Add precautions so that threads won't race to exit1() and get stuck there.

[dragonfly.git] / sys / kern / uipc_socket2.c

/*
 * Copyright (c) 2005 Jeffrey M. Hsu.  All rights reserved.
 * Copyright (c) 1982, 1986, 1988, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)uipc_socket2.c      8.1 (Berkeley) 6/10/93
 * $FreeBSD: src/sys/kern/uipc_socket2.c,v 1.55.2.17 2002/08/31 19:04:55 dwmalone Exp $
 * $DragonFly: src/sys/kern/uipc_socket2.c,v 1.26 2006/12/23 23:47:54 swildner Exp $
 */

#include "opt_param.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/domain.h>
#include <sys/file.h>   /* for maxfiles */
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/resourcevar.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/aio.h> /* for aio_swake proto */
#include <sys/event.h>

#include <sys/thread2.h>
#include <sys/msgport2.h>

int     maxsockets;

/*
 * Primitive routines for operating on sockets and socket buffers
 */

u_long  sb_max = SB_MAX;
u_long  sb_max_adj =
    SB_MAX * MCLBYTES / (MSIZE + MCLBYTES); /* adjusted sb_max */

static  u_long sb_efficiency = 8;       /* parameter for sbreserve() */

/*
 * Procedures to manipulate state flags of socket
 * and do appropriate wakeups.  Normal sequence from the
 * active (originating) side is that soisconnecting() is
 * called during processing of connect() call,
 * resulting in an eventual call to soisconnected() if/when the
 * connection is established.  When the connection is torn down
 * soisdisconnecting() is called during processing of disconnect() call,
 * and soisdisconnected() is called when the connection to the peer
 * is totally severed.  The semantics of these routines are such that
 * connectionless protocols can call soisconnected() and soisdisconnected()
 * only, bypassing the in-progress calls when setting up a ``connection''
 * takes no time.
 *
 * From the passive side, a socket is created with
 * two queues of sockets: so_incomp for connections in progress
 * and so_comp for connections already made and awaiting user acceptance.
 * As a protocol is preparing incoming connections, it creates a socket
 * structure queued on so_incomp by calling sonewconn().  When the connection
 * is established, soisconnected() is called, and transfers the
 * socket structure to so_comp, making it available to accept().
 *
 * If a socket is closed with sockets on either
 * so_incomp or so_comp, these sockets are dropped.
 *
 * If higher level protocols are implemented in
 * the kernel, the wakeups done here will sometimes
 * cause software-interrupt process scheduling.
 */

void
soisconnecting(struct socket *so)
{

        so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= SS_ISCONNECTING;
}

void
soisconnected(struct socket *so)
{
        struct socket *head = so->so_head;

        so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
        so->so_state |= SS_ISCONNECTED;
        if (head && (so->so_state & SS_INCOMP)) {
                if ((so->so_options & SO_ACCEPTFILTER) != 0) {
                        so->so_upcall = head->so_accf->so_accept_filter->accf_callback;
                        so->so_upcallarg = head->so_accf->so_accept_filter_arg;
                        so->so_rcv.sb_flags |= SB_UPCALL;
                        so->so_options &= ~SO_ACCEPTFILTER;
                        so->so_upcall(so, so->so_upcallarg, 0);
                        return;
                }
                TAILQ_REMOVE(&head->so_incomp, so, so_list);
                head->so_incqlen--;
                so->so_state &= ~SS_INCOMP;
                TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                head->so_qlen++;
                so->so_state |= SS_COMP;
                sorwakeup(head);
                wakeup_one(&head->so_timeo);
        } else {
                wakeup(&so->so_timeo);
                sorwakeup(so);
                sowwakeup(so);
        }
}

void
soisdisconnecting(struct socket *so)
{

        so->so_state &= ~SS_ISCONNECTING;
        so->so_state |= (SS_ISDISCONNECTING|SS_CANTRCVMORE|SS_CANTSENDMORE);
        wakeup((caddr_t)&so->so_timeo);
        sowwakeup(so);
        sorwakeup(so);
}

void
soisdisconnected(struct socket *so)
{

        so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);
        wakeup((caddr_t)&so->so_timeo);
        sbdrop(&so->so_snd, so->so_snd.sb_cc);
        sowwakeup(so);
        sorwakeup(so);
}

/*
 * When an attempt at a new connection is noted on a socket
 * which accepts connections, sonewconn is called.  If the
 * connection is possible (subject to space constraints, etc.)
 * then we allocate a new structure, propoerly linked into the
 * data structure of the original socket, and return this.
 * Connstatus may be 0, or SO_ISCONFIRMING, or SO_ISCONNECTED.
 */
struct socket *
sonewconn(struct socket *head, int connstatus)
{
        struct socket *so;
        struct pru_attach_info ai;

        if (head->so_qlen > 3 * head->so_qlimit / 2)
                return ((struct socket *)0);
        so = soalloc(1);
        if (so == NULL)
                return (NULL);
        if ((head->so_options & SO_ACCEPTFILTER) != 0)
                connstatus = 0;
        so->so_head = head;
        so->so_type = head->so_type;
        so->so_options = head->so_options &~ SO_ACCEPTCONN;
        so->so_linger = head->so_linger;
        so->so_state = head->so_state | SS_NOFDREF;
        so->so_proto = head->so_proto;
        so->so_timeo = head->so_timeo;
        so->so_cred = crhold(head->so_cred);
        ai.sb_rlimit = NULL;
        ai.p_ucred = NULL;
        ai.fd_rdir = NULL;              /* jail code cruft XXX JH */
        if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat, NULL) ||
            /* Directly call function since we're already at protocol level. */
            (*so->so_proto->pr_usrreqs->pru_attach)(so, 0, &ai)) {
                sodealloc(so);
                return ((struct socket *)0);
        }

        if (connstatus) {
                TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                so->so_state |= SS_COMP;
                head->so_qlen++;
        } else {
                if (head->so_incqlen > head->so_qlimit) {
                        struct socket *sp;
                        sp = TAILQ_FIRST(&head->so_incomp);
                        (void) soabort(sp);
                }
                TAILQ_INSERT_TAIL(&head->so_incomp, so, so_list);
                so->so_state |= SS_INCOMP;
                head->so_incqlen++;
        }
        if (connstatus) {
                sorwakeup(head);
                wakeup((caddr_t)&head->so_timeo);
                so->so_state |= connstatus;
        }
        return (so);
}

/*
 * Socantsendmore indicates that no more data will be sent on the
 * socket; it would normally be applied to a socket when the user
 * informs the system that no more data is to be sent, by the protocol
 * code (in case PRU_SHUTDOWN).  Socantrcvmore indicates that no more data
 * will be received, and will normally be applied to the socket by a
 * protocol when it detects that the peer will send no more data.
 * Data queued for reading in the socket may yet be read.
 */

void
socantsendmore(struct socket *so)
{

        so->so_state |= SS_CANTSENDMORE;
        sowwakeup(so);
}

void
socantrcvmore(struct socket *so)
{

        so->so_state |= SS_CANTRCVMORE;
        sorwakeup(so);
}

/*
 * Wait for data to arrive at/drain from a socket buffer.
 */
int
sbwait(struct sockbuf *sb)
{

        sb->sb_flags |= SB_WAIT;
        return (tsleep((caddr_t)&sb->sb_cc,
                        ((sb->sb_flags & SB_NOINTR) ? 0 : PCATCH),
                        "sbwait",
                        sb->sb_timeo));
}

/*
 * Lock a sockbuf already known to be locked;
 * return any error returned from sleep (EINTR).
 */
int
sb_lock(struct sockbuf *sb)
{
        int error;

        while (sb->sb_flags & SB_LOCK) {
                sb->sb_flags |= SB_WANT;
                error = tsleep((caddr_t)&sb->sb_flags,
                            ((sb->sb_flags & SB_NOINTR) ? 0 : PCATCH),
                            "sblock", 0);
                if (error)
                        return (error);
        }
        sb->sb_flags |= SB_LOCK;
        return (0);
}

/*
 * Wakeup processes waiting on a socket buffer.  Do asynchronous notification
 * via SIGIO if the socket has the SS_ASYNC flag set.
 */
void
sowakeup(struct socket *so, struct sockbuf *sb)
{
        struct selinfo *selinfo = &sb->sb_sel;

        selwakeup(selinfo);
        sb->sb_flags &= ~SB_SEL;
        if (sb->sb_flags & SB_WAIT) {
                sb->sb_flags &= ~SB_WAIT;
                wakeup((caddr_t)&sb->sb_cc);
        }
        if ((so->so_state & SS_ASYNC) && so->so_sigio != NULL)
                pgsigio(so->so_sigio, SIGIO, 0);
        if (sb->sb_flags & SB_UPCALL)
                (*so->so_upcall)(so, so->so_upcallarg, MB_DONTWAIT);
        if (sb->sb_flags & SB_AIO)
                aio_swake(so, sb);
        KNOTE(&selinfo->si_note, 0);
        if (sb->sb_flags & SB_MEVENT) {
                struct netmsg_so_notify *msg, *nmsg;

                TAILQ_FOREACH_MUTABLE(msg, &selinfo->si_mlist, nm_list, nmsg) {
                        if (msg->nm_predicate((struct netmsg *)msg)) {
                                TAILQ_REMOVE(&selinfo->si_mlist, msg, nm_list);
                                lwkt_replymsg(&msg->nm_lmsg, 
                                                msg->nm_lmsg.ms_error);
                        }
                }
                if (TAILQ_EMPTY(&sb->sb_sel.si_mlist))
                        sb->sb_flags &= ~SB_MEVENT;
        }
}

/*
 * Socket buffer (struct sockbuf) utility routines.
 *
 * Each socket contains two socket buffers: one for sending data and
 * one for receiving data.  Each buffer contains a queue of mbufs,
 * information about the number of mbufs and amount of data in the
 * queue, and other fields allowing select() statements and notification
 * on data availability to be implemented.
 *
 * Data stored in a socket buffer is maintained as a list of records.
 * Each record is a list of mbufs chained together with the m_next
 * field.  Records are chained together with the m_nextpkt field. The upper
 * level routine soreceive() expects the following conventions to be
 * observed when placing information in the receive buffer:
 *
 * 1. If the protocol requires each message be preceded by the sender's
 *    name, then a record containing that name must be present before
 *    any associated data (mbuf's must be of type MT_SONAME).
 * 2. If the protocol supports the exchange of ``access rights'' (really
 *    just additional data associated with the message), and there are
 *    ``rights'' to be received, then a record containing this data
 *    should be present (mbuf's must be of type MT_RIGHTS).
 * 3. If a name or rights record exists, then it must be followed by
 *    a data record, perhaps of zero length.
 *
 * Before using a new socket structure it is first necessary to reserve
 * buffer space to the socket, by calling sbreserve().  This should commit
 * some of the available buffer space in the system buffer pool for the
 * socket (currently, it does nothing but enforce limits).  The space
 * should be released by calling sbrelease() when the socket is destroyed.
 */

int
soreserve(struct socket *so, u_long sndcc, u_long rcvcc, struct rlimit *rl)
{
        if (sbreserve(&so->so_snd, sndcc, so, rl) == 0)
                goto bad;
        if (sbreserve(&so->so_rcv, rcvcc, so, rl) == 0)
                goto bad2;
        if (so->so_rcv.sb_lowat == 0)
                so->so_rcv.sb_lowat = 1;
        if (so->so_snd.sb_lowat == 0)
                so->so_snd.sb_lowat = MCLBYTES;
        if (so->so_snd.sb_lowat > so->so_snd.sb_hiwat)
                so->so_snd.sb_lowat = so->so_snd.sb_hiwat;
        return (0);
bad2:
        sbrelease(&so->so_snd, so);
bad:
        return (ENOBUFS);
}

static int
sysctl_handle_sb_max(SYSCTL_HANDLER_ARGS)
{
        int error = 0;
        u_long old_sb_max = sb_max;

        error = SYSCTL_OUT(req, arg1, sizeof(int));
        if (error || !req->newptr)
                return (error);
        error = SYSCTL_IN(req, arg1, sizeof(int));
        if (error)
                return (error);
        if (sb_max < MSIZE + MCLBYTES) {
                sb_max = old_sb_max;
                return (EINVAL);
        }
        sb_max_adj = (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES);
        return (0);
}
        
/*
 * Allot mbufs to a sockbuf.
 * Attempt to scale mbmax so that mbcnt doesn't become limiting
 * if buffering efficiency is near the normal case.
 */
int
sbreserve(struct sockbuf *sb, u_long cc, struct socket *so, struct rlimit *rl)
{

        /*
         * rl will only be NULL when we're in an interrupt (eg, in tcp_input)
         * or when called from netgraph (ie, ngd_attach)
         */
        if (cc > sb_max_adj)
                return (0);
        if (!chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, cc,
                       rl ? rl->rlim_cur : RLIM_INFINITY)) {
                return (0);
        }
        sb->sb_mbmax = min(cc * sb_efficiency, sb_max);
        if (sb->sb_lowat > sb->sb_hiwat)
                sb->sb_lowat = sb->sb_hiwat;
        return (1);
}

/*
 * Free mbufs held by a socket, and reserved mbuf space.
 */
void
sbrelease(struct sockbuf *sb, struct socket *so)
{

        sbflush(sb);
        (void)chgsbsize(so->so_cred->cr_uidinfo, &sb->sb_hiwat, 0,
            RLIM_INFINITY);
        sb->sb_mbmax = 0;
}

/*
 * Routines to add and remove
 * data from an mbuf queue.
 *
 * The routines sbappend() or sbappendrecord() are normally called to
 * append new mbufs to a socket buffer, after checking that adequate
 * space is available, comparing the function sbspace() with the amount
 * of data to be added.  sbappendrecord() differs from sbappend() in
 * that data supplied is treated as the beginning of a new record.
 * To place a sender's address, optional access rights, and data in a
 * socket receive buffer, sbappendaddr() should be used.  To place
 * access rights and data in a socket receive buffer, sbappendrights()
 * should be used.  In either case, the new data begins a new record.
 * Note that unlike sbappend() and sbappendrecord(), these routines check
 * for the caller that there will be enough space to store the data.
 * Each fails if there is not enough space, or if it cannot find mbufs
 * to store additional information in.
 *
 * Reliable protocols may use the socket send buffer to hold data
 * awaiting acknowledgement.  Data is normally copied from a socket
 * send buffer in a protocol with m_copy for output to a peer,
 * and then removing the data from the socket buffer with sbdrop()
 * or sbdroprecord() when the data is acknowledged by the peer.
 */

/*
 * Append mbuf chain m to the last record in the
 * socket buffer sb.  The additional space associated
 * the mbuf chain is recorded in sb.  Empty mbufs are
 * discarded and mbufs are compacted where possible.
 */
void
sbappend(struct sockbuf *sb, struct mbuf *m)
{
        struct mbuf *n;

        if (m) {
                n = sb->sb_mb;
                if (n) {
                        while (n->m_nextpkt)
                                n = n->m_nextpkt;
                        do {
                                if (n->m_flags & M_EOR) {
                                        /* XXXXXX!!!! */
                                        sbappendrecord(sb, m);
                                        return;
                                }
                        } while (n->m_next && (n = n->m_next));
                }
                sbcompress(sb, m, n);
        }
}

/*
 * sbappendstream() is an optimized form of sbappend() for protocols
 * such as TCP that only have one record in the socket buffer, are
 * not PR_ATOMIC, nor allow MT_CONTROL data.  A protocol that uses
 * sbappendstream() must use sbappendstream() exclusively.
 */
void
sbappendstream(struct sockbuf *sb, struct mbuf *m)
{
        KKASSERT(m->m_nextpkt == NULL);
        sbcompress(sb, m, sb->sb_lastmbuf);
}

#ifdef SOCKBUF_DEBUG

void
_sbcheck(struct sockbuf *sb)
{
        struct mbuf *m;
        struct mbuf *n = NULL;
        u_long len = 0, mbcnt = 0;

        for (m = sb->sb_mb; m; m = n) {
            n = m->m_nextpkt;
            if (n == NULL && sb->sb_lastrecord != m) {
                    kprintf("sockbuf %p mismatched lastrecord %p vs %p\n", sb, sb->sb_lastrecord, m);
                    panic("sbcheck1");
                
            }
            for (; m; m = m->m_next) {
                len += m->m_len;
                mbcnt += MSIZE;
                if (m->m_flags & M_EXT) /*XXX*/ /* pretty sure this is bogus */
                        mbcnt += m->m_ext.ext_size;
                if (n == NULL && m->m_next == NULL) {
                        if (sb->sb_lastmbuf != m) {
                                kprintf("sockbuf %p mismatched lastmbuf %p vs %p\n", sb, sb->sb_lastmbuf, m);
                                panic("sbcheck2");
                        }
                }
            }
        }
        if (sb->sb_mb == NULL) {
            if (sb->sb_lastrecord != NULL) {
                kprintf("sockbuf %p is empty, lastrecord not NULL: %p\n",
                        sb, sb->sb_lastrecord);
                panic("sbcheck3");
            }
            if (sb->sb_lastmbuf != NULL) {
                kprintf("sockbuf %p is empty, lastmbuf not NULL: %p\n",
                        sb, sb->sb_lastmbuf);
                panic("sbcheck4");
            }
        }
        if (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
                kprintf("sockbuf %p cc %ld != %ld || mbcnt %ld != %ld\n",
                    sb, len, sb->sb_cc, mbcnt, sb->sb_mbcnt);
                panic("sbcheck5");
        }
}

#endif

/*
 * Same as sbappend(), except the mbuf chain begins a new record.
 */
void
sbappendrecord(struct sockbuf *sb, struct mbuf *m0)
{
        struct mbuf *firstmbuf;
        struct mbuf *secondmbuf;

        if (m0 == NULL)
                return;

        sbcheck(sb);

        /*
         * Break the first mbuf off from the rest of the mbuf chain.
         */
        firstmbuf = m0;
        secondmbuf = m0->m_next;
        m0->m_next = NULL;

        /*
         * Insert the first mbuf of the m0 mbuf chain as the last record of
         * the sockbuf.  Note this permits zero length records!  Keep the
         * sockbuf state consistent.
         */
        if (sb->sb_mb == NULL)
                sb->sb_mb = firstmbuf;
        else
                sb->sb_lastrecord->m_nextpkt = firstmbuf;
        sb->sb_lastrecord = firstmbuf;  /* update hint for new last record */
        sb->sb_lastmbuf = firstmbuf;    /* update hint for new last mbuf */

        if ((firstmbuf->m_flags & M_EOR) && (secondmbuf != NULL)) {
                /* propagate the EOR flag */
                firstmbuf->m_flags &= ~M_EOR;
                secondmbuf->m_flags |= M_EOR;
        }

        /*
         * The succeeding call to sbcompress() omits accounting for
         * the first mbuf, so do it here.
         */
        sballoc(sb, firstmbuf);

        /* Compact the rest of the mbuf chain in after the first mbuf. */
        sbcompress(sb, secondmbuf, firstmbuf);
}

#if 0
/*
 * As above except that OOB data is inserted at the beginning of the sockbuf,
 * but after any other OOB data.
 */
void
sbinsertoob(struct sockbuf *sb, struct mbuf *m0)
{
        struct mbuf *m;
        struct mbuf **mp;

        if (m0 == NULL)
                return;
        for (mp = &sb->sb_mb; *mp ; mp = &((*mp)->m_nextpkt)) {
            m = *mp;
            again:
                switch (m->m_type) {

                case MT_OOBDATA:
                        continue;               /* WANT next train */

                case MT_CONTROL:
                        m = m->m_next;
                        if (m)
                                goto again;     /* inspect THIS train further */
                }
                break;
        }
        /*
         * Put the first mbuf on the queue.
         * Note this permits zero length records.
         */
        sballoc(sb, m0);
        m0->m_nextpkt = *mp;
        *mp = m0;
        if (m0->m_nextpkt == NULL)
                sb->sb_lastrecord = m0;

        m = m0->m_next;
        m0->m_next = NULL;
        if (m && (m0->m_flags & M_EOR)) {
                m0->m_flags &= ~M_EOR;
                m->m_flags |= M_EOR;
        }
        sbcompress(sb, m, m0);
}
#endif

/*
 * Append address and data, and optionally, control (ancillary) data
 * to the receive queue of a socket.  If present,
 * m0 must include a packet header with total length.
 * Returns 0 if no space in sockbuf or insufficient mbufs.
 */
int
sbappendaddr(struct sockbuf *sb, const struct sockaddr *asa, struct mbuf *m0,
             struct mbuf *control)
{
        struct mbuf *m, *n;
        int space = asa->sa_len;

        if (m0 && (m0->m_flags & M_PKTHDR) == 0)
                panic("sbappendaddr");
        sbcheck(sb);

        if (m0)
                space += m0->m_pkthdr.len;
        for (n = control; n; n = n->m_next) {
                space += n->m_len;
                if (n->m_next == 0)     /* keep pointer to last control buf */
                        break;
        }
        if (space > sbspace(sb))
                return (0);
        if (asa->sa_len > MLEN)
                return (0);
        MGET(m, MB_DONTWAIT, MT_SONAME);
        if (m == NULL)
                return (0);
        KKASSERT(m->m_nextpkt == NULL);
        m->m_len = asa->sa_len;
        bcopy(asa, mtod(m, caddr_t), asa->sa_len);
        if (n)
                n->m_next = m0;         /* concatenate data to control */
        else
                control = m0;
        m->m_next = control;
        for (n = m; n; n = n->m_next)
                sballoc(sb, n);

        if (sb->sb_mb == NULL)
                sb->sb_mb = m;
        else
                sb->sb_lastrecord->m_nextpkt = m;
        sb->sb_lastrecord = m;
        while (m->m_next)
                m = m->m_next;
        sb->sb_lastmbuf = m;

        return (1);
}

/*
 * Append control information followed by data.
 * control must be non-null.
 */
int
sbappendcontrol(struct sockbuf *sb, struct mbuf *m0, struct mbuf *control)
{
        struct mbuf *n;
        u_int length, cmbcnt, m0mbcnt;

        KASSERT(control != NULL, ("sbappendcontrol"));
        KKASSERT(control->m_nextpkt == NULL);
        sbcheck(sb);

        length = m_countm(control, &n, &cmbcnt) + m_countm(m0, NULL, &m0mbcnt);
        if (length > sbspace(sb))
                return (0);

        n->m_next = m0;                 /* concatenate data to control */

        if (sb->sb_mb == NULL)
                sb->sb_mb = control;
        else
                sb->sb_lastrecord->m_nextpkt = control;
        sb->sb_lastrecord = control;
        sb->sb_lastmbuf = m0;

        sb->sb_cc += length;
        sb->sb_mbcnt += cmbcnt + m0mbcnt;

        return (1);
}

/*
 * Compress mbuf chain m into the socket buffer sb following mbuf tailm.
 * If tailm is null, the buffer is presumed empty.  Also, as a side-effect,
 * increment the sockbuf counts for each mbuf in the chain.
 */
void
sbcompress(struct sockbuf *sb, struct mbuf *m, struct mbuf *tailm)
{
        int eor = 0;
        struct mbuf *free_chain = NULL;

        sbcheck(sb);
        while (m) {
                struct mbuf *o;

                eor |= m->m_flags & M_EOR;
                /*
                 * Disregard empty mbufs as long as we don't encounter
                 * an end-of-record or there is a trailing mbuf of
                 * the same type to propagate the EOR flag to.
                 *
                 * Defer the m_free() call because it can block and break
                 * the atomicy of the sockbuf.
                 */
                if (m->m_len == 0 &&
                    (eor == 0 ||
                     (((o = m->m_next) || (o = tailm)) &&
                      o->m_type == m->m_type))) {
                        o = m->m_next;
                        m->m_next = free_chain;
                        free_chain = m;
                        m = o;
                        continue;
                }

                /* See if we can coalesce with preceding mbuf. */
                if (tailm && !(tailm->m_flags & M_EOR) && M_WRITABLE(tailm) &&
                    m->m_len <= MCLBYTES / 4 && /* XXX: Don't copy too much */
                    m->m_len <= M_TRAILINGSPACE(tailm) &&
                    tailm->m_type == m->m_type) {
                        bcopy(mtod(m, caddr_t),
                              mtod(tailm, caddr_t) + tailm->m_len,
                              (unsigned)m->m_len);
                        tailm->m_len += m->m_len;
                        sb->sb_cc += m->m_len;          /* update sb counter */
                        o = m->m_next;
                        m->m_next = free_chain;
                        free_chain = m;
                        m = o;
                        continue;
                }

                /* Insert whole mbuf. */
                if (tailm == NULL) {
                        KASSERT(sb->sb_mb == NULL,
                                ("sbcompress: sb_mb not NULL"));
                        sb->sb_mb = m;          /* only mbuf in sockbuf */
                        sb->sb_lastrecord = m;  /* new last record */
                } else {
                        tailm->m_next = m;      /* tack m on following tailm */
                }
                sb->sb_lastmbuf = m;    /* update last mbuf hint */

                tailm = m;      /* just inserted mbuf becomes the new tail */
                m = m->m_next;          /* advance to next mbuf */
                tailm->m_next = NULL;   /* split inserted mbuf off from chain */

                /* update sb counters for just added mbuf */
                sballoc(sb, tailm);

                /* clear EOR on intermediate mbufs */
                tailm->m_flags &= ~M_EOR;
        }

        /*
         * Propogate EOR to the last mbuf
         */
        if (eor) {
                if (tailm)
                        tailm->m_flags |= eor;
                else
                        kprintf("semi-panic: sbcompress");
        }

        /*
         * Clean up any defered frees.
         */
        while (free_chain)
                free_chain = m_free(free_chain);

        sbcheck(sb);
}

/*
 * Free all mbufs in a sockbuf.
 * Check that all resources are reclaimed.
 */
void
sbflush(struct sockbuf *sb)
{

        if (sb->sb_flags & SB_LOCK)
                panic("sbflush: locked");
        while (sb->sb_mbcnt) {
                /*
                 * Don't call sbdrop(sb, 0) if the leading mbuf is non-empty:
                 * we would loop forever. Panic instead.
                 */
                if (!sb->sb_cc && (sb->sb_mb == NULL || sb->sb_mb->m_len))
                        break;
                sbdrop(sb, (int)sb->sb_cc);
        }
        KASSERT(!(sb->sb_cc || sb->sb_mb || sb->sb_mbcnt || sb->sb_lastmbuf),
            ("sbflush: cc %ld || mb %p || mbcnt %ld || lastmbuf %p",
            sb->sb_cc, sb->sb_mb, sb->sb_mbcnt, sb->sb_lastmbuf));
}

/*
 * Drop data from (the front of) a sockbuf.
 */
void
sbdrop(struct sockbuf *sb, int len)
{
        struct mbuf *m;
        struct mbuf *free_chain = NULL;

        sbcheck(sb);
        crit_enter();

        /*
         * Remove mbufs from multiple records until the count is exhausted.
         */
        m = sb->sb_mb;
        while (m && len > 0) {
                if (m->m_len > len) {
                        m->m_len -= len;
                        m->m_data += len;
                        sb->sb_cc -= len;
                        break;
                }
                len -= m->m_len;
                m = sbunlinkmbuf(sb, m, &free_chain);
                if (m == NULL && len)
                        m = sb->sb_mb;
        }

        /*
         * Remove any trailing 0-length mbufs in the current record.  If
         * the last record for which data was removed is now empty, m will be
         * NULL.
         */
        while (m && m->m_len == 0) {
                m = sbunlinkmbuf(sb, m, &free_chain);
        }
        crit_exit();
        if (free_chain)
                m_freem(free_chain);
        sbcheck(sb);
}

/*
 * Drop a record off the front of a sockbuf and move the next record
 * to the front.
 *
 * Must be called while holding a critical section.
 */
void
sbdroprecord(struct sockbuf *sb)
{
        struct mbuf *m;
        struct mbuf *n;

        sbcheck(sb);
        m = sb->sb_mb;
        if (m) {
                if ((sb->sb_mb = m->m_nextpkt) == NULL) {
                        sb->sb_lastrecord = NULL;
                        sb->sb_lastmbuf = NULL;
                }
                m->m_nextpkt = NULL;
                for (n = m; n; n = n->m_next)
                        sbfree(sb, n);
                m_freem(m);
                sbcheck(sb);
        }
}

/*
 * Drop the first mbuf off the sockbuf and move the next mbuf to the front.
 * Currently only the head mbuf of the sockbuf may be dropped this way.
 *
 * The next mbuf in the same record as the mbuf being removed is returned
 * or NULL if the record is exhausted.  Note that other records may remain
 * in the sockbuf when NULL is returned.
 *
 * Must be called while holding a critical section.
 */
struct mbuf *
sbunlinkmbuf(struct sockbuf *sb, struct mbuf *m, struct mbuf **free_chain)
{
        struct mbuf *n;

        KKASSERT(sb->sb_mb == m);
        sbfree(sb, m);
        n = m->m_next;
        if (n) {
                sb->sb_mb = n;
                if (sb->sb_lastrecord == m)
                        sb->sb_lastrecord = n;
                KKASSERT(sb->sb_lastmbuf != m);
                n->m_nextpkt = m->m_nextpkt;
        } else {
                sb->sb_mb = m->m_nextpkt;
                if (sb->sb_lastrecord == m) {
                        KKASSERT(sb->sb_mb == NULL);
                        sb->sb_lastrecord = NULL;
                }
                if (sb->sb_mb == NULL)
                        sb->sb_lastmbuf = NULL;
        }
        m->m_nextpkt = NULL;
        if (free_chain) {
                m->m_next = *free_chain;
                *free_chain = m;
        } else {
                m->m_next = NULL;
        }
        return(n);
}

/*
 * Create a "control" mbuf containing the specified data
 * with the specified type for presentation on a socket buffer.
 */
struct mbuf *
sbcreatecontrol(caddr_t p, int size, int type, int level)
{
        struct cmsghdr *cp;
        struct mbuf *m;

        if (CMSG_SPACE((u_int)size) > MCLBYTES)
                return (NULL);
        m = m_getl(CMSG_SPACE((u_int)size), MB_DONTWAIT, MT_CONTROL, 0, NULL);
        if (m == NULL)
                return (NULL);
        m->m_len = CMSG_SPACE(size);
        cp = mtod(m, struct cmsghdr *);
        if (p != NULL)
                memcpy(CMSG_DATA(cp), p, size);
        cp->cmsg_len = CMSG_LEN(size);
        cp->cmsg_level = level;
        cp->cmsg_type = type;
        return (m);
}

/*
 * Some routines that return EOPNOTSUPP for entry points that are not
 * supported by a protocol.  Fill in as needed.
 */
int
pru_accept_notsupp(struct socket *so, struct sockaddr **nam)
{
        return EOPNOTSUPP;
}

int
pru_connect_notsupp(struct socket *so, struct sockaddr *nam, struct thread *td)
{
        return EOPNOTSUPP;
}

int
pru_connect2_notsupp(struct socket *so1, struct socket *so2)
{
        return EOPNOTSUPP;
}

int
pru_control_notsupp(struct socket *so, u_long cmd, caddr_t data,
                    struct ifnet *ifp, struct thread *td)
{
        return EOPNOTSUPP;
}

int
pru_listen_notsupp(struct socket *so, struct thread *td)
{
        return EOPNOTSUPP;
}

int
pru_rcvd_notsupp(struct socket *so, int flags)
{
        return EOPNOTSUPP;
}

int
pru_rcvoob_notsupp(struct socket *so, struct mbuf *m, int flags)
{
        return EOPNOTSUPP;
}

/*
 * This isn't really a ``null'' operation, but it's the default one
 * and doesn't do anything destructive.
 */
int
pru_sense_null(struct socket *so, struct stat *sb)
{
        sb->st_blksize = so->so_snd.sb_hiwat;
        return 0;
}

/*
 * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.  Callers
 * of this routine assume that it always succeeds, so we have to use a 
 * blockable allocation even though we might be called from a critical thread.
 */
struct sockaddr *
dup_sockaddr(const struct sockaddr *sa)
{
        struct sockaddr *sa2;

        sa2 = kmalloc(sa->sa_len, M_SONAME, M_INTWAIT);
        bcopy(sa, sa2, sa->sa_len);
        return (sa2);
}

/*
 * Create an external-format (``xsocket'') structure using the information
 * in the kernel-format socket structure pointed to by so.  This is done
 * to reduce the spew of irrelevant information over this interface,
 * to isolate user code from changes in the kernel structure, and
 * potentially to provide information-hiding if we decide that
 * some of this information should be hidden from users.
 */
void
sotoxsocket(struct socket *so, struct xsocket *xso)
{
        xso->xso_len = sizeof *xso;
        xso->xso_so = so;
        xso->so_type = so->so_type;
        xso->so_options = so->so_options;
        xso->so_linger = so->so_linger;
        xso->so_state = so->so_state;
        xso->so_pcb = so->so_pcb;
        xso->xso_protocol = so->so_proto->pr_protocol;
        xso->xso_family = so->so_proto->pr_domain->dom_family;
        xso->so_qlen = so->so_qlen;
        xso->so_incqlen = so->so_incqlen;
        xso->so_qlimit = so->so_qlimit;
        xso->so_timeo = so->so_timeo;
        xso->so_error = so->so_error;
        xso->so_pgid = so->so_sigio ? so->so_sigio->sio_pgid : 0;
        xso->so_oobmark = so->so_oobmark;
        sbtoxsockbuf(&so->so_snd, &xso->so_snd);
        sbtoxsockbuf(&so->so_rcv, &xso->so_rcv);
        xso->so_uid = so->so_cred->cr_uid;
}

/*
 * This does the same for sockbufs.  Note that the xsockbuf structure,
 * since it is always embedded in a socket, does not include a self
 * pointer nor a length.  We make this entry point public in case
 * some other mechanism needs it.
 */
void
sbtoxsockbuf(struct sockbuf *sb, struct xsockbuf *xsb)
{
        xsb->sb_cc = sb->sb_cc;
        xsb->sb_hiwat = sb->sb_hiwat;
        xsb->sb_mbcnt = sb->sb_mbcnt;
        xsb->sb_mbmax = sb->sb_mbmax;
        xsb->sb_lowat = sb->sb_lowat;
        xsb->sb_flags = sb->sb_flags;
        xsb->sb_timeo = sb->sb_timeo;
}

/*
 * Here is the definition of some of the basic objects in the kern.ipc
 * branch of the MIB.
 */
SYSCTL_NODE(_kern, KERN_IPC, ipc, CTLFLAG_RW, 0, "IPC");

/* This takes the place of kern.maxsockbuf, which moved to kern.ipc. */
static int dummy;
SYSCTL_INT(_kern, KERN_DUMMY, dummy, CTLFLAG_RW, &dummy, 0, "");
SYSCTL_OID(_kern_ipc, KIPC_MAXSOCKBUF, maxsockbuf, CTLTYPE_INT|CTLFLAG_RW, 
    &sb_max, 0, sysctl_handle_sb_max, "I", "Maximum socket buffer size");
SYSCTL_INT(_kern_ipc, OID_AUTO, maxsockets, CTLFLAG_RD, 
    &maxsockets, 0, "Maximum number of sockets avaliable");
SYSCTL_INT(_kern_ipc, KIPC_SOCKBUF_WASTE, sockbuf_waste_factor, CTLFLAG_RW,
    &sb_efficiency, 0, "");

/*
 * Initialise maxsockets 
 */
static void
init_maxsockets(void *ignored)
{
    TUNABLE_INT_FETCH("kern.ipc.maxsockets", &maxsockets);
    maxsockets = imax(maxsockets, imax(maxfiles, nmbclusters));
}
SYSINIT(param, SI_SUB_TUNABLES, SI_ORDER_ANY, init_maxsockets, NULL);