MFC r295583, r295584, r295729, r295730:

[FreeBSD/FreeBSD.git] / sys / netinet6 / nd6_rtr.c

/*-
 * 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.
 *
 *      $KAME: nd6_rtr.c,v 1.111 2001/04/27 01:37:15 jinmei Exp $
 */

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

#include "opt_inet.h"
#include "opt_inet6.h"

#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/lock.h>
#include <sys/errno.h>
#include <sys/rwlock.h>
#include <sys/syslog.h>
#include <sys/queue.h>

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

#include <netinet/in.h>
#include <net/if_llatbl.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>

static int rtpref(struct nd_defrouter *);
static struct nd_defrouter *defrtrlist_update(struct nd_defrouter *);
static int prelist_update(struct nd_prefixctl *, struct nd_defrouter *,
    struct mbuf *, int);
static struct in6_ifaddr *in6_ifadd(struct nd_prefixctl *, 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 defrouter_delreq(struct nd_defrouter *);
static void nd6_rtmsg(int, struct rtentry *);

static int in6_init_prefix_ltimes(struct nd_prefix *);
static void in6_init_address_ltimes(struct nd_prefix *,
        struct in6_addrlifetime *);

static int nd6_prefix_onlink(struct nd_prefix *);
static int nd6_prefix_offlink(struct nd_prefix *);

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

VNET_DECLARE(int, nd6_recalc_reachtm_interval);
#define V_nd6_recalc_reachtm_interval   VNET(nd6_recalc_reachtm_interval)

static VNET_DEFINE(struct ifnet *, nd6_defifp);
VNET_DEFINE(int, nd6_defifindex);
#define V_nd6_defifp                    VNET(nd6_defifp)

VNET_DEFINE(int, ip6_use_tempaddr) = 0;

VNET_DEFINE(int, ip6_desync_factor);
VNET_DEFINE(u_int32_t, ip6_temp_preferred_lifetime) = DEF_TEMP_PREFERRED_LIFETIME;
VNET_DEFINE(u_int32_t, ip6_temp_valid_lifetime) = DEF_TEMP_VALID_LIFETIME;

VNET_DEFINE(int, ip6_temp_regen_advance) = TEMPADDR_REGEN_ADVANCE;

/* 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 */

/*
 * 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;
        char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];

        /*
         * Accept RS only when V_ip6_forwarding=1 and the interface has
         * no ND6_IFF_ACCEPT_RTADV.
         */
        if (!V_ip6_forwarding || ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV)
                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(ip6bufs, &ip6->ip6_src),
                    ip6_sprintf(ip6bufd, &ip6->ip6_dst), if_name(ifp)));
                goto bad;
        }

        /*
         * Don't update the neighbor cache, if src = ::.
         * This indicates that the src has no IP address assigned yet.
         */
        if (IN6_IS_ADDR_UNSPECIFIED(&saddr6))
                goto freeit;

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len,);
        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_INC(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(ip6bufs, &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_INC(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 = ND_IFINFO(ifp);
        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;
        char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];

        /*
         * We only accept RAs only when the per-interface flag
         * ND6_IFF_ACCEPT_RTADV is on the receiving interface.
         */
        if (!(ndi->flags & ND6_IFF_ACCEPT_RTADV))
                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(ip6bufs, &ip6->ip6_src),
                    ip6_sprintf(ip6bufd, &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(ip6bufs, &saddr6)));
                goto bad;
        }

#ifndef PULLDOWN_TEST
        IP6_EXTHDR_CHECK(m, off, icmp6len,);
        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_INC(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;

        bzero(&dr0, sizeof(dr0));
        dr0.rtaddr = saddr6;
        dr0.raflags = nd_ra->nd_ra_flags_reserved;
        /*
         * Effectively-disable routes from RA messages when
         * ND6_IFF_NO_RADR enabled on the receiving interface or
         * (ip6.forwarding == 1 && ip6.rfc6204w3 != 1).
         */
        if (ndi->flags & ND6_IFF_NO_RADR)
                dr0.rtlifetime = 0;
        else if (V_ip6_forwarding && !V_ip6_rfc6204w3)
                dr0.rtlifetime = 0;
        else
                dr0.rtlifetime = ntohs(nd_ra->nd_ra_router_lifetime);
        dr0.expire = time_uptime + 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 = V_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) {
                if (ndi->chlim < nd_ra->nd_ra_curhoplimit)
                        ndi->chlim = nd_ra->nd_ra_curhoplimit;
                else if (ndi->chlim != nd_ra->nd_ra_curhoplimit) {
                        log(LOG_ERR, "RA with a lower CurHopLimit sent from "
                            "%s on %s (current = %d, received = %d). "
                            "Ignored.\n", ip6_sprintf(ip6bufs, &ip6->ip6_src),
                            if_name(ifp), ndi->chlim, nd_ra->nd_ra_curhoplimit);
                }
        }
        dr = defrtrlist_update(&dr0);
    }

        /*
         * prefix
         */
        if (ndopts.nd_opts_pi) {
                struct nd_opt_hdr *pt;
                struct nd_opt_prefix_info *pi = NULL;
                struct nd_prefixctl 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(ip6bufs,
                                        &pi->nd_opt_pi_prefix)));
                                continue;
                        }

                        bzero(&pr, sizeof(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 = (struct ifnet *)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);
                        (void)prelist_update(&pr, dr, m, mcast);
                }
        }

        /*
         * MTU
         */
        if (ndopts.nd_opts_mtu && ndopts.nd_opts_mtu->nd_opt_mtu_len == 1) {
                u_long mtu;
                u_long maxmtu;

                mtu = (u_long)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=%lu sent from %s, ignoring\n",
                            mtu, ip6_sprintf(ip6bufs, &ip6->ip6_src)));
                        goto skip;
                }

                /* upper bound */
                maxmtu = (ndi->maxmtu && ndi->maxmtu < ifp->if_mtu)
                    ? ndi->maxmtu : ifp->if_mtu;
                if (mtu <= maxmtu) {
                        int change = (ndi->linkmtu != mtu);

                        ndi->linkmtu = mtu;
                        if (change) /* in6_maxmtu may change */
                                in6_setmaxmtu();
                } else {
                        nd6log((LOG_INFO, "nd6_ra_input: bogus mtu "
                            "mtu=%lu sent from %s; "
                            "exceeds maxmtu %lu, ignoring\n",
                            mtu, ip6_sprintf(ip6bufs, &ip6->ip6_src), maxmtu));
                }
        }

 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(ip6bufs, &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.
         */
        pfxlist_onlink_check();
    }

 freeit:
        m_freem(m);
        return;

 bad:
        ICMP6STAT_INC(icp6s_badra);
        m_freem(m);
}

/*
 * default router list proccessing sub routines
 */

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

        bzero((caddr_t)&info, sizeof(info));
        info.rti_info[RTAX_DST] = rt_key(rt);
        info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
        info.rti_info[RTAX_NETMASK] = rt_mask(rt);
        ifp = rt->rt_ifp;
        if (ifp != NULL) {
                IF_ADDR_RLOCK(ifp);
                ifa = TAILQ_FIRST(&ifp->if_addrhead);
                info.rti_info[RTAX_IFP] = ifa->ifa_addr;
                ifa_ref(ifa);
                IF_ADDR_RUNLOCK(ifp);
                info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;
        } else
                ifa = NULL;

        rt_missmsg_fib(cmd, &info, rt->rt_flags, 0, rt->rt_fibnum);
        if (ifa != NULL)
                ifa_free(ifa);
}

static void
defrouter_addreq(struct nd_defrouter *new)
{
        struct sockaddr_in6 def, mask, gate;
        struct rtentry *newrt = NULL;
        int error;

        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 = gate.sin6_family = AF_INET6;
        gate.sin6_addr = new->rtaddr;

        error = in6_rtrequest(RTM_ADD, (struct sockaddr *)&def,
            (struct sockaddr *)&gate, (struct sockaddr *)&mask,
            RTF_GATEWAY, &newrt, RT_DEFAULT_FIB);
        if (newrt) {
                nd6_rtmsg(RTM_ADD, newrt); /* tell user process */
                RTFREE(newrt);
        }
        if (error == 0)
                new->installed = 1;
}

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

        TAILQ_FOREACH(dr, &V_nd_defrouter, dr_entry) {
                if (dr->ifp == ifp && IN6_ARE_ADDR_EQUAL(addr, &dr->rtaddr))
                        return (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.
 */
static void
defrouter_delreq(struct nd_defrouter *dr)
{
        struct sockaddr_in6 def, mask, gate;
        struct rtentry *oldrt = NULL;

        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 = gate.sin6_family = AF_INET6;
        gate.sin6_addr = dr->rtaddr;

        in6_rtrequest(RTM_DELETE, (struct sockaddr *)&def,
            (struct sockaddr *)&gate,
            (struct sockaddr *)&mask, RTF_GATEWAY, &oldrt, RT_DEFAULT_FIB);
        if (oldrt) {
                nd6_rtmsg(RTM_DELETE, oldrt);
                RTFREE(oldrt);
        }

        dr->installed = 0;
}

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

        TAILQ_FOREACH(dr, &V_nd_defrouter, dr_entry)
                defrouter_delreq(dr);

        /*
         * XXX should we also nuke any default routers in the kernel, by
         * going through them by rtalloc1()?
         */
}

void
defrtrlist_del(struct nd_defrouter *dr)
{
        struct nd_defrouter *deldr = NULL;
        struct nd_prefix *pr;

        /*
         * Flush all the routing table entries that use the router
         * as a next hop.
         */
        if (ND_IFINFO(dr->ifp)->flags & ND6_IFF_ACCEPT_RTADV)
                rt6_flush(&dr->rtaddr, dr->ifp);

        if (dr->installed) {
                deldr = dr;
                defrouter_delreq(dr);
        }
        TAILQ_REMOVE(&V_nd_defrouter, dr, dr_entry);

        /*
         * Also delete all the pointers to the router in each prefix lists.
         */
        LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                struct nd_pfxrouter *pfxrtr;
                if ((pfxrtr = pfxrtr_lookup(pr, dr)) != NULL)
                        pfxrtr_del(pfxrtr);
        }
        pfxlist_onlink_check();

        /*
         * If the router is the primary one, choose a new one.
         * Note that defrouter_select() will remove the current gateway
         * from the routing table.
         */
        if (deldr)
                defrouter_select();

        free(dr, M_IP6NDP);
}

/*
 * 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.
 *
 * 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.
 *
 * At this moment, we do not try to install more than one default router,
 * even when the multipath routing is available, because we're not sure about
 * the benefits for stub hosts comparing to the risk of making the code
 * complicated and the possibility of introducing bugs.
 */
void
defrouter_select(void)
{
        struct nd_defrouter *dr, *selected_dr = NULL, *installed_dr = NULL;
        struct llentry *ln = NULL;

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

        /*
         * 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().
         */
        TAILQ_FOREACH(dr, &V_nd_defrouter, dr_entry) {
                IF_AFDATA_RLOCK(dr->ifp);
                if (selected_dr == NULL &&
                    (ln = nd6_lookup(&dr->rtaddr, 0, dr->ifp)) &&
                    ND6_IS_LLINFO_PROBREACH(ln)) {
                        selected_dr = dr;
                }
                IF_AFDATA_RUNLOCK(dr->ifp);
                if (ln != NULL) {
                        LLE_RUNLOCK(ln);
                        ln = NULL;
                }

                if (dr->installed && installed_dr == NULL)
                        installed_dr = dr;
                else if (dr->installed && installed_dr) {
                        /* this should not happen.  warn for diagnosis. */
                        log(LOG_ERR, "defrouter_select: more than one router"
                            " is installed\n");
                }
        }
        /*
         * If none of the default routers was found to be reachable,
         * round-robin the list regardless of preference.
         * 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 (selected_dr == NULL) {
                if (installed_dr == NULL || !TAILQ_NEXT(installed_dr, dr_entry))
                        selected_dr = TAILQ_FIRST(&V_nd_defrouter);
                else
                        selected_dr = TAILQ_NEXT(installed_dr, dr_entry);
        } else if (installed_dr) {
                IF_AFDATA_RLOCK(installed_dr->ifp);
                if ((ln = nd6_lookup(&installed_dr->rtaddr, 0, installed_dr->ifp)) &&
                    ND6_IS_LLINFO_PROBREACH(ln) &&
                    rtpref(selected_dr) <= rtpref(installed_dr)) {
                        selected_dr = installed_dr;
                }
                IF_AFDATA_RUNLOCK(installed_dr->ifp);
                if (ln != NULL)
                        LLE_RUNLOCK(ln);
        }

        /*
         * If the selected router is different than the installed one,
         * remove the installed router and install the selected one.
         * Note that the selected router is never NULL here.
         */
        if (installed_dr != selected_dr) {
                if (installed_dr)
                        defrouter_delreq(installed_dr);
                defrouter_addreq(selected_dr);
        }
}

/*
 * for default router selection
 * regards router-preference field as a 2-bit signed integer
 */
static int
rtpref(struct nd_defrouter *dr)
{
        switch (dr->raflags & 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->raflags);
                return (RTPREF_INVALID);
        }
        /* NOTREACHED */
}

static struct nd_defrouter *
defrtrlist_update(struct nd_defrouter *new)
{
        struct nd_defrouter *dr, *n;
        int oldpref;

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

                oldpref = rtpref(dr);

                /* override */
                dr->raflags = new->raflags; /* 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. Also make sure the selected
                 * router is still installed in the kernel.
                 */
                if (dr->installed && rtpref(new) == oldpref)
                        return (dr);

                /*
                 * The preferred router may have changed, so relocate this
                 * router.
                 */
                TAILQ_REMOVE(&V_nd_defrouter, dr, dr_entry);
                n = dr;
                goto insert;
        }

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

        n = malloc(sizeof(*n), M_IP6NDP, M_NOWAIT | M_ZERO);
        if (n == NULL)
                return (NULL);
        memcpy(n, new, sizeof(*n));

insert:
        /*
         * Insert the new router in the Default Router List;
         * The Default Router List should be in the descending order
         * of router-preferece.  Routers with the same preference are
         * sorted in the arriving time order.
         */

        /* insert at the end of the group */
        TAILQ_FOREACH(dr, &V_nd_defrouter, dr_entry) {
                if (rtpref(n) > rtpref(dr))
                        break;
        }
        if (dr)
                TAILQ_INSERT_BEFORE(dr, n, dr_entry);
        else
                TAILQ_INSERT_TAIL(&V_nd_defrouter, n, dr_entry);

        defrouter_select();

        return (n);
}

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

        LIST_FOREACH(search, &pr->ndpr_advrtrs, pfr_entry) {
                if (search->router == dr)
                        break;
        }

        return (search);
}

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

        new = malloc(sizeof(*new), M_IP6NDP, M_NOWAIT | M_ZERO);
        if (new == NULL)
                return;
        new->router = dr;

        LIST_INSERT_HEAD(&pr->ndpr_advrtrs, new, pfr_entry);

        pfxlist_onlink_check();
}

static void
pfxrtr_del(struct nd_pfxrouter *pfr)
{
        LIST_REMOVE(pfr, pfr_entry);
        free(pfr, M_IP6NDP);
}

struct nd_prefix *
nd6_prefix_lookup(struct nd_prefixctl *key)
{
        struct nd_prefix *search;

        LIST_FOREACH(search, &V_nd_prefix, ndpr_entry) {
                if (key->ndpr_ifp == search->ndpr_ifp &&
                    key->ndpr_plen == search->ndpr_plen &&
                    in6_are_prefix_equal(&key->ndpr_prefix.sin6_addr,
                    &search->ndpr_prefix.sin6_addr, key->ndpr_plen)) {
                        break;
                }
        }

        return (search);
}

int
nd6_prelist_add(struct nd_prefixctl *pr, struct nd_defrouter *dr,
    struct nd_prefix **newp)
{
        struct nd_prefix *new = NULL;
        int error = 0;
        int i;
        char ip6buf[INET6_ADDRSTRLEN];

        new = malloc(sizeof(*new), M_IP6NDP, M_NOWAIT | M_ZERO);
        if (new == NULL)
                return (ENOMEM);
        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 ((error = in6_init_prefix_ltimes(new)) != 0) {
                free(new, M_IP6NDP);
                return(error);
        }
        new->ndpr_lastupdate = time_uptime;
        if (newp != NULL)
                *newp = new;

        /* 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];

        /* link ndpr_entry to nd_prefix list */
        LIST_INSERT_HEAD(&V_nd_prefix, new, ndpr_entry);

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

                if ((e = nd6_prefix_onlink(new)) != 0) {
                        nd6log((LOG_ERR, "nd6_prelist_add: failed to make "
                            "the prefix %s/%d on-link on %s (errno=%d)\n",
                            ip6_sprintf(ip6buf, &pr->ndpr_prefix.sin6_addr),
                            pr->ndpr_plen, if_name(pr->ndpr_ifp), e));
                        /* proceed anyway. XXX: is it correct? */
                }
        }

        if (dr)
                pfxrtr_add(new, dr);

        return 0;
}

void
prelist_remove(struct nd_prefix *pr)
{
        struct nd_pfxrouter *pfr, *next;
        int e;
        char ip6buf[INET6_ADDRSTRLEN];

        /* 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) != 0 &&
            (e = nd6_prefix_offlink(pr)) != 0) {
                nd6log((LOG_ERR, "prelist_remove: failed to make %s/%d offlink "
                    "on %s, errno=%d\n",
                    ip6_sprintf(ip6buf, &pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(pr->ndpr_ifp), e));
                /* what should we do? */
        }

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

        /* unlink ndpr_entry from nd_prefix list */
        LIST_REMOVE(pr, ndpr_entry);

        /* free list of routers that advertised the prefix */
        LIST_FOREACH_SAFE(pfr, &pr->ndpr_advrtrs, pfr_entry, next) {
                pfxrtr_del(pfr);
        }
        free(pr, M_IP6NDP);

        pfxlist_onlink_check();
}

/*
 * dr - may be NULL
 */

static int
prelist_update(struct nd_prefixctl *new, struct nd_defrouter *dr,
    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;
        char ip6buf[INET6_ADDRSTRLEN];

        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));
#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.
                 */
                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;
                        (void)in6_init_prefix_ltimes(pr); /* XXX error case? */
                        pr->ndpr_lastupdate = time_uptime;
                }

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

                        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(ip6buf,
                                            &pr->ndpr_prefix.sin6_addr),
                                    pr->ndpr_plen, if_name(pr->ndpr_ifp), e));
                                /* proceed anyway. XXX: is it correct? */
                        }
                }

                if (dr && pfxrtr_lookup(pr, dr) == NULL)
                        pfxrtr_add(pr, dr);
        } 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;

                error = nd6_prelist_add(new, dr, &newpr);
                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(ip6buf, &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.
                 */
                if (newpr->ndpr_raf_onlink == 0) {
                        newpr->ndpr_vltime = 0;
                        newpr->ndpr_pltime = 0;
                        in6_init_prefix_ltimes(newpr);
                }

                pr = 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 end;

        /*
         * 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".
         */
        IF_ADDR_RLOCK(ifp);
        TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                struct in6_ifaddr *ifa6;
                u_int32_t remaininglifetime;

                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;

                ifa6 = (struct in6_ifaddr *)ifa;

                /*
                 * We only consider autoconfigured addresses as per rfc2462bis.
                 */
                if (!(ifa6->ia6_flags & IN6_IFF_AUTOCONF))
                        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)
                        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)
                        continue;

                if (ia6_match == NULL) /* remember the first one */
                        ia6_match = ifa6;

                /*
                 * 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 (time_uptime - 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 -
                            (time_uptime - 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;

                in6_init_address_ltimes(pr, &lt6_tmp);

                /*
                 * We need to treat lifetimes for temporary addresses
                 * differently, according to
                 * draft-ietf-ipv6-privacy-addrs-v2-01.txt 3.3 (1);
                 * we only update the lifetimes when they are in the maximum
                 * intervals.
                 */
                if ((ifa6->ia6_flags & IN6_IFF_TEMPORARY) != 0) {
                        u_int32_t maxvltime, maxpltime;

                        if (V_ip6_temp_valid_lifetime >
                            (u_int32_t)((time_uptime - ifa6->ia6_createtime) +
                            V_ip6_desync_factor)) {
                                maxvltime = V_ip6_temp_valid_lifetime -
                                    (time_uptime - ifa6->ia6_createtime) -
                                    V_ip6_desync_factor;
                        } else
                                maxvltime = 0;
                        if (V_ip6_temp_preferred_lifetime >
                            (u_int32_t)((time_uptime - ifa6->ia6_createtime) +
                            V_ip6_desync_factor)) {
                                maxpltime = V_ip6_temp_preferred_lifetime -
                                    (time_uptime - ifa6->ia6_createtime) -
                                    V_ip6_desync_factor;
                        } else
                                maxpltime = 0;

                        if (lt6_tmp.ia6t_vltime == ND6_INFINITE_LIFETIME ||
                            lt6_tmp.ia6t_vltime > maxvltime) {
                                lt6_tmp.ia6t_vltime = maxvltime;
                        }
                        if (lt6_tmp.ia6t_pltime == ND6_INFINITE_LIFETIME ||
                            lt6_tmp.ia6t_pltime > maxpltime) {
                                lt6_tmp.ia6t_pltime = maxpltime;
                        }
                }
                ifa6->ia6_lifetime = lt6_tmp;
                ifa6->ia6_updatetime = time_uptime;
        }
        IF_ADDR_RUNLOCK(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;
                }
                if (ifidlen + pr->ndpr_plen != 128) {
                        nd6log((LOG_INFO,
                            "prelist_update: invalid prefixlen "
                            "%d for %s, ignored\n",
                            pr->ndpr_plen, if_name(ifp)));
                        goto end;
                }

                if ((ia6 = in6_ifadd(new, mcast)) != NULL) {
                        /*
                         * note that we should use pr (not new) for reference.
                         */
                        pr->ndpr_refcnt++;
                        ia6->ia6_ndpr = pr;

                        /*
                         * RFC 3041 3.3 (2).
                         * When a new public address is created as described
                         * in RFC2462, also create a new temporary address.
                         *
                         * RFC 3041 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 (V_ip6_use_tempaddr) {
                                int e;
                                if ((e = in6_tmpifadd(ia6, 1, 1)) != 0) {
                                        nd6log((LOG_NOTICE, "prelist_update: "
                                            "failed to create a temporary "
                                            "address, errno=%d\n",
                                            e));
                                }
                        }
                        ifa_free(&ia6->ia_ifa);

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

 end:
        return error;
}

/*
 * 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 llentry *ln;
        int canreach;

        LIST_FOREACH(pfxrtr, &pr->ndpr_advrtrs, pfr_entry) {
                IF_AFDATA_RLOCK(pfxrtr->router->ifp);
                ln = nd6_lookup(&pfxrtr->router->rtaddr, 0, pfxrtr->router->ifp);
                IF_AFDATA_RUNLOCK(pfxrtr->router->ifp);
                if (ln == NULL)
                        continue;
                canreach = ND6_IS_LLINFO_PROBREACH(ln);
                LLE_RUNLOCK(ln);
                if (canreach)
                        break;
        }
        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()
{
        struct nd_prefix *pr;
        struct in6_ifaddr *ifa;
        struct nd_defrouter *dr;
        struct nd_pfxrouter *pfxrtr = NULL;

        /*
         * Check if there is a prefix that has a reachable advertising
         * router.
         */
        LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                if (pr->ndpr_raf_onlink && find_pfxlist_reachable_router(pr))
                        break;
        }

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

                        LIST_FOREACH(pr0, &V_nd_prefix, ndpr_entry) {
                                if ((pfxrtr = pfxrtr_lookup(pr0, dr)) != NULL)
                                        break;
                        }
                        if (pfxrtr != NULL)
                                break;
                }
        }
        if (pr != NULL || (!TAILQ_EMPTY(&V_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.
                 */
                LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                        /* XXX: a link-local prefix should never be detached */
                        if (IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr))
                                continue;

                        /*
                         * we aren't interested in prefixes without the L bit
                         * set.
                         */
                        if (pr->ndpr_raf_onlink == 0)
                                continue;

                        if (pr->ndpr_raf_auto == 0)
                                continue;

                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                            find_pfxlist_reachable_router(pr) == NULL)
                                pr->ndpr_stateflags |= NDPRF_DETACHED;
                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
                            find_pfxlist_reachable_router(pr) != 0)
                                pr->ndpr_stateflags &= ~NDPRF_DETACHED;
                }
        } else {
                /* there is no prefix that has a reachable router */
                LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                        if (IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr))
                                continue;

                        if (pr->ndpr_raf_onlink == 0)
                                continue;

                        if (pr->ndpr_raf_auto == 0)
                                continue;

                        if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0)
                                pr->ndpr_stateflags &= ~NDPRF_DETACHED;
                }
        }

        /*
         * 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.
         */
        LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                int e;
                char ip6buf[INET6_ADDRSTRLEN];

                if (IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr))
                        continue;

                if (pr->ndpr_raf_onlink == 0)
                        continue;

                if (pr->ndpr_raf_auto == 0)
                        continue;

                if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
                    (pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                        if ((e = nd6_prefix_offlink(pr)) != 0) {
                                nd6log((LOG_ERR,
                                    "pfxlist_onlink_check: failed to "
                                    "make %s/%d offlink, errno=%d\n",
                                    ip6_sprintf(ip6buf,
                                            &pr->ndpr_prefix.sin6_addr),
                                            pr->ndpr_plen, e));
                        }
                }
                if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
                    (pr->ndpr_stateflags & NDPRF_ONLINK) == 0 &&
                    pr->ndpr_raf_onlink) {
                        if ((e = nd6_prefix_onlink(pr)) != 0) {
                                nd6log((LOG_ERR,
                                    "pfxlist_onlink_check: failed to "
                                    "make %s/%d onlink, errno=%d\n",
                                    ip6_sprintf(ip6buf,
                                            &pr->ndpr_prefix.sin6_addr),
                                            pr->ndpr_plen, e));
                        }
                }
        }

        /*
         * 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.
         *
         * XXXRW: in6_ifaddrhead locking.
         */
        TAILQ_FOREACH(ifa, &V_in6_ifaddrhead, ia_link) {
                if (!(ifa->ia6_flags & IN6_IFF_AUTOCONF))
                        continue;

                if (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...
                         */
                        continue;
                }

                if (find_pfxlist_reachable_router(ifa->ia6_ndpr))
                        break;
        }
        if (ifa) {
                TAILQ_FOREACH(ifa, &V_in6_ifaddrhead, ia_link) {
                        if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0)
                                continue;

                        if (ifa->ia6_ndpr == NULL) /* XXX: see above. */
                                continue;

                        if (find_pfxlist_reachable_router(ifa->ia6_ndpr)) {
                                if (ifa->ia6_flags & IN6_IFF_DETACHED) {
                                        ifa->ia6_flags &= ~IN6_IFF_DETACHED;
                                        ifa->ia6_flags |= IN6_IFF_TENTATIVE;
                                        nd6_dad_start((struct ifaddr *)ifa, 0);
                                }
                        } else {
                                ifa->ia6_flags |= IN6_IFF_DETACHED;
                        }
                }
        }
        else {
                TAILQ_FOREACH(ifa, &V_in6_ifaddrhead, ia_link) {
                        if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0)
                                continue;

                        if (ifa->ia6_flags & IN6_IFF_DETACHED) {
                                ifa->ia6_flags &= ~IN6_IFF_DETACHED;
                                ifa->ia6_flags |= IN6_IFF_TENTATIVE;
                                /* Do we need a delay in this case? */
                                nd6_dad_start((struct ifaddr *)ifa, 0);
                        }
                }
        }
}

static int
nd6_prefix_onlink_rtrequest(struct nd_prefix *pr, struct ifaddr *ifa)
{
        static struct sockaddr_dl null_sdl = {sizeof(null_sdl), AF_LINK};
        struct radix_node_head *rnh;
        struct rtentry *rt;
        struct sockaddr_in6 mask6;
        u_long rtflags;
        int error, a_failure, fibnum;

        /*
         * 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;
        rtflags = (ifa->ifa_flags & ~IFA_RTSELF) | RTF_UP;

        a_failure = 0;
        for (fibnum = 0; fibnum < rt_numfibs; fibnum++) {

                rt = NULL;
                error = in6_rtrequest(RTM_ADD,
                    (struct sockaddr *)&pr->ndpr_prefix, ifa->ifa_addr,
                    (struct sockaddr *)&mask6, rtflags, &rt, fibnum);
                if (error == 0) {
                        KASSERT(rt != NULL, ("%s: in6_rtrequest return no "
                            "error(%d) but rt is NULL, pr=%p, ifa=%p", __func__,
                            error, pr, ifa));

                        rnh = rt_tables_get_rnh(rt->rt_fibnum, AF_INET6);
                        /* XXX what if rhn == NULL? */
                        RADIX_NODE_HEAD_LOCK(rnh);
                        RT_LOCK(rt);
                        if (rt_setgate(rt, rt_key(rt),
                            (struct sockaddr *)&null_sdl) == 0) {
                                struct sockaddr_dl *dl;

                                dl = (struct sockaddr_dl *)rt->rt_gateway;
                                dl->sdl_type = rt->rt_ifp->if_type;
                                dl->sdl_index = rt->rt_ifp->if_index;
                        }
                        RADIX_NODE_HEAD_UNLOCK(rnh);
                        nd6_rtmsg(RTM_ADD, rt);
                        RT_UNLOCK(rt);
                        pr->ndpr_stateflags |= NDPRF_ONLINK;
                } else {
                        char ip6buf[INET6_ADDRSTRLEN];
                        char ip6bufg[INET6_ADDRSTRLEN];
                        char ip6bufm[INET6_ADDRSTRLEN];
                        struct sockaddr_in6 *sin6;

                        sin6 = (struct sockaddr_in6 *)ifa->ifa_addr;
                        nd6log((LOG_ERR, "nd6_prefix_onlink: failed to add "
                            "route for a prefix (%s/%d) on %s, gw=%s, mask=%s, "
                            "flags=%lx errno = %d\n",
                            ip6_sprintf(ip6buf, &pr->ndpr_prefix.sin6_addr),
                            pr->ndpr_plen, if_name(pr->ndpr_ifp),
                            ip6_sprintf(ip6bufg, &sin6->sin6_addr),
                            ip6_sprintf(ip6bufm, &mask6.sin6_addr),
                            rtflags, error));

                        /* Save last error to return, see rtinit(). */
                        a_failure = error;
                }

                if (rt != NULL) {
                        RT_LOCK(rt);
                        RT_REMREF(rt);
                        RT_UNLOCK(rt);
                }
        }

        /* Return the last error we got. */
        return (a_failure);
}

static int
nd6_prefix_onlink(struct nd_prefix *pr)
{
        struct ifaddr *ifa;
        struct ifnet *ifp = pr->ndpr_ifp;
        struct nd_prefix *opr;
        int error = 0;
        char ip6buf[INET6_ADDRSTRLEN];

        /* sanity check */
        if ((pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                nd6log((LOG_ERR,
                    "nd6_prefix_onlink: %s/%d is already on-link\n",
                    ip6_sprintf(ip6buf, &pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen));
                return (EEXIST);
        }

        /*
         * 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.
         * Although such a configuration is expected to be rare, we explicitly
         * allow it.
         */
        LIST_FOREACH(opr, &V_nd_prefix, ndpr_entry) {
                if (opr == pr)
                        continue;

                if ((opr->ndpr_stateflags & NDPRF_ONLINK) == 0)
                        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))
                        return (0);
        }

        /*
         * 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) {
                /* XXX: freebsd does not have ifa_ifwithaf */
                IF_ADDR_RLOCK(ifp);
                TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                        if (ifa->ifa_addr->sa_family == AF_INET6)
                                break;
                }
                if (ifa != NULL)
                        ifa_ref(ifa);
                IF_ADDR_RUNLOCK(ifp);
                /* should we care about ia6_flags? */
        }
        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(ip6buf, &pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen, if_name(ifp)));
                return (0);
        }

        error = nd6_prefix_onlink_rtrequest(pr, ifa);

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

        return (error);
}

static int
nd6_prefix_offlink(struct nd_prefix *pr)
{
        int error = 0;
        struct ifnet *ifp = pr->ndpr_ifp;
        struct nd_prefix *opr;
        struct sockaddr_in6 sa6, mask6;
        struct rtentry *rt;
        char ip6buf[INET6_ADDRSTRLEN];
        int fibnum, a_failure;

        /* sanity check */
        if ((pr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
                nd6log((LOG_ERR,
                    "nd6_prefix_offlink: %s/%d is already off-link\n",
                    ip6_sprintf(ip6buf, &pr->ndpr_prefix.sin6_addr),
                    pr->ndpr_plen));
                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));

        a_failure = 0;
        for (fibnum = 0; fibnum < rt_numfibs; fibnum++) {
                rt = NULL;
                error = in6_rtrequest(RTM_DELETE, (struct sockaddr *)&sa6, NULL,
                    (struct sockaddr *)&mask6, 0, &rt, fibnum);
                if (error == 0) {
                        /* report the route deletion to the routing socket. */
                        if (rt != NULL)
                                nd6_rtmsg(RTM_DELETE, rt);
                } else {
                        /* Save last error to return, see rtinit(). */
                        a_failure = error;
                }
                if (rt != NULL) {
                        RTFREE(rt);
                }
        }
        error = a_failure;
        a_failure = 1;
        if (error == 0) {
                pr->ndpr_stateflags &= ~NDPRF_ONLINK;

                /*
                 * 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.
                 */
                LIST_FOREACH(opr, &V_nd_prefix, ndpr_entry) {
                        if (opr == pr)
                                continue;

                        if ((opr->ndpr_stateflags & NDPRF_ONLINK) != 0)
                                continue;

                        /*
                         * KAME specific: detached prefixes should not be
                         * on-link.
                         */
                        if ((opr->ndpr_stateflags & NDPRF_DETACHED) != 0)
                                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)) {
                                int e;

                                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(ip6buf,
                                                &opr->ndpr_prefix.sin6_addr),
                                            opr->ndpr_plen, if_name(ifp),
                                            if_name(opr->ndpr_ifp), e));
                                } else
                                        a_failure = 0;
                        }
                }
        } else {
                /* XXX: can we still set the NDPRF_ONLINK flag? */
                nd6log((LOG_ERR,
                    "nd6_prefix_offlink: failed to delete route: "
                    "%s/%d on %s (errno = %d)\n",
                    ip6_sprintf(ip6buf, &sa6.sin6_addr), pr->ndpr_plen,
                    if_name(ifp), error));
        }

        if (a_failure)
                lltable_prefix_free(AF_INET6, (struct sockaddr *)&sa6,
                    (struct sockaddr *)&mask6, LLE_STATIC);

        return (error);
}

static struct in6_ifaddr *
in6_ifadd(struct nd_prefixctl *pr, int mcast)
{
        struct ifnet *ifp = pr->ndpr_ifp;
        struct ifaddr *ifa;
        struct in6_aliasreq ifra;
        struct in6_ifaddr *ia, *ib;
        int error, plen0;
        struct in6_addr mask;
        int prefixlen = pr->ndpr_plen;
        int updateflags;
        char ip6buf[INET6_ADDRSTRLEN];

        in6_prefixlen2mask(&mask, 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.
         */
        ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(ifp, 0); /* 0 is OK? */
        if (ifa)
                ib = (struct in6_ifaddr *)ifa;
        else
                return NULL;

        /* prefixlen + ifidlen must be equal to 128 */
        plen0 = in6_mask2len(&ib->ia_prefixmask.sin6_addr, NULL);
        if (prefixlen != plen0) {
                ifa_free(ifa);
                nd6log((LOG_INFO, "in6_ifadd: wrong prefixlen for %s "
                    "(prefix=%d ifid=%d)\n",
                    if_name(ifp), prefixlen, 128 - plen0));
                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 */
        ifra.ifra_addr.sin6_addr = pr->ndpr_prefix.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]);
        ifa_free(ifa);

        /* 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 */

        /*
         * 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.
         */
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp,
            &ifra.ifra_addr.sin6_addr);
        if (ifa != NULL) {
                ifa_free(ifa);
                /* this should be rare enough to make an explicit log */
                log(LOG_INFO, "in6_ifadd: %s is already configured\n",
                    ip6_sprintf(ip6buf, &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;
        if ((error = in6_update_ifa(ifp, &ifra, NULL, updateflags)) != 0) {
                nd6log((LOG_ERR,
                    "in6_ifadd: failed to make ifaddr %s on %s (errno=%d)\n",
                    ip6_sprintf(ip6buf, &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);
        /*
         * XXXRW: Assumption of non-NULLness here might not be true with
         * fine-grained locking -- should we validate it?  Or just return
         * earlier ifa rather than looking it up again?
         */
        return (ia);            /* this is always non-NULL  and referenced. */
}

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

        bzero(&ifra, sizeof(ifra));
        strncpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
        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];
        }

  again:
        if (in6_get_tmpifid(ifp, (u_int8_t *)randid,
            (const u_int8_t *)&ia0->ia_addr.sin6_addr.s6_addr[8], forcegen)) {
                nd6log((LOG_NOTICE, "in6_tmpifadd: failed to find a good "
                    "random IFID\n"));
                return (EINVAL);
        }
        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.
         */
        IN6_IFADDR_RLOCK();
        TAILQ_FOREACH(ia, &V_in6_ifaddrhead, ia_link) {
                if (IN6_ARE_ADDR_EQUAL(&ia->ia_addr.sin6_addr,
                    &ifra.ifra_addr.sin6_addr)) {
                        if (trylimit-- == 0) {
                                IN6_IFADDR_RUNLOCK();
                                /*
                                 * Give up.  Something strange should have
                                 * happened.
                                 */
                                nd6log((LOG_NOTICE, "in6_tmpifadd: failed to "
                                    "find a unique random IFID\n"));
                                return (EEXIST);
                        }
                        IN6_IFADDR_RUNLOCK();
                        forcegen = 1;
                        goto again;
                }
        }
        IN6_IFADDR_RUNLOCK();

        /*
         * 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.
         */
        if (ia0->ia6_lifetime.ia6t_vltime != ND6_INFINITE_LIFETIME) {
                vltime0 = IFA6_IS_INVALID(ia0) ? 0 :
                    (ia0->ia6_lifetime.ia6t_vltime -
                    (time_uptime - ia0->ia6_updatetime));
                if (vltime0 > V_ip6_temp_valid_lifetime)
                        vltime0 = V_ip6_temp_valid_lifetime;
        } else
                vltime0 = V_ip6_temp_valid_lifetime;
        if (ia0->ia6_lifetime.ia6t_pltime != ND6_INFINITE_LIFETIME) {
                pltime0 = IFA6_IS_DEPRECATED(ia0) ? 0 :
                    (ia0->ia6_lifetime.ia6t_pltime -
                    (time_uptime - ia0->ia6_updatetime));
                if (pltime0 > V_ip6_temp_preferred_lifetime - V_ip6_desync_factor){
                        pltime0 = V_ip6_temp_preferred_lifetime -
                            V_ip6_desync_factor;
                }
        } else
                pltime0 = V_ip6_temp_preferred_lifetime - V_ip6_desync_factor;
        ifra.ifra_lifetime.ia6t_vltime = vltime0;
        ifra.ifra_lifetime.ia6t_pltime = pltime0;

        /*
         * A temporary address is created only if this calculated Preferred
         * Lifetime is greater than REGEN_ADVANCE time units.
         */
        if (ifra.ifra_lifetime.ia6t_pltime <= V_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 (delay)
                updateflags |= IN6_IFAUPDATE_DADDELAY;
        if ((error = in6_update_ifa(ifp, &ifra, NULL, updateflags)) != 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 */
        }
        newia->ia6_ndpr = ia0->ia6_ndpr;
        newia->ia6_ndpr->ndpr_refcnt++;
        ifa_free(&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.
         */
        pfxlist_onlink_check();

        return (0);
}

static int
in6_init_prefix_ltimes(struct nd_prefix *ndpr)
{
        if (ndpr->ndpr_pltime == ND6_INFINITE_LIFETIME)
                ndpr->ndpr_preferred = 0;
        else
                ndpr->ndpr_preferred = time_uptime + ndpr->ndpr_pltime;
        if (ndpr->ndpr_vltime == ND6_INFINITE_LIFETIME)
                ndpr->ndpr_expire = 0;
        else
                ndpr->ndpr_expire = time_uptime + ndpr->ndpr_vltime;

        return 0;
}

static void
in6_init_address_ltimes(struct nd_prefix *new, struct in6_addrlifetime *lt6)
{
        /* init ia6t_expire */
        if (lt6->ia6t_vltime == ND6_INFINITE_LIFETIME)
                lt6->ia6t_expire = 0;
        else {
                lt6->ia6t_expire = time_uptime;
                lt6->ia6t_expire += lt6->ia6t_vltime;
        }

        /* init ia6t_preferred */
        if (lt6->ia6t_pltime == ND6_INFINITE_LIFETIME)
                lt6->ia6t_preferred = 0;
        else {
                lt6->ia6t_preferred = time_uptime;
                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;
        u_int fibnum;

        /* We'll care only link-local addresses */
        if (!IN6_IS_ADDR_LINKLOCAL(gateway))
                return;

        /* XXX Do we really need to walk any but the default FIB? */
        for (fibnum = 0; fibnum < rt_numfibs; fibnum++) {
                rnh = rt_tables_get_rnh(fibnum, AF_INET6);
                if (rnh == NULL)
                        continue;

                RADIX_NODE_HEAD_LOCK(rnh);
                rnh->rnh_walktree(rnh, rt6_deleteroute, (void *)gateway);
                RADIX_NODE_HEAD_UNLOCK(rnh);
        }
}

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;

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

        if (!IN6_ARE_ADDR_EQUAL(gate, &SIN6(rt->rt_gateway)->sin6_addr)) {
                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)
                return (0);

        /*
         * We delete only host route. This means, in particular, we don't
         * delete default route.
         */
        if ((rt->rt_flags & RTF_HOST) == 0)
                return (0);

        return (in6_rtrequest(RTM_DELETE, rt_key(rt), rt->rt_gateway,
            rt_mask(rt), rt->rt_flags, NULL, rt->rt_fibnum));
#undef SIN6
}

int
nd6_setdefaultiface(int ifindex)
{
        int error = 0;

        if (ifindex < 0 || V_if_index < ifindex)
                return (EINVAL);
        if (ifindex != 0 && !ifnet_byindex(ifindex))
                return (EINVAL);

        if (V_nd6_defifindex != ifindex) {
                V_nd6_defifindex = ifindex;
                if (V_nd6_defifindex > 0)
                        V_nd6_defifp = ifnet_byindex(V_nd6_defifindex);
                else
                        V_nd6_defifp = NULL;

                /*
                 * 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(V_nd6_defifp);
        }

        return (error);
}