xnu-1699.32.7.tar.gz

[apple/xnu.git] / bsd / netinet6 / nd6_rtr.c

/*
 * Copyright (c) 2003-2011 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/nd6_rtr.c,v 1.11 2002/04/19 04:46:23 suz Exp $       */
/*      $KAME: nd6_rtr.c,v 1.111 2001/04/27 01:37:15 jinmei 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.
 */


#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/queue.h>
#include <sys/mcache.h>

#include <kern/lock.h>
#include <kern/zalloc.h>
#include <machine/machine_routines.h>

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

#include <netinet/in.h>
#include <netinet6/in6_var.h>
#include <netinet6/in6_ifattach.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/nd6.h>
#include <netinet/icmp6.h>
#include <netinet6/scope6_var.h>

#include <net/net_osdep.h>

#define SDL(s)  ((struct sockaddr_dl *)s)

static struct nd_defrouter *defrtrlist_update_common(struct nd_defrouter *,
    boolean_t);
static struct nd_defrouter *defrtrlist_update(struct nd_defrouter *);

static struct in6_ifaddr *in6_ifadd(struct nd_prefix *, int);
static void defrtrlist_sync(struct ifnet *);

static void defrouter_select_common(struct ifnet *, int);

static struct nd_pfxrouter *pfxrtr_lookup(struct nd_prefix *,
        struct nd_defrouter *);
static void pfxrtr_add(struct nd_prefix *, struct nd_defrouter *);
static void pfxrtr_del(struct nd_pfxrouter *);
static struct nd_pfxrouter *find_pfxlist_reachable_router(struct nd_prefix *);
static void nd6_rtmsg(int, struct rtentry *);

static int nd6_prefix_onlink_common(struct nd_prefix *, boolean_t,
    unsigned int);
static struct nd_prefix *nd6_prefix_equal_lookup(struct nd_prefix *, boolean_t);
static void nd6_prefix_sync(struct ifnet *);

static void in6_init_address_ltimes(struct nd_prefix *,
    struct in6_addrlifetime *, boolean_t);

static int rt6_deleteroute(struct radix_node *, void *);

static struct nd_defrouter *nddr_alloc(int);
static void nddr_free(struct nd_defrouter *);
static void nddr_trace(struct nd_defrouter *, int);

static struct nd_prefix *ndpr_alloc(int);
static void ndpr_free(struct nd_prefix *);
static void ndpr_trace(struct nd_prefix *, int);

extern int nd6_recalc_reachtm_interval;

static struct ifnet *nd6_defifp;
int nd6_defifindex;
static unsigned int nd6_defrouter_genid;

int ip6_use_tempaddr = 1; /* use temp addr by default for testing now */

int nd6_accept_6to4 = 1;

int ip6_desync_factor;
u_int32_t ip6_temp_preferred_lifetime = DEF_TEMP_PREFERRED_LIFETIME;
u_int32_t ip6_temp_valid_lifetime = DEF_TEMP_VALID_LIFETIME;
/*
 * shorter lifetimes for debugging purposes.
u_int32_t ip6_temp_preferred_lifetime = 800;
static u_int32_t ip6_temp_valid_lifetime = 1800;
*/
int ip6_temp_regen_advance = TEMPADDR_REGEN_ADVANCE;

extern lck_mtx_t *nd6_mutex;

/* Serialization variables for single thread access to nd_prefix */
static boolean_t nd_prefix_busy;
static void *nd_prefix_waitchan = &nd_prefix_busy;
static int nd_prefix_waiters = 0;

/* Serialization variables for single thread access to nd_defrouter */
static boolean_t nd_defrouter_busy;
static void *nd_defrouter_waitchan = &nd_defrouter_busy;
static int nd_defrouter_waiters = 0;

/* RTPREF_MEDIUM has to be 0! */
#define RTPREF_HIGH     1
#define RTPREF_MEDIUM   0
#define RTPREF_LOW      (-1)
#define RTPREF_RESERVED (-2)
#define RTPREF_INVALID  (-3)    /* internal */

#define NDPR_TRACE_HIST_SIZE    32              /* size of trace history */

/* For gdb */
__private_extern__ unsigned int ndpr_trace_hist_size = NDPR_TRACE_HIST_SIZE;

struct nd_prefix_dbg {
        struct nd_prefix        ndpr_pr;                /* nd_prefix */
        u_int16_t               ndpr_refhold_cnt;       /* # of ref */
        u_int16_t               ndpr_refrele_cnt;       /* # of rele */
        /*
         * Circular lists of ndpr_addref and ndpr_remref callers.
         */
        ctrace_t                ndpr_refhold[NDPR_TRACE_HIST_SIZE];
        ctrace_t                ndpr_refrele[NDPR_TRACE_HIST_SIZE];
};

static unsigned int ndpr_debug;                 /* debug flags */
static unsigned int ndpr_size;                  /* size of zone element */
static struct zone *ndpr_zone;                  /* zone for nd_prefix */

#define NDPR_ZONE_MAX   64                      /* maximum elements in zone */
#define NDPR_ZONE_NAME  "nd6_prefix"            /* zone name */

#define NDDR_TRACE_HIST_SIZE    32              /* size of trace history */

/* For gdb */
__private_extern__ unsigned int nddr_trace_hist_size = NDDR_TRACE_HIST_SIZE;

struct nd_defrouter_dbg {
        struct nd_defrouter     nddr_dr;                /* nd_defrouter */
        uint16_t                nddr_refhold_cnt;       /* # of ref */
        uint16_t                nddr_refrele_cnt;       /* # of rele */
        /*
         * Circular lists of ndpr_addref and ndpr_remref callers.
         */
        ctrace_t                nddr_refhold[NDDR_TRACE_HIST_SIZE];
        ctrace_t                nddr_refrele[NDDR_TRACE_HIST_SIZE];
};

static unsigned int nddr_debug;                 /* debug flags */
static unsigned int nddr_size;                  /* size of zone element */
static struct zone *nddr_zone;                  /* zone for nd_defrouter */

#define NDDR_ZONE_MAX   64                      /* maximum elements in zone */
#define NDDR_ZONE_NAME  "nd6_defrouter"         /* zone name */

static unsigned int ndprtr_size;                /* size of zone element */
static struct zone *ndprtr_zone;                /* zone for nd_pfxrouter */

#define NDPRTR_ZONE_MAX 64                      /* maximum elements in zone */
#define NDPRTR_ZONE_NAME "nd6_pfxrouter"        /* zone name */

void
nd6_rtr_init(void)
{
        PE_parse_boot_argn("ifa_debug", &ndpr_debug, sizeof (ndpr_debug));
        PE_parse_boot_argn("ifa_debug", &nddr_debug, sizeof (nddr_debug));

        ndpr_size = (ndpr_debug == 0) ? sizeof (struct nd_prefix) :
            sizeof (struct nd_prefix_dbg);
        ndpr_zone = zinit(ndpr_size, NDPR_ZONE_MAX * ndpr_size, 0,
            NDPR_ZONE_NAME);
        if (ndpr_zone == NULL) {
                panic("%s: failed allocating %s", __func__, NDPR_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(ndpr_zone, Z_EXPAND, TRUE);
        zone_change(ndpr_zone, Z_CALLERACCT, FALSE);

        nddr_size = (nddr_debug == 0) ? sizeof (struct nd_defrouter) :
            sizeof (struct nd_defrouter_dbg);
        nddr_zone = zinit(nddr_size, NDDR_ZONE_MAX * nddr_size, 0,
            NDDR_ZONE_NAME);
        if (nddr_zone == NULL) {
                panic("%s: failed allocating %s", __func__, NDDR_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(nddr_zone, Z_EXPAND, TRUE);
        zone_change(nddr_zone, Z_CALLERACCT, FALSE);

        ndprtr_size = sizeof (struct nd_pfxrouter);
        ndprtr_zone = zinit(ndprtr_size, NDPRTR_ZONE_MAX * ndprtr_size, 0,
            NDPRTR_ZONE_NAME);
        if (ndprtr_zone == NULL) {
                panic("%s: failed allocating %s", __func__, NDPRTR_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(ndprtr_zone, Z_EXPAND, TRUE);
        zone_change(ndprtr_zone, Z_CALLERACCT, FALSE);
}

/*
 * Receive Router Solicitation Message - just for routers.
 * Router solicitation/advertisement is mostly managed by userland program
 * (rtadvd) so here we have no function like nd6_ra_output().
 *
 * Based on RFC 2461
 */
void
nd6_rs_input(
        struct  mbuf *m,
        int off,
        int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_router_solicit *nd_rs;
        struct in6_addr saddr6 = ip6->ip6_src;
        char *lladdr = NULL;
        int lladdrlen = 0;
        union nd_opts ndopts;

        /* If I'm not a router, ignore it. */
        if (ip6_accept_rtadv != 0 || (ifp->if_eflags & IFEF_ACCEPT_RTADVD) || ip6_forwarding != 1)
                goto freeit;

        /* Sanity checks */
        if (ip6->ip6_hlim != 255) {
                nd6log((LOG_ERR,
                    "nd6_rs_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp)));
                goto bad;
        }

        /*
         * Don't update the neighbor cache, if src = :: or a non-neighbor.
         * The former case indicates that the src has no IP address assigned
         * yet.  See nd6_ns_input() for the latter case.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src))
                goto freeit;
        else {
                struct sockaddr_in6 src_sa6;

                bzero(&src_sa6, sizeof(src_sa6));
                src_sa6.sin6_family = AF_INET6;
                src_sa6.sin6_len = sizeof(src_sa6);
                src_sa6.sin6_addr = ip6->ip6_src;
                if (!nd6_is_addr_neighbor(&src_sa6, ifp, 0)) {
                        nd6log((LOG_INFO, "nd6_rs_input: "
                                "RS packet from non-neighbor\n"));
                        goto freeit;
                }
        }

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len, return);
        nd_rs = (struct nd_router_solicit *)((caddr_t)ip6 + off);
#else
        IP6_EXTHDR_GET(nd_rs, struct nd_router_solicit *, m, off, icmp6len);
        if (nd_rs == NULL) {
                icmp6stat.icp6s_tooshort++;
                return;
        }
#endif

        icmp6len -= sizeof(*nd_rs);
        nd6_option_init(nd_rs + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log((LOG_INFO,
                    "nd6_rs_input: invalid ND option, ignored\n"));
                /* nd6_options have incremented stats */
                goto freeit;
        }

        if (ndopts.nd_opts_src_lladdr) {
                lladdr = (char *)(ndopts.nd_opts_src_lladdr + 1);
                lladdrlen = ndopts.nd_opts_src_lladdr->nd_opt_len << 3;
        }

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log((LOG_INFO,
                    "nd6_rs_input: lladdrlen mismatch for %s "
                    "(if %d, RS packet %d)\n",
                        ip6_sprintf(&saddr6), ifp->if_addrlen, lladdrlen - 2));
                goto bad;
        }

        nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, ND_ROUTER_SOLICIT, 0);

 freeit:
        m_freem(m);
        return;

 bad:
        icmp6stat.icp6s_badrs++;
        m_freem(m);
}

/*
 * Receive Router Advertisement Message.
 *
 * Based on RFC 2461
 * TODO: on-link bit on prefix information
 * TODO: ND_RA_FLAG_{OTHER,MANAGED} processing
 */
void
nd6_ra_input(
        struct  mbuf *m,
        int off, 
        int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct nd_ifinfo *ndi = NULL;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_router_advert *nd_ra;
        struct in6_addr saddr6 = ip6->ip6_src;
        int mcast = 0;
        union nd_opts ndopts;
        struct nd_defrouter *dr = NULL;
        struct timeval timenow;

        getmicrotime(&timenow);

        if (ip6_accept_rtadv == 0 && ((ifp->if_eflags & IFEF_ACCEPT_RTADVD) == 0))
                goto freeit;

        if (ip6->ip6_hlim != 255) {
                nd6log((LOG_ERR,
                    "nd6_ra_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp)));
                goto bad;
        }

        if (!IN6_IS_ADDR_LINKLOCAL(&saddr6)) {
                nd6log((LOG_ERR,
                    "nd6_ra_input: src %s is not link-local\n",
                    ip6_sprintf(&saddr6)));
                goto bad;
        }

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len, return);
        nd_ra = (struct nd_router_advert *)((caddr_t)ip6 + off);
#else
        IP6_EXTHDR_GET(nd_ra, struct nd_router_advert *, m, off, icmp6len);
        if (nd_ra == NULL) {
                icmp6stat.icp6s_tooshort++;
                return;
        }
#endif

        icmp6len -= sizeof(*nd_ra);
        nd6_option_init(nd_ra + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log((LOG_INFO,
                    "nd6_ra_input: invalid ND option, ignored\n"));
                /* nd6_options have incremented stats */
                goto freeit;
        }

    {
        struct nd_defrouter dr0;
        u_int32_t advreachable = nd_ra->nd_ra_reachable;

        /* remember if this is a multicasted advertisement */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst))
                mcast = 1;

        lck_rw_lock_shared(nd_if_rwlock);
        if (ifp->if_index >= nd_ifinfo_indexlim) {
                lck_rw_done(nd_if_rwlock);
                goto freeit;
        }
        ndi = &nd_ifinfo[ifp->if_index];
        bzero(&dr0, sizeof (dr0));
        dr0.rtaddr = saddr6;
        dr0.flags  = nd_ra->nd_ra_flags_reserved;
        dr0.rtlifetime = ntohs(nd_ra->nd_ra_router_lifetime);
        dr0.expire = timenow.tv_sec + dr0.rtlifetime;
        dr0.ifp = ifp;
        /* unspecified or not? (RFC 2461 6.3.4) */
        if (advreachable) {
                advreachable = ntohl(advreachable);
                if (advreachable <= MAX_REACHABLE_TIME &&
                    ndi->basereachable != advreachable) {
                        ndi->basereachable = advreachable;
                        ndi->reachable = ND_COMPUTE_RTIME(ndi->basereachable);
                        ndi->recalctm = nd6_recalc_reachtm_interval; /* reset */
                }
        }
        if (nd_ra->nd_ra_retransmit)
                ndi->retrans = ntohl(nd_ra->nd_ra_retransmit);
        if (nd_ra->nd_ra_curhoplimit)
                ndi->chlim = nd_ra->nd_ra_curhoplimit;
        lck_rw_done(nd_if_rwlock);
        ndi = NULL;
        lck_mtx_lock(nd6_mutex);
        dr = defrtrlist_update(&dr0);
        lck_mtx_unlock(nd6_mutex);
    }

        /*
         * prefix
         */
        if (ndopts.nd_opts_pi) {
                struct nd_opt_hdr *pt;
                struct nd_opt_prefix_info *pi = NULL;
                struct nd_prefix pr;

                for (pt = (struct nd_opt_hdr *)ndopts.nd_opts_pi;
                     pt <= (struct nd_opt_hdr *)ndopts.nd_opts_pi_end;
                     pt = (struct nd_opt_hdr *)((caddr_t)pt +
                                                (pt->nd_opt_len << 3))) {
                        if (pt->nd_opt_type != ND_OPT_PREFIX_INFORMATION)
                                continue;
                        pi = (struct nd_opt_prefix_info *)pt;

                        if (pi->nd_opt_pi_len != 4) {
                                nd6log((LOG_INFO,
                                    "nd6_ra_input: invalid option "
                                    "len %d for prefix information option, "
                                    "ignored\n", pi->nd_opt_pi_len));
                                continue;
                        }

                        if (128 < pi->nd_opt_pi_prefix_len) {
                                nd6log((LOG_INFO,
                                    "nd6_ra_input: invalid prefix "
                                    "len %d for prefix information option, "
                                    "ignored\n", pi->nd_opt_pi_prefix_len));
                                continue;
                        }

                        if (IN6_IS_ADDR_MULTICAST(&pi->nd_opt_pi_prefix)
                         || IN6_IS_ADDR_LINKLOCAL(&pi->nd_opt_pi_prefix)) {
                                nd6log((LOG_INFO,
                                    "nd6_ra_input: invalid prefix "
                                    "%s, ignored\n",
                                    ip6_sprintf(&pi->nd_opt_pi_prefix)));
                                continue;
                        }

                        bzero(&pr, sizeof(pr));
                        lck_mtx_init(&pr.ndpr_lock, ifa_mtx_grp, ifa_mtx_attr);
                        NDPR_LOCK(&pr);
                        pr.ndpr_prefix.sin6_family = AF_INET6;
                        pr.ndpr_prefix.sin6_len = sizeof(pr.ndpr_prefix);
                        pr.ndpr_prefix.sin6_addr = pi->nd_opt_pi_prefix;
                        pr.ndpr_ifp = m->m_pkthdr.rcvif;

                        pr.ndpr_raf_onlink = (pi->nd_opt_pi_flags_reserved &
                                              ND_OPT_PI_FLAG_ONLINK) ? 1 : 0;
                        pr.ndpr_raf_auto = (pi->nd_opt_pi_flags_reserved &
                                            ND_OPT_PI_FLAG_AUTO) ? 1 : 0;
                        pr.ndpr_plen = pi->nd_opt_pi_prefix_len;
                        pr.ndpr_vltime = ntohl(pi->nd_opt_pi_valid_time);
                        pr.ndpr_pltime =
                                ntohl(pi->nd_opt_pi_preferred_time);

                        /*
                         * Exceptions to stateless autoconfiguration processing:
                         * + nd6_accept_6to4 == 0 && address has 6to4 prefix
                         * + ip6_only_allow_rfc4193_prefix != 0 && address not RFC 4193
                         */
                        if (ip6_only_allow_rfc4193_prefix &&
                            !IN6_IS_ADDR_UNIQUE_LOCAL(&pi->nd_opt_pi_prefix)) {
                                nd6log((LOG_INFO,
                                    "nd6_ra_input: no SLAAC on prefix %s [not RFC 4193]\n",
                                    ip6_sprintf(&pi->nd_opt_pi_prefix)));
                                pr.ndpr_raf_auto = 0;
                        }
                        else if (!nd6_accept_6to4 &&
                                     IN6_IS_ADDR_6TO4(&pi->nd_opt_pi_prefix)) {
                                nd6log((LOG_INFO,
                                    "nd6_ra_input: no SLAAC on prefix %s [6to4]\n",
                                    ip6_sprintf(&pi->nd_opt_pi_prefix)));
                                pr.ndpr_raf_auto = 0;
                        }

                        if (in6_init_prefix_ltimes(&pr)) {
                                NDPR_UNLOCK(&pr);
                                lck_mtx_destroy(&pr.ndpr_lock, ifa_mtx_grp);
                                continue; /* prefix lifetime init failed */
                        } else {
                                NDPR_UNLOCK(&pr);
                        }
                        (void)prelist_update(&pr, dr, m, mcast);
                        lck_mtx_destroy(&pr.ndpr_lock, ifa_mtx_grp);
                }
        }

        /*
         * MTU
         */
        if (ndopts.nd_opts_mtu && ndopts.nd_opts_mtu->nd_opt_mtu_len == 1) {
                u_int32_t mtu = ntohl(ndopts.nd_opts_mtu->nd_opt_mtu_mtu);

                /* lower bound */
                if (mtu < IPV6_MMTU) {
                        nd6log((LOG_INFO, "nd6_ra_input: bogus mtu option "
                            "mtu=%d sent from %s, ignoring\n",
                            mtu, ip6_sprintf(&ip6->ip6_src)));
                        goto skip;
                }

                lck_rw_lock_shared(nd_if_rwlock);
                if (ifp->if_index >= nd_ifinfo_indexlim) {
                        lck_rw_done(nd_if_rwlock);
                        goto freeit;
                }
                ndi = &nd_ifinfo[ifp->if_index];
                /* upper bound */
                if (ndi->maxmtu) {
                        if (mtu <= ndi->maxmtu) {
                                int change = (ndi->linkmtu != mtu);

                                ndi->linkmtu = mtu;
                                lck_rw_done(nd_if_rwlock);
                                if (change) /* in6_maxmtu may change */
                                        in6_setmaxmtu();
                        } else {
                                nd6log((LOG_INFO, "nd6_ra_input: bogus mtu "
                                    "mtu=%d sent from %s; "
                                    "exceeds maxmtu %d, ignoring\n",
                                    mtu, ip6_sprintf(&ip6->ip6_src),
                                    ndi->maxmtu));
                                lck_rw_done(nd_if_rwlock);
                        }
                } else {
                        lck_rw_done(nd_if_rwlock);
                        nd6log((LOG_INFO, "nd6_ra_input: mtu option "
                            "mtu=%d sent from %s; maxmtu unknown, "
                            "ignoring\n",
                            mtu, ip6_sprintf(&ip6->ip6_src)));
                }
                ndi = NULL;
        }

 skip:
        
        /*
         * Source link layer address
         */
    {
        char *lladdr = NULL;
        int lladdrlen = 0;
        
        if (ndopts.nd_opts_src_lladdr) {
                lladdr = (char *)(ndopts.nd_opts_src_lladdr + 1);
                lladdrlen = ndopts.nd_opts_src_lladdr->nd_opt_len << 3;
        }

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log((LOG_INFO,
                    "nd6_ra_input: lladdrlen mismatch for %s "
                    "(if %d, RA packet %d)\n",
                        ip6_sprintf(&saddr6), ifp->if_addrlen, lladdrlen - 2));
                goto bad;
        }

        nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, ND_ROUTER_ADVERT, 0);

        /*
         * Installing a link-layer address might change the state of the
         * router's neighbor cache, which might also affect our on-link
         * detection of adveritsed prefixes.
         */
        lck_mtx_lock(nd6_mutex);
        pfxlist_onlink_check();
        lck_mtx_unlock(nd6_mutex);
    }

 freeit:
        m_freem(m);
        if (dr)
                NDDR_REMREF(dr);
        return;

 bad:
        icmp6stat.icp6s_badra++;
        goto freeit;
}

/*
 * default router list proccessing sub routines
 */

/* tell the change to user processes watching the routing socket. */
static void
nd6_rtmsg(cmd, rt)
        int cmd;
        struct rtentry *rt;
{
        struct rt_addrinfo info;
        struct ifnet *ifp = rt->rt_ifp;

        RT_LOCK_ASSERT_HELD(rt);

        bzero((caddr_t)&info, sizeof(info));
        /* Lock ifp for if_lladdr */
        ifnet_lock_shared(ifp);
        info.rti_info[RTAX_DST] = rt_key(rt);
        info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
        info.rti_info[RTAX_NETMASK] = rt_mask(rt);
        /*
         * ifa_addr pointers for both should always be valid
         * in this context; no need to hold locks.
         */
        info.rti_info[RTAX_IFP] = ifp->if_lladdr->ifa_addr;
        info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;

        rt_missmsg(cmd, &info, rt->rt_flags, 0);
        ifnet_lock_done(ifp);
}

void
defrouter_addreq(struct nd_defrouter *new, boolean_t scoped)
{
        struct sockaddr_in6 def, mask, gate;
        struct rtentry *newrt = NULL;
        unsigned int ifscope;
        int err;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        if (new->stateflags & NDDRF_INSTALLED)
                return;

        nd6log2((LOG_INFO, "%s: adding default router %s, scoped=%d, "
            "static=%d\n", if_name(new->ifp), ip6_sprintf(&new->rtaddr),
            scoped, (new->stateflags & NDDRF_STATIC) ? 1 : 0));

        Bzero(&def, sizeof(def));
        Bzero(&mask, sizeof(mask));
        Bzero(&gate, sizeof(gate));

        def.sin6_len = mask.sin6_len = gate.sin6_len
                = sizeof(struct sockaddr_in6);
        def.sin6_family = mask.sin6_family = gate.sin6_family = AF_INET6;
        gate.sin6_addr = new->rtaddr;

        ifscope = scoped ? new->ifp->if_index : IFSCOPE_NONE;

        err = rtrequest_scoped(RTM_ADD, (struct sockaddr *)&def,
            (struct sockaddr *)&gate, (struct sockaddr *)&mask,
            RTF_GATEWAY, &newrt, ifscope);

        if (newrt) {
                RT_LOCK(newrt);
                nd6_rtmsg(RTM_ADD, newrt); /* tell user process */
                RT_REMREF_LOCKED(newrt);
                RT_UNLOCK(newrt);
                new->stateflags |= NDDRF_INSTALLED;
                if (ifscope != IFSCOPE_NONE)
                        new->stateflags |= NDDRF_IFSCOPE;
                new->genid = nd6_defrouter_genid;
        } else {
                nd6log((LOG_ERR, "%s: failed to add default router "
                    "%s on %s scoped %d (errno = %d)\n", __func__,
                    ip6_sprintf(&gate.sin6_addr), if_name(new->ifp),
                    (ifscope != IFSCOPE_NONE), err));
        }
        new->err = err;
}

struct nd_defrouter *
defrouter_lookup(
        struct in6_addr *addr,
        struct ifnet *ifp)
{
        struct nd_defrouter *dr;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        for (dr = TAILQ_FIRST(&nd_defrouter); dr;
             dr = TAILQ_NEXT(dr, dr_entry)) {
                NDDR_LOCK(dr);
                if (dr->ifp == ifp && IN6_ARE_ADDR_EQUAL(addr, &dr->rtaddr)) {
                        NDDR_ADDREF_LOCKED(dr);
                        NDDR_UNLOCK(dr);
                        return(dr);
                }
                NDDR_UNLOCK(dr);
        }

        return (NULL);          /* search failed */
}

/*
 * Remove the default route for a given router.
 * This is just a subroutine function for defrouter_select(), and should
 * not be called from anywhere else.
 */
void
defrouter_delreq(struct nd_defrouter *dr)
{
        struct sockaddr_in6 def, mask, gate;
        struct rtentry *oldrt = NULL;
        unsigned int ifscope;
        int err;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        /* ifp would be NULL for the "drany" case */
        if (dr->ifp != NULL && !(dr->stateflags & NDDRF_INSTALLED))
                return;

        NDDR_LOCK_ASSERT_HELD(dr);

        nd6log2((LOG_INFO, "%s: removing default router %s, scoped=%d, "
            "static=%d\n", dr->ifp != NULL ? if_name(dr->ifp) : "ANY",
            ip6_sprintf(&dr->rtaddr), (dr->stateflags & NDDRF_IFSCOPE) ? 1 : 0,
            (dr->stateflags & NDDRF_STATIC) ? 1 : 0));

        Bzero(&def, sizeof(def));
        Bzero(&mask, sizeof(mask));
        Bzero(&gate, sizeof(gate));

        def.sin6_len = mask.sin6_len = gate.sin6_len
                = sizeof(struct sockaddr_in6);
        def.sin6_family = mask.sin6_family = gate.sin6_family = AF_INET6;
        gate.sin6_addr = dr->rtaddr;

        if (dr->ifp != NULL) {
                ifscope = (dr->stateflags & NDDRF_IFSCOPE) ?
                    dr->ifp->if_index : IFSCOPE_NONE;
        } else {
                ifscope = IFSCOPE_NONE;
        }
        err = rtrequest_scoped(RTM_DELETE,
            (struct sockaddr *)&def, (struct sockaddr *)&gate,
            (struct sockaddr *)&mask, RTF_GATEWAY, &oldrt, ifscope);

        if (oldrt) {
                RT_LOCK(oldrt);
                nd6_rtmsg(RTM_DELETE, oldrt);
                RT_UNLOCK(oldrt);
                rtfree(oldrt);
        } else if (err != ESRCH) {
                nd6log((LOG_ERR, "%s: failed to delete default router "
                    "%s on %s scoped %d (errno = %d)\n", __func__,
                    ip6_sprintf(&gate.sin6_addr), dr->ifp != NULL ?
                    if_name(dr->ifp) : "ANY", (ifscope != IFSCOPE_NONE), err));
        }
        /* ESRCH means it's no longer in the routing table; ignore it */
        if (oldrt != NULL || err == ESRCH) {
                dr->stateflags &= ~NDDRF_INSTALLED;
                if (ifscope != IFSCOPE_NONE)
                        dr->stateflags &= ~NDDRF_IFSCOPE;
        }
        dr->err = 0;
}


/*
 * remove all default routes from default router list
 */
void
defrouter_reset(void)
{
        struct nd_defrouter *dr, drany;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        dr = TAILQ_FIRST(&nd_defrouter);
        while (dr) {
                NDDR_LOCK(dr);
                if (dr->stateflags & NDDRF_INSTALLED) {
                        NDDR_ADDREF_LOCKED(dr);
                        NDDR_UNLOCK(dr);
                        lck_mtx_unlock(nd6_mutex);
                        NDDR_LOCK(dr);
                        defrouter_delreq(dr);
                        NDDR_UNLOCK(dr);
                        lck_mtx_lock(nd6_mutex);
                        NDDR_REMREF(dr);
                        dr = TAILQ_FIRST(&nd_defrouter);
                } else {
                        NDDR_UNLOCK(dr);
                        dr = TAILQ_NEXT(dr, dr_entry);
                }
        }

        /* Nuke primary (non-scoped) default router */
        if (ip6_doscopedroute) {
                bzero(&drany, sizeof (drany));
                lck_mtx_init(&drany.nddr_lock, ifa_mtx_grp, ifa_mtx_attr);
                lck_mtx_unlock(nd6_mutex);
                NDDR_LOCK(&drany);
                defrouter_delreq(&drany);
                NDDR_UNLOCK(&drany);
                lck_mtx_destroy(&drany.nddr_lock, ifa_mtx_grp);
                lck_mtx_lock(nd6_mutex);
        }

}

int
defrtrlist_ioctl(u_long cmd, caddr_t data)
{
        struct in6_defrouter_32 *r_32 = (struct in6_defrouter_32 *)data;
        struct in6_defrouter_64 *r_64 = (struct in6_defrouter_64 *)data;
        struct nd_defrouter dr0;
        unsigned int ifindex;
        struct ifnet *dr_ifp;
        int error = 0, add = 0;

        switch (cmd) {
        case SIOCDRADD_IN6_32:
        case SIOCDRADD_IN6_64:
                ++add;
                /* FALLTHRU */
        case SIOCDRDEL_IN6_32:
        case SIOCDRDEL_IN6_64:
                bzero(&dr0, sizeof (dr0));
                if (cmd == SIOCDRADD_IN6_64 || cmd == SIOCDRDEL_IN6_64) {
                        dr0.rtaddr = r_64->rtaddr.sin6_addr;
                        dr0.flags = r_64->flags;
                        ifindex = r_64->if_index;
                } else {
                        dr0.rtaddr = r_32->rtaddr.sin6_addr;
                        dr0.flags = r_32->flags;
                        ifindex = r_32->if_index;
                }
                ifnet_head_lock_shared();
                /* Don't need to check is ifindex is < 0 since it's unsigned */
                if (if_index < ifindex ||
                    (dr_ifp = ifindex2ifnet[ifindex]) == NULL) {
                        ifnet_head_done();
                        error = EINVAL;
                        break;
                }
                dr0.ifp = dr_ifp;
                ifnet_head_done();

                if (IN6_IS_SCOPE_EMBED(&dr0.rtaddr)) {
                        uint16_t *scope = &dr0.rtaddr.s6_addr16[1];

                        if (*scope == 0) {
                                *scope = htons(dr_ifp->if_index);
                        } else if (*scope != htons(dr_ifp->if_index)) {
                                error = EINVAL;
                                break;
                        }
                }

                if (add)
                        error = defrtrlist_add_static(&dr0);
                if (!add || error != 0) {
                        int err = defrtrlist_del_static(&dr0);
                        if (!add)
                                error = err;
                }
                break;

        default:
                error = EOPNOTSUPP; /* check for safety */
                break;
        }

        return (error);
}

void
defrtrlist_del(struct nd_defrouter *dr)
{
        struct nd_defrouter *deldr = NULL;
        struct nd_prefix *pr;
        struct ifnet *ifp = dr->ifp;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        /*
         * Flush all the routing table entries that use the router
         * as a next hop.
         */
        if (!ip6_forwarding &&
            (ip6_accept_rtadv || (ifp->if_eflags & IFEF_ACCEPT_RTADVD))) {
                /* above is a good condition? */
                NDDR_ADDREF(dr);
                lck_mtx_unlock(nd6_mutex);
                rt6_flush(&dr->rtaddr, ifp);
                lck_mtx_lock(nd6_mutex);
                NDDR_REMREF(dr);
        }

        if (dr == TAILQ_FIRST(&nd_defrouter))
                deldr = dr;     /* The router is primary. */

        TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);
        ++nd6_defrouter_genid;

        nd6log2((LOG_INFO, "%s: freeing defrouter %s\n", if_name(dr->ifp),
            ip6_sprintf(&dr->rtaddr)));

        /*
         * Delete it from the routing table.
         */
        NDDR_ADDREF(dr);
        lck_mtx_unlock(nd6_mutex);
        NDDR_LOCK(dr);
        defrouter_delreq(dr);
        NDDR_UNLOCK(dr);
        lck_mtx_lock(nd6_mutex);
        NDDR_REMREF(dr);

        /*
         * Also delete all the pointers to the router in each prefix lists.
         */
        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                struct nd_pfxrouter *pfxrtr;

                NDPR_LOCK(pr);
                if ((pfxrtr = pfxrtr_lookup(pr, dr)) != NULL)
                        pfxrtr_del(pfxrtr);
                NDPR_UNLOCK(pr);
        }

        pfxlist_onlink_check();

        /*
         * If the router is the primary one, choose a new one.  If Scoped
         * Routing is enabled, always try to pick another eligible router
         * on this interface.
         */
        if ((deldr || ip6_doscopedroute) && !ip6_forwarding &&
            (ip6_accept_rtadv || (ifp->if_eflags & IFEF_ACCEPT_RTADVD)))
                defrouter_select(ifp);

        lck_rw_lock_shared(nd_if_rwlock);
        if (ifp->if_index < nd_ifinfo_indexlim) {
                struct nd_ifinfo *ndi = &nd_ifinfo[ifp->if_index];
                atomic_add_32(&ndi->ndefrouters, -1);
                if (ndi->ndefrouters < 0) {
                        log(LOG_WARNING, "defrtrlist_del: negative "
                            "count on %s\n", if_name(ifp));
                }
        }
        lck_rw_done(nd_if_rwlock);

        NDDR_REMREF(dr);        /* remove list reference */
}

int
defrtrlist_add_static(struct nd_defrouter *new)
{
        struct nd_defrouter *dr;
        int err = 0;

        new->rtlifetime = -1;
        new->stateflags |= NDDRF_STATIC;

        /* we only want the preference level */
        new->flags &= ND_RA_FLAG_RTPREF_MASK;

        lck_mtx_lock(nd6_mutex);
        dr = defrouter_lookup(&new->rtaddr, new->ifp);
        if (dr != NULL && !(dr->stateflags & NDDRF_STATIC)) {
                err = EINVAL;
        } else {
                if (dr != NULL)
                        NDDR_REMREF(dr);
                dr = defrtrlist_update(new);
                if (dr != NULL)
                        err = dr->err;
                else
                        err = ENOMEM;
        }
        if (dr != NULL)
                NDDR_REMREF(dr);
        lck_mtx_unlock(nd6_mutex);

        return (err);
}

int
defrtrlist_del_static(struct nd_defrouter *new)
{
        struct nd_defrouter *dr;

        lck_mtx_lock(nd6_mutex);
        dr = defrouter_lookup(&new->rtaddr, new->ifp);
        if (dr == NULL || !(dr->stateflags & NDDRF_STATIC)) {
                if (dr != NULL)
                        NDDR_REMREF(dr);
                dr = NULL;
        } else {
                defrtrlist_del(dr);
                NDDR_REMREF(dr);
        }
        lck_mtx_unlock(nd6_mutex);

        return (dr != NULL ? 0 : EINVAL);
}

/*
 * for default router selection
 * regards router-preference field as a 2-bit signed integer
 */
static int
rtpref(struct nd_defrouter *dr)
{
        switch (dr->flags & ND_RA_FLAG_RTPREF_MASK) {
        case ND_RA_FLAG_RTPREF_HIGH:
                return (RTPREF_HIGH);
        case ND_RA_FLAG_RTPREF_MEDIUM:
        case ND_RA_FLAG_RTPREF_RSV:
                return (RTPREF_MEDIUM);
        case ND_RA_FLAG_RTPREF_LOW:
                return (RTPREF_LOW);
        default:
                /*
                 * This case should never happen.  If it did, it would mean a
                 * serious bug of kernel internal.  We thus always bark here.
                 * Or, can we even panic?
                 */
                log(LOG_ERR, "rtpref: impossible RA flag %x\n", dr->flags);
                return (RTPREF_INVALID);
        }
        /* NOTREACHED */
}

/*
 * Default Router Selection according to Section 6.3.6 of RFC 2461 and
 * draft-ietf-ipngwg-router-selection:
 *
 * 1) Routers that are reachable or probably reachable should be preferred.
 *    If we have more than one (probably) reachable router, prefer ones
 *    with the highest router preference.
 * 2) When no routers on the list are known to be reachable or
 *    probably reachable, routers SHOULD be selected in a round-robin
 *    fashion, regardless of router preference values.
 * 3) If the Default Router List is empty, assume that all
 *    destinations are on-link.
 *
 * When Scoped Routing is enabled, the selection logic is amended as follows:
 *
 * a) When a default interface is specified, the primary/non-scoped default
 *    router will be set to the reachable router on that link (if any) with
 *    the highest router preference.
 * b) When there are more than one routers on the same link, the one with
 *    the highest router preference will be installed, either as scoped or
 *    non-scoped route entry.  If they all share the same preference value,
 *    the one installed will be the static or the first encountered reachable
 *    router, i.e. static one wins over dynamic.
 * c) When no routers on the list are known to be reachable, or probably
 *    reachable, no round-robin selection will take place when the default
 *    interface is set.
 *
 * We assume nd_defrouter is sorted by router preference value.
 * Since the code below covers both with and without router preference cases,
 * we do not need to classify the cases by ifdef.
 */
static void
defrouter_select_common(struct ifnet *ifp, int ignore)
{
        struct nd_defrouter *dr, *selected_dr = NULL, *installed_dr = NULL;
        struct nd_defrouter *installed_dr0 = NULL;
        struct rtentry *rt = NULL;
        struct llinfo_nd6 *ln = NULL;
        int  update = 0;
        boolean_t found_installedrt = FALSE;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        /*
         * This function should be called only when acting as an autoconfigured
         * host.  Although the remaining part of this function is not effective
         * if the node is not an autoconfigured host, we explicitly exclude
         * such cases here for safety.
         */
        if (ip6_forwarding || (!ignore && !ip6_accept_rtadv &&
            !(ifp->if_eflags & IFEF_ACCEPT_RTADVD))) {
                nd6log((LOG_WARNING,
                    "defrouter_select: called unexpectedly (forwarding=%d, "
                    "accept_rtadv=%d)\n", ip6_forwarding, ip6_accept_rtadv));
                return;
        }

        /*
         * Let's handle easy case (3) first:
         * If default router list is empty, there's nothing to be done.
         */
        if (!TAILQ_FIRST(&nd_defrouter))
                return;

        /*
         * Due to the number of times we drop nd6_mutex, we need to
         * serialize this function.
         */
        while (nd_defrouter_busy) {
                nd_defrouter_waiters++;
                msleep(nd_defrouter_waitchan, nd6_mutex, (PZERO-1),
                    __func__, NULL);
                lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        }
        nd_defrouter_busy = TRUE;

        /*
         * Search for a (probably) reachable router from the list.
         * We just pick up the first reachable one (if any), assuming that
         * the ordering rule of the list described in defrtrlist_update().
         *
         * For all intents and purposes of Scoped Routing:
         *      selected_dr     = candidate for primary router
         *      installed_dr    = currently installed primary router
         */
        for (dr = TAILQ_FIRST(&nd_defrouter); dr;
             dr = TAILQ_NEXT(dr, dr_entry)) {
                boolean_t reachable;

                /* Callee returns a locked route upon success */
                reachable = FALSE;
                NDDR_ADDREF(dr);        /* for this for loop */
                lck_mtx_unlock(nd6_mutex);
                if ((rt = nd6_lookup(&dr->rtaddr, 0, dr->ifp, 0)) != NULL) {
                        RT_LOCK_ASSERT_HELD(rt);
                        if ((ln = rt->rt_llinfo) != NULL &&
                            ND6_IS_LLINFO_PROBREACH(ln)) {
                                reachable = TRUE;
                                if (selected_dr == NULL &&
                                    (!ip6_doscopedroute ||
                                    dr->ifp == nd6_defifp)) {
                                        selected_dr = dr;
                                        NDDR_ADDREF(selected_dr);
                                }
                        }
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        rt = NULL;
                }
                lck_mtx_lock(nd6_mutex);

                /* Handle case (b) */
                if (ip6_doscopedroute && dr->ifp == nd6_defifp &&
                    (selected_dr == NULL || rtpref(dr) > rtpref(selected_dr) ||
                    (rtpref(dr) == rtpref(selected_dr) &&
                    (dr->stateflags & NDDRF_STATIC) &&
                    !(selected_dr->stateflags & NDDRF_STATIC)))) {
                        if (selected_dr)
                                NDDR_REMREF(selected_dr);
                        selected_dr = dr;
                        NDDR_ADDREF(selected_dr);
                }

                if (!(dr->stateflags & NDDRF_INSTALLED)) {
                        /*
                         * If the router hasn't been installed and it is
                         * reachable, try to install it later on below.
                         * If it's static, try to install it anyway.
                         */
                        if (reachable || (dr->stateflags & NDDRF_STATIC)) {
                                dr->genid = -1;
                                ++update;
                                nd6log2((LOG_INFO, "%s: possible router %s, "
                                    "scoped=%d, static=%d\n", if_name(dr->ifp),
                                    ip6_sprintf(&dr->rtaddr),
                                    (dr->stateflags & NDDRF_IFSCOPE) ? 1 : 0,
                                    (dr->stateflags & NDDRF_STATIC) ? 1 : 0));
                        }
                        NDDR_REMREF(dr);        /* for this for loop */
                        continue;
                }

                /* Record the currently installed primary/non-scoped router */
                if (!ip6_doscopedroute || !(dr->stateflags & NDDRF_IFSCOPE)) {
                        if (installed_dr == NULL) {
                                installed_dr = dr;
                                NDDR_ADDREF(installed_dr);
                        } else {
                                /* this should not happen; warn for diagnosis */
                                log(LOG_ERR, "defrouter_select: more than one "
                                    "%s default router is installed\n",
                                    ip6_doscopedroute ? "non-scoped" : "");
                        }
                }
                NDDR_REMREF(dr);        /* for this for loop */
        }

        /* If none was selected, use the currently installed one */
        if (ip6_doscopedroute && selected_dr == NULL && installed_dr != NULL) {
                selected_dr = installed_dr;
                NDDR_ADDREF(selected_dr);
        }

        /*
         * Install the unreachable one(s) if necesssary.
         */
        for (dr = TAILQ_FIRST(&nd_defrouter); dr;
             dr = TAILQ_NEXT(dr, dr_entry)) {
                struct nd_defrouter *_dr;

                if (!ip6_doscopedroute)
                        break;

                NDDR_LOCK(dr);

                /* If already (or will be) installed, skip */
                if ((dr->stateflags & NDDRF_INSTALLED) || dr->genid == -1) {
                        NDDR_UNLOCK(dr);
                        continue;
                }

                /* See if there is already a default router for the link */
                for (_dr = TAILQ_FIRST(&nd_defrouter); _dr;
                     _dr = TAILQ_NEXT(_dr, dr_entry)) {
                        if (_dr != dr)
                                NDDR_LOCK(_dr);
                        if (_dr == dr || _dr->ifp != dr->ifp) {
                                if (_dr != dr)
                                        NDDR_UNLOCK(_dr);
                                continue;
                        }

                        if ((_dr->stateflags & NDDRF_INSTALLED) ||
                            _dr->genid == -1) {
                                if (_dr != dr)
                                        NDDR_UNLOCK(_dr);
                                break;
                        }
                        if (_dr != dr)
                                NDDR_UNLOCK(_dr);
                }

                /* If none so far, schedule it to be installed below */
                if (_dr == NULL) {
                        dr->genid = -1;
                        ++update;
                        nd6log2((LOG_INFO, "%s: possible router %s, "
                            "static=%d (unreachable)\n", if_name(dr->ifp),
                            ip6_sprintf(&dr->rtaddr),
                            (dr->stateflags & NDDRF_STATIC) ? 1 : 0));
                }
                NDDR_UNLOCK(dr);
        }

        dr = selected_dr;
        if (dr != NULL) {
                nd6log2((LOG_INFO, "%s: considering primary default router %s, "
                    "static=%d [round 1]\n", if_name(dr->ifp),
                    ip6_sprintf(&dr->rtaddr),
                    (dr->stateflags & NDDRF_STATIC) ? 1 : 0));
        }

        /*
         * If none of the default routers was found to be reachable,
         * round-robin the list regardless of preference, except when
         * Scoped Routing is enabled per case (c).
         *
         * Otherwise, if we have an installed router, check if the selected
         * (reachable) router should really be preferred to the installed one.
         * We only prefer the new router when the old one is not reachable
         * or when the new one has a really higher preference value.
         */
        if (!ip6_doscopedroute && selected_dr == NULL) {
                if (installed_dr == NULL ||
                    !TAILQ_NEXT(installed_dr, dr_entry)) {
                        selected_dr = TAILQ_FIRST(&nd_defrouter);
                        if (selected_dr)
                                NDDR_ADDREF(selected_dr);
                } else {
                        selected_dr = TAILQ_NEXT(installed_dr, dr_entry);
                        if (selected_dr)
                                NDDR_ADDREF(selected_dr);
                }
        } else if (selected_dr != NULL && installed_dr != NULL) {
                lck_mtx_unlock(nd6_mutex);
                rt = nd6_lookup(&installed_dr->rtaddr, 0, installed_dr->ifp, 0);
                if (rt) {
                        RT_LOCK_ASSERT_HELD(rt);
                        if ((ln = (struct llinfo_nd6 *)rt->rt_llinfo) &&
                            ND6_IS_LLINFO_PROBREACH(ln) &&
                            (!ip6_doscopedroute ||
                                installed_dr->ifp == nd6_defifp) &&
                            rtpref(selected_dr) <= rtpref(installed_dr)) {
                                NDDR_REMREF(selected_dr);
                                selected_dr = installed_dr;
                                NDDR_ADDREF(selected_dr);
                        }
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        rt = NULL;
                        found_installedrt = TRUE;
                }
                lck_mtx_lock(nd6_mutex);
        }

        if (ip6_doscopedroute) {
                /*
                 * If the installed primary router is not on the current
                 * IPv6 default interface, demote it to a scoped entry.
                 */
                if (installed_dr != NULL && installed_dr->ifp != nd6_defifp &&
                    !(installed_dr->stateflags & NDDRF_IFSCOPE)) {
                        if (selected_dr != NULL &&
                            selected_dr->ifp != nd6_defifp) {
                                NDDR_REMREF(selected_dr);
                                selected_dr = NULL;
                        }
                        ++update;
                }

                /*
                 * If the selected router is currently scoped, make sure
                 * we update (it needs to be promoted to primary.)
                 */
                if (selected_dr != NULL &&
                    (selected_dr->stateflags & NDDRF_IFSCOPE))
                        ++update;

                /*
                 * If the installed router is no longe reachable, remove
                 * it and install the selected router instead.
                 */
                if (installed_dr != NULL && selected_dr != NULL &&
                    installed_dr != selected_dr && found_installedrt == FALSE) {
                        installed_dr0 = installed_dr;   /* skip it below */
                        /* NB: we previousled referenced installed_dr */
                        installed_dr = NULL;
                        selected_dr->genid = -1;
                        ++update;
                }
        }

        /*
         * If Scoped Routing is enabled and there's nothing to update,
         * just return.  Otherwise, if Scoped Routing is disabled and if
         * the selected router is different than the installed one,
         * remove the installed router and install the selected one.
         */
        dr = selected_dr;
        VERIFY(dr != NULL || ip6_doscopedroute);
        if (!ip6_doscopedroute || !update) {
                if (dr == NULL)
                        goto out;

                if (dr != installed_dr) {
                        nd6log2((LOG_INFO, "%s: no update, selected router %s, "
                            "installed router %s\n", if_name(dr->ifp),
                            ip6_sprintf(&dr->rtaddr), installed_dr != NULL ?
                            ip6_sprintf(&installed_dr->rtaddr) : "NONE"));
                } else {
                        nd6log2((LOG_INFO, "%s: no update, router is %s\n",
                            if_name(dr->ifp), ip6_sprintf(&dr->rtaddr)));
                }
                if (!ip6_doscopedroute && installed_dr != dr) {
                        /* 
                         * No need to ADDREF dr because at this point
                         * dr points to selected_dr, which already holds
                         * a reference.
                         */
                        lck_mtx_unlock(nd6_mutex);
                        if (installed_dr) {
                                NDDR_LOCK(installed_dr);
                                defrouter_delreq(installed_dr);
                                NDDR_UNLOCK(installed_dr);
                        }
                        NDDR_LOCK(dr);
                        defrouter_addreq(dr, FALSE);
                        NDDR_UNLOCK(dr);
                        lck_mtx_lock(nd6_mutex);
                }
                goto out;
        }

        /*
         * Scoped Routing is enabled and we need to update.  The selected
         * router needs to be installed as primary/non-scoped entry.  If
         * there is any existing entry that is non-scoped, remove it from
         * the routing table and reinstall it as scoped entry.
         */
        if (dr != NULL) {
                nd6log2((LOG_INFO, "%s: considering primary default router %s, "
                    "static=%d [round 2]\n", if_name(dr->ifp),
                    ip6_sprintf(&dr->rtaddr),
                    (dr->stateflags & NDDRF_STATIC) ? 1 : 0));
        }

        /*
         * On the following while loops we use two flags:
         *   dr->genid
         *   NDDRF_PROCESSED
         *
         * genid is used to skip entries that are not to be added/removed on the
         * second while loop.
         * NDDRF_PROCESSED is used to skip entries that were already processed.
         * This is necessary because we drop the nd6_mutex and start the while
         * loop again.
         */
        TAILQ_FOREACH(dr, &nd_defrouter, dr_entry) {
                NDDR_LOCK(dr);
                VERIFY((dr->stateflags & NDDRF_PROCESSED) == 0);
                NDDR_UNLOCK(dr);
        }
        /* Remove conflicting entries */
        dr = TAILQ_FIRST(&nd_defrouter);
        while (dr) {
                NDDR_LOCK(dr);
                if (!(dr->stateflags & NDDRF_INSTALLED) ||
                    dr->stateflags & NDDRF_PROCESSED) {
                        NDDR_UNLOCK(dr);
                        dr = TAILQ_NEXT(dr, dr_entry);
                        continue;
                }
                dr->stateflags |= NDDRF_PROCESSED;

                /* A NULL selected_dr will remove primary default route */
                if ((dr == selected_dr && (dr->stateflags & NDDRF_IFSCOPE)) ||
                    (dr != selected_dr && !(dr->stateflags & NDDRF_IFSCOPE))) {
                        NDDR_ADDREF_LOCKED(dr);
                        NDDR_UNLOCK(dr);
                        lck_mtx_unlock(nd6_mutex);
                        NDDR_LOCK(dr);
                        defrouter_delreq(dr);
                        NDDR_UNLOCK(dr);
                        lck_mtx_lock(nd6_mutex);
                        NDDR_LOCK(dr);
                        if (dr && dr != installed_dr0)
                                dr->genid = -1;
                        NDDR_UNLOCK(dr);
                        NDDR_REMREF(dr);
                        /*
                         * Since we lost nd6_mutex, we have to start over.
                         */
                        dr = TAILQ_FIRST(&nd_defrouter);
                        continue;
                }
                NDDR_UNLOCK(dr);
                dr = TAILQ_NEXT(dr, dr_entry);
        }

        /* -1 is a special number, make sure we don't use it for genid */
        if (++nd6_defrouter_genid == -1)
                nd6_defrouter_genid = 1;

        TAILQ_FOREACH(dr, &nd_defrouter, dr_entry) {
                NDDR_LOCK(dr);
                dr->stateflags &= ~NDDRF_PROCESSED;
                NDDR_UNLOCK(dr);
        }
        /* Add the entries back */
        dr = TAILQ_FIRST(&nd_defrouter);
        while (dr) {
                struct nd_defrouter *_dr;

                NDDR_LOCK(dr);
                if (dr->stateflags & NDDRF_PROCESSED ||
                    dr->genid != -1) {
                        NDDR_UNLOCK(dr);
                        dr = TAILQ_NEXT(dr, dr_entry);
                        continue;
                }
                dr->stateflags |= NDDRF_PROCESSED;

                /* Handle case (b) */
                for (_dr = TAILQ_FIRST(&nd_defrouter); _dr;
                     _dr = TAILQ_NEXT(_dr, dr_entry)) {
                        if (_dr == dr)
                                continue;
                        /*
                         * This is safe because we previously checked if
                         * _dr == dr.
                         */
                        NDDR_LOCK(_dr);
                        if (_dr->ifp == dr->ifp && rtpref(_dr) >= rtpref(dr) &&
                            (_dr->stateflags & NDDRF_INSTALLED)) {
                                NDDR_ADDREF_LOCKED(_dr);
                                NDDR_UNLOCK(_dr);
                                break;
                        }
                        NDDR_UNLOCK(_dr);
                }

                /* If same preference and i/f, static entry takes precedence */
                if (_dr != NULL && rtpref(_dr) == rtpref(dr) &&
                    !(_dr->stateflags & NDDRF_STATIC) &&
                    (dr->stateflags & NDDRF_STATIC)) {
                        lck_mtx_unlock(nd6_mutex);
                        NDDR_LOCK(_dr);
                        defrouter_delreq(_dr);
                        NDDR_UNLOCK(_dr);
                        lck_mtx_lock(nd6_mutex);
                        NDDR_REMREF(_dr);
                        _dr = NULL;
                }

                if (_dr == NULL && !(dr->stateflags & NDDRF_INSTALLED)) {
                        NDDR_ADDREF_LOCKED(dr);
                        NDDR_UNLOCK(dr);
                        lck_mtx_unlock(nd6_mutex);
                        NDDR_LOCK(dr);
                        defrouter_addreq(dr, (selected_dr == NULL ||
                            dr->ifp != selected_dr->ifp));
                        dr->genid = nd6_defrouter_genid;
                        NDDR_UNLOCK(dr);
                        lck_mtx_lock(nd6_mutex);
                        NDDR_REMREF(dr);
                        /*
                         * Since we lost nd6_mutex, we have to start over.
                         */
                        dr = TAILQ_FIRST(&nd_defrouter);
                        continue;
                }
                NDDR_UNLOCK(dr);
                dr = TAILQ_NEXT(dr, dr_entry);
        }
out:
        TAILQ_FOREACH(dr, &nd_defrouter, dr_entry) {
                NDDR_LOCK(dr);
                dr->stateflags &= ~NDDRF_PROCESSED;
                NDDR_UNLOCK(dr);
        }
        if (selected_dr)
                NDDR_REMREF(selected_dr);
        if (installed_dr)
                NDDR_REMREF(installed_dr);
        if (installed_dr0)
                NDDR_REMREF(installed_dr0);
        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        VERIFY(nd_defrouter_busy);
        nd_defrouter_busy = FALSE;
        if (nd_defrouter_waiters > 0) {
                nd_defrouter_waiters = 0;
                wakeup(nd_defrouter_waitchan);
        }
}

void
defrouter_select(struct ifnet *ifp)
{
        return (defrouter_select_common(ifp, 0));
}

static struct nd_defrouter *
defrtrlist_update_common(struct nd_defrouter *new, boolean_t scoped)
{
        struct nd_defrouter *dr, *n;
        struct ifnet *ifp = new->ifp;
        struct nd_ifinfo *ndi;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        if ((dr = defrouter_lookup(&new->rtaddr, ifp)) != NULL) {
                /* entry exists */
                if (new->rtlifetime == 0) {
                        defrtrlist_del(dr);
                        NDDR_REMREF(dr);
                        dr = NULL;
                } else {
                        int oldpref = rtpref(dr);

                        /* override */
                        dr->flags = new->flags; /* xxx flag check */
                        dr->rtlifetime = new->rtlifetime;
                        dr->expire = new->expire;

                        /*
                         * If the preference does not change, there's no need
                         * to sort the entries.  If Scoped Routing is enabled,
                         * put the primary/non-scoped router at the top of the
                         * list of routers in the same preference band, unless
                         * it's already at that position.
                         */
                        if (ip6_doscopedroute) {
                                struct nd_defrouter *p = NULL;

                                /* same preference and scoped; just return */
                                if (rtpref(new) == oldpref && scoped)
                                        return (dr);

                                n = TAILQ_FIRST(&nd_defrouter);
                                while (n != NULL) {
                                        /* preference changed; sort it */
                                        if (rtpref(new) != oldpref)
                                                break;

                                        /* not at the top of band; sort it */
                                        if (n != dr && rtpref(n) == oldpref &&
                                            (!p || rtpref(p) > rtpref(n)))
                                                break;

                                        p = n;
                                        n = TAILQ_NEXT(n, dr_entry);
                                }

                                /* nothing has changed, just return */
                                if (n == NULL && (scoped ||
                                    !(dr->stateflags & NDDRF_IFSCOPE)))
                                        return (dr);
                        } else if (rtpref(new) == oldpref) {
                                return (dr);
                        }

                        /*
                         * preferred router may be changed, so relocate
                         * this router.
                         * XXX: calling TAILQ_REMOVE directly is a bad manner.
                         * However, since defrtrlist_del() has many side
                         * effects, we intentionally do so here.
                         * defrouter_select() below will handle routing
                         * changes later.
                         */
                        TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);
                        new->stateflags = dr->stateflags;
                        new->stateflags &= ~NDDRF_PROCESSED;

                        lck_rw_lock_shared(nd_if_rwlock);
                        VERIFY(ifp->if_index < nd_ifinfo_indexlim);
                        ndi = &nd_ifinfo[ifp->if_index];
                        lck_rw_done(nd_if_rwlock);
                        n = dr;
                        goto insert;
                }
                return (dr);
        }

        VERIFY(dr == NULL);

        /* entry does not exist */
        if (new->rtlifetime == 0) {
                return(NULL);
        }

        n = nddr_alloc(M_WAITOK);
        if (n == NULL) {
                return(NULL);
        }

        lck_rw_lock_shared(nd_if_rwlock);
        ndi = &nd_ifinfo[ifp->if_index];
        if (ifp->if_index >= nd_ifinfo_indexlim)
                goto freeit;
        if (ip6_maxifdefrouters >= 0 &&
            ndi->ndefrouters >= ip6_maxifdefrouters) {
freeit:
                lck_rw_done(nd_if_rwlock);
                nddr_free(n);
                return (NULL);
        }

        NDDR_ADDREF(n); /* for the nd_defrouter list */
        NDDR_ADDREF(n); /* for the caller */

        ++nd6_defrouter_genid;
        atomic_add_32(&ndi->ndefrouters, 1);
        lck_rw_done(nd_if_rwlock);

        nd6log2((LOG_INFO, "%s: allocating defrouter %s\n", if_name(ifp),
            ip6_sprintf(&new->rtaddr)));

        NDDR_LOCK(n);
        memcpy(&n->rtaddr, &new->rtaddr, sizeof(n->rtaddr));
        n->flags = new->flags;
        n->stateflags = new->stateflags;
        n->stateflags &= ~NDDRF_PROCESSED;
        n->rtlifetime = new->rtlifetime;
        n->expire = new->expire;
        n->ifp = new->ifp;
        n->genid = new->genid;
        n->err = new->err;
        NDDR_UNLOCK(n);
insert:

        /*
         * Insert the new router in the Default Router List;
         * The Default Router List should be in the descending order
         * of router-preferece.  When Scoped Routing is disabled, routers
         * with the same preference are sorted in the arriving time order;
         * otherwise, the first entry in the list of routers having the same
         * preference is the primary default router, when the interface used
         * by the entry is the default interface.
         */

        /* insert at the end of the group */
        for (dr = TAILQ_FIRST(&nd_defrouter); dr;
             dr = TAILQ_NEXT(dr, dr_entry)) {
                if (rtpref(n) > rtpref(dr) ||
                    (ip6_doscopedroute && !scoped && rtpref(n) == rtpref(dr)))
                        break;
        }
        if (dr)
                TAILQ_INSERT_BEFORE(dr, n, dr_entry);
        else
                TAILQ_INSERT_TAIL(&nd_defrouter, n, dr_entry);

        /* Ignore auto-configuration checks for static route entries */
        defrouter_select_common(ifp, (n->stateflags & NDDRF_STATIC));

        return (n);
}

static struct nd_defrouter *
defrtrlist_update(struct nd_defrouter *new)
{
        struct nd_defrouter *dr;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        dr = defrtrlist_update_common(new,
            (nd6_defifp != NULL && new->ifp != nd6_defifp));

        return (dr);
}

static void
defrtrlist_sync(struct ifnet *ifp)
{
        struct nd_defrouter *dr, new;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        if (!ip6_doscopedroute) {
                defrouter_select(ifp);
                return;
        }

        for (dr = TAILQ_FIRST(&nd_defrouter); dr;
             dr = TAILQ_NEXT(dr, dr_entry)) {
                NDDR_LOCK(dr);
                if (dr->ifp == ifp && (dr->stateflags & NDDRF_INSTALLED))
                        break;
                NDDR_UNLOCK(dr);
        }

        if (dr == NULL) {
                /*
                 * Set ignore flag; the chosen default interface might
                 * not be configured to accept RAs.
                 */
                defrouter_select_common(ifp, 1);
        } else {
                memcpy(&new.rtaddr, &dr->rtaddr, sizeof(new.rtaddr));
                new.flags = dr->flags;
                new.stateflags = dr->stateflags;
                new.stateflags &= ~NDDRF_PROCESSED;
                new.rtlifetime = dr->rtlifetime;
                new.expire = dr->expire;
                new.ifp = dr->ifp;
                new.genid = dr->genid;
                new.err = dr->err;
                NDDR_UNLOCK(dr);
                dr = defrtrlist_update_common(&new, FALSE);
                if (dr)
                        NDDR_REMREF(dr);
        }
}

static struct nd_pfxrouter *
pfxrtr_lookup(struct nd_prefix *pr, struct nd_defrouter *dr)
{
        struct nd_pfxrouter *search;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        NDPR_LOCK_ASSERT_HELD(pr);

        for (search = pr->ndpr_advrtrs.lh_first; search;
            search = search->pfr_next) {
                if (search->router == dr)
                        break;
        }

        return(search);
}

static void
pfxrtr_add(struct nd_prefix *pr, struct nd_defrouter *dr)
{
        struct nd_pfxrouter *new;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        NDPR_LOCK_ASSERT_NOTHELD(pr);

        new = zalloc(ndprtr_zone);
        if (new == NULL)
                return;
        bzero(new, sizeof(*new));
        new->router = dr;

        NDPR_LOCK(pr);
        LIST_INSERT_HEAD(&pr->ndpr_advrtrs, new, pfr_entry);
        NDPR_UNLOCK(pr);
        
        pfxlist_onlink_check();
}

static void
pfxrtr_del(
        struct nd_pfxrouter *pfr)
{
        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        LIST_REMOVE(pfr, pfr_entry);
        zfree(ndprtr_zone, pfr);
}

struct nd_prefix *
nd6_prefix_lookup(struct nd_prefix *pr)
{
        struct nd_prefix *search;

        lck_mtx_lock(nd6_mutex);
        for (search = nd_prefix.lh_first; search; search = search->ndpr_next) {
                NDPR_LOCK(search);
                if (pr->ndpr_ifp == search->ndpr_ifp &&
                    pr->ndpr_plen == search->ndpr_plen &&
                    in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr,
                    &search->ndpr_prefix.sin6_addr, pr->ndpr_plen)) {
                        NDPR_ADDREF_LOCKED(search);
                        NDPR_UNLOCK(search);
                        break;
                }
                NDPR_UNLOCK(search);
        }
        lck_mtx_unlock(nd6_mutex);

        return(search);
}

static void
purge_detached(struct ifnet *ifp)
{
        struct nd_prefix *pr, *pr_next;
        struct in6_ifaddr *ia;
        struct ifaddr *ifa, *ifa_next;

        lck_mtx_lock(nd6_mutex);

        pr = nd_prefix.lh_first;
repeat:
        while (pr) {
                pr_next = pr->ndpr_next;
                NDPR_LOCK(pr);
                if (pr->ndpr_ifp != ifp ||
                    IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr) ||
                    ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                    !LIST_EMPTY(&pr->ndpr_advrtrs))) {
                        NDPR_UNLOCK(pr);
                        pr = pr_next;
                        continue;
                }
                NDPR_UNLOCK(pr);
                ifnet_lock_shared(ifp);
                for (ifa = ifp->if_addrlist.tqh_first; ifa; ifa = ifa_next) {
                        ifa_next = ifa->ifa_list.tqe_next;
                        IFA_LOCK(ifa);
                        if (ifa->ifa_addr->sa_family != AF_INET6) {
                                IFA_UNLOCK(ifa);
                                continue;
                        }
                        ia = (struct in6_ifaddr *)ifa;
                        if ((ia->ia6_flags & IN6_IFF_AUTOCONF) ==
                            IN6_IFF_AUTOCONF && ia->ia6_ndpr == pr) {
                                IFA_ADDREF_LOCKED(ifa); /* for us */
                                IFA_UNLOCK(ifa);
                                /*
                                 * Purging the address requires writer access
                                 * to the address list, so drop the ifnet lock
                                 * now and repeat from beginning.
                                 */
                                ifnet_lock_done(ifp);
                                lck_mtx_unlock(nd6_mutex);
                                in6_purgeaddr(ifa);
                                lck_mtx_lock(nd6_mutex);
                                IFA_REMREF(ifa); /* drop ours */
                                pr = nd_prefix.lh_first;
                                goto repeat;
                        }
                        IFA_UNLOCK(ifa);
                }
                ifnet_lock_done(ifp);
                NDPR_LOCK(pr);
                if (pr->ndpr_addrcnt == 0) {
                        NDPR_ADDREF_LOCKED(pr);
                        prelist_remove(pr);
                        NDPR_UNLOCK(pr);
                        NDPR_REMREF(pr);
                } else {
                        NDPR_UNLOCK(pr);
                }
                pr = pr_next;
        }

        lck_mtx_unlock(nd6_mutex);
}

int
nd6_prelist_add(struct nd_prefix *pr, struct nd_defrouter *dr,
    struct nd_prefix **newp, boolean_t force_scoped)
{
        struct nd_prefix *new = NULL;
        struct ifnet *ifp = pr->ndpr_ifp;
        struct nd_ifinfo *ndi = NULL;
        int i, error;
        struct timeval timenow;

        getmicrotime(&timenow);

        if (ip6_maxifprefixes >= 0) {
                lck_rw_lock_shared(nd_if_rwlock);
                if (ifp->if_index >= nd_ifinfo_indexlim) {
                        lck_rw_done(nd_if_rwlock);
                        return (EINVAL);
                }
                ndi = &nd_ifinfo[ifp->if_index];
                if (ndi->nprefixes >= ip6_maxifprefixes / 2) {
                        lck_rw_done(nd_if_rwlock);
                        purge_detached(ifp);
                        lck_rw_lock_shared(nd_if_rwlock);
                        /*
                         * Refresh pointer since nd_ifinfo[] may have grown;
                         * repeating the bounds check against nd_ifinfo_indexlim
                         * isn't necessary since the array never shrinks.
                         */
                        ndi = &nd_ifinfo[ifp->if_index];
                }
                if (ndi->nprefixes >= ip6_maxifprefixes) {
                        lck_rw_done(nd_if_rwlock);
                        return(ENOMEM);
                }
                lck_rw_done(nd_if_rwlock);
        }

        new = ndpr_alloc(M_WAITOK);
        if (new == NULL)
                return ENOMEM;

        NDPR_LOCK(new);
        NDPR_LOCK(pr);
        new->ndpr_ifp = pr->ndpr_ifp;
        new->ndpr_prefix = pr->ndpr_prefix;
        new->ndpr_plen = pr->ndpr_plen;
        new->ndpr_vltime = pr->ndpr_vltime;
        new->ndpr_pltime = pr->ndpr_pltime;
        new->ndpr_flags = pr->ndpr_flags;
        if (pr->ndpr_stateflags & NDPRF_STATIC)
                new->ndpr_stateflags |= NDPRF_STATIC;
        NDPR_UNLOCK(pr);
        if ((error = in6_init_prefix_ltimes(new)) != 0) {
                NDPR_UNLOCK(new);
                ndpr_free(new);
                return(error);
        }
        new->ndpr_lastupdate = timenow.tv_sec;
        if (newp != NULL) {
                *newp = new;
                NDPR_ADDREF_LOCKED(new);        /* for caller */
        }
        /* initialization */
        LIST_INIT(&new->ndpr_advrtrs);
        in6_prefixlen2mask(&new->ndpr_mask, new->ndpr_plen);
        /* make prefix in the canonical form */
        for (i = 0; i < 4; i++)
                new->ndpr_prefix.sin6_addr.s6_addr32[i] &=
                        new->ndpr_mask.s6_addr32[i];

        NDPR_UNLOCK(new);

        lck_mtx_lock(nd6_mutex);
        /* link ndpr_entry to nd_prefix list */
        LIST_INSERT_HEAD(&nd_prefix, new, ndpr_entry);
        new->ndpr_debug |= IFD_ATTACHED;
        NDPR_ADDREF(new);       /* for nd_prefix list */

        /* ND_OPT_PI_FLAG_ONLINK processing */
        if (new->ndpr_raf_onlink) {
                int e;

                if ((e = nd6_prefix_onlink_common(new, force_scoped,
                    new->ndpr_ifp->if_index)) != 0) {
                        nd6log((LOG_ERR, "nd6_prelist_add: failed to make "
                            "the prefix %s/%d on-link %s on %s (errno=%d)\n",
                            ip6_sprintf(&new->ndpr_prefix.sin6_addr),
                            new->ndpr_plen, force_scoped ? "scoped" :
                            "non-scoped", if_name(ifp), e));
                        /* proceed anyway. XXX: is it correct? */
                }
        }

        if (dr) {
                pfxrtr_add(new, dr);
        }

        lck_rw_lock_shared(nd_if_rwlock);
        /*
         * Refresh pointer since nd_ifinfo[] may have grown;
         * repeating the bounds check against nd_ifinfo_indexlim
         * isn't necessary since the array never shrinks.
         */
        ndi = &nd_ifinfo[ifp->if_index];
        atomic_add_32(&ndi->nprefixes, 1);
        lck_rw_done(nd_if_rwlock);

        lck_mtx_unlock(nd6_mutex);

        return 0;
}

/*
 * Caller must have held an extra reference on nd_prefix.
 */
void
prelist_remove(struct nd_prefix *pr)
{
        struct nd_pfxrouter *pfr, *next;
        struct ifnet *ifp = pr->ndpr_ifp;
        int e;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        NDPR_LOCK_ASSERT_HELD(pr);

        /* make sure to invalidate the prefix until it is really freed. */
        pr->ndpr_vltime = 0;
        pr->ndpr_pltime = 0;

        /*
         * Though these flags are now meaningless, we'd rather keep the value
         * of pr->ndpr_raf_onlink and pr->ndpr_raf_auto not to confuse users
         * when executing "ndp -p".
         */

        if ((pr->ndpr_stateflags & NDPRF_ONLINK)) {
                NDPR_ADDREF_LOCKED(pr);
                NDPR_UNLOCK(pr);
                lck_mtx_unlock(nd6_mutex);
                if ((e = nd6_prefix_offlink(pr)) != 0) {
                        nd6log((LOG_ERR, "prelist_remove: failed to make "
                            "%s/%d offlink on %s, errno=%d\n",
                            ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                            pr->ndpr_plen, if_name(ifp), e));
                        /* what should we do? */
                }
                lck_mtx_lock(nd6_mutex);
                NDPR_LOCK(pr);
                if (NDPR_REMREF_LOCKED(pr) == NULL)
                        return;
        }

        if (pr->ndpr_addrcnt > 0)
                return; /* notice here? */

        /* unlink ndpr_entry from nd_prefix list */
        LIST_REMOVE(pr, ndpr_entry);
        pr->ndpr_debug &= ~IFD_ATTACHED;

        /* free list of routers that adversed the prefix */
        for (pfr = pr->ndpr_advrtrs.lh_first; pfr; pfr = next) {
                next = pfr->pfr_next;
                pfxrtr_del(pfr);
        }

        lck_rw_lock_shared(nd_if_rwlock);
        if (ifp->if_index < nd_ifinfo_indexlim) {
                struct nd_ifinfo *ndi = &nd_ifinfo[ifp->if_index];
                atomic_add_32(&ndi->nprefixes, -1);
                if (ndi->nprefixes < 0) {
                        log(LOG_WARNING, "prelist_remove: negative "
                            "count on %s\n", if_name(ifp));
                }
        }
        lck_rw_done(nd_if_rwlock);

        /* This must not be the last reference to the nd_prefix */
        if (NDPR_REMREF_LOCKED(pr) == NULL) {
                panic("%s: unexpected (missing) refcnt ndpr=%p", __func__, pr);
                /* NOTREACHED */
        }

        pfxlist_onlink_check();
}

int
prelist_update(
        struct nd_prefix *new,
        struct nd_defrouter *dr, /* may be NULL */
        struct mbuf *m,
        int mcast)
{
        struct in6_ifaddr *ia6 = NULL, *ia6_match = NULL;
        struct ifaddr *ifa;
        struct ifnet *ifp = new->ndpr_ifp;
        struct nd_prefix *pr;
        int error = 0;
        int newprefix = 0;
        int auth;
        struct in6_addrlifetime lt6_tmp;
        struct timeval timenow;

        /* no need to lock "new" here, as it is local to the caller */
        NDPR_LOCK_ASSERT_NOTHELD(new);

        auth = 0;
        if (m) {
                /*
                 * Authenticity for NA consists authentication for
                 * both IP header and IP datagrams, doesn't it ?
                 */
#if defined(M_AUTHIPHDR) && defined(M_AUTHIPDGM)
                auth = (m->m_flags & M_AUTHIPHDR
                     && m->m_flags & M_AUTHIPDGM) ? 1 : 0;
#endif
        }


        if ((pr = nd6_prefix_lookup(new)) != NULL) {
                /*
                 * nd6_prefix_lookup() ensures that pr and new have the same
                 * prefix on a same interface.
                 */

                /*
                 * Update prefix information.  Note that the on-link (L) bit
                 * and the autonomous (A) bit should NOT be changed from 1
                 * to 0.
                 */
                lck_mtx_lock(nd6_mutex);
                NDPR_LOCK(pr);
                if (new->ndpr_raf_onlink == 1)
                        pr->ndpr_raf_onlink = 1;
                if (new->ndpr_raf_auto == 1)
                        pr->ndpr_raf_auto = 1;
                if (new->ndpr_raf_onlink) {
                        pr->ndpr_vltime = new->ndpr_vltime;
                        pr->ndpr_pltime = new->ndpr_pltime;
                        pr->ndpr_preferred = new->ndpr_preferred;
                        pr->ndpr_expire = new->ndpr_expire;
                }

                if (new->ndpr_raf_onlink &&
                    (pr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
                        int e;

                        NDPR_UNLOCK(pr);
                        if ((e = nd6_prefix_onlink(pr)) != 0) {
                                nd6log((LOG_ERR,
                                    "prelist_update: failed to make "
                                    "the prefix %s/%d on-link on %s "
                                    "(errno=%d)\n",
                                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                                    pr->ndpr_plen, if_name(pr->ndpr_ifp), e));
                                /* proceed anyway. XXX: is it correct? */
                        }
                        NDPR_LOCK(pr);
                }

                if (dr && pfxrtr_lookup(pr, dr) == NULL) {
                        NDPR_UNLOCK(pr);
                        pfxrtr_add(pr, dr);
                } else {
                        NDPR_UNLOCK(pr);
                }
                lck_mtx_unlock(nd6_mutex);
        } else {
                struct nd_prefix *newpr = NULL;

                newprefix = 1;

                if (new->ndpr_vltime == 0)
                        goto end;
                if (new->ndpr_raf_onlink == 0 && new->ndpr_raf_auto == 0)
                        goto end;

                bzero(&new->ndpr_addr, sizeof(struct in6_addr));

                error = nd6_prelist_add(new, dr, &newpr, FALSE);
                if (error != 0 || newpr == NULL) {
                        nd6log((LOG_NOTICE, "prelist_update: "
                            "nd6_prelist_add failed for %s/%d on %s "
                            "errno=%d, returnpr=%p\n",
                            ip6_sprintf(&new->ndpr_prefix.sin6_addr),
                                        new->ndpr_plen, if_name(new->ndpr_ifp),
                                        error, newpr));
                        goto end; /* we should just give up in this case. */
                }

                /*
                 * XXX: from the ND point of view, we can ignore a prefix
                 * with the on-link bit being zero.  However, we need a
                 * prefix structure for references from autoconfigured
                 * addresses.  Thus, we explicitly make sure that the prefix
                 * itself expires now.
                 */
                NDPR_LOCK(newpr);
                if (newpr->ndpr_raf_onlink == 0) {
                        newpr->ndpr_vltime = 0;
                        newpr->ndpr_pltime = 0;
                        in6_init_prefix_ltimes(newpr);
                }

                pr = newpr;
                NDPR_UNLOCK(newpr);
        }

        /*
         * Address autoconfiguration based on Section 5.5.3 of RFC 2462.
         * Note that pr must be non NULL at this point.
         */

        /* 5.5.3 (a). Ignore the prefix without the A bit set. */
        if (!new->ndpr_raf_auto)
                goto afteraddrconf;

        /*
         * 5.5.3 (b). the link-local prefix should have been ignored in
         * nd6_ra_input.
         */

        /* 5.5.3 (c). Consistency check on lifetimes: pltime <= vltime. */
        if (new->ndpr_pltime > new->ndpr_vltime) {
                error = EINVAL; /* XXX: won't be used */
                goto end;
        }

        /*
         * 5.5.3 (d).  If the prefix advertised is not equal to the prefix of
         * an address configured by stateless autoconfiguration already in the
         * list of addresses associated with the interface, and the Valid
         * Lifetime is not 0, form an address.  We first check if we have
         * a matching prefix.
         * Note: we apply a clarification in rfc2462bis-02 here.  We only
         * consider autoconfigured addresses while RFC2462 simply said
         * "address".
         */

        getmicrotime(&timenow);

        ifnet_lock_shared(ifp);
        TAILQ_FOREACH(ifa, &ifp->if_addrlist, ifa_list)
        {
                struct in6_ifaddr *ifa6;
                u_int32_t remaininglifetime;

                IFA_LOCK(ifa);
                if (ifa->ifa_addr->sa_family != AF_INET6) {
                        IFA_UNLOCK(ifa);
                        continue;
                }
                ifa6 = (struct in6_ifaddr *)ifa;

                /*
                 * We only consider autoconfigured addresses as per rfc2462bis.
                 */
                if (!(ifa6->ia6_flags & IN6_IFF_AUTOCONF)) {
                        IFA_UNLOCK(ifa);
                        continue;
                }
                /*
                 * Spec is not clear here, but I believe we should concentrate
                 * on unicast (i.e. not anycast) addresses.
                 * XXX: other ia6_flags? detached or duplicated?
                 */
                if ((ifa6->ia6_flags & IN6_IFF_ANYCAST) != 0) {
                        IFA_UNLOCK(ifa);
                        continue;
                }
                /*
                 * Ignore the address if it is not associated with a prefix
                 * or is associated with a prefix that is different from this
                 * one.  (pr is never NULL here)
                 */
                if (ifa6->ia6_ndpr != pr) {
                        IFA_UNLOCK(ifa);
                        continue;
                }

                if (ia6_match == NULL) { /* remember the first one */
                        ia6_match = ifa6;
                        IFA_ADDREF_LOCKED(ifa); /* for ia6_match */
                }

                /*
                 * An already autoconfigured address matched.  Now that we
                 * are sure there is at least one matched address, we can
                 * proceed to 5.5.3. (e): update the lifetimes according to the
                 * "two hours" rule and the privacy extension.
                 * We apply some clarifications in rfc2462bis:
                 * - use remaininglifetime instead of storedlifetime as a
                 *   variable name
                 * - remove the dead code in the "two-hour" rule
                 */
#define TWOHOUR         (120*60)
                lt6_tmp = ifa6->ia6_lifetime;

                if (lt6_tmp.ia6t_vltime == ND6_INFINITE_LIFETIME)
                        remaininglifetime = ND6_INFINITE_LIFETIME;
                else if (timenow.tv_sec - ifa6->ia6_updatetime >
                         lt6_tmp.ia6t_vltime) {
                        /*
                         * The case of "invalid" address.  We should usually
                         * not see this case.
                         */
                        remaininglifetime = 0;
                } else
                        remaininglifetime = lt6_tmp.ia6t_vltime -
                            (timenow.tv_sec - ifa6->ia6_updatetime);

                /* when not updating, keep the current stored lifetime. */
                lt6_tmp.ia6t_vltime = remaininglifetime;

                if (TWOHOUR < new->ndpr_vltime ||
                    remaininglifetime < new->ndpr_vltime) {
                        lt6_tmp.ia6t_vltime = new->ndpr_vltime;
                } else if (remaininglifetime <= TWOHOUR) {
                        if (auth) {
                                lt6_tmp.ia6t_vltime = new->ndpr_vltime;
                        }
                } else {
                        /*
                         * new->ndpr_vltime <= TWOHOUR &&
                         * TWOHOUR < remaininglifetime
                         */
                        lt6_tmp.ia6t_vltime = TWOHOUR;
                }

                /* The 2 hour rule is not imposed for preferred lifetime. */
                lt6_tmp.ia6t_pltime = new->ndpr_pltime;

                /* Special handling for lifetimes of temporary addresses. */
                if ((ifa6->ia6_flags & IN6_IFF_TEMPORARY) != 0) {
                        u_int32_t maxvltime, maxpltime;
                        
                        /* Constrain lifetimes to system limits. */
                        if (lt6_tmp.ia6t_vltime > ip6_temp_valid_lifetime)
                                lt6_tmp.ia6t_vltime = ip6_temp_valid_lifetime;
                        if (lt6_tmp.ia6t_pltime > ip6_temp_preferred_lifetime)
                                lt6_tmp.ia6t_pltime =
                                    ip6_temp_preferred_lifetime -
                                    ip6_desync_factor;

                        /*
                         * According to RFC 4941, section 3.3 (1), we only
                         * update the lifetimes when they are in the maximum
                         * intervals.
                         */
                        if (ip6_temp_valid_lifetime >
                            (u_int32_t)((timenow.tv_sec - ifa6->ia6_createtime) +
                            ip6_desync_factor)) {
                                maxvltime = ip6_temp_valid_lifetime -
                                    (timenow.tv_sec - ifa6->ia6_createtime) -
                                    ip6_desync_factor;
                        } else
                                maxvltime = 0;
                        if (ip6_temp_preferred_lifetime >
                            (u_int32_t)((timenow.tv_sec - ifa6->ia6_createtime) +
                            ip6_desync_factor)) {
                                maxpltime = ip6_temp_preferred_lifetime -
                                    (timenow.tv_sec - ifa6->ia6_createtime) -
                                    ip6_desync_factor;
                        } else
                                maxpltime = 0;

                        if (lt6_tmp.ia6t_vltime > maxvltime)
                                lt6_tmp.ia6t_vltime = maxvltime;
                        if (lt6_tmp.ia6t_pltime > maxpltime)
                                lt6_tmp.ia6t_pltime = maxpltime;
                }

                in6_init_address_ltimes(pr, &lt6_tmp,
                    !!(ifa6->ia6_flags & IN6_IFF_TEMPORARY));
                
                ifa6->ia6_lifetime = lt6_tmp;
                ifa6->ia6_updatetime = timenow.tv_sec;
                IFA_UNLOCK(ifa);
        }
        ifnet_lock_done(ifp);
        if (ia6_match == NULL && new->ndpr_vltime) {
                int ifidlen;

                /*
                 * 5.5.3 (d) (continued)
                 * No address matched and the valid lifetime is non-zero.
                 * Create a new address.
                 */

                /*
                 * Prefix Length check:
                 * If the sum of the prefix length and interface identifier
                 * length does not equal 128 bits, the Prefix Information
                 * option MUST be ignored.  The length of the interface
                 * identifier is defined in a separate link-type specific
                 * document.
                 */
                ifidlen = in6_if2idlen(ifp);
                if (ifidlen < 0) {
                        /* this should not happen, so we always log it. */
                        log(LOG_ERR, "prelist_update: IFID undefined (%s)\n",
                            if_name(ifp));
                        goto end;
                }
                NDPR_LOCK(pr);
                if (ifidlen + pr->ndpr_plen != 128) {
                        nd6log((LOG_INFO,
                            "prelist_update: invalid prefixlen "
                            "%d for %s, ignored\n",
                            pr->ndpr_plen, if_name(ifp)));
                        NDPR_UNLOCK(pr);
                        goto end;
                }
                NDPR_UNLOCK(pr);

                if ((ia6 = in6_ifadd(new, mcast)) != NULL) {
                        /*
                         * note that we should use pr (not new) for reference.
                         */
                        IFA_LOCK(&ia6->ia_ifa);
                        NDPR_LOCK(pr);
                        ia6->ia6_ndpr = pr;
                        NDPR_ADDREF_LOCKED(pr); /* for addr reference */
                        pr->ndpr_addrcnt++;
                        VERIFY(pr->ndpr_addrcnt != 0);
                        NDPR_UNLOCK(pr);
                        IFA_UNLOCK(&ia6->ia_ifa);

                        /*
                         * RFC 4941 3.3 (2).
                         * When a new public address is created as described
                         * in RFC2462, also create a new temporary address.
                         *
                         * RFC 4941 3.5.
                         * When an interface connects to a new link, a new
                         * randomized interface identifier should be generated
                         * immediately together with a new set of temporary
                         * addresses.  Thus, we specifiy 1 as the 2nd arg of
                         * in6_tmpifadd().
                         */
                        if (ip6_use_tempaddr) {
                                int e;
                                if ((e = in6_tmpifadd(ia6, 1, M_WAITOK)) != 0) {
                                        nd6log((LOG_NOTICE, "prelist_update: "
                                            "failed to create a temporary "
                                            "address, errno=%d\n",
                                            e));
                                }
                        }
                        IFA_REMREF(&ia6->ia_ifa);
                        ia6 = NULL;

                        /*
                         * A newly added address might affect the status
                         * of other addresses, so we check and update it.
                         * XXX: what if address duplication happens?
                         */
                        lck_mtx_lock(nd6_mutex);
                        pfxlist_onlink_check();
                        lck_mtx_unlock(nd6_mutex);
                } else {
                        /* just set an error. do not bark here. */
                        error = EADDRNOTAVAIL; /* XXX: might be unused. */
                }
        }

afteraddrconf:

end:
        if (pr != NULL)
                NDPR_REMREF(pr);
        if (ia6_match != NULL)
                IFA_REMREF(&ia6_match->ia_ifa);
        return error;
}

/*
 * Neighbor Discover Default Router structure reference counting routines.
 */
static struct nd_defrouter *
nddr_alloc(int how)
{
        struct nd_defrouter *dr;

        dr = (how == M_WAITOK) ? zalloc(nddr_zone) : zalloc_noblock(nddr_zone);
        if (dr != NULL) {
                bzero(dr, nddr_size);
                lck_mtx_init(&dr->nddr_lock, ifa_mtx_grp, ifa_mtx_attr);
                dr->nddr_debug |= IFD_ALLOC;
                if (nddr_debug != 0) {
                        dr->nddr_debug |= IFD_DEBUG;
                        dr->nddr_trace = nddr_trace;
                }
        }
        return (dr);
}

static void
nddr_free(struct nd_defrouter *dr)
{
        NDDR_LOCK(dr);
        if (dr->nddr_debug & IFD_ATTACHED) {
                panic("%s: attached nddr %p is being freed", __func__, dr);
                /* NOTREACHED */
        } else if (!(dr->nddr_debug & IFD_ALLOC)) {
                panic("%s: nddr %p cannot be freed", __func__, dr);
                /* NOTREACHED */
        }
        dr->nddr_debug &= ~IFD_ALLOC;
        NDDR_UNLOCK(dr);

        lck_mtx_destroy(&dr->nddr_lock, ifa_mtx_grp);
        zfree(nddr_zone, dr);
}

static void
nddr_trace(struct nd_defrouter *dr, int refhold)
{
        struct nd_defrouter_dbg *dr_dbg = (struct nd_defrouter_dbg *)dr;
        ctrace_t *tr;
        uint32_t idx;
        uint16_t *cnt;

        if (!(dr->nddr_debug & IFD_DEBUG)) {
                panic("%s: nddr %p has no debug structure", __func__, dr);
                /* NOTREACHED */
        }
        if (refhold) {
                cnt = &dr_dbg->nddr_refhold_cnt;
                tr = dr_dbg->nddr_refhold;
        } else {
                cnt = &dr_dbg->nddr_refrele_cnt;
                tr = dr_dbg->nddr_refrele;
        }

        idx = atomic_add_16_ov(cnt, 1) % NDDR_TRACE_HIST_SIZE;
        ctrace_record(&tr[idx]);
}

void
nddr_addref(struct nd_defrouter *nddr, int locked)
{

        if (!locked)
                NDDR_LOCK_SPIN(nddr);
        else
                NDDR_LOCK_ASSERT_HELD(nddr);

        if (++nddr->nddr_refcount == 0) {
                panic("%s: nddr %p wraparound refcnt\n", __func__, nddr);
                /* NOTREACHED */
        } else if (nddr->nddr_trace != NULL) {
                (*nddr->nddr_trace)(nddr, TRUE);
        }

        if (!locked)
                NDDR_UNLOCK(nddr);
}

struct nd_defrouter *
nddr_remref(struct nd_defrouter *nddr, int locked)
{

        if (!locked)
                NDDR_LOCK_SPIN(nddr);
        else
                NDDR_LOCK_ASSERT_HELD(nddr);

        if (nddr->nddr_refcount == 0) {
                panic("%s: nddr %p negative refcnt\n", __func__, nddr);
                /* NOTREACHED */
        } else if (nddr->nddr_trace != NULL) {
                (*nddr->nddr_trace)(nddr, FALSE);
        }

        if (--nddr->nddr_refcount == 0) {
                NDDR_UNLOCK(nddr);
                nddr_free(nddr);
                nddr = NULL;
        }

        if (!locked && nddr != NULL)
                NDDR_UNLOCK(nddr);

        return (nddr);
}

/*
 * Neighbor Discover Prefix structure reference counting routines.
 */
static struct nd_prefix *
ndpr_alloc(int how)
{
        struct nd_prefix *pr;

        pr = (how == M_WAITOK) ? zalloc(ndpr_zone) : zalloc_noblock(ndpr_zone);
        if (pr != NULL) {
                bzero(pr, ndpr_size);
                lck_mtx_init(&pr->ndpr_lock, ifa_mtx_grp, ifa_mtx_attr);
                pr->ndpr_debug |= IFD_ALLOC;
                if (ndpr_debug != 0) {
                        pr->ndpr_debug |= IFD_DEBUG;
                        pr->ndpr_trace = ndpr_trace;
                }
        }
        return (pr);
}

static void
ndpr_free(struct nd_prefix *pr)
{
        NDPR_LOCK(pr);
        if (pr->ndpr_debug & IFD_ATTACHED) {
                panic("%s: attached ndpr %p is being freed", __func__, pr);
                /* NOTREACHED */
        } else if (!(pr->ndpr_debug & IFD_ALLOC)) {
                panic("%s: ndpr %p cannot be freed", __func__, pr);
                /* NOTREACHED */
        }
        pr->ndpr_debug &= ~IFD_ALLOC;
        NDPR_UNLOCK(pr);

        lck_mtx_destroy(&pr->ndpr_lock, ifa_mtx_grp);
        zfree(ndpr_zone, pr);
}

static void
ndpr_trace(struct nd_prefix *pr, int refhold)
{
        struct nd_prefix_dbg *pr_dbg = (struct nd_prefix_dbg *)pr;
        ctrace_t *tr;
        u_int32_t idx;
        u_int16_t *cnt;

        if (!(pr->ndpr_debug & IFD_DEBUG)) {
                panic("%s: ndpr %p has no debug structure", __func__, pr);
                /* NOTREACHED */
        }
        if (refhold) {
                cnt = &pr_dbg->ndpr_refhold_cnt;
                tr = pr_dbg->ndpr_refhold;
        } else {
                cnt = &pr_dbg->ndpr_refrele_cnt;
                tr = pr_dbg->ndpr_refrele;
        }

        idx = atomic_add_16_ov(cnt, 1) % NDPR_TRACE_HIST_SIZE;
        ctrace_record(&tr[idx]);
}

void
ndpr_addref(struct nd_prefix *ndpr, int locked)
{
        if (!locked)
                NDPR_LOCK_SPIN(ndpr);
        else
                NDPR_LOCK_ASSERT_HELD(ndpr);

        if (++ndpr->ndpr_refcount == 0) {
                panic("%s: ndpr %p wraparound refcnt\n", __func__, ndpr);
                /* NOTREACHED */
        } else if (ndpr->ndpr_trace != NULL) {
                (*ndpr->ndpr_trace)(ndpr, TRUE);
        }

        if (!locked)
                NDPR_UNLOCK(ndpr);
}

struct nd_prefix *
ndpr_remref(struct nd_prefix *ndpr, int locked)
{
        if (!locked)
                NDPR_LOCK_SPIN(ndpr);
        else
                NDPR_LOCK_ASSERT_HELD(ndpr);

        if (ndpr->ndpr_refcount == 0) {
                panic("%s: ndpr %p negative refcnt\n", __func__, ndpr);
                /* NOTREACHED */
        } else if (ndpr->ndpr_trace != NULL) {
                (*ndpr->ndpr_trace)(ndpr, FALSE);
        }

        if (--ndpr->ndpr_refcount == 0) {
                if (ndpr->ndpr_addrcnt != 0) {
                        panic("%s: freeing ndpr %p with outstanding address "
                            "reference (%d)", __func__, ndpr,
                            ndpr->ndpr_addrcnt);
                        /* NOTREACHED */
                }
                NDPR_UNLOCK(ndpr);
                ndpr_free(ndpr);
                ndpr = NULL;
        }

        if (!locked && ndpr != NULL)
                NDPR_UNLOCK(ndpr);

        return (ndpr);
}

/*
 * A supplement function used in the on-link detection below;
 * detect if a given prefix has a (probably) reachable advertising router.
 * XXX: lengthy function name...
 */
static struct nd_pfxrouter *
find_pfxlist_reachable_router(struct nd_prefix *pr)
{
        struct nd_pfxrouter *pfxrtr;
        struct rtentry *rt;
        struct llinfo_nd6 *ln;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        NDPR_LOCK_ASSERT_HELD(pr);

        for (pfxrtr = LIST_FIRST(&pr->ndpr_advrtrs); pfxrtr;
             pfxrtr = LIST_NEXT(pfxrtr, pfr_entry)) {
                NDPR_UNLOCK(pr);
                lck_mtx_unlock(nd6_mutex);
                /* Callee returns a locked route upon success */
                if ((rt = nd6_lookup(&pfxrtr->router->rtaddr, 0,
                    pfxrtr->router->ifp, 0)) != NULL) {
                        RT_LOCK_ASSERT_HELD(rt);
                        if ((ln = rt->rt_llinfo) != NULL &&
                            ND6_IS_LLINFO_PROBREACH(ln)) {
                                RT_REMREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_lock(nd6_mutex);
                                NDPR_LOCK(pr);
                                break;  /* found */
                        }
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                }
                lck_mtx_lock(nd6_mutex);
                NDPR_LOCK(pr);
        }
        NDPR_LOCK_ASSERT_HELD(pr);

        return (pfxrtr);

}

/*
 * Check if each prefix in the prefix list has at least one available router
 * that advertised the prefix (a router is "available" if its neighbor cache
 * entry is reachable or probably reachable).
 * If the check fails, the prefix may be off-link, because, for example,
 * we have moved from the network but the lifetime of the prefix has not
 * expired yet.  So we should not use the prefix if there is another prefix
 * that has an available router.
 * But, if there is no prefix that has an available router, we still regards
 * all the prefixes as on-link.  This is because we can't tell if all the
 * routers are simply dead or if we really moved from the network and there
 * is no router around us.
 */
void
pfxlist_onlink_check(void)
{
        struct nd_prefix *pr, *prclear;
        struct in6_ifaddr *ifa;
        struct nd_defrouter *dr;
        struct nd_pfxrouter *pfxrtr = NULL;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        while (nd_prefix_busy) {
                nd_prefix_waiters++;
                msleep(nd_prefix_waitchan, nd6_mutex, (PZERO-1),
                    __func__, NULL);
                lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);
        }
        nd_prefix_busy = TRUE;

        /*
         * Check if there is a prefix that has a reachable advertising
         * router.
         */
        pr = nd_prefix.lh_first;
        while (pr) {
                NDPR_LOCK(pr);
                if (pr->ndpr_stateflags & NDPRF_PROCESSED) {
                        NDPR_UNLOCK(pr);
                        pr = pr->ndpr_next;
                        continue;
                }
                NDPR_ADDREF_LOCKED(pr);
                if (pr->ndpr_raf_onlink && find_pfxlist_reachable_router(pr) &&
                    (pr->ndpr_debug & IFD_ATTACHED)) {
                        NDPR_UNLOCK(pr);
                        NDPR_REMREF(pr);
                        break;
                }
                pr->ndpr_stateflags |= NDPRF_PROCESSED;
                NDPR_UNLOCK(pr);
                NDPR_REMREF(pr);
                /*
                 * Since find_pfxlist_reachable_router() drops the nd6_mutex, we
                 * have to start over, but the NDPRF_PROCESSED flag will stop
                 * us from checking the same prefix twice.
                 */
                pr = nd_prefix.lh_first;
        }
        LIST_FOREACH(prclear, &nd_prefix, ndpr_entry) {
                NDPR_LOCK(prclear);
                prclear->ndpr_stateflags &= ~NDPRF_PROCESSED;
                NDPR_UNLOCK(prclear);
        }

        /*
         * If we have no such prefix, check whether we still have a router
         * that does not advertise any prefixes.
         */
        if (pr == NULL) {
                for (dr = TAILQ_FIRST(&nd_defrouter); dr;
                    dr = TAILQ_NEXT(dr, dr_entry)) {
                        struct nd_prefix *pr0;

                        for (pr0 = nd_prefix.lh_first; pr0;
                            pr0 = pr0->ndpr_next) {
                                NDPR_LOCK(pr0);
                                if ((pfxrtr = pfxrtr_lookup(pr0, dr)) != NULL) {
                                        NDPR_UNLOCK(pr0);
                                        break;
                                }
                                NDPR_UNLOCK(pr0);
                        }
                        if (pfxrtr != NULL)
                                break;
                }
        }
        if (pr != NULL || (TAILQ_FIRST(&nd_defrouter) && pfxrtr == NULL)) {
                /*
                 * There is at least one prefix that has a reachable router,
                 * or at least a router which probably does not advertise
                 * any prefixes.  The latter would be the case when we move
                 * to a new link where we have a router that does not provide
                 * prefixes and we configure an address by hand.
                 * Detach prefixes which have no reachable advertising
                 * router, and attach other prefixes.
                 */
                pr = nd_prefix.lh_first;
                while (pr) {
                        NDPR_LOCK(pr);
                        /*
                         * We aren't interested prefixes already processed,
                         * nor in prefixes without the L bit
                         * set nor in static prefixes
                         */
                        if (pr->ndpr_raf_onlink == 0 ||
                            pr->ndpr_stateflags & NDPRF_PROCESSED ||
                            pr->ndpr_stateflags & NDPRF_STATIC) {
                                NDPR_UNLOCK(pr);
                                pr = pr->ndpr_next;
                                continue;
                        }
                        NDPR_ADDREF_LOCKED(pr);
                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                            find_pfxlist_reachable_router(pr) == NULL &&
                            (pr->ndpr_debug & IFD_ATTACHED))
                                pr->ndpr_stateflags |= NDPRF_DETACHED;
                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
                            find_pfxlist_reachable_router(pr) != NULL &&
                            (pr->ndpr_debug & IFD_ATTACHED))
                                pr->ndpr_stateflags &= ~NDPRF_DETACHED;
                        pr->ndpr_stateflags |= NDPRF_PROCESSED;
                        NDPR_UNLOCK(pr);
                        NDPR_REMREF(pr);
                        /*
                         * Since find_pfxlist_reachable_router() drops the
                         * nd6_mutex, we have to start over, but the
                         * NDPRF_PROCESSED flag will stop us from checking
                         * the same prefix twice.
                         */
                        pr = nd_prefix.lh_first;
                }
        } else {
                /* there is no prefix that has a reachable router */
                for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                        NDPR_LOCK(pr);
                        if (pr->ndpr_raf_onlink == 0 ||
                            pr->ndpr_stateflags & NDPRF_STATIC) {
                                NDPR_UNLOCK(pr);
                                continue;
                        }
                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0)
                                pr->ndpr_stateflags &= ~NDPRF_DETACHED;
                        NDPR_UNLOCK(pr);
                }
        }
        LIST_FOREACH(prclear, &nd_prefix, ndpr_entry) {
                NDPR_LOCK(prclear);
                prclear->ndpr_stateflags &= ~NDPRF_PROCESSED;
                NDPR_UNLOCK(prclear);
        }
        VERIFY(nd_prefix_busy);
        nd_prefix_busy = FALSE;
        if (nd_prefix_waiters > 0) {
                nd_prefix_waiters = 0;
                wakeup(nd_prefix_waitchan);
        }

        /*
         * Remove each interface route associated with a (just) detached
         * prefix, and reinstall the interface route for a (just) attached
         * prefix.  Note that all attempt of reinstallation does not
         * necessarily success, when a same prefix is shared among multiple
         * interfaces.  Such cases will be handled in nd6_prefix_onlink,
         * so we don't have to care about them.
         */
        pr = nd_prefix.lh_first;
        while (pr) {
                int e;

                NDPR_LOCK(pr);
                if (pr->ndpr_raf_onlink == 0 ||
                    pr->ndpr_stateflags & NDPRF_STATIC) {
                        NDPR_UNLOCK(pr);
                        pr = pr->ndpr_next;
                        continue;
                }
                if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
                    (pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                        NDPR_UNLOCK(pr);
                        lck_mtx_unlock(nd6_mutex);
                        if ((e = nd6_prefix_offlink(pr)) != 0) {
                                nd6log((LOG_ERR,
                                    "pfxlist_onlink_check: failed to "
                                    "make %s/%d offlink, errno=%d\n",
                                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                                    pr->ndpr_plen, e));
                        }
                        lck_mtx_lock(nd6_mutex);
                        pr = nd_prefix.lh_first;
                        continue;
                }
                if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                    (pr->ndpr_stateflags & NDPRF_ONLINK) == 0 &&
                    pr->ndpr_raf_onlink) {
                        NDPR_UNLOCK(pr);
                        if ((e = nd6_prefix_onlink(pr)) != 0) {
                                nd6log((LOG_ERR,
                                    "pfxlist_onlink_check: failed to "
                                    "make %s/%d offlink, errno=%d\n",
                                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                                    pr->ndpr_plen, e));
                        }
                } else {
                        NDPR_UNLOCK(pr);
                }
                pr = pr->ndpr_next;
        }

        /*
         * Changes on the prefix status might affect address status as well.
         * Make sure that all addresses derived from an attached prefix are
         * attached, and that all addresses derived from a detached prefix are
         * detached.  Note, however, that a manually configured address should
         * always be attached.
         * The precise detection logic is same as the one for prefixes.
         */
        lck_rw_lock_shared(&in6_ifaddr_rwlock);
        for (ifa = in6_ifaddrs; ifa; ifa = ifa->ia_next) {
                struct nd_prefix *ndpr;

                IFA_LOCK(&ifa->ia_ifa);
                if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0) {
                        IFA_UNLOCK(&ifa->ia_ifa);
                        continue;
                }
                if ((ndpr = ifa->ia6_ndpr) == NULL) {
                        /*
                         * This can happen when we first configure the address
                         * (i.e. the address exists, but the prefix does not).
                         * XXX: complicated relationships...
                         */
                        IFA_UNLOCK(&ifa->ia_ifa);
                        continue;
                }
                NDPR_ADDREF(ndpr);
                IFA_UNLOCK(&ifa->ia_ifa);

                NDPR_LOCK(ndpr);
                if (find_pfxlist_reachable_router(ndpr)) {
                        NDPR_UNLOCK(ndpr);
                        NDPR_REMREF(ndpr);
                        break;
                }
                NDPR_UNLOCK(ndpr);
                NDPR_REMREF(ndpr);
        }
        if (ifa) {
                for (ifa = in6_ifaddrs; ifa; ifa = ifa->ia_next) {
                        struct nd_prefix *ndpr;

                        IFA_LOCK(&ifa->ia_ifa);
                        if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0) {
                                IFA_UNLOCK(&ifa->ia_ifa);
                                continue;
                        }
                        if ((ndpr = ifa->ia6_ndpr) == NULL) {
                                /* XXX: see above. */
                                IFA_UNLOCK(&ifa->ia_ifa);
                                continue;
                        }
                        NDPR_ADDREF(ndpr);
                        IFA_UNLOCK(&ifa->ia_ifa);
                        NDPR_LOCK(ndpr);
                        if (find_pfxlist_reachable_router(ndpr)) {
                                NDPR_UNLOCK(ndpr);
                                IFA_LOCK(&ifa->ia_ifa);
                                if (ifa->ia6_flags & IN6_IFF_DETACHED) {
                                        ifa->ia6_flags &= ~IN6_IFF_DETACHED;
                                        ifa->ia6_flags |= IN6_IFF_TENTATIVE;
                                        IFA_UNLOCK(&ifa->ia_ifa);
                                        nd6_dad_start((struct ifaddr *)ifa, 0);
                                } else {
                                        IFA_UNLOCK(&ifa->ia_ifa);
                                }
                        } else {
                                NDPR_UNLOCK(ndpr);
                                IFA_LOCK(&ifa->ia_ifa);
                                ifa->ia6_flags |= IN6_IFF_DETACHED;
                                IFA_UNLOCK(&ifa->ia_ifa);
                        }
                        NDPR_REMREF(ndpr);
                }
        }
        else {
                for (ifa = in6_ifaddrs; ifa; ifa = ifa->ia_next) {
                        IFA_LOCK(&ifa->ia_ifa);
                        if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0) {
                                IFA_UNLOCK(&ifa->ia_ifa);
                                continue;
                        }
                        if (ifa->ia6_flags & IN6_IFF_DETACHED) {
                                ifa->ia6_flags &= ~IN6_IFF_DETACHED;
                                ifa->ia6_flags |= IN6_IFF_TENTATIVE;
                                IFA_UNLOCK(&ifa->ia_ifa);
                                /* Do we need a delay in this case? */
                                nd6_dad_start((struct ifaddr *)ifa, 0);
                        } else {
                                IFA_UNLOCK(&ifa->ia_ifa);
                        }
                }
        }
        lck_rw_done(&in6_ifaddr_rwlock);
}

static struct nd_prefix *
nd6_prefix_equal_lookup(struct nd_prefix *pr, boolean_t primary_only)
{
        struct nd_prefix *opr;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        for (opr = nd_prefix.lh_first; opr; opr = opr->ndpr_next) {
                if (opr == pr)
                        continue;

                NDPR_LOCK(opr);
                if ((opr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
                        NDPR_UNLOCK(opr);
                        continue;
                }
                if (opr->ndpr_plen == pr->ndpr_plen &&
                    in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr,
                    &opr->ndpr_prefix.sin6_addr, pr->ndpr_plen) &&
                    (!primary_only ||
                    !(opr->ndpr_stateflags & NDPRF_IFSCOPE))) {
                        NDPR_ADDREF_LOCKED(opr);
                        NDPR_UNLOCK(opr);
                        return (opr);
                }
                NDPR_UNLOCK(opr);
        }
        return (NULL);
}

/*
 * Synchronize the interface routes of similar prefixes on different
 * interfaces; the one using the default interface would be (re)installed
 * as a primary/non-scoped entry, and the rest as scoped entri(es).
 */
static void
nd6_prefix_sync(struct ifnet *ifp)
{
        struct nd_prefix *pr, *opr;
        int err = 0;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        if (!ip6_doscopedroute || ifp == NULL)
                return;

        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }
                if (pr->ndpr_ifp == ifp &&
                    (pr->ndpr_stateflags & NDPRF_IFSCOPE) &&
                    !IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr)) {
                        NDPR_UNLOCK(pr);
                        break;
                }
                NDPR_UNLOCK(pr);
        }

        if (pr == NULL)
                return;

        /* Remove conflicting entries */
        opr = nd6_prefix_equal_lookup(pr, TRUE);
        if (opr != NULL) {
                lck_mtx_unlock(nd6_mutex);
                err = nd6_prefix_offlink(opr);
                lck_mtx_lock(nd6_mutex);
                if (err != 0) {
                        nd6log((LOG_ERR,
                            "%s: failed to make %s/%d offlink on %s, "
                            "errno=%d\n", __func__,
                            ip6_sprintf(&opr->ndpr_prefix.sin6_addr),
                            opr->ndpr_plen, if_name(opr->ndpr_ifp), err));
                }
        } else {
                nd6log((LOG_ERR,
                    "%s: scoped %s/%d on %s has no matching unscoped prefix\n",
                    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp)));
        }

        lck_mtx_unlock(nd6_mutex);
        err = nd6_prefix_offlink(pr);
        lck_mtx_lock(nd6_mutex);
        if (err != 0) {
                nd6log((LOG_ERR,
                    "%s: failed to make %s/%d offlink on %s, errno=%d\n",
                    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp), err));
        }

        /* Add the entries back */
        if (opr != NULL) {
                err = nd6_prefix_onlink_scoped(opr, opr->ndpr_ifp->if_index);
                if (err != 0) {
                        nd6log((LOG_ERR,
                            "%s: failed to make %s/%d scoped onlink on %s, "
                            "errno=%d\n", __func__,
                            ip6_sprintf(&opr->ndpr_prefix.sin6_addr),
                            opr->ndpr_plen, if_name(opr->ndpr_ifp), err));
                }
        }

        err = nd6_prefix_onlink_scoped(pr, IFSCOPE_NONE);
        if (err != 0) {
                nd6log((LOG_ERR,
                    "%s: failed to make %s/%d onlink on %s, errno=%d\n",
                    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp), err));
        }

        if (err != 0) {
                nd6log((LOG_ERR,
                    "%s: error promoting %s/%d to %s from %s\n",
                    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp),
                    (opr != NULL) ? if_name(opr->ndpr_ifp) : "NONE"));
        } else {
                nd6log2((LOG_INFO,
                    "%s: %s/%d promoted, previously on %s\n",
                    if_name(pr->ndpr_ifp),
                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr), pr->ndpr_plen,
                    (opr != NULL) ? if_name(opr->ndpr_ifp) : "NONE"));
        }

        if (opr != NULL)
                NDPR_REMREF(opr);
}

static int
nd6_prefix_onlink_common(struct nd_prefix *pr, boolean_t force_scoped,
    unsigned int ifscope)
{
        struct ifaddr *ifa;
        struct ifnet *ifp = pr->ndpr_ifp;
        struct sockaddr_in6 mask6, prefix;
        struct nd_prefix *opr;
        u_int32_t rtflags;
        int error = 0;
        struct rtentry *rt = NULL;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        /* sanity check */
        NDPR_LOCK(pr);
        if ((pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                nd6log((LOG_ERR,
                    "nd6_prefix_onlink: %s/%d on %s scoped=%d is already "
                     "on-link\n", ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                     pr->ndpr_plen, if_name(pr->ndpr_ifp),
                     (pr->ndpr_stateflags & NDPRF_IFSCOPE) ? 1 : 0);
                NDPR_UNLOCK(pr);
                return (EEXIST));
        }
        NDPR_UNLOCK(pr);

        /*
         * Add the interface route associated with the prefix.  Before
         * installing the route, check if there's the same prefix on another
         * interface, and the prefix has already installed the interface route.
         */
        opr = nd6_prefix_equal_lookup(pr, FALSE);
        if (opr != NULL)
                NDPR_REMREF(opr);

        if (!ip6_doscopedroute) {
                /* if an interface route already exists, just return */
                if (opr != NULL)
                        return (0);
                ifscope = IFSCOPE_NONE;
        } else if (!force_scoped) {
                /*
                 * If a primary/non-scoped interface route already exists,
                 * install the new one as a scoped entry.  If the existing
                 * interface route is scoped, install new as non-scoped.
                 */
                ifscope = (opr != NULL) ? ifp->if_index : IFSCOPE_NONE;
                opr = nd6_prefix_equal_lookup(pr, TRUE);
                if (opr != NULL)
                        NDPR_REMREF(opr);
                else if (ifscope != IFSCOPE_NONE)
                        ifscope = IFSCOPE_NONE;
        }

        /*
         * We prefer link-local addresses as the associated interface address.
         */
        /* search for a link-local addr */
        ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(ifp,
                                                      IN6_IFF_NOTREADY|
                                                      IN6_IFF_ANYCAST);
        if (ifa == NULL) {
                struct in6_ifaddr *ia6;
                ifnet_lock_shared(ifp);
                IFP_TO_IA6(ifp, ia6);
                ifnet_lock_done(ifp);
                if (ia6 != NULL)
                        ifa = &ia6->ia_ifa;
                /* should we care about ia6_flags? */
        }
        NDPR_LOCK(pr);
        if (ifa == NULL) {
                /*
                 * This can still happen, when, for example, we receive an RA
                 * containing a prefix with the L bit set and the A bit clear,
                 * after removing all IPv6 addresses on the receiving
                 * interface.  This should, of course, be rare though.
                 */
                nd6log((LOG_NOTICE,
                    "nd6_prefix_onlink: failed to find any ifaddr"
                    " to add route for a prefix(%s/%d) on %s\n",
                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(ifp)));
                NDPR_UNLOCK(pr);
                return (0);
        }

        /*
         * in6_ifinit() sets nd6_rtrequest to ifa_rtrequest for all ifaddrs.
         * ifa->ifa_rtrequest = nd6_rtrequest;
         */
        bzero(&mask6, sizeof(mask6));
        mask6.sin6_len = sizeof(mask6);
        mask6.sin6_addr = pr->ndpr_mask;
        prefix = pr->ndpr_prefix;
        NDPR_UNLOCK(pr);

        IFA_LOCK_SPIN(ifa);
        rtflags = ifa->ifa_flags | RTF_CLONING | RTF_UP;
        IFA_UNLOCK(ifa);
        if (nd6_need_cache(ifp)) {
                /* explicitly set in case ifa_flags does not set the flag. */
                rtflags |= RTF_CLONING;
        } else {
                /*
                 * explicitly clear the cloning bit in case ifa_flags sets it.
                 */
                rtflags &= ~RTF_CLONING;
        }

        lck_mtx_unlock(nd6_mutex);

        error = rtrequest_scoped(RTM_ADD, (struct sockaddr *)&prefix,
            ifa->ifa_addr, (struct sockaddr *)&mask6, rtflags, &rt,
            ifscope);

        if (rt != NULL) {
                RT_LOCK(rt);
                nd6_rtmsg(RTM_ADD, rt);
                RT_UNLOCK(rt);
                RT_REMREF(rt);
        } else {
                NDPR_LOCK(pr);
                nd6log((LOG_ERR, "nd6_prefix_onlink: failed to add route for a"
                    " prefix (%s/%d) on %s, gw=%s, mask=%s, flags=%lx,"
                    " scoped=%d, errno = %d\n",
                    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(ifp),
                    ip6_sprintf(&((struct sockaddr_in6 *)ifa->ifa_addr)->sin6_addr),
                    ip6_sprintf(&mask6.sin6_addr), rtflags,
                    (ifscope != IFSCOPE_NONE), error));
                NDPR_UNLOCK(pr);
        }

        lck_mtx_lock(nd6_mutex);

        NDPR_LOCK(pr);
        pr->ndpr_stateflags &= ~NDPRF_IFSCOPE;
        if (rt != NULL || error == EEXIST) {
                pr->ndpr_stateflags |= NDPRF_ONLINK;
                if (ifscope != IFSCOPE_NONE)
                        pr->ndpr_stateflags |= NDPRF_IFSCOPE;
        }
        NDPR_UNLOCK(pr);

        IFA_REMREF(ifa);

        return (error);
}

int
nd6_prefix_onlink(struct nd_prefix *pr)
{
        return (nd6_prefix_onlink_common(pr, FALSE, IFSCOPE_NONE));
}

int
nd6_prefix_onlink_scoped(struct nd_prefix *pr, unsigned int ifscope)
{
        return (nd6_prefix_onlink_common(pr, TRUE, ifscope));
}

int
nd6_prefix_offlink(struct nd_prefix *pr)
{
        int plen, error = 0;
        struct ifnet *ifp = pr->ndpr_ifp;
        struct nd_prefix *opr;
        struct sockaddr_in6 sa6, mask6, prefix;
        struct rtentry *rt = NULL;
        unsigned int ifscope;

        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        /* sanity check */
        NDPR_LOCK(pr);
        if ((pr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
                nd6log((LOG_ERR,
                    "nd6_prefix_offlink: %s/%d on %s scoped=%d is already "
                    "off-link\n", ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp),
                    (pr->ndpr_stateflags & NDPRF_IFSCOPE) ? 1 : 0));
                NDPR_UNLOCK(pr);
                return (EEXIST);
        }

        bzero(&sa6, sizeof(sa6));
        sa6.sin6_family = AF_INET6;
        sa6.sin6_len = sizeof(sa6);
        bcopy(&pr->ndpr_prefix.sin6_addr, &sa6.sin6_addr,
              sizeof(struct in6_addr));
        bzero(&mask6, sizeof(mask6));
        mask6.sin6_family = AF_INET6;
        mask6.sin6_len = sizeof(sa6);
        bcopy(&pr->ndpr_mask, &mask6.sin6_addr, sizeof(struct in6_addr));
        prefix = pr->ndpr_prefix;
        plen = pr->ndpr_plen;
        NDPR_UNLOCK(pr);

        ifscope = (pr->ndpr_stateflags & NDPRF_IFSCOPE) ?
            ifp->if_index : IFSCOPE_NONE;

        error = rtrequest_scoped(RTM_DELETE, (struct sockaddr *)&sa6,
            NULL, (struct sockaddr *)&mask6, 0, &rt, ifscope);

        if (rt != NULL) {
                /* report the route deletion to the routing socket. */
                RT_LOCK(rt);
                nd6_rtmsg(RTM_DELETE, rt);
                RT_UNLOCK(rt);
                rtfree(rt);

                /*
                 * The following check takes place only when Scoped Routing
                 * is not enabled.  There might be the same prefix on another
                 * interface, the prefix which could not be on-link just
                 * because we have the interface route (see comments in
                 * nd6_prefix_onlink).  If there's one, try to make the prefix
                 * on-link on the interface.
                 */
                lck_mtx_lock(nd6_mutex);
                opr = nd_prefix.lh_first;
                while (opr) {
                        /* does not apply in the Scoped Routing case */
                        if (ip6_doscopedroute)
                                break;

                        if (opr == pr) {
                                opr = opr->ndpr_next;
                                continue;
                        }

                        NDPR_LOCK(opr);
                        if ((opr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                                NDPR_UNLOCK(opr);
                                opr = opr->ndpr_next;
                                continue;
                        }
                        /*
                         * KAME specific: detached prefixes should not be
                         * on-link.
                         */
                        if ((opr->ndpr_stateflags & NDPRF_DETACHED) != 0) {
                                NDPR_UNLOCK(opr);
                                opr = opr->ndpr_next;
                                continue;
                        }
                        if (opr->ndpr_plen == plen &&
                            in6_are_prefix_equal(&prefix.sin6_addr,
                            &opr->ndpr_prefix.sin6_addr, plen)) {
                                int e;

                                NDPR_UNLOCK(opr);
                                lck_mtx_unlock(nd6_mutex);
                                if ((e = nd6_prefix_onlink(opr)) != 0) {
                                        nd6log((LOG_ERR,
                                            "nd6_prefix_offlink: failed to "
                                            "recover a prefix %s/%d from %s "
                                            "to %s (errno = %d)\n",
                                            ip6_sprintf(&opr->ndpr_prefix.sin6_addr),
                                            opr->ndpr_plen, if_name(ifp),
                                            if_name(opr->ndpr_ifp), e));
                                }
                                lck_mtx_lock(nd6_mutex);
                                opr = nd_prefix.lh_first;
                        } else {
                                NDPR_UNLOCK(opr);
                                opr = opr->ndpr_next;
                        }
                }
                lck_mtx_unlock(nd6_mutex);
        } else {
                nd6log((LOG_ERR,
                    "nd6_prefix_offlink: failed to delete route: "
                    "%s/%d on %s, scoped %d, (errno = %d)\n",
                    ip6_sprintf(&sa6.sin6_addr), plen, if_name(ifp),
                    (ifscope != IFSCOPE_NONE), error));
        }

        NDPR_LOCK(pr);
        pr->ndpr_stateflags &= ~(NDPRF_ONLINK | NDPRF_IFSCOPE);
        NDPR_UNLOCK(pr);

        return (error);
}

static struct in6_ifaddr *
in6_ifadd(
        struct nd_prefix *pr,
        int mcast)
{
        struct ifnet *ifp = pr->ndpr_ifp;
        struct in6_aliasreq ifra;
        struct in6_ifaddr *ia, *ib;
        int error, plen0;
        int updateflags;
        struct in6_addr mask;
        int prefixlen;

        /*
         * find a link-local address (will be interface ID).
         * Is it really mandatory? Theoretically, a global or a site-local
         * address can be configured without a link-local address, if we
         * have a unique interface identifier...
         *
         * it is not mandatory to have a link-local address, we can generate
         * interface identifier on the fly.  we do this because:
         * (1) it should be the easiest way to find interface identifier.
         * (2) RFC2462 5.4 suggesting the use of the same interface identifier
         * for multiple addresses on a single interface, and possible shortcut
         * of DAD.  we omitted DAD for this reason in the past.
         * (3) a user can prevent autoconfiguration of global address
         * by removing link-local address by hand (this is partly because we
         * don't have other way to control the use of IPv6 on an interface.
         * this has been our design choice - cf. NRL's "ifconfig auto").
         * (4) it is easier to manage when an interface has addresses
         * with the same interface identifier, than to have multiple addresses
         * with different interface identifiers.
         */
        ib = in6ifa_ifpforlinklocal(ifp, 0);/* 0 is OK? */
        if (ib == NULL)
                return (NULL);

        IFA_LOCK(&ib->ia_ifa);
        NDPR_LOCK(pr);
        prefixlen = pr->ndpr_plen;
        in6_len2mask(&mask, prefixlen);
        plen0 = in6_mask2len(&ib->ia_prefixmask.sin6_addr, NULL);
        /* prefixlen + ifidlen must be equal to 128 */
        if (prefixlen != plen0) {
                nd6log((LOG_INFO, "in6_ifadd: wrong prefixlen for %s "
                    "(prefix=%d ifid=%d)\n",
                    if_name(ifp), prefixlen, 128 - plen0));
                NDPR_UNLOCK(pr);
                IFA_UNLOCK(&ib->ia_ifa);
                IFA_REMREF(&ib->ia_ifa);
                return (NULL);
        }

        /* make ifaddr */

        bzero(&ifra, sizeof(ifra));
        /*
         * in6_update_ifa() does not use ifra_name, but we accurately set it
         * for safety.
         */
        strncpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
        ifra.ifra_addr.sin6_family = AF_INET6;
        ifra.ifra_addr.sin6_len = sizeof(struct sockaddr_in6);
        /* prefix */
        bcopy(&pr->ndpr_prefix.sin6_addr, &ifra.ifra_addr.sin6_addr,
              sizeof(ifra.ifra_addr.sin6_addr));
        ifra.ifra_addr.sin6_addr.s6_addr32[0] &= mask.s6_addr32[0];
        ifra.ifra_addr.sin6_addr.s6_addr32[1] &= mask.s6_addr32[1];
        ifra.ifra_addr.sin6_addr.s6_addr32[2] &= mask.s6_addr32[2];
        ifra.ifra_addr.sin6_addr.s6_addr32[3] &= mask.s6_addr32[3];

        /* interface ID */
        ifra.ifra_addr.sin6_addr.s6_addr32[0] |=
            (ib->ia_addr.sin6_addr.s6_addr32[0] & ~mask.s6_addr32[0]);
        ifra.ifra_addr.sin6_addr.s6_addr32[1] |=
            (ib->ia_addr.sin6_addr.s6_addr32[1] & ~mask.s6_addr32[1]);
        ifra.ifra_addr.sin6_addr.s6_addr32[2] |=
            (ib->ia_addr.sin6_addr.s6_addr32[2] & ~mask.s6_addr32[2]);
        ifra.ifra_addr.sin6_addr.s6_addr32[3] |=
            (ib->ia_addr.sin6_addr.s6_addr32[3] & ~mask.s6_addr32[3]);

        /* new prefix mask. */
        ifra.ifra_prefixmask.sin6_len = sizeof(struct sockaddr_in6);
        ifra.ifra_prefixmask.sin6_family = AF_INET6;
        bcopy(&mask, &ifra.ifra_prefixmask.sin6_addr,
              sizeof(ifra.ifra_prefixmask.sin6_addr));

        /* lifetimes. */
        ifra.ifra_lifetime.ia6t_vltime = pr->ndpr_vltime;
        ifra.ifra_lifetime.ia6t_pltime = pr->ndpr_pltime;

        /* XXX: scope zone ID? */

        ifra.ifra_flags |= IN6_IFF_AUTOCONF; /* obey autoconf */

        NDPR_UNLOCK(pr);
        IFA_UNLOCK(&ib->ia_ifa);
        IFA_REMREF(&ib->ia_ifa);

        /*
         * Make sure that we do not have this address already.  This should
         * usually not happen, but we can still see this case, e.g., if we
         * have manually configured the exact address to be configured.
         */
        if ((ib = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr)) != NULL) {
                IFA_REMREF(&ib->ia_ifa);
                /* this should be rare enough to make an explicit log */
                log(LOG_INFO, "in6_ifadd: %s is already configured\n",
                    ip6_sprintf(&ifra.ifra_addr.sin6_addr));
                return (NULL);
        }

        /*
         * Allocate ifaddr structure, link into chain, etc.
         * If we are going to create a new address upon receiving a multicasted
         * RA, we need to impose a random delay before starting DAD.
         * [draft-ietf-ipv6-rfc2462bis-02.txt, Section 5.4.2]
         */
        updateflags = 0;
        if (mcast)
                updateflags |= IN6_IFAUPDATE_DADDELAY;
        error = in6_update_ifa(ifp, &ifra, NULL, updateflags, M_WAITOK);
        if (error != 0) {
                nd6log((LOG_ERR,
                    "in6_ifadd: failed to make ifaddr %s on %s (errno=%d)\n",
                    ip6_sprintf(&ifra.ifra_addr.sin6_addr), if_name(ifp),
                    error));
                return(NULL);   /* ifaddr must not have been allocated. */
        }

        ia = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr);

        in6_post_msg(ifp, KEV_INET6_NEW_RTADV_ADDR, ia); 

        return(ia);             /* this must NOT be NULL. */
}

#define IA6_NONCONST(i) ((struct in6_ifaddr *)(uintptr_t)(i))

int
in6_tmpifadd(
        const struct in6_ifaddr *ia0, /* corresponding public address */
        int forcegen,
        int how)
{
        struct ifnet *ifp = ia0->ia_ifa.ifa_ifp;
        struct in6_ifaddr *ia, *newia;
        struct in6_aliasreq ifra;
        int i, error;
        int trylimit = 3;       /* XXX: adhoc value */
        int updateflags;
        u_int32_t randid[2];
        time_t vltime0, pltime0;
        struct timeval timenow;
        struct in6_addr addr;
        struct nd_prefix *ndpr;

        getmicrotime(&timenow);

        bzero(&ifra, sizeof(ifra));
        strncpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
        IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
        ifra.ifra_addr = ia0->ia_addr;
        /* copy prefix mask */
        ifra.ifra_prefixmask = ia0->ia_prefixmask;
        /* clear the old IFID */
        for (i = 0; i < 4; i++) {
                ifra.ifra_addr.sin6_addr.s6_addr32[i]
                        &= ifra.ifra_prefixmask.sin6_addr.s6_addr32[i];
        }
        addr = ia0->ia_addr.sin6_addr;
        IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);

again:
        in6_get_tmpifid(ifp, (u_int8_t *)randid,
            (const u_int8_t *)&addr.s6_addr[8], forcegen);

        ifra.ifra_addr.sin6_addr.s6_addr32[2] |=
            (randid[0] & ~(ifra.ifra_prefixmask.sin6_addr.s6_addr32[2]));
        ifra.ifra_addr.sin6_addr.s6_addr32[3] |=
            (randid[1] & ~(ifra.ifra_prefixmask.sin6_addr.s6_addr32[3]));

        /*
         * in6_get_tmpifid() quite likely provided a unique interface ID.
         * However, we may still have a chance to see collision, because
         * there may be a time lag between generation of the ID and generation
         * of the address.  So, we'll do one more sanity check.
         */
        if ((ia = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr)) != NULL) {
                IFA_REMREF(&ia->ia_ifa);
                if (trylimit-- == 0) {
                        nd6log((LOG_NOTICE, "in6_tmpifadd: failed to find "
                            "a unique random IFID\n"));
                        return(EEXIST);
                }
                forcegen = 1;
                goto again;
        }

        /*
         * The Valid Lifetime is the lower of the Valid Lifetime of the
         * public address or TEMP_VALID_LIFETIME.
         * The Preferred Lifetime is the lower of the Preferred Lifetime
         * of the public address or TEMP_PREFERRED_LIFETIME -
         * DESYNC_FACTOR.
         */
        IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
        vltime0 = IFA6_IS_INVALID(ia0)
            ? 0
            : (ia0->ia6_lifetime.ia6t_vltime -
              (timenow.tv_sec - ia0->ia6_updatetime));
        if (vltime0 > ip6_temp_valid_lifetime)
                vltime0 = ip6_temp_valid_lifetime;
        pltime0 = IFA6_IS_DEPRECATED(ia0)
            ? 0
            : (ia0->ia6_lifetime.ia6t_pltime -
              (timenow.tv_sec - ia0->ia6_updatetime));
        if (pltime0 > ip6_temp_preferred_lifetime - ip6_desync_factor)
                pltime0 = ip6_temp_preferred_lifetime - ip6_desync_factor;
        ifra.ifra_lifetime.ia6t_vltime = vltime0;
        ifra.ifra_lifetime.ia6t_pltime = pltime0;
        IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
        /*
         * A temporary address is created only if this calculated Preferred
         * Lifetime is greater than REGEN_ADVANCE time units.
         */
        if (ifra.ifra_lifetime.ia6t_pltime <= ip6_temp_regen_advance)
                return(0);

        /* XXX: scope zone ID? */

        ifra.ifra_flags |= (IN6_IFF_AUTOCONF|IN6_IFF_TEMPORARY);

        /* allocate ifaddr structure, link into chain, etc. */
        updateflags = 0;

        if (how)
                updateflags |= IN6_IFAUPDATE_DADDELAY;

        if ((error = in6_update_ifa(ifp, &ifra, NULL, updateflags, how)) != 0)
                return (error);

        newia = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr);
        if (newia == NULL) {    /* XXX: can it happen? */
                nd6log((LOG_ERR,
                    "in6_tmpifadd: ifa update succeeded, but we got "
                    "no ifaddr\n"));
                return(EINVAL); /* XXX */
        }
        IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
        ndpr = ia0->ia6_ndpr;
        if (ndpr == NULL) {
                /*
                 * We lost the race with another thread that has purged
                 * ia0 address; in this case, purge the tmp addr as well.
                 */
                nd6log((LOG_ERR, "in6_tmpifadd: no public address\n"));
                VERIFY(!(ia0->ia6_flags & IN6_IFF_AUTOCONF));
                IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
                in6_purgeaddr(&newia->ia_ifa);
                IFA_REMREF(&newia->ia_ifa);
                return (EADDRNOTAVAIL);
        }
        NDPR_ADDREF(ndpr);      /* for us */
        IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
        IFA_LOCK(&newia->ia_ifa);
        if (newia->ia6_ndpr != NULL) {
                NDPR_LOCK(newia->ia6_ndpr);
                VERIFY(newia->ia6_ndpr->ndpr_addrcnt != 0);
                newia->ia6_ndpr->ndpr_addrcnt--;
                NDPR_UNLOCK(newia->ia6_ndpr);
                NDPR_REMREF(newia->ia6_ndpr);   /* release addr reference */
        }
        newia->ia6_ndpr = ndpr;
        NDPR_LOCK(newia->ia6_ndpr);
        newia->ia6_ndpr->ndpr_addrcnt++;
        VERIFY(newia->ia6_ndpr->ndpr_addrcnt != 0);
        NDPR_ADDREF_LOCKED(newia->ia6_ndpr);    /* for addr reference */
        NDPR_UNLOCK(newia->ia6_ndpr);
        IFA_UNLOCK(&newia->ia_ifa);
        /*
         * A newly added address might affect the status of other addresses.
         * XXX: when the temporary address is generated with a new public
         * address, the onlink check is redundant.  However, it would be safe
         * to do the check explicitly everywhere a new address is generated,
         * and, in fact, we surely need the check when we create a new
         * temporary address due to deprecation of an old temporary address.
         */
        lck_mtx_lock(nd6_mutex);
        pfxlist_onlink_check();
        lck_mtx_unlock(nd6_mutex);
        IFA_REMREF(&newia->ia_ifa);

        /* remove our reference */
        NDPR_REMREF(ndpr);

        return(0);
}
#undef IA6_NONCONST

int
in6_init_prefix_ltimes(struct nd_prefix *ndpr)
{
        struct timeval timenow;

        NDPR_LOCK_ASSERT_HELD(ndpr);

        getmicrotime(&timenow);
        /* check if preferred lifetime > valid lifetime.  RFC2462 5.5.3 (c) */
        if (ndpr->ndpr_pltime > ndpr->ndpr_vltime) {
                nd6log((LOG_INFO, "in6_init_prefix_ltimes: preferred lifetime"
                    "(%d) is greater than valid lifetime(%d)\n",
                    (u_int)ndpr->ndpr_pltime, (u_int)ndpr->ndpr_vltime));
                return (EINVAL);
        }
        if (ndpr->ndpr_pltime == ND6_INFINITE_LIFETIME)
                ndpr->ndpr_preferred = 0;
        else
                ndpr->ndpr_preferred = timenow.tv_sec + ndpr->ndpr_pltime;
        if (ndpr->ndpr_vltime == ND6_INFINITE_LIFETIME)
                ndpr->ndpr_expire = 0;
        else
                ndpr->ndpr_expire = timenow.tv_sec + ndpr->ndpr_vltime;

        return 0;
}

static void
in6_init_address_ltimes(__unused struct nd_prefix *new,
    struct in6_addrlifetime *lt6, boolean_t is_temporary)
{
        struct timeval timenow;

        getmicrotime(&timenow);
        /* Valid lifetime must not be updated unless explicitly specified. */
        /* init ia6t_expire */
        if (!is_temporary && lt6->ia6t_vltime == ND6_INFINITE_LIFETIME)
                lt6->ia6t_expire = 0;
        else {
                lt6->ia6t_expire = timenow.tv_sec;
                lt6->ia6t_expire += lt6->ia6t_vltime;
        }

        /* init ia6t_preferred */
        if (!is_temporary && lt6->ia6t_pltime == ND6_INFINITE_LIFETIME)
                lt6->ia6t_preferred = 0;
        else {
                lt6->ia6t_preferred = timenow.tv_sec;
                lt6->ia6t_preferred += lt6->ia6t_pltime;
        }
}

/*
 * Delete all the routing table entries that use the specified gateway.
 * XXX: this function causes search through all entries of routing table, so
 * it shouldn't be called when acting as a router.
 */
void
rt6_flush(
        struct in6_addr *gateway,
        struct ifnet *ifp)
{
        struct radix_node_head *rnh = rt_tables[AF_INET6];

        /* We'll care only link-local addresses */
        if (!IN6_IS_ADDR_LINKLOCAL(gateway)) {
                return;
        }
        lck_mtx_lock(rnh_lock);
        /* XXX: hack for KAME's link-local address kludge */
        gateway->s6_addr16[1] = htons(ifp->if_index);

        rnh->rnh_walktree(rnh, rt6_deleteroute, (void *)gateway);
        lck_mtx_unlock(rnh_lock);
}

static int
rt6_deleteroute(
        struct radix_node *rn,
        void *arg)
{
#define SIN6(s) ((struct sockaddr_in6 *)s)
        struct rtentry *rt = (struct rtentry *)rn;
        struct in6_addr *gate = (struct in6_addr *)arg;

        lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);

        RT_LOCK(rt);
        if (rt->rt_gateway == NULL || rt->rt_gateway->sa_family != AF_INET6) {
                RT_UNLOCK(rt);
                return(0);
        }

        if (!IN6_ARE_ADDR_EQUAL(gate, &SIN6(rt->rt_gateway)->sin6_addr)) {
                RT_UNLOCK(rt);
                return(0);
        }
        /*
         * Do not delete a static route.
         * XXX: this seems to be a bit ad-hoc. Should we consider the
         * 'cloned' bit instead?
         */
        if ((rt->rt_flags & RTF_STATIC) != 0) {
                RT_UNLOCK(rt);
                return(0);
        }
        /*
         * We delete only host route. This means, in particular, we don't
         * delete default route.
         */
        if ((rt->rt_flags & RTF_HOST) == 0) {
                RT_UNLOCK(rt);
                return(0);
        }

        /*
         * Safe to drop rt_lock and use rt_key, rt_gateway, since holding
         * rnh_lock here prevents another thread from calling rt_setgate()
         * on this route.
         */
        RT_UNLOCK(rt);
        return (rtrequest_locked(RTM_DELETE, rt_key(rt), rt->rt_gateway,
            rt_mask(rt), rt->rt_flags, 0));
#undef SIN6
}

int
nd6_setdefaultiface(
        int ifindex)
{
        int error = 0;
        ifnet_t def_ifp = NULL;
        
        lck_mtx_assert(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

        ifnet_head_lock_shared();
        if (ifindex < 0 || if_index < ifindex) {
                ifnet_head_done();
                return(EINVAL);
        }
        def_ifp = ifindex2ifnet[ifindex];
        ifnet_head_done();

        lck_mtx_lock(nd6_mutex);
        if (nd6_defifindex != ifindex) {
                struct ifnet *odef_ifp = nd6_defifp;

                nd6_defifindex = ifindex;
                if (nd6_defifindex > 0)
                        nd6_defifp = def_ifp;
                else
                        nd6_defifp = NULL;

                if (nd6_defifp != NULL)
                        nd6log((LOG_INFO, "%s: is now the default "
                            "interface (was %s)\n", if_name(nd6_defifp),
                            odef_ifp != NULL ? if_name(odef_ifp) : "NONE"));
                else
                        nd6log((LOG_INFO, "No default interface set\n"));

                /*
                 * If the Default Router List is empty, install a route
                 * to the specified interface as default or remove the default
                 * route when the default interface becomes canceled.
                 * The check for the queue is actually redundant, but
                 * we do this here to avoid re-install the default route
                 * if the list is NOT empty.
                 */
                if (ip6_doscopedroute || TAILQ_FIRST(&nd_defrouter) == NULL) {
                        defrtrlist_sync(nd6_defifp);
                        nd6_prefix_sync(nd6_defifp);
                }

                /*
                 * Our current implementation assumes one-to-one maping between
                 * interfaces and links, so it would be natural to use the
                 * default interface as the default link.
                 */
                scope6_setdefault(nd6_defifp);
        }
        lck_mtx_unlock(nd6_mutex);

        return(error);
}