Return to uipc_socket2.c CVS log

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Turn sblock() to `sb_lock' rwlock(9) wrapper for all sockets.

Unify behaviour to all sockets. Now sblock() should be always
taken before solock() in all involved paths as sosend(), soreceive(),
sorflush() and sosplice(). sblock() is fine-grained lock which
serializes socket send and receive routines on `so_rcv' or `so_snd'
buffers. There is no big problem to wait netlock while holding sblock().

This unification removes a lot of temporary "sb_flags & SB_MTXLOCK" code
from sockets layer. This unification makes straight "solock()" and
"sblock()" lock order, no more solock() -> sblock() -> sounlock() ->
solock() -> sbunlock() -> sounlock() chains in sosend() and soreceive()
paths. This unification brings witness(4) support for sblock(), include
NFS involved sockets, which is useful.

Since the witness(4) support was introduced to sblock() with this diff,
some new witness reports appeared.

bulk(1) tests by tb, ok bluhm

/*	$OpenBSD: uipc_socket2.c,v 1.155 2024/05/17 19:11:14 mvs Exp $	*/
/*	$NetBSD: uipc_socket2.c,v 1.11 1996/02/04 02:17:55 christos Exp $	*/

/*
 * 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. 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
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/domain.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/signalvar.h>
#include <sys/pool.h>

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

u_long	sb_max = SB_MAX;		/* patchable */

extern struct pool mclpools[];
extern struct pool mbpool;

/*
 * 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_q0 for connections in progress
 * and so_q for connections already made and awaiting user acceptance.
 * As a protocol is preparing incoming connections, it creates a socket
 * structure queued on so_q0 by calling sonewconn().  When the connection
 * is established, soisconnected() is called, and transfers the
 * socket structure to so_q, making it available to accept().
 *
 * If a socket is closed with sockets on either
 * so_q0 or so_q, 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)
{
	soassertlocked(so);
	so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
	so->so_state |= SS_ISCONNECTING;
}

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

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

	if (head != NULL && so->so_onq == &head->so_q0) {
		int persocket = solock_persocket(so);

		if (persocket) {
			soref(so);
			soref(head);

			sounlock(so);
			solock(head);
			solock(so);

			if (so->so_onq != &head->so_q0) {
				sounlock(head);
				sorele(head);
				sorele(so);

				return;
			}

			sorele(head);
			sorele(so);
		}

		soqremque(so, 0);
		soqinsque(head, so, 1);
		sorwakeup(head);
		wakeup_one(&head->so_timeo);

		if (persocket)
			sounlock(head);
	} else {
		wakeup(&so->so_timeo);
		sorwakeup(so);
		sowwakeup(so);
	}
}

void
soisdisconnecting(struct socket *so)
{
	soassertlocked(so);
	so->so_state &= ~SS_ISCONNECTING;
	so->so_state |= SS_ISDISCONNECTING;

	mtx_enter(&so->so_rcv.sb_mtx);
	so->so_rcv.sb_state |= SS_CANTRCVMORE;
	mtx_leave(&so->so_rcv.sb_mtx);

	mtx_enter(&so->so_snd.sb_mtx);
	so->so_snd.sb_state |= SS_CANTSENDMORE;
	mtx_leave(&so->so_snd.sb_mtx);

	wakeup(&so->so_timeo);
	sowwakeup(so);
	sorwakeup(so);
}

void
soisdisconnected(struct socket *so)
{
	soassertlocked(so);
	so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
	so->so_state |= SS_ISDISCONNECTED;

	mtx_enter(&so->so_rcv.sb_mtx);
	so->so_rcv.sb_state |= SS_CANTRCVMORE;
	mtx_leave(&so->so_rcv.sb_mtx);

	mtx_enter(&so->so_snd.sb_mtx);
	so->so_snd.sb_state |= SS_CANTSENDMORE;
	mtx_leave(&so->so_snd.sb_mtx);

	wakeup(&so->so_timeo);
	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, properly linked into the
 * data structure of the original socket, and return this.
 * Connstatus may be 0 or SS_ISCONNECTED.
 */
struct socket *
sonewconn(struct socket *head, int connstatus, int wait)
{
	struct socket *so;
	int persocket = solock_persocket(head);
	int soqueue = connstatus ? 1 : 0;

	/*
	 * XXXSMP as long as `so' and `head' share the same lock, we
	 * can call soreserve() and pr_attach() below w/o explicitly
	 * locking `so'.
	 */
	soassertlocked(head);

	if (m_pool_used() > 95)
		return (NULL);
	if (head->so_qlen + head->so_q0len > head->so_qlimit * 3)
		return (NULL);
	so = soalloc(head->so_proto, wait);
	if (so == NULL)
		return (NULL);
	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_euid = head->so_euid;
	so->so_ruid = head->so_ruid;
	so->so_egid = head->so_egid;
	so->so_rgid = head->so_rgid;
	so->so_cpid = head->so_cpid;

	/*
	 * Lock order will be `head' -> `so' while these sockets are linked.
	 */
	if (persocket)
		solock(so);

	/*
	 * Inherit watermarks but those may get clamped in low mem situations.
	 */
	if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat))
		goto fail;

	mtx_enter(&head->so_snd.sb_mtx);
	so->so_snd.sb_wat = head->so_snd.sb_wat;
	so->so_snd.sb_lowat = head->so_snd.sb_lowat;
	so->so_snd.sb_timeo_nsecs = head->so_snd.sb_timeo_nsecs;
	mtx_leave(&head->so_snd.sb_mtx);

	mtx_enter(&head->so_rcv.sb_mtx);
	so->so_rcv.sb_wat = head->so_rcv.sb_wat;
	so->so_rcv.sb_lowat = head->so_rcv.sb_lowat;
	so->so_rcv.sb_timeo_nsecs = head->so_rcv.sb_timeo_nsecs;
	mtx_leave(&head->so_rcv.sb_mtx);

	sigio_copy(&so->so_sigio, &head->so_sigio);

	soqinsque(head, so, soqueue);
	if (pru_attach(so, 0, wait) != 0) {
		soqremque(so, soqueue);
		goto fail;
	}
	if (connstatus) {
		so->so_state |= connstatus;
		sorwakeup(head);
		wakeup(&head->so_timeo);
	}

	if (persocket)
		sounlock(so);

	return (so);

fail:
	if (persocket)
		sounlock(so);
	sigio_free(&so->so_sigio);
	klist_free(&so->so_rcv.sb_klist);
	klist_free(&so->so_snd.sb_klist);
	pool_put(&socket_pool, so);

	return (NULL);
}

void
soqinsque(struct socket *head, struct socket *so, int q)
{
	soassertlocked(head);
	soassertlocked(so);

	KASSERT(so->so_onq == NULL);

	so->so_head = head;
	if (q == 0) {
		head->so_q0len++;
		so->so_onq = &head->so_q0;
	} else {
		head->so_qlen++;
		so->so_onq = &head->so_q;
	}
	TAILQ_INSERT_TAIL(so->so_onq, so, so_qe);
}

int
soqremque(struct socket *so, int q)
{
	struct socket *head = so->so_head;

	soassertlocked(so);
	soassertlocked(head);

	if (q == 0) {
		if (so->so_onq != &head->so_q0)
			return (0);
		head->so_q0len--;
	} else {
		if (so->so_onq != &head->so_q)
			return (0);
		head->so_qlen--;
	}
	TAILQ_REMOVE(so->so_onq, so, so_qe);
	so->so_onq = NULL;
	so->so_head = NULL;
	return (1);
}

/*
 * 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)
{
	soassertlocked(so);
	mtx_enter(&so->so_snd.sb_mtx);
	so->so_snd.sb_state |= SS_CANTSENDMORE;
	mtx_leave(&so->so_snd.sb_mtx);
	sowwakeup(so);
}

void
socantrcvmore(struct socket *so)
{
	if ((so->so_rcv.sb_flags & SB_MTXLOCK) == 0)
		soassertlocked(so);

	mtx_enter(&so->so_rcv.sb_mtx);
	so->so_rcv.sb_state |= SS_CANTRCVMORE;
	mtx_leave(&so->so_rcv.sb_mtx);
	sorwakeup(so);
}

void
solock(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		NET_LOCK();
		break;
	default:
		rw_enter_write(&so->so_lock);
		break;
	}
}

void
solock_shared(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		if (so->so_proto->pr_usrreqs->pru_lock != NULL) {
			NET_LOCK_SHARED();
			rw_enter_write(&so->so_lock);
		} else
			NET_LOCK();
		break;
	default:
		rw_enter_write(&so->so_lock);
		break;
	}
}

int
solock_persocket(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		return 0;
	default:
		return 1;
	}
}

void
solock_pair(struct socket *so1, struct socket *so2)
{
	KASSERT(so1 != so2);
	KASSERT(so1->so_type == so2->so_type);
	KASSERT(solock_persocket(so1));

	if (so1 < so2) {
		solock(so1);
		solock(so2);
	} else {
		solock(so2);
		solock(so1);
	}
}

void
sounlock(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		NET_UNLOCK();
		break;
	default:
		rw_exit_write(&so->so_lock);
		break;
	}
}

void
sounlock_shared(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		if (so->so_proto->pr_usrreqs->pru_unlock != NULL) {
			rw_exit_write(&so->so_lock);
			NET_UNLOCK_SHARED();
		} else
			NET_UNLOCK();
		break;
	default:
		rw_exit_write(&so->so_lock);
		break;
	}
}

void
soassertlocked_readonly(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		NET_ASSERT_LOCKED();
		break;
	default:
		rw_assert_wrlock(&so->so_lock);
		break;
	}
}

void
soassertlocked(struct socket *so)
{
	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		if (rw_status(&netlock) == RW_READ) {
			NET_ASSERT_LOCKED();

			if (splassert_ctl > 0 && pru_locked(so) == 0 &&
			    rw_status(&so->so_lock) != RW_WRITE)
				splassert_fail(0, RW_WRITE, __func__);
		} else
			NET_ASSERT_LOCKED_EXCLUSIVE();
		break;
	default:
		rw_assert_wrlock(&so->so_lock);
		break;
	}
}

int
sosleep_nsec(struct socket *so, void *ident, int prio, const char *wmesg,
    uint64_t nsecs)
{
	int ret;

	switch (so->so_proto->pr_domain->dom_family) {
	case PF_INET:
	case PF_INET6:
		if (so->so_proto->pr_usrreqs->pru_unlock != NULL &&
		    rw_status(&netlock) == RW_READ) {
			rw_exit_write(&so->so_lock);
		}
		ret = rwsleep_nsec(ident, &netlock, prio, wmesg, nsecs);
		if (so->so_proto->pr_usrreqs->pru_lock != NULL &&
		    rw_status(&netlock) == RW_READ) {
			rw_enter_write(&so->so_lock);
		}
		break;
	default:
		ret = rwsleep_nsec(ident, &so->so_lock, prio, wmesg, nsecs);
		break;
	}

	return ret;
}

void
sbmtxassertlocked(struct socket *so, struct sockbuf *sb)
{
	if (sb->sb_flags & SB_MTXLOCK) {
		if (splassert_ctl > 0 && mtx_owned(&sb->sb_mtx) == 0)
			splassert_fail(0, RW_WRITE, __func__);
	} else
		soassertlocked(so);
}

/*
 * Wait for data to arrive at/drain from a socket buffer.
 */
int
sbwait(struct socket *so, struct sockbuf *sb)
{
	uint64_t timeo_nsecs;
	int prio = (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH;

	if (sb->sb_flags & SB_MTXLOCK) {
		MUTEX_ASSERT_LOCKED(&sb->sb_mtx);

		sb->sb_flags |= SB_WAIT;
		return msleep_nsec(&sb->sb_cc, &sb->sb_mtx, prio, "sbwait",
		    sb->sb_timeo_nsecs);
	}

	soassertlocked(so);

	mtx_enter(&sb->sb_mtx);
	timeo_nsecs = sb->sb_timeo_nsecs;
	sb->sb_flags |= SB_WAIT;
	mtx_leave(&sb->sb_mtx);

	return sosleep_nsec(so, &sb->sb_cc, prio, "netio", timeo_nsecs);
}

int
sblock(struct sockbuf *sb, int flags)
{
	int rwflags = RW_WRITE, error;

	if (!(flags & SBL_NOINTR || sb->sb_flags & SB_NOINTR))
		rwflags |= RW_INTR;
	if (!(flags & SBL_WAIT))
		rwflags |= RW_NOSLEEP;

	error = rw_enter(&sb->sb_lock, rwflags);
	if (error == EBUSY)
		error = EWOULDBLOCK;

	return error;
}

void
sbunlock(struct sockbuf *sb)
{
	rw_exit(&sb->sb_lock);
}

/*
 * Wakeup processes waiting on a socket buffer.
 * Do asynchronous notification via SIGIO
 * if the socket buffer has the SB_ASYNC flag set.
 */
void
sowakeup(struct socket *so, struct sockbuf *sb)
{
	int dowakeup = 0, dopgsigio = 0;

	mtx_enter(&sb->sb_mtx);
	if (sb->sb_flags & SB_WAIT) {
		sb->sb_flags &= ~SB_WAIT;
		dowakeup = 1;
	}
	if (sb->sb_flags & SB_ASYNC)
		dopgsigio = 1;

	knote_locked(&sb->sb_klist, 0);
	mtx_leave(&sb->sb_mtx);

	if (dowakeup)
		wakeup(&sb->sb_cc);

	if (dopgsigio)
		pgsigio(&so->so_sigio, SIGIO, 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_CONTROL).
 * 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)
{
	soassertlocked(so);

	mtx_enter(&so->so_rcv.sb_mtx);
	mtx_enter(&so->so_snd.sb_mtx);
	if (sbreserve(so, &so->so_snd, sndcc))
		goto bad;
	so->so_snd.sb_wat = sndcc;
	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;
	if (sbreserve(so, &so->so_rcv, rcvcc))
		goto bad2;
	so->so_rcv.sb_wat = rcvcc;
	if (so->so_rcv.sb_lowat == 0)
		so->so_rcv.sb_lowat = 1;
	mtx_leave(&so->so_snd.sb_mtx);
	mtx_leave(&so->so_rcv.sb_mtx);

	return (0);
bad2:
	sbrelease(so, &so->so_snd);
bad:
	mtx_leave(&so->so_snd.sb_mtx);
	mtx_leave(&so->so_rcv.sb_mtx);
	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(struct socket *so, struct sockbuf *sb, u_long cc)
{
	sbmtxassertlocked(so, sb);

	if (cc == 0 || cc > sb_max)
		return (1);
	sb->sb_hiwat = cc;
	sb->sb_mbmax = max(3 * MAXMCLBYTES, cc * 8);
	if (sb->sb_lowat > sb->sb_hiwat)
		sb->sb_lowat = sb->sb_hiwat;
	return (0);
}

/*
 * In low memory situation, do not accept any greater than normal request.
 */
int
sbcheckreserve(u_long cnt, u_long defcnt)
{
	if (cnt > defcnt && sbchecklowmem())
		return (ENOBUFS);
	return (0);
}

int
sbchecklowmem(void)
{
	static int sblowmem;
	unsigned int used = m_pool_used();

	if (used < 60)
		sblowmem = 0;
	else if (used > 80)
		sblowmem = 1;

	return (sblowmem);
}

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

	sbflush(so, sb);
	sb->sb_hiwat = 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_copym 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.
 */

#ifdef SOCKBUF_DEBUG
void
sblastrecordchk(struct sockbuf *sb, const char *where)
{
	struct mbuf *m = sb->sb_mb;

	while (m && m->m_nextpkt)
		m = m->m_nextpkt;

	if (m != sb->sb_lastrecord) {
		printf("sblastrecordchk: sb_mb %p sb_lastrecord %p last %p\n",
		    sb->sb_mb, sb->sb_lastrecord, m);
		printf("packet chain:\n");
		for (m = sb->sb_mb; m != NULL; m = m->m_nextpkt)
			printf("\t%p\n", m);
		panic("sblastrecordchk from %s", where);
	}
}

void
sblastmbufchk(struct sockbuf *sb, const char *where)
{
	struct mbuf *m = sb->sb_mb;
	struct mbuf *n;

	while (m && m->m_nextpkt)
		m = m->m_nextpkt;

	while (m && m->m_next)
		m = m->m_next;

	if (m != sb->sb_mbtail) {
		printf("sblastmbufchk: sb_mb %p sb_mbtail %p last %p\n",
		    sb->sb_mb, sb->sb_mbtail, m);
		printf("packet tree:\n");
		for (m = sb->sb_mb; m != NULL; m = m->m_nextpkt) {
			printf("\t");
			for (n = m; n != NULL; n = n->m_next)
				printf("%p ", n);
			printf("\n");
		}
		panic("sblastmbufchk from %s", where);
	}
}
#endif /* SOCKBUF_DEBUG */

#define	SBLINKRECORD(sb, m0)						\
do {									\
	if ((sb)->sb_lastrecord != NULL)				\
		(sb)->sb_lastrecord->m_nextpkt = (m0);			\
	else								\
		(sb)->sb_mb = (m0);					\
	(sb)->sb_lastrecord = (m0);					\
} while (/*CONSTCOND*/0)

/*
 * 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 socket *so, struct sockbuf *sb, struct mbuf *m)
{
	struct mbuf *n;

	if (m == NULL)
		return;

	sbmtxassertlocked(so, sb);
	SBLASTRECORDCHK(sb, "sbappend 1");

	if ((n = sb->sb_lastrecord) != NULL) {
		/*
		 * XXX Would like to simply use sb_mbtail here, but
		 * XXX I need to verify that I won't miss an EOR that
		 * XXX way.
		 */
		do {
			if (n->m_flags & M_EOR) {
				sbappendrecord(so, sb, m); /* XXXXXX!!!! */
				return;
			}
		} while (n->m_next && (n = n->m_next));
	} else {
		/*
		 * If this is the first record in the socket buffer, it's
		 * also the last record.
		 */
		sb->sb_lastrecord = m;
	}
	sbcompress(so, sb, m, n);
	SBLASTRECORDCHK(sb, "sbappend 2");
}

/*
 * This version of sbappend() should only be used when the caller
 * absolutely knows that there will never be more than one record
 * in the socket buffer, that is, a stream protocol (such as TCP).
 */
void
sbappendstream(struct socket *so, struct sockbuf *sb, struct mbuf *m)
{
	KASSERT(sb == &so->so_rcv || sb == &so->so_snd);
	soassertlocked(so);
	KDASSERT(m->m_nextpkt == NULL);
	KASSERT(sb->sb_mb == sb->sb_lastrecord);

	SBLASTMBUFCHK(sb, __func__);

	sbcompress(so, sb, m, sb->sb_mbtail);

	sb->sb_lastrecord = sb->sb_mb;
	SBLASTRECORDCHK(sb, __func__);
}

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

	for (m = sb->sb_mb; m; m = m->m_nextpkt) {
		for (n = m; n; n = n->m_next) {
			len += n->m_len;
			mbcnt += MSIZE;
			if (n->m_flags & M_EXT)
				mbcnt += n->m_ext.ext_size;
			if (m != n && n->m_nextpkt)
				panic("sbcheck nextpkt");
		}
	}
	if (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
		printf("cc %lu != %lu || mbcnt %lu != %lu\n", len, sb->sb_cc,
		    mbcnt, sb->sb_mbcnt);
		panic("sbcheck");
	}
}
#endif

/*
 * As above, except the mbuf chain
 * begins a new record.
 */
void
sbappendrecord(struct socket *so, struct sockbuf *sb, struct mbuf *m0)
{
	struct mbuf *m;

	sbmtxassertlocked(so, sb);

	if (m0 == NULL)
		return;

	/*
	 * Put the first mbuf on the queue.
	 * Note this permits zero length records.
	 */
	sballoc(so, sb, m0);
	SBLASTRECORDCHK(sb, "sbappendrecord 1");
	SBLINKRECORD(sb, 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(so, sb, m, m0);
	SBLASTRECORDCHK(sb, "sbappendrecord 2");
}

/*
 * 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 socket *so, struct sockbuf *sb, const struct sockaddr *asa,
    struct mbuf *m0, struct mbuf *control)
{
	struct mbuf *m, *n, *nlast;
	int space = asa->sa_len;

	sbmtxassertlocked(so, sb);

	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 == NULL)	/* keep pointer to last control buf */
			break;
	}
	if (space > sbspace(so, sb))
		return (0);
	if (asa->sa_len > MLEN)
		return (0);
	MGET(m, M_DONTWAIT, MT_SONAME);
	if (m == NULL)
		return (0);
	m->m_len = asa->sa_len;
	memcpy(mtod(m, caddr_t), asa, asa->sa_len);
	if (n)
		n->m_next = m0;		/* concatenate data to control */
	else
		control = m0;
	m->m_next = control;

	SBLASTRECORDCHK(sb, "sbappendaddr 1");

	for (n = m; n->m_next != NULL; n = n->m_next)
		sballoc(so, sb, n);
	sballoc(so, sb, n);
	nlast = n;
	SBLINKRECORD(sb, m);

	sb->sb_mbtail = nlast;
	SBLASTMBUFCHK(sb, "sbappendaddr");

	SBLASTRECORDCHK(sb, "sbappendaddr 2");

	return (1);
}

int
sbappendcontrol(struct socket *so, struct sockbuf *sb, struct mbuf *m0,
    struct mbuf *control)
{
	struct mbuf *m, *mlast, *n;
	int eor = 0, space = 0;

	sbmtxassertlocked(so, sb);

	if (control == NULL)
		panic("sbappendcontrol");
	for (m = control; ; m = m->m_next) {
		space += m->m_len;
		if (m->m_next == NULL)
			break;
	}
	n = m;			/* save pointer to last control buffer */
	for (m = m0; m; m = m->m_next) {
		space += m->m_len;
		eor |= m->m_flags & M_EOR;
		if (eor) {
			if (m->m_next == NULL)
				m->m_flags |= M_EOR;
			else
				m->m_flags &= ~M_EOR;
		}
	}
	if (space > sbspace(so, sb))
		return (0);
	n->m_next = m0;			/* concatenate data to control */

	SBLASTRECORDCHK(sb, "sbappendcontrol 1");

	for (m = control; m->m_next != NULL; m = m->m_next)
		sballoc(so, sb, m);
	sballoc(so, sb, m);
	mlast = m;
	SBLINKRECORD(sb, control);

	sb->sb_mbtail = mlast;
	SBLASTMBUFCHK(sb, "sbappendcontrol");

	SBLASTRECORDCHK(sb, "sbappendcontrol 2");

	return (1);
}

/*
 * Compress mbuf chain m into the socket
 * buffer sb following mbuf n.  If n
 * is null, the buffer is presumed empty.
 */
void
sbcompress(struct socket *so, struct sockbuf *sb, struct mbuf *m,
    struct mbuf *n)
{
	int eor = 0;
	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))) {
			if (sb->sb_lastrecord == m)
				sb->sb_lastrecord = m->m_next;
			m = m_free(m);
			continue;
		}
		if (n && (n->m_flags & M_EOR) == 0 &&
		    /* m_trailingspace() checks buffer writeability */
		    m->m_len <= ((n->m_flags & M_EXT)? n->m_ext.ext_size :
		       MCLBYTES) / 4 && /* XXX Don't copy too much */
		    m->m_len <= m_trailingspace(n) &&
		    n->m_type == m->m_type) {
			memcpy(mtod(n, caddr_t) + n->m_len, mtod(m, caddr_t),
			    m->m_len);
			n->m_len += m->m_len;
			sb->sb_cc += m->m_len;
			if (m->m_type != MT_CONTROL && m->m_type != MT_SONAME)
				sb->sb_datacc += m->m_len;
			m = m_free(m);
			continue;
		}
		if (n)
			n->m_next = m;
		else
			sb->sb_mb = m;
		sb->sb_mbtail = m;
		sballoc(so, sb, m);
		n = m;
		m->m_flags &= ~M_EOR;
		m = m->m_next;
		n->m_next = NULL;
	}
	if (eor) {
		if (n)
			n->m_flags |= eor;
		else
			printf("semi-panic: sbcompress");
	}
	SBLASTMBUFCHK(sb, __func__);
}

/*
 * Free all mbufs in a sockbuf.
 * Check that all resources are reclaimed.
 */
void
sbflush(struct socket *so, struct sockbuf *sb)
{
	KASSERT(sb == &so->so_rcv || sb == &so->so_snd);
	rw_assert_unlocked(&sb->sb_lock);

	while (sb->sb_mbcnt)
		sbdrop(so, sb, (int)sb->sb_cc);

	KASSERT(sb->sb_cc == 0);
	KASSERT(sb->sb_datacc == 0);
	KASSERT(sb->sb_mb == NULL);
	KASSERT(sb->sb_mbtail == NULL);
	KASSERT(sb->sb_lastrecord == NULL);
}

/*
 * Drop data from (the front of) a sockbuf.
 */
void
sbdrop(struct socket *so, struct sockbuf *sb, int len)
{
	struct mbuf *m, *mn;
	struct mbuf *next;

	sbmtxassertlocked(so, sb);

	next = (m = sb->sb_mb) ? m->m_nextpkt : NULL;
	while (len > 0) {
		if (m == NULL) {
			if (next == NULL)
				panic("sbdrop");
			m = next;
			next = m->m_nextpkt;
			continue;
		}
		if (m->m_len > len) {
			m->m_len -= len;
			m->m_data += len;
			sb->sb_cc -= len;
			if (m->m_type != MT_CONTROL && m->m_type != MT_SONAME)
				sb->sb_datacc -= len;
			break;
		}
		len -= m->m_len;
		sbfree(so, sb, m);
		mn = m_free(m);
		m = mn;
	}
	while (m && m->m_len == 0) {
		sbfree(so, sb, m);
		mn = m_free(m);
		m = mn;
	}
	if (m) {
		sb->sb_mb = m;
		m->m_nextpkt = next;
	} else
		sb->sb_mb = next;
	/*
	 * First part is an inline SB_EMPTY_FIXUP().  Second part
	 * makes sure sb_lastrecord is up-to-date if we dropped
	 * part of the last record.
	 */
	m = sb->sb_mb;
	if (m == NULL) {
		sb->sb_mbtail = NULL;
		sb->sb_lastrecord = NULL;
	} else if (m->m_nextpkt == NULL)
		sb->sb_lastrecord = m;
}

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

	m = sb->sb_mb;
	if (m) {
		sb->sb_mb = m->m_nextpkt;
		do {
			sbfree(so, sb, m);
			mn = m_free(m);
		} while ((m = mn) != NULL);
	}
	SB_EMPTY_FIXUP(sb);
}

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

	if (CMSG_SPACE(size) > MCLBYTES) {
		printf("sbcreatecontrol: message too large %zu\n", size);
		return (NULL);
	}

	if ((m = m_get(M_DONTWAIT, MT_CONTROL)) == NULL)
		return (NULL);
	if (CMSG_SPACE(size) > MLEN) {
		MCLGET(m, M_DONTWAIT);
		if ((m->m_flags & M_EXT) == 0) {
			m_free(m);
			return NULL;
		}
	}
	cp = mtod(m, struct cmsghdr *);
	memset(cp, 0, CMSG_SPACE(size));
	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);
}