5045 use atomic_{inc,dec}_* instead of atomic_add_*

[illumos-gate.git] / usr / src / uts / common / rpc / svc_clts.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) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
/*        All Rights Reserved   */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

/*
 * svc_clts.c
 * Server side for RPC in the kernel.
 *
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/file.h>
#include <sys/stream.h>
#include <sys/strsun.h>
#include <sys/strsubr.h>
#include <sys/tihdr.h>
#include <sys/tiuser.h>
#include <sys/t_kuser.h>
#include <sys/fcntl.h>
#include <sys/errno.h>
#include <sys/kmem.h>
#include <sys/systm.h>
#include <sys/cmn_err.h>
#include <sys/kstat.h>
#include <sys/vtrace.h>
#include <sys/debug.h>

#include <rpc/types.h>
#include <rpc/xdr.h>
#include <rpc/auth.h>
#include <rpc/clnt.h>
#include <rpc/rpc_msg.h>
#include <rpc/svc.h>
#include <inet/ip.h>

/*
 * Routines exported through ops vector.
 */
static bool_t           svc_clts_krecv(SVCXPRT *, mblk_t *, struct rpc_msg *);
static bool_t           svc_clts_ksend(SVCXPRT *, struct rpc_msg *);
static bool_t           svc_clts_kgetargs(SVCXPRT *, xdrproc_t, caddr_t);
static bool_t           svc_clts_kfreeargs(SVCXPRT *, xdrproc_t, caddr_t);
static void             svc_clts_kdestroy(SVCMASTERXPRT *);
static int              svc_clts_kdup(struct svc_req *, caddr_t, int,
                                struct dupreq **, bool_t *);
static void             svc_clts_kdupdone(struct dupreq *, caddr_t,
                                void (*)(), int, int);
static int32_t          *svc_clts_kgetres(SVCXPRT *, int);
static void             svc_clts_kclone_destroy(SVCXPRT *);
static void             svc_clts_kfreeres(SVCXPRT *);
static void             svc_clts_kstart(SVCMASTERXPRT *);
static void             svc_clts_kclone_xprt(SVCXPRT *, SVCXPRT *);
static void             svc_clts_ktattrs(SVCXPRT *, int, void **);

/*
 * Server transport operations vector.
 */
struct svc_ops svc_clts_op = {
        svc_clts_krecv,         /* Get requests */
        svc_clts_kgetargs,      /* Deserialize arguments */
        svc_clts_ksend,         /* Send reply */
        svc_clts_kfreeargs,     /* Free argument data space */
        svc_clts_kdestroy,      /* Destroy transport handle */
        svc_clts_kdup,          /* Check entry in dup req cache */
        svc_clts_kdupdone,      /* Mark entry in dup req cache as done */
        svc_clts_kgetres,       /* Get pointer to response buffer */
        svc_clts_kfreeres,      /* Destroy pre-serialized response header */
        svc_clts_kclone_destroy, /* Destroy a clone xprt */
        svc_clts_kstart,        /* Tell `ready-to-receive' to rpcmod */
        svc_clts_kclone_xprt,   /* transport specific clone xprt function */
        svc_clts_ktattrs        /* Transport specific attributes. */
};

/*
 * Transport private data.
 * Kept in xprt->xp_p2buf.
 */
struct udp_data {
        mblk_t  *ud_resp;                       /* buffer for response */
        mblk_t  *ud_inmp;                       /* mblk chain of request */
};

#define UD_MAXSIZE      8800
#define UD_INITSIZE     2048

/*
 * Connectionless server statistics
 */
static const struct rpc_clts_server {
        kstat_named_t   rscalls;
        kstat_named_t   rsbadcalls;
        kstat_named_t   rsnullrecv;
        kstat_named_t   rsbadlen;
        kstat_named_t   rsxdrcall;
        kstat_named_t   rsdupchecks;
        kstat_named_t   rsdupreqs;
} clts_rsstat_tmpl = {
        { "calls",      KSTAT_DATA_UINT64 },
        { "badcalls",   KSTAT_DATA_UINT64 },
        { "nullrecv",   KSTAT_DATA_UINT64 },
        { "badlen",     KSTAT_DATA_UINT64 },
        { "xdrcall",    KSTAT_DATA_UINT64 },
        { "dupchecks",  KSTAT_DATA_UINT64 },
        { "dupreqs",    KSTAT_DATA_UINT64 }
};

static uint_t clts_rsstat_ndata =
        sizeof (clts_rsstat_tmpl) / sizeof (kstat_named_t);

#define CLONE2STATS(clone_xprt) \
        (struct rpc_clts_server *)(clone_xprt)->xp_master->xp_p2

#define RSSTAT_INCR(stats, x)   \
        atomic_inc_64(&(stats)->x.value.ui64)

/*
 * Create a transport record.
 * The transport record, output buffer, and private data structure
 * are allocated.  The output buffer is serialized into using xdrmem.
 * There is one transport record per user process which implements a
 * set of services.
 */
/* ARGSUSED */
int
svc_clts_kcreate(file_t *fp, uint_t sendsz, struct T_info_ack *tinfo,
    SVCMASTERXPRT **nxprt)
{
        SVCMASTERXPRT *xprt;
        struct rpcstat *rpcstat;

        if (nxprt == NULL)
                return (EINVAL);

        rpcstat = zone_getspecific(rpcstat_zone_key, curproc->p_zone);
        ASSERT(rpcstat != NULL);

        xprt = kmem_zalloc(sizeof (*xprt), KM_SLEEP);
        xprt->xp_lcladdr.buf = kmem_zalloc(sizeof (sin6_t), KM_SLEEP);
        xprt->xp_p2 = (caddr_t)rpcstat->rpc_clts_server;
        xprt->xp_ops = &svc_clts_op;
        xprt->xp_msg_size = tinfo->TSDU_size;

        xprt->xp_rtaddr.buf = NULL;
        xprt->xp_rtaddr.maxlen = tinfo->ADDR_size;
        xprt->xp_rtaddr.len = 0;

        *nxprt = xprt;

        return (0);
}

/*
 * Destroy a transport record.
 * Frees the space allocated for a transport record.
 */
static void
svc_clts_kdestroy(SVCMASTERXPRT *xprt)
{
        if (xprt->xp_netid)
                kmem_free(xprt->xp_netid, strlen(xprt->xp_netid) + 1);
        if (xprt->xp_addrmask.maxlen)
                kmem_free(xprt->xp_addrmask.buf, xprt->xp_addrmask.maxlen);

        mutex_destroy(&xprt->xp_req_lock);
        mutex_destroy(&xprt->xp_thread_lock);

        kmem_free(xprt->xp_lcladdr.buf, sizeof (sin6_t));
        kmem_free(xprt, sizeof (SVCMASTERXPRT));
}

/*
 * Transport-type specific part of svc_xprt_cleanup().
 * Frees the message buffer space allocated for a clone of a transport record
 */
static void
svc_clts_kclone_destroy(SVCXPRT *clone_xprt)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;

        if (ud->ud_resp) {
                /*
                 * There should not be any left over results buffer.
                 */
                ASSERT(ud->ud_resp->b_cont == NULL);

                /*
                 * Free the T_UNITDATA_{REQ/IND} that svc_clts_krecv
                 * saved.
                 */
                freeb(ud->ud_resp);
        }
        if (ud->ud_inmp)
                freemsg(ud->ud_inmp);
}

/*
 * svc_tli_kcreate() calls this function at the end to tell
 * rpcmod that the transport is ready to receive requests.
 */
/* ARGSUSED */
static void
svc_clts_kstart(SVCMASTERXPRT *xprt)
{
}

static void
svc_clts_kclone_xprt(SVCXPRT *src_xprt, SVCXPRT *dst_xprt)
{
        struct udp_data *ud_src =
            (struct udp_data *)src_xprt->xp_p2buf;
        struct udp_data *ud_dst =
            (struct udp_data *)dst_xprt->xp_p2buf;

        if (ud_src->ud_resp)
                ud_dst->ud_resp = dupb(ud_src->ud_resp);

}

static void
svc_clts_ktattrs(SVCXPRT *clone_xprt, int attrflag, void **tattr)
{
        *tattr = NULL;

        switch (attrflag) {
        case SVC_TATTR_ADDRMASK:
                *tattr = (void *)&clone_xprt->xp_master->xp_addrmask;
        }
}

/*
 * Receive rpc requests.
 * Pulls a request in off the socket, checks if the packet is intact,
 * and deserializes the call packet.
 */
static bool_t
svc_clts_krecv(SVCXPRT *clone_xprt, mblk_t *mp, struct rpc_msg *msg)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;
        XDR *xdrs = &clone_xprt->xp_xdrin;
        struct rpc_clts_server *stats = CLONE2STATS(clone_xprt);
        union T_primitives *pptr;
        int hdrsz;
        cred_t *cr;

        TRACE_0(TR_FAC_KRPC, TR_SVC_CLTS_KRECV_START,
            "svc_clts_krecv_start:");

        RSSTAT_INCR(stats, rscalls);

        /*
         * The incoming request should start with an M_PROTO message.
         */
        if (mp->b_datap->db_type != M_PROTO) {
                goto bad;
        }

        /*
         * The incoming request should be an T_UNITDTA_IND.  There
         * might be other messages coming up the stream, but we can
         * ignore them.
         */
        pptr = (union T_primitives *)mp->b_rptr;
        if (pptr->type != T_UNITDATA_IND) {
                goto bad;
        }
        /*
         * Do some checking to make sure that the header at least looks okay.
         */
        hdrsz = (int)(mp->b_wptr - mp->b_rptr);
        if (hdrsz < TUNITDATAINDSZ ||
            hdrsz < (pptr->unitdata_ind.OPT_offset +
            pptr->unitdata_ind.OPT_length) ||
            hdrsz < (pptr->unitdata_ind.SRC_offset +
            pptr->unitdata_ind.SRC_length)) {
                goto bad;
        }

        /*
         * Make sure that the transport provided a usable address.
         */
        if (pptr->unitdata_ind.SRC_length <= 0) {
                goto bad;
        }
        /*
         * Point the remote transport address in the service_transport
         * handle at the address in the request.
         */
        clone_xprt->xp_rtaddr.buf = (char *)mp->b_rptr +
            pptr->unitdata_ind.SRC_offset;
        clone_xprt->xp_rtaddr.len = pptr->unitdata_ind.SRC_length;

        /*
         * Copy the local transport address in the service_transport
         * handle at the address in the request. We will have only
         * the local IP address in options.
         */
        ((sin_t *)(clone_xprt->xp_lcladdr.buf))->sin_family = AF_UNSPEC;
        if (pptr->unitdata_ind.OPT_length && pptr->unitdata_ind.OPT_offset) {
                char *dstopt = (char *)mp->b_rptr +
                    pptr->unitdata_ind.OPT_offset;
                struct T_opthdr *toh = (struct T_opthdr *)dstopt;

                if (toh->level == IPPROTO_IPV6 && toh->status == 0 &&
                    toh->name == IPV6_PKTINFO) {
                        struct in6_pktinfo *pkti;

                        dstopt += sizeof (struct T_opthdr);
                        pkti = (struct in6_pktinfo *)dstopt;
                        ((sin6_t *)(clone_xprt->xp_lcladdr.buf))->sin6_addr
                            = pkti->ipi6_addr;
                        ((sin6_t *)(clone_xprt->xp_lcladdr.buf))->sin6_family
                            = AF_INET6;
                } else if (toh->level == IPPROTO_IP && toh->status == 0 &&
                    toh->name == IP_RECVDSTADDR) {
                        dstopt += sizeof (struct T_opthdr);
                        ((sin_t *)(clone_xprt->xp_lcladdr.buf))->sin_addr
                            = *(struct in_addr *)dstopt;
                        ((sin_t *)(clone_xprt->xp_lcladdr.buf))->sin_family
                            = AF_INET;
                }
        }

        /*
         * Save the first mblk which contains the T_unidata_ind in
         * ud_resp.  It will be used to generate the T_unitdata_req
         * during the reply.
         * We reuse any options in the T_unitdata_ind for the T_unitdata_req
         * since we must pass any SCM_UCRED across in order for TX to
         * work. We also make sure any cred_t is carried across.
         */
        if (ud->ud_resp) {
                if (ud->ud_resp->b_cont != NULL) {
                        cmn_err(CE_WARN, "svc_clts_krecv: ud_resp %p, "
                            "b_cont %p", (void *)ud->ud_resp,
                            (void *)ud->ud_resp->b_cont);
                }
                freeb(ud->ud_resp);
        }
        /* Move any cred_t to the first mblk in the message */
        cr = msg_getcred(mp, NULL);
        if (cr != NULL)
                mblk_setcred(mp, cr, NOPID);

        ud->ud_resp = mp;
        mp = mp->b_cont;
        ud->ud_resp->b_cont = NULL;

        xdrmblk_init(xdrs, mp, XDR_DECODE, 0);

        TRACE_0(TR_FAC_KRPC, TR_XDR_CALLMSG_START,
            "xdr_callmsg_start:");
        if (! xdr_callmsg(xdrs, msg)) {
                TRACE_1(TR_FAC_KRPC, TR_XDR_CALLMSG_END,
                    "xdr_callmsg_end:(%S)", "bad");
                RSSTAT_INCR(stats, rsxdrcall);
                goto bad;
        }
        TRACE_1(TR_FAC_KRPC, TR_XDR_CALLMSG_END,
            "xdr_callmsg_end:(%S)", "good");

        clone_xprt->xp_xid = msg->rm_xid;
        ud->ud_inmp = mp;

        TRACE_1(TR_FAC_KRPC, TR_SVC_CLTS_KRECV_END,
            "svc_clts_krecv_end:(%S)", "good");
        return (TRUE);

bad:
        freemsg(mp);
        if (ud->ud_resp) {
                /*
                 * There should not be any left over results buffer.
                 */
                ASSERT(ud->ud_resp->b_cont == NULL);
                freeb(ud->ud_resp);
                ud->ud_resp = NULL;
        }

        RSSTAT_INCR(stats, rsbadcalls);
        TRACE_1(TR_FAC_KRPC, TR_SVC_CLTS_KRECV_END,
            "svc_clts_krecv_end:(%S)", "bad");
        return (FALSE);
}

/*
 * Send rpc reply.
 * Serialize the reply packet into the output buffer then
 * call t_ksndudata to send it.
 */
static bool_t
svc_clts_ksend(SVCXPRT *clone_xprt, struct rpc_msg *msg)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;
        XDR *xdrs = &clone_xprt->xp_xdrout;
        int stat = FALSE;
        mblk_t *mp;
        int msgsz;
        struct T_unitdata_req *udreq;
        xdrproc_t xdr_results;
        caddr_t xdr_location;
        bool_t has_args;

        TRACE_0(TR_FAC_KRPC, TR_SVC_CLTS_KSEND_START,
            "svc_clts_ksend_start:");

        ASSERT(ud->ud_resp != NULL);

        /*
         * If there is a result procedure specified in the reply message,
         * it will be processed in the xdr_replymsg and SVCAUTH_WRAP.
         * We need to make sure it won't be processed twice, so we null
         * it for xdr_replymsg here.
         */
        has_args = FALSE;
        if (msg->rm_reply.rp_stat == MSG_ACCEPTED &&
            msg->rm_reply.rp_acpt.ar_stat == SUCCESS) {
                if ((xdr_results = msg->acpted_rply.ar_results.proc) != NULL) {
                        has_args = TRUE;
                        xdr_location = msg->acpted_rply.ar_results.where;
                        msg->acpted_rply.ar_results.proc = xdr_void;
                        msg->acpted_rply.ar_results.where = NULL;
                }
        }

        if (ud->ud_resp->b_cont == NULL) {
                /*
                 * Allocate an initial mblk for the response data.
                 */
                while ((mp = allocb(UD_INITSIZE, BPRI_LO)) == NULL) {
                        if (strwaitbuf(UD_INITSIZE, BPRI_LO)) {
                                TRACE_1(TR_FAC_KRPC, TR_SVC_CLTS_KSEND_END,
                                    "svc_clts_ksend_end:(%S)", "strwaitbuf");
                                return (FALSE);
                        }
                }

                /*
                 * Initialize the XDR decode stream.  Additional mblks
                 * will be allocated if necessary.  They will be UD_MAXSIZE
                 * sized.
                 */
                xdrmblk_init(xdrs, mp, XDR_ENCODE, UD_MAXSIZE);

                /*
                 * Leave some space for protocol headers.
                 */
                (void) XDR_SETPOS(xdrs, 512);
                mp->b_rptr += 512;

                msg->rm_xid = clone_xprt->xp_xid;

                ud->ud_resp->b_cont = mp;

                TRACE_0(TR_FAC_KRPC, TR_XDR_REPLYMSG_START,
                    "xdr_replymsg_start:");
                if (!(xdr_replymsg(xdrs, msg) &&
                    (!has_args || SVCAUTH_WRAP(&clone_xprt->xp_auth, xdrs,
                    xdr_results, xdr_location)))) {
                        TRACE_1(TR_FAC_KRPC, TR_XDR_REPLYMSG_END,
                            "xdr_replymsg_end:(%S)", "bad");
                        RPCLOG0(1, "xdr_replymsg/SVCAUTH_WRAP failed\n");
                        goto out;
                }
                TRACE_1(TR_FAC_KRPC, TR_XDR_REPLYMSG_END,
                    "xdr_replymsg_end:(%S)", "good");

        } else if (!(xdr_replymsg_body(xdrs, msg) &&
            (!has_args || SVCAUTH_WRAP(&clone_xprt->xp_auth, xdrs,
            xdr_results, xdr_location)))) {
                RPCLOG0(1, "xdr_replymsg_body/SVCAUTH_WRAP failed\n");
                goto out;
        }

        msgsz = (int)xmsgsize(ud->ud_resp->b_cont);

        if (msgsz <= 0 || (clone_xprt->xp_msg_size != -1 &&
            msgsz > clone_xprt->xp_msg_size)) {
#ifdef  DEBUG
                cmn_err(CE_NOTE,
"KRPC: server response message of %d bytes; transport limits are [0, %d]",
                    msgsz, clone_xprt->xp_msg_size);
#endif
                goto out;
        }

        /*
         * Construct the T_unitdata_req.  We take advantage of the fact that
         * T_unitdata_ind looks just like T_unitdata_req, except for the
         * primitive type.  Reusing it means we preserve the SCM_UCRED, and
         * we must preserve it for TX to work.
         *
         * This has the side effect that we can also pass certain receive-side
         * options like IPV6_PKTINFO back down the send side.  This implies
         * that we can not ASSERT on a non-NULL db_credp when we have send-side
         * options in UDP.
         */
        ASSERT(MBLKL(ud->ud_resp) >= TUNITDATAREQSZ);
        udreq = (struct T_unitdata_req *)ud->ud_resp->b_rptr;
        ASSERT(udreq->PRIM_type == T_UNITDATA_IND);
        udreq->PRIM_type = T_UNITDATA_REQ;

        /*
         * If the local IPv4 transport address is known use it as a source
         * address for the outgoing UDP packet.
         */
        if (((sin_t *)(clone_xprt->xp_lcladdr.buf))->sin_family == AF_INET) {
                struct T_opthdr *opthdr;
                in_pktinfo_t *pktinfo;
                size_t size;

                if (udreq->DEST_length == 0)
                        udreq->OPT_offset = _TPI_ALIGN_TOPT(TUNITDATAREQSZ);
                else
                        udreq->OPT_offset = _TPI_ALIGN_TOPT(udreq->DEST_offset +
                            udreq->DEST_length);

                udreq->OPT_length = sizeof (struct T_opthdr) +
                    sizeof (in_pktinfo_t);

                size = udreq->OPT_length + udreq->OPT_offset;

                /* make sure we have enough space for the option data */
                mp = reallocb(ud->ud_resp, size, 1);
                if (mp == NULL)
                        goto out;
                ud->ud_resp = mp;
                udreq = (struct T_unitdata_req *)mp->b_rptr;

                /* set desired option header */
                opthdr = (struct T_opthdr *)(mp->b_rptr + udreq->OPT_offset);
                opthdr->len = udreq->OPT_length;
                opthdr->level = IPPROTO_IP;
                opthdr->name = IP_PKTINFO;

                /*
                 * 1. set source IP of outbound packet
                 * 2. value '0' for index means IP layer uses this as source
                 *    address
                 */
                pktinfo = (in_pktinfo_t *)(opthdr + 1);
                (void) memset(pktinfo, 0, sizeof (in_pktinfo_t));
                pktinfo->ipi_spec_dst.s_addr =
                    ((sin_t *)(clone_xprt->xp_lcladdr.buf))->sin_addr.s_addr;
                pktinfo->ipi_ifindex = 0;

                /* adjust the end of active data */
                mp->b_wptr = mp->b_rptr + size;
        }

        put(clone_xprt->xp_wq, ud->ud_resp);
        stat = TRUE;
        ud->ud_resp = NULL;

out:
        if (stat == FALSE) {
                freemsg(ud->ud_resp);
                ud->ud_resp = NULL;
        }

        /*
         * This is completely disgusting.  If public is set it is
         * a pointer to a structure whose first field is the address
         * of the function to free that structure and any related
         * stuff.  (see rrokfree in nfs_xdr.c).
         */
        if (xdrs->x_public) {
                /* LINTED pointer alignment */
                (**((int (**)())xdrs->x_public))(xdrs->x_public);
        }

        TRACE_1(TR_FAC_KRPC, TR_SVC_CLTS_KSEND_END,
            "svc_clts_ksend_end:(%S)", "done");
        return (stat);
}

/*
 * Deserialize arguments.
 */
static bool_t
svc_clts_kgetargs(SVCXPRT *clone_xprt, xdrproc_t xdr_args,
    caddr_t args_ptr)
{

        /* LINTED pointer alignment */
        return (SVCAUTH_UNWRAP(&clone_xprt->xp_auth, &clone_xprt->xp_xdrin,
            xdr_args, args_ptr));

}

static bool_t
svc_clts_kfreeargs(SVCXPRT *clone_xprt, xdrproc_t xdr_args,
    caddr_t args_ptr)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;
        XDR *xdrs = &clone_xprt->xp_xdrin;
        bool_t retval;

        if (args_ptr) {
                xdrs->x_op = XDR_FREE;
                retval = (*xdr_args)(xdrs, args_ptr);
        } else
                retval = TRUE;

        if (ud->ud_inmp) {
                freemsg(ud->ud_inmp);
                ud->ud_inmp = NULL;
        }

        return (retval);
}

static int32_t *
svc_clts_kgetres(SVCXPRT *clone_xprt, int size)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;
        XDR *xdrs = &clone_xprt->xp_xdrout;
        mblk_t *mp;
        int32_t *buf;
        struct rpc_msg rply;

        /*
         * Allocate an initial mblk for the response data.
         */
        while ((mp = allocb(UD_INITSIZE, BPRI_LO)) == NULL) {
                if (strwaitbuf(UD_INITSIZE, BPRI_LO)) {
                        return (FALSE);
                }
        }

        mp->b_cont = NULL;

        /*
         * Initialize the XDR decode stream.  Additional mblks
         * will be allocated if necessary.  They will be UD_MAXSIZE
         * sized.
         */
        xdrmblk_init(xdrs, mp, XDR_ENCODE, UD_MAXSIZE);

        /*
         * Leave some space for protocol headers.
         */
        (void) XDR_SETPOS(xdrs, 512);
        mp->b_rptr += 512;

        /*
         * Assume a successful RPC since most of them are.
         */
        rply.rm_xid = clone_xprt->xp_xid;
        rply.rm_direction = REPLY;
        rply.rm_reply.rp_stat = MSG_ACCEPTED;
        rply.acpted_rply.ar_verf = clone_xprt->xp_verf;
        rply.acpted_rply.ar_stat = SUCCESS;

        if (!xdr_replymsg_hdr(xdrs, &rply)) {
                freeb(mp);
                return (NULL);
        }

        buf = XDR_INLINE(xdrs, size);

        if (buf == NULL)
                freeb(mp);
        else
                ud->ud_resp->b_cont = mp;

        return (buf);
}

static void
svc_clts_kfreeres(SVCXPRT *clone_xprt)
{
        /* LINTED pointer alignment */
        struct udp_data *ud = (struct udp_data *)clone_xprt->xp_p2buf;

        if (ud->ud_resp == NULL || ud->ud_resp->b_cont == NULL)
                return;

        /*
         * SVC_FREERES() is called whenever the server decides not to
         * send normal reply. Thus, we expect only one mblk to be allocated,
         * because we have not attempted any XDR encoding.
         * If we do any XDR encoding and we get an error, then SVC_REPLY()
         * will freemsg(ud->ud_resp);
         */
        ASSERT(ud->ud_resp->b_cont->b_cont == NULL);
        freeb(ud->ud_resp->b_cont);
        ud->ud_resp->b_cont = NULL;
}

/*
 * the dup cacheing routines below provide a cache of non-failure
 * transaction id's.  rpc service routines can use this to detect
 * retransmissions and re-send a non-failure response.
 */

/*
 * MAXDUPREQS is the number of cached items.  It should be adjusted
 * to the service load so that there is likely to be a response entry
 * when the first retransmission comes in.
 */
#define MAXDUPREQS      1024

/*
 * This should be appropriately scaled to MAXDUPREQS.
 */
#define DRHASHSZ        257

#if ((DRHASHSZ & (DRHASHSZ - 1)) == 0)
#define XIDHASH(xid)    ((xid) & (DRHASHSZ - 1))
#else
#define XIDHASH(xid)    ((xid) % DRHASHSZ)
#endif
#define DRHASH(dr)      XIDHASH((dr)->dr_xid)
#define REQTOXID(req)   ((req)->rq_xprt->xp_xid)

static int      ndupreqs = 0;
int     maxdupreqs = MAXDUPREQS;
static kmutex_t dupreq_lock;
static struct dupreq *drhashtbl[DRHASHSZ];
static int      drhashstat[DRHASHSZ];

static void unhash(struct dupreq *);

/*
 * drmru points to the head of a circular linked list in lru order.
 * drmru->dr_next == drlru
 */
struct dupreq *drmru;

/*
 * PSARC 2003/523 Contract Private Interface
 * svc_clts_kdup
 * Changes must be reviewed by Solaris File Sharing
 * Changes must be communicated to contract-2003-523@sun.com
 *
 * svc_clts_kdup searches the request cache and returns 0 if the
 * request is not found in the cache.  If it is found, then it
 * returns the state of the request (in progress or done) and
 * the status or attributes that were part of the original reply.
 *
 * If DUP_DONE (there is a duplicate) svc_clts_kdup copies over the
 * value of the response. In that case, also return in *dupcachedp
 * whether the response free routine is cached in the dupreq - in which case
 * the caller should not be freeing it, because it will be done later
 * in the svc_clts_kdup code when the dupreq is reused.
 */
static int
svc_clts_kdup(struct svc_req *req, caddr_t res, int size, struct dupreq **drpp,
        bool_t *dupcachedp)
{
        struct rpc_clts_server *stats = CLONE2STATS(req->rq_xprt);
        struct dupreq *dr;
        uint32_t xid;
        uint32_t drhash;
        int status;

        xid = REQTOXID(req);
        mutex_enter(&dupreq_lock);
        RSSTAT_INCR(stats, rsdupchecks);
        /*
         * Check to see whether an entry already exists in the cache.
         */
        dr = drhashtbl[XIDHASH(xid)];
        while (dr != NULL) {
                if (dr->dr_xid == xid &&
                    dr->dr_proc == req->rq_proc &&
                    dr->dr_prog == req->rq_prog &&
                    dr->dr_vers == req->rq_vers &&
                    dr->dr_addr.len == req->rq_xprt->xp_rtaddr.len &&
                    bcmp(dr->dr_addr.buf, req->rq_xprt->xp_rtaddr.buf,
                    dr->dr_addr.len) == 0) {
                        status = dr->dr_status;
                        if (status == DUP_DONE) {
                                bcopy(dr->dr_resp.buf, res, size);
                                if (dupcachedp != NULL)
                                        *dupcachedp = (dr->dr_resfree != NULL);
                        } else {
                                dr->dr_status = DUP_INPROGRESS;
                                *drpp = dr;
                        }
                        RSSTAT_INCR(stats, rsdupreqs);
                        mutex_exit(&dupreq_lock);
                        return (status);
                }
                dr = dr->dr_chain;
        }

        /*
         * There wasn't an entry, either allocate a new one or recycle
         * an old one.
         */
        if (ndupreqs < maxdupreqs) {
                dr = kmem_alloc(sizeof (*dr), KM_NOSLEEP);
                if (dr == NULL) {
                        mutex_exit(&dupreq_lock);
                        return (DUP_ERROR);
                }
                dr->dr_resp.buf = NULL;
                dr->dr_resp.maxlen = 0;
                dr->dr_addr.buf = NULL;
                dr->dr_addr.maxlen = 0;
                if (drmru) {
                        dr->dr_next = drmru->dr_next;
                        drmru->dr_next = dr;
                } else {
                        dr->dr_next = dr;
                }
                ndupreqs++;
        } else {
                dr = drmru->dr_next;
                while (dr->dr_status == DUP_INPROGRESS) {
                        dr = dr->dr_next;
                        if (dr == drmru->dr_next) {
                                cmn_err(CE_WARN, "svc_clts_kdup no slots free");
                                mutex_exit(&dupreq_lock);
                                return (DUP_ERROR);
                        }
                }
                unhash(dr);
                if (dr->dr_resfree) {
                        (*dr->dr_resfree)(dr->dr_resp.buf);
                }
        }
        dr->dr_resfree = NULL;
        drmru = dr;

        dr->dr_xid = REQTOXID(req);
        dr->dr_prog = req->rq_prog;
        dr->dr_vers = req->rq_vers;
        dr->dr_proc = req->rq_proc;
        if (dr->dr_addr.maxlen < req->rq_xprt->xp_rtaddr.len) {
                if (dr->dr_addr.buf != NULL)
                        kmem_free(dr->dr_addr.buf, dr->dr_addr.maxlen);
                dr->dr_addr.maxlen = req->rq_xprt->xp_rtaddr.len;
                dr->dr_addr.buf = kmem_alloc(dr->dr_addr.maxlen,
                    KM_NOSLEEP);
                if (dr->dr_addr.buf == NULL) {
                        dr->dr_addr.maxlen = 0;
                        dr->dr_status = DUP_DROP;
                        mutex_exit(&dupreq_lock);
                        return (DUP_ERROR);
                }
        }
        dr->dr_addr.len = req->rq_xprt->xp_rtaddr.len;
        bcopy(req->rq_xprt->xp_rtaddr.buf, dr->dr_addr.buf, dr->dr_addr.len);
        if (dr->dr_resp.maxlen < size) {
                if (dr->dr_resp.buf != NULL)
                        kmem_free(dr->dr_resp.buf, dr->dr_resp.maxlen);
                dr->dr_resp.maxlen = (unsigned int)size;
                dr->dr_resp.buf = kmem_alloc(size, KM_NOSLEEP);
                if (dr->dr_resp.buf == NULL) {
                        dr->dr_resp.maxlen = 0;
                        dr->dr_status = DUP_DROP;
                        mutex_exit(&dupreq_lock);
                        return (DUP_ERROR);
                }
        }
        dr->dr_status = DUP_INPROGRESS;

        drhash = (uint32_t)DRHASH(dr);
        dr->dr_chain = drhashtbl[drhash];
        drhashtbl[drhash] = dr;
        drhashstat[drhash]++;
        mutex_exit(&dupreq_lock);
        *drpp = dr;
        return (DUP_NEW);
}

/*
 * PSARC 2003/523 Contract Private Interface
 * svc_clts_kdupdone
 * Changes must be reviewed by Solaris File Sharing
 * Changes must be communicated to contract-2003-523@sun.com
 *
 * svc_clts_kdupdone marks the request done (DUP_DONE or DUP_DROP)
 * and stores the response.
 */
static void
svc_clts_kdupdone(struct dupreq *dr, caddr_t res, void (*dis_resfree)(),
        int size, int status)
{

        ASSERT(dr->dr_resfree == NULL);
        if (status == DUP_DONE) {
                bcopy(res, dr->dr_resp.buf, size);
                dr->dr_resfree = dis_resfree;
        }
        dr->dr_status = status;
}

/*
 * This routine expects that the mutex, dupreq_lock, is already held.
 */
static void
unhash(struct dupreq *dr)
{
        struct dupreq *drt;
        struct dupreq *drtprev = NULL;
        uint32_t drhash;

        ASSERT(MUTEX_HELD(&dupreq_lock));

        drhash = (uint32_t)DRHASH(dr);
        drt = drhashtbl[drhash];
        while (drt != NULL) {
                if (drt == dr) {
                        drhashstat[drhash]--;
                        if (drtprev == NULL) {
                                drhashtbl[drhash] = drt->dr_chain;
                        } else {
                                drtprev->dr_chain = drt->dr_chain;
                        }
                        return;
                }
                drtprev = drt;
                drt = drt->dr_chain;
        }
}

void
svc_clts_stats_init(zoneid_t zoneid, struct rpc_clts_server **statsp)
{
        kstat_t *ksp;
        kstat_named_t *knp;

        knp = rpcstat_zone_init_common(zoneid, "unix", "rpc_clts_server",
            (const kstat_named_t *)&clts_rsstat_tmpl,
            sizeof (clts_rsstat_tmpl));
        /*
         * Backwards compatibility for old kstat clients
         */
        ksp = kstat_create_zone("unix", 0, "rpc_server", "rpc",
            KSTAT_TYPE_NAMED, clts_rsstat_ndata,
            KSTAT_FLAG_VIRTUAL | KSTAT_FLAG_WRITABLE, zoneid);
        if (ksp) {
                ksp->ks_data = knp;
                kstat_install(ksp);
        }
        *statsp = (struct rpc_clts_server *)knp;
}

void
svc_clts_stats_fini(zoneid_t zoneid, struct rpc_clts_server **statsp)
{
        rpcstat_zone_fini_common(zoneid, "unix", "rpc_clts_server");
        kstat_delete_byname_zone("unix", 0, "rpc_server", zoneid);
        kmem_free(*statsp, sizeof (clts_rsstat_tmpl));
}

void
svc_clts_init()
{
        /*
         * Check to make sure that the clts private data will fit into
         * the stack buffer allocated by svc_run.  The compiler should
         * remove this check, but it's a safety net if the udp_data
         * structure ever changes.
         */
        /*CONSTANTCONDITION*/
        ASSERT(sizeof (struct udp_data) <= SVC_P2LEN);

        mutex_init(&dupreq_lock, NULL, MUTEX_DEFAULT, NULL);
}