/*      $OpenBSD: nd6.c,v 1.305 2025/11/27 21:54:28 bluhm Exp $ */
/*      $KAME: nd6.c,v 1.280 2002/06/08 19:52:07 itojun Exp $   */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/timeout.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/pool.h>
#include <sys/errno.h>
#include <sys/ioctl.h>
#include <sys/syslog.h>
#include <sys/queue.h>
#include <sys/stdint.h>
#include <sys/task.h>

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

#include <netinet/in.h>
#include <netinet/if_ether.h>

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

/*
 * Locks used to protect struct members in this file:
 *      a       atomic operations
 *      I       immutable after creation
 *      K       kernel lock
 *      m       nd6 mutex, needed when net lock is shared
 *      N       net lock
 */

#define ND6_SLOWTIMER_INTERVAL (60 * 60) /* 1 hour */
#define ND6_RECALC_REACHTM_INTERVAL (60 * 120) /* 2 hours */

/* timer values */
time_t  nd6_timer_next  = -1;   /* [N] at which uptime nd6_timer runs */
time_t  nd6_expire_next = -1;   /* at which uptime nd6_expire runs */
int     nd6_delay       = 5;    /* [a] delay first probe time 5 second */
int     nd6_umaxtries   = 3;    /* [a] maximum unicast query */
int     nd6_mmaxtries   = 3;    /* [a] maximum multicast query */
const int nd6_gctimer   = (60 * 60 * 24); /* 1 day: garbage collection timer */

/* preventing too many loops in ND option parsing */
int nd6_maxndopt = 10;  /* max # of ND options allowed */

/* llinfo_nd6 live time, rt_llinfo and RTF_LLINFO are protected by nd6_mtx */
struct mutex nd6_mtx = MUTEX_INITIALIZER(IPL_SOFTNET);

TAILQ_HEAD(llinfo_nd6_head, llinfo_nd6) nd6_list =
    TAILQ_HEAD_INITIALIZER(nd6_list);
                                /* [m] list of llinfo_nd6 structures */
struct  pool nd6_pool;          /* [I] pool for llinfo_nd6 structures */
int     nd6_inuse;              /* [m] limit neighbor discovery routes */
unsigned int    ln_hold_total;  /* [a] packets currently in the nd6 queue */

void nd6_timer(void *);
void nd6_slowtimo(void *);
void nd6_expire(void *);
void nd6_expire_timer(void *);
void nd6_invalidate(struct rtentry *);
void nd6_free(struct rtentry *, struct ifnet *ifp, int);
int nd6_llinfo_timer(struct rtentry *, int);

struct timeout nd6_timer_to;
struct timeout nd6_slowtimo_ch;
struct timeout nd6_expire_timeout;
struct task nd6_expire_task;

void
nd6_init(void)
{
        pool_init(&nd6_pool, sizeof(struct llinfo_nd6), 0,
            IPL_SOFTNET, 0, "nd6", NULL);

        task_set(&nd6_expire_task, nd6_expire, NULL);

        /* start timer */
        timeout_set_proc(&nd6_timer_to, nd6_timer, NULL);
        timeout_set_proc(&nd6_slowtimo_ch, nd6_slowtimo, NULL);
        timeout_add_sec(&nd6_slowtimo_ch, ND6_SLOWTIMER_INTERVAL);
        timeout_set(&nd6_expire_timeout, nd6_expire_timer, NULL);
}

void
nd6_ifattach(struct ifnet *ifp)
{
        struct nd_ifinfo *nd;

        nd = malloc(sizeof(*nd), M_IP6NDP, M_WAITOK | M_ZERO);

        nd->reachable = ND_COMPUTE_RTIME(REACHABLE_TIME);

        ifp->if_nd = nd;
}

void
nd6_ifdetach(struct ifnet *ifp)
{
        struct nd_ifinfo *nd = ifp->if_nd;

        free(nd, M_IP6NDP, sizeof(*nd));
}

/*
 * Parse multiple ND options.
 * This function is much easier to use, for ND routines that do not need
 * multiple options of the same type.
 */
int
nd6_options(void *opt, int icmp6len, struct nd_opts *ndopts)
{
        struct nd_opt_hdr *nd_opt, *next_opt, *last_opt;
        int i = 0;

        bzero(ndopts, sizeof(*ndopts));

        if (icmp6len == 0)
                return 0;

        next_opt = opt;
        last_opt = (struct nd_opt_hdr *)((u_char *)opt + icmp6len);

        while (next_opt != NULL) {
                int olen;

                nd_opt = next_opt;

                /* make sure nd_opt_len is inside the buffer */
                if ((caddr_t)&nd_opt->nd_opt_len >= (caddr_t)last_opt)
                        goto invalid;

                /* every option must have a length greater than zero */
                olen = nd_opt->nd_opt_len << 3;
                if (olen == 0)
                        goto invalid;

                next_opt = (struct nd_opt_hdr *)((caddr_t)nd_opt + olen);
                if (next_opt > last_opt) {
                        /* option overruns the end of buffer */
                        goto invalid;
                } else if (next_opt == last_opt) {
                        /* reached the end of options chain */
                        next_opt = NULL;
                }

                switch (nd_opt->nd_opt_type) {
                case ND_OPT_SOURCE_LINKADDR:
                        if (ndopts->nd_opts_src_lladdr == NULL)
                                ndopts->nd_opts_src_lladdr = nd_opt;
                        break;
                case ND_OPT_TARGET_LINKADDR:
                        if (ndopts->nd_opts_tgt_lladdr == NULL)
                                ndopts->nd_opts_tgt_lladdr = nd_opt;
                        break;
                case ND_OPT_MTU:
                case ND_OPT_REDIRECTED_HEADER:
                case ND_OPT_PREFIX_INFORMATION:
                case ND_OPT_DNSSL:
                case ND_OPT_RDNSS:
                        /* Don't warn, not used by kernel */
                        break;
                default:
                        /*
                         * Unknown options must be silently ignored,
                         * to accommodate future extension to the protocol.
                         */
                        break;
                }

                i++;
                if (i > nd6_maxndopt) {
                        icmp6stat_inc(icp6s_nd_toomanyopt);
                        break;
                }
        }

        return 0;

invalid:
        bzero(ndopts, sizeof(*ndopts));
        icmp6stat_inc(icp6s_nd_badopt);
        return -1;
}

/*
 * ND6 timer routine to handle ND6 entries
 */
void
nd6_llinfo_settimer(const struct llinfo_nd6 *ln, unsigned int secs)
{
        time_t expire = getuptime() + secs;

        NET_ASSERT_LOCKED();
        KASSERT(!ISSET(ln->ln_rt->rt_flags, RTF_LOCAL));

        ln->ln_rt->rt_expire = expire;
        if (!timeout_pending(&nd6_timer_to) || expire < nd6_timer_next) {
                nd6_timer_next = expire;
                timeout_add_sec(&nd6_timer_to, secs);
        }
}

static struct llinfo_nd6 *
nd6_iterator(struct llinfo_nd6 *ln, struct llinfo_nd6_iterator *iter)
{
        struct llinfo_nd6 *tmp;

        MUTEX_ASSERT_LOCKED(&nd6_mtx);

        if (ln)
                tmp = TAILQ_NEXT((struct llinfo_nd6 *)iter, ln_list);
        else
                tmp = TAILQ_FIRST(&nd6_list);

        while (tmp && tmp->ln_rt == NULL)
                tmp = TAILQ_NEXT(tmp, ln_list);

        if (ln) {
                TAILQ_REMOVE(&nd6_list, (struct llinfo_nd6 *)iter, ln_list);
                if (refcnt_rele(&ln->ln_refcnt))
                        pool_put(&nd6_pool, ln);
        }
        if (tmp) {
                TAILQ_INSERT_AFTER(&nd6_list, tmp, (struct llinfo_nd6 *)iter,
                    ln_list);
                refcnt_take(&tmp->ln_refcnt);
        }

        return tmp;
}

void
nd6_timer(void *unused)
{
        struct llinfo_nd6_iterator iter = { .ln_rt = NULL };
        struct llinfo_nd6 *ln = NULL;
        time_t uptime, expire;
        int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);
        int secs;

        uptime = getuptime();
        expire = uptime + nd6_gctimer;

        mtx_enter(&nd6_mtx);
        while ((ln = nd6_iterator(ln, &iter)) != NULL) {
                struct rtentry *rt = ln->ln_rt;

                if (rt->rt_expire && rt->rt_expire <= uptime) {
                        rtref(rt);
                        mtx_leave(&nd6_mtx);
                        NET_LOCK();
                        if (!nd6_llinfo_timer(rt, i_am_router)) {
                                if (rt->rt_expire && rt->rt_expire < expire)
                                        expire = rt->rt_expire;
                        }
                        NET_UNLOCK();
                        rtfree(rt);
                        mtx_enter(&nd6_mtx);
                } else if (rt->rt_expire && rt->rt_expire < expire)
                        expire = rt->rt_expire;
        }
        mtx_leave(&nd6_mtx);

        secs = expire - uptime;
        if (secs < 1)
                secs = 1;

        NET_LOCK();
        if (!TAILQ_EMPTY(&nd6_list)) {
                nd6_timer_next = uptime + secs;
                timeout_add_sec(&nd6_timer_to, secs);
        }
        NET_UNLOCK();
}

/*
 * ND timer state handling.
 *
 * Returns 1 if `rt' should no longer be used, 0 otherwise.
 */
int
nd6_llinfo_timer(struct rtentry *rt, int i_am_router)
{
        struct llinfo_nd6 *ln = (struct llinfo_nd6 *)rt->rt_llinfo;
        struct sockaddr_in6 *dst = satosin6(rt_key(rt));
        struct ifnet *ifp;

        NET_ASSERT_LOCKED_EXCLUSIVE();

        /* might have been freed between leave nd6_mtx and enter net lock */
        if (!ISSET(rt->rt_flags, RTF_LLINFO))
                return 0;

        if ((ifp = if_get(rt->rt_ifidx)) == NULL)
                return 1;

        switch (ln->ln_state) {
        case ND6_LLINFO_INCOMPLETE:
                if (ln->ln_asked < atomic_load_int(&nd6_mmaxtries)) {
                        ln->ln_asked++;
                        nd6_llinfo_settimer(ln, RETRANS_TIMER / 1000);
                        nd6_ns_output(ifp, NULL, &dst->sin6_addr,
                            &ln->ln_saddr6, 0);
                } else {
                        struct mbuf_list ml;
                        struct mbuf *m;
                        unsigned int len;

                        mq_delist(&ln->ln_mq, &ml);
                        len = ml_len(&ml);
                        while ((m = ml_dequeue(&ml)) != NULL) {
                                /*
                                 * Fake rcvif to make the ICMP error
                                 * more helpful in diagnosing for the
                                 * receiver.
                                 * XXX: should we consider older rcvif?
                                 */
                                m->m_pkthdr.ph_ifidx = rt->rt_ifidx;

                                icmp6_error(m, ICMP6_DST_UNREACH,
                                    ICMP6_DST_UNREACH_ADDR, 0);
                        }

                        /* XXXSMP we also discard if other CPU enqueues */
                        if (mq_len(&ln->ln_mq) > 0) {
                                /* mbuf is back in queue. Discard. */
                                atomic_sub_int(&ln_hold_total,
                                    len + mq_purge(&ln->ln_mq));
                        } else
                                atomic_sub_int(&ln_hold_total, len);

                        nd6_free(rt, ifp, i_am_router);
                        ln = NULL;
                }
                break;

        case ND6_LLINFO_REACHABLE:
                if (!ND6_LLINFO_PERMANENT(ln)) {
                        ln->ln_state = ND6_LLINFO_STALE;
                        nd6_llinfo_settimer(ln, nd6_gctimer);
                }
                break;

        case ND6_LLINFO_STALE:
        case ND6_LLINFO_PURGE:
                /* Garbage Collection(RFC 2461 5.3) */
                if (!ND6_LLINFO_PERMANENT(ln)) {
                        nd6_free(rt, ifp, i_am_router);
                        ln = NULL;
                }
                break;

        case ND6_LLINFO_DELAY:
                /* We need NUD */
                ln->ln_asked = 1;
                ln->ln_state = ND6_LLINFO_PROBE;
                nd6_llinfo_settimer(ln, RETRANS_TIMER / 1000);
                nd6_ns_output(ifp, &dst->sin6_addr, &dst->sin6_addr,
                    &ln->ln_saddr6, 0);
                break;

        case ND6_LLINFO_PROBE:
                if (ln->ln_asked < atomic_load_int(&nd6_umaxtries)) {
                        ln->ln_asked++;
                        nd6_llinfo_settimer(ln, RETRANS_TIMER / 1000);
                        nd6_ns_output(ifp, &dst->sin6_addr, &dst->sin6_addr,
                            &ln->ln_saddr6, 0);
                } else {
                        nd6_free(rt, ifp, i_am_router);
                        ln = NULL;
                }
                break;
        }

        if_put(ifp);

        return (ln == NULL);
}

void
nd6_expire_timer_update(struct in6_ifaddr *ia6)
{
        time_t expire_time = INT64_MAX;

        if (ia6->ia6_lifetime.ia6t_vltime != ND6_INFINITE_LIFETIME)
                expire_time = ia6->ia6_lifetime.ia6t_expire;

        if (!(ia6->ia6_flags & IN6_IFF_DEPRECATED) &&
            ia6->ia6_lifetime.ia6t_pltime != ND6_INFINITE_LIFETIME &&
            expire_time > ia6->ia6_lifetime.ia6t_preferred)
                expire_time = ia6->ia6_lifetime.ia6t_preferred;

        if (expire_time == INT64_MAX)
                return;

        /*
         * IFA6_IS_INVALID() and IFA6_IS_DEPRECATED() check for uptime
         * greater than ia6t_expire or ia6t_preferred, not greater or equal.
         * Schedule timeout one second later so that either IFA6_IS_INVALID()
         * or IFA6_IS_DEPRECATED() is true.
         */
        expire_time++;

        if (!timeout_pending(&nd6_expire_timeout) ||
            nd6_expire_next > expire_time) {
                int secs;

                secs = expire_time - getuptime();
                if (secs < 0)
                        secs = 0;

                timeout_add_sec(&nd6_expire_timeout, secs);
                nd6_expire_next = expire_time;
        }
}

/*
 * Expire interface addresses.
 */
void
nd6_expire(void *unused)
{
        struct ifnet *ifp;

        NET_LOCK();

        TAILQ_FOREACH(ifp, &ifnetlist, if_list) {
                struct ifaddr *ifa, *nifa;
                struct in6_ifaddr *ia6;

                TAILQ_FOREACH_SAFE(ifa, &ifp->if_addrlist, ifa_list, nifa) {
                        if (ifa->ifa_addr->sa_family != AF_INET6)
                                continue;
                        ia6 = ifatoia6(ifa);
                        /* check address lifetime */
                        if (IFA6_IS_INVALID(ia6)) {
                                in6_purgeaddr(&ia6->ia_ifa);
                        } else {
                                if (IFA6_IS_DEPRECATED(ia6))
                                        ia6->ia6_flags |= IN6_IFF_DEPRECATED;
                                nd6_expire_timer_update(ia6);
                        }
                }
        }

        NET_UNLOCK();
}

void
nd6_expire_timer(void *unused)
{
        task_add(net_tq(0), &nd6_expire_task);
}

/*
 * Nuke neighbor cache/prefix/default router management table, right before
 * ifp goes away.
 */
void
nd6_purge(struct ifnet *ifp)
{
        struct llinfo_nd6_iterator iter = { .ln_rt = NULL };
        struct llinfo_nd6 *ln = NULL;
        int i_am_router = (atomic_load_int(&ip6_forwarding) != 0);

        /*
         * Nuke neighbor cache entries for the ifp.
         */
        mtx_enter(&nd6_mtx);
        while ((ln = nd6_iterator(ln, &iter)) != NULL) {
                struct rtentry *rt = ln->ln_rt;
                struct sockaddr_dl *sdl;

                if (rt != NULL && rt->rt_gateway != NULL &&
                    rt->rt_gateway->sa_family == AF_LINK) {
                        sdl = satosdl(rt->rt_gateway);
                        if (sdl->sdl_index == ifp->if_index) {
                                rtref(rt);
                                mtx_leave(&nd6_mtx);
                                nd6_free(rt, ifp, i_am_router);
                                rtfree(rt);
                                mtx_enter(&nd6_mtx);
                        }
                }
        }
        mtx_leave(&nd6_mtx);
}

struct rtentry *
nd6_lookup(const struct in6_addr *addr6, int create, struct ifnet *ifp,
    u_int rtableid)
{
        struct rtentry *rt;
        struct sockaddr_in6 sin6;
        int flags;

        bzero(&sin6, sizeof(sin6));
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        sin6.sin6_family = AF_INET6;
        sin6.sin6_addr = *addr6;
        flags = (create) ? RT_RESOLVE : 0;

        rt = rtalloc(sin6tosa(&sin6), flags, rtableid);
        if (rt != NULL && (rt->rt_flags & RTF_LLINFO) == 0) {
                /*
                 * This is the case for the default route.
                 * If we want to create a neighbor cache for the address, we
                 * should free the route for the destination and allocate an
                 * interface route.
                 */
                if (create) {
                        rtfree(rt);
                        rt = NULL;
                }
        }
        if (rt == NULL) {
                if (create && ifp) {
                        struct rt_addrinfo info;
                        struct llinfo_nd6 *ln;
                        struct ifaddr *ifa;
                        int error;

                        /*
                         * If no route is available and create is set,
                         * we allocate a host route for the destination
                         * and treat it like an interface route.
                         * This hack is necessary for a neighbor which can't
                         * be covered by our own prefix.
                         */
                        ifa = ifaof_ifpforaddr(sin6tosa(&sin6), ifp);
                        if (ifa == NULL)
                                return (NULL);

                        /*
                         * Create a new route.  RTF_LLINFO is necessary
                         * to create a Neighbor Cache entry for the
                         * destination in nd6_rtrequest which will be
                         * called in rtrequest.
                         */
                        bzero(&info, sizeof(info));
                        info.rti_ifa = ifa;
                        info.rti_flags = RTF_HOST | RTF_LLINFO;
                        info.rti_info[RTAX_DST] = sin6tosa(&sin6);
                        info.rti_info[RTAX_GATEWAY] = sdltosa(ifp->if_sadl);
                        error = rtrequest(RTM_ADD, &info, RTP_CONNECTED, &rt,
                            rtableid);
                        if (error)
                                return (NULL);
                        mtx_enter(&nd6_mtx);
                        ln = (struct llinfo_nd6 *)rt->rt_llinfo;
                        if (ln != NULL)
                                ln->ln_state = ND6_LLINFO_NOSTATE;
                        mtx_leave(&nd6_mtx);
                } else
                        return (NULL);
        }
        /*
         * Validation for the entry.
         * Note that the check for rt_llinfo is necessary because a cloned
         * route from a parent route that has the L flag (e.g. the default
         * route to a p2p interface) may have the flag, too, while the
         * destination is not actually a neighbor.
         */
        if ((rt->rt_flags & RTF_GATEWAY) || (rt->rt_flags & RTF_LLINFO) == 0 ||
            rt->rt_gateway->sa_family != AF_LINK || rt->rt_llinfo == NULL ||
            (ifp != NULL && rt->rt_ifidx != ifp->if_index)) {
                rtfree(rt);
                return (NULL);
        }
        return (rt);
}

/*
 * Detect if a given IPv6 address identifies a neighbor on a given link.
 * XXX: should take care of the destination of a p2p link?
 */
int
nd6_is_addr_neighbor(const struct sockaddr_in6 *addr, struct ifnet *ifp)
{
        struct in6_ifaddr *ia6;
        struct ifaddr *ifa;
        struct rtentry *rt;

        /*
         * A link-local address is always a neighbor.
         * XXX: we should use the sin6_scope_id field rather than the embedded
         * interface index.
         * XXX: a link does not necessarily specify a single interface.
         */
        if (IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr) &&
            ntohs(*(u_int16_t *)&addr->sin6_addr.s6_addr[2]) == ifp->if_index)
                return (1);

        TAILQ_FOREACH(ifa, &ifp->if_addrlist, ifa_list) {
                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;

                ia6 = ifatoia6(ifa);

                /* Prefix check down below. */
                if (ia6->ia6_flags & IN6_IFF_AUTOCONF)
                        continue;

                if (IN6_ARE_MASKED_ADDR_EQUAL(&addr->sin6_addr,
                    &ia6->ia_addr.sin6_addr,
                    &ia6->ia_prefixmask.sin6_addr))
                        return (1);
        }

        /*
         * Even if the address matches none of our addresses, it might be
         * in the neighbor cache.
         */
        rt = nd6_lookup(&addr->sin6_addr, 0, ifp, ifp->if_rdomain);
        if (rt != NULL) {
                rtfree(rt);
                return (1);
        }

        return (0);
}

void
nd6_invalidate(struct rtentry *rt)
{
        struct llinfo_nd6 *ln;
        struct sockaddr_dl *sdl = satosdl(rt->rt_gateway);

        mtx_enter(&nd6_mtx);
        ln = (struct llinfo_nd6 *)rt->rt_llinfo;
        if (ln == NULL) {
                mtx_leave(&nd6_mtx);
                return;
        }
        atomic_sub_int(&ln_hold_total, mq_purge(&ln->ln_mq));
        sdl->sdl_alen = 0;
        ln->ln_state = ND6_LLINFO_INCOMPLETE;
        ln->ln_asked = 0;
        mtx_leave(&nd6_mtx);
}

/*
 * Free an nd6 llinfo entry.
 */
void
nd6_free(struct rtentry *rt, struct ifnet *ifp, int i_am_router)
{
        struct llinfo_nd6 *ln = (struct llinfo_nd6 *)rt->rt_llinfo;
        struct in6_addr in6 = satosin6(rt_key(rt))->sin6_addr;

        NET_ASSERT_LOCKED_EXCLUSIVE();

        if (!i_am_router) {
                if (ln->ln_router) {
                        /*
                         * rt6_flush must be called whether or not the neighbor
                         * is in the Default Router List.
                         * See a corresponding comment in nd6_na_input().
                         */
                        rt6_flush(&in6, ifp);
                }
        }

        KASSERT(!ISSET(rt->rt_flags, RTF_LOCAL));
        nd6_invalidate(rt);

        /*
         * Detach the route from the routing tree and the list of neighbor
         * caches, and disable the route entry not to be used in already
         * cached routes.
         */
        if (!ISSET(rt->rt_flags, RTF_STATIC|RTF_CACHED))
                rtdeletemsg(rt, ifp, ifp->if_rdomain);
}

void
nd6_rtrequest(struct ifnet *ifp, int req, struct rtentry *rt)
{
        struct sockaddr *gate = rt->rt_gateway;
        struct llinfo_nd6 *ln;
        struct ifaddr *ifa;
        struct in6_ifaddr *ifa6;

        if (ISSET(rt->rt_flags, RTF_GATEWAY|RTF_MULTICAST|RTF_MPLS))
                return;

        if (nd6_need_cache(ifp) == 0 && (rt->rt_flags & RTF_HOST) == 0) {
                /*
                 * This is probably an interface direct route for a link
                 * which does not need neighbor caches (e.g. fe80::%lo0/64).
                 * We do not need special treatment below for such a route.
                 * Moreover, the RTF_LLINFO flag which would be set below
                 * would annoy the ndp(8) command.
                 */
                return;
        }

        if (req == RTM_RESOLVE && nd6_need_cache(ifp) == 0) {
                /*
                 * For routing daemons like ospf6d we allow neighbor discovery
                 * based on the cloning route only.  This allows us to send
                 * packets directly into a network without having an address
                 * with matching prefix on the interface.  If the cloning
                 * route is used for an 6to4 interface, we would mistakenly
                 * make a neighbor cache for the host route, and would see
                 * strange neighbor solicitation for the corresponding
                 * destination.  In order to avoid confusion, we check if the
                 * interface is suitable for neighbor discovery, and stop the
                 * process if not.  Additionally, we remove the LLINFO flag
                 * so that ndp(8) will not try to get the neighbor information
                 * of the destination.
                 */
                rt->rt_flags &= ~RTF_LLINFO;
                return;
        }

        switch (req) {
        case RTM_ADD:
                if (rt->rt_flags & RTF_CLONING) {
                        rt->rt_expire = 0;
                        break;
                }
                if ((rt->rt_flags & RTF_LOCAL) && rt->rt_llinfo == NULL)
                        rt->rt_expire = 0;
                /* FALLTHROUGH */
        case RTM_RESOLVE:
                if (gate->sa_family != AF_LINK ||
                    gate->sa_len < sizeof(struct sockaddr_dl)) {
                        log(LOG_DEBUG, "%s: bad gateway value: %s\n",
                            __func__, ifp->if_xname);
                        break;
                }
                satosdl(gate)->sdl_type = ifp->if_type;
                satosdl(gate)->sdl_index = ifp->if_index;
                /*
                 * Case 2: This route may come from cloning, or a manual route
                 * add with a LL address.
                 */
                ln = pool_get(&nd6_pool, PR_NOWAIT | PR_ZERO);
                if (ln == NULL) {
                        log(LOG_DEBUG, "%s: pool get failed\n", __func__);
                        break;
                }

                mtx_enter(&nd6_mtx);
                if (rt->rt_llinfo != NULL) {
                        /* we lost the race, another thread has entered it */
                        mtx_leave(&nd6_mtx);
                        pool_put(&nd6_pool, ln);
                        break;
                }
                nd6_inuse++;
                refcnt_init(&ln->ln_refcnt);
                mq_init(&ln->ln_mq, LN_HOLD_QUEUE, IPL_SOFTNET);
                rt->rt_llinfo = (caddr_t)ln;
                ln->ln_rt = rt;
                rt->rt_flags |= RTF_LLINFO;
                TAILQ_INSERT_HEAD(&nd6_list, ln, ln_list);
                /* this is required for "ndp" command. - shin */
                if (req == RTM_ADD) {
                        /*
                         * gate should have some valid AF_LINK entry,
                         * and ln expire should have some lifetime
                         * which is specified by ndp command.
                         */
                        ln->ln_state = ND6_LLINFO_REACHABLE;
                } else {
                        /*
                         * When req == RTM_RESOLVE, rt is created and
                         * initialized in rtrequest(), so rt_expire is 0.
                         */
                        ln->ln_state = ND6_LLINFO_NOSTATE;
                        nd6_llinfo_settimer(ln, 0);
                }

                /*
                 * If we have too many cache entries, initiate immediate
                 * purging for some "less recently used" entries.  Note that
                 * we cannot directly call nd6_free() here because it would
                 * cause re-entering rtable related routines triggering
                 * lock-order-reversal problems.
                 */
                if (nd6_inuse >= atomic_load_int(&ip6_neighborgcthresh)) {
                        int i;

                        for (i = 0; i < 10; i++) {
                                struct llinfo_nd6 *ln_end;

                                ln_end = TAILQ_LAST(&nd6_list, llinfo_nd6_head);
                                if (ln_end == ln)
                                        break;
                                /* cannot move the iterator, try next time */
                                if (ln_end->ln_rt == NULL)
                                        break;

                                /* Move this entry to the head */
                                TAILQ_REMOVE(&nd6_list, ln_end, ln_list);
                                TAILQ_INSERT_HEAD(&nd6_list, ln_end, ln_list);

                                if (ND6_LLINFO_PERMANENT(ln_end))
                                        continue;

                                if (ln_end->ln_state > ND6_LLINFO_INCOMPLETE)
                                        ln_end->ln_state = ND6_LLINFO_STALE;
                                else
                                        ln_end->ln_state = ND6_LLINFO_PURGE;
                                nd6_llinfo_settimer(ln_end, 0);
                        }
                }

                /*
                 * check if rt_key(rt) is one of my address assigned
                 * to the interface.
                 */
                ifa6 = in6ifa_ifpwithaddr(ifp,
                    &satosin6(rt_key(rt))->sin6_addr);
                ifa = ifa6 ? &ifa6->ia_ifa : NULL;
                if (ifa != NULL ||
                    (rt->rt_flags & RTF_ANNOUNCE)) {
                        ln->ln_state = ND6_LLINFO_REACHABLE;
                        rt->rt_expire = 0;
                }
                mtx_leave(&nd6_mtx);

                /* join solicited node multicast for proxy ND */
                if (ifa == NULL &&
                    (rt->rt_flags & RTF_ANNOUNCE) &&
                    (ifp->if_flags & IFF_MULTICAST)) {
                        struct in6_addr llsol;
                        int error;

                        llsol = satosin6(rt_key(rt))->sin6_addr;
                        llsol.s6_addr16[0] = htons(0xff02);
                        llsol.s6_addr16[1] = htons(ifp->if_index);
                        llsol.s6_addr32[1] = 0;
                        llsol.s6_addr32[2] = htonl(1);
                        llsol.s6_addr8[12] = 0xff;

                        KERNEL_LOCK();
                        in6_addmulti(&llsol, ifp, &error);
                        KERNEL_UNLOCK();
                }
                break;

        case RTM_DELETE:
                mtx_enter(&nd6_mtx);
                ln = (struct llinfo_nd6 *)rt->rt_llinfo;
                if (ln == NULL) {
                        /* we lost the race, another thread has removed it */
                        mtx_leave(&nd6_mtx);
                        break;
                }
                nd6_inuse--;
                TAILQ_REMOVE(&nd6_list, ln, ln_list);
                rt->rt_expire = 0;
                rt->rt_llinfo = NULL;
                rt->rt_flags &= ~RTF_LLINFO;
                atomic_sub_int(&ln_hold_total, mq_purge(&ln->ln_mq));
                mtx_leave(&nd6_mtx);

                if (refcnt_rele(&ln->ln_refcnt))
                        pool_put(&nd6_pool, ln);

                /* leave from solicited node multicast for proxy ND */
                if ((rt->rt_flags & RTF_ANNOUNCE) != 0 &&
                    (ifp->if_flags & IFF_MULTICAST) != 0) {
                        struct in6_addr llsol;
                        struct in6_multi *in6m;

                        llsol = satosin6(rt_key(rt))->sin6_addr;
                        llsol.s6_addr16[0] = htons(0xff02);
                        llsol.s6_addr16[1] = htons(ifp->if_index);
                        llsol.s6_addr32[1] = 0;
                        llsol.s6_addr32[2] = htonl(1);
                        llsol.s6_addr8[12] = 0xff;

                        KERNEL_LOCK();
                        in6m = in6_lookupmulti(&llsol, ifp);
                        if (in6m)
                                in6_delmulti(in6m);
                        KERNEL_UNLOCK();
                }
                break;

        case RTM_INVALIDATE:
                if (!ISSET(rt->rt_flags, RTF_LOCAL))
                        nd6_invalidate(rt);
                break;
        }
}

int
nd6_ioctl(u_long cmd, caddr_t data, struct ifnet *ifp)
{
        struct in6_ndireq *ndi = (struct in6_ndireq *)data;
        struct in6_nbrinfo *nbi = (struct in6_nbrinfo *)data;
        struct rtentry *rt;

        switch (cmd) {
        case SIOCGIFINFO_IN6:
                NET_LOCK_SHARED();
                ndi->ndi = *ifp->if_nd;
                NET_UNLOCK_SHARED();
                return (0);
        case SIOCGNBRINFO_IN6:
        {
                struct llinfo_nd6 *ln;
                struct in6_addr nb_addr = nbi->addr; /* make local for safety */
                time_t expire;

                NET_LOCK_SHARED();
                /*
                 * XXX: KAME specific hack for scoped addresses
                 *      XXXX: for other scopes than link-local?
                 */
                if (IN6_IS_ADDR_LINKLOCAL(&nb_addr) ||
                    IN6_IS_ADDR_MC_LINKLOCAL(&nb_addr)) {
                        u_int16_t *idp = (u_int16_t *)&nb_addr.s6_addr[2];

                        if (*idp == 0)
                                *idp = htons(ifp->if_index);
                }

                rt = nd6_lookup(&nb_addr, 0, ifp, ifp->if_rdomain);
                mtx_enter(&nd6_mtx);
                if (rt == NULL ||
                    (ln = (struct llinfo_nd6 *)rt->rt_llinfo) == NULL) {
                        mtx_leave(&nd6_mtx);
                        rtfree(rt);
                        NET_UNLOCK_SHARED();
                        return (EINVAL);
                }
                expire = ln->ln_rt->rt_expire;
                if (expire != 0) {
                        expire -= getuptime();
                        expire += gettime();
                }

                nbi->state = ln->ln_state;
                nbi->asked = ln->ln_asked;
                nbi->isrouter = ln->ln_router;
                nbi->expire = expire;
                mtx_leave(&nd6_mtx);

                rtfree(rt);
                NET_UNLOCK_SHARED();
                return (0);
        }
        }
        return (0);
}

/*
 * Create neighbor cache entry and cache link-layer address,
 * on reception of inbound ND6 packets.  (RS/RA/NS/redirect)
 *
 * type - ICMP6 type
 * code - type dependent information
 */
void
nd6_cache_lladdr(struct ifnet *ifp, const struct in6_addr *from, char *lladdr,
    int lladdrlen, int type, int code, int i_am_router)
{
        struct rtentry *rt;
        struct llinfo_nd6 *ln;
        int is_newentry;
        struct sockaddr_dl *sdl;
        int do_update;
        int olladdr;
        int llchange;
        int newstate = 0;

        NET_ASSERT_LOCKED_EXCLUSIVE();

        if (!ifp)
                panic("%s: ifp == NULL", __func__);
        if (!from)
                panic("%s: from == NULL", __func__);

        /* nothing must be updated for unspecified address */
        if (IN6_IS_ADDR_UNSPECIFIED(from))
                return;

        /*
         * Validation about ifp->if_addrlen and lladdrlen must be done in
         * the caller.
         *
         * XXX If the link does not have link-layer address, what should
         * we do? (ifp->if_addrlen == 0)
         * Spec says nothing in sections for RA, RS and NA.  There's small
         * description on it in NS section (RFC 2461 7.2.3).
         */

        rt = nd6_lookup(from, 0, ifp, ifp->if_rdomain);
        if (rt == NULL) {
                rt = nd6_lookup(from, 1, ifp, ifp->if_rdomain);
                is_newentry = 1;
        } else {
                /* do not overwrite local or static entry */
                if (ISSET(rt->rt_flags, RTF_STATIC|RTF_LOCAL)) {
                        rtfree(rt);
                        return;
                }
                is_newentry = 0;
        }

        if (!rt)
                return;
        if ((rt->rt_flags & (RTF_GATEWAY | RTF_LLINFO)) != RTF_LLINFO) {
fail:
                nd6_free(rt, ifp, i_am_router);
                rtfree(rt);
                return;
        }
        ln = (struct llinfo_nd6 *)rt->rt_llinfo;
        if (ln == NULL)
                goto fail;
        if (rt->rt_gateway == NULL)
                goto fail;
        if (rt->rt_gateway->sa_family != AF_LINK)
                goto fail;
        sdl = satosdl(rt->rt_gateway);

        olladdr = (sdl->sdl_alen) ? 1 : 0;
        if (olladdr && lladdr) {
                if (bcmp(lladdr, LLADDR(sdl), ifp->if_addrlen))
                        llchange = 1;
                else
                        llchange = 0;
        } else
                llchange = 0;

        /*
         * newentry olladdr  lladdr  llchange   (*=record)
         *      0       n       n       --      (1)
         *      0       y       n       --      (2)
         *      0       n       y       --      (3) * STALE
         *      0       y       y       n       (4) *
         *      0       y       y       y       (5) * STALE
         *      1       --      n       --      (6)   NOSTATE(= PASSIVE)
         *      1       --      y       --      (7) * STALE
         */

        if (llchange) {
                char addr[INET6_ADDRSTRLEN];
                log(LOG_INFO, "ndp info overwritten for %s by %s on %s\n",
                    inet_ntop(AF_INET6, from, addr, sizeof(addr)),
                    ether_sprintf(lladdr), ifp->if_xname);
        }
        if (lladdr) {           /* (3-5) and (7) */
                /*
                 * Record source link-layer address
                 * XXX is it dependent to ifp->if_type?
                 */
                sdl->sdl_alen = ifp->if_addrlen;
                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
        }

        if (!is_newentry) {
                if ((!olladdr && lladdr) ||             /* (3) */
                    (olladdr && lladdr && llchange)) {  /* (5) */
                        do_update = 1;
                        newstate = ND6_LLINFO_STALE;
                } else                                  /* (1-2,4) */
                        do_update = 0;
        } else {
                do_update = 1;
                if (!lladdr)                            /* (6) */
                        newstate = ND6_LLINFO_NOSTATE;
                else                                    /* (7) */
                        newstate = ND6_LLINFO_STALE;
        }

        if (do_update) {
                /*
                 * Update the state of the neighbor cache.
                 */
                ln->ln_state = newstate;

                if (ln->ln_state == ND6_LLINFO_STALE) {
                        /*
                         * Since nd6_resolve() in ifp->if_output() will cause
                         * state transition to DELAY and reset the timer,
                         * we must set the timer now, although it is actually
                         * meaningless.
                         */
                        nd6_llinfo_settimer(ln, nd6_gctimer);
                        if_output_mq(ifp, &ln->ln_mq, &ln_hold_total,
                            rt_key(rt), rt);
                } else if (ln->ln_state == ND6_LLINFO_INCOMPLETE) {
                        /* probe right away */
                        nd6_llinfo_settimer(ln, 0);
                }
        }

        /*
         * ICMP6 type dependent behavior.
         *
         * NS: clear IsRouter if new entry
         * RS: clear IsRouter
         * RA: set IsRouter if there's lladdr
         * redir: clear IsRouter if new entry
         *
         * RA case, (1):
         * The spec says that we must set IsRouter in the following cases:
         * - If lladdr exist, set IsRouter.  This means (1-5).
         * - If it is old entry (!newentry), set IsRouter.  This means (7).
         * So, based on the spec, in (1-5) and (7) cases we must set IsRouter.
         * A question arises for (1) case.  (1) case has no lladdr in the
         * neighbor cache, this is similar to (6).
         * This case is rare but we figured that we MUST NOT set IsRouter.
         *
         * newentry olladdr  lladdr  llchange       NS  RS  RA  redir
         *                                                      D R
         *      0       n       n       --      (1)     c   ?     s
         *      0       y       n       --      (2)     c   s     s
         *      0       n       y       --      (3)     c   s     s
         *      0       y       y       n       (4)     c   s     s
         *      0       y       y       y       (5)     c   s     s
         *      1       --      n       --      (6) c   c       c s
         *      1       --      y       --      (7) c   c   s   c s
         *
         *                                      (c=clear s=set)
         */
        switch (type & 0xff) {
        case ND_NEIGHBOR_SOLICIT:
                /*
                 * New entry must have is_router flag cleared.
                 */
                if (is_newentry)        /* (6-7) */
                        ln->ln_router = 0;
                break;
        case ND_REDIRECT:
                /*
                 * If the icmp is a redirect to a better router, always set the
                 * is_router flag.  Otherwise, if the entry is newly created,
                 * clear the flag.  [RFC 2461, sec 8.3]
                 */
                if (code == ND_REDIRECT_ROUTER)
                        ln->ln_router = 1;
                else if (is_newentry) /* (6-7) */
                        ln->ln_router = 0;
                break;
        case ND_ROUTER_SOLICIT:
                /*
                 * is_router flag must always be cleared.
                 */
                ln->ln_router = 0;
                break;
        case ND_ROUTER_ADVERT:
                /*
                 * Mark an entry with lladdr as a router.
                 */
                if ((!is_newentry && (olladdr || lladdr)) ||    /* (2-5) */
                    (is_newentry && lladdr)) {                  /* (7) */
                        ln->ln_router = 1;
                }
                break;
        }

        rtfree(rt);
}

void
nd6_slowtimo(void *ignored_arg)
{
        struct nd_ifinfo *nd6if;
        struct ifnet *ifp;

        NET_LOCK();

        timeout_add_sec(&nd6_slowtimo_ch, ND6_SLOWTIMER_INTERVAL);

        TAILQ_FOREACH(ifp, &ifnetlist, if_list) {
                nd6if = ifp->if_nd;
                if ((nd6if->recalctm -= ND6_SLOWTIMER_INTERVAL) <= 0) {
                        /*
                         * Since reachable time rarely changes by router
                         * advertisements, we SHOULD insure that a new random
                         * value gets recomputed at least once every few hours.
                         * (RFC 2461, 6.3.4)
                         */
                        nd6if->recalctm = ND6_RECALC_REACHTM_INTERVAL;
                        nd6if->reachable = ND_COMPUTE_RTIME(REACHABLE_TIME);
                }
        }
        NET_UNLOCK();
}

int
nd6_resolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
    struct sockaddr *dst, u_char *desten)
{
        struct sockaddr_dl *sdl;
        struct rtentry *rt;
        struct llinfo_nd6 *ln;
        struct in6_addr saddr6;
        time_t uptime;
        int solicit = 0;

        if (m->m_flags & M_MCAST) {
                ETHER_MAP_IPV6_MULTICAST(&satosin6(dst)->sin6_addr, desten);
                return (0);
        }

        uptime = getuptime();
        rt = rt_getll(rt0);

        if (rt == NULL || (ISSET(rt->rt_flags, RTF_REJECT) &&
            (rt->rt_expire == 0 || rt->rt_expire > uptime))) {
                m_freem(m);
                return (rt == rt0 ? EHOSTDOWN : EHOSTUNREACH);
        }

        /*
         * Address resolution or Neighbor Unreachability Detection
         * for the next hop.
         * At this point, the destination of the packet must be a unicast
         * or an anycast address(i.e. not a multicast).
         */
        if (!ISSET(rt->rt_flags, RTF_LLINFO)) {
                char addr[INET6_ADDRSTRLEN];
                log(LOG_DEBUG, "%s: %s: route contains no ND information\n",
                    __func__, inet_ntop(AF_INET6,
                    &satosin6(rt_key(rt))->sin6_addr, addr, sizeof(addr)));
                goto bad;
        }

        if (rt->rt_gateway->sa_family != AF_LINK) {
                printf("%s: something odd happens\n", __func__);
                goto bad;
        }

        mtx_enter(&nd6_mtx);
        ln = (struct llinfo_nd6 *)rt->rt_llinfo;
        if (ln == NULL) {
                mtx_leave(&nd6_mtx);
                goto bad;
        }

        /*
         * Move this entry to the head of the queue so that it is less likely
         * for this entry to be a target of forced garbage collection (see
         * nd6_rtrequest()).
         */
        TAILQ_REMOVE(&nd6_list, ln, ln_list);
        TAILQ_INSERT_HEAD(&nd6_list, ln, ln_list);

        /*
         * The first time we send a packet to a neighbor whose entry is
         * STALE, we have to change the state to DELAY and set a timer to
         * expire in DELAY_FIRST_PROBE_TIME seconds to ensure we do
         * neighbor unreachability detection on expiration.
         * (RFC 2461 7.3.3)
         */
        if (ln->ln_state == ND6_LLINFO_STALE) {
                ln->ln_asked = 0;
                ln->ln_state = ND6_LLINFO_DELAY;
                nd6_llinfo_settimer(ln, atomic_load_int(&nd6_delay));
        }

        /*
         * If the neighbor cache entry has a state other than INCOMPLETE
         * (i.e. its link-layer address is already resolved), just
         * send the packet.
         */
        if (ln->ln_state > ND6_LLINFO_INCOMPLETE) {
                mtx_leave(&nd6_mtx);

                sdl = satosdl(rt->rt_gateway);
                if (sdl->sdl_alen != ETHER_ADDR_LEN) {
                        char addr[INET6_ADDRSTRLEN];
                        log(LOG_DEBUG, "%s: %s: incorrect nd6 information\n",
                            __func__,
                            inet_ntop(AF_INET6, &satosin6(dst)->sin6_addr,
                                addr, sizeof(addr)));
                        goto bad;
                }

                bcopy(LLADDR(sdl), desten, sdl->sdl_alen);
                return (0);
        }

        /*
         * There is a neighbor cache entry, but no ethernet address
         * response yet.  Insert mbuf in hold queue if below limit.
         * If above the limit free the queue without queuing the new packet.
         */
        if (ln->ln_state == ND6_LLINFO_NOSTATE)
                ln->ln_state = ND6_LLINFO_INCOMPLETE;
        /* source address of prompting packet is needed by nd6_ns_output() */
        if (m->m_len >= sizeof(struct ip6_hdr)) {
                memcpy(&ln->ln_saddr6, &mtod(m, struct ip6_hdr *)->ip6_src,
                    sizeof(ln->ln_saddr6));
        }
        if (atomic_inc_int_nv(&ln_hold_total) <= LN_HOLD_TOTAL) {
                if (mq_push(&ln->ln_mq, m) != 0)
                        atomic_dec_int(&ln_hold_total);
        } else {
                atomic_sub_int(&ln_hold_total, mq_purge(&ln->ln_mq) + 1);
                m_freem(m);
        }

        /*
         * If there has been no NS for the neighbor after entering the
         * INCOMPLETE state, send the first solicitation.
         */
        if (!ND6_LLINFO_PERMANENT(ln) && ln->ln_asked == 0) {
                ln->ln_asked++;
                nd6_llinfo_settimer(ln, RETRANS_TIMER / 1000);
                saddr6 = ln->ln_saddr6;
                solicit = 1;
        }
        mtx_leave(&nd6_mtx);

        if (solicit)
                nd6_ns_output(ifp, NULL, &satosin6(dst)->sin6_addr, &saddr6, 0);
        return (EAGAIN);

bad:
        m_freem(m);
        return (EINVAL);
}

int
nd6_need_cache(struct ifnet *ifp)
{
        /*
         * RFC2893 says:
         * - unidirectional tunnels needs no ND
         */
        switch (ifp->if_type) {
        case IFT_ETHER:
        case IFT_IEEE80211:
        case IFT_CARP:
                return (1);
        default:
                return (0);
        }
}