp->sd_struionak = bp->b_next;
                        bp->b_next = NULL;
                        bp->b_datap->db_type = M_IOCNAK;
                        /*
                         * Protect against the driver passing up
                         * messages after it has done a qprocsoff.
                         */
                        if (_OTHERQ(q)->q_next == NULL)
                                freemsg(bp);
                        else {
                                mutex_exit(&stp->sd_lock);
                                qreply(q, bp);
                                mutex_enter(&stp->sd_lock);
                        }
                }
                ASSERT(MUTEX_HELD(&stp->sd_lock));
                if (error == 0 || error == EWOULDBLOCK) {
                        if ((bp = uiod.d_mp) != NULL) {
                                *errorp = 0;
                                ASSERT(MUTEX_HELD(&stp->sd_lock));
                                if (iovlen != 0)
                                        kmem_free(uiod.d_iov, iovlen);
                                return (bp);
                        }
                        error = 0;
                } else if (error == EINVAL) {
                        /*
                         * The stream plumbing must have
                         * changed while we were away, so
                         * just turn off rwnext()s.
                         */
                        error = 0;
                } else if (error == EBUSY) {
                        /*
                         * The module might have data in transit using putnext
                         * Fall back on waiting + getq.
                         */
                        error = 0;
                } else {
                        *errorp = error;
                        ASSERT(MUTEX_HELD(&stp->sd_lock));
                        if (iovlen != 0)
                                kmem_free(uiod.d_iov, iovlen);
                        return (NULL);
                }

                if (iovlen != 0)
                        kmem_free(uiod.d_iov, iovlen);

                /*
                 * Try a getq in case a rwnext() generated mblk
                 * has bubbled up via strrput().
                 */
        }
        *errorp = 0;
        ASSERT(MUTEX_HELD(&stp->sd_lock));

        /*
         * If we have a valid uio, try and use this as a guide for how
         * many bytes to retrieve from the queue via getq_noenab().
         * Doing this can avoid unneccesary counting of overlong
         * messages in putback(). We currently only do this for sockets
         * and only if there is no sd_rputdatafunc hook.
         *
         * The sd_rputdatafunc hook transforms the entire message
         * before any bytes in it can be given to a client. So, rbytes
         * must be 0 if there is a hook.
         */
        if ((uiop != NULL) && (stp->sd_vnode->v_type == VSOCK) &&
            (stp->sd_rputdatafunc == NULL))
                rbytes = uiop->uio_resid;

        return (getq_noenab(q, rbytes));
}

/*
 * Copy out the message pointed to by `bp' into the uio pointed to by `uiop'.
 * If the message does not fit in the uio the remainder of it is returned;
 * otherwise NULL is returned.  Any embedded zero-length mblk_t's are
 * consumed, even if uio_resid reaches zero.  On error, `*errorp' is set to
 * the error code, the message is consumed, and NULL is returned.
 */
static mblk_t *
struiocopyout(mblk_t *bp, struct uio *uiop, int *errorp)
{
        int error;
        ptrdiff_t n;
        mblk_t *nbp;

        ASSERT(bp->b_wptr >= bp->b_rptr);

        do {
                if ((n = MIN(uiop->uio_resid, MBLKL(bp))) != 0) {
                        ASSERT(n > 0);

                        error = uiomove(bp->b_rptr, n, UIO_READ, uiop);
                        if (error != 0) {
                                freemsg(bp);
                                *errorp = error;
                                return (NULL);
                        }
                }

                bp->b_rptr += n;
                while (bp != NULL && (bp->b_rptr >= bp->b_wptr)) {
                        nbp = bp;
                        bp = bp->b_cont;
                        freeb(nbp);
                }
        } while (bp != NULL && uiop->uio_resid > 0);

        *errorp = 0;
        return (bp);
}

/*
 * Read a stream according to the mode flags in sd_flag:
 *
 * (default mode)               - Byte stream, msg boundaries are ignored
 * RD_MSGDIS (msg discard)      - Read on msg boundaries and throw away
 *                              any data remaining in msg
 * RD_MSGNODIS (msg non-discard) - Read on msg boundaries and put back
 *                              any remaining data on head of read queue
 *
 * Consume readable messages on the front of the queue until
 * ttolwp(curthread)->lwp_count
 * is satisfied, the readable messages are exhausted, or a message
 * boundary is reached in a message mode.  If no data was read and
 * the stream was not opened with the NDELAY flag, block until data arrives.
 * Otherwise return the data read and update the count.
 *
 * In default mode a 0 length message signifies end-of-file and terminates
 * a read in progress.  The 0 length message is removed from the queue
 * only if it is the only message read (no data is read).
 *
 * An attempt to read an M_PROTO or M_PCPROTO message results in an
 * EBADMSG error return, unless either RD_PROTDAT or RD_PROTDIS are set.
 * If RD_PROTDAT is set, M_PROTO and M_PCPROTO messages are read as data.
 * If RD_PROTDIS is set, the M_PROTO and M_PCPROTO parts of the message
 * are unlinked from and M_DATA blocks in the message, the protos are
 * thrown away, and the data is read.
 */
/* ARGSUSED */
int
strread(struct vnode *vp, struct uio *uiop, cred_t *crp)
{
        struct stdata *stp;
        mblk_t *bp, *nbp;
        queue_t *q;
        int error = 0;
        uint_t old_sd_flag;
        int first;
        char rflg;
        uint_t mark;            /* Contains MSG*MARK and _LASTMARK */
#define _LASTMARK       0x8000  /* Distinct from MSG*MARK */
        short delim;
        unsigned char pri = 0;
        char waitflag;
        unsigned char type;

        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRREAD_ENTER, "strread:%p", vp);
        ASSERT(vp->v_stream);
        stp = vp->v_stream;

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCREAD)) != 0) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        if (stp->sd_flag & (STRDERR|STPLEX)) {
                error = strgeterr(stp, STRDERR|STPLEX, 0);
                if (error != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
        }

        /*
         * Loop terminates when uiop->uio_resid == 0.
         */
        rflg = 0;
        waitflag = READWAIT;
        q = _RD(stp->sd_wrq);
        for (;;) {
                ASSERT(MUTEX_HELD(&stp->sd_lock));
                old_sd_flag = stp->sd_flag;
                mark = 0;
                delim = 0;
                first = 1;
                while ((bp = strget(stp, q, uiop, first, &error)) == NULL) {
                        int done = 0;

                        ASSERT(MUTEX_HELD(&stp->sd_lock));

                        if (error != 0)
                                goto oops;

                        if (stp->sd_flag & (STRHUP|STREOF)) {
                                goto oops;
                        }
                        if (rflg && !(stp->sd_flag & STRDELIM)) {
                                goto oops;
                        }
                        /*
                         * If a read(fd,buf,0) has been done, there is no
                         * need to sleep. We always have zero bytes to
                         * return.
                         */
                        if (uiop->uio_resid == 0) {
                                goto oops;
                        }

                        qbackenable(q, 0);

                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRREAD_WAIT,
                            "strread calls strwaitq:%p, %p, %p",
                            vp, uiop, crp);
                        if ((error = strwaitq(stp, waitflag, uiop->uio_resid,
                            uiop->uio_fmode, -1, &done)) != 0 || done) {
                                TRACE_3(TR_FAC_STREAMS_FR, TR_STRREAD_DONE,
                                    "strread error or done:%p, %p, %p",
                                    vp, uiop, crp);
                                if ((uiop->uio_fmode & FNDELAY) &&
                                    (stp->sd_flag & OLDNDELAY) &&
                                    (error == EAGAIN))
                                        error = 0;
                                goto oops;
                        }
                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRREAD_AWAKE,
                            "strread awakes:%p, %p, %p", vp, uiop, crp);
                        if ((error = i_straccess(stp, JCREAD)) != 0) {
                                goto oops;
                        }
                        first = 0;
                }

                ASSERT(MUTEX_HELD(&stp->sd_lock));
                ASSERT(bp);
                pri = bp->b_band;
                /*
                 * Extract any mark information. If the message is not
                 * completely consumed this information will be put in the mblk
                 * that is putback.
                 * If MSGMARKNEXT is set and the message is completely consumed
                 * the STRATMARK flag will be set below. Likewise, if
                 * MSGNOTMARKNEXT is set and the message is
                 * completely consumed STRNOTATMARK will be set.
                 *
                 * For some unknown reason strread only breaks the read at the
                 * last mark.
                 */
                mark = bp->b_flag & (MSGMARK | MSGMARKNEXT | MSGNOTMARKNEXT);
                ASSERT((mark & (MSGMARKNEXT|MSGNOTMARKNEXT)) !=
                    (MSGMARKNEXT|MSGNOTMARKNEXT));
                if (mark != 0 && bp == stp->sd_mark) {
                        if (rflg) {
                                putback(stp, q, bp, pri);
                                goto oops;
                        }
                        mark |= _LASTMARK;
                        stp->sd_mark = NULL;
                }
                if ((stp->sd_flag & STRDELIM) && (bp->b_flag & MSGDELIM))
                        delim = 1;
                mutex_exit(&stp->sd_lock);

                if (STREAM_NEEDSERVICE(stp))
                        stream_runservice(stp);

                type = bp->b_datap->db_type;

                switch (type) {

                case M_DATA:
ismdata:
                        if (msgnodata(bp)) {
                                if (mark || delim) {
                                        freemsg(bp);
                                } else if (rflg) {

                                        /*
                                         * If already read data put zero
                                         * length message back on queue else
                                         * free msg and return 0.
                                         */
                                        bp->b_band = pri;
                                        mutex_enter(&stp->sd_lock);
                                        putback(stp, q, bp, pri);
                                        mutex_exit(&stp->sd_lock);
                                } else {
                                        freemsg(bp);
                                }
                                error =  0;
                                goto oops1;
                        }

                        rflg = 1;
                        waitflag |= NOINTR;
                        bp = struiocopyout(bp, uiop, &error);
                        if (error != 0)
                                goto oops1;

                        mutex_enter(&stp->sd_lock);
                        if (bp) {
                                /*
                                 * Have remaining data in message.
                                 * Free msg if in discard mode.
                                 */
                                if (stp->sd_read_opt & RD_MSGDIS) {
                                        freemsg(bp);
                                } else {
                                        bp->b_band = pri;
                                        if ((mark & _LASTMARK) &&
                                            (stp->sd_mark == NULL))
                                                stp->sd_mark = bp;
                                        bp->b_flag |= mark & ~_LASTMARK;
                                        if (delim)
                                                bp->b_flag |= MSGDELIM;
                                        if (msgnodata(bp))
                                                freemsg(bp);
                                        else
                                                putback(stp, q, bp, pri);
                                }
                        } else {
                                /*
                                 * Consumed the complete message.
                                 * Move the MSG*MARKNEXT information
                                 * to the stream head just in case
                                 * the read queue becomes empty.
                                 *
                                 * If the stream head was at the mark
                                 * (STRATMARK) before we dropped sd_lock above
                                 * and some data was consumed then we have
                                 * moved past the mark thus STRATMARK is
                                 * cleared. However, if a message arrived in
                                 * strrput during the copyout above causing
                                 * STRATMARK to be set we can not clear that
                                 * flag.
                                 */
                                if (mark &
                                    (MSGMARKNEXT|MSGNOTMARKNEXT|MSGMARK)) {
                                        if (mark & MSGMARKNEXT) {
                                                stp->sd_flag &= ~STRNOTATMARK;
                                                stp->sd_flag |= STRATMARK;
                                        } else if (mark & MSGNOTMARKNEXT) {
                                                stp->sd_flag &= ~STRATMARK;
                                                stp->sd_flag |= STRNOTATMARK;
                                        } else {
                                                stp->sd_flag &=
                                                    ~(STRATMARK|STRNOTATMARK);
                                        }
                                } else if (rflg && (old_sd_flag & STRATMARK)) {
                                        stp->sd_flag &= ~STRATMARK;
                                }
                        }

                        /*
                         * Check for signal messages at the front of the read
                         * queue and generate the signal(s) if appropriate.
                         * The only signal that can be on queue is M_SIG at
                         * this point.
                         */
                        while ((((bp = q->q_first)) != NULL) &&
                            (bp->b_datap->db_type == M_SIG)) {
                                bp = getq_noenab(q, 0);
                                /*
                                 * sd_lock is held so the content of the
                                 * read queue can not change.
                                 */
                                ASSERT(bp != NULL && DB_TYPE(bp) == M_SIG);
                                strsignal_nolock(stp, *bp->b_rptr, bp->b_band);
                                mutex_exit(&stp->sd_lock);
                                freemsg(bp);
                                if (STREAM_NEEDSERVICE(stp))
                                        stream_runservice(stp);
                                mutex_enter(&stp->sd_lock);
                        }

                        if ((uiop->uio_resid == 0) || (mark & _LASTMARK) ||
                            delim ||
                            (stp->sd_read_opt & (RD_MSGDIS|RD_MSGNODIS))) {
                                goto oops;
                        }
                        continue;

                case M_SIG:
                        strsignal(stp, *bp->b_rptr, (int32_t)bp->b_band);
                        freemsg(bp);
                        mutex_enter(&stp->sd_lock);
                        continue;

                case M_PROTO:
                case M_PCPROTO:
                        /*
                         * Only data messages are readable.
                         * Any others generate an error, unless
                         * RD_PROTDIS or RD_PROTDAT is set.
                         */
                        if (stp->sd_read_opt & RD_PROTDAT) {
                                for (nbp = bp; nbp; nbp = nbp->b_next) {
                                        if ((nbp->b_datap->db_type ==
                                            M_PROTO) ||
                                            (nbp->b_datap->db_type ==
                                            M_PCPROTO)) {
                                                nbp->b_datap->db_type = M_DATA;
                                        } else {
                                                break;
                                        }
                                }
                                /*
                                 * clear stream head hi pri flag based on
                                 * first message
                                 */
                                if (type == M_PCPROTO) {
                                        mutex_enter(&stp->sd_lock);
                                        stp->sd_flag &= ~STRPRI;
                                        mutex_exit(&stp->sd_lock);
                                }
                                goto ismdata;
                        } else if (stp->sd_read_opt & RD_PROTDIS) {
                                /*
                                 * discard non-data messages
                                 */
                                while (bp &&
                                    ((bp->b_datap->db_type == M_PROTO) ||
                                    (bp->b_datap->db_type == M_PCPROTO))) {
                                        nbp = unlinkb(bp);
                                        freeb(bp);
                                        bp = nbp;
                                }
                                /*
                                 * clear stream head hi pri flag based on
                                 * first message
                                 */
                                if (type == M_PCPROTO) {
                                        mutex_enter(&stp->sd_lock);
                                        stp->sd_flag &= ~STRPRI;
                                        mutex_exit(&stp->sd_lock);
                                }
                                if (bp) {
                                        bp->b_band = pri;
                                        goto ismdata;
                                } else {
                                        break;
                                }
                        }
                        /* FALLTHRU */
                case M_PASSFP:
                        if ((bp->b_datap->db_type == M_PASSFP) &&
                            (stp->sd_read_opt & RD_PROTDIS)) {
                                freemsg(bp);
                                break;
                        }
                        mutex_enter(&stp->sd_lock);
                        putback(stp, q, bp, pri);
                        mutex_exit(&stp->sd_lock);
                        if (rflg == 0)
                                error = EBADMSG;
                        goto oops1;

                default:
                        /*
                         * Garbage on stream head read queue.
                         */
                        cmn_err(CE_WARN, "bad %x found at stream head\n",
                            bp->b_datap->db_type);
                        freemsg(bp);
                        goto oops1;
                }
                mutex_enter(&stp->sd_lock);
        }
oops:
        mutex_exit(&stp->sd_lock);
oops1:
        qbackenable(q, pri);
        return (error);
#undef  _LASTMARK
}

/*
 * Default processing of M_PROTO/M_PCPROTO messages.
 * Determine which wakeups and signals are needed.
 * This can be replaced by a user-specified procedure for kernel users
 * of STREAMS.
 */
/* ARGSUSED */
mblk_t *
strrput_proto(vnode_t *vp, mblk_t *mp,
    strwakeup_t *wakeups, strsigset_t *firstmsgsigs,
    strsigset_t *allmsgsigs, strpollset_t *pollwakeups)
{
        *wakeups = RSLEEP;
        *allmsgsigs = 0;

        switch (mp->b_datap->db_type) {
        case M_PROTO:
                if (mp->b_band == 0) {
                        *firstmsgsigs = S_INPUT | S_RDNORM;
                        *pollwakeups = POLLIN | POLLRDNORM;
                } else {
                        *firstmsgsigs = S_INPUT | S_RDBAND;
                        *pollwakeups = POLLIN | POLLRDBAND;
                }
                break;
        case M_PCPROTO:
                *firstmsgsigs = S_HIPRI;
                *pollwakeups = POLLPRI;
                break;
        }
        return (mp);
}

/*
 * Default processing of everything but M_DATA, M_PROTO, M_PCPROTO and
 * M_PASSFP messages.
 * Determine which wakeups and signals are needed.
 * This can be replaced by a user-specified procedure for kernel users
 * of STREAMS.
 */
/* ARGSUSED */
mblk_t *
strrput_misc(vnode_t *vp, mblk_t *mp,
    strwakeup_t *wakeups, strsigset_t *firstmsgsigs,
    strsigset_t *allmsgsigs, strpollset_t *pollwakeups)
{
        *wakeups = 0;
        *firstmsgsigs = 0;
        *allmsgsigs = 0;
        *pollwakeups = 0;
        return (mp);
}

/*
 * Stream read put procedure.  Called from downstream driver/module
 * with messages for the stream head.  Data, protocol, and in-stream
 * signal messages are placed on the queue, others are handled directly.
 */
int
strrput(queue_t *q, mblk_t *bp)
{
        struct stdata   *stp;
        ulong_t         rput_opt;
        strwakeup_t     wakeups;
        strsigset_t     firstmsgsigs;   /* Signals if first message on queue */
        strsigset_t     allmsgsigs;     /* Signals for all messages */
        strsigset_t     signals;        /* Signals events to generate */
        strpollset_t    pollwakeups;
        mblk_t          *nextbp;
        uchar_t         band = 0;
        int             hipri_sig;

        stp = (struct stdata *)q->q_ptr;
        /*
         * Use rput_opt for optimized access to the SR_ flags except
         * SR_POLLIN. That flag has to be checked under sd_lock since it
         * is modified by strpoll().
         */
        rput_opt = stp->sd_rput_opt;

        ASSERT(qclaimed(q));
        TRACE_2(TR_FAC_STREAMS_FR, TR_STRRPUT_ENTER,
            "strrput called with message type:q %p bp %p", q, bp);

        /*
         * Perform initial processing and pass to the parameterized functions.
         */
        ASSERT(bp->b_next == NULL);

        switch (bp->b_datap->db_type) {
        case M_DATA:
                /*
                 * sockfs is the only consumer of STREOF and when it is set,
                 * it implies that the receiver is not interested in receiving
                 * any more data, hence the mblk is freed to prevent unnecessary
                 * message queueing at the stream head.
                 */
                if (stp->sd_flag == STREOF) {
                        freemsg(bp);
                        return (0);
                }
                if ((rput_opt & SR_IGN_ZEROLEN) &&
                    bp->b_rptr == bp->b_wptr && msgnodata(bp)) {
                        /*
                         * Ignore zero-length M_DATA messages. These might be
                         * generated by some transports.
                         * The zero-length M_DATA messages, even if they
                         * are ignored, should effect the atmark tracking and
                         * should wake up a thread sleeping in strwaitmark.
                         */
                        mutex_enter(&stp->sd_lock);
                        if (bp->b_flag & MSGMARKNEXT) {
                                /*
                                 * Record the position of the mark either
                                 * in q_last or in STRATMARK.
                                 */
                                if (q->q_last != NULL) {
                                        q->q_last->b_flag &= ~MSGNOTMARKNEXT;
                                        q->q_last->b_flag |= MSGMARKNEXT;
                                } else {
                                        stp->sd_flag &= ~STRNOTATMARK;
                                        stp->sd_flag |= STRATMARK;
                                }
                        } else if (bp->b_flag & MSGNOTMARKNEXT) {
                                /*
                                 * Record that this is not the position of
                                 * the mark either in q_last or in
                                 * STRNOTATMARK.
                                 */
                                if (q->q_last != NULL) {
                                        q->q_last->b_flag &= ~MSGMARKNEXT;
                                        q->q_last->b_flag |= MSGNOTMARKNEXT;
                                } else {
                                        stp->sd_flag &= ~STRATMARK;
                                        stp->sd_flag |= STRNOTATMARK;
                                }
                        }
                        if (stp->sd_flag & RSLEEP) {
                                stp->sd_flag &= ~RSLEEP;
                                cv_broadcast(&q->q_wait);
                        }
                        mutex_exit(&stp->sd_lock);
                        freemsg(bp);
                        return (0);
                }
                wakeups = RSLEEP;
                if (bp->b_band == 0) {
                        firstmsgsigs = S_INPUT | S_RDNORM;
                        pollwakeups = POLLIN | POLLRDNORM;
                } else {
                        firstmsgsigs = S_INPUT | S_RDBAND;
                        pollwakeups = POLLIN | POLLRDBAND;
                }
                if (rput_opt & SR_SIGALLDATA)
                        allmsgsigs = firstmsgsigs;
                else
                        allmsgsigs = 0;

                mutex_enter(&stp->sd_lock);
                if ((rput_opt & SR_CONSOL_DATA) &&
                    (q->q_last != NULL) &&
                    (bp->b_flag & (MSGMARK|MSGDELIM)) == 0) {
                        /*
                         * Consolidate an M_DATA message onto an M_DATA,
                         * M_PROTO, or M_PCPROTO by merging it with q_last.
                         * The consolidation does not take place if
                         * the old message is marked with either of the
                         * marks or the delim flag or if the new
                         * message is marked with MSGMARK. The MSGMARK
                         * check is needed to handle the odd semantics of
                         * MSGMARK where essentially the whole message
                         * is to be treated as marked.
                         * Carry any MSGMARKNEXT  and MSGNOTMARKNEXT from the
                         * new message to the front of the b_cont chain.
                         */
                        mblk_t *lbp = q->q_last;
                        unsigned char db_type = lbp->b_datap->db_type;

                        if ((db_type == M_DATA || db_type == M_PROTO ||
                            db_type == M_PCPROTO) &&
                            !(lbp->b_flag & (MSGDELIM|MSGMARK|MSGMARKNEXT))) {
                                rmvq_noenab(q, lbp);
                                /*
                                 * The first message in the b_cont list
                                 * tracks MSGMARKNEXT and MSGNOTMARKNEXT.
                                 * We need to handle the case where we
                                 * are appending:
                                 *
                                 * 1) a MSGMARKNEXT to a MSGNOTMARKNEXT.
                                 * 2) a MSGMARKNEXT to a plain message.
                                 * 3) a MSGNOTMARKNEXT to a plain message
                                 * 4) a MSGNOTMARKNEXT to a MSGNOTMARKNEXT
                                 *    message.
                                 *
                                 * Thus we never append a MSGMARKNEXT or
                                 * MSGNOTMARKNEXT to a MSGMARKNEXT message.
                                 */
                                if (bp->b_flag & MSGMARKNEXT) {
                                        lbp->b_flag |= MSGMARKNEXT;
                                        lbp->b_flag &= ~MSGNOTMARKNEXT;
                                        bp->b_flag &= ~MSGMARKNEXT;
                                } else if (bp->b_flag & MSGNOTMARKNEXT) {
                                        lbp->b_flag |= MSGNOTMARKNEXT;
                                        bp->b_flag &= ~MSGNOTMARKNEXT;
                                }

                                linkb(lbp, bp);
                                bp = lbp;
                                /*
                                 * The new message logically isn't the first
                                 * even though the q_first check below thinks
                                 * it is. Clear the firstmsgsigs to make it
                                 * not appear to be first.
                                 */
                                firstmsgsigs = 0;
                        }
                }
                break;

        case M_PASSFP:
                wakeups = RSLEEP;
                allmsgsigs = 0;
                if (bp->b_band == 0) {
                        firstmsgsigs = S_INPUT | S_RDNORM;
                        pollwakeups = POLLIN | POLLRDNORM;
                } else {
                        firstmsgsigs = S_INPUT | S_RDBAND;
                        pollwakeups = POLLIN | POLLRDBAND;
                }
                mutex_enter(&stp->sd_lock);
                break;

        case M_PROTO:
        case M_PCPROTO:
                ASSERT(stp->sd_rprotofunc != NULL);
                bp = (stp->sd_rprotofunc)(stp->sd_vnode, bp,
                    &wakeups, &firstmsgsigs, &allmsgsigs, &pollwakeups);
#define ALLSIG  (S_INPUT|S_HIPRI|S_OUTPUT|S_MSG|S_ERROR|S_HANGUP|S_RDNORM|\
                S_WRNORM|S_RDBAND|S_WRBAND|S_BANDURG)
#define ALLPOLL (POLLIN|POLLPRI|POLLOUT|POLLRDNORM|POLLWRNORM|POLLRDBAND|\
                POLLWRBAND)

                ASSERT((wakeups & ~(RSLEEP|WSLEEP)) == 0);
                ASSERT((firstmsgsigs & ~ALLSIG) == 0);
                ASSERT((allmsgsigs & ~ALLSIG) == 0);
                ASSERT((pollwakeups & ~ALLPOLL) == 0);

                mutex_enter(&stp->sd_lock);
                break;

        default:
                ASSERT(stp->sd_rmiscfunc != NULL);
                bp = (stp->sd_rmiscfunc)(stp->sd_vnode, bp,
                    &wakeups, &firstmsgsigs, &allmsgsigs, &pollwakeups);
                ASSERT((wakeups & ~(RSLEEP|WSLEEP)) == 0);
                ASSERT((firstmsgsigs & ~ALLSIG) == 0);
                ASSERT((allmsgsigs & ~ALLSIG) == 0);
                ASSERT((pollwakeups & ~ALLPOLL) == 0);
#undef  ALLSIG
#undef  ALLPOLL
                mutex_enter(&stp->sd_lock);
                break;
        }
        ASSERT(MUTEX_HELD(&stp->sd_lock));

        /* By default generate superset of signals */
        signals = (firstmsgsigs | allmsgsigs);

        /*
         * The  proto and misc functions can return multiple messages
         * as a b_next chain. Such messages are processed separately.
         */
one_more:
        hipri_sig = 0;
        if (bp == NULL) {
                nextbp = NULL;
        } else {
                nextbp = bp->b_next;
                bp->b_next = NULL;

                switch (bp->b_datap->db_type) {
                case M_PCPROTO:
                        /*
                         * Only one priority protocol message is allowed at the
                         * stream head at a time.
                         */
                        if (stp->sd_flag & STRPRI) {
                                TRACE_0(TR_FAC_STREAMS_FR, TR_STRRPUT_PROTERR,
                                    "M_PCPROTO already at head");
                                freemsg(bp);
                                mutex_exit(&stp->sd_lock);
                                goto done;
                        }
                        stp->sd_flag |= STRPRI;
                        hipri_sig = 1;
                        /* FALLTHRU */
                case M_DATA:
                case M_PROTO:
                case M_PASSFP:
                        band = bp->b_band;
                        /*
                         * Marking doesn't work well when messages
                         * are marked in more than one band.  We only
                         * remember the last message received, even if
                         * it is placed on the queue ahead of other
                         * marked messages.
                         */
                        if (bp->b_flag & MSGMARK)
                                stp->sd_mark = bp;
                        (void) putq(q, bp);

                        /*
                         * If message is a PCPROTO message, always use
                         * firstmsgsigs to determine if a signal should be
                         * sent as strrput is the only place to send
                         * signals for PCPROTO. Other messages are based on
                         * the STRGETINPROG flag. The flag determines if
                         * strrput or (k)strgetmsg will be responsible for
                         * sending the signals, in the firstmsgsigs case.
                         */
                        if ((hipri_sig == 1) ||
                            (((stp->sd_flag & STRGETINPROG) == 0) &&
                            (q->q_first == bp)))
                                signals = (firstmsgsigs | allmsgsigs);
                        else
                                signals = allmsgsigs;
                        break;

                default:
                        mutex_exit(&stp->sd_lock);
                        (void) strrput_nondata(q, bp);
                        mutex_enter(&stp->sd_lock);
                        break;
                }
        }
        ASSERT(MUTEX_HELD(&stp->sd_lock));
        /*
         * Wake sleeping read/getmsg and cancel deferred wakeup
         */
        if (wakeups & RSLEEP)
                stp->sd_wakeq &= ~RSLEEP;

        wakeups &= stp->sd_flag;
        if (wakeups & RSLEEP) {
                stp->sd_flag &= ~RSLEEP;
                cv_broadcast(&q->q_wait);
        }
        if (wakeups & WSLEEP) {
                stp->sd_flag &= ~WSLEEP;
                cv_broadcast(&_WR(q)->q_wait);
        }

        if (pollwakeups != 0) {
                if (pollwakeups == (POLLIN | POLLRDNORM)) {
                        /*
                         * Can't use rput_opt since it was not
                         * read when sd_lock was held and SR_POLLIN is changed
                         * by strpoll() under sd_lock.
                         */
                        if (!(stp->sd_rput_opt & SR_POLLIN))
                                goto no_pollwake;
                        stp->sd_rput_opt &= ~SR_POLLIN;
                }
                mutex_exit(&stp->sd_lock);
                pollwakeup(&stp->sd_pollist, pollwakeups);
                mutex_enter(&stp->sd_lock);
        }
no_pollwake:

        /*
         * strsendsig can handle multiple signals with a
         * single call.
         */
        if (stp->sd_sigflags & signals)
                strsendsig(stp->sd_siglist, signals, band, 0);
        mutex_exit(&stp->sd_lock);


done:
        if (nextbp == NULL)
                return (0);

        /*
         * Any signals were handled the first time.
         * Wakeups and pollwakeups are redone to avoid any race
         * conditions - all the messages are not queued until the
         * last message has been processed by strrput.
         */
        bp = nextbp;
        signals = firstmsgsigs = allmsgsigs = 0;
        mutex_enter(&stp->sd_lock);
        goto one_more;
}

static void
log_dupioc(queue_t *rq, mblk_t *bp)
{
        queue_t *wq, *qp;
        char *modnames, *mnp, *dname;
        size_t maxmodstr;
        boolean_t islast;

        /*
         * Allocate a buffer large enough to hold the names of nstrpush modules
         * and one driver, with spaces between and NUL terminator.  If we can't
         * get memory, then we'll just log the driver name.
         */
        maxmodstr = nstrpush * (FMNAMESZ + 1);
        mnp = modnames = kmem_alloc(maxmodstr, KM_NOSLEEP);

        /* march down write side to print log message down to the driver */
        wq = WR(rq);

        /* make sure q_next doesn't shift around while we're grabbing data */
        claimstr(wq);
        qp = wq->q_next;
        do {
                dname = Q2NAME(qp);
                islast = !SAMESTR(qp) || qp->q_next == NULL;
                if (modnames == NULL) {
                        /*
                         * If we don't have memory, then get the driver name in
                         * the log where we can see it.  Note that memory
                         * pressure is a possible cause of these sorts of bugs.
                         */
                        if (islast) {
                                modnames = dname;
                                maxmodstr = 0;
                        }
                } else {
                        mnp += snprintf(mnp, FMNAMESZ + 1, "%s", dname);
                        if (!islast)
                                *mnp++ = ' ';
                }
                qp = qp->q_next;
        } while (!islast);
        releasestr(wq);
        /* Cannot happen unless stream head is corrupt. */
        ASSERT(modnames != NULL);
        (void) strlog(rq->q_qinfo->qi_minfo->mi_idnum, 0, 1,
            SL_CONSOLE|SL_TRACE|SL_ERROR,
            "Warning: stream %p received duplicate %X M_IOC%s; module list: %s",
            rq->q_ptr, ((struct iocblk *)bp->b_rptr)->ioc_cmd,
            (DB_TYPE(bp) == M_IOCACK ? "ACK" : "NAK"), modnames);
        if (maxmodstr != 0)
                kmem_free(modnames, maxmodstr);
}

int
strrput_nondata(queue_t *q, mblk_t *bp)
{
        struct stdata *stp;
        struct iocblk *iocbp;
        struct stroptions *sop;
        struct copyreq *reqp;
        struct copyresp *resp;
        unsigned char bpri;
        unsigned char  flushed_already = 0;

        stp = (struct stdata *)q->q_ptr;

        ASSERT(!(stp->sd_flag & STPLEX));
        ASSERT(qclaimed(q));

        switch (bp->b_datap->db_type) {
        case M_ERROR:
                /*
                 * An error has occurred downstream, the errno is in the first
                 * bytes of the message.
                 */
                if ((bp->b_wptr - bp->b_rptr) == 2) {   /* New flavor */
                        unsigned char rw = 0;

                        mutex_enter(&stp->sd_lock);
                        if (*bp->b_rptr != NOERROR) {   /* read error */
                                if (*bp->b_rptr != 0) {
                                        if (stp->sd_flag & STRDERR)
                                                flushed_already |= FLUSHR;
                                        stp->sd_flag |= STRDERR;
                                        rw |= FLUSHR;
                                } else {
                                        stp->sd_flag &= ~STRDERR;
                                }
                                stp->sd_rerror = *bp->b_rptr;
                        }
                        bp->b_rptr++;
                        if (*bp->b_rptr != NOERROR) {   /* write error */
                                if (*bp->b_rptr != 0) {
                                        if (stp->sd_flag & STWRERR)
                                                flushed_already |= FLUSHW;
                                        stp->sd_flag |= STWRERR;
                                        rw |= FLUSHW;
                                } else {
                                        stp->sd_flag &= ~STWRERR;
                                }
                                stp->sd_werror = *bp->b_rptr;
                        }
                        if (rw) {
                                TRACE_2(TR_FAC_STREAMS_FR, TR_STRRPUT_WAKE,
                                    "strrput cv_broadcast:q %p, bp %p",
                                    q, bp);
                                cv_broadcast(&q->q_wait); /* readers */
                                cv_broadcast(&_WR(q)->q_wait); /* writers */
                                cv_broadcast(&stp->sd_monitor); /* ioctllers */

                                mutex_exit(&stp->sd_lock);
                                pollwakeup(&stp->sd_pollist, POLLERR);
                                mutex_enter(&stp->sd_lock);

                                if (stp->sd_sigflags & S_ERROR)
                                        strsendsig(stp->sd_siglist, S_ERROR, 0,
                                            ((rw & FLUSHR) ? stp->sd_rerror :
                                            stp->sd_werror));
                                mutex_exit(&stp->sd_lock);
                                /*
                                 * Send the M_FLUSH only
                                 * for the first M_ERROR
                                 * message on the stream
                                 */
                                if (flushed_already == rw) {
                                        freemsg(bp);
                                        return (0);
                                }

                                bp->b_datap->db_type = M_FLUSH;
                                *bp->b_rptr = rw;
                                bp->b_wptr = bp->b_rptr + 1;
                                /*
                                 * Protect against the driver
                                 * passing up messages after
                                 * it has done a qprocsoff
                                 */
                                if (_OTHERQ(q)->q_next == NULL)
                                        freemsg(bp);
                                else
                                        qreply(q, bp);
                                return (0);
                        } else
                                mutex_exit(&stp->sd_lock);
                } else if (*bp->b_rptr != 0) {          /* Old flavor */
                                if (stp->sd_flag & (STRDERR|STWRERR))
                                        flushed_already = FLUSHRW;
                                mutex_enter(&stp->sd_lock);
                                stp->sd_flag |= (STRDERR|STWRERR);
                                stp->sd_rerror = *bp->b_rptr;
                                stp->sd_werror = *bp->b_rptr;
                                TRACE_2(TR_FAC_STREAMS_FR,
                                    TR_STRRPUT_WAKE2,
                                    "strrput wakeup #2:q %p, bp %p", q, bp);
                                cv_broadcast(&q->q_wait); /* the readers */
                                cv_broadcast(&_WR(q)->q_wait); /* the writers */
                                cv_broadcast(&stp->sd_monitor); /* ioctllers */

                                mutex_exit(&stp->sd_lock);
                                pollwakeup(&stp->sd_pollist, POLLERR);
                                mutex_enter(&stp->sd_lock);

                                if (stp->sd_sigflags & S_ERROR)
                                        strsendsig(stp->sd_siglist, S_ERROR, 0,
                                            (stp->sd_werror ? stp->sd_werror :
                                            stp->sd_rerror));
                                mutex_exit(&stp->sd_lock);

                                /*
                                 * Send the M_FLUSH only
                                 * for the first M_ERROR
                                 * message on the stream
                                 */
                                if (flushed_already != FLUSHRW) {
                                        bp->b_datap->db_type = M_FLUSH;
                                        *bp->b_rptr = FLUSHRW;
                                        /*
                                         * Protect against the driver passing up
                                         * messages after it has done a
                                         * qprocsoff.
                                         */
                                        if (_OTHERQ(q)->q_next == NULL)
                                                freemsg(bp);
                                        else
                                                qreply(q, bp);
                                        return (0);
                                }
                }
                freemsg(bp);
                return (0);

        case M_HANGUP:

                freemsg(bp);
                mutex_enter(&stp->sd_lock);
                stp->sd_werror = ENXIO;
                stp->sd_flag |= STRHUP;
                stp->sd_flag &= ~(WSLEEP|RSLEEP);

                /*
                 * send signal if controlling tty
                 */

                if (stp->sd_sidp) {
                        prsignal(stp->sd_sidp, SIGHUP);
                        if (stp->sd_sidp != stp->sd_pgidp)
                                pgsignal(stp->sd_pgidp, SIGTSTP);
                }

                /*
                 * wake up read, write, and exception pollers and
                 * reset wakeup mechanism.
                 */
                cv_broadcast(&q->q_wait);       /* the readers */
                cv_broadcast(&_WR(q)->q_wait);  /* the writers */
                cv_broadcast(&stp->sd_monitor); /* the ioctllers */
                strhup(stp);
                mutex_exit(&stp->sd_lock);
                return (0);

        case M_UNHANGUP:
                freemsg(bp);
                mutex_enter(&stp->sd_lock);
                stp->sd_werror = 0;
                stp->sd_flag &= ~STRHUP;
                mutex_exit(&stp->sd_lock);
                return (0);

        case M_SIG:
                /*
                 * Someone downstream wants to post a signal.  The
                 * signal to post is contained in the first byte of the
                 * message.  If the message would go on the front of
                 * the queue, send a signal to the process group
                 * (if not SIGPOLL) or to the siglist processes
                 * (SIGPOLL).  If something is already on the queue,
                 * OR if we are delivering a delayed suspend (*sigh*
                 * another "tty" hack) and there's no one sleeping already,
                 * just enqueue the message.
                 */
                mutex_enter(&stp->sd_lock);
                if (q->q_first || (*bp->b_rptr == SIGTSTP &&
                    !(stp->sd_flag & RSLEEP))) {
                        (void) putq(q, bp);
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }
                mutex_exit(&stp->sd_lock);
                /* FALLTHRU */

        case M_PCSIG:
                /*
                 * Don't enqueue, just post the signal.
                 */
                strsignal(stp, *bp->b_rptr, 0L);
                freemsg(bp);
                return (0);

        case M_CMD:
                if (MBLKL(bp) != sizeof (cmdblk_t)) {
                        freemsg(bp);
                        return (0);
                }

                mutex_enter(&stp->sd_lock);
                if (stp->sd_flag & STRCMDWAIT) {
                        ASSERT(stp->sd_cmdblk == NULL);
                        stp->sd_cmdblk = bp;
                        cv_broadcast(&stp->sd_monitor);
                        mutex_exit(&stp->sd_lock);
                } else {
                        mutex_exit(&stp->sd_lock);
                        freemsg(bp);
                }
                return (0);

        case M_FLUSH:
                /*
                 * Flush queues.  The indication of which queues to flush
                 * is in the first byte of the message.  If the read queue
                 * is specified, then flush it.  If FLUSHBAND is set, just
                 * flush the band specified by the second byte of the message.
                 *
                 * If a module has issued a M_SETOPT to not flush hi
                 * priority messages off of the stream head, then pass this
                 * flag into the flushq code to preserve such messages.
                 */

                if (*bp->b_rptr & FLUSHR) {
                        mutex_enter(&stp->sd_lock);
                        if (*bp->b_rptr & FLUSHBAND) {
                                ASSERT((bp->b_wptr - bp->b_rptr) >= 2);
                                flushband(q, *(bp->b_rptr + 1), FLUSHALL);
                        } else
                                flushq_common(q, FLUSHALL,
                                    stp->sd_read_opt & RFLUSHPCPROT);
                        if ((q->q_first == NULL) ||
                            (q->q_first->b_datap->db_type < QPCTL))
                                stp->sd_flag &= ~STRPRI;
                        else {
                                ASSERT(stp->sd_flag & STRPRI);
                        }
                        mutex_exit(&stp->sd_lock);
                }
                if ((*bp->b_rptr & FLUSHW) && !(bp->b_flag & MSGNOLOOP)) {
                        *bp->b_rptr &= ~FLUSHR;
                        bp->b_flag |= MSGNOLOOP;
                        /*
                         * Protect against the driver passing up
                         * messages after it has done a qprocsoff.
                         */
                        if (_OTHERQ(q)->q_next == NULL)
                                freemsg(bp);
                        else
                                qreply(q, bp);
                        return (0);
                }
                freemsg(bp);
                return (0);

        case M_IOCACK:
        case M_IOCNAK:
                iocbp = (struct iocblk *)bp->b_rptr;
                /*
                 * If not waiting for ACK or NAK then just free msg.
                 * If incorrect id sequence number then just free msg.
                 * If already have ACK or NAK for user then this is a
                 *    duplicate, display a warning and free the msg.
                 */
                mutex_enter(&stp->sd_lock);
                if ((stp->sd_flag & IOCWAIT) == 0 || stp->sd_iocblk ||
                    (stp->sd_iocid != iocbp->ioc_id)) {
                        /*
                         * If the ACK/NAK is a dup, display a message
                         * Dup is when sd_iocid == ioc_id, and
                         * sd_iocblk == <valid ptr> or -1 (the former
                         * is when an ioctl has been put on the stream
                         * head, but has not yet been consumed, the
                         * later is when it has been consumed).
                         */
                        if ((stp->sd_iocid == iocbp->ioc_id) &&
                            (stp->sd_iocblk != NULL)) {
                                log_dupioc(q, bp);
                        }
                        freemsg(bp);
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }

                /*
                 * Assign ACK or NAK to user and wake up.
                 */
                stp->sd_iocblk = bp;
                cv_broadcast(&stp->sd_monitor);
                mutex_exit(&stp->sd_lock);
                return (0);

        case M_COPYIN:
        case M_COPYOUT:
                reqp = (struct copyreq *)bp->b_rptr;

                /*
                 * If not waiting for ACK or NAK then just fail request.
                 * If already have ACK, NAK, or copy request, then just
                 * fail request.
                 * If incorrect id sequence number then just fail request.
                 */
                mutex_enter(&stp->sd_lock);
                if ((stp->sd_flag & IOCWAIT) == 0 || stp->sd_iocblk ||
                    (stp->sd_iocid != reqp->cq_id)) {
                        if (bp->b_cont) {
                                freemsg(bp->b_cont);
                                bp->b_cont = NULL;
                        }
                        bp->b_datap->db_type = M_IOCDATA;
                        bp->b_wptr = bp->b_rptr + sizeof (struct copyresp);
                        resp = (struct copyresp *)bp->b_rptr;
                        resp->cp_rval = (caddr_t)1;     /* failure */
                        mutex_exit(&stp->sd_lock);
                        putnext(stp->sd_wrq, bp);
                        return (0);
                }

                /*
                 * Assign copy request to user and wake up.
                 */
                stp->sd_iocblk = bp;
                cv_broadcast(&stp->sd_monitor);
                mutex_exit(&stp->sd_lock);
                return (0);

        case M_SETOPTS:
                /*
                 * Set stream head options (read option, write offset,
                 * min/max packet size, and/or high/low water marks for
                 * the read side only).
                 */

                bpri = 0;
                sop = (struct stroptions *)bp->b_rptr;
                mutex_enter(&stp->sd_lock);
                if (sop->so_flags & SO_READOPT) {
                        switch (sop->so_readopt & RMODEMASK) {
                        case RNORM:
                                stp->sd_read_opt &= ~(RD_MSGDIS | RD_MSGNODIS);
                                break;

                        case RMSGD:
                                stp->sd_read_opt =
                                    ((stp->sd_read_opt & ~RD_MSGNODIS) |
                                    RD_MSGDIS);
                                break;

                        case RMSGN:
                                stp->sd_read_opt =
                                    ((stp->sd_read_opt & ~RD_MSGDIS) |
                                    RD_MSGNODIS);
                                break;
                        }
                        switch (sop->so_readopt & RPROTMASK) {
                        case RPROTNORM:
                                stp->sd_read_opt &= ~(RD_PROTDAT | RD_PROTDIS);
                                break;

                        case RPROTDAT:
                                stp->sd_read_opt =
                                    ((stp->sd_read_opt & ~RD_PROTDIS) |
                                    RD_PROTDAT);
                                break;

                        case RPROTDIS:
                                stp->sd_read_opt =
                                    ((stp->sd_read_opt & ~RD_PROTDAT) |
                                    RD_PROTDIS);
                                break;
                        }
                        switch (sop->so_readopt & RFLUSHMASK) {
                        case RFLUSHPCPROT:
                                /*
                                 * This sets the stream head to NOT flush
                                 * M_PCPROTO messages.
                                 */
                                stp->sd_read_opt |= RFLUSHPCPROT;
                                break;
                        }
                }
                if (sop->so_flags & SO_ERROPT) {
                        switch (sop->so_erropt & RERRMASK) {
                        case RERRNORM:
                                stp->sd_flag &= ~STRDERRNONPERSIST;
                                break;
                        case RERRNONPERSIST:
                                stp->sd_flag |= STRDERRNONPERSIST;
                                break;
                        }
                        switch (sop->so_erropt & WERRMASK) {
                        case WERRNORM:
                                stp->sd_flag &= ~STWRERRNONPERSIST;
                                break;
                        case WERRNONPERSIST:
                                stp->sd_flag |= STWRERRNONPERSIST;
                                break;
                        }
                }
                if (sop->so_flags & SO_COPYOPT) {
                        if (sop->so_copyopt & ZCVMSAFE) {
                                stp->sd_copyflag |= STZCVMSAFE;
                                stp->sd_copyflag &= ~STZCVMUNSAFE;
                        } else if (sop->so_copyopt & ZCVMUNSAFE) {
                                stp->sd_copyflag |= STZCVMUNSAFE;
                                stp->sd_copyflag &= ~STZCVMSAFE;
                        }

                        if (sop->so_copyopt & COPYCACHED) {
                                stp->sd_copyflag |= STRCOPYCACHED;
                        }
                }
                if (sop->so_flags & SO_WROFF)
                        stp->sd_wroff = sop->so_wroff;
                if (sop->so_flags & SO_TAIL)
                        stp->sd_tail = sop->so_tail;
                if (sop->so_flags & SO_MINPSZ)
                        q->q_minpsz = sop->so_minpsz;
                if (sop->so_flags & SO_MAXPSZ)
                        q->q_maxpsz = sop->so_maxpsz;
                if (sop->so_flags & SO_MAXBLK)
                        stp->sd_maxblk = sop->so_maxblk;
                if (sop->so_flags & SO_HIWAT) {
                        if (sop->so_flags & SO_BAND) {
                                if (strqset(q, QHIWAT,
                                    sop->so_band, sop->so_hiwat)) {
                                        cmn_err(CE_WARN, "strrput: could not "
                                            "allocate qband\n");
                                } else {
                                        bpri = sop->so_band;
                                }
                        } else {
                                q->q_hiwat = sop->so_hiwat;
                        }
                }
                if (sop->so_flags & SO_LOWAT) {
                        if (sop->so_flags & SO_BAND) {
                                if (strqset(q, QLOWAT,
                                    sop->so_band, sop->so_lowat)) {
                                        cmn_err(CE_WARN, "strrput: could not "
                                            "allocate qband\n");
                                } else {
                                        bpri = sop->so_band;
                                }
                        } else {
                                q->q_lowat = sop->so_lowat;
                        }
                }
                if (sop->so_flags & SO_MREADON)
                        stp->sd_flag |= SNDMREAD;
                if (sop->so_flags & SO_MREADOFF)
                        stp->sd_flag &= ~SNDMREAD;
                if (sop->so_flags & SO_NDELON)
                        stp->sd_flag |= OLDNDELAY;
                if (sop->so_flags & SO_NDELOFF)
                        stp->sd_flag &= ~OLDNDELAY;
                if (sop->so_flags & SO_ISTTY)
                        stp->sd_flag |= STRISTTY;
                if (sop->so_flags & SO_ISNTTY)
                        stp->sd_flag &= ~STRISTTY;
                if (sop->so_flags & SO_TOSTOP)
                        stp->sd_flag |= STRTOSTOP;
                if (sop->so_flags & SO_TONSTOP)
                        stp->sd_flag &= ~STRTOSTOP;
                if (sop->so_flags & SO_DELIM)
                        stp->sd_flag |= STRDELIM;
                if (sop->so_flags & SO_NODELIM)
                        stp->sd_flag &= ~STRDELIM;

                mutex_exit(&stp->sd_lock);
                freemsg(bp);

                /* Check backenable in case the water marks changed */
                qbackenable(q, bpri);
                return (0);

        /*
         * The following set of cases deal with situations where two stream
         * heads are connected to each other (twisted streams).  These messages
         * have no meaning at the stream head.
         */
        case M_BREAK:
        case M_CTL:
        case M_DELAY:
        case M_START:
        case M_STOP:
        case M_IOCDATA:
        case M_STARTI:
        case M_STOPI:
                freemsg(bp);
                return (0);

        case M_IOCTL:
                /*
                 * Always NAK this condition
                 * (makes no sense)
                 * If there is one or more threads in the read side
                 * rwnext we have to defer the nacking until that thread
                 * returns (in strget).
                 */
                mutex_enter(&stp->sd_lock);
                if (stp->sd_struiodnak != 0) {
                        /*
                         * Defer NAK to the streamhead. Queue at the end
                         * the list.
                         */
                        mblk_t *mp = stp->sd_struionak;

                        while (mp && mp->b_next)
                                mp = mp->b_next;
                        if (mp)
                                mp->b_next = bp;
                        else
                                stp->sd_struionak = bp;
                        bp->b_next = NULL;
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }
                mutex_exit(&stp->sd_lock);

                bp->b_datap->db_type = M_IOCNAK;
                /*
                 * Protect against the driver passing up
                 * messages after it has done a qprocsoff.
                 */
                if (_OTHERQ(q)->q_next == NULL)
                        freemsg(bp);
                else
                        qreply(q, bp);
                return (0);

        default:
#ifdef DEBUG
                cmn_err(CE_WARN,
                    "bad message type %x received at stream head\n",
                    bp->b_datap->db_type);
#endif
                freemsg(bp);
                return (0);
        }

        /* NOTREACHED */
}

/*
 * Check if the stream pointed to by `stp' can be written to, and return an
 * error code if not.  If `eiohup' is set, then return EIO if STRHUP is set.
 * If `sigpipeok' is set and the SW_SIGPIPE option is enabled on the stream,
 * then always return EPIPE and send a SIGPIPE to the invoking thread.
 */
static int
strwriteable(struct stdata *stp, boolean_t eiohup, boolean_t sigpipeok)
{
        int error;

        ASSERT(MUTEX_HELD(&stp->sd_lock));

        /*
         * For modem support, POSIX states that on writes, EIO should
         * be returned if the stream has been hung up.
         */
        if (eiohup && (stp->sd_flag & (STPLEX|STRHUP)) == STRHUP)
                error = EIO;
        else
                error = strgeterr(stp, STRHUP|STPLEX|STWRERR, 0);

        if (error != 0) {
                if (!(stp->sd_flag & STPLEX) &&
                    (stp->sd_wput_opt & SW_SIGPIPE) && sigpipeok) {
                        tsignal(curthread, SIGPIPE);
                        error = EPIPE;
                }
        }

        return (error);
}

/*
 * Copyin and send data down a stream.
 * The caller will allocate and copyin any control part that precedes the
 * message and pass that in as mctl.
 *
 * Caller should *not* hold sd_lock.
 * When EWOULDBLOCK is returned the caller has to redo the canputnext
 * under sd_lock in order to avoid missing a backenabling wakeup.
 *
 * Use iosize = -1 to not send any M_DATA. iosize = 0 sends zero-length M_DATA.
 *
 * Set MSG_IGNFLOW in flags to ignore flow control for hipri messages.
 * For sync streams we can only ignore flow control by reverting to using
 * putnext.
 *
 * If sd_maxblk is less than *iosize this routine might return without
 * transferring all of *iosize. In all cases, on return *iosize will contain
 * the amount of data that was transferred.
 */
static int
strput(struct stdata *stp, mblk_t *mctl, struct uio *uiop, ssize_t *iosize,
    int b_flag, int pri, int flags)
{
        struiod_t uiod;
        struct iovec buf[IOV_MAX_STACK];
        int iovlen = 0;
        mblk_t *mp;
        queue_t *wqp = stp->sd_wrq;
        int error = 0;
        ssize_t count = *iosize;

        ASSERT(MUTEX_NOT_HELD(&stp->sd_lock));

        if (uiop != NULL && count >= 0)
                flags |= stp->sd_struiowrq ? STRUIO_POSTPONE : 0;

        if (!(flags & STRUIO_POSTPONE)) {
                /*
                 * Use regular canputnext, strmakedata, putnext sequence.
                 */
                if (pri == 0) {
                        if (!canputnext(wqp) && !(flags & MSG_IGNFLOW)) {
                                freemsg(mctl);
                                return (EWOULDBLOCK);
                        }
                } else {
                        if (!(flags & MSG_IGNFLOW) && !bcanputnext(wqp, pri)) {
                                freemsg(mctl);
                                return (EWOULDBLOCK);
                        }
                }

                if ((error = strmakedata(iosize, uiop, stp, flags,
                    &mp)) != 0) {
                        freemsg(mctl);
                        /*
                         * need to change return code to ENOMEM
                         * so that this is not confused with
                         * flow control, EAGAIN.
                         */

                        if (error == EAGAIN)
                                return (ENOMEM);
                        else
                                return (error);
                }
                if (mctl != NULL) {
                        if (mctl->b_cont == NULL)
                                mctl->b_cont = mp;
                        else if (mp != NULL)
                                linkb(mctl, mp);
                        mp = mctl;
                } else if (mp == NULL)
                        return (0);

                mp->b_flag |= b_flag;
                mp->b_band = (uchar_t)pri;

                if (flags & MSG_IGNFLOW) {
                        /*
                         * XXX Hack: Don't get stuck running service
                         * procedures. This is needed for sockfs when
                         * sending the unbind message out of the rput
                         * procedure - we don't want a put procedure
                         * to run service procedures.
                         */
                        putnext(wqp, mp);
                } else {
                        stream_willservice(stp);
                        putnext(wqp, mp);
                        stream_runservice(stp);
                }
                return (0);
        }
        /*
         * Stream supports rwnext() for the write side.
         */
        if ((error = strmakedata(iosize, uiop, stp, flags, &mp)) != 0) {
                freemsg(mctl);
                /*
                 * map EAGAIN to ENOMEM since EAGAIN means "flow controlled".
                 */
                return (error == EAGAIN ? ENOMEM : error);
        }
        if (mctl != NULL) {
                if (mctl->b_cont == NULL)
                        mctl->b_cont = mp;
                else if (mp != NULL)
                        linkb(mctl, mp);
                mp = mctl;
        } else if (mp == NULL) {
                return (0);
        }

        mp->b_flag |= b_flag;
        mp->b_band = (uchar_t)pri;

        if (uiop->uio_iovcnt > IOV_MAX_STACK) {
                iovlen = uiop->uio_iovcnt * sizeof (iovec_t);
                uiod.d_iov = kmem_alloc(iovlen, KM_SLEEP);
        } else {
                uiod.d_iov = buf;
        }

        (void) uiodup(uiop, &uiod.d_uio, uiod.d_iov, uiop->uio_iovcnt);
        uiod.d_uio.uio_offset = 0;
        uiod.d_mp = mp;
        error = rwnext(wqp, &uiod);
        if (! uiod.d_mp) {
                uioskip(uiop, *iosize);
                if (iovlen != 0)
                        kmem_free(uiod.d_iov, iovlen);
                return (error);
        }
        ASSERT(mp == uiod.d_mp);
        if (error == EINVAL) {
                /*
                 * The stream plumbing must have changed while
                 * we were away, so just turn off rwnext()s.
                 */
                error = 0;
        } else if (error == EBUSY || error == EWOULDBLOCK) {
                /*
                 * Couldn't enter a perimeter or took a page fault,
                 * so fall-back to putnext().
                 */
                error = 0;
        } else {
                freemsg(mp);
                if (iovlen != 0)
                        kmem_free(uiod.d_iov, iovlen);
                return (error);
        }
        /* Have to check canput before consuming data from the uio */
        if (pri == 0) {
                if (!canputnext(wqp) && !(flags & MSG_IGNFLOW)) {
                        freemsg(mp);
                        if (iovlen != 0)
                                kmem_free(uiod.d_iov, iovlen);
                        return (EWOULDBLOCK);
                }
        } else {
                if (!bcanputnext(wqp, pri) && !(flags & MSG_IGNFLOW)) {
                        freemsg(mp);
                        if (iovlen != 0)
                                kmem_free(uiod.d_iov, iovlen);
                        return (EWOULDBLOCK);
                }
        }
        ASSERT(mp == uiod.d_mp);
        /* Copyin data from the uio */
        if ((error = struioget(wqp, mp, &uiod, 0)) != 0) {
                freemsg(mp);
                if (iovlen != 0)
                        kmem_free(uiod.d_iov, iovlen);
                return (error);
        }
        uioskip(uiop, *iosize);
        if (flags & MSG_IGNFLOW) {
                /*
                 * XXX Hack: Don't get stuck running service procedures.
                 * This is needed for sockfs when sending the unbind message
                 * out of the rput procedure - we don't want a put procedure
                 * to run service procedures.
                 */
                putnext(wqp, mp);
        } else {
                stream_willservice(stp);
                putnext(wqp, mp);
                stream_runservice(stp);
        }
        if (iovlen != 0)
                kmem_free(uiod.d_iov, iovlen);
        return (0);
}

/*
 * Write attempts to break the write request into messages conforming
 * with the minimum and maximum packet sizes set downstream.
 *
 * Write will not block if downstream queue is full and
 * O_NDELAY is set, otherwise it will block waiting for the queue to get room.
 *
 * A write of zero bytes gets packaged into a zero length message and sent
 * downstream like any other message.
 *
 * If buffers of the requested sizes are not available, the write will
 * sleep until the buffers become available.
 *
 * Write (if specified) will supply a write offset in a message if it
 * makes sense. This can be specified by downstream modules as part of
 * a M_SETOPTS message.  Write will not supply the write offset if it
 * cannot supply any data in a buffer.  In other words, write will never
 * send down an empty packet due to a write offset.
 */
/* ARGSUSED2 */
int
strwrite(struct vnode *vp, struct uio *uiop, cred_t *crp)
{
        return (strwrite_common(vp, uiop, crp, 0));
}

/* ARGSUSED2 */
int
strwrite_common(struct vnode *vp, struct uio *uiop, cred_t *crp, int wflag)
{
        struct stdata *stp;
        struct queue *wqp;
        ssize_t rmin, rmax;
        ssize_t iosize;
        int waitflag;
        int tempmode;
        int error = 0;
        int b_flag;

        ASSERT(vp->v_stream);
        stp = vp->v_stream;

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCWRITE)) != 0) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        if (stp->sd_flag & (STWRERR|STRHUP|STPLEX)) {
                error = strwriteable(stp, B_TRUE, B_TRUE);
                if (error != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
        }

        mutex_exit(&stp->sd_lock);

        wqp = stp->sd_wrq;

        /* get these values from them cached in the stream head */
        rmin = stp->sd_qn_minpsz;
        rmax = stp->sd_qn_maxpsz;

        /*
         * Check the min/max packet size constraints.  If min packet size
         * is non-zero, the write cannot be split into multiple messages
         * and still guarantee the size constraints.
         */
        TRACE_1(TR_FAC_STREAMS_FR, TR_STRWRITE_IN, "strwrite in:q %p", wqp);

        ASSERT((rmax >= 0) || (rmax == INFPSZ));
        if (rmax == 0) {
                return (0);
        }
        if (rmin > 0) {
                if (uiop->uio_resid < rmin) {
                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRWRITE_OUT,
                            "strwrite out:q %p out %d error %d",
                            wqp, 0, ERANGE);
                        return (ERANGE);
                }
                if ((rmax != INFPSZ) && (uiop->uio_resid > rmax)) {
                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRWRITE_OUT,
                            "strwrite out:q %p out %d error %d",
                            wqp, 1, ERANGE);
                        return (ERANGE);
                }
        }

        /*
         * Do until count satisfied or error.
         */
        waitflag = WRITEWAIT | wflag;
        if (stp->sd_flag & OLDNDELAY)
                tempmode = uiop->uio_fmode & ~FNDELAY;
        else
                tempmode = uiop->uio_fmode;

        if (rmax == INFPSZ)
                rmax = uiop->uio_resid;

        /*
         * Note that tempmode does not get used in strput/strmakedata
         * but only in strwaitq. The other routines use uio_fmode
         * unmodified.
         */

        while (1) {     /* breaks when uio_resid reaches zero */
                /*
                 * Determine the size of the next message to be
                 * packaged.  May have to break write into several
                 * messages based on max packet size.
                 */
                iosize = MIN(uiop->uio_resid, rmax);

                /*
                 * Put block downstream when flow control allows it.
                 */
                if ((stp->sd_flag & STRDELIM) && (uiop->uio_resid == iosize))
                        b_flag = MSGDELIM;
                else
                        b_flag = 0;

                for (;;) {
                        int done = 0;

                        error = strput(stp, NULL, uiop, &iosize, b_flag, 0, 0);
                        if (error == 0)
                                break;
                        if (error != EWOULDBLOCK)
                                goto out;

                        mutex_enter(&stp->sd_lock);
                        /*
                         * Check for a missed wakeup.
                         * Needed since strput did not hold sd_lock across
                         * the canputnext.
                         */
                        if (canputnext(wqp)) {
                                /* Try again */
                                mutex_exit(&stp->sd_lock);
                                continue;
                        }
                        TRACE_1(TR_FAC_STREAMS_FR, TR_STRWRITE_WAIT,
                            "strwrite wait:q %p wait", wqp);
                        if ((error = strwaitq(stp, waitflag, (ssize_t)0,
                            tempmode, -1, &done)) != 0 || done) {
                                mutex_exit(&stp->sd_lock);
                                if ((vp->v_type == VFIFO) &&
                                    (uiop->uio_fmode & FNDELAY) &&
                                    (error == EAGAIN))
                                        error = 0;
                                goto out;
                        }
                        TRACE_1(TR_FAC_STREAMS_FR, TR_STRWRITE_WAKE,
                            "strwrite wake:q %p awakes", wqp);
                        if ((error = i_straccess(stp, JCWRITE)) != 0) {
                                mutex_exit(&stp->sd_lock);
                                goto out;
                        }
                        mutex_exit(&stp->sd_lock);
                }
                waitflag |= NOINTR;
                TRACE_2(TR_FAC_STREAMS_FR, TR_STRWRITE_RESID,
                    "strwrite resid:q %p uiop %p", wqp, uiop);
                if (uiop->uio_resid) {
                        /* Recheck for errors - needed for sockets */
                        if ((stp->sd_wput_opt & SW_RECHECK_ERR) &&
                            (stp->sd_flag & (STWRERR|STRHUP|STPLEX))) {
                                mutex_enter(&stp->sd_lock);
                                error = strwriteable(stp, B_FALSE, B_TRUE);
                                mutex_exit(&stp->sd_lock);
                                if (error != 0)
                                        return (error);
                        }
                        continue;
                }
                break;
        }
out:
        /*
         * For historical reasons, applications expect EAGAIN when a data
         * mblk_t cannot be allocated, so change ENOMEM back to EAGAIN.
         */
        if (error == ENOMEM)
                error = EAGAIN;
        TRACE_3(TR_FAC_STREAMS_FR, TR_STRWRITE_OUT,
            "strwrite out:q %p out %d error %d", wqp, 2, error);
        return (error);
}

/*
 * Stream head write service routine.
 * Its job is to wake up any sleeping writers when a queue
 * downstream needs data (part of the flow control in putq and getq).
 * It also must wake anyone sleeping on a poll().
 * For stream head right below mux module, it must also invoke put procedure
 * of next downstream module.
 */
int
strwsrv(queue_t *q)
{
        struct stdata *stp;
        queue_t *tq;
        qband_t *qbp;
        int i;
        qband_t *myqbp;
        int isevent;
        unsigned char   qbf[NBAND];     /* band flushing backenable flags */

        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRWSRV, "strwsrv:q %p", q);
        stp = (struct stdata *)q->q_ptr;
        ASSERT(qclaimed(q));
        mutex_enter(&stp->sd_lock);
        ASSERT(!(stp->sd_flag & STPLEX));

        if (stp->sd_flag & WSLEEP) {
                stp->sd_flag &= ~WSLEEP;
                cv_broadcast(&q->q_wait);
        }
        mutex_exit(&stp->sd_lock);

        /* The other end of a stream pipe went away. */
        if ((tq = q->q_next) == NULL) {
                return (0);
        }

        /* Find the next module forward that has a service procedure */
        claimstr(q);
        tq = q->q_nfsrv;
        ASSERT(tq != NULL);

        if ((q->q_flag & QBACK)) {
                if ((tq->q_flag & QFULL)) {
                        mutex_enter(QLOCK(tq));
                        if (!(tq->q_flag & QFULL)) {
                                mutex_exit(QLOCK(tq));
                                goto wakeup;
                        }
                        /*
                         * The queue must have become full again. Set QWANTW
                         * again so strwsrv will be back enabled when
                         * the queue becomes non-full next time.
                         */
                        tq->q_flag |= QWANTW;
                        mutex_exit(QLOCK(tq));
                } else {
                wakeup:
                        pollwakeup(&stp->sd_pollist, POLLWRNORM);
                        mutex_enter(&stp->sd_lock);
                        if (stp->sd_sigflags & S_WRNORM)
                                strsendsig(stp->sd_siglist, S_WRNORM, 0, 0);
                        mutex_exit(&stp->sd_lock);
                }
        }

        isevent = 0;
        i = 1;
        bzero((caddr_t)qbf, NBAND);
        mutex_enter(QLOCK(tq));
        if ((myqbp = q->q_bandp) != NULL)
                for (qbp = tq->q_bandp; qbp && myqbp; qbp = qbp->qb_next) {
                        ASSERT(myqbp);
                        if ((myqbp->qb_flag & QB_BACK)) {
                                if (qbp->qb_flag & QB_FULL) {
                                        /*
                                         * The band must have become full again.
                                         * Set QB_WANTW again so strwsrv will
                                         * be back enabled when the band becomes
                                         * non-full next time.
                                         */
                                        qbp->qb_flag |= QB_WANTW;
                                } else {
                                        isevent = 1;
                                        qbf[i] = 1;
                                }
                        }
                        myqbp = myqbp->qb_next;
                        i++;
                }
        mutex_exit(QLOCK(tq));

        if (isevent) {
                for (i = tq->q_nband; i; i--) {
                        if (qbf[i]) {
                                pollwakeup(&stp->sd_pollist, POLLWRBAND);
                                mutex_enter(&stp->sd_lock);
                                if (stp->sd_sigflags & S_WRBAND)
                                        strsendsig(stp->sd_siglist, S_WRBAND,
                                            (uchar_t)i, 0);
                                mutex_exit(&stp->sd_lock);
                        }
                }
        }

        releasestr(q);
        return (0);
}

/*
 * Special case of strcopyin/strcopyout for copying
 * struct strioctl that can deal with both data
 * models.
 */

#ifdef  _LP64

static int
strcopyin_strioctl(void *from, void *to, int flag, int copyflag)
{
        struct  strioctl32 strioc32;
        struct  strioctl *striocp;

        if (copyflag & U_TO_K) {
                ASSERT((copyflag & K_TO_K) == 0);

                if ((flag & FMODELS) == DATAMODEL_ILP32) {
                        if (copyin(from, &strioc32, sizeof (strioc32)))
                                return (EFAULT);

                        striocp = (struct strioctl *)to;
                        striocp->ic_cmd = strioc32.ic_cmd;
                        striocp->ic_timout = strioc32.ic_timout;
                        striocp->ic_len = strioc32.ic_len;
                        striocp->ic_dp  = (char *)(uintptr_t)strioc32.ic_dp;

                } else { /* NATIVE data model */
                        if (copyin(from, to, sizeof (struct strioctl))) {
                                return (EFAULT);
                        } else {
                                return (0);
                        }
                }
        } else {
                ASSERT(copyflag & K_TO_K);
                bcopy(from, to, sizeof (struct strioctl));
        }
        return (0);
}

static int
strcopyout_strioctl(void *from, void *to, int flag, int copyflag)
{
        struct  strioctl32 strioc32;
        struct  strioctl *striocp;

        if (copyflag & U_TO_K) {
                ASSERT((copyflag & K_TO_K) == 0);

                if ((flag & FMODELS) == DATAMODEL_ILP32) {
                        striocp = (struct strioctl *)from;
                        strioc32.ic_cmd = striocp->ic_cmd;
                        strioc32.ic_timout = striocp->ic_timout;
                        strioc32.ic_len = striocp->ic_len;
                        strioc32.ic_dp  = (caddr32_t)(uintptr_t)striocp->ic_dp;
                        ASSERT((char *)(uintptr_t)strioc32.ic_dp ==
                            striocp->ic_dp);

                        if (copyout(&strioc32, to, sizeof (strioc32)))
                                return (EFAULT);

                } else { /* NATIVE data model */
                        if (copyout(from, to, sizeof (struct strioctl))) {
                                return (EFAULT);
                        } else {
                                return (0);
                        }
                }
        } else {
                ASSERT(copyflag & K_TO_K);
                bcopy(from, to, sizeof (struct strioctl));
        }
        return (0);
}

#else   /* ! _LP64 */

/* ARGSUSED2 */
static int
strcopyin_strioctl(void *from, void *to, int flag, int copyflag)
{
        return (strcopyin(from, to, sizeof (struct strioctl), copyflag));
}

/* ARGSUSED2 */
static int
strcopyout_strioctl(void *from, void *to, int flag, int copyflag)
{
        return (strcopyout(from, to, sizeof (struct strioctl), copyflag));
}

#endif  /* _LP64 */

/*
 * Determine type of job control semantics expected by user.  The
 * possibilities are:
 *      JCREAD  - Behaves like read() on fd; send SIGTTIN
 *      JCWRITE - Behaves like write() on fd; send SIGTTOU if TOSTOP set
 *      JCSETP  - Sets a value in the stream; send SIGTTOU, ignore TOSTOP
 *      JCGETP  - Gets a value in the stream; no signals.
 * See straccess in strsubr.c for usage of these values.
 *
 * This routine also returns -1 for I_STR as a special case; the
 * caller must call again with the real ioctl number for
 * classification.
 */
static int
job_control_type(int cmd)
{
        switch (cmd) {
        case I_STR:
                return (-1);

        case I_RECVFD:
        case I_E_RECVFD:
                return (JCREAD);

        case I_FDINSERT:
        case I_SENDFD:
                return (JCWRITE);

        case TCSETA:
        case TCSETAW:
        case TCSETAF:
        case TCSBRK:
        case TCXONC:
        case TCFLSH:
        case TCDSET:    /* Obsolete */
        case TIOCSWINSZ:
        case TCSETS:
        case TCSETSW:
        case TCSETSF:
        case TIOCSETD:
        case TIOCHPCL:
        case TIOCSETP:
        case TIOCSETN:
        case TIOCEXCL:
        case TIOCNXCL:
        case TIOCFLUSH:
        case TIOCSETC:
        case TIOCLBIS:
        case TIOCLBIC:
        case TIOCLSET:
        case TIOCSBRK:
        case TIOCCBRK:
        case TIOCSDTR:
        case TIOCCDTR:
        case TIOCSLTC:
        case TIOCSTOP:
        case TIOCSTART:
        case TIOCSTI:
        case TIOCSPGRP:
        case TIOCMSET:
        case TIOCMBIS:
        case TIOCMBIC:
        case TIOCREMOTE:
        case TIOCSIGNAL:
        case LDSETT:
        case LDSMAP:    /* Obsolete */
        case DIOCSETP:
        case I_FLUSH:
        case I_SRDOPT:
        case I_SETSIG:
        case I_SWROPT:
        case I_FLUSHBAND:
        case I_SETCLTIME:
        case I_SERROPT:
        case I_ESETSIG:
        case FIONBIO:
        case FIOASYNC:
        case FIOSETOWN:
        case JBOOT:     /* Obsolete */
        case JTERM:     /* Obsolete */
        case JTIMOM:    /* Obsolete */
        case JZOMBOOT:  /* Obsolete */
        case JAGENT:    /* Obsolete */
        case JTRUN:     /* Obsolete */
        case JXTPROTO:  /* Obsolete */
                return (JCSETP);
        }

        return (JCGETP);
}

/*
 * ioctl for streams
 */
int
strioctl(struct vnode *vp, int cmd, intptr_t arg, int flag, int copyflag,
    cred_t *crp, int *rvalp)
{
        struct stdata *stp;
        struct strcmd *scp;
        struct strioctl strioc;
        struct uio uio;
        struct iovec iov;
        int access;
        mblk_t *mp;
        int error = 0;
        int done = 0;
        ssize_t rmin, rmax;
        queue_t *wrq;
        queue_t *rdq;
        boolean_t kioctl = B_FALSE;

        if (flag & FKIOCTL) {
                copyflag = K_TO_K;
                kioctl = B_TRUE;
        }
        ASSERT(vp->v_stream);
        ASSERT(copyflag == U_TO_K || copyflag == K_TO_K);
        stp = vp->v_stream;

        TRACE_3(TR_FAC_STREAMS_FR, TR_IOCTL_ENTER,
            "strioctl:stp %p cmd %X arg %lX", stp, cmd, arg);

        /*
         * If the copy is kernel to kernel, make sure that the FNATIVE
         * flag is set.  After this it would be a serious error to have
         * no model flag.
         */
        if (copyflag == K_TO_K)
                flag = (flag & ~FMODELS) | FNATIVE;

        ASSERT((flag & FMODELS) != 0);

        wrq = stp->sd_wrq;
        rdq = _RD(wrq);

        access = job_control_type(cmd);

        /* We should never see these here, should be handled by iwscn */
        if (cmd == SRIOCSREDIR || cmd == SRIOCISREDIR)
                return (EINVAL);

        mutex_enter(&stp->sd_lock);
        if ((access != -1) && ((error = i_straccess(stp, access)) != 0)) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }
        mutex_exit(&stp->sd_lock);

        /*
         * Check for sgttyb-related ioctls first, and complain as
         * necessary.
         */
        switch (cmd) {
        case TIOCGETP:
        case TIOCSETP:
        case TIOCSETN:
                if (sgttyb_handling >= 2 && !sgttyb_complaint) {
                        sgttyb_complaint = B_TRUE;
                        cmn_err(CE_NOTE,
                            "application used obsolete TIOC[GS]ET");
                }
                if (sgttyb_handling >= 3) {
                        tsignal(curthread, SIGSYS);
                        return (EIO);
                }
                break;
        }

        mutex_enter(&stp->sd_lock);

        switch (cmd) {
        case I_RECVFD:
        case I_E_RECVFD:
        case I_PEEK:
        case I_NREAD:
        case FIONREAD:
        case FIORDCHK:
        case I_ATMARK:
        case FIONBIO:
        case FIOASYNC:
                if (stp->sd_flag & (STRDERR|STPLEX)) {
                        error = strgeterr(stp, STRDERR|STPLEX, 0);
                        if (error != 0) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                }
                break;

        default:
                if (stp->sd_flag & (STRDERR|STWRERR|STPLEX)) {
                        error = strgeterr(stp, STRDERR|STWRERR|STPLEX, 0);
                        if (error != 0) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                }
        }

        mutex_exit(&stp->sd_lock);

        switch (cmd) {
        default:
                /*
                 * The stream head has hardcoded knowledge of a
                 * miscellaneous collection of terminal-, keyboard- and
                 * mouse-related ioctls, enumerated below.  This hardcoded
                 * knowledge allows the stream head to automatically
                 * convert transparent ioctl requests made by userland
                 * programs into I_STR ioctls which many old STREAMS
                 * modules and drivers require.
                 *
                 * No new ioctls should ever be added to this list.
                 * Instead, the STREAMS module or driver should be written
                 * to either handle transparent ioctls or require any
                 * userland programs to use I_STR ioctls (by returning
                 * EINVAL to any transparent ioctl requests).
                 *
                 * More importantly, removing ioctls from this list should
                 * be done with the utmost care, since our STREAMS modules
                 * and drivers *count* on the stream head performing this
                 * conversion, and thus may panic while processing
                 * transparent ioctl request for one of these ioctls (keep
                 * in mind that third party modules and drivers may have
                 * similar problems).
                 */
                if (((cmd & IOCTYPE) == LDIOC) ||
                    ((cmd & IOCTYPE) == tIOC) ||
                    ((cmd & IOCTYPE) == TIOC) ||
                    ((cmd & IOCTYPE) == KIOC) ||
                    ((cmd & IOCTYPE) == MSIOC) ||
                    ((cmd & IOCTYPE) == VUIOC)) {
                        /*
                         * The ioctl is a tty ioctl - set up strioc buffer
                         * and call strdoioctl() to do the work.
                         */
                        if (stp->sd_flag & STRHUP)
                                return (ENXIO);
                        strioc.ic_cmd = cmd;
                        strioc.ic_timout = INFTIM;

                        switch (cmd) {

                        case TCXONC:
                        case TCSBRK:
                        case TCFLSH:
                        case TCDSET:
                                {
                                int native_arg = (int)arg;
                                strioc.ic_len = sizeof (int);
                                strioc.ic_dp = (char *)&native_arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    K_TO_K, crp, rvalp));
                                }

                        case TCSETA:
                        case TCSETAW:
                        case TCSETAF:
                                strioc.ic_len = sizeof (struct termio);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TCSETS:
                        case TCSETSW:
                        case TCSETSF:
                                strioc.ic_len = sizeof (struct termios);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case LDSETT:
                                strioc.ic_len = sizeof (struct termcb);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TIOCSETP:
                                strioc.ic_len = sizeof (struct sgttyb);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TIOCSTI:
                                if ((flag & FREAD) == 0 &&
                                    secpolicy_sti(crp) != 0) {
                                        return (EPERM);
                                }
                                mutex_enter(&stp->sd_lock);
                                mutex_enter(&curproc->p_splock);
                                if (stp->sd_sidp != curproc->p_sessp->s_sidp &&
                                    secpolicy_sti(crp) != 0) {
                                        mutex_exit(&curproc->p_splock);
                                        mutex_exit(&stp->sd_lock);
                                        return (EACCES);
                                }
                                mutex_exit(&curproc->p_splock);
                                mutex_exit(&stp->sd_lock);

                                strioc.ic_len = sizeof (char);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TIOCSWINSZ:
                                strioc.ic_len = sizeof (struct winsize);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TIOCSSIZE:
                                strioc.ic_len = sizeof (struct ttysize);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case TIOCSSOFTCAR:
                        case KIOCTRANS:
                        case KIOCTRANSABLE:
                        case KIOCCMD:
                        case KIOCSDIRECT:
                        case KIOCSCOMPAT:
                        case KIOCSKABORTEN:
                        case KIOCSRPTDELAY:
                        case KIOCSRPTRATE:
                        case VUIDSFORMAT:
                        case TIOCSPPS:
                                strioc.ic_len = sizeof (int);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case KIOCSETKEY:
                        case KIOCGETKEY:
                                strioc.ic_len = sizeof (struct kiockey);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case KIOCSKEY:
                        case KIOCGKEY:
                                strioc.ic_len = sizeof (struct kiockeymap);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case KIOCSLED:
                                /* arg is a pointer to char */
                                strioc.ic_len = sizeof (char);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case MSIOSETPARMS:
                                strioc.ic_len = sizeof (Ms_parms);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        case VUIDSADDR:
                        case VUIDGADDR:
                                strioc.ic_len = sizeof (struct vuid_addr_probe);
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));

                        /*
                         * These M_IOCTL's don't require any data to be sent
                         * downstream, and the driver will allocate and link
                         * on its own mblk_t upon M_IOCACK -- thus we set
                         * ic_len to zero and set ic_dp to arg so we know
                         * where to copyout to later.
                         */
                        case TIOCGSOFTCAR:
                        case TIOCGWINSZ:
                        case TIOCGSIZE:
                        case KIOCGTRANS:
                        case KIOCGTRANSABLE:
                        case KIOCTYPE:
                        case KIOCGDIRECT:
                        case KIOCGCOMPAT:
                        case KIOCLAYOUT:
                        case KIOCGLED:
                        case MSIOGETPARMS:
                        case MSIOBUTTONS:
                        case VUIDGFORMAT:
                        case TIOCGPPS:
                        case TIOCGPPSEV:
                        case TCGETA:
                        case TCGETS:
                        case LDGETT:
                        case TIOCGETP:
                        case KIOCGRPTDELAY:
                        case KIOCGRPTRATE:
                                strioc.ic_len = 0;
                                strioc.ic_dp = (char *)arg;
                                return (strdoioctl(stp, &strioc, flag,
                                    copyflag, crp, rvalp));
                        }
                }

                /*
                 * Unknown cmd - send it down as a transparent ioctl.
                 */
                strioc.ic_cmd = cmd;
                strioc.ic_timout = INFTIM;
                strioc.ic_len = TRANSPARENT;
                strioc.ic_dp = (char *)&arg;

                return (strdoioctl(stp, &strioc, flag, copyflag, crp, rvalp));

        case I_STR:
                /*
                 * Stream ioctl.  Read in an strioctl buffer from the user
                 * along with any data specified and send it downstream.
                 * Strdoioctl will wait allow only one ioctl message at
                 * a time, and waits for the acknowledgement.
                 */

                if (stp->sd_flag & STRHUP)
                        return (ENXIO);

                error = strcopyin_strioctl((void *)arg, &strioc, flag,
                    copyflag);
                if (error != 0)
                        return (error);

                if ((strioc.ic_len < 0) || (strioc.ic_timout < -1))
                        return (EINVAL);

                access = job_control_type(strioc.ic_cmd);
                mutex_enter(&stp->sd_lock);
                if ((access != -1) &&
                    ((error = i_straccess(stp, access)) != 0)) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                mutex_exit(&stp->sd_lock);

                /*
                 * The I_STR facility provides a trap door for malicious
                 * code to send down bogus streamio(7I) ioctl commands to
                 * unsuspecting STREAMS modules and drivers which expect to
                 * only get these messages from the stream head.
                 * Explicitly prohibit any streamio ioctls which can be
                 * passed downstream by the stream head.  Note that we do
                 * not block all streamio ioctls because the ioctl
                 * numberspace is not well managed and thus it's possible
                 * that a module or driver's ioctl numbers may accidentally
                 * collide with them.
                 */
                switch (strioc.ic_cmd) {
                case I_LINK:
                case I_PLINK:
                case I_UNLINK:
                case I_PUNLINK:
                case _I_GETPEERCRED:
                case _I_PLINK_LH:
                        return (EINVAL);
                }

                error = strdoioctl(stp, &strioc, flag, copyflag, crp, rvalp);
                if (error == 0) {
                        error = strcopyout_strioctl(&strioc, (void *)arg,
                            flag, copyflag);
                }
                return (error);

        case _I_CMD:
                /*
                 * Like I_STR, but without using M_IOC* messages and without
                 * copyins/copyouts beyond the passed-in argument.
                 */
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);

                if ((scp = kmem_alloc(sizeof (strcmd_t), KM_NOSLEEP)) == NULL)
                        return (ENOMEM);

                if (copyin((void *)arg, scp, sizeof (strcmd_t))) {
                        kmem_free(scp, sizeof (strcmd_t));
                        return (EFAULT);
                }

                access = job_control_type(scp->sc_cmd);
                mutex_enter(&stp->sd_lock);
                if (access != -1 && (error = i_straccess(stp, access)) != 0) {
                        mutex_exit(&stp->sd_lock);
                        kmem_free(scp, sizeof (strcmd_t));
                        return (error);
                }
                mutex_exit(&stp->sd_lock);

                *rvalp = 0;
                if ((error = strdocmd(stp, scp, crp)) == 0) {
                        if (copyout(scp, (void *)arg, sizeof (strcmd_t)))
                                error = EFAULT;
                }
                kmem_free(scp, sizeof (strcmd_t));
                return (error);

        case I_NREAD:
                /*
                 * Return number of bytes of data in first message
                 * in queue in "arg" and return the number of messages
                 * in queue in return value.
                 */
        {
                size_t  size;
                int     retval;
                int     count = 0;

                mutex_enter(QLOCK(rdq));

                size = msgdsize(rdq->q_first);
                for (mp = rdq->q_first; mp != NULL; mp = mp->b_next)
                        count++;

                mutex_exit(QLOCK(rdq));
                if (stp->sd_struiordq) {
                        infod_t infod;

                        infod.d_cmd = INFOD_COUNT;
                        infod.d_count = 0;
                        if (count == 0) {
                                infod.d_cmd |= INFOD_FIRSTBYTES;
                                infod.d_bytes = 0;
                        }
                        infod.d_res = 0;
                        (void) infonext(rdq, &infod);
                        count += infod.d_count;
                        if (infod.d_res & INFOD_FIRSTBYTES)
                                size = infod.d_bytes;
                }

                /*
                 * Drop down from size_t to the "int" required by the
                 * interface.  Cap at INT_MAX.
                 */
                retval = MIN(size, INT_MAX);
                error = strcopyout(&retval, (void *)arg, sizeof (retval),
                    copyflag);
                if (!error)
                        *rvalp = count;
                return (error);
        }

        case FIONREAD:
                /*
                 * Return number of bytes of data in all data messages
                 * in queue in "arg".
                 */
        {
                size_t  size = 0;
                int     retval;

                mutex_enter(QLOCK(rdq));
                for (mp = rdq->q_first; mp != NULL; mp = mp->b_next)
                        size += msgdsize(mp);
                mutex_exit(QLOCK(rdq));

                if (stp->sd_struiordq) {
                        infod_t infod;

                        infod.d_cmd = INFOD_BYTES;
                        infod.d_res = 0;
                        infod.d_bytes = 0;
                        (void) infonext(rdq, &infod);
                        size += infod.d_bytes;
                }

                /*
                 * Drop down from size_t to the "int" required by the
                 * interface.  Cap at INT_MAX.
                 */
                retval = MIN(size, INT_MAX);
                error = strcopyout(&retval, (void *)arg, sizeof (retval),
                    copyflag);

                *rvalp = 0;
                return (error);
        }
        case FIORDCHK:
                /*
                 * FIORDCHK does not use arg value (like FIONREAD),
                 * instead a count is returned. I_NREAD value may
                 * not be accurate but safe. The real thing to do is
                 * to add the msgdsizes of all data  messages until
                 * a non-data message.
                 */
        {
                size_t size = 0;

                mutex_enter(QLOCK(rdq));
                for (mp = rdq->q_first; mp != NULL; mp = mp->b_next)
                        size += msgdsize(mp);
                mutex_exit(QLOCK(rdq));

                if (stp->sd_struiordq) {
                        infod_t infod;

                        infod.d_cmd = INFOD_BYTES;
                        infod.d_res = 0;
                        infod.d_bytes = 0;
                        (void) infonext(rdq, &infod);
                        size += infod.d_bytes;
                }

                /*
                 * Since ioctl returns an int, and memory sizes under
                 * LP64 may not fit, we return INT_MAX if the count was
                 * actually greater.
                 */
                *rvalp = MIN(size, INT_MAX);
                return (0);
        }

        case I_FIND:
                /*
                 * Get module name.
                 */
        {
                char mname[FMNAMESZ + 1];
                queue_t *q;

                error = (copyflag & U_TO_K ? copyinstr : copystr)((void *)arg,
                    mname, FMNAMESZ + 1, NULL);
                if (error)
                        return ((error == ENAMETOOLONG) ? EINVAL : EFAULT);

                /*
                 * Return EINVAL if we're handed a bogus module name.
                 */
                if (fmodsw_find(mname, FMODSW_LOAD) == NULL) {
                        TRACE_0(TR_FAC_STREAMS_FR,
                            TR_I_CANT_FIND, "couldn't I_FIND");
                        return (EINVAL);
                }

                *rvalp = 0;

                /* Look downstream to see if module is there. */
                claimstr(stp->sd_wrq);
                for (q = stp->sd_wrq->q_next; q; q = q->q_next) {
                        if (q->q_flag & QREADR) {
                                q = NULL;
                                break;
                        }
                        if (strcmp(mname, Q2NAME(q)) == 0)
                                break;
                }
                releasestr(stp->sd_wrq);

                *rvalp = (q ? 1 : 0);
                return (error);
        }

        case I_PUSH:
        case __I_PUSH_NOCTTY:
                /*
                 * Push a module.
                 * For the case __I_PUSH_NOCTTY push a module but
                 * do not allocate controlling tty. See bugid 4025044
                 */

        {
                char mname[FMNAMESZ + 1];
                fmodsw_impl_t *fp;
                dev_t dummydev;

                if (stp->sd_flag & STRHUP)
                        return (ENXIO);

                /*
                 * Get module name and look up in fmodsw.
                 */
                error = (copyflag & U_TO_K ? copyinstr : copystr)((void *)arg,
                    mname, FMNAMESZ + 1, NULL);
                if (error)
                        return ((error == ENAMETOOLONG) ? EINVAL : EFAULT);

                if ((fp = fmodsw_find(mname, FMODSW_HOLD | FMODSW_LOAD)) ==
                    NULL)
                        return (EINVAL);

                TRACE_2(TR_FAC_STREAMS_FR, TR_I_PUSH,
                    "I_PUSH:fp %p stp %p", fp, stp);

                /*
                 * If the module is flagged as single-instance, then check
                 * to see if the module is already pushed. If it is, return
                 * as if the push was successful.
                 */
                if (fp->f_qflag & _QSINGLE_INSTANCE) {
                        queue_t *q;

                        claimstr(stp->sd_wrq);
                        for (q = stp->sd_wrq->q_next; q; q = q->q_next) {
                                if (q->q_flag & QREADR) {
                                        q = NULL;
                                        break;
                                }
                                if (strcmp(mname, Q2NAME(q)) == 0)
                                        break;
                        }
                        releasestr(stp->sd_wrq);
                        if (q != NULL) {
                                fmodsw_rele(fp);
                                return (0);
                        }
                }

                if (error = strstartplumb(stp, flag, cmd)) {
                        fmodsw_rele(fp);
                        return (error);
                }

                /*
                 * See if any more modules can be pushed on this stream.
                 * Note that this check must be done after strstartplumb()
                 * since otherwise multiple threads issuing I_PUSHes on
                 * the same stream will be able to exceed nstrpush.
                 */
                mutex_enter(&stp->sd_lock);
                if (stp->sd_pushcnt >= nstrpush) {
                        fmodsw_rele(fp);
                        strendplumb(stp);
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }
                mutex_exit(&stp->sd_lock);

                /*
                 * Push new module and call its open routine
                 * via qattach().  Modules don't change device
                 * numbers, so just ignore dummydev here.
                 */
                dummydev = vp->v_rdev;
                if ((error = qattach(rdq, &dummydev, 0, crp, fp,
                    B_FALSE)) == 0) {
                        if (vp->v_type == VCHR && /* sorry, no pipes allowed */
                            (cmd == I_PUSH) && (stp->sd_flag & STRISTTY)) {
                                /*
                                 * try to allocate it as a controlling terminal
                                 */
                                (void) strctty(stp);
                        }
                }

                mutex_enter(&stp->sd_lock);

                /*
                 * As a performance concern we are caching the values of
                 * q_minpsz and q_maxpsz of the module below the stream
                 * head in the stream head.
                 */
                mutex_enter(QLOCK(stp->sd_wrq->q_next));
                rmin = stp->sd_wrq->q_next->q_minpsz;
                rmax = stp->sd_wrq->q_next->q_maxpsz;
                mutex_exit(QLOCK(stp->sd_wrq->q_next));

                /* Do this processing here as a performance concern */
                if (strmsgsz != 0) {
                        if (rmax == INFPSZ)
                                rmax = strmsgsz;
                        else  {
                                if (vp->v_type == VFIFO)
                                        rmax = MIN(PIPE_BUF, rmax);
                                else    rmax = MIN(strmsgsz, rmax);
                        }
                }

                mutex_enter(QLOCK(wrq));
                stp->sd_qn_minpsz = rmin;
                stp->sd_qn_maxpsz = rmax;
                mutex_exit(QLOCK(wrq));

                strendplumb(stp);
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        case I_POP:
        {
                queue_t *q;

                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                if (!wrq->q_next)       /* for broken pipes */
                        return (EINVAL);

                if (error = strstartplumb(stp, flag, cmd))
                        return (error);

                /*
                 * If there is an anchor on this stream and popping
                 * the current module would attempt to pop through the
                 * anchor, then disallow the pop unless we have sufficient
                 * privileges; take the cheapest (non-locking) check
                 * first.
                 */
                if (secpolicy_ip_config(crp, B_TRUE) != 0 ||
                    (stp->sd_anchorzone != crgetzoneid(crp))) {
                        mutex_enter(&stp->sd_lock);
                        /*
                         * Anchors only apply if there's at least one
                         * module on the stream (sd_pushcnt > 0).
                         */
                        if (stp->sd_pushcnt > 0 &&
                            stp->sd_pushcnt == stp->sd_anchor &&
                            stp->sd_vnode->v_type != VFIFO) {
                                strendplumb(stp);
                                mutex_exit(&stp->sd_lock);
                                if (stp->sd_anchorzone != crgetzoneid(crp))
                                        return (EINVAL);
                                /* Audit and report error */
                                return (secpolicy_ip_config(crp, B_FALSE));
                        }
                        mutex_exit(&stp->sd_lock);
                }

                q = wrq->q_next;
                TRACE_2(TR_FAC_STREAMS_FR, TR_I_POP,
                    "I_POP:%p from %p", q, stp);
                if (q->q_next == NULL || (q->q_flag & (QREADR|QISDRV))) {
                        error = EINVAL;
                } else {
                        qdetach(_RD(q), 1, flag, crp, B_FALSE);
                        error = 0;
                }
                mutex_enter(&stp->sd_lock);

                /*
                 * As a performance concern we are caching the values of
                 * q_minpsz and q_maxpsz of the module below the stream
                 * head in the stream head.
                 */
                mutex_enter(QLOCK(wrq->q_next));
                rmin = wrq->q_next->q_minpsz;
                rmax = wrq->q_next->q_maxpsz;
                mutex_exit(QLOCK(wrq->q_next));

                /* Do this processing here as a performance concern */
                if (strmsgsz != 0) {
                        if (rmax == INFPSZ)
                                rmax = strmsgsz;
                        else  {
                                if (vp->v_type == VFIFO)
                                        rmax = MIN(PIPE_BUF, rmax);
                                else    rmax = MIN(strmsgsz, rmax);
                        }
                }

                mutex_enter(QLOCK(wrq));
                stp->sd_qn_minpsz = rmin;
                stp->sd_qn_maxpsz = rmax;
                mutex_exit(QLOCK(wrq));

                /* If we popped through the anchor, then reset the anchor. */
                if (stp->sd_pushcnt < stp->sd_anchor) {
                        stp->sd_anchor = 0;
                        stp->sd_anchorzone = 0;
                }
                strendplumb(stp);
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        case _I_MUXID2FD:
        {
                /*
                 * Create a fd for a I_PLINK'ed lower stream with a given
                 * muxid.  With the fd, application can send down ioctls,
                 * like I_LIST, to the previously I_PLINK'ed stream.  Note
                 * that after getting the fd, the application has to do an
                 * I_PUNLINK on the muxid before it can do any operation
                 * on the lower stream.  This is required by spec1170.
                 *
                 * The fd used to do this ioctl should point to the same
                 * controlling device used to do the I_PLINK.  If it uses
                 * a different stream or an invalid muxid, I_MUXID2FD will
                 * fail.  The error code is set to EINVAL.
                 *
                 * The intended use of this interface is the following.
                 * An application I_PLINK'ed a stream and exits.  The fd
                 * to the lower stream is gone.  Another application
                 * wants to get a fd to the lower stream, it uses I_MUXID2FD.
                 */
                int muxid = (int)arg;
                int fd;
                linkinfo_t *linkp;
                struct file *fp;
                netstack_t *ns;
                str_stack_t *ss;

                /*
                 * Do not allow the wildcard muxid.  This ioctl is not
                 * intended to find arbitrary link.
                 */
                if (muxid == 0) {
                        return (EINVAL);
                }

                ns = netstack_find_by_cred(crp);
                ASSERT(ns != NULL);
                ss = ns->netstack_str;
                ASSERT(ss != NULL);

                mutex_enter(&muxifier);
                linkp = findlinks(vp->v_stream, muxid, LINKPERSIST, ss);
                if (linkp == NULL) {
                        mutex_exit(&muxifier);
                        netstack_rele(ss->ss_netstack);
                        return (EINVAL);
                }

                if ((fd = ufalloc(0)) == -1) {
                        mutex_exit(&muxifier);
                        netstack_rele(ss->ss_netstack);
                        return (EMFILE);
                }
                fp = linkp->li_fpdown;
                mutex_enter(&fp->f_tlock);
                fp->f_count++;
                mutex_exit(&fp->f_tlock);
                mutex_exit(&muxifier);
                setf(fd, fp);
                *rvalp = fd;
                netstack_rele(ss->ss_netstack);
                return (0);
        }

        case _I_INSERT:
        {
                /*
                 * To insert a module to a given position in a stream.
                 * In the first release, only allow privileged user
                 * to use this ioctl. Furthermore, the insert is only allowed
                 * below an anchor if the zoneid is the same as the zoneid
                 * which created the anchor.
                 *
                 * Note that we do not plan to support this ioctl
                 * on pipes in the first release.  We want to learn more
                 * about the implications of these ioctls before extending
                 * their support.  And we do not think these features are
                 * valuable for pipes.
                 */
                STRUCT_DECL(strmodconf, strmodinsert);
                char mod_name[FMNAMESZ + 1];
                fmodsw_impl_t *fp;
                dev_t dummydev;
                queue_t *tmp_wrq;
                int pos;
                boolean_t is_insert;

                STRUCT_INIT(strmodinsert, flag);
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                if (STRMATED(stp))
                        return (EINVAL);
                if ((error = secpolicy_net_config(crp, B_FALSE)) != 0)
                        return (error);
                if (stp->sd_anchor != 0 &&
                    stp->sd_anchorzone != crgetzoneid(crp))
                        return (EINVAL);

                error = strcopyin((void *)arg, STRUCT_BUF(strmodinsert),
                    STRUCT_SIZE(strmodinsert), copyflag);
                if (error)
                        return (error);

                /*
                 * Get module name and look up in fmodsw.
                 */
                error = (copyflag & U_TO_K ? copyinstr :
                    copystr)(STRUCT_FGETP(strmodinsert, mod_name),
                    mod_name, FMNAMESZ + 1, NULL);
                if (error)
                        return ((error == ENAMETOOLONG) ? EINVAL : EFAULT);

                if ((fp = fmodsw_find(mod_name, FMODSW_HOLD | FMODSW_LOAD)) ==
                    NULL)
                        return (EINVAL);

                if (error = strstartplumb(stp, flag, cmd)) {
                        fmodsw_rele(fp);
                        return (error);
                }

                /*
                 * Is this _I_INSERT just like an I_PUSH?  We need to know
                 * this because we do some optimizations if this is a
                 * module being pushed.
                 */
                pos = STRUCT_FGET(strmodinsert, pos);
                is_insert = (pos != 0);

                /*
                 * Make sure pos is valid.  Even though it is not an I_PUSH,
                 * we impose the same limit on the number of modules in a
                 * stream.
                 */
                mutex_enter(&stp->sd_lock);
                if (stp->sd_pushcnt >= nstrpush || pos < 0 ||
                    pos > stp->sd_pushcnt) {
                        fmodsw_rele(fp);
                        strendplumb(stp);
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }
                if (stp->sd_anchor != 0) {
                        /*
                         * Is this insert below the anchor?
                         * Pushcnt hasn't been increased yet hence
                         * we test for greater than here, and greater or
                         * equal after qattach.
                         */
                        if (pos > (stp->sd_pushcnt - stp->sd_anchor) &&
                            stp->sd_anchorzone != crgetzoneid(crp)) {
                                fmodsw_rele(fp);
                                strendplumb(stp);
                                mutex_exit(&stp->sd_lock);
                                return (EPERM);
                        }
                }

                mutex_exit(&stp->sd_lock);

                /*
                 * First find the correct position this module to
                 * be inserted.  We don't need to call claimstr()
                 * as the stream should not be changing at this point.
                 *
                 * Insert new module and call its open routine
                 * via qattach().  Modules don't change device
                 * numbers, so just ignore dummydev here.
                 */
                for (tmp_wrq = stp->sd_wrq; pos > 0;
                    tmp_wrq = tmp_wrq->q_next, pos--) {
                        ASSERT(SAMESTR(tmp_wrq));
                }
                dummydev = vp->v_rdev;
                if ((error = qattach(_RD(tmp_wrq), &dummydev, 0, crp,
                    fp, is_insert)) != 0) {
                        mutex_enter(&stp->sd_lock);
                        strendplumb(stp);
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }

                mutex_enter(&stp->sd_lock);

                /*
                 * As a performance concern we are caching the values of
                 * q_minpsz and q_maxpsz of the module below the stream
                 * head in the stream head.
                 */
                if (!is_insert) {
                        mutex_enter(QLOCK(stp->sd_wrq->q_next));
                        rmin = stp->sd_wrq->q_next->q_minpsz;
                        rmax = stp->sd_wrq->q_next->q_maxpsz;
                        mutex_exit(QLOCK(stp->sd_wrq->q_next));

                        /* Do this processing here as a performance concern */
                        if (strmsgsz != 0) {
                                if (rmax == INFPSZ) {
                                        rmax = strmsgsz;
                                } else  {
                                        rmax = MIN(strmsgsz, rmax);
                                }
                        }

                        mutex_enter(QLOCK(wrq));
                        stp->sd_qn_minpsz = rmin;
                        stp->sd_qn_maxpsz = rmax;
                        mutex_exit(QLOCK(wrq));
                }

                /*
                 * Need to update the anchor value if this module is
                 * inserted below the anchor point.
                 */
                if (stp->sd_anchor != 0) {
                        pos = STRUCT_FGET(strmodinsert, pos);
                        if (pos >= (stp->sd_pushcnt - stp->sd_anchor))
                                stp->sd_anchor++;
                }

                strendplumb(stp);
                mutex_exit(&stp->sd_lock);
                return (0);
        }

        case _I_REMOVE:
        {
                /*
                 * To remove a module with a given name in a stream.  The
                 * caller of this ioctl needs to provide both the name and
                 * the position of the module to be removed.  This eliminates
                 * the ambiguity of removal if a module is inserted/pushed
                 * multiple times in a stream.  In the first release, only
                 * allow privileged user to use this ioctl.
                 * Furthermore, the remove is only allowed
                 * below an anchor if the zoneid is the same as the zoneid
                 * which created the anchor.
                 *
                 * Note that we do not plan to support this ioctl
                 * on pipes in the first release.  We want to learn more
                 * about the implications of these ioctls before extending
                 * their support.  And we do not think these features are
                 * valuable for pipes.
                 *
                 * Also note that _I_REMOVE cannot be used to remove a
                 * driver or the stream head.
                 */
                STRUCT_DECL(strmodconf, strmodremove);
                queue_t *q;
                int pos;
                char mod_name[FMNAMESZ + 1];
                boolean_t is_remove;

                STRUCT_INIT(strmodremove, flag);
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                if (STRMATED(stp))
                        return (EINVAL);
                if ((error = secpolicy_net_config(crp, B_FALSE)) != 0)
                        return (error);
                if (stp->sd_anchor != 0 &&
                    stp->sd_anchorzone != crgetzoneid(crp))
                        return (EINVAL);

                error = strcopyin((void *)arg, STRUCT_BUF(strmodremove),
                    STRUCT_SIZE(strmodremove), copyflag);
                if (error)
                        return (error);

                error = (copyflag & U_TO_K ? copyinstr :
                    copystr)(STRUCT_FGETP(strmodremove, mod_name),
                    mod_name, FMNAMESZ + 1, NULL);
                if (error)
                        return ((error == ENAMETOOLONG) ? EINVAL : EFAULT);

                if ((error = strstartplumb(stp, flag, cmd)) != 0)
                        return (error);

                /*
                 * Match the name of given module to the name of module at
                 * the given position.
                 */
                pos = STRUCT_FGET(strmodremove, pos);

                is_remove = (pos != 0);
                for (q = stp->sd_wrq->q_next; SAMESTR(q) && pos > 0;
                    q = q->q_next, pos--)
                        ;
                if (pos > 0 || !SAMESTR(q) ||
                    strcmp(Q2NAME(q), mod_name) != 0) {
                        mutex_enter(&stp->sd_lock);
                        strendplumb(stp);
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }

                /*
                 * If the position is at or below an anchor, then the zoneid
                 * must match the zoneid that created the anchor.
                 */
                if (stp->sd_anchor != 0) {
                        pos = STRUCT_FGET(strmodremove, pos);
                        if (pos >= (stp->sd_pushcnt - stp->sd_anchor) &&
                            stp->sd_anchorzone != crgetzoneid(crp)) {
                                mutex_enter(&stp->sd_lock);
                                strendplumb(stp);
                                mutex_exit(&stp->sd_lock);
                                return (EPERM);
                        }
                }


                ASSERT(!(q->q_flag & QREADR));
                qdetach(_RD(q), 1, flag, crp, is_remove);

                mutex_enter(&stp->sd_lock);

                /*
                 * As a performance concern we are caching the values of
                 * q_minpsz and q_maxpsz of the module below the stream
                 * head in the stream head.
                 */
                if (!is_remove) {
                        mutex_enter(QLOCK(wrq->q_next));
                        rmin = wrq->q_next->q_minpsz;
                        rmax = wrq->q_next->q_maxpsz;
                        mutex_exit(QLOCK(wrq->q_next));

                        /* Do this processing here as a performance concern */
                        if (strmsgsz != 0) {
                                if (rmax == INFPSZ)
                                        rmax = strmsgsz;
                                else  {
                                        if (vp->v_type == VFIFO)
                                                rmax = MIN(PIPE_BUF, rmax);
                                        else    rmax = MIN(strmsgsz, rmax);
                                }
                        }

                        mutex_enter(QLOCK(wrq));
                        stp->sd_qn_minpsz = rmin;
                        stp->sd_qn_maxpsz = rmax;
                        mutex_exit(QLOCK(wrq));
                }

                /*
                 * Need to update the anchor value if this module is removed
                 * at or below the anchor point.  If the removed module is at
                 * the anchor point, remove the anchor for this stream if
                 * there is no module above the anchor point.  Otherwise, if
                 * the removed module is below the anchor point, decrement the
                 * anchor point by 1.
                 */
                if (stp->sd_anchor != 0) {
                        pos = STRUCT_FGET(strmodremove, pos);
                        if (pos == stp->sd_pushcnt - stp->sd_anchor + 1)
                                stp->sd_anchor = 0;
                        else if (pos > (stp->sd_pushcnt - stp->sd_anchor + 1))
                                stp->sd_anchor--;
                }

                strendplumb(stp);
                mutex_exit(&stp->sd_lock);
                return (0);
        }

        case I_ANCHOR:
                /*
                 * Set the anchor position on the stream to reside at
                 * the top module (in other words, the top module
                 * cannot be popped).  Anchors with a FIFO make no
                 * obvious sense, so they're not allowed.
                 */
                mutex_enter(&stp->sd_lock);

                if (stp->sd_vnode->v_type == VFIFO) {
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }
                /* Only allow the same zoneid to update the anchor */
                if (stp->sd_anchor != 0 &&
                    stp->sd_anchorzone != crgetzoneid(crp)) {
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }
                stp->sd_anchor = stp->sd_pushcnt;
                stp->sd_anchorzone = crgetzoneid(crp);
                mutex_exit(&stp->sd_lock);
                return (0);

        case I_LOOK:
                /*
                 * Get name of first module downstream.
                 * If no module, return an error.
                 */
                claimstr(wrq);
                if (_SAMESTR(wrq) && wrq->q_next->q_next != NULL) {
                        char *name = Q2NAME(wrq->q_next);

                        error = strcopyout(name, (void *)arg, strlen(name) + 1,
                            copyflag);
                        releasestr(wrq);
                        return (error);
                }
                releasestr(wrq);
                return (EINVAL);

        case I_LINK:
        case I_PLINK:
                /*
                 * Link a multiplexor.
                 */
                return (mlink(vp, cmd, (int)arg, crp, rvalp, 0));

        case _I_PLINK_LH:
                /*
                 * Link a multiplexor: Call must originate from kernel.
                 */
                if (kioctl)
                        return (ldi_mlink_lh(vp, cmd, arg, crp, rvalp));

                return (EINVAL);
        case I_UNLINK:
        case I_PUNLINK:
                /*
                 * Unlink a multiplexor.
                 * If arg is -1, unlink all links for which this is the
                 * controlling stream.  Otherwise, arg is an index number
                 * for a link to be removed.
                 */
        {
                struct linkinfo *linkp;
                int native_arg = (int)arg;
                int type;
                netstack_t *ns;
                str_stack_t *ss;

                TRACE_1(TR_FAC_STREAMS_FR,
                    TR_I_UNLINK, "I_UNLINK/I_PUNLINK:%p", stp);
                if (vp->v_type == VFIFO) {
                        return (EINVAL);
                }
                if (cmd == I_UNLINK)
                        type = LINKNORMAL;
                else    /* I_PUNLINK */
                        type = LINKPERSIST;
                if (native_arg == 0) {
                        return (EINVAL);
                }
                ns = netstack_find_by_cred(crp);
                ASSERT(ns != NULL);
                ss = ns->netstack_str;
                ASSERT(ss != NULL);

                if (native_arg == MUXID_ALL)
                        error = munlinkall(stp, type, crp, rvalp, ss);
                else {
                        mutex_enter(&muxifier);
                        if (!(linkp = findlinks(stp, (int)arg, type, ss))) {
                                /* invalid user supplied index number */
                                mutex_exit(&muxifier);
                                netstack_rele(ss->ss_netstack);
                                return (EINVAL);
                        }
                        /* munlink drops the muxifier lock */
                        error = munlink(stp, linkp, type, crp, rvalp, ss);
                }
                netstack_rele(ss->ss_netstack);
                return (error);
        }

        case I_FLUSH:
                /*
                 * send a flush message downstream
                 * flush message can indicate
                 * FLUSHR - flush read queue
                 * FLUSHW - flush write queue
                 * FLUSHRW - flush read/write queue
                 */
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                if (arg & ~FLUSHRW)
                        return (EINVAL);

                for (;;) {
                        if (putnextctl1(stp->sd_wrq, M_FLUSH, (int)arg)) {
                                break;
                        }
                        if (error = strwaitbuf(1, BPRI_HI)) {
                                return (error);
                        }
                }

                /*
                 * Send down an unsupported ioctl and wait for the nack
                 * in order to allow the M_FLUSH to propagate back
                 * up to the stream head.
                 * Replaces if (qready()) runqueues();
                 */
                strioc.ic_cmd = -1;     /* The unsupported ioctl */
                strioc.ic_timout = 0;
                strioc.ic_len = 0;
                strioc.ic_dp = NULL;
                (void) strdoioctl(stp, &strioc, flag, K_TO_K, crp, rvalp);
                *rvalp = 0;
                return (0);

        case I_FLUSHBAND:
        {
                struct bandinfo binfo;

                error = strcopyin((void *)arg, &binfo, sizeof (binfo),
                    copyflag);
                if (error)
                        return (error);
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                if (binfo.bi_flag & ~FLUSHRW)
                        return (EINVAL);
                while (!(mp = allocb(2, BPRI_HI))) {
                        if (error = strwaitbuf(2, BPRI_HI))
                                return (error);
                }
                mp->b_datap->db_type = M_FLUSH;
                *mp->b_wptr++ = binfo.bi_flag | FLUSHBAND;
                *mp->b_wptr++ = binfo.bi_pri;
                putnext(stp->sd_wrq, mp);
                /*
                 * Send down an unsupported ioctl and wait for the nack
                 * in order to allow the M_FLUSH to propagate back
                 * up to the stream head.
                 * Replaces if (qready()) runqueues();
                 */
                strioc.ic_cmd = -1;     /* The unsupported ioctl */
                strioc.ic_timout = 0;
                strioc.ic_len = 0;
                strioc.ic_dp = NULL;
                (void) strdoioctl(stp, &strioc, flag, K_TO_K, crp, rvalp);
                *rvalp = 0;
                return (0);
        }

        case I_SRDOPT:
                /*
                 * Set read options
                 *
                 * RNORM - default stream mode
                 * RMSGN - message no discard
                 * RMSGD - message discard
                 * RPROTNORM - fail read with EBADMSG for M_[PC]PROTOs
                 * RPROTDAT - convert M_[PC]PROTOs to M_DATAs
                 * RPROTDIS - discard M_[PC]PROTOs and retain M_DATAs
                 */
                if (arg & ~(RMODEMASK | RPROTMASK))
                        return (EINVAL);

                if ((arg & (RMSGD|RMSGN)) == (RMSGD|RMSGN))
                        return (EINVAL);

                mutex_enter(&stp->sd_lock);
                switch (arg & RMODEMASK) {
                case RNORM:
                        stp->sd_read_opt &= ~(RD_MSGDIS | RD_MSGNODIS);
                        break;
                case RMSGD:
                        stp->sd_read_opt = (stp->sd_read_opt & ~RD_MSGNODIS) |
                            RD_MSGDIS;
                        break;
                case RMSGN:
                        stp->sd_read_opt = (stp->sd_read_opt & ~RD_MSGDIS) |
                            RD_MSGNODIS;
                        break;
                }

                switch (arg & RPROTMASK) {
                case RPROTNORM:
                        stp->sd_read_opt &= ~(RD_PROTDAT | RD_PROTDIS);
                        break;

                case RPROTDAT:
                        stp->sd_read_opt = ((stp->sd_read_opt & ~RD_PROTDIS) |
                            RD_PROTDAT);
                        break;

                case RPROTDIS:
                        stp->sd_read_opt = ((stp->sd_read_opt & ~RD_PROTDAT) |
                            RD_PROTDIS);
                        break;
                }
                mutex_exit(&stp->sd_lock);
                return (0);

        case I_GRDOPT:
                /*
                 * Get read option and return the value
                 * to spot pointed to by arg
                 */
        {
                int rdopt;

                rdopt = ((stp->sd_read_opt & RD_MSGDIS) ? RMSGD :
                    ((stp->sd_read_opt & RD_MSGNODIS) ? RMSGN : RNORM));
                rdopt |= ((stp->sd_read_opt & RD_PROTDAT) ? RPROTDAT :
                    ((stp->sd_read_opt & RD_PROTDIS) ? RPROTDIS : RPROTNORM));

                return (strcopyout(&rdopt, (void *)arg, sizeof (int),
                    copyflag));
        }

        case I_SERROPT:
                /*
                 * Set error options
                 *
                 * RERRNORM - persistent read errors
                 * RERRNONPERSIST - non-persistent read errors
                 * WERRNORM - persistent write errors
                 * WERRNONPERSIST - non-persistent write errors
                 */
                if (arg & ~(RERRMASK | WERRMASK))
                        return (EINVAL);

                mutex_enter(&stp->sd_lock);
                switch (arg & RERRMASK) {
                case RERRNORM:
                        stp->sd_flag &= ~STRDERRNONPERSIST;
                        break;
                case RERRNONPERSIST:
                        stp->sd_flag |= STRDERRNONPERSIST;
                        break;
                }
                switch (arg & WERRMASK) {
                case WERRNORM:
                        stp->sd_flag &= ~STWRERRNONPERSIST;
                        break;
                case WERRNONPERSIST:
                        stp->sd_flag |= STWRERRNONPERSIST;
                        break;
                }
                mutex_exit(&stp->sd_lock);
                return (0);

        case I_GERROPT:
                /*
                 * Get error option and return the value
                 * to spot pointed to by arg
                 */
        {
                int erropt = 0;

                erropt |= (stp->sd_flag & STRDERRNONPERSIST) ? RERRNONPERSIST :
                    RERRNORM;
                erropt |= (stp->sd_flag & STWRERRNONPERSIST) ? WERRNONPERSIST :
                    WERRNORM;
                return (strcopyout(&erropt, (void *)arg, sizeof (int),
                    copyflag));
        }

        case I_SETSIG:
                /*
                 * Register the calling proc to receive the SIGPOLL
                 * signal based on the events given in arg.  If
                 * arg is zero, remove the proc from register list.
                 */
        {
                strsig_t *ssp, *pssp;
                struct pid *pidp;

                pssp = NULL;
                pidp = curproc->p_pidp;
                /*
                 * Hold sd_lock to prevent traversal of sd_siglist while
                 * it is modified.
                 */
                mutex_enter(&stp->sd_lock);
                for (ssp = stp->sd_siglist; ssp && (ssp->ss_pidp != pidp);
                    pssp = ssp, ssp = ssp->ss_next)
                        ;

                if (arg) {
                        if (arg & ~(S_INPUT|S_HIPRI|S_MSG|S_HANGUP|S_ERROR|
                            S_RDNORM|S_WRNORM|S_RDBAND|S_WRBAND|S_BANDURG)) {
                                mutex_exit(&stp->sd_lock);
                                return (EINVAL);
                        }
                        if ((arg & S_BANDURG) && !(arg & S_RDBAND)) {
                                mutex_exit(&stp->sd_lock);
                                return (EINVAL);
                        }

                        /*
                         * If proc not already registered, add it
                         * to list.
                         */
                        if (!ssp) {
                                ssp = kmem_alloc(sizeof (strsig_t), KM_SLEEP);
                                ssp->ss_pidp = pidp;
                                ssp->ss_pid = pidp->pid_id;
                                ssp->ss_next = NULL;
                                if (pssp)
                                        pssp->ss_next = ssp;
                                else
                                        stp->sd_siglist = ssp;
                                mutex_enter(&pidlock);
                                PID_HOLD(pidp);
                                mutex_exit(&pidlock);
                        }

                        /*
                         * Set events.
                         */
                        ssp->ss_events = (int)arg;
                } else {
                        /*
                         * Remove proc from register list.
                         */
                        if (ssp) {
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                if (pssp)
                                        pssp->ss_next = ssp->ss_next;
                                else
                                        stp->sd_siglist = ssp->ss_next;
                                kmem_free(ssp, sizeof (strsig_t));
                        } else {
                                mutex_exit(&stp->sd_lock);
                                return (EINVAL);
                        }
                }

                /*
                 * Recalculate OR of sig events.
                 */
                stp->sd_sigflags = 0;
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        stp->sd_sigflags |= ssp->ss_events;
                mutex_exit(&stp->sd_lock);
                return (0);
        }

        case I_GETSIG:
                /*
                 * Return (in arg) the current registration of events
                 * for which the calling proc is to be signaled.
                 */
        {
                struct strsig *ssp;
                struct pid  *pidp;

                pidp = curproc->p_pidp;
                mutex_enter(&stp->sd_lock);
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        if (ssp->ss_pidp == pidp) {
                                error = strcopyout(&ssp->ss_events, (void *)arg,
                                    sizeof (int), copyflag);
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                mutex_exit(&stp->sd_lock);
                return (EINVAL);
        }

        case I_ESETSIG:
                /*
                 * Register the ss_pid to receive the SIGPOLL
                 * signal based on the events is ss_events arg.  If
                 * ss_events is zero, remove the proc from register list.
                 */
        {
                struct strsig *ssp, *pssp;
                struct proc *proc;
                struct pid  *pidp;
                pid_t pid;
                struct strsigset ss;

                error = strcopyin((void *)arg, &ss, sizeof (ss), copyflag);
                if (error)
                        return (error);

                pid = ss.ss_pid;

                if (ss.ss_events != 0) {
                        /*
                         * Permissions check by sending signal 0.
                         * Note that when kill fails it does a set_errno
                         * causing the system call to fail.
                         */
                        error = kill(pid, 0);
                        if (error) {
                                return (error);
                        }
                }
                mutex_enter(&pidlock);
                if (pid == 0)
                        proc = curproc;
                else if (pid < 0)
                        proc = pgfind(-pid);
                else
                        proc = prfind(pid);
                if (proc == NULL) {
                        mutex_exit(&pidlock);
                        return (ESRCH);
                }
                if (pid < 0)
                        pidp = proc->p_pgidp;
                else
                        pidp = proc->p_pidp;
                ASSERT(pidp);
                /*
                 * Get a hold on the pid structure while referencing it.
                 * There is a separate PID_HOLD should it be inserted
                 * in the list below.
                 */
                PID_HOLD(pidp);
                mutex_exit(&pidlock);

                pssp = NULL;
                /*
                 * Hold sd_lock to prevent traversal of sd_siglist while
                 * it is modified.
                 */
                mutex_enter(&stp->sd_lock);
                for (ssp = stp->sd_siglist; ssp && (ssp->ss_pid != pid);
                    pssp = ssp, ssp = ssp->ss_next)
                        ;

                if (ss.ss_events) {
                        if (ss.ss_events &
                            ~(S_INPUT|S_HIPRI|S_MSG|S_HANGUP|S_ERROR|
                            S_RDNORM|S_WRNORM|S_RDBAND|S_WRBAND|S_BANDURG)) {
                                mutex_exit(&stp->sd_lock);
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                return (EINVAL);
                        }
                        if ((ss.ss_events & S_BANDURG) &&
                            !(ss.ss_events & S_RDBAND)) {
                                mutex_exit(&stp->sd_lock);
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                return (EINVAL);
                        }

                        /*
                         * If proc not already registered, add it
                         * to list.
                         */
                        if (!ssp) {
                                ssp = kmem_alloc(sizeof (strsig_t), KM_SLEEP);
                                ssp->ss_pidp = pidp;
                                ssp->ss_pid = pid;
                                ssp->ss_next = NULL;
                                if (pssp)
                                        pssp->ss_next = ssp;
                                else
                                        stp->sd_siglist = ssp;
                                mutex_enter(&pidlock);
                                PID_HOLD(pidp);
                                mutex_exit(&pidlock);
                        }

                        /*
                         * Set events.
                         */
                        ssp->ss_events = ss.ss_events;
                } else {
                        /*
                         * Remove proc from register list.
                         */
                        if (ssp) {
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                if (pssp)
                                        pssp->ss_next = ssp->ss_next;
                                else
                                        stp->sd_siglist = ssp->ss_next;
                                kmem_free(ssp, sizeof (strsig_t));
                        } else {
                                mutex_exit(&stp->sd_lock);
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                return (EINVAL);
                        }
                }

                /*
                 * Recalculate OR of sig events.
                 */
                stp->sd_sigflags = 0;
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        stp->sd_sigflags |= ssp->ss_events;
                mutex_exit(&stp->sd_lock);
                mutex_enter(&pidlock);
                PID_RELE(pidp);
                mutex_exit(&pidlock);
                return (0);
        }

        case I_EGETSIG:
                /*
                 * Return (in arg) the current registration of events
                 * for which the calling proc is to be signaled.
                 */
        {
                struct strsig *ssp;
                struct proc *proc;
                pid_t pid;
                struct pid  *pidp;
                struct strsigset ss;

                error = strcopyin((void *)arg, &ss, sizeof (ss), copyflag);
                if (error)
                        return (error);

                pid = ss.ss_pid;
                mutex_enter(&pidlock);
                if (pid == 0)
                        proc = curproc;
                else if (pid < 0)
                        proc = pgfind(-pid);
                else
                        proc = prfind(pid);
                if (proc == NULL) {
                        mutex_exit(&pidlock);
                        return (ESRCH);
                }
                if (pid < 0)
                        pidp = proc->p_pgidp;
                else
                        pidp = proc->p_pidp;

                /* Prevent the pidp from being reassigned */
                PID_HOLD(pidp);
                mutex_exit(&pidlock);

                mutex_enter(&stp->sd_lock);
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        if (ssp->ss_pid == pid) {
                                ss.ss_pid = ssp->ss_pid;
                                ss.ss_events = ssp->ss_events;
                                error = strcopyout(&ss, (void *)arg,
                                    sizeof (struct strsigset), copyflag);
                                mutex_exit(&stp->sd_lock);
                                mutex_enter(&pidlock);
                                PID_RELE(pidp);
                                mutex_exit(&pidlock);
                                return (error);
                        }
                mutex_exit(&stp->sd_lock);
                mutex_enter(&pidlock);
                PID_RELE(pidp);
                mutex_exit(&pidlock);
                return (EINVAL);
        }

        case I_PEEK:
        {
                STRUCT_DECL(strpeek, strpeek);
                size_t n;
                mblk_t *fmp, *tmp_mp = NULL;

                STRUCT_INIT(strpeek, flag);

                error = strcopyin((void *)arg, STRUCT_BUF(strpeek),
                    STRUCT_SIZE(strpeek), copyflag);
                if (error)
                        return (error);

                mutex_enter(QLOCK(rdq));
                /*
                 * Skip the invalid messages
                 */
                for (mp = rdq->q_first; mp != NULL; mp = mp->b_next)
                        if (mp->b_datap->db_type != M_SIG)
                                break;

                /*
                 * If user has requested to peek at a high priority message
                 * and first message is not, return 0
                 */
                if (mp != NULL) {
                        if ((STRUCT_FGET(strpeek, flags) & RS_HIPRI) &&
                            queclass(mp) == QNORM) {
                                *rvalp = 0;
                                mutex_exit(QLOCK(rdq));
                                return (0);
                        }
                } else if (stp->sd_struiordq == NULL ||
                    (STRUCT_FGET(strpeek, flags) & RS_HIPRI)) {
                        /*
                         * No mblks to look at at the streamhead and
                         * 1). This isn't a synch stream or
                         * 2). This is a synch stream but caller wants high
                         *      priority messages which is not supported by
                         *      the synch stream. (it only supports QNORM)
                         */
                        *rvalp = 0;
                        mutex_exit(QLOCK(rdq));
                        return (0);
                }

                fmp = mp;

                if (mp && mp->b_datap->db_type == M_PASSFP) {
                        mutex_exit(QLOCK(rdq));
                        return (EBADMSG);
                }

                ASSERT(mp == NULL || mp->b_datap->db_type == M_PCPROTO ||
                    mp->b_datap->db_type == M_PROTO ||
                    mp->b_datap->db_type == M_DATA);

                if (mp && mp->b_datap->db_type == M_PCPROTO) {
                        STRUCT_FSET(strpeek, flags, RS_HIPRI);
                } else {
                        STRUCT_FSET(strpeek, flags, 0);
                }


                if (mp && ((tmp_mp = dupmsg(mp)) == NULL)) {
                        mutex_exit(QLOCK(rdq));
                        return (ENOSR);
                }
                mutex_exit(QLOCK(rdq));

                /*
                 * set mp = tmp_mp, so that I_PEEK processing can continue.
                 * tmp_mp is used to free the dup'd message.
                 */
                mp = tmp_mp;

                uio.uio_fmode = 0;
                uio.uio_extflg = UIO_COPY_CACHED;
                uio.uio_segflg = (copyflag == U_TO_K) ? UIO_USERSPACE :
                    UIO_SYSSPACE;
                uio.uio_limit = 0;
                /*
                 * First process PROTO blocks, if any.
                 * If user doesn't want to get ctl info by setting maxlen <= 0,
                 * then set len to -1/0 and skip control blocks part.
                 */
                if (STRUCT_FGET(strpeek, ctlbuf.maxlen) < 0)
                        STRUCT_FSET(strpeek, ctlbuf.len, -1);
                else if (STRUCT_FGET(strpeek, ctlbuf.maxlen) == 0)
                        STRUCT_FSET(strpeek, ctlbuf.len, 0);
                else {
                        int     ctl_part = 0;

                        iov.iov_base = STRUCT_FGETP(strpeek, ctlbuf.buf);
                        iov.iov_len = STRUCT_FGET(strpeek, ctlbuf.maxlen);
                        uio.uio_iov = &iov;
                        uio.uio_resid = iov.iov_len;
                        uio.uio_loffset = 0;
                        uio.uio_iovcnt = 1;
                        while (mp && mp->b_datap->db_type != M_DATA &&
                            uio.uio_resid >= 0) {
                                ASSERT(STRUCT_FGET(strpeek, flags) == 0 ?
                                    mp->b_datap->db_type == M_PROTO :
                                    mp->b_datap->db_type == M_PCPROTO);

                                if ((n = MIN(uio.uio_resid,
                                    mp->b_wptr - mp->b_rptr)) != 0 &&
                                    (error = uiomove((char *)mp->b_rptr, n,
                                    UIO_READ, &uio)) != 0) {
                                        freemsg(tmp_mp);
                                        return (error);
                                }
                                ctl_part = 1;
                                mp = mp->b_cont;
                        }
                        /* No ctl message */
                        if (ctl_part == 0)
                                STRUCT_FSET(strpeek, ctlbuf.len, -1);
                        else
                                STRUCT_FSET(strpeek, ctlbuf.len,
                                    STRUCT_FGET(strpeek, ctlbuf.maxlen) -
                                    uio.uio_resid);
                }

                /*
                 * Now process DATA blocks, if any.
                 * If user doesn't want to get data info by setting maxlen <= 0,
                 * then set len to -1/0 and skip data blocks part.
                 */
                if (STRUCT_FGET(strpeek, databuf.maxlen) < 0)
                        STRUCT_FSET(strpeek, databuf.len, -1);
                else if (STRUCT_FGET(strpeek, databuf.maxlen) == 0)
                        STRUCT_FSET(strpeek, databuf.len, 0);
                else {
                        int     data_part = 0;

                        iov.iov_base = STRUCT_FGETP(strpeek, databuf.buf);
                        iov.iov_len = STRUCT_FGET(strpeek, databuf.maxlen);
                        uio.uio_iov = &iov;
                        uio.uio_resid = iov.iov_len;
                        uio.uio_loffset = 0;
                        uio.uio_iovcnt = 1;
                        while (mp && uio.uio_resid) {
                                if (mp->b_datap->db_type == M_DATA) {
                                        if ((n = MIN(uio.uio_resid,
                                            mp->b_wptr - mp->b_rptr)) != 0 &&
                                            (error = uiomove((char *)mp->b_rptr,
                                            n, UIO_READ, &uio)) != 0) {
                                                freemsg(tmp_mp);
                                                return (error);
                                        }
                                        data_part = 1;
                                }
                                ASSERT(data_part == 0 ||
                                    mp->b_datap->db_type == M_DATA);
                                mp = mp->b_cont;
                        }
                        /* No data message */
                        if (data_part == 0)
                                STRUCT_FSET(strpeek, databuf.len, -1);
                        else
                                STRUCT_FSET(strpeek, databuf.len,
                                    STRUCT_FGET(strpeek, databuf.maxlen) -
                                    uio.uio_resid);
                }
                freemsg(tmp_mp);

                /*
                 * It is a synch stream and user wants to get
                 * data (maxlen > 0).
                 * uio setup is done by the codes that process DATA
                 * blocks above.
                 */
                if ((fmp == NULL) && STRUCT_FGET(strpeek, databuf.maxlen) > 0) {
                        infod_t infod;

                        infod.d_cmd = INFOD_COPYOUT;
                        infod.d_res = 0;
                        infod.d_uiop = &uio;
                        error = infonext(rdq, &infod);
                        if (error == EINVAL || error == EBUSY)
                                error = 0;
                        if (error)
                                return (error);
                        STRUCT_FSET(strpeek, databuf.len, STRUCT_FGET(strpeek,
                            databuf.maxlen) - uio.uio_resid);
                        if (STRUCT_FGET(strpeek, databuf.len) == 0) {
                                /*
                                 * No data found by the infonext().
                                 */
                                STRUCT_FSET(strpeek, databuf.len, -1);
                        }
                }
                error = strcopyout(STRUCT_BUF(strpeek), (void *)arg,
                    STRUCT_SIZE(strpeek), copyflag);
                if (error) {
                        return (error);
                }
                /*
                 * If there is no message retrieved, set return code to 0
                 * otherwise, set it to 1.
                 */
                if (STRUCT_FGET(strpeek, ctlbuf.len) == -1 &&
                    STRUCT_FGET(strpeek, databuf.len) == -1)
                        *rvalp = 0;
                else
                        *rvalp = 1;
                return (0);
        }

        case I_FDINSERT:
        {
                STRUCT_DECL(strfdinsert, strfdinsert);
                struct file *resftp;
                struct stdata *resstp;
                t_uscalar_t     ival;
                ssize_t msgsize;
                struct strbuf mctl;

                STRUCT_INIT(strfdinsert, flag);
                if (stp->sd_flag & STRHUP)
                        return (ENXIO);
                /*
                 * STRDERR, STWRERR and STPLEX tested above.
                 */
                error = strcopyin((void *)arg, STRUCT_BUF(strfdinsert),
                    STRUCT_SIZE(strfdinsert), copyflag);
                if (error)
                        return (error);

                if (STRUCT_FGET(strfdinsert, offset) < 0 ||
                    (STRUCT_FGET(strfdinsert, offset) %
                    sizeof (t_uscalar_t)) != 0)
                        return (EINVAL);
                if ((resftp = getf(STRUCT_FGET(strfdinsert, fildes))) != NULL) {
                        if ((resstp = resftp->f_vnode->v_stream) == NULL) {
                                releasef(STRUCT_FGET(strfdinsert, fildes));
                                return (EINVAL);
                        }
                } else
                        return (EINVAL);

                mutex_enter(&resstp->sd_lock);
                if (resstp->sd_flag & (STRDERR|STWRERR|STRHUP|STPLEX)) {
                        error = strgeterr(resstp,
                            STRDERR|STWRERR|STRHUP|STPLEX, 0);
                        if (error != 0) {
                                mutex_exit(&resstp->sd_lock);
                                releasef(STRUCT_FGET(strfdinsert, fildes));
                                return (error);
                        }
                }
                mutex_exit(&resstp->sd_lock);

#ifdef  _ILP32
                {
                        queue_t *q;
                        queue_t *mate = NULL;

                        /* get read queue of stream terminus */
                        claimstr(resstp->sd_wrq);
                        for (q = resstp->sd_wrq->q_next; q->q_next != NULL;
                            q = q->q_next)
                                if (!STRMATED(resstp) && STREAM(q) != resstp &&
                                    mate == NULL) {
                                        ASSERT(q->q_qinfo->qi_srvp);
                                        ASSERT(_OTHERQ(q)->q_qinfo->qi_srvp);
                                        claimstr(q);
                                        mate = q;
                                }
                        q = _RD(q);
                        if (mate)
                                releasestr(mate);
                        releasestr(resstp->sd_wrq);
                        ival = (t_uscalar_t)q;
                }
#else
                ival = (t_uscalar_t)getminor(resftp->f_vnode->v_rdev);
#endif  /* _ILP32 */

                if (STRUCT_FGET(strfdinsert, ctlbuf.len) <
                    STRUCT_FGET(strfdinsert, offset) + sizeof (t_uscalar_t)) {
                        releasef(STRUCT_FGET(strfdinsert, fildes));
                        return (EINVAL);
                }

                /*
                 * Check for legal flag value.
                 */
                if (STRUCT_FGET(strfdinsert, flags) & ~RS_HIPRI) {
                        releasef(STRUCT_FGET(strfdinsert, fildes));
                        return (EINVAL);
                }

                /* get these values from those cached in the stream head */
                mutex_enter(QLOCK(stp->sd_wrq));
                rmin = stp->sd_qn_minpsz;
                rmax = stp->sd_qn_maxpsz;
                mutex_exit(QLOCK(stp->sd_wrq));

                /*
                 * Make sure ctl and data sizes together fall within
                 * the limits of the max and min receive packet sizes
                 * and do not exceed system limit.  A negative data
                 * length means that no data part is to be sent.
                 */
                ASSERT((rmax >= 0) || (rmax == INFPSZ));
                if (rmax == 0) {
                        releasef(STRUCT_FGET(strfdinsert, fildes));
                        return (ERANGE);
                }
                if ((msgsize = STRUCT_FGET(strfdinsert, databuf.len)) < 0)
                        msgsize = 0;
                if ((msgsize < rmin) ||
                    ((msgsize > rmax) && (rmax != INFPSZ)) ||
                    (STRUCT_FGET(strfdinsert, ctlbuf.len) > strctlsz)) {
                        releasef(STRUCT_FGET(strfdinsert, fildes));
                        return (ERANGE);
                }

                mutex_enter(&stp->sd_lock);
                while (!(STRUCT_FGET(strfdinsert, flags) & RS_HIPRI) &&
                    !canputnext(stp->sd_wrq)) {
                        if ((error = strwaitq(stp, WRITEWAIT, (ssize_t)0,
                            flag, -1, &done)) != 0 || done) {
                                mutex_exit(&stp->sd_lock);
                                releasef(STRUCT_FGET(strfdinsert, fildes));
                                return (error);
                        }
                        if ((error = i_straccess(stp, access)) != 0) {
                                mutex_exit(&stp->sd_lock);
                                releasef(
                                    STRUCT_FGET(strfdinsert, fildes));
                                return (error);
                        }
                }
                mutex_exit(&stp->sd_lock);

                /*
                 * Copy strfdinsert.ctlbuf into native form of
                 * ctlbuf to pass down into strmakemsg().
                 */
                mctl.maxlen = STRUCT_FGET(strfdinsert, ctlbuf.maxlen);
                mctl.len = STRUCT_FGET(strfdinsert, ctlbuf.len);
                mctl.buf = STRUCT_FGETP(strfdinsert, ctlbuf.buf);

                iov.iov_base = STRUCT_FGETP(strfdinsert, databuf.buf);
                iov.iov_len = STRUCT_FGET(strfdinsert, databuf.len);
                uio.uio_iov = &iov;
                uio.uio_iovcnt = 1;
                uio.uio_loffset = 0;
                uio.uio_segflg = (copyflag == U_TO_K) ? UIO_USERSPACE :
                    UIO_SYSSPACE;
                uio.uio_fmode = 0;
                uio.uio_extflg = UIO_COPY_CACHED;
                uio.uio_resid = iov.iov_len;
                if ((error = strmakemsg(&mctl,
                    &msgsize, &uio, stp,
                    STRUCT_FGET(strfdinsert, flags), &mp)) != 0 || !mp) {
                        STRUCT_FSET(strfdinsert, databuf.len, msgsize);
                        releasef(STRUCT_FGET(strfdinsert, fildes));
                        return (error);
                }

                STRUCT_FSET(strfdinsert, databuf.len, msgsize);

                /*
                 * Place the possibly reencoded queue pointer 'offset' bytes
                 * from the start of the control portion of the message.
                 */
                *((t_uscalar_t *)(mp->b_rptr +
                    STRUCT_FGET(strfdinsert, offset))) = ival;

                /*
                 * Put message downstream.
                 */
                stream_willservice(stp);
                putnext(stp->sd_wrq, mp);
                stream_runservice(stp);
                releasef(STRUCT_FGET(strfdinsert, fildes));
                return (error);
        }

        case I_SENDFD:
        {
                struct file *fp;

                if ((fp = getf((int)arg)) == NULL)
                        return (EBADF);
                error = do_sendfp(stp, fp, crp);
                releasef((int)arg);
                return (error);
        }

        case I_RECVFD:
        case I_E_RECVFD:
        {
                struct k_strrecvfd *srf;
                int i, fd;

                mutex_enter(&stp->sd_lock);
                while (!(mp = getq(rdq))) {
                        if (stp->sd_flag & (STRHUP|STREOF)) {
                                mutex_exit(&stp->sd_lock);
                                return (ENXIO);
                        }
                        if ((error = strwaitq(stp, GETWAIT, (ssize_t)0,
                            flag, -1, &done)) != 0 || done) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                        if ((error = i_straccess(stp, access)) != 0) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                }
                if (mp->b_datap->db_type != M_PASSFP) {
                        putback(stp, rdq, mp, mp->b_band);
                        mutex_exit(&stp->sd_lock);
                        return (EBADMSG);
                }
                mutex_exit(&stp->sd_lock);

                srf = (struct k_strrecvfd *)mp->b_rptr;
                if ((fd = ufalloc(0)) == -1) {
                        mutex_enter(&stp->sd_lock);
                        putback(stp, rdq, mp, mp->b_band);
                        mutex_exit(&stp->sd_lock);
                        return (EMFILE);
                }
                if (cmd == I_RECVFD) {
                        struct o_strrecvfd      ostrfd;

                        /* check to see if uid/gid values are too large. */

                        if (srf->uid > (o_uid_t)USHRT_MAX ||
                            srf->gid > (o_gid_t)USHRT_MAX) {
                                mutex_enter(&stp->sd_lock);
                                putback(stp, rdq, mp, mp->b_band);
                                mutex_exit(&stp->sd_lock);
                                setf(fd, NULL); /* release fd entry */
                                return (EOVERFLOW);
                        }

                        ostrfd.fd = fd;
                        ostrfd.uid = (o_uid_t)srf->uid;
                        ostrfd.gid = (o_gid_t)srf->gid;

                        /* Null the filler bits */
                        for (i = 0; i < 8; i++)
                                ostrfd.fill[i] = 0;

                        error = strcopyout(&ostrfd, (void *)arg,
                            sizeof (struct o_strrecvfd), copyflag);
                } else {                /* I_E_RECVFD */
                        struct strrecvfd        strfd;

                        strfd.fd = fd;
                        strfd.uid = srf->uid;
                        strfd.gid = srf->gid;

                        /* null the filler bits */
                        for (i = 0; i < 8; i++)
                                strfd.fill[i] = 0;

                        error = strcopyout(&strfd, (void *)arg,
                            sizeof (struct strrecvfd), copyflag);
                }

                if (error) {
                        setf(fd, NULL); /* release fd entry */
                        mutex_enter(&stp->sd_lock);
                        putback(stp, rdq, mp, mp->b_band);
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }

                /*
                 * Always increment f_count since the freemsg() below will
                 * always call free_passfp() which performs a closef().
                 */
                mutex_enter(&srf->fp->f_tlock);
                srf->fp->f_count++;
                mutex_exit(&srf->fp->f_tlock);
                setf(fd, srf->fp);
                freemsg(mp);
                return (0);
        }

        case I_SWROPT:
                /*
                 * Set/clear the write options. arg is a bit
                 * mask with any of the following bits set...
                 *      SNDZERO - send zero length message
                 *      SNDPIPE - send sigpipe to process if
                 *              sd_werror is set and process is
                 *              doing a write or putmsg.
                 * The new stream head write options should reflect
                 * what is in arg.
                 */
                if (arg & ~(SNDZERO|SNDPIPE))
                        return (EINVAL);

                mutex_enter(&stp->sd_lock);
                stp->sd_wput_opt &= ~(SW_SIGPIPE|SW_SNDZERO);
                if (arg & SNDZERO)
                        stp->sd_wput_opt |= SW_SNDZERO;
                if (arg & SNDPIPE)
                        stp->sd_wput_opt |= SW_SIGPIPE;
                mutex_exit(&stp->sd_lock);
                return (0);

        case I_GWROPT:
        {
                int wropt = 0;

                if (stp->sd_wput_opt & SW_SNDZERO)
                        wropt |= SNDZERO;
                if (stp->sd_wput_opt & SW_SIGPIPE)
                        wropt |= SNDPIPE;
                return (strcopyout(&wropt, (void *)arg, sizeof (wropt),
                    copyflag));
        }

        case I_LIST:
                /*
                 * Returns all the modules found on this stream,
                 * upto the driver. If argument is NULL, return the
                 * number of modules (including driver). If argument
                 * is not NULL, copy the names into the structure
                 * provided.
                 */

        {
                queue_t *q;
                char *qname;
                int i, nmods;
                struct str_mlist *mlist;
                STRUCT_DECL(str_list, strlist);

                if (arg == (intptr_t)NULL) {
                        /* Return number of modules plus driver */
                        if (stp->sd_vnode->v_type == VFIFO)
                                *rvalp = stp->sd_pushcnt;
                        else
                                *rvalp = stp->sd_pushcnt + 1;
                        return (0);
                }

                STRUCT_INIT(strlist, flag);

                error = strcopyin((void *)arg, STRUCT_BUF(strlist),
                    STRUCT_SIZE(strlist), copyflag);
                if (error != 0)
                        return (error);

                mlist = STRUCT_FGETP(strlist, sl_modlist);
                nmods = STRUCT_FGET(strlist, sl_nmods);
                if (nmods <= 0)
                        return (EINVAL);

                claimstr(stp->sd_wrq);
                q = stp->sd_wrq;
                for (i = 0; i < nmods && _SAMESTR(q); i++, q = q->q_next) {
                        qname = Q2NAME(q->q_next);
                        error = strcopyout(qname, &mlist[i], strlen(qname) + 1,
                            copyflag);
                        if (error != 0) {
                                releasestr(stp->sd_wrq);
                                return (error);
                        }
                }
                releasestr(stp->sd_wrq);
                return (strcopyout(&i, (void *)arg, sizeof (int), copyflag));
        }

        case I_CKBAND:
        {
                queue_t *q;
                qband_t *qbp;

                if ((arg < 0) || (arg >= NBAND))
                        return (EINVAL);
                q = _RD(stp->sd_wrq);
                mutex_enter(QLOCK(q));
                if (arg > (int)q->q_nband) {
                        *rvalp = 0;
                } else {
                        if (arg == 0) {
                                if (q->q_first)
                                        *rvalp = 1;
                                else
                                        *rvalp = 0;
                        } else {
                                qbp = q->q_bandp;
                                while (--arg > 0)
                                        qbp = qbp->qb_next;
                                if (qbp->qb_first)
                                        *rvalp = 1;
                                else
                                        *rvalp = 0;
                        }
                }
                mutex_exit(QLOCK(q));
                return (0);
        }

        case I_GETBAND:
        {
                int intpri;
                queue_t *q;

                q = _RD(stp->sd_wrq);
                mutex_enter(QLOCK(q));
                mp = q->q_first;
                if (!mp) {
                        mutex_exit(QLOCK(q));
                        return (ENODATA);
                }
                intpri = (int)mp->b_band;
                error = strcopyout(&intpri, (void *)arg, sizeof (int),
                    copyflag);
                mutex_exit(QLOCK(q));
                return (error);
        }

        case I_ATMARK:
        {
                queue_t *q;

                if (arg & ~(ANYMARK|LASTMARK))
                        return (EINVAL);
                q = _RD(stp->sd_wrq);
                mutex_enter(&stp->sd_lock);
                if ((stp->sd_flag & STRATMARK) && (arg == ANYMARK)) {
                        *rvalp = 1;
                } else {
                        mutex_enter(QLOCK(q));
                        mp = q->q_first;

                        if (mp == NULL)
                                *rvalp = 0;
                        else if ((arg == ANYMARK) && (mp->b_flag & MSGMARK))
                                *rvalp = 1;
                        else if ((arg == LASTMARK) && (mp == stp->sd_mark))
                                *rvalp = 1;
                        else
                                *rvalp = 0;
                        mutex_exit(QLOCK(q));
                }
                mutex_exit(&stp->sd_lock);
                return (0);
        }

        case I_CANPUT:
        {
                char band;

                if ((arg < 0) || (arg >= NBAND))
                        return (EINVAL);
                band = (char)arg;
                *rvalp = bcanputnext(stp->sd_wrq, band);
                return (0);
        }

        case I_SETCLTIME:
        {
                int closetime;

                error = strcopyin((void *)arg, &closetime, sizeof (int),
                    copyflag);
                if (error)
                        return (error);
                if (closetime < 0)
                        return (EINVAL);

                stp->sd_closetime = closetime;
                return (0);
        }

        case I_GETCLTIME:
        {
                int closetime;

                closetime = stp->sd_closetime;
                return (strcopyout(&closetime, (void *)arg, sizeof (int),
                    copyflag));
        }

        case TIOCGSID:
        {
                pid_t sid;

                mutex_enter(&stp->sd_lock);
                if (stp->sd_sidp == NULL) {
                        mutex_exit(&stp->sd_lock);
                        return (ENOTTY);
                }
                sid = stp->sd_sidp->pid_id;
                mutex_exit(&stp->sd_lock);
                return (strcopyout(&sid, (void *)arg, sizeof (pid_t),
                    copyflag));
        }

        case TIOCSPGRP:
        {
                pid_t pgrp;
                proc_t *q;
                pid_t   sid, fg_pgid, bg_pgid;

                if (error = strcopyin((void *)arg, &pgrp, sizeof (pid_t),
                    copyflag))
                        return (error);
                mutex_enter(&stp->sd_lock);
                mutex_enter(&pidlock);
                if (stp->sd_sidp != ttoproc(curthread)->p_sessp->s_sidp) {
                        mutex_exit(&pidlock);
                        mutex_exit(&stp->sd_lock);
                        return (ENOTTY);
                }
                if (pgrp == stp->sd_pgidp->pid_id) {
                        mutex_exit(&pidlock);
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }
                if (pgrp <= 0 || pgrp >= maxpid) {
                        mutex_exit(&pidlock);
                        mutex_exit(&stp->sd_lock);
                        return (EINVAL);
                }
                if ((q = pgfind(pgrp)) == NULL ||
                    q->p_sessp != ttoproc(curthread)->p_sessp) {
                        mutex_exit(&pidlock);
                        mutex_exit(&stp->sd_lock);
                        return (EPERM);
                }
                sid = stp->sd_sidp->pid_id;
                fg_pgid = q->p_pgrp;
                bg_pgid = stp->sd_pgidp->pid_id;
                CL_SET_PROCESS_GROUP(curthread, sid, bg_pgid, fg_pgid);
                PID_RELE(stp->sd_pgidp);
                ctty_clear_sighuped();
                stp->sd_pgidp = q->p_pgidp;
                PID_HOLD(stp->sd_pgidp);
                mutex_exit(&pidlock);
                mutex_exit(&stp->sd_lock);
                return (0);
        }

        case TIOCGPGRP:
        {
                pid_t pgrp;

                mutex_enter(&stp->sd_lock);
                if (stp->sd_sidp == NULL) {
                        mutex_exit(&stp->sd_lock);
                        return (ENOTTY);
                }
                pgrp = stp->sd_pgidp->pid_id;
                mutex_exit(&stp->sd_lock);
                return (strcopyout(&pgrp, (void *)arg, sizeof (pid_t),
                    copyflag));
        }

        case TIOCSCTTY:
        {
                return (strctty(stp));
        }

        case TIOCNOTTY:
        {
                /* freectty() always assumes curproc. */
                if (freectty(B_FALSE) != 0)
                        return (0);
                return (ENOTTY);
        }

        case FIONBIO:
        case FIOASYNC:
                return (0);     /* handled by the upper layer */
        }
}

/*
 * Custom free routine used for M_PASSFP messages.
 */
static void
free_passfp(struct k_strrecvfd *srf)
{
        (void) closef(srf->fp);
        kmem_free(srf, sizeof (struct k_strrecvfd) + sizeof (frtn_t));
}

/* ARGSUSED */
int
do_sendfp(struct stdata *stp, struct file *fp, struct cred *cr)
{
        queue_t *qp, *nextqp;
        struct k_strrecvfd *srf;
        mblk_t *mp;
        frtn_t *frtnp;
        size_t bufsize;
        queue_t *mate = NULL;
        syncq_t *sq = NULL;
        int retval = 0;

        if (stp->sd_flag & STRHUP)
                return (ENXIO);

        claimstr(stp->sd_wrq);

        /* Fastpath, we have a pipe, and we are already mated, use it. */
        if (STRMATED(stp)) {
                qp = _RD(stp->sd_mate->sd_wrq);
                claimstr(qp);
                mate = qp;
        } else { /* Not already mated. */

                /*
                 * Walk the stream to the end of this one.
                 * assumes that the claimstr() will prevent
                 * plumbing between the stream head and the
                 * driver from changing
                 */
                qp = stp->sd_wrq;

                /*
                 * Loop until we reach the end of this stream.
                 * On completion, qp points to the write queue
                 * at the end of the stream, or the read queue
                 * at the stream head if this is a fifo.
                 */
                while (((qp = qp->q_next) != NULL) && _SAMESTR(qp))
                        ;

                /*
                 * Just in case we get a q_next which is NULL, but
                 * not at the end of the stream.  This is actually
                 * broken, so we set an assert to catch it in
                 * debug, and set an error and return if not debug.
                 */
                ASSERT(qp);
                if (qp == NULL) {
                        releasestr(stp->sd_wrq);
                        return (EINVAL);
                }

                /*
                 * Enter the syncq for the driver, so (hopefully)
                 * the queue values will not change on us.
                 * XXXX - This will only prevent the race IFF only
                 *   the write side modifies the q_next member, and
                 *   the put procedure is protected by at least
                 *   MT_PERQ.
                 */
                if ((sq = qp->q_syncq) != NULL)
                        entersq(sq, SQ_PUT);

                /* Now get the q_next value from this qp. */
                nextqp = qp->q_next;

                /*
                 * If nextqp exists and the other stream is different
                 * from this one claim the stream, set the mate, and
                 * get the read queue at the stream head of the other
                 * stream.  Assumes that nextqp was at least valid when
                 * we got it.  Hopefully the entersq of the driver
                 * will prevent it from changing on us.
                 */
                if ((nextqp != NULL) && (STREAM(nextqp) != stp)) {
                        ASSERT(qp->q_qinfo->qi_srvp);
                        ASSERT(_OTHERQ(qp)->q_qinfo->qi_srvp);
                        ASSERT(_OTHERQ(qp->q_next)->q_qinfo->qi_srvp);
                        claimstr(nextqp);

                        /* Make sure we still have a q_next */
                        if (nextqp != qp->q_next) {
                                releasestr(stp->sd_wrq);
                                releasestr(nextqp);
                                return (EINVAL);
                        }

                        qp = _RD(STREAM(nextqp)->sd_wrq);
                        mate = qp;
                }
                /* If we entered the synq above, leave it. */
                if (sq != NULL)
                        leavesq(sq, SQ_PUT);
        } /*  STRMATED(STP)  */

        /* XXX prevents substitution of the ops vector */
        if (qp->q_qinfo != &strdata && qp->q_qinfo != &fifo_strdata) {
                retval = EINVAL;
                goto out;
        }

        if (qp->q_flag & QFULL) {
                retval = EAGAIN;
                goto out;
        }

        /*
         * Since M_PASSFP messages include a file descriptor, we use
         * esballoc() and specify a custom free routine (free_passfp()) that
         * will close the descriptor as part of freeing the message.  For
         * convenience, we stash the frtn_t right after the data block.
         */
        bufsize = sizeof (struct k_strrecvfd) + sizeof (frtn_t);
        srf = kmem_alloc(bufsize, KM_NOSLEEP);
        if (srf == NULL) {
                retval = EAGAIN;
                goto out;
        }

        frtnp = (frtn_t *)(srf + 1);
        frtnp->free_arg = (caddr_t)srf;
        frtnp->free_func = free_passfp;

        mp = esballoc((uchar_t *)srf, bufsize, BPRI_MED, frtnp);
        if (mp == NULL) {
                kmem_free(srf, bufsize);
                retval = EAGAIN;
                goto out;
        }
        mp->b_wptr += sizeof (struct k_strrecvfd);
        mp->b_datap->db_type = M_PASSFP;

        srf->fp = fp;
        srf->uid = crgetuid(curthread->t_cred);
        srf->gid = crgetgid(curthread->t_cred);
        mutex_enter(&fp->f_tlock);
        fp->f_count++;
        mutex_exit(&fp->f_tlock);

        put(qp, mp);
out:
        releasestr(stp->sd_wrq);
        if (mate)
                releasestr(mate);
        return (retval);
}

/*
 * Send an ioctl message downstream and wait for acknowledgement.
 * flags may be set to either U_TO_K or K_TO_K and a combination
 * of STR_NOERROR or STR_NOSIG
 * STR_NOSIG: Signals are essentially ignored or held and have
 *      no effect for the duration of the call.
 * STR_NOERROR: Ignores stream head read, write and hup errors.
 *      Additionally, if an existing ioctl times out, it is assumed
 *      lost and and this ioctl will continue as if the previous ioctl had
 *      finished.  ETIME may be returned if this ioctl times out (i.e.
 *      ic_timout is not INFTIM).  Non-stream head errors may be returned if
 *      the ioc_error indicates that the driver/module had problems,
 *      an EFAULT was found when accessing user data, a lack of
 *      resources, etc.
 */
int
strdoioctl(
        struct stdata *stp,
        struct strioctl *strioc,
        int fflags,             /* file flags with model info */
        int flag,
        cred_t *crp,
        int *rvalp)
{
        mblk_t *bp;
        struct iocblk *iocbp;
        struct copyreq *reqp;
        struct copyresp *resp;
        int id;
        int transparent = 0;
        int error = 0;
        int len = 0;
        caddr_t taddr;
        int copyflag = (flag & (U_TO_K | K_TO_K));
        int sigflag = (flag & STR_NOSIG);
        int errs;
        uint_t waitflags;
        boolean_t set_iocwaitne = B_FALSE;

        ASSERT(copyflag == U_TO_K || copyflag == K_TO_K);
        ASSERT((fflags & FMODELS) != 0);

        TRACE_2(TR_FAC_STREAMS_FR,
            TR_STRDOIOCTL,
            "strdoioctl:stp %p strioc %p", stp, strioc);
        if (strioc->ic_len == TRANSPARENT) {    /* send arg in M_DATA block */
                transparent = 1;
                strioc->ic_len = sizeof (intptr_t);
        }

        if (strioc->ic_len < 0 || (strmsgsz > 0 && strioc->ic_len > strmsgsz))
                return (EINVAL);

        if ((bp = allocb_cred_wait(sizeof (union ioctypes), sigflag, &error,
            crp, curproc->p_pid)) == NULL)
                        return (error);

        bzero(bp->b_wptr, sizeof (union ioctypes));

        iocbp = (struct iocblk *)bp->b_wptr;
        iocbp->ioc_count = strioc->ic_len;
        iocbp->ioc_cmd = strioc->ic_cmd;
        iocbp->ioc_flag = (fflags & FMODELS);

        crhold(crp);
        iocbp->ioc_cr = crp;
        DB_TYPE(bp) = M_IOCTL;
        bp->b_wptr += sizeof (struct iocblk);

        if (flag & STR_NOERROR)
                errs = STPLEX;
        else
                errs = STRHUP|STRDERR|STWRERR|STPLEX;

        /*
         * If there is data to copy into ioctl block, do so.
         */
        if (iocbp->ioc_count > 0) {
                if (transparent)
                        /*
                         * Note: STR_NOERROR does not have an effect
                         * in putiocd()
                         */
                        id = K_TO_K | sigflag;
                else
                        id = flag;
                if ((error = putiocd(bp, strioc->ic_dp, id, crp)) != 0) {
                        freemsg(bp);
                        crfree(crp);
                        return (error);
                }

                /*
                 * We could have slept copying in user pages.
                 * Recheck the stream head state (the other end
                 * of a pipe could have gone away).
                 */
                if (stp->sd_flag & errs) {
                        mutex_enter(&stp->sd_lock);
                        error = strgeterr(stp, errs, 0);
                        mutex_exit(&stp->sd_lock);
                        if (error != 0) {
                                freemsg(bp);
                                crfree(crp);
                                return (error);
                        }
                }
        }
        if (transparent)
                iocbp->ioc_count = TRANSPARENT;

        /*
         * Block for up to STRTIMOUT milliseconds if there is an outstanding
         * ioctl for this stream already running.  All processes
         * sleeping here will be awakened as a result of an ACK
         * or NAK being received for the outstanding ioctl, or
         * as a result of the timer expiring on the outstanding
         * ioctl (a failure), or as a result of any waiting
         * process's timer expiring (also a failure).
         */

        error = 0;
        mutex_enter(&stp->sd_lock);
        while ((stp->sd_flag & IOCWAIT) ||
            (!set_iocwaitne && (stp->sd_flag & IOCWAITNE))) {
                clock_t cv_rval;

                TRACE_0(TR_FAC_STREAMS_FR,
                    TR_STRDOIOCTL_WAIT,
                    "strdoioctl sleeps - IOCWAIT");
                cv_rval = str_cv_wait(&stp->sd_iocmonitor, &stp->sd_lock,
                    STRTIMOUT, sigflag);
                if (cv_rval <= 0) {
                        if (cv_rval == 0) {
                                error = EINTR;
                        } else {
                                if (flag & STR_NOERROR) {
                                        /*
                                         * Terminating current ioctl in
                                         * progress -- assume it got lost and
                                         * wake up the other thread so that the
                                         * operation completes.
                                         */
                                        if (!(stp->sd_flag & IOCWAITNE)) {
                                                set_iocwaitne = B_TRUE;
                                                stp->sd_flag |= IOCWAITNE;
                                                cv_broadcast(&stp->sd_monitor);
                                        }
                                        /*
                                         * Otherwise, there's a running
                                         * STR_NOERROR -- we have no choice
                                         * here but to wait forever (or until
                                         * interrupted).
                                         */
                                } else {
                                        /*
                                         * pending ioctl has caused
                                         * us to time out
                                         */
                                        error = ETIME;
                                }
                        }
                } else if ((stp->sd_flag & errs)) {
                        error = strgeterr(stp, errs, 0);
                }
                if (error) {
                        mutex_exit(&stp->sd_lock);
                        freemsg(bp);
                        crfree(crp);
                        return (error);
                }
        }

        /*
         * Have control of ioctl mechanism.
         * Send down ioctl packet and wait for response.
         */
        if (stp->sd_iocblk != (mblk_t *)-1) {
                freemsg(stp->sd_iocblk);
        }
        stp->sd_iocblk = NULL;

        /*
         * If this is marked with 'noerror' (internal; mostly
         * I_{P,}{UN,}LINK), then make sure nobody else is able to get
         * in here by setting IOCWAITNE.
         */
        waitflags = IOCWAIT;
        if (flag & STR_NOERROR)
                waitflags |= IOCWAITNE;

        stp->sd_flag |= waitflags;

        /*
         * Assign sequence number.
         */
        iocbp->ioc_id = stp->sd_iocid = getiocseqno();

        mutex_exit(&stp->sd_lock);

        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRDOIOCTL_PUT, "strdoioctl put: stp %p", stp);
        stream_willservice(stp);
        putnext(stp->sd_wrq, bp);
        stream_runservice(stp);

        /*
         * Timed wait for acknowledgment.  The wait time is limited by the
         * timeout value, which must be a positive integer (number of
         * milliseconds) to wait, or 0 (use default value of STRTIMOUT
         * milliseconds), or -1 (wait forever).  This will be awakened
         * either by an ACK/NAK message arriving, the timer expiring, or
         * the timer expiring on another ioctl waiting for control of the
         * mechanism.
         */
waitioc:
        mutex_enter(&stp->sd_lock);


        /*
         * If the reply has already arrived, don't sleep.  If awakened from
         * the sleep, fail only if the reply has not arrived by then.
         * Otherwise, process the reply.
         */
        while (!stp->sd_iocblk) {
                clock_t cv_rval;

                if (stp->sd_flag & errs) {
                        error = strgeterr(stp, errs, 0);
                        if (error != 0) {
                                stp->sd_flag &= ~waitflags;
                                cv_broadcast(&stp->sd_iocmonitor);
                                mutex_exit(&stp->sd_lock);
                                crfree(crp);
                                return (error);
                        }
                }

                TRACE_0(TR_FAC_STREAMS_FR,
                    TR_STRDOIOCTL_WAIT2,
                    "strdoioctl sleeps awaiting reply");
                ASSERT(error == 0);

                cv_rval = str_cv_wait(&stp->sd_monitor, &stp->sd_lock,
                    (strioc->ic_timout ?
                    strioc->ic_timout * 1000 : STRTIMOUT), sigflag);

                /*
                 * There are four possible cases here: interrupt, timeout,
                 * wakeup by IOCWAITNE (above), or wakeup by strrput_nondata (a
                 * valid M_IOCTL reply).
                 *
                 * If we've been awakened by a STR_NOERROR ioctl on some other
                 * thread, then sd_iocblk will still be NULL, and IOCWAITNE
                 * will be set.  Pretend as if we just timed out.  Note that
                 * this other thread waited at least STRTIMOUT before trying to
                 * awaken our thread, so this is indistinguishable (even for
                 * INFTIM) from the case where we failed with ETIME waiting on
                 * IOCWAIT in the prior loop.
                 */
                if (cv_rval > 0 && !(flag & STR_NOERROR) &&
                    stp->sd_iocblk == NULL && (stp->sd_flag & IOCWAITNE)) {
                        cv_rval = -1;
                }

                /*
                 * note: STR_NOERROR does not protect
                 * us here.. use ic_timout < 0
                 */
                if (cv_rval <= 0) {
                        if (cv_rval == 0) {
                                error = EINTR;
                        } else {
                                error =  ETIME;
                        }
                        /*
                         * A message could have come in after we were scheduled
                         * but before we were actually run.
                         */
                        bp = stp->sd_iocblk;
                        stp->sd_iocblk = NULL;
                        if (bp != NULL) {
                                if ((bp->b_datap->db_type == M_COPYIN) ||
                                    (bp->b_datap->db_type == M_COPYOUT)) {
                                        mutex_exit(&stp->sd_lock);
                                        if (bp->b_cont) {
                                                freemsg(bp->b_cont);
                                                bp->b_cont = NULL;
                                        }
                                        bp->b_datap->db_type = M_IOCDATA;
                                        bp->b_wptr = bp->b_rptr +
                                            sizeof (struct copyresp);
                                        resp = (struct copyresp *)bp->b_rptr;
                                        resp->cp_rval =
                                            (caddr_t)1; /* failure */
                                        stream_willservice(stp);
                                        putnext(stp->sd_wrq, bp);
                                        stream_runservice(stp);
                                        mutex_enter(&stp->sd_lock);
                                } else {
                                        freemsg(bp);
                                }
                        }
                        stp->sd_flag &= ~waitflags;
                        cv_broadcast(&stp->sd_iocmonitor);
                        mutex_exit(&stp->sd_lock);
                        crfree(crp);
                        return (error);
                }
        }
        bp = stp->sd_iocblk;
        /*
         * Note: it is strictly impossible to get here with sd_iocblk set to
         * -1.  This is because the initial loop above doesn't allow any new
         * ioctls into the fray until all others have passed this point.
         */
        ASSERT(bp != NULL && bp != (mblk_t *)-1);
        TRACE_1(TR_FAC_STREAMS_FR,
            TR_STRDOIOCTL_ACK, "strdoioctl got reply: bp %p", bp);
        if ((bp->b_datap->db_type == M_IOCACK) ||
            (bp->b_datap->db_type == M_IOCNAK)) {
                /* for detection of duplicate ioctl replies */
                stp->sd_iocblk = (mblk_t *)-1;
                stp->sd_flag &= ~waitflags;
                cv_broadcast(&stp->sd_iocmonitor);
                mutex_exit(&stp->sd_lock);
        } else {
                /*
                 * flags not cleared here because we're still doing
                 * copy in/out for ioctl.
                 */
                stp->sd_iocblk = NULL;
                mutex_exit(&stp->sd_lock);
        }


        /*
         * Have received acknowledgment.
         */

        switch (bp->b_datap->db_type) {
        case M_IOCACK:
                /*
                 * Positive ack.
                 */
                iocbp = (struct iocblk *)bp->b_rptr;

                /*
                 * Set error if indicated.
                 */
                if (iocbp->ioc_error) {
                        error = iocbp->ioc_error;
                        break;
                }

                /*
                 * Set return value.
                 */
                *rvalp = iocbp->ioc_rval;

                /*
                 * Data may have been returned in ACK message (ioc_count > 0).
                 * If so, copy it out to the user's buffer.
                 */
                if (iocbp->ioc_count && !transparent) {
                        if (error = getiocd(bp, strioc->ic_dp, copyflag))
                                break;
                }
                if (!transparent) {
                        if (len)        /* an M_COPYOUT was used with I_STR */
                                strioc->ic_len = len;
                        else
                                strioc->ic_len = (int)iocbp->ioc_count;
                }
                break;

        case M_IOCNAK:
                /*
                 * Negative ack.
                 *
                 * The only thing to do is set error as specified
                 * in neg ack packet.
                 */
                iocbp = (struct iocblk *)bp->b_rptr;

                error = (iocbp->ioc_error ? iocbp->ioc_error : EINVAL);
                break;

        case M_COPYIN:
                /*
                 * Driver or module has requested user ioctl data.
                 */
                reqp = (struct copyreq *)bp->b_rptr;

                /*
                 * M_COPYIN should *never* have a message attached, though
                 * it's harmless if it does -- thus, panic on a DEBUG
                 * kernel and just free it on a non-DEBUG build.
                 */
                ASSERT(bp->b_cont == NULL);
                if (bp->b_cont != NULL) {
                        freemsg(bp->b_cont);
                        bp->b_cont = NULL;
                }

                error = putiocd(bp, reqp->cq_addr, flag, crp);
                if (error && bp->b_cont) {
                        freemsg(bp->b_cont);
                        bp->b_cont = NULL;
                }

                bp->b_wptr = bp->b_rptr + sizeof (struct copyresp);
                bp->b_datap->db_type = M_IOCDATA;

                mblk_setcred(bp, crp, curproc->p_pid);
                resp = (struct copyresp *)bp->b_rptr;
                resp->cp_rval = (caddr_t)(uintptr_t)error;
                resp->cp_flag = (fflags & FMODELS);

                stream_willservice(stp);
                putnext(stp->sd_wrq, bp);
                stream_runservice(stp);

                if (error) {
                        mutex_enter(&stp->sd_lock);
                        stp->sd_flag &= ~waitflags;
                        cv_broadcast(&stp->sd_iocmonitor);
                        mutex_exit(&stp->sd_lock);
                        crfree(crp);
                        return (error);
                }

                goto waitioc;

        case M_COPYOUT:
                /*
                 * Driver or module has ioctl data for a user.
                 */
                reqp = (struct copyreq *)bp->b_rptr;
                ASSERT(bp->b_cont != NULL);

                /*
                 * Always (transparent or non-transparent )
                 * use the address specified in the request
                 */
                taddr = reqp->cq_addr;
                if (!transparent)
                        len = (int)reqp->cq_size;

                /* copyout data to the provided address */
                error = getiocd(bp, taddr, copyflag);

                freemsg(bp->b_cont);
                bp->b_cont = NULL;

                bp->b_wptr = bp->b_rptr + sizeof (struct copyresp);
                bp->b_datap->db_type = M_IOCDATA;

                mblk_setcred(bp, crp, curproc->p_pid);
                resp = (struct copyresp *)bp->b_rptr;
                resp->cp_rval = (caddr_t)(uintptr_t)error;
                resp->cp_flag = (fflags & FMODELS);

                stream_willservice(stp);
                putnext(stp->sd_wrq, bp);
                stream_runservice(stp);

                if (error) {
                        mutex_enter(&stp->sd_lock);
                        stp->sd_flag &= ~waitflags;
                        cv_broadcast(&stp->sd_iocmonitor);
                        mutex_exit(&stp->sd_lock);
                        crfree(crp);
                        return (error);
                }
                goto waitioc;

        default:
                ASSERT(0);
                mutex_enter(&stp->sd_lock);
                stp->sd_flag &= ~waitflags;
                cv_broadcast(&stp->sd_iocmonitor);
                mutex_exit(&stp->sd_lock);
                break;
        }

        freemsg(bp);
        crfree(crp);
        return (error);
}

/*
 * Send an M_CMD message downstream and wait for a reply.  This is a ptools
 * special used to retrieve information from modules/drivers a stream without
 * being subjected to flow control or interfering with pending messages on the
 * stream (e.g. an ioctl in flight).
 */
int
strdocmd(struct stdata *stp, struct strcmd *scp, cred_t *crp)
{
        mblk_t *mp;
        struct cmdblk *cmdp;
        int error = 0;
        int errs = STRHUP|STRDERR|STWRERR|STPLEX;
        clock_t rval, timeout = STRTIMOUT;

        if (scp->sc_len < 0 || scp->sc_len > sizeof (scp->sc_buf) ||
            scp->sc_timeout < -1)
                return (EINVAL);

        if (scp->sc_timeout > 0)
                timeout = scp->sc_timeout * MILLISEC;

        if ((mp = allocb_cred(sizeof (struct cmdblk), crp,
            curproc->p_pid)) == NULL)
                return (ENOMEM);

        crhold(crp);

        cmdp = (struct cmdblk *)mp->b_wptr;
        cmdp->cb_cr = crp;
        cmdp->cb_cmd = scp->sc_cmd;
        cmdp->cb_len = scp->sc_len;
        cmdp->cb_error = 0;
        mp->b_wptr += sizeof (struct cmdblk);

        DB_TYPE(mp) = M_CMD;
        DB_CPID(mp) = curproc->p_pid;

        /*
         * Copy in the payload.
         */
        if (cmdp->cb_len > 0) {
                mp->b_cont = allocb_cred(sizeof (scp->sc_buf), crp,
                    curproc->p_pid);
                if (mp->b_cont == NULL) {
                        error = ENOMEM;
                        goto out;
                }

                /* cb_len comes from sc_len, which has already been checked */
                ASSERT(cmdp->cb_len <= sizeof (scp->sc_buf));
                (void) bcopy(scp->sc_buf, mp->b_cont->b_wptr, cmdp->cb_len);
                mp->b_cont->b_wptr += cmdp->cb_len;
                DB_CPID(mp->b_cont) = curproc->p_pid;
        }

        /*
         * Since this mechanism is strictly for ptools, and since only one
         * process can be grabbed at a time, we simply fail if there's
         * currently an operation pending.
         */
        mutex_enter(&stp->sd_lock);
        if (stp->sd_flag & STRCMDWAIT) {
                mutex_exit(&stp->sd_lock);
                error = EBUSY;
                goto out;
        }
        stp->sd_flag |= STRCMDWAIT;
        ASSERT(stp->sd_cmdblk == NULL);
        mutex_exit(&stp->sd_lock);

        putnext(stp->sd_wrq, mp);
        mp = NULL;

        /*
         * Timed wait for acknowledgment.  If the reply has already arrived,
         * don't sleep.  If awakened from the sleep, fail only if the reply
         * has not arrived by then.  Otherwise, process the reply.
         */
        mutex_enter(&stp->sd_lock);
        while (stp->sd_cmdblk == NULL) {
                if (stp->sd_flag & errs) {
                        if ((error = strgeterr(stp, errs, 0)) != 0)
                                goto waitout;
                }

                rval = str_cv_wait(&stp->sd_monitor, &stp->sd_lock, timeout, 0);
                if (stp->sd_cmdblk != NULL)
                        break;

                if (rval <= 0) {
                        error = (rval == 0) ? EINTR : ETIME;
                        goto waitout;
                }
        }

        /*
         * We received a reply.
         */
        mp = stp->sd_cmdblk;
        stp->sd_cmdblk = NULL;
        ASSERT(mp != NULL && DB_TYPE(mp) == M_CMD);
        ASSERT(stp->sd_flag & STRCMDWAIT);
        stp->sd_flag &= ~STRCMDWAIT;
        mutex_exit(&stp->sd_lock);

        cmdp = (struct cmdblk *)mp->b_rptr;
        if ((error = cmdp->cb_error) != 0)
                goto out;

        /*
         * Data may have been returned in the reply (cb_len > 0).
         * If so, copy it out to the user's buffer.
         */
        if (cmdp->cb_len > 0) {
                if (mp->b_cont == NULL || MBLKL(mp->b_cont) < cmdp->cb_len) {
                        error = EPROTO;
                        goto out;
                }

                cmdp->cb_len = MIN(cmdp->cb_len, sizeof (scp->sc_buf));
                (void) bcopy(mp->b_cont->b_rptr, scp->sc_buf, cmdp->cb_len);
        }
        scp->sc_len = cmdp->cb_len;
out:
        freemsg(mp);
        crfree(crp);
        return (error);
waitout:
        ASSERT(stp->sd_cmdblk == NULL);
        stp->sd_flag &= ~STRCMDWAIT;
        mutex_exit(&stp->sd_lock);
        crfree(crp);
        return (error);
}

/*
 * For the SunOS keyboard driver.
 * Return the next available "ioctl" sequence number.
 * Exported, so that streams modules can send "ioctl" messages
 * downstream from their open routine.
 */
int
getiocseqno(void)
{
        int     i;

        mutex_enter(&strresources);
        i = ++ioc_id;
        mutex_exit(&strresources);
        return (i);
}

/*
 * Get the next message from the read queue.  If the message is
 * priority, STRPRI will have been set by strrput().  This flag
 * should be reset only when the entire message at the front of the
 * queue as been consumed.
 *
 * NOTE: strgetmsg and kstrgetmsg have much of the logic in common.
 */
int
strgetmsg(
        struct vnode *vp,
        struct strbuf *mctl,
        struct strbuf *mdata,
        unsigned char *prip,
        int *flagsp,
        int fmode,
        rval_t *rvp)
{
        struct stdata *stp;
        mblk_t *bp, *nbp;
        mblk_t *savemp = NULL;
        mblk_t *savemptail = NULL;
        uint_t old_sd_flag;
        int flg;
        int more = 0;
        int error = 0;
        char first = 1;
        uint_t mark;            /* Contains MSG*MARK and _LASTMARK */
#define _LASTMARK       0x8000  /* Distinct from MSG*MARK */
        unsigned char pri = 0;
        queue_t *q;
        int     pr = 0;                 /* Partial read successful */
        struct uio uios;
        struct uio *uiop = &uios;
        struct iovec iovs;
        unsigned char type;

        TRACE_1(TR_FAC_STREAMS_FR, TR_STRGETMSG_ENTER,
            "strgetmsg:%p", vp);

        ASSERT(vp->v_stream);
        stp = vp->v_stream;
        rvp->r_val1 = 0;

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCREAD)) != 0) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        if (stp->sd_flag & (STRDERR|STPLEX)) {
                error = strgeterr(stp, STRDERR|STPLEX, 0);
                if (error != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
        }
        mutex_exit(&stp->sd_lock);

        switch (*flagsp) {
        case MSG_HIPRI:
                if (*prip != 0)
                        return (EINVAL);
                break;

        case MSG_ANY:
        case MSG_BAND:
                break;

        default:
                return (EINVAL);
        }
        /*
         * Setup uio and iov for data part
         */
        iovs.iov_base = mdata->buf;
        iovs.iov_len = mdata->maxlen;
        uios.uio_iov = &iovs;
        uios.uio_iovcnt = 1;
        uios.uio_loffset = 0;
        uios.uio_segflg = UIO_USERSPACE;
        uios.uio_fmode = 0;
        uios.uio_extflg = UIO_COPY_CACHED;
        uios.uio_resid = mdata->maxlen;
        uios.uio_offset = 0;

        q = _RD(stp->sd_wrq);
        mutex_enter(&stp->sd_lock);
        old_sd_flag = stp->sd_flag;
        mark = 0;
        for (;;) {
                int done = 0;
                mblk_t *q_first = q->q_first;

                /*
                 * Get the next message of appropriate priority
                 * from the stream head.  If the caller is interested
                 * in band or hipri messages, then they should already
                 * be enqueued at the stream head.  On the other hand
                 * if the caller wants normal (band 0) messages, they
                 * might be deferred in a synchronous stream and they
                 * will need to be pulled up.
                 *
                 * After we have dequeued a message, we might find that
                 * it was a deferred M_SIG that was enqueued at the
                 * stream head.  It must now be posted as part of the
                 * read by calling strsignal_nolock().
                 *
                 * Also note that strrput does not enqueue an M_PCSIG,
                 * and there cannot be more than one hipri message,
                 * so there was no need to have the M_PCSIG case.
                 *
                 * At some time it might be nice to try and wrap the
                 * functionality of kstrgetmsg() and strgetmsg() into
                 * a common routine so to reduce the amount of replicated
                 * code (since they are extremely similar).
                 */
                if (!(*flagsp & (MSG_HIPRI|MSG_BAND))) {
                        /* Asking for normal, band0 data */
                        bp = strget(stp, q, uiop, first, &error);
                        ASSERT(MUTEX_HELD(&stp->sd_lock));
                        if (bp != NULL) {
                                if (DB_TYPE(bp) == M_SIG) {
                                        strsignal_nolock(stp, *bp->b_rptr,
                                            bp->b_band);
                                        freemsg(bp);
                                        continue;
                                } else {
                                        break;
                                }
                        }
                        if (error != 0)
                                goto getmout;

                /*
                 * We can't depend on the value of STRPRI here because
                 * the stream head may be in transit. Therefore, we
                 * must look at the type of the first message to
                 * determine if a high priority messages is waiting
                 */
                } else if ((*flagsp & MSG_HIPRI) && q_first != NULL &&
                    DB_TYPE(q_first) >= QPCTL &&
                    (bp = getq_noenab(q, 0)) != NULL) {
                        /* Asked for HIPRI and got one */
                        ASSERT(DB_TYPE(bp) >= QPCTL);
                        break;
                } else if ((*flagsp & MSG_BAND) && q_first != NULL &&
                    ((q_first->b_band >= *prip) || DB_TYPE(q_first) >= QPCTL) &&
                    (bp = getq_noenab(q, 0)) != NULL) {
                        /*
                         * Asked for at least band "prip" and got either at
                         * least that band or a hipri message.
                         */
                        ASSERT(bp->b_band >= *prip || DB_TYPE(bp) >= QPCTL);
                        if (DB_TYPE(bp) == M_SIG) {
                                strsignal_nolock(stp, *bp->b_rptr, bp->b_band);
                                freemsg(bp);
                                continue;
                        } else {
                                break;
                        }
                }

                /* No data. Time to sleep? */
                qbackenable(q, 0);

                /*
                 * If STRHUP or STREOF, return 0 length control and data.
                 * If resid is 0, then a read(fd,buf,0) was done. Do not
                 * sleep to satisfy this request because by default we have
                 * zero bytes to return.
                 */
                if ((stp->sd_flag & (STRHUP|STREOF)) || (mctl->maxlen == 0 &&
                    mdata->maxlen == 0)) {
                        mctl->len = mdata->len = 0;
                        *flagsp = 0;
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }
                TRACE_2(TR_FAC_STREAMS_FR, TR_STRGETMSG_WAIT,
                    "strgetmsg calls strwaitq:%p, %p",
                    vp, uiop);
                if (((error = strwaitq(stp, GETWAIT, (ssize_t)0, fmode, -1,
                    &done)) != 0) || done) {
                        TRACE_2(TR_FAC_STREAMS_FR, TR_STRGETMSG_DONE,
                            "strgetmsg error or done:%p, %p",
                            vp, uiop);
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                TRACE_2(TR_FAC_STREAMS_FR, TR_STRGETMSG_AWAKE,
                    "strgetmsg awakes:%p, %p", vp, uiop);
                if ((error = i_straccess(stp, JCREAD)) != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                first = 0;
        }
        ASSERT(bp != NULL);
        /*
         * Extract any mark information. If the message is not completely
         * consumed this information will be put in the mblk
         * that is putback.
         * If MSGMARKNEXT is set and the message is completely consumed
         * the STRATMARK flag will be set below. Likewise, if
         * MSGNOTMARKNEXT is set and the message is
         * completely consumed STRNOTATMARK will be set.
         */
        mark = bp->b_flag & (MSGMARK | MSGMARKNEXT | MSGNOTMARKNEXT);
        ASSERT((mark & (MSGMARKNEXT|MSGNOTMARKNEXT)) !=
            (MSGMARKNEXT|MSGNOTMARKNEXT));
        if (mark != 0 && bp == stp->sd_mark) {
                mark |= _LASTMARK;
                stp->sd_mark = NULL;
        }
        /*
         * keep track of the original message type and priority
         */
        pri = bp->b_band;
        type = bp->b_datap->db_type;
        if (type == M_PASSFP) {
                if ((mark & _LASTMARK) && (stp->sd_mark == NULL))
                        stp->sd_mark = bp;
                bp->b_flag |= mark & ~_LASTMARK;
                putback(stp, q, bp, pri);
                qbackenable(q, pri);
                mutex_exit(&stp->sd_lock);
                return (EBADMSG);
        }
        ASSERT(type != M_SIG);

        /*
         * Set this flag so strrput will not generate signals. Need to
         * make sure this flag is cleared before leaving this routine
         * else signals will stop being sent.
         */
        stp->sd_flag |= STRGETINPROG;
        mutex_exit(&stp->sd_lock);

        if (STREAM_NEEDSERVICE(stp))
                stream_runservice(stp);

        /*
         * Set HIPRI flag if message is priority.
         */
        if (type >= QPCTL)
                flg = MSG_HIPRI;
        else
                flg = MSG_BAND;

        /*
         * First process PROTO or PCPROTO blocks, if any.
         */
        if (mctl->maxlen >= 0 && type != M_DATA) {
                size_t  n, bcnt;
                char    *ubuf;

                bcnt = mctl->maxlen;
                ubuf = mctl->buf;
                while (bp != NULL && bp->b_datap->db_type != M_DATA) {
                        if ((n = MIN(bcnt, bp->b_wptr - bp->b_rptr)) != 0 &&
                            copyout(bp->b_rptr, ubuf, n)) {
                                error = EFAULT;
                                mutex_enter(&stp->sd_lock);
                                /*
                                 * clear stream head pri flag based on
                                 * first message type
                                 */
                                if (type >= QPCTL) {
                                        ASSERT(type == M_PCPROTO);
                                        stp->sd_flag &= ~STRPRI;
                                }
                                more = 0;
                                freemsg(bp);
                                goto getmout;
                        }
                        ubuf += n;
                        bp->b_rptr += n;
                        if (bp->b_rptr >= bp->b_wptr) {
                                nbp = bp;
                                bp = bp->b_cont;
                                freeb(nbp);
                        }
                        ASSERT(n <= bcnt);
                        bcnt -= n;
                        if (bcnt == 0)
                                break;
                }
                mctl->len = mctl->maxlen - bcnt;
        } else
                mctl->len = -1;

        if (bp && bp->b_datap->db_type != M_DATA) {
                /*
                 * More PROTO blocks in msg.
                 */
                more |= MORECTL;
                savemp = bp;
                while (bp && bp->b_datap->db_type != M_DATA) {
                        savemptail = bp;
                        bp = bp->b_cont;
                }
                savemptail->b_cont = NULL;
        }

        /*
         * Now process DATA blocks, if any.
         */
        if (mdata->maxlen >= 0 && bp) {
                /*
                 * struiocopyout will consume a potential zero-length
                 * M_DATA even if uio_resid is zero.
                 */
                size_t oldresid = uiop->uio_resid;

                bp = struiocopyout(bp, uiop, &error);
                if (error != 0) {
                        mutex_enter(&stp->sd_lock);
                        /*
                         * clear stream head hi pri flag based on
                         * first message
                         */
                        if (type >= QPCTL) {
                                ASSERT(type == M_PCPROTO);
                                stp->sd_flag &= ~STRPRI;
                        }
                        more = 0;
                        freemsg(savemp);
                        goto getmout;
                }
                /*
                 * (pr == 1) indicates a partial read.
                 */
                if (oldresid > uiop->uio_resid)
                        pr = 1;
                mdata->len = mdata->maxlen - uiop->uio_resid;
        } else
                mdata->len = -1;

        if (bp) {                       /* more data blocks in msg */
                more |= MOREDATA;
                if (savemp)
                        savemptail->b_cont = bp;
                else
                        savemp = bp;
        }

        mutex_enter(&stp->sd_lock);
        if (savemp) {
                if (pr && (savemp->b_datap->db_type == M_DATA) &&
                    msgnodata(savemp)) {
                        /*
                         * Avoid queuing a zero-length tail part of
                         * a message. pr=1 indicates that we read some of
                         * the message.
                         */
                        freemsg(savemp);
                        more &= ~MOREDATA;
                        /*
                         * clear stream head hi pri flag based on
                         * first message
                         */
                        if (type >= QPCTL) {
                                ASSERT(type == M_PCPROTO);
                                stp->sd_flag &= ~STRPRI;
                        }
                } else {
                        savemp->b_band = pri;
                        /*
                         * If the first message was HIPRI and the one we're
                         * putting back isn't, then clear STRPRI, otherwise
                         * set STRPRI again.  Note that we must set STRPRI
                         * again since the flush logic in strrput_nondata()
                         * may have cleared it while we had sd_lock dropped.
                         */
                        if (type >= QPCTL) {
                                ASSERT(type == M_PCPROTO);
                                if (queclass(savemp) < QPCTL)
                                        stp->sd_flag &= ~STRPRI;
                                else
                                        stp->sd_flag |= STRPRI;
                        } else if (queclass(savemp) >= QPCTL) {
                                /*
                                 * The first message was not a HIPRI message,
                                 * but the one we are about to putback is.
                                 * For simplicitly, we do not allow for HIPRI
                                 * messages to be embedded in the message
                                 * body, so just force it to same type as
                                 * first message.
                                 */
                                ASSERT(type == M_DATA || type == M_PROTO);
                                ASSERT(savemp->b_datap->db_type == M_PCPROTO);
                                savemp->b_datap->db_type = type;
                        }
                        if (mark != 0) {
                                savemp->b_flag |= mark & ~_LASTMARK;
                                if ((mark & _LASTMARK) &&
                                    (stp->sd_mark == NULL)) {
                                        /*
                                         * If another marked message arrived
                                         * while sd_lock was not held sd_mark
                                         * would be non-NULL.
                                         */
                                        stp->sd_mark = savemp;
                                }
                        }
                        putback(stp, q, savemp, pri);
                }
        } else {
                /*
                 * The complete message was consumed.
                 *
                 * If another M_PCPROTO arrived while sd_lock was not held
                 * it would have been discarded since STRPRI was still set.
                 *
                 * Move the MSG*MARKNEXT information
                 * to the stream head just in case
                 * the read queue becomes empty.
                 * clear stream head hi pri flag based on
                 * first message
                 *
                 * If the stream head was at the mark
                 * (STRATMARK) before we dropped sd_lock above
                 * and some data was consumed then we have
                 * moved past the mark thus STRATMARK is
                 * cleared. However, if a message arrived in
                 * strrput during the copyout above causing
                 * STRATMARK to be set we can not clear that
                 * flag.
                 */
                if (type >= QPCTL) {
                        ASSERT(type == M_PCPROTO);
                        stp->sd_flag &= ~STRPRI;
                }
                if (mark & (MSGMARKNEXT|MSGNOTMARKNEXT|MSGMARK)) {
                        if (mark & MSGMARKNEXT) {
                                stp->sd_flag &= ~STRNOTATMARK;
                                stp->sd_flag |= STRATMARK;
                        } else if (mark & MSGNOTMARKNEXT) {
                                stp->sd_flag &= ~STRATMARK;
                                stp->sd_flag |= STRNOTATMARK;
                        } else {
                                stp->sd_flag &= ~(STRATMARK|STRNOTATMARK);
                        }
                } else if (pr && (old_sd_flag & STRATMARK)) {
                        stp->sd_flag &= ~STRATMARK;
                }
        }

        *flagsp = flg;
        *prip = pri;

        /*
         * Getmsg cleanup processing - if the state of the queue has changed
         * some signals may need to be sent and/or poll awakened.
         */
getmout:
        qbackenable(q, pri);

        /*
         * We dropped the stream head lock above. Send all M_SIG messages
         * before processing stream head for SIGPOLL messages.
         */
        ASSERT(MUTEX_HELD(&stp->sd_lock));
        while ((bp = q->q_first) != NULL &&
            (bp->b_datap->db_type == M_SIG)) {
                /*
                 * sd_lock is held so the content of the read queue can not
                 * change.
                 */
                bp = getq(q);
                ASSERT(bp != NULL && bp->b_datap->db_type == M_SIG);

                strsignal_nolock(stp, *bp->b_rptr, bp->b_band);
                mutex_exit(&stp->sd_lock);
                freemsg(bp);
                if (STREAM_NEEDSERVICE(stp))
                        stream_runservice(stp);
                mutex_enter(&stp->sd_lock);
        }

        /*
         * stream head cannot change while we make the determination
         * whether or not to send a signal. Drop the flag to allow strrput
         * to send firstmsgsigs again.
         */
        stp->sd_flag &= ~STRGETINPROG;

        /*
         * If the type of message at the front of the queue changed
         * due to the receive the appropriate signals and pollwakeup events
         * are generated. The type of changes are:
         *      Processed a hipri message, q_first is not hipri.
         *      Processed a band X message, and q_first is band Y.
         * The generated signals and pollwakeups are identical to what
         * strrput() generates should the message that is now on q_first
         * arrive to an empty read queue.
         *
         * Note: only strrput will send a signal for a hipri message.
         */
        if ((bp = q->q_first) != NULL && !(stp->sd_flag & STRPRI)) {
                strsigset_t signals = 0;
                strpollset_t pollwakeups = 0;

                if (flg & MSG_HIPRI) {
                        /*
                         * Removed a hipri message. Regular data at
                         * the front of  the queue.
                         */
                        if (bp->b_band == 0) {
                                signals = S_INPUT | S_RDNORM;
                                pollwakeups = POLLIN | POLLRDNORM;
                        } else {
                                signals = S_INPUT | S_RDBAND;
                                pollwakeups = POLLIN | POLLRDBAND;
                        }
                } else if (pri != bp->b_band) {
                        /*
                         * The band is different for the new q_first.
                         */
                        if (bp->b_band == 0) {
                                signals = S_RDNORM;
                                pollwakeups = POLLIN | POLLRDNORM;
                        } else {
                                signals = S_RDBAND;
                                pollwakeups = POLLIN | POLLRDBAND;
                        }
                }

                if (pollwakeups != 0) {
                        if (pollwakeups == (POLLIN | POLLRDNORM)) {
                                if (!(stp->sd_rput_opt & SR_POLLIN))
                                        goto no_pollwake;
                                stp->sd_rput_opt &= ~SR_POLLIN;
                        }
                        mutex_exit(&stp->sd_lock);
                        pollwakeup(&stp->sd_pollist, pollwakeups);
                        mutex_enter(&stp->sd_lock);
                }
no_pollwake:

                if (stp->sd_sigflags & signals)
                        strsendsig(stp->sd_siglist, signals, bp->b_band, 0);
        }
        mutex_exit(&stp->sd_lock);

        rvp->r_val1 = more;
        return (error);
#undef  _LASTMARK
}

/*
 * Get the next message from the read queue.  If the message is
 * priority, STRPRI will have been set by strrput().  This flag
 * should be reset only when the entire message at the front of the
 * queue as been consumed.
 *
 * If uiop is NULL all data is returned in mctlp.
 * Note that a NULL uiop implies that FNDELAY and FNONBLOCK are assumed
 * not enabled.
 * The timeout parameter is in milliseconds; -1 for infinity.
 * This routine handles the consolidation private flags:
 *      MSG_IGNERROR    Ignore any stream head error except STPLEX.
 *      MSG_DELAYERROR  Defer the error check until the queue is empty.
 *      MSG_HOLDSIG     Hold signals while waiting for data.
 *      MSG_IPEEK       Only peek at messages.
 *      MSG_DISCARDTAIL Discard the tail M_DATA part of the message
 *                      that doesn't fit.
 *      MSG_NOMARK      If the message is marked leave it on the queue.
 *
 * NOTE: strgetmsg and kstrgetmsg have much of the logic in common.
 */
int
kstrgetmsg(
        struct vnode *vp,
        mblk_t **mctlp,
        struct uio *uiop,
        unsigned char *prip,
        int *flagsp,
        clock_t timout,
        rval_t *rvp)
{
        struct stdata *stp;
        mblk_t *bp, *nbp;
        mblk_t *savemp = NULL;
        mblk_t *savemptail = NULL;
        int flags;
        uint_t old_sd_flag;
        int flg;
        int more = 0;
        int error = 0;
        char first = 1;
        uint_t mark;            /* Contains MSG*MARK and _LASTMARK */
#define _LASTMARK       0x8000  /* Distinct from MSG*MARK */
        unsigned char pri = 0;
        queue_t *q;
        int     pr = 0;                 /* Partial read successful */
        unsigned char type;

        TRACE_1(TR_FAC_STREAMS_FR, TR_KSTRGETMSG_ENTER,
            "kstrgetmsg:%p", vp);

        ASSERT(vp->v_stream);
        stp = vp->v_stream;
        rvp->r_val1 = 0;

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCREAD)) != 0) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        flags = *flagsp;
        if (stp->sd_flag & (STRDERR|STPLEX)) {
                if ((stp->sd_flag & STPLEX) ||
                    (flags & (MSG_IGNERROR|MSG_DELAYERROR)) == 0) {
                        error = strgeterr(stp, STRDERR|STPLEX,
                            (flags & MSG_IPEEK));
                        if (error != 0) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                }
        }
        mutex_exit(&stp->sd_lock);

        switch (flags & (MSG_HIPRI|MSG_ANY|MSG_BAND)) {
        case MSG_HIPRI:
                if (*prip != 0)
                        return (EINVAL);
                break;

        case MSG_ANY:
        case MSG_BAND:
                break;

        default:
                return (EINVAL);
        }

retry:
        q = _RD(stp->sd_wrq);
        mutex_enter(&stp->sd_lock);
        old_sd_flag = stp->sd_flag;
        mark = 0;
        for (;;) {
                int done = 0;
                int waitflag;
                int fmode;
                mblk_t *q_first = q->q_first;

                /*
                 * This section of the code operates just like the code
                 * in strgetmsg().  There is a comment there about what
                 * is going on here.
                 */
                if (!(flags & (MSG_HIPRI|MSG_BAND))) {
                        /* Asking for normal, band0 data */
                        bp = strget(stp, q, uiop, first, &error);
                        ASSERT(MUTEX_HELD(&stp->sd_lock));
                        if (bp != NULL) {
                                if (DB_TYPE(bp) == M_SIG) {
                                        strsignal_nolock(stp, *bp->b_rptr,
                                            bp->b_band);
                                        freemsg(bp);
                                        continue;
                                } else {
                                        break;
                                }
                        }
                        if (error != 0) {
                                goto getmout;
                        }
                /*
                 * We can't depend on the value of STRPRI here because
                 * the stream head may be in transit. Therefore, we
                 * must look at the type of the first message to
                 * determine if a high priority messages is waiting
                 */
                } else if ((flags & MSG_HIPRI) && q_first != NULL &&
                    DB_TYPE(q_first) >= QPCTL &&
                    (bp = getq_noenab(q, 0)) != NULL) {
                        ASSERT(DB_TYPE(bp) >= QPCTL);
                        break;
                } else if ((flags & MSG_BAND) && q_first != NULL &&
                    ((q_first->b_band >= *prip) || DB_TYPE(q_first) >= QPCTL) &&
                    (bp = getq_noenab(q, 0)) != NULL) {
                        /*
                         * Asked for at least band "prip" and got either at
                         * least that band or a hipri message.
                         */
                        ASSERT(bp->b_band >= *prip || DB_TYPE(bp) >= QPCTL);
                        if (DB_TYPE(bp) == M_SIG) {
                                strsignal_nolock(stp, *bp->b_rptr, bp->b_band);
                                freemsg(bp);
                                continue;
                        } else {
                                break;
                        }
                }

                /* No data. Time to sleep? */
                qbackenable(q, 0);

                /*
                 * Delayed error notification?
                 */
                if ((stp->sd_flag & (STRDERR|STPLEX)) &&
                    (flags & (MSG_IGNERROR|MSG_DELAYERROR)) == MSG_DELAYERROR) {
                        error = strgeterr(stp, STRDERR|STPLEX,
                            (flags & MSG_IPEEK));
                        if (error != 0) {
                                mutex_exit(&stp->sd_lock);
                                return (error);
                        }
                }

                /*
                 * If STRHUP or STREOF, return 0 length control and data.
                 * If a read(fd,buf,0) has been done, do not sleep, just
                 * return.
                 *
                 * If mctlp == NULL and uiop == NULL, then the code will
                 * do the strwaitq. This is an understood way of saying
                 * sleep "polling" until a message is received.
                 */
                if ((stp->sd_flag & (STRHUP|STREOF)) ||
                    (uiop != NULL && uiop->uio_resid == 0)) {
                        if (mctlp != NULL)
                                *mctlp = NULL;
                        *flagsp = 0;
                        mutex_exit(&stp->sd_lock);
                        return (0);
                }

                waitflag = GETWAIT;
                if (flags &
                    (MSG_HOLDSIG|MSG_IGNERROR|MSG_IPEEK|MSG_DELAYERROR)) {
                        if (flags & MSG_HOLDSIG)
                                waitflag |= STR_NOSIG;
                        if (flags & MSG_IGNERROR)
                                waitflag |= STR_NOERROR;
                        if (flags & MSG_IPEEK)
                                waitflag |= STR_PEEK;
                        if (flags & MSG_DELAYERROR)
                                waitflag |= STR_DELAYERR;
                }
                if (uiop != NULL)
                        fmode = uiop->uio_fmode;
                else
                        fmode = 0;

                TRACE_2(TR_FAC_STREAMS_FR, TR_KSTRGETMSG_WAIT,
                    "kstrgetmsg calls strwaitq:%p, %p",
                    vp, uiop);
                if (((error = strwaitq(stp, waitflag, (ssize_t)0,
                    fmode, timout, &done))) != 0 || done) {
                        TRACE_2(TR_FAC_STREAMS_FR, TR_KSTRGETMSG_DONE,
                            "kstrgetmsg error or done:%p, %p",
                            vp, uiop);
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                TRACE_2(TR_FAC_STREAMS_FR, TR_KSTRGETMSG_AWAKE,
                    "kstrgetmsg awakes:%p, %p", vp, uiop);
                if ((error = i_straccess(stp, JCREAD)) != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                first = 0;
        }
        ASSERT(bp != NULL);
        /*
         * Extract any mark information. If the message is not completely
         * consumed this information will be put in the mblk
         * that is putback.
         * If MSGMARKNEXT is set and the message is completely consumed
         * the STRATMARK flag will be set below. Likewise, if
         * MSGNOTMARKNEXT is set and the message is
         * completely consumed STRNOTATMARK will be set.
         */
        mark = bp->b_flag & (MSGMARK | MSGMARKNEXT | MSGNOTMARKNEXT);
        ASSERT((mark & (MSGMARKNEXT|MSGNOTMARKNEXT)) !=
            (MSGMARKNEXT|MSGNOTMARKNEXT));
        pri = bp->b_band;
        if (mark != 0) {
                /*
                 * If the caller doesn't want the mark return.
                 * Used to implement MSG_WAITALL in sockets.
                 */
                if (flags & MSG_NOMARK) {
                        putback(stp, q, bp, pri);
                        qbackenable(q, pri);
                        mutex_exit(&stp->sd_lock);
                        return (EWOULDBLOCK);
                }
                if (bp == stp->sd_mark) {
                        mark |= _LASTMARK;
                        stp->sd_mark = NULL;
                }
        }

        /*
         * keep track of the first message type
         */
        type = bp->b_datap->db_type;

        if (bp->b_datap->db_type == M_PASSFP) {
                if ((mark & _LASTMARK) && (stp->sd_mark == NULL))
                        stp->sd_mark = bp;
                bp->b_flag |= mark & ~_LASTMARK;
                putback(stp, q, bp, pri);
                qbackenable(q, pri);
                mutex_exit(&stp->sd_lock);
                return (EBADMSG);
        }
        ASSERT(type != M_SIG);

        if (flags & MSG_IPEEK) {
                /*
                 * Clear any struioflag - we do the uiomove over again
                 * when peeking since it simplifies the code.
                 *
                 * Dup the message and put the original back on the queue.
                 * If dupmsg() fails, try again with copymsg() to see if
                 * there is indeed a shortage of memory.  dupmsg() may fail
                 * if db_ref in any of the messages reaches its limit.
                 */

                if ((nbp = dupmsg(bp)) == NULL && (nbp = copymsg(bp)) == NULL) {
                        /*
                         * Restore the state of the stream head since we
                         * need to drop sd_lock (strwaitbuf is sleeping).
                         */
                        size_t size = msgdsize(bp);

                        if ((mark & _LASTMARK) && (stp->sd_mark == NULL))
                                stp->sd_mark = bp;
                        bp->b_flag |= mark & ~_LASTMARK;
                        putback(stp, q, bp, pri);
                        mutex_exit(&stp->sd_lock);
                        error = strwaitbuf(size, BPRI_HI);
                        if (error) {
                                /*
                                 * There is no net change to the queue thus
                                 * no need to qbackenable.
                                 */
                                return (error);
                        }
                        goto retry;
                }

                if ((mark & _LASTMARK) && (stp->sd_mark == NULL))
                        stp->sd_mark = bp;
                bp->b_flag |= mark & ~_LASTMARK;
                putback(stp, q, bp, pri);
                bp = nbp;
        }

        /*
         * Set this flag so strrput will not generate signals. Need to
         * make sure this flag is cleared before leaving this routine
         * else signals will stop being sent.
         */
        stp->sd_flag |= STRGETINPROG;
        mutex_exit(&stp->sd_lock);

        if ((stp->sd_rputdatafunc != NULL) && (DB_TYPE(bp) == M_DATA)) {
                mblk_t *tmp, *prevmp;

                /*
                 * Put first non-data mblk back to stream head and
                 * cut the mblk chain so sd_rputdatafunc only sees
                 * M_DATA mblks. We can skip the first mblk since it
                 * is M_DATA according to the condition above.
                 */
                for (prevmp = bp, tmp = bp->b_cont; tmp != NULL;
                    prevmp = tmp, tmp = tmp->b_cont) {
                        if (DB_TYPE(tmp) != M_DATA) {
                                prevmp->b_cont = NULL;
                                mutex_enter(&stp->sd_lock);
                                putback(stp, q, tmp, tmp->b_band);
                                mutex_exit(&stp->sd_lock);
                                break;
                        }
                }

                bp = (stp->sd_rputdatafunc)(stp->sd_vnode, bp,
                    NULL, NULL, NULL, NULL);

                if (bp == NULL)
                        goto retry;
        }

        if (STREAM_NEEDSERVICE(stp))
                stream_runservice(stp);

        /*
         * Set HIPRI flag if message is priority.
         */
        if (type >= QPCTL)
                flg = MSG_HIPRI;
        else
                flg = MSG_BAND;

        /*
         * First process PROTO or PCPROTO blocks, if any.
         */
        if (mctlp != NULL && type != M_DATA) {
                mblk_t *nbp;

                *mctlp = bp;
                while (bp->b_cont && bp->b_cont->b_datap->db_type != M_DATA)
                        bp = bp->b_cont;
                nbp = bp->b_cont;
                bp->b_cont = NULL;
                bp = nbp;
        }

        if (bp && bp->b_datap->db_type != M_DATA) {
                /*
                 * More PROTO blocks in msg. Will only happen if mctlp is NULL.
                 */
                more |= MORECTL;
                savemp = bp;
                while (bp && bp->b_datap->db_type != M_DATA) {
                        savemptail = bp;
                        bp = bp->b_cont;
                }
                savemptail->b_cont = NULL;
        }

        /*
         * Now process DATA blocks, if any.
         */
        if (uiop == NULL) {
                /* Append data to tail of mctlp */

                if (mctlp != NULL) {
                        mblk_t **mpp = mctlp;

                        while (*mpp != NULL)
                                mpp = &((*mpp)->b_cont);
                        *mpp = bp;
                        bp = NULL;
                }
        } else if (uiop->uio_resid >= 0 && bp) {
                size_t oldresid = uiop->uio_resid;

                /*
                 * If a streams message is likely to consist
                 * of many small mblks, it is pulled up into
                 * one continuous chunk of memory.
                 * The size of the first mblk may be bogus because
                 * successive read() calls on the socket reduce
                 * the size of this mblk until it is exhausted
                 * and then the code walks on to the next. Thus
                 * the size of the mblk may not be the original size
                 * that was passed up, it's simply a remainder
                 * and hence can be very small without any
                 * implication that the packet is badly fragmented.
                 * So the size of the possible second mblk is
                 * used to spot a badly fragmented packet.
                 * see longer comment at top of page
                 * by mblk_pull_len declaration.
                 */

                if (bp->b_cont != NULL && MBLKL(bp->b_cont) < mblk_pull_len) {
                        (void) pullupmsg(bp, -1);
                }

                bp = struiocopyout(bp, uiop, &error);
                if (error != 0) {
                        if (mctlp != NULL) {
                                freemsg(*mctlp);
                                *mctlp = NULL;
                        } else
                                freemsg(savemp);
                        mutex_enter(&stp->sd_lock);
                        /*
                         * clear stream head hi pri flag based on
                         * first message
                         */
                        if (!(flags & MSG_IPEEK) && (type >= QPCTL)) {
                                ASSERT(type == M_PCPROTO);
                                stp->sd_flag &= ~STRPRI;
                        }
                        more = 0;
                        goto getmout;
                }
                /*
                 * (pr == 1) indicates a partial read.
                 */
                if (oldresid > uiop->uio_resid)
                        pr = 1;
        }

        if (bp) {                       /* more data blocks in msg */
                more |= MOREDATA;
                if (savemp)
                        savemptail->b_cont = bp;
                else
                        savemp = bp;
        }

        mutex_enter(&stp->sd_lock);
        if (savemp) {
                if (flags & (MSG_IPEEK|MSG_DISCARDTAIL)) {
                        /*
                         * When MSG_DISCARDTAIL is set or
                         * when peeking discard any tail. When peeking this
                         * is the tail of the dup that was copied out - the
                         * message has already been putback on the queue.
                         * Return MOREDATA to the caller even though the data
                         * is discarded. This is used by sockets (to
                         * set MSG_TRUNC).
                         */
                        freemsg(savemp);
                        if (!(flags & MSG_IPEEK) && (type >= QPCTL)) {
                                ASSERT(type == M_PCPROTO);
                                stp->sd_flag &= ~STRPRI;
                        }
                } else if (pr && (savemp->b_datap->db_type == M_DATA) &&
                    msgnodata(savemp)) {
                        /*
                         * Avoid queuing a zero-length tail part of
                         * a message. pr=1 indicates that we read some of
                         * the message.
                         */
                        freemsg(savemp);
                        more &= ~MOREDATA;
                        if (type >= QPCTL) {
                                ASSERT(type == M_PCPROTO);
                                stp->sd_flag &= ~STRPRI;
                        }
                } else {
                        savemp->b_band = pri;
                        /*
                         * If the first message was HIPRI and the one we're
                         * putting back isn't, then clear STRPRI, otherwise
                         * set STRPRI again.  Note that we must set STRPRI
                         * again since the flush logic in strrput_nondata()
                         * may have cleared it while we had sd_lock dropped.
                         */

                        if (type >= QPCTL) {
                                ASSERT(type == M_PCPROTO);
                                if (queclass(savemp) < QPCTL)
                                        stp->sd_flag &= ~STRPRI;
                                else
                                        stp->sd_flag |= STRPRI;
                        } else if (queclass(savemp) >= QPCTL) {
                                /*
                                 * The first message was not a HIPRI message,
                                 * but the one we are about to putback is.
                                 * For simplicitly, we do not allow for HIPRI
                                 * messages to be embedded in the message
                                 * body, so just force it to same type as
                                 * first message.
                                 */
                                ASSERT(type == M_DATA || type == M_PROTO);
                                ASSERT(savemp->b_datap->db_type == M_PCPROTO);
                                savemp->b_datap->db_type = type;
                        }
                        if (mark != 0) {
                                if ((mark & _LASTMARK) &&
                                    (stp->sd_mark == NULL)) {
                                        /*
                                         * If another marked message arrived
                                         * while sd_lock was not held sd_mark
                                         * would be non-NULL.
                                         */
                                        stp->sd_mark = savemp;
                                }
                                savemp->b_flag |= mark & ~_LASTMARK;
                        }
                        putback(stp, q, savemp, pri);
                }
        } else if (!(flags & MSG_IPEEK)) {
                /*
                 * The complete message was consumed.
                 *
                 * If another M_PCPROTO arrived while sd_lock was not held
                 * it would have been discarded since STRPRI was still set.
                 *
                 * Move the MSG*MARKNEXT information
                 * to the stream head just in case
                 * the read queue becomes empty.
                 * clear stream head hi pri flag based on
                 * first message
                 *
                 * If the stream head was at the mark
                 * (STRATMARK) before we dropped sd_lock above
                 * and some data was consumed then we have
                 * moved past the mark thus STRATMARK is
                 * cleared. However, if a message arrived in
                 * strrput during the copyout above causing
                 * STRATMARK to be set we can not clear that
                 * flag.
                 * XXX A "perimeter" would help by single-threading strrput,
                 * strread, strgetmsg and kstrgetmsg.
                 */
                if (type >= QPCTL) {
                        ASSERT(type == M_PCPROTO);
                        stp->sd_flag &= ~STRPRI;
                }
                if (mark & (MSGMARKNEXT|MSGNOTMARKNEXT|MSGMARK)) {
                        if (mark & MSGMARKNEXT) {
                                stp->sd_flag &= ~STRNOTATMARK;
                                stp->sd_flag |= STRATMARK;
                        } else if (mark & MSGNOTMARKNEXT) {
                                stp->sd_flag &= ~STRATMARK;
                                stp->sd_flag |= STRNOTATMARK;
                        } else {
                                stp->sd_flag &= ~(STRATMARK|STRNOTATMARK);
                        }
                } else if (pr && (old_sd_flag & STRATMARK)) {
                        stp->sd_flag &= ~STRATMARK;
                }
        }

        *flagsp = flg;
        *prip = pri;

        /*
         * Getmsg cleanup processing - if the state of the queue has changed
         * some signals may need to be sent and/or poll awakened.
         */
getmout:
        qbackenable(q, pri);

        /*
         * We dropped the stream head lock above. Send all M_SIG messages
         * before processing stream head for SIGPOLL messages.
         */
        ASSERT(MUTEX_HELD(&stp->sd_lock));
        while ((bp = q->q_first) != NULL &&
            (bp->b_datap->db_type == M_SIG)) {
                /*
                 * sd_lock is held so the content of the read queue can not
                 * change.
                 */
                bp = getq(q);
                ASSERT(bp != NULL && bp->b_datap->db_type == M_SIG);

                strsignal_nolock(stp, *bp->b_rptr, bp->b_band);
                mutex_exit(&stp->sd_lock);
                freemsg(bp);
                if (STREAM_NEEDSERVICE(stp))
                        stream_runservice(stp);
                mutex_enter(&stp->sd_lock);
        }

        /*
         * stream head cannot change while we make the determination
         * whether or not to send a signal. Drop the flag to allow strrput
         * to send firstmsgsigs again.
         */
        stp->sd_flag &= ~STRGETINPROG;

        /*
         * If the type of message at the front of the queue changed
         * due to the receive the appropriate signals and pollwakeup events
         * are generated. The type of changes are:
         *      Processed a hipri message, q_first is not hipri.
         *      Processed a band X message, and q_first is band Y.
         * The generated signals and pollwakeups are identical to what
         * strrput() generates should the message that is now on q_first
         * arrive to an empty read queue.
         *
         * Note: only strrput will send a signal for a hipri message.
         */
        if ((bp = q->q_first) != NULL && !(stp->sd_flag & STRPRI)) {
                strsigset_t signals = 0;
                strpollset_t pollwakeups = 0;

                if (flg & MSG_HIPRI) {
                        /*
                         * Removed a hipri message. Regular data at
                         * the front of  the queue.
                         */
                        if (bp->b_band == 0) {
                                signals = S_INPUT | S_RDNORM;
                                pollwakeups = POLLIN | POLLRDNORM;
                        } else {
                                signals = S_INPUT | S_RDBAND;
                                pollwakeups = POLLIN | POLLRDBAND;
                        }
                } else if (pri != bp->b_band) {
                        /*
                         * The band is different for the new q_first.
                         */
                        if (bp->b_band == 0) {
                                signals = S_RDNORM;
                                pollwakeups = POLLIN | POLLRDNORM;
                        } else {
                                signals = S_RDBAND;
                                pollwakeups = POLLIN | POLLRDBAND;
                        }
                }

                if (pollwakeups != 0) {
                        if (pollwakeups == (POLLIN | POLLRDNORM)) {
                                if (!(stp->sd_rput_opt & SR_POLLIN))
                                        goto no_pollwake;
                                stp->sd_rput_opt &= ~SR_POLLIN;
                        }
                        mutex_exit(&stp->sd_lock);
                        pollwakeup(&stp->sd_pollist, pollwakeups);
                        mutex_enter(&stp->sd_lock);
                }
no_pollwake:

                if (stp->sd_sigflags & signals)
                        strsendsig(stp->sd_siglist, signals, bp->b_band, 0);
        }
        mutex_exit(&stp->sd_lock);

        rvp->r_val1 = more;
        return (error);
#undef  _LASTMARK
}

/*
 * Put a message downstream.
 *
 * NOTE: strputmsg and kstrputmsg have much of the logic in common.
 */
int
strputmsg(
        struct vnode *vp,
        struct strbuf *mctl,
        struct strbuf *mdata,
        unsigned char pri,
        int flag,
        int fmode)
{
        struct stdata *stp;
        queue_t *wqp;
        mblk_t *mp;
        ssize_t msgsize;
        ssize_t rmin, rmax;
        int error;
        struct uio uios;
        struct uio *uiop = &uios;
        struct iovec iovs;
        int xpg4 = 0;

        ASSERT(vp->v_stream);
        stp = vp->v_stream;
        wqp = stp->sd_wrq;

        /*
         * If it is an XPG4 application, we need to send
         * SIGPIPE below
         */

        xpg4 = (flag & MSG_XPG4) ? 1 : 0;
        flag &= ~MSG_XPG4;

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCWRITE)) != 0) {
                mutex_exit(&stp->sd_lock);
                return (error);
        }

        if (stp->sd_flag & (STWRERR|STRHUP|STPLEX)) {
                error = strwriteable(stp, B_FALSE, xpg4);
                if (error != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
        }

        mutex_exit(&stp->sd_lock);

        /*
         * Check for legal flag value.
         */
        switch (flag) {
        case MSG_HIPRI:
                if ((mctl->len < 0) || (pri != 0))
                        return (EINVAL);
                break;
        case MSG_BAND:
                break;

        default:
                return (EINVAL);
        }

        TRACE_1(TR_FAC_STREAMS_FR, TR_STRPUTMSG_IN,
            "strputmsg in:stp %p", stp);

        /* get these values from those cached in the stream head */
        rmin = stp->sd_qn_minpsz;
        rmax = stp->sd_qn_maxpsz;

        /*
         * Make sure ctl and data sizes together fall within the
         * limits of the max and min receive packet sizes and do
         * not exceed system limit.
         */
        ASSERT((rmax >= 0) || (rmax == INFPSZ));
        if (rmax == 0) {
                return (ERANGE);
        }
        /*
         * Use the MAXIMUM of sd_maxblk and q_maxpsz.
         * Needed to prevent partial failures in the strmakedata loop.
         */
        if (stp->sd_maxblk != INFPSZ && rmax != INFPSZ && rmax < stp->sd_maxblk)
                rmax = stp->sd_maxblk;

        if ((msgsize = mdata->len) < 0) {
                msgsize = 0;
                rmin = 0;       /* no range check for NULL data part */
        }
        if ((msgsize < rmin) ||
            ((msgsize > rmax) && (rmax != INFPSZ)) ||
            (mctl->len > strctlsz)) {
                return (ERANGE);
        }

        /*
         * Setup uio and iov for data part
         */
        iovs.iov_base = mdata->buf;
        iovs.iov_len = msgsize;
        uios.uio_iov = &iovs;
        uios.uio_iovcnt = 1;
        uios.uio_loffset = 0;
        uios.uio_segflg = UIO_USERSPACE;
        uios.uio_fmode = fmode;
        uios.uio_extflg = UIO_COPY_DEFAULT;
        uios.uio_resid = msgsize;
        uios.uio_offset = 0;

        /* Ignore flow control in strput for HIPRI */
        if (flag & MSG_HIPRI)
                flag |= MSG_IGNFLOW;

        for (;;) {
                int done = 0;

                /*
                 * strput will always free the ctl mblk - even when strput
                 * fails.
                 */
                if ((error = strmakectl(mctl, flag, fmode, &mp)) != 0) {
                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRPUTMSG_OUT,
                            "strputmsg out:stp %p out %d error %d",
                            stp, 1, error);
                        return (error);
                }
                /*
                 * Verify that the whole message can be transferred by
                 * strput.
                 */
                ASSERT(stp->sd_maxblk == INFPSZ ||
                    stp->sd_maxblk >= mdata->len);

                msgsize = mdata->len;
                error = strput(stp, mp, uiop, &msgsize, 0, pri, flag);
                mdata->len = msgsize;

                if (error == 0)
                        break;

                if (error != EWOULDBLOCK)
                        goto out;

                mutex_enter(&stp->sd_lock);
                /*
                 * Check for a missed wakeup.
                 * Needed since strput did not hold sd_lock across
                 * the canputnext.
                 */
                if (bcanputnext(wqp, pri)) {
                        /* Try again */
                        mutex_exit(&stp->sd_lock);
                        continue;
                }
                TRACE_2(TR_FAC_STREAMS_FR, TR_STRPUTMSG_WAIT,
                    "strputmsg wait:stp %p waits pri %d", stp, pri);
                if (((error = strwaitq(stp, WRITEWAIT, (ssize_t)0, fmode, -1,
                    &done)) != 0) || done) {
                        mutex_exit(&stp->sd_lock);
                        TRACE_3(TR_FAC_STREAMS_FR, TR_STRPUTMSG_OUT,
                            "strputmsg out:q %p out %d error %d",
                            stp, 0, error);
                        return (error);
                }
                TRACE_1(TR_FAC_STREAMS_FR, TR_STRPUTMSG_WAKE,
                    "strputmsg wake:stp %p wakes", stp);
                if ((error = i_straccess(stp, JCWRITE)) != 0) {
                        mutex_exit(&stp->sd_lock);
                        return (error);
                }
                mutex_exit(&stp->sd_lock);
        }
out:
        /*
         * For historic reasons, applications expect EAGAIN
         * when data mblk could not be allocated. so change
         * ENOMEM back to EAGAIN
         */
        if (error == ENOMEM)
                error = EAGAIN;
        TRACE_3(TR_FAC_STREAMS_FR, TR_STRPUTMSG_OUT,
            "strputmsg out:stp %p out %d error %d", stp, 2, error);
        return (error);
}

/*
 * Put a message downstream.
 * Can send only an M_PROTO/M_PCPROTO by passing in a NULL uiop.
 * The fmode flag (NDELAY, NONBLOCK) is the or of the flags in the uio
 * and the fmode parameter.
 *
 * This routine handles the consolidation private flags:
 *      MSG_IGNERROR    Ignore any stream head error except STPLEX.
 *      MSG_HOLDSIG     Hold signals while waiting for data.
 *      MSG_IGNFLOW     Don't check streams flow control.
 *
 * NOTE: strputmsg and kstrputmsg have much of the logic in common.
 */
int
kstrputmsg(
        struct vnode *vp,
        mblk_t *mctl,
        struct uio *uiop,
        ssize_t msgsize,
        unsigned char pri,
        int flag,
        int fmode)
{
        struct stdata *stp;
        queue_t *wqp;
        ssize_t rmin, rmax;
        int error;

        ASSERT(vp->v_stream);
        stp = vp->v_stream;
        wqp = stp->sd_wrq;
        if (mctl == NULL)
                return (EINVAL);

        mutex_enter(&stp->sd_lock);

        if ((error = i_straccess(stp, JCWRITE)) != 0) {
                mutex_exit(&stp->sd_lock);
                freemsg(mctl);
                return (error);
        }

        if ((stp->sd_flag & STPLEX) || !(flag & MSG_IGNERROR)) {
                if (stp->sd_flag & (STWRERR|STRHUP|STPLEX)) {
                        error = strwriteable(stp, B_FALSE, B_TRUE);
                        if (error != 0) {
                                mutex_exit(&stp->sd_lock);
                                freemsg(mctl);
                                return (error);
                        }
                }
        }

        mutex_exit(&stp->sd_lock);

        /*
         * Check for legal flag value.
         */
        switch (flag & (MSG_HIPRI|MSG_BAND|MSG_ANY)) {
        case MSG_HIPRI:
                if (pri != 0) {
                        freemsg(mctl);
                        return (EINVAL);
                }
                break;
        case MSG_BAND:
                break;
        default:
                freemsg(mctl);
                return (EINVAL);
        }

        TRACE_1(TR_FAC_STREAMS_FR, TR_KSTRPUTMSG_IN,
            "kstrputmsg in:stp %p", stp);

        /* get these values from those cached in the stream head */
        rmin = stp->sd_qn_minpsz;
        rmax = stp->sd_qn_maxpsz;

        /*
         * Make sure ctl and data sizes together fall within the
         * limits of the max and min receive packet sizes and do
         * not exceed system limit.
         */
        ASSERT((rmax >= 0) || (rmax == INFPSZ));
        if (rmax == 0) {
                freemsg(mctl);
                return (ERANGE);
        }
        /*
         * Use the MAXIMUM of sd_maxblk and q_maxpsz.
         * Needed to prevent partial failures in the strmakedata loop.
         */
        if (stp->sd_maxblk != INFPSZ && rmax != INFPSZ && rmax < stp->sd_maxblk)
                rmax = stp->sd_maxblk;

        if (uiop == NULL) {
                msgsize = -1;
                rmin = -1;      /* no range check for NULL data part */
        } else {
                /* Use uio flags as well as the fmode parameter flags */
                fmode |= uiop->uio_fmode;

                if ((msgsize < rmin) ||
                    ((msgsize > rmax) && (rmax != INFPSZ))) {
                        freemsg(mctl);
                        return (ERANGE);
                }
        }

        /* Ignore flow control in strput for HIPRI */
        if (flag & MSG_HIPRI)
                flag |= MSG_IGNFLOW;

        for (;;) {
                int done = 0;
                int waitflag;
                mblk_t *mp;

                /*
                 * strput will always free the ctl mblk - even when strput
                 * fails. If MSG_IGNFLOW is set then any error returned
                 * will cause us to break the loop, so we don't need a copy
                 * of the message. If MSG_IGNFLOW is not set, then we can
                 * get hit by flow control and be forced to try again. In
                 * this case we need to have a copy of the message. We
                 * do this using copymsg since the message may get modified
                 * by something below us.
                 *
                 * We've observed that many TPI providers do not check db_ref
                 * on the control messages but blindly reuse them for the
                 * T_OK_ACK/T_ERROR_ACK. Thus using copymsg is more
                 * friendly to such providers than using dupmsg. Also, note
                 * that sockfs uses MSG_IGNFLOW for all TPI control messages.
                 * Only data messages are subject to flow control, hence
                 * subject to this copymsg.
                 */
                if (flag & MSG_IGNFLOW) {
                        mp = mctl;
                        mctl = NULL;
                } else {
                        do {
                                /*
                                 * If a message has a free pointer, the message
                                 * must be dupmsg to maintain this pointer.
                                 * Code using this facility must be sure
                                 * that modules below will not change the
                                 * contents of the dblk without checking db_ref
                                 * first. If db_ref is > 1, then the module
                                 * needs to do a copymsg first. Otherwise,
                                 * the contents of the dblk may become
                                 * inconsistent because the freesmg/freeb below
                                 * may end up calling atomic_add_32_nv.
                                 * The atomic_add_32_nv in freeb (accessing
                                 * all of db_ref, db_type, db_flags, and
                                 * db_struioflag) does not prevent other threads
                                 * from concurrently trying to modify e.g.
                                 * db_type.
                                 */
                                if (mctl->b_datap->db_frtnp != NULL)
                                        mp = dupmsg(mctl);
                                else
                                        mp = copymsg(mctl);

                                if (mp != NULL)
                                        break;

                                error = strwaitbuf(msgdsize(mctl), BPRI_MED);
                                if (error) {
                                        freemsg(mctl);
                                        return (error);
                                }
                        } while (mp == NULL);
                }
                /*
                 * Verify that all of msgsize can be transferred by
                 * strput.
                 */
                ASSERT(stp->sd_maxblk == INFPSZ || stp->sd_maxblk >= msgsize);
                error = strput(stp, mp, uiop, &msgsize, 0, pri, flag);
                if (error == 0)
                        break;

                if (error != EWOULDBLOCK)
                        goto out;

                /*
                 * IF MSG_IGNFLOW is set we should have broken out of loop
                 * above.
                 */
                ASSERT(!(flag & MSG_IGNFLOW));
                mutex_enter(&stp->sd_lock);
                /*
                 * Check for a missed wakeup.
                 * Needed since strput did not hold sd_lock across
                 * the canputnext.
                 */
                if (bcanputnext(wqp, pri)) {
                        /* Try again */
                        mutex_exit(&stp->sd_lock);
                        continue;
                }
                TRACE_2(TR_FAC_STREAMS_FR, TR_KSTRPUTMSG_WAIT,
                    "kstrputmsg wait:stp %p waits pri %d", stp, pri);

                waitflag = WRITEWAIT;
                if (flag & (MSG_HOLDSIG|MSG_IGNERROR)) {
                        if (flag & MSG_HOLDSIG)
                                waitflag |= STR_NOSIG;
                        if (flag & MSG_IGNERROR)
                                waitflag |= STR_NOERROR;
                }
                if (((error = strwaitq(stp, waitflag,
                    (ssize_t)0, fmode, -1, &done)) != 0) || done) {
                        mutex_exit(&stp->sd_lock);
                        TRACE_3(TR_FAC_STREAMS_FR, TR_KSTRPUTMSG_OUT,
                            "kstrputmsg out:stp %p out %d error %d",
                            stp, 0, error);
                        freemsg(mctl);
                        return (error);
                }
                TRACE_1(TR_FAC_STREAMS_FR, TR_KSTRPUTMSG_WAKE,
                    "kstrputmsg wake:stp %p wakes", stp);
                if ((error = i_straccess(stp, JCWRITE)) != 0) {
                        mutex_exit(&stp->sd_lock);
                        freemsg(mctl);
                        return (error);
                }
                mutex_exit(&stp->sd_lock);
        }
out:
        freemsg(mctl);
        /*
         * For historic reasons, applications expect EAGAIN
         * when data mblk could not be allocated. so change
         * ENOMEM back to EAGAIN
         */
        if (error == ENOMEM)
                error = EAGAIN;
        TRACE_3(TR_FAC_STREAMS_FR, TR_KSTRPUTMSG_OUT,
            "kstrputmsg out:stp %p out %d error %d", stp, 2, error);
        return (error);
}

/*
 * Determines whether the necessary conditions are set on a stream
 * for it to be readable, writeable, or have exceptions.
 *
 * strpoll handles the consolidation private events:
 *      POLLNOERR       Do not return POLLERR even if there are stream
 *                      head errors.
 *                      Used by sockfs.
 *      POLLRDDATA      Do not return POLLIN unless at least one message on
 *                      the queue contains one or more M_DATA mblks. Thus
 *                      when this flag is set a queue with only
 *                      M_PROTO/M_PCPROTO mblks does not return POLLIN.
 *                      Used by sockfs to ignore T_EXDATA_IND messages.
 *
 * Note: POLLRDDATA assumes that synch streams only return messages with
 * an M_DATA attached (i.e. not messages consisting of only
 * an M_PROTO/M_PCPROTO part).
 */
int
strpoll(struct stdata *stp, short events_arg, int anyyet, short *reventsp,
    struct pollhead **phpp)
{
        int events = (ushort_t)events_arg;
        int retevents = 0;
        mblk_t *mp;
        qband_t *qbp;
        long sd_flags = stp->sd_flag;
        int headlocked = 0;

        /*
         * For performance, a single 'if' tests for most possible edge
         * conditions in one shot
         */
        if (sd_flags & (STPLEX | STRDERR | STWRERR)) {
                if (sd_flags & STPLEX) {
                        *reventsp = POLLNVAL;
                        return (EINVAL);
                }
                if (((events & (POLLIN | POLLRDNORM | POLLRDBAND | POLLPRI)) &&
                    (sd_flags & STRDERR)) ||
                    ((events & (POLLOUT | POLLWRNORM | POLLWRBAND)) &&
                    (sd_flags & STWRERR))) {
                        if (!(events & POLLNOERR)) {
                                *reventsp = POLLERR;
                                return (0);
                        }
                }
        }
        if (sd_flags & STRHUP) {
                retevents |= POLLHUP;
        } else if (events & (POLLWRNORM | POLLWRBAND)) {
                queue_t *tq;
                queue_t *qp = stp->sd_wrq;

                claimstr(qp);
                /* Find next module forward that has a service procedure */
                tq = qp->q_next->q_nfsrv;
                ASSERT(tq != NULL);

                if (polllock(&stp->sd_pollist, QLOCK(tq)) != 0) {
                        releasestr(qp);
                        *reventsp = POLLNVAL;
                        return (0);
                }
                if (events & POLLWRNORM) {
                        queue_t *sqp;

                        if (tq->q_flag & QFULL)
                                /* ensure backq svc procedure runs */
                                tq->q_flag |= QWANTW;
                        else if ((sqp = stp->sd_struiowrq) != NULL) {
                                /* Check sync stream barrier write q */
                                mutex_exit(QLOCK(tq));
                                if (polllock(&stp->sd_pollist,
                                    QLOCK(sqp)) != 0) {
                                        releasestr(qp);
                                        *reventsp = POLLNVAL;
                                        return (0);
                                }
                                if (sqp->q_flag & QFULL)
                                        /* ensure pollwakeup() is done */
                                        sqp->q_flag |= QWANTWSYNC;
                                else
                                        retevents |= POLLOUT;
                                /* More write events to process ??? */
                                if (! (events & POLLWRBAND)) {
                                        mutex_exit(QLOCK(sqp));
                                        releasestr(qp);
                                        goto chkrd;
                                }
                                mutex_exit(QLOCK(sqp));
                                if (polllock(&stp->sd_pollist,
                                    QLOCK(tq)) != 0) {
                                        releasestr(qp);
                                        *reventsp = POLLNVAL;
                                        return (0);
                                }
                        } else
                                retevents |= POLLOUT;
                }
                if (events & POLLWRBAND) {
                        qbp = tq->q_bandp;
                        if (qbp) {
                                while (qbp) {
                                        if (qbp->qb_flag & QB_FULL)
                                                qbp->qb_flag |= QB_WANTW;
                                        else
                                                retevents |= POLLWRBAND;
                                        qbp = qbp->qb_next;
                                }
                        } else {
                                retevents |= POLLWRBAND;
                        }
                }
                mutex_exit(QLOCK(tq));
                releasestr(qp);
        }
chkrd:
        if (sd_flags & STRPRI) {
                retevents |= (events & POLLPRI);
        } else if (events & (POLLRDNORM | POLLRDBAND | POLLIN)) {
                queue_t *qp = _RD(stp->sd_wrq);
                int normevents = (events & (POLLIN | POLLRDNORM));

                /*
                 * Note: Need to do polllock() here since ps_lock may be
                 * held. See bug 4191544.
                 */
                if (polllock(&stp->sd_pollist, &stp->sd_lock) != 0) {
                        *reventsp = POLLNVAL;
                        return (0);
                }
                headlocked = 1;
                mp = qp->q_first;
                while (mp) {
                        /*
                         * For POLLRDDATA we scan b_cont and b_next until we
                         * find an M_DATA.
                         */
                        if ((events & POLLRDDATA) &&
                            mp->b_datap->db_type != M_DATA) {
                                mblk_t *nmp = mp->b_cont;

                                while (nmp != NULL &&
                                    nmp->b_datap->db_type != M_DATA)
                                        nmp = nmp->b_cont;
                                if (nmp == NULL) {
                                        mp = mp->b_next;
                                        continue;
                                }
                        }
                        if (mp->b_band == 0)
                                retevents |= normevents;
                        else
                                retevents |= (events & (POLLIN | POLLRDBAND));
                        break;
                }
                if (!(retevents & normevents) && (stp->sd_wakeq & RSLEEP)) {
                        /*
                         * Sync stream barrier read queue has data.
                         */
                        retevents |= normevents;
                }
                /* Treat eof as normal data */
                if (sd_flags & STREOF)
                        retevents |= normevents;
        }

        /*
         * Pass back a pollhead if no events are pending or if edge-triggering
         * has been configured on this resource.
         */
        if ((retevents == 0 && !anyyet) || (events & POLLET)) {
                *phpp = &stp->sd_pollist;
                if (headlocked == 0) {
                        if (polllock(&stp->sd_pollist, &stp->sd_lock) != 0) {
                                *reventsp = POLLNVAL;
                                return (0);
                        }
                        headlocked = 1;
                }
                stp->sd_rput_opt |= SR_POLLIN;
        }

        *reventsp = (short)retevents;
        if (headlocked)
                mutex_exit(&stp->sd_lock);
        return (0);
}

/*
 * The purpose of putback() is to assure sleeping polls/reads
 * are awakened when there are no new messages arriving at the,
 * stream head, and a message is placed back on the read queue.
 *
 * sd_lock must be held when messages are placed back on stream
 * head.  (getq() holds sd_lock when it removes messages from
 * the queue)
 */

static void
putback(struct stdata *stp, queue_t *q, mblk_t *bp, int band)
{
        mblk_t  *qfirst;
        ASSERT(MUTEX_HELD(&stp->sd_lock));

        /*
         * As a result of lock-step ordering around q_lock and sd_lock,
         * it's possible for function calls like putnext() and
         * canputnext() to get an inaccurate picture of how much
         * data is really being processed at the stream head.
         * We only consolidate with existing messages on the queue
         * if the length of the message we want to put back is smaller
         * than the queue hiwater mark.
         */
        if ((stp->sd_rput_opt & SR_CONSOL_DATA) &&
            (DB_TYPE(bp) == M_DATA) && ((qfirst = q->q_first) != NULL) &&
            (DB_TYPE(qfirst) == M_DATA) &&
            ((qfirst->b_flag & (MSGMARK|MSGDELIM)) == 0) &&
            ((bp->b_flag & (MSGMARK|MSGDELIM|MSGMARKNEXT)) == 0) &&
            (mp_cont_len(bp, NULL) < q->q_hiwat)) {
                /*
                 * We use the same logic as defined in strrput()
                 * but in reverse as we are putting back onto the
                 * queue and want to retain byte ordering.
                 * Consolidate M_DATA messages with M_DATA ONLY.
                 * strrput() allows the consolidation of M_DATA onto
                 * M_PROTO | M_PCPROTO but not the other way round.
                 *
                 * The consolidation does not take place if the message
                 * we are returning to the queue is marked with either
                 * of the marks or the delim flag or if q_first
                 * is marked with MSGMARK. The MSGMARK check is needed to
                 * handle the odd semantics of MSGMARK where essentially
                 * the whole message is to be treated as marked.
                 * Carry any MSGMARKNEXT and MSGNOTMARKNEXT from q_first
                 * to the front of the b_cont chain.
                 */
                rmvq_noenab(q, qfirst);

                /*
                 * The first message in the b_cont list
                 * tracks MSGMARKNEXT and MSGNOTMARKNEXT.
                 * We need to handle the case where we
                 * are appending:
                 *
                 * 1) a MSGMARKNEXT to a MSGNOTMARKNEXT.
                 * 2) a MSGMARKNEXT to a plain message.
                 * 3) a MSGNOTMARKNEXT to a plain message
                 * 4) a MSGNOTMARKNEXT to a MSGNOTMARKNEXT
                 *    message.
                 *
                 * Thus we never append a MSGMARKNEXT or
                 * MSGNOTMARKNEXT to a MSGMARKNEXT message.
                 */
                if (qfirst->b_flag & MSGMARKNEXT) {
                        bp->b_flag |= MSGMARKNEXT;
                        bp->b_flag &= ~MSGNOTMARKNEXT;
                        qfirst->b_flag &= ~MSGMARKNEXT;
                } else if (qfirst->b_flag & MSGNOTMARKNEXT) {
                        bp->b_flag |= MSGNOTMARKNEXT;
                        qfirst->b_flag &= ~MSGNOTMARKNEXT;
                }

                linkb(bp, qfirst);
        }
        (void) putbq(q, bp);

        /*
         * A message may have come in when the sd_lock was dropped in the
         * calling routine. If this is the case and STR*ATMARK info was
         * received, need to move that from the stream head to the q_last
         * so that SIOCATMARK can return the proper value.
         */
        if (stp->sd_flag & (STRATMARK | STRNOTATMARK)) {
                unsigned short *flagp = &q->q_last->b_flag;
                uint_t b_flag = (uint_t)*flagp;

                if (stp->sd_flag & STRATMARK) {
                        b_flag &= ~MSGNOTMARKNEXT;
                        b_flag |= MSGMARKNEXT;
                        stp->sd_flag &= ~STRATMARK;
                } else {
                        b_flag &= ~MSGMARKNEXT;
                        b_flag |= MSGNOTMARKNEXT;
                        stp->sd_flag &= ~STRNOTATMARK;
                }
                *flagp = (unsigned short) b_flag;
        }

#ifdef  DEBUG
        /*
         * Make sure that the flags are not messed up.
         */
        {
                mblk_t *mp;
                mp = q->q_last;
                while (mp != NULL) {
                        ASSERT((mp->b_flag & (MSGMARKNEXT|MSGNOTMARKNEXT)) !=
                            (MSGMARKNEXT|MSGNOTMARKNEXT));
                        mp = mp->b_cont;
                }
        }
#endif
        if (q->q_first == bp) {
                short pollevents;

                if (stp->sd_flag & RSLEEP) {
                        stp->sd_flag &= ~RSLEEP;
                        cv_broadcast(&q->q_wait);
                }
                if (stp->sd_flag & STRPRI) {
                        pollevents = POLLPRI;
                } else {
                        if (band == 0) {
                                if (!(stp->sd_rput_opt & SR_POLLIN))
                                        return;
                                stp->sd_rput_opt &= ~SR_POLLIN;
                                pollevents = POLLIN | POLLRDNORM;
                        } else {
                                pollevents = POLLIN | POLLRDBAND;
                        }
                }
                mutex_exit(&stp->sd_lock);
                pollwakeup(&stp->sd_pollist, pollevents);
                mutex_enter(&stp->sd_lock);
        }
}

/*
 * Return the held vnode attached to the stream head of a
 * given queue
 * It is the responsibility of the calling routine to ensure
 * that the queue does not go away (e.g. pop).
 */
vnode_t *
strq2vp(queue_t *qp)
{
        vnode_t *vp;
        vp = STREAM(qp)->sd_vnode;
        ASSERT(vp != NULL);
        VN_HOLD(vp);
        return (vp);
}

/*
 * return the stream head write queue for the given vp
 * It is the responsibility of the calling routine to ensure
 * that the stream or vnode do not close.
 */
queue_t *
strvp2wq(vnode_t *vp)
{
        ASSERT(vp->v_stream != NULL);
        return (vp->v_stream->sd_wrq);
}

/*
 * pollwakeup stream head
 * It is the responsibility of the calling routine to ensure
 * that the stream or vnode do not close.
 */
void
strpollwakeup(vnode_t *vp, short event)
{
        ASSERT(vp->v_stream);
        pollwakeup(&vp->v_stream->sd_pollist, event);
}

/*
 * Mate the stream heads of two vnodes together. If the two vnodes are the
 * same, we just make the write-side point at the read-side -- otherwise,
 * we do a full mate.  Only works on vnodes associated with streams that are
 * still being built and thus have only a stream head.
 */
void
strmate(vnode_t *vp1, vnode_t *vp2)
{
        queue_t *wrq1 = strvp2wq(vp1);
        queue_t *wrq2 = strvp2wq(vp2);

        /*
         * Verify that there are no modules on the stream yet.  We also
         * rely on the stream head always having a service procedure to
         * avoid tweaking q_nfsrv.
         */
        ASSERT(wrq1->q_next == NULL && wrq2->q_next == NULL);
        ASSERT(wrq1->q_qinfo->qi_srvp != NULL);
        ASSERT(wrq2->q_qinfo->qi_srvp != NULL);

        /*
         * If the queues are the same, just twist; otherwise do a full mate.
         */
        if (wrq1 == wrq2) {
                wrq1->q_next = _RD(wrq1);
        } else {
                wrq1->q_next = _RD(wrq2);
                wrq2->q_next = _RD(wrq1);
                STREAM(wrq1)->sd_mate = STREAM(wrq2);
                STREAM(wrq1)->sd_flag |= STRMATE;
                STREAM(wrq2)->sd_mate = STREAM(wrq1);
                STREAM(wrq2)->sd_flag |= STRMATE;
        }
}

/*
 * XXX will go away when console is correctly fixed.
 * Clean up the console PIDS, from previous I_SETSIG,
 * called only for cnopen which never calls strclean().
 */
void
str_cn_clean(struct vnode *vp)
{
        strsig_t *ssp, *pssp, *tssp;
        struct stdata *stp;
        struct pid  *pidp;
        int update = 0;

        ASSERT(vp->v_stream);
        stp = vp->v_stream;
        pssp = NULL;
        mutex_enter(&stp->sd_lock);
        ssp = stp->sd_siglist;
        while (ssp) {
                mutex_enter(&pidlock);
                pidp = ssp->ss_pidp;
                /*
                 * Get rid of PID if the proc is gone.
                 */
                if (pidp->pid_prinactive) {
                        tssp = ssp->ss_next;
                        if (pssp)
                                pssp->ss_next = tssp;
                        else
                                stp->sd_siglist = tssp;
                        ASSERT(pidp->pid_ref <= 1);
                        PID_RELE(ssp->ss_pidp);
                        mutex_exit(&pidlock);
                        kmem_free(ssp, sizeof (strsig_t));
                        update = 1;
                        ssp = tssp;
                        continue;
                } else
                        mutex_exit(&pidlock);
                pssp = ssp;
                ssp = ssp->ss_next;
        }
        if (update) {
                stp->sd_sigflags = 0;
                for (ssp = stp->sd_siglist; ssp; ssp = ssp->ss_next)
                        stp->sd_sigflags |= ssp->ss_events;
        }
        mutex_exit(&stp->sd_lock);
}

/*
 * Return B_TRUE if there is data in the message, B_FALSE otherwise.
 */
static boolean_t
msghasdata(mblk_t *bp)
{
        for (; bp; bp = bp->b_cont)
                if (bp->b_datap->db_type == M_DATA) {
                        ASSERT(bp->b_wptr >= bp->b_rptr);
                        if (bp->b_wptr > bp->b_rptr)
                                return (B_TRUE);
                }
        return (B_FALSE);
}