uipc_usrreq.c

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/*-
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.
 * Copyright (c) 2004-2009 Robert N. M. Watson
 * 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.
 * 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
 */

/*
 * UNIX Domain (Local) Sockets
 *
 * This is an implementation of UNIX (local) domain sockets.  Each socket has
 * an associated struct unpcb (UNIX protocol control block).  Stream sockets
 * may be connected to 0 or 1 other socket.  Datagram sockets may be
 * connected to 0, 1, or many other sockets.  Sockets may be created and
 * connected in pairs (socketpair(2)), or bound/connected to using the file
 * system name space.  For most purposes, only the receive socket buffer is
 * used, as sending on one socket delivers directly to the receive socket
 * buffer of a second socket.
 *
 * The implementation is substantially complicated by the fact that
 * "ancillary data", such as file descriptors or credentials, may be passed
 * across UNIX domain sockets.  The potential for passing UNIX domain sockets
 * over other UNIX domain sockets requires the implementation of a simple
 * garbage collector to find and tear down cycles of disconnected sockets.
 *
 * TODO:
 *      RDM
 *      distinguish datagram size limits from flow control limits in SEQPACKET
 *      rethink name space problems
 *      need a proper out-of-band
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/domain.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>         /* XXX must be before <sys/file.h> */
#include <sys/eventhandler.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/queue.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/signalvar.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/taskqueue.h>
#include <sys/un.h>
#include <sys/unpcb.h>
#include <sys/vnode.h>

#include <net/vnet.h>

#ifdef DDB
#include <ddb/ddb.h>
#endif

#include <security/mac/mac_framework.h>

#include <vm/uma.h>

/*
 * Locking key:
 * (l)  Locked using list lock
 * (g)  Locked using linkage lock
 */

static uma_zone_t       unp_zone;
static unp_gen_t        unp_gencnt;     /* (l) */
static u_int            unp_count;      /* (l) Count of local sockets. */
static ino_t            unp_ino;        /* Prototype for fake inode numbers. */
static int              unp_rights;     /* (g) File descriptors in flight. */
static struct unp_head  unp_shead;      /* (l) List of stream sockets. */
static struct unp_head  unp_dhead;      /* (l) List of datagram sockets. */
static struct unp_head  unp_sphead;     /* (l) List of seqpacket sockets. */

struct unp_defer {
        SLIST_ENTRY(unp_defer) ud_link;
        struct file *ud_fp;
};
static SLIST_HEAD(, unp_defer) unp_defers;
static int unp_defers_count;

static const struct sockaddr    sun_noname = { sizeof(sun_noname), AF_LOCAL };

/*
 * Garbage collection of cyclic file descriptor/socket references occurs
 * asynchronously in a taskqueue context in order to avoid recursion and
 * reentrance in the UNIX domain socket, file descriptor, and socket layer
 * code.  See unp_gc() for a full description.
 */
static struct timeout_task unp_gc_task;

/*
 * The close of unix domain sockets attached as SCM_RIGHTS is
 * postponed to the taskqueue, to avoid arbitrary recursion depth.
 * The attached sockets might have another sockets attached.
 */
static struct task      unp_defer_task;

/*
 * 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_long   unpst_sendspace = PIPSIZ;
static u_long   unpst_recvspace = PIPSIZ;
static u_long   unpdg_sendspace = 2*1024;       /* really max datagram size */
static u_long   unpdg_recvspace = 4*1024;
static u_long   unpsp_sendspace = PIPSIZ;       /* really max datagram size */
static u_long   unpsp_recvspace = PIPSIZ;

static SYSCTL_NODE(_net, PF_LOCAL, local, CTLFLAG_RW, 0, "Local domain");
static SYSCTL_NODE(_net_local, SOCK_STREAM, stream, CTLFLAG_RW, 0,
    "SOCK_STREAM");
static SYSCTL_NODE(_net_local, SOCK_DGRAM, dgram, CTLFLAG_RW, 0, "SOCK_DGRAM");
static SYSCTL_NODE(_net_local, SOCK_SEQPACKET, seqpacket, CTLFLAG_RW, 0,
    "SOCK_SEQPACKET");

SYSCTL_ULONG(_net_local_stream, OID_AUTO, sendspace, CTLFLAG_RW,
           &unpst_sendspace, 0, "Default stream send space.");
SYSCTL_ULONG(_net_local_stream, OID_AUTO, recvspace, CTLFLAG_RW,
           &unpst_recvspace, 0, "Default stream receive space.");
SYSCTL_ULONG(_net_local_dgram, OID_AUTO, maxdgram, CTLFLAG_RW,
           &unpdg_sendspace, 0, "Default datagram send space.");
SYSCTL_ULONG(_net_local_dgram, OID_AUTO, recvspace, CTLFLAG_RW,
           &unpdg_recvspace, 0, "Default datagram receive space.");
SYSCTL_ULONG(_net_local_seqpacket, OID_AUTO, maxseqpacket, CTLFLAG_RW,
           &unpsp_sendspace, 0, "Default seqpacket send space.");
SYSCTL_ULONG(_net_local_seqpacket, OID_AUTO, recvspace, CTLFLAG_RW,
           &unpsp_recvspace, 0, "Default seqpacket receive space.");
SYSCTL_INT(_net_local, OID_AUTO, inflight, CTLFLAG_RD, &unp_rights, 0,
    "File descriptors in flight.");
SYSCTL_INT(_net_local, OID_AUTO, deferred, CTLFLAG_RD,
    &unp_defers_count, 0,
    "File descriptors deferred to taskqueue for close.");

/*
 * Locking and synchronization:
 *
 * Three types of locks exit in the local domain socket implementation: a
 * global list mutex, a global linkage rwlock, and per-unpcb mutexes.  Of the
 * global locks, the list lock protects the socket count, global generation
 * number, and stream/datagram global lists.  The linkage lock protects the
 * interconnection of unpcbs, the v_socket and unp_vnode pointers, and can be
 * held exclusively over the acquisition of multiple unpcb locks to prevent
 * deadlock.
 *
 * UNIX domain sockets each have an unpcb hung off of their so_pcb pointer,
 * allocated in pru_attach() and freed in pru_detach().  The validity of that
 * pointer is an invariant, so no lock is required to dereference the so_pcb
 * pointer if a valid socket reference is held by the caller.  In practice,
 * this is always true during operations performed on a socket.  Each unpcb
 * has a back-pointer to its socket, unp_socket, which will be stable under
 * the same circumstances.
 *
 * This pointer may only be safely dereferenced as long as a valid reference
 * to the unpcb is held.  Typically, this reference will be from the socket,
 * or from another unpcb when the referring unpcb's lock is held (in order
 * that the reference not be invalidated during use).  For example, to follow
 * unp->unp_conn->unp_socket, you need unlock the lock on unp, not unp_conn,
 * as unp_socket remains valid as long as the reference to unp_conn is valid.
 *
 * Fields of unpcbss are locked using a per-unpcb lock, unp_mtx.  Individual
 * atomic reads without the lock may be performed "lockless", but more
 * complex reads and read-modify-writes require the mutex to be held.  No
 * lock order is defined between unpcb locks -- multiple unpcb locks may be
 * acquired at the same time only when holding the linkage rwlock
 * exclusively, which prevents deadlocks.
 *
 * Blocking with UNIX domain sockets is a tricky issue: unlike most network
 * protocols, bind() is a non-atomic operation, and connect() requires
 * potential sleeping in the protocol, due to potentially waiting on local or
 * distributed file systems.  We try to separate "lookup" operations, which
 * may sleep, and the IPC operations themselves, which typically can occur
 * with relative atomicity as locks can be held over the entire operation.
 *
 * Another tricky issue is simultaneous multi-threaded or multi-process
 * access to a single UNIX domain socket.  These are handled by the flags
 * UNP_CONNECTING and UNP_BINDING, which prevent concurrent connecting or
 * binding, both of which involve dropping UNIX domain socket locks in order
 * to perform namei() and other file system operations.
 */
static struct rwlock    unp_link_rwlock;
static struct mtx       unp_list_lock;
static struct mtx       unp_defers_lock;

#define UNP_LINK_LOCK_INIT()            rw_init(&unp_link_rwlock,       \
                                            "unp_link_rwlock")

#define UNP_LINK_LOCK_ASSERT()  rw_assert(&unp_link_rwlock,     \
                                            RA_LOCKED)
#define UNP_LINK_UNLOCK_ASSERT()        rw_assert(&unp_link_rwlock,     \
                                            RA_UNLOCKED)

#define UNP_LINK_RLOCK()                rw_rlock(&unp_link_rwlock)
#define UNP_LINK_RUNLOCK()              rw_runlock(&unp_link_rwlock)
#define UNP_LINK_WLOCK()                rw_wlock(&unp_link_rwlock)
#define UNP_LINK_WUNLOCK()              rw_wunlock(&unp_link_rwlock)
#define UNP_LINK_WLOCK_ASSERT()         rw_assert(&unp_link_rwlock,     \
                                            RA_WLOCKED)

#define UNP_LIST_LOCK_INIT()            mtx_init(&unp_list_lock,        \
                                            "unp_list_lock", NULL, MTX_DEF)
#define UNP_LIST_LOCK()                 mtx_lock(&unp_list_lock)
#define UNP_LIST_UNLOCK()               mtx_unlock(&unp_list_lock)

#define UNP_DEFERRED_LOCK_INIT()        mtx_init(&unp_defers_lock, \
                                            "unp_defer", NULL, MTX_DEF)
#define UNP_DEFERRED_LOCK()             mtx_lock(&unp_defers_lock)
#define UNP_DEFERRED_UNLOCK()           mtx_unlock(&unp_defers_lock)

#define UNP_PCB_LOCK_INIT(unp)          mtx_init(&(unp)->unp_mtx,       \
                                            "unp_mtx", "unp_mtx",       \
                                            MTX_DUPOK|MTX_DEF|MTX_RECURSE)
#define UNP_PCB_LOCK_DESTROY(unp)       mtx_destroy(&(unp)->unp_mtx)
#define UNP_PCB_LOCK(unp)               mtx_lock(&(unp)->unp_mtx)
#define UNP_PCB_UNLOCK(unp)             mtx_unlock(&(unp)->unp_mtx)
#define UNP_PCB_LOCK_ASSERT(unp)        mtx_assert(&(unp)->unp_mtx, MA_OWNED)

static int      uipc_connect2(struct socket *, struct socket *);
static int      uipc_ctloutput(struct socket *, struct sockopt *);
static int      unp_connect(struct socket *, struct sockaddr *,
                    struct thread *);
static int      unp_connect2(struct socket *so, struct socket *so2, int);
static void     unp_disconnect(struct unpcb *unp, struct unpcb *unp2);
static void     unp_dispose(struct mbuf *);
static void     unp_shutdown(struct unpcb *);
static void     unp_drop(struct unpcb *, int);
static void     unp_gc(__unused void *, int);
static void     unp_scan(struct mbuf *, void (*)(struct file *));
static void     unp_discard(struct file *);
static void     unp_freerights(struct file **, int);
static void     unp_init(void);
static int      unp_internalize(struct mbuf **, struct thread *);
static void     unp_internalize_fp(struct file *);
static int      unp_externalize(struct mbuf *, struct mbuf **);
static int      unp_externalize_fp(struct file *);
static struct mbuf      *unp_addsockcred(struct thread *, struct mbuf *);
static void     unp_process_defers(void * __unused, int);

/*
 * Definitions of protocols supported in the LOCAL domain.
 */
static struct domain localdomain;
static struct pr_usrreqs uipc_usrreqs_dgram, uipc_usrreqs_stream;
static struct pr_usrreqs uipc_usrreqs_seqpacket;
static struct protosw localsw[] = {
{
        .pr_type =              SOCK_STREAM,
        .pr_domain =            &localdomain,
        .pr_flags =             PR_CONNREQUIRED|PR_WANTRCVD|PR_RIGHTS,
        .pr_ctloutput =         &uipc_ctloutput,
        .pr_usrreqs =           &uipc_usrreqs_stream
},
{
        .pr_type =              SOCK_DGRAM,
        .pr_domain =            &localdomain,
        .pr_flags =             PR_ATOMIC|PR_ADDR|PR_RIGHTS,
        .pr_ctloutput =         &uipc_ctloutput,
        .pr_usrreqs =           &uipc_usrreqs_dgram
},
{
        .pr_type =              SOCK_SEQPACKET,
        .pr_domain =            &localdomain,

        /*
         * XXXRW: For now, PR_ADDR because soreceive will bump into them
         * due to our use of sbappendaddr.  A new sbappend variants is needed
         * that supports both atomic record writes and control data.
         */
        .pr_flags =             PR_ADDR|PR_ATOMIC|PR_CONNREQUIRED|PR_WANTRCVD|
                                    PR_RIGHTS,
        .pr_ctloutput =         &uipc_ctloutput,
        .pr_usrreqs =           &uipc_usrreqs_seqpacket,
},
};

static struct domain localdomain = {
        .dom_family =           AF_LOCAL,
        .dom_name =             "local",
        .dom_init =             unp_init,
        .dom_externalize =      unp_externalize,
        .dom_dispose =          unp_dispose,
        .dom_protosw =          localsw,
        .dom_protoswNPROTOSW =  &localsw[sizeof(localsw)/sizeof(localsw[0])]
};
DOMAIN_SET(local);

static void
uipc_abort(struct socket *so)
{
        struct unpcb *unp, *unp2;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_abort: unp == NULL"));

        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        unp2 = unp->unp_conn;
        if (unp2 != NULL) {
                UNP_PCB_LOCK(unp2);
                unp_drop(unp2, ECONNABORTED);
                UNP_PCB_UNLOCK(unp2);
        }
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
}

static int
uipc_accept(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp, *unp2;
        const struct sockaddr *sa;

        /*
         * Pass back name of connected socket, if it was bound and we are
         * still connected (our peer may have closed already!).
         */
        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_accept: unp == NULL"));

        *nam = malloc(sizeof(struct sockaddr_un), M_SONAME, M_WAITOK);
        UNP_LINK_RLOCK();
        unp2 = unp->unp_conn;
        if (unp2 != NULL && unp2->unp_addr != NULL) {
                UNP_PCB_LOCK(unp2);
                sa = (struct sockaddr *) unp2->unp_addr;
                bcopy(sa, *nam, sa->sa_len);
                UNP_PCB_UNLOCK(unp2);
        } else {
                sa = &sun_noname;
                bcopy(sa, *nam, sa->sa_len);
        }
        UNP_LINK_RUNLOCK();
        return (0);
}

static int
uipc_attach(struct socket *so, int proto, struct thread *td)
{
        u_long sendspace, recvspace;
        struct unpcb *unp;
        int error;

        KASSERT(so->so_pcb == NULL, ("uipc_attach: so_pcb != NULL"));
        if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
                switch (so->so_type) {
                case SOCK_STREAM:
                        sendspace = unpst_sendspace;
                        recvspace = unpst_recvspace;
                        break;

                case SOCK_DGRAM:
                        sendspace = unpdg_sendspace;
                        recvspace = unpdg_recvspace;
                        break;

                case SOCK_SEQPACKET:
                        sendspace = unpsp_sendspace;
                        recvspace = unpsp_recvspace;
                        break;

                default:
                        panic("uipc_attach");
                }
                error = soreserve(so, sendspace, recvspace);
                if (error)
                        return (error);
        }
        unp = uma_zalloc(unp_zone, M_NOWAIT | M_ZERO);
        if (unp == NULL)
                return (ENOBUFS);
        LIST_INIT(&unp->unp_refs);
        UNP_PCB_LOCK_INIT(unp);
        unp->unp_socket = so;
        so->so_pcb = unp;
        unp->unp_refcount = 1;

        UNP_LIST_LOCK();
        unp->unp_gencnt = ++unp_gencnt;
        unp_count++;
        switch (so->so_type) {
        case SOCK_STREAM:
                LIST_INSERT_HEAD(&unp_shead, unp, unp_link);
                break;

        case SOCK_DGRAM:
                LIST_INSERT_HEAD(&unp_dhead, unp, unp_link);
                break;

        case SOCK_SEQPACKET:
                LIST_INSERT_HEAD(&unp_sphead, unp, unp_link);
                break;

        default:
                panic("uipc_attach");
        }
        UNP_LIST_UNLOCK();

        return (0);
}

static int
uipc_bind(struct socket *so, struct sockaddr *nam, struct thread *td)
{
        struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        struct vattr vattr;
        int error, namelen, vfslocked;
        struct nameidata nd;
        struct unpcb *unp;
        struct vnode *vp;
        struct mount *mp;
        char *buf;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_bind: unp == NULL"));

        if (soun->sun_len > sizeof(struct sockaddr_un))
                return (EINVAL);
        namelen = soun->sun_len - offsetof(struct sockaddr_un, sun_path);
        if (namelen <= 0)
                return (EINVAL);

        /*
         * We don't allow simultaneous bind() calls on a single UNIX domain
         * socket, so flag in-progress operations, and return an error if an
         * operation is already in progress.
         *
         * Historically, we have not allowed a socket to be rebound, so this
         * also returns an error.  Not allowing re-binding simplifies the
         * implementation and avoids a great many possible failure modes.
         */
        UNP_PCB_LOCK(unp);
        if (unp->unp_vnode != NULL) {
                UNP_PCB_UNLOCK(unp);
                return (EINVAL);
        }
        if (unp->unp_flags & UNP_BINDING) {
                UNP_PCB_UNLOCK(unp);
                return (EALREADY);
        }
        unp->unp_flags |= UNP_BINDING;
        UNP_PCB_UNLOCK(unp);

        buf = malloc(namelen + 1, M_TEMP, M_WAITOK);
        bcopy(soun->sun_path, buf, namelen);
        buf[namelen] = 0;

restart:
        vfslocked = 0;
        NDINIT(&nd, CREATE, MPSAFE | NOFOLLOW | LOCKPARENT | SAVENAME,
            UIO_SYSSPACE, buf, td);
/* SHOULD BE ABLE TO ADOPT EXISTING AND wakeup() ALA FIFO's */
        error = namei(&nd);
        if (error)
                goto error;
        vp = nd.ni_vp;
        vfslocked = NDHASGIANT(&nd);
        if (vp != NULL || vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
                NDFREE(&nd, NDF_ONLY_PNBUF);
                if (nd.ni_dvp == vp)
                        vrele(nd.ni_dvp);
                else
                        vput(nd.ni_dvp);
                if (vp != NULL) {
                        vrele(vp);
                        error = EADDRINUSE;
                        goto error;
                }
                error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH);
                if (error)
                        goto error;
                VFS_UNLOCK_GIANT(vfslocked);
                goto restart;
        }
        VATTR_NULL(&vattr);
        vattr.va_type = VSOCK;
        vattr.va_mode = (ACCESSPERMS & ~td->td_proc->p_fd->fd_cmask);
#ifdef MAC
        error = mac_vnode_check_create(td->td_ucred, nd.ni_dvp, &nd.ni_cnd,
            &vattr);
#endif
        if (error == 0)
                error = VOP_CREATE(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &vattr);
        NDFREE(&nd, NDF_ONLY_PNBUF);
        vput(nd.ni_dvp);
        if (error) {
                vn_finished_write(mp);
                goto error;
        }
        vp = nd.ni_vp;
        ASSERT_VOP_ELOCKED(vp, "uipc_bind");
        soun = (struct sockaddr_un *)sodupsockaddr(nam, M_WAITOK);

        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        VOP_UNP_BIND(vp, unp->unp_socket);
        unp->unp_vnode = vp;
        unp->unp_addr = soun;
        unp->unp_flags &= ~UNP_BINDING;
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
        VOP_UNLOCK(vp, 0);
        vn_finished_write(mp);
        VFS_UNLOCK_GIANT(vfslocked);
        free(buf, M_TEMP);
        return (0);

error:
        VFS_UNLOCK_GIANT(vfslocked);
        UNP_PCB_LOCK(unp);
        unp->unp_flags &= ~UNP_BINDING;
        UNP_PCB_UNLOCK(unp);
        free(buf, M_TEMP);
        return (error);
}

static int
uipc_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
{
        int error;

        KASSERT(td == curthread, ("uipc_connect: td != curthread"));
        UNP_LINK_WLOCK();
        error = unp_connect(so, nam, td);
        UNP_LINK_WUNLOCK();
        return (error);
}

static void
uipc_close(struct socket *so)
{
        struct unpcb *unp, *unp2;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_close: unp == NULL"));

        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        unp2 = unp->unp_conn;
        if (unp2 != NULL) {
                UNP_PCB_LOCK(unp2);
                unp_disconnect(unp, unp2);
                UNP_PCB_UNLOCK(unp2);
        }
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
}

static int
uipc_connect2(struct socket *so1, struct socket *so2)
{
        struct unpcb *unp, *unp2;
        int error;

        UNP_LINK_WLOCK();
        unp = so1->so_pcb;
        KASSERT(unp != NULL, ("uipc_connect2: unp == NULL"));
        UNP_PCB_LOCK(unp);
        unp2 = so2->so_pcb;
        KASSERT(unp2 != NULL, ("uipc_connect2: unp2 == NULL"));
        UNP_PCB_LOCK(unp2);
        error = unp_connect2(so1, so2, PRU_CONNECT2);
        UNP_PCB_UNLOCK(unp2);
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
        return (error);
}

static void
uipc_detach(struct socket *so)
{
        struct unpcb *unp, *unp2;
        struct sockaddr_un *saved_unp_addr;
        struct vnode *vp;
        int freeunp, local_unp_rights;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_detach: unp == NULL"));

        UNP_LINK_WLOCK();
        UNP_LIST_LOCK();
        UNP_PCB_LOCK(unp);
        LIST_REMOVE(unp, unp_link);
        unp->unp_gencnt = ++unp_gencnt;
        --unp_count;
        UNP_LIST_UNLOCK();

        /*
         * XXXRW: Should assert vp->v_socket == so.
         */
        if ((vp = unp->unp_vnode) != NULL) {
                VOP_UNP_DETACH(vp);
                unp->unp_vnode = NULL;
        }
        unp2 = unp->unp_conn;
        if (unp2 != NULL) {
                UNP_PCB_LOCK(unp2);
                unp_disconnect(unp, unp2);
                UNP_PCB_UNLOCK(unp2);
        }

        /*
         * We hold the linkage lock exclusively, so it's OK to acquire
         * multiple pcb locks at a time.
         */
        while (!LIST_EMPTY(&unp->unp_refs)) {
                struct unpcb *ref = LIST_FIRST(&unp->unp_refs);

                UNP_PCB_LOCK(ref);
                unp_drop(ref, ECONNRESET);
                UNP_PCB_UNLOCK(ref);
        }
        local_unp_rights = unp_rights;
        UNP_LINK_WUNLOCK();
        unp->unp_socket->so_pcb = NULL;
        saved_unp_addr = unp->unp_addr;
        unp->unp_addr = NULL;
        unp->unp_refcount--;
        freeunp = (unp->unp_refcount == 0);
        if (saved_unp_addr != NULL)
                free(saved_unp_addr, M_SONAME);
        if (freeunp) {
                UNP_PCB_LOCK_DESTROY(unp);
                uma_zfree(unp_zone, unp);
        } else
                UNP_PCB_UNLOCK(unp);
        if (vp) {
                int vfslocked;

                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                vrele(vp);
                VFS_UNLOCK_GIANT(vfslocked);
        }
        if (local_unp_rights)
                taskqueue_enqueue_timeout(taskqueue_thread, &unp_gc_task, -1);
}

static int
uipc_disconnect(struct socket *so)
{
        struct unpcb *unp, *unp2;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_disconnect: unp == NULL"));

        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        unp2 = unp->unp_conn;
        if (unp2 != NULL) {
                UNP_PCB_LOCK(unp2);
                unp_disconnect(unp, unp2);
                UNP_PCB_UNLOCK(unp2);
        }
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
        return (0);
}

static int
uipc_listen(struct socket *so, int backlog, struct thread *td)
{
        struct unpcb *unp;
        int error;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_listen: unp == NULL"));

        UNP_PCB_LOCK(unp);
        if (unp->unp_vnode == NULL) {
                UNP_PCB_UNLOCK(unp);
                return (EINVAL);
        }

        SOCK_LOCK(so);
        error = solisten_proto_check(so);
        if (error == 0) {
                cru2x(td->td_ucred, &unp->unp_peercred);
                unp->unp_flags |= UNP_HAVEPCCACHED;
                solisten_proto(so, backlog);
        }
        SOCK_UNLOCK(so);
        UNP_PCB_UNLOCK(unp);
        return (error);
}

static int
uipc_peeraddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp, *unp2;
        const struct sockaddr *sa;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_peeraddr: unp == NULL"));

        *nam = malloc(sizeof(struct sockaddr_un), M_SONAME, M_WAITOK);
        UNP_LINK_RLOCK();
        /*
         * XXX: It seems that this test always fails even when connection is
         * established.  So, this else clause is added as workaround to
         * return PF_LOCAL sockaddr.
         */
        unp2 = unp->unp_conn;
        if (unp2 != NULL) {
                UNP_PCB_LOCK(unp2);
                if (unp2->unp_addr != NULL)
                        sa = (struct sockaddr *) unp2->unp_addr;
                else
                        sa = &sun_noname;
                bcopy(sa, *nam, sa->sa_len);
                UNP_PCB_UNLOCK(unp2);
        } else {
                sa = &sun_noname;
                bcopy(sa, *nam, sa->sa_len);
        }
        UNP_LINK_RUNLOCK();
        return (0);
}

static int
uipc_rcvd(struct socket *so, int flags)
{
        struct unpcb *unp, *unp2;
        struct socket *so2;
        u_int mbcnt, sbcc;
        u_long newhiwat;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_rcvd: unp == NULL"));

        if (so->so_type != SOCK_STREAM && so->so_type != SOCK_SEQPACKET)
                panic("uipc_rcvd socktype %d", so->so_type);

        /*
         * Adjust backpressure on sender and wakeup any waiting to write.
         *
         * The unp lock is acquired to maintain the validity of the unp_conn
         * pointer; no lock on unp2 is required as unp2->unp_socket will be
         * static as long as we don't permit unp2 to disconnect from unp,
         * which is prevented by the lock on unp.  We cache values from
         * so_rcv to avoid holding the so_rcv lock over the entire
         * transaction on the remote so_snd.
         */
        SOCKBUF_LOCK(&so->so_rcv);
        mbcnt = so->so_rcv.sb_mbcnt;
        sbcc = so->so_rcv.sb_cc;
        SOCKBUF_UNLOCK(&so->so_rcv);
        UNP_PCB_LOCK(unp);
        unp2 = unp->unp_conn;
        if (unp2 == NULL) {
                UNP_PCB_UNLOCK(unp);
                return (0);
        }
        so2 = unp2->unp_socket;
        SOCKBUF_LOCK(&so2->so_snd);
        so2->so_snd.sb_mbmax += unp->unp_mbcnt - mbcnt;
        newhiwat = so2->so_snd.sb_hiwat + unp->unp_cc - sbcc;
        (void)chgsbsize(so2->so_cred->cr_uidinfo, &so2->so_snd.sb_hiwat,
            newhiwat, RLIM_INFINITY);
        sowwakeup_locked(so2);
        unp->unp_mbcnt = mbcnt;
        unp->unp_cc = sbcc;
        UNP_PCB_UNLOCK(unp);
        return (0);
}

static int
uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
    struct mbuf *control, struct thread *td)
{
        struct unpcb *unp, *unp2;
        struct socket *so2;
        u_int mbcnt_delta, sbcc;
        u_int newhiwat;
        int error = 0;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_send: unp == NULL"));

        if (flags & PRUS_OOB) {
                error = EOPNOTSUPP;
                goto release;
        }
        if (control != NULL && (error = unp_internalize(&control, td)))
                goto release;
        if ((nam != NULL) || (flags & PRUS_EOF))
                UNP_LINK_WLOCK();
        else
                UNP_LINK_RLOCK();
        switch (so->so_type) {
        case SOCK_DGRAM:
        {
                const struct sockaddr *from;

                unp2 = unp->unp_conn;
                if (nam != NULL) {
                        UNP_LINK_WLOCK_ASSERT();
                        if (unp2 != NULL) {
                                error = EISCONN;
                                break;
                        }
                        error = unp_connect(so, nam, td);
                        if (error)
                                break;
                        unp2 = unp->unp_conn;
                }

                /*
                 * Because connect() and send() are non-atomic in a sendto()
                 * with a target address, it's possible that the socket will
                 * have disconnected before the send() can run.  In that case
                 * return the slightly counter-intuitive but otherwise
                 * correct error that the socket is not connected.
                 */
                if (unp2 == NULL) {
                        error = ENOTCONN;
                        break;
                }
                /* Lockless read. */
                if (unp2->unp_flags & UNP_WANTCRED)
                        control = unp_addsockcred(td, control);
                UNP_PCB_LOCK(unp);
                if (unp->unp_addr != NULL)
                        from = (struct sockaddr *)unp->unp_addr;
                else
                        from = &sun_noname;
                so2 = unp2->unp_socket;
                SOCKBUF_LOCK(&so2->so_rcv);
                if (sbappendaddr_locked(&so2->so_rcv, from, m,
                    control)) {
                        sorwakeup_locked(so2);
                        m = NULL;
                        control = NULL;
                } else {
                        SOCKBUF_UNLOCK(&so2->so_rcv);
                        error = ENOBUFS;
                }
                if (nam != NULL) {
                        UNP_LINK_WLOCK_ASSERT();
                        UNP_PCB_LOCK(unp2);
                        unp_disconnect(unp, unp2);
                        UNP_PCB_UNLOCK(unp2);
                }
                UNP_PCB_UNLOCK(unp);
                break;
        }

        case SOCK_SEQPACKET:
        case SOCK_STREAM:
                if ((so->so_state & SS_ISCONNECTED) == 0) {
                        if (nam != NULL) {
                                UNP_LINK_WLOCK_ASSERT();
                                error = unp_connect(so, nam, td);
                                if (error)
                                        break;  /* XXX */
                        } else {
                                error = ENOTCONN;
                                break;
                        }
                }

                /* Lockless read. */
                if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                        error = EPIPE;
                        break;
                }

                /*
                 * Because connect() and send() are non-atomic in a sendto()
                 * with a target address, it's possible that the socket will
                 * have disconnected before the send() can run.  In that case
                 * return the slightly counter-intuitive but otherwise
                 * correct error that the socket is not connected.
                 *
                 * Locking here must be done carefully: the linkage lock
                 * prevents interconnections between unpcbs from changing, so
                 * we can traverse from unp to unp2 without acquiring unp's
                 * lock.  Socket buffer locks follow unpcb locks, so we can
                 * acquire both remote and lock socket buffer locks.
                 */
                unp2 = unp->unp_conn;
                if (unp2 == NULL) {
                        error = ENOTCONN;
                        break;
                }
                so2 = unp2->unp_socket;
                UNP_PCB_LOCK(unp2);
                SOCKBUF_LOCK(&so2->so_rcv);
                if (unp2->unp_flags & UNP_WANTCRED) {
                        /*
                         * Credentials are passed only once on SOCK_STREAM
                         * and SOCK_SEQPACKET.
                         */
                        unp2->unp_flags &= ~UNP_WANTCRED;
                        control = unp_addsockcred(td, control);
                }
                /*
                 * Send to paired receive port, and then reduce send buffer
                 * hiwater marks to maintain backpressure.  Wake up readers.
                 */
                switch (so->so_type) {
                case SOCK_STREAM:
                        if (control != NULL) {
                                if (sbappendcontrol_locked(&so2->so_rcv, m,
                                    control))
                                        control = NULL;
                        } else
                                sbappend_locked(&so2->so_rcv, m);
                        break;

                case SOCK_SEQPACKET: {
                        const struct sockaddr *from;

                        from = &sun_noname;
                        /*
                         * Don't check for space available in so2->so_rcv.
                         * Unix domain sockets only check for space in the
                         * sending sockbuf, and that check is performed one
                         * level up the stack.
                         */
                        if (sbappendaddr_nospacecheck_locked(&so2->so_rcv,
                                from, m, control))
                                control = NULL;
                        break;
                        }
                }

                /*
                 * XXXRW: While fine for SOCK_STREAM, this conflates maximum
                 * datagram size and back-pressure for SOCK_SEQPACKET, which
                 * can lead to undesired return of EMSGSIZE on send instead
                 * of more desirable blocking.
                 */
                mbcnt_delta = so2->so_rcv.sb_mbcnt - unp2->unp_mbcnt;
                unp2->unp_mbcnt = so2->so_rcv.sb_mbcnt;
                sbcc = so2->so_rcv.sb_cc;
                sorwakeup_locked(so2);

                SOCKBUF_LOCK(&so->so_snd);
                if ((int)so->so_snd.sb_hiwat >= (int)(sbcc - unp2->unp_cc))
                        newhiwat = so->so_snd.sb_hiwat - (sbcc - unp2->unp_cc);
                else
                        newhiwat = 0;
                (void)chgsbsize(so->so_cred->cr_uidinfo, &so->so_snd.sb_hiwat,
                    newhiwat, RLIM_INFINITY);
                so->so_snd.sb_mbmax -= mbcnt_delta;
                SOCKBUF_UNLOCK(&so->so_snd);
                unp2->unp_cc = sbcc;
                UNP_PCB_UNLOCK(unp2);
                m = NULL;
                break;

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

        /*
         * PRUS_EOF is equivalent to pru_send followed by pru_shutdown.
         */
        if (flags & PRUS_EOF) {
                UNP_PCB_LOCK(unp);
                socantsendmore(so);
                unp_shutdown(unp);
                UNP_PCB_UNLOCK(unp);
        }

        if ((nam != NULL) || (flags & PRUS_EOF))
                UNP_LINK_WUNLOCK();
        else
                UNP_LINK_RUNLOCK();

        if (control != NULL && error != 0)
                unp_dispose(control);

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

static int
uipc_sense(struct socket *so, struct stat *sb)
{
        struct unpcb *unp, *unp2;
        struct socket *so2;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_sense: unp == NULL"));

        sb->st_blksize = so->so_snd.sb_hiwat;
        UNP_LINK_RLOCK();
        UNP_PCB_LOCK(unp);
        unp2 = unp->unp_conn;
        if ((so->so_type == SOCK_STREAM || so->so_type == SOCK_SEQPACKET) &&
            unp2 != NULL) {
                so2 = unp2->unp_socket;
                sb->st_blksize += so2->so_rcv.sb_cc;
        }
        sb->st_dev = NODEV;
        if (unp->unp_ino == 0)
                unp->unp_ino = (++unp_ino == 0) ? ++unp_ino : unp_ino;
        sb->st_ino = unp->unp_ino;
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_RUNLOCK();
        return (0);
}

static int
uipc_shutdown(struct socket *so)
{
        struct unpcb *unp;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_shutdown: unp == NULL"));

        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        socantsendmore(so);
        unp_shutdown(unp);
        UNP_PCB_UNLOCK(unp);
        UNP_LINK_WUNLOCK();
        return (0);
}

static int
uipc_sockaddr(struct socket *so, struct sockaddr **nam)
{
        struct unpcb *unp;
        const struct sockaddr *sa;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_sockaddr: unp == NULL"));

        *nam = malloc(sizeof(struct sockaddr_un), M_SONAME, M_WAITOK);
        UNP_PCB_LOCK(unp);
        if (unp->unp_addr != NULL)
                sa = (struct sockaddr *) unp->unp_addr;
        else
                sa = &sun_noname;
        bcopy(sa, *nam, sa->sa_len);
        UNP_PCB_UNLOCK(unp);
        return (0);
}

static struct pr_usrreqs uipc_usrreqs_dgram = {
        .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_soreceive =        soreceive_dgram,
        .pru_close =            uipc_close,
};

static struct pr_usrreqs uipc_usrreqs_seqpacket = {
        .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_soreceive =        soreceive_generic,      /* XXX: or...? */
        .pru_close =            uipc_close,
};

static struct pr_usrreqs uipc_usrreqs_stream = {
        .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_soreceive =        soreceive_generic,
        .pru_close =            uipc_close,
};

static int
uipc_ctloutput(struct socket *so, struct sockopt *sopt)
{
        struct unpcb *unp;
        struct xucred xu;
        int error, optval;

        if (sopt->sopt_level != 0)
                return (EINVAL);

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("uipc_ctloutput: unp == NULL"));
        error = 0;
        switch (sopt->sopt_dir) {
        case SOPT_GET:
                switch (sopt->sopt_name) {
                case LOCAL_PEERCRED:
                        UNP_PCB_LOCK(unp);
                        if (unp->unp_flags & UNP_HAVEPC)
                                xu = unp->unp_peercred;
                        else {
                                if (so->so_type == SOCK_STREAM)
                                        error = ENOTCONN;
                                else
                                        error = EINVAL;
                        }
                        UNP_PCB_UNLOCK(unp);
                        if (error == 0)
                                error = sooptcopyout(sopt, &xu, sizeof(xu));
                        break;

                case LOCAL_CREDS:
                        /* Unlocked read. */
                        optval = unp->unp_flags & UNP_WANTCRED ? 1 : 0;
                        error = sooptcopyout(sopt, &optval, sizeof(optval));
                        break;

                case LOCAL_CONNWAIT:
                        /* Unlocked read. */
                        optval = unp->unp_flags & UNP_CONNWAIT ? 1 : 0;
                        error = sooptcopyout(sopt, &optval, sizeof(optval));
                        break;

                default:
                        error = EOPNOTSUPP;
                        break;
                }
                break;

        case SOPT_SET:
                switch (sopt->sopt_name) {
                case LOCAL_CREDS:
                case LOCAL_CONNWAIT:
                        error = sooptcopyin(sopt, &optval, sizeof(optval),
                                            sizeof(optval));
                        if (error)
                                break;

#define OPTSET(bit) do {                                                \
        UNP_PCB_LOCK(unp);                                              \
        if (optval)                                                     \
                unp->unp_flags |= bit;                                  \
        else                                                            \
                unp->unp_flags &= ~bit;                                 \
        UNP_PCB_UNLOCK(unp);                                            \
} while (0)

                        switch (sopt->sopt_name) {
                        case LOCAL_CREDS:
                                OPTSET(UNP_WANTCRED);
                                break;

                        case LOCAL_CONNWAIT:
                                OPTSET(UNP_CONNWAIT);
                                break;

                        default:
                                break;
                        }
                        break;
#undef  OPTSET
                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }
        return (error);
}

static int
unp_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
{
        struct sockaddr_un *soun = (struct sockaddr_un *)nam;
        struct vnode *vp;
        struct socket *so2, *so3;
        struct unpcb *unp, *unp2, *unp3;
        int error, len, vfslocked;
        struct nameidata nd;
        char buf[SOCK_MAXADDRLEN];
        struct sockaddr *sa;

        UNP_LINK_WLOCK_ASSERT();

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("unp_connect: unp == NULL"));

        if (nam->sa_len > sizeof(struct sockaddr_un))
                return (EINVAL);
        len = nam->sa_len - offsetof(struct sockaddr_un, sun_path);
        if (len <= 0)
                return (EINVAL);
        bcopy(soun->sun_path, buf, len);
        buf[len] = 0;

        UNP_PCB_LOCK(unp);
        if (unp->unp_flags & UNP_CONNECTING) {
                UNP_PCB_UNLOCK(unp);
                return (EALREADY);
        }
        UNP_LINK_WUNLOCK();
        unp->unp_flags |= UNP_CONNECTING;
        UNP_PCB_UNLOCK(unp);

        sa = malloc(sizeof(struct sockaddr_un), M_SONAME, M_WAITOK);
        NDINIT(&nd, LOOKUP, MPSAFE | FOLLOW | LOCKSHARED | LOCKLEAF,
            UIO_SYSSPACE, buf, td);
        error = namei(&nd);
        if (error)
                vp = NULL;
        else
                vp = nd.ni_vp;
        ASSERT_VOP_LOCKED(vp, "unp_connect");
        vfslocked = NDHASGIANT(&nd);
        NDFREE(&nd, NDF_ONLY_PNBUF);
        if (error)
                goto bad;

        if (vp->v_type != VSOCK) {
                error = ENOTSOCK;
                goto bad;
        }
#ifdef MAC
        error = mac_vnode_check_open(td->td_ucred, vp, VWRITE | VREAD);
        if (error)
                goto bad;
#endif
        error = VOP_ACCESS(vp, VWRITE, td->td_ucred, td);
        if (error)
                goto bad;
        VFS_UNLOCK_GIANT(vfslocked);

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("unp_connect: unp == NULL"));

        /*
         * Lock linkage lock for two reasons: make sure v_socket is stable,
         * and to protect simultaneous locking of multiple pcbs.
         */
        UNP_LINK_WLOCK();
        VOP_UNP_CONNECT(vp, &so2);
        if (so2 == NULL) {
                error = ECONNREFUSED;
                goto bad2;
        }
        if (so->so_type != so2->so_type) {
                error = EPROTOTYPE;
                goto bad2;
        }
        if (so->so_proto->pr_flags & PR_CONNREQUIRED) {
                if (so2->so_options & SO_ACCEPTCONN) {
                        CURVNET_SET(so2->so_vnet);
                        so3 = sonewconn(so2, 0);
                        CURVNET_RESTORE();
                } else
                        so3 = NULL;
                if (so3 == NULL) {
                        error = ECONNREFUSED;
                        goto bad2;
                }
                unp = sotounpcb(so);
                unp2 = sotounpcb(so2);
                unp3 = sotounpcb(so3);
                UNP_PCB_LOCK(unp);
                UNP_PCB_LOCK(unp2);
                UNP_PCB_LOCK(unp3);
                if (unp2->unp_addr != NULL) {
                        bcopy(unp2->unp_addr, sa, unp2->unp_addr->sun_len);
                        unp3->unp_addr = (struct sockaddr_un *) sa;
                        sa = NULL;
                }

                /*
                 * The connector's (client's) credentials are copied from its
                 * process structure at the time of connect() (which is now).
                 */
                cru2x(td->td_ucred, &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(); uipc_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"));
                memcpy(&unp->unp_peercred, &unp2->unp_peercred,
                    sizeof(unp->unp_peercred));
                unp->unp_flags |= UNP_HAVEPC;
                if (unp2->unp_flags & UNP_WANTCRED)
                        unp3->unp_flags |= UNP_WANTCRED;
                UNP_PCB_UNLOCK(unp3);
                UNP_PCB_UNLOCK(unp2);
                UNP_PCB_UNLOCK(unp);
#ifdef MAC
                mac_socketpeer_set_from_socket(so, so3);
                mac_socketpeer_set_from_socket(so3, so);
#endif

                so2 = so3;
        }
        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("unp_connect: unp == NULL"));
        unp2 = sotounpcb(so2);
        KASSERT(unp2 != NULL, ("unp_connect: unp2 == NULL"));
        UNP_PCB_LOCK(unp);
        UNP_PCB_LOCK(unp2);
        error = unp_connect2(so, so2, PRU_CONNECT);
        UNP_PCB_UNLOCK(unp2);
        UNP_PCB_UNLOCK(unp);
bad2:
        UNP_LINK_WUNLOCK();
        if (vfslocked)
                /* 
                 * Giant has been previously acquired. This means filesystem
                 * isn't MPSAFE.  Do it once again.
                 */
                mtx_lock(&Giant);
bad:
        if (vp != NULL)
                vput(vp);
        VFS_UNLOCK_GIANT(vfslocked);
        free(sa, M_SONAME);
        UNP_LINK_WLOCK();
        UNP_PCB_LOCK(unp);
        unp->unp_flags &= ~UNP_CONNECTING;
        UNP_PCB_UNLOCK(unp);
        return (error);
}

static int
unp_connect2(struct socket *so, struct socket *so2, int req)
{
        struct unpcb *unp;
        struct unpcb *unp2;

        unp = sotounpcb(so);
        KASSERT(unp != NULL, ("unp_connect2: unp == NULL"));
        unp2 = sotounpcb(so2);
        KASSERT(unp2 != NULL, ("unp_connect2: unp2 == NULL"));

        UNP_LINK_WLOCK_ASSERT();
        UNP_PCB_LOCK_ASSERT(unp);
        UNP_PCB_LOCK_ASSERT(unp2);

        if (so2->so_type != so->so_type)
                return (EPROTOTYPE);
        unp->unp_conn = unp2;

        switch (so->so_type) {
        case SOCK_DGRAM:
                LIST_INSERT_HEAD(&unp2->unp_refs, unp, unp_reflink);
                soisconnected(so);
                break;

        case SOCK_STREAM:
        case SOCK_SEQPACKET:
                unp2->unp_conn = unp;
                if (req == PRU_CONNECT &&
                    ((unp->unp_flags | unp2->unp_flags) & UNP_CONNWAIT))
                        soisconnecting(so);
                else
                        soisconnected(so);
                soisconnected(so2);
                break;

        default:
                panic("unp_connect2");
        }
        return (0);
}

static void
unp_disconnect(struct unpcb *unp, struct unpcb *unp2)
{
        struct socket *so;

        KASSERT(unp2 != NULL, ("unp_disconnect: unp2 == NULL"));

        UNP_LINK_WLOCK_ASSERT();
        UNP_PCB_LOCK_ASSERT(unp);
        UNP_PCB_LOCK_ASSERT(unp2);

        unp->unp_conn = NULL;
        switch (unp->unp_socket->so_type) {
        case SOCK_DGRAM:
                LIST_REMOVE(unp, unp_reflink);
                so = unp->unp_socket;
                SOCK_LOCK(so);
                so->so_state &= ~SS_ISCONNECTED;
                SOCK_UNLOCK(so);
                break;

        case SOCK_STREAM:
        case SOCK_SEQPACKET:
                soisdisconnected(unp->unp_socket);
                unp2->unp_conn = NULL;
                soisdisconnected(unp2->unp_socket);
                break;
        }
}

/*
 * unp_pcblist() walks the global list of struct unpcb's to generate a
 * pointer list, bumping the refcount on each unpcb.  It then copies them out
 * sequentially, validating the generation number on each to see if it has
 * been detached.  All of this is necessary because copyout() may sleep on
 * disk I/O.
 */
static int
unp_pcblist(SYSCTL_HANDLER_ARGS)
{
        int error, i, n;
        int freeunp;
        struct unpcb *unp, **unp_list;
        unp_gen_t gencnt;
        struct xunpgen *xug;
        struct unp_head *head;
        struct xunpcb *xu;

        switch ((intptr_t)arg1) {
        case SOCK_STREAM:
                head = &unp_shead;
                break;

        case SOCK_DGRAM:
                head = &unp_dhead;
                break;

        case SOCK_SEQPACKET:
                head = &unp_sphead;
                break;

        default:
                panic("unp_pcblist: arg1 %d", (int)(intptr_t)arg1);
        }

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

        if (req->newptr != NULL)
                return (EPERM);

        /*
         * OK, now we're committed to doing something.
         */
        xug = malloc(sizeof(*xug), M_TEMP, M_WAITOK);
        UNP_LIST_LOCK();
        gencnt = unp_gencnt;
        n = unp_count;
        UNP_LIST_UNLOCK();

        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) {
                free(xug, M_TEMP);
                return (error);
        }

        unp_list = malloc(n * sizeof *unp_list, M_TEMP, M_WAITOK);

        UNP_LIST_LOCK();
        for (unp = LIST_FIRST(head), i = 0; unp && i < n;
             unp = LIST_NEXT(unp, unp_link)) {
                UNP_PCB_LOCK(unp);
                if (unp->unp_gencnt <= gencnt) {
                        if (cr_cansee(req->td->td_ucred,
                            unp->unp_socket->so_cred)) {
                                UNP_PCB_UNLOCK(unp);
                                continue;
                        }
                        unp_list[i++] = unp;
                        unp->unp_refcount++;
                }
                UNP_PCB_UNLOCK(unp);
        }
        UNP_LIST_UNLOCK();
        n = i;                  /* In case we lost some during malloc. */

        error = 0;
        xu = malloc(sizeof(*xu), M_TEMP, M_WAITOK | M_ZERO);
        for (i = 0; i < n; i++) {
                unp = unp_list[i];
                UNP_PCB_LOCK(unp);
                unp->unp_refcount--;
                if (unp->unp_refcount != 0 && unp->unp_gencnt <= gencnt) {
                        xu->xu_len = sizeof *xu;
                        xu->xu_unpp = unp;
                        /*
                         * XXX - need more locking here to protect against
                         * connect/disconnect races for SMP.
                         */
                        if (unp->unp_addr != NULL)
                                bcopy(unp->unp_addr, &xu->xu_addr,
                                      unp->unp_addr->sun_len);
                        if (unp->unp_conn != NULL &&
                            unp->unp_conn->unp_addr != NULL)
                                bcopy(unp->unp_conn->unp_addr,
                                      &xu->xu_caddr,
                                      unp->unp_conn->unp_addr->sun_len);
                        bcopy(unp, &xu->xu_unp, sizeof *unp);
                        sotoxsocket(unp->unp_socket, &xu->xu_socket);
                        UNP_PCB_UNLOCK(unp);
                        error = SYSCTL_OUT(req, xu, sizeof *xu);
                } else {
                        freeunp = (unp->unp_refcount == 0);
                        UNP_PCB_UNLOCK(unp);
                        if (freeunp) {
                                UNP_PCB_LOCK_DESTROY(unp);
                                uma_zfree(unp_zone, unp);
                        }
                }
        }
        free(xu, M_TEMP);
        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.
                 */
                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);
        free(xug, M_TEMP);
        return (error);
}

SYSCTL_PROC(_net_local_dgram, OID_AUTO, pcblist, CTLTYPE_OPAQUE | CTLFLAG_RD,
    (void *)(intptr_t)SOCK_DGRAM, 0, unp_pcblist, "S,xunpcb",
    "List of active local datagram sockets");
SYSCTL_PROC(_net_local_stream, OID_AUTO, pcblist, CTLTYPE_OPAQUE | CTLFLAG_RD,
    (void *)(intptr_t)SOCK_STREAM, 0, unp_pcblist, "S,xunpcb",
    "List of active local stream sockets");
SYSCTL_PROC(_net_local_seqpacket, OID_AUTO, pcblist,
    CTLTYPE_OPAQUE | CTLFLAG_RD,
    (void *)(intptr_t)SOCK_SEQPACKET, 0, unp_pcblist, "S,xunpcb",
    "List of active local seqpacket sockets");

static void
unp_shutdown(struct unpcb *unp)
{
        struct unpcb *unp2;
        struct socket *so;

        UNP_LINK_WLOCK_ASSERT();
        UNP_PCB_LOCK_ASSERT(unp);

        unp2 = unp->unp_conn;
        if ((unp->unp_socket->so_type == SOCK_STREAM ||
            (unp->unp_socket->so_type == SOCK_SEQPACKET)) && unp2 != NULL) {
                so = unp2->unp_socket;
                if (so != NULL)
                        socantrcvmore(so);
        }
}

static void
unp_drop(struct unpcb *unp, int errno)
{
        struct socket *so = unp->unp_socket;
        struct unpcb *unp2;

        UNP_LINK_WLOCK_ASSERT();
        UNP_PCB_LOCK_ASSERT(unp);

        so->so_error = errno;
        unp2 = unp->unp_conn;
        if (unp2 == NULL)
                return;
        UNP_PCB_LOCK(unp2);
        unp_disconnect(unp, unp2);
        UNP_PCB_UNLOCK(unp2);
}

static void
unp_freerights(struct file **rp, int fdcount)
{
        int i;
        struct file *fp;

        for (i = 0; i < fdcount; i++) {
                fp = *rp;
                *rp++ = NULL;
                unp_discard(fp);
        }
}

static int
unp_externalize(struct mbuf *control, struct mbuf **controlp)
{
        struct thread *td = curthread;          /* XXX */
        struct cmsghdr *cm = mtod(control, struct cmsghdr *);
        int i;
        int *fdp;
        struct file **rp;
        struct file *fp;
        void *data;
        socklen_t clen = control->m_len, datalen;
        int error, newfds;
        u_int newlen;

        UNP_LINK_UNLOCK_ASSERT();

        error = 0;
        if (controlp != NULL) /* controlp == NULL => free control messages */
                *controlp = NULL;
        while (cm != NULL) {
                if (sizeof(*cm) > clen || cm->cmsg_len > clen) {
                        error = EINVAL;
                        break;
                }
                data = CMSG_DATA(cm);
                datalen = (caddr_t)cm + cm->cmsg_len - (caddr_t)data;
                if (cm->cmsg_level == SOL_SOCKET
                    && cm->cmsg_type == SCM_RIGHTS) {
                        newfds = datalen / sizeof(struct file *);
                        rp = data;

                        /* If we're not outputting the descriptors free them. */
                        if (error || controlp == NULL) {
                                unp_freerights(rp, newfds);
                                goto next;
                        }
                        FILEDESC_XLOCK(td->td_proc->p_fd);
                        /*
                         * 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.
                         */
                        newlen = newfds * sizeof(int);
                        *controlp = sbcreatecontrol(NULL, newlen,
                            SCM_RIGHTS, SOL_SOCKET);
                        if (*controlp == NULL) {
                                FILEDESC_XUNLOCK(td->td_proc->p_fd);
                                error = E2BIG;
                                unp_freerights(rp, newfds);
                                goto next;
                        }

                        fdp = (int *)
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *));
                        if (fdallocn(td, 0, fdp, newfds) != 0) {
                                FILEDESC_XUNLOCK(td->td_proc->p_fd);
                                error = EMSGSIZE;
                                unp_freerights(rp, newfds);
                                m_freem(*controlp);
                                *controlp = NULL;
                                goto next;
                        }
                        for (i = 0; i < newfds; i++) {
                                fp = *rp++;
                                td->td_proc->p_fd->fd_ofiles[fdp[i]] = fp;
                                unp_externalize_fp(fp);
                        }
                        FILEDESC_XUNLOCK(td->td_proc->p_fd);
                } else {
                        /* We can just copy anything else across. */
                        if (error || controlp == NULL)
                                goto next;
                        *controlp = sbcreatecontrol(NULL, datalen,
                            cm->cmsg_type, cm->cmsg_level);
                        if (*controlp == NULL) {
                                error = ENOBUFS;
                                goto next;
                        }
                        bcopy(data,
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *)),
                            datalen);
                }
                controlp = &(*controlp)->m_next;

next:
                if (CMSG_SPACE(datalen) < clen) {
                        clen -= CMSG_SPACE(datalen);
                        cm = (struct cmsghdr *)
                            ((caddr_t)cm + CMSG_SPACE(datalen));
                } else {
                        clen = 0;
                        cm = NULL;
                }
        }

        m_freem(control);
        return (error);
}

static void
unp_zone_change(void *tag)
{

        uma_zone_set_max(unp_zone, maxsockets);
}

static void
unp_init(void)
{

#ifdef VIMAGE
        if (!IS_DEFAULT_VNET(curvnet))
                return;
#endif
        unp_zone = uma_zcreate("unpcb", sizeof(struct unpcb), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, 0);
        if (unp_zone == NULL)
                panic("unp_init");
        uma_zone_set_max(unp_zone, maxsockets);
        EVENTHANDLER_REGISTER(maxsockets_change, unp_zone_change,
            NULL, EVENTHANDLER_PRI_ANY);
        LIST_INIT(&unp_dhead);
        LIST_INIT(&unp_shead);
        LIST_INIT(&unp_sphead);
        SLIST_INIT(&unp_defers);
        TIMEOUT_TASK_INIT(taskqueue_thread, &unp_gc_task, 0, unp_gc, NULL);
        TASK_INIT(&unp_defer_task, 0, unp_process_defers, NULL);
        UNP_LINK_LOCK_INIT();
        UNP_LIST_LOCK_INIT();
        UNP_DEFERRED_LOCK_INIT();
}

static int
unp_internalize(struct mbuf **controlp, struct thread *td)
{
        struct mbuf *control = *controlp;
        struct proc *p = td->td_proc;
        struct filedesc *fdescp = p->p_fd;
        struct bintime *bt;
        struct cmsghdr *cm = mtod(control, struct cmsghdr *);
        struct cmsgcred *cmcred;
        struct file **rp;
        struct file *fp;
        struct timeval *tv;
        int i, fd, *fdp;
        void *data;
        socklen_t clen = control->m_len, datalen;
        int error, oldfds;
        u_int newlen;

        UNP_LINK_UNLOCK_ASSERT();

        error = 0;
        *controlp = NULL;
        while (cm != NULL) {
                if (sizeof(*cm) > clen || cm->cmsg_level != SOL_SOCKET
                    || cm->cmsg_len > clen) {
                        error = EINVAL;
                        goto out;
                }
                data = CMSG_DATA(cm);
                datalen = (caddr_t)cm + cm->cmsg_len - (caddr_t)data;

                switch (cm->cmsg_type) {
                /*
                 * Fill in credential information.
                 */
                case SCM_CREDS:
                        *controlp = sbcreatecontrol(NULL, sizeof(*cmcred),
                            SCM_CREDS, SOL_SOCKET);
                        if (*controlp == NULL) {
                                error = ENOBUFS;
                                goto out;
                        }
                        cmcred = (struct cmsgcred *)
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *));
                        cmcred->cmcred_pid = p->p_pid;
                        cmcred->cmcred_uid = td->td_ucred->cr_ruid;
                        cmcred->cmcred_gid = td->td_ucred->cr_rgid;
                        cmcred->cmcred_euid = td->td_ucred->cr_uid;
                        cmcred->cmcred_ngroups = MIN(td->td_ucred->cr_ngroups,
                            CMGROUP_MAX);
                        for (i = 0; i < cmcred->cmcred_ngroups; i++)
                                cmcred->cmcred_groups[i] =
                                    td->td_ucred->cr_groups[i];
                        break;

                case SCM_RIGHTS:
                        oldfds = datalen / sizeof (int);
                        /*
                         * Check that all the FDs passed in refer to legal
                         * files.  If not, reject the entire operation.
                         */
                        fdp = data;
                        FILEDESC_SLOCK(fdescp);
                        for (i = 0; i < oldfds; i++) {
                                fd = *fdp++;
                                if ((unsigned)fd >= fdescp->fd_nfiles ||
                                    fdescp->fd_ofiles[fd] == NULL) {
                                        FILEDESC_SUNLOCK(fdescp);
                                        error = EBADF;
                                        goto out;
                                }
                                fp = fdescp->fd_ofiles[fd];
                                if (!(fp->f_ops->fo_flags & DFLAG_PASSABLE)) {
                                        FILEDESC_SUNLOCK(fdescp);
                                        error = EOPNOTSUPP;
                                        goto out;
                                }

                        }

                        /*
                         * Now replace the integer FDs with pointers to the
                         * associated global file table entry..
                         */
                        newlen = oldfds * sizeof(struct file *);
                        *controlp = sbcreatecontrol(NULL, newlen,
                            SCM_RIGHTS, SOL_SOCKET);
                        if (*controlp == NULL) {
                                FILEDESC_SUNLOCK(fdescp);
                                error = E2BIG;
                                goto out;
                        }
                        fdp = data;
                        rp = (struct file **)
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *));
                        for (i = 0; i < oldfds; i++) {
                                fp = fdescp->fd_ofiles[*fdp++];
                                *rp++ = fp;
                                unp_internalize_fp(fp);
                        }
                        FILEDESC_SUNLOCK(fdescp);
                        break;

                case SCM_TIMESTAMP:
                        *controlp = sbcreatecontrol(NULL, sizeof(*tv),
                            SCM_TIMESTAMP, SOL_SOCKET);
                        if (*controlp == NULL) {
                                error = ENOBUFS;
                                goto out;
                        }
                        tv = (struct timeval *)
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *));
                        microtime(tv);
                        break;

                case SCM_BINTIME:
                        *controlp = sbcreatecontrol(NULL, sizeof(*bt),
                            SCM_BINTIME, SOL_SOCKET);
                        if (*controlp == NULL) {
                                error = ENOBUFS;
                                goto out;
                        }
                        bt = (struct bintime *)
                            CMSG_DATA(mtod(*controlp, struct cmsghdr *));
                        bintime(bt);
                        break;

                default:
                        error = EINVAL;
                        goto out;
                }

                controlp = &(*controlp)->m_next;
                if (CMSG_SPACE(datalen) < clen) {
                        clen -= CMSG_SPACE(datalen);
                        cm = (struct cmsghdr *)
                            ((caddr_t)cm + CMSG_SPACE(datalen));
                } else {
                        clen = 0;
                        cm = NULL;
                }
        }

out:
        m_freem(control);
        return (error);
}

static struct mbuf *
unp_addsockcred(struct thread *td, struct mbuf *control)
{
        struct mbuf *m, *n, *n_prev;
        struct sockcred *sc;
        const struct cmsghdr *cm;
        int ngroups;
        int i;

        ngroups = MIN(td->td_ucred->cr_ngroups, CMGROUP_MAX);
        m = sbcreatecontrol(NULL, SOCKCREDSIZE(ngroups), SCM_CREDS, SOL_SOCKET);
        if (m == NULL)
                return (control);

        sc = (struct sockcred *) CMSG_DATA(mtod(m, struct cmsghdr *));
        sc->sc_uid = td->td_ucred->cr_ruid;
        sc->sc_euid = td->td_ucred->cr_uid;
        sc->sc_gid = td->td_ucred->cr_rgid;
        sc->sc_egid = td->td_ucred->cr_gid;
        sc->sc_ngroups = ngroups;
        for (i = 0; i < sc->sc_ngroups; i++)
                sc->sc_groups[i] = td->td_ucred->cr_groups[i];

        /*
         * Unlink SCM_CREDS control messages (struct cmsgcred), since just
         * created SCM_CREDS control message (struct sockcred) has another
         * format.
         */
        if (control != NULL)
                for (n = control, n_prev = NULL; n != NULL;) {
                        cm = mtod(n, struct cmsghdr *);
                        if (cm->cmsg_level == SOL_SOCKET &&
                            cm->cmsg_type == SCM_CREDS) {
                                if (n_prev == NULL)
                                        control = n->m_next;
                                else
                                        n_prev->m_next = n->m_next;
                                n = m_free(n);
                        } else {
                                n_prev = n;
                                n = n->m_next;
                        }
                }

        /* Prepend it to the head. */
        m->m_next = control;
        return (m);
}

static struct unpcb *
fptounp(struct file *fp)
{
        struct socket *so;

        if (fp->f_type != DTYPE_SOCKET)
                return (NULL);
        if ((so = fp->f_data) == NULL)
                return (NULL);
        if (so->so_proto->pr_domain != &localdomain)
                return (NULL);
        return sotounpcb(so);
}

static void
unp_discard(struct file *fp)
{
        struct unp_defer *dr;

        if (unp_externalize_fp(fp)) {
                dr = malloc(sizeof(*dr), M_TEMP, M_WAITOK);
                dr->ud_fp = fp;
                UNP_DEFERRED_LOCK();
                SLIST_INSERT_HEAD(&unp_defers, dr, ud_link);
                UNP_DEFERRED_UNLOCK();
                atomic_add_int(&unp_defers_count, 1);
                taskqueue_enqueue(taskqueue_thread, &unp_defer_task);
        } else
                (void) closef(fp, (struct thread *)NULL);
}

static void
unp_process_defers(void *arg __unused, int pending)
{
        struct unp_defer *dr;
        SLIST_HEAD(, unp_defer) drl;
        int count;

        SLIST_INIT(&drl);
        for (;;) {
                UNP_DEFERRED_LOCK();
                if (SLIST_FIRST(&unp_defers) == NULL) {
                        UNP_DEFERRED_UNLOCK();
                        break;
                }
                SLIST_SWAP(&unp_defers, &drl, unp_defer);
                UNP_DEFERRED_UNLOCK();
                count = 0;
                while ((dr = SLIST_FIRST(&drl)) != NULL) {
                        SLIST_REMOVE_HEAD(&drl, ud_link);
                        closef(dr->ud_fp, NULL);
                        free(dr, M_TEMP);
                        count++;
                }
                atomic_add_int(&unp_defers_count, -count);
        }
}

static void
unp_internalize_fp(struct file *fp)
{
        struct unpcb *unp;

        UNP_LINK_WLOCK();
        if ((unp = fptounp(fp)) != NULL) {
                unp->unp_file = fp;
                unp->unp_msgcount++;
        }
        fhold(fp);
        unp_rights++;
        UNP_LINK_WUNLOCK();
}

static int
unp_externalize_fp(struct file *fp)
{
        struct unpcb *unp;
        int ret;

        UNP_LINK_WLOCK();
        if ((unp = fptounp(fp)) != NULL) {
                unp->unp_msgcount--;
                ret = 1;
        } else
                ret = 0;
        unp_rights--;
        UNP_LINK_WUNLOCK();
        return (ret);
}

/*
 * unp_defer indicates whether additional work has been defered for a future
 * pass through unp_gc().  It is thread local and does not require explicit
 * synchronization.
 */
static int      unp_marked;
static int      unp_unreachable;

static void
unp_accessable(struct file *fp)
{
        struct unpcb *unp;

        if ((unp = fptounp(fp)) == NULL)
                return;
        if (unp->unp_gcflag & UNPGC_REF)
                return;
        unp->unp_gcflag &= ~UNPGC_DEAD;
        unp->unp_gcflag |= UNPGC_REF;
        unp_marked++;
}

static void
unp_gc_process(struct unpcb *unp)
{
        struct socket *soa;
        struct socket *so;
        struct file *fp;

        /* Already processed. */
        if (unp->unp_gcflag & UNPGC_SCANNED)
                return;
        fp = unp->unp_file;

        /*
         * Check for a socket potentially in a cycle.  It must be in a
         * queue as indicated by msgcount, and this must equal the file
         * reference count.  Note that when msgcount is 0 the file is NULL.
         */
        if ((unp->unp_gcflag & UNPGC_REF) == 0 && fp &&
            unp->unp_msgcount != 0 && fp->f_count == unp->unp_msgcount) {
                unp->unp_gcflag |= UNPGC_DEAD;
                unp_unreachable++;
                return;
        }

        /*
         * Mark all sockets we reference with RIGHTS.
         */
        so = unp->unp_socket;
        SOCKBUF_LOCK(&so->so_rcv);
        unp_scan(so->so_rcv.sb_mb, unp_accessable);
        SOCKBUF_UNLOCK(&so->so_rcv);

        /*
         * Mark all sockets in our accept queue.
         */
        ACCEPT_LOCK();
        TAILQ_FOREACH(soa, &so->so_comp, so_list) {
                SOCKBUF_LOCK(&soa->so_rcv);
                unp_scan(soa->so_rcv.sb_mb, unp_accessable);
                SOCKBUF_UNLOCK(&soa->so_rcv);
        }
        ACCEPT_UNLOCK();
        unp->unp_gcflag |= UNPGC_SCANNED;
}

static int unp_recycled;
SYSCTL_INT(_net_local, OID_AUTO, recycled, CTLFLAG_RD, &unp_recycled, 0, 
    "Number of unreachable sockets claimed by the garbage collector.");

static int unp_taskcount;
SYSCTL_INT(_net_local, OID_AUTO, taskcount, CTLFLAG_RD, &unp_taskcount, 0, 
    "Number of times the garbage collector has run.");

static void
unp_gc(__unused void *arg, int pending)
{
        struct unp_head *heads[] = { &unp_dhead, &unp_shead, &unp_sphead,
                                    NULL };
        struct unp_head **head;
        struct file *f, **unref;
        struct unpcb *unp;
        int i, total;

        unp_taskcount++;
        UNP_LIST_LOCK();
        /*
         * First clear all gc flags from previous runs.
         */
        for (head = heads; *head != NULL; head++)
                LIST_FOREACH(unp, *head, unp_link)
                        unp->unp_gcflag = 0;

        /*
         * Scan marking all reachable sockets with UNPGC_REF.  Once a socket
         * is reachable all of the sockets it references are reachable.
         * Stop the scan once we do a complete loop without discovering
         * a new reachable socket.
         */
        do {
                unp_unreachable = 0;
                unp_marked = 0;
                for (head = heads; *head != NULL; head++)
                        LIST_FOREACH(unp, *head, unp_link)
                                unp_gc_process(unp);
        } while (unp_marked);
        UNP_LIST_UNLOCK();
        if (unp_unreachable == 0)
                return;

        /*
         * Allocate space for a local list of dead unpcbs.
         */
        unref = malloc(unp_unreachable * sizeof(struct file *),
            M_TEMP, M_WAITOK);

        /*
         * Iterate looking for sockets which have been specifically marked
         * as as unreachable and store them locally.
         */
        UNP_LINK_RLOCK();
        UNP_LIST_LOCK();
        for (total = 0, head = heads; *head != NULL; head++)
                LIST_FOREACH(unp, *head, unp_link)
                        if ((unp->unp_gcflag & UNPGC_DEAD) != 0) {
                                f = unp->unp_file;
                                if (unp->unp_msgcount == 0 || f == NULL ||
                                    f->f_count != unp->unp_msgcount)
                                        continue;
                                unref[total++] = f;
                                fhold(f);
                                KASSERT(total <= unp_unreachable,
                                    ("unp_gc: incorrect unreachable count."));
                        }
        UNP_LIST_UNLOCK();
        UNP_LINK_RUNLOCK();

        /*
         * Now flush all sockets, free'ing rights.  This will free the
         * struct files associated with these sockets but leave each socket
         * with one remaining ref.
         */
        for (i = 0; i < total; i++) {
                struct socket *so;

                so = unref[i]->f_data;
                CURVNET_SET(so->so_vnet);
                sorflush(so);
                CURVNET_RESTORE();
        }

        /*
         * And finally release the sockets so they can be reclaimed.
         */
        for (i = 0; i < total; i++)
                fdrop(unref[i], NULL);
        unp_recycled += total;
        free(unref, M_TEMP);
}

static void
unp_dispose(struct mbuf *m)
{

        if (m)
                unp_scan(m, unp_discard);
}

static void
unp_scan(struct mbuf *m0, void (*op)(struct file *))
{
        struct mbuf *m;
        struct file **rp;
        struct cmsghdr *cm;
        void *data;
        int i;
        socklen_t clen, datalen;
        int qfds;

        while (m0 != NULL) {
                for (m = m0; m; m = m->m_next) {
                        if (m->m_type != MT_CONTROL)
                                continue;

                        cm = mtod(m, struct cmsghdr *);
                        clen = m->m_len;

                        while (cm != NULL) {
                                if (sizeof(*cm) > clen || cm->cmsg_len > clen)
                                        break;

                                data = CMSG_DATA(cm);
                                datalen = (caddr_t)cm + cm->cmsg_len
                                    - (caddr_t)data;

                                if (cm->cmsg_level == SOL_SOCKET &&
                                    cm->cmsg_type == SCM_RIGHTS) {
                                        qfds = datalen / sizeof (struct file *);
                                        rp = data;
                                        for (i = 0; i < qfds; i++)
                                                (*op)(*rp++);
                                }

                                if (CMSG_SPACE(datalen) < clen) {
                                        clen -= CMSG_SPACE(datalen);
                                        cm = (struct cmsghdr *)
                                            ((caddr_t)cm + CMSG_SPACE(datalen));
                                } else {
                                        clen = 0;
                                        cm = NULL;
                                }
                        }
                }
                m0 = m0->m_act;
        }
}

/*
 * A helper function called by VFS before socket-type vnode reclamation.
 * For an active vnode it clears unp_vnode pointer and decrements unp_vnode
 * use count.
 */
void
vfs_unp_reclaim(struct vnode *vp)
{
        struct socket *so;
        struct unpcb *unp;
        int active;

        ASSERT_VOP_ELOCKED(vp, "vfs_unp_reclaim");
        KASSERT(vp->v_type == VSOCK,
            ("vfs_unp_reclaim: vp->v_type != VSOCK"));

        active = 0;
        UNP_LINK_WLOCK();
        VOP_UNP_CONNECT(vp, &so);
        if (so == NULL)
                goto done;
        unp = sotounpcb(so);
        if (unp == NULL)
                goto done;
        UNP_PCB_LOCK(unp);
        if (unp->unp_vnode == vp) {
                VOP_UNP_DETACH(vp);
                unp->unp_vnode = NULL;
                active = 1;
        }
        UNP_PCB_UNLOCK(unp);
done:
        UNP_LINK_WUNLOCK();
        if (active)
                vunref(vp);
}

#ifdef DDB
static void
db_print_indent(int indent)
{
        int i;

        for (i = 0; i < indent; i++)
                db_printf(" ");
}

static void
db_print_unpflags(int unp_flags)
{
        int comma;

        comma = 0;
        if (unp_flags & UNP_HAVEPC) {
                db_printf("%sUNP_HAVEPC", comma ? ", " : "");
                comma = 1;
        }
        if (unp_flags & UNP_HAVEPCCACHED) {
                db_printf("%sUNP_HAVEPCCACHED", comma ? ", " : "");
                comma = 1;
        }
        if (unp_flags & UNP_WANTCRED) {
                db_printf("%sUNP_WANTCRED", comma ? ", " : "");
                comma = 1;
        }
        if (unp_flags & UNP_CONNWAIT) {
                db_printf("%sUNP_CONNWAIT", comma ? ", " : "");
                comma = 1;
        }
        if (unp_flags & UNP_CONNECTING) {
                db_printf("%sUNP_CONNECTING", comma ? ", " : "");
                comma = 1;
        }
        if (unp_flags & UNP_BINDING) {
                db_printf("%sUNP_BINDING", comma ? ", " : "");
                comma = 1;
        }
}

static void
db_print_xucred(int indent, struct xucred *xu)
{
        int comma, i;

        db_print_indent(indent);
        db_printf("cr_version: %u   cr_uid: %u   cr_ngroups: %d\n",
            xu->cr_version, xu->cr_uid, xu->cr_ngroups);
        db_print_indent(indent);
        db_printf("cr_groups: ");
        comma = 0;
        for (i = 0; i < xu->cr_ngroups; i++) {
                db_printf("%s%u", comma ? ", " : "", xu->cr_groups[i]);
                comma = 1;
        }
        db_printf("\n");
}

static void
db_print_unprefs(int indent, struct unp_head *uh)
{
        struct unpcb *unp;
        int counter;

        counter = 0;
        LIST_FOREACH(unp, uh, unp_reflink) {
                if (counter % 4 == 0)
                        db_print_indent(indent);
                db_printf("%p  ", unp);
                if (counter % 4 == 3)
                        db_printf("\n");
                counter++;
        }
        if (counter != 0 && counter % 4 != 0)
                db_printf("\n");
}

DB_SHOW_COMMAND(unpcb, db_show_unpcb)
{
        struct unpcb *unp;

        if (!have_addr) {
                db_printf("usage: show unpcb <addr>\n");
                return;
        }
        unp = (struct unpcb *)addr;

        db_printf("unp_socket: %p   unp_vnode: %p\n", unp->unp_socket,
            unp->unp_vnode);

        db_printf("unp_ino: %d   unp_conn: %p\n", unp->unp_ino,
            unp->unp_conn);

        db_printf("unp_refs:\n");
        db_print_unprefs(2, &unp->unp_refs);

        /* XXXRW: Would be nice to print the full address, if any. */
        db_printf("unp_addr: %p\n", unp->unp_addr);

        db_printf("unp_cc: %d   unp_mbcnt: %d   unp_gencnt: %llu\n",
            unp->unp_cc, unp->unp_mbcnt,
            (unsigned long long)unp->unp_gencnt);

        db_printf("unp_flags: %x (", unp->unp_flags);
        db_print_unpflags(unp->unp_flags);
        db_printf(")\n");

        db_printf("unp_peercred:\n");
        db_print_xucred(2, &unp->unp_peercred);

        db_printf("unp_refcount: %u\n", unp->unp_refcount);
}
#endif