[apple/xnu.git] / bsd / kern / uipc_socket2.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1998, 1999 Apple Computer, Inc. All Rights Reserved */
/* Copyright (c) 1995 NeXT Computer, Inc. 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 1.55.2.9 2001/07/26 18:53:02 peter Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/domain.h>
#include <sys/kernel.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/ev.h>
#include <kern/locks.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <sys/kdebug.h>

#define DBG_FNC_SBDROP  NETDBG_CODE(DBG_NETSOCK, 4)
#define DBG_FNC_SBAPPEND        NETDBG_CODE(DBG_NETSOCK, 5)

static int sbcompress(struct sockbuf *, struct mbuf *, struct mbuf *);

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

u_long  sb_max = SB_MAX;                /* XXX should be static */

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(so)
        register struct socket *so;
{

        so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= SS_ISCONNECTING;
        
        sflt_notify(so, sock_evt_connecting, NULL);
}

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

        so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
        so->so_state |= SS_ISCONNECTED;
        
        sflt_notify(so, sock_evt_connected, NULL);
        
        if (head && (so->so_state & SS_INCOMP)) {
                so->so_state &= ~SS_INCOMP;
                so->so_state |= SS_COMP;
                if (head->so_proto->pr_getlock != NULL) {
                        socket_unlock(so, 0);
                        socket_lock(head, 1);
                }
                postevent(head, 0, EV_RCONN);
                TAILQ_REMOVE(&head->so_incomp, so, so_list);
                head->so_incqlen--;
                TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                sorwakeup(head);
                wakeup_one((caddr_t)&head->so_timeo);
                if (head->so_proto->pr_getlock != NULL) {
                        socket_unlock(head, 1);
                        socket_lock(so, 0);
                }
        } else {
                postevent(so, 0, EV_WCONN);
                wakeup((caddr_t)&so->so_timeo);
                sorwakeup(so);
                sowwakeup(so);
        }
}

void
soisdisconnecting(so)
        register struct socket *so;
{
        so->so_state &= ~SS_ISCONNECTING;
        so->so_state |= (SS_ISDISCONNECTING|SS_CANTRCVMORE|SS_CANTSENDMORE);
        sflt_notify(so, sock_evt_disconnecting, NULL);
        wakeup((caddr_t)&so->so_timeo);
        sowwakeup(so);
        sorwakeup(so);
}

void
soisdisconnected(so)
        register struct socket *so;
{
        so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);
        sflt_notify(so, sock_evt_disconnected, NULL);
        wakeup((caddr_t)&so->so_timeo);
        sowwakeup(so);
        sorwakeup(so);
}

/*
 * Return a random connection that hasn't been serviced yet and
 * is eligible for discard.  There is a one in qlen chance that
 * we will return a null, saying that there are no dropable
 * requests.  In this case, the protocol specific code should drop
 * the new request.  This insures fairness.
 *
 * This may be used in conjunction with protocol specific queue
 * congestion routines.
 */
struct socket *
sodropablereq(head)
        register struct socket *head;
{
        struct socket *so, *sonext = NULL;
        unsigned int i, j, qlen;
        static int rnd;
        static struct timeval old_runtime;
        static unsigned int cur_cnt, old_cnt;
        struct timeval tv;

        microtime(&tv);
        if ((i = (tv.tv_sec - old_runtime.tv_sec)) != 0) {
                old_runtime = tv;
                old_cnt = cur_cnt / i;
                cur_cnt = 0;
        }

        so = TAILQ_FIRST(&head->so_incomp);
        if (!so)
                return (NULL);

        qlen = head->so_incqlen;
        if (++cur_cnt > qlen || old_cnt > qlen) {
                rnd = (314159 * rnd + 66329) & 0xffff;
                j = ((qlen + 1) * rnd) >> 16;
//###LD To clean up
                while (j-- && so) {
//                      if (in_pcb_checkstate(so->so_pcb, WNT_ACQUIRE, 0) != WNT_STOPUSING) {
                                socket_lock(so, 1);
                                sonext = TAILQ_NEXT(so, so_list);
//                              in_pcb_check_state(so->so_pcb, WNT_RELEASE, 0);
                                socket_unlock(so, 1);   
                                so = sonext;
                }
        }

//      if (in_pcb_checkstate(so->so_pcb, WNT_ACQUIRE, 0) == WNT_STOPUSING) 
//              return (NULL);
//      else
                return (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.
 */
static struct socket *
sonewconn_internal(head, connstatus)
        register struct socket *head;
        int connstatus;
{
        int error = 0;
        register struct socket *so;
        lck_mtx_t *mutex_held;

        if (head->so_proto->pr_getlock != NULL) 
                mutex_held = (*head->so_proto->pr_getlock)(head, 0);
        else 
                mutex_held = head->so_proto->pr_domain->dom_mtx;
        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

        if (head->so_qlen > 3 * head->so_qlimit / 2)
                return ((struct socket *)0);
        so = soalloc(1, head->so_proto->pr_domain->dom_family, head->so_type);
        if (so == NULL)
                return ((struct socket *)0);
        /* check if head was closed during the soalloc */
        if (head->so_proto == NULL) {
          sodealloc(so);
          return ((struct socket *)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_pgid  = head->so_pgid;
        so->so_uid = head->so_uid;
        so->so_usecount = 1;
        so->next_lock_lr = 0;
        so->next_unlock_lr = 0;

#ifdef __APPLE__
        so->so_rcv.sb_flags |= SB_RECV; /* XXX */
        so->so_rcv.sb_so = so->so_snd.sb_so = so;
        TAILQ_INIT(&so->so_evlist);
#endif

        if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat)) {
                sflt_termsock(so);
                sodealloc(so);
                return ((struct socket *)0);
        }

        /*
         * Must be done with head unlocked to avoid deadlock for protocol with per socket mutexes.
         */
        if (head->so_proto->pr_unlock)
                socket_unlock(head, 0);
        if (((*so->so_proto->pr_usrreqs->pru_attach)(so, 0, NULL) != 0) || error) {
                sflt_termsock(so);
                sodealloc(so);
                if (head->so_proto->pr_unlock)
                        socket_lock(head, 0);
                return ((struct socket *)0);
        }
        if (head->so_proto->pr_unlock)
                socket_lock(head, 0);
#ifdef __APPLE__
        so->so_proto->pr_domain->dom_refs++;
#endif

        if (connstatus) {
                TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                so->so_state |= SS_COMP;
        } else {
                TAILQ_INSERT_TAIL(&head->so_incomp, so, so_list);
                so->so_state |= SS_INCOMP;
                head->so_incqlen++;
        }
        head->so_qlen++;

#ifdef __APPLE__
        /* Attach socket filters for this protocol */
        sflt_initsock(so);
#endif
        if (connstatus) {
                so->so_state |= connstatus;
                sorwakeup(head);
                wakeup((caddr_t)&head->so_timeo);
        }
        return (so);
}


struct socket *
sonewconn(
        struct socket *head,
        int connstatus,
        const struct sockaddr *from)
{
        int error = 0;
        struct socket_filter_entry      *filter;
        int                                                     filtered = 0;
        
        error = 0;
        for (filter = head->so_filt; filter && (error == 0);
                 filter = filter->sfe_next_onsocket) {
                if (filter->sfe_filter->sf_filter.sf_connect_in) {
                        if (filtered == 0) {
                                filtered = 1;
                                sflt_use(head);
                                socket_unlock(head, 0);
                        }
                        error = filter->sfe_filter->sf_filter.sf_connect_in(
                                                filter->sfe_cookie, head, from);
                }
        }
        if (filtered != 0) {
                socket_lock(head, 0);
                sflt_unuse(head);
        }
        
        if (error) {
                return NULL;
        }
        
        return sonewconn_internal(head, connstatus);
}

/*
 * 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(so)
        struct socket *so;
{
        so->so_state |= SS_CANTSENDMORE;
        sflt_notify(so, sock_evt_cantsendmore, NULL);
        sowwakeup(so);
}

void
socantrcvmore(so)
        struct socket *so;
{
        so->so_state |= SS_CANTRCVMORE;
        sflt_notify(so, sock_evt_cantrecvmore, NULL);
        sorwakeup(so);
}

/*
 * Wait for data to arrive at/drain from a socket buffer.
 */
int
sbwait(sb)
        struct sockbuf *sb;
{
        int error = 0, lr_saved;
        struct socket *so = sb->sb_so;
        lck_mtx_t *mutex_held;
        struct timespec ts;

        lr_saved = (unsigned int) __builtin_return_address(0);
        
        if (so->so_proto->pr_getlock != NULL) 
                mutex_held = (*so->so_proto->pr_getlock)(so, 0);
        else 
                mutex_held = so->so_proto->pr_domain->dom_mtx;

        sb->sb_flags |= SB_WAIT;

        if (so->so_usecount < 1)
                panic("sbwait: so=%x refcount=%d\n", so, so->so_usecount);
        ts.tv_sec = sb->sb_timeo.tv_sec;
        ts.tv_nsec = sb->sb_timeo.tv_usec * 1000;
        error = msleep((caddr_t)&sb->sb_cc, mutex_held,
                (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH, "sbwait",
                &ts);

        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

        if (so->so_usecount < 1)
                panic("sbwait: so=%x refcount=%d\n", so, so->so_usecount);

        if ((so->so_state & SS_DRAINING)) {
                error = EBADF;
        }

        return (error);
}

/*
 * Lock a sockbuf already known to be locked;
 * return any error returned from sleep (EINTR).
 */
int
sb_lock(sb)
        register struct sockbuf *sb;
{
        struct socket *so = sb->sb_so;
        lck_mtx_t * mutex_held;
        int error = 0;
        
        if (so == NULL)
                panic("sb_lock: null so back pointer sb=%x\n", sb);

        while (sb->sb_flags & SB_LOCK) {
                sb->sb_flags |= SB_WANT;
                if (so->so_proto->pr_getlock != NULL) 
                        mutex_held = (*so->so_proto->pr_getlock)(so, 0);
                else
                        mutex_held = so->so_proto->pr_domain->dom_mtx;
                if (so->so_usecount < 1)
                        panic("sb_lock: so=%x refcount=%d\n", so, so->so_usecount);

                error = msleep((caddr_t)&sb->sb_flags, mutex_held,
                        (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH, "sblock", 0);
                if (so->so_usecount < 1)
                        panic("sb_lock: 2 so=%x refcount=%d\n", so, so->so_usecount);
                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(so, sb)
        register struct socket *so;
        register struct sockbuf *sb;
{
        struct proc *p = current_proc();
        sb->sb_flags &= ~SB_SEL;
        selwakeup(&sb->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) {
                if (so->so_pgid < 0)
                        gsignal(-so->so_pgid, SIGIO);
                else if (so->so_pgid > 0 && (p = pfind(so->so_pgid)) != 0)
                        psignal(p, SIGIO);
        }
        if (sb->sb_flags & SB_KNOTE) {
                KNOTE(&sb->sb_sel.si_note, SO_FILT_HINT_LOCKED);
        }
        if (sb->sb_flags & SB_UPCALL) {
                socket_unlock(so, 0);
                (*so->so_upcall)(so, so->so_upcallarg, M_DONTWAIT);
                socket_lock(so, 0);
        }
}

/*
 * 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(so, sndcc, rcvcc)
        register struct socket *so;
        u_long sndcc, rcvcc;
{

        if (sbreserve(&so->so_snd, sndcc) == 0)
                goto bad;
        if (sbreserve(&so->so_rcv, rcvcc) == 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:
#ifdef __APPLE__
        selthreadclear(&so->so_snd.sb_sel);
#endif
        sbrelease(&so->so_snd);
bad:
        return (ENOBUFS);
}

/*
 * 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(sb, cc)
        struct sockbuf *sb;
        u_long cc;
{
        if ((u_quad_t)cc > (u_quad_t)sb_max * MCLBYTES / (MSIZE + MCLBYTES))
                return (0);
        sb->sb_hiwat = cc;
        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.
 */
 /*  WARNING needs to do selthreadclear() before calling this */
void
sbrelease(sb)
        struct sockbuf *sb;
{

        sbflush(sb);
        sb->sb_hiwat = 0;
        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.
 */
int
sbappend(sb, m)
        struct sockbuf *sb;
        struct mbuf *m;
{
        register struct mbuf *n, *sb_first;
        int result = 0;
        int error = 0;
        int     filtered = 0;


        KERNEL_DEBUG((DBG_FNC_SBAPPEND | DBG_FUNC_START), sb, m->m_len, 0, 0, 0);

        if (m == 0)
                return 0;
        
again:
        sb_first = n = sb->sb_mb;
        if (n) {
                while (n->m_nextpkt)
                        n = n->m_nextpkt;
                do {
                        if (n->m_flags & M_EOR) {
                                result = sbappendrecord(sb, m); /* XXXXXX!!!! */
                                KERNEL_DEBUG((DBG_FNC_SBAPPEND | DBG_FUNC_END), sb, sb->sb_cc, 0, 0, 0);
                                return result;
                        }
                } while (n->m_next && (n = n->m_next));
        }
        
        if (!filtered && (sb->sb_flags & SB_RECV) != 0) {
                error = sflt_data_in(sb->sb_so, NULL, &m, NULL, 0, &filtered);
                if (error) {
                        /* no data was appended, caller should not call sowakeup */
                        return 0;
                }
                
                /*
                  If we any filters, the socket lock was dropped. n and sb_first
                  cached data from the socket buffer. This cache is not valid
                  since we dropped the lock. We must start over. Since filtered
                  is set we won't run through the filters a second time. We just
                  set n and sb_start again.
                */
                if (filtered)
                        goto again;
        }

        result = sbcompress(sb, m, n);

        KERNEL_DEBUG((DBG_FNC_SBAPPEND | DBG_FUNC_END), sb, sb->sb_cc, 0, 0, 0);
        
        return result;
}

#ifdef SOCKBUF_DEBUG
void
sbcheck(sb)
        register struct sockbuf *sb;
{
        register struct mbuf *m;
        register struct mbuf *n = 0;
        register u_long len = 0, mbcnt = 0;
        lck_mtx_t *mutex_held;

        if (sb->sb_so->so_proto->pr_getlock != NULL) 
                mutex_held = (*sb->sb_so->so_proto->pr_getlock)(sb->sb_so, 0);
        else 
                mutex_held = sb->sb_so->so_proto->pr_domain->dom_mtx;

        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

        if (sbchecking == 0)
                return;

        for (m = sb->sb_mb; m; m = n) {
            n = m->m_nextpkt;
            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 (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
                panic("cc %ld != %ld || mbcnt %ld != %ld\n", len, sb->sb_cc,
                    mbcnt, sb->sb_mbcnt);
        }
}
#endif

/*
 * As above, except the mbuf chain
 * begins a new record.
 */
int
sbappendrecord(sb, m0)
        register struct sockbuf *sb;
        struct mbuf *m0;
{
        register struct mbuf *m;
        int result = 0;

        if (m0 == 0)
                return 0;
    
        if ((sb->sb_flags & SB_RECV) != 0) {
                int error = sflt_data_in(sb->sb_so, NULL, &m0, NULL, sock_data_filt_flag_record, NULL);
                if (error != 0) {
                        if (error != EJUSTRETURN)
                                m_freem(m0);
                        return 0;
                }
        }
    
        m = sb->sb_mb;
        if (m)
                while (m->m_nextpkt)
                        m = m->m_nextpkt;
        /*
         * Put the first mbuf on the queue.
         * Note this permits zero length records.
         */
        sballoc(sb, m0);
        if (m)
                m->m_nextpkt = m0;
        else
                sb->sb_mb = m0;
        m = m0->m_next;
        m0->m_next = 0;
        if (m && (m0->m_flags & M_EOR)) {
                m0->m_flags &= ~M_EOR;
                m->m_flags |= M_EOR;
        }
        return sbcompress(sb, m, m0);
}

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

        if (m0 == 0)
                return 0;
        
        if ((sb->sb_flags & SB_RECV) != 0) {
                int error = sflt_data_in(sb->sb_so, NULL, &m0, NULL,
                                                                 sock_data_filt_flag_oob, NULL);
                
                if (error) {
                        if (error != EJUSTRETURN) {
                                m_freem(m0);
                        }
                        return 0;
                }
        }
    
        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;
        m = m0->m_next;
        m0->m_next = 0;
        if (m && (m0->m_flags & M_EOR)) {
                m0->m_flags &= ~M_EOR;
                m->m_flags |= M_EOR;
        }
        return sbcompress(sb, m, m0);
}

/*
 * 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.
 */
static int
sbappendaddr_internal(sb, asa, m0, control)
        register struct sockbuf *sb;
        struct sockaddr *asa;
        struct mbuf *m0, *control;
{
        register struct mbuf *m, *n;
        int space = asa->sa_len;

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

        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, M_DONTWAIT, MT_SONAME);
        if (m == 0)
                return (0);
        m->m_len = asa->sa_len;
        bcopy((caddr_t)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);
        n = sb->sb_mb;
        if (n) {
                while (n->m_nextpkt)
                        n = n->m_nextpkt;
                n->m_nextpkt = m;
        } else
                sb->sb_mb = m;
        postevent(0,sb,EV_RWBYTES);
        return (1);
}

int
sbappendaddr(
        struct sockbuf* sb,
        struct sockaddr* asa,
        struct mbuf *m0,
        struct mbuf *control,
        int     *error_out)
{
        int result = 0;
        
        if (error_out) *error_out = 0;
        
        if (m0 && (m0->m_flags & M_PKTHDR) == 0)
                panic("sbappendaddrorfree");
        
        /* Call socket data in filters */
        if ((sb->sb_flags & SB_RECV) != 0) {
                int error;
                error = sflt_data_in(sb->sb_so, asa, &m0, &control, 0, NULL);
                if (error) {
                        if (error != EJUSTRETURN) {
                                if (m0) m_freem(m0);
                                if (control) m_freem(control);
                                if (error_out) *error_out = error;
                        }
                        return 0;
                }
        }
        
        result = sbappendaddr_internal(sb, asa, m0, control);
        if (result == 0) {
                if (m0) m_freem(m0);
                if (control) m_freem(control);
                if (error_out) *error_out = ENOBUFS;
        }
        
        return result;
}

static int
sbappendcontrol_internal(sb, m0, control)
        struct sockbuf *sb;
        struct mbuf *control, *m0;
{
        register struct mbuf *m, *n;
        int space = 0;

        if (control == 0)
                panic("sbappendcontrol");

        for (m = control; ; m = m->m_next) {
                space += m->m_len;
                if (m->m_next == 0)
                        break;
        }
        n = m;                  /* save pointer to last control buffer */
        for (m = m0; m; m = m->m_next)
                space += m->m_len;
        if (space > sbspace(sb))
                return (0);
        n->m_next = m0;                 /* concatenate data to control */
        for (m = control; m; m = m->m_next)
                sballoc(sb, m);
        n = sb->sb_mb;
        if (n) {
                while (n->m_nextpkt)
                        n = n->m_nextpkt;
                n->m_nextpkt = control;
        } else
                sb->sb_mb = control;
        postevent(0,sb,EV_RWBYTES);
        return (1);
}

int
sbappendcontrol(
        struct sockbuf  *sb,
        struct mbuf             *m0,
        struct mbuf             *control,
        int                             *error_out)
{
        int result = 0;
        
        if (error_out) *error_out = 0;
        
        if (sb->sb_flags & SB_RECV) {
                int error;
                error = sflt_data_in(sb->sb_so, NULL, &m0, &control, 0, NULL);
                if (error) {
                        if (error != EJUSTRETURN) {
                                if (m0) m_freem(m0);
                                if (control) m_freem(control);
                                if (error_out) *error_out = error;
                        }
                        return 0;
                }
        }
        
        result = sbappendcontrol_internal(sb, m0, control);
        if (result == 0) {
                if (m0) m_freem(m0);
                if (control) m_freem(control);
                if (error_out) *error_out = ENOBUFS;
        }
        
        return result;
}

/*
 * Compress mbuf chain m into the socket
 * buffer sb following mbuf n.  If n
 * is null, the buffer is presumed empty.
 */
static int
sbcompress(sb, m, n)
        register struct sockbuf *sb;
        register struct mbuf *m, *n;
{
        register int eor = 0;
        register struct mbuf *o;

        while (m) {
                eor |= m->m_flags & M_EOR;
                if (m->m_len == 0 &&
                    (eor == 0 ||
                     (((o = m->m_next) || (o = n)) &&
                      o->m_type == m->m_type))) {
                        m = m_free(m);
                        continue;
                }
                if (n && (n->m_flags & M_EOR) == 0 &&
#ifndef __APPLE__
                    M_WRITABLE(n) &&
#endif
                    m->m_len <= MCLBYTES / 4 && /* XXX: Don't copy too much */
                    m->m_len <= M_TRAILINGSPACE(n) &&
                    n->m_type == m->m_type) {
                        bcopy(mtod(m, caddr_t), mtod(n, caddr_t) + n->m_len,
                            (unsigned)m->m_len);
                        n->m_len += m->m_len;
                        sb->sb_cc += m->m_len;
                        m = m_free(m);
                        continue;
                }
                if (n)
                        n->m_next = m;
                else
                        sb->sb_mb = m;
                sballoc(sb, m);
                n = m;
                m->m_flags &= ~M_EOR;
                m = m->m_next;
                n->m_next = 0;
        }
        if (eor) {
                if (n)
                        n->m_flags |= eor;
                else
                        printf("semi-panic: sbcompress\n");
        }
        postevent(0,sb, EV_RWBYTES);
        return 1;
}

/*
 * Free all mbufs in a sockbuf.
 * Check that all resources are reclaimed.
 */
void
sbflush(sb)
        register struct sockbuf *sb;
{
        if (sb->sb_so == NULL)
                panic ("sbflush sb->sb_so already null sb=%x\n", sb);
        (void)sblock(sb, M_WAIT);
        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);
        }
        if (sb->sb_cc || sb->sb_mb || sb->sb_mbcnt || sb->sb_so == NULL)
                panic("sbflush: cc %ld || mb %p || mbcnt %ld sb_so=%x", sb->sb_cc, (void *)sb->sb_mb, sb->sb_mbcnt, sb->sb_so);

        postevent(0, sb, EV_RWBYTES);
        sbunlock(sb, 1);        /* keep socket locked */

}

/*
 * Drop data from (the front of) a sockbuf.
 * use m_freem_list to free the mbuf structures
 * under a single lock... this is done by pruning
 * the top of the tree from the body by keeping track
 * of where we get to in the tree and then zeroing the
 * two pertinent pointers m_nextpkt and m_next
 * the socket buffer is then updated to point at the new
 * top of the tree and the pruned area is released via
 * m_freem_list.
 */
void
sbdrop(sb, len)
        register struct sockbuf *sb;
        register int len;
{
        register struct mbuf *m, *free_list, *ml;
        struct mbuf *next, *last;

        KERNEL_DEBUG((DBG_FNC_SBDROP | DBG_FUNC_START), sb, len, 0, 0, 0);

        next = (m = sb->sb_mb) ? m->m_nextpkt : 0;
        free_list = last = m;
        ml = (struct mbuf *)0;

        while (len > 0) {
                if (m == 0) {
                  if (next == 0) {
                    /* temporarily replacing this panic with printf because
                     * it occurs occasionally when closing a socket when there
                     * is no harm in ignoring it.  This problem will be investigated
                     * further.
                     */
                    /* panic("sbdrop"); */
                    printf("sbdrop - count not zero\n");
                    len = 0;
                    /* zero the counts. if we have no mbufs, we have no data (PR-2986815) */
                    sb->sb_cc = 0;
                    sb->sb_mbcnt = 0;
                    break;
                  }
                  m = last = next;
                  next = m->m_nextpkt;
                  continue;
                }
                if (m->m_len > len) {
                        m->m_len -= len;
                        m->m_data += len;
                        sb->sb_cc -= len;
                        break;
                }
                len -= m->m_len;
                sbfree(sb, m);

                ml = m;
                m = m->m_next;
        }
        while (m && m->m_len == 0) {
                sbfree(sb, m);

                ml = m;
                m = m->m_next;
        }
        if (ml) {
                ml->m_next = (struct mbuf *)0;
                last->m_nextpkt = (struct mbuf *)0;
                m_freem_list(free_list);
        }
        if (m) {
                sb->sb_mb = m;
                m->m_nextpkt = next;
        } else
                sb->sb_mb = next;

        postevent(0, sb, EV_RWBYTES);

        KERNEL_DEBUG((DBG_FNC_SBDROP | DBG_FUNC_END), sb, 0, 0, 0, 0);
}

/*
 * Drop a record off the front of a sockbuf
 * and move the next record to the front.
 */
void
sbdroprecord(sb)
        register struct sockbuf *sb;
{
        register struct mbuf *m, *mn;

        m = sb->sb_mb;
        if (m) {
                sb->sb_mb = m->m_nextpkt;
                do {
                        sbfree(sb, m);
                        MFREE(m, mn);
                        m = mn;
                } while (m);
        }
        postevent(0, sb, EV_RWBYTES);
}

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

        if (CMSG_SPACE((u_int)size) > MLEN)
                return ((struct mbuf *) NULL);
        if ((m = m_get(M_DONTWAIT, MT_CONTROL)) == NULL)
                return ((struct mbuf *) NULL);
        cp = mtod(m, struct cmsghdr *);
        /* XXX check size? */
        (void)memcpy(CMSG_DATA(cp), p, size);
        m->m_len = CMSG_SPACE(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_abort_notsupp(struct socket *so)
{
        return EOPNOTSUPP;
}


int
pru_accept_notsupp(struct socket *so, struct sockaddr **nam)
{
        return EOPNOTSUPP;
}

int
pru_attach_notsupp(struct socket *so, int proto, struct proc *p)
{
        return EOPNOTSUPP;
}

int
pru_bind_notsupp(struct socket *so, struct sockaddr *nam, struct proc *p)
{
        return EOPNOTSUPP;
}

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

int
pru_detach_notsupp(struct socket *so)
{
        return EOPNOTSUPP;
}

int
pru_disconnect_notsupp(struct socket *so)
{
        return EOPNOTSUPP;
}

int
pru_listen_notsupp(struct socket *so, struct proc *p)
{
        return EOPNOTSUPP;
}

int
pru_peeraddr_notsupp(struct socket *so, struct sockaddr **nam)
{
        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;
}

int
pru_send_notsupp(struct socket *so, int flags, struct mbuf *m,
                 struct sockaddr *addr, struct mbuf *control,
                 struct proc *p)

{
        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;
}


int     pru_sosend_notsupp(struct socket *so, struct sockaddr *addr,
                   struct uio *uio, struct mbuf *top,
                   struct mbuf *control, int flags)

{
    return EOPNOTSUPP;
}

int     pru_soreceive_notsupp(struct socket *so, 
                      struct sockaddr **paddr,
                      struct uio *uio, struct mbuf **mp0,
                      struct mbuf **controlp, int *flagsp)
{
    return EOPNOTSUPP;
}

int

pru_shutdown_notsupp(struct socket *so)
{
        return EOPNOTSUPP;
}

int
pru_sockaddr_notsupp(struct socket *so, struct sockaddr **nam)
{
        return EOPNOTSUPP;
}

int     pru_sosend(struct socket *so, struct sockaddr *addr,
                   struct uio *uio, struct mbuf *top,
                   struct mbuf *control, int flags)
{
        return EOPNOTSUPP;
}

int     pru_soreceive(struct socket *so,
                      struct sockaddr **paddr,
                      struct uio *uio, struct mbuf **mp0,
                      struct mbuf **controlp, int *flagsp)
{
        return EOPNOTSUPP;
}


int
pru_sopoll_notsupp(__unused struct socket *so, __unused int events,
                   __unused kauth_cred_t cred, __unused void *wql)
{
    return EOPNOTSUPP;
}


#ifdef __APPLE__
/*
 * The following are macros on BSD and functions on Darwin
 */

/*
 * Do we need to notify the other side when I/O is possible?
 */

int 
sb_notify(struct sockbuf *sb)
{
        return ((sb->sb_flags & (SB_WAIT|SB_SEL|SB_ASYNC|SB_UPCALL|SB_KNOTE)) != 0); 
}

/*
 * How much space is there in a socket buffer (so->so_snd or so->so_rcv)?
 * This is problematical if the fields are unsigned, as the space might
 * still be negative (cc > hiwat or mbcnt > mbmax).  Should detect
 * overflow and return 0.  Should use "lmin" but it doesn't exist now.
 */
long
sbspace(struct sockbuf *sb)
{
    return ((long) imin((int)(sb->sb_hiwat - sb->sb_cc), 
         (int)(sb->sb_mbmax - sb->sb_mbcnt)));
}

/* do we have to send all at once on a socket? */
int
sosendallatonce(struct socket *so)
{
    return (so->so_proto->pr_flags & PR_ATOMIC);
}

/* can we read something from so? */
int
soreadable(struct socket *so)
{
    return (so->so_rcv.sb_cc >= so->so_rcv.sb_lowat || 
        (so->so_state & SS_CANTRCVMORE) || 
        so->so_comp.tqh_first || so->so_error);
}

/* can we write something to so? */

int
sowriteable(struct socket *so)
{
    return ((sbspace(&(so)->so_snd) >= (so)->so_snd.sb_lowat && 
        ((so->so_state&SS_ISCONNECTED) || 
          (so->so_proto->pr_flags&PR_CONNREQUIRED)==0)) || 
     (so->so_state & SS_CANTSENDMORE) || 
     so->so_error);
}

/* adjust counters in sb reflecting allocation of m */

void
sballoc(struct sockbuf *sb, struct mbuf *m)
{
        sb->sb_cc += m->m_len; 
        sb->sb_mbcnt += MSIZE; 
        if (m->m_flags & M_EXT) 
                sb->sb_mbcnt += m->m_ext.ext_size; 
}

/* adjust counters in sb reflecting freeing of m */
void
sbfree(struct sockbuf *sb, struct mbuf *m)
{
        sb->sb_cc -= m->m_len; 
        sb->sb_mbcnt -= MSIZE; 
        if (m->m_flags & M_EXT) 
                sb->sb_mbcnt -= m->m_ext.ext_size; 
}

/*
 * Set lock on sockbuf sb; sleep if lock is already held.
 * Unless SB_NOINTR is set on sockbuf, sleep is interruptible.
 * Returns error without lock if sleep is interrupted.
 */
int
sblock(struct sockbuf *sb, int wf)
{
        return(sb->sb_flags & SB_LOCK ? 
                ((wf == M_WAIT) ? sb_lock(sb) : EWOULDBLOCK) : 
                (sb->sb_flags |= SB_LOCK), 0);
}

/* release lock on sockbuf sb */
void
sbunlock(struct sockbuf *sb, int keeplocked)
{
        struct socket *so = sb->sb_so;
        int lr_saved;
        lck_mtx_t *mutex_held;


        lr_saved = (unsigned int) __builtin_return_address(0);

        sb->sb_flags &= ~SB_LOCK; 

        if (so->so_proto->pr_getlock != NULL) 
                mutex_held = (*so->so_proto->pr_getlock)(so, 0);
        else 
                mutex_held = so->so_proto->pr_domain->dom_mtx;

        if (keeplocked == 0)
                lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

        if (sb->sb_flags & SB_WANT) { 
                sb->sb_flags &= ~SB_WANT; 
                if (so->so_usecount < 0)
                        panic("sbunlock: b4 wakeup so=%x ref=%d lr=%x sb_flags=%x\n", sb->sb_so, so->so_usecount, lr_saved, sb->sb_flags);

                wakeup((caddr_t)&(sb)->sb_flags); 
        } 
        if (keeplocked == 0) {  /* unlock on exit */
                so->so_usecount--;
                if (so->so_usecount < 0)
                        panic("sbunlock: unlock on exit so=%x lr=%x sb_flags=%x\n", so, so->so_usecount,lr_saved, sb->sb_flags);
                so->unlock_lr[so->next_unlock_lr] = (void *)lr_saved;
                so->next_unlock_lr = (so->next_unlock_lr+1) % SO_LCKDBG_MAX;
                lck_mtx_unlock(mutex_held);
        }
}

void
sorwakeup(struct socket * so)
{
  if (sb_notify(&so->so_rcv)) 
        sowakeup(so, &so->so_rcv); 
}

void
sowwakeup(struct socket * so)
{
  if (sb_notify(&so->so_snd)) 
        sowakeup(so, &so->so_snd); 
}
#endif __APPLE__

/*
 * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.
 */
struct sockaddr *
dup_sockaddr(sa, canwait)
        struct sockaddr *sa;
        int canwait;
{
        struct sockaddr *sa2;

        MALLOC(sa2, struct sockaddr *, sa->sa_len, M_SONAME, 
               canwait ? M_WAITOK : M_NOWAIT);
        if (sa2)
                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;
        if (so->so_proto) {
                xso->xso_protocol = so->so_proto->pr_protocol;
                xso->xso_family = so->so_proto->pr_domain->dom_family;
        }
        else 
                xso->xso_protocol = xso->xso_family = 0;
        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_pgid;
        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_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 = (u_long)(sb->sb_timeo.tv_sec * hz) + sb->sb_timeo.tv_usec / tick;
        if (xsb->sb_timeo == 0 && sb->sb_timeo.tv_usec != 0)
                xsb->sb_timeo = 1;
}

/*
 * 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_INT(_kern_ipc, KIPC_MAXSOCKBUF, maxsockbuf, CTLFLAG_RW, 
    &sb_max, 0, "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, "");
SYSCTL_INT(_kern_ipc, KIPC_NMBCLUSTERS, nmbclusters, CTLFLAG_RD, &nmbclusters, 0, "");