[apple/xnu.git] / bsd / netinet6 / in6_src.c

/*
 * Copyright (c) 2000-2011 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@
 */

/*      $FreeBSD: src/sys/netinet6/in6_src.c,v 1.1.2.2 2001/07/03 11:01:52 ume Exp $    */
/*      $KAME: in6_src.c,v 1.37 2001/03/29 05:34:31 itojun Exp $        */

/*
 * 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/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/kauth.h>
#include <sys/priv.h>
#include <kern/lock.h>

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

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>

#include <net/net_osdep.h>

#include "loop.h"

SYSCTL_DECL(_net_inet6_ip6);

static int ip6_select_srcif_debug = 0;
SYSCTL_INT(_net_inet6_ip6, OID_AUTO, select_srcif_debug,
    CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_select_srcif_debug, 0,
    "log source interface selection debug info");

#define ADDR_LABEL_NOTAPP (-1)
struct in6_addrpolicy defaultaddrpolicy;

int ip6_prefer_tempaddr = 1;
#ifdef ENABLE_ADDRSEL
extern lck_mtx_t *addrsel_mutex;
#define ADDRSEL_LOCK()          lck_mtx_lock(addrsel_mutex)
#define ADDRSEL_UNLOCK()        lck_mtx_unlock(addrsel_mutex)
#else
#define ADDRSEL_LOCK()
#define ADDRSEL_UNLOCK()
#endif

static int selectroute(struct sockaddr_in6 *, struct sockaddr_in6 *,
        struct ip6_pktopts *, struct ip6_moptions *, struct route_in6 *,
        struct ifnet **, struct rtentry **, int, int, unsigned int,
        unsigned int);
static int in6_selectif(struct sockaddr_in6 *, struct ip6_pktopts *,
        struct ip6_moptions *, struct route_in6 *ro, unsigned int,
        unsigned int, struct ifnet **);
static void init_policy_queue(void);
static int add_addrsel_policyent(const struct in6_addrpolicy *);
#ifdef ENABLE_ADDRSEL
static int delete_addrsel_policyent(const struct in6_addrpolicy *);
#endif
static int walk_addrsel_policy(int (*)(const struct in6_addrpolicy *, void *),
        void *);
static int dump_addrsel_policyent(const struct in6_addrpolicy *, void *);
static struct in6_addrpolicy *match_addrsel_policy(struct sockaddr_in6 *);
void addrsel_policy_init(void);

/*
 * Return an IPv6 address, which is the most appropriate for a given
 * destination and user specified options.
 * If necessary, this function lookups the routing table and returns
 * an entry to the caller for later use.
 */
#define REPLACE(r) do {\
        if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
                sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
                ip6stat.ip6s_sources_rule[(r)]++; \
        goto replace; \
} while(0)
#define NEXTSRC(r) do {\
        if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
                sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
                ip6stat.ip6s_sources_rule[(r)]++; \
        goto next;              /* XXX: we can't use 'continue' here */ \
} while(0)
#define BREAK(r) do { \
        if ((r) < sizeof(ip6stat.ip6s_sources_rule) / \
                sizeof(ip6stat.ip6s_sources_rule[0])) /* check for safety */ \
                ip6stat.ip6s_sources_rule[(r)]++; \
        goto out;               /* XXX: we can't use 'break' here */ \
} while(0)

struct in6_addr *
in6_selectsrc(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
    struct inpcb *inp, struct route_in6 *ro,
    struct ifnet **ifpp, struct in6_addr *src_storage, unsigned int ifscope,
    int *errorp)
{
        struct in6_addr dst;
        struct ifnet *ifp = NULL;
        struct in6_ifaddr *ia = NULL, *ia_best = NULL;
        struct in6_pktinfo *pi = NULL;
        int dst_scope = -1, best_scope = -1, best_matchlen = -1;
        struct in6_addrpolicy *dst_policy = NULL, *best_policy = NULL;
        u_int32_t odstzone;
        int prefer_tempaddr;
        struct ip6_moptions *mopts;
        struct timeval timenow;
        unsigned int nocell;
        boolean_t islocal = FALSE;

        getmicrotime(&timenow);

        dst = dstsock->sin6_addr; /* make a copy for local operation */
        *errorp = 0;
        if (ifpp != NULL)
                *ifpp = NULL;

        if (inp != NULL) {
                mopts = inp->in6p_moptions;
                nocell = (inp->inp_flags & INP_NO_IFT_CELLULAR) ? 1 : 0;
        } else {
                mopts = NULL;
                nocell = 0;
        }

        /*
         * If the source address is explicitly specified by the caller,
         * check if the requested source address is indeed a unicast address
         * assigned to the node, and can be used as the packet's source
         * address.  If everything is okay, use the address as source.
         */
        if (opts && (pi = opts->ip6po_pktinfo) &&
            !IN6_IS_ADDR_UNSPECIFIED(&pi->ipi6_addr)) {
                struct sockaddr_in6 srcsock;
                struct in6_ifaddr *ia6;

                /* get the outgoing interface */
                if ((*errorp = in6_selectif(dstsock, opts, mopts, ro, ifscope,
                    nocell, &ifp)) != 0) {
                        return (NULL);
                }

                /*
                 * determine the appropriate zone id of the source based on
                 * the zone of the destination and the outgoing interface.
                 * If the specified address is ambiguous wrt the scope zone,
                 * the interface must be specified; otherwise, ifa_ifwithaddr()
                 * will fail matching the address.
                 */
                bzero(&srcsock, sizeof(srcsock));
                srcsock.sin6_family = AF_INET6;
                srcsock.sin6_len = sizeof(srcsock);
                srcsock.sin6_addr = pi->ipi6_addr;
                if (ifp) {
                        *errorp = in6_setscope(&srcsock.sin6_addr, ifp, NULL);
                        if (*errorp != 0) {
                                ifnet_release(ifp);
                                return (NULL);
                        }
                }
                ia6 = (struct in6_ifaddr *)ifa_ifwithaddr((struct sockaddr *)(&srcsock));
                if (ia6 == NULL) {
                        *errorp = EADDRNOTAVAIL;
                        if (ifp != NULL)
                                ifnet_release(ifp);
                        return (NULL);
                }
                IFA_LOCK_SPIN(&ia6->ia_ifa);
                if ((ia6->ia6_flags & (IN6_IFF_ANYCAST | IN6_IFF_NOTREADY)) ||
                    (nocell && (ia6->ia_ifa.ifa_ifp->if_type == IFT_CELLULAR))) {
                        IFA_UNLOCK(&ia6->ia_ifa);
                        IFA_REMREF(&ia6->ia_ifa);
                        *errorp = EADDRNOTAVAIL;
                        if (ifp != NULL)
                                ifnet_release(ifp);
                        return (NULL);
                }

                *src_storage = satosin6(&ia6->ia_addr)->sin6_addr;
                IFA_UNLOCK(&ia6->ia_ifa);
                IFA_REMREF(&ia6->ia_ifa);
                if (ifpp != NULL) {
                        /* if ifp is non-NULL, refcnt held in in6_selectif() */
                        *ifpp = ifp;
                } else if (ifp != NULL) {
                        ifnet_release(ifp);
                }
                return (src_storage);
        }

        /*
         * Otherwise, if the socket has already bound the source, just use it.
         */
        if (inp != NULL && !IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) 
                return (&inp->in6p_laddr);

        /*
         * If the address is not specified, choose the best one based on
         * the outgoing interface and the destination address.
         */

        /* get the outgoing interface */
        if ((*errorp = in6_selectif(dstsock, opts, mopts, ro, ifscope, nocell,
            &ifp)) != 0)
                return (NULL);

#ifdef DIAGNOSTIC
        if (ifp == NULL)        /* this should not happen */
                panic("in6_selectsrc: NULL ifp");
#endif
        *errorp = in6_setscope(&dst, ifp, &odstzone);
        if (*errorp != 0) {
                if (ifp != NULL)
                        ifnet_release(ifp);
                return (NULL);
        }
        lck_rw_lock_shared(&in6_ifaddr_rwlock);

        for (ia = in6_ifaddrs; ia; ia = ia->ia_next) {
                int new_scope = -1, new_matchlen = -1;
                struct in6_addrpolicy *new_policy = NULL;
                u_int32_t srczone, osrczone, dstzone;
                struct in6_addr src;
                struct ifnet *ifp1 = ia->ia_ifp;

                IFA_LOCK(&ia->ia_ifa);
                /*
                 * We'll never take an address that breaks the scope zone
                 * of the destination.  We also skip an address if its zone
                 * does not contain the outgoing interface.
                 * XXX: we should probably use sin6_scope_id here.
                 */
                if (in6_setscope(&dst, ifp1, &dstzone) ||
                    odstzone != dstzone)
                        goto next;

                src = ia->ia_addr.sin6_addr;
                if (in6_setscope(&src, ifp, &osrczone) ||
                    in6_setscope(&src, ifp1, &srczone) ||
                    osrczone != srczone)
                        goto next;

                /* avoid unusable addresses */
                if ((ia->ia6_flags &
                     (IN6_IFF_NOTREADY | IN6_IFF_ANYCAST | IN6_IFF_DETACHED)))
                        goto next;

                if (!ip6_use_deprecated && IFA6_IS_DEPRECATED(ia))
                        goto next;

                /* Rule 1: Prefer same address */
                if (IN6_ARE_ADDR_EQUAL(&dst, &ia->ia_addr.sin6_addr))
                        BREAK(1); /* there should be no better candidate */

                if (ia_best == NULL)
                        REPLACE(0);

                /* Rule 2: Prefer appropriate scope */
                if (dst_scope < 0)
                        dst_scope = in6_addrscope(&dst);
                new_scope = in6_addrscope(&ia->ia_addr.sin6_addr);
                if (IN6_ARE_SCOPE_CMP(best_scope, new_scope) < 0) {
                        if (IN6_ARE_SCOPE_CMP(best_scope, dst_scope) < 0)
                                REPLACE(2);
                        NEXTSRC(2);
                } else if (IN6_ARE_SCOPE_CMP(new_scope, best_scope) < 0) {
                        if (IN6_ARE_SCOPE_CMP(new_scope, dst_scope) < 0)
                                NEXTSRC(2);
                        REPLACE(2);
                }

                /*
                 * Rule 3: Avoid deprecated addresses.  Note that the case of
                 * !ip6_use_deprecated is already rejected above.
                 */
                if (!IFA6_IS_DEPRECATED(ia_best) && IFA6_IS_DEPRECATED(ia))
                        NEXTSRC(3);
                if (IFA6_IS_DEPRECATED(ia_best) && !IFA6_IS_DEPRECATED(ia))
                        REPLACE(3);

                /* Rule 4: Prefer home addresses */
                /*
                 * XXX: This is a TODO.  We should probably merge the MIP6
                 * case above.
                 */

                /* Rule 5: Prefer outgoing interface */
                if (ia_best->ia_ifp == ifp && ia->ia_ifp != ifp)
                        NEXTSRC(5);
                if (ia_best->ia_ifp != ifp && ia->ia_ifp == ifp)
                        REPLACE(5);

                /*
                 * Rule 6: Prefer matching label
                 * Note that best_policy should be non-NULL here.
                 */
                if (dst_policy == NULL)
                        dst_policy = in6_addrsel_lookup_policy(dstsock);
                if (dst_policy->label != ADDR_LABEL_NOTAPP) {
                        new_policy = in6_addrsel_lookup_policy(&ia->ia_addr);
                        if (dst_policy->label == best_policy->label &&
                            dst_policy->label != new_policy->label)
                                NEXTSRC(6);
                        if (dst_policy->label != best_policy->label &&
                            dst_policy->label == new_policy->label)
                                REPLACE(6);
                }

                /*
                 * Rule 7: Prefer public addresses.
                 * We allow users to reverse the logic by configuring
                 * a sysctl variable, so that privacy conscious users can
                 * always prefer temporary addresses.
                 * Don't use temporary addresses for local destinations or
                 * for multicast addresses unless we were passed in an option.
                 */
                if (IN6_IS_ADDR_MULTICAST(&dst) ||
                    in6_matchlen(&ia_best->ia_addr.sin6_addr, &dst) >=
                    in6_mask2len(&ia_best->ia_prefixmask.sin6_addr, NULL))
                        islocal = TRUE;
                if (opts == NULL ||
                    opts->ip6po_prefer_tempaddr == IP6PO_TEMPADDR_SYSTEM) {
                        prefer_tempaddr = islocal ? 0 : ip6_prefer_tempaddr;
                } else if (opts->ip6po_prefer_tempaddr ==
                    IP6PO_TEMPADDR_NOTPREFER) {
                        prefer_tempaddr = 0;
                } else
                        prefer_tempaddr = 1;
                if (!(ia_best->ia6_flags & IN6_IFF_TEMPORARY) &&
                    (ia->ia6_flags & IN6_IFF_TEMPORARY)) {
                        if (prefer_tempaddr)
                                REPLACE(7);
                        else
                                NEXTSRC(7);
                }
                if ((ia_best->ia6_flags & IN6_IFF_TEMPORARY) &&
                    !(ia->ia6_flags & IN6_IFF_TEMPORARY)) {
                        if (prefer_tempaddr)
                                NEXTSRC(7);
                        else
                                REPLACE(7);
                }

                /*
                 * Rule 8: prefer addresses on alive interfaces.
                 * This is a KAME specific rule.
                 */
                if ((ia_best->ia_ifp->if_flags & IFF_UP) &&
                    !(ia->ia_ifp->if_flags & IFF_UP))
                        NEXTSRC(8);
                if (!(ia_best->ia_ifp->if_flags & IFF_UP) &&
                    (ia->ia_ifp->if_flags & IFF_UP))
                        REPLACE(8);

                /*
                 * Rule 14: Use longest matching prefix.
                 * Note: in the address selection draft, this rule is
                 * documented as "Rule 8".  However, since it is also
                 * documented that this rule can be overridden, we assign
                 * a large number so that it is easy to assign smaller numbers
                 * to more preferred rules.
                 */
                new_matchlen = in6_matchlen(&ia->ia_addr.sin6_addr, &dst);
                if (best_matchlen < new_matchlen)
                        REPLACE(14);
                if (new_matchlen < best_matchlen)
                        NEXTSRC(14);

                /* Rule 15 is reserved. */

                /*
                 * Last resort: just keep the current candidate.
                 * Or, do we need more rules?
                 */
                IFA_UNLOCK(&ia->ia_ifa);
                continue;

replace:
                best_scope = (new_scope >= 0 ? new_scope :
                              in6_addrscope(&ia->ia_addr.sin6_addr));
                best_policy = (new_policy ? new_policy :
                               in6_addrsel_lookup_policy(&ia->ia_addr));
                best_matchlen = (new_matchlen >= 0 ? new_matchlen :
                                 in6_matchlen(&ia->ia_addr.sin6_addr, &dst));
                IFA_ADDREF_LOCKED(&ia->ia_ifa); /* for ia_best */
                IFA_UNLOCK(&ia->ia_ifa);
                if (ia_best != NULL)
                        IFA_REMREF(&ia_best->ia_ifa);
                ia_best = ia;
                continue;

next:
                IFA_UNLOCK(&ia->ia_ifa);
                continue;

out:
                IFA_ADDREF_LOCKED(&ia->ia_ifa); /* for ia_best */
                IFA_UNLOCK(&ia->ia_ifa);
                if (ia_best != NULL)
                        IFA_REMREF(&ia_best->ia_ifa);
                ia_best = ia;
                break;
        }

        lck_rw_done(&in6_ifaddr_rwlock);

        if (nocell && ia_best != NULL &&
            (ia_best->ia_ifa.ifa_ifp->if_type == IFT_CELLULAR)) {
                IFA_REMREF(&ia_best->ia_ifa);
                ia_best = NULL;
        }

        if ( (ia = ia_best) == NULL) {
                *errorp = EADDRNOTAVAIL;
                if (ifp != NULL)
                        ifnet_release(ifp);
                return (NULL);
        }

        IFA_LOCK_SPIN(&ia->ia_ifa);
        *src_storage = satosin6(&ia->ia_addr)->sin6_addr;
        IFA_UNLOCK(&ia->ia_ifa);
        IFA_REMREF(&ia->ia_ifa);
        if (ifpp != NULL) {
                /* if ifp is non-NULL, refcnt held in in6_selectif() */
                *ifpp = ifp;
        } else if (ifp != NULL) {
                ifnet_release(ifp);
        }
        return (src_storage);
}

/*
 * Given a source IPv6 address (and route, if available), determine the best
 * interface to send the packet from.  Checking for (and updating) the
 * ROF_SRCIF_SELECTED flag in the pcb-supplied route placeholder is done
 * without any locks, based on the assumption that in the event this is
 * called from ip6_output(), the output operation is single-threaded per-pcb,
 * i.e. for any given pcb there can only be one thread performing output at
 * the IPv6 layer.
 *
 * This routine is analogous to in_selectsrcif() for IPv4.
 *
 * clone - meaningful only for bsdi and freebsd
 */
static int
selectroute(struct sockaddr_in6 *srcsock, struct sockaddr_in6 *dstsock,
    struct ip6_pktopts *opts, struct ip6_moptions *mopts, struct route_in6 *ro,
    struct ifnet **retifp, struct rtentry **retrt, int clone,
    int norouteok, unsigned int ifscope, unsigned int nocell)
{
        int error = 0;
        struct ifnet *ifp = NULL;
        struct route_in6 *route = NULL;
        struct sockaddr_in6 *sin6_next;
        struct in6_pktinfo *pi = NULL;
        struct in6_addr *dst = &dstsock->sin6_addr;
        struct ifaddr *ifa = NULL;
        char s_src[MAX_IPv6_STR_LEN], s_dst[MAX_IPv6_STR_LEN];
        boolean_t select_srcif;

#if 0
        char ip6buf[INET6_ADDRSTRLEN];

        if (dstsock->sin6_addr.s6_addr32[0] == 0 &&
            dstsock->sin6_addr.s6_addr32[1] == 0 &&
            !IN6_IS_ADDR_LOOPBACK(&dstsock->sin6_addr)) {
                printf("in6_selectroute: strange destination %s\n",
                       ip6_sprintf(ip6buf, &dstsock->sin6_addr));
        } else {
                printf("in6_selectroute: destination = %s%%%d\n",
                       ip6_sprintf(ip6buf, &dstsock->sin6_addr),
                       dstsock->sin6_scope_id); /* for debug */
        }
#endif

        if (retifp != NULL)
                *retifp = NULL;

        if (retrt != NULL)
                *retrt = NULL;

        if (ip6_select_srcif_debug) {
                struct in6_addr src;
                src = (srcsock != NULL) ? srcsock->sin6_addr : in6addr_any;
                (void) inet_ntop(AF_INET6, &src, s_src, sizeof (s_src));
                (void) inet_ntop(AF_INET6, dst, s_dst, sizeof (s_dst));
        }

        /*
         * If the destination address is UNSPECIFIED addr, bail out.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(dst)) {
                error = EHOSTUNREACH;
                goto done;
        }

        /*
         * Perform source interface selection only if Scoped Routing
         * is enabled and a source address that isn't unspecified.
         */
        select_srcif = (ip6_doscopedroute && srcsock != NULL &&
            !IN6_IS_ADDR_UNSPECIFIED(&srcsock->sin6_addr));

        /*
         * If Scoped Routing is disabled, ignore the given ifscope.
         * Otherwise even if source selection won't be performed,
         * we still obey IPV6_BOUND_IF.
         */
        if (!ip6_doscopedroute && ifscope != IFSCOPE_NONE)
                ifscope = IFSCOPE_NONE;

        /* If the caller specified the outgoing interface explicitly, use it */
        if (opts != NULL && (pi = opts->ip6po_pktinfo) != NULL &&
            pi->ipi6_ifindex != 0) {
                /*
                 * If IPV6_PKTINFO takes precedence over IPV6_BOUND_IF.
                 */
                ifscope = pi->ipi6_ifindex;
                ifnet_head_lock_shared();
                /* ifp may be NULL if detached or out of range */
                ifp = (ifscope <= if_index) ? ifindex2ifnet[ifscope] : NULL;
                ifnet_head_done();
                if (norouteok || retrt == NULL || IN6_IS_ADDR_MULTICAST(dst)) {
                        /*
                         * We do not have to check or get the route for
                         * multicast.  If the caller didn't ask/care for
                         * the route and we have no interface to use,
                         * it's an error.
                         */
                        if (ifp == NULL)
                                error = EHOSTUNREACH;
                        goto done;
                } else {
                        goto getsrcif;
                }
        }

        /*
         * If the destination address is a multicast address and the outgoing
         * interface for the address is specified by the caller, use it.
         */
        if (IN6_IS_ADDR_MULTICAST(dst) && mopts != NULL) {
                IM6O_LOCK(mopts);
                if ((ifp = mopts->im6o_multicast_ifp) != NULL) {
                        IM6O_UNLOCK(mopts);
                        goto done; /* we do not need a route for multicast. */
                }
                IM6O_UNLOCK(mopts);
        }

getsrcif:
        /*
         * If the outgoing interface was not set via IPV6_BOUND_IF or
         * IPV6_PKTINFO, use the scope ID in the destination address.
         */
        if (ip6_doscopedroute && ifscope == IFSCOPE_NONE)
                ifscope = dstsock->sin6_scope_id;

        /*
         * Perform source interface selection; the source IPv6 address
         * must belong to one of the addresses of the interface used
         * by the route.  For performance reasons, do this only if
         * there is no route, or if the routing table has changed,
         * or if we haven't done source interface selection on this
         * route (for this PCB instance) before.
         */
        if (!select_srcif || (ro != NULL && ro->ro_rt != NULL &&
            (ro->ro_rt->rt_flags & RTF_UP) &&
            ro->ro_rt->generation_id == route_generation &&
            (ro->ro_flags & ROF_SRCIF_SELECTED))) {
                if (ro != NULL && ro->ro_rt != NULL) {
                        ifa = ro->ro_rt->rt_ifa;
                        IFA_ADDREF(ifa);
                }
                goto getroute;
        }

        /*
         * Given the source IPv6 address, find a suitable source interface
         * to use for transmission; if a scope ID has been specified,
         * optimize the search by looking at the addresses only for that
         * interface.  This is still suboptimal, however, as we need to
         * traverse the per-interface list.
         */
        if (ifscope != IFSCOPE_NONE || (ro != NULL && ro->ro_rt != NULL)) {
                unsigned int scope = ifscope;
                struct ifnet *rt_ifp;

                rt_ifp = (ro->ro_rt != NULL) ? ro->ro_rt->rt_ifp : NULL;

                /*
                 * If no scope is specified and the route is stale (pointing
                 * to a defunct interface) use the current primary interface;
                 * this happens when switching between interfaces configured
                 * with the same IPv6 address.  Otherwise pick up the scope
                 * information from the route; the ULP may have looked up a
                 * correct route and we just need to verify it here and mark
                 * it with the ROF_SRCIF_SELECTED flag below.
                 */
                if (scope == IFSCOPE_NONE) {
                        scope = rt_ifp->if_index;
                        if (scope != get_primary_ifscope(AF_INET6) &&
                            ro->ro_rt->generation_id != route_generation)
                                scope = get_primary_ifscope(AF_INET6);
                }

                ifa = (struct ifaddr *)
                    ifa_foraddr6_scoped(&srcsock->sin6_addr, scope);

                if (ip6_select_srcif_debug && ifa != NULL) {
                        if (ro->ro_rt != NULL) {
                                printf("%s->%s ifscope %d->%d ifa_if %s "
                                    "ro_if %s\n", s_src, s_dst, ifscope,
                                    scope, if_name(ifa->ifa_ifp),
                                    if_name(rt_ifp));
                        } else {
                                printf("%s->%s ifscope %d->%d ifa_if %s\n",
                                    s_src, s_dst, ifscope, scope,
                                    if_name(ifa->ifa_ifp));
                        }
                }
        }

        /*
         * Slow path; search for an interface having the corresponding source
         * IPv6 address if the scope was not specified by the caller, and:
         *
         *   1) There currently isn't any route, or,
         *   2) The interface used by the route does not own that source
         *      IPv6 address; in this case, the route will get blown away
         *      and we'll do a more specific scoped search using the newly
         *      found interface.
         */
        if (ifa == NULL && ifscope == IFSCOPE_NONE) {
                ifa = (struct ifaddr *)ifa_foraddr6(&srcsock->sin6_addr);

                if (ip6_select_srcif_debug && ifa != NULL) {
                        printf("%s->%s ifscope %d ifa_if %s\n",
                            s_src, s_dst, ifscope, if_name(ifa->ifa_ifp));
                }

        }

getroute:
        if (ifa != NULL)
                ifscope = ifa->ifa_ifp->if_index;

        /*
         * If the next hop address for the packet is specified by the caller,
         * use it as the gateway.
         */
        if (opts != NULL && opts->ip6po_nexthop != NULL) {
                struct route_in6 *ron;

                sin6_next = satosin6(opts->ip6po_nexthop);

                /* at this moment, we only support AF_INET6 next hops */
                if (sin6_next->sin6_family != AF_INET6) {
                        error = EAFNOSUPPORT; /* or should we proceed? */
                        goto done;
                }

                /*
                 * If the next hop is an IPv6 address, then the node identified
                 * by that address must be a neighbor of the sending host.
                 */
                ron = &opts->ip6po_nextroute;
                if (ron->ro_rt != NULL)
                        RT_LOCK(ron->ro_rt);
                if ((ron->ro_rt != NULL &&
                    ((ron->ro_rt->rt_flags & (RTF_UP | RTF_LLINFO)) !=
                    (RTF_UP | RTF_LLINFO) ||
                    ron->ro_rt->generation_id != route_generation ||
                    (select_srcif && (ifa == NULL ||
                    ifa->ifa_ifp != ron->ro_rt->rt_ifp)))) ||
                    !IN6_ARE_ADDR_EQUAL(&satosin6(&ron->ro_dst)->sin6_addr,
                    &sin6_next->sin6_addr)) {
                        if (ron->ro_rt != NULL) {
                                RT_UNLOCK(ron->ro_rt);
                                rtfree(ron->ro_rt);
                                ron->ro_rt = NULL;
                        }
                        *satosin6(&ron->ro_dst) = *sin6_next;
                }
                if (ron->ro_rt == NULL) {
                        rtalloc_scoped((struct route *)ron, ifscope);
                        if (ron->ro_rt != NULL)
                                RT_LOCK(ron->ro_rt);
                        if (ron->ro_rt == NULL ||
                            !(ron->ro_rt->rt_flags & RTF_LLINFO) ||
                            !IN6_ARE_ADDR_EQUAL(&satosin6(rt_key(ron->ro_rt))->
                            sin6_addr, &sin6_next->sin6_addr)) {
                                if (ron->ro_rt != NULL) {
                                        RT_UNLOCK(ron->ro_rt);
                                        rtfree(ron->ro_rt);
                                        ron->ro_rt = NULL;
                                }
                                error = EHOSTUNREACH;
                                goto done;
                        }
                }
                route = ron;
                ifp = ron->ro_rt->rt_ifp;

                /*
                 * When cloning is required, try to allocate a route to the
                 * destination so that the caller can store path MTU
                 * information.
                 */
                if (!clone) {
                        if (select_srcif) {
                                /* Keep the route locked */
                                goto validateroute;
                        }
                        RT_UNLOCK(ron->ro_rt);
                        goto done;
                }
                RT_UNLOCK(ron->ro_rt);
        }

        /*
         * Use a cached route if it exists and is valid, else try to allocate
         * a new one.  Note that we should check the address family of the
         * cached destination, in case of sharing the cache with IPv4.
         */
        if (ro == NULL)
                goto done;
        if (ro->ro_rt != NULL)
                RT_LOCK(ro->ro_rt);
        if (ro->ro_rt != NULL && (!(ro->ro_rt->rt_flags & RTF_UP) ||
            satosin6(&ro->ro_dst)->sin6_family != AF_INET6 ||
            ro->ro_rt->generation_id != route_generation ||
            !IN6_ARE_ADDR_EQUAL(&satosin6(&ro->ro_dst)->sin6_addr, dst) ||
            (select_srcif && (ifa == NULL ||
            ifa->ifa_ifp != ro->ro_rt->rt_ifp)))) {
                RT_UNLOCK(ro->ro_rt);
                rtfree(ro->ro_rt);
                ro->ro_rt = NULL;
        }
        if (ro->ro_rt == NULL) {
                struct sockaddr_in6 *sa6;

                if (ro->ro_rt != NULL)
                        RT_UNLOCK(ro->ro_rt);
                /* No route yet, so try to acquire one */
                bzero(&ro->ro_dst, sizeof(struct sockaddr_in6));
                sa6 = (struct sockaddr_in6 *)&ro->ro_dst;
                sa6->sin6_family = AF_INET6;
                sa6->sin6_len = sizeof(struct sockaddr_in6);
                sa6->sin6_addr = *dst;
                if (IN6_IS_ADDR_MULTICAST(dst)) {
                        ro->ro_rt = rtalloc1_scoped(
                            &((struct route *)ro)->ro_dst, 0, 0, ifscope);
                } else {
                        rtalloc_scoped((struct route *)ro, ifscope);
                }
                if (ro->ro_rt != NULL)
                        RT_LOCK(ro->ro_rt);
        }

        /*
         * Do not care about the result if we have the nexthop
         * explicitly specified (in case we're asked to clone.)
         */
        if (opts != NULL && opts->ip6po_nexthop != NULL) {
                if (ro->ro_rt != NULL)
                        RT_UNLOCK(ro->ro_rt);
                goto done;
        }

        if (ro->ro_rt != NULL) {
                RT_LOCK_ASSERT_HELD(ro->ro_rt);
                ifp = ro->ro_rt->rt_ifp;
        } else {
                error = EHOSTUNREACH;
        }
        route = ro;

validateroute:
        if (select_srcif) {
                boolean_t has_route = (route != NULL && route->ro_rt != NULL);

                if (has_route)
                        RT_LOCK_ASSERT_HELD(route->ro_rt);
                /*
                 * If there is a non-loopback route with the wrong interface,
                 * or if there is no interface configured with such an address,
                 * blow it away.  Except for local/loopback, we look for one
                 * with a matching interface scope/index.
                 */
                if (has_route && (ifa == NULL ||
                    (ifa->ifa_ifp != ifp && ifp != lo_ifp) ||
                    !(route->ro_rt->rt_flags & RTF_UP))) {
                        if (ip6_select_srcif_debug) {
                                if (ifa != NULL) {
                                        printf("%s->%s ifscope %d ro_if %s "
                                            "!= ifa_if %s (cached route "
                                            "cleared)\n", s_src, s_dst,
                                            ifscope, if_name(ifp),
                                            if_name(ifa->ifa_ifp));
                                } else {
                                        printf("%s->%s ifscope %d ro_if %s "
                                            "(no ifa_if found)\n", s_src,
                                            s_dst, ifscope, if_name(ifp));
                                }
                        }
                        RT_UNLOCK(route->ro_rt);
                        rtfree(route->ro_rt);
                        route->ro_rt = NULL;
                        route->ro_flags &= ~ROF_SRCIF_SELECTED;
                        error = EHOSTUNREACH;
                        /* Undo the settings done above */
                        route = NULL;
                        ifp = NULL;
                } else if (has_route) {
                        route->ro_flags |= ROF_SRCIF_SELECTED;
                        route->ro_rt->generation_id = route_generation;
                        RT_UNLOCK(route->ro_rt);
                }
        } else {
                if (ro->ro_rt != NULL)
                        RT_UNLOCK(ro->ro_rt);
                if (ifp != NULL && opts != NULL &&
                    opts->ip6po_pktinfo != NULL &&
                    opts->ip6po_pktinfo->ipi6_ifindex != 0) {
                        /*
                         * Check if the outgoing interface conflicts with the
                         * interface specified by ipi6_ifindex (if specified).
                         * Note that loopback interface is always okay.
                         * (this may happen when we are sending a packet to
                         * one of our own addresses.)
                         */
                        if (!(ifp->if_flags & IFF_LOOPBACK) && ifp->if_index !=
                            opts->ip6po_pktinfo->ipi6_ifindex) {
                                error = EHOSTUNREACH;
                                goto done;
                        }
                }
        }

done:
        if (nocell && error == 0) {
                if ((ifp != NULL && ifp->if_type == IFT_CELLULAR) ||
                    (route != NULL && route->ro_rt != NULL &&
                    route->ro_rt->rt_ifp->if_type == IFT_CELLULAR)) {
                        if (route != NULL && route->ro_rt != NULL) {
                                rtfree(route->ro_rt);
                                route->ro_rt = NULL;
                                route->ro_flags &= ~ROF_SRCIF_SELECTED;
                                route = NULL;
                        }
                        ifp = NULL;
                        error = EHOSTUNREACH;
                }
        }

        if (ifp == NULL && (route == NULL || route->ro_rt == NULL)) {
                /*
                 * This can happen if the caller did not pass a cached route
                 * nor any other hints.  We treat this case an error.
                 */
                error = EHOSTUNREACH;
        }
        if (error == EHOSTUNREACH)
                ip6stat.ip6s_noroute++;

        if (error == 0) {
                if (retifp != NULL) {
                        if (ifp != NULL)
                                ifnet_reference(ifp);   /* for caller */
                        *retifp = ifp;
                }
                if (retrt != NULL && route != NULL)
                        *retrt = route->ro_rt;  /* ro_rt may be NULL */
        } else if (select_srcif && ip6_select_srcif_debug) {
                printf("%s->%s ifscope %d ifa_if %s ro_if %s (error=%d)\n",
                    s_src, s_dst, ifscope,
                    (ifa != NULL) ? if_name(ifa->ifa_ifp) : "NONE",
                    (ifp != NULL) ? if_name(ifp) : "NONE", error);
        }

        if (ifa != NULL)
                IFA_REMREF(ifa);

        return (error);
}

static int
in6_selectif(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
    struct ip6_moptions *mopts, struct route_in6 *ro, unsigned int ifscope,
    unsigned int nocell, struct ifnet **retifp)
{
        int error;
        struct route_in6 sro;
        struct rtentry *rt = NULL;

        if (ro == NULL) {
                bzero(&sro, sizeof(sro));
                ro = &sro;
        }

        if ((error = selectroute(NULL, dstsock, opts, mopts, ro, retifp,
            &rt, 0, 1, ifscope, nocell)) != 0) {
                if (ro == &sro && rt && rt == sro.ro_rt)
                        rtfree(rt);
                return (error);
        }

        /*
         * do not use a rejected or black hole route.
         * XXX: this check should be done in the L2 output routine.
         * However, if we skipped this check here, we'd see the following
         * scenario:
         * - install a rejected route for a scoped address prefix
         *   (like fe80::/10)
         * - send a packet to a destination that matches the scoped prefix,
         *   with ambiguity about the scope zone.
         * - pick the outgoing interface from the route, and disambiguate the
         *   scope zone with the interface.
         * - ip6_output() would try to get another route with the "new"
         *   destination, which may be valid.
         * - we'd see no error on output.
         * Although this may not be very harmful, it should still be confusing.
         * We thus reject the case here.
         */
        if (rt && (rt->rt_flags & (RTF_REJECT | RTF_BLACKHOLE))) {
                int flags = (rt->rt_flags & RTF_HOST ? EHOSTUNREACH : ENETUNREACH);

                if (ro == &sro && rt && rt == sro.ro_rt)
                        rtfree(rt);
                return (flags);
        }

        /*
         * Adjust the "outgoing" interface.  If we're going to loop the packet
         * back to ourselves, the ifp would be the loopback interface.
         * However, we'd rather know the interface associated to the
         * destination address (which should probably be one of our own
         * addresses.)
         */
        if (rt && rt->rt_ifa && rt->rt_ifa->ifa_ifp) {
                if (*retifp != NULL)
                        ifnet_release(*retifp);
                *retifp = rt->rt_ifa->ifa_ifp;
                ifnet_reference(*retifp);
        }

        if (ro == &sro && rt && rt == sro.ro_rt)
                rtfree(rt);
        return (0);
}

/*
 * clone - meaningful only for bsdi and freebsd
 */
int
in6_selectroute(struct sockaddr_in6 *srcsock, struct sockaddr_in6 *dstsock,
    struct ip6_pktopts *opts, struct ip6_moptions *mopts, struct route_in6 *ro,
    struct ifnet **retifp, struct rtentry **retrt, int clone,
    unsigned int ifscope, unsigned int nocell)
{

        return (selectroute(srcsock, dstsock, opts, mopts, ro, retifp,
            retrt, clone, 0, ifscope, nocell));
}

/*
 * Default hop limit selection. The precedence is as follows:
 * 1. Hoplimit value specified via ioctl.
 * 2. (If the outgoing interface is detected) the current
 *     hop limit of the interface specified by router advertisement.
 * 3. The system default hoplimit.
*/
int
in6_selecthlim(
        struct in6pcb *in6p,
        struct ifnet *ifp)
{
        if (in6p && in6p->in6p_hops >= 0) {
                return(in6p->in6p_hops);
        } else {
                lck_rw_lock_shared(nd_if_rwlock);
                if (ifp && ifp->if_index < nd_ifinfo_indexlim) {
                        u_int8_t chlim = nd_ifinfo[ifp->if_index].chlim;
                        lck_rw_done(nd_if_rwlock);
                        return (chlim);
                } else {
                        lck_rw_done(nd_if_rwlock);
                        return(ip6_defhlim);
                }
        }
}

/*
 * XXX: this is borrowed from in6_pcbbind(). If possible, we should
 * share this function by all *bsd*...
 */
int
in6_pcbsetport(
        __unused struct in6_addr *laddr,
        struct inpcb *inp,
        struct proc *p,
        int locked)
{
        struct socket *so = inp->inp_socket;
        u_int16_t lport = 0, first, last, *lastport;
        int count, error = 0, wild = 0;
        struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
        kauth_cred_t cred;
        if (!locked) { /* Make sure we don't run into a deadlock: 4052373 */
                if (!lck_rw_try_lock_exclusive(pcbinfo->mtx)) {
                        socket_unlock(inp->inp_socket, 0);
                        lck_rw_lock_exclusive(pcbinfo->mtx);
                        socket_lock(inp->inp_socket, 0);
                }
        }

        /* XXX: this is redundant when called from in6_pcbbind */
        if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT)) == 0)
                wild = INPLOOKUP_WILDCARD;

        inp->inp_flags |= INP_ANONPORT;

        if (inp->inp_flags & INP_HIGHPORT) {
                first = ipport_hifirstauto;     /* sysctl */
                last  = ipport_hilastauto;
                lastport = &pcbinfo->lasthi;
        } else if (inp->inp_flags & INP_LOWPORT) {
                cred = kauth_cred_proc_ref(p);
                error = priv_check_cred(cred, PRIV_NETINET_RESERVEDPORT, 0);
                kauth_cred_unref(&cred);
                if (error != 0) {
                        if (!locked)
                                lck_rw_done(pcbinfo->mtx);
                        return error;
                }
                first = ipport_lowfirstauto;    /* 1023 */
                last  = ipport_lowlastauto;     /* 600 */
                lastport = &pcbinfo->lastlow;
        } else {
                first = ipport_firstauto;       /* sysctl */
                last  = ipport_lastauto;
                lastport = &pcbinfo->lastport;
        }
        /*
         * Simple check to ensure all ports are not used up causing
         * a deadlock here.
         *
         * We split the two cases (up and down) so that the direction
         * is not being tested on each round of the loop.
         */
        if (first > last) {
                /*
                 * counting down
                 */
                count = first - last;

                do {
                        if (count-- < 0) {      /* completely used? */
                                /*
                                 * Undo any address bind that may have
                                 * occurred above.
                                 */
                                inp->in6p_laddr = in6addr_any;
                                inp->in6p_last_outif = 0;
                                if (!locked)
                                        lck_rw_done(pcbinfo->mtx);
                                return (EAGAIN);
                        }
                        --*lastport;
                        if (*lastport > first || *lastport < last)
                                *lastport = first;
                        lport = htons(*lastport);
                } while (in6_pcblookup_local(pcbinfo,
                                             &inp->in6p_laddr, lport, wild));
        } else {
                /*
                         * counting up
                         */
                count = last - first;

                do {
                        if (count-- < 0) {      /* completely used? */
                                /*
                                 * Undo any address bind that may have
                                 * occurred above.
                                 */
                                inp->in6p_laddr = in6addr_any;
                                inp->in6p_last_outif = 0;
                                if (!locked)
                                        lck_rw_done(pcbinfo->mtx);
                                return (EAGAIN);
                        }
                        ++*lastport;
                        if (*lastport < first || *lastport > last)
                                *lastport = first;
                        lport = htons(*lastport);
                } while (in6_pcblookup_local(pcbinfo,
                                             &inp->in6p_laddr, lport, wild));
        }

        inp->inp_lport = lport;
        if (in_pcbinshash(inp, 1) != 0) {
                inp->in6p_laddr = in6addr_any;
                inp->inp_lport = 0;
                inp->in6p_last_outif = 0;
                if (!locked)
                        lck_rw_done(pcbinfo->mtx);
                return (EAGAIN);
        }

        if (!locked)
                lck_rw_done(pcbinfo->mtx);
        return(0);
}

/*
 * * The followings are implementation of the policy table using a
 * * simple tail queue.
 * * XXX such details should be hidden.
 * * XXX implementation using binary tree should be more efficient.
 * */
struct addrsel_policyent {
        TAILQ_ENTRY(addrsel_policyent) ape_entry;
        struct in6_addrpolicy ape_policy;
};

TAILQ_HEAD(addrsel_policyhead, addrsel_policyent);

struct addrsel_policyhead addrsel_policytab;

static void
init_policy_queue(void)
{

        TAILQ_INIT(&addrsel_policytab);
}

void
addrsel_policy_init(void)
{
        /*
         * Default address selection policy based on RFC 3484 and
         * draft-arifumi-6man-rfc3484-revise-03.
         */
        static const struct in6_addrpolicy defaddrsel[] = {
                /* localhost */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6ADDR_LOOPBACK_INIT,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK128,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 60,
                  .label    = 0 },
                /* ULA */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = {{{ 0xfc }}},
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK7,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 50,
                  .label    = 1 },
                /* any IPv6 src */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6ADDR_ANY_INIT,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK0,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 40,
                  .label    = 2 },
                /* any IPv4 src */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6ADDR_V4MAPPED_INIT,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK96,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 30,
                  .label    = 3 },
                /* 6to4 */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = {{{ 0x20, 0x02 }}},
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK16,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 20,
                  .label    = 4 },
                /* Teredo */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr   = {{{ 0x20, 0x01 }}},
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr   = IN6MASK32,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 10,
                  .label    = 5 },
                /* v4 compat addresses */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr = IN6ADDR_ANY_INIT,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr = IN6MASK96,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 1,
                  .label    = 10 },
                /* site-local (deprecated) */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr = {{{ 0xfe, 0xc0 }}},
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr = IN6MASK16,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 1,
                  .label    = 11 },
                /* 6bone (deprecated) */
                { .addr     = { .sin6_family = AF_INET6,
                                .sin6_addr = {{{ 0x3f, 0xfe }}},
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .addrmask = { .sin6_family = AF_INET6,
                                .sin6_addr = IN6MASK16,
                                .sin6_len    = sizeof(struct sockaddr_in6) },
                  .preced   = 1,
                  .label    = 12 },
        };
        int i;

        init_policy_queue();

        /* initialize the "last resort" policy */
        bzero(&defaultaddrpolicy, sizeof(defaultaddrpolicy));
        defaultaddrpolicy.label = ADDR_LABEL_NOTAPP;

        for (i = 0; i < sizeof(defaddrsel) / sizeof(defaddrsel[0]); i++)
                add_addrsel_policyent(&defaddrsel[i]);

}

struct in6_addrpolicy *
in6_addrsel_lookup_policy(struct sockaddr_in6 *key)
{
        struct in6_addrpolicy *match = NULL;

        ADDRSEL_LOCK();
        match = match_addrsel_policy(key);

        if (match == NULL)
                match = &defaultaddrpolicy;
        else
                match->use++;
        ADDRSEL_UNLOCK();

        return (match);
}

static struct in6_addrpolicy *
match_addrsel_policy(struct sockaddr_in6 *key)
{
        struct addrsel_policyent *pent;
        struct in6_addrpolicy *bestpol = NULL, *pol;
        int matchlen, bestmatchlen = -1;
        u_char *mp, *ep, *k, *p, m;

        TAILQ_FOREACH(pent, &addrsel_policytab, ape_entry) {
                matchlen = 0;

                pol = &pent->ape_policy;
                mp = (u_char *)&pol->addrmask.sin6_addr;
                ep = mp + 16;   /* XXX: scope field? */
                k = (u_char *)&key->sin6_addr;
                p = (u_char *)&pol->addr.sin6_addr;
                for (; mp < ep && *mp; mp++, k++, p++) {
                        m = *mp;
                        if ((*k & m) != *p)
                                goto next; /* not match */
                        if (m == 0xff) /* short cut for a typical case */
                                matchlen += 8;
                        else {
                                while (m >= 0x80) {
                                        matchlen++;
                                        m <<= 1;
                                }
                        }
                }

                /* matched.  check if this is better than the current best. */
                if (bestpol == NULL ||
                    matchlen > bestmatchlen) {
                        bestpol = pol;
                        bestmatchlen = matchlen;
                }

          next:
                continue;
        }

        return (bestpol);
} 

static int
add_addrsel_policyent(const struct in6_addrpolicy *newpolicy)
{
        struct addrsel_policyent *new, *pol;

        MALLOC(new, struct addrsel_policyent *, sizeof(*new), M_IFADDR,
               M_WAITOK);

        ADDRSEL_LOCK();

        /* duplication check */
        TAILQ_FOREACH(pol, &addrsel_policytab, ape_entry) {
                if (IN6_ARE_ADDR_EQUAL(&newpolicy->addr.sin6_addr,
                                       &pol->ape_policy.addr.sin6_addr) &&
                    IN6_ARE_ADDR_EQUAL(&newpolicy->addrmask.sin6_addr,
                                       &pol->ape_policy.addrmask.sin6_addr)) {
                        ADDRSEL_UNLOCK();
                        FREE(new, M_IFADDR);
                        return (EEXIST);        /* or override it? */
                }
        }

        bzero(new, sizeof(*new));

        /* XXX: should validate entry */
        new->ape_policy = *newpolicy;

        TAILQ_INSERT_TAIL(&addrsel_policytab, new, ape_entry);
        ADDRSEL_UNLOCK();

        return (0);
}
#ifdef ENABLE_ADDRSEL
static int
delete_addrsel_policyent(const struct in6_addrpolicy *key)
{
        struct addrsel_policyent *pol;


        ADDRSEL_LOCK();

        /* search for the entry in the table */
        TAILQ_FOREACH(pol, &addrsel_policytab, ape_entry) {
                if (IN6_ARE_ADDR_EQUAL(&key->addr.sin6_addr,
                    &pol->ape_policy.addr.sin6_addr) &&
                    IN6_ARE_ADDR_EQUAL(&key->addrmask.sin6_addr,
                    &pol->ape_policy.addrmask.sin6_addr)) {
                        break;
                }
        }
        if (pol == NULL) {
                ADDRSEL_UNLOCK();
                return (ESRCH);
        }

        TAILQ_REMOVE(&addrsel_policytab, pol, ape_entry);
        FREE(pol, M_IFADDR);
        pol = NULL;
        ADDRSEL_UNLOCK();

        return (0);
}
#endif /* ENABLE_ADDRSEL */

int
walk_addrsel_policy(int (*callback)(const struct in6_addrpolicy *, void *),
    void *w)
{
        struct addrsel_policyent *pol;
        int error = 0;

        ADDRSEL_LOCK();
        TAILQ_FOREACH(pol, &addrsel_policytab, ape_entry) {
                if ((error = (*callback)(&pol->ape_policy, w)) != 0) {
                        ADDRSEL_UNLOCK();
                        return (error);
                }
        }
        ADDRSEL_UNLOCK();
        return (error);
}
/*
 * Subroutines to manage the address selection policy table via sysctl.
 */
struct walkarg {
        struct sysctl_req *w_req;
};


static int
dump_addrsel_policyent(const struct in6_addrpolicy *pol, void *arg)
{
        int error = 0;
        struct walkarg *w = arg;

        error = SYSCTL_OUT(w->w_req, pol, sizeof(*pol));

        return (error);
}

static int
in6_src_sysctl SYSCTL_HANDLER_ARGS 
{
#pragma unused(oidp, arg1, arg2)
struct walkarg w;

        if (req->newptr)
                return EPERM;
        bzero(&w, sizeof(w));
        w.w_req = req;

        return (walk_addrsel_policy(dump_addrsel_policyent, &w));
}


SYSCTL_NODE(_net_inet6_ip6, IPV6CTL_ADDRCTLPOLICY, addrctlpolicy,
        CTLFLAG_RD | CTLFLAG_LOCKED, in6_src_sysctl, "");
int
in6_src_ioctl(u_long cmd, caddr_t data)
{
        int i;
        struct in6_addrpolicy ent0;

        if (cmd != SIOCAADDRCTL_POLICY && cmd != SIOCDADDRCTL_POLICY)
                return (EOPNOTSUPP); /* check for safety */

        ent0 = *(struct in6_addrpolicy *)data;

        if (ent0.label == ADDR_LABEL_NOTAPP)
                return (EINVAL);
        /* check if the prefix mask is consecutive. */
        if (in6_mask2len(&ent0.addrmask.sin6_addr, NULL) < 0)
                return (EINVAL);
        /* clear trailing garbages (if any) of the prefix address. */
        for (i = 0; i < 4; i++) {
                ent0.addr.sin6_addr.s6_addr32[i] &=
                        ent0.addrmask.sin6_addr.s6_addr32[i];
        }
        ent0.use = 0;

        switch (cmd) {
        case SIOCAADDRCTL_POLICY:
#ifdef ENABLE_ADDRSEL
                return (add_addrsel_policyent(&ent0));
#else
                return (ENOTSUP);
#endif
        case SIOCDADDRCTL_POLICY:
#ifdef ENABLE_ADDRSEL
                return (delete_addrsel_policyent(&ent0));
#else
                return (ENOTSUP);
#endif
        }

        return (0);             /* XXX: compromise compilers */
}

/*
 * generate kernel-internal form (scopeid embedded into s6_addr16[1]).
 * If the address scope of is link-local, embed the interface index in the
 * address.  The routine determines our precedence
 * between advanced API scope/interface specification and basic API
 * specification.
 *
 * this function should be nuked in the future, when we get rid of
 * embedded scopeid thing.
 *
 * XXX actually, it is over-specification to return ifp against sin6_scope_id.
 * there can be multiple interfaces that belong to a particular scope zone
 * (in specification, we have 1:N mapping between a scope zone and interfaces).
 * we may want to change the function to return something other than ifp.
 */
int
in6_embedscope(
        struct in6_addr *in6,
        const struct sockaddr_in6 *sin6,
        struct in6pcb *in6p,
        struct ifnet **ifpp,
        struct ip6_pktopts *opt)
{
        struct ifnet *ifp = NULL;
        u_int32_t scopeid;
        struct ip6_pktopts *optp = NULL;

        *in6 = sin6->sin6_addr;
        scopeid = sin6->sin6_scope_id;
        if (ifpp != NULL)
                *ifpp = NULL;

        /*
         * don't try to read sin6->sin6_addr beyond here, since the caller may
         * ask us to overwrite existing sockaddr_in6
         */

#ifdef ENABLE_DEFAULT_SCOPE
        if (scopeid == 0)
                scopeid = scope6_addr2default(in6);
#endif

        if (IN6_IS_SCOPE_LINKLOCAL(in6)) {
                struct in6_pktinfo *pi;
                struct ifnet *im6o_multicast_ifp = NULL;

                if (in6p != NULL && IN6_IS_ADDR_MULTICAST(in6) &&
                    in6p->in6p_moptions != NULL) {
                        IM6O_LOCK(in6p->in6p_moptions);
                        im6o_multicast_ifp =
                            in6p->in6p_moptions->im6o_multicast_ifp;
                        IM6O_UNLOCK(in6p->in6p_moptions);
                }

                if (opt)
                        optp = opt;
                else if (in6p)
                        optp = in6p->in6p_outputopts;
                /*
                 * KAME assumption: link id == interface id
                 */
                ifnet_head_lock_shared();
                if (in6p && optp && (pi = optp->ip6po_pktinfo) &&
                    pi->ipi6_ifindex) {
                        ifp = ifindex2ifnet[pi->ipi6_ifindex];
                        in6->s6_addr16[1] = htons(pi->ipi6_ifindex);
                } else if (in6p && IN6_IS_ADDR_MULTICAST(in6) &&
                    in6p->in6p_moptions != NULL && im6o_multicast_ifp != NULL) {
                        ifp = im6o_multicast_ifp;
                        in6->s6_addr16[1] = htons(ifp->if_index);
                } else if (scopeid) {
                        /* 
                         * Since scopeid is unsigned, we only have to check it
                         * against if_index
                         */
                        if (if_index < scopeid) {
                                ifnet_head_done();
                                return ENXIO;  /* XXX EINVAL? */

                        }
                        ifp = ifindex2ifnet[scopeid];
                        /*XXX assignment to 16bit from 32bit variable */
                        in6->s6_addr16[1] = htons(scopeid & 0xffff);
                }
                ifnet_head_done();

                if (ifpp != NULL) {
                        if (ifp != NULL)
                                ifnet_reference(ifp);   /* for caller */
                        *ifpp = ifp;
                }
        }

        return 0;
}

/*
 * generate standard sockaddr_in6 from embedded form.
 * touches sin6_addr and sin6_scope_id only.
 *
 * this function should be nuked in the future, when we get rid of
 * embedded scopeid thing.
 */
int
in6_recoverscope(
        struct sockaddr_in6 *sin6,
        const struct in6_addr *in6,
        struct ifnet *ifp)
{
        u_int32_t scopeid;

        sin6->sin6_addr = *in6;

        /*
         * don't try to read *in6 beyond here, since the caller may
         * ask us to overwrite existing sockaddr_in6
         */

        sin6->sin6_scope_id = 0;
        if (IN6_IS_SCOPE_LINKLOCAL(in6)) {
                /*
                 * KAME assumption: link id == interface id
                 */
                scopeid = ntohs(sin6->sin6_addr.s6_addr16[1]);
                if (scopeid) {
                        /* 
                         * sanity check 
                         *
                         * Since scopeid is unsigned, we only have to check it
                         * against if_index
                         */
                        if (if_index < scopeid)
                                return ENXIO;
                        if (ifp && ifp->if_index != scopeid)
                                return ENXIO;
                        sin6->sin6_addr.s6_addr16[1] = 0;
                        sin6->sin6_scope_id = scopeid;
                }
        }

        return 0;
}