xnu-6153.121.1.tar.gz

[apple/xnu.git] / bsd / netinet6 / nd6.c

/*
 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * 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.
 */

/*
 * XXX
 * KAME 970409 note:
 * BSD/OS version heavily modifies this code, related to llinfo.
 * Since we don't have BSD/OS version of net/route.c in our hand,
 * I left the code mostly as it was in 970310.  -- itojun
 */

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

#include <dev/random/randomdev.h>

#include <kern/queue.h>
#include <kern/zalloc.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/if_llreach.h>
#include <net/route.h>
#include <net/dlil.h>
#include <net/ntstat.h>
#include <net/net_osdep.h>
#include <net/nwk_wq.h>

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

#include <os/log.h>

#include "loop.h"

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

#define equal(a1, a2) (bcmp((caddr_t)(a1), (caddr_t)(a2), (a1)->sa_len) == 0)

/* timer values */
int     nd6_prune       = 1;    /* walk list every 1 seconds */
int     nd6_prune_lazy  = 5;    /* lazily walk list every 5 seconds */
int     nd6_delay       = 5;    /* delay first probe time 5 second */
int     nd6_umaxtries   = 3;    /* maximum unicast query */
int     nd6_mmaxtries   = 3;    /* maximum multicast query */
int     nd6_useloopback = 1;    /* use loopback interface for local traffic */
int     nd6_gctimer     = (60 * 60 * 24); /* 1 day: garbage collection timer */

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

int nd6_maxqueuelen = 1; /* max # of packets cached in unresolved ND entries */

#if ND6_DEBUG
int nd6_debug = 1;
#else
int nd6_debug = 0;
#endif

int nd6_optimistic_dad =
    (ND6_OPTIMISTIC_DAD_LINKLOCAL | ND6_OPTIMISTIC_DAD_AUTOCONF |
    ND6_OPTIMISTIC_DAD_TEMPORARY | ND6_OPTIMISTIC_DAD_DYNAMIC |
    ND6_OPTIMISTIC_DAD_SECURED | ND6_OPTIMISTIC_DAD_MANUAL);

/* for debugging? */
static int nd6_inuse, nd6_allocated;

/*
 * Synchronization notes:
 *
 * The global list of ND entries are stored in llinfo_nd6; an entry
 * gets inserted into the list when the route is created and gets
 * removed from the list when it is deleted; this is done as part
 * of RTM_ADD/RTM_RESOLVE/RTM_DELETE in nd6_rtrequest().
 *
 * Because rnh_lock and rt_lock for the entry are held during those
 * operations, the same locks (and thus lock ordering) must be used
 * elsewhere to access the relevant data structure fields:
 *
 * ln_next, ln_prev, ln_rt
 *
 *      - Routing lock (rnh_lock)
 *
 * ln_hold, ln_asked, ln_expire, ln_state, ln_router, ln_flags,
 * ln_llreach, ln_lastused
 *
 *      - Routing entry lock (rt_lock)
 *
 * Due to the dependency on rt_lock, llinfo_nd6 has the same lifetime
 * as the route entry itself.  When a route is deleted (RTM_DELETE),
 * it is simply removed from the global list but the memory is not
 * freed until the route itself is freed.
 */
struct llinfo_nd6 llinfo_nd6 = {
        .ln_next = &llinfo_nd6,
        .ln_prev = &llinfo_nd6,
};

static lck_grp_attr_t   *nd_if_lock_grp_attr = NULL;
static lck_grp_t        *nd_if_lock_grp = NULL;
static lck_attr_t       *nd_if_lock_attr = NULL;

/* Protected by nd6_mutex */
struct nd_drhead nd_defrouter;
struct nd_prhead nd_prefix = { .lh_first = 0 };

/*
 * nd6_timeout() is scheduled on a demand basis.  nd6_timeout_run is used
 * to indicate whether or not a timeout has been scheduled.  The rnh_lock
 * mutex is used to protect this scheduling; it is a natural choice given
 * the work done in the timer callback.  Unfortunately, there are cases
 * when nd6_timeout() needs to be scheduled while rnh_lock cannot be easily
 * held, due to lock ordering.  In those cases, we utilize a "demand" counter
 * nd6_sched_timeout_want which can be atomically incremented without
 * having to hold rnh_lock.  On places where we acquire rnh_lock, such as
 * nd6_rtrequest(), we check this counter and schedule the timer if it is
 * non-zero.  The increment happens on various places when we allocate
 * new ND entries, default routers, prefixes and addresses.
 */
static int nd6_timeout_run;             /* nd6_timeout is scheduled to run */
static void nd6_timeout(void *);
int nd6_sched_timeout_want;             /* demand count for timer to be sched */
static boolean_t nd6_fast_timer_on = FALSE;

/* Serialization variables for nd6_service(), protected by rnh_lock */
static boolean_t nd6_service_busy;
static void *nd6_service_wc = &nd6_service_busy;
static int nd6_service_waiters = 0;

int nd6_recalc_reachtm_interval = ND6_RECALC_REACHTM_INTERVAL;
static struct sockaddr_in6 all1_sa;

static int regen_tmpaddr(struct in6_ifaddr *);
extern lck_mtx_t *nd6_mutex;

static struct llinfo_nd6 *nd6_llinfo_alloc(int);
static void nd6_llinfo_free(void *);
static void nd6_llinfo_purge(struct rtentry *);
static void nd6_llinfo_get_ri(struct rtentry *, struct rt_reach_info *);
static void nd6_llinfo_get_iflri(struct rtentry *, struct ifnet_llreach_info *);
static void nd6_llinfo_refresh(struct rtentry *);
static uint64_t ln_getexpire(struct llinfo_nd6 *);

static void nd6_service(void *);
static void nd6_slowtimo(void *);
static int nd6_is_new_addr_neighbor(struct sockaddr_in6 *, struct ifnet *);
static int nd6_siocgdrlst(void *, int);
static int nd6_siocgprlst(void *, int);

static int nd6_sysctl_drlist SYSCTL_HANDLER_ARGS;
static int nd6_sysctl_prlist SYSCTL_HANDLER_ARGS;

/*
 * Insertion and removal from llinfo_nd6 must be done with rnh_lock held.
 */
#define LN_DEQUEUE(_ln) do {                                            \
        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);                 \
        RT_LOCK_ASSERT_HELD((_ln)->ln_rt);                              \
        (_ln)->ln_next->ln_prev = (_ln)->ln_prev;                       \
        (_ln)->ln_prev->ln_next = (_ln)->ln_next;                       \
        (_ln)->ln_prev = (_ln)->ln_next = NULL;                         \
        (_ln)->ln_flags &= ~ND6_LNF_IN_USE;                             \
} while (0)

#define LN_INSERTHEAD(_ln) do {                                         \
        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);                 \
        RT_LOCK_ASSERT_HELD((_ln)->ln_rt);                              \
        (_ln)->ln_next = llinfo_nd6.ln_next;                            \
        llinfo_nd6.ln_next = (_ln);                                     \
        (_ln)->ln_prev = &llinfo_nd6;                                   \
        (_ln)->ln_next->ln_prev = (_ln);                                \
        (_ln)->ln_flags |= ND6_LNF_IN_USE;                              \
} while (0)

static struct zone *llinfo_nd6_zone;
#define LLINFO_ND6_ZONE_MAX     256             /* maximum elements in zone */
#define LLINFO_ND6_ZONE_NAME    "llinfo_nd6"    /* name for zone */

extern int tvtohz(struct timeval *);

static int nd6_init_done;

SYSCTL_DECL(_net_inet6_icmp6);

SYSCTL_PROC(_net_inet6_icmp6, ICMPV6CTL_ND6_DRLIST, nd6_drlist,
    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
    nd6_sysctl_drlist, "S,in6_defrouter", "");

SYSCTL_PROC(_net_inet6_icmp6, ICMPV6CTL_ND6_PRLIST, nd6_prlist,
    CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0,
    nd6_sysctl_prlist, "S,in6_defrouter", "");

SYSCTL_DECL(_net_inet6_ip6);

static int ip6_maxchainsent = 0;
SYSCTL_INT(_net_inet6_ip6, OID_AUTO, maxchainsent,
    CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_maxchainsent, 0,
    "use dlil_output_list");

void
nd6_init(void)
{
        int i;

        VERIFY(!nd6_init_done);

        all1_sa.sin6_family = AF_INET6;
        all1_sa.sin6_len = sizeof(struct sockaddr_in6);
        for (i = 0; i < sizeof(all1_sa.sin6_addr); i++) {
                all1_sa.sin6_addr.s6_addr[i] = 0xff;
        }

        /* initialization of the default router list */
        TAILQ_INIT(&nd_defrouter);

        nd_if_lock_grp_attr = lck_grp_attr_alloc_init();
        nd_if_lock_grp = lck_grp_alloc_init("nd_if_lock", nd_if_lock_grp_attr);
        nd_if_lock_attr = lck_attr_alloc_init();

        llinfo_nd6_zone = zinit(sizeof(struct llinfo_nd6),
            LLINFO_ND6_ZONE_MAX * sizeof(struct llinfo_nd6), 0,
            LLINFO_ND6_ZONE_NAME);
        if (llinfo_nd6_zone == NULL) {
                panic("%s: failed allocating llinfo_nd6_zone", __func__);
        }

        zone_change(llinfo_nd6_zone, Z_EXPAND, TRUE);
        zone_change(llinfo_nd6_zone, Z_CALLERACCT, FALSE);

        nd6_nbr_init();
        nd6_rtr_init();
        nd6_prproxy_init();

        nd6_init_done = 1;

        /* start timer */
        timeout(nd6_slowtimo, NULL, ND6_SLOWTIMER_INTERVAL * hz);
}

static struct llinfo_nd6 *
nd6_llinfo_alloc(int how)
{
        struct llinfo_nd6 *ln;

        ln = (how == M_WAITOK) ? zalloc(llinfo_nd6_zone) :
            zalloc_noblock(llinfo_nd6_zone);
        if (ln != NULL) {
                bzero(ln, sizeof(*ln));
        }

        return ln;
}

static void
nd6_llinfo_free(void *arg)
{
        struct llinfo_nd6 *ln = arg;

        if (ln->ln_next != NULL || ln->ln_prev != NULL) {
                panic("%s: trying to free %p when it is in use", __func__, ln);
                /* NOTREACHED */
        }

        /* Just in case there's anything there, free it */
        if (ln->ln_hold != NULL) {
                m_freem_list(ln->ln_hold);
                ln->ln_hold = NULL;
        }

        /* Purge any link-layer info caching */
        VERIFY(ln->ln_rt->rt_llinfo == ln);
        if (ln->ln_rt->rt_llinfo_purge != NULL) {
                ln->ln_rt->rt_llinfo_purge(ln->ln_rt);
        }

        zfree(llinfo_nd6_zone, ln);
}

static void
nd6_llinfo_purge(struct rtentry *rt)
{
        struct llinfo_nd6 *ln = rt->rt_llinfo;

        RT_LOCK_ASSERT_HELD(rt);
        VERIFY(rt->rt_llinfo_purge == nd6_llinfo_purge && ln != NULL);

        if (ln->ln_llreach != NULL) {
                RT_CONVERT_LOCK(rt);
                ifnet_llreach_free(ln->ln_llreach);
                ln->ln_llreach = NULL;
        }
        ln->ln_lastused = 0;
}

static void
nd6_llinfo_get_ri(struct rtentry *rt, struct rt_reach_info *ri)
{
        struct llinfo_nd6 *ln = rt->rt_llinfo;
        struct if_llreach *lr = ln->ln_llreach;

        if (lr == NULL) {
                bzero(ri, sizeof(*ri));
                ri->ri_rssi = IFNET_RSSI_UNKNOWN;
                ri->ri_lqm = IFNET_LQM_THRESH_OFF;
                ri->ri_npm = IFNET_NPM_THRESH_UNKNOWN;
        } else {
                IFLR_LOCK(lr);
                /* Export to rt_reach_info structure */
                ifnet_lr2ri(lr, ri);
                /* Export ND6 send expiration (calendar) time */
                ri->ri_snd_expire =
                    ifnet_llreach_up2calexp(lr, ln->ln_lastused);
                IFLR_UNLOCK(lr);
        }
}

static void
nd6_llinfo_get_iflri(struct rtentry *rt, struct ifnet_llreach_info *iflri)
{
        struct llinfo_nd6 *ln = rt->rt_llinfo;
        struct if_llreach *lr = ln->ln_llreach;

        if (lr == NULL) {
                bzero(iflri, sizeof(*iflri));
                iflri->iflri_rssi = IFNET_RSSI_UNKNOWN;
                iflri->iflri_lqm = IFNET_LQM_THRESH_OFF;
                iflri->iflri_npm = IFNET_NPM_THRESH_UNKNOWN;
        } else {
                IFLR_LOCK(lr);
                /* Export to ifnet_llreach_info structure */
                ifnet_lr2iflri(lr, iflri);
                /* Export ND6 send expiration (uptime) time */
                iflri->iflri_snd_expire =
                    ifnet_llreach_up2upexp(lr, ln->ln_lastused);
                IFLR_UNLOCK(lr);
        }
}

static void
nd6_llinfo_refresh(struct rtentry *rt)
{
        struct llinfo_nd6 *ln = rt->rt_llinfo;
        uint64_t timenow = net_uptime();
        /*
         * Can't refresh permanent, static or entries that are
         * not direct host entries
         */
        if (!ln || ln->ln_expire == 0 ||
            (rt->rt_flags & RTF_STATIC) ||
            !(rt->rt_flags & RTF_LLINFO)) {
                return;
        }

        if ((ln->ln_state > ND6_LLINFO_INCOMPLETE) &&
            (ln->ln_state < ND6_LLINFO_PROBE)) {
                if (ln->ln_expire > timenow) {
                        ln_setexpire(ln, timenow);
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_PROBE);
                }
        }
        return;
}

const char *
ndcache_state2str(short ndp_state)
{
        const char *ndp_state_str = "UNKNOWN";
        switch (ndp_state) {
        case ND6_LLINFO_PURGE:
                ndp_state_str = "ND6_LLINFO_PURGE";
                break;
        case ND6_LLINFO_NOSTATE:
                ndp_state_str = "ND6_LLINFO_NOSTATE";
                break;
        case ND6_LLINFO_INCOMPLETE:
                ndp_state_str = "ND6_LLINFO_INCOMPLETE";
                break;
        case ND6_LLINFO_REACHABLE:
                ndp_state_str = "ND6_LLINFO_REACHABLE";
                break;
        case ND6_LLINFO_STALE:
                ndp_state_str = "ND6_LLINFO_STALE";
                break;
        case ND6_LLINFO_DELAY:
                ndp_state_str = "ND6_LLINFO_DELAY";
                break;
        case ND6_LLINFO_PROBE:
                ndp_state_str = "ND6_LLINFO_PROBE";
                break;
        default:
                /* Init'd to UNKNOWN */
                break;
        }
        return ndp_state_str;
}

void
ln_setexpire(struct llinfo_nd6 *ln, uint64_t expiry)
{
        ln->ln_expire = expiry;
}

static uint64_t
ln_getexpire(struct llinfo_nd6 *ln)
{
        struct timeval caltime;
        uint64_t expiry;

        if (ln->ln_expire != 0) {
                struct rtentry *rt = ln->ln_rt;

                VERIFY(rt != NULL);
                /* account for system time change */
                getmicrotime(&caltime);

                rt->base_calendartime +=
                    NET_CALCULATE_CLOCKSKEW(caltime,
                    rt->base_calendartime, net_uptime(), rt->base_uptime);

                expiry = rt->base_calendartime +
                    ln->ln_expire - rt->base_uptime;
        } else {
                expiry = 0;
        }
        return expiry;
}

void
nd6_ifreset(struct ifnet *ifp)
{
        struct nd_ifinfo *ndi = ND_IFINFO(ifp);
        VERIFY(NULL != ndi);
        VERIFY(ndi->initialized);

        LCK_MTX_ASSERT(&ndi->lock, LCK_MTX_ASSERT_OWNED);
        ndi->linkmtu = ifp->if_mtu;
        ndi->chlim = IPV6_DEFHLIM;
        ndi->basereachable = REACHABLE_TIME;
        ndi->reachable = ND_COMPUTE_RTIME(ndi->basereachable);
        ndi->retrans = RETRANS_TIMER;
}

void
nd6_ifattach(struct ifnet *ifp)
{
        struct nd_ifinfo *ndi = ND_IFINFO(ifp);

        VERIFY(NULL != ndi);
        if (!ndi->initialized) {
                lck_mtx_init(&ndi->lock, nd_if_lock_grp, nd_if_lock_attr);
                ndi->flags = ND6_IFF_PERFORMNUD;
                ndi->flags |= ND6_IFF_DAD;
                ndi->initialized = TRUE;
        }

        lck_mtx_lock(&ndi->lock);

        if (!(ifp->if_flags & IFF_MULTICAST)) {
                ndi->flags |= ND6_IFF_IFDISABLED;
        }

        nd6_ifreset(ifp);
        lck_mtx_unlock(&ndi->lock);
        nd6_setmtu(ifp);

        nd6log0(info,
            "Reinit'd ND information for interface %s\n",
            if_name(ifp));
        return;
}

#if 0
/*
 * XXX Look more into this. Especially since we recycle ifnets and do delayed
 * cleanup
 */
void
nd6_ifdetach(struct nd_ifinfo *nd)
{
        /* XXX destroy nd's lock? */
        FREE(nd, M_IP6NDP);
}
#endif

void
nd6_setmtu(struct ifnet *ifp)
{
        struct nd_ifinfo *ndi = ND_IFINFO(ifp);
        u_int32_t oldmaxmtu, maxmtu;

        if ((NULL == ndi) || (FALSE == ndi->initialized)) {
                return;
        }

        lck_mtx_lock(&ndi->lock);
        oldmaxmtu = ndi->maxmtu;

        /*
         * The ND level maxmtu is somewhat redundant to the interface MTU
         * and is an implementation artifact of KAME.  Instead of hard-
         * limiting the maxmtu based on the interface type here, we simply
         * take the if_mtu value since SIOCSIFMTU would have taken care of
         * the sanity checks related to the maximum MTU allowed for the
         * interface (a value that is known only by the interface layer),
         * by sending the request down via ifnet_ioctl().  The use of the
         * ND level maxmtu and linkmtu are done via IN6_LINKMTU() which
         * does further checking against if_mtu.
         */
        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 oldmaxmtu is necessary to restrict the
         * log to the case of changing the MTU, not initializing it.
         */
        if (oldmaxmtu >= IPV6_MMTU && ndi->maxmtu < IPV6_MMTU) {
                log(LOG_NOTICE, "nd6_setmtu: "
                    "new link MTU on %s (%u) is too small for IPv6\n",
                    if_name(ifp), (uint32_t)ndi->maxmtu);
        }
        ndi->linkmtu = ifp->if_mtu;
        lck_mtx_unlock(&ndi->lock);

        /* also adjust in6_maxmtu if necessary. */
        if (maxmtu > in6_maxmtu) {
                in6_setmaxmtu();
        }
}

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;

        if (!ndopts) {
                panic("ndopts == NULL in nd6_option\n");
        }
        if (!ndopts->nd_opts_last) {
                panic("uninitialized ndopts in nd6_option\n");
        }
        if (!ndopts->nd_opts_search) {
                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;

        if (ndopts == NULL) {
                panic("ndopts == NULL in nd6_options");
        }
        if (ndopts->nd_opts_last == NULL) {
                panic("uninitialized ndopts in nd6_options");
        }
        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.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(error,
                                    "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;
                case ND_OPT_RDNSS:
                case ND_OPT_DNSSL:
                        /* ignore */
                        break;
                default:
                        /*
                         * Unknown options must be silently ignored,
                         * to accomodate future extension to the protocol.
                         */
                        nd6log(debug,
                            "nd6_options: unsupported option %d - "
                            "option ignored\n", nd_opt->nd_opt_type);
                }

skip1:
                i++;
                if (i > nd6_maxndopt) {
                        icmp6stat.icp6s_nd_toomanyopt++;
                        nd6log(info, "too many loop in nd opt\n");
                        break;
                }

                if (ndopts->nd_opts_done) {
                        break;
                }
        }

        return 0;
}

struct nd6svc_arg {
        int draining;
        uint32_t killed;
        uint32_t aging_lazy;
        uint32_t aging;
        uint32_t sticky;
        uint32_t found;
};

/*
 * ND6 service routine to expire default route list and prefix list
 */
static void
nd6_service(void *arg)
{
        struct nd6svc_arg *ap = arg;
        struct llinfo_nd6 *ln;
        struct nd_defrouter *dr = NULL;
        struct nd_prefix *pr = NULL;
        struct ifnet *ifp = NULL;
        struct in6_ifaddr *ia6, *nia6;
        uint64_t timenow;
        boolean_t send_nc_failure_kev = FALSE;
        struct nd_drhead nd_defrouter_tmp;
        struct nd_defrouter *ndr = NULL;
        struct radix_node_head  *rnh = rt_tables[AF_INET6];

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
        /*
         * Since we may drop rnh_lock and nd6_mutex below, we want
         * to run this entire operation single threaded.
         */
        while (nd6_service_busy) {
                nd6log2(debug, "%s: %s is blocked by %d waiters\n",
                    __func__, ap->draining ? "drainer" : "timer",
                    nd6_service_waiters);
                nd6_service_waiters++;
                (void) msleep(nd6_service_wc, rnh_lock, (PZERO - 1),
                    __func__, NULL);
                LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
        }

        /* We are busy now; tell everyone else to go away */
        nd6_service_busy = TRUE;

        net_update_uptime();
        timenow = net_uptime();
again:
        /*
         * send_nc_failure_kev gets set when default router's IPv6 address
         * can't be resolved.
         * That can happen either:
         * 1. When the entry has resolved once but can't be
         * resolved later and the neighbor cache entry for gateway is deleted
         * after max probe attempts.
         *
         * 2. When the entry is in ND6_LLINFO_INCOMPLETE but can not be resolved
         * after max neighbor address resolution attempts.
         *
         * Both set send_nc_failure_kev to true. ifp is also set to the previous
         * neighbor cache entry's route's ifp.
         * Once we are done sending the notification, set send_nc_failure_kev
         * to false to stop sending false notifications for non default router
         * neighbors.
         *
         * We may to send more information like Gateway's IP that could not be
         * resolved, however right now we do not install more than one default
         * route per interface in the routing table.
         */
        if (send_nc_failure_kev && ifp != NULL &&
            ifp->if_addrlen == IF_LLREACH_MAXLEN) {
                struct kev_msg ev_msg;
                struct kev_nd6_ndfailure nd6_ndfailure;
                bzero(&ev_msg, sizeof(ev_msg));
                bzero(&nd6_ndfailure, sizeof(nd6_ndfailure));
                ev_msg.vendor_code      = KEV_VENDOR_APPLE;
                ev_msg.kev_class        = KEV_NETWORK_CLASS;
                ev_msg.kev_subclass     = KEV_ND6_SUBCLASS;
                ev_msg.event_code       = KEV_ND6_NDFAILURE;

                nd6_ndfailure.link_data.if_family = ifp->if_family;
                nd6_ndfailure.link_data.if_unit = ifp->if_unit;
                strlcpy(nd6_ndfailure.link_data.if_name,
                    ifp->if_name,
                    sizeof(nd6_ndfailure.link_data.if_name));
                ev_msg.dv[0].data_ptr = &nd6_ndfailure;
                ev_msg.dv[0].data_length =
                    sizeof(nd6_ndfailure);
                dlil_post_complete_msg(NULL, &ev_msg);
        }

        send_nc_failure_kev = FALSE;
        ifp = NULL;
        /*
         * The global list llinfo_nd6 is modified by nd6_request() and is
         * therefore protected by rnh_lock.  For obvious reasons, we cannot
         * hold rnh_lock across calls that might lead to code paths which
         * attempt to acquire rnh_lock, else we deadlock.  Hence for such
         * cases we drop rt_lock and rnh_lock, make the calls, and repeat the
         * loop.  To ensure that we don't process the same entry more than
         * once in a single timeout, we mark the "already-seen" entries with
         * ND6_LNF_TIMER_SKIP flag.  At the end of the loop, we do a second
         * pass thru the entries and clear the flag so they can be processed
         * during the next timeout.
         */
        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);

        ln = llinfo_nd6.ln_next;
        while (ln != NULL && ln != &llinfo_nd6) {
                struct rtentry *rt;
                struct sockaddr_in6 *dst;
                struct llinfo_nd6 *next;
                u_int32_t retrans, flags;
                struct nd_ifinfo *ndi = NULL;
                boolean_t is_router = FALSE;

                /* ln_next/prev/rt is protected by rnh_lock */
                next = ln->ln_next;
                rt = ln->ln_rt;
                RT_LOCK(rt);

                /* We've seen this already; skip it */
                if (ln->ln_flags & ND6_LNF_TIMER_SKIP) {
                        RT_UNLOCK(rt);
                        ln = next;
                        continue;
                }
                ap->found++;

                /* rt->rt_ifp should never be NULL */
                if ((ifp = rt->rt_ifp) == NULL) {
                        panic("%s: ln(%p) rt(%p) rt_ifp == NULL", __func__,
                            ln, rt);
                        /* NOTREACHED */
                }

                /* rt_llinfo must always be equal to ln */
                if ((struct llinfo_nd6 *)rt->rt_llinfo != ln) {
                        panic("%s: rt_llinfo(%p) is not equal to ln(%p)",
                            __func__, rt->rt_llinfo, ln);
                        /* NOTREACHED */
                }

                /* rt_key should never be NULL */
                dst = SIN6(rt_key(rt));
                if (dst == NULL) {
                        panic("%s: rt(%p) key is NULL ln(%p)", __func__,
                            rt, ln);
                        /* NOTREACHED */
                }

                /* Set the flag in case we jump to "again" */
                ln->ln_flags |= ND6_LNF_TIMER_SKIP;

                if (ln->ln_expire == 0 || (rt->rt_flags & RTF_STATIC)) {
                        ap->sticky++;
                } else if (ap->draining && (rt->rt_refcnt == 0)) {
                        /*
                         * If we are draining, immediately purge non-static
                         * entries without oustanding route refcnt.
                         */
                        if (ln->ln_state > ND6_LLINFO_INCOMPLETE) {
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                        } else {
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_PURGE);
                        }
                        ln_setexpire(ln, timenow);
                }

                /*
                 * If the entry has not expired, skip it.  Take note on the
                 * state, as entries that are in the STALE state are simply
                 * waiting to be garbage collected, in which case we can
                 * relax the callout scheduling (use nd6_prune_lazy).
                 */
                if (ln->ln_expire > timenow) {
                        switch (ln->ln_state) {
                        case ND6_LLINFO_STALE:
                                ap->aging_lazy++;
                                break;
                        default:
                                ap->aging++;
                                break;
                        }
                        RT_UNLOCK(rt);
                        ln = next;
                        continue;
                }

                ndi = ND_IFINFO(ifp);
                VERIFY(ndi->initialized);
                retrans = ndi->retrans;
                flags = ndi->flags;

                RT_LOCK_ASSERT_HELD(rt);
                is_router = (rt->rt_flags & RTF_ROUTER) ? TRUE : FALSE;

                switch (ln->ln_state) {
                case ND6_LLINFO_INCOMPLETE:
                        if (ln->ln_asked < nd6_mmaxtries) {
                                struct ifnet *exclifp = ln->ln_exclifp;
                                ln->ln_asked++;
                                ln_setexpire(ln, timenow + retrans / 1000);
                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                if (ip6_forwarding) {
                                        nd6_prproxy_ns_output(ifp, exclifp,
                                            NULL, &dst->sin6_addr, ln);
                                } else {
                                        nd6_ns_output(ifp, NULL,
                                            &dst->sin6_addr, ln, NULL);
                                }
                                RT_REMREF(rt);
                                ap->aging++;
                                lck_mtx_lock(rnh_lock);
                        } else {
                                struct mbuf *m = ln->ln_hold;
                                ln->ln_hold = NULL;
                                send_nc_failure_kev = is_router;
                                if (m != NULL) {
                                        RT_ADDREF_LOCKED(rt);
                                        RT_UNLOCK(rt);
                                        lck_mtx_unlock(rnh_lock);

                                        struct mbuf *mnext;
                                        while (m) {
                                                mnext = m->m_nextpkt;
                                                m->m_nextpkt = NULL;
                                                m->m_pkthdr.rcvif = ifp;
                                                icmp6_error_flag(m, ICMP6_DST_UNREACH,
                                                    ICMP6_DST_UNREACH_ADDR, 0, 0);
                                                m = mnext;
                                        }
                                } else {
                                        RT_ADDREF_LOCKED(rt);
                                        RT_UNLOCK(rt);
                                        lck_mtx_unlock(rnh_lock);
                                }

                                /*
                                 * Enqueue work item to invoke callback for
                                 * this route entry
                                 */
                                route_event_enqueue_nwk_wq_entry(rt, NULL,
                                    ROUTE_LLENTRY_UNREACH, NULL, FALSE);
                                nd6_free(rt);
                                ap->killed++;
                                lck_mtx_lock(rnh_lock);
                                /*
                                 * nd6_free above would flush out the routing table of
                                 * any cloned routes with same next-hop.
                                 * Walk the tree anyways as there could be static routes
                                 * left.
                                 *
                                 * We also already have a reference to rt that gets freed right
                                 * after the block below executes. Don't need an extra reference
                                 * on rt here.
                                 */
                                if (is_router) {
                                        struct route_event rt_ev;
                                        route_event_init(&rt_ev, rt, NULL, ROUTE_LLENTRY_UNREACH);
                                        (void) rnh->rnh_walktree(rnh, route_event_walktree, (void *)&rt_ev);
                                }
                                rtfree_locked(rt);
                        }
                        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
                        goto again;

                case ND6_LLINFO_REACHABLE:
                        if (ln->ln_expire != 0) {
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                                ln_setexpire(ln, timenow + nd6_gctimer);
                                ap->aging_lazy++;
                                /*
                                 * Enqueue work item to invoke callback for
                                 * this route entry
                                 */
                                route_event_enqueue_nwk_wq_entry(rt, NULL,
                                    ROUTE_LLENTRY_STALE, NULL, TRUE);

                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                if (is_router) {
                                        struct route_event rt_ev;
                                        route_event_init(&rt_ev, rt, NULL, ROUTE_LLENTRY_STALE);
                                        (void) rnh->rnh_walktree(rnh, route_event_walktree, (void *)&rt_ev);
                                }
                                rtfree_locked(rt);
                        } else {
                                RT_UNLOCK(rt);
                        }
                        break;

                case ND6_LLINFO_STALE:
                case ND6_LLINFO_PURGE:
                        /* Garbage Collection(RFC 4861 5.3) */
                        if (ln->ln_expire != 0) {
                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                nd6_free(rt);
                                ap->killed++;
                                lck_mtx_lock(rnh_lock);
                                rtfree_locked(rt);
                                goto again;
                        } else {
                                RT_UNLOCK(rt);
                        }
                        break;

                case ND6_LLINFO_DELAY:
                        if ((flags & ND6_IFF_PERFORMNUD) != 0) {
                                /* We need NUD */
                                ln->ln_asked = 1;
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_PROBE);
                                ln_setexpire(ln, timenow + retrans / 1000);
                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                nd6_ns_output(ifp, &dst->sin6_addr,
                                    &dst->sin6_addr, ln, NULL);
                                RT_REMREF(rt);
                                ap->aging++;
                                lck_mtx_lock(rnh_lock);
                                goto again;
                        }
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE); /* XXX */
                        ln_setexpire(ln, timenow + nd6_gctimer);
                        RT_UNLOCK(rt);
                        ap->aging_lazy++;
                        break;

                case ND6_LLINFO_PROBE:
                        if (ln->ln_asked < nd6_umaxtries) {
                                ln->ln_asked++;
                                ln_setexpire(ln, timenow + retrans / 1000);
                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                nd6_ns_output(ifp, &dst->sin6_addr,
                                    &dst->sin6_addr, ln, NULL);
                                RT_REMREF(rt);
                                ap->aging++;
                                lck_mtx_lock(rnh_lock);
                        } else {
                                is_router = (rt->rt_flags & RTF_ROUTER) ? TRUE : FALSE;
                                send_nc_failure_kev = is_router;
                                RT_ADDREF_LOCKED(rt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                nd6_free(rt);
                                ap->killed++;

                                /*
                                 * Enqueue work item to invoke callback for
                                 * this route entry
                                 */
                                route_event_enqueue_nwk_wq_entry(rt, NULL,
                                    ROUTE_LLENTRY_UNREACH, NULL, FALSE);

                                lck_mtx_lock(rnh_lock);
                                /*
                                 * nd6_free above would flush out the routing table of
                                 * any cloned routes with same next-hop.
                                 * Walk the tree anyways as there could be static routes
                                 * left.
                                 *
                                 * We also already have a reference to rt that gets freed right
                                 * after the block below executes. Don't need an extra reference
                                 * on rt here.
                                 */
                                if (is_router) {
                                        struct route_event rt_ev;
                                        route_event_init(&rt_ev, rt, NULL, ROUTE_LLENTRY_UNREACH);
                                        (void) rnh->rnh_walktree(rnh,
                                            route_event_walktree, (void *)&rt_ev);
                                }
                                rtfree_locked(rt);
                        }
                        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
                        goto again;

                default:
                        RT_UNLOCK(rt);
                        break;
                }
                ln = next;
        }
        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);

        /* Now clear the flag from all entries */
        ln = llinfo_nd6.ln_next;
        while (ln != NULL && ln != &llinfo_nd6) {
                struct rtentry *rt = ln->ln_rt;
                struct llinfo_nd6 *next = ln->ln_next;

                RT_LOCK_SPIN(rt);
                if (ln->ln_flags & ND6_LNF_TIMER_SKIP) {
                        ln->ln_flags &= ~ND6_LNF_TIMER_SKIP;
                }
                RT_UNLOCK(rt);
                ln = next;
        }
        lck_mtx_unlock(rnh_lock);

        /* expire default router list */
        TAILQ_INIT(&nd_defrouter_tmp);

        lck_mtx_lock(nd6_mutex);
        TAILQ_FOREACH_SAFE(dr, &nd_defrouter, dr_entry, ndr) {
                ap->found++;
                if (dr->expire != 0 && dr->expire < timenow) {
                        VERIFY(dr->ifp != NULL);
                        in6_ifstat_inc(dr->ifp, ifs6_defrtr_expiry_cnt);
                        in6_event_enqueue_nwk_wq_entry(IN6_NDP_RTR_EXPIRY, dr->ifp,
                            &dr->rtaddr, dr->rtlifetime);
                        if (dr->ifp != NULL &&
                            dr->ifp->if_type == IFT_CELLULAR) {
                                /*
                                 * Some buggy cellular gateways may not send
                                 * periodic router advertisements.
                                 * Or they may send it with router lifetime
                                 * value that is less than the configured Max and Min
                                 * Router Advertisement interval.
                                 * To top that an idle device may not wake up
                                 * when periodic RA is received on cellular
                                 * interface.
                                 * We could send RS on every wake but RFC
                                 * 4861 precludes that.
                                 * The addresses are of infinite lifetimes
                                 * and are tied to the lifetime of the bearer,
                                 * so keeping the addresses and just getting rid of
                                 * the router does not help us anyways.
                                 * If there's network renumbering, a lifetime with
                                 * value 0 would remove the default router.
                                 * Also it will get deleted as part of purge when
                                 * the PDP context is torn down and configured again.
                                 * For that reason, do not expire the default router
                                 * learned on cellular interface. Ever.
                                 */
                                dr->expire += dr->rtlifetime;
                                nd6log2(debug,
                                    "%s: Refreshing expired default router entry "
                                    "%s for interface %s\n", __func__,
                                    ip6_sprintf(&dr->rtaddr), if_name(dr->ifp));
                        } else {
                                ap->killed++;
                                /*
                                 * Remove the entry from default router list
                                 * and add it to the temp list.
                                 * nd_defrouter_tmp will be a local temporary
                                 * list as no one else can get the same
                                 * removed entry once it is removed from default
                                 * router list.
                                 * Remove the reference after calling defrtrlist_del
                                 */
                                TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);
                                TAILQ_INSERT_TAIL(&nd_defrouter_tmp, dr, dr_entry);
                        }
                } else {
                        if (dr->expire == 0 || (dr->stateflags & NDDRF_STATIC)) {
                                ap->sticky++;
                        } else {
                                ap->aging_lazy++;
                        }
                }
        }

        /*
         * Keep the following  separate from the above
         * iteration of nd_defrouter because it's not safe
         * to call defrtrlist_del while iterating global default
         * router list. Global list has to be traversed
         * while holding nd6_mutex throughout.
         *
         * The following call to defrtrlist_del should be
         * safe as we are iterating a local list of
         * default routers.
         */
        TAILQ_FOREACH_SAFE(dr, &nd_defrouter_tmp, dr_entry, ndr) {
                TAILQ_REMOVE(&nd_defrouter_tmp, dr, dr_entry);
                defrtrlist_del(dr);
                NDDR_REMREF(dr);        /* remove list reference */
        }

        /*
         * Also check if default router selection needs to be triggered
         * for default interface, to avoid an issue with co-existence of
         * static un-scoped default route configuration and default router
         * discovery/selection.
         */
        if (trigger_v6_defrtr_select) {
                defrouter_select(NULL);
                trigger_v6_defrtr_select = FALSE;
        }
        lck_mtx_unlock(nd6_mutex);

        /*
         * 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.
         */
addrloop:
        lck_rw_lock_exclusive(&in6_ifaddr_rwlock);
        for (ia6 = in6_ifaddrs; ia6; ia6 = nia6) {
                int oldflags = ia6->ia6_flags;
                ap->found++;
                nia6 = ia6->ia_next;
                IFA_LOCK(&ia6->ia_ifa);
                /*
                 * Extra reference for ourselves; it's no-op if
                 * we don't have to regenerate temporary address,
                 * otherwise it protects the address from going
                 * away since we drop in6_ifaddr_rwlock below.
                 */
                IFA_ADDREF_LOCKED(&ia6->ia_ifa);
                /* check address lifetime */
                if (IFA6_IS_INVALID(ia6, timenow)) {
                        /*
                         * 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 (ip6_use_tempaddr &&
                            (ia6->ia6_flags & IN6_IFF_TEMPORARY) != 0) {
                                /*
                                 * NOTE: We have to drop the lock here
                                 * because regen_tmpaddr() eventually calls
                                 * in6_update_ifa(), which must take the lock
                                 * and would otherwise cause a hang.  This is
                                 * safe because the goto addrloop leads to a
                                 * re-evaluation of the in6_ifaddrs list
                                 */
                                IFA_UNLOCK(&ia6->ia_ifa);
                                lck_rw_done(&in6_ifaddr_rwlock);
                                (void) regen_tmpaddr(ia6);
                        } else {
                                IFA_UNLOCK(&ia6->ia_ifa);
                                lck_rw_done(&in6_ifaddr_rwlock);
                        }

                        /*
                         * Purging the address would have caused
                         * in6_ifaddr_rwlock to be dropped and reacquired;
                         * therefore search again from the beginning
                         * of in6_ifaddrs list.
                         */
                        in6_purgeaddr(&ia6->ia_ifa);
                        ap->killed++;

                        if ((ia6->ia6_flags & IN6_IFF_TEMPORARY) == 0) {
                                in6_ifstat_inc(ia6->ia_ifa.ifa_ifp, ifs6_addr_expiry_cnt);
                                in6_event_enqueue_nwk_wq_entry(IN6_NDP_ADDR_EXPIRY,
                                    ia6->ia_ifa.ifa_ifp, &ia6->ia_addr.sin6_addr,
                                    0);
                        }
                        /* Release extra reference taken above */
                        IFA_REMREF(&ia6->ia_ifa);
                        goto addrloop;
                }
                /*
                 * The lazy timer runs every nd6_prune_lazy seconds with at
                 * most "2 * nd6_prune_lazy - 1" leeway. We consider the worst
                 * case here and make sure we schedule the regular timer if an
                 * interface address is about to expire.
                 */
                if (IFA6_IS_INVALID(ia6, timenow + 3 * nd6_prune_lazy)) {
                        ap->aging++;
                } else {
                        ap->aging_lazy++;
                }
                IFA_LOCK_ASSERT_HELD(&ia6->ia_ifa);
                if (IFA6_IS_DEPRECATED(ia6, timenow)) {
                        ia6->ia6_flags |= IN6_IFF_DEPRECATED;

                        if ((oldflags & IN6_IFF_DEPRECATED) == 0) {
                                /*
                                 * Only enqueue the Deprecated event when the address just
                                 * becomes deprecated.
                                 * Keep it limited to the stable address as it is common for
                                 * older temporary addresses to get deprecated while we generate
                                 * new ones.
                                 */
                                if ((ia6->ia6_flags & IN6_IFF_TEMPORARY) == 0) {
                                        in6_event_enqueue_nwk_wq_entry(IN6_ADDR_MARKED_DEPRECATED,
                                            ia6->ia_ifa.ifa_ifp, &ia6->ia_addr.sin6_addr,
                                            0);
                                }
                        }
                        /*
                         * If a temporary address has just become deprecated,
                         * regenerate a new one if possible.
                         */
                        if (ip6_use_tempaddr &&
                            (ia6->ia6_flags & IN6_IFF_TEMPORARY) != 0 &&
                            (oldflags & IN6_IFF_DEPRECATED) == 0) {
                                /* see NOTE above */
                                IFA_UNLOCK(&ia6->ia_ifa);
                                lck_rw_done(&in6_ifaddr_rwlock);
                                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??
                                         */
                                        /* Release extra reference */
                                        IFA_REMREF(&ia6->ia_ifa);
                                        goto addrloop;
                                }
                                lck_rw_lock_exclusive(&in6_ifaddr_rwlock);
                        } else {
                                IFA_UNLOCK(&ia6->ia_ifa);
                        }
                } else {
                        /*
                         * A new RA might have made a deprecated address
                         * preferred.
                         */
                        ia6->ia6_flags &= ~IN6_IFF_DEPRECATED;
                        IFA_UNLOCK(&ia6->ia_ifa);
                }
                LCK_RW_ASSERT(&in6_ifaddr_rwlock, LCK_RW_ASSERT_EXCLUSIVE);
                /* Release extra reference taken above */
                IFA_REMREF(&ia6->ia_ifa);
        }
        lck_rw_done(&in6_ifaddr_rwlock);

        lck_mtx_lock(nd6_mutex);
        /* expire prefix list */
        pr = nd_prefix.lh_first;
        while (pr != NULL) {
                ap->found++;
                /*
                 * check prefix lifetime.
                 * since pltime is just for autoconf, pltime processing for
                 * prefix is not necessary.
                 */
                NDPR_LOCK(pr);
                if (pr->ndpr_stateflags & NDPRF_PROCESSED_SERVICE ||
                    pr->ndpr_stateflags & NDPRF_DEFUNCT) {
                        pr->ndpr_stateflags |= NDPRF_PROCESSED_SERVICE;
                        NDPR_UNLOCK(pr);
                        pr = pr->ndpr_next;
                        continue;
                }
                if (pr->ndpr_expire != 0 && pr->ndpr_expire < timenow) {
                        /*
                         * address expiration and prefix expiration are
                         * separate. NEVER perform in6_purgeaddr here.
                         */
                        pr->ndpr_stateflags |= NDPRF_PROCESSED_SERVICE;
                        NDPR_ADDREF_LOCKED(pr);
                        prelist_remove(pr);
                        NDPR_UNLOCK(pr);

                        in6_ifstat_inc(pr->ndpr_ifp, ifs6_pfx_expiry_cnt);
                        in6_event_enqueue_nwk_wq_entry(IN6_NDP_PFX_EXPIRY,
                            pr->ndpr_ifp, &pr->ndpr_prefix.sin6_addr,
                            0);
                        NDPR_REMREF(pr);
                        pfxlist_onlink_check();
                        pr = nd_prefix.lh_first;
                        ap->killed++;
                } else {
                        if (pr->ndpr_expire == 0 ||
                            (pr->ndpr_stateflags & NDPRF_STATIC)) {
                                ap->sticky++;
                        } else {
                                ap->aging_lazy++;
                        }
                        pr->ndpr_stateflags |= NDPRF_PROCESSED_SERVICE;
                        NDPR_UNLOCK(pr);
                        pr = pr->ndpr_next;
                }
        }
        LIST_FOREACH(pr, &nd_prefix, ndpr_entry) {
                NDPR_LOCK(pr);
                pr->ndpr_stateflags &= ~NDPRF_PROCESSED_SERVICE;
                NDPR_UNLOCK(pr);
        }
        lck_mtx_unlock(nd6_mutex);

        lck_mtx_lock(rnh_lock);
        /* We're done; let others enter */
        nd6_service_busy = FALSE;
        if (nd6_service_waiters > 0) {
                nd6_service_waiters = 0;
                wakeup(nd6_service_wc);
        }
}


static int nd6_need_draining = 0;

void
nd6_drain(void *arg)
{
#pragma unused(arg)
        nd6log2(debug, "%s: draining ND6 entries\n", __func__);

        lck_mtx_lock(rnh_lock);
        nd6_need_draining = 1;
        nd6_sched_timeout(NULL, NULL);
        lck_mtx_unlock(rnh_lock);
}

/*
 * We use the ``arg'' variable to decide whether or not the timer we're
 * running is the fast timer. We do this to reset the nd6_fast_timer_on
 * variable so that later we don't end up ignoring a ``fast timer''
 * request if the 5 second timer is running (see nd6_sched_timeout).
 */
static void
nd6_timeout(void *arg)
{
        struct nd6svc_arg sarg;
        uint32_t buf;

        lck_mtx_lock(rnh_lock);
        bzero(&sarg, sizeof(sarg));
        if (nd6_need_draining != 0) {
                nd6_need_draining = 0;
                sarg.draining = 1;
        }
        nd6_service(&sarg);
        nd6log2(debug, "%s: found %u, aging_lazy %u, aging %u, "
            "sticky %u, killed %u\n", __func__, sarg.found, sarg.aging_lazy,
            sarg.aging, sarg.sticky, sarg.killed);
        /* re-arm the timer if there's work to do */
        nd6_timeout_run--;
        VERIFY(nd6_timeout_run >= 0 && nd6_timeout_run < 2);
        if (arg == &nd6_fast_timer_on) {
                nd6_fast_timer_on = FALSE;
        }
        if (sarg.aging_lazy > 0 || sarg.aging > 0 || nd6_sched_timeout_want) {
                struct timeval atv, ltv, *leeway;
                int lazy = nd6_prune_lazy;

                if (sarg.aging > 0 || lazy < 1) {
                        atv.tv_usec = 0;
                        atv.tv_sec = nd6_prune;
                        leeway = NULL;
                } else {
                        VERIFY(lazy >= 1);
                        atv.tv_usec = 0;
                        atv.tv_sec = MAX(nd6_prune, lazy);
                        ltv.tv_usec = 0;
                        read_frandom(&buf, sizeof(buf));
                        ltv.tv_sec = MAX(buf % lazy, 1) * 2;
                        leeway = &ltv;
                }
                nd6_sched_timeout(&atv, leeway);
        } else if (nd6_debug) {
                nd6log2(debug, "%s: not rescheduling timer\n", __func__);
        }
        lck_mtx_unlock(rnh_lock);
}

void
nd6_sched_timeout(struct timeval *atv, struct timeval *ltv)
{
        struct timeval tv;

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
        if (atv == NULL) {
                tv.tv_usec = 0;
                tv.tv_sec = MAX(nd6_prune, 1);
                atv = &tv;
                ltv = NULL;     /* ignore leeway */
        }
        /* see comments on top of this file */
        if (nd6_timeout_run == 0) {
                if (ltv == NULL) {
                        nd6log2(debug, "%s: timer scheduled in "
                            "T+%llus.%lluu (demand %d)\n", __func__,
                            (uint64_t)atv->tv_sec, (uint64_t)atv->tv_usec,
                            nd6_sched_timeout_want);
                        nd6_fast_timer_on = TRUE;
                        timeout(nd6_timeout, &nd6_fast_timer_on, tvtohz(atv));
                } else {
                        nd6log2(debug, "%s: timer scheduled in "
                            "T+%llus.%lluu with %llus.%lluu leeway "
                            "(demand %d)\n", __func__, (uint64_t)atv->tv_sec,
                            (uint64_t)atv->tv_usec, (uint64_t)ltv->tv_sec,
                            (uint64_t)ltv->tv_usec, nd6_sched_timeout_want);
                        nd6_fast_timer_on = FALSE;
                        timeout_with_leeway(nd6_timeout, NULL,
                            tvtohz(atv), tvtohz(ltv));
                }
                nd6_timeout_run++;
                nd6_sched_timeout_want = 0;
        } else if (nd6_timeout_run == 1 && ltv == NULL &&
            nd6_fast_timer_on == FALSE) {
                nd6log2(debug, "%s: fast timer scheduled in "
                    "T+%llus.%lluu (demand %d)\n", __func__,
                    (uint64_t)atv->tv_sec, (uint64_t)atv->tv_usec,
                    nd6_sched_timeout_want);
                nd6_fast_timer_on = TRUE;
                nd6_sched_timeout_want = 0;
                nd6_timeout_run++;
                timeout(nd6_timeout, &nd6_fast_timer_on, tvtohz(atv));
        } else {
                if (ltv == NULL) {
                        nd6log2(debug, "%s: not scheduling timer: "
                            "timers %d, fast_timer %d, T+%llus.%lluu\n",
                            __func__, nd6_timeout_run, nd6_fast_timer_on,
                            (uint64_t)atv->tv_sec, (uint64_t)atv->tv_usec);
                } else {
                        nd6log2(debug, "%s: not scheduling timer: "
                            "timers %d, fast_timer %d, T+%llus.%lluu "
                            "with %llus.%lluu leeway\n", __func__,
                            nd6_timeout_run, nd6_fast_timer_on,
                            (uint64_t)atv->tv_sec, (uint64_t)atv->tv_usec,
                            (uint64_t)ltv->tv_sec, (uint64_t)ltv->tv_usec);
                }
        }
}

/*
 * ND6 router advertisement kernel notification
 */
void
nd6_post_msg(u_int32_t code, struct nd_prefix_list *prefix_list,
    u_int32_t list_length, u_int32_t mtu)
{
        struct kev_msg ev_msg;
        struct kev_nd6_ra_data nd6_ra_msg_data;
        struct nd_prefix_list *itr = prefix_list;

        bzero(&ev_msg, sizeof(struct kev_msg));
        ev_msg.vendor_code      = KEV_VENDOR_APPLE;
        ev_msg.kev_class        = KEV_NETWORK_CLASS;
        ev_msg.kev_subclass     = KEV_ND6_SUBCLASS;
        ev_msg.event_code       = code;

        bzero(&nd6_ra_msg_data, sizeof(nd6_ra_msg_data));

        if (mtu > 0 && mtu >= IPV6_MMTU) {
                nd6_ra_msg_data.mtu = mtu;
                nd6_ra_msg_data.flags |= KEV_ND6_DATA_VALID_MTU;
        }

        if (list_length > 0 && prefix_list != NULL) {
                nd6_ra_msg_data.list_length = list_length;
                nd6_ra_msg_data.flags |= KEV_ND6_DATA_VALID_PREFIX;
        }

        while (itr != NULL && nd6_ra_msg_data.list_index < list_length) {
                bcopy(&itr->pr.ndpr_prefix, &nd6_ra_msg_data.prefix.prefix,
                    sizeof(nd6_ra_msg_data.prefix.prefix));
                nd6_ra_msg_data.prefix.raflags = itr->pr.ndpr_raf;
                nd6_ra_msg_data.prefix.prefixlen = itr->pr.ndpr_plen;
                nd6_ra_msg_data.prefix.origin = PR_ORIG_RA;
                nd6_ra_msg_data.prefix.vltime = itr->pr.ndpr_vltime;
                nd6_ra_msg_data.prefix.pltime = itr->pr.ndpr_pltime;
                nd6_ra_msg_data.prefix.expire = ndpr_getexpire(&itr->pr);
                nd6_ra_msg_data.prefix.flags = itr->pr.ndpr_stateflags;
                nd6_ra_msg_data.prefix.refcnt = itr->pr.ndpr_addrcnt;
                nd6_ra_msg_data.prefix.if_index = itr->pr.ndpr_ifp->if_index;

                /* send the message up */
                ev_msg.dv[0].data_ptr           = &nd6_ra_msg_data;
                ev_msg.dv[0].data_length        = sizeof(nd6_ra_msg_data);
                ev_msg.dv[1].data_length        = 0;
                dlil_post_complete_msg(NULL, &ev_msg);

                /* clean up for the next prefix */
                bzero(&nd6_ra_msg_data.prefix, sizeof(nd6_ra_msg_data.prefix));
                itr = itr->next;
                nd6_ra_msg_data.list_index++;
        }
}

/*
 * Regenerate deprecated/invalidated temporary address
 */
static int
regen_tmpaddr(struct in6_ifaddr *ia6)
{
        struct ifaddr *ifa;
        struct ifnet *ifp;
        struct in6_ifaddr *public_ifa6 = NULL;
        uint64_t timenow = net_uptime();

        ifp = ia6->ia_ifa.ifa_ifp;
        ifnet_lock_shared(ifp);
        TAILQ_FOREACH(ifa, &ifp->if_addrlist, ifa_list) {
                struct in6_ifaddr *it6;

                IFA_LOCK(ifa);
                if (ifa->ifa_addr->sa_family != AF_INET6) {
                        IFA_UNLOCK(ifa);
                        continue;
                }
                it6 = (struct in6_ifaddr *)ifa;

                /* ignore no autoconf addresses. */
                if ((it6->ia6_flags & IN6_IFF_AUTOCONF) == 0) {
                        IFA_UNLOCK(ifa);
                        continue;
                }
                /* ignore autoconf addresses with different prefixes. */
                if (it6->ia6_ndpr == NULL || it6->ia6_ndpr != ia6->ia6_ndpr) {
                        IFA_UNLOCK(ifa);
                        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, timenow)) {
                        IFA_UNLOCK(ifa);
                        if (public_ifa6 != NULL) {
                                IFA_REMREF(&public_ifa6->ia_ifa);
                        }
                        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, timenow)) {
                        IFA_ADDREF_LOCKED(ifa); /* for public_ifa6 */
                        IFA_UNLOCK(ifa);
                        if (public_ifa6 != NULL) {
                                IFA_REMREF(&public_ifa6->ia_ifa);
                        }
                        public_ifa6 = it6;
                } else {
                        IFA_UNLOCK(ifa);
                }
        }
        ifnet_lock_done(ifp);

        if (public_ifa6 != NULL) {
                int e;

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

        return -1;
}

/*
 * Nuke neighbor cache/prefix/default router management table, right before
 * ifp goes away.
 */
void
nd6_purge(struct ifnet *ifp)
{
        struct llinfo_nd6 *ln;
        struct nd_defrouter *dr, *ndr;
        struct nd_prefix *pr, *npr;
        boolean_t removed;
        struct nd_drhead nd_defrouter_tmp;

        TAILQ_INIT(&nd_defrouter_tmp);

        /* Nuke default router list entries toward ifp */
        lck_mtx_lock(nd6_mutex);
        TAILQ_FOREACH_SAFE(dr, &nd_defrouter, dr_entry, ndr) {
                if (dr->ifp != ifp) {
                        continue;
                }
                /*
                 * Remove the entry from default router list
                 * and add it to the temp list.
                 * nd_defrouter_tmp will be a local temporary
                 * list as no one else can get the same
                 * removed entry once it is removed from default
                 * router list.
                 * Remove the reference after calling defrtrlist_del.
                 *
                 * The uninstalled entries have to be iterated first
                 * when we call defrtrlist_del.
                 * This is to ensure that we don't end up calling
                 * default router  selection when there are other
                 * uninstalled candidate default routers on
                 * the interface.
                 * If we don't respect that order, we may end
                 * up missing out on some entries.
                 *
                 * For that reason, installed ones must be inserted
                 * at the tail and uninstalled ones at the head
                 */
                TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);

                if (dr->stateflags & NDDRF_INSTALLED) {
                        TAILQ_INSERT_TAIL(&nd_defrouter_tmp, dr, dr_entry);
                } else {
                        TAILQ_INSERT_HEAD(&nd_defrouter_tmp, dr, dr_entry);
                }
        }

        /*
         * The following call to defrtrlist_del should be
         * safe as we are iterating a local list of
         * default routers.
         *
         * We don't really need nd6_mutex here but keeping
         * it as it is to avoid changing assertios held in
         * the functions in the call-path.
         */
        TAILQ_FOREACH_SAFE(dr, &nd_defrouter_tmp, dr_entry, ndr) {
                TAILQ_REMOVE(&nd_defrouter_tmp, dr, dr_entry);
                defrtrlist_del(dr);
                NDDR_REMREF(dr);        /* remove list reference */
        }

        /* Nuke prefix list entries toward ifp */
        removed = FALSE;
        for (pr = nd_prefix.lh_first; pr; pr = npr) {
                NDPR_LOCK(pr);
                npr = pr->ndpr_next;
                if (pr->ndpr_ifp == ifp &&
                    !(pr->ndpr_stateflags & NDPRF_DEFUNCT)) {
                        /*
                         * Because if_detach() does *not* release prefixes
                         * while purging addresses the reference count will
                         * still be above zero. We therefore reset it to
                         * make sure that the prefix really gets purged.
                         */
                        pr->ndpr_addrcnt = 0;

                        /*
                         * Previously, pr->ndpr_addr is removed as well,
                         * but I strongly believe we don't have to do it.
                         * nd6_purge() is only called from in6_ifdetach(),
                         * which removes all the associated interface addresses
                         * by itself.
                         * (jinmei@kame.net 20010129)
                         */
                        NDPR_ADDREF_LOCKED(pr);
                        prelist_remove(pr);
                        NDPR_UNLOCK(pr);
                        NDPR_REMREF(pr);
                        removed = TRUE;
                        npr = nd_prefix.lh_first;
                } else {
                        NDPR_UNLOCK(pr);
                }
        }
        if (removed) {
                pfxlist_onlink_check();
        }
        lck_mtx_unlock(nd6_mutex);

        /* cancel default outgoing interface setting */
        if (nd6_defifindex == ifp->if_index) {
                nd6_setdefaultiface(0);
        }

        /*
         * Perform default router selection even when we are a router,
         * if Scoped Routing is enabled.
         */
        lck_mtx_lock(nd6_mutex);
        /* refresh default router list */
        defrouter_select(ifp);
        lck_mtx_unlock(nd6_mutex);

        /*
         * Nuke neighbor cache entries for the ifp.
         * Note that rt->rt_ifp may not be the same as ifp,
         * due to KAME goto ours hack.  See RTM_RESOLVE case in
         * nd6_rtrequest(), and ip6_input().
         */
again:
        lck_mtx_lock(rnh_lock);
        ln = llinfo_nd6.ln_next;
        while (ln != NULL && ln != &llinfo_nd6) {
                struct rtentry *rt;
                struct llinfo_nd6 *nln;

                nln = ln->ln_next;
                rt = ln->ln_rt;
                RT_LOCK(rt);
                if (rt->rt_gateway != NULL &&
                    rt->rt_gateway->sa_family == AF_LINK &&
                    SDL(rt->rt_gateway)->sdl_index == ifp->if_index) {
                        RT_ADDREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        lck_mtx_unlock(rnh_lock);
                        /*
                         * See comments on nd6_service() for reasons why
                         * this loop is repeated; we bite the costs of
                         * going thru the same llinfo_nd6 more than once
                         * here, since this purge happens during detach,
                         * and that unlike the timer case, it's possible
                         * there's more than one purges happening at the
                         * same time (thus a flag wouldn't buy anything).
                         */
                        nd6_free(rt);
                        RT_REMREF(rt);
                        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
                        goto again;
                } else {
                        RT_UNLOCK(rt);
                }
                ln = nln;
        }
        lck_mtx_unlock(rnh_lock);
}

/*
 * Upon success, the returned route will be locked and the caller is
 * responsible for releasing the reference and doing RT_UNLOCK(rt).
 * This routine does not require rnh_lock to be held by the caller,
 * although it needs to be indicated of such a case in order to call
 * the correct variant of the relevant routing routines.
 */
struct rtentry *
nd6_lookup(struct in6_addr *addr6, int create, struct ifnet *ifp, int rt_locked)
{
        struct rtentry *rt;
        struct sockaddr_in6 sin6;
        unsigned int ifscope;

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

        ifscope = (ifp != NULL) ? ifp->if_index : IFSCOPE_NONE;
        if (rt_locked) {
                LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
                rt = rtalloc1_scoped_locked(SA(&sin6), create, 0, ifscope);
        } else {
                rt = rtalloc1_scoped(SA(&sin6), create, 0, ifscope);
        }

        if (rt != NULL) {
                RT_LOCK(rt);
                if ((rt->rt_flags & RTF_LLINFO) == 0) {
                        /*
                         * This is the case for the default route.
                         * If we want to create a neighbor cache for the
                         * address, we should free the route for the
                         * destination and allocate an interface route.
                         */
                        if (create) {
                                RT_UNLOCK(rt);
                                if (rt_locked) {
                                        rtfree_locked(rt);
                                } else {
                                        rtfree(rt);
                                }
                                rt = NULL;
                        }
                }
        }
        if (rt == NULL) {
                if (create && ifp) {
                        struct ifaddr *ifa;
                        u_int32_t ifa_flags;
                        int e;

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

                        /*
                         * Create a new route.  RTF_LLINFO is necessary
                         * to create a Neighbor Cache entry for the
                         * destination in nd6_rtrequest which will be
                         * called in rtrequest via ifa->ifa_rtrequest.
                         */
                        if (!rt_locked) {
                                lck_mtx_lock(rnh_lock);
                        }
                        IFA_LOCK_SPIN(ifa);
                        ifa_flags = ifa->ifa_flags;
                        IFA_UNLOCK(ifa);
                        if ((e = rtrequest_scoped_locked(RTM_ADD,
                            SA(&sin6), ifa->ifa_addr, SA(&all1_sa),
                            (ifa_flags | RTF_HOST | RTF_LLINFO) &
                            ~RTF_CLONING, &rt, ifscope)) != 0) {
                                if (e != EEXIST) {
                                        log(LOG_ERR, "%s: failed to add route "
                                            "for a neighbor(%s), errno=%d\n",
                                            __func__, ip6_sprintf(addr6), e);
                                }
                        }
                        if (!rt_locked) {
                                lck_mtx_unlock(rnh_lock);
                        }
                        IFA_REMREF(ifa);
                        if (rt == NULL) {
                                return NULL;
                        }

                        RT_LOCK(rt);
                        if (rt->rt_llinfo) {
                                struct llinfo_nd6 *ln = rt->rt_llinfo;
                                struct nd_ifinfo *ndi = ND_IFINFO(rt->rt_ifp);

                                VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
                                /*
                                 * For interface's that do not perform NUD
                                 * neighbor cache entres must always be marked
                                 * reachable with no expiry
                                 */
                                if (ndi->flags & ND6_IFF_PERFORMNUD) {
                                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_NOSTATE);
                                } else {
                                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                                        ln_setexpire(ln, 0);
                                }
                        }
                } else {
                        return NULL;
                }
        }
        RT_LOCK_ASSERT_HELD(rt);
        /*
         * Validation for the entry.
         * Note that the check for rt_llinfo is necessary because a cloned
         * route from a parent route that has the L flag (e.g. the default
         * route to a p2p interface) may have the flag, too, while the
         * destination is not actually a neighbor.
         * XXX: we can't use rt->rt_ifp to check for the interface, since
         *      it might be the loopback interface if the entry is for our
         *      own address on a non-loopback interface. Instead, we should
         *      use rt->rt_ifa->ifa_ifp, which would specify the REAL
         *      interface.
         * Note also that ifa_ifp and ifp may differ when we connect two
         * interfaces to a same link, install a link prefix to an interface,
         * and try to install a neighbor cache on an interface that does not
         * have a route to the prefix.
         *
         * If the address is from a proxied prefix, the ifa_ifp and ifp might
         * not match, because nd6_na_input() could have modified the ifp
         * of the route to point to the interface where the NA arrived on,
         * hence the test for RTF_PROXY.
         */
        if ((rt->rt_flags & RTF_GATEWAY) || (rt->rt_flags & RTF_LLINFO) == 0 ||
            rt->rt_gateway->sa_family != AF_LINK || rt->rt_llinfo == NULL ||
            (ifp && rt->rt_ifa->ifa_ifp != ifp &&
            !(rt->rt_flags & RTF_PROXY))) {
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
                if (create) {
                        log(LOG_DEBUG, "%s: failed to lookup %s "
                            "(if = %s)\n", __func__, ip6_sprintf(addr6),
                            ifp ? if_name(ifp) : "unspec");
                        /* xxx more logs... kazu */
                }
                return NULL;
        }
        /*
         * Caller needs to release reference and call RT_UNLOCK(rt).
         */
        return rt;
}

/*
 * Test whether a given IPv6 address is a neighbor or not, ignoring
 * the actual neighbor cache.  The neighbor cache is ignored in order
 * to not reenter the routing code from within itself.
 */
static int
nd6_is_new_addr_neighbor(struct sockaddr_in6 *addr, struct ifnet *ifp)
{
        struct nd_prefix *pr;
        struct ifaddr *dstaddr;

        LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        /*
         * 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, FALSE)) {
                        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;
                }
        }

        /*
         * If the address matches one of our addresses,
         * it should be a neighbor.
         * If the address matches one of our on-link prefixes, it should be a
         * neighbor.
         */
        for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
                NDPR_LOCK(pr);
                if (pr->ndpr_ifp != ifp) {
                        NDPR_UNLOCK(pr);
                        continue;
                }
                if (!(pr->ndpr_stateflags & NDPRF_ONLINK)) {
                        NDPR_UNLOCK(pr);
                        continue;
                }
                if (IN6_ARE_MASKED_ADDR_EQUAL(&pr->ndpr_prefix.sin6_addr,
                    &addr->sin6_addr, &pr->ndpr_mask)) {
                        NDPR_UNLOCK(pr);
                        return 1;
                }
                NDPR_UNLOCK(pr);
        }

        /*
         * If the address is assigned on the node of the other side of
         * a p2p interface, the address should be a neighbor.
         */
        dstaddr = ifa_ifwithdstaddr(SA(addr));
        if (dstaddr != NULL) {
                if (dstaddr->ifa_ifp == ifp) {
                        IFA_REMREF(dstaddr);
                        return 1;
                }
                IFA_REMREF(dstaddr);
                dstaddr = NULL;
        }

        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(struct sockaddr_in6 *addr, struct ifnet *ifp,
    int rt_locked)
{
        struct rtentry *rt;

        LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);
        lck_mtx_lock(nd6_mutex);
        if (nd6_is_new_addr_neighbor(addr, ifp)) {
                lck_mtx_unlock(nd6_mutex);
                return 1;
        }
        lck_mtx_unlock(nd6_mutex);

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

        return 0;
}

/*
 * 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.
 */
void
nd6_free(struct rtentry *rt)
{
        struct llinfo_nd6 *ln = NULL;
        struct in6_addr in6 = {};
        struct nd_defrouter *dr = NULL;

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
        RT_LOCK_ASSERT_NOTHELD(rt);
        lck_mtx_lock(nd6_mutex);

        RT_LOCK(rt);
        RT_ADDREF_LOCKED(rt);   /* Extra ref */
        ln = rt->rt_llinfo;
        in6 = SIN6(rt_key(rt))->sin6_addr;

        /*
         * Prevent another thread from modifying rt_key, rt_gateway
         * via rt_setgate() after the rt_lock is dropped by marking
         * the route as defunct.
         */
        rt->rt_flags |= RTF_CONDEMNED;

        /*
         * We used to have pfctlinput(PRC_HOSTDEAD) here.  Even though it is
         * not harmful, it was not really necessary.  Perform default router
         * selection even when we are a router, if Scoped Routing is enabled.
         */
        dr = defrouter_lookup(&SIN6(rt_key(rt))->sin6_addr, rt->rt_ifp);

        if ((ln && ln->ln_router) || dr) {
                /*
                 * rt6_flush must be called whether or not the neighbor
                 * is in the Default Router List.
                 * See a corresponding comment in nd6_na_input().
                 */
                RT_UNLOCK(rt);
                lck_mtx_unlock(nd6_mutex);
                rt6_flush(&in6, rt->rt_ifp);
                lck_mtx_lock(nd6_mutex);
        } else {
                RT_UNLOCK(rt);
        }

        if (dr) {
                NDDR_REMREF(dr);
                /*
                 * Unreachablity 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.
                 */
                RT_LOCK_SPIN(rt);
                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_INCOMPLETE);

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

                /*
                 * refresh default router list
                 */
                defrouter_select(rt->rt_ifp);
        }
        RT_LOCK_ASSERT_NOTHELD(rt);
        lck_mtx_unlock(nd6_mutex);
        /*
         * Detach the route from the routing tree and the list of neighbor
         * caches, and disable the route entry not to be used in already
         * cached routes.
         */
        (void) rtrequest(RTM_DELETE, rt_key(rt), NULL, rt_mask(rt), 0, NULL);

        /* Extra ref held above; now free it */
        rtfree(rt);
}

void
nd6_rtrequest(int req, struct rtentry *rt, struct sockaddr *sa)
{
#pragma unused(sa)
        struct sockaddr *gate = rt->rt_gateway;
        struct llinfo_nd6 *ln = rt->rt_llinfo;
        static struct sockaddr_dl null_sdl =
        { .sdl_len = sizeof(null_sdl), .sdl_family = AF_LINK };
        struct ifnet *ifp = rt->rt_ifp;
        struct ifaddr *ifa;
        uint64_t timenow;
        char buf[MAX_IPv6_STR_LEN];
        struct nd_ifinfo *ndi = ND_IFINFO(rt->rt_ifp);

        VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
        VERIFY(nd6_init_done);
        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);
        RT_LOCK_ASSERT_HELD(rt);

        /*
         * We have rnh_lock held, see if we need to schedule the timer;
         * we might do this again below during RTM_RESOLVE, but doing it
         * now handles all other cases.
         */
        if (nd6_sched_timeout_want) {
                nd6_sched_timeout(NULL, NULL);
        }

        if (rt->rt_flags & RTF_GATEWAY) {
                return;
        }

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

        if (req == RTM_RESOLVE) {
                int no_nd_cache;

                if (!nd6_need_cache(ifp)) {     /* stf case */
                        no_nd_cache = 1;
                } else {
                        struct sockaddr_in6 sin6;

                        rtkey_to_sa6(rt, &sin6);
                        /*
                         * nd6_is_addr_neighbor() may call nd6_lookup(),
                         * therefore we drop rt_lock to avoid deadlock
                         * during the lookup.
                         */
                        RT_ADDREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        no_nd_cache = !nd6_is_addr_neighbor(&sin6, ifp, 1);
                        RT_LOCK(rt);
                        RT_REMREF_LOCKED(rt);
                }

                /*
                 * FreeBSD and BSD/OS often make a cloned host route based
                 * on a less-specific route (e.g. the default route).
                 * If the less specific route does not have a "gateway"
                 * (this is the case when the route just goes to a p2p or an
                 * stf interface), we'll mistakenly make a neighbor cache for
                 * the host route, and will see strange neighbor solicitation
                 * for the corresponding destination.  In order to avoid the
                 * confusion, we check if the destination of the route is
                 * a neighbor in terms of neighbor discovery, and stop the
                 * process if not.  Additionally, we remove the LLINFO flag
                 * so that ndp(8) will not try to get the neighbor information
                 * of the destination.
                 */
                if (no_nd_cache) {
                        rt->rt_flags &= ~RTF_LLINFO;
                        return;
                }
        }

        timenow = net_uptime();

        switch (req) {
        case RTM_ADD:
                /*
                 * There is no backward compatibility :)
                 *
                 * if ((rt->rt_flags & RTF_HOST) == 0 &&
                 *      SIN(rt_mask(rt))->sin_addr.s_addr != 0xffffffff)
                 *              rt->rt_flags |= RTF_CLONING;
                 */
                if ((rt->rt_flags & RTF_CLONING) ||
                    ((rt->rt_flags & RTF_LLINFO) && ln == NULL)) {
                        /*
                         * Case 1: This route should come from a route to
                         * interface (RTF_CLONING case) or the route should be
                         * treated as on-link but is currently not
                         * (RTF_LLINFO && ln == NULL case).
                         */
                        if (rt_setgate(rt, rt_key(rt), SA(&null_sdl)) == 0) {
                                gate = rt->rt_gateway;
                                SDL(gate)->sdl_type = ifp->if_type;
                                SDL(gate)->sdl_index = ifp->if_index;
                                /*
                                 * In case we're called before 1.0 sec.
                                 * has elapsed.
                                 */
                                if (ln != NULL) {
                                        ln_setexpire(ln,
                                            (ifp->if_eflags & IFEF_IPV6_ND6ALT)
                                            ? 0 : MAX(timenow, 1));
                                }
                        }
                        if (rt->rt_flags & RTF_CLONING) {
                                break;
                        }
                }
        /*
         * In IPv4 code, we try to annonuce new RTF_ANNOUNCE entry here.
         * We don't do that here since llinfo is not ready yet.
         *
         * There are also couple of other things to be discussed:
         * - unsolicited NA code needs improvement beforehand
         * - RFC4861 says we MAY send multicast unsolicited NA
         *   (7.2.6 paragraph 4), however, it also says that we
         *   SHOULD provide a mechanism to prevent multicast NA storm.
         *   we don't have anything like it right now.
         *   note that the mechanism needs a mutual agreement
         *   between proxies, which means that we need to implement
         *   a new protocol, or a new kludge.
         * - from RFC4861 6.2.4, host MUST NOT send an unsolicited RA.
         *   we need to check ip6forwarding before sending it.
         *   (or should we allow proxy ND configuration only for
         *   routers?  there's no mention about proxy ND from hosts)
         */
        /* FALLTHROUGH */
        case RTM_RESOLVE:
                if (!(ifp->if_flags & (IFF_POINTOPOINT | IFF_LOOPBACK))) {
                        /*
                         * Address resolution isn't necessary for a point to
                         * point link, so we can skip this test for a p2p link.
                         */
                        if (gate->sa_family != AF_LINK ||
                            gate->sa_len < sizeof(null_sdl)) {
                                /* Don't complain in case of RTM_ADD */
                                if (req == RTM_RESOLVE) {
                                        log(LOG_ERR, "%s: route to %s has bad "
                                            "gateway address (sa_family %u "
                                            "sa_len %u) on %s\n", __func__,
                                            inet_ntop(AF_INET6,
                                            &SIN6(rt_key(rt))->sin6_addr, buf,
                                            sizeof(buf)), gate->sa_family,
                                            gate->sa_len, if_name(ifp));
                                }
                                break;
                        }
                        SDL(gate)->sdl_type = ifp->if_type;
                        SDL(gate)->sdl_index = ifp->if_index;
                }
                if (ln != NULL) {
                        break;  /* This happens on a route change */
                }
                /*
                 * Case 2: This route may come from cloning, or a manual route
                 * add with a LL address.
                 */
                rt->rt_llinfo = ln = nd6_llinfo_alloc(M_WAITOK);
                if (ln == NULL) {
                        break;
                }

                nd6_allocated++;
                rt->rt_llinfo_get_ri    = nd6_llinfo_get_ri;
                rt->rt_llinfo_get_iflri = nd6_llinfo_get_iflri;
                rt->rt_llinfo_purge     = nd6_llinfo_purge;
                rt->rt_llinfo_free      = nd6_llinfo_free;
                rt->rt_llinfo_refresh   = nd6_llinfo_refresh;
                rt->rt_flags |= RTF_LLINFO;
                ln->ln_rt = rt;
                /* this is required for "ndp" command. - shin */
                /*
                 * For interface's that do not perform NUD
                 * neighbor cache entries must always be marked
                 * reachable with no expiry
                 */
                if ((req == RTM_ADD) ||
                    !(ndi->flags & ND6_IFF_PERFORMNUD)) {
                        /*
                         * gate should have some valid AF_LINK entry,
                         * and ln->ln_expire should have some lifetime
                         * which is specified by ndp command.
                         */
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                        ln_setexpire(ln, 0);
                } else {
                        /*
                         * When req == RTM_RESOLVE, rt is created and
                         * initialized in rtrequest(), so rt_expire is 0.
                         */
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_NOSTATE);
                        /* In case we're called before 1.0 sec. has elapsed */
                        ln_setexpire(ln, (ifp->if_eflags & IFEF_IPV6_ND6ALT) ?
                            0 : MAX(timenow, 1));
                }
                LN_INSERTHEAD(ln);
                nd6_inuse++;

                /* We have at least one entry; arm the timer if not already */
                nd6_sched_timeout(NULL, NULL);

                /*
                 * If we have too many cache entries, initiate immediate
                 * purging for some "less recently used" entries.  Note that
                 * we cannot directly call nd6_free() here because it would
                 * cause re-entering rtable related routines triggering an LOR
                 * problem.
                 */
                if (ip6_neighborgcthresh > 0 &&
                    nd6_inuse >= ip6_neighborgcthresh) {
                        int i;

                        for (i = 0; i < 10 && llinfo_nd6.ln_prev != ln; i++) {
                                struct llinfo_nd6 *ln_end = llinfo_nd6.ln_prev;
                                struct rtentry *rt_end = ln_end->ln_rt;

                                /* Move this entry to the head */
                                RT_LOCK(rt_end);
                                LN_DEQUEUE(ln_end);
                                LN_INSERTHEAD(ln_end);

                                if (ln_end->ln_expire == 0) {
                                        RT_UNLOCK(rt_end);
                                        continue;
                                }
                                if (ln_end->ln_state > ND6_LLINFO_INCOMPLETE) {
                                        ND6_CACHE_STATE_TRANSITION(ln_end, ND6_LLINFO_STALE);
                                } else {
                                        ND6_CACHE_STATE_TRANSITION(ln_end, ND6_LLINFO_PURGE);
                                }
                                ln_setexpire(ln_end, timenow);
                                RT_UNLOCK(rt_end);
                        }
                }

                /*
                 * check if rt_key(rt) is one of my address assigned
                 * to the interface.
                 */
                ifa = (struct ifaddr *)in6ifa_ifpwithaddr(rt->rt_ifp,
                    &SIN6(rt_key(rt))->sin6_addr);
                if (ifa != NULL) {
                        caddr_t macp = nd6_ifptomac(ifp);
                        ln_setexpire(ln, 0);
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                        if (macp != NULL) {
                                Bcopy(macp, LLADDR(SDL(gate)), ifp->if_addrlen);
                                SDL(gate)->sdl_alen = ifp->if_addrlen;
                        }
                        if (nd6_useloopback) {
                                if (rt->rt_ifp != lo_ifp) {
                                        /*
                                         * Purge any link-layer info caching.
                                         */
                                        if (rt->rt_llinfo_purge != NULL) {
                                                rt->rt_llinfo_purge(rt);
                                        }

                                        /*
                                         * Adjust route ref count for the
                                         * interfaces.
                                         */
                                        if (rt->rt_if_ref_fn != NULL) {
                                                rt->rt_if_ref_fn(lo_ifp, 1);
                                                rt->rt_if_ref_fn(rt->rt_ifp,
                                                    -1);
                                        }
                                }
                                rt->rt_ifp = lo_ifp;
                                /*
                                 * If rmx_mtu is not locked, update it
                                 * to the MTU used by the new interface.
                                 */
                                if (!(rt->rt_rmx.rmx_locks & RTV_MTU)) {
                                        rt->rt_rmx.rmx_mtu = rt->rt_ifp->if_mtu;
                                }
                                /*
                                 * Make sure rt_ifa be equal to the ifaddr
                                 * corresponding to the address.
                                 * We need this because when we refer
                                 * rt_ifa->ia6_flags in ip6_input, we assume
                                 * that the rt_ifa points to the address instead
                                 * of the loopback address.
                                 */
                                if (ifa != rt->rt_ifa) {
                                        rtsetifa(rt, ifa);
                                }
                        }
                        IFA_REMREF(ifa);
                } else if (rt->rt_flags & RTF_ANNOUNCE) {
                        ln_setexpire(ln, 0);
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);

                        /* join solicited node multicast for proxy ND */
                        if (ifp->if_flags & IFF_MULTICAST) {
                                struct in6_addr llsol;
                                struct in6_multi *in6m;
                                int error;

                                llsol = SIN6(rt_key(rt))->sin6_addr;
                                llsol.s6_addr32[0] = IPV6_ADDR_INT32_MLL;
                                llsol.s6_addr32[1] = 0;
                                llsol.s6_addr32[2] = htonl(1);
                                llsol.s6_addr8[12] = 0xff;
                                if (in6_setscope(&llsol, ifp, NULL)) {
                                        break;
                                }
                                error = in6_mc_join(ifp, &llsol,
                                    NULL, &in6m, 0);
                                if (error) {
                                        nd6log(error, "%s: failed to join "
                                            "%s (errno=%d)\n", if_name(ifp),
                                            ip6_sprintf(&llsol), error);
                                } else {
                                        IN6M_REMREF(in6m);
                                }
                        }
                }
                break;

        case RTM_DELETE:
                if (ln == NULL) {
                        break;
                }
                /* leave from solicited node multicast for proxy ND */
                if ((rt->rt_flags & RTF_ANNOUNCE) &&
                    (ifp->if_flags & IFF_MULTICAST)) {
                        struct in6_addr llsol;
                        struct in6_multi *in6m;

                        llsol = SIN6(rt_key(rt))->sin6_addr;
                        llsol.s6_addr32[0] = IPV6_ADDR_INT32_MLL;
                        llsol.s6_addr32[1] = 0;
                        llsol.s6_addr32[2] = htonl(1);
                        llsol.s6_addr8[12] = 0xff;
                        if (in6_setscope(&llsol, ifp, NULL) == 0) {
                                in6_multihead_lock_shared();
                                IN6_LOOKUP_MULTI(&llsol, ifp, in6m);
                                in6_multihead_lock_done();
                                if (in6m != NULL) {
                                        in6_mc_leave(in6m, NULL);
                                        IN6M_REMREF(in6m);
                                }
                        }
                }
                nd6_inuse--;
                /*
                 * Unchain it but defer the actual freeing until the route
                 * itself is to be freed.  rt->rt_llinfo still points to
                 * llinfo_nd6, and likewise, ln->ln_rt stil points to this
                 * route entry, except that RTF_LLINFO is now cleared.
                 */
                if (ln->ln_flags & ND6_LNF_IN_USE) {
                        LN_DEQUEUE(ln);
                }

                /*
                 * Purge any link-layer info caching.
                 */
                if (rt->rt_llinfo_purge != NULL) {
                        rt->rt_llinfo_purge(rt);
                }

                rt->rt_flags &= ~RTF_LLINFO;
                if (ln->ln_hold != NULL) {
                        m_freem_list(ln->ln_hold);
                        ln->ln_hold = NULL;
                }
        }
}

static int
nd6_siocgdrlst(void *data, int data_is_64)
{
        struct in6_drlist_32 *drl_32;
        struct nd_defrouter *dr;
        int i = 0;

        LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        dr = TAILQ_FIRST(&nd_defrouter);

        /* XXX Handle mapped defrouter entries */
        /* For 64-bit process */
        if (data_is_64) {
                struct in6_drlist_64 *drl_64;

                drl_64 = _MALLOC(sizeof(*drl_64), M_TEMP, M_WAITOK | M_ZERO);
                if (drl_64 == NULL) {
                        return ENOMEM;
                }

                /* preserve the interface name */
                bcopy(data, drl_64, sizeof(drl_64->ifname));

                while (dr && i < DRLSTSIZ) {
                        drl_64->defrouter[i].rtaddr = dr->rtaddr;
                        if (IN6_IS_ADDR_LINKLOCAL(
                                    &drl_64->defrouter[i].rtaddr)) {
                                /* XXX: need to this hack for KAME stack */
                                drl_64->defrouter[i].rtaddr.s6_addr16[1] = 0;
                        } else {
                                log(LOG_ERR,
                                    "default router list contains a "
                                    "non-linklocal address(%s)\n",
                                    ip6_sprintf(&drl_64->defrouter[i].rtaddr));
                        }
                        drl_64->defrouter[i].flags = dr->flags;
                        drl_64->defrouter[i].rtlifetime = dr->rtlifetime;
                        drl_64->defrouter[i].expire = nddr_getexpire(dr);
                        drl_64->defrouter[i].if_index = dr->ifp->if_index;
                        i++;
                        dr = TAILQ_NEXT(dr, dr_entry);
                }
                bcopy(drl_64, data, sizeof(*drl_64));
                _FREE(drl_64, M_TEMP);
                return 0;
        }

        /* For 32-bit process */
        drl_32 = _MALLOC(sizeof(*drl_32), M_TEMP, M_WAITOK | M_ZERO);
        if (drl_32 == NULL) {
                return ENOMEM;
        }

        /* preserve the interface name */
        bcopy(data, drl_32, sizeof(drl_32->ifname));

        while (dr != NULL && i < DRLSTSIZ) {
                drl_32->defrouter[i].rtaddr = dr->rtaddr;
                if (IN6_IS_ADDR_LINKLOCAL(&drl_32->defrouter[i].rtaddr)) {
                        /* XXX: need to this hack for KAME stack */
                        drl_32->defrouter[i].rtaddr.s6_addr16[1] = 0;
                } else {
                        log(LOG_ERR,
                            "default router list contains a "
                            "non-linklocal address(%s)\n",
                            ip6_sprintf(&drl_32->defrouter[i].rtaddr));
                }
                drl_32->defrouter[i].flags = dr->flags;
                drl_32->defrouter[i].rtlifetime = dr->rtlifetime;
                drl_32->defrouter[i].expire = nddr_getexpire(dr);
                drl_32->defrouter[i].if_index = dr->ifp->if_index;
                i++;
                dr = TAILQ_NEXT(dr, dr_entry);
        }
        bcopy(drl_32, data, sizeof(*drl_32));
        _FREE(drl_32, M_TEMP);
        return 0;
}

/*
 * XXX meaning of fields, especialy "raflags", is very
 * differnet between RA prefix list and RR/static prefix list.
 * how about separating ioctls into two?
 */
static int
nd6_siocgprlst(void *data, int data_is_64)
{
        struct in6_prlist_32 *prl_32;
        struct nd_prefix *pr;
        int i = 0;

        LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

        pr = nd_prefix.lh_first;

        /* XXX Handle mapped defrouter entries */
        /* For 64-bit process */
        if (data_is_64) {
                struct in6_prlist_64 *prl_64;

                prl_64 = _MALLOC(sizeof(*prl_64), M_TEMP, M_WAITOK | M_ZERO);
                if (prl_64 == NULL) {
                        return ENOMEM;
                }

                /* preserve the interface name */
                bcopy(data, prl_64, sizeof(prl_64->ifname));

                while (pr && i < PRLSTSIZ) {
                        struct nd_pfxrouter *pfr;
                        int j;

                        NDPR_LOCK(pr);
                        (void) in6_embedscope(&prl_64->prefix[i].prefix,
                            &pr->ndpr_prefix, NULL, NULL, NULL);
                        prl_64->prefix[i].raflags = pr->ndpr_raf;
                        prl_64->prefix[i].prefixlen = pr->ndpr_plen;
                        prl_64->prefix[i].vltime = pr->ndpr_vltime;
                        prl_64->prefix[i].pltime = pr->ndpr_pltime;
                        prl_64->prefix[i].if_index = pr->ndpr_ifp->if_index;
                        prl_64->prefix[i].expire = ndpr_getexpire(pr);

                        pfr = pr->ndpr_advrtrs.lh_first;
                        j = 0;
                        while (pfr) {
                                if (j < DRLSTSIZ) {
#define RTRADDR prl_64->prefix[i].advrtr[j]
                                        RTRADDR = pfr->router->rtaddr;
                                        if (IN6_IS_ADDR_LINKLOCAL(&RTRADDR)) {
                                                /* XXX: hack for KAME */
                                                RTRADDR.s6_addr16[1] = 0;
                                        } else {
                                                log(LOG_ERR,
                                                    "a router(%s) advertises "
                                                    "a prefix with "
                                                    "non-link local address\n",
                                                    ip6_sprintf(&RTRADDR));
                                        }
#undef RTRADDR
                                }
                                j++;
                                pfr = pfr->pfr_next;
                        }
                        prl_64->prefix[i].advrtrs = j;
                        prl_64->prefix[i].origin = PR_ORIG_RA;
                        NDPR_UNLOCK(pr);

                        i++;
                        pr = pr->ndpr_next;
                }
                bcopy(prl_64, data, sizeof(*prl_64));
                _FREE(prl_64, M_TEMP);
                return 0;
        }

        /* For 32-bit process */
        prl_32 = _MALLOC(sizeof(*prl_32), M_TEMP, M_WAITOK | M_ZERO);
        if (prl_32 == NULL) {
                return ENOMEM;
        }

        /* preserve the interface name */
        bcopy(data, prl_32, sizeof(prl_32->ifname));

        while (pr && i < PRLSTSIZ) {
                struct nd_pfxrouter *pfr;
                int j;

                NDPR_LOCK(pr);
                (void) in6_embedscope(&prl_32->prefix[i].prefix,
                    &pr->ndpr_prefix, NULL, NULL, NULL);
                prl_32->prefix[i].raflags = pr->ndpr_raf;
                prl_32->prefix[i].prefixlen = pr->ndpr_plen;
                prl_32->prefix[i].vltime = pr->ndpr_vltime;
                prl_32->prefix[i].pltime = pr->ndpr_pltime;
                prl_32->prefix[i].if_index = pr->ndpr_ifp->if_index;
                prl_32->prefix[i].expire = ndpr_getexpire(pr);

                pfr = pr->ndpr_advrtrs.lh_first;
                j = 0;
                while (pfr) {
                        if (j < DRLSTSIZ) {
#define RTRADDR prl_32->prefix[i].advrtr[j]
                                RTRADDR = pfr->router->rtaddr;
                                if (IN6_IS_ADDR_LINKLOCAL(&RTRADDR)) {
                                        /* XXX: hack for KAME */
                                        RTRADDR.s6_addr16[1] = 0;
                                } else {
                                        log(LOG_ERR,
                                            "a router(%s) advertises "
                                            "a prefix with "
                                            "non-link local address\n",
                                            ip6_sprintf(&RTRADDR));
                                }
#undef RTRADDR
                        }
                        j++;
                        pfr = pfr->pfr_next;
                }
                prl_32->prefix[i].advrtrs = j;
                prl_32->prefix[i].origin = PR_ORIG_RA;
                NDPR_UNLOCK(pr);

                i++;
                pr = pr->ndpr_next;
        }
        bcopy(prl_32, data, sizeof(*prl_32));
        _FREE(prl_32, M_TEMP);
        return 0;
}

int
nd6_ioctl(u_long cmd, caddr_t data, struct ifnet *ifp)
{
        struct nd_defrouter *dr;
        struct nd_prefix *pr;
        struct rtentry *rt;
        int error = 0;

        VERIFY(ifp != NULL);

        switch (cmd) {
        case SIOCGDRLST_IN6_32:         /* struct in6_drlist_32 */
        case SIOCGDRLST_IN6_64:         /* struct in6_drlist_64 */
                /*
                 * obsolete API, use sysctl under net.inet6.icmp6
                 */
                lck_mtx_lock(nd6_mutex);
                error = nd6_siocgdrlst(data, cmd == SIOCGDRLST_IN6_64);
                lck_mtx_unlock(nd6_mutex);
                break;

        case SIOCGPRLST_IN6_32:         /* struct in6_prlist_32 */
        case SIOCGPRLST_IN6_64:         /* struct in6_prlist_64 */
                /*
                 * obsolete API, use sysctl under net.inet6.icmp6
                 */
                lck_mtx_lock(nd6_mutex);
                error = nd6_siocgprlst(data, cmd == SIOCGPRLST_IN6_64);
                lck_mtx_unlock(nd6_mutex);
                break;

        case OSIOCGIFINFO_IN6:          /* struct in6_ondireq */
        case SIOCGIFINFO_IN6: {         /* struct in6_ondireq */
                u_int32_t linkmtu;
                struct in6_ondireq *ondi = (struct in6_ondireq *)(void *)data;
                struct nd_ifinfo *ndi;
                /*
                 * SIOCGIFINFO_IN6 ioctl is encoded with in6_ondireq
                 * instead of in6_ndireq, so we treat it as such.
                 */
                ndi = ND_IFINFO(ifp);
                if ((NULL == ndi) || (FALSE == ndi->initialized)) {
                        error = EINVAL;
                        break;
                }
                lck_mtx_lock(&ndi->lock);
                linkmtu = IN6_LINKMTU(ifp);
                bcopy(&linkmtu, &ondi->ndi.linkmtu, sizeof(linkmtu));
                bcopy(&ndi->maxmtu, &ondi->ndi.maxmtu,
                    sizeof(u_int32_t));
                bcopy(&ndi->basereachable, &ondi->ndi.basereachable,
                    sizeof(u_int32_t));
                bcopy(&ndi->reachable, &ondi->ndi.reachable,
                    sizeof(u_int32_t));
                bcopy(&ndi->retrans, &ondi->ndi.retrans,
                    sizeof(u_int32_t));
                bcopy(&ndi->flags, &ondi->ndi.flags,
                    sizeof(u_int32_t));
                bcopy(&ndi->recalctm, &ondi->ndi.recalctm,
                    sizeof(int));
                ondi->ndi.chlim = ndi->chlim;
                ondi->ndi.receivedra = 0;
                lck_mtx_unlock(&ndi->lock);
                break;
        }

        case SIOCSIFINFO_FLAGS: {       /* struct in6_ndireq */
                /*
                 * XXX BSD has a bunch of checks here to ensure
                 * that interface disabled flag is not reset if
                 * link local address has failed DAD.
                 * Investigate that part.
                 */
                struct in6_ndireq *cndi = (struct in6_ndireq *)(void *)data;
                u_int32_t oflags, flags;
                struct nd_ifinfo *ndi = ND_IFINFO(ifp);

                /* XXX: almost all other fields of cndi->ndi is unused */
                if ((NULL == ndi) || !ndi->initialized) {
                        error = EINVAL;
                        break;
                }

                lck_mtx_lock(&ndi->lock);
                oflags = ndi->flags;
                bcopy(&cndi->ndi.flags, &(ndi->flags), sizeof(flags));
                flags = ndi->flags;
                lck_mtx_unlock(&ndi->lock);

                if (oflags == flags) {
                        break;
                }

                error = nd6_setifinfo(ifp, oflags, flags);
                break;
        }

        case SIOCSNDFLUSH_IN6:          /* struct in6_ifreq */
                /* flush default router list */
                /*
                 * xxx sumikawa: should not delete route if default
                 * route equals to the top of default router list
                 */
                lck_mtx_lock(nd6_mutex);
                defrouter_reset();
                defrouter_select(ifp);
                lck_mtx_unlock(nd6_mutex);
                /* xxx sumikawa: flush prefix list */
                break;

        case SIOCSPFXFLUSH_IN6: {       /* struct in6_ifreq */
                /* flush all the prefix advertised by routers */
                struct nd_prefix *next = NULL;

                lck_mtx_lock(nd6_mutex);
                for (pr = nd_prefix.lh_first; pr; pr = next) {
                        struct in6_ifaddr *ia = NULL;
                        bool iterate_pfxlist_again = false;

                        next = pr->ndpr_next;

                        NDPR_LOCK(pr);
                        if (IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr)) {
                                NDPR_UNLOCK(pr);
                                continue; /* XXX */
                        }
                        if (ifp != lo_ifp && pr->ndpr_ifp != ifp) {
                                NDPR_UNLOCK(pr);
                                continue;
                        }
                        /* do we really have to remove addresses as well? */
                        NDPR_ADDREF_LOCKED(pr);
                        NDPR_UNLOCK(pr);
                        lck_rw_lock_exclusive(&in6_ifaddr_rwlock);
                        ia = in6_ifaddrs;
                        while (ia != NULL) {
                                IFA_LOCK(&ia->ia_ifa);
                                if ((ia->ia6_flags & IN6_IFF_AUTOCONF) == 0) {
                                        IFA_UNLOCK(&ia->ia_ifa);
                                        ia = ia->ia_next;
                                        continue;
                                }

                                if (ia->ia6_ndpr == pr) {
                                        IFA_ADDREF_LOCKED(&ia->ia_ifa);
                                        IFA_UNLOCK(&ia->ia_ifa);
                                        lck_rw_done(&in6_ifaddr_rwlock);
                                        lck_mtx_unlock(nd6_mutex);
                                        in6_purgeaddr(&ia->ia_ifa);
                                        IFA_REMREF(&ia->ia_ifa);
                                        lck_mtx_lock(nd6_mutex);
                                        lck_rw_lock_exclusive(
                                                &in6_ifaddr_rwlock);
                                        /*
                                         * Purging the address caused
                                         * in6_ifaddr_rwlock to be
                                         * dropped and
                                         * reacquired; therefore search again
                                         * from the beginning of in6_ifaddrs.
                                         * The same applies for the prefix list.
                                         */
                                        ia = in6_ifaddrs;
                                        iterate_pfxlist_again = true;
                                        continue;
                                }
                                IFA_UNLOCK(&ia->ia_ifa);
                                ia = ia->ia_next;
                        }
                        lck_rw_done(&in6_ifaddr_rwlock);
                        NDPR_LOCK(pr);
                        prelist_remove(pr);
                        NDPR_UNLOCK(pr);
                        pfxlist_onlink_check();
                        NDPR_REMREF(pr);
                        if (iterate_pfxlist_again) {
                                next = nd_prefix.lh_first;
                        }
                }
                lck_mtx_unlock(nd6_mutex);
                break;
        }

        case SIOCSRTRFLUSH_IN6: {       /* struct in6_ifreq */
                /* flush all the default routers */
                struct nd_defrouter *next;
                struct nd_drhead nd_defrouter_tmp;

                TAILQ_INIT(&nd_defrouter_tmp);
                lck_mtx_lock(nd6_mutex);
                if ((dr = TAILQ_FIRST(&nd_defrouter)) != NULL) {
                        /*
                         * The first entry of the list may be stored in
                         * the routing table, so we'll delete it later.
                         */
                        for (dr = TAILQ_NEXT(dr, dr_entry); dr; dr = next) {
                                next = TAILQ_NEXT(dr, dr_entry);
                                if (ifp == lo_ifp || dr->ifp == ifp) {
                                        /*
                                         * Remove the entry from default router list
                                         * and add it to the temp list.
                                         * nd_defrouter_tmp will be a local temporary
                                         * list as no one else can get the same
                                         * removed entry once it is removed from default
                                         * router list.
                                         * Remove the reference after calling defrtrlist_de
                                         */
                                        TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);
                                        TAILQ_INSERT_TAIL(&nd_defrouter_tmp, dr, dr_entry);
                                }
                        }

                        dr = TAILQ_FIRST(&nd_defrouter);
                        if (ifp == lo_ifp ||
                            dr->ifp == ifp) {
                                TAILQ_REMOVE(&nd_defrouter, dr, dr_entry);
                                TAILQ_INSERT_TAIL(&nd_defrouter_tmp, dr, dr_entry);
                        }
                }

                /*
                 * Keep the following separate from the above iteration of
                 * nd_defrouter because it's not safe to call
                 * defrtrlist_del while iterating global default
                 * router list. Global list has to be traversed
                 * while holding nd6_mutex throughout.
                 *
                 * The following call to defrtrlist_del should be
                 * safe as we are iterating a local list of
                 * default routers.
                 */
                TAILQ_FOREACH_SAFE(dr, &nd_defrouter_tmp, dr_entry, next) {
                        TAILQ_REMOVE(&nd_defrouter_tmp, dr, dr_entry);
                        defrtrlist_del(dr);
                        NDDR_REMREF(dr);        /* remove list reference */
                }
                lck_mtx_unlock(nd6_mutex);
                break;
        }

        case SIOCGNBRINFO_IN6_32: {     /* struct in6_nbrinfo_32 */
                struct llinfo_nd6 *ln;
                struct in6_nbrinfo_32 nbi_32;
                struct in6_addr nb_addr; /* make local for safety */

                bcopy(data, &nbi_32, sizeof(nbi_32));
                nb_addr = nbi_32.addr;
                /*
                 * XXX: KAME specific hack for scoped addresses
                 *      XXXX: for other scopes than link-local?
                 */
                if (IN6_IS_ADDR_LINKLOCAL(&nbi_32.addr) ||
                    IN6_IS_ADDR_MC_LINKLOCAL(&nbi_32.addr)) {
                        u_int16_t *idp =
                            (u_int16_t *)(void *)&nb_addr.s6_addr[2];

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

                /* Callee returns a locked route upon success */
                if ((rt = nd6_lookup(&nb_addr, 0, ifp, 0)) == NULL) {
                        error = EINVAL;
                        break;
                }
                RT_LOCK_ASSERT_HELD(rt);
                ln = rt->rt_llinfo;
                nbi_32.state = ln->ln_state;
                nbi_32.asked = ln->ln_asked;
                nbi_32.isrouter = ln->ln_router;
                nbi_32.expire = ln_getexpire(ln);
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
                bcopy(&nbi_32, data, sizeof(nbi_32));
                break;
        }

        case SIOCGNBRINFO_IN6_64: {     /* struct in6_nbrinfo_64 */
                struct llinfo_nd6 *ln;
                struct in6_nbrinfo_64 nbi_64;
                struct in6_addr nb_addr; /* make local for safety */

                bcopy(data, &nbi_64, sizeof(nbi_64));
                nb_addr = nbi_64.addr;
                /*
                 * XXX: KAME specific hack for scoped addresses
                 *      XXXX: for other scopes than link-local?
                 */
                if (IN6_IS_ADDR_LINKLOCAL(&nbi_64.addr) ||
                    IN6_IS_ADDR_MC_LINKLOCAL(&nbi_64.addr)) {
                        u_int16_t *idp =
                            (u_int16_t *)(void *)&nb_addr.s6_addr[2];

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

                /* Callee returns a locked route upon success */
                if ((rt = nd6_lookup(&nb_addr, 0, ifp, 0)) == NULL) {
                        error = EINVAL;
                        break;
                }
                RT_LOCK_ASSERT_HELD(rt);
                ln = rt->rt_llinfo;
                nbi_64.state = ln->ln_state;
                nbi_64.asked = ln->ln_asked;
                nbi_64.isrouter = ln->ln_router;
                nbi_64.expire = ln_getexpire(ln);
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
                bcopy(&nbi_64, data, sizeof(nbi_64));
                break;
        }

        case SIOCGDEFIFACE_IN6_32:      /* struct in6_ndifreq_32 */
        case SIOCGDEFIFACE_IN6_64: {    /* struct in6_ndifreq_64 */
                struct in6_ndifreq_64 *ndif_64 =
                    (struct in6_ndifreq_64 *)(void *)data;
                struct in6_ndifreq_32 *ndif_32 =
                    (struct in6_ndifreq_32 *)(void *)data;

                if (cmd == SIOCGDEFIFACE_IN6_64) {
                        u_int64_t j = nd6_defifindex;
                        __nochk_bcopy(&j, &ndif_64->ifindex, sizeof(j));
                } else {
                        bcopy(&nd6_defifindex, &ndif_32->ifindex,
                            sizeof(u_int32_t));
                }
                break;
        }

        case SIOCSDEFIFACE_IN6_32:      /* struct in6_ndifreq_32 */
        case SIOCSDEFIFACE_IN6_64: {    /* struct in6_ndifreq_64 */
                struct in6_ndifreq_64 *ndif_64 =
                    (struct in6_ndifreq_64 *)(void *)data;
                struct in6_ndifreq_32 *ndif_32 =
                    (struct in6_ndifreq_32 *)(void *)data;
                u_int32_t idx;

                if (cmd == SIOCSDEFIFACE_IN6_64) {
                        u_int64_t j;
                        __nochk_bcopy(&ndif_64->ifindex, &j, sizeof(j));
                        idx = (u_int32_t)j;
                } else {
                        bcopy(&ndif_32->ifindex, &idx, sizeof(idx));
                }

                error = nd6_setdefaultiface(idx);
                return error;
                /* NOTREACHED */
        }
        case SIOCGIFCGAPREP_IN6:
        case SIOCSIFCGAPREP_IN6:
        {
                struct in6_cgareq *p_cgareq =
                    (struct in6_cgareq *)(void *)data;
                struct nd_ifinfo *ndi = ND_IFINFO(ifp);

                struct in6_cga_modifier *req_cga_mod =
                    &(p_cgareq->cgar_cgaprep.cga_modifier);
                struct in6_cga_modifier *ndi_cga_mod = NULL;

                if ((NULL == ndi) || !ndi->initialized) {
                        error = EINVAL;
                        break;
                }

                lck_mtx_lock(&ndi->lock);
                ndi_cga_mod = &(ndi->local_cga_modifier);

                if (cmd == SIOCSIFCGAPREP_IN6) {
                        bcopy(req_cga_mod, ndi_cga_mod, sizeof(*ndi_cga_mod));
                        ndi->cga_initialized = TRUE;
                } else {
                        bcopy(ndi_cga_mod, req_cga_mod, sizeof(*req_cga_mod));
                }

                lck_mtx_unlock(&ndi->lock);
                return error;
                /* NOTREACHED */
        }
        }
        return error;
}

/*
 * Create neighbor cache entry and cache link-layer address,
 * on reception of inbound ND6 packets. (RS/RA/NS/redirect)
 */
void
nd6_cache_lladdr(struct ifnet *ifp, struct in6_addr *from, char *lladdr,
    int lladdrlen, int type, int code)
{
#pragma unused(lladdrlen)
        struct rtentry *rt = NULL;
        struct llinfo_nd6 *ln = NULL;
        int is_newentry;
        struct sockaddr_dl *sdl = NULL;
        int do_update;
        int olladdr;
        int llchange;
        int newstate = 0;
        uint64_t timenow;
        boolean_t sched_timeout = FALSE;
        struct nd_ifinfo *ndi = NULL;

        if (ifp == NULL) {
                panic("ifp == NULL in nd6_cache_lladdr");
        }
        if (from == NULL) {
                panic("from == NULL in nd6_cache_lladdr");
        }

        /* 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.
         */
        timenow = net_uptime();

        rt = nd6_lookup(from, 0, ifp, 0);
        if (rt == NULL) {
                if ((rt = nd6_lookup(from, 1, ifp, 0)) == NULL) {
                        return;
                }
                RT_LOCK_ASSERT_HELD(rt);
                is_newentry = 1;
        } else {
                RT_LOCK_ASSERT_HELD(rt);
                /* do nothing if static ndp is set */
                if (rt->rt_flags & RTF_STATIC) {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        return;
                }
                is_newentry = 0;
        }

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

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

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

        if (lladdr != NULL) {           /* (3-5) and (7) */
                /*
                 * Record source link-layer address
                 * XXX is it dependent to ifp->if_type?
                 */
                sdl->sdl_alen = ifp->if_addrlen;
                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);

                /* cache the gateway (sender HW) address */
                nd6_llreach_alloc(rt, ifp, LLADDR(sdl), sdl->sdl_alen, FALSE);
        }

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

        /*
         * For interface's that do not perform NUD
         * neighbor cache entres must always be marked
         * reachable with no expiry
         */
        ndi = ND_IFINFO(ifp);
        VERIFY((NULL != ndi) && (TRUE == ndi->initialized));

        if (ndi && !(ndi->flags & ND6_IFF_PERFORMNUD)) {
                newstate = ND6_LLINFO_REACHABLE;
                ln_setexpire(ln, 0);
        }

        if (do_update) {
                /*
                 * Update the state of the neighbor cache.
                 */
                ND6_CACHE_STATE_TRANSITION(ln, newstate);

                if ((ln->ln_state == ND6_LLINFO_STALE) ||
                    (ln->ln_state == ND6_LLINFO_REACHABLE)) {
                        struct mbuf *m = ln->ln_hold;
                        /*
                         * XXX: since nd6_output() below will cause
                         * state tansition to DELAY and reset the timer,
                         * we must set the timer now, although it is actually
                         * meaningless.
                         */
                        if (ln->ln_state == ND6_LLINFO_STALE) {
                                ln_setexpire(ln, timenow + nd6_gctimer);
                        }

                        ln->ln_hold = NULL;
                        if (m != NULL) {
                                struct sockaddr_in6 sin6;

                                rtkey_to_sa6(rt, &sin6);
                                /*
                                 * we assume ifp is not a p2p here, so just
                                 * set the 2nd argument as the 1st one.
                                 */
                                RT_UNLOCK(rt);
                                nd6_output_list(ifp, ifp, m, &sin6, rt, NULL);
                                RT_LOCK(rt);
                        }
                } else if (ln->ln_state == ND6_LLINFO_INCOMPLETE) {
                        /* probe right away */
                        ln_setexpire(ln, timenow);
                        sched_timeout = TRUE;
                }
        }

        /*
         * 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.
         *
         * newentry olladdr  lladdr  llchange       NS  RS      RA      redir
         *                                                              D R
         *      0       n       n       --      (1)     c       ?       s
         *      0       y       n       --      (2)     c       s       s
         *      0       n       y       --      (3)     c       s       s
         *      0       y       y       n       (4)     c       s       s
         *      0       y       y       y       (5)     c       s       s
         *      1       --      n       --      (6) c   c               c s
         *      1       --      y       --      (7) c   c       s       c s
         *
         *                                      (c=clear s=set)
         */
        switch (type & 0xff) {
        case ND_NEIGHBOR_SOLICIT:
                /*
                 * New entry must have is_router flag cleared.
                 */
                if (is_newentry) {      /* (6-7) */
                        ln->ln_router = 0;
                }
                break;
        case ND_REDIRECT:
                /*
                 * If the ICMP message is a Redirect to a better router, always
                 * set the is_router flag.  Otherwise, if the entry is newly
                 * created, then clear the flag.  [RFC 4861, sec 8.3]
                 */
                if (code == ND_REDIRECT_ROUTER) {
                        ln->ln_router = 1;
                } else if (is_newentry) { /* (6-7) */
                        ln->ln_router = 0;
                }
                break;
        case ND_ROUTER_SOLICIT:
                /*
                 * is_router flag must always be cleared.
                 */
                ln->ln_router = 0;
                break;
        case ND_ROUTER_ADVERT:
                /*
                 * Mark an entry with lladdr as a router.
                 */
                if ((!is_newentry && (olladdr || lladdr)) ||    /* (2-5) */
                    (is_newentry && lladdr)) {                  /* (7) */
                        ln->ln_router = 1;
                }
                break;
        }

        if (do_update) {
                int route_ev_code = 0;

                if (llchange) {
                        route_ev_code = ROUTE_LLENTRY_CHANGED;
                } else {
                        route_ev_code = ROUTE_LLENTRY_RESOLVED;
                }

                /* Enqueue work item to invoke callback for this route entry */
                route_event_enqueue_nwk_wq_entry(rt, NULL, route_ev_code, NULL, TRUE);

                if (ln->ln_router || (rt->rt_flags & RTF_ROUTER)) {
                        struct radix_node_head  *rnh = NULL;
                        struct route_event rt_ev;
                        route_event_init(&rt_ev, rt, NULL, llchange ? ROUTE_LLENTRY_CHANGED :
                            ROUTE_LLENTRY_RESOLVED);
                        /*
                         * We already have a valid reference on rt.
                         * The function frees that before returning.
                         * We therefore don't need an extra reference here
                         */
                        RT_UNLOCK(rt);
                        lck_mtx_lock(rnh_lock);

                        rnh = rt_tables[AF_INET6];
                        if (rnh != NULL) {
                                (void) rnh->rnh_walktree(rnh, route_event_walktree,
                                    (void *)&rt_ev);
                        }
                        lck_mtx_unlock(rnh_lock);
                        RT_LOCK(rt);
                }
        }

        /*
         * 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?
         *
         * Note: Perform default router selection even when we are a router,
         * if Scoped Routing is enabled.
         */
        if (do_update && ln->ln_router) {
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
                lck_mtx_lock(nd6_mutex);
                defrouter_select(ifp);
                lck_mtx_unlock(nd6_mutex);
        } else {
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
        }
        if (sched_timeout) {
                lck_mtx_lock(rnh_lock);
                nd6_sched_timeout(NULL, NULL);
                lck_mtx_unlock(rnh_lock);
        }
}

static void
nd6_slowtimo(void *arg)
{
#pragma unused(arg)
        struct nd_ifinfo *nd6if = NULL;
        struct ifnet *ifp = NULL;

        ifnet_head_lock_shared();
        for (ifp = ifnet_head.tqh_first; ifp;
            ifp = ifp->if_link.tqe_next) {
                nd6if = ND_IFINFO(ifp);
                if ((NULL == nd6if) || (FALSE == nd6if->initialized)) {
                        continue;
                }

                lck_mtx_lock(&nd6if->lock);
                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 4861, 6.3.4)
                         */
                        nd6if->recalctm = nd6_recalc_reachtm_interval;
                        nd6if->reachable =
                            ND_COMPUTE_RTIME(nd6if->basereachable);
                }
                lck_mtx_unlock(&nd6if->lock);
        }
        ifnet_head_done();
        timeout(nd6_slowtimo, NULL, ND6_SLOWTIMER_INTERVAL * hz);
}

int
nd6_output(struct ifnet *ifp, struct ifnet *origifp, struct mbuf *m0,
    struct sockaddr_in6 *dst, struct rtentry *hint0, struct flowadv *adv)
{
        return nd6_output_list(ifp, origifp, m0, dst, hint0, adv);
}

/*
 * nd6_output_list()
 *
 * Assumption: route determination for first packet can be correctly applied to
 * all packets in the chain.
 */
#define senderr(e) { error = (e); goto bad; }
int
nd6_output_list(struct ifnet *ifp, struct ifnet *origifp, struct mbuf *m0,
    struct sockaddr_in6 *dst, struct rtentry *hint0, struct flowadv *adv)
{
        struct rtentry *rt = hint0, *hint = hint0;
        struct llinfo_nd6 *ln = NULL;
        int error = 0;
        uint64_t timenow;
        struct rtentry *rtrele = NULL;
        struct nd_ifinfo *ndi = NULL;

        if (rt != NULL) {
                RT_LOCK_SPIN(rt);
                RT_ADDREF_LOCKED(rt);
        }

        if (IN6_IS_ADDR_MULTICAST(&dst->sin6_addr) || !nd6_need_cache(ifp)) {
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                }
                goto sendpkt;
        }

        /*
         * Next hop determination.  Because we may involve the gateway route
         * in addition to the original route, locking is rather complicated.
         * The general concept is that regardless of whether the route points
         * to the original route or to the gateway route, this routine takes
         * an extra reference on such a route.  This extra reference will be
         * released at the end.
         *
         * Care must be taken to ensure that the "hint0" route never gets freed
         * via rtfree(), since the caller may have stored it inside a struct
         * route with a reference held for that placeholder.
         *
         * This logic is similar to, though not exactly the same as the one
         * used by route_to_gwroute().
         */
        if (rt != NULL) {
                /*
                 * We have a reference to "rt" by now (or below via rtalloc1),
                 * which will either be released or freed at the end of this
                 * routine.
                 */
                RT_LOCK_ASSERT_HELD(rt);
                if (!(rt->rt_flags & RTF_UP)) {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        if ((hint = rt = rtalloc1_scoped(SA(dst), 1, 0,
                            ifp->if_index)) != NULL) {
                                RT_LOCK_SPIN(rt);
                                if (rt->rt_ifp != ifp) {
                                        /* XXX: loop care? */
                                        RT_UNLOCK(rt);
                                        error = nd6_output_list(ifp, origifp, m0,
                                            dst, rt, adv);
                                        rtfree(rt);
                                        return error;
                                }
                        } else {
                                senderr(EHOSTUNREACH);
                        }
                }

                if (rt->rt_flags & RTF_GATEWAY) {
                        struct rtentry *gwrt;
                        struct in6_ifaddr *ia6 = NULL;
                        struct sockaddr_in6 gw6;

                        rtgw_to_sa6(rt, &gw6);
                        /*
                         * Must drop rt_lock since nd6_is_addr_neighbor()
                         * calls nd6_lookup() and acquires rnh_lock.
                         */
                        RT_UNLOCK(rt);

                        /*
                         * We skip link-layer address resolution and NUD
                         * if the gateway is not a neighbor from ND point
                         * of view, regardless of the value of nd_ifinfo.flags.
                         * The second condition is a bit tricky; we skip
                         * if the gateway is our own address, which is
                         * sometimes used to install a route to a p2p link.
                         */
                        if (!nd6_is_addr_neighbor(&gw6, ifp, 0) ||
                            (ia6 = in6ifa_ifpwithaddr(ifp, &gw6.sin6_addr))) {
                                /*
                                 * We allow this kind of tricky route only
                                 * when the outgoing interface is p2p.
                                 * XXX: we may need a more generic rule here.
                                 */
                                if (ia6 != NULL) {
                                        IFA_REMREF(&ia6->ia_ifa);
                                }
                                if ((ifp->if_flags & IFF_POINTOPOINT) == 0) {
                                        senderr(EHOSTUNREACH);
                                }
                                goto sendpkt;
                        }

                        RT_LOCK_SPIN(rt);
                        gw6 = *(SIN6(rt->rt_gateway));

                        /* If hint is now down, give up */
                        if (!(rt->rt_flags & RTF_UP)) {
                                RT_UNLOCK(rt);
                                senderr(EHOSTUNREACH);
                        }

                        /* If there's no gateway route, look it up */
                        if ((gwrt = rt->rt_gwroute) == NULL) {
                                RT_UNLOCK(rt);
                                goto lookup;
                        }
                        /* Become a regular mutex */
                        RT_CONVERT_LOCK(rt);

                        /*
                         * Take gwrt's lock while holding route's lock;
                         * this is okay since gwrt never points back
                         * to rt, so no lock ordering issues.
                         */
                        RT_LOCK_SPIN(gwrt);
                        if (!(gwrt->rt_flags & RTF_UP)) {
                                rt->rt_gwroute = NULL;
                                RT_UNLOCK(gwrt);
                                RT_UNLOCK(rt);
                                rtfree(gwrt);
lookup:
                                lck_mtx_lock(rnh_lock);
                                gwrt = rtalloc1_scoped_locked(SA(&gw6), 1, 0,
                                    ifp->if_index);

                                RT_LOCK(rt);
                                /*
                                 * Bail out if the route is down, no route
                                 * to gateway, circular route, or if the
                                 * gateway portion of "rt" has changed.
                                 */
                                if (!(rt->rt_flags & RTF_UP) ||
                                    gwrt == NULL || gwrt == rt ||
                                    !equal(SA(&gw6), rt->rt_gateway)) {
                                        if (gwrt == rt) {
                                                RT_REMREF_LOCKED(gwrt);
                                                gwrt = NULL;
                                        }
                                        RT_UNLOCK(rt);
                                        if (gwrt != NULL) {
                                                rtfree_locked(gwrt);
                                        }
                                        lck_mtx_unlock(rnh_lock);
                                        senderr(EHOSTUNREACH);
                                }
                                VERIFY(gwrt != NULL);
                                /*
                                 * Set gateway route; callee adds ref to gwrt;
                                 * gwrt has an extra ref from rtalloc1() for
                                 * this routine.
                                 */
                                rt_set_gwroute(rt, rt_key(rt), gwrt);
                                RT_UNLOCK(rt);
                                lck_mtx_unlock(rnh_lock);
                                /* Remember to release/free "rt" at the end */
                                rtrele = rt;
                                rt = gwrt;
                        } else {
                                RT_ADDREF_LOCKED(gwrt);
                                RT_UNLOCK(gwrt);
                                RT_UNLOCK(rt);
                                /* Remember to release/free "rt" at the end */
                                rtrele = rt;
                                rt = gwrt;
                        }
                        VERIFY(rt == gwrt);

                        /*
                         * This is an opportunity to revalidate the parent
                         * route's gwroute, in case it now points to a dead
                         * route entry.  Parent route won't go away since the
                         * clone (hint) holds a reference to it.  rt == gwrt.
                         */
                        RT_LOCK_SPIN(hint);
                        if ((hint->rt_flags & (RTF_WASCLONED | RTF_UP)) ==
                            (RTF_WASCLONED | RTF_UP)) {
                                struct rtentry *prt = hint->rt_parent;
                                VERIFY(prt != NULL);

                                RT_CONVERT_LOCK(hint);
                                RT_ADDREF(prt);
                                RT_UNLOCK(hint);
                                rt_revalidate_gwroute(prt, rt);
                                RT_REMREF(prt);
                        } else {
                                RT_UNLOCK(hint);
                        }

                        RT_LOCK_SPIN(rt);
                        /* rt == gwrt; if it is now down, give up */
                        if (!(rt->rt_flags & RTF_UP)) {
                                RT_UNLOCK(rt);
                                rtfree(rt);
                                rt = NULL;
                                /* "rtrele" == original "rt" */
                                senderr(EHOSTUNREACH);
                        }
                }

                /* Become a regular mutex */
                RT_CONVERT_LOCK(rt);
        }

        /*
         * 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).
         */

        /* Look up the neighbor cache for the nexthop */
        if (rt && (rt->rt_flags & RTF_LLINFO) != 0) {
                ln = rt->rt_llinfo;
        } else {
                struct sockaddr_in6 sin6;
                /*
                 * Clear out Scope ID field in case it is set.
                 */
                sin6 = *dst;
                sin6.sin6_scope_id = 0;
                /*
                 * 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.
                 * Must drop rt_lock since nd6_is_addr_neighbor() calls
                 * nd6_lookup() and acquires rnh_lock.
                 */
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                }
                if (nd6_is_addr_neighbor(&sin6, ifp, 0)) {
                        /* "rtrele" may have been used, so clean up "rt" now */
                        if (rt != NULL) {
                                /* Don't free "hint0" */
                                if (rt == hint0) {
                                        RT_REMREF(rt);
                                } else {
                                        rtfree(rt);
                                }
                        }
                        /* Callee returns a locked route upon success */
                        rt = nd6_lookup(&dst->sin6_addr, 1, ifp, 0);
                        if (rt != NULL) {
                                RT_LOCK_ASSERT_HELD(rt);
                                ln = rt->rt_llinfo;
                        }
                } else if (rt != NULL) {
                        RT_LOCK(rt);
                }
        }

        if (!ln || !rt) {
                if (rt != NULL) {
                        RT_UNLOCK(rt);
                }
                ndi = ND_IFINFO(ifp);
                VERIFY(ndi != NULL && ndi->initialized);
                lck_mtx_lock(&ndi->lock);
                if ((ifp->if_flags & IFF_POINTOPOINT) == 0 &&
                    !(ndi->flags & ND6_IFF_PERFORMNUD)) {
                        lck_mtx_unlock(&ndi->lock);
                        log(LOG_DEBUG,
                            "nd6_output: can't allocate llinfo for %s "
                            "(ln=0x%llx, rt=0x%llx)\n",
                            ip6_sprintf(&dst->sin6_addr),
                            (uint64_t)VM_KERNEL_ADDRPERM(ln),
                            (uint64_t)VM_KERNEL_ADDRPERM(rt));
                        senderr(EIO);   /* XXX: good error? */
                }
                lck_mtx_unlock(&ndi->lock);

                goto sendpkt;   /* send anyway */
        }

        net_update_uptime();
        timenow = net_uptime();

        /* We don't have to do link-layer address resolution on a p2p link. */
        if ((ifp->if_flags & IFF_POINTOPOINT) != 0 &&
            ln->ln_state < ND6_LLINFO_REACHABLE) {
                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                ln_setexpire(ln, timenow + nd6_gctimer);
        }

        /*
         * 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 4861 7.3.3)
         */
        if (ln->ln_state == ND6_LLINFO_STALE) {
                ln->ln_asked = 0;
                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_DELAY);
                ln_setexpire(ln, timenow + nd6_delay);
                /* N.B.: we will re-arm the timer below. */
                _CASSERT(ND6_LLINFO_DELAY > ND6_LLINFO_INCOMPLETE);
        }

        /*
         * If the neighbor cache entry has a state other than INCOMPLETE
         * (i.e. its link-layer address is already resolved), just
         * send the packet.
         */
        if (ln->ln_state > ND6_LLINFO_INCOMPLETE) {
                RT_UNLOCK(rt);
                /*
                 * Move this entry to the head of the queue so that it is
                 * less likely for this entry to be a target of forced
                 * garbage collection (see nd6_rtrequest()).  Do this only
                 * if the entry is non-permanent (as permanent ones will
                 * never be purged), and if the number of active entries
                 * is at least half of the threshold.
                 */
                if (ln->ln_state == ND6_LLINFO_DELAY ||
                    (ln->ln_expire != 0 && ip6_neighborgcthresh > 0 &&
                    nd6_inuse >= (ip6_neighborgcthresh >> 1))) {
                        lck_mtx_lock(rnh_lock);
                        if (ln->ln_state == ND6_LLINFO_DELAY) {
                                nd6_sched_timeout(NULL, NULL);
                        }
                        if (ln->ln_expire != 0 && ip6_neighborgcthresh > 0 &&
                            nd6_inuse >= (ip6_neighborgcthresh >> 1)) {
                                RT_LOCK_SPIN(rt);
                                if (ln->ln_flags & ND6_LNF_IN_USE) {
                                        LN_DEQUEUE(ln);
                                        LN_INSERTHEAD(ln);
                                }
                                RT_UNLOCK(rt);
                        }
                        lck_mtx_unlock(rnh_lock);
                }
                goto sendpkt;
        }

        /*
         * If this is a prefix proxy route, record the inbound interface
         * so that it can be excluded from the list of interfaces eligible
         * for forwarding the proxied NS in nd6_prproxy_ns_output().
         */
        if (rt->rt_flags & RTF_PROXY) {
                ln->ln_exclifp = ((origifp == ifp) ? NULL : origifp);
        }

        /*
         * There is a neighbor cache entry, but no ethernet address
         * response yet.  Replace the held mbuf (if any) with this
         * latest one.
         *
         * This code conforms to the rate-limiting rule described in Section
         * 7.2.2 of RFC 4861, because the timer is set correctly after sending
         * an NS below.
         */
        if (ln->ln_state == ND6_LLINFO_NOSTATE) {
                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_INCOMPLETE);
        }
        if (ln->ln_hold) {
                m_freem_list(ln->ln_hold);
        }
        ln->ln_hold = m0;
        if (!ND6_LLINFO_PERMANENT(ln) && ln->ln_asked == 0) {
                ln->ln_asked++;
                ndi = ND_IFINFO(ifp);
                VERIFY(ndi != NULL && ndi->initialized);
                lck_mtx_lock(&ndi->lock);
                ln_setexpire(ln, timenow + ndi->retrans / 1000);
                lck_mtx_unlock(&ndi->lock);
                RT_UNLOCK(rt);
                /* We still have a reference on rt (for ln) */
                if (ip6_forwarding) {
                        nd6_prproxy_ns_output(ifp, origifp, NULL,
                            &dst->sin6_addr, ln);
                } else {
                        nd6_ns_output(ifp, NULL, &dst->sin6_addr, ln, NULL);
                }
                lck_mtx_lock(rnh_lock);
                nd6_sched_timeout(NULL, NULL);
                lck_mtx_unlock(rnh_lock);
        } else {
                RT_UNLOCK(rt);
        }
        /*
         * Move this entry to the head of the queue so that it is
         * less likely for this entry to be a target of forced
         * garbage collection (see nd6_rtrequest()).  Do this only
         * if the entry is non-permanent (as permanent ones will
         * never be purged), and if the number of active entries
         * is at least half of the threshold.
         */
        if (ln->ln_expire != 0 && ip6_neighborgcthresh > 0 &&
            nd6_inuse >= (ip6_neighborgcthresh >> 1)) {
                lck_mtx_lock(rnh_lock);
                RT_LOCK_SPIN(rt);
                if (ln->ln_flags & ND6_LNF_IN_USE) {
                        LN_DEQUEUE(ln);
                        LN_INSERTHEAD(ln);
                }
                /* Clean up "rt" now while we can */
                if (rt == hint0) {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                } else {
                        RT_UNLOCK(rt);
                        rtfree_locked(rt);
                }
                rt = NULL;      /* "rt" has been taken care of */
                lck_mtx_unlock(rnh_lock);
        }
        error = 0;
        goto release;

sendpkt:
        if (rt != NULL) {
                RT_LOCK_ASSERT_NOTHELD(rt);
        }

        /* discard the packet if IPv6 operation is disabled on the interface */
        if (ifp->if_eflags & IFEF_IPV6_DISABLED) {
                error = ENETDOWN; /* better error? */
                goto bad;
        }

        if (ifp->if_flags & IFF_LOOPBACK) {
                /* forwarding rules require the original scope_id */
                m0->m_pkthdr.rcvif = origifp;
                error = dlil_output(origifp, PF_INET6, m0, (caddr_t)rt,
                    SA(dst), 0, adv);
                goto release;
        } else {
                /* Do not allow loopback address to wind up on a wire */
                struct ip6_hdr *ip6 = mtod(m0, struct ip6_hdr *);

                if ((IN6_IS_ADDR_LOOPBACK(&ip6->ip6_src) ||
                    IN6_IS_ADDR_LOOPBACK(&ip6->ip6_dst))) {
                        ip6stat.ip6s_badscope++;
                        error = EADDRNOTAVAIL;
                        goto bad;
                }
        }

        if (rt != NULL) {
                RT_LOCK_SPIN(rt);
                /* Mark use timestamp */
                if (rt->rt_llinfo != NULL) {
                        nd6_llreach_use(rt->rt_llinfo);
                }
                RT_UNLOCK(rt);
        }

        struct mbuf *mcur = m0;
        uint32_t pktcnt = 0;

        while (mcur) {
                if (hint != NULL && nstat_collect) {
                        int scnt;

                        if ((mcur->m_pkthdr.csum_flags & CSUM_TSO_IPV6) &&
                            (mcur->m_pkthdr.tso_segsz > 0)) {
                                scnt = mcur->m_pkthdr.len / mcur->m_pkthdr.tso_segsz;
                        } else {
                                scnt = 1;
                        }

                        nstat_route_tx(hint, scnt, mcur->m_pkthdr.len, 0);
                }
                pktcnt++;

                mcur->m_pkthdr.rcvif = NULL;
                mcur = mcur->m_nextpkt;
        }
        if (pktcnt > ip6_maxchainsent) {
                ip6_maxchainsent = pktcnt;
        }
        error = dlil_output(ifp, PF_INET6, m0, (caddr_t)rt, SA(dst), 0, adv);
        goto release;

bad:
        if (m0 != NULL) {
                m_freem_list(m0);
        }

release:
        /* Clean up "rt" unless it's already been done */
        if (rt != NULL) {
                RT_LOCK_SPIN(rt);
                if (rt == hint0) {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                } else {
                        RT_UNLOCK(rt);
                        rtfree(rt);
                }
        }
        /* And now clean up "rtrele" if there is any */
        if (rtrele != NULL) {
                RT_LOCK_SPIN(rtrele);
                if (rtrele == hint0) {
                        RT_REMREF_LOCKED(rtrele);
                        RT_UNLOCK(rtrele);
                } else {
                        RT_UNLOCK(rtrele);
                        rtfree(rtrele);
                }
        }
        return error;
}
#undef senderr

int
nd6_need_cache(struct ifnet *ifp)
{
        /*
         * XXX: we currently do not make neighbor cache on any interface
         * other than ARCnet, Ethernet, FDDI and GIF.
         *
         * RFC2893 says:
         * - unidirectional tunnels needs no ND
         */
        switch (ifp->if_type) {
        case IFT_ARCNET:
        case IFT_ETHER:
        case IFT_FDDI:
        case IFT_IEEE1394:
        case IFT_L2VLAN:
        case IFT_IEEE8023ADLAG:
#if IFT_IEEE80211
        case IFT_IEEE80211:
#endif
        case IFT_GIF:           /* XXX need more cases? */
        case IFT_PPP:
#if IFT_TUNNEL
        case IFT_TUNNEL:
#endif
        case IFT_BRIDGE:
        case IFT_CELLULAR:
        case IFT_6LOWPAN:
                return 1;
        default:
                return 0;
        }
}

int
nd6_storelladdr(struct ifnet *ifp, struct rtentry *rt, struct mbuf *m,
    struct sockaddr *dst, u_char *desten)
{
        int i;
        struct sockaddr_dl *sdl;

        if (m->m_flags & M_MCAST) {
                switch (ifp->if_type) {
                case IFT_ETHER:
                case IFT_FDDI:
                case IFT_L2VLAN:
                case IFT_IEEE8023ADLAG:
#if IFT_IEEE80211
                case IFT_IEEE80211:
#endif
                case IFT_BRIDGE:
                        ETHER_MAP_IPV6_MULTICAST(&SIN6(dst)->sin6_addr, desten);
                        return 1;
                case IFT_IEEE1394:
                        for (i = 0; i < ifp->if_addrlen; i++) {
                                desten[i] = ~0;
                        }
                        return 1;
                case IFT_ARCNET:
                        *desten = 0;
                        return 1;
                default:
                        return 0; /* caller will free mbuf */
                }
        }

        if (rt == NULL) {
                /* this could happen, if we could not allocate memory */
                return 0; /* caller will free mbuf */
        }
        RT_LOCK(rt);
        if (rt->rt_gateway->sa_family != AF_LINK) {
                printf("nd6_storelladdr: something odd happens\n");
                RT_UNLOCK(rt);
                return 0; /* caller will free mbuf */
        }
        sdl = SDL(rt->rt_gateway);
        if (sdl->sdl_alen == 0) {
                /* this should be impossible, but we bark here for debugging */
                printf("nd6_storelladdr: sdl_alen == 0\n");
                RT_UNLOCK(rt);
                return 0; /* caller will free mbuf */
        }

        bcopy(LLADDR(sdl), desten, sdl->sdl_alen);
        RT_UNLOCK(rt);
        return 1;
}

/*
 * This is the ND pre-output routine; care must be taken to ensure that
 * the "hint" route never gets freed via rtfree(), since the caller may
 * have stored it inside a struct route with a reference held for that
 * placeholder.
 */
errno_t
nd6_lookup_ipv6(ifnet_t  ifp, const struct sockaddr_in6 *ip6_dest,
    struct sockaddr_dl *ll_dest, size_t ll_dest_len, route_t hint,
    mbuf_t packet)
{
        route_t route = hint;
        errno_t result = 0;
        struct sockaddr_dl *sdl = NULL;
        size_t  copy_len;

        if (ifp == NULL || ip6_dest == NULL) {
                return EINVAL;
        }

        if (ip6_dest->sin6_family != AF_INET6) {
                return EAFNOSUPPORT;
        }

        if ((ifp->if_flags & (IFF_UP | IFF_RUNNING)) != (IFF_UP | IFF_RUNNING)) {
                return ENETDOWN;
        }

        if (hint != NULL) {
                /*
                 * Callee holds a reference on the route and returns
                 * with the route entry locked, upon success.
                 */
                result = route_to_gwroute((const struct sockaddr *)ip6_dest,
                    hint, &route);
                if (result != 0) {
                        return result;
                }
                if (route != NULL) {
                        RT_LOCK_ASSERT_HELD(route);
                }
        }

        if ((packet != NULL && (packet->m_flags & M_MCAST) != 0) ||
            ((ifp->if_flags & IFF_MULTICAST) &&
            IN6_IS_ADDR_MULTICAST(&ip6_dest->sin6_addr))) {
                if (route != NULL) {
                        RT_UNLOCK(route);
                }
                result = dlil_resolve_multi(ifp,
                    (const struct sockaddr *)ip6_dest,
                    SA(ll_dest), ll_dest_len);
                if (route != NULL) {
                        RT_LOCK(route);
                }
                goto release;
        } else if (route == NULL) {
                /*
                 * rdar://24596652
                 * For unicast, lookup existing ND6 entries but
                 * do not trigger a resolution
                 */
                lck_mtx_lock(rnh_lock);
                route = rt_lookup(TRUE,
                    __DECONST(struct sockaddr *, ip6_dest), NULL,
                    rt_tables[AF_INET6], ifp->if_index);
                lck_mtx_unlock(rnh_lock);

                if (route != NULL) {
                        RT_LOCK(route);
                }
        }

        if (route == NULL) {
                /*
                 * This could happen, if we could not allocate memory or
                 * if route_to_gwroute() didn't return a route.
                 */
                result = ENOBUFS;
                goto release;
        }

        if (route->rt_gateway->sa_family != AF_LINK) {
                printf("%s: route %s on %s%d gateway address not AF_LINK\n",
                    __func__, ip6_sprintf(&ip6_dest->sin6_addr),
                    route->rt_ifp->if_name, route->rt_ifp->if_unit);
                result = EADDRNOTAVAIL;
                goto release;
        }

        sdl = SDL(route->rt_gateway);
        if (sdl->sdl_alen == 0) {
                /* this should be impossible, but we bark here for debugging */
                printf("%s: route %s on %s%d sdl_alen == 0\n", __func__,
                    ip6_sprintf(&ip6_dest->sin6_addr), route->rt_ifp->if_name,
                    route->rt_ifp->if_unit);
                result = EHOSTUNREACH;
                goto release;
        }

        copy_len = sdl->sdl_len <= ll_dest_len ? sdl->sdl_len : ll_dest_len;
        bcopy(sdl, ll_dest, copy_len);

release:
        if (route != NULL) {
                if (route == hint) {
                        RT_REMREF_LOCKED(route);
                        RT_UNLOCK(route);
                } else {
                        RT_UNLOCK(route);
                        rtfree(route);
                }
        }
        return result;
}

#if (DEVELOPMENT || DEBUG)

static int sysctl_nd6_lookup_ipv6 SYSCTL_HANDLER_ARGS;
SYSCTL_PROC(_net_inet6_icmp6, OID_AUTO, nd6_lookup_ipv6,
    CTLTYPE_STRUCT | CTLFLAG_RW | CTLFLAG_LOCKED, 0, 0,
    sysctl_nd6_lookup_ipv6, "S", "");

int
sysctl_nd6_lookup_ipv6 SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        int error = 0;
        struct nd6_lookup_ipv6_args nd6_lookup_ipv6_args;
        ifnet_t ifp = NULL;

        /*
         * Only root can lookup MAC addresses
         */
        error = proc_suser(current_proc());
        if (error != 0) {
                nd6log0(error, "%s: proc_suser() error %d\n",
                    __func__, error);
                goto done;
        }
        if (req->oldptr == USER_ADDR_NULL) {
                req->oldidx = sizeof(struct nd6_lookup_ipv6_args);
        }
        if (req->newptr == USER_ADDR_NULL) {
                goto done;
        }
        if (req->oldlen != sizeof(struct nd6_lookup_ipv6_args) ||
            req->newlen != sizeof(struct nd6_lookup_ipv6_args)) {
                error = EINVAL;
                nd6log0(error, "%s: bad req, error %d\n",
                    __func__, error);
                goto done;
        }
        error = SYSCTL_IN(req, &nd6_lookup_ipv6_args,
            sizeof(struct nd6_lookup_ipv6_args));
        if (error != 0) {
                nd6log0(error, "%s: SYSCTL_IN() error %d\n",
                    __func__, error);
                goto done;
        }

        if (nd6_lookup_ipv6_args.ll_dest_len > sizeof(nd6_lookup_ipv6_args.ll_dest_)) {
                error = EINVAL;
                nd6log0(error, "%s: bad ll_dest_len, error %d\n",
                    __func__, error);
                goto done;
        }

        /* Make sure to terminate the string */
        nd6_lookup_ipv6_args.ifname[IFNAMSIZ - 1] = 0;

        error = ifnet_find_by_name(nd6_lookup_ipv6_args.ifname, &ifp);
        if (error != 0) {
                nd6log0(error, "%s: ifnet_find_by_name() error %d\n",
                    __func__, error);
                goto done;
        }

        error = nd6_lookup_ipv6(ifp, &nd6_lookup_ipv6_args.ip6_dest,
            &nd6_lookup_ipv6_args.ll_dest_._sdl,
            nd6_lookup_ipv6_args.ll_dest_len, NULL, NULL);
        if (error != 0) {
                nd6log0(error, "%s: nd6_lookup_ipv6() error %d\n",
                    __func__, error);
                goto done;
        }

        error = SYSCTL_OUT(req, &nd6_lookup_ipv6_args,
            sizeof(struct nd6_lookup_ipv6_args));
        if (error != 0) {
                nd6log0(error, "%s: SYSCTL_OUT() error %d\n",
                    __func__, error);
                goto done;
        }
done:
        return error;
}

#endif /* (DEVELOPEMENT || DEBUG) */

int
nd6_setifinfo(struct ifnet *ifp, u_int32_t before, u_int32_t after)
{
        uint32_t b, a;
        int err = 0;

        /*
         * Handle ND6_IFF_IFDISABLED
         */
        if ((before & ND6_IFF_IFDISABLED) ||
            (after & ND6_IFF_IFDISABLED)) {
                b = (before & ND6_IFF_IFDISABLED);
                a = (after & ND6_IFF_IFDISABLED);

                if (b != a && (err = nd6_if_disable(ifp,
                    ((int32_t)(a - b) > 0))) != 0) {
                        goto done;
                }
        }

        /*
         * Handle ND6_IFF_PROXY_PREFIXES
         */
        if ((before & ND6_IFF_PROXY_PREFIXES) ||
            (after & ND6_IFF_PROXY_PREFIXES)) {
                b = (before & ND6_IFF_PROXY_PREFIXES);
                a = (after & ND6_IFF_PROXY_PREFIXES);

                if (b != a && (err = nd6_if_prproxy(ifp,
                    ((int32_t)(a - b) > 0))) != 0) {
                        goto done;
                }
        }
done:
        return err;
}

/*
 * Enable/disable IPv6 on an interface, called as part of
 * setting/clearing ND6_IFF_IFDISABLED, or during DAD failure.
 */
int
nd6_if_disable(struct ifnet *ifp, boolean_t enable)
{
        ifnet_lock_shared(ifp);
        if (enable) {
                ifp->if_eflags |= IFEF_IPV6_DISABLED;
        } else {
                ifp->if_eflags &= ~IFEF_IPV6_DISABLED;
        }
        ifnet_lock_done(ifp);

        return 0;
}

static int
nd6_sysctl_drlist SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        char pbuf[MAX_IPv6_STR_LEN];
        struct nd_defrouter *dr;
        int error = 0;

        if (req->newptr != USER_ADDR_NULL) {
                return EPERM;
        }

        /* XXX Handle mapped defrouter entries */
        lck_mtx_lock(nd6_mutex);
        if (proc_is64bit(req->p)) {
                struct in6_defrouter_64 d;

                bzero(&d, sizeof(d));
                d.rtaddr.sin6_family = AF_INET6;
                d.rtaddr.sin6_len = sizeof(d.rtaddr);

                TAILQ_FOREACH(dr, &nd_defrouter, dr_entry) {
                        d.rtaddr.sin6_addr = dr->rtaddr;
                        if (in6_recoverscope(&d.rtaddr,
                            &dr->rtaddr, dr->ifp) != 0) {
                                log(LOG_ERR, "scope error in default router "
                                    "list (%s)\n", inet_ntop(AF_INET6,
                                    &dr->rtaddr, pbuf, sizeof(pbuf)));
                        }
                        d.flags = dr->flags;
                        d.stateflags = dr->stateflags;
                        d.rtlifetime = dr->rtlifetime;
                        d.expire = nddr_getexpire(dr);
                        d.if_index = dr->ifp->if_index;
                        error = SYSCTL_OUT(req, &d, sizeof(d));
                        if (error != 0) {
                                break;
                        }
                }
        } else {
                struct in6_defrouter_32 d;

                bzero(&d, sizeof(d));
                d.rtaddr.sin6_family = AF_INET6;
                d.rtaddr.sin6_len = sizeof(d.rtaddr);

                TAILQ_FOREACH(dr, &nd_defrouter, dr_entry) {
                        d.rtaddr.sin6_addr = dr->rtaddr;
                        if (in6_recoverscope(&d.rtaddr,
                            &dr->rtaddr, dr->ifp) != 0) {
                                log(LOG_ERR, "scope error in default router "
                                    "list (%s)\n", inet_ntop(AF_INET6,
                                    &dr->rtaddr, pbuf, sizeof(pbuf)));
                        }
                        d.flags = dr->flags;
                        d.stateflags = dr->stateflags;
                        d.rtlifetime = dr->rtlifetime;
                        d.expire = nddr_getexpire(dr);
                        d.if_index = dr->ifp->if_index;
                        error = SYSCTL_OUT(req, &d, sizeof(d));
                        if (error != 0) {
                                break;
                        }
                }
        }
        lck_mtx_unlock(nd6_mutex);
        return error;
}

static int
nd6_sysctl_prlist SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)
        char pbuf[MAX_IPv6_STR_LEN];
        struct nd_pfxrouter *pfr;
        struct sockaddr_in6 s6;
        struct nd_prefix *pr;
        int error = 0;

        if (req->newptr != USER_ADDR_NULL) {
                return EPERM;
        }

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

        /* XXX Handle mapped defrouter entries */
        lck_mtx_lock(nd6_mutex);
        if (proc_is64bit(req->p)) {
                struct in6_prefix_64 p;

                bzero(&p, sizeof(p));
                p.origin = PR_ORIG_RA;

                LIST_FOREACH(pr, &nd_prefix, ndpr_entry) {
                        NDPR_LOCK(pr);
                        p.prefix = pr->ndpr_prefix;
                        if (in6_recoverscope(&p.prefix,
                            &pr->ndpr_prefix.sin6_addr, pr->ndpr_ifp) != 0) {
                                log(LOG_ERR, "scope error in "
                                    "prefix list (%s)\n", inet_ntop(AF_INET6,
                                    &p.prefix.sin6_addr, pbuf, sizeof(pbuf)));
                        }
                        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;
                        p.expire = ndpr_getexpire(pr);
                        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) {
                                NDPR_UNLOCK(pr);
                                break;
                        }
                        LIST_FOREACH(pfr, &pr->ndpr_advrtrs, pfr_entry) {
                                s6.sin6_addr = pfr->router->rtaddr;
                                if (in6_recoverscope(&s6, &pfr->router->rtaddr,
                                    pfr->router->ifp) != 0) {
                                        log(LOG_ERR,
                                            "scope error in prefix list (%s)\n",
                                            inet_ntop(AF_INET6, &s6.sin6_addr,
                                            pbuf, sizeof(pbuf)));
                                }
                                error = SYSCTL_OUT(req, &s6, sizeof(s6));
                                if (error != 0) {
                                        break;
                                }
                        }
                        NDPR_UNLOCK(pr);
                        if (error != 0) {
                                break;
                        }
                }
        } else {
                struct in6_prefix_32 p;

                bzero(&p, sizeof(p));
                p.origin = PR_ORIG_RA;

                LIST_FOREACH(pr, &nd_prefix, ndpr_entry) {
                        NDPR_LOCK(pr);
                        p.prefix = pr->ndpr_prefix;
                        if (in6_recoverscope(&p.prefix,
                            &pr->ndpr_prefix.sin6_addr, pr->ndpr_ifp) != 0) {
                                log(LOG_ERR,
                                    "scope error in prefix list (%s)\n",
                                    inet_ntop(AF_INET6, &p.prefix.sin6_addr,
                                    pbuf, sizeof(pbuf)));
                        }
                        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;
                        p.expire = ndpr_getexpire(pr);
                        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) {
                                NDPR_UNLOCK(pr);
                                break;
                        }
                        LIST_FOREACH(pfr, &pr->ndpr_advrtrs, pfr_entry) {
                                s6.sin6_addr = pfr->router->rtaddr;
                                if (in6_recoverscope(&s6, &pfr->router->rtaddr,
                                    pfr->router->ifp) != 0) {
                                        log(LOG_ERR,
                                            "scope error in prefix list (%s)\n",
                                            inet_ntop(AF_INET6, &s6.sin6_addr,
                                            pbuf, sizeof(pbuf)));
                                }
                                error = SYSCTL_OUT(req, &s6, sizeof(s6));
                                if (error != 0) {
                                        break;
                                }
                        }
                        NDPR_UNLOCK(pr);
                        if (error != 0) {
                                break;
                        }
                }
        }
        lck_mtx_unlock(nd6_mutex);

        return error;
}

void
in6_ifaddr_set_dadprogress(struct in6_ifaddr *ia)
{
        struct ifnet* ifp = ia->ia_ifp;
        uint32_t flags = IN6_IFF_TENTATIVE;
        uint32_t optdad = nd6_optimistic_dad;
        struct nd_ifinfo *ndi = NULL;

        ndi = ND_IFINFO(ifp);
        VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
        if (!(ndi->flags & ND6_IFF_DAD)) {
                return;
        }

        if (optdad) {
                if ((ifp->if_eflags & IFEF_IPV6_ROUTER) != 0) {
                        optdad = 0;
                } else {
                        lck_mtx_lock(&ndi->lock);
                        if ((ndi->flags & ND6_IFF_REPLICATED) != 0) {
                                optdad = 0;
                        }
                        lck_mtx_unlock(&ndi->lock);
                }
        }

        if (optdad) {
                if ((optdad & ND6_OPTIMISTIC_DAD_LINKLOCAL) &&
                    IN6_IS_ADDR_LINKLOCAL(&ia->ia_addr.sin6_addr)) {
                        flags = IN6_IFF_OPTIMISTIC;
                } else if ((optdad & ND6_OPTIMISTIC_DAD_AUTOCONF) &&
                    (ia->ia6_flags & IN6_IFF_AUTOCONF)) {
                        if (ia->ia6_flags & IN6_IFF_TEMPORARY) {
                                if (optdad & ND6_OPTIMISTIC_DAD_TEMPORARY) {
                                        flags = IN6_IFF_OPTIMISTIC;
                                }
                        } else if (ia->ia6_flags & IN6_IFF_SECURED) {
                                if (optdad & ND6_OPTIMISTIC_DAD_SECURED) {
                                        flags = IN6_IFF_OPTIMISTIC;
                                }
                        } else {
                                /*
                                 * Keeping the behavior for temp and CGA
                                 * SLAAC addresses to have a knob for optimistic
                                 * DAD.
                                 * Other than that if ND6_OPTIMISTIC_DAD_AUTOCONF
                                 * is set, we should default to optimistic
                                 * DAD.
                                 * For now this means SLAAC addresses with interface
                                 * identifier derived from modified EUI-64 bit
                                 * identifiers.
                                 */
                                flags = IN6_IFF_OPTIMISTIC;
                        }
                } else if ((optdad & ND6_OPTIMISTIC_DAD_DYNAMIC) &&
                    (ia->ia6_flags & IN6_IFF_DYNAMIC)) {
                        if (ia->ia6_flags & IN6_IFF_TEMPORARY) {
                                if (optdad & ND6_OPTIMISTIC_DAD_TEMPORARY) {
                                        flags = IN6_IFF_OPTIMISTIC;
                                }
                        } else {
                                flags = IN6_IFF_OPTIMISTIC;
                        }
                } else if ((optdad & ND6_OPTIMISTIC_DAD_MANUAL) &&
                    (ia->ia6_flags & IN6_IFF_OPTIMISTIC)) {
                        /*
                         * rdar://17483438
                         * Bypass tentative for address assignments
                         * not covered above (e.g. manual) upon request
                         */
                        if (!IN6_IS_ADDR_LINKLOCAL(&ia->ia_addr.sin6_addr) &&
                            !(ia->ia6_flags & IN6_IFF_AUTOCONF) &&
                            !(ia->ia6_flags & IN6_IFF_DYNAMIC)) {
                                flags = IN6_IFF_OPTIMISTIC;
                        }
                }
        }

        ia->ia6_flags &= ~(IN6_IFF_DUPLICATED | IN6_IFF_DADPROGRESS);
        ia->ia6_flags |= flags;

        nd6log2(debug, "%s - %s ifp %s ia6_flags 0x%x\n",
            __func__,
            ip6_sprintf(&ia->ia_addr.sin6_addr),
            if_name(ia->ia_ifp),
            ia->ia6_flags);
}