FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_socket.c

     /*-
      * Copyright (c) 1982, 1986, 1988, 1990, 1993
      *      The Regents of the University of California.
      * Copyright (c) 2004 The FreeBSD Foundation
      * Copyright (c) 2004-2008 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.
     *
     *      @(#)uipc_socket.c       8.3 (Berkeley) 4/15/94
     */
    
    /*
     * Comments on the socket life cycle:
     *
     * soalloc() sets of socket layer state for a socket, called only by
     * socreate() and sonewconn().  Socket layer private.
     *
     * sodealloc() tears down socket layer state for a socket, called only by
     * sofree() and sonewconn().  Socket layer private.
     *
     * pru_attach() associates protocol layer state with an allocated socket;
     * called only once, may fail, aborting socket allocation.  This is called
     * from socreate() and sonewconn().  Socket layer private.
     *
     * pru_detach() disassociates protocol layer state from an attached socket,
     * and will be called exactly once for sockets in which pru_attach() has
     * been successfully called.  If pru_attach() returned an error,
     * pru_detach() will not be called.  Socket layer private.
     *
     * pru_abort() and pru_close() notify the protocol layer that the last
     * consumer of a socket is starting to tear down the socket, and that the
     * protocol should terminate the connection.  Historically, pru_abort() also
     * detached protocol state from the socket state, but this is no longer the
     * case.
     *
     * socreate() creates a socket and attaches protocol state.  This is a public
     * interface that may be used by socket layer consumers to create new
     * sockets.
     *
     * sonewconn() creates a socket and attaches protocol state.  This is a
     * public interface  that may be used by protocols to create new sockets when
     * a new connection is received and will be available for accept() on a
     * listen socket.
     *
     * soclose() destroys a socket after possibly waiting for it to disconnect.
     * This is a public interface that socket consumers should use to close and
     * release a socket when done with it.
     *
     * soabort() destroys a socket without waiting for it to disconnect (used
     * only for incoming connections that are already partially or fully
     * connected).  This is used internally by the socket layer when clearing
     * listen socket queues (due to overflow or close on the listen socket), but
     * is also a public interface protocols may use to abort connections in
     * their incomplete listen queues should they no longer be required.  Sockets
     * placed in completed connection listen queues should not be aborted for
     * reasons described in the comment above the soclose() implementation.  This
     * is not a general purpose close routine, and except in the specific
     * circumstances described here, should not be used.
     *
     * sofree() will free a socket and its protocol state if all references on
     * the socket have been released, and is the public interface to attempt to
     * free a socket when a reference is removed.  This is a socket layer private
     * interface.
     *
     * NOTE: In addition to socreate() and soclose(), which provide a single
     * socket reference to the consumer to be managed as required, there are two
     * calls to explicitly manage socket references, soref(), and sorele().
     * Currently, these are generally required only when transitioning a socket
     * from a listen queue to a file descriptor, in order to prevent garbage
     * collection of the socket at an untimely moment.  For a number of reasons,
     * these interfaces are not preferred, and should be avoided.
     * 
     * NOTE: With regard to VNETs the general rule is that callers do not set
     * curvnet. Exceptions to this rule include soabort(), sodisconnect(),
     * sofree() (and with that sorele(), sotryfree()), as well as sonewconn()
     * and sorflush(), which are usually called from a pre-set VNET context.
    * sopoll() currently does not need a VNET context to be set.
    */
   
   #include <sys/cdefs.h>
   __FBSDID("$FreeBSD: releng/8.3/sys/kern/uipc_socket.c 232370 2012-03-02 00:15:13Z hrs $");
   
   #include "opt_inet.h"
   #include "opt_inet6.h"
   #include "opt_zero.h"
   #include "opt_compat.h"
   
   #include <sys/param.h>
   #include <sys/systm.h>
   #include <sys/fcntl.h>
   #include <sys/limits.h>
   #include <sys/lock.h>
   #include <sys/mac.h>
   #include <sys/malloc.h>
   #include <sys/mbuf.h>
   #include <sys/mutex.h>
   #include <sys/domain.h>
   #include <sys/file.h>                   /* for struct knote */
   #include <sys/kernel.h>
   #include <sys/event.h>
   #include <sys/eventhandler.h>
   #include <sys/poll.h>
   #include <sys/proc.h>
   #include <sys/protosw.h>
   #include <sys/socket.h>
   #include <sys/socketvar.h>
   #include <sys/resourcevar.h>
   #include <net/route.h>
   #include <sys/signalvar.h>
   #include <sys/stat.h>
   #include <sys/sx.h>
   #include <sys/sysctl.h>
   #include <sys/uio.h>
   #include <sys/jail.h>
   
   #include <net/vnet.h>
   
   #include <security/mac/mac_framework.h>
   
   #include <vm/uma.h>
   
   #ifdef COMPAT_FREEBSD32
   #include <sys/mount.h>
   #include <sys/sysent.h>
   #include <compat/freebsd32/freebsd32.h>
   #endif
   
   static int      soreceive_rcvoob(struct socket *so, struct uio *uio,
                       int flags);
   
   static void     filt_sordetach(struct knote *kn);
   static int      filt_soread(struct knote *kn, long hint);
   static void     filt_sowdetach(struct knote *kn);
   static int      filt_sowrite(struct knote *kn, long hint);
   static int      filt_solisten(struct knote *kn, long hint);
   
   static struct filterops solisten_filtops =
           { 1, NULL, filt_sordetach, filt_solisten };
   static struct filterops soread_filtops =
           { 1, NULL, filt_sordetach, filt_soread };
   static struct filterops sowrite_filtops =
           { 1, NULL, filt_sowdetach, filt_sowrite };
   
   uma_zone_t socket_zone;
   so_gen_t        so_gencnt;      /* generation count for sockets */
   
   int     maxsockets;
   
   MALLOC_DEFINE(M_SONAME, "soname", "socket name");
   MALLOC_DEFINE(M_PCB, "pcb", "protocol control block");
   
   #define VNET_SO_ASSERT(so)                                              \
           VNET_ASSERT(curvnet != NULL,                                    \
               ("%s:%d curvnet is NULL, so=%p", __func__, __LINE__, (so)));
   
   static int somaxconn = SOMAXCONN;
   static int sysctl_somaxconn(SYSCTL_HANDLER_ARGS);
   /* XXX: we dont have SYSCTL_USHORT */
   SYSCTL_PROC(_kern_ipc, KIPC_SOMAXCONN, somaxconn, CTLTYPE_UINT | CTLFLAG_RW,
       0, sizeof(int), sysctl_somaxconn, "I", "Maximum pending socket connection "
       "queue size");
   static int numopensockets;
   SYSCTL_INT(_kern_ipc, OID_AUTO, numopensockets, CTLFLAG_RD,
       &numopensockets, 0, "Number of open sockets");
   #ifdef ZERO_COPY_SOCKETS
   /* These aren't static because they're used in other files. */
   int so_zero_copy_send = 1;
   int so_zero_copy_receive = 1;
   SYSCTL_NODE(_kern_ipc, OID_AUTO, zero_copy, CTLFLAG_RD, 0,
       "Zero copy controls");
   SYSCTL_INT(_kern_ipc_zero_copy, OID_AUTO, receive, CTLFLAG_RW,
       &so_zero_copy_receive, 0, "Enable zero copy receive");
   SYSCTL_INT(_kern_ipc_zero_copy, OID_AUTO, send, CTLFLAG_RW,
       &so_zero_copy_send, 0, "Enable zero copy send");
   #endif /* ZERO_COPY_SOCKETS */
   
   /*
    * accept_mtx locks down per-socket fields relating to accept queues.  See
    * socketvar.h for an annotation of the protected fields of struct socket.
    */
   struct mtx accept_mtx;
   MTX_SYSINIT(accept_mtx, &accept_mtx, "accept", MTX_DEF);
   
   /*
    * so_global_mtx protects so_gencnt, numopensockets, and the per-socket
    * so_gencnt field.
    */
   static struct mtx so_global_mtx;
   MTX_SYSINIT(so_global_mtx, &so_global_mtx, "so_glabel", MTX_DEF);
   
   /*
    * General IPC sysctl name space, used by sockets and a variety of other IPC
    * types.
    */
   SYSCTL_NODE(_kern, KERN_IPC, ipc, CTLFLAG_RW, 0, "IPC");
   
   /*
    * Sysctl to get and set the maximum global sockets limit.  Notify protocols
    * of the change so that they can update their dependent limits as required.
    */
   static int
   sysctl_maxsockets(SYSCTL_HANDLER_ARGS)
   {
           int error, newmaxsockets;
   
           newmaxsockets = maxsockets;
           error = sysctl_handle_int(oidp, &newmaxsockets, 0, req);
           if (error == 0 && req->newptr) {
                   if (newmaxsockets > maxsockets) {
                           maxsockets = newmaxsockets;
                           if (maxsockets > ((maxfiles / 4) * 3)) {
                                   maxfiles = (maxsockets * 5) / 4;
                                   maxfilesperproc = (maxfiles * 9) / 10;
                           }
                           EVENTHANDLER_INVOKE(maxsockets_change);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   
   SYSCTL_PROC(_kern_ipc, OID_AUTO, maxsockets, CTLTYPE_INT|CTLFLAG_RW,
       &maxsockets, 0, sysctl_maxsockets, "IU",
       "Maximum number of sockets avaliable");
   
   /*
    * Initialise maxsockets.  This SYSINIT must be run after
    * tunable_mbinit().
    */
   static void
   init_maxsockets(void *ignored)
   {
   
           TUNABLE_INT_FETCH("kern.ipc.maxsockets", &maxsockets);
           maxsockets = imax(maxsockets, imax(maxfiles, nmbclusters));
   }
   SYSINIT(param, SI_SUB_TUNABLES, SI_ORDER_ANY, init_maxsockets, NULL);
   
   /*
    * Socket operation routines.  These routines are called by the routines in
    * sys_socket.c or from a system process, and implement the semantics of
    * socket operations by switching out to the protocol specific routines.
    */
   
   /*
    * Get a socket structure from our zone, and initialize it.  Note that it
    * would probably be better to allocate socket and PCB at the same time, but
    * I'm not convinced that all the protocols can be easily modified to do
    * this.
    *
    * soalloc() returns a socket with a ref count of 0.
    */
   static struct socket *
   soalloc(struct vnet *vnet)
   {
           struct socket *so;
   
           so = uma_zalloc(socket_zone, M_NOWAIT | M_ZERO);
           if (so == NULL)
                   return (NULL);
   #ifdef MAC
           if (mac_socket_init(so, M_NOWAIT) != 0) {
                   uma_zfree(socket_zone, so);
                   return (NULL);
           }
   #endif
           SOCKBUF_LOCK_INIT(&so->so_snd, "so_snd");
           SOCKBUF_LOCK_INIT(&so->so_rcv, "so_rcv");
           sx_init(&so->so_snd.sb_sx, "so_snd_sx");
           sx_init(&so->so_rcv.sb_sx, "so_rcv_sx");
           TAILQ_INIT(&so->so_aiojobq);
           mtx_lock(&so_global_mtx);
           so->so_gencnt = ++so_gencnt;
           ++numopensockets;
   #ifdef VIMAGE
           VNET_ASSERT(vnet != NULL, ("%s:%d vnet is NULL, so=%p",
               __func__, __LINE__, so));
           vnet->vnet_sockcnt++;
           so->so_vnet = vnet;
   #endif
           mtx_unlock(&so_global_mtx);
           return (so);
   }
   
   /*
    * Free the storage associated with a socket at the socket layer, tear down
    * locks, labels, etc.  All protocol state is assumed already to have been
    * torn down (and possibly never set up) by the caller.
    */
   static void
   sodealloc(struct socket *so)
   {
   
           KASSERT(so->so_count == 0, ("sodealloc(): so_count %d", so->so_count));
           KASSERT(so->so_pcb == NULL, ("sodealloc(): so_pcb != NULL"));
   
           mtx_lock(&so_global_mtx);
           so->so_gencnt = ++so_gencnt;
           --numopensockets;       /* Could be below, but faster here. */
   #ifdef VIMAGE
           VNET_ASSERT(so->so_vnet != NULL, ("%s:%d so_vnet is NULL, so=%p",
               __func__, __LINE__, so));
           so->so_vnet->vnet_sockcnt--;
   #endif
           mtx_unlock(&so_global_mtx);
           if (so->so_rcv.sb_hiwat)
                   (void)chgsbsize(so->so_cred->cr_uidinfo,
                       &so->so_rcv.sb_hiwat, 0, RLIM_INFINITY);
           if (so->so_snd.sb_hiwat)
                   (void)chgsbsize(so->so_cred->cr_uidinfo,
                       &so->so_snd.sb_hiwat, 0, RLIM_INFINITY);
   #ifdef INET
           /* remove acccept filter if one is present. */
           if (so->so_accf != NULL)
                   do_setopt_accept_filter(so, NULL);
   #endif
   #ifdef MAC
           mac_socket_destroy(so);
   #endif
           crfree(so->so_cred);
           sx_destroy(&so->so_snd.sb_sx);
           sx_destroy(&so->so_rcv.sb_sx);
           SOCKBUF_LOCK_DESTROY(&so->so_snd);
           SOCKBUF_LOCK_DESTROY(&so->so_rcv);
           uma_zfree(socket_zone, so);
   }
   
   /*
    * socreate returns a socket with a ref count of 1.  The socket should be
    * closed with soclose().
    */
   int
   socreate(int dom, struct socket **aso, int type, int proto,
       struct ucred *cred, struct thread *td)
   {
           struct protosw *prp;
           struct socket *so;
           int error;
   
           if (proto)
                   prp = pffindproto(dom, proto, type);
           else
                   prp = pffindtype(dom, type);
   
           if (prp == NULL || prp->pr_usrreqs->pru_attach == NULL ||
               prp->pr_usrreqs->pru_attach == pru_attach_notsupp)
                   return (EPROTONOSUPPORT);
   
           if (prison_check_af(cred, prp->pr_domain->dom_family) != 0)
                   return (EPROTONOSUPPORT);
   
           if (prp->pr_type != type)
                   return (EPROTOTYPE);
           so = soalloc(CRED_TO_VNET(cred));
           if (so == NULL)
                   return (ENOBUFS);
   
           TAILQ_INIT(&so->so_incomp);
           TAILQ_INIT(&so->so_comp);
           so->so_type = type;
           so->so_cred = crhold(cred);
           if ((prp->pr_domain->dom_family == PF_INET) ||
               (prp->pr_domain->dom_family == PF_ROUTE))
                   so->so_fibnum = td->td_proc->p_fibnum;
           else
                   so->so_fibnum = 0;
           so->so_proto = prp;
   #ifdef MAC
           mac_socket_create(cred, so);
   #endif
           knlist_init_mtx(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv));
           knlist_init_mtx(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd));
           so->so_count = 1;
           /*
            * Auto-sizing of socket buffers is managed by the protocols and
            * the appropriate flags must be set in the pru_attach function.
            */
           CURVNET_SET(so->so_vnet);
           error = (*prp->pr_usrreqs->pru_attach)(so, proto, td);
           CURVNET_RESTORE();
           if (error) {
                   KASSERT(so->so_count == 1, ("socreate: so_count %d",
                       so->so_count));
                   so->so_count = 0;
                   sodealloc(so);
                   return (error);
           }
           *aso = so;
           return (0);
   }
   
   #ifdef REGRESSION
   static int regression_sonewconn_earlytest = 1;
   SYSCTL_INT(_regression, OID_AUTO, sonewconn_earlytest, CTLFLAG_RW,
       &regression_sonewconn_earlytest, 0, "Perform early sonewconn limit test");
   #endif
   
   /*
    * When an attempt at a new connection is noted on a socket which accepts
    * connections, sonewconn is called.  If the connection is possible (subject
    * to space constraints, etc.) then we allocate a new structure, propoerly
    * linked into the data structure of the original socket, and return this.
    * Connstatus may be 0, or SO_ISCONFIRMING, or SO_ISCONNECTED.
    *
    * Note: the ref count on the socket is 0 on return.
    */
   struct socket *
   sonewconn(struct socket *head, int connstatus)
   {
           struct socket *so;
           int over;
   
           ACCEPT_LOCK();
           over = (head->so_qlen > 3 * head->so_qlimit / 2);
           ACCEPT_UNLOCK();
   #ifdef REGRESSION
           if (regression_sonewconn_earlytest && over)
   #else
           if (over)
   #endif
                   return (NULL);
           VNET_ASSERT(head->so_vnet != NULL, ("%s:%d so_vnet is NULL, head=%p",
               __func__, __LINE__, head));
           so = soalloc(head->so_vnet);
           if (so == NULL)
                   return (NULL);
           if ((head->so_options & SO_ACCEPTFILTER) != 0)
                   connstatus = 0;
           so->so_head = head;
           so->so_type = head->so_type;
           so->so_options = head->so_options &~ SO_ACCEPTCONN;
           so->so_linger = head->so_linger;
           so->so_state = head->so_state | SS_NOFDREF;
           so->so_fibnum = head->so_fibnum;
           so->so_proto = head->so_proto;
           so->so_cred = crhold(head->so_cred);
   #ifdef MAC
           mac_socket_newconn(head, so);
   #endif
           knlist_init_mtx(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv));
           knlist_init_mtx(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd));
           VNET_SO_ASSERT(head);
           if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat) ||
               (*so->so_proto->pr_usrreqs->pru_attach)(so, 0, NULL)) {
                   sodealloc(so);
                   return (NULL);
           }
           so->so_rcv.sb_lowat = head->so_rcv.sb_lowat;
           so->so_snd.sb_lowat = head->so_snd.sb_lowat;
           so->so_rcv.sb_timeo = head->so_rcv.sb_timeo;
           so->so_snd.sb_timeo = head->so_snd.sb_timeo;
           so->so_rcv.sb_flags |= head->so_rcv.sb_flags & SB_AUTOSIZE;
           so->so_snd.sb_flags |= head->so_snd.sb_flags & SB_AUTOSIZE;
           so->so_state |= connstatus;
           ACCEPT_LOCK();
           if (connstatus) {
                   TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                   so->so_qstate |= SQ_COMP;
                   head->so_qlen++;
           } else {
                   /*
                    * Keep removing sockets from the head until there's room for
                    * us to insert on the tail.  In pre-locking revisions, this
                    * was a simple if(), but as we could be racing with other
                    * threads and soabort() requires dropping locks, we must
                    * loop waiting for the condition to be true.
                    */
                   while (head->so_incqlen > head->so_qlimit) {
                           struct socket *sp;
                           sp = TAILQ_FIRST(&head->so_incomp);
                           TAILQ_REMOVE(&head->so_incomp, sp, so_list);
                           head->so_incqlen--;
                           sp->so_qstate &= ~SQ_INCOMP;
                           sp->so_head = NULL;
                           ACCEPT_UNLOCK();
                           soabort(sp);
                           ACCEPT_LOCK();
                   }
                   TAILQ_INSERT_TAIL(&head->so_incomp, so, so_list);
                   so->so_qstate |= SQ_INCOMP;
                   head->so_incqlen++;
           }
           ACCEPT_UNLOCK();
           if (connstatus) {
                   sorwakeup(head);
                   wakeup_one(&head->so_timeo);
           }
           return (so);
   }
   
   int
   sobind(struct socket *so, struct sockaddr *nam, struct thread *td)
   {
           int error;
   
           CURVNET_SET(so->so_vnet);
           error = (*so->so_proto->pr_usrreqs->pru_bind)(so, nam, td);
           CURVNET_RESTORE();
           return error;
   }
   
   /*
    * solisten() transitions a socket from a non-listening state to a listening
    * state, but can also be used to update the listen queue depth on an
    * existing listen socket.  The protocol will call back into the sockets
    * layer using solisten_proto_check() and solisten_proto() to check and set
    * socket-layer listen state.  Call backs are used so that the protocol can
    * acquire both protocol and socket layer locks in whatever order is required
    * by the protocol.
    *
    * Protocol implementors are advised to hold the socket lock across the
    * socket-layer test and set to avoid races at the socket layer.
    */
   int
   solisten(struct socket *so, int backlog, struct thread *td)
   {
           int error;
   
           CURVNET_SET(so->so_vnet);
           error = (*so->so_proto->pr_usrreqs->pru_listen)(so, backlog, td);
           CURVNET_RESTORE();
           return error;
   }
   
   int
   solisten_proto_check(struct socket *so)
   {
   
           SOCK_LOCK_ASSERT(so);
   
           if (so->so_state & (SS_ISCONNECTED | SS_ISCONNECTING |
               SS_ISDISCONNECTING))
                   return (EINVAL);
           return (0);
   }
   
   void
   solisten_proto(struct socket *so, int backlog)
   {
   
           SOCK_LOCK_ASSERT(so);
   
           if (backlog < 0 || backlog > somaxconn)
                   backlog = somaxconn;
           so->so_qlimit = backlog;
           so->so_options |= SO_ACCEPTCONN;
   }
   
   /*
    * Attempt to free a socket.  This should really be sotryfree().
    *
    * sofree() will succeed if:
    *
    * - There are no outstanding file descriptor references or related consumers
    *   (so_count == 0).
    *
    * - The socket has been closed by user space, if ever open (SS_NOFDREF).
    *
    * - The protocol does not have an outstanding strong reference on the socket
    *   (SS_PROTOREF).
    *
    * - The socket is not in a completed connection queue, so a process has been
    *   notified that it is present.  If it is removed, the user process may
    *   block in accept() despite select() saying the socket was ready.
    *
    * Otherwise, it will quietly abort so that a future call to sofree(), when
    * conditions are right, can succeed.
    */
   void
   sofree(struct socket *so)
   {
           struct protosw *pr = so->so_proto;
           struct socket *head;
   
           ACCEPT_LOCK_ASSERT();
           SOCK_LOCK_ASSERT(so);
   
           if ((so->so_state & SS_NOFDREF) == 0 || so->so_count != 0 ||
               (so->so_state & SS_PROTOREF) || (so->so_qstate & SQ_COMP)) {
                   SOCK_UNLOCK(so);
                   ACCEPT_UNLOCK();
                   return;
           }
   
           head = so->so_head;
           if (head != NULL) {
                   KASSERT((so->so_qstate & SQ_COMP) != 0 ||
                       (so->so_qstate & SQ_INCOMP) != 0,
                       ("sofree: so_head != NULL, but neither SQ_COMP nor "
                       "SQ_INCOMP"));
                   KASSERT((so->so_qstate & SQ_COMP) == 0 ||
                       (so->so_qstate & SQ_INCOMP) == 0,
                       ("sofree: so->so_qstate is SQ_COMP and also SQ_INCOMP"));
                   TAILQ_REMOVE(&head->so_incomp, so, so_list);
                   head->so_incqlen--;
                   so->so_qstate &= ~SQ_INCOMP;
                   so->so_head = NULL;
           }
           KASSERT((so->so_qstate & SQ_COMP) == 0 &&
               (so->so_qstate & SQ_INCOMP) == 0,
               ("sofree: so_head == NULL, but still SQ_COMP(%d) or SQ_INCOMP(%d)",
               so->so_qstate & SQ_COMP, so->so_qstate & SQ_INCOMP));
           if (so->so_options & SO_ACCEPTCONN) {
                   KASSERT((TAILQ_EMPTY(&so->so_comp)), ("sofree: so_comp populated"));
                   KASSERT((TAILQ_EMPTY(&so->so_incomp)), ("sofree: so_comp populated"));
           }
           SOCK_UNLOCK(so);
           ACCEPT_UNLOCK();
   
           VNET_SO_ASSERT(so);
           if (pr->pr_flags & PR_RIGHTS && pr->pr_domain->dom_dispose != NULL)
                   (*pr->pr_domain->dom_dispose)(so->so_rcv.sb_mb);
           if (pr->pr_usrreqs->pru_detach != NULL)
                   (*pr->pr_usrreqs->pru_detach)(so);
   
           /*
            * From this point on, we assume that no other references to this
            * socket exist anywhere else in the stack.  Therefore, no locks need
            * to be acquired or held.
            *
            * We used to do a lot of socket buffer and socket locking here, as
            * well as invoke sorflush() and perform wakeups.  The direct call to
            * dom_dispose() and sbrelease_internal() are an inlining of what was
            * necessary from sorflush().
            *
            * Notice that the socket buffer and kqueue state are torn down
            * before calling pru_detach.  This means that protocols shold not
            * assume they can perform socket wakeups, etc, in their detach code.
            */
           sbdestroy(&so->so_snd, so);
           sbdestroy(&so->so_rcv, so);
           seldrain(&so->so_snd.sb_sel);
           seldrain(&so->so_rcv.sb_sel);
           knlist_destroy(&so->so_rcv.sb_sel.si_note);
           knlist_destroy(&so->so_snd.sb_sel.si_note);
           sodealloc(so);
   }
   
   /*
    * Close a socket on last file table reference removal.  Initiate disconnect
    * if connected.  Free socket when disconnect complete.
    *
    * This function will sorele() the socket.  Note that soclose() may be called
    * prior to the ref count reaching zero.  The actual socket structure will
    * not be freed until the ref count reaches zero.
    */
   int
   soclose(struct socket *so)
   {
           int error = 0;
   
           KASSERT(!(so->so_state & SS_NOFDREF), ("soclose: SS_NOFDREF on enter"));
   
           CURVNET_SET(so->so_vnet);
           funsetown(&so->so_sigio);
           if (so->so_state & SS_ISCONNECTED) {
                   if ((so->so_state & SS_ISDISCONNECTING) == 0) {
                           error = sodisconnect(so);
                           if (error) {
                                   if (error == ENOTCONN)
                                           error = 0;
                                   goto drop;
                           }
                   }
                   if (so->so_options & SO_LINGER) {
                           if ((so->so_state & SS_ISDISCONNECTING) &&
                               (so->so_state & SS_NBIO))
                                   goto drop;
                           while (so->so_state & SS_ISCONNECTED) {
                                   error = tsleep(&so->so_timeo,
                                       PSOCK | PCATCH, "soclos", so->so_linger * hz);
                                   if (error)
                                           break;
                           }
                   }
           }
   
   drop:
           if (so->so_proto->pr_usrreqs->pru_close != NULL)
                   (*so->so_proto->pr_usrreqs->pru_close)(so);
           if (so->so_options & SO_ACCEPTCONN) {
                   struct socket *sp;
                   ACCEPT_LOCK();
                   while ((sp = TAILQ_FIRST(&so->so_incomp)) != NULL) {
                           TAILQ_REMOVE(&so->so_incomp, sp, so_list);
                           so->so_incqlen--;
                           sp->so_qstate &= ~SQ_INCOMP;
                           sp->so_head = NULL;
                           ACCEPT_UNLOCK();
                           soabort(sp);
                           ACCEPT_LOCK();
                   }
                   while ((sp = TAILQ_FIRST(&so->so_comp)) != NULL) {
                           TAILQ_REMOVE(&so->so_comp, sp, so_list);
                           so->so_qlen--;
                           sp->so_qstate &= ~SQ_COMP;
                           sp->so_head = NULL;
                           ACCEPT_UNLOCK();
                           soabort(sp);
                           ACCEPT_LOCK();
                   }
                   ACCEPT_UNLOCK();
           }
           ACCEPT_LOCK();
           SOCK_LOCK(so);
           KASSERT((so->so_state & SS_NOFDREF) == 0, ("soclose: NOFDREF"));
           so->so_state |= SS_NOFDREF;
           sorele(so);
           CURVNET_RESTORE();
           return (error);
   }
   
   /*
    * soabort() is used to abruptly tear down a connection, such as when a
    * resource limit is reached (listen queue depth exceeded), or if a listen
    * socket is closed while there are sockets waiting to be accepted.
    *
    * This interface is tricky, because it is called on an unreferenced socket,
    * and must be called only by a thread that has actually removed the socket
    * from the listen queue it was on, or races with other threads are risked.
    *
    * This interface will call into the protocol code, so must not be called
    * with any socket locks held.  Protocols do call it while holding their own
    * recursible protocol mutexes, but this is something that should be subject
    * to review in the future.
    */
   void
   soabort(struct socket *so)
   {
   
           /*
            * In as much as is possible, assert that no references to this
            * socket are held.  This is not quite the same as asserting that the
            * current thread is responsible for arranging for no references, but
            * is as close as we can get for now.
            */
           KASSERT(so->so_count == 0, ("soabort: so_count"));
           KASSERT((so->so_state & SS_PROTOREF) == 0, ("soabort: SS_PROTOREF"));
           KASSERT(so->so_state & SS_NOFDREF, ("soabort: !SS_NOFDREF"));
           KASSERT((so->so_state & SQ_COMP) == 0, ("soabort: SQ_COMP"));
           KASSERT((so->so_state & SQ_INCOMP) == 0, ("soabort: SQ_INCOMP"));
           VNET_SO_ASSERT(so);
   
           if (so->so_proto->pr_usrreqs->pru_abort != NULL)
                   (*so->so_proto->pr_usrreqs->pru_abort)(so);
           ACCEPT_LOCK();
           SOCK_LOCK(so);
           sofree(so);
   }
   
   int
   soaccept(struct socket *so, struct sockaddr **nam)
   {
           int error;
   
           SOCK_LOCK(so);
           KASSERT((so->so_state & SS_NOFDREF) != 0, ("soaccept: !NOFDREF"));
           so->so_state &= ~SS_NOFDREF;
           SOCK_UNLOCK(so);
   
           CURVNET_SET(so->so_vnet);
           error = (*so->so_proto->pr_usrreqs->pru_accept)(so, nam);
           CURVNET_RESTORE();
           return (error);
   }
   
   int
   soconnect(struct socket *so, struct sockaddr *nam, struct thread *td)
   {
           int error;
   
           if (so->so_options & SO_ACCEPTCONN)
                   return (EOPNOTSUPP);
   
           CURVNET_SET(so->so_vnet);
           /*
            * If protocol is connection-based, can only connect once.
            * Otherwise, if connected, try to disconnect first.  This allows
            * user to disconnect by connecting to, e.g., a null address.
            */
           if (so->so_state & (SS_ISCONNECTED|SS_ISCONNECTING) &&
               ((so->so_proto->pr_flags & PR_CONNREQUIRED) ||
               (error = sodisconnect(so)))) {
                   error = EISCONN;
           } else {
                   /*
                    * Prevent accumulated error from previous connection from
                    * biting us.
                    */
                   so->so_error = 0;
                   error = (*so->so_proto->pr_usrreqs->pru_connect)(so, nam, td);
           }
           CURVNET_RESTORE();
   
           return (error);
   }
   
   int
   soconnect2(struct socket *so1, struct socket *so2)
   {
           int error;
   
           CURVNET_SET(so1->so_vnet);
           error = (*so1->so_proto->pr_usrreqs->pru_connect2)(so1, so2);
           CURVNET_RESTORE();
           return (error);
   }
   
   int
   sodisconnect(struct socket *so)
   {
           int error;
   
           if ((so->so_state & SS_ISCONNECTED) == 0)
                   return (ENOTCONN);
           if (so->so_state & SS_ISDISCONNECTING)
                   return (EALREADY);
           VNET_SO_ASSERT(so);
           error = (*so->so_proto->pr_usrreqs->pru_disconnect)(so);
           return (error);
   }
   
   #ifdef ZERO_COPY_SOCKETS
   struct so_zerocopy_stats{
           int size_ok;
           int align_ok;
           int found_ifp;
   };
   struct so_zerocopy_stats so_zerocp_stats = {0,0,0};
   #include <netinet/in.h>
   #include <net/route.h>
   #include <netinet/in_pcb.h>
   #include <vm/vm.h>
   #include <vm/vm_page.h>
   #include <vm/vm_object.h>
   
   /*
    * sosend_copyin() is only used if zero copy sockets are enabled.  Otherwise
    * sosend_dgram() and sosend_generic() use m_uiotombuf().
    * 
    * sosend_copyin() accepts a uio and prepares an mbuf chain holding part or
    * all of the data referenced by the uio.  If desired, it uses zero-copy.
    * *space will be updated to reflect data copied in.
    *
    * NB: If atomic I/O is requested, the caller must already have checked that
    * space can hold resid bytes.
    *
    * NB: In the event of an error, the caller may need to free the partial
    * chain pointed to by *mpp.  The contents of both *uio and *space may be
    * modified even in the case of an error.
    */
   static int
   sosend_copyin(struct uio *uio, struct mbuf **retmp, int atomic, long *space,
       int flags)
   {
           struct mbuf *m, **mp, *top;
           long len, resid;
           int error;
   #ifdef ZERO_COPY_SOCKETS
           int cow_send;
   #endif
   
           *retmp = top = NULL;
           mp = &top;
           len = 0;
           resid = uio->uio_resid;
           error = 0;
           do {
   #ifdef ZERO_COPY_SOCKETS
                   cow_send = 0;
   #endif /* ZERO_COPY_SOCKETS */
                   if (resid >= MINCLSIZE) {
   #ifdef ZERO_COPY_SOCKETS
                           if (top == NULL) {
                                   m = m_gethdr(M_WAITOK, MT_DATA);
                                   m->m_pkthdr.len = 0;
                                   m->m_pkthdr.rcvif = NULL;
                           } else
                                   m = m_get(M_WAITOK, MT_DATA);
                           if (so_zero_copy_send &&
                               resid>=PAGE_SIZE &&
                               *space>=PAGE_SIZE &&
                               uio->uio_iov->iov_len>=PAGE_SIZE) {
                                   so_zerocp_stats.size_ok++;
                                   so_zerocp_stats.align_ok++;
                                   cow_send = socow_setup(m, uio);
                                   len = cow_send;
                           }
                           if (!cow_send) {
                                   m_clget(m, M_WAITOK);
                                   len = min(min(MCLBYTES, resid), *space);
                           }
   #else /* ZERO_COPY_SOCKETS */
                           if (top == NULL) {
                                   m = m_getcl(M_WAIT, MT_DATA, M_PKTHDR);
                                   m->m_pkthdr.len = 0;
                                   m->m_pkthdr.rcvif = NULL;
                           } else
                                   m = m_getcl(M_WAIT, MT_DATA, 0);
                           len = min(min(MCLBYTES, resid), *space);
   #endif /* ZERO_COPY_SOCKETS */
                   } else {
                           if (top == NULL) {
                                   m = m_gethdr(M_WAIT, MT_DATA);
                                   m->m_pkthdr.len = 0;
                                   m->m_pkthdr.rcvif = NULL;
   
                                   len = min(min(MHLEN, resid), *space);
                                   /*
                                    * For datagram protocols, leave room
                                    * for protocol headers in first mbuf.
                                    */
                                   if (atomic && m && len < MHLEN)
                                           MH_ALIGN(m, len);
                           } else {
                                   m = m_get(M_WAIT, MT_DATA);
                                   len = min(min(MLEN, resid), *space);
                           }
                   }
                   if (m == NULL) {
                           error = ENOBUFS;
                           goto out;
                   }
   
                   *space -= len;
   #ifdef ZERO_COPY_SOCKETS
                   if (cow_send)
                           error = 0;
                   else
   #endif /* ZERO_COPY_SOCKETS */
                   error = uiomove(mtod(m, void *), (int)len, uio);
                   resid = uio->uio_resid;
                   m->m_len = len;
                   *mp = m;
                   top->m_pkthdr.len += len;
                   if (error)
                           goto out;
                   mp = &m->m_next;
                   if (resid <= 0) {
                           if (flags & MSG_EOR)
                                   top->m_flags |= M_EOR;
                           break;
                   }
           } while (*space > 0 && atomic);
   out:
           *retmp = top;
           return (error);
   }
   #endif /*ZERO_COPY_SOCKETS*/
   
   #define SBLOCKWAIT(f)   (((f) & MSG_DONTWAIT) ? 0 : SBL_WAIT)
   
   int
   sosend_dgram(struct socket *so, struct sockaddr *addr, struct uio *uio,
       struct mbuf *top, struct mbuf *control, int flags, struct thread *td)
   {
           long space, resid;
           int clen = 0, error, dontroute;
   #ifdef ZERO_COPY_SOCKETS
           int atomic = sosendallatonce(so) || top;
   #endif
   
           KASSERT(so->so_type == SOCK_DGRAM, ("sodgram_send: !SOCK_DGRAM"));
           KASSERT(so->so_proto->pr_flags & PR_ATOMIC,
               ("sodgram_send: !PR_ATOMIC"));
   
           if (uio != NULL)
                   resid = uio->uio_resid;
           else
                   resid = top->m_pkthdr.len;
           /*
            * In theory resid should be unsigned.  However, space must be
            * signed, as it might be less than 0 if we over-committed, and we
            * must use a signed comparison of space and resid.  On the other
            * hand, a negative resid causes us to loop sending 0-length
            * segments to the protocol.
           */
          if (resid < 0) {
                  error = EINVAL;
                  goto out;
          }
  
          dontroute =
              (flags & MSG_DONTROUTE) && (so->so_options & SO_DONTROUTE) == 0;
          if (td != NULL)
                  td->td_ru.ru_msgsnd++;
          if (control != NULL)
                  clen = control->m_len;
  
          SOCKBUF_LOCK(&so->so_snd);
          if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                  SOCKBUF_UNLOCK(&so->so_snd);
                  error = EPIPE;
                  goto out;
          }
          if (so->so_error) {
                  error = so->so_error;
                  so->so_error = 0;
                  SOCKBUF_UNLOCK(&so->so_snd);
                  goto out;
          }
          if ((so->so_state & SS_ISCONNECTED) == 0) {
                  /*
                   * `sendto' and `sendmsg' is allowed on a connection-based
                   * socket if it supports implied connect.  Return ENOTCONN if
                   * not connected and no address is supplied.
                   */
                  if ((so->so_proto->pr_flags & PR_CONNREQUIRED) &&
                      (so->so_proto->pr_flags & PR_IMPLOPCL) == 0) {
                          if ((so->so_state & SS_ISCONFIRMING) == 0 &&
                              !(resid == 0 && clen != 0)) {
                                  SOCKBUF_UNLOCK(&so->so_snd);
                                  error = ENOTCONN;
                                  goto out;
                          }
                  } else if (addr == NULL) {
                          if (so->so_proto->pr_flags & PR_CONNREQUIRED)
                                  error = ENOTCONN;
                          else
                                  error = EDESTADDRREQ;
                          SOCKBUF_UNLOCK(&so->so_snd);
                          goto out;
                  }
          }
  
          /*
           * Do we need MSG_OOB support in SOCK_DGRAM?  Signs here may be a
           * problem and need fixing.
           */
          space = sbspace(&so->so_snd);
          if (flags & MSG_OOB)
                  space += 1024;
          space -= clen;
          SOCKBUF_UNLOCK(&so->so_snd);
          if (resid > space) {
                  error = EMSGSIZE;
                  goto out;
          }
          if (uio == NULL) {
                  resid = 0;
                  if (flags & MSG_EOR)
                          top->m_flags |= M_EOR;
          } else {
  #ifdef ZERO_COPY_SOCKETS
                  error = sosend_copyin(uio, &top, atomic, &space, flags);
                  if (error)
                          goto out;
  #else
                  /*
                   * Copy the data from userland into a mbuf chain.
                   * If no data is to be copied in, a single empty mbuf
                   * is returned.
                   */
                  top = m_uiotombuf(uio, M_WAITOK, space, max_hdr,
                      (M_PKTHDR | ((flags & MSG_EOR) ? M_EOR : 0)));
                  if (top == NULL) {
                          error = EFAULT; /* only possible error */
                          goto out;
                  }
                  space -= resid - uio->uio_resid;
  #endif
                  resid = uio->uio_resid;
          }
          KASSERT(resid == 0, ("sosend_dgram: resid != 0"));
          /*
           * XXXRW: Frobbing SO_DONTROUTE here is even worse without sblock
           * than with.
           */
          if (dontroute) {
                  SOCK_LOCK(so);
                  so->so_options |= SO_DONTROUTE;
                  SOCK_UNLOCK(so);
          }
          /*
           * XXX all the SBS_CANTSENDMORE checks previously done could be out
           * of date.  We could have recieved a reset packet in an interrupt or
           * maybe we slept while doing page faults in uiomove() etc.  We could
           * probably recheck again inside the locking protection here, but
           * there are probably other places that this also happens.  We must
           * rethink this.
           */
          VNET_SO_ASSERT(so);
          error = (*so->so_proto->pr_usrreqs->pru_send)(so,
              (flags & MSG_OOB) ? PRUS_OOB :
          /*
           * If the user set MSG_EOF, the protocol understands this flag and
           * nothing left to send then use PRU_SEND_EOF instead of PRU_SEND.
           */
              ((flags & MSG_EOF) &&
               (so->so_proto->pr_flags & PR_IMPLOPCL) &&
               (resid <= 0)) ?
                  PRUS_EOF :
                  /* If there is more to send set PRUS_MORETOCOME */
                  (resid > 0 && space > 0) ? PRUS_MORETOCOME : 0,
                  top, addr, control, td);
          if (dontroute) {
                  SOCK_LOCK(so);
                  so->so_options &= ~SO_DONTROUTE;
                  SOCK_UNLOCK(so);
          }
          clen = 0;
          control = NULL;
          top = NULL;
  out:
          if (top != NULL)
                  m_freem(top);
          if (control != NULL)
                  m_freem(control);
          return (error);
  }
  
  /*
   * Send on a socket.  If send must go all at once and message is larger than
   * send buffering, then hard error.  Lock against other senders.  If must go
   * all at once and not enough room now, then inform user that this would
   * block and do nothing.  Otherwise, if nonblocking, send as much as
   * possible.  The data to be sent is described by "uio" if nonzero, otherwise
   * by the mbuf chain "top" (which must be null if uio is not).  Data provided
   * in mbuf chain must be small enough to send all at once.
   *
   * Returns nonzero on error, timeout or signal; callers must check for short
   * counts if EINTR/ERESTART are returned.  Data and control buffers are freed
   * on return.
   */
  int
  sosend_generic(struct socket *so, struct sockaddr *addr, struct uio *uio,
      struct mbuf *top, struct mbuf *control, int flags, struct thread *td)
  {
          long space, resid;
          int clen = 0, error, dontroute;
          int atomic = sosendallatonce(so) || top;
  
          if (uio != NULL)
                  resid = uio->uio_resid;
          else
                  resid = top->m_pkthdr.len;
          /*
           * In theory resid should be unsigned.  However, space must be
           * signed, as it might be less than 0 if we over-committed, and we
           * must use a signed comparison of space and resid.  On the other
           * hand, a negative resid causes us to loop sending 0-length
           * segments to the protocol.
           *
           * Also check to make sure that MSG_EOR isn't used on SOCK_STREAM
           * type sockets since that's an error.
           */
          if (resid < 0 || (so->so_type == SOCK_STREAM && (flags & MSG_EOR))) {
                  error = EINVAL;
                  goto out;
          }
  
          dontroute =
              (flags & MSG_DONTROUTE) && (so->so_options & SO_DONTROUTE) == 0 &&
              (so->so_proto->pr_flags & PR_ATOMIC);
          if (td != NULL)
                  td->td_ru.ru_msgsnd++;
          if (control != NULL)
                  clen = control->m_len;
  
          error = sblock(&so->so_snd, SBLOCKWAIT(flags));
          if (error)
                  goto out;
  
  restart:
          do {
                  SOCKBUF_LOCK(&so->so_snd);
                  if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                          SOCKBUF_UNLOCK(&so->so_snd);
                          error = EPIPE;
                          goto release;
                  }
                  if (so->so_error) {
                          error = so->so_error;
                          so->so_error = 0;
                          SOCKBUF_UNLOCK(&so->so_snd);
                          goto release;
                  }
                  if ((so->so_state & SS_ISCONNECTED) == 0) {
                          /*
                           * `sendto' and `sendmsg' is allowed on a connection-
                           * based socket if it supports implied connect.
                           * Return ENOTCONN if not connected and no address is
                           * supplied.
                           */
                          if ((so->so_proto->pr_flags & PR_CONNREQUIRED) &&
                              (so->so_proto->pr_flags & PR_IMPLOPCL) == 0) {
                                  if ((so->so_state & SS_ISCONFIRMING) == 0 &&
                                      !(resid == 0 && clen != 0)) {
                                          SOCKBUF_UNLOCK(&so->so_snd);
                                          error = ENOTCONN;
                                          goto release;
                                  }
                          } else if (addr == NULL) {
                                  SOCKBUF_UNLOCK(&so->so_snd);
                                  if (so->so_proto->pr_flags & PR_CONNREQUIRED)
                                          error = ENOTCONN;
                                  else
                                          error = EDESTADDRREQ;
                                  goto release;
                          }
                  }
                  space = sbspace(&so->so_snd);
                  if (flags & MSG_OOB)
                          space += 1024;
                  if ((atomic && resid > so->so_snd.sb_hiwat) ||
                      clen > so->so_snd.sb_hiwat) {
                          SOCKBUF_UNLOCK(&so->so_snd);
                          error = EMSGSIZE;
                          goto release;
                  }
                  if (space < resid + clen &&
                      (atomic || space < so->so_snd.sb_lowat || space < clen)) {
                          if ((so->so_state & SS_NBIO) || (flags & MSG_NBIO)) {
                                  SOCKBUF_UNLOCK(&so->so_snd);
                                  error = EWOULDBLOCK;
                                  goto release;
                          }
                          error = sbwait(&so->so_snd);
                          SOCKBUF_UNLOCK(&so->so_snd);
                          if (error)
                                  goto release;
                          goto restart;
                  }
                  SOCKBUF_UNLOCK(&so->so_snd);
                  space -= clen;
                  do {
                          if (uio == NULL) {
                                  resid = 0;
                                  if (flags & MSG_EOR)
                                          top->m_flags |= M_EOR;
                          } else {
  #ifdef ZERO_COPY_SOCKETS
                                  error = sosend_copyin(uio, &top, atomic,
                                      &space, flags);
                                  if (error != 0)
                                          goto release;
  #else
                                  /*
                                   * Copy the data from userland into a mbuf
                                   * chain.  If no data is to be copied in,
                                   * a single empty mbuf is returned.
                                   */
                                  top = m_uiotombuf(uio, M_WAITOK, space,
                                      (atomic ? max_hdr : 0),
                                      (atomic ? M_PKTHDR : 0) |
                                      ((flags & MSG_EOR) ? M_EOR : 0));
                                  if (top == NULL) {
                                          error = EFAULT; /* only possible error */
                                          goto release;
                                  }
                                  space -= resid - uio->uio_resid;
  #endif
                                  resid = uio->uio_resid;
                          }
                          if (dontroute) {
                                  SOCK_LOCK(so);
                                  so->so_options |= SO_DONTROUTE;
                                  SOCK_UNLOCK(so);
                          }
                          /*
                           * XXX all the SBS_CANTSENDMORE checks previously
                           * done could be out of date.  We could have recieved
                           * a reset packet in an interrupt or maybe we slept
                           * while doing page faults in uiomove() etc.  We
                           * could probably recheck again inside the locking
                           * protection here, but there are probably other
                           * places that this also happens.  We must rethink
                           * this.
                           */
                          VNET_SO_ASSERT(so);
                          error = (*so->so_proto->pr_usrreqs->pru_send)(so,
                              (flags & MSG_OOB) ? PRUS_OOB :
                          /*
                           * If the user set MSG_EOF, the protocol understands
                           * this flag and nothing left to send then use
                           * PRU_SEND_EOF instead of PRU_SEND.
                           */
                              ((flags & MSG_EOF) &&
                               (so->so_proto->pr_flags & PR_IMPLOPCL) &&
                               (resid <= 0)) ?
                                  PRUS_EOF :
                          /* If there is more to send set PRUS_MORETOCOME. */
                              (resid > 0 && space > 0) ? PRUS_MORETOCOME : 0,
                              top, addr, control, td);
                          if (dontroute) {
                                  SOCK_LOCK(so);
                                  so->so_options &= ~SO_DONTROUTE;
                                  SOCK_UNLOCK(so);
                          }
                          clen = 0;
                          control = NULL;
                          top = NULL;
                          if (error)
                                  goto release;
                  } while (resid && space > 0);
          } while (resid);
  
  release:
          sbunlock(&so->so_snd);
  out:
          if (top != NULL)
                  m_freem(top);
          if (control != NULL)
                  m_freem(control);
          return (error);
  }
  
  int
  sosend(struct socket *so, struct sockaddr *addr, struct uio *uio,
      struct mbuf *top, struct mbuf *control, int flags, struct thread *td)
  {
          int error;
  
          CURVNET_SET(so->so_vnet);
          error = so->so_proto->pr_usrreqs->pru_sosend(so, addr, uio, top,
              control, flags, td);
          CURVNET_RESTORE();
          return (error);
  }
  
  /*
   * The part of soreceive() that implements reading non-inline out-of-band
   * data from a socket.  For more complete comments, see soreceive(), from
   * which this code originated.
   *
   * Note that soreceive_rcvoob(), unlike the remainder of soreceive(), is
   * unable to return an mbuf chain to the caller.
   */
  static int
  soreceive_rcvoob(struct socket *so, struct uio *uio, int flags)
  {
          struct protosw *pr = so->so_proto;
          struct mbuf *m;
          int error;
  
          KASSERT(flags & MSG_OOB, ("soreceive_rcvoob: (flags & MSG_OOB) == 0"));
          VNET_SO_ASSERT(so);
  
          m = m_get(M_WAIT, MT_DATA);
          error = (*pr->pr_usrreqs->pru_rcvoob)(so, m, flags & MSG_PEEK);
          if (error)
                  goto bad;
          do {
  #ifdef ZERO_COPY_SOCKETS
                  if (so_zero_copy_receive) {
                          int disposable;
  
                          if ((m->m_flags & M_EXT)
                           && (m->m_ext.ext_type == EXT_DISPOSABLE))
                                  disposable = 1;
                          else
                                  disposable = 0;
  
                          error = uiomoveco(mtod(m, void *),
                                            min(uio->uio_resid, m->m_len),
                                            uio, disposable);
                  } else
  #endif /* ZERO_COPY_SOCKETS */
                  error = uiomove(mtod(m, void *),
                      (int) min(uio->uio_resid, m->m_len), uio);
                  m = m_free(m);
          } while (uio->uio_resid && error == 0 && m);
  bad:
          if (m != NULL)
                  m_freem(m);
          return (error);
  }
  
  /*
   * Following replacement or removal of the first mbuf on the first mbuf chain
   * of a socket buffer, push necessary state changes back into the socket
   * buffer so that other consumers see the values consistently.  'nextrecord'
   * is the callers locally stored value of the original value of
   * sb->sb_mb->m_nextpkt which must be restored when the lead mbuf changes.
   * NOTE: 'nextrecord' may be NULL.
   */
  static __inline void
  sockbuf_pushsync(struct sockbuf *sb, struct mbuf *nextrecord)
  {
  
          SOCKBUF_LOCK_ASSERT(sb);
          /*
           * First, update for the new value of nextrecord.  If necessary, make
           * it the first record.
           */
          if (sb->sb_mb != NULL)
                  sb->sb_mb->m_nextpkt = nextrecord;
          else
                  sb->sb_mb = nextrecord;
  
          /*
           * Now update any dependent socket buffer fields to reflect the new
           * state.  This is an expanded inline of SB_EMPTY_FIXUP(), with the
           * addition of a second clause that takes care of the case where
           * sb_mb has been updated, but remains the last record.
           */
          if (sb->sb_mb == NULL) {
                  sb->sb_mbtail = NULL;
                  sb->sb_lastrecord = NULL;
          } else if (sb->sb_mb->m_nextpkt == NULL)
                  sb->sb_lastrecord = sb->sb_mb;
  }
  
  
  /*
   * Implement receive operations on a socket.  We depend on the way that
   * records are added to the sockbuf by sbappend.  In particular, each record
   * (mbufs linked through m_next) must begin with an address if the protocol
   * so specifies, followed by an optional mbuf or mbufs containing ancillary
   * data, and then zero or more mbufs of data.  In order to allow parallelism
   * between network receive and copying to user space, as well as avoid
   * sleeping with a mutex held, we release the socket buffer mutex during the
   * user space copy.  Although the sockbuf is locked, new data may still be
   * appended, and thus we must maintain consistency of the sockbuf during that
   * time.
   *
   * The caller may receive the data as a single mbuf chain by supplying an
   * mbuf **mp0 for use in returning the chain.  The uio is then used only for
   * the count in uio_resid.
   */
  int
  soreceive_generic(struct socket *so, struct sockaddr **psa, struct uio *uio,
      struct mbuf **mp0, struct mbuf **controlp, int *flagsp)
  {
          struct mbuf *m, **mp;
          int flags, len, error, offset;
          struct protosw *pr = so->so_proto;
          struct mbuf *nextrecord;
          int moff, type = 0;
          int orig_resid = uio->uio_resid;
  
          mp = mp0;
          if (psa != NULL)
                  *psa = NULL;
          if (controlp != NULL)
                  *controlp = NULL;
          if (flagsp != NULL)
                  flags = *flagsp &~ MSG_EOR;
          else
                  flags = 0;
          if (flags & MSG_OOB)
                  return (soreceive_rcvoob(so, uio, flags));
          if (mp != NULL)
                  *mp = NULL;
          if ((pr->pr_flags & PR_WANTRCVD) && (so->so_state & SS_ISCONFIRMING)
              && uio->uio_resid) {
                  VNET_SO_ASSERT(so);
                  (*pr->pr_usrreqs->pru_rcvd)(so, 0);
          }
  
          error = sblock(&so->so_rcv, SBLOCKWAIT(flags));
          if (error)
                  return (error);
  
  restart:
          SOCKBUF_LOCK(&so->so_rcv);
          m = so->so_rcv.sb_mb;
          /*
           * If we have less data than requested, block awaiting more (subject
           * to any timeout) if:
           *   1. the current count is less than the low water mark, or
           *   2. MSG_WAITALL is set, and it is possible to do the entire
           *      receive operation at once if we block (resid <= hiwat).
           *   3. MSG_DONTWAIT is not set
           * If MSG_WAITALL is set but resid is larger than the receive buffer,
           * we have to do the receive in sections, and thus risk returning a
           * short count if a timeout or signal occurs after we start.
           */
          if (m == NULL || (((flags & MSG_DONTWAIT) == 0 &&
              so->so_rcv.sb_cc < uio->uio_resid) &&
              (so->so_rcv.sb_cc < so->so_rcv.sb_lowat ||
              ((flags & MSG_WAITALL) && uio->uio_resid <= so->so_rcv.sb_hiwat)) &&
              m->m_nextpkt == NULL && (pr->pr_flags & PR_ATOMIC) == 0)) {
                  KASSERT(m != NULL || !so->so_rcv.sb_cc,
                      ("receive: m == %p so->so_rcv.sb_cc == %u",
                      m, so->so_rcv.sb_cc));
                  if (so->so_error) {
                          if (m != NULL)
                                  goto dontblock;
                          error = so->so_error;
                          if ((flags & MSG_PEEK) == 0)
                                  so->so_error = 0;
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          goto release;
                  }
                  SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                  if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
                          if (m == NULL) {
                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                  goto release;
                          } else
                                  goto dontblock;
                  }
                  for (; m != NULL; m = m->m_next)
                          if (m->m_type == MT_OOBDATA  || (m->m_flags & M_EOR)) {
                                  m = so->so_rcv.sb_mb;
                                  goto dontblock;
                          }
                  if ((so->so_state & (SS_ISCONNECTED|SS_ISCONNECTING)) == 0 &&
                      (so->so_proto->pr_flags & PR_CONNREQUIRED)) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          error = ENOTCONN;
                          goto release;
                  }
                  if (uio->uio_resid == 0) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          goto release;
                  }
                  if ((so->so_state & SS_NBIO) ||
                      (flags & (MSG_DONTWAIT|MSG_NBIO))) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          error = EWOULDBLOCK;
                          goto release;
                  }
                  SBLASTRECORDCHK(&so->so_rcv);
                  SBLASTMBUFCHK(&so->so_rcv);
                  error = sbwait(&so->so_rcv);
                  SOCKBUF_UNLOCK(&so->so_rcv);
                  if (error)
                          goto release;
                  goto restart;
          }
  dontblock:
          /*
           * From this point onward, we maintain 'nextrecord' as a cache of the
           * pointer to the next record in the socket buffer.  We must keep the
           * various socket buffer pointers and local stack versions of the
           * pointers in sync, pushing out modifications before dropping the
           * socket buffer mutex, and re-reading them when picking it up.
           *
           * Otherwise, we will race with the network stack appending new data
           * or records onto the socket buffer by using inconsistent/stale
           * versions of the field, possibly resulting in socket buffer
           * corruption.
           *
           * By holding the high-level sblock(), we prevent simultaneous
           * readers from pulling off the front of the socket buffer.
           */
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
          if (uio->uio_td)
                  uio->uio_td->td_ru.ru_msgrcv++;
          KASSERT(m == so->so_rcv.sb_mb, ("soreceive: m != so->so_rcv.sb_mb"));
          SBLASTRECORDCHK(&so->so_rcv);
          SBLASTMBUFCHK(&so->so_rcv);
          nextrecord = m->m_nextpkt;
          if (pr->pr_flags & PR_ADDR) {
                  KASSERT(m->m_type == MT_SONAME,
                      ("m->m_type == %d", m->m_type));
                  orig_resid = 0;
                  if (psa != NULL)
                          *psa = sodupsockaddr(mtod(m, struct sockaddr *),
                              M_NOWAIT);
                  if (flags & MSG_PEEK) {
                          m = m->m_next;
                  } else {
                          sbfree(&so->so_rcv, m);
                          so->so_rcv.sb_mb = m_free(m);
                          m = so->so_rcv.sb_mb;
                          sockbuf_pushsync(&so->so_rcv, nextrecord);
                  }
          }
  
          /*
           * Process one or more MT_CONTROL mbufs present before any data mbufs
           * in the first mbuf chain on the socket buffer.  If MSG_PEEK, we
           * just copy the data; if !MSG_PEEK, we call into the protocol to
           * perform externalization (or freeing if controlp == NULL).
           */
          if (m != NULL && m->m_type == MT_CONTROL) {
                  struct mbuf *cm = NULL, *cmn;
                  struct mbuf **cme = &cm;
  
                  do {
                          if (flags & MSG_PEEK) {
                                  if (controlp != NULL) {
                                          *controlp = m_copy(m, 0, m->m_len);
                                          controlp = &(*controlp)->m_next;
                                  }
                                  m = m->m_next;
                          } else {
                                  sbfree(&so->so_rcv, m);
                                  so->so_rcv.sb_mb = m->m_next;
                                  m->m_next = NULL;
                                  *cme = m;
                                  cme = &(*cme)->m_next;
                                  m = so->so_rcv.sb_mb;
                          }
                  } while (m != NULL && m->m_type == MT_CONTROL);
                  if ((flags & MSG_PEEK) == 0)
                          sockbuf_pushsync(&so->so_rcv, nextrecord);
                  while (cm != NULL) {
                          cmn = cm->m_next;
                          cm->m_next = NULL;
                          if (pr->pr_domain->dom_externalize != NULL) {
                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                  VNET_SO_ASSERT(so);
                                  error = (*pr->pr_domain->dom_externalize)
                                      (cm, controlp);
                                  SOCKBUF_LOCK(&so->so_rcv);
                          } else if (controlp != NULL)
                                  *controlp = cm;
                          else
                                  m_freem(cm);
                          if (controlp != NULL) {
                                  orig_resid = 0;
                                  while (*controlp != NULL)
                                          controlp = &(*controlp)->m_next;
                          }
                          cm = cmn;
                  }
                  if (m != NULL)
                          nextrecord = so->so_rcv.sb_mb->m_nextpkt;
                  else
                          nextrecord = so->so_rcv.sb_mb;
                  orig_resid = 0;
          }
          if (m != NULL) {
                  if ((flags & MSG_PEEK) == 0) {
                          KASSERT(m->m_nextpkt == nextrecord,
                              ("soreceive: post-control, nextrecord !sync"));
                          if (nextrecord == NULL) {
                                  KASSERT(so->so_rcv.sb_mb == m,
                                      ("soreceive: post-control, sb_mb!=m"));
                                  KASSERT(so->so_rcv.sb_lastrecord == m,
                                      ("soreceive: post-control, lastrecord!=m"));
                          }
                  }
                  type = m->m_type;
                  if (type == MT_OOBDATA)
                          flags |= MSG_OOB;
          } else {
                  if ((flags & MSG_PEEK) == 0) {
                          KASSERT(so->so_rcv.sb_mb == nextrecord,
                              ("soreceive: sb_mb != nextrecord"));
                          if (so->so_rcv.sb_mb == NULL) {
                                  KASSERT(so->so_rcv.sb_lastrecord == NULL,
                                      ("soreceive: sb_lastercord != NULL"));
                          }
                  }
          }
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
          SBLASTRECORDCHK(&so->so_rcv);
          SBLASTMBUFCHK(&so->so_rcv);
  
          /*
           * Now continue to read any data mbufs off of the head of the socket
           * buffer until the read request is satisfied.  Note that 'type' is
           * used to store the type of any mbuf reads that have happened so far
           * such that soreceive() can stop reading if the type changes, which
           * causes soreceive() to return only one of regular data and inline
           * out-of-band data in a single socket receive operation.
           */
          moff = 0;
          offset = 0;
          while (m != NULL && uio->uio_resid > 0 && error == 0) {
                  /*
                   * If the type of mbuf has changed since the last mbuf
                   * examined ('type'), end the receive operation.
                   */
                  SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                  if (m->m_type == MT_OOBDATA) {
                          if (type != MT_OOBDATA)
                                  break;
                  } else if (type == MT_OOBDATA)
                          break;
                  else
                      KASSERT(m->m_type == MT_DATA,
                          ("m->m_type == %d", m->m_type));
                  so->so_rcv.sb_state &= ~SBS_RCVATMARK;
                  len = uio->uio_resid;
                  if (so->so_oobmark && len > so->so_oobmark - offset)
                          len = so->so_oobmark - offset;
                  if (len > m->m_len - moff)
                          len = m->m_len - moff;
                  /*
                   * If mp is set, just pass back the mbufs.  Otherwise copy
                   * them out via the uio, then free.  Sockbuf must be
                   * consistent here (points to current mbuf, it points to next
                   * record) when we drop priority; we must note any additions
                   * to the sockbuf when we block interrupts again.
                   */
                  if (mp == NULL) {
                          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                          SBLASTRECORDCHK(&so->so_rcv);
                          SBLASTMBUFCHK(&so->so_rcv);
                          SOCKBUF_UNLOCK(&so->so_rcv);
  #ifdef ZERO_COPY_SOCKETS
                          if (so_zero_copy_receive) {
                                  int disposable;
  
                                  if ((m->m_flags & M_EXT)
                                   && (m->m_ext.ext_type == EXT_DISPOSABLE))
                                          disposable = 1;
                                  else
                                          disposable = 0;
  
                                  error = uiomoveco(mtod(m, char *) + moff,
                                                    (int)len, uio,
                                                    disposable);
                          } else
  #endif /* ZERO_COPY_SOCKETS */
                          error = uiomove(mtod(m, char *) + moff, (int)len, uio);
                          SOCKBUF_LOCK(&so->so_rcv);
                          if (error) {
                                  /*
                                   * The MT_SONAME mbuf has already been removed
                                   * from the record, so it is necessary to
                                   * remove the data mbufs, if any, to preserve
                                   * the invariant in the case of PR_ADDR that
                                   * requires MT_SONAME mbufs at the head of
                                   * each record.
                                   */
                                  if (m && pr->pr_flags & PR_ATOMIC &&
                                      ((flags & MSG_PEEK) == 0))
                                          (void)sbdroprecord_locked(&so->so_rcv);
                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                  goto release;
                          }
                  } else
                          uio->uio_resid -= len;
                  SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                  if (len == m->m_len - moff) {
                          if (m->m_flags & M_EOR)
                                  flags |= MSG_EOR;
                          if (flags & MSG_PEEK) {
                                  m = m->m_next;
                                  moff = 0;
                          } else {
                                  nextrecord = m->m_nextpkt;
                                  sbfree(&so->so_rcv, m);
                                  if (mp != NULL) {
                                          *mp = m;
                                          mp = &m->m_next;
                                          so->so_rcv.sb_mb = m = m->m_next;
                                          *mp = NULL;
                                  } else {
                                          so->so_rcv.sb_mb = m_free(m);
                                          m = so->so_rcv.sb_mb;
                                  }
                                  sockbuf_pushsync(&so->so_rcv, nextrecord);
                                  SBLASTRECORDCHK(&so->so_rcv);
                                  SBLASTMBUFCHK(&so->so_rcv);
                          }
                  } else {
                          if (flags & MSG_PEEK)
                                  moff += len;
                          else {
                                  if (mp != NULL) {
                                          int copy_flag;
  
                                          if (flags & MSG_DONTWAIT)
                                                  copy_flag = M_DONTWAIT;
                                          else
                                                  copy_flag = M_WAIT;
                                          if (copy_flag == M_WAIT)
                                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                          *mp = m_copym(m, 0, len, copy_flag);
                                          if (copy_flag == M_WAIT)
                                                  SOCKBUF_LOCK(&so->so_rcv);
                                          if (*mp == NULL) {
                                                  /*
                                                   * m_copym() couldn't
                                                   * allocate an mbuf.  Adjust
                                                   * uio_resid back (it was
                                                   * adjusted down by len
                                                   * bytes, which we didn't end
                                                   * up "copying" over).
                                                   */
                                                  uio->uio_resid += len;
                                                  break;
                                          }
                                  }
                                  m->m_data += len;
                                  m->m_len -= len;
                                  so->so_rcv.sb_cc -= len;
                          }
                  }
                  SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                  if (so->so_oobmark) {
                          if ((flags & MSG_PEEK) == 0) {
                                  so->so_oobmark -= len;
                                  if (so->so_oobmark == 0) {
                                          so->so_rcv.sb_state |= SBS_RCVATMARK;
                                          break;
                                  }
                          } else {
                                  offset += len;
                                  if (offset == so->so_oobmark)
                                          break;
                          }
                  }
                  if (flags & MSG_EOR)
                          break;
                  /*
                   * If the MSG_WAITALL flag is set (for non-atomic socket), we
                   * must not quit until "uio->uio_resid == 0" or an error
                   * termination.  If a signal/timeout occurs, return with a
                   * short count but without error.  Keep sockbuf locked
                   * against other readers.
                   */
                  while (flags & MSG_WAITALL && m == NULL && uio->uio_resid > 0 &&
                      !sosendallatonce(so) && nextrecord == NULL) {
                          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
                          if (so->so_error || so->so_rcv.sb_state & SBS_CANTRCVMORE)
                                  break;
                          /*
                           * Notify the protocol that some data has been
                           * drained before blocking.
                           */
                          if (pr->pr_flags & PR_WANTRCVD) {
                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                  VNET_SO_ASSERT(so);
                                  (*pr->pr_usrreqs->pru_rcvd)(so, flags);
                                  SOCKBUF_LOCK(&so->so_rcv);
                          }
                          SBLASTRECORDCHK(&so->so_rcv);
                          SBLASTMBUFCHK(&so->so_rcv);
                          /*
                           * We could receive some data while was notifying
                           * the protocol. Skip blocking in this case.
                           */
                          if (so->so_rcv.sb_mb == NULL) {
                                  error = sbwait(&so->so_rcv);
                                  if (error) {
                                          SOCKBUF_UNLOCK(&so->so_rcv);
                                          goto release;
                                  }
                          }
                          m = so->so_rcv.sb_mb;
                          if (m != NULL)
                                  nextrecord = m->m_nextpkt;
                  }
          }
  
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
          if (m != NULL && pr->pr_flags & PR_ATOMIC) {
                  flags |= MSG_TRUNC;
                  if ((flags & MSG_PEEK) == 0)
                          (void) sbdroprecord_locked(&so->so_rcv);
          }
          if ((flags & MSG_PEEK) == 0) {
                  if (m == NULL) {
                          /*
                           * First part is an inline SB_EMPTY_FIXUP().  Second
                           * part makes sure sb_lastrecord is up-to-date if
                           * there is still data in the socket buffer.
                           */
                          so->so_rcv.sb_mb = nextrecord;
                          if (so->so_rcv.sb_mb == NULL) {
                                  so->so_rcv.sb_mbtail = NULL;
                                  so->so_rcv.sb_lastrecord = NULL;
                          } else if (nextrecord->m_nextpkt == NULL)
                                  so->so_rcv.sb_lastrecord = nextrecord;
                  }
                  SBLASTRECORDCHK(&so->so_rcv);
                  SBLASTMBUFCHK(&so->so_rcv);
                  /*
                   * If soreceive() is being done from the socket callback,
                   * then don't need to generate ACK to peer to update window,
                   * since ACK will be generated on return to TCP.
                   */
                  if (!(flags & MSG_SOCALLBCK) &&
                      (pr->pr_flags & PR_WANTRCVD)) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          VNET_SO_ASSERT(so);
                          (*pr->pr_usrreqs->pru_rcvd)(so, flags);
                          SOCKBUF_LOCK(&so->so_rcv);
                  }
          }
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
          if (orig_resid == uio->uio_resid && orig_resid &&
              (flags & MSG_EOR) == 0 && (so->so_rcv.sb_state & SBS_CANTRCVMORE) == 0) {
                  SOCKBUF_UNLOCK(&so->so_rcv);
                  goto restart;
          }
          SOCKBUF_UNLOCK(&so->so_rcv);
  
          if (flagsp != NULL)
                  *flagsp |= flags;
  release:
          sbunlock(&so->so_rcv);
          return (error);
  }
  
  /*
   * Optimized version of soreceive() for stream (TCP) sockets.
   */
  int
  soreceive_stream(struct socket *so, struct sockaddr **psa, struct uio *uio,
      struct mbuf **mp0, struct mbuf **controlp, int *flagsp)
  {
          int len = 0, error = 0, flags, oresid;
          struct sockbuf *sb;
          struct mbuf *m, *n = NULL;
  
          /* We only do stream sockets. */
          if (so->so_type != SOCK_STREAM)
                  return (EINVAL);
          if (psa != NULL)
                  *psa = NULL;
          if (controlp != NULL)
                  return (EINVAL);
          if (flagsp != NULL)
                  flags = *flagsp &~ MSG_EOR;
          else
                  flags = 0;
          if (flags & MSG_OOB)
                  return (soreceive_rcvoob(so, uio, flags));
          if (mp0 != NULL)
                  *mp0 = NULL;
  
          sb = &so->so_rcv;
  
          /* Prevent other readers from entering the socket. */
          error = sblock(sb, SBLOCKWAIT(flags));
          if (error)
                  goto out;
          SOCKBUF_LOCK(sb);
  
          /* Easy one, no space to copyout anything. */
          if (uio->uio_resid == 0) {
                  error = EINVAL;
                  goto out;
          }
          oresid = uio->uio_resid;
  
          /* We will never ever get anything unless we are connected. */
          if (!(so->so_state & (SS_ISCONNECTED|SS_ISDISCONNECTED))) {
                  /* When disconnecting there may be still some data left. */
                  if (sb->sb_cc > 0)
                          goto deliver;
                  if (!(so->so_state & SS_ISDISCONNECTED))
                          error = ENOTCONN;
                  goto out;
          }
  
          /* Socket buffer is empty and we shall not block. */
          if (sb->sb_cc == 0 &&
              ((sb->sb_flags & SS_NBIO) || (flags & (MSG_DONTWAIT|MSG_NBIO)))) {
                  error = EAGAIN;
                  goto out;
          }
  
  restart:
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
  
          /* Abort if socket has reported problems. */
          if (so->so_error) {
                  if (sb->sb_cc > 0)
                          goto deliver;
                  if (oresid > uio->uio_resid)
                          goto out;
                  error = so->so_error;
                  if (!(flags & MSG_PEEK))
                          so->so_error = 0;
                  goto out;
          }
  
          /* Door is closed.  Deliver what is left, if any. */
          if (sb->sb_state & SBS_CANTRCVMORE) {
                  if (sb->sb_cc > 0)
                          goto deliver;
                  else
                          goto out;
          }
  
          /* Socket buffer got some data that we shall deliver now. */
          if (sb->sb_cc > 0 && !(flags & MSG_WAITALL) &&
              ((sb->sb_flags & SS_NBIO) ||
               (flags & (MSG_DONTWAIT|MSG_NBIO)) ||
               sb->sb_cc >= sb->sb_lowat ||
               sb->sb_cc >= uio->uio_resid ||
               sb->sb_cc >= sb->sb_hiwat) ) {
                  goto deliver;
          }
  
          /* On MSG_WAITALL we must wait until all data or error arrives. */
          if ((flags & MSG_WAITALL) &&
              (sb->sb_cc >= uio->uio_resid || sb->sb_cc >= sb->sb_lowat))
                  goto deliver;
  
          /*
           * Wait and block until (more) data comes in.
           * NB: Drops the sockbuf lock during wait.
           */
          error = sbwait(sb);
          if (error)
                  goto out;
          goto restart;
  
  deliver:
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
          KASSERT(sb->sb_cc > 0, ("%s: sockbuf empty", __func__));
          KASSERT(sb->sb_mb != NULL, ("%s: sb_mb == NULL", __func__));
  
          /* Statistics. */
          if (uio->uio_td)
                  uio->uio_td->td_ru.ru_msgrcv++;
  
          /* Fill uio until full or current end of socket buffer is reached. */
          len = min(uio->uio_resid, sb->sb_cc);
          if (mp0 != NULL) {
                  /* Dequeue as many mbufs as possible. */
                  if (!(flags & MSG_PEEK) && len >= sb->sb_mb->m_len) {
                          for (*mp0 = m = sb->sb_mb;
                               m != NULL && m->m_len <= len;
                               m = m->m_next) {
                                  len -= m->m_len;
                                  uio->uio_resid -= m->m_len;
                                  sbfree(sb, m);
                                  n = m;
                          }
                          sb->sb_mb = m;
                          if (sb->sb_mb == NULL)
                                  SB_EMPTY_FIXUP(sb);
                          n->m_next = NULL;
                  }
                  /* Copy the remainder. */
                  if (len > 0) {
                          KASSERT(sb->sb_mb != NULL,
                              ("%s: len > 0 && sb->sb_mb empty", __func__));
  
                          m = m_copym(sb->sb_mb, 0, len, M_DONTWAIT);
                          if (m == NULL)
                                  len = 0;        /* Don't flush data from sockbuf. */
                          else
                                  uio->uio_resid -= m->m_len;
                          if (*mp0 != NULL)
                                  n->m_next = m;
                          else
                                  *mp0 = m;
                          if (*mp0 == NULL) {
                                  error = ENOBUFS;
                                  goto out;
                          }
                  }
          } else {
                  /* NB: Must unlock socket buffer as uiomove may sleep. */
                  SOCKBUF_UNLOCK(sb);
                  error = m_mbuftouio(uio, sb->sb_mb, len);
                  SOCKBUF_LOCK(sb);
                  if (error)
                          goto out;
          }
          SBLASTRECORDCHK(sb);
          SBLASTMBUFCHK(sb);
  
          /*
           * Remove the delivered data from the socket buffer unless we
           * were only peeking.
           */
          if (!(flags & MSG_PEEK)) {
                  if (len > 0)
                          sbdrop_locked(sb, len);
  
                  /* Notify protocol that we drained some data. */
                  if ((so->so_proto->pr_flags & PR_WANTRCVD) &&
                      (((flags & MSG_WAITALL) && uio->uio_resid > 0) ||
                       !(flags & MSG_SOCALLBCK))) {
                          SOCKBUF_UNLOCK(sb);
                          VNET_SO_ASSERT(so);
                          (*so->so_proto->pr_usrreqs->pru_rcvd)(so, flags);
                          SOCKBUF_LOCK(sb);
                  }
          }
  
          /*
           * For MSG_WAITALL we may have to loop again and wait for
           * more data to come in.
           */
          if ((flags & MSG_WAITALL) && uio->uio_resid > 0)
                  goto restart;
  out:
          SOCKBUF_LOCK_ASSERT(sb);
          SBLASTRECORDCHK(sb);
          SBLASTMBUFCHK(sb);
          SOCKBUF_UNLOCK(sb);
          sbunlock(sb);
          return (error);
  }
  
  /*
   * Optimized version of soreceive() for simple datagram cases from userspace.
   * Unlike in the stream case, we're able to drop a datagram if copyout()
   * fails, and because we handle datagrams atomically, we don't need to use a
   * sleep lock to prevent I/O interlacing.
   */
  int
  soreceive_dgram(struct socket *so, struct sockaddr **psa, struct uio *uio,
      struct mbuf **mp0, struct mbuf **controlp, int *flagsp)
  {
          struct mbuf *m, *m2;
          int flags, len, error;
          struct protosw *pr = so->so_proto;
          struct mbuf *nextrecord;
  
          if (psa != NULL)
                  *psa = NULL;
          if (controlp != NULL)
                  *controlp = NULL;
          if (flagsp != NULL)
                  flags = *flagsp &~ MSG_EOR;
          else
                  flags = 0;
  
          /*
           * For any complicated cases, fall back to the full
           * soreceive_generic().
           */
          if (mp0 != NULL || (flags & MSG_PEEK) || (flags & MSG_OOB))
                  return (soreceive_generic(so, psa, uio, mp0, controlp,
                      flagsp));
  
          /*
           * Enforce restrictions on use.
           */
          KASSERT((pr->pr_flags & PR_WANTRCVD) == 0,
              ("soreceive_dgram: wantrcvd"));
          KASSERT(pr->pr_flags & PR_ATOMIC, ("soreceive_dgram: !atomic"));
          KASSERT((so->so_rcv.sb_state & SBS_RCVATMARK) == 0,
              ("soreceive_dgram: SBS_RCVATMARK"));
          KASSERT((so->so_proto->pr_flags & PR_CONNREQUIRED) == 0,
              ("soreceive_dgram: P_CONNREQUIRED"));
  
          /*
           * Loop blocking while waiting for a datagram.
           */
          SOCKBUF_LOCK(&so->so_rcv);
          while ((m = so->so_rcv.sb_mb) == NULL) {
                  KASSERT(so->so_rcv.sb_cc == 0,
                      ("soreceive_dgram: sb_mb NULL but sb_cc %u",
                      so->so_rcv.sb_cc));
                  if (so->so_error) {
                          error = so->so_error;
                          so->so_error = 0;
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          return (error);
                  }
                  if (so->so_rcv.sb_state & SBS_CANTRCVMORE ||
                      uio->uio_resid == 0) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          return (0);
                  }
                  if ((so->so_state & SS_NBIO) ||
                      (flags & (MSG_DONTWAIT|MSG_NBIO))) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          return (EWOULDBLOCK);
                  }
                  SBLASTRECORDCHK(&so->so_rcv);
                  SBLASTMBUFCHK(&so->so_rcv);
                  error = sbwait(&so->so_rcv);
                  if (error) {
                          SOCKBUF_UNLOCK(&so->so_rcv);
                          return (error);
                  }
          }
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
  
          if (uio->uio_td)
                  uio->uio_td->td_ru.ru_msgrcv++;
          SBLASTRECORDCHK(&so->so_rcv);
          SBLASTMBUFCHK(&so->so_rcv);
          nextrecord = m->m_nextpkt;
          if (nextrecord == NULL) {
                  KASSERT(so->so_rcv.sb_lastrecord == m,
                      ("soreceive_dgram: lastrecord != m"));
          }
  
          KASSERT(so->so_rcv.sb_mb->m_nextpkt == nextrecord,
              ("soreceive_dgram: m_nextpkt != nextrecord"));
  
          /*
           * Pull 'm' and its chain off the front of the packet queue.
           */
          so->so_rcv.sb_mb = NULL;
          sockbuf_pushsync(&so->so_rcv, nextrecord);
  
          /*
           * Walk 'm's chain and free that many bytes from the socket buffer.
           */
          for (m2 = m; m2 != NULL; m2 = m2->m_next)
                  sbfree(&so->so_rcv, m2);
  
          /*
           * Do a few last checks before we let go of the lock.
           */
          SBLASTRECORDCHK(&so->so_rcv);
          SBLASTMBUFCHK(&so->so_rcv);
          SOCKBUF_UNLOCK(&so->so_rcv);
  
          if (pr->pr_flags & PR_ADDR) {
                  KASSERT(m->m_type == MT_SONAME,
                      ("m->m_type == %d", m->m_type));
                  if (psa != NULL)
                          *psa = sodupsockaddr(mtod(m, struct sockaddr *),
                              M_NOWAIT);
                  m = m_free(m);
          }
          if (m == NULL) {
                  /* XXXRW: Can this happen? */
                  return (0);
          }
  
          /*
           * Packet to copyout() is now in 'm' and it is disconnected from the
           * queue.
           *
           * Process one or more MT_CONTROL mbufs present before any data mbufs
           * in the first mbuf chain on the socket buffer.  We call into the
           * protocol to perform externalization (or freeing if controlp ==
           * NULL).
           */
          if (m->m_type == MT_CONTROL) {
                  struct mbuf *cm = NULL, *cmn;
                  struct mbuf **cme = &cm;
  
                  do {
                          m2 = m->m_next;
                          m->m_next = NULL;
                          *cme = m;
                          cme = &(*cme)->m_next;
                          m = m2;
                  } while (m != NULL && m->m_type == MT_CONTROL);
                  while (cm != NULL) {
                          cmn = cm->m_next;
                          cm->m_next = NULL;
                          if (pr->pr_domain->dom_externalize != NULL) {
                                  error = (*pr->pr_domain->dom_externalize)
                                      (cm, controlp);
                          } else if (controlp != NULL)
                                  *controlp = cm;
                          else
                                  m_freem(cm);
                          if (controlp != NULL) {
                                  while (*controlp != NULL)
                                          controlp = &(*controlp)->m_next;
                          }
                          cm = cmn;
                  }
          }
          KASSERT(m->m_type == MT_DATA, ("soreceive_dgram: !data"));
  
          while (m != NULL && uio->uio_resid > 0) {
                  len = uio->uio_resid;
                  if (len > m->m_len)
                          len = m->m_len;
                  error = uiomove(mtod(m, char *), (int)len, uio);
                  if (error) {
                          m_freem(m);
                          return (error);
                  }
                  if (len == m->m_len)
                          m = m_free(m);
                  else {
                          m->m_data += len;
                          m->m_len -= len;
                  }
          }
          if (m != NULL)
                  flags |= MSG_TRUNC;
          m_freem(m);
          if (flagsp != NULL)
                  *flagsp |= flags;
          return (0);
  }
  
  int
  soreceive(struct socket *so, struct sockaddr **psa, struct uio *uio,
      struct mbuf **mp0, struct mbuf **controlp, int *flagsp)
  {
          int error;
  
          CURVNET_SET(so->so_vnet);
          error = (so->so_proto->pr_usrreqs->pru_soreceive(so, psa, uio, mp0,
              controlp, flagsp));
          CURVNET_RESTORE();
          return (error);
  }
  
  int
  soshutdown(struct socket *so, int how)
  {
          struct protosw *pr = so->so_proto;
          int error;
  
          if (!(how == SHUT_RD || how == SHUT_WR || how == SHUT_RDWR))
                  return (EINVAL);
  
          CURVNET_SET(so->so_vnet);
          if (pr->pr_usrreqs->pru_flush != NULL) {
                  (*pr->pr_usrreqs->pru_flush)(so, how);
          }
          if (how != SHUT_WR)
                  sorflush(so);
          if (how != SHUT_RD) {
                  error = (*pr->pr_usrreqs->pru_shutdown)(so);
                  CURVNET_RESTORE();
                  return (error);
          }
          CURVNET_RESTORE();
          return (0);
  }
  
  void
  sorflush(struct socket *so)
  {
          struct sockbuf *sb = &so->so_rcv;
          struct protosw *pr = so->so_proto;
          struct sockbuf asb;
  
          VNET_SO_ASSERT(so);
  
          /*
           * In order to avoid calling dom_dispose with the socket buffer mutex
           * held, and in order to generally avoid holding the lock for a long
           * time, we make a copy of the socket buffer and clear the original
           * (except locks, state).  The new socket buffer copy won't have
           * initialized locks so we can only call routines that won't use or
           * assert those locks.
           *
           * Dislodge threads currently blocked in receive and wait to acquire
           * a lock against other simultaneous readers before clearing the
           * socket buffer.  Don't let our acquire be interrupted by a signal
           * despite any existing socket disposition on interruptable waiting.
           */
          socantrcvmore(so);
          (void) sblock(sb, SBL_WAIT | SBL_NOINTR);
  
          /*
           * Invalidate/clear most of the sockbuf structure, but leave selinfo
           * and mutex data unchanged.
           */
          SOCKBUF_LOCK(sb);
          bzero(&asb, offsetof(struct sockbuf, sb_startzero));
          bcopy(&sb->sb_startzero, &asb.sb_startzero,
              sizeof(*sb) - offsetof(struct sockbuf, sb_startzero));
          bzero(&sb->sb_startzero,
              sizeof(*sb) - offsetof(struct sockbuf, sb_startzero));
          SOCKBUF_UNLOCK(sb);
          sbunlock(sb);
  
          /*
           * Dispose of special rights and flush the socket buffer.  Don't call
           * any unsafe routines (that rely on locks being initialized) on asb.
           */
          if (pr->pr_flags & PR_RIGHTS && pr->pr_domain->dom_dispose != NULL)
                  (*pr->pr_domain->dom_dispose)(asb.sb_mb);
          sbrelease_internal(&asb, so);
  }
  
  /*
   * Perhaps this routine, and sooptcopyout(), below, ought to come in an
   * additional variant to handle the case where the option value needs to be
   * some kind of integer, but not a specific size.  In addition to their use
   * here, these functions are also called by the protocol-level pr_ctloutput()
   * routines.
   */
  int
  sooptcopyin(struct sockopt *sopt, void *buf, size_t len, size_t minlen)
  {
          size_t  valsize;
  
          /*
           * If the user gives us more than we wanted, we ignore it, but if we
           * don't get the minimum length the caller wants, we return EINVAL.
           * On success, sopt->sopt_valsize is set to however much we actually
           * retrieved.
           */
          if ((valsize = sopt->sopt_valsize) < minlen)
                  return EINVAL;
          if (valsize > len)
                  sopt->sopt_valsize = valsize = len;
  
          if (sopt->sopt_td != NULL)
                  return (copyin(sopt->sopt_val, buf, valsize));
  
          bcopy(sopt->sopt_val, buf, valsize);
          return (0);
  }
  
  /*
   * Kernel version of setsockopt(2).
   *
   * XXX: optlen is size_t, not socklen_t
   */
  int
  so_setsockopt(struct socket *so, int level, int optname, void *optval,
      size_t optlen)
  {
          struct sockopt sopt;
  
          sopt.sopt_level = level;
          sopt.sopt_name = optname;
          sopt.sopt_dir = SOPT_SET;
          sopt.sopt_val = optval;
          sopt.sopt_valsize = optlen;
          sopt.sopt_td = NULL;
          return (sosetopt(so, &sopt));
  }
  
  int
  sosetopt(struct socket *so, struct sockopt *sopt)
  {
          int     error, optval;
          struct  linger l;
          struct  timeval tv;
          u_long  val;
  #ifdef MAC
          struct mac extmac;
  #endif
  
          CURVNET_SET(so->so_vnet);
          error = 0;
          if (sopt->sopt_level != SOL_SOCKET) {
                  if (so->so_proto && so->so_proto->pr_ctloutput) {
                          error = (*so->so_proto->pr_ctloutput)(so, sopt);
                          CURVNET_RESTORE();
                          return (error);
                  }
                  error = ENOPROTOOPT;
          } else {
                  switch (sopt->sopt_name) {
  #ifdef INET
                  case SO_ACCEPTFILTER:
                          error = do_setopt_accept_filter(so, sopt);
                          if (error)
                                  goto bad;
                          break;
  #endif
                  case SO_LINGER:
                          error = sooptcopyin(sopt, &l, sizeof l, sizeof l);
                          if (error)
                                  goto bad;
  
                          SOCK_LOCK(so);
                          so->so_linger = l.l_linger;
                          if (l.l_onoff)
                                  so->so_options |= SO_LINGER;
                          else
                                  so->so_options &= ~SO_LINGER;
                          SOCK_UNLOCK(so);
                          break;
  
                  case SO_DEBUG:
                  case SO_KEEPALIVE:
                  case SO_DONTROUTE:
                  case SO_USELOOPBACK:
                  case SO_BROADCAST:
                  case SO_REUSEADDR:
                  case SO_REUSEPORT:
                  case SO_OOBINLINE:
                  case SO_TIMESTAMP:
                  case SO_BINTIME:
                  case SO_NOSIGPIPE:
                  case SO_NO_DDP:
                  case SO_NO_OFFLOAD:
                          error = sooptcopyin(sopt, &optval, sizeof optval,
                                              sizeof optval);
                          if (error)
                                  goto bad;
                          SOCK_LOCK(so);
                          if (optval)
                                  so->so_options |= sopt->sopt_name;
                          else
                                  so->so_options &= ~sopt->sopt_name;
                          SOCK_UNLOCK(so);
                          break;
  
                  case SO_SETFIB:
                          error = sooptcopyin(sopt, &optval, sizeof optval,
                                              sizeof optval);
                          if (optval < 0 || optval >= rt_numfibs) {
                                  error = EINVAL;
                                  goto bad;
                          }
                          if (so->so_proto != NULL &&
                             ((so->so_proto->pr_domain->dom_family == PF_INET) ||
                             (so->so_proto->pr_domain->dom_family == PF_ROUTE))) {
                                  so->so_fibnum = optval;
                                  /* Note: ignore error */
                                  if (so->so_proto->pr_ctloutput)
                                          (*so->so_proto->pr_ctloutput)(so, sopt);
                          } else {
                                  so->so_fibnum = 0;
                          }
                          break;
                  case SO_SNDBUF:
                  case SO_RCVBUF:
                  case SO_SNDLOWAT:
                  case SO_RCVLOWAT:
                          error = sooptcopyin(sopt, &optval, sizeof optval,
                                              sizeof optval);
                          if (error)
                                  goto bad;
  
                          /*
                           * Values < 1 make no sense for any of these options,
                           * so disallow them.
                           */
                          if (optval < 1) {
                                  error = EINVAL;
                                  goto bad;
                          }
  
                          switch (sopt->sopt_name) {
                          case SO_SNDBUF:
                          case SO_RCVBUF:
                                  if (sbreserve(sopt->sopt_name == SO_SNDBUF ?
                                      &so->so_snd : &so->so_rcv, (u_long)optval,
                                      so, curthread) == 0) {
                                          error = ENOBUFS;
                                          goto bad;
                                  }
                                  (sopt->sopt_name == SO_SNDBUF ? &so->so_snd :
                                      &so->so_rcv)->sb_flags &= ~SB_AUTOSIZE;
                                  break;
  
                          /*
                           * Make sure the low-water is never greater than the
                           * high-water.
                           */
                          case SO_SNDLOWAT:
                                  SOCKBUF_LOCK(&so->so_snd);
                                  so->so_snd.sb_lowat =
                                      (optval > so->so_snd.sb_hiwat) ?
                                      so->so_snd.sb_hiwat : optval;
                                  SOCKBUF_UNLOCK(&so->so_snd);
                                  break;
                          case SO_RCVLOWAT:
                                  SOCKBUF_LOCK(&so->so_rcv);
                                  so->so_rcv.sb_lowat =
                                      (optval > so->so_rcv.sb_hiwat) ?
                                      so->so_rcv.sb_hiwat : optval;
                                  SOCKBUF_UNLOCK(&so->so_rcv);
                                  break;
                          }
                          break;
  
                  case SO_SNDTIMEO:
                  case SO_RCVTIMEO:
  #ifdef COMPAT_FREEBSD32
                          if (SV_CURPROC_FLAG(SV_ILP32)) {
                                  struct timeval32 tv32;
  
                                  error = sooptcopyin(sopt, &tv32, sizeof tv32,
                                      sizeof tv32);
                                  CP(tv32, tv, tv_sec);
                                  CP(tv32, tv, tv_usec);
                          } else
  #endif
                                  error = sooptcopyin(sopt, &tv, sizeof tv,
                                      sizeof tv);
                          if (error)
                                  goto bad;
  
                          /* assert(hz > 0); */
                          if (tv.tv_sec < 0 || tv.tv_sec > INT_MAX / hz ||
                              tv.tv_usec < 0 || tv.tv_usec >= 1000000) {
                                  error = EDOM;
                                  goto bad;
                          }
                          /* assert(tick > 0); */
                          /* assert(ULONG_MAX - INT_MAX >= 1000000); */
                          val = (u_long)(tv.tv_sec * hz) + tv.tv_usec / tick;
                          if (val > INT_MAX) {
                                  error = EDOM;
                                  goto bad;
                          }
                          if (val == 0 && tv.tv_usec != 0)
                                  val = 1;
  
                          switch (sopt->sopt_name) {
                          case SO_SNDTIMEO:
                                  so->so_snd.sb_timeo = val;
                                  break;
                          case SO_RCVTIMEO:
                                  so->so_rcv.sb_timeo = val;
                                  break;
                          }
                          break;
  
                  case SO_LABEL:
  #ifdef MAC
                          error = sooptcopyin(sopt, &extmac, sizeof extmac,
                              sizeof extmac);
                          if (error)
                                  goto bad;
                          error = mac_setsockopt_label(sopt->sopt_td->td_ucred,
                              so, &extmac);
  #else
                          error = EOPNOTSUPP;
  #endif
                          break;
  
                  default:
                          error = ENOPROTOOPT;
                          break;
                  }
                  if (error == 0 && so->so_proto != NULL &&
                      so->so_proto->pr_ctloutput != NULL) {
                          (void) ((*so->so_proto->pr_ctloutput)
                                    (so, sopt));
                  }
          }
  bad:
          CURVNET_RESTORE();
          return (error);
  }
  
  /*
   * Helper routine for getsockopt.
   */
  int
  sooptcopyout(struct sockopt *sopt, const void *buf, size_t len)
  {
          int     error;
          size_t  valsize;
  
          error = 0;
  
          /*
           * Documented get behavior is that we always return a value, possibly
           * truncated to fit in the user's buffer.  Traditional behavior is
           * that we always tell the user precisely how much we copied, rather
           * than something useful like the total amount we had available for
           * her.  Note that this interface is not idempotent; the entire
           * answer must generated ahead of time.
           */
          valsize = min(len, sopt->sopt_valsize);
          sopt->sopt_valsize = valsize;
          if (sopt->sopt_val != NULL) {
                  if (sopt->sopt_td != NULL)
                          error = copyout(buf, sopt->sopt_val, valsize);
                  else
                          bcopy(buf, sopt->sopt_val, valsize);
          }
          return (error);
  }
  
  int
  sogetopt(struct socket *so, struct sockopt *sopt)
  {
          int     error, optval;
          struct  linger l;
          struct  timeval tv;
  #ifdef MAC
          struct mac extmac;
  #endif
  
          CURVNET_SET(so->so_vnet);
          error = 0;
          if (sopt->sopt_level != SOL_SOCKET) {
                  if (so->so_proto && so->so_proto->pr_ctloutput)
                          error = (*so->so_proto->pr_ctloutput)(so, sopt);
                  else
                          error = ENOPROTOOPT;
                  CURVNET_RESTORE();
                  return (error);
          } else {
                  switch (sopt->sopt_name) {
  #ifdef INET
                  case SO_ACCEPTFILTER:
                          error = do_getopt_accept_filter(so, sopt);
                          break;
  #endif
                  case SO_LINGER:
                          SOCK_LOCK(so);
                          l.l_onoff = so->so_options & SO_LINGER;
                          l.l_linger = so->so_linger;
                          SOCK_UNLOCK(so);
                          error = sooptcopyout(sopt, &l, sizeof l);
                          break;
  
                  case SO_USELOOPBACK:
                  case SO_DONTROUTE:
                  case SO_DEBUG:
                  case SO_KEEPALIVE:
                  case SO_REUSEADDR:
                  case SO_REUSEPORT:
                  case SO_BROADCAST:
                  case SO_OOBINLINE:
                  case SO_ACCEPTCONN:
                  case SO_TIMESTAMP:
                  case SO_BINTIME:
                  case SO_NOSIGPIPE:
                          optval = so->so_options & sopt->sopt_name;
  integer:
                          error = sooptcopyout(sopt, &optval, sizeof optval);
                          break;
  
                  case SO_TYPE:
                          optval = so->so_type;
                          goto integer;
  
                  case SO_ERROR:
                          SOCK_LOCK(so);
                          optval = so->so_error;
                          so->so_error = 0;
                          SOCK_UNLOCK(so);
                          goto integer;
  
                  case SO_SNDBUF:
                          optval = so->so_snd.sb_hiwat;
                          goto integer;
  
                  case SO_RCVBUF:
                          optval = so->so_rcv.sb_hiwat;
                          goto integer;
  
                  case SO_SNDLOWAT:
                          optval = so->so_snd.sb_lowat;
                          goto integer;
  
                  case SO_RCVLOWAT:
                          optval = so->so_rcv.sb_lowat;
                          goto integer;
  
                  case SO_SNDTIMEO:
                  case SO_RCVTIMEO:
                          optval = (sopt->sopt_name == SO_SNDTIMEO ?
                                    so->so_snd.sb_timeo : so->so_rcv.sb_timeo);
  
                          tv.tv_sec = optval / hz;
                          tv.tv_usec = (optval % hz) * tick;
  #ifdef COMPAT_FREEBSD32
                          if (SV_CURPROC_FLAG(SV_ILP32)) {
                                  struct timeval32 tv32;
  
                                  CP(tv, tv32, tv_sec);
                                  CP(tv, tv32, tv_usec);
                                  error = sooptcopyout(sopt, &tv32, sizeof tv32);
                          } else
  #endif
                                  error = sooptcopyout(sopt, &tv, sizeof tv);
                          break;
  
                  case SO_LABEL:
  #ifdef MAC
                          error = sooptcopyin(sopt, &extmac, sizeof(extmac),
                              sizeof(extmac));
                          if (error)
                                  goto bad;
                          error = mac_getsockopt_label(sopt->sopt_td->td_ucred,
                              so, &extmac);
                          if (error)
                                  goto bad;
                          error = sooptcopyout(sopt, &extmac, sizeof extmac);
  #else
                          error = EOPNOTSUPP;
  #endif
                          break;
  
                  case SO_PEERLABEL:
  #ifdef MAC
                          error = sooptcopyin(sopt, &extmac, sizeof(extmac),
                              sizeof(extmac));
                          if (error)
                                  goto bad;
                          error = mac_getsockopt_peerlabel(
                              sopt->sopt_td->td_ucred, so, &extmac);
                          if (error)
                                  goto bad;
                          error = sooptcopyout(sopt, &extmac, sizeof extmac);
  #else
                          error = EOPNOTSUPP;
  #endif
                          break;
  
                  case SO_LISTENQLIMIT:
                          optval = so->so_qlimit;
                          goto integer;
  
                  case SO_LISTENQLEN:
                          optval = so->so_qlen;
                          goto integer;
  
                  case SO_LISTENINCQLEN:
                          optval = so->so_incqlen;
                          goto integer;
  
                  default:
                          error = ENOPROTOOPT;
                          break;
                  }
          }
  #ifdef MAC
  bad:
  #endif
          CURVNET_RESTORE();
          return (error);
  }
  
  /* XXX; prepare mbuf for (__FreeBSD__ < 3) routines. */
  int
  soopt_getm(struct sockopt *sopt, struct mbuf **mp)
  {
          struct mbuf *m, *m_prev;
          int sopt_size = sopt->sopt_valsize;
  
          MGET(m, sopt->sopt_td ? M_WAIT : M_DONTWAIT, MT_DATA);
          if (m == NULL)
                  return ENOBUFS;
          if (sopt_size > MLEN) {
                  MCLGET(m, sopt->sopt_td ? M_WAIT : M_DONTWAIT);
                  if ((m->m_flags & M_EXT) == 0) {
                          m_free(m);
                          return ENOBUFS;
                  }
                  m->m_len = min(MCLBYTES, sopt_size);
          } else {
                  m->m_len = min(MLEN, sopt_size);
          }
          sopt_size -= m->m_len;
          *mp = m;
          m_prev = m;
  
          while (sopt_size) {
                  MGET(m, sopt->sopt_td ? M_WAIT : M_DONTWAIT, MT_DATA);
                  if (m == NULL) {
                          m_freem(*mp);
                          return ENOBUFS;
                  }
                  if (sopt_size > MLEN) {
                          MCLGET(m, sopt->sopt_td != NULL ? M_WAIT :
                              M_DONTWAIT);
                          if ((m->m_flags & M_EXT) == 0) {
                                  m_freem(m);
                                  m_freem(*mp);
                                  return ENOBUFS;
                          }
                          m->m_len = min(MCLBYTES, sopt_size);
                  } else {
                          m->m_len = min(MLEN, sopt_size);
                  }
                  sopt_size -= m->m_len;
                  m_prev->m_next = m;
                  m_prev = m;
          }
          return (0);
  }
  
  /* XXX; copyin sopt data into mbuf chain for (__FreeBSD__ < 3) routines. */
  int
  soopt_mcopyin(struct sockopt *sopt, struct mbuf *m)
  {
          struct mbuf *m0 = m;
  
          if (sopt->sopt_val == NULL)
                  return (0);
          while (m != NULL && sopt->sopt_valsize >= m->m_len) {
                  if (sopt->sopt_td != NULL) {
                          int error;
  
                          error = copyin(sopt->sopt_val, mtod(m, char *),
                                         m->m_len);
                          if (error != 0) {
                                  m_freem(m0);
                                  return(error);
                          }
                  } else
                          bcopy(sopt->sopt_val, mtod(m, char *), m->m_len);
                  sopt->sopt_valsize -= m->m_len;
                  sopt->sopt_val = (char *)sopt->sopt_val + m->m_len;
                  m = m->m_next;
          }
          if (m != NULL) /* should be allocated enoughly at ip6_sooptmcopyin() */
                  panic("ip6_sooptmcopyin");
          return (0);
  }
  
  /* XXX; copyout mbuf chain data into soopt for (__FreeBSD__ < 3) routines. */
  int
  soopt_mcopyout(struct sockopt *sopt, struct mbuf *m)
  {
          struct mbuf *m0 = m;
          size_t valsize = 0;
  
          if (sopt->sopt_val == NULL)
                  return (0);
          while (m != NULL && sopt->sopt_valsize >= m->m_len) {
                  if (sopt->sopt_td != NULL) {
                          int error;
  
                          error = copyout(mtod(m, char *), sopt->sopt_val,
                                         m->m_len);
                          if (error != 0) {
                                  m_freem(m0);
                                  return(error);
                          }
                  } else
                          bcopy(mtod(m, char *), sopt->sopt_val, m->m_len);
                 sopt->sopt_valsize -= m->m_len;
                 sopt->sopt_val = (char *)sopt->sopt_val + m->m_len;
                 valsize += m->m_len;
                 m = m->m_next;
          }
          if (m != NULL) {
                  /* enough soopt buffer should be given from user-land */
                  m_freem(m0);
                  return(EINVAL);
          }
          sopt->sopt_valsize = valsize;
          return (0);
  }
  
  /*
   * sohasoutofband(): protocol notifies socket layer of the arrival of new
   * out-of-band data, which will then notify socket consumers.
   */
  void
  sohasoutofband(struct socket *so)
  {
  
          if (so->so_sigio != NULL)
                  pgsigio(&so->so_sigio, SIGURG, 0);
          selwakeuppri(&so->so_rcv.sb_sel, PSOCK);
  }
  
  int
  sopoll(struct socket *so, int events, struct ucred *active_cred,
      struct thread *td)
  {
  
          /*
           * We do not need to set or assert curvnet as long as everyone uses
           * sopoll_generic().
           */
          return (so->so_proto->pr_usrreqs->pru_sopoll(so, events, active_cred,
              td));
  }
  
  int
  sopoll_generic(struct socket *so, int events, struct ucred *active_cred,
      struct thread *td)
  {
          int revents = 0;
  
          SOCKBUF_LOCK(&so->so_snd);
          SOCKBUF_LOCK(&so->so_rcv);
          if (events & (POLLIN | POLLRDNORM))
                  if (soreadabledata(so))
                          revents |= events & (POLLIN | POLLRDNORM);
  
          if (events & (POLLOUT | POLLWRNORM))
                  if (sowriteable(so))
                          revents |= events & (POLLOUT | POLLWRNORM);
  
          if (events & (POLLPRI | POLLRDBAND))
                  if (so->so_oobmark || (so->so_rcv.sb_state & SBS_RCVATMARK))
                          revents |= events & (POLLPRI | POLLRDBAND);
  
          if ((events & POLLINIGNEOF) == 0) {
                  if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
                          revents |= events & (POLLIN | POLLRDNORM);
                          if (so->so_snd.sb_state & SBS_CANTSENDMORE)
                                  revents |= POLLHUP;
                  }
          }
  
          if (revents == 0) {
                  if (events & (POLLIN | POLLPRI | POLLRDNORM | POLLRDBAND)) {
                          selrecord(td, &so->so_rcv.sb_sel);
                          so->so_rcv.sb_flags |= SB_SEL;
                  }
  
                  if (events & (POLLOUT | POLLWRNORM)) {
                          selrecord(td, &so->so_snd.sb_sel);
                          so->so_snd.sb_flags |= SB_SEL;
                  }
          }
  
          SOCKBUF_UNLOCK(&so->so_rcv);
          SOCKBUF_UNLOCK(&so->so_snd);
          return (revents);
  }
  
  int
  soo_kqfilter(struct file *fp, struct knote *kn)
  {
          struct socket *so = kn->kn_fp->f_data;
          struct sockbuf *sb;
  
          switch (kn->kn_filter) {
          case EVFILT_READ:
                  if (so->so_options & SO_ACCEPTCONN)
                          kn->kn_fop = &solisten_filtops;
                  else
                          kn->kn_fop = &soread_filtops;
                  sb = &so->so_rcv;
                  break;
          case EVFILT_WRITE:
                  kn->kn_fop = &sowrite_filtops;
                  sb = &so->so_snd;
                  break;
          default:
                  return (EINVAL);
          }
  
          SOCKBUF_LOCK(sb);
          knlist_add(&sb->sb_sel.si_note, kn, 1);
          sb->sb_flags |= SB_KNOTE;
          SOCKBUF_UNLOCK(sb);
          return (0);
  }
  
  /*
   * Some routines that return EOPNOTSUPP for entry points that are not
   * supported by a protocol.  Fill in as needed.
   */
  int
  pru_accept_notsupp(struct socket *so, struct sockaddr **nam)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_attach_notsupp(struct socket *so, int proto, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_bind_notsupp(struct socket *so, struct sockaddr *nam, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_connect_notsupp(struct socket *so, struct sockaddr *nam, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_connect2_notsupp(struct socket *so1, struct socket *so2)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_control_notsupp(struct socket *so, u_long cmd, caddr_t data,
      struct ifnet *ifp, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_disconnect_notsupp(struct socket *so)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_listen_notsupp(struct socket *so, int backlog, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_peeraddr_notsupp(struct socket *so, struct sockaddr **nam)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_rcvd_notsupp(struct socket *so, int flags)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_rcvoob_notsupp(struct socket *so, struct mbuf *m, int flags)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_send_notsupp(struct socket *so, int flags, struct mbuf *m,
      struct sockaddr *addr, struct mbuf *control, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  /*
   * This isn't really a ``null'' operation, but it's the default one and
   * doesn't do anything destructive.
   */
  int
  pru_sense_null(struct socket *so, struct stat *sb)
  {
  
          sb->st_blksize = so->so_snd.sb_hiwat;
          return 0;
  }
  
  int
  pru_shutdown_notsupp(struct socket *so)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_sockaddr_notsupp(struct socket *so, struct sockaddr **nam)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_sosend_notsupp(struct socket *so, struct sockaddr *addr, struct uio *uio,
      struct mbuf *top, struct mbuf *control, int flags, struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_soreceive_notsupp(struct socket *so, struct sockaddr **paddr,
      struct uio *uio, struct mbuf **mp0, struct mbuf **controlp, int *flagsp)
  {
  
          return EOPNOTSUPP;
  }
  
  int
  pru_sopoll_notsupp(struct socket *so, int events, struct ucred *cred,
      struct thread *td)
  {
  
          return EOPNOTSUPP;
  }
  
  static void
  filt_sordetach(struct knote *kn)
  {
          struct socket *so = kn->kn_fp->f_data;
  
          SOCKBUF_LOCK(&so->so_rcv);
          knlist_remove(&so->so_rcv.sb_sel.si_note, kn, 1);
          if (knlist_empty(&so->so_rcv.sb_sel.si_note))
                  so->so_rcv.sb_flags &= ~SB_KNOTE;
          SOCKBUF_UNLOCK(&so->so_rcv);
  }
  
  /*ARGSUSED*/
  static int
  filt_soread(struct knote *kn, long hint)
  {
          struct socket *so;
  
          so = kn->kn_fp->f_data;
          SOCKBUF_LOCK_ASSERT(&so->so_rcv);
  
          kn->kn_data = so->so_rcv.sb_cc - so->so_rcv.sb_ctl;
          if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
                  kn->kn_flags |= EV_EOF;
                  kn->kn_fflags = so->so_error;
                  return (1);
          } else if (so->so_error)        /* temporary udp error */
                  return (1);
          else if (kn->kn_sfflags & NOTE_LOWAT)
                  return (kn->kn_data >= kn->kn_sdata);
          else
                  return (so->so_rcv.sb_cc >= so->so_rcv.sb_lowat);
  }
  
  static void
  filt_sowdetach(struct knote *kn)
  {
          struct socket *so = kn->kn_fp->f_data;
  
          SOCKBUF_LOCK(&so->so_snd);
          knlist_remove(&so->so_snd.sb_sel.si_note, kn, 1);
          if (knlist_empty(&so->so_snd.sb_sel.si_note))
                  so->so_snd.sb_flags &= ~SB_KNOTE;
          SOCKBUF_UNLOCK(&so->so_snd);
  }
  
  /*ARGSUSED*/
  static int
  filt_sowrite(struct knote *kn, long hint)
  {
          struct socket *so;
  
          so = kn->kn_fp->f_data;
          SOCKBUF_LOCK_ASSERT(&so->so_snd);
          kn->kn_data = sbspace(&so->so_snd);
          if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
                  kn->kn_flags |= EV_EOF;
                  kn->kn_fflags = so->so_error;
                  return (1);
          } else if (so->so_error)        /* temporary udp error */
                  return (1);
          else if (((so->so_state & SS_ISCONNECTED) == 0) &&
              (so->so_proto->pr_flags & PR_CONNREQUIRED))
                  return (0);
          else if (kn->kn_sfflags & NOTE_LOWAT)
                  return (kn->kn_data >= kn->kn_sdata);
          else
                  return (kn->kn_data >= so->so_snd.sb_lowat);
  }
  
  /*ARGSUSED*/
  static int
  filt_solisten(struct knote *kn, long hint)
  {
          struct socket *so = kn->kn_fp->f_data;
  
          kn->kn_data = so->so_qlen;
          return (! TAILQ_EMPTY(&so->so_comp));
  }
  
  int
  socheckuid(struct socket *so, uid_t uid)
  {
  
          if (so == NULL)
                  return (EPERM);
          if (so->so_cred->cr_uid != uid)
                  return (EPERM);
          return (0);
  }
  
  static int
  sysctl_somaxconn(SYSCTL_HANDLER_ARGS)
  {
          int error;
          int val;
  
          val = somaxconn;
          error = sysctl_handle_int(oidp, &val, 0, req);
          if (error || !req->newptr )
                  return (error);
  
          if (val < 1 || val > USHRT_MAX)
                  return (EINVAL);
  
          somaxconn = val;
          return (0);
  }
  
  /*
   * These functions are used by protocols to notify the socket layer (and its
   * consumers) of state changes in the sockets driven by protocol-side events.
   */
  
  /*
   * Procedures to manipulate state flags of socket and do appropriate wakeups.
   *
   * Normal sequence from the active (originating) side is that
   * soisconnecting() is called during processing of connect() call, resulting
   * in an eventual call to soisconnected() if/when the connection is
   * established.  When the connection is torn down soisdisconnecting() is
   * called during processing of disconnect() call, and soisdisconnected() is
   * called when the connection to the peer is totally severed.  The semantics
   * of these routines are such that connectionless protocols can call
   * soisconnected() and soisdisconnected() only, bypassing the in-progress
   * calls when setting up a ``connection'' takes no time.
   *
   * From the passive side, a socket is created with two queues of sockets:
   * so_incomp for connections in progress and so_comp for connections already
   * made and awaiting user acceptance.  As a protocol is preparing incoming
   * connections, it creates a socket structure queued on so_incomp by calling
   * sonewconn().  When the connection is established, soisconnected() is
   * called, and transfers the socket structure to so_comp, making it available
   * to accept().
   *
   * If a socket is closed with sockets on either so_incomp or so_comp, these
   * sockets are dropped.
   *
   * If higher-level protocols are implemented in the kernel, the wakeups done
   * here will sometimes cause software-interrupt process scheduling.
   */
  void
  soisconnecting(struct socket *so)
  {
  
          SOCK_LOCK(so);
          so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
          so->so_state |= SS_ISCONNECTING;
          SOCK_UNLOCK(so);
  }
  
  void
  soisconnected(struct socket *so)
  {
          struct socket *head;    
          int ret;
  
  restart:
          ACCEPT_LOCK();
          SOCK_LOCK(so);
          so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
          so->so_state |= SS_ISCONNECTED;
          head = so->so_head;
          if (head != NULL && (so->so_qstate & SQ_INCOMP)) {
                  if ((so->so_options & SO_ACCEPTFILTER) == 0) {
                          SOCK_UNLOCK(so);
                          TAILQ_REMOVE(&head->so_incomp, so, so_list);
                          head->so_incqlen--;
                          so->so_qstate &= ~SQ_INCOMP;
                          TAILQ_INSERT_TAIL(&head->so_comp, so, so_list);
                          head->so_qlen++;
                          so->so_qstate |= SQ_COMP;
                          ACCEPT_UNLOCK();
                          sorwakeup(head);
                          wakeup_one(&head->so_timeo);
                  } else {
                          ACCEPT_UNLOCK();
                          soupcall_set(so, SO_RCV,
                              head->so_accf->so_accept_filter->accf_callback,
                              head->so_accf->so_accept_filter_arg);
                          so->so_options &= ~SO_ACCEPTFILTER;
                          ret = head->so_accf->so_accept_filter->accf_callback(so,
                              head->so_accf->so_accept_filter_arg, M_DONTWAIT);
                          if (ret == SU_ISCONNECTED)
                                  soupcall_clear(so, SO_RCV);
                          SOCK_UNLOCK(so);
                          if (ret == SU_ISCONNECTED)
                                  goto restart;
                  }
                  return;
          }
          SOCK_UNLOCK(so);
          ACCEPT_UNLOCK();
          wakeup(&so->so_timeo);
          sorwakeup(so);
          sowwakeup(so);
  }
  
  void
  soisdisconnecting(struct socket *so)
  {
  
          /*
           * Note: This code assumes that SOCK_LOCK(so) and
           * SOCKBUF_LOCK(&so->so_rcv) are the same.
           */
          SOCKBUF_LOCK(&so->so_rcv);
          so->so_state &= ~SS_ISCONNECTING;
          so->so_state |= SS_ISDISCONNECTING;
          so->so_rcv.sb_state |= SBS_CANTRCVMORE;
          sorwakeup_locked(so);
          SOCKBUF_LOCK(&so->so_snd);
          so->so_snd.sb_state |= SBS_CANTSENDMORE;
          sowwakeup_locked(so);
          wakeup(&so->so_timeo);
  }
  
  void
  soisdisconnected(struct socket *so)
  {
  
          /*
           * Note: This code assumes that SOCK_LOCK(so) and
           * SOCKBUF_LOCK(&so->so_rcv) are the same.
           */
          SOCKBUF_LOCK(&so->so_rcv);
          so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
          so->so_state |= SS_ISDISCONNECTED;
          so->so_rcv.sb_state |= SBS_CANTRCVMORE;
          sorwakeup_locked(so);
          SOCKBUF_LOCK(&so->so_snd);
          so->so_snd.sb_state |= SBS_CANTSENDMORE;
          sbdrop_locked(&so->so_snd, so->so_snd.sb_cc);
          sowwakeup_locked(so);
          wakeup(&so->so_timeo);
  }
  
  /*
   * Make a copy of a sockaddr in a malloced buffer of type M_SONAME.
   */
  struct sockaddr *
  sodupsockaddr(const struct sockaddr *sa, int mflags)
  {
          struct sockaddr *sa2;
  
          sa2 = malloc(sa->sa_len, M_SONAME, mflags);
          if (sa2)
                  bcopy(sa, sa2, sa->sa_len);
          return sa2;
  }
  
  /*
   * Register per-socket buffer upcalls.
   */
  void
  soupcall_set(struct socket *so, int which,
      int (*func)(struct socket *, void *, int), void *arg)
  {
          struct sockbuf *sb;
          
          switch (which) {
          case SO_RCV:
                  sb = &so->so_rcv;
                  break;
          case SO_SND:
                  sb = &so->so_snd;
                  break;
          default:
                  panic("soupcall_set: bad which");
          }
          SOCKBUF_LOCK_ASSERT(sb);
  #if 0
          /* XXX: accf_http actually wants to do this on purpose. */
          KASSERT(sb->sb_upcall == NULL, ("soupcall_set: overwriting upcall"));
  #endif
          sb->sb_upcall = func;
          sb->sb_upcallarg = arg;
          sb->sb_flags |= SB_UPCALL;
  }
  
  void
  soupcall_clear(struct socket *so, int which)
  {
          struct sockbuf *sb;
  
          switch (which) {
          case SO_RCV:
                  sb = &so->so_rcv;
                  break;
          case SO_SND:
                  sb = &so->so_snd;
                  break;
          default:
                  panic("soupcall_clear: bad which");
          }
          SOCKBUF_LOCK_ASSERT(sb);
          KASSERT(sb->sb_upcall != NULL, ("soupcall_clear: no upcall to clear"));
          sb->sb_upcall = NULL;
          sb->sb_upcallarg = NULL;
          sb->sb_flags &= ~SB_UPCALL;
  }
  
  /*
   * Create an external-format (``xsocket'') structure using the information in
   * the kernel-format socket structure pointed to by so.  This is done to
   * reduce the spew of irrelevant information over this interface, to isolate
   * user code from changes in the kernel structure, and potentially to provide
   * information-hiding if we decide that some of this information should be
   * hidden from users.
   */
  void
  sotoxsocket(struct socket *so, struct xsocket *xso)
  {
  
          xso->xso_len = sizeof *xso;
          xso->xso_so = so;
          xso->so_type = so->so_type;
          xso->so_options = so->so_options;
          xso->so_linger = so->so_linger;
          xso->so_state = so->so_state;
          xso->so_pcb = so->so_pcb;
          xso->xso_protocol = so->so_proto->pr_protocol;
          xso->xso_family = so->so_proto->pr_domain->dom_family;
          xso->so_qlen = so->so_qlen;
          xso->so_incqlen = so->so_incqlen;
          xso->so_qlimit = so->so_qlimit;
          xso->so_timeo = so->so_timeo;
          xso->so_error = so->so_error;
          xso->so_pgid = so->so_sigio ? so->so_sigio->sio_pgid : 0;
          xso->so_oobmark = so->so_oobmark;
          sbtoxsockbuf(&so->so_snd, &xso->so_snd);
          sbtoxsockbuf(&so->so_rcv, &xso->so_rcv);
          xso->so_uid = so->so_cred->cr_uid;
  }
  
  
  /*
   * Socket accessor functions to provide external consumers with
   * a safe interface to socket state
   *
   */
  
  void
  so_listeners_apply_all(struct socket *so, void (*func)(struct socket *, void *), void *arg)
  {
          
          TAILQ_FOREACH(so, &so->so_comp, so_list)
                  func(so, arg);
  }
  
  struct sockbuf *
  so_sockbuf_rcv(struct socket *so)
  {
  
          return (&so->so_rcv);
  }
  
  struct sockbuf *
  so_sockbuf_snd(struct socket *so)
  {
  
          return (&so->so_snd);
  }
  
  int
  so_state_get(const struct socket *so)
  {
  
          return (so->so_state);
  }
  
  void
  so_state_set(struct socket *so, int val)
  {
  
          so->so_state = val;
  }
  
  int
  so_options_get(const struct socket *so)
  {
  
          return (so->so_options);
  }
  
  void
  so_options_set(struct socket *so, int val)
  {
  
          so->so_options = val;
  }
  
  int
  so_error_get(const struct socket *so)
  {
  
          return (so->so_error);
  }
  
  void
  so_error_set(struct socket *so, int val)
  {
  
          so->so_error = val;
  }
  
  int
  so_linger_get(const struct socket *so)
  {
  
          return (so->so_linger);
  }
  
  void
  so_linger_set(struct socket *so, int val)
  {
  
          so->so_linger = val;
  }
  
  struct protosw *
  so_protosw_get(const struct socket *so)
  {
  
          return (so->so_proto);
  }
  
  void
  so_protosw_set(struct socket *so, struct protosw *val)
  {
  
          so->so_proto = val;
  }
  
  void
  so_sorwakeup(struct socket *so)
  {
  
          sorwakeup(so);
  }
  
  void
  so_sowwakeup(struct socket *so)
  {
  
          sowwakeup(so);
  }
  
  void
  so_sorwakeup_locked(struct socket *so)
  {
  
          sorwakeup_locked(so);
  }
  
  void
  so_sowwakeup_locked(struct socket *so)
  {
  
          sowwakeup_locked(so);
  }
  
  void
  so_lock(struct socket *so)
  {
          SOCK_LOCK(so);
  }
  
  void
  so_unlock(struct socket *so)
  {
          SOCK_UNLOCK(so);
  }