xnu-3247.10.11.tar.gz

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

/*
 * Copyright (c) 2000-2014 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) 1982, 1986, 1989, 1991, 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.
 *
 *      From: @(#)uipc_usrreq.c 8.3 (Berkeley) 1/4/94
 */
/*
 * 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/kernel.h>
#include <sys/domain.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>         /* XXX must be before <sys/file.h> */
#include <sys/file_internal.h>
#include <sys/guarded.h>
#include <sys/filedesc.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/namei.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/un.h>
#include <sys/unpcb.h>
#include <sys/vnode_internal.h>
#include <sys/kdebug.h>
#include <sys/mcache.h>

#include <kern/zalloc.h>
#include <kern/locks.h>

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

#include <mach/vm_param.h>

/*
 * Maximum number of FDs that can be passed in an mbuf
 */
#define UIPC_MAX_CMSG_FD        512

#define f_msgcount f_fglob->fg_msgcount
#define f_cred f_fglob->fg_cred
#define f_ops f_fglob->fg_ops
#define f_offset f_fglob->fg_offset
#define f_data f_fglob->fg_data
struct  zone *unp_zone;
static  unp_gen_t unp_gencnt;
static  u_int unp_count;

static  lck_attr_t              *unp_mtx_attr;
static  lck_grp_t               *unp_mtx_grp;
static  lck_grp_attr_t          *unp_mtx_grp_attr;
static  lck_rw_t                *unp_list_mtx;

static  lck_mtx_t               *unp_disconnect_lock;
static  lck_mtx_t               *unp_connect_lock;
static  u_int                   disconnect_in_progress;

extern lck_mtx_t *uipc_lock;
static  struct unp_head unp_shead, unp_dhead;

/*
 * mDNSResponder tracing.  When enabled, endpoints connected to
 * /var/run/mDNSResponder will be traced; during each send on
 * the traced socket, we log the PID and process name of the
 * sending process.  We also print out a bit of info related
 * to the data itself; this assumes ipc_msg_hdr in dnssd_ipc.h
 * of mDNSResponder stays the same.
 */
#define MDNSRESPONDER_PATH      "/var/run/mDNSResponder"

static int unpst_tracemdns;     /* enable tracing */

#define MDNS_IPC_MSG_HDR_VERSION_1      1

struct mdns_ipc_msg_hdr {
        uint32_t version;
        uint32_t datalen;
        uint32_t ipc_flags;
        uint32_t op;
        union {
                void *context;
                uint32_t u32[2];
        } __attribute__((packed));
        uint32_t reg_index;
} __attribute__((packed));

/*
 * Unix communications domain.
 *
 * TODO:
 *      SEQPACKET, RDM
 *      rethink name space problems
 *      need a proper out-of-band
 *      lock pushdown
 */
static struct   sockaddr sun_noname = { sizeof (sun_noname), AF_LOCAL, { 0 } };
static ino_t    unp_ino;                /* prototype for fake inode numbers */

static int      unp_attach(struct socket *);
static void     unp_detach(struct unpcb *);
static int      unp_bind(struct unpcb *, struct sockaddr *, proc_t);
static int      unp_connect(struct socket *, struct sockaddr *, proc_t);
static void     unp_disconnect(struct unpcb *);
static void     unp_shutdown(struct unpcb *);
static void     unp_drop(struct unpcb *, int);
__private_extern__ void unp_gc(void);
static void     unp_scan(struct mbuf *, void (*)(struct fileglob *, void *arg), void *arg);
static void     unp_mark(struct fileglob *, __unused void *);
static void     unp_discard(struct fileglob *, void *);
static int      unp_internalize(struct mbuf *, proc_t);
static int      unp_listen(struct unpcb *, proc_t);
static void     unpcb_to_compat(struct unpcb *, struct unpcb_compat *);
static void     unp_get_locks_in_order(struct socket *so, struct socket *conn_so);

static void 
unp_get_locks_in_order(struct socket *so, struct socket *conn_so) 
{
        if (so < conn_so) {
                socket_lock(conn_so, 1);
        } else {
                struct unpcb *unp = sotounpcb(so);
                unp->unp_flags |= UNP_DONTDISCONNECT;
                unp->rw_thrcount++;
                socket_unlock(so, 0);

                /* Get the locks in the correct order */
                socket_lock(conn_so, 1);
                socket_lock(so, 0);
                unp->rw_thrcount--;
                if (unp->rw_thrcount == 0) {
                        unp->unp_flags &= ~UNP_DONTDISCONNECT;
                        wakeup(unp);
                }
        }
}

static int
uipc_abort(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);
        unp_drop(unp, ECONNABORTED);
        unp_detach(unp);
        sofree(so);
        return (0);
}

static int
uipc_accept(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);

        /*
         * Pass back name of connected socket,
         * if it was bound and we are still connected
         * (our peer may have closed already!).
         */
        if (unp->unp_conn && unp->unp_conn->unp_addr) {
                *nam = dup_sockaddr((struct sockaddr *)
                    unp->unp_conn->unp_addr, 1);
        } else {
                *nam = dup_sockaddr((struct sockaddr *)&sun_noname, 1);
        }
        return (0);
}

/*
 * Returns:     0                       Success
 *              EISCONN
 *      unp_attach:
 */
static int
uipc_attach(struct socket *so, __unused int proto, __unused proc_t p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp != 0)
                return (EISCONN);
        return (unp_attach(so));
}

static int
uipc_bind(struct socket *so, struct sockaddr *nam, proc_t p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);

        return (unp_bind(unp, nam, p));
}

/*
 * Returns:     0                       Success
 *              EINVAL
 *      unp_connect:???                 [See elsewhere in this file]
 */
static int
uipc_connect(struct socket *so, struct sockaddr *nam, proc_t p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);
        return (unp_connect(so, nam, p));
}

/*
 * Returns:     0                       Success
 *              EINVAL
 *      unp_connect2:EPROTOTYPE         Protocol wrong type for socket
 *      unp_connect2:EINVAL             Invalid argument
 */
static int
uipc_connect2(struct socket *so1, struct socket *so2)
{
        struct unpcb *unp = sotounpcb(so1);

        if (unp == 0)
                return (EINVAL);

        return (unp_connect2(so1, so2));
}

/* control is EOPNOTSUPP */

static int
uipc_detach(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);

        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        unp_detach(unp);
        return (0);
}

static int
uipc_disconnect(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);
        unp_disconnect(unp);
        return (0);
}

/*
 * Returns:     0                       Success
 *              EINVAL
 */
static int
uipc_listen(struct socket *so, __unused proc_t p)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0 || unp->unp_vnode == 0)
                return (EINVAL);
        return (unp_listen(unp, p));
}

static int
uipc_peeraddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == NULL)
                return (EINVAL);
        if (unp->unp_conn != NULL && unp->unp_conn->unp_addr != NULL) {
                *nam = dup_sockaddr((struct sockaddr *)
                    unp->unp_conn->unp_addr, 1);
        } else {
                *nam = dup_sockaddr((struct sockaddr *)&sun_noname, 1);
        }
        return (0);
}

static int
uipc_rcvd(struct socket *so, __unused int flags)
{
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;

        if (unp == 0)
                return (EINVAL);
        switch (so->so_type) {
        case SOCK_DGRAM:
                panic("uipc_rcvd DGRAM?");
                /*NOTREACHED*/

        case SOCK_STREAM:
#define rcv (&so->so_rcv)
#define snd (&so2->so_snd)
                if (unp->unp_conn == 0)
                        break;
                
                so2 = unp->unp_conn->unp_socket;
                unp_get_locks_in_order(so, so2);
                /*
                 * Adjust backpressure on sender
                 * and wakeup any waiting to write.
                 */
                snd->sb_mbmax += unp->unp_mbcnt - rcv->sb_mbcnt;
                unp->unp_mbcnt = rcv->sb_mbcnt;
                snd->sb_hiwat += unp->unp_cc - rcv->sb_cc;
                unp->unp_cc = rcv->sb_cc;
                sowwakeup(so2);

                socket_unlock(so2, 1);

#undef snd
#undef rcv
                break;

        default:
                panic("uipc_rcvd unknown socktype");
        }
        return (0);
}

/* pru_rcvoob is EOPNOTSUPP */

/*
 * Returns:     0                       Success
 *              EINVAL
 *              EOPNOTSUPP
 *              EPIPE
 *              ENOTCONN
 *              EISCONN
 *      unp_internalize:EINVAL
 *      unp_internalize:EBADF
 *      unp_connect:EAFNOSUPPORT        Address family not supported
 *      unp_connect:EINVAL              Invalid argument
 *      unp_connect:ENOTSOCK            Not a socket
 *      unp_connect:ECONNREFUSED        Connection refused
 *      unp_connect:EISCONN             Socket is connected
 *      unp_connect:EPROTOTYPE          Protocol wrong type for socket
 *      unp_connect:???
 *      sbappendaddr:ENOBUFS            [5th argument, contents modified]
 *      sbappendaddr:???                [whatever a filter author chooses]
 */
static int
uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
    struct mbuf *control, proc_t p)
{
        int error = 0;
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;

        if (unp == 0) {
                error = EINVAL;
                goto release;
        }
        if (flags & PRUS_OOB) {
                error = EOPNOTSUPP;
                goto release;
        }

        if (control) {
                /* release lock to avoid deadlock (4436174) */
                socket_unlock(so, 0);
                error = unp_internalize(control, p);
                socket_lock(so, 0);
                if (error)
                        goto release;
        }

        switch (so->so_type) {
        case SOCK_DGRAM:
        {
                struct sockaddr *from;

                if (nam) {
                        if (unp->unp_conn) {
                                error = EISCONN;
                                break;
                        }
                        error = unp_connect(so, nam, p);
                        if (error)
                                break;
                } else {
                        if (unp->unp_conn == 0) {
                                error = ENOTCONN;
                                break;
                        }
                }

                so2 = unp->unp_conn->unp_socket;
                if (so != so2)
                        unp_get_locks_in_order(so, so2);

                if (unp->unp_addr)
                        from = (struct sockaddr *)unp->unp_addr;
                else
                        from = &sun_noname;
                /*
                 * sbappendaddr() will fail when the receiver runs out of
                 * space; in contrast to SOCK_STREAM, we will lose messages
                 * for the SOCK_DGRAM case when the receiver's queue overflows.
                 * SB_UNIX on the socket buffer implies that the callee will
                 * not free the control message, if any, because we would need
                 * to call unp_dispose() on it.
                 */
                if (sbappendaddr(&so2->so_rcv, from, m, control, &error)) {
                        control = NULL;
                        sorwakeup(so2);
                } else if (control != NULL && error == 0) {
                        /* A socket filter took control; don't touch it */
                        control = NULL;
                }

                if (so != so2) 
                        socket_unlock(so2, 1);

                m = NULL;
                if (nam)
                        unp_disconnect(unp);
                break;
        }

        case SOCK_STREAM: {
                int didreceive = 0;
#define rcv (&so2->so_rcv)
#define snd (&so->so_snd)
                /* Connect if not connected yet. */
                /*
                 * Note: A better implementation would complain
                 * if not equal to the peer's address.
                 */
                if ((so->so_state & SS_ISCONNECTED) == 0) {
                        if (nam) {
                                error = unp_connect(so, nam, p);
                                if (error)
                                        break;  /* XXX */
                        } else {
                                error = ENOTCONN;
                                break;
                        }
                }

                if (so->so_state & SS_CANTSENDMORE) {
                        error = EPIPE;
                        break;
                }
                if (unp->unp_conn == 0)
                        panic("uipc_send connected but no connection?");

                so2 = unp->unp_conn->unp_socket;
                unp_get_locks_in_order(so, so2);

                /* Check socket state again as we might have unlocked the socket 
                 * while trying to get the locks in order
                 */

                if ((so->so_state & SS_CANTSENDMORE)) {
                        error = EPIPE;
                        socket_unlock(so2, 1);
                        break;
                }       

                if (unp->unp_flags & UNP_TRACE_MDNS) {
                        struct mdns_ipc_msg_hdr hdr;

                        if (mbuf_copydata(m, 0, sizeof (hdr), &hdr) == 0 &&
                            hdr.version  == ntohl(MDNS_IPC_MSG_HDR_VERSION_1)) {
                                printf("%s[mDNSResponder] pid=%d (%s): op=0x%x\n",
                                    __func__, p->p_pid, p->p_comm, ntohl(hdr.op));
                        }
                }

                /*
                 * Send to paired receive port, and then reduce send buffer
                 * hiwater marks to maintain backpressure.  Wake up readers.
                 * SB_UNIX flag will allow new record to be appended to the
                 * receiver's queue even when it is already full.  It is
                 * possible, however, that append might fail.  In that case,
                 * we will need to call unp_dispose() on the control message;
                 * the callee will not free it since SB_UNIX is set.
                 */
                didreceive = control ?
                    sbappendcontrol(rcv, m, control, &error) : sbappend(rcv, m);

                snd->sb_mbmax -= rcv->sb_mbcnt - unp->unp_conn->unp_mbcnt;
                unp->unp_conn->unp_mbcnt = rcv->sb_mbcnt;
                if ((int32_t)snd->sb_hiwat >= 
                    (int32_t)(rcv->sb_cc - unp->unp_conn->unp_cc)) {
                        snd->sb_hiwat -= rcv->sb_cc - unp->unp_conn->unp_cc;
                } else {
                        snd->sb_hiwat = 0;
                }
                unp->unp_conn->unp_cc = rcv->sb_cc;
                if (didreceive) {
                        control = NULL;
                        sorwakeup(so2);
                } else if (control != NULL && error == 0) {
                        /* A socket filter took control; don't touch it */
                        control = NULL;
                }

                socket_unlock(so2, 1);
                m = NULL;
#undef snd
#undef rcv
                }
                break;

        default:
                panic("uipc_send unknown socktype");
        }

        /*
         * SEND_EOF is equivalent to a SEND followed by
         * a SHUTDOWN.
         */
        if (flags & PRUS_EOF) {
                socantsendmore(so);
                unp_shutdown(unp);
        }

        if (control && error != 0) {
                socket_unlock(so, 0);
                unp_dispose(control);
                socket_lock(so, 0);
        }

release:
        if (control)
                m_freem(control);
        if (m)
                m_freem(m);
        return (error);
}

static int
uipc_sense(struct socket *so, void *ub, int isstat64)
{
        struct unpcb *unp = sotounpcb(so);
        struct socket *so2;
        blksize_t blksize;

        if (unp == 0)
                return (EINVAL);

        blksize = so->so_snd.sb_hiwat;
        if (so->so_type == SOCK_STREAM && unp->unp_conn != 0) {
                so2 = unp->unp_conn->unp_socket;
                blksize += so2->so_rcv.sb_cc;
        }
        if (unp->unp_ino == 0)
                unp->unp_ino = unp_ino++;

        if (isstat64 != 0) {
                struct stat64  *sb64;

                sb64 = (struct stat64 *)ub;
                sb64->st_blksize = blksize;
                sb64->st_dev = NODEV;
                sb64->st_ino = (ino64_t)unp->unp_ino;
        } else {
                struct stat *sb;

                sb = (struct stat *)ub;
                sb->st_blksize = blksize;
                sb->st_dev = NODEV;
                sb->st_ino = (ino_t)(uintptr_t)unp->unp_ino;
        }

        return (0);
}

/*
 * Returns:     0               Success
 *              EINVAL
 *
 * Notes:       This is not strictly correct, as unp_shutdown() also calls
 *              socantrcvmore().  These should maybe both be conditionalized
 *              on the 'how' argument in soshutdown() as called from the
 *              shutdown() system call.
 */
static int
uipc_shutdown(struct socket *so)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == 0)
                return (EINVAL);
        socantsendmore(so);
        unp_shutdown(unp);
        return (0);
}

/*
 * Returns:     0                       Success
 *              EINVAL                  Invalid argument
 */
static int
uipc_sockaddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp = sotounpcb(so);

        if (unp == NULL)
                return (EINVAL);
        if (unp->unp_addr != NULL) {
                *nam = dup_sockaddr((struct sockaddr *)unp->unp_addr, 1);
        } else {
                *nam = dup_sockaddr((struct sockaddr *)&sun_noname, 1);
        }
        return (0);
}

struct pr_usrreqs uipc_usrreqs = {
        .pru_abort =            uipc_abort,
        .pru_accept =           uipc_accept,
        .pru_attach =           uipc_attach,
        .pru_bind =             uipc_bind,
        .pru_connect =          uipc_connect,
        .pru_connect2 =         uipc_connect2,
        .pru_detach =           uipc_detach,
        .pru_disconnect =       uipc_disconnect,
        .pru_listen =           uipc_listen,
        .pru_peeraddr =         uipc_peeraddr,
        .pru_rcvd =             uipc_rcvd,
        .pru_send =             uipc_send,
        .pru_sense =            uipc_sense,
        .pru_shutdown =         uipc_shutdown,
        .pru_sockaddr =         uipc_sockaddr,
        .pru_sosend =           sosend,
        .pru_soreceive =        soreceive,
};

int
uipc_ctloutput(struct socket *so, struct sockopt *sopt)
{
        struct unpcb *unp = sotounpcb(so);
        int error = 0;
        pid_t peerpid;
        struct socket *peerso;

        switch (sopt->sopt_dir) {
        case SOPT_GET:
                switch (sopt->sopt_name) {
                case LOCAL_PEERCRED:
                        if (unp->unp_flags & UNP_HAVEPC) {
                                error = sooptcopyout(sopt, &unp->unp_peercred,
                                    sizeof (unp->unp_peercred));
                        } else {
                                if (so->so_type == SOCK_STREAM)
                                        error = ENOTCONN;
                                else
                                        error = EINVAL;
                        }
                        break;
                case LOCAL_PEERPID:
                case LOCAL_PEEREPID:
                        if (unp->unp_conn == NULL) {
                                error = ENOTCONN;
                                break;
                        }
                        peerso = unp->unp_conn->unp_socket;
                        if (peerso == NULL)
                                panic("peer is connected but has no socket?");
                        unp_get_locks_in_order(so, peerso);
                        if (sopt->sopt_name == LOCAL_PEEREPID &&
                            peerso->so_flags & SOF_DELEGATED)
                                peerpid = peerso->e_pid;
                        else
                                peerpid = peerso->last_pid;
                        socket_unlock(peerso, 1);
                        error = sooptcopyout(sopt, &peerpid, sizeof (peerpid));
                        break;
                case LOCAL_PEERUUID:
                case LOCAL_PEEREUUID:
                        if (unp->unp_conn == NULL) {
                                error = ENOTCONN;
                                break;
                        }
                        peerso = unp->unp_conn->unp_socket;
                        if (peerso == NULL)
                                panic("peer is connected but has no socket?");
                        unp_get_locks_in_order(so, peerso);
                        if (sopt->sopt_name == LOCAL_PEEREUUID &&
                            peerso->so_flags & SOF_DELEGATED)
                                error = sooptcopyout(sopt, &peerso->e_uuid,
                                    sizeof (peerso->e_uuid));
                        else
                                error = sooptcopyout(sopt, &peerso->last_uuid,
                                    sizeof (peerso->last_uuid));
                        socket_unlock(peerso, 1);
                        break;
                default:
                        error = EOPNOTSUPP;
                        break;
                }
                break;
        case SOPT_SET:
        default:
                error = EOPNOTSUPP;
                break;
        }

        return (error);
}

/*
 * Both send and receive buffers are allocated PIPSIZ bytes of buffering
 * for stream sockets, although the total for sender and receiver is
 * actually only PIPSIZ.
 * Datagram sockets really use the sendspace as the maximum datagram size,
 * and don't really want to reserve the sendspace.  Their recvspace should
 * be large enough for at least one max-size datagram plus address.
 */
#ifndef PIPSIZ
#define PIPSIZ  8192
#endif
static u_int32_t        unpst_sendspace = PIPSIZ;
static u_int32_t        unpst_recvspace = PIPSIZ;
static u_int32_t        unpdg_sendspace = 2*1024;       /* really max datagram size */
static u_int32_t        unpdg_recvspace = 4*1024;

static int      unp_rights;                     /* file descriptors in flight */
static int      unp_disposed;                   /* discarded file descriptors */

SYSCTL_DECL(_net_local_stream);
SYSCTL_INT(_net_local_stream, OID_AUTO, sendspace, CTLFLAG_RW | CTLFLAG_LOCKED,
   &unpst_sendspace, 0, "");
SYSCTL_INT(_net_local_stream, OID_AUTO, recvspace, CTLFLAG_RW | CTLFLAG_LOCKED,
   &unpst_recvspace, 0, "");
SYSCTL_INT(_net_local_stream, OID_AUTO, tracemdns, CTLFLAG_RW | CTLFLAG_LOCKED,
   &unpst_tracemdns, 0, "");
SYSCTL_DECL(_net_local_dgram);
SYSCTL_INT(_net_local_dgram, OID_AUTO, maxdgram, CTLFLAG_RW | CTLFLAG_LOCKED,
   &unpdg_sendspace, 0, "");
SYSCTL_INT(_net_local_dgram, OID_AUTO, recvspace, CTLFLAG_RW | CTLFLAG_LOCKED,
   &unpdg_recvspace, 0, "");
SYSCTL_DECL(_net_local);
SYSCTL_INT(_net_local, OID_AUTO, inflight, CTLFLAG_RD | CTLFLAG_LOCKED, &unp_rights, 0, "");

/*
 * Returns:     0                       Success
 *              ENOBUFS
 *      soreserve:ENOBUFS
 */
static int
unp_attach(struct socket *so)
{
        struct unpcb *unp;
        int error = 0;

        if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
                switch (so->so_type) {

                case SOCK_STREAM:
                        error = soreserve(so, unpst_sendspace, unpst_recvspace);
                        break;

                case SOCK_DGRAM:
                        error = soreserve(so, unpdg_sendspace, unpdg_recvspace);
                        break;

                default:
                        panic("unp_attach");
                }
                if (error)
                        return (error);
        }
        unp = (struct unpcb *)zalloc(unp_zone);
        if (unp == NULL)
                return (ENOBUFS);
        bzero(unp, sizeof (*unp));

        lck_mtx_init(&unp->unp_mtx, 
                unp_mtx_grp, unp_mtx_attr);

        lck_rw_lock_exclusive(unp_list_mtx);
        LIST_INIT(&unp->unp_refs);
        unp->unp_socket = so;
        unp->unp_gencnt = ++unp_gencnt;
        unp_count++;
        LIST_INSERT_HEAD(so->so_type == SOCK_DGRAM ?
            &unp_dhead : &unp_shead, unp, unp_link);
        lck_rw_done(unp_list_mtx);
        so->so_pcb = (caddr_t)unp;
        /*
         * Mark AF_UNIX socket buffers accordingly so that:
         *
         * a. In the SOCK_STREAM case, socket buffer append won't fail due to
         *    the lack of space; this essentially loosens the sbspace() check,
         *    since there is disconnect between sosend() and uipc_send() with
         *    respect to flow control that might result in our dropping the
         *    data in uipc_send().  By setting this, we allow for slightly
         *    more records to be appended to the receiving socket to avoid
         *    losing data (which we can't afford in the SOCK_STREAM case).
         *    Flow control still takes place since we adjust the sender's
         *    hiwat during each send.  This doesn't affect the SOCK_DGRAM
         *    case and append would still fail when the queue overflows.
         *
         * b. In the presence of control messages containing internalized
         *    file descriptors, the append routines will not free them since
         *    we'd need to undo the work first via unp_dispose().
         */
        so->so_rcv.sb_flags |= SB_UNIX;
        so->so_snd.sb_flags |= SB_UNIX;
        return (0);
}

static void
unp_detach(struct unpcb *unp)
{
        int so_locked = 1;

        lck_rw_lock_exclusive(unp_list_mtx);
        LIST_REMOVE(unp, unp_link);
        --unp_count; 
        ++unp_gencnt;
        lck_rw_done(unp_list_mtx);
        if (unp->unp_vnode) {
                struct vnode *tvp = NULL;
                socket_unlock(unp->unp_socket, 0);

                /* Holding unp_connect_lock will avoid a race between
                 * a thread closing the listening socket and a thread
                 * connecting to it.
                 */
                lck_mtx_lock(unp_connect_lock);
                socket_lock(unp->unp_socket, 0);
                if (unp->unp_vnode) {
                        tvp = unp->unp_vnode;
                        unp->unp_vnode->v_socket = NULL;
                        unp->unp_vnode = NULL;
                }
                lck_mtx_unlock(unp_connect_lock);
                if (tvp != NULL)
                        vnode_rele(tvp);                /* drop the usecount */
        }
        if (unp->unp_conn)
                unp_disconnect(unp);
        while (unp->unp_refs.lh_first) {
                struct unpcb *unp2 = NULL;

                /* This datagram socket is connected to one or more
                 * sockets. In order to avoid a race condition between removing
                 * this reference and closing the connected socket, we need 
                 * to check disconnect_in_progress
                 */
                if (so_locked == 1) {
                        socket_unlock(unp->unp_socket, 0);
                        so_locked = 0;
                }
                lck_mtx_lock(unp_disconnect_lock);
                while (disconnect_in_progress != 0) {
                        (void)msleep((caddr_t)&disconnect_in_progress, unp_disconnect_lock,
                                PSOCK, "disconnect", NULL);
                }
                disconnect_in_progress = 1;
                lck_mtx_unlock(unp_disconnect_lock);

                /* Now we are sure that any unpcb socket disconnect is not happening */
                if (unp->unp_refs.lh_first != NULL) {
                        unp2 = unp->unp_refs.lh_first;
                        socket_lock(unp2->unp_socket, 1);
                }
                
                lck_mtx_lock(unp_disconnect_lock);
                disconnect_in_progress = 0;
                wakeup(&disconnect_in_progress);
                lck_mtx_unlock(unp_disconnect_lock);
                        
                if (unp2 != NULL) {
                        /* We already locked this socket and have a reference on it */
                        unp_drop(unp2, ECONNRESET);
                        socket_unlock(unp2->unp_socket, 1);
                }
        }

        if (so_locked == 0) {
                socket_lock(unp->unp_socket, 0);
                so_locked = 1;
        }
        soisdisconnected(unp->unp_socket);
        /* makes sure we're getting dealloced */
        unp->unp_socket->so_flags |= SOF_PCBCLEARING;
}

/*
 * Returns:     0                       Success
 *              EAFNOSUPPORT
 *              EINVAL
 *              EADDRINUSE
 *              namei:???               [anything namei can return]
 *              vnode_authorize:???     [anything vnode_authorize can return]
 *
 * Notes:       p at this point is the current process, as this function is
 *              only called by sobind().
 */
static int
unp_bind(
        struct unpcb *unp,
        struct sockaddr *nam,
        proc_t p)
{
        struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        struct vnode *vp, *dvp;
        struct vnode_attr va;
        vfs_context_t ctx = vfs_context_current();
        int error, namelen;
        struct nameidata nd;
        struct socket *so = unp->unp_socket;
        char buf[SOCK_MAXADDRLEN];

        if (nam->sa_family != 0 && nam->sa_family != AF_UNIX) {
                return (EAFNOSUPPORT);
        }

        if (unp->unp_vnode != NULL)
                return (EINVAL);
        namelen = soun->sun_len - offsetof(struct sockaddr_un, sun_path);
        if (namelen <= 0)
                return (EINVAL);

        socket_unlock(so, 0);

        strlcpy(buf, soun->sun_path, namelen+1);
        NDINIT(&nd, CREATE, OP_MKFIFO, FOLLOW | LOCKPARENT, UIO_SYSSPACE,
            CAST_USER_ADDR_T(buf), ctx);
        /* SHOULD BE ABLE TO ADOPT EXISTING AND wakeup() ALA FIFO's */
        error = namei(&nd);
        if (error) {
                socket_lock(so, 0);
                return (error);
        }
        dvp = nd.ni_dvp;
        vp = nd.ni_vp;

        if (vp != NULL) {
                /*
                 * need to do this before the vnode_put of dvp
                 * since we may have to release an fs_nodelock
                 */
                nameidone(&nd);

                vnode_put(dvp);
                vnode_put(vp);

                socket_lock(so, 0);
                return (EADDRINUSE);
        }

        VATTR_INIT(&va);
        VATTR_SET(&va, va_type, VSOCK);
        VATTR_SET(&va, va_mode, (ACCESSPERMS & ~p->p_fd->fd_cmask));

#if CONFIG_MACF
        error = mac_vnode_check_create(ctx,
            nd.ni_dvp, &nd.ni_cnd, &va);

        if (error == 0)
#endif /* CONFIG_MACF */
#if CONFIG_MACF_SOCKET_SUBSET
        error = mac_vnode_check_uipc_bind(ctx,
            nd.ni_dvp, &nd.ni_cnd, &va);

        if (error == 0)
#endif /* MAC_SOCKET_SUBSET */
        /* authorize before creating */
        error = vnode_authorize(dvp, NULL, KAUTH_VNODE_ADD_FILE, ctx);

        if (!error) {
                /* create the socket */
                error = vn_create(dvp, &vp, &nd, &va, 0, 0, NULL, ctx);
        }

        nameidone(&nd);
        vnode_put(dvp);

        if (error) {
                socket_lock(so, 0);
                return (error);
        }
        vnode_ref(vp);  /* gain a longterm reference */
        socket_lock(so, 0);
        vp->v_socket = unp->unp_socket;
        unp->unp_vnode = vp;
        unp->unp_addr = (struct sockaddr_un *)dup_sockaddr(nam, 1);
        vnode_put(vp);          /* drop the iocount */

        return (0);
}


/*
 * Returns:     0                       Success
 *              EAFNOSUPPORT            Address family not supported
 *              EINVAL                  Invalid argument
 *              ENOTSOCK                Not a socket
 *              ECONNREFUSED            Connection refused
 *              EPROTOTYPE              Protocol wrong type for socket
 *              EISCONN                 Socket is connected
 *      unp_connect2:EPROTOTYPE         Protocol wrong type for socket
 *      unp_connect2:EINVAL             Invalid argument
 *      namei:???                       [anything namei can return]
 *      vnode_authorize:????            [anything vnode_authorize can return]
 *
 * Notes:       p at this point is the current process, as this function is
 *              only called by sosend(), sendfile(), and soconnectlock().
 */
static int
unp_connect(struct socket *so, struct sockaddr *nam, __unused proc_t p)
{
        struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        struct vnode *vp;
        struct socket *so2, *so3, *list_so=NULL;
        struct unpcb *unp, *unp2, *unp3;
        vfs_context_t ctx = vfs_context_current();
        int error, len;
        struct nameidata nd;
        char buf[SOCK_MAXADDRLEN];

        if (nam->sa_family != 0 && nam->sa_family != AF_UNIX) {
                return (EAFNOSUPPORT);
        }

        unp = sotounpcb(so);
        so2 = so3 = NULL;

        len = nam->sa_len - offsetof(struct sockaddr_un, sun_path);
        if (len <= 0)
                return (EINVAL);

        strlcpy(buf, soun->sun_path, len+1);
        socket_unlock(so, 0);

        NDINIT(&nd, LOOKUP, OP_LOOKUP, FOLLOW | LOCKLEAF, UIO_SYSSPACE,
            CAST_USER_ADDR_T(buf), ctx);
        error = namei(&nd);
        if (error) {
                socket_lock(so, 0);
                return (error);
        }
        nameidone(&nd);
        vp = nd.ni_vp;
        if (vp->v_type != VSOCK) {
                error = ENOTSOCK;
                socket_lock(so, 0);
                goto out;
        }

#if CONFIG_MACF_SOCKET_SUBSET
        error = mac_vnode_check_uipc_connect(ctx, vp);
        if (error) {
                socket_lock(so, 0);
                goto out;
        }
#endif /* MAC_SOCKET_SUBSET */

        error = vnode_authorize(vp, NULL, KAUTH_VNODE_WRITE_DATA, ctx);
        if (error) {
                socket_lock(so, 0);
                goto out;
        }

        lck_mtx_lock(unp_connect_lock);

        if (vp->v_socket == 0) {
                lck_mtx_unlock(unp_connect_lock);
                error = ECONNREFUSED;
                socket_lock(so, 0);
                goto out;
        }

        socket_lock(vp->v_socket, 1); /* Get a reference on the listening socket */
        so2 = vp->v_socket;
        lck_mtx_unlock(unp_connect_lock);


        if (so2->so_pcb == NULL) {
                error = ECONNREFUSED;
                if (so != so2) {
                        socket_unlock(so2, 1);
                        socket_lock(so, 0);
                } else {
                        /* Release the reference held for the listen socket */
                        so2->so_usecount--;
                }
                goto out;
        }

        if (so < so2) {
                socket_unlock(so2, 0);
                socket_lock(so, 0);
                socket_lock(so2, 0);
        } else if (so > so2) {
                socket_lock(so, 0);
        }
        /*
         * Check if socket was connected while we were trying to
         * get the socket locks in order.
         * XXX - probably shouldn't return an error for SOCK_DGRAM
         */
        if ((so->so_state & SS_ISCONNECTED) != 0) {
                error = EISCONN;
                goto decref_out;
        }

        if (so->so_type != so2->so_type) {
                error = EPROTOTYPE;
                goto decref_out;
        }

        if (so->so_proto->pr_flags & PR_CONNREQUIRED) {
                /* Release the incoming socket but keep a reference */
                socket_unlock(so, 0);

                if ((so2->so_options & SO_ACCEPTCONN) == 0 ||
                    (so3 = sonewconn(so2, 0, nam)) == 0) {
                        error = ECONNREFUSED;
                        if (so != so2) {
                                socket_unlock(so2, 1);
                                socket_lock(so, 0);
                        } else {
                                socket_lock(so, 0);
                                /* Release the reference held for
                                 * listen socket.
                                 */
                                so2->so_usecount--;
                        }
                        goto out;
                }
                unp2 = sotounpcb(so2);
                unp3 = sotounpcb(so3);
                if (unp2->unp_addr)
                        unp3->unp_addr = (struct sockaddr_un *)
                            dup_sockaddr((struct sockaddr *)unp2->unp_addr, 1);

                /*
                 * unp_peercred management:
                 *
                 * The connecter's (client's) credentials are copied
                 * from its process structure at the time of connect()
                 * (which is now).
                 */
                cru2x(vfs_context_ucred(ctx), &unp3->unp_peercred);
                unp3->unp_flags |= UNP_HAVEPC;
                /*
                 * The receiver's (server's) credentials are copied
                 * from the unp_peercred member of socket on which the
                 * former called listen(); unp_listen() cached that
                 * process's credentials at that time so we can use
                 * them now.
                 */
                KASSERT(unp2->unp_flags & UNP_HAVEPCCACHED,
                    ("unp_connect: listener without cached peercred"));

                /* Here we need to have both so and so2 locks and so2
                 * is already locked. Lock ordering is required.
                 */
                if (so < so2) {
                        socket_unlock(so2, 0);
                        socket_lock(so, 0);
                        socket_lock(so2, 0);
                } else {
                        socket_lock(so, 0);
                }

                /* Check again if the socket state changed when its lock was released */
                if ((so->so_state & SS_ISCONNECTED) != 0) {
                        error = EISCONN;
                        socket_unlock(so2, 1);
                        socket_lock(so3, 0);
                        sofreelastref(so3, 1);
                        goto out;
                }
                memcpy(&unp->unp_peercred, &unp2->unp_peercred,
                    sizeof (unp->unp_peercred));
                unp->unp_flags |= UNP_HAVEPC;

#if CONFIG_MACF_SOCKET
                /* XXXMAC: recursive lock: SOCK_LOCK(so); */
                mac_socketpeer_label_associate_socket(so, so3);
                mac_socketpeer_label_associate_socket(so3, so);
                /* XXXMAC: SOCK_UNLOCK(so); */
#endif /* MAC_SOCKET */

                /* Hold the reference on listening socket until the end */
                socket_unlock(so2, 0);
                list_so = so2;

                /* Lock ordering doesn't matter because so3 was just created */
                socket_lock(so3, 1);
                so2 = so3;

                /*
                 * Enable tracing for mDNSResponder endpoints.  (The use
                 * of sizeof instead of strlen below takes the null
                 * terminating character into account.)
                 */
                if (unpst_tracemdns &&
                    !strncmp(soun->sun_path, MDNSRESPONDER_PATH,
                    sizeof (MDNSRESPONDER_PATH))) {
                        unp->unp_flags |= UNP_TRACE_MDNS;
                        unp2->unp_flags |= UNP_TRACE_MDNS;
                }
        }
        
        error = unp_connect2(so, so2);

decref_out:
        if (so2 != NULL) {
                if (so != so2) {
                        socket_unlock(so2, 1);
                } else {
                        /* Release the extra reference held for the listen socket.
                         * This is possible only for SOCK_DGRAM sockets. We refuse
                         * connecting to the same socket for SOCK_STREAM sockets.
                         */
                        so2->so_usecount--;
                }
        }

        if (list_so != NULL) {
                socket_lock(list_so, 0);
                socket_unlock(list_so, 1);
        }

out:
        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        vnode_put(vp);
        return (error);
}

/*
 * Returns:     0                       Success
 *              EPROTOTYPE              Protocol wrong type for socket
 *              EINVAL                  Invalid argument
 */
int
unp_connect2(struct socket *so, struct socket *so2)
{
        struct unpcb *unp = sotounpcb(so);
        struct unpcb *unp2;

        if (so2->so_type != so->so_type)
                return (EPROTOTYPE);

        unp2 = sotounpcb(so2);

        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        lck_mtx_assert(&unp2->unp_mtx, LCK_MTX_ASSERT_OWNED);

        /* Verify both sockets are still opened */
        if (unp == 0 || unp2 == 0)
                return (EINVAL);

        unp->unp_conn = unp2;
        so2->so_usecount++; 
        
        switch (so->so_type) {

        case SOCK_DGRAM:
                LIST_INSERT_HEAD(&unp2->unp_refs, unp, unp_reflink);

                if (so != so2) {        
                        /* Avoid lock order reversals due to drop/acquire in soisconnected. */
                        /* Keep an extra reference on so2 that will be dropped
                         * soon after getting the locks in order 
                         */ 
                        socket_unlock(so2, 0);
                        soisconnected(so);
                        unp_get_locks_in_order(so, so2);
                        so2->so_usecount--;
                } else {
                        soisconnected(so);
                }

                break;

        case SOCK_STREAM:
                /* This takes care of socketpair */
                if (!(unp->unp_flags & UNP_HAVEPC) &&
                    !(unp2->unp_flags & UNP_HAVEPC)) {
                        cru2x(kauth_cred_get(), &unp->unp_peercred);
                        unp->unp_flags |= UNP_HAVEPC;

                        cru2x(kauth_cred_get(), &unp2->unp_peercred);
                        unp2->unp_flags |= UNP_HAVEPC;
                }
                unp2->unp_conn = unp;
                so->so_usecount++;

                /* Avoid lock order reversals due to drop/acquire in soisconnected. */
                socket_unlock(so, 0);
                soisconnected(so2);

                /* Keep an extra reference on so2, that will be dropped soon after
                 * getting the locks in order again.
                 */
                socket_unlock(so2, 0);

                socket_lock(so, 0);
                soisconnected(so);

                unp_get_locks_in_order(so, so2);
                /* Decrement the extra reference left before */
                so2->so_usecount--;
                break;

        default:
                panic("unknown socket type %d in unp_connect2", so->so_type);
        }
        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        lck_mtx_assert(&unp2->unp_mtx, LCK_MTX_ASSERT_OWNED);
        return (0);
}

static void
unp_disconnect(struct unpcb *unp)
{
        struct unpcb *unp2 = NULL;
        struct socket *so2 = NULL, *so;
        struct socket *waitso;
        int so_locked = 1, strdisconn = 0;

        so = unp->unp_socket;
        if (unp->unp_conn == NULL) {
                return;
        }
        lck_mtx_lock(unp_disconnect_lock);
        while (disconnect_in_progress != 0) {
                if (so_locked == 1) {
                        socket_unlock(so, 0);
                        so_locked = 0;
                }
                (void)msleep((caddr_t)&disconnect_in_progress, unp_disconnect_lock,
                        PSOCK, "disconnect", NULL);
        }
        disconnect_in_progress = 1;
        lck_mtx_unlock(unp_disconnect_lock);

        if (so_locked == 0) {
                socket_lock(so, 0);
                so_locked = 1;
        }

        unp2 = unp->unp_conn;

        if (unp2 == 0 || unp2->unp_socket == NULL) {
                goto out;
        }
        so2 = unp2->unp_socket;

try_again:
        if (so == so2) {
                if (so_locked == 0) {
                        socket_lock(so, 0);
                }
                waitso = so;
        } else if (so < so2) {
                if (so_locked == 0) {
                        socket_lock(so, 0);
                }
                socket_lock(so2, 1);
                waitso = so2;
        } else {
                if (so_locked == 1) { 
                        socket_unlock(so, 0);
                }
                socket_lock(so2, 1);
                socket_lock(so, 0);
                waitso = so;
        }
        so_locked = 1;

        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        lck_mtx_assert(&unp2->unp_mtx, LCK_MTX_ASSERT_OWNED);

        /* Check for the UNP_DONTDISCONNECT flag, if it
         * is set, release both sockets and go to sleep
         */
        
        if ((((struct unpcb *)waitso->so_pcb)->unp_flags & UNP_DONTDISCONNECT) != 0) {
                if (so != so2) {
                        socket_unlock(so2, 1);
                }
                so_locked = 0;

                (void)msleep(waitso->so_pcb, &unp->unp_mtx, 
                        PSOCK | PDROP, "unpdisconnect", NULL);
                goto try_again;
        }
        
        if (unp->unp_conn == NULL) {
                panic("unp_conn became NULL after sleep");
        }

        unp->unp_conn = NULL;
        so2->so_usecount--;

        if (unp->unp_flags & UNP_TRACE_MDNS)
                unp->unp_flags &= ~UNP_TRACE_MDNS;

        switch (unp->unp_socket->so_type) {

        case SOCK_DGRAM:
                LIST_REMOVE(unp, unp_reflink);
                unp->unp_socket->so_state &= ~SS_ISCONNECTED;
                if (so != so2)
                        socket_unlock(so2, 1);
                break;

        case SOCK_STREAM:
                unp2->unp_conn = NULL;
                so->so_usecount--;

                /* Set the socket state correctly but do a wakeup later when
                 * we release all locks except the socket lock, this will avoid
                 * a deadlock.
                 */
                unp->unp_socket->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
                unp->unp_socket->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);

                unp2->unp_socket->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
                unp->unp_socket->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE|SS_ISDISCONNECTED);

                if (unp2->unp_flags & UNP_TRACE_MDNS)
                        unp2->unp_flags &= ~UNP_TRACE_MDNS;

                strdisconn = 1;
                break;
        default:
                panic("unknown socket type %d", so->so_type);
        }
out:
        lck_mtx_lock(unp_disconnect_lock);
        disconnect_in_progress = 0;
        wakeup(&disconnect_in_progress);
        lck_mtx_unlock(unp_disconnect_lock);

        if (strdisconn) {
                socket_unlock(so, 0);
                soisdisconnected(so2);
                socket_unlock(so2, 1);

                socket_lock(so,0);
                soisdisconnected(so);
        }
        lck_mtx_assert(&unp->unp_mtx, LCK_MTX_ASSERT_OWNED);
        return;
}

/*
 * unpcb_to_compat copies specific bits of a unpcb to a unpcb_compat format.
 * The unpcb_compat data structure is passed to user space and must not change.
 */
static void
unpcb_to_compat(struct unpcb *up, struct unpcb_compat *cp)
{
#if defined(__LP64__)
        cp->unp_link.le_next = (u_int32_t)
            VM_KERNEL_ADDRPERM(up->unp_link.le_next);
        cp->unp_link.le_prev = (u_int32_t)
            VM_KERNEL_ADDRPERM(up->unp_link.le_prev);
#else
        cp->unp_link.le_next = (struct unpcb_compat *)
            VM_KERNEL_ADDRPERM(up->unp_link.le_next);
        cp->unp_link.le_prev = (struct unpcb_compat **)
            VM_KERNEL_ADDRPERM(up->unp_link.le_prev);
#endif
        cp->unp_socket = (_UNPCB_PTR(struct socket *))
            VM_KERNEL_ADDRPERM(up->unp_socket);
        cp->unp_vnode = (_UNPCB_PTR(struct vnode *))
            VM_KERNEL_ADDRPERM(up->unp_vnode);
        cp->unp_ino = up->unp_ino;
        cp->unp_conn = (_UNPCB_PTR(struct unpcb_compat *))
            VM_KERNEL_ADDRPERM(up->unp_conn);
        cp->unp_refs = (u_int32_t)VM_KERNEL_ADDRPERM(up->unp_refs.lh_first);
#if defined(__LP64__)
        cp->unp_reflink.le_next =
            (u_int32_t)VM_KERNEL_ADDRPERM(up->unp_reflink.le_next);
        cp->unp_reflink.le_prev =
            (u_int32_t)VM_KERNEL_ADDRPERM(up->unp_reflink.le_prev);
#else
        cp->unp_reflink.le_next =
            (struct unpcb_compat *)VM_KERNEL_ADDRPERM(up->unp_reflink.le_next);
        cp->unp_reflink.le_prev =
            (struct unpcb_compat **)VM_KERNEL_ADDRPERM(up->unp_reflink.le_prev);
#endif
        cp->unp_addr = (_UNPCB_PTR(struct sockaddr_un *))
            VM_KERNEL_ADDRPERM(up->unp_addr);
        cp->unp_cc = up->unp_cc;
        cp->unp_mbcnt = up->unp_mbcnt;
        cp->unp_gencnt = up->unp_gencnt;
}

static int
unp_pcblist SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp,arg2)
        int error, i, n;
        struct unpcb *unp, **unp_list;
        unp_gen_t gencnt;
        struct xunpgen xug;
        struct unp_head *head;

        lck_rw_lock_shared(unp_list_mtx);
        head = ((intptr_t)arg1 == SOCK_DGRAM ? &unp_dhead : &unp_shead);

        /*
         * The process of preparing the PCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        if (req->oldptr == USER_ADDR_NULL) {
                n = unp_count;
                req->oldidx = 2 * sizeof (xug) + (n + n / 8) *
                    sizeof (struct xunpcb);
                lck_rw_done(unp_list_mtx);
                return (0);
        }

        if (req->newptr != USER_ADDR_NULL) {
                lck_rw_done(unp_list_mtx);
                return (EPERM);
        }

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = unp_gencnt;
        n = unp_count;

        bzero(&xug, sizeof (xug));
        xug.xug_len = sizeof (xug);
        xug.xug_count = n;
        xug.xug_gen = gencnt;
        xug.xug_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xug, sizeof (xug));
        if (error) {
                lck_rw_done(unp_list_mtx);
                return (error);
        }

        /*
         * We are done if there is no pcb
         */
        if (n == 0)  {
                lck_rw_done(unp_list_mtx);
                return (0);
        }

        MALLOC(unp_list, struct unpcb **, n * sizeof (*unp_list),
            M_TEMP, M_WAITOK);
        if (unp_list == 0) {
                lck_rw_done(unp_list_mtx);
                return (ENOMEM);
        }

        for (unp = head->lh_first, i = 0; unp && i < n;
            unp = unp->unp_link.le_next) {
                if (unp->unp_gencnt <= gencnt)
                        unp_list[i++] = unp;
        }
        n = i;                  /* in case we lost some during malloc */

        error = 0;
        for (i = 0; i < n; i++) {
                unp = unp_list[i];
                if (unp->unp_gencnt <= gencnt) {
                        struct xunpcb xu;

                        bzero(&xu, sizeof (xu));
                        xu.xu_len = sizeof (xu);
                        xu.xu_unpp = (_UNPCB_PTR(struct unpcb_compat *))
                            VM_KERNEL_ADDRPERM(unp);
                        /*
                         * XXX - need more locking here to protect against
                         * connect/disconnect races for SMP.
                         */
                        if (unp->unp_addr)
                                bcopy(unp->unp_addr, &xu.xu_addr,
                                    unp->unp_addr->sun_len);
                        if (unp->unp_conn && unp->unp_conn->unp_addr)
                                bcopy(unp->unp_conn->unp_addr,
                                    &xu.xu_caddr,
                                    unp->unp_conn->unp_addr->sun_len);
                        unpcb_to_compat(unp, &xu.xu_unp);
                        sotoxsocket(unp->unp_socket, &xu.xu_socket);
                        error = SYSCTL_OUT(req, &xu, sizeof (xu));
                }
        }
        if (!error) {
                /*
                 * Give the user an updated idea of our state.
                 * If the generation differs from what we told
                 * her before, she knows that something happened
                 * while we were processing this request, and it
                 * might be necessary to retry.
                 */
                bzero(&xug, sizeof (xug));
                xug.xug_len = sizeof (xug);
                xug.xug_gen = unp_gencnt;
                xug.xug_sogen = so_gencnt;
                xug.xug_count = unp_count;
                error = SYSCTL_OUT(req, &xug, sizeof (xug));
        }
        FREE(unp_list, M_TEMP);
        lck_rw_done(unp_list_mtx);
        return (error);
}

SYSCTL_PROC(_net_local_dgram, OID_AUTO, pcblist,
            CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
            (caddr_t)(long)SOCK_DGRAM, 0, unp_pcblist, "S,xunpcb",
            "List of active local datagram sockets");
SYSCTL_PROC(_net_local_stream, OID_AUTO, pcblist,
            CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
            (caddr_t)(long)SOCK_STREAM, 0, unp_pcblist, "S,xunpcb",
            "List of active local stream sockets");


static int
unp_pcblist64 SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp,arg2)
        int error, i, n;
        struct unpcb *unp, **unp_list;
        unp_gen_t gencnt;
        struct xunpgen xug;
        struct unp_head *head;

        lck_rw_lock_shared(unp_list_mtx);
        head = ((intptr_t)arg1 == SOCK_DGRAM ? &unp_dhead : &unp_shead);

        /*
         * The process of preparing the PCB list is too time-consuming and
         * resource-intensive to repeat twice on every request.
         */
        if (req->oldptr == USER_ADDR_NULL) {
                n = unp_count;
                req->oldidx = 2 * sizeof (xug) + (n + n / 8) *
                    (sizeof (struct xunpcb64)); 
                lck_rw_done(unp_list_mtx);
                return (0);
        }

        if (req->newptr != USER_ADDR_NULL) {
                lck_rw_done(unp_list_mtx);
                return (EPERM);
        }

        /*
         * OK, now we're committed to doing something.
         */
        gencnt = unp_gencnt;
        n = unp_count;

        bzero(&xug, sizeof (xug));
        xug.xug_len = sizeof (xug);
        xug.xug_count = n;
        xug.xug_gen = gencnt;
        xug.xug_sogen = so_gencnt;
        error = SYSCTL_OUT(req, &xug, sizeof (xug));
        if (error) {
                lck_rw_done(unp_list_mtx);
                return (error);
        }

        /*
         * We are done if there is no pcb
         */
        if (n == 0)  {
                lck_rw_done(unp_list_mtx);
                return (0);
        }

        MALLOC(unp_list, struct unpcb **, n * sizeof (*unp_list),
            M_TEMP, M_WAITOK);
        if (unp_list == 0) {
                lck_rw_done(unp_list_mtx);
                return (ENOMEM);
        }

        for (unp = head->lh_first, i = 0; unp && i < n;
            unp = unp->unp_link.le_next) {
                if (unp->unp_gencnt <= gencnt)
                        unp_list[i++] = unp;
        }
        n = i;                  /* in case we lost some during malloc */

        error = 0;
        for (i = 0; i < n; i++) {
                unp = unp_list[i];
                if (unp->unp_gencnt <= gencnt) {
                        struct xunpcb64 xu;
                        size_t          xu_len = sizeof(struct xunpcb64);

                        bzero(&xu, xu_len);
                        xu.xu_len = xu_len;
                        xu.xu_unpp = (u_int64_t)VM_KERNEL_ADDRPERM(unp);
                        xu.xunp_link.le_next = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_link.le_next);
                        xu.xunp_link.le_prev = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_link.le_prev);
                        xu.xunp_socket = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_socket);
                        xu.xunp_vnode = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_vnode);
                        xu.xunp_ino = unp->unp_ino;
                        xu.xunp_conn = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_conn);
                        xu.xunp_refs = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_refs.lh_first);
                        xu.xunp_reflink.le_next = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_reflink.le_next);
                        xu.xunp_reflink.le_prev = (u_int64_t)
                            VM_KERNEL_ADDRPERM(unp->unp_reflink.le_prev);
                        xu.xunp_cc = unp->unp_cc;
                        xu.xunp_mbcnt = unp->unp_mbcnt;
                        xu.xunp_gencnt = unp->unp_gencnt;

                        if (unp->unp_socket)
                                sotoxsocket64(unp->unp_socket, &xu.xu_socket);

                        /*
                         * XXX - need more locking here to protect against
                         * connect/disconnect races for SMP.
                         */
                        if (unp->unp_addr)
                                bcopy(unp->unp_addr, &xu.xunp_addr,
                                    unp->unp_addr->sun_len);
                        if (unp->unp_conn && unp->unp_conn->unp_addr)
                                bcopy(unp->unp_conn->unp_addr,
                                    &xu.xunp_caddr,
                                    unp->unp_conn->unp_addr->sun_len);

                        error = SYSCTL_OUT(req, &xu, xu_len);
                }
        }
        if (!error) {
                /*
                 * Give the user an updated idea of our state.
                 * If the generation differs from what we told
                 * her before, she knows that something happened
                 * while we were processing this request, and it
                 * might be necessary to retry.
                 */
                bzero(&xug, sizeof (xug));
                xug.xug_len = sizeof (xug);
                xug.xug_gen = unp_gencnt;
                xug.xug_sogen = so_gencnt;
                xug.xug_count = unp_count;
                error = SYSCTL_OUT(req, &xug, sizeof (xug));
        }
        FREE(unp_list, M_TEMP);
        lck_rw_done(unp_list_mtx);
        return (error);
}

SYSCTL_PROC(_net_local_dgram, OID_AUTO, pcblist64,
            CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
            (caddr_t)(long)SOCK_DGRAM, 0, unp_pcblist64, "S,xunpcb64",
            "List of active local datagram sockets 64 bit");
SYSCTL_PROC(_net_local_stream, OID_AUTO, pcblist64,
            CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED,
            (caddr_t)(long)SOCK_STREAM, 0, unp_pcblist64, "S,xunpcb64",
            "List of active local stream sockets 64 bit");


static void
unp_shutdown(struct unpcb *unp)
{
        struct socket *so = unp->unp_socket;
        struct socket *so2;
        if (unp->unp_socket->so_type == SOCK_STREAM && unp->unp_conn) {
                so2 = unp->unp_conn->unp_socket;
                unp_get_locks_in_order(so, so2);
                socantrcvmore(so2);
                socket_unlock(so2, 1);
        }
}

static void
unp_drop(struct unpcb *unp, int errno)
{
        struct socket *so = unp->unp_socket;

        so->so_error = errno;
        unp_disconnect(unp);
}

/*
 * Returns:     0                       Success
 *              EMSGSIZE                The new fd's will not fit
 *              ENOBUFS                 Cannot alloc struct fileproc
 */
int
unp_externalize(struct mbuf *rights)
{
        proc_t p = current_proc();              /* XXX */
        int i;
        struct cmsghdr *cm = mtod(rights, struct cmsghdr *);
        struct fileglob **rp = (struct fileglob **)(cm + 1);
        int *fds = (int *)(cm + 1);
        struct fileproc *fp;
        struct fileglob **fgl;
        int newfds = (cm->cmsg_len - sizeof (*cm)) / sizeof (int);
        int f, error = 0;

        MALLOC(fgl, struct fileglob **, newfds * sizeof (struct fileglob *),
                M_TEMP, M_WAITOK);
        if (fgl == NULL) {
                error = ENOMEM;
                goto discard;
        }

        proc_fdlock(p);

        /*
         * if the new FD's will not fit, then we free them all
         */
        if (!fdavail(p, newfds)) {
                proc_fdunlock(p);
                error = EMSGSIZE;
                goto discard;
        }
        /*
         * now change each pointer to an fd in the global table to
         * an integer that is the index to the local fd table entry
         * that we set up to point to the global one we are transferring.
         * XXX (1) this assumes a pointer and int are the same size, 
         * XXX     or the mbuf can hold the expansion
         * XXX (2) allocation failures should be non-fatal
         */
        for (i = 0; i < newfds; i++) {
#if CONFIG_MACF_SOCKET
                /*
                 * If receive access is denied, don't pass along
                 * and error message, just discard the descriptor.
                 */
                if (mac_file_check_receive(kauth_cred_get(), rp[i])) {
                        proc_fdunlock(p);
                        unp_discard(rp[i], p);
                        fds[i] = 0;
                        proc_fdlock(p);
                        continue;
                }
#endif
                if (fdalloc(p, 0, &f))
                        panic("unp_externalize:fdalloc");
                fp = fileproc_alloc_init(NULL);
                if (fp == NULL)
                        panic("unp_externalize: MALLOC_ZONE");
                fp->f_iocount = 0;
                fp->f_fglob = rp[i];
                if (fg_removeuipc_mark(rp[i]))
                        fgl[i] = rp[i];
                else
                        fgl[i] = NULL;
                procfdtbl_releasefd(p, f, fp);
                fds[i] = f;
        }
        proc_fdunlock(p);

        for (i = 0; i < newfds; i++) {
                if (fgl[i] != NULL) {
                        VERIFY(fgl[i]->fg_lflags & FG_RMMSGQ);
                        fg_removeuipc(fgl[i]);
                }
                if (fds[i])
                        (void) OSAddAtomic(-1, &unp_rights);
        }

discard:
        if (fgl)
                FREE(fgl, M_TEMP);
        if (error) {
                for (i = 0; i < newfds; i++) {
                        unp_discard(*rp, p);
                        *rp++ = NULL;
                }
        }
        return (error);
}

void
unp_init(void)
{
        _CASSERT(UIPC_MAX_CMSG_FD >= (MCLBYTES / sizeof(int)));
        unp_zone = zinit(sizeof (struct unpcb),
            (nmbclusters * sizeof (struct unpcb)), 4096, "unpzone");

        if (unp_zone == 0)
                panic("unp_init");
        LIST_INIT(&unp_dhead);
        LIST_INIT(&unp_shead);

        /*
         * allocate lock group attribute and group for udp pcb mutexes
         */
        unp_mtx_grp_attr = lck_grp_attr_alloc_init();

        unp_mtx_grp = lck_grp_alloc_init("unp_list", unp_mtx_grp_attr);

        unp_mtx_attr = lck_attr_alloc_init();

        if ((unp_list_mtx = lck_rw_alloc_init(unp_mtx_grp,
            unp_mtx_attr)) == NULL)
                return; /* pretty much dead if this fails... */

        if ((unp_disconnect_lock = lck_mtx_alloc_init(unp_mtx_grp,
                unp_mtx_attr)) == NULL)
                return;

        if ((unp_connect_lock = lck_mtx_alloc_init(unp_mtx_grp,
                unp_mtx_attr)) == NULL)
                return;
}

#ifndef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif

/*
 * Returns:     0                       Success
 *              EINVAL
 *      fdgetf_noref:EBADF
 */
static int
unp_internalize(struct mbuf *control, proc_t p)
{
        struct cmsghdr *cm = mtod(control, struct cmsghdr *);
        int *fds;
        struct fileglob **rp;
        struct fileproc *fp;
        int i, error;
        int oldfds;
        uint8_t fg_ins[UIPC_MAX_CMSG_FD / 8];

        /* 64bit: cmsg_len is 'uint32_t', m_len is 'long' */
        if (cm->cmsg_type != SCM_RIGHTS || cm->cmsg_level != SOL_SOCKET ||
            (socklen_t)cm->cmsg_len != (socklen_t)control->m_len) {
                return (EINVAL);
        }
        oldfds = (cm->cmsg_len - sizeof (*cm)) / sizeof (int);
        bzero(fg_ins, sizeof(fg_ins));

        proc_fdlock(p);
        fds = (int *)(cm + 1);

        for (i = 0; i < oldfds; i++) {
                struct fileproc *tmpfp;
                if (((error = fdgetf_noref(p, fds[i], &tmpfp)) != 0)) {
                        proc_fdunlock(p);
                        return (error);
                } else if (!file_issendable(p, tmpfp)) {
                        proc_fdunlock(p);
                        return (EINVAL);
                } else if (FP_ISGUARDED(tmpfp, GUARD_SOCKET_IPC)) {
                        error = fp_guard_exception(p,
                                fds[i], tmpfp, kGUARD_EXC_SOCKET_IPC);
                        proc_fdunlock(p);
                        return (error);
                }
        }
        rp = (struct fileglob **)(cm + 1);

        /* On K64 we need to walk backwards because a fileglob * is twice the size of an fd 
         * and doing them in-order would result in stomping over unprocessed fd's
         */
        for (i = (oldfds - 1); i >= 0; i--) {
                (void) fdgetf_noref(p, fds[i], &fp);
                if (fg_insertuipc_mark(fp->f_fglob))
                        fg_ins[i / 8] |= 0x80 >> (i % 8);
                rp[i] = fp->f_fglob;
        }
        proc_fdunlock(p);

        for (i = 0; i < oldfds; i++) {
                if (fg_ins[i / 8] & (0x80 >> (i % 8))) {
                        VERIFY(rp[i]->fg_lflags & FG_INSMSGQ);
                        fg_insertuipc(rp[i]);
                }
                (void) OSAddAtomic(1, &unp_rights);
        }

        return (0);
}

static int      unp_defer, unp_gcing, unp_gcwait;
static thread_t unp_gcthread = NULL;

/* always called under uipc_lock */
void
unp_gc_wait(void)
{
        if (unp_gcthread == current_thread())
                return;

        while (unp_gcing != 0) {
                unp_gcwait = 1;
                msleep(&unp_gcing, uipc_lock, 0 , "unp_gc_wait", NULL);
        }
}


__private_extern__ void
unp_gc(void)
{
        struct fileglob *fg, *nextfg;
        struct socket *so;
        static struct fileglob **extra_ref;
        struct fileglob **fpp;
        int nunref, i;
        int need_gcwakeup = 0;

        lck_mtx_lock(uipc_lock);
        if (unp_gcing) {
                lck_mtx_unlock(uipc_lock);
                return;
        }
        unp_gcing = 1;
        unp_defer = 0;
        unp_gcthread = current_thread();
        lck_mtx_unlock(uipc_lock);
        /*
         * before going through all this, set all FDs to
         * be NOT defered and NOT externally accessible
         */
        for (fg = fmsghead.lh_first; fg != 0; fg = fg->f_msglist.le_next) {
                lck_mtx_lock(&fg->fg_lock);
                fg->fg_flag &= ~(FMARK|FDEFER);
                lck_mtx_unlock(&fg->fg_lock);
        }
        do {
                for (fg = fmsghead.lh_first; fg != 0;
                    fg = fg->f_msglist.le_next) {
                        lck_mtx_lock(&fg->fg_lock);
                        /*
                         * If the file is not open, skip it
                         */
                        if (fg->fg_count == 0) {
                                lck_mtx_unlock(&fg->fg_lock);
                                continue;
                        }
                        /*
                         * If we already marked it as 'defer'  in a
                         * previous pass, then try process it this time
                         * and un-mark it
                         */
                        if (fg->fg_flag & FDEFER) {
                                fg->fg_flag &= ~FDEFER;
                                unp_defer--;
                        } else {
                                /*
                                 * if it's not defered, then check if it's
                                 * already marked.. if so skip it
                                 */
                                if (fg->fg_flag & FMARK) {
                                        lck_mtx_unlock(&fg->fg_lock);
                                        continue;
                                }
                                /*
                                 * If all references are from messages
                                 * in transit, then skip it. it's not
                                 * externally accessible.
                                 */
                                if (fg->fg_count == fg->fg_msgcount) {
                                        lck_mtx_unlock(&fg->fg_lock);
                                        continue;
                                }
                                /*
                                 * If it got this far then it must be
                                 * externally accessible.
                                 */
                                fg->fg_flag |= FMARK;
                        }
                        /*
                         * either it was defered, or it is externally
                         * accessible and not already marked so.
                         * Now check if it is possibly one of OUR sockets.
                         */
                        if (FILEGLOB_DTYPE(fg) != DTYPE_SOCKET ||
                            (so = (struct socket *)fg->fg_data) == 0) {
                                lck_mtx_unlock(&fg->fg_lock);
                                continue;
                        }
                        if (so->so_proto->pr_domain != localdomain ||
                            (so->so_proto->pr_flags&PR_RIGHTS) == 0) {
                                lck_mtx_unlock(&fg->fg_lock);
                                continue;
                        }
#ifdef notdef
                        if (so->so_rcv.sb_flags & SB_LOCK) {
                                /*
                                 * This is problematical; it's not clear
                                 * we need to wait for the sockbuf to be
                                 * unlocked (on a uniprocessor, at least),
                                 * and it's also not clear what to do
                                 * if sbwait returns an error due to receipt
                                 * of a signal.  If sbwait does return
                                 * an error, we'll go into an infinite
                                 * loop.  Delete all of this for now.
                                 */
                                (void) sbwait(&so->so_rcv);
                                goto restart;
                        }
#endif
                        /*
                         * So, Ok, it's one of our sockets and it IS externally
                         * accessible (or was defered). Now we look
                         * to see if we hold any file descriptors in its
                         * message buffers. Follow those links and mark them
                         * as accessible too.
                         *
                         * In case a file is passed onto itself we need to 
                         * release the file lock.
                         */
                        lck_mtx_unlock(&fg->fg_lock);

                        unp_scan(so->so_rcv.sb_mb, unp_mark, 0);
                }
        } while (unp_defer);
        /*
         * We grab an extra reference to each of the file table entries
         * that are not otherwise accessible and then free the rights
         * that are stored in messages on them.
         *
         * The bug in the orginal code is a little tricky, so I'll describe
         * what's wrong with it here.
         *
         * It is incorrect to simply unp_discard each entry for f_msgcount
         * times -- consider the case of sockets A and B that contain
         * references to each other.  On a last close of some other socket,
         * we trigger a gc since the number of outstanding rights (unp_rights)
         * is non-zero.  If during the sweep phase the gc code un_discards,
         * we end up doing a (full) closef on the descriptor.  A closef on A
         * results in the following chain.  Closef calls soo_close, which
         * calls soclose.   Soclose calls first (through the switch
         * uipc_usrreq) unp_detach, which re-invokes unp_gc.  Unp_gc simply
         * returns because the previous instance had set unp_gcing, and
         * we return all the way back to soclose, which marks the socket
         * with SS_NOFDREF, and then calls sofree.  Sofree calls sorflush
         * to free up the rights that are queued in messages on the socket A,
         * i.e., the reference on B.  The sorflush calls via the dom_dispose
         * switch unp_dispose, which unp_scans with unp_discard.  This second
         * instance of unp_discard just calls closef on B.
         *
         * Well, a similar chain occurs on B, resulting in a sorflush on B,
         * which results in another closef on A.  Unfortunately, A is already
         * being closed, and the descriptor has already been marked with
         * SS_NOFDREF, and soclose panics at this point.
         *
         * Here, we first take an extra reference to each inaccessible
         * descriptor.  Then, we call sorflush ourself, since we know
         * it is a Unix domain socket anyhow.  After we destroy all the
         * rights carried in messages, we do a last closef to get rid
         * of our extra reference.  This is the last close, and the
         * unp_detach etc will shut down the socket.
         *
         * 91/09/19, bsy@cs.cmu.edu
         */
        extra_ref = _MALLOC(nfiles * sizeof (struct fileglob *),
            M_FILEGLOB, M_WAITOK);
        if (extra_ref == NULL)
                goto bail;
        for (nunref = 0, fg = fmsghead.lh_first, fpp = extra_ref; fg != 0;
            fg = nextfg) {
                lck_mtx_lock(&fg->fg_lock);

                nextfg = fg->f_msglist.le_next;
                /*
                 * If it's not open, skip it
                 */
                if (fg->fg_count == 0) {
                        lck_mtx_unlock(&fg->fg_lock);
                        continue;
                }
                /*
                 * If all refs are from msgs, and it's not marked accessible
                 * then it must be referenced from some unreachable cycle
                 * of (shut-down) FDs, so include it in our
                 * list of FDs to remove
                 */
                if (fg->fg_count == fg->fg_msgcount && !(fg->fg_flag & FMARK)) {
                        fg->fg_count++;
                        *fpp++ = fg;
                        nunref++;
                }
                lck_mtx_unlock(&fg->fg_lock);
        }
        /*
         * for each FD on our hit list, do the following two things
         */
        for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp) {
                struct fileglob *tfg;

                tfg = *fpp;

                if (FILEGLOB_DTYPE(tfg) == DTYPE_SOCKET &&
                    tfg->fg_data != NULL) {
                        so = (struct socket *)(tfg->fg_data);

                        socket_lock(so, 0);
                        
                        sorflush(so);

                        socket_unlock(so, 0);
                }
        }
        for (i = nunref, fpp = extra_ref; --i >= 0; ++fpp)
                closef_locked((struct fileproc *)0, *fpp, (proc_t)NULL);

        FREE((caddr_t)extra_ref, M_FILEGLOB);
bail:
        lck_mtx_lock(uipc_lock);
        unp_gcing = 0;
        unp_gcthread = NULL;

        if (unp_gcwait != 0) {
                unp_gcwait = 0;
                need_gcwakeup = 1;
        }
        lck_mtx_unlock(uipc_lock);

        if (need_gcwakeup != 0)
                wakeup(&unp_gcing);
}

void
unp_dispose(struct mbuf *m)
{
        if (m) {
                unp_scan(m, unp_discard, NULL);
        }
}

/*
 * Returns:     0                       Success
 */
static int
unp_listen(struct unpcb *unp, proc_t p)
{
        kauth_cred_t safecred = kauth_cred_proc_ref(p);
        cru2x(safecred, &unp->unp_peercred);
        kauth_cred_unref(&safecred);
        unp->unp_flags |= UNP_HAVEPCCACHED;
        return (0);
}

static void
unp_scan(struct mbuf *m0, void (*op)(struct fileglob *, void *arg), void *arg)
{
        struct mbuf *m;
        struct fileglob **rp;
        struct cmsghdr *cm;
        int i;
        int qfds;

        while (m0) {
                for (m = m0; m; m = m->m_next)
                        if (m->m_type == MT_CONTROL &&
                            (size_t)m->m_len >= sizeof (*cm)) {
                                cm = mtod(m, struct cmsghdr *);
                                if (cm->cmsg_level != SOL_SOCKET ||
                                    cm->cmsg_type != SCM_RIGHTS)
                                        continue;
                                qfds = (cm->cmsg_len - sizeof (*cm)) /
                                    sizeof (int);
                                rp = (struct fileglob **)(cm + 1);
                                for (i = 0; i < qfds; i++)
                                        (*op)(*rp++, arg);
                                break;          /* XXX, but saves time */
                        }
                m0 = m0->m_act;
        }
}

static void
unp_mark(struct fileglob *fg, __unused void *arg)
{
        lck_mtx_lock(&fg->fg_lock);

        if (fg->fg_flag & FMARK) {
                lck_mtx_unlock(&fg->fg_lock);
                return;
        }
        fg->fg_flag |= (FMARK|FDEFER);

        lck_mtx_unlock(&fg->fg_lock);

        unp_defer++;
}

static void
unp_discard(struct fileglob *fg, void *p)
{
        if (p == NULL)
                p = current_proc();             /* XXX */

        (void) OSAddAtomic(1, &unp_disposed);
        if (fg_removeuipc_mark(fg)) {
                VERIFY(fg->fg_lflags & FG_RMMSGQ);
                fg_removeuipc(fg);
        }
        (void) OSAddAtomic(-1, &unp_rights);

        proc_fdlock(p);
        (void) closef_locked((struct fileproc *)0, fg, p);
        proc_fdunlock(p);
}

int
unp_lock(struct socket *so, int refcount, void * lr)
 {
        void * lr_saved;
        if (lr == 0)
                lr_saved = (void *)  __builtin_return_address(0);
        else lr_saved = lr;

        if (so->so_pcb) {
                lck_mtx_lock(&((struct unpcb *)so->so_pcb)->unp_mtx);
        } else  {
                panic("unp_lock: so=%p NO PCB! lr=%p ref=0x%x\n", 
                        so, lr_saved, so->so_usecount);
        }

        if (so->so_usecount < 0)
                panic("unp_lock: so=%p so_pcb=%p lr=%p ref=0x%x\n",
                so, so->so_pcb, lr_saved, so->so_usecount);

        if (refcount)
                so->so_usecount++;

        so->lock_lr[so->next_lock_lr] = lr_saved;
        so->next_lock_lr = (so->next_lock_lr+1) % SO_LCKDBG_MAX;
        return (0);
}

int
unp_unlock(struct socket *so, int refcount, void * lr)
{
        void * lr_saved;
        lck_mtx_t * mutex_held = NULL;
        struct unpcb *unp = sotounpcb(so);

        if (lr == 0)
                lr_saved = (void *) __builtin_return_address(0);
        else lr_saved = lr;

        if (refcount)
                so->so_usecount--;

        if (so->so_usecount < 0)
                panic("unp_unlock: so=%p usecount=%x\n", so, so->so_usecount);
        if (so->so_pcb == NULL) {
                panic("unp_unlock: so=%p NO PCB usecount=%x\n", so, so->so_usecount);
        } else {
                mutex_held = &((struct unpcb *)so->so_pcb)->unp_mtx;
        }
        lck_mtx_assert(mutex_held, LCK_MTX_ASSERT_OWNED);
        so->unlock_lr[so->next_unlock_lr] = lr_saved;
        so->next_unlock_lr = (so->next_unlock_lr+1) % SO_LCKDBG_MAX;

        if (so->so_usecount == 0 && (so->so_flags & SOF_PCBCLEARING)) {
                sofreelastref(so, 1);

                if (unp->unp_addr)
                        FREE(unp->unp_addr, M_SONAME);
                
                lck_mtx_unlock(mutex_held);

                lck_mtx_destroy(&unp->unp_mtx, unp_mtx_grp);
                zfree(unp_zone, unp);

                unp_gc();
        } else {
                lck_mtx_unlock(mutex_held);
        }

        return (0);
}

lck_mtx_t *
unp_getlock(struct socket *so, __unused int locktype)
{
        struct unpcb *unp = (struct unpcb *)so->so_pcb;


        if (so->so_pcb)  {
                if (so->so_usecount < 0)
                        panic("unp_getlock: so=%p usecount=%x\n", so, so->so_usecount);
                return(&unp->unp_mtx);
        } else {
                panic("unp_getlock: so=%p NULL so_pcb\n", so);
                return (so->so_proto->pr_domain->dom_mtx);
        }
}