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

/*
 * Copyright (c) 1998-2012 Apple 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) 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 $
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#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/mcache.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>
#include <libkern/OSAtomic.h>

#if CONFIG_MACF
#include <security/mac_framework.h>
#endif

#include <mach/vm_param.h>

/* TODO: this should be in a header file somewhere */
extern void postevent(struct socket *, struct sockbuf *, int);

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

static inline void sbcompress(struct sockbuf *, struct mbuf *, struct mbuf *);
static struct socket *sonewconn_internal(struct socket *, int);
static int sbappendaddr_internal(struct sockbuf *, struct sockaddr *,
    struct mbuf *, struct mbuf *);
static int sbappendcontrol_internal(struct sockbuf *, struct mbuf *,
    struct mbuf *);

/*
 * Primitive routines for operating on sockets and socket buffers
 */
static int soqlimitcompat = 1;
static int soqlencomp = 0;

/* Based on the number of mbuf clusters configured, high_sb_max and sb_max can get 
 * scaled up or down to suit that memory configuration. high_sb_max is a higher 
 * limit on sb_max that is checked when sb_max gets set through sysctl.
 */

u_int32_t       sb_max = SB_MAX;                /* XXX should be static */
u_int32_t       high_sb_max = SB_MAX;

static  u_int32_t sb_efficiency = 8;    /* parameter for sbreserve() */
__private_extern__ int32_t total_sbmb_cnt = 0;

/* Control whether to throttle sockets eligible to be throttled */
__private_extern__ u_int32_t net_io_policy_throttled = 0;
static int sysctl_io_policy_throttled SYSCTL_HANDLER_ARGS;

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

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

        sflt_notify(so, sock_evt_connecting, NULL);
}

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

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

        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);
                soevent(so, SO_FILT_HINT_LOCKED);
        }
}

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

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

/* This function will issue a wakeup like soisdisconnected but it will not
 * notify the socket filters. This will avoid unlocking the socket
 * in the midst of closing it.
 */
void
sodisconnectwakeup(struct socket *so)
{
        so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
        so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);
        soevent(so, SO_FILT_HINT_LOCKED);
        wakeup((caddr_t)&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, 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(struct socket *head, int connstatus)
{
        int so_qlen, error = 0;
        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 (!soqlencomp) {
                /*
                 * This is the default case; so_qlen represents the
                 * sum of both incomplete and completed queues.
                 */
                so_qlen = head->so_qlen;
        } else {
                /*
                 * When kern.ipc.soqlencomp is set to 1, so_qlen
                 * represents only the completed queue.  Since we
                 * cannot let the incomplete queue goes unbounded
                 * (in case of SYN flood), we cap the incomplete
                 * queue length to at most somaxconn, and use that
                 * as so_qlen so that we fail immediately below.
                 */
                so_qlen = head->so_qlen - head->so_incqlen;
                if (head->so_incqlen > somaxconn)
                        so_qlen = somaxconn;
        }

        if (so_qlen >=
            (soqlimitcompat ? head->so_qlimit : (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_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;
        kauth_cred_ref(head->so_cred);
        so->so_cred = head->so_cred;
        so->last_pid = head->last_pid;
        so->last_upid = head->last_upid;
        /* inherit socket options stored in so_flags */
        so->so_flags = head->so_flags & (SOF_NOSIGPIPE |
                                         SOF_NOADDRAVAIL |
                                         SOF_REUSESHAREUID | 
                                         SOF_NOTIFYCONFLICT | 
                                         SOF_BINDRANDOMPORT | 
                                         SOF_NPX_SETOPTSHUT |
                                         SOF_NODEFUNCT |
                                         SOF_PRIVILEGED_TRAFFIC_CLASS|
                                         SOF_NOTSENT_LOWAT |
                                         SOF_USELRO);
        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 CONFIG_MACF_SOCKET
        mac_socket_label_associate_accept(head, so);
#endif

        /* inherit traffic management properties of listener */
        so->so_traffic_mgt_flags = head->so_traffic_mgt_flags & (TRAFFIC_MGT_SO_BACKGROUND);
        so->so_background_thread = head->so_background_thread;
        so->so_traffic_class = head->so_traffic_class;

        if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat)) {
                sodealloc(so);
                return ((struct socket *)0);
        }
        so->so_rcv.sb_flags |= (head->so_rcv.sb_flags & SB_USRSIZE);
        so->so_snd.sb_flags |= (head->so_snd.sb_flags & SB_USRSIZE);

        /*
         * 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) {
                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);
                /* Radar 7385998 Recheck that the head is still accepting
                 * to avoid race condition when head is getting closed.
                 */
                if ((head->so_options & SO_ACCEPTCONN) == 0) {
                        so->so_state &= ~SS_NOFDREF;
                        soclose(so);
                        return ((struct socket *)0);
                }
        }

#ifdef __APPLE__
        so->so_proto->pr_domain->dom_refs++;
#endif
        /* Insert in head appropriate lists */
        so->so_head = head;

        /* Since this socket is going to be inserted into the incomp
         * queue, it can be picked up by another thread in 
         * tcp_dropdropablreq to get dropped before it is setup.. 
         * To prevent this race, set in-progress flag which can be
         * cleared later
         */
        so->so_flags |= SOF_INCOMP_INPROGRESS;

        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 = sflt_connectin(head, from);
        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(struct socket *so)
{
        so->so_state |= SS_CANTSENDMORE;
        soevent(so, SO_FILT_HINT_LOCKED);
        sflt_notify(so, sock_evt_cantsendmore, NULL);
        sowwakeup(so);
}

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

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

        lr_saved = (uintptr_t) __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;
        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

        sb->sb_flags |= SB_WAIT;

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

        if ((so->so_state & SS_DRAINING) || (so->so_flags & SOF_DEFUNCT)) {
                error = EBADF;
                if (so->so_flags & SOF_DEFUNCT) {
                        SODEFUNCTLOG(("%s[%d]: defunct so %p [%d,%d] (%d)\n",
                            __func__, proc_selfpid(), so, INP_SOCKAF(so),
                            INP_SOCKTYPE(so), error));
                }
        }

        return (error);
}

/*
 * Lock a sockbuf already known to be locked;
 * return any error returned from sleep (EINTR).
 *
 * Returns:     0                       Success
 *              EINTR
 */
int
sb_lock(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=%p\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;
                lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

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

                error = msleep((caddr_t)&sb->sb_flags, mutex_held,
                    (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH,
                    "sb_lock", 0);
                if (so->so_usecount < 1)
                        panic("sb_lock: 2 so=%p refcount=%d\n", so,
                            so->so_usecount);

                if (error == 0 && (so->so_flags & SOF_DEFUNCT)) {
                        error = EBADF;
                        SODEFUNCTLOG(("%s[%d]: defunct so %p [%d,%d] (%d)\n",
                            __func__, proc_selfpid(), so, INP_SOCKAF(so),
                            INP_SOCKTYPE(so), error));
                }

                if (error)
                        return (error);
        }
        sb->sb_flags |= SB_LOCK;
        return (0);
}

void
sbwakeup(struct sockbuf *sb)
{
        if (sb->sb_flags & SB_WAIT) {
                sb->sb_flags &= ~SB_WAIT;
                wakeup((caddr_t)&sb->sb_cc);
        }
}

/*
 * Wakeup processes waiting on a socket buffer.
 * Do asynchronous notification via SIGIO
 * if the socket has the SS_ASYNC flag set.
 */
void
sowakeup(struct socket *so, struct sockbuf *sb)
{
        if (so->so_flags & SOF_DEFUNCT) {
                SODEFUNCTLOG(("%s[%d]: defunct so %p [%d,%d] si 0x%x, "
                    "fl 0x%x [%s]\n", __func__, proc_selfpid(), so,
                    INP_SOCKAF(so), INP_SOCKTYPE(so),
                    (uint32_t)sb->sb_sel.si_flags, (uint16_t)sb->sb_flags,
                    (sb->sb_flags & SB_RECV) ? "rcv" : "snd"));
        }

        sb->sb_flags &= ~SB_SEL;
        selwakeup(&sb->sb_sel);
        sbwakeup(sb);
        if (so->so_state & SS_ASYNC) {
                if (so->so_pgid < 0)
                        gsignal(-so->so_pgid, SIGIO);
                else if (so->so_pgid > 0)
                        proc_signal(so->so_pgid, SIGIO);
        }
        if (sb->sb_flags & SB_KNOTE) {
                KNOTE(&sb->sb_sel.si_note, SO_FILT_HINT_LOCKED);
        }
        if (sb->sb_flags & SB_UPCALL) {
                void (*so_upcall)(struct socket *, caddr_t, int);
                caddr_t so_upcallarg;

                so_upcall = so->so_upcall;
                so_upcallarg = so->so_upcallarg;
                /* Let close know that we're about to do an upcall */
                so->so_upcallusecount++;

                socket_unlock(so, 0);
                (*so_upcall)(so, so_upcallarg, M_DONTWAIT);
                socket_lock(so, 0);

                so->so_upcallusecount--;
                /* Tell close that it's safe to proceed */
                if (so->so_flags & SOF_CLOSEWAIT && so->so_upcallusecount == 0)
                        wakeup((caddr_t)&so->so_upcall);
        }
}

/*
 * 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.
 */

/*
 * Returns:     0                       Success
 *              ENOBUFS
 */
int
soreserve(struct socket *so, u_int32_t sndcc, u_int32_t rcvcc)
{

        if (sbreserve(&so->so_snd, sndcc) == 0)
                goto bad;
        else
                so->so_snd.sb_idealsize = sndcc;

        if (sbreserve(&so->so_rcv, rcvcc) == 0)
                goto bad2;
        else
                so->so_rcv.sb_idealsize = rcvcc;

        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(struct sockbuf *sb, u_int32_t 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(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(struct sockbuf *sb, struct mbuf *m)
{
        struct socket *so = sb->sb_so;

        if (m == NULL || (sb->sb_flags & SB_DROP)) {
                if (m != NULL)
                        m_freem(m);
                return (0);
        }

        SBLASTRECORDCHK(sb, "sbappend 1");

        if (sb->sb_lastrecord != NULL && (sb->sb_mbtail->m_flags & M_EOR))
                return (sbappendrecord(sb, m));

        if (sb->sb_flags & SB_RECV) {
                int error = sflt_data_in(so, NULL, &m, NULL, 0);
                SBLASTRECORDCHK(sb, "sbappend 2");
                if (error != 0) {
                        if (error != EJUSTRETURN)
                                m_freem(m);
                        return (0);
                }
        }

        /* If this is the first record, it's also the last record */
        if (sb->sb_lastrecord == NULL)
                sb->sb_lastrecord = m;

        sbcompress(sb, m, sb->sb_mbtail);
        SBLASTRECORDCHK(sb, "sbappend 3");
        return (1);
}

/*
 * Similar to sbappend, except that this is optimized for stream sockets.
 */
int
sbappendstream(struct sockbuf *sb, struct mbuf *m)
{
        struct socket *so = sb->sb_so;

        if (m->m_nextpkt != NULL || (sb->sb_mb != sb->sb_lastrecord))
                panic("sbappendstream: nexpkt %p || mb %p != lastrecord %p\n",
                    m->m_nextpkt, sb->sb_mb, sb->sb_lastrecord);

        SBLASTMBUFCHK(sb, __func__);

        if (m == NULL || (sb->sb_flags & SB_DROP)) {
                if (m != NULL)
                        m_freem(m);
                return (0);
        }

        if (sb->sb_flags & SB_RECV) {
                int error = sflt_data_in(so, NULL, &m, NULL, 0);
                SBLASTRECORDCHK(sb, "sbappendstream 1");
                if (error != 0) {
                        if (error != EJUSTRETURN)
                                m_freem(m);
                        return (0);
                }
        }

        sbcompress(sb, m, sb->sb_mbtail);
        sb->sb_lastrecord = sb->sb_mb;
        SBLASTRECORDCHK(sb, "sbappendstream 2");
        return (1);
}

#ifdef SOCKBUF_DEBUG
void
sbcheck(struct sockbuf *sb)
{
        struct mbuf *m;
        struct mbuf *n = 0;
        u_int32_t 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;
                        /* XXX pretty sure this is bogus */
                        if (m->m_flags & M_EXT)
                                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

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: mb %p 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: mb %p 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);
        }
}

/*
 * Similar to sbappend, except the mbuf chain begins a new record.
 */
int
sbappendrecord(struct sockbuf *sb, struct mbuf *m0)
{
        struct mbuf *m;
        int space = 0;

        if (m0 == NULL || (sb->sb_flags & SB_DROP)) {
                if (m0 != NULL)
                        m_freem(m0);
                return (0);
        }

        for (m = m0; m != NULL; m = m->m_next)
                space += m->m_len;

        if (space > sbspace(sb) && !(sb->sb_flags & SB_UNIX)) {
                m_freem(m0);
                return (0);
        }

        if (sb->sb_flags & SB_RECV) {
                int error = sflt_data_in(sb->sb_so, NULL, &m0, NULL,
                    sock_data_filt_flag_record);
                if (error != 0) {
                        SBLASTRECORDCHK(sb, "sbappendrecord 1");
                        if (error != EJUSTRETURN)
                                m_freem(m0);
                        return (0);
                }
        }

        /*
         * Note this permits zero length records.
         */
        sballoc(sb, m0);
        SBLASTRECORDCHK(sb, "sbappendrecord 2");
        if (sb->sb_lastrecord != NULL) {
                sb->sb_lastrecord->m_nextpkt = m0;
        }  else {
                sb->sb_mb = m0;
        }
        sb->sb_lastrecord = m0;
        sb->sb_mbtail = 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;
        }
        sbcompress(sb, m, m0);
        SBLASTRECORDCHK(sb, "sbappendrecord 3");
        return (1);
}

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

        if (m0 == 0)
                return (0);

        SBLASTRECORDCHK(sb, "sbinsertoob 1");

        if ((sb->sb_flags & SB_RECV) != 0) {
                int error = sflt_data_in(sb->sb_so, NULL, &m0, NULL,
                    sock_data_filt_flag_oob);

                SBLASTRECORDCHK(sb, "sbinsertoob 2");
                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;
        if (*mp == NULL) {
                /* m0 is actually the new tail */
                sb->sb_lastrecord = m0;
        }
        *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;
        }
        sbcompress(sb, m, m0);
        SBLASTRECORDCHK(sb, "sbinsertoob 3");
        return (1);
}

/*
 * 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.
 *
 * Returns:     0                       No space/out of mbufs
 *              1                       Success
 */
static int
sbappendaddr_internal(struct sockbuf *sb, struct sockaddr *asa,
    struct mbuf *m0, struct mbuf *control)
{
        struct mbuf *m, *n, *nlast;
        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;

        SBLASTRECORDCHK(sb, "sbappendadddr 1");

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

        if (sb->sb_lastrecord != NULL) {
                sb->sb_lastrecord->m_nextpkt = m;
        } else {
                sb->sb_mb = m;
        }
        sb->sb_lastrecord = m;
        sb->sb_mbtail = nlast;

        SBLASTMBUFCHK(sb, __func__);
        SBLASTRECORDCHK(sb, "sbappendadddr 2");

        postevent(0, sb, EV_RWBYTES);
        return (1);
}

/*
 * Returns:     0                       Error: No space/out of mbufs/etc.
 *              1                       Success
 *
 * Imputed:     (*error_out)            errno for error
 *              ENOBUFS
 *      sflt_data_in:???                [whatever a filter author chooses]
 */
int
sbappendaddr(struct sockbuf *sb, struct sockaddr *asa, struct mbuf *m0,
    struct mbuf *control, int *error_out)
{
        int result = 0;
        boolean_t sb_unix = (sb->sb_flags & SB_UNIX);

        if (error_out)
                *error_out = 0;

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

        if (sb->sb_flags & SB_DROP) {
                if (m0 != NULL)
                        m_freem(m0);
                if (control != NULL && !sb_unix)
                        m_freem(control);
                if (error_out != NULL)
                        *error_out = EINVAL;
                return (0);
        }

        /* 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);
                SBLASTRECORDCHK(sb, __func__);
                if (error) {
                        if (error != EJUSTRETURN) {
                                if (m0)
                                        m_freem(m0);
                                if (control != NULL && !sb_unix)
                                        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 != NULL && !sb_unix)
                        m_freem(control);
                if (error_out)
                        *error_out = ENOBUFS;
        }

        return (result);
}

static int
sbappendcontrol_internal(struct sockbuf *sb, struct mbuf *m0,
    struct mbuf *control)
{
        struct mbuf *m, *mlast, *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) && !(sb->sb_flags & SB_UNIX))
                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(sb, m);
        sballoc(sb, m);
        mlast = m;

        if (sb->sb_lastrecord != NULL) {
                sb->sb_lastrecord->m_nextpkt = control;
        } else {
                sb->sb_mb = control;
        }
        sb->sb_lastrecord = control;
        sb->sb_mbtail = mlast;

        SBLASTMBUFCHK(sb, __func__);
        SBLASTRECORDCHK(sb, "sbappendcontrol 2");

        postevent(0, sb, EV_RWBYTES);
        return (1);
}

int
sbappendcontrol(struct sockbuf *sb, struct mbuf *m0, struct mbuf *control,
    int *error_out)
{
        int result = 0;
        boolean_t sb_unix = (sb->sb_flags & SB_UNIX);

        if (error_out)
                *error_out = 0;

        if (sb->sb_flags & SB_DROP) {
                if (m0 != NULL)
                        m_freem(m0);
                if (control != NULL && !sb_unix)
                        m_freem(control);
                if (error_out != NULL)
                        *error_out = EINVAL;
                return (0);
        }

        if (sb->sb_flags & SB_RECV) {
                int error;

                error = sflt_data_in(sb->sb_so, NULL, &m0, &control, 0);
                SBLASTRECORDCHK(sb, __func__);
                if (error) {
                        if (error != EJUSTRETURN) {
                                if (m0)
                                        m_freem(m0);
                                if (control != NULL && !sb_unix)
                                        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 != NULL && !sb_unix)
                        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 inline void
sbcompress(struct sockbuf *sb, struct mbuf *m, struct mbuf *n)
{
        int eor = 0;
        struct mbuf *o;

        if (m == NULL) {
                /* There is nothing to compress; just update the tail */
                for (; n->m_next != NULL; n = n->m_next)
                        ;
                sb->sb_mbtail = n;
                goto done;
        }

        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 &&
#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;
                        if (m->m_type != MT_DATA && m->m_type != MT_HEADER &&
                                m->m_type != MT_OOBDATA)
                                /* XXX: Probably don't need.*/
                                sb->sb_ctl += m->m_len;
                        m = m_free(m);
                        continue;
                }
                if (n)
                        n->m_next = m;
                else
                        sb->sb_mb = m;
                sb->sb_mbtail = 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");
        }
done:
        SBLASTMBUFCHK(sb, __func__);
        postevent(0, sb, EV_RWBYTES);
}

void
sb_empty_assert(struct sockbuf *sb, const char *where)
{
        if (!(sb->sb_cc == 0 && sb->sb_mb == NULL && sb->sb_mbcnt == 0 &&
            sb->sb_mbtail == NULL && sb->sb_lastrecord == NULL)) {
                panic("%s: sb %p so %p cc %d mbcnt %d mb %p mbtail %p "
                    "lastrecord %p\n", where, sb, sb->sb_so, sb->sb_cc,
                    sb->sb_mbcnt, sb->sb_mb, sb->sb_mbtail, sb->sb_lastrecord);
                /* NOTREACHED */
        }
}

/*
 * Free all mbufs in a sockbuf.
 * Check that all resources are reclaimed.
 */
void
sbflush(struct sockbuf *sb)
{
        if (sb->sb_so == NULL)
                panic("sbflush sb->sb_so already null sb=%p\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);
        }
        sb_empty_assert(sb, __func__);
        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(struct sockbuf *sb, int len)
{
        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;
                        if (m->m_type != MT_DATA && m->m_type != MT_HEADER &&
                                m->m_type != MT_OOBDATA)
                                sb->sb_ctl -= 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;
        }

        /*
         * 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;
        }

        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(struct sockbuf *sb)
{
        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);
        }
        SB_EMPTY_FIXUP(sb);
        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(caddr_t p, int size, int type, int level)
{
        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 *);
        VERIFY(IS_P2ALIGNED(cp, sizeof (u_int32_t)));
        /* 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);
}

struct mbuf**
sbcreatecontrol_mbuf(caddr_t p, int size, int type, int level, struct mbuf** mp)
{
        struct mbuf* m;
        struct cmsghdr *cp;

        if (*mp == NULL){
                *mp = sbcreatecontrol(p, size, type, level);
                return mp;
        }

        if (CMSG_SPACE((u_int)size) + (*mp)->m_len > MLEN){
                mp = &(*mp)->m_next;
                *mp = sbcreatecontrol(p, size, type, level);
                return mp;
        }

        m = *mp;

        cp = (struct cmsghdr *)(void *)(mtod(m, char *) + m->m_len);
        /* CMSG_SPACE ensures 32-bit alignment */
        VERIFY(IS_P2ALIGNED(cp, sizeof (u_int32_t)));
        m->m_len += CMSG_SPACE(size);

        /* XXX check size? */
        (void) memcpy(CMSG_DATA(cp), p, size);
        cp->cmsg_len = CMSG_LEN(size);
        cp->cmsg_level = level;
        cp->cmsg_type = type;

        return mp;
}


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

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

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

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

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

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

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

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

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

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

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

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

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

int
pru_send_notsupp(__unused struct socket *so, __unused int flags,
    __unused struct mbuf *m, __unused struct sockaddr *addr,
    __unused struct mbuf *control, __unused 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, void *ub, int isstat64)
{
        if (isstat64 != 0) {
                struct stat64 *sb64;

                sb64 = (struct stat64 *)ub;
                sb64->st_blksize = so->so_snd.sb_hiwat;
        } else {
                struct stat *sb;

                sb = (struct stat *)ub;
                sb->st_blksize = so->so_snd.sb_hiwat;
        }

        return (0);
}


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

{
        return (EOPNOTSUPP);
}

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

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

int
pru_sockaddr_notsupp(__unused struct socket *so, __unused struct sockaddr **nam)
{
        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.  
 */
int
sbspace(struct sockbuf *sb)
{
        int space =
                imin((int)(sb->sb_hiwat - sb->sb_cc),
                (int)(sb->sb_mbmax - sb->sb_mbcnt));
        if (space < 0)
                space = 0;

        return space;
}

/* 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 ((!so_wait_for_if_feedback(so) &&
            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)
{
        u_int32_t cnt = 1;
        sb->sb_cc += m->m_len; 
        if (m->m_type != MT_DATA && m->m_type != MT_HEADER && 
                m->m_type != MT_OOBDATA)
                sb->sb_ctl += m->m_len;
        sb->sb_mbcnt += MSIZE; 
        
        if (m->m_flags & M_EXT) {
                sb->sb_mbcnt += m->m_ext.ext_size; 
                cnt += (m->m_ext.ext_size >> MSIZESHIFT) ;
        }
        OSAddAtomic(cnt, &total_sbmb_cnt);
        VERIFY(total_sbmb_cnt > 0);
}

/* adjust counters in sb reflecting freeing of m */
void
sbfree(struct sockbuf *sb, struct mbuf *m)
{
        int cnt = -1;

        sb->sb_cc -= m->m_len;
        if (m->m_type != MT_DATA && m->m_type != MT_HEADER &&     
                m->m_type != MT_OOBDATA)
                sb->sb_ctl -= m->m_len;
        sb->sb_mbcnt -= MSIZE; 
        if (m->m_flags & M_EXT) {
                sb->sb_mbcnt -= m->m_ext.ext_size; 
                cnt -= (m->m_ext.ext_size >> MSIZESHIFT) ;
        }
        OSAddAtomic(cnt, &total_sbmb_cnt);
        VERIFY(total_sbmb_cnt >= 0);
}

/*
 * 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.
 *
 * Returns:     0                       Success
 *              EWOULDBLOCK
 *      sb_lock:EINTR
 */
int
sblock(struct sockbuf *sb, int wf)
{
        int error = 0;

        if (sb->sb_flags & SB_LOCK)
                error = (wf == M_WAIT) ? sb_lock(sb) : EWOULDBLOCK;
        else
                sb->sb_flags |= SB_LOCK;

        return (error);
}

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

        lr_saved = __builtin_return_address(0);

        sb->sb_flags &= ~SB_LOCK;

        if (sb->sb_flags & SB_WANT) {
                sb->sb_flags &= ~SB_WANT;
                if (so->so_usecount < 0) {
                        panic("sbunlock: b4 wakeup so=%p ref=%d lr=%p "
                            "sb_flags=%x lrh= %s\n", sb->sb_so, so->so_usecount,
                            lr_saved, sb->sb_flags, solockhistory_nr(so));
                        /* NOTREACHED */
                }
                wakeup((caddr_t)&(sb)->sb_flags);
        }
        if (keeplocked == 0) {  /* unlock on exit */
                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;

                lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);

                so->so_usecount--;
                if (so->so_usecount < 0)
                        panic("sbunlock: unlock on exit so=%p ref=%d lr=%p "
                            "sb_flags=%x lrh= %s\n", so, so->so_usecount, lr_saved,
                            sb->sb_flags, solockhistory_nr(so));
                so->unlock_lr[so->next_unlock_lr] = 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);
}

void
soevent(struct socket *so, long hint)
{
        if (so->so_flags & SOF_KNOTE)
                KNOTE(&so->so_klist, hint);
}

#endif /* __APPLE__ */

/*
 * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.
 */
struct sockaddr *
dup_sockaddr(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 = (_XSOCKET_PTR(struct socket *))VM_KERNEL_ADDRPERM(so);
        xso->so_type = so->so_type;
        xso->so_options = (short)(so->so_options & 0xffff);
        xso->so_linger = so->so_linger;
        xso->so_state = so->so_state;
        xso->so_pcb = (_XSOCKET_PTR(caddr_t))VM_KERNEL_ADDRPERM(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 = kauth_cred_getuid(so->so_cred);
}


#if !CONFIG_EMBEDDED

void
sotoxsocket64(struct socket *so, struct xsocket64 *xso)
{
        xso->xso_len = sizeof (*xso);
        xso->xso_so = (u_int64_t)VM_KERNEL_ADDRPERM(so);
        xso->so_type = so->so_type;
        xso->so_options = (short)(so->so_options & 0xffff);
        xso->so_linger = so->so_linger;
        xso->so_state = so->so_state;
        xso->so_pcb = (u_int64_t)VM_KERNEL_ADDRPERM(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 = kauth_cred_getuid(so->so_cred);
}

#endif /* !CONFIG_EMBEDDED */

/*
 * 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 = (short)
            (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;
}

/*
 * Based on the policy set by an all knowing decison maker, throttle sockets
 * that either have been marked as belonging to "background" process.
 */
int
soisthrottled(struct socket *so)
{
        /*
         * On non-embedded, we rely on implicit throttling by the application,
         * as we're missing the system-wide "decision maker".
         */
        return (
#if CONFIG_EMBEDDED
            net_io_policy_throttled &&
#endif /* CONFIG_EMBEDDED */
            (so->so_traffic_mgt_flags & TRAFFIC_MGT_SO_BACKGROUND));
}

int
soisprivilegedtraffic(struct socket *so)
{
        return (so->so_flags & SOF_PRIVILEGED_TRAFFIC_CLASS);
}

/*
 * 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|CTLFLAG_LOCKED|CTLFLAG_ANYBODY, 0, "IPC");

/* Check that the maximum socket buffer size is within a range */

static int
sysctl_sb_max(__unused struct sysctl_oid *oidp, __unused void *arg1,
        __unused int arg2, struct sysctl_req *req)
{
        u_int32_t new_value;
        int changed = 0;
        int error = sysctl_io_number(req, sb_max, sizeof(u_int32_t), &new_value,
                &changed);
        if (!error && changed) {
                if (new_value > LOW_SB_MAX && 
                        new_value <= high_sb_max ) {
                        sb_max = new_value;
                } else {
                        error = ERANGE;
                }
        }
        return error;
}

static int
sysctl_io_policy_throttled SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int i, err;

        i = net_io_policy_throttled;

        err = sysctl_handle_int(oidp, &i, 0, req);
        if (err != 0 || req->newptr == USER_ADDR_NULL)
                return (err);

        if (i != net_io_policy_throttled)
                SOTHROTTLELOG(("throttle: network IO policy throttling is "
                    "now %s\n", i ? "ON" : "OFF"));

        net_io_policy_throttled = i;

        return (err);
}

SYSCTL_PROC(_kern_ipc, KIPC_MAXSOCKBUF, maxsockbuf, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
    &sb_max, 0, &sysctl_sb_max, "IU", "Maximum socket buffer size");

SYSCTL_INT(_kern_ipc, OID_AUTO, maxsockets, CTLFLAG_RD | CTLFLAG_LOCKED,
    &maxsockets, 0, "Maximum number of sockets avaliable");
SYSCTL_INT(_kern_ipc, KIPC_SOCKBUF_WASTE, sockbuf_waste_factor, CTLFLAG_RW | CTLFLAG_LOCKED,
    &sb_efficiency, 0, "");
SYSCTL_INT(_kern_ipc, KIPC_NMBCLUSTERS, nmbclusters, CTLFLAG_RD | CTLFLAG_LOCKED,
    &nmbclusters, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, njcl, CTLFLAG_RD | CTLFLAG_LOCKED, &njcl, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, njclbytes, CTLFLAG_RD | CTLFLAG_LOCKED, &njclbytes, 0, "");
SYSCTL_INT(_kern_ipc, KIPC_SOQLIMITCOMPAT, soqlimitcompat, CTLFLAG_RW | CTLFLAG_LOCKED,
    &soqlimitcompat, 1, "Enable socket queue limit compatibility");
SYSCTL_INT(_kern_ipc, OID_AUTO, soqlencomp, CTLFLAG_RW | CTLFLAG_LOCKED,
    &soqlencomp, 0, "Listen backlog represents only complete queue");

SYSCTL_NODE(_kern_ipc, OID_AUTO, io_policy, CTLFLAG_RW, 0, "network IO policy");

SYSCTL_PROC(_kern_ipc_io_policy, OID_AUTO, throttled,
    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, &net_io_policy_throttled, 0,
    sysctl_io_policy_throttled, "I", "");