[apple/xnu.git] / bsd / netinet6 / in6_pcb.c

/*
 * Copyright (c) 2003-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project 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 PROJECT 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 PROJECT 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.
 *
 */

/*
 * Copyright (c) 1982, 1986, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)in_pcb.c    8.2 (Berkeley) 1/4/94
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sockio.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/priv.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/ntstat.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip6.h>
#include <netinet/ip_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/nd6.h>
#include <netinet/in_pcb.h>
#include <netinet6/in6_pcb.h>
#include <net/if_types.h>
#include <net/if_var.h>

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

#if IPSEC
#include <netinet6/ipsec.h>
#if INET6
#include <netinet6/ipsec6.h>
#endif
#include <netinet6/ah.h>
#if INET6
#include <netinet6/ah6.h>
#endif
#include <netkey/key.h>
#endif /* IPSEC */

#if NECP
#include <net/necp.h>
#endif /* NECP */

/*
 * in6_pcblookup_local_and_cleanup does everything
 * in6_pcblookup_local does but it checks for a socket
 * that's going away. Since we know that the lock is
 * held read+write when this function is called, we
 * can safely dispose of this socket like the slow
 * timer would usually do and return NULL. This is
 * great for bind.
 */
static struct inpcb *
in6_pcblookup_local_and_cleanup(struct inpcbinfo *pcbinfo,
    struct in6_addr *laddr, u_int lport_arg, int wild_okay)
{
        struct inpcb *inp;

        /* Perform normal lookup */
        inp = in6_pcblookup_local(pcbinfo, laddr, lport_arg, wild_okay);

        /* Check if we found a match but it's waiting to be disposed */
        if (inp != NULL && inp->inp_wantcnt == WNT_STOPUSING) {
                struct socket *so = inp->inp_socket;

                lck_mtx_lock(&inp->inpcb_mtx);

                if (so->so_usecount == 0) {
                        if (inp->inp_state != INPCB_STATE_DEAD)
                                in6_pcbdetach(inp);
                        in_pcbdispose(inp);     /* will unlock & destroy */
                        inp = NULL;
                } else {
                        lck_mtx_unlock(&inp->inpcb_mtx);
                }
        }

        return (inp);
}

/*
 * Bind an INPCB to an address and/or port.  This routine should not alter
 * the caller-supplied local address "nam".
 */
int
in6_pcbbind(struct inpcb *inp, struct sockaddr *nam, struct proc *p)
{
        struct socket *so = inp->inp_socket;
        struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
        u_short lport = 0;
        int wild = 0, reuseport = (so->so_options & SO_REUSEPORT);
        struct ifnet *outif = NULL;
        struct sockaddr_in6 sin6;
        int error;
        kauth_cred_t cred;

        if (!in6_ifaddrs) /* XXX broken! */
                return (EADDRNOTAVAIL);
        if (inp->inp_lport || !IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
                return (EINVAL);
        if (!(so->so_options & (SO_REUSEADDR|SO_REUSEPORT)))
                wild = 1;
        socket_unlock(so, 0); /* keep reference */
        lck_rw_lock_exclusive(pcbinfo->ipi_lock);

        bzero(&sin6, sizeof (sin6));
        if (nam != NULL) {
                if (nam->sa_len != sizeof (struct sockaddr_in6)) {
                        lck_rw_done(pcbinfo->ipi_lock);
                        socket_lock(so, 0);
                        return (EINVAL);
                }
                /*
                 * family check.
                 */
                if (nam->sa_family != AF_INET6) {
                        lck_rw_done(pcbinfo->ipi_lock);
                        socket_lock(so, 0);
                        return (EAFNOSUPPORT);
                }
                lport = SIN6(nam)->sin6_port;

                *(&sin6) = *SIN6(nam);

                /* KAME hack: embed scopeid */
                if (in6_embedscope(&sin6.sin6_addr, &sin6, inp, NULL,
                    NULL) != 0) {
                        lck_rw_done(pcbinfo->ipi_lock);
                        socket_lock(so, 0);
                        return (EINVAL);
                }

                /* Sanitize local copy for address searches */
                sin6.sin6_flowinfo = 0;
                sin6.sin6_scope_id = 0;
                sin6.sin6_port = 0;

                if (IN6_IS_ADDR_MULTICAST(&sin6.sin6_addr)) {
                        /*
                         * Treat SO_REUSEADDR as SO_REUSEPORT for multicast;
                         * allow compepte duplication of binding if
                         * SO_REUSEPORT is set, or if SO_REUSEADDR is set
                         * and a multicast address is bound on both
                         * new and duplicated sockets.
                         */
                        if (so->so_options & SO_REUSEADDR)
                                reuseport = SO_REUSEADDR|SO_REUSEPORT;
                } else if (!IN6_IS_ADDR_UNSPECIFIED(&sin6.sin6_addr)) {
                        struct ifaddr *ifa;

                        ifa = ifa_ifwithaddr(SA(&sin6));
                        if (ifa == NULL) {
                                lck_rw_done(pcbinfo->ipi_lock);
                                socket_lock(so, 0);
                                return (EADDRNOTAVAIL);
                        } else {
                                /*
                                 * XXX: bind to an anycast address might
                                 * accidentally cause sending a packet with
                                 * anycast source address.  We should allow
                                 * to bind to a deprecated address, since
                                 * the application dare to use it.
                                 */
                                IFA_LOCK_SPIN(ifa);
                                if (((struct in6_ifaddr *)ifa)->ia6_flags &
                                    (IN6_IFF_ANYCAST|IN6_IFF_NOTREADY|
                                    IN6_IFF_DETACHED)) {
                                        IFA_UNLOCK(ifa);
                                        IFA_REMREF(ifa);
                                        lck_rw_done(pcbinfo->ipi_lock);
                                        socket_lock(so, 0);
                                        return (EADDRNOTAVAIL);
                                }
                                /*
                                 * Opportunistically determine the outbound
                                 * interface that may be used; this may not
                                 * hold true if we end up using a route
                                 * going over a different interface, e.g.
                                 * when sending to a local address.  This
                                 * will get updated again after sending.
                                 */
                                outif = ifa->ifa_ifp;
                                IFA_UNLOCK(ifa);
                                IFA_REMREF(ifa);
                        }
                }
                if (lport != 0) {
                        struct inpcb *t;
                        uid_t u;

                        /* GROSS */
                        if (ntohs(lport) < IPV6PORT_RESERVED) {
                                cred = kauth_cred_proc_ref(p);
                                error = priv_check_cred(cred,
                                    PRIV_NETINET_RESERVEDPORT, 0);
                                kauth_cred_unref(&cred);
                                if (error != 0) {
                                        lck_rw_done(pcbinfo->ipi_lock);
                                        socket_lock(so, 0);
                                        return (EACCES);
                                }
                        }
                        if (!IN6_IS_ADDR_MULTICAST(&sin6.sin6_addr) &&
                            (u = kauth_cred_getuid(so->so_cred)) != 0) {
                                t = in6_pcblookup_local_and_cleanup(pcbinfo,
                                    &sin6.sin6_addr, lport,
                                    INPLOOKUP_WILDCARD);
                                if (t != NULL && (!IN6_IS_ADDR_UNSPECIFIED(
                                    &sin6.sin6_addr) ||
                                    !IN6_IS_ADDR_UNSPECIFIED(&t->in6p_laddr) ||
                                    !(t->inp_socket->so_options &
                                    SO_REUSEPORT)) && (u != kauth_cred_getuid(
                                    t->inp_socket->so_cred)) &&
                                    !(t->inp_socket->so_flags &
                                    SOF_REUSESHAREUID)) {
                                        lck_rw_done(pcbinfo->ipi_lock);
                                        socket_lock(so, 0);
                                        return (EADDRINUSE);
                                }
                                if (!(inp->inp_flags & IN6P_IPV6_V6ONLY) &&
                                    IN6_IS_ADDR_UNSPECIFIED(&sin6.sin6_addr)) {
                                        struct sockaddr_in sin;

                                        in6_sin6_2_sin(&sin, &sin6);
                                        t = in_pcblookup_local_and_cleanup(
                                            pcbinfo, sin.sin_addr, lport,
                                            INPLOOKUP_WILDCARD);
                                        if (t != NULL &&
                                            !(t->inp_socket->so_options &
                                            SO_REUSEPORT) &&
                                            (kauth_cred_getuid(so->so_cred) !=
                                            kauth_cred_getuid(t->inp_socket->
                                            so_cred)) && (t->inp_laddr.s_addr !=
                                            INADDR_ANY || SOCK_DOM(so) ==
                                            SOCK_DOM(t->inp_socket))) {
                                                lck_rw_done(pcbinfo->ipi_lock);
                                                socket_lock(so, 0);
                                                return (EADDRINUSE);
                                        }
                                }
                        }
                        t = in6_pcblookup_local_and_cleanup(pcbinfo,
                            &sin6.sin6_addr, lport, wild);
                        if (t != NULL &&
                            (reuseport & t->inp_socket->so_options) == 0) {
                                lck_rw_done(pcbinfo->ipi_lock);
                                socket_lock(so, 0);
                                return (EADDRINUSE);
                        }
                        if (!(inp->inp_flags & IN6P_IPV6_V6ONLY) &&
                            IN6_IS_ADDR_UNSPECIFIED(&sin6.sin6_addr)) {
                                struct sockaddr_in sin;

                                in6_sin6_2_sin(&sin, &sin6);
                                t = in_pcblookup_local_and_cleanup(pcbinfo,
                                    sin.sin_addr, lport, wild);
                                if (t != NULL && (reuseport &
                                    t->inp_socket->so_options) == 0 &&
                                    (t->inp_laddr.s_addr != INADDR_ANY ||
                                    SOCK_DOM(so) == SOCK_DOM(t->inp_socket))) {
                                        lck_rw_done(pcbinfo->ipi_lock);
                                        socket_lock(so, 0);
                                        return (EADDRINUSE);
                                }
                        }
                }
        }

        socket_lock(so, 0);
        /* check if the socket got bound when the lock was released */
        if (inp->inp_lport || !IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) {
                lck_rw_done(pcbinfo->ipi_lock);
                return (EINVAL);
        }

        if (!IN6_IS_ADDR_UNSPECIFIED(&sin6.sin6_addr)) {
                inp->in6p_laddr = sin6.sin6_addr;
                inp->in6p_last_outifp = outif;
        }

        if (lport == 0) {
                int e;
                if ((e = in6_pcbsetport(&inp->in6p_laddr, inp, p, 1)) != 0) {
                        /* Undo any address bind from above. */
                        inp->in6p_laddr = in6addr_any;
                        inp->in6p_last_outifp = NULL;   
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (e);
                }
        } else {
                inp->inp_lport = lport;
                if (in_pcbinshash(inp, 1) != 0) {
                        inp->in6p_laddr = in6addr_any;
                        inp->inp_lport = 0;
                        inp->in6p_last_outifp = NULL;
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (EAGAIN);
                }
        }
        lck_rw_done(pcbinfo->ipi_lock);
        sflt_notify(so, sock_evt_bound, NULL);
        return (0);
}

/*
 * Transform old in6_pcbconnect() into an inner subroutine for new
 * in6_pcbconnect(); do some validity-checking on the remote address
 * (in "nam") and then determine local host address (i.e., which
 * interface) to use to access that remote host.
 *
 * This routine may alter the caller-supplied remote address "nam".
 *
 * This routine might return an ifp with a reference held if the caller
 * provides a non-NULL outif, even in the error case.  The caller is
 * responsible for releasing its reference.
 */
int
in6_pcbladdr(struct inpcb *inp, struct sockaddr *nam,
    struct in6_addr *plocal_addr6, struct ifnet **outif)
{
        struct in6_addr *addr6 = NULL;
        struct in6_addr src_storage;
        int error = 0;
        unsigned int ifscope;

        if (outif != NULL)
                *outif = NULL;
        if (nam->sa_len != sizeof (struct sockaddr_in6))
                return (EINVAL);
        if (SIN6(nam)->sin6_family != AF_INET6)
                return (EAFNOSUPPORT);
        if (SIN6(nam)->sin6_port == 0)
                return (EADDRNOTAVAIL);

        /* KAME hack: embed scopeid */
        if (in6_embedscope(&SIN6(nam)->sin6_addr, SIN6(nam), inp, NULL, NULL) != 0)
                return (EINVAL);

        if (in6_ifaddrs) {
                /*
                 * If the destination address is UNSPECIFIED addr,
                 * use the loopback addr, e.g ::1.
                 */
                if (IN6_IS_ADDR_UNSPECIFIED(&SIN6(nam)->sin6_addr))
                        SIN6(nam)->sin6_addr = in6addr_loopback;
        }

        ifscope = (inp->inp_flags & INP_BOUND_IF) ?
            inp->inp_boundifp->if_index : IFSCOPE_NONE;

        /*
         * XXX: in6_selectsrc might replace the bound local address
         * with the address specified by setsockopt(IPV6_PKTINFO).
         * Is it the intended behavior?
         *
         * in6_selectsrc() might return outif with its reference held
         * even in the error case; caller always needs to release it
         * if non-NULL.
         */
        addr6 = in6_selectsrc(SIN6(nam), inp->in6p_outputopts, inp,
            &inp->in6p_route, outif, &src_storage, ifscope, &error);

        if (outif != NULL) {
                struct rtentry *rt = inp->in6p_route.ro_rt;
                /*
                 * If in6_selectsrc() returns a route, it should be one
                 * which points to the same ifp as outif.  Just in case
                 * it isn't, use the one from the route for consistency.
                 * Otherwise if there is no route, leave outif alone as
                 * it could still be useful to the caller.
                 */
                if (rt != NULL && rt->rt_ifp != *outif) {
                        ifnet_reference(rt->rt_ifp);    /* for caller */
                        if (*outif != NULL)
                                ifnet_release(*outif);
                        *outif = rt->rt_ifp;
                }
        }

        if (addr6 == NULL) {
                if (outif != NULL && (*outif) != NULL &&
                    inp_restricted_send(inp, *outif)) {
                        soevent(inp->inp_socket,
                            (SO_FILT_HINT_LOCKED | SO_FILT_HINT_IFDENIED));
                        error = EHOSTUNREACH;
                }
                if (error == 0)
                        error = EADDRNOTAVAIL;
                return (error);
        }

        *plocal_addr6 = *addr6;
        /*
         * Don't do pcblookup call here; return interface in
         * plocal_addr6 and exit to caller, that will do the lookup.
         */
        return (0);
}

/*
 * Outer subroutine:
 * Connect from a socket to a specified address.
 * Both address and port must be specified in argument sin.
 * If don't have a local address for this socket yet,
 * then pick one.
 */
int
in6_pcbconnect(struct inpcb *inp, struct sockaddr *nam, struct proc *p)
{
        struct in6_addr addr6;
        struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)(void *)nam;
        struct inpcb *pcb;
        int error = 0;
        struct ifnet *outif = NULL;
        struct socket *so = inp->inp_socket;

        /*
         * Call inner routine, to assign local interface address.
         * in6_pcbladdr() may automatically fill in sin6_scope_id.
         *
         * in6_pcbladdr() might return an ifp with its reference held
         * even in the error case, so make sure that it's released
         * whenever it's non-NULL.
         */
        if ((error = in6_pcbladdr(inp, nam, &addr6, &outif)) != 0) {
                if (outif != NULL && inp_restricted_send(inp, outif)) 
                        soevent(so,
                            (SO_FILT_HINT_LOCKED | SO_FILT_HINT_IFDENIED));
                goto done;
        }
        socket_unlock(so, 0);
        pcb = in6_pcblookup_hash(inp->inp_pcbinfo, &sin6->sin6_addr,
            sin6->sin6_port, IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr) ?
            &addr6 : &inp->in6p_laddr, inp->inp_lport, 0, NULL);
        socket_lock(so, 0);
        if (pcb != NULL) {
                in_pcb_checkstate(pcb, WNT_RELEASE, pcb == inp ? 1 : 0);
                error = EADDRINUSE;
                goto done;
        }
        if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) {
                if (inp->inp_lport == 0) {
                        error = in6_pcbbind(inp, NULL, p);
                        if (error)
                                goto done;
                }
                inp->in6p_laddr = addr6;
                inp->in6p_last_outifp = outif;  /* no reference needed */
                inp->in6p_flags |= INP_IN6ADDR_ANY;
        }
        if (!lck_rw_try_lock_exclusive(inp->inp_pcbinfo->ipi_lock)) {
                /* lock inversion issue, mostly with udp multicast packets */
                socket_unlock(so, 0);
                lck_rw_lock_exclusive(inp->inp_pcbinfo->ipi_lock);
                socket_lock(so, 0);
        }
        inp->in6p_faddr = sin6->sin6_addr;
        inp->inp_fport = sin6->sin6_port;
        if (nstat_collect && SOCK_PROTO(so) == IPPROTO_UDP)
                nstat_pcb_invalidate_cache(inp);
        in_pcbrehash(inp);
        lck_rw_done(inp->inp_pcbinfo->ipi_lock);

done:
        if (outif != NULL)
                ifnet_release(outif);

        return (error);
}

void
in6_pcbdisconnect(struct inpcb *inp)
{
        struct socket *so = inp->inp_socket;

        if (!lck_rw_try_lock_exclusive(inp->inp_pcbinfo->ipi_lock)) {
                /* lock inversion issue, mostly with udp multicast packets */
                socket_unlock(so, 0);
                lck_rw_lock_exclusive(inp->inp_pcbinfo->ipi_lock);
                socket_lock(so, 0);
        }
        if (nstat_collect && SOCK_PROTO(so) == IPPROTO_UDP)
                nstat_pcb_cache(inp);
        bzero((caddr_t)&inp->in6p_faddr, sizeof (inp->in6p_faddr));
        inp->inp_fport = 0;
        /* clear flowinfo - RFC 6437 */
        inp->inp_flow &= ~IPV6_FLOWLABEL_MASK;
        in_pcbrehash(inp);
        lck_rw_done(inp->inp_pcbinfo->ipi_lock);
        /*
         * A multipath subflow socket would have its SS_NOFDREF set by default,
         * so check for SOF_MP_SUBFLOW socket flag before detaching the PCB;
         * when the socket is closed for real, SOF_MP_SUBFLOW would be cleared.
         */
        if (!(so->so_flags & SOF_MP_SUBFLOW) && (so->so_state & SS_NOFDREF))
                in6_pcbdetach(inp);
}

void
in6_pcbdetach(struct inpcb *inp)
{
        struct socket *so = inp->inp_socket;

        if (so->so_pcb == NULL) {
                /* PCB has been disposed */
                panic("%s: inp=%p so=%p proto=%d so_pcb is null!\n", __func__,
                    inp, so, SOCK_PROTO(so));
                /* NOTREACHED */
        }
        
#if IPSEC
        if (inp->in6p_sp != NULL) {
                (void) ipsec6_delete_pcbpolicy(inp);
        }
#endif /* IPSEC */

        /*
         * Let NetworkStatistics know this PCB is going away
         * before we detach it.
         */
        if (nstat_collect &&
            (SOCK_PROTO(so) == IPPROTO_TCP || SOCK_PROTO(so) == IPPROTO_UDP))
                nstat_pcb_detach(inp);
        /* mark socket state as dead */
        if (in_pcb_checkstate(inp, WNT_STOPUSING, 1) != WNT_STOPUSING) {
                panic("%s: so=%p proto=%d couldn't set to STOPUSING\n",
                    __func__, so, SOCK_PROTO(so));
                /* NOTREACHED */
        }

        if (!(so->so_flags & SOF_PCBCLEARING)) {
                struct ip_moptions *imo;
                struct ip6_moptions *im6o;

                inp->inp_vflag = 0;
                if (inp->in6p_options != NULL) {
                        m_freem(inp->in6p_options);
                        inp->in6p_options = NULL;
                }
                ip6_freepcbopts(inp->in6p_outputopts);
                ROUTE_RELEASE(&inp->in6p_route);
                /* free IPv4 related resources in case of mapped addr */
                if (inp->inp_options != NULL) {
                        (void) m_free(inp->inp_options);
                        inp->inp_options = NULL;
                }
                im6o = inp->in6p_moptions;
                inp->in6p_moptions = NULL;
                if (im6o != NULL)
                        IM6O_REMREF(im6o);

                imo = inp->inp_moptions;
                inp->inp_moptions = NULL;
                if (imo != NULL)
                        IMO_REMREF(imo);
                sofreelastref(so, 0);
                inp->inp_state = INPCB_STATE_DEAD;
                /* makes sure we're not called twice from so_close */
                so->so_flags |= SOF_PCBCLEARING;
 
                inpcb_gc_sched(inp->inp_pcbinfo, INPCB_TIMER_FAST);
        }
}

struct sockaddr *
in6_sockaddr(in_port_t port, struct in6_addr *addr_p)
{
        struct sockaddr_in6 *sin6;

        MALLOC(sin6, struct sockaddr_in6 *, sizeof (*sin6), M_SONAME, M_WAITOK);
        if (sin6 == NULL)
                return (NULL);
        bzero(sin6, sizeof (*sin6));
        sin6->sin6_family = AF_INET6;
        sin6->sin6_len = sizeof (*sin6);
        sin6->sin6_port = port;
        sin6->sin6_addr = *addr_p;

        /* would be good to use sa6_recoverscope(), except for locking  */
        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr))
                sin6->sin6_scope_id = ntohs(sin6->sin6_addr.s6_addr16[1]);
        else
                sin6->sin6_scope_id = 0;        /* XXX */
        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr))
                sin6->sin6_addr.s6_addr16[1] = 0;

        return ((struct sockaddr *)sin6);
}

void
in6_sockaddr_s(in_port_t port, struct in6_addr *addr_p,
    struct sockaddr_in6 *sin6)
{
        bzero(sin6, sizeof (*sin6));
        sin6->sin6_family = AF_INET6;
        sin6->sin6_len = sizeof (*sin6);
        sin6->sin6_port = port;
        sin6->sin6_addr = *addr_p;

        /* would be good to use sa6_recoverscope(), except for locking  */
        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr))
                sin6->sin6_scope_id = ntohs(sin6->sin6_addr.s6_addr16[1]);
        else
                sin6->sin6_scope_id = 0;        /* XXX */
        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr))
                sin6->sin6_addr.s6_addr16[1] = 0;
}

/*
 * The calling convention of in6_getsockaddr() and in6_getpeeraddr() was
 * modified to match the pru_sockaddr() and pru_peeraddr() entry points
 * in struct pr_usrreqs, so that protocols can just reference then directly
 * without the need for a wrapper function.
 */
int
in6_getsockaddr(struct socket *so, struct sockaddr **nam)
{
        struct inpcb *inp;
        struct in6_addr addr;
        in_port_t port;

        if ((inp = sotoinpcb(so)) == NULL)
                return (EINVAL);

        port = inp->inp_lport;
        addr = inp->in6p_laddr;

        *nam = in6_sockaddr(port, &addr);
        if (*nam == NULL)
                return (ENOBUFS);
        return (0);
}

int
in6_getsockaddr_s(struct socket *so, struct sockaddr_storage *ss)
{
        struct inpcb *inp;
        struct in6_addr addr;
        in_port_t port;

        VERIFY(ss != NULL);
        bzero(ss, sizeof (*ss));

        if ((inp = sotoinpcb(so)) == NULL
#if NECP
                || (necp_socket_should_use_flow_divert(inp))
#endif /* NECP */
                )
                return (inp == NULL ? EINVAL : EPROTOTYPE);

        port = inp->inp_lport;
        addr = inp->in6p_laddr;

        in6_sockaddr_s(port, &addr, SIN6(ss));
        return (0);
}

int
in6_getpeeraddr(struct socket *so, struct sockaddr **nam)
{
        struct inpcb *inp;
        struct in6_addr addr;
        in_port_t port;

        if ((inp = sotoinpcb(so)) == NULL)
                return (EINVAL);

        port = inp->inp_fport;
        addr = inp->in6p_faddr;

        *nam = in6_sockaddr(port, &addr);
        if (*nam == NULL)
                return (ENOBUFS);
        return (0);
}

int
in6_getpeeraddr_s(struct socket *so, struct sockaddr_storage *ss)
{
        struct inpcb *inp;
        struct in6_addr addr;
        in_port_t port;

        VERIFY(ss != NULL);
        bzero(ss, sizeof (*ss));

        if ((inp = sotoinpcb(so)) == NULL
#if NECP
                || (necp_socket_should_use_flow_divert(inp))
#endif /* NECP */
                )
                return (inp == NULL ? EINVAL : EPROTOTYPE);

        port = inp->inp_fport;
        addr = inp->in6p_faddr;

        in6_sockaddr_s(port, &addr, SIN6(ss));
        return (0);
}

int
in6_mapped_sockaddr(struct socket *so, struct sockaddr **nam)
{
        struct  inpcb *inp = sotoinpcb(so);
        int     error;

        if (inp == NULL)
                return (EINVAL);
        if (inp->inp_vflag & INP_IPV4) {
                error = in_getsockaddr(so, nam);
                if (error == 0)
                        error = in6_sin_2_v4mapsin6_in_sock(nam);
        } else {
                /* scope issues will be handled in in6_getsockaddr(). */
                error = in6_getsockaddr(so, nam);
        }
        return (error);
}

int
in6_mapped_peeraddr(struct socket *so, struct sockaddr **nam)
{
        struct  inpcb *inp = sotoinpcb(so);
        int     error;

        if (inp == NULL)
                return (EINVAL);
        if (inp->inp_vflag & INP_IPV4) {
                error = in_getpeeraddr(so, nam);
                if (error == 0)
                        error = in6_sin_2_v4mapsin6_in_sock(nam);
        } else {
                /* scope issues will be handled in in6_getpeeraddr(). */
                error = in6_getpeeraddr(so, nam);
        }
        return (error);
}

/*
 * Pass some notification to all connections of a protocol
 * associated with address dst.  The local address and/or port numbers
 * may be specified to limit the search.  The "usual action" will be
 * taken, depending on the ctlinput cmd.  The caller must filter any
 * cmds that are uninteresting (e.g., no error in the map).
 * Call the protocol specific routine (if any) to report
 * any errors for each matching socket.
 */
void
in6_pcbnotify(struct inpcbinfo *pcbinfo, struct sockaddr *dst, u_int fport_arg,
    const struct sockaddr *src, u_int lport_arg, int cmd, void *cmdarg,
    void (*notify)(struct inpcb *, int))
{
        struct inpcbhead *head = pcbinfo->ipi_listhead;
        struct inpcb *inp, *ninp;
        struct sockaddr_in6 sa6_src, *sa6_dst;
        u_short fport = fport_arg, lport = lport_arg;
        u_int32_t flowinfo;
        int errno;

        if ((unsigned)cmd >= PRC_NCMDS || dst->sa_family != AF_INET6)
                return;

        sa6_dst = (struct sockaddr_in6 *)(void *)dst;
        if (IN6_IS_ADDR_UNSPECIFIED(&sa6_dst->sin6_addr))
                return;

        /*
         * note that src can be NULL when we get notify by local fragmentation.
         */
        sa6_src = (src == NULL) ?
            sa6_any : *(struct sockaddr_in6 *)(uintptr_t)(size_t)src;
        flowinfo = sa6_src.sin6_flowinfo;

        /*
         * Redirects go to all references to the destination,
         * and use in6_rtchange to invalidate the route cache.
         * Dead host indications: also use in6_rtchange to invalidate
         * the cache, and deliver the error to all the sockets.
         * Otherwise, if we have knowledge of the local port and address,
         * deliver only to that socket.
         */
        if (PRC_IS_REDIRECT(cmd) || cmd == PRC_HOSTDEAD) {
                fport = 0;
                lport = 0;
                bzero((caddr_t)&sa6_src.sin6_addr, sizeof (sa6_src.sin6_addr));

                if (cmd != PRC_HOSTDEAD)
                        notify = in6_rtchange;
        }
        errno = inet6ctlerrmap[cmd];
        lck_rw_lock_shared(pcbinfo->ipi_lock);
        for (inp = LIST_FIRST(head); inp != NULL; inp = ninp) {
                ninp = LIST_NEXT(inp, inp_list);

                if (!(inp->inp_vflag & INP_IPV6))
                        continue;

                /*
                 * If the error designates a new path MTU for a destination
                 * and the application (associated with this socket) wanted to
                 * know the value, notify. Note that we notify for all
                 * disconnected sockets if the corresponding application
                 * wanted. This is because some UDP applications keep sending
                 * sockets disconnected.
                 * XXX: should we avoid to notify the value to TCP sockets?
                 */
                if (cmd == PRC_MSGSIZE && (inp->inp_flags & IN6P_MTU) != 0 &&
                    (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) ||
                    IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr,
                    &sa6_dst->sin6_addr))) {
                        ip6_notify_pmtu(inp, (struct sockaddr_in6 *)(void *)dst,
                            (u_int32_t *)cmdarg);
                }

                /*
                 * Detect if we should notify the error. If no source and
                 * destination ports are specifed, but non-zero flowinfo and
                 * local address match, notify the error. This is the case
                 * when the error is delivered with an encrypted buffer
                 * by ESP. Otherwise, just compare addresses and ports
                 * as usual.
                 */
                if (lport == 0 && fport == 0 && flowinfo &&
                    inp->inp_socket != NULL &&
                    flowinfo == (inp->inp_flow & IPV6_FLOWLABEL_MASK) &&
                    IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr, &sa6_src.sin6_addr))
                        goto do_notify;
                else if (!IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr,
                    &sa6_dst->sin6_addr) || inp->inp_socket == NULL ||
                    (lport && inp->inp_lport != lport) ||
                    (!IN6_IS_ADDR_UNSPECIFIED(&sa6_src.sin6_addr) &&
                    !IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr,
                    &sa6_src.sin6_addr)) || (fport && inp->inp_fport != fport))
                        continue;

do_notify:
                if (notify) {
                        if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) ==
                            WNT_STOPUSING)
                                continue;
                        socket_lock(inp->inp_socket, 1);
                        (*notify)(inp, errno);
                        (void) in_pcb_checkstate(inp, WNT_RELEASE, 1);
                        socket_unlock(inp->inp_socket, 1);
                }
        }
        lck_rw_done(pcbinfo->ipi_lock);
}

/*
 * Lookup a PCB based on the local address and port.
 */
struct inpcb *
in6_pcblookup_local(struct inpcbinfo *pcbinfo, struct in6_addr *laddr,
    u_int lport_arg, int wild_okay)
{
        struct inpcb *inp;
        int matchwild = 3, wildcard;
        u_short lport = lport_arg;
        struct inpcbporthead *porthash;
        struct inpcb *match = NULL;
        struct inpcbport *phd;

        if (!wild_okay) {
                struct inpcbhead *head;
                /*
                 * Look for an unconnected (wildcard foreign addr) PCB that
                 * matches the local address and port we're looking for.
                 */
                head = &pcbinfo->ipi_hashbase[INP_PCBHASH(INADDR_ANY, lport, 0,
                    pcbinfo->ipi_hashmask)];
                LIST_FOREACH(inp, head, inp_hash) {
                        if (!(inp->inp_vflag & INP_IPV6))
                                continue;
                        if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
                            IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr, laddr) &&
                            inp->inp_lport == lport) {
                                /*
                                 * Found.
                                 */
                                return (inp);
                        }
                }
                /*
                 * Not found.
                 */
                return (NULL);
        }
        /*
         * Best fit PCB lookup.
         *
         * First see if this local port is in use by looking on the
         * port hash list.
         */
        porthash = &pcbinfo->ipi_porthashbase[INP_PCBPORTHASH(lport,
            pcbinfo->ipi_porthashmask)];
        LIST_FOREACH(phd, porthash, phd_hash) {
                if (phd->phd_port == lport)
                        break;
        }
        if (phd != NULL) {
                /*
                 * Port is in use by one or more PCBs. Look for best
                 * fit.
                 */
                LIST_FOREACH(inp, &phd->phd_pcblist, inp_portlist) {
                        wildcard = 0;
                        if (!(inp->inp_vflag & INP_IPV6))
                                continue;
                        if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr))
                                wildcard++;
                        if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) {
                                if (IN6_IS_ADDR_UNSPECIFIED(laddr))
                                        wildcard++;
                                else if (!IN6_ARE_ADDR_EQUAL(
                                    &inp->in6p_laddr, laddr))
                                        continue;
                        } else {
                                if (!IN6_IS_ADDR_UNSPECIFIED(laddr))
                                        wildcard++;
                        }
                        if (wildcard < matchwild) {
                                match = inp;
                                matchwild = wildcard;
                                if (matchwild == 0) {
                                        break;
                                }
                        }
                }
        }
        return (match);
}

/*
 * Check for alternatives when higher level complains
 * about service problems.  For now, invalidate cached
 * routing information.  If the route was created dynamically
 * (by a redirect), time to try a default gateway again.
 */
void
in6_losing(struct inpcb *in6p)
{
        struct rtentry *rt;

        if ((rt = in6p->in6p_route.ro_rt) != NULL) {
                RT_LOCK(rt);
                if (rt->rt_flags & RTF_DYNAMIC) {
                        /*
                         * Prevent another thread from modifying rt_key,
                         * rt_gateway via rt_setgate() after the rt_lock
                         * is dropped by marking the route as defunct.
                         */
                        rt->rt_flags |= RTF_CONDEMNED;
                        RT_UNLOCK(rt);
                        (void) rtrequest(RTM_DELETE, rt_key(rt),
                            rt->rt_gateway, rt_mask(rt), rt->rt_flags, NULL);
                } else {
                        RT_UNLOCK(rt);
                }
                /*
                 * A new route can be allocated
                 * the next time output is attempted.
                 */
        }
        ROUTE_RELEASE(&in6p->in6p_route);
}

/*
 * After a routing change, flush old routing
 * and allocate a (hopefully) better one.
 */
void
in6_rtchange(struct inpcb *inp, int errno)
{
#pragma unused(errno)
        /*
         * A new route can be allocated the next time
         * output is attempted.
         */
        ROUTE_RELEASE(&inp->in6p_route);
}

/*
 * Check if PCB exists hash list. Also returns uid and gid of socket
 */
int
in6_pcblookup_hash_exists(struct inpcbinfo *pcbinfo, struct in6_addr *faddr,
    u_int fport_arg, struct in6_addr *laddr, u_int lport_arg, int wildcard,
    uid_t *uid, gid_t *gid, struct ifnet *ifp)
{
        struct inpcbhead *head;
        struct inpcb *inp;
        u_short fport = fport_arg, lport = lport_arg;
        int found;

        *uid = UID_MAX;
        *gid = GID_MAX;

        lck_rw_lock_shared(pcbinfo->ipi_lock);

        /*
         * First look for an exact match.
         */
        head = &pcbinfo->ipi_hashbase[INP_PCBHASH(faddr->s6_addr32[3] /* XXX */,
            lport, fport, pcbinfo->ipi_hashmask)];
        LIST_FOREACH(inp, head, inp_hash) {
                if (!(inp->inp_vflag & INP_IPV6))
                        continue;

                if (inp_restricted_recv(inp, ifp))
                        continue;

                if (IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, faddr) &&
                    IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr, laddr) &&
                    inp->inp_fport == fport &&
                    inp->inp_lport == lport) {
                        if ((found = (inp->inp_socket != NULL))) {
                                /*
                                 * Found. Check if pcb is still valid
                                 */
                                *uid = kauth_cred_getuid(
                                    inp->inp_socket->so_cred);
                                *gid = kauth_cred_getgid(
                                    inp->inp_socket->so_cred);
                        }
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (found);
                }
        }
        if (wildcard) {
                struct inpcb *local_wild = NULL;

                head = &pcbinfo->ipi_hashbase[INP_PCBHASH(INADDR_ANY, lport, 0,
                    pcbinfo->ipi_hashmask)];
                LIST_FOREACH(inp, head, inp_hash) {
                        if (!(inp->inp_vflag & INP_IPV6))
                                continue;

                        if (inp_restricted_recv(inp, ifp))
                                continue;

                        if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
                            inp->inp_lport == lport) {
                                if (IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr,
                                    laddr)) {
                                        found = (inp->inp_socket != NULL);
                                        if (found) {
                                                *uid = kauth_cred_getuid(
                                                    inp->inp_socket->so_cred);
                                                *gid = kauth_cred_getgid(
                                                    inp->inp_socket->so_cred);
                                        }
                                        lck_rw_done(pcbinfo->ipi_lock);
                                        return (found);
                                } else if (IN6_IS_ADDR_UNSPECIFIED(
                                    &inp->in6p_laddr)) {
                                        local_wild = inp;
                                }
                        }
                }
                if (local_wild) {
                        if ((found = (local_wild->inp_socket != NULL))) {
                                *uid = kauth_cred_getuid(
                                    local_wild->inp_socket->so_cred);
                                *gid = kauth_cred_getgid(
                                    local_wild->inp_socket->so_cred);
                        }
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (found);
                }
        }

        /*
         * Not found.
         */
        lck_rw_done(pcbinfo->ipi_lock);
        return (0);
}

/*
 * Lookup PCB in hash list.
 */
struct inpcb *
in6_pcblookup_hash(struct inpcbinfo *pcbinfo, struct in6_addr *faddr,
    u_int fport_arg, struct in6_addr *laddr, u_int lport_arg, int wildcard,
    struct ifnet *ifp)
{
        struct inpcbhead *head;
        struct inpcb *inp;
        u_short fport = fport_arg, lport = lport_arg;

        lck_rw_lock_shared(pcbinfo->ipi_lock);

        /*
         * First look for an exact match.
         */
        head = &pcbinfo->ipi_hashbase[INP_PCBHASH(faddr->s6_addr32[3] /* XXX */,
            lport, fport, pcbinfo->ipi_hashmask)];
        LIST_FOREACH(inp, head, inp_hash) {
                if (!(inp->inp_vflag & INP_IPV6))
                        continue;

                if (inp_restricted_recv(inp, ifp))
                        continue;

                if (IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, faddr) &&
                    IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr, laddr) &&
                    inp->inp_fport == fport &&
                    inp->inp_lport == lport) {
                        /*
                         * Found. Check if pcb is still valid
                         */
                        if (in_pcb_checkstate(inp, WNT_ACQUIRE, 0) !=
                            WNT_STOPUSING) {
                                lck_rw_done(pcbinfo->ipi_lock);
                                return (inp);
                        } else {
                                /* it's there but dead, say it isn't found */
                                lck_rw_done(pcbinfo->ipi_lock);
                                return (NULL);
                        }
                }
        }
        if (wildcard) {
                struct inpcb *local_wild = NULL;

                head = &pcbinfo->ipi_hashbase[INP_PCBHASH(INADDR_ANY, lport, 0,
                    pcbinfo->ipi_hashmask)];
                LIST_FOREACH(inp, head, inp_hash) {
                        if (!(inp->inp_vflag & INP_IPV6))
                                continue;

                        if (inp_restricted_recv(inp, ifp))
                                continue;

                        if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
                            inp->inp_lport == lport) {
                                if (IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr,
                                    laddr)) {
                                        if (in_pcb_checkstate(inp, WNT_ACQUIRE,
                                            0) != WNT_STOPUSING) {
                                                lck_rw_done(pcbinfo->ipi_lock);
                                                return (inp);
                                        } else {
                                                /* dead; say it isn't found */
                                                lck_rw_done(pcbinfo->ipi_lock);
                                                return (NULL);
                                        }
                                } else if (IN6_IS_ADDR_UNSPECIFIED(
                                    &inp->in6p_laddr)) {
                                        local_wild = inp;
                                }
                        }
                }
                if (local_wild && in_pcb_checkstate(local_wild,
                    WNT_ACQUIRE, 0) != WNT_STOPUSING) {
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (local_wild);
                } else {
                        lck_rw_done(pcbinfo->ipi_lock);
                        return (NULL);
                }
        }

        /*
         * Not found.
         */
        lck_rw_done(pcbinfo->ipi_lock);
        return (NULL);
}

void
init_sin6(struct sockaddr_in6 *sin6, struct mbuf *m)
{
        struct ip6_hdr *ip;

        ip = mtod(m, struct ip6_hdr *);
        bzero(sin6, sizeof (*sin6));
        sin6->sin6_len = sizeof (*sin6);
        sin6->sin6_family = AF_INET6;
        sin6->sin6_addr = ip->ip6_src;
        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr)) {
                sin6->sin6_addr.s6_addr16[1] = 0;
                if ((m->m_pkthdr.pkt_flags & (PKTF_LOOP|PKTF_IFAINFO)) ==
                    (PKTF_LOOP|PKTF_IFAINFO))
                        sin6->sin6_scope_id = m->m_pkthdr.src_ifindex;
                else if (m->m_pkthdr.rcvif != NULL)
                        sin6->sin6_scope_id = m->m_pkthdr.rcvif->if_index;
        }
}

/*
 * The following routines implement this scheme:
 *
 * Callers of ip6_output() that intend to cache the route in the inpcb pass
 * a local copy of the struct route to ip6_output().  Using a local copy of
 * the cached route significantly simplifies things as IP no longer has to
 * worry about having exclusive access to the passed in struct route, since
 * it's defined in the caller's stack; in essence, this allows for a lock-
 * less operation when updating the struct route at the IP level and below,
 * whenever necessary. The scheme works as follows:
 *
 * Prior to dropping the socket's lock and calling ip6_output(), the caller
 * copies the struct route from the inpcb into its stack, and adds a reference
 * to the cached route entry, if there was any.  The socket's lock is then
 * dropped and ip6_output() is called with a pointer to the copy of struct
 * route defined on the stack (not to the one in the inpcb.)
 *
 * Upon returning from ip6_output(), the caller then acquires the socket's
 * lock and synchronizes the cache; if there is no route cached in the inpcb,
 * it copies the local copy of struct route (which may or may not contain any
 * route) back into the cache; otherwise, if the inpcb has a route cached in
 * it, the one in the local copy will be freed, if there's any.  Trashing the
 * cached route in the inpcb can be avoided because ip6_output() is single-
 * threaded per-PCB (i.e. multiple transmits on a PCB are always serialized
 * by the socket/transport layer.)
 */
void
in6p_route_copyout(struct inpcb *inp, struct route_in6 *dst)
{
        struct route_in6 *src = &inp->in6p_route;

        lck_mtx_assert(&inp->inpcb_mtx, LCK_MTX_ASSERT_OWNED);

        /* Minor sanity check */
        if (src->ro_rt != NULL && rt_key(src->ro_rt)->sa_family != AF_INET6)
                panic("%s: wrong or corrupted route: %p", __func__, src);

        route_copyout((struct route *)dst, (struct route *)src, sizeof (*dst));
}

void
in6p_route_copyin(struct inpcb *inp, struct route_in6 *src)
{
        struct route_in6 *dst = &inp->in6p_route;

        lck_mtx_assert(&inp->inpcb_mtx, LCK_MTX_ASSERT_OWNED);

        /* Minor sanity check */
        if (src->ro_rt != NULL && rt_key(src->ro_rt)->sa_family != AF_INET6)
                panic("%s: wrong or corrupted route: %p", __func__, src);

        route_copyin((struct route *)src, (struct route *)dst, sizeof (*src));
}