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[FreeBSD/FreeBSD.git] / sys / netinet6 / nd6.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.c,v 1.144 2001/05/24 07:44:00 itojun Exp $
 */

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

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

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/eventhandler.h>
#include <sys/callout.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/protosw.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/rwlock.h>
#include <sys/queue.h>
#include <sys/sdt.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/if_private.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/route/route_ctl.h>
#include <net/route/nhop.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <net/if_llatbl.h>
#include <netinet/if_ether.h>
#include <netinet6/in6_fib.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>
#include <netinet6/in6_ifattach.h>
#include <netinet/icmp6.h>
#include <netinet6/send.h>

#include <sys/limits.h>

#include <security/mac/mac_framework.h>

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

#define SIN6(s) ((const struct sockaddr_in6 *)(s))

MALLOC_DEFINE(M_IP6NDP, "ip6ndp", "IPv6 Neighbor Discovery");

/* timer values */
VNET_DEFINE(int, nd6_prune)     = 1;    /* walk list every 1 seconds */
VNET_DEFINE(int, nd6_delay)     = 5;    /* delay first probe time 5 second */
VNET_DEFINE(int, nd6_umaxtries) = 3;    /* maximum unicast query */
VNET_DEFINE(int, nd6_mmaxtries) = 3;    /* maximum multicast query */
VNET_DEFINE(int, nd6_useloopback) = 1;  /* use loopback interface for
                                         * local traffic */
VNET_DEFINE(int, nd6_gctimer)   = (60 * 60 * 24); /* 1 day: garbage
                                         * collection timer */

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

VNET_DEFINE(int, nd6_maxnudhint) = 0;   /* max # of subsequent upper
                                         * layer hints */
VNET_DEFINE_STATIC(int, nd6_maxqueuelen) = 16; /* max pkts cached in unresolved
                                         * ND entries */
#define V_nd6_maxndopt                  VNET(nd6_maxndopt)
#define V_nd6_maxqueuelen               VNET(nd6_maxqueuelen)

#ifdef ND6_DEBUG
VNET_DEFINE(int, nd6_debug) = 1;
#else
VNET_DEFINE(int, nd6_debug) = 0;
#endif

static eventhandler_tag lle_event_eh, iflladdr_event_eh, ifnet_link_event_eh;

VNET_DEFINE(struct nd_prhead, nd_prefix);
VNET_DEFINE(struct rwlock, nd6_lock);
VNET_DEFINE(uint64_t, nd6_list_genid);
VNET_DEFINE(struct mtx, nd6_onlink_mtx);

VNET_DEFINE(int, nd6_recalc_reachtm_interval) = ND6_RECALC_REACHTM_INTERVAL;
#define V_nd6_recalc_reachtm_interval   VNET(nd6_recalc_reachtm_interval)

int     (*send_sendso_input_hook)(struct mbuf *, struct ifnet *, int, int);

static bool nd6_is_new_addr_neighbor(const struct sockaddr_in6 *,
        struct ifnet *);
static void nd6_setmtu0(struct ifnet *, struct nd_ifinfo *);
static void nd6_slowtimo(void *);
static int regen_tmpaddr(struct in6_ifaddr *);
static void nd6_free(struct llentry **, int);
static void nd6_free_redirect(const struct llentry *);
static void nd6_llinfo_timer(void *);
static void nd6_llinfo_settimer_locked(struct llentry *, long);
static int nd6_resolve_slow(struct ifnet *, int, int, struct mbuf *,
    const struct sockaddr_in6 *, u_char *, uint32_t *, struct llentry **);
static int nd6_need_cache(struct ifnet *);

VNET_DEFINE_STATIC(struct callout, nd6_slowtimo_ch);
#define V_nd6_slowtimo_ch               VNET(nd6_slowtimo_ch)

VNET_DEFINE_STATIC(struct callout, nd6_timer_ch);
#define V_nd6_timer_ch                  VNET(nd6_timer_ch)

SYSCTL_DECL(_net_inet6_icmp6);

static void
nd6_lle_event(void *arg __unused, struct llentry *lle, int evt)
{
        struct rt_addrinfo rtinfo;
        struct sockaddr_in6 dst;
        struct sockaddr_dl gw;
        struct ifnet *ifp;
        int type;
        int fibnum;

        LLE_WLOCK_ASSERT(lle);

        if (lltable_get_af(lle->lle_tbl) != AF_INET6)
                return;

        switch (evt) {
        case LLENTRY_RESOLVED:
                type = RTM_ADD;
                KASSERT(lle->la_flags & LLE_VALID,
                    ("%s: %p resolved but not valid?", __func__, lle));
                break;
        case LLENTRY_EXPIRED:
                type = RTM_DELETE;
                break;
        default:
                return;
        }

        ifp = lltable_get_ifp(lle->lle_tbl);

        bzero(&dst, sizeof(dst));
        bzero(&gw, sizeof(gw));
        bzero(&rtinfo, sizeof(rtinfo));
        lltable_fill_sa_entry(lle, (struct sockaddr *)&dst);
        dst.sin6_scope_id = in6_getscopezone(ifp,
            in6_addrscope(&dst.sin6_addr));
        gw.sdl_len = sizeof(struct sockaddr_dl);
        gw.sdl_family = AF_LINK;
        gw.sdl_alen = ifp->if_addrlen;
        gw.sdl_index = ifp->if_index;
        gw.sdl_type = ifp->if_type;
        if (evt == LLENTRY_RESOLVED)
                bcopy(lle->ll_addr, gw.sdl_data, ifp->if_addrlen);
        rtinfo.rti_info[RTAX_DST] = (struct sockaddr *)&dst;
        rtinfo.rti_info[RTAX_GATEWAY] = (struct sockaddr *)&gw;
        rtinfo.rti_addrs = RTA_DST | RTA_GATEWAY;
        fibnum = V_rt_add_addr_allfibs ? RT_ALL_FIBS : ifp->if_fib;
        rt_missmsg_fib(type, &rtinfo, RTF_HOST | RTF_LLDATA | (
            type == RTM_ADD ? RTF_UP: 0), 0, fibnum);
}

/*
 * A handler for interface link layer address change event.
 */
static void
nd6_iflladdr(void *arg __unused, struct ifnet *ifp)
{
        if (ifp->if_afdata[AF_INET6] == NULL)
                return;

        lltable_update_ifaddr(LLTABLE6(ifp));
}

void
nd6_init(void)
{

        mtx_init(&V_nd6_onlink_mtx, "nd6 onlink", NULL, MTX_DEF);
        rw_init(&V_nd6_lock, "nd6 list");

        LIST_INIT(&V_nd_prefix);
        nd6_defrouter_init();

        /* Start timers. */
        callout_init(&V_nd6_slowtimo_ch, 1);
        callout_reset(&V_nd6_slowtimo_ch, ND6_SLOWTIMER_INTERVAL * hz,
            nd6_slowtimo, curvnet);

        callout_init(&V_nd6_timer_ch, 1);
        callout_reset(&V_nd6_timer_ch, hz, nd6_timer, curvnet);

        nd6_dad_init();
        if (IS_DEFAULT_VNET(curvnet)) {
                lle_event_eh = EVENTHANDLER_REGISTER(lle_event, nd6_lle_event,
                    NULL, EVENTHANDLER_PRI_ANY);
                iflladdr_event_eh = EVENTHANDLER_REGISTER(iflladdr_event,
                    nd6_iflladdr, NULL, EVENTHANDLER_PRI_ANY);
                ifnet_link_event_eh = EVENTHANDLER_REGISTER(ifnet_link_event,
                    nd6_ifnet_link_event, NULL, EVENTHANDLER_PRI_ANY);
        }
}

#ifdef VIMAGE
void
nd6_destroy(void)
{

        callout_drain(&V_nd6_slowtimo_ch);
        callout_drain(&V_nd6_timer_ch);
        if (IS_DEFAULT_VNET(curvnet)) {
                EVENTHANDLER_DEREGISTER(ifnet_link_event, ifnet_link_event_eh);
                EVENTHANDLER_DEREGISTER(lle_event, lle_event_eh);
                EVENTHANDLER_DEREGISTER(iflladdr_event, iflladdr_event_eh);
        }
        rw_destroy(&V_nd6_lock);
        mtx_destroy(&V_nd6_onlink_mtx);
}
#endif

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

        nd = malloc(sizeof(*nd), M_IP6NDP, M_WAITOK | M_ZERO);
        nd->initialized = 1;

        nd->chlim = IPV6_DEFHLIM;
        nd->basereachable = REACHABLE_TIME;
        nd->reachable = ND_COMPUTE_RTIME(nd->basereachable);
        nd->retrans = RETRANS_TIMER;

        nd->flags = ND6_IFF_PERFORMNUD;

        /* Set IPv6 disabled on all interfaces but loopback by default. */
        if ((ifp->if_flags & IFF_LOOPBACK) == 0)
                nd->flags |= ND6_IFF_IFDISABLED;

        /* A loopback interface always has ND6_IFF_AUTO_LINKLOCAL.
         * XXXHRS: Clear ND6_IFF_AUTO_LINKLOCAL on an IFT_BRIDGE interface by
         * default regardless of the V_ip6_auto_linklocal configuration to
         * give a reasonable default behavior.
         */
        if ((V_ip6_auto_linklocal && ifp->if_type != IFT_BRIDGE &&
            ifp->if_type != IFT_WIREGUARD) || (ifp->if_flags & IFF_LOOPBACK))
                nd->flags |= ND6_IFF_AUTO_LINKLOCAL;
        /*
         * A loopback interface does not need to accept RTADV.
         * XXXHRS: Clear ND6_IFF_ACCEPT_RTADV on an IFT_BRIDGE interface by
         * default regardless of the V_ip6_accept_rtadv configuration to
         * prevent the interface from accepting RA messages arrived
         * on one of the member interfaces with ND6_IFF_ACCEPT_RTADV.
         */
        if (V_ip6_accept_rtadv &&
            !(ifp->if_flags & IFF_LOOPBACK) &&
            (ifp->if_type != IFT_BRIDGE)) {
                        nd->flags |= ND6_IFF_ACCEPT_RTADV;
                        /* If we globally accept rtadv, assume IPv6 on. */
                        nd->flags &= ~ND6_IFF_IFDISABLED;
        }
        if (V_ip6_no_radr && !(ifp->if_flags & IFF_LOOPBACK))
                nd->flags |= ND6_IFF_NO_RADR;

        /* XXX: we cannot call nd6_setmtu since ifp is not fully initialized */
        nd6_setmtu0(ifp, nd);

        return nd;
}

void
nd6_ifdetach(struct ifnet *ifp, struct nd_ifinfo *nd)
{
        struct epoch_tracker et;
        struct ifaddr *ifa, *next;

        NET_EPOCH_ENTER(et);
        CK_STAILQ_FOREACH_SAFE(ifa, &ifp->if_addrhead, ifa_link, next) {
                if (ifa->ifa_addr->sa_family != AF_INET6)
                        continue;

                /* stop DAD processing */
                nd6_dad_stop(ifa);
        }
        NET_EPOCH_EXIT(et);

        free(nd, M_IP6NDP);
}

/*
 * Reset ND level link MTU. This function is called when the physical MTU
 * changes, which means we might have to adjust the ND level MTU.
 */
void
nd6_setmtu(struct ifnet *ifp)
{
        if (ifp->if_afdata[AF_INET6] == NULL)
                return;

        nd6_setmtu0(ifp, ND_IFINFO(ifp));
}

/* XXX todo: do not maintain copy of ifp->if_mtu in ndi->maxmtu */
void
nd6_setmtu0(struct ifnet *ifp, struct nd_ifinfo *ndi)
{
        u_int32_t omaxmtu;

        omaxmtu = ndi->maxmtu;
        ndi->maxmtu = ifp->if_mtu;

        /*
         * Decreasing the interface MTU under IPV6 minimum MTU may cause
         * undesirable situation.  We thus notify the operator of the change
         * explicitly.  The check for omaxmtu is necessary to restrict the
         * log to the case of changing the MTU, not initializing it.
         */
        if (omaxmtu >= IPV6_MMTU && ndi->maxmtu < IPV6_MMTU) {
                log(LOG_NOTICE, "nd6_setmtu0: "
                    "new link MTU on %s (%lu) is too small for IPv6\n",
                    if_name(ifp), (unsigned long)ndi->maxmtu);
        }

        if (ndi->maxmtu > V_in6_maxmtu)
                in6_setmaxmtu(); /* check all interfaces just in case */

}

void
nd6_option_init(void *opt, int icmp6len, union nd_opts *ndopts)
{

        bzero(ndopts, sizeof(*ndopts));
        ndopts->nd_opts_search = (struct nd_opt_hdr *)opt;
        ndopts->nd_opts_last
                = (struct nd_opt_hdr *)(((u_char *)opt) + icmp6len);

        if (icmp6len == 0) {
                ndopts->nd_opts_done = 1;
                ndopts->nd_opts_search = NULL;
        }
}

/*
 * Take one ND option.
 */
struct nd_opt_hdr *
nd6_option(union nd_opts *ndopts)
{
        struct nd_opt_hdr *nd_opt;
        int olen;

        KASSERT(ndopts != NULL, ("%s: ndopts == NULL", __func__));
        KASSERT(ndopts->nd_opts_last != NULL, ("%s: uninitialized ndopts",
            __func__));
        if (ndopts->nd_opts_search == NULL)
                return NULL;
        if (ndopts->nd_opts_done)
                return NULL;

        nd_opt = ndopts->nd_opts_search;

        /* make sure nd_opt_len is inside the buffer */
        if ((caddr_t)&nd_opt->nd_opt_len >= (caddr_t)ndopts->nd_opts_last) {
                bzero(ndopts, sizeof(*ndopts));
                return NULL;
        }

        olen = nd_opt->nd_opt_len << 3;
        if (olen == 0) {
                /*
                 * Message validation requires that all included
                 * options have a length that is greater than zero.
                 */
                bzero(ndopts, sizeof(*ndopts));
                return NULL;
        }

        ndopts->nd_opts_search = (struct nd_opt_hdr *)((caddr_t)nd_opt + olen);
        if (ndopts->nd_opts_search > ndopts->nd_opts_last) {
                /* option overruns the end of buffer, invalid */
                bzero(ndopts, sizeof(*ndopts));
                return NULL;
        } else if (ndopts->nd_opts_search == ndopts->nd_opts_last) {
                /* reached the end of options chain */
                ndopts->nd_opts_done = 1;
                ndopts->nd_opts_search = NULL;
        }
        return nd_opt;
}

/*
 * 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(union nd_opts *ndopts)
{
        struct nd_opt_hdr *nd_opt;
        int i = 0;

        KASSERT(ndopts != NULL, ("%s: ndopts == NULL", __func__));
        KASSERT(ndopts->nd_opts_last != NULL, ("%s: uninitialized ndopts",
            __func__));
        if (ndopts->nd_opts_search == NULL)
                return 0;

        while (1) {
                nd_opt = nd6_option(ndopts);
                if (nd_opt == NULL && ndopts->nd_opts_last == NULL) {
                        /*
                         * Message validation requires that all included
                         * options have a length that is greater than zero.
                         */
                        ICMP6STAT_INC(icp6s_nd_badopt);
                        bzero(ndopts, sizeof(*ndopts));
                        return -1;
                }

                if (nd_opt == NULL)
                        goto skip1;

                switch (nd_opt->nd_opt_type) {
                case ND_OPT_SOURCE_LINKADDR:
                case ND_OPT_TARGET_LINKADDR:
                case ND_OPT_MTU:
                case ND_OPT_REDIRECTED_HEADER:
                case ND_OPT_NONCE:
                        if (ndopts->nd_opt_array[nd_opt->nd_opt_type]) {
                                nd6log((LOG_INFO,
                                    "duplicated ND6 option found (type=%d)\n",
                                    nd_opt->nd_opt_type));
                                /* XXX bark? */
                        } else {
                                ndopts->nd_opt_array[nd_opt->nd_opt_type]
                                        = nd_opt;
                        }
                        break;
                case ND_OPT_PREFIX_INFORMATION:
                        if (ndopts->nd_opt_array[nd_opt->nd_opt_type] == 0) {
                                ndopts->nd_opt_array[nd_opt->nd_opt_type]
                                        = nd_opt;
                        }
                        ndopts->nd_opts_pi_end =
                                (struct nd_opt_prefix_info *)nd_opt;
                        break;
                /* What about ND_OPT_ROUTE_INFO? RFC 4191 */
                case ND_OPT_RDNSS:      /* RFC 6106 */
                case ND_OPT_DNSSL:      /* RFC 6106 */
                        /*
                         * Silently ignore options we know and do not care about
                         * in the kernel.
                         */
                        break;
                default:
                        /*
                         * Unknown options must be silently ignored,
                         * to accommodate future extension to the protocol.
                         */
                        nd6log((LOG_DEBUG,
                            "nd6_options: unsupported option %d - "
                            "option ignored\n", nd_opt->nd_opt_type));
                }

skip1:
                i++;
                if (i > V_nd6_maxndopt) {
                        ICMP6STAT_INC(icp6s_nd_toomanyopt);
                        nd6log((LOG_INFO, "too many loop in nd opt\n"));
                        break;
                }

                if (ndopts->nd_opts_done)
                        break;
        }

        return 0;
}

/*
 * ND6 timer routine to handle ND6 entries
 */
static void
nd6_llinfo_settimer_locked(struct llentry *ln, long tick)
{
        int canceled;

        LLE_WLOCK_ASSERT(ln);

        /* Do not schedule timers for child LLEs. */
        if (ln->la_flags & LLE_CHILD)
                return;

        if (tick < 0) {
                ln->la_expire = 0;
                ln->ln_ntick = 0;
                canceled = callout_stop(&ln->lle_timer);
        } else {
                ln->la_expire = time_uptime + tick / hz;
                LLE_ADDREF(ln);
                if (tick > INT_MAX) {
                        ln->ln_ntick = tick - INT_MAX;
                        canceled = callout_reset(&ln->lle_timer, INT_MAX,
                            nd6_llinfo_timer, ln);
                } else {
                        ln->ln_ntick = 0;
                        canceled = callout_reset(&ln->lle_timer, tick,
                            nd6_llinfo_timer, ln);
                }
        }
        if (canceled > 0)
                LLE_REMREF(ln);
}

/*
 * Gets source address of the first packet in hold queue
 * and stores it in @src.
 * Returns pointer to @src (if hold queue is not empty) or NULL.
 *
 * Set noinline to be dtrace-friendly
 */
static __noinline struct in6_addr *
nd6_llinfo_get_holdsrc(struct llentry *ln, struct in6_addr *src)
{
        struct ip6_hdr hdr;
        struct mbuf *m;

        if (ln->la_hold == NULL)
                return (NULL);

        /*
         * assume every packet in la_hold has the same IP header
         */
        m = ln->la_hold;
        if (sizeof(hdr) > m->m_len)
                return (NULL);

        m_copydata(m, 0, sizeof(hdr), (caddr_t)&hdr);
        *src = hdr.ip6_src;

        return (src);
}

/*
 * Checks if we need to switch from STALE state.
 *
 * RFC 4861 requires switching from STALE to DELAY state
 * on first packet matching entry, waiting V_nd6_delay and
 * transition to PROBE state (if upper layer confirmation was
 * not received).
 *
 * This code performs a bit differently:
 * On packet hit we don't change state (but desired state
 * can be guessed by control plane). However, after V_nd6_delay
 * seconds code will transition to PROBE state (so DELAY state
 * is kinda skipped in most situations).
 *
 * Typically, V_nd6_gctimer is bigger than V_nd6_delay, so
 * we perform the following upon entering STALE state:
 *
 * 1) Arm timer to run each V_nd6_delay seconds to make sure that
 * if packet was transmitted at the start of given interval, we
 * would be able to switch to PROBE state in V_nd6_delay seconds
 * as user expects.
 *
 * 2) Reschedule timer until original V_nd6_gctimer expires keeping
 * lle in STALE state (remaining timer value stored in lle_remtime).
 *
 * 3) Reschedule timer if packet was transmitted less that V_nd6_delay
 * seconds ago.
 *
 * Returns non-zero value if the entry is still STALE (storing
 * the next timer interval in @pdelay).
 *
 * Returns zero value if original timer expired or we need to switch to
 * PROBE (store that in @do_switch variable).
 */
static int
nd6_is_stale(struct llentry *lle, long *pdelay, int *do_switch)
{
        int nd_delay, nd_gctimer;
        time_t lle_hittime;
        long delay;

        *do_switch = 0;
        nd_gctimer = V_nd6_gctimer;
        nd_delay = V_nd6_delay;

        lle_hittime = llentry_get_hittime(lle);

        if (lle_hittime == 0) {
                /*
                 * Datapath feedback has been requested upon entering
                 * STALE state. No packets has been passed using this lle.
                 * Ask for the timer reschedule and keep STALE state.
                 */
                delay = (long)(MIN(nd_gctimer, nd_delay));
                delay *= hz;
                if (lle->lle_remtime > delay)
                        lle->lle_remtime -= delay;
                else {
                        delay = lle->lle_remtime;
                        lle->lle_remtime = 0;
                }

                if (delay == 0) {
                        /*
                         * The original ng6_gctime timeout ended,
                         * no more rescheduling.
                         */
                        return (0);
                }

                *pdelay = delay;
                return (1);
        }

        /*
         * Packet received. Verify timestamp
         */
        delay = (long)(time_uptime - lle_hittime);
        if (delay < nd_delay) {
                /*
                 * V_nd6_delay still not passed since the first
                 * hit in STALE state.
                 * Reschedule timer and return.
                 */
                *pdelay = (long)(nd_delay - delay) * hz;
                return (1);
        }

        /* Request switching to probe */
        *do_switch = 1;
        return (0);
}

/*
 * Switch @lle state to new state optionally arming timers.
 *
 * Set noinline to be dtrace-friendly
 */
__noinline void
nd6_llinfo_setstate(struct llentry *lle, int newstate)
{
        struct ifnet *ifp;
        int nd_gctimer, nd_delay;
        long delay, remtime;

        delay = 0;
        remtime = 0;

        switch (newstate) {
        case ND6_LLINFO_INCOMPLETE:
                ifp = lle->lle_tbl->llt_ifp;
                delay = (long)ND_IFINFO(ifp)->retrans * hz / 1000;
                break;
        case ND6_LLINFO_REACHABLE:
                if (!ND6_LLINFO_PERMANENT(lle)) {
                        ifp = lle->lle_tbl->llt_ifp;
                        delay = (long)ND_IFINFO(ifp)->reachable * hz;
                }
                break;
        case ND6_LLINFO_STALE:

                llentry_request_feedback(lle);
                nd_delay = V_nd6_delay;
                nd_gctimer = V_nd6_gctimer;

                delay = (long)(MIN(nd_gctimer, nd_delay)) * hz;
                remtime = (long)nd_gctimer * hz - delay;
                break;
        case ND6_LLINFO_DELAY:
                lle->la_asked = 0;
                delay = (long)V_nd6_delay * hz;
                break;
        }

        if (delay > 0)
                nd6_llinfo_settimer_locked(lle, delay);

        lle->lle_remtime = remtime;
        lle->ln_state = newstate;
}

/*
 * Timer-dependent part of nd state machine.
 *
 * Set noinline to be dtrace-friendly
 */
static __noinline void
nd6_llinfo_timer(void *arg)
{
        struct epoch_tracker et;
        struct llentry *ln;
        struct in6_addr *dst, *pdst, *psrc, src;
        struct ifnet *ifp;
        struct nd_ifinfo *ndi;
        int do_switch, send_ns;
        long delay;

        KASSERT(arg != NULL, ("%s: arg NULL", __func__));
        ln = (struct llentry *)arg;
        ifp = lltable_get_ifp(ln->lle_tbl);
        CURVNET_SET(ifp->if_vnet);

        ND6_RLOCK();
        LLE_WLOCK(ln);
        if (callout_pending(&ln->lle_timer)) {
                /*
                 * Here we are a bit odd here in the treatment of 
                 * active/pending. If the pending bit is set, it got
                 * rescheduled before I ran. The active
                 * bit we ignore, since if it was stopped
                 * in ll_tablefree() and was currently running
                 * it would have return 0 so the code would
                 * not have deleted it since the callout could
                 * not be stopped so we want to go through
                 * with the delete here now. If the callout
                 * was restarted, the pending bit will be back on and
                 * we just want to bail since the callout_reset would
                 * return 1 and our reference would have been removed
                 * by nd6_llinfo_settimer_locked above since canceled
                 * would have been 1.
                 */
                LLE_WUNLOCK(ln);
                ND6_RUNLOCK();
                CURVNET_RESTORE();
                return;
        }
        NET_EPOCH_ENTER(et);
        ndi = ND_IFINFO(ifp);
        send_ns = 0;
        dst = &ln->r_l3addr.addr6;
        pdst = dst;

        if (ln->ln_ntick > 0) {
                if (ln->ln_ntick > INT_MAX) {
                        ln->ln_ntick -= INT_MAX;
                        nd6_llinfo_settimer_locked(ln, INT_MAX);
                } else {
                        ln->ln_ntick = 0;
                        nd6_llinfo_settimer_locked(ln, ln->ln_ntick);
                }
                goto done;
        }

        if (ln->la_flags & LLE_STATIC) {
                goto done;
        }

        if (ln->la_flags & LLE_DELETED) {
                nd6_free(&ln, 0);
                goto done;
        }

        switch (ln->ln_state) {
        case ND6_LLINFO_INCOMPLETE:
                if (ln->la_asked < V_nd6_mmaxtries) {
                        ln->la_asked++;
                        send_ns = 1;
                        /* Send NS to multicast address */
                        pdst = NULL;
                } else {
                        struct mbuf *m;

                        ICMP6STAT_ADD(icp6s_dropped, ln->la_numheld);

                        m = ln->la_hold;
                        if (m != NULL) {
                                /*
                                 * assuming every packet in la_hold has the
                                 * same IP header.  Send error after unlock.
                                 */
                                ln->la_hold = m->m_nextpkt;
                                m->m_nextpkt = NULL;
                                ln->la_numheld--;
                        }
                        nd6_free(&ln, 0);
                        if (m != NULL) {
                                struct mbuf *n = m;

                                /*
                                 * if there are any ummapped mbufs, we
                                 * must free them, rather than using
                                 * them for an ICMP, as they cannot be
                                 * checksummed.
                                 */
                                while ((n = n->m_next) != NULL) {
                                        if (n->m_flags & M_EXTPG)
                                                break;
                                }
                                if (n != NULL) {
                                        m_freem(m);
                                        m = NULL;
                                } else {
                                        icmp6_error2(m, ICMP6_DST_UNREACH,
                                            ICMP6_DST_UNREACH_ADDR, 0, ifp);
                                }
                        }
                }
                break;
        case ND6_LLINFO_REACHABLE:
                if (!ND6_LLINFO_PERMANENT(ln))
                        nd6_llinfo_setstate(ln, ND6_LLINFO_STALE);
                break;

        case ND6_LLINFO_STALE:
                if (nd6_is_stale(ln, &delay, &do_switch) != 0) {
                        /*
                         * No packet has used this entry and GC timeout
                         * has not been passed. Reschedule timer and
                         * return.
                         */
                        nd6_llinfo_settimer_locked(ln, delay);
                        break;
                }

                if (do_switch == 0) {
                        /*
                         * GC timer has ended and entry hasn't been used.
                         * Run Garbage collector (RFC 4861, 5.3)
                         */
                        if (!ND6_LLINFO_PERMANENT(ln))
                                nd6_free(&ln, 1);
                        break;
                }

                /* Entry has been used AND delay timer has ended. */

                /* FALLTHROUGH */

        case ND6_LLINFO_DELAY:
                if (ndi && (ndi->flags & ND6_IFF_PERFORMNUD) != 0) {
                        /* We need NUD */
                        ln->la_asked = 1;
                        nd6_llinfo_setstate(ln, ND6_LLINFO_PROBE);
                        send_ns = 1;
                } else
                        nd6_llinfo_setstate(ln, ND6_LLINFO_STALE); /* XXX */
                break;
        case ND6_LLINFO_PROBE:
                if (ln->la_asked < V_nd6_umaxtries) {
                        ln->la_asked++;
                        send_ns = 1;
                } else {
                        nd6_free(&ln, 0);
                }
                break;
        default:
                panic("%s: paths in a dark night can be confusing: %d",
                    __func__, ln->ln_state);
        }
done:
        if (ln != NULL)
                ND6_RUNLOCK();
        if (send_ns != 0) {
                nd6_llinfo_settimer_locked(ln, (long)ndi->retrans * hz / 1000);
                psrc = nd6_llinfo_get_holdsrc(ln, &src);
                LLE_FREE_LOCKED(ln);
                ln = NULL;
                nd6_ns_output(ifp, psrc, pdst, dst, NULL);
        }

        if (ln != NULL)
                LLE_FREE_LOCKED(ln);
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
}

/*
 * ND6 timer routine to expire default route list and prefix list
 */
void
nd6_timer(void *arg)
{
        CURVNET_SET((struct vnet *) arg);
        struct epoch_tracker et;
        struct nd_prhead prl;
        struct nd_prefix *pr, *npr;
        struct ifnet *ifp;
        struct in6_ifaddr *ia6, *nia6;
        uint64_t genid;

        LIST_INIT(&prl);

        NET_EPOCH_ENTER(et);
        nd6_defrouter_timer();

        /*
         * expire interface addresses.
         * in the past the loop was inside prefix expiry processing.
         * However, from a stricter speci-confrmance standpoint, we should
         * rather separate address lifetimes and prefix lifetimes.
         *
         * XXXRW: in6_ifaddrhead locking.
         */
  addrloop:
        CK_STAILQ_FOREACH_SAFE(ia6, &V_in6_ifaddrhead, ia_link, nia6) {
                /* check address lifetime */
                if (IFA6_IS_INVALID(ia6)) {
                        int regen = 0;

                        /*
                         * If the expiring address is temporary, try
                         * regenerating a new one.  This would be useful when
                         * we suspended a laptop PC, then turned it on after a
                         * period that could invalidate all temporary
                         * addresses.  Although we may have to restart the
                         * loop (see below), it must be after purging the
                         * address.  Otherwise, we'd see an infinite loop of
                         * regeneration.
                         */
                        if (V_ip6_use_tempaddr &&
                            (ia6->ia6_flags & IN6_IFF_TEMPORARY) != 0) {
                                if (regen_tmpaddr(ia6) == 0)
                                        regen = 1;
                        }

                        in6_purgeaddr(&ia6->ia_ifa);

                        if (regen)
                                goto addrloop; /* XXX: see below */
                } else if (IFA6_IS_DEPRECATED(ia6)) {
                        int oldflags = ia6->ia6_flags;

                        ia6->ia6_flags |= IN6_IFF_DEPRECATED;

                        /*
                         * If a temporary address has just become deprecated,
                         * regenerate a new one if possible.
                         */
                        if (V_ip6_use_tempaddr &&
                            (ia6->ia6_flags & IN6_IFF_TEMPORARY) != 0 &&
                            (oldflags & IN6_IFF_DEPRECATED) == 0) {
                                if (regen_tmpaddr(ia6) == 0) {
                                        /*
                                         * A new temporary address is
                                         * generated.
                                         * XXX: this means the address chain
                                         * has changed while we are still in
                                         * the loop.  Although the change
                                         * would not cause disaster (because
                                         * it's not a deletion, but an
                                         * addition,) we'd rather restart the
                                         * loop just for safety.  Or does this
                                         * significantly reduce performance??
                                         */
                                        goto addrloop;
                                }
                        }
                } else if ((ia6->ia6_flags & IN6_IFF_TENTATIVE) != 0) {
                        /*
                         * Schedule DAD for a tentative address.  This happens
                         * if the interface was down or not running
                         * when the address was configured.
                         */
                        int delay;

                        delay = arc4random() %
                            (MAX_RTR_SOLICITATION_DELAY * hz);
                        nd6_dad_start((struct ifaddr *)ia6, delay);
                } else {
                        /*
                         * Check status of the interface.  If it is down,
                         * mark the address as tentative for future DAD.
                         */
                        ifp = ia6->ia_ifp;
                        if ((ND_IFINFO(ifp)->flags & ND6_IFF_NO_DAD) == 0 &&
                            ((ifp->if_flags & IFF_UP) == 0 ||
                            (ifp->if_drv_flags & IFF_DRV_RUNNING) == 0 ||
                            (ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED) != 0)){
                                ia6->ia6_flags &= ~IN6_IFF_DUPLICATED;
                                ia6->ia6_flags |= IN6_IFF_TENTATIVE;
                        }

                        /*
                         * A new RA might have made a deprecated address
                         * preferred.
                         */
                        ia6->ia6_flags &= ~IN6_IFF_DEPRECATED;
                }
        }
        NET_EPOCH_EXIT(et);

        ND6_WLOCK();
restart:
        LIST_FOREACH_SAFE(pr, &V_nd_prefix, ndpr_entry, npr) {
                /*
                 * Expire prefixes. Since the pltime is only used for
                 * autoconfigured addresses, pltime processing for prefixes is
                 * not necessary.
                 *
                 * Only unlink after all derived addresses have expired. This
                 * may not occur until two hours after the prefix has expired
                 * per RFC 4862. If the prefix expires before its derived
                 * addresses, mark it off-link. This will be done automatically
                 * after unlinking if no address references remain.
                 */
                if (pr->ndpr_vltime == ND6_INFINITE_LIFETIME ||
                    time_uptime - pr->ndpr_lastupdate <= pr->ndpr_vltime)
                        continue;

                if (pr->ndpr_addrcnt == 0) {
                        nd6_prefix_unlink(pr, &prl);
                        continue;
                }
                if ((pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
                        genid = V_nd6_list_genid;
                        nd6_prefix_ref(pr);
                        ND6_WUNLOCK();
                        ND6_ONLINK_LOCK();
                        (void)nd6_prefix_offlink(pr);
                        ND6_ONLINK_UNLOCK();
                        ND6_WLOCK();
                        nd6_prefix_rele(pr);
                        if (genid != V_nd6_list_genid)
                                goto restart;
                }
        }
        ND6_WUNLOCK();

        while ((pr = LIST_FIRST(&prl)) != NULL) {
                LIST_REMOVE(pr, ndpr_entry);
                nd6_prefix_del(pr);
        }

        callout_reset(&V_nd6_timer_ch, V_nd6_prune * hz,
            nd6_timer, curvnet);

        CURVNET_RESTORE();
}

/*
 * ia6 - deprecated/invalidated temporary address
 */
static int
regen_tmpaddr(struct in6_ifaddr *ia6)
{
        struct ifaddr *ifa;
        struct ifnet *ifp;
        struct in6_ifaddr *public_ifa6 = NULL;

        NET_EPOCH_ASSERT();

        ifp = ia6->ia_ifa.ifa_ifp;
        CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                struct in6_ifaddr *it6;

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

                it6 = (struct in6_ifaddr *)ifa;

                /* ignore no autoconf addresses. */
                if ((it6->ia6_flags & IN6_IFF_AUTOCONF) == 0)
                        continue;

                /* ignore autoconf addresses with different prefixes. */
                if (it6->ia6_ndpr == NULL || it6->ia6_ndpr != ia6->ia6_ndpr)
                        continue;

                /*
                 * Now we are looking at an autoconf address with the same
                 * prefix as ours.  If the address is temporary and is still
                 * preferred, do not create another one.  It would be rare, but
                 * could happen, for example, when we resume a laptop PC after
                 * a long period.
                 */
                if ((it6->ia6_flags & IN6_IFF_TEMPORARY) != 0 &&
                    !IFA6_IS_DEPRECATED(it6)) {
                        public_ifa6 = NULL;
                        break;
                }

                /*
                 * This is a public autoconf address that has the same prefix
                 * as ours.  If it is preferred, keep it.  We can't break the
                 * loop here, because there may be a still-preferred temporary
                 * address with the prefix.
                 */
                if (!IFA6_IS_DEPRECATED(it6))
                        public_ifa6 = it6;
        }
        if (public_ifa6 != NULL)
                ifa_ref(&public_ifa6->ia_ifa);

        if (public_ifa6 != NULL) {
                int e;

                if ((e = in6_tmpifadd(public_ifa6, 0, 0)) != 0) {
                        ifa_free(&public_ifa6->ia_ifa);
                        log(LOG_NOTICE, "regen_tmpaddr: failed to create a new"
                            " tmp addr,errno=%d\n", e);
                        return (-1);
                }
                ifa_free(&public_ifa6->ia_ifa);
                return (0);
        }

        return (-1);
}

/*
 * Remove prefix and default router list entries corresponding to ifp. Neighbor
 * cache entries are freed in in6_domifdetach().
 */
void
nd6_purge(struct ifnet *ifp)
{
        struct nd_prhead prl;
        struct nd_prefix *pr, *npr;

        LIST_INIT(&prl);

        /* Purge default router list entries toward ifp. */
        nd6_defrouter_purge(ifp);

        ND6_WLOCK();
        /*
         * Remove prefixes on ifp. We should have already removed addresses on
         * this interface, so no addresses should be referencing these prefixes.
         */
        LIST_FOREACH_SAFE(pr, &V_nd_prefix, ndpr_entry, npr) {
                if (pr->ndpr_ifp == ifp)
                        nd6_prefix_unlink(pr, &prl);
        }
        ND6_WUNLOCK();

        /* Delete the unlinked prefix objects. */
        while ((pr = LIST_FIRST(&prl)) != NULL) {
                LIST_REMOVE(pr, ndpr_entry);
                nd6_prefix_del(pr);
        }

        /* cancel default outgoing interface setting */
        if (V_nd6_defifindex == ifp->if_index)
                nd6_setdefaultiface(0);

        if (ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV) {
                /* Refresh default router list. */
                defrouter_select_fib(ifp->if_fib);
        }
}

/* 
 * the caller acquires and releases the lock on the lltbls
 * Returns the llentry locked
 */
struct llentry *
nd6_lookup(const struct in6_addr *addr6, int flags, struct ifnet *ifp)
{
        struct sockaddr_in6 sin6;
        struct llentry *ln;

        bzero(&sin6, sizeof(sin6));
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        sin6.sin6_family = AF_INET6;
        sin6.sin6_addr = *addr6;

        IF_AFDATA_LOCK_ASSERT(ifp);

        ln = lla_lookup(LLTABLE6(ifp), flags, (struct sockaddr *)&sin6);

        return (ln);
}

static struct llentry *
nd6_alloc(const struct in6_addr *addr6, int flags, struct ifnet *ifp)
{
        struct sockaddr_in6 sin6;
        struct llentry *ln;

        bzero(&sin6, sizeof(sin6));
        sin6.sin6_len = sizeof(struct sockaddr_in6);
        sin6.sin6_family = AF_INET6;
        sin6.sin6_addr = *addr6;

        ln = lltable_alloc_entry(LLTABLE6(ifp), 0, (struct sockaddr *)&sin6);
        if (ln != NULL)
                ln->ln_state = ND6_LLINFO_NOSTATE;

        return (ln);
}

/*
 * Test whether a given IPv6 address can be a neighbor.
 */
static bool
nd6_is_new_addr_neighbor(const struct sockaddr_in6 *addr, struct ifnet *ifp)
{

        /*
         * A link-local address is always a neighbor.
         * XXX: a link does not necessarily specify a single interface.
         */
        if (IN6_IS_ADDR_LINKLOCAL(&addr->sin6_addr)) {
                struct sockaddr_in6 sin6_copy;
                u_int32_t zone;

                /*
                 * We need sin6_copy since sa6_recoverscope() may modify the
                 * content (XXX).
                 */
                sin6_copy = *addr;
                if (sa6_recoverscope(&sin6_copy))
                        return (0); /* XXX: should be impossible */
                if (in6_setscope(&sin6_copy.sin6_addr, ifp, &zone))
                        return (0);
                if (sin6_copy.sin6_scope_id == zone)
                        return (1);
                else
                        return (0);
        }
        /* Checking global unicast */

        /* If an address is directly reachable, it is a neigbor */
        struct nhop_object *nh;
        nh = fib6_lookup(ifp->if_fib, &addr->sin6_addr, 0, NHR_NONE, 0);
        if (nh != NULL && nh->nh_aifp == ifp && (nh->nh_flags & NHF_GATEWAY) == 0)
                return (true);

        /*
         * Check prefixes with desired on-link state, as some may be not
         * installed in the routing table.
         */
        bool matched = false;
        struct nd_prefix *pr;
        ND6_RLOCK();
        LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                if (pr->ndpr_ifp != ifp)
                        continue;
                if ((pr->ndpr_stateflags & NDPRF_ONLINK) == 0)
                        continue;
                if (IN6_ARE_MASKED_ADDR_EQUAL(&pr->ndpr_prefix.sin6_addr,
                    &addr->sin6_addr, &pr->ndpr_mask)) {
                        matched = true;
                        break;
                }
        }
        ND6_RUNLOCK();
        if (matched)
                return (true);

        /*
         * If the address is assigned on the node of the other side of
         * a p2p interface, the address should be a neighbor.
         */
        if (ifp->if_flags & IFF_POINTOPOINT) {
                struct ifaddr *ifa;

                CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                        if (ifa->ifa_addr->sa_family != addr->sin6_family)
                                continue;
                        if (ifa->ifa_dstaddr != NULL &&
                            sa_equal(addr, ifa->ifa_dstaddr)) {
                                return (true);
                        }
                }
        }

        /*
         * If the default router list is empty, all addresses are regarded
         * as on-link, and thus, as a neighbor.
         */
        if (ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV &&
            nd6_defrouter_list_empty() &&
            V_nd6_defifindex == ifp->if_index) {
                return (1);
        }

        return (0);
}

/*
 * 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 llentry *lle;
        int rc = 0;

        NET_EPOCH_ASSERT();
        IF_AFDATA_UNLOCK_ASSERT(ifp);
        if (nd6_is_new_addr_neighbor(addr, ifp))
                return (1);

        /*
         * Even if the address matches none of our addresses, it might be
         * in the neighbor cache.
         */
        if ((lle = nd6_lookup(&addr->sin6_addr, LLE_SF(AF_INET6, 0), ifp)) != NULL) {
                LLE_RUNLOCK(lle);
                rc = 1;
        }
        return (rc);
}

static __noinline void
nd6_free_children(struct llentry *lle)
{
        struct llentry *child_lle;

        NET_EPOCH_ASSERT();
        LLE_WLOCK_ASSERT(lle);

        while ((child_lle = CK_SLIST_FIRST(&lle->lle_children)) != NULL) {
                LLE_WLOCK(child_lle);
                lltable_unlink_child_entry(child_lle);
                llentry_free(child_lle);
        }
}

/*
 * Tries to update @lle address/prepend data with new @lladdr.
 *
 * Returns true on success.
 * In any case, @lle is returned wlocked.
 */
static __noinline bool
nd6_try_set_entry_addr_locked(struct ifnet *ifp, struct llentry *lle, char *lladdr)
{
        u_char buf[LLE_MAX_LINKHDR];
        int fam, off;
        size_t sz;

        sz = sizeof(buf);
        if (lltable_calc_llheader(ifp, AF_INET6, lladdr, buf, &sz, &off) != 0)
                return (false);

        /* Update data */
        lltable_set_entry_addr(ifp, lle, buf, sz, off);

        struct llentry *child_lle;
        CK_SLIST_FOREACH(child_lle, &lle->lle_children, lle_child_next) {
                LLE_WLOCK(child_lle);
                fam = child_lle->r_family;
                sz = sizeof(buf);
                if (lltable_calc_llheader(ifp, fam, lladdr, buf, &sz, &off) == 0) {
                        /* success */
                        lltable_set_entry_addr(ifp, child_lle, buf, sz, off);
                        child_lle->ln_state = ND6_LLINFO_REACHABLE;
                }
                LLE_WUNLOCK(child_lle);
        }

        return (true);
}

bool
nd6_try_set_entry_addr(struct ifnet *ifp, struct llentry *lle, char *lladdr)
{
        NET_EPOCH_ASSERT();
        LLE_WLOCK_ASSERT(lle);

        if (!lltable_acquire_wlock(ifp, lle))
                return (false);
        bool ret = nd6_try_set_entry_addr_locked(ifp, lle, lladdr);
        IF_AFDATA_WUNLOCK(ifp);

        return (ret);
}

/*
 * Free an nd6 llinfo entry.
 * Since the function would cause significant changes in the kernel, DO NOT
 * make it global, unless you have a strong reason for the change, and are sure
 * that the change is safe.
 *
 * Set noinline to be dtrace-friendly
 */
static __noinline void
nd6_free(struct llentry **lnp, int gc)
{
        struct ifnet *ifp;
        struct llentry *ln;
        struct nd_defrouter *dr;

        ln = *lnp;
        *lnp = NULL;

        LLE_WLOCK_ASSERT(ln);
        ND6_RLOCK_ASSERT();

        KASSERT((ln->la_flags & LLE_CHILD) == 0, ("child lle"));

        ifp = lltable_get_ifp(ln->lle_tbl);
        if ((ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV) != 0)
                dr = defrouter_lookup_locked(&ln->r_l3addr.addr6, ifp);
        else
                dr = NULL;
        ND6_RUNLOCK();

        if ((ln->la_flags & LLE_DELETED) == 0)
                EVENTHANDLER_INVOKE(lle_event, ln, LLENTRY_EXPIRED);

        /*
         * we used to have pfctlinput(PRC_HOSTDEAD) here.
         * even though it is not harmful, it was not really necessary.
         */

        /* cancel timer */
        nd6_llinfo_settimer_locked(ln, -1);

        if (ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV) {
                if (dr != NULL && dr->expire &&
                    ln->ln_state == ND6_LLINFO_STALE && gc) {
                        /*
                         * If the reason for the deletion is just garbage
                         * collection, and the neighbor is an active default
                         * router, do not delete it.  Instead, reset the GC
                         * timer using the router's lifetime.
                         * Simply deleting the entry would affect default
                         * router selection, which is not necessarily a good
                         * thing, especially when we're using router preference
                         * values.
                         * XXX: the check for ln_state would be redundant,
                         *      but we intentionally keep it just in case.
                         */
                        if (dr->expire > time_uptime)
                                nd6_llinfo_settimer_locked(ln,
                                    (dr->expire - time_uptime) * hz);
                        else
                                nd6_llinfo_settimer_locked(ln,
                                    (long)V_nd6_gctimer * hz);

                        LLE_REMREF(ln);
                        LLE_WUNLOCK(ln);
                        defrouter_rele(dr);
                        return;
                }

                if (dr) {
                        /*
                         * Unreachability of a router might affect the default
                         * router selection and on-link detection of advertised
                         * prefixes.
                         */

                        /*
                         * Temporarily fake the state to choose a new default
                         * router and to perform on-link determination of
                         * prefixes correctly.
                         * Below the state will be set correctly,
                         * or the entry itself will be deleted.
                         */
                        ln->ln_state = ND6_LLINFO_INCOMPLETE;
                }

                if (ln->ln_router || dr) {
                        /*
                         * We need to unlock to avoid a LOR with rt6_flush() with the
                         * rnh and for the calls to pfxlist_onlink_check() and
                         * defrouter_select_fib() in the block further down for calls
                         * into nd6_lookup().  We still hold a ref.
                         */
                        LLE_WUNLOCK(ln);

                        /*
                         * 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(&ln->r_l3addr.addr6, ifp);
                }

                if (dr) {
                        /*
                         * Since defrouter_select_fib() does not affect the
                         * on-link determination and MIP6 needs the check
                         * before the default router selection, we perform
                         * the check now.
                         */
                        pfxlist_onlink_check();

                        /*
                         * Refresh default router list.
                         */
                        defrouter_select_fib(dr->ifp->if_fib);
                }

                /*
                 * If this entry was added by an on-link redirect, remove the
                 * corresponding host route.
                 */
                if (ln->la_flags & LLE_REDIRECT)
                        nd6_free_redirect(ln);

                if (ln->ln_router || dr)
                        LLE_WLOCK(ln);
        }

        /*
         * Save to unlock. We still hold an extra reference and will not
         * free(9) in llentry_free() if someone else holds one as well.
         */
        LLE_WUNLOCK(ln);
        IF_AFDATA_LOCK(ifp);
        LLE_WLOCK(ln);
        /* Guard against race with other llentry_free(). */
        if (ln->la_flags & LLE_LINKED) {
                /* Remove callout reference */
                LLE_REMREF(ln);
                lltable_unlink_entry(ln->lle_tbl, ln);
        }
        IF_AFDATA_UNLOCK(ifp);

        nd6_free_children(ln);

        llentry_free(ln);
        if (dr != NULL)
                defrouter_rele(dr);
}

static int
nd6_isdynrte(const struct rtentry *rt, const struct nhop_object *nh, void *xap)
{

        if (nh->nh_flags & NHF_REDIRECT)
                return (1);

        return (0);
}

/*
 * Remove the rtentry for the given llentry,
 * both of which were installed by a redirect.
 */
static void
nd6_free_redirect(const struct llentry *ln)
{
        int fibnum;
        struct sockaddr_in6 sin6;
        struct rib_cmd_info rc;
        struct epoch_tracker et;

        lltable_fill_sa_entry(ln, (struct sockaddr *)&sin6);

        NET_EPOCH_ENTER(et);
        for (fibnum = 0; fibnum < rt_numfibs; fibnum++)
                rib_del_route_px(fibnum, (struct sockaddr *)&sin6, 128,
                    nd6_isdynrte, NULL, 0, &rc);
        NET_EPOCH_EXIT(et);
}

/*
 * Updates status of the default router route.
 */
static void
check_release_defrouter(const struct rib_cmd_info *rc, void *_cbdata)
{
        struct nd_defrouter *dr;
        struct nhop_object *nh;

        nh = rc->rc_nh_old;

        if ((nh != NULL) && (nh->nh_flags & NHF_DEFAULT)) {
                dr = defrouter_lookup(&nh->gw6_sa.sin6_addr, nh->nh_ifp);
                if (dr != NULL) {
                        dr->installed = 0;
                        defrouter_rele(dr);
                }
        }
}

void
nd6_subscription_cb(struct rib_head *rnh, struct rib_cmd_info *rc, void *arg)
{

#ifdef ROUTE_MPATH
        rib_decompose_notification(rc, check_release_defrouter, NULL);
#else
        check_release_defrouter(rc, NULL);
#endif
}

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 in6_ndifreq *ndif = (struct in6_ndifreq *)data;
        struct epoch_tracker et;
        int error = 0;

        if (ifp->if_afdata[AF_INET6] == NULL)
                return (EPFNOSUPPORT);
        switch (cmd) {
        case OSIOCGIFINFO_IN6:
#define ND      ndi->ndi
                /* XXX: old ndp(8) assumes a positive value for linkmtu. */
                bzero(&ND, sizeof(ND));
                ND.linkmtu = IN6_LINKMTU(ifp);
                ND.maxmtu = ND_IFINFO(ifp)->maxmtu;
                ND.basereachable = ND_IFINFO(ifp)->basereachable;
                ND.reachable = ND_IFINFO(ifp)->reachable;
                ND.retrans = ND_IFINFO(ifp)->retrans;
                ND.flags = ND_IFINFO(ifp)->flags;
                ND.recalctm = ND_IFINFO(ifp)->recalctm;
                ND.chlim = ND_IFINFO(ifp)->chlim;
                break;
        case SIOCGIFINFO_IN6:
                ND = *ND_IFINFO(ifp);
                break;
        case SIOCSIFINFO_IN6:
                /*
                 * used to change host variables from userland.
                 * intended for a use on router to reflect RA configurations.
                 */
                /* 0 means 'unspecified' */
                if (ND.linkmtu != 0) {
                        if (ND.linkmtu < IPV6_MMTU ||
                            ND.linkmtu > IN6_LINKMTU(ifp)) {
                                error = EINVAL;
                                break;
                        }
                        ND_IFINFO(ifp)->linkmtu = ND.linkmtu;
                }

                if (ND.basereachable != 0) {
                        int obasereachable = ND_IFINFO(ifp)->basereachable;

                        ND_IFINFO(ifp)->basereachable = ND.basereachable;
                        if (ND.basereachable != obasereachable)
                                ND_IFINFO(ifp)->reachable =
                                    ND_COMPUTE_RTIME(ND.basereachable);
                }
                if (ND.retrans != 0)
                        ND_IFINFO(ifp)->retrans = ND.retrans;
                if (ND.chlim != 0)
                        ND_IFINFO(ifp)->chlim = ND.chlim;
                /* FALLTHROUGH */
        case SIOCSIFINFO_FLAGS:
        {
                struct ifaddr *ifa;
                struct in6_ifaddr *ia;

                if ((ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED) &&
                    !(ND.flags & ND6_IFF_IFDISABLED)) {
                        /* ifdisabled 1->0 transision */

                        /*
                         * If the interface is marked as ND6_IFF_IFDISABLED and
                         * has an link-local address with IN6_IFF_DUPLICATED,
                         * do not clear ND6_IFF_IFDISABLED.
                         * See RFC 4862, Section 5.4.5.
                         */
                        NET_EPOCH_ENTER(et);
                        CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                                if (ifa->ifa_addr->sa_family != AF_INET6)
                                        continue;
                                ia = (struct in6_ifaddr *)ifa;
                                if ((ia->ia6_flags & IN6_IFF_DUPLICATED) &&
                                    IN6_IS_ADDR_LINKLOCAL(IA6_IN6(ia)))
                                        break;
                        }
                        NET_EPOCH_EXIT(et);

                        if (ifa != NULL) {
                                /* LLA is duplicated. */
                                ND.flags |= ND6_IFF_IFDISABLED;
                                log(LOG_ERR, "Cannot enable an interface"
                                    " with a link-local address marked"
                                    " duplicate.\n");
                        } else {
                                ND_IFINFO(ifp)->flags &= ~ND6_IFF_IFDISABLED;
                                if (ifp->if_flags & IFF_UP)
                                        in6_if_up(ifp);
                        }
                } else if (!(ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED) &&
                            (ND.flags & ND6_IFF_IFDISABLED)) {
                        /* ifdisabled 0->1 transision */
                        /* Mark all IPv6 address as tentative. */

                        ND_IFINFO(ifp)->flags |= ND6_IFF_IFDISABLED;
                        if (V_ip6_dad_count > 0 &&
                            (ND_IFINFO(ifp)->flags & ND6_IFF_NO_DAD) == 0) {
                                NET_EPOCH_ENTER(et);
                                CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead,
                                    ifa_link) {
                                        if (ifa->ifa_addr->sa_family !=
                                            AF_INET6)
                                                continue;
                                        ia = (struct in6_ifaddr *)ifa;
                                        ia->ia6_flags |= IN6_IFF_TENTATIVE;
                                }
                                NET_EPOCH_EXIT(et);
                        }
                }

                if (ND.flags & ND6_IFF_AUTO_LINKLOCAL) {
                        if (!(ND_IFINFO(ifp)->flags & ND6_IFF_AUTO_LINKLOCAL)) {
                                /* auto_linklocal 0->1 transision */

                                /* If no link-local address on ifp, configure */
                                ND_IFINFO(ifp)->flags |= ND6_IFF_AUTO_LINKLOCAL;
                                in6_ifattach(ifp, NULL);
                        } else if (!(ND.flags & ND6_IFF_IFDISABLED) &&
                            ifp->if_flags & IFF_UP) {
                                /*
                                 * When the IF already has
                                 * ND6_IFF_AUTO_LINKLOCAL, no link-local
                                 * address is assigned, and IFF_UP, try to
                                 * assign one.
                                 */
                                NET_EPOCH_ENTER(et);
                                CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead,
                                    ifa_link) {
                                        if (ifa->ifa_addr->sa_family !=
                                            AF_INET6)
                                                continue;
                                        ia = (struct in6_ifaddr *)ifa;
                                        if (IN6_IS_ADDR_LINKLOCAL(IA6_IN6(ia)))
                                                break;
                                }
                                NET_EPOCH_EXIT(et);
                                if (ifa != NULL)
                                        /* No LLA is configured. */
                                        in6_ifattach(ifp, NULL);
                        }
                }
                ND_IFINFO(ifp)->flags = ND.flags;
                break;
        }
#undef ND
        case SIOCSNDFLUSH_IN6:  /* XXX: the ioctl name is confusing... */
                /* sync kernel routing table with the default router list */
                defrouter_reset();
                defrouter_select_fib(RT_ALL_FIBS);
                break;
        case SIOCSPFXFLUSH_IN6:
        {
                /* flush all the prefix advertised by routers */
                struct in6_ifaddr *ia, *ia_next;
                struct nd_prefix *pr, *next;
                struct nd_prhead prl;

                LIST_INIT(&prl);

                ND6_WLOCK();
                LIST_FOREACH_SAFE(pr, &V_nd_prefix, ndpr_entry, next) {
                        if (pr->ndpr_raf_ra_derived)
                                nd6_prefix_unlink(pr, &prl);
                }
                ND6_WUNLOCK();

                while ((pr = LIST_FIRST(&prl)) != NULL) {
                        LIST_REMOVE(pr, ndpr_entry);
                        /* XXXRW: in6_ifaddrhead locking. */
                        CK_STAILQ_FOREACH_SAFE(ia, &V_in6_ifaddrhead, ia_link,
                            ia_next) {
                                if ((ia->ia6_flags & IN6_IFF_AUTOCONF) == 0)
                                        continue;

                                if (ia->ia6_ndpr == pr)
                                        in6_purgeaddr(&ia->ia_ifa);
                        }
                        nd6_prefix_del(pr);
                }
                break;
        }
        case SIOCSRTRFLUSH_IN6:
        {
                /* flush all the default routers */

                defrouter_reset();
                nd6_defrouter_flush_all();
                defrouter_select_fib(RT_ALL_FIBS);
                break;
        }
        case SIOCGNBRINFO_IN6:
        {
                struct llentry *ln;
                struct in6_addr nb_addr = nbi->addr; /* make local for safety */

                if ((error = in6_setscope(&nb_addr, ifp, NULL)) != 0)
                        return (error);

                NET_EPOCH_ENTER(et);
                ln = nd6_lookup(&nb_addr, LLE_SF(AF_INET6, 0), ifp);
                NET_EPOCH_EXIT(et);

                if (ln == NULL) {
                        error = EINVAL;
                        break;
                }
                nbi->state = ln->ln_state;
                nbi->asked = ln->la_asked;
                nbi->isrouter = ln->ln_router;
                if (ln->la_expire == 0)
                        nbi->expire = 0;
                else
                        nbi->expire = ln->la_expire + ln->lle_remtime / hz +
                            (time_second - time_uptime);
                LLE_RUNLOCK(ln);
                break;
        }
        case SIOCGDEFIFACE_IN6: /* XXX: should be implemented as a sysctl? */
                ndif->ifindex = V_nd6_defifindex;
                break;
        case SIOCSDEFIFACE_IN6: /* XXX: should be implemented as a sysctl? */
                return (nd6_setdefaultiface(ndif->ifindex));
        }
        return (error);
}

/*
 * Calculates new isRouter value based on provided parameters and
 * returns it.
 */
static int
nd6_is_router(int type, int code, int is_new, int old_addr, int new_addr,
    int ln_router)
{

        /*
         * 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 quetion 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.
         *
         *   is_new  old_addr new_addr      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       (4)     c   s     s
         *      0       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_new)                                     /* (6-7) */
                        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_router = 1;
                else {
                        if (is_new)                             /* (6-7) */
                                ln_router = 0;
                }
                break;
        case ND_ROUTER_SOLICIT:
                /*
                 * is_router flag must always be cleared.
                 */
                ln_router = 0;
                break;
        case ND_ROUTER_ADVERT:
                /*
                 * Mark an entry with lladdr as a router.
                 */
                if ((!is_new && (old_addr || new_addr)) ||      /* (2-5) */
                    (is_new && new_addr)) {                     /* (7) */
                        ln_router = 1;
                }
                break;
        }

        return (ln_router);
}

/*
 * 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, struct in6_addr *from, char *lladdr,
    int lladdrlen, int type, int code)
{
        struct llentry *ln = NULL, *ln_tmp;
        int is_newentry;
        int do_update;
        int olladdr;
        int llchange;
        int flags;
        uint16_t router = 0;
        struct mbuf *chain = NULL;
        u_char linkhdr[LLE_MAX_LINKHDR];
        size_t linkhdrsize;
        int lladdr_off;

        NET_EPOCH_ASSERT();
        IF_AFDATA_UNLOCK_ASSERT(ifp);

        KASSERT(ifp != NULL, ("%s: ifp == NULL", __func__));
        KASSERT(from != NULL, ("%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 adderss, 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).
         */
        flags = lladdr ? LLE_EXCLUSIVE : 0;
        ln = nd6_lookup(from, LLE_SF(AF_INET6, flags), ifp);
        is_newentry = 0;
        if (ln == NULL) {
                flags |= LLE_EXCLUSIVE;
                ln = nd6_alloc(from, 0, ifp);
                if (ln == NULL)
                        return;

                /*
                 * Since we already know all the data for the new entry,
                 * fill it before insertion.
                 */
                if (lladdr != NULL) {
                        linkhdrsize = sizeof(linkhdr);
                        if (lltable_calc_llheader(ifp, AF_INET6, lladdr,
                            linkhdr, &linkhdrsize, &lladdr_off) != 0) {
                                lltable_free_entry(LLTABLE6(ifp), ln);
                                return;
                        }
                        lltable_set_entry_addr(ifp, ln, linkhdr, linkhdrsize,
                            lladdr_off);
                }

                IF_AFDATA_WLOCK(ifp);
                LLE_WLOCK(ln);
                /* Prefer any existing lle over newly-created one */
                ln_tmp = nd6_lookup(from, LLE_SF(AF_INET6, LLE_EXCLUSIVE), ifp);
                if (ln_tmp == NULL)
                        lltable_link_entry(LLTABLE6(ifp), ln);
                IF_AFDATA_WUNLOCK(ifp);
                if (ln_tmp == NULL) {
                        /* No existing lle, mark as new entry (6,7) */
                        is_newentry = 1;
                        if (lladdr != NULL) {   /* (7) */
                                nd6_llinfo_setstate(ln, ND6_LLINFO_STALE);
                                EVENTHANDLER_INVOKE(lle_event, ln,
                                    LLENTRY_RESOLVED);
                        }
                } else {
                        lltable_free_entry(LLTABLE6(ifp), ln);
                        ln = ln_tmp;
                        ln_tmp = NULL;
                }
        } 
        /* do nothing if static ndp is set */
        if ((ln->la_flags & LLE_STATIC)) {
                if (flags & LLE_EXCLUSIVE)
                        LLE_WUNLOCK(ln);
                else
                        LLE_RUNLOCK(ln);
                return;
        }

        olladdr = (ln->la_flags & LLE_VALID) ? 1 : 0;
        if (olladdr && lladdr) {
                llchange = bcmp(lladdr, ln->ll_addr,
                    ifp->if_addrlen);
        } else if (!olladdr && lladdr)
                llchange = 1;
        else
                llchange = 0;

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

        do_update = 0;
        if (is_newentry == 0 && llchange != 0) {
                do_update = 1;  /* (3,5) */

                /*
                 * Record source link-layer address
                 * XXX is it dependent to ifp->if_type?
                 */
                if (!nd6_try_set_entry_addr(ifp, ln, lladdr)) {
                        /* Entry was deleted */
                        LLE_WUNLOCK(ln);
                        return;
                }

                nd6_llinfo_setstate(ln, ND6_LLINFO_STALE);

                EVENTHANDLER_INVOKE(lle_event, ln, LLENTRY_RESOLVED);

                if (ln->la_hold != NULL)
                        chain = nd6_grab_holdchain(ln);
        }

        /* Calculates new router status */
        router = nd6_is_router(type, code, is_newentry, olladdr,
            lladdr != NULL ? 1 : 0, ln->ln_router);

        ln->ln_router = router;
        /* Mark non-router redirects with special flag */
        if ((type & 0xFF) == ND_REDIRECT && code != ND_REDIRECT_ROUTER)
                ln->la_flags |= LLE_REDIRECT;

        if (flags & LLE_EXCLUSIVE)
                LLE_WUNLOCK(ln);
        else
                LLE_RUNLOCK(ln);

        if (chain != NULL)
                nd6_flush_holdchain(ifp, ln, chain);
        if (do_update)
                nd6_flush_children_holdchain(ifp, ln);

        /*
         * When the link-layer address of a router changes, select the
         * best router again.  In particular, when the neighbor entry is newly
         * created, it might affect the selection policy.
         * Question: can we restrict the first condition to the "is_newentry"
         * case?
         * XXX: when we hear an RA from a new router with the link-layer
         * address option, defrouter_select_fib() is called twice, since
         * defrtrlist_update called the function as well.  However, I believe
         * we can compromise the overhead, since it only happens the first
         * time.
         * XXX: although defrouter_select_fib() should not have a bad effect
         * for those are not autoconfigured hosts, we explicitly avoid such
         * cases for safety.
         */
        if ((do_update || is_newentry) && router &&
            ND_IFINFO(ifp)->flags & ND6_IFF_ACCEPT_RTADV) {
                /*
                 * guaranteed recursion
                 */
                defrouter_select_fib(ifp->if_fib);
        }
}

static void
nd6_slowtimo(void *arg)
{
        struct epoch_tracker et;
        CURVNET_SET((struct vnet *) arg);
        struct nd_ifinfo *nd6if;
        struct ifnet *ifp;

        callout_reset(&V_nd6_slowtimo_ch, ND6_SLOWTIMER_INTERVAL * hz,
            nd6_slowtimo, curvnet);
        NET_EPOCH_ENTER(et);
        CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
                if (ifp->if_afdata[AF_INET6] == NULL)
                        continue;
                nd6if = ND_IFINFO(ifp);
                if (nd6if->basereachable && /* already initialized */
                    (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 = V_nd6_recalc_reachtm_interval;
                        nd6if->reachable = ND_COMPUTE_RTIME(nd6if->basereachable);
                }
        }
        NET_EPOCH_EXIT(et);
        CURVNET_RESTORE();
}

struct mbuf *
nd6_grab_holdchain(struct llentry *ln)
{
        struct mbuf *chain;

        LLE_WLOCK_ASSERT(ln);

        chain = ln->la_hold;
        ln->la_hold = NULL;
        ln->la_numheld = 0;

        if (ln->ln_state == ND6_LLINFO_STALE) {
                /*
                 * The first time we send a packet to a
                 * neighbor whose entry is STALE, we have
                 * to change the state to DELAY and a sets
                 * a timer to expire in DELAY_FIRST_PROBE_TIME
                 * seconds to ensure do neighbor unreachability
                 * detection on expiration.
                 * (RFC 2461 7.3.3)
                 */
                nd6_llinfo_setstate(ln, ND6_LLINFO_DELAY);
        }

        return (chain);
}

int
nd6_output_ifp(struct ifnet *ifp, struct ifnet *origifp, struct mbuf *m,
    struct sockaddr_in6 *dst, struct route *ro)
{
        int error;
        int ip6len;
        struct ip6_hdr *ip6;
        struct m_tag *mtag;

#ifdef MAC
        mac_netinet6_nd6_send(ifp, m);
#endif

        /*
         * If called from nd6_ns_output() (NS), nd6_na_output() (NA),
         * icmp6_redirect_output() (REDIRECT) or from rip6_output() (RS, RA
         * as handled by rtsol and rtadvd), mbufs will be tagged for SeND
         * to be diverted to user space.  When re-injected into the kernel,
         * send_output() will directly dispatch them to the outgoing interface.
         */
        if (send_sendso_input_hook != NULL) {
                mtag = m_tag_find(m, PACKET_TAG_ND_OUTGOING, NULL);
                if (mtag != NULL) {
                        ip6 = mtod(m, struct ip6_hdr *);
                        ip6len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
                        /* Use the SEND socket */
                        error = send_sendso_input_hook(m, ifp, SND_OUT,
                            ip6len);
                        /* -1 == no app on SEND socket */
                        if (error == 0 || error != -1)
                            return (error);
                }
        }

        m_clrprotoflags(m);     /* Avoid confusing lower layers. */
        IP_PROBE(send, NULL, NULL, mtod(m, struct ip6_hdr *), ifp, NULL,
            mtod(m, struct ip6_hdr *));

        if ((ifp->if_flags & IFF_LOOPBACK) == 0)
                origifp = ifp;

        error = (*ifp->if_output)(origifp, m, (struct sockaddr *)dst, ro);
        return (error);
}

/*
 * Lookup link headerfor @sa_dst address. Stores found
 * data in @desten buffer. Copy of lle ln_flags can be also
 * saved in @pflags if @pflags is non-NULL.
 *
 * If destination LLE does not exists or lle state modification
 * is required, call "slow" version.
 *
 * Return values:
 * - 0 on success (address copied to buffer).
 * - EWOULDBLOCK (no local error, but address is still unresolved)
 * - other errors (alloc failure, etc)
 */
int
nd6_resolve(struct ifnet *ifp, int gw_flags, struct mbuf *m,
    const struct sockaddr *sa_dst, u_char *desten, uint32_t *pflags,
    struct llentry **plle)
{
        struct llentry *ln = NULL;
        const struct sockaddr_in6 *dst6;

        NET_EPOCH_ASSERT();

        if (pflags != NULL)
                *pflags = 0;

        dst6 = (const struct sockaddr_in6 *)sa_dst;

        /* discard the packet if IPv6 operation is disabled on the interface */
        if ((ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED)) {
                m_freem(m);
                return (ENETDOWN); /* better error? */
        }

        if (m != NULL && m->m_flags & M_MCAST) {
                switch (ifp->if_type) {
                case IFT_ETHER:
                case IFT_L2VLAN:
                case IFT_BRIDGE:
                        ETHER_MAP_IPV6_MULTICAST(&dst6->sin6_addr,
                                                 desten);
                        return (0);
                default:
                        m_freem(m);
                        return (EAFNOSUPPORT);
                }
        }

        int family = gw_flags >> 16;
        int lookup_flags = plle ? LLE_EXCLUSIVE : LLE_UNLOCKED;
        ln = nd6_lookup(&dst6->sin6_addr, LLE_SF(family, lookup_flags), ifp);
        if (ln != NULL && (ln->r_flags & RLLE_VALID) != 0) {
                /* Entry found, let's copy lle info */
                bcopy(ln->r_linkdata, desten, ln->r_hdrlen);
                if (pflags != NULL)
                        *pflags = LLE_VALID | (ln->r_flags & RLLE_IFADDR);
                llentry_provide_feedback(ln);
                if (plle) {
                        LLE_ADDREF(ln);
                        *plle = ln;
                        LLE_WUNLOCK(ln);
                }
                return (0);
        } else if (plle && ln)
                LLE_WUNLOCK(ln);

        return (nd6_resolve_slow(ifp, family, 0, m, dst6, desten, pflags, plle));
}

/*
 * Finds or creates a new llentry for @addr and @family.
 * Returns wlocked llentry or NULL.
 *
 *
 * Child LLEs.
 *
 * Do not have their own state machine (gets marked as static)
 *  settimer bails out for child LLEs just in case.
 *
 * Locking order: parent lle gets locked first, chen goes the child.
 */
static __noinline struct llentry *
nd6_get_llentry(struct ifnet *ifp, const struct in6_addr *addr, int family)
{
        struct llentry *child_lle = NULL;
        struct llentry *lle, *lle_tmp;

        lle = nd6_alloc(addr, 0, ifp);
        if (lle != NULL && family != AF_INET6) {
                child_lle = nd6_alloc(addr, 0, ifp);
                if (child_lle == NULL) {
                        lltable_free_entry(LLTABLE6(ifp), lle);
                        return (NULL);
                }
                child_lle->r_family = family;
                child_lle->la_flags |= LLE_CHILD | LLE_STATIC;
                child_lle->ln_state = ND6_LLINFO_INCOMPLETE;
        }

        if (lle == NULL) {
                char ip6buf[INET6_ADDRSTRLEN];
                log(LOG_DEBUG,
                    "nd6_get_llentry: can't allocate llinfo for %s "
                    "(ln=%p)\n",
                    ip6_sprintf(ip6buf, addr), lle);
                return (NULL);
        }

        IF_AFDATA_WLOCK(ifp);
        LLE_WLOCK(lle);
        /* Prefer any existing entry over newly-created one */
        lle_tmp = nd6_lookup(addr, LLE_SF(AF_INET6, LLE_EXCLUSIVE), ifp);
        if (lle_tmp == NULL)
                lltable_link_entry(LLTABLE6(ifp), lle);
        else {
                lltable_free_entry(LLTABLE6(ifp), lle);
                lle = lle_tmp;
        }
        if (child_lle != NULL) {
                /* Check if child lle for the same family exists */
                lle_tmp = llentry_lookup_family(lle, child_lle->r_family);
                LLE_WLOCK(child_lle);
                if (lle_tmp == NULL) {
                        /* Attach */
                        lltable_link_child_entry(lle, child_lle);
                } else {
                        /* child lle already exists, free newly-created one */
                        lltable_free_entry(LLTABLE6(ifp), child_lle);
                        child_lle = lle_tmp;
                }
                LLE_WUNLOCK(lle);
                lle = child_lle;
        }
        IF_AFDATA_WUNLOCK(ifp);
        return (lle);
}

/*
 * Do L2 address resolution for @sa_dst address. Stores found
 * address in @desten buffer. Copy of lle ln_flags can be also
 * saved in @pflags if @pflags is non-NULL.
 *
 * Heavy version.
 * Function assume that destination LLE does not exist,
 * is invalid or stale, so LLE_EXCLUSIVE lock needs to be acquired.
 *
 * Set noinline to be dtrace-friendly
 */
static __noinline int
nd6_resolve_slow(struct ifnet *ifp, int family, int flags, struct mbuf *m,
    const struct sockaddr_in6 *dst, u_char *desten, uint32_t *pflags,
    struct llentry **plle)
{
        struct llentry *lle = NULL;
        struct in6_addr *psrc, src;
        int send_ns, ll_len;
        char *lladdr;

        NET_EPOCH_ASSERT();

        /*
         * 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).
         */
        lle = nd6_lookup(&dst->sin6_addr, LLE_SF(family, LLE_EXCLUSIVE), ifp);
        if ((lle == NULL) && nd6_is_addr_neighbor(dst, ifp))  {
                /*
                 * Since nd6_is_addr_neighbor() internally calls nd6_lookup(),
                 * the condition below is not very efficient.  But we believe
                 * it is tolerable, because this should be a rare case.
                 */
                lle = nd6_get_llentry(ifp, &dst->sin6_addr, family);
        }

        if (lle == NULL) {
                m_freem(m);
                return (ENOBUFS);
        }

        LLE_WLOCK_ASSERT(lle);

        /*
         * The first time we send a packet to a neighbor whose entry is
         * STALE, we have to change the state to DELAY and a sets a timer to
         * expire in DELAY_FIRST_PROBE_TIME seconds to ensure do
         * neighbor unreachability detection on expiration.
         * (RFC 2461 7.3.3)
         */
        if ((!(lle->la_flags & LLE_CHILD)) && (lle->ln_state == ND6_LLINFO_STALE))
                nd6_llinfo_setstate(lle, ND6_LLINFO_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 (lle->ln_state > ND6_LLINFO_INCOMPLETE) {
                if (flags & LLE_ADDRONLY) {
                        lladdr = lle->ll_addr;
                        ll_len = ifp->if_addrlen;
                } else {
                        lladdr = lle->r_linkdata;
                        ll_len = lle->r_hdrlen;
                }
                bcopy(lladdr, desten, ll_len);
                if (pflags != NULL)
                        *pflags = lle->la_flags;
                if (plle) {
                        LLE_ADDREF(lle);
                        *plle = lle;
                }
                LLE_WUNLOCK(lle);
                return (0);
        }

        /*
         * There is a neighbor cache entry, but no ethernet address
         * response yet.  Append this latest packet to the end of the
         * packet queue in the mbuf.  When it exceeds nd6_maxqueuelen,
         * the oldest packet in the queue will be removed.
         */
        if (m != NULL) {
                size_t dropped;

                dropped = lltable_append_entry_queue(lle, m, V_nd6_maxqueuelen);
                ICMP6STAT_ADD(icp6s_dropped, dropped);
        }

        /*
         * If there has been no NS for the neighbor after entering the
         * INCOMPLETE state, send the first solicitation.
         * Note that for newly-created lle la_asked will be 0,
         * so we will transition from ND6_LLINFO_NOSTATE to
         * ND6_LLINFO_INCOMPLETE state here.
         */
        psrc = NULL;
        send_ns = 0;

        /* If we have child lle, switch to the parent to send NS */
        if (lle->la_flags & LLE_CHILD) {
                struct llentry *lle_parent = lle->lle_parent;
                LLE_WUNLOCK(lle);
                lle = lle_parent;
                LLE_WLOCK(lle);
        }
        if (lle->la_asked == 0) {
                lle->la_asked++;
                send_ns = 1;
                psrc = nd6_llinfo_get_holdsrc(lle, &src);

                nd6_llinfo_setstate(lle, ND6_LLINFO_INCOMPLETE);
        }
        LLE_WUNLOCK(lle);
        if (send_ns != 0)
                nd6_ns_output(ifp, psrc, NULL, &dst->sin6_addr, NULL);

        return (EWOULDBLOCK);
}

/*
 * Do L2 address resolution for @sa_dst address. Stores found
 * address in @desten buffer. Copy of lle ln_flags can be also
 * saved in @pflags if @pflags is non-NULL.
 *
 * Return values:
 * - 0 on success (address copied to buffer).
 * - EWOULDBLOCK (no local error, but address is still unresolved)
 * - other errors (alloc failure, etc)
 */
int
nd6_resolve_addr(struct ifnet *ifp, int flags, const struct sockaddr *dst,
    char *desten, uint32_t *pflags)
{
        int error;

        flags |= LLE_ADDRONLY;
        error = nd6_resolve_slow(ifp, AF_INET6, flags, NULL,
            (const struct sockaddr_in6 *)dst, desten, pflags, NULL);
        return (error);
}

int
nd6_flush_holdchain(struct ifnet *ifp, struct llentry *lle, struct mbuf *chain)
{
        struct mbuf *m, *m_head;
        struct sockaddr_in6 dst6;
        int error = 0;

        NET_EPOCH_ASSERT();

        struct route_in6 ro = {
                .ro_prepend = lle->r_linkdata,
                .ro_plen = lle->r_hdrlen,
        };

        lltable_fill_sa_entry(lle, (struct sockaddr *)&dst6);
        m_head = chain;

        while (m_head) {
                m = m_head;
                m_head = m_head->m_nextpkt;
                m->m_nextpkt = NULL;
                error = nd6_output_ifp(ifp, ifp, m, &dst6, (struct route *)&ro);
        }

        /*
         * XXX
         * note that intermediate errors are blindly ignored
         */
        return (error);
}

__noinline void
nd6_flush_children_holdchain(struct ifnet *ifp, struct llentry *lle)
{
        struct llentry *child_lle;
        struct mbuf *chain;

        NET_EPOCH_ASSERT();

        CK_SLIST_FOREACH(child_lle, &lle->lle_children, lle_child_next) {
                LLE_WLOCK(child_lle);
                chain = nd6_grab_holdchain(child_lle);
                LLE_WUNLOCK(child_lle);
                nd6_flush_holdchain(ifp, child_lle, chain);
        }
}

static int
nd6_need_cache(struct ifnet *ifp)
{
        /*
         * XXX: we currently do not make neighbor cache on any interface
         * other than Ethernet and GIF.
         *
         * RFC2893 says:
         * - unidirectional tunnels needs no ND
         */
        switch (ifp->if_type) {
        case IFT_ETHER:
        case IFT_IEEE1394:
        case IFT_L2VLAN:
        case IFT_INFINIBAND:
        case IFT_BRIDGE:
        case IFT_PROPVIRTUAL:
                return (1);
        default:
                return (0);
        }
}

/*
 * Add pernament ND6 link-layer record for given
 * interface address.
 *
 * Very similar to IPv4 arp_ifinit(), but:
 * 1) IPv6 DAD is performed in different place
 * 2) It is called by IPv6 protocol stack in contrast to
 * arp_ifinit() which is typically called in SIOCSIFADDR
 * driver ioctl handler.
 *
 */
int
nd6_add_ifa_lle(struct in6_ifaddr *ia)
{
        struct ifnet *ifp;
        struct llentry *ln, *ln_tmp;
        struct sockaddr *dst;

        ifp = ia->ia_ifa.ifa_ifp;
        if (nd6_need_cache(ifp) == 0)
                return (0);

        dst = (struct sockaddr *)&ia->ia_addr;
        ln = lltable_alloc_entry(LLTABLE6(ifp), LLE_IFADDR, dst);
        if (ln == NULL)
                return (ENOBUFS);

        IF_AFDATA_WLOCK(ifp);
        LLE_WLOCK(ln);
        /* Unlink any entry if exists */
        ln_tmp = lla_lookup(LLTABLE6(ifp), LLE_SF(AF_INET6, LLE_EXCLUSIVE), dst);
        if (ln_tmp != NULL)
                lltable_unlink_entry(LLTABLE6(ifp), ln_tmp);
        lltable_link_entry(LLTABLE6(ifp), ln);
        IF_AFDATA_WUNLOCK(ifp);

        if (ln_tmp != NULL)
                EVENTHANDLER_INVOKE(lle_event, ln_tmp, LLENTRY_EXPIRED);
        EVENTHANDLER_INVOKE(lle_event, ln, LLENTRY_RESOLVED);

        LLE_WUNLOCK(ln);
        if (ln_tmp != NULL)
                llentry_free(ln_tmp);

        return (0);
}

/*
 * Removes either all lle entries for given @ia, or lle
 * corresponding to @ia address.
 */
void
nd6_rem_ifa_lle(struct in6_ifaddr *ia, int all)
{
        struct sockaddr_in6 mask, addr;
        struct sockaddr *saddr, *smask;
        struct ifnet *ifp;

        ifp = ia->ia_ifa.ifa_ifp;
        memcpy(&addr, &ia->ia_addr, sizeof(ia->ia_addr));
        memcpy(&mask, &ia->ia_prefixmask, sizeof(ia->ia_prefixmask));
        saddr = (struct sockaddr *)&addr;
        smask = (struct sockaddr *)&mask;

        if (all != 0)
                lltable_prefix_free(AF_INET6, saddr, smask, LLE_STATIC);
        else
                lltable_delete_addr(LLTABLE6(ifp), LLE_IFADDR, saddr);
}

static int
nd6_sysctl_prlist(SYSCTL_HANDLER_ARGS)
{
        struct in6_prefix p;
        struct sockaddr_in6 s6;
        struct nd_prefix *pr;
        struct nd_pfxrouter *pfr;
        time_t maxexpire;
        int error;
        char ip6buf[INET6_ADDRSTRLEN];

        if (req->newptr)
                return (EPERM);

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);

        bzero(&p, sizeof(p));
        p.origin = PR_ORIG_RA;
        bzero(&s6, sizeof(s6));
        s6.sin6_family = AF_INET6;
        s6.sin6_len = sizeof(s6);

        ND6_RLOCK();
        LIST_FOREACH(pr, &V_nd_prefix, ndpr_entry) {
                if (!pr->ndpr_raf_ra_derived)
                        continue;
                p.prefix = pr->ndpr_prefix;
                if (sa6_recoverscope(&p.prefix)) {
                        log(LOG_ERR, "scope error in prefix list (%s)\n",
                            ip6_sprintf(ip6buf, &p.prefix.sin6_addr));
                        /* XXX: press on... */
                }
                p.raflags = pr->ndpr_raf;
                p.prefixlen = pr->ndpr_plen;
                p.vltime = pr->ndpr_vltime;
                p.pltime = pr->ndpr_pltime;
                p.if_index = pr->ndpr_ifp->if_index;
                if (pr->ndpr_vltime == ND6_INFINITE_LIFETIME)
                        p.expire = 0;
                else {
                        /* XXX: we assume time_t is signed. */
                        maxexpire = (-1) &
                            ~((time_t)1 << ((sizeof(maxexpire) * 8) - 1));
                        if (pr->ndpr_vltime < maxexpire - pr->ndpr_lastupdate)
                                p.expire = pr->ndpr_lastupdate +
                                    pr->ndpr_vltime +
                                    (time_second - time_uptime);
                        else
                                p.expire = maxexpire;
                }
                p.refcnt = pr->ndpr_addrcnt;
                p.flags = pr->ndpr_stateflags;
                p.advrtrs = 0;
                LIST_FOREACH(pfr, &pr->ndpr_advrtrs, pfr_entry)
                        p.advrtrs++;
                error = SYSCTL_OUT(req, &p, sizeof(p));
                if (error != 0)
                        break;
                LIST_FOREACH(pfr, &pr->ndpr_advrtrs, pfr_entry) {
                        s6.sin6_addr = pfr->router->rtaddr;
                        if (sa6_recoverscope(&s6))
                                log(LOG_ERR,
                                    "scope error in prefix list (%s)\n",
                                    ip6_sprintf(ip6buf, &pfr->router->rtaddr));
                        error = SYSCTL_OUT(req, &s6, sizeof(s6));
                        if (error != 0)
                                goto out;
                }
        }
out:
        ND6_RUNLOCK();
        return (error);
}
SYSCTL_PROC(_net_inet6_icmp6, ICMPV6CTL_ND6_PRLIST, nd6_prlist,
        CTLTYPE_OPAQUE | CTLFLAG_RD | CTLFLAG_MPSAFE,
        NULL, 0, nd6_sysctl_prlist, "S,in6_prefix",
        "NDP prefix list");
SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_ND6_MAXQLEN, nd6_maxqueuelen,
        CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nd6_maxqueuelen), 1, "");
SYSCTL_INT(_net_inet6_icmp6, OID_AUTO, nd6_gctimer,
        CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nd6_gctimer), (60 * 60 * 24), "");