xnu-7195.101.1.tar.gz

[apple/xnu.git] / bsd / netinet6 / nd6_nbr.c

/*
 * Copyright (c) 2000-2020 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/errno.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>
#include <sys/mcache.h>
#include <sys/protosw.h>
#include <kern/queue.h>
#include <dev/random/randomdev.h>

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

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

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

#if IPSEC
#include <netinet6/ipsec.h>
#include <netinet6/ipsec6.h>
#endif

struct dadq;
static struct dadq *nd6_dad_find(struct ifaddr *, struct nd_opt_nonce *);
void nd6_dad_stoptimer(struct ifaddr *);
static void nd6_dad_timer(struct ifaddr *);
static void nd6_dad_ns_output(struct dadq *, struct ifaddr *);
static void nd6_dad_ns_input(struct ifaddr *, char *, int, struct nd_opt_nonce *);
static struct mbuf *nd6_dad_na_input(struct mbuf *, struct ifnet *,
    struct in6_addr *, caddr_t, int);
static void dad_addref(struct dadq *, int);
static void dad_remref(struct dadq *);
static struct dadq *nd6_dad_attach(struct dadq *, struct ifaddr *);
static void nd6_dad_detach(struct dadq *, struct ifaddr *);
static void nd6_dad_duplicated(struct ifaddr *);

static int dad_maxtry = 15;     /* max # of *tries* to transmit DAD packet */

#define DAD_LOCK_ASSERT_HELD(_dp)                                       \
        LCK_MTX_ASSERT(&(_dp)->dad_lock, LCK_MTX_ASSERT_OWNED)

#define DAD_LOCK_ASSERT_NOTHELD(_dp)                                    \
        LCK_MTX_ASSERT(&(_dp)->dad_lock, LCK_MTX_ASSERT_NOTOWNED)

#define DAD_LOCK(_dp)                                                   \
        lck_mtx_lock(&(_dp)->dad_lock)

#define DAD_LOCK_SPIN(_dp)                                              \
        lck_mtx_lock_spin(&(_dp)->dad_lock)

#define DAD_CONVERT_LOCK(_dp) do {                                      \
        DAD_LOCK_ASSERT_HELD(_dp);                                      \
        lck_mtx_convert_spin(&(_dp)->dad_lock);                         \
} while (0)

#define DAD_UNLOCK(_dp)                                                 \
        lck_mtx_unlock(&(_dp)->dad_lock)

#define DAD_ADDREF(_dp)                                                 \
        dad_addref(_dp, 0)

#define DAD_ADDREF_LOCKED(_dp)                                          \
        dad_addref(_dp, 1)

#define DAD_REMREF(_dp)                                                 \
        dad_remref(_dp)

extern lck_mtx_t *dad6_mutex;
extern lck_mtx_t *nd6_mutex;

static int nd6_llreach_base = 30;        /* seconds */

static struct sockaddr_in6 hostrtmask;

SYSCTL_DECL(_net_inet6_icmp6);
SYSCTL_INT(_net_inet6_icmp6, OID_AUTO, nd6_llreach_base,
    CTLFLAG_RW | CTLFLAG_LOCKED, &nd6_llreach_base, 0,
    "default ND6 link-layer reachability max lifetime (in seconds)");

int dad_enhanced = ND6_DAD_ENHANCED_DEFAULT;
SYSCTL_DECL(_net_inet6_ip6);
SYSCTL_INT(_net_inet6_ip6, OID_AUTO, dad_enhanced, CTLFLAG_RW | CTLFLAG_LOCKED,
    &dad_enhanced, 0,
    "Enable Enhanced DAD, which adds a random nonce to NS messages for DAD.");

/*
 * Obtain a link-layer source cache entry for the sender.
 *
 * NOTE: This is currently only for ND6/Ethernet.
 */
void
nd6_llreach_alloc(struct rtentry *rt, struct ifnet *ifp, void *addr,
    unsigned int alen, boolean_t solicited)
{
        struct llinfo_nd6 *ln = rt->rt_llinfo;

        if (nd6_llreach_base != 0 &&
            (ln->ln_expire != 0 || (ifp->if_eflags & IFEF_IPV6_ND6ALT) != 0) &&
            !(rt->rt_ifp->if_flags & IFF_LOOPBACK) &&
            ifp->if_addrlen == IF_LLREACH_MAXLEN &&     /* Ethernet */
            alen == ifp->if_addrlen) {
                struct if_llreach *lr;
                const char *why = NULL, *type = "";

                /* Become a regular mutex, just in case */
                RT_CONVERT_LOCK(rt);

                if ((lr = ln->ln_llreach) != NULL) {
                        type = (solicited ? "ND6 advertisement" :
                            "ND6 unsolicited announcement");
                        /*
                         * If target has changed, create a new record;
                         * otherwise keep existing record.
                         */
                        IFLR_LOCK(lr);
                        if (bcmp(addr, lr->lr_key.addr, alen) != 0) {
                                IFLR_UNLOCK(lr);
                                /* Purge any link-layer info caching */
                                VERIFY(rt->rt_llinfo_purge != NULL);
                                rt->rt_llinfo_purge(rt);
                                lr = NULL;
                                why = " for different target HW address; "
                                    "using new llreach record";
                        } else {
                                lr->lr_probes = 0;      /* reset probe count */
                                IFLR_UNLOCK(lr);
                                if (solicited) {
                                        why = " for same target HW address; "
                                            "keeping existing llreach record";
                                }
                        }
                }

                if (lr == NULL) {
                        lr = ln->ln_llreach = ifnet_llreach_alloc(ifp,
                            ETHERTYPE_IPV6, addr, alen, nd6_llreach_base);
                        if (lr != NULL) {
                                lr->lr_probes = 0;      /* reset probe count */
                                if (why == NULL) {
                                        why = "creating new llreach record";
                                }
                        }
                }

                if (nd6_debug && lr != NULL && why != NULL) {
                        char tmp[MAX_IPv6_STR_LEN];

                        nd6log(debug, "%s: %s%s for %s\n", if_name(ifp),
                            type, why, inet_ntop(AF_INET6,
                            &SIN6(rt_key(rt))->sin6_addr, tmp, sizeof(tmp)));
                }
        }
}

void
nd6_llreach_use(struct llinfo_nd6 *ln)
{
        if (ln->ln_llreach != NULL) {
                ln->ln_lastused = net_uptime();
        }
}

/*
 * Input a Neighbor Solicitation Message.
 *
 * Based on RFC 4861
 * Based on RFC 4862 (duplicate address detection)
 */
void
nd6_ns_input(
        struct mbuf *m,
        int off,
        int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_neighbor_solicit *nd_ns = NULL;
        struct in6_addr saddr6 = ip6->ip6_src;
        struct in6_addr daddr6 = ip6->ip6_dst;
        struct in6_addr taddr6 = {};
        struct in6_addr myaddr6 = {};
        char *lladdr = NULL;
        struct ifaddr *ifa = NULL;
        int lladdrlen = 0;
        int anycast = 0, proxy = 0, dadprogress = 0;
        int tlladdr = 0;
        union nd_opts ndopts = {};
        struct sockaddr_dl proxydl = {};
        boolean_t advrouter = FALSE;
        boolean_t is_dad_probe = FALSE;
        int oflgclr = 0;

        /* Expect 32-bit aligned data pointer on strict-align platforms */
        MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);

        IP6_EXTHDR_CHECK(m, off, icmp6len, return );
        ip6 = mtod(m, struct ip6_hdr *);
        nd_ns = (struct nd_neighbor_solicit *)((caddr_t)ip6 + off);
        m->m_pkthdr.pkt_flags |= PKTF_INET6_RESOLVE;

        taddr6 = nd_ns->nd_ns_target;
        if (in6_setscope(&taddr6, ifp, NULL) != 0) {
                goto bad;
        }

        if (ip6->ip6_hlim != IPV6_MAXHLIM) {
                nd6log(error,
                    "nd6_ns_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp));
                goto bad;
        }

        is_dad_probe = IN6_IS_ADDR_UNSPECIFIED(&saddr6);
        if (is_dad_probe) {
                /* dst has to be a solicited node multicast address. */
                if (daddr6.s6_addr16[0] == IPV6_ADDR_INT16_MLL &&
                    /* don't check ifindex portion */
                    daddr6.s6_addr32[1] == 0 &&
                    daddr6.s6_addr32[2] == IPV6_ADDR_INT32_ONE &&
                    daddr6.s6_addr8[12] == 0xff) {
                        ; /* good */
                } else {
                        nd6log(info, "nd6_ns_input: bad DAD packet "
                            "(wrong ip6 dst)\n");
                        goto bad;
                }
        } else if (!nd6_onlink_ns_rfc4861) {
                struct sockaddr_in6 src_sa6;

                /*
                 * According to recent IETF discussions, it is not a good idea
                 * to accept a NS from an address which would not be deemed
                 * to be a neighbor otherwise.  This point is expected to be
                 * clarified in future revisions of the specification.
                 */
                bzero(&src_sa6, sizeof(src_sa6));
                src_sa6.sin6_family = AF_INET6;
                src_sa6.sin6_len = sizeof(src_sa6);
                src_sa6.sin6_addr = saddr6;
                if (!nd6_is_addr_neighbor(&src_sa6, ifp, 0)) {
                        nd6log(info, "nd6_ns_input: "
                            "NS packet from non-neighbor\n");
                        goto bad;
                }
        }

        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                nd6log(info, "nd6_ns_input: bad NS target (multicast)\n");
                goto bad;
        }

        icmp6len -= sizeof(*nd_ns);
        nd6_option_init(nd_ns + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log(info,
                    "nd6_ns_input: invalid ND option, ignored\n");
                /* nd6_options have incremented stats */
                goto freeit;
        }

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

        if (is_dad_probe && lladdr) {
                nd6log(info, "nd6_ns_input: bad DAD packet "
                    "(link-layer address option)\n");
                goto bad;
        }

        /*
         * Attaching target link-layer address to the NA?
         * (RFC 2461 7.2.4)
         *
         * NS IP dst is unicast/anycast                 MUST NOT add
         * NS IP dst is solicited-node multicast        MUST add
         *
         * In implementation, we add target link-layer address by default.
         * We do not add one in MUST NOT cases.
         */
        if (!IN6_IS_ADDR_MULTICAST(&daddr6)) {
                tlladdr = 0;
        } else {
                tlladdr = 1;
        }

        /*
         * Target address (taddr6) must be either:
         * (1) Valid unicast/anycast address for my receiving interface,
         * (2) Unicast address for which I'm offering proxy service, or
         * (3) "tentative" or "optimistic" address [DAD is in progress].
         */
        /* (1) and (3) check. */
        ifa = (struct ifaddr *)in6ifa_ifpwithaddr(ifp, &taddr6);

        /* (2) check. */
        if (ifa == NULL) {
                struct rtentry *rt;
                struct sockaddr_in6 tsin6;

                bzero(&tsin6, sizeof tsin6);
                tsin6.sin6_len = sizeof(struct sockaddr_in6);
                tsin6.sin6_family = AF_INET6;
                tsin6.sin6_addr = taddr6;

                rt = rtalloc1_scoped((struct sockaddr *)&tsin6, 0, 0,
                    ifp->if_index);

                if (rt != NULL) {
                        RT_LOCK(rt);
                        if ((rt->rt_flags & RTF_ANNOUNCE) != 0 &&
                            rt->rt_gateway->sa_family == AF_LINK) {
                                /*
                                 * proxy NDP for single entry
                                 */
                                ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(
                                        ifp, IN6_IFF_NOTREADY | IN6_IFF_ANYCAST);
                                if (ifa) {
                                        proxy = 1;
                                        proxydl = *SDL(rt->rt_gateway);
                                }
                        }
                        RT_UNLOCK(rt);
                        rtfree(rt);
                }
        }
        if (ifa == NULL && ip6_forwarding && nd6_prproxy) {
                /*
                 * Is the target address part of the prefix that is being
                 * proxied and installed on another interface?
                 */
                ifa = (struct ifaddr *)in6ifa_prproxyaddr(&taddr6);
        }
        if (ifa == NULL) {
                /*
                 * We've got an NS packet, and we don't have that address
                 * assigned for us.  We MUST silently ignore it on this
                 * interface, c.f. RFC 4861 7.2.3.
                 *
                 * Forwarding associated with NDPRF_PRPROXY may apply.
                 */
                if (ip6_forwarding && nd6_prproxy) {
                        nd6_prproxy_ns_input(ifp, &saddr6, lladdr,
                            lladdrlen, &daddr6, &taddr6,
                            (ndopts.nd_opts_nonce == NULL) ? NULL :
                            ndopts.nd_opts_nonce->nd_opt_nonce);
                }
                goto freeit;
        }
        IFA_LOCK(ifa);
        myaddr6 = *IFA_IN6(ifa);
        anycast = ((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_ANYCAST;
        dadprogress =
            ((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_DADPROGRESS;
        if (((struct in6_ifaddr *)ifa)->ia6_flags & IN6_IFF_DUPLICATED) {
                IFA_UNLOCK(ifa);
                goto freeit;
        }
        IFA_UNLOCK(ifa);

        if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                nd6log(info,
                    "nd6_ns_input: lladdrlen mismatch for %s "
                    "(if %d, NS packet %d)\n",
                    ip6_sprintf(&taddr6), ifp->if_addrlen, lladdrlen - 2);
                goto bad;
        }

        if (IN6_ARE_ADDR_EQUAL(&myaddr6, &saddr6)) {
                nd6log(info,
                    "nd6_ns_input: duplicate IP6 address %s\n",
                    ip6_sprintf(&saddr6));
                goto freeit;
        }

        /*
         * We have neighbor solicitation packet, with target address equals to
         * one of my DAD in-progress addresses.
         *
         * src addr     how to process?
         * ---          ---
         * multicast    of course, invalid (rejected in ip6_input)
         * unicast      somebody is doing address resolution
         * unspec       dup address detection
         *
         * The processing is defined in the "draft standard" RFC 4862 (and by
         * RFC 4429, which is a "proposed standard" update to its obsolete
         * predecessor, RFC 2462)  The reason optimistic DAD is not included
         * in RFC 4862 is entirely due to IETF procedural considerations.
         */
        if (dadprogress) {
                /*
                 * If source address is unspecified address, it is for
                 * duplicate address detection.
                 *
                 * If not, the packet is for addess resolution;
                 * silently ignore it when not optimistic
                 *
                 * Per RFC 4429 the reply for an optimistic address must
                 * have the Override flag cleared
                 */
                if (!is_dad_probe && (dadprogress & IN6_IFF_OPTIMISTIC) != 0) {
                        oflgclr = 1;
                } else {
                        if (is_dad_probe) {
                                nd6_dad_ns_input(ifa, lladdr, lladdrlen, ndopts.nd_opts_nonce);
                        }

                        goto freeit;
                }
        }

        /* Are we an advertising router on this interface? */
        advrouter = (ifp->if_ipv6_router_mode != IPV6_ROUTER_MODE_DISABLED);

        /*
         * If the source address is unspecified address, entries must not
         * be created or updated.
         * It looks that sender is performing DAD.  If I'm using the address,
         * and it's a "preferred" address, i.e. not optimistic, then output NA
         * toward all-node multicast address, to tell the sender that I'm using
         * the address.
         * S bit ("solicited") must be zero.
         */
        if (is_dad_probe) {
                saddr6 = in6addr_linklocal_allnodes;
                if (in6_setscope(&saddr6, ifp, NULL) != 0) {
                        goto bad;
                }
                if ((dadprogress & IN6_IFF_OPTIMISTIC) == 0) {
                        nd6_na_output(ifp, &saddr6, &taddr6,
                            ((anycast || proxy || !tlladdr) ? 0 :
                            ND_NA_FLAG_OVERRIDE) | (advrouter ?
                            ND_NA_FLAG_ROUTER : 0), tlladdr, proxy ?
                            (struct sockaddr *)&proxydl : NULL);
                }
                goto freeit;
        }

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

        nd6_na_output(ifp, &saddr6, &taddr6,
            ((anycast || proxy || !tlladdr || oflgclr) ? 0 : ND_NA_FLAG_OVERRIDE) |
            (advrouter ? ND_NA_FLAG_ROUTER : 0) | ND_NA_FLAG_SOLICITED,
            tlladdr, proxy ? (struct sockaddr *)&proxydl : NULL);
freeit:
        m_freem(m);
        if (ifa != NULL) {
                IFA_REMREF(ifa);
        }
        return;

bad:
        nd6log(error, "nd6_ns_input: src=%s\n", ip6_sprintf(&saddr6));
        nd6log(error, "nd6_ns_input: dst=%s\n", ip6_sprintf(&daddr6));
        nd6log(error, "nd6_ns_input: tgt=%s\n", ip6_sprintf(&taddr6));
        icmp6stat.icp6s_badns++;
        m_freem(m);
        if (ifa != NULL) {
                IFA_REMREF(ifa);
        }
}

/*
 * Output a Neighbor Solicitation Message. Caller specifies:
 *      - ICMP6 header source IP6 address
 *      - ND6 header target IP6 address
 *      - ND6 header source datalink address
 *
 * Based on RFC 4861
 * Based on RFC 4862 (duplicate address detection)
 * Based on RFC 4429 (optimistic duplicate address detection)
 *
 * Caller must bump up ln->ln_rt refcnt to make sure 'ln' doesn't go
 * away if there is a llinfo_nd6 passed in.
 */
void
nd6_ns_output(
        struct ifnet *ifp,
        const struct in6_addr *daddr6,
        const struct in6_addr *taddr6,
        struct llinfo_nd6 *ln,  /* for source address determination */
        uint8_t *nonce) /* duplicated address detection */
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_solicit *nd_ns;
        struct in6_ifaddr *ia = NULL;
        struct in6_addr *src, src_in, src_storage;
        struct ip6_moptions *im6o = NULL;
        struct ifnet *outif = NULL;
        int icmp6len;
        int maxlen;
        int flags;
        caddr_t mac;
        struct route_in6 ro;
        struct ip6_out_args ip6oa;
        u_int32_t rtflags = 0;
        boolean_t is_optimistic = FALSE;

        if ((ifp->if_eflags & IFEF_IPV6_ND6ALT) || IN6_IS_ADDR_MULTICAST(taddr6)) {
                return;
        }

        bzero(&ro, sizeof(ro));
        bzero(&ip6oa, sizeof(ip6oa));
        ip6oa.ip6oa_boundif = ifp->if_index;
        ip6oa.ip6oa_flags = IP6OAF_SELECT_SRCIF | IP6OAF_BOUND_SRCADDR |
            IP6OAF_AWDL_UNRESTRICTED | IP6OAF_INTCOPROC_ALLOWED;
        ip6oa.ip6oa_sotc = SO_TC_UNSPEC;
        ip6oa.ip6oa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;

        ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF;

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_ns);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        if (max_linkhdr + maxlen >= MCLBYTES) {
#if DIAGNOSTIC
                printf("nd6_ns_output: max_linkhdr + maxlen >= MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        MGETHDR(m, M_DONTWAIT, MT_DATA);        /* XXXMAC: mac_create_mbuf_linklayer() probably */
        if (m && max_linkhdr + maxlen >= MHLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0) {
                        m_free(m);
                        m = NULL;
                }
        }
        if (m == NULL) {
                return;
        }
        m->m_pkthdr.rcvif = NULL;

        if (daddr6 == NULL || IN6_IS_ADDR_MULTICAST(daddr6)) {
                m->m_flags |= M_MCAST;

                im6o = ip6_allocmoptions(Z_NOWAIT);
                if (im6o == NULL) {
                        m_freem(m);
                        return;
                }

                im6o->im6o_multicast_ifp = ifp;
                im6o->im6o_multicast_hlim = IPV6_MAXHLIM;
                im6o->im6o_multicast_loop = 0;
        }

        icmp6len = sizeof(*nd_ns);
        m->m_pkthdr.len = m->m_len = sizeof(*ip6) + icmp6len;
        m->m_data += max_linkhdr;       /* or MH_ALIGN() equivalent? */

        /* fill neighbor solicitation packet */
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        /* ip6->ip6_plen will be set later */
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_hlim = IPV6_MAXHLIM;
        if (daddr6) {
                ip6->ip6_dst = *daddr6;
        } else {
                ip6->ip6_dst.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
                ip6->ip6_dst.s6_addr16[1] = 0;
                ip6->ip6_dst.s6_addr32[1] = 0;
                ip6->ip6_dst.s6_addr32[2] = IPV6_ADDR_INT32_ONE;
                ip6->ip6_dst.s6_addr32[3] = taddr6->s6_addr32[3];
                ip6->ip6_dst.s6_addr8[12] = 0xff;
                if (in6_setscope(&ip6->ip6_dst, ifp, NULL) != 0) {
                        goto bad;
                }
        }
        if (nonce == NULL) {
                /*
                 * RFC2461 7.2.2:
                 * "If the source address of the packet prompting the
                 * solicitation is the same as one of the addresses assigned
                 * to the outgoing interface, that address SHOULD be placed
                 * in the IP Source Address of the outgoing solicitation.
                 * Otherwise, any one of the addresses assigned to the
                 * interface should be used."
                 *
                 * We use the source address for the prompting packet
                 * (saddr6), if:
                 * - saddr6 is given from the caller (by giving "ln"), and
                 * - saddr6 belongs to the outgoing interface.
                 * Otherwise, we perform the source address selection as usual.
                 */
                struct ip6_hdr *hip6;           /* hold ip6 */
                struct in6_addr *hsrc = NULL;

                /* Caller holds ref on this route */
                if (ln != NULL) {
                        RT_LOCK(ln->ln_rt);
                        /*
                         * assuming every packet in ln_hold has the same IP
                         * header
                         */
                        if (ln->ln_hold != NULL) {
                                hip6 = mtod(ln->ln_hold, struct ip6_hdr *);
                                /* XXX pullup? */
                                if (sizeof(*hip6) < ln->ln_hold->m_len) {
                                        hsrc = &hip6->ip6_src;
                                } else {
                                        hsrc = NULL;
                                }
                        }
                        /* Update probe count, if applicable */
                        if (ln->ln_llreach != NULL) {
                                IFLR_LOCK_SPIN(ln->ln_llreach);
                                ln->ln_llreach->lr_probes++;
                                IFLR_UNLOCK(ln->ln_llreach);
                        }
                        rtflags = ln->ln_rt->rt_flags;
                        RT_UNLOCK(ln->ln_rt);
                }
                if (hsrc != NULL && (ia = in6ifa_ifpwithaddr(ifp, hsrc)) &&
                    (ia->ia6_flags & IN6_IFF_OPTIMISTIC) == 0) {
                        src = hsrc;
                } else {
                        int error;
                        struct sockaddr_in6 dst_sa;

                        bzero(&dst_sa, sizeof(dst_sa));
                        dst_sa.sin6_family = AF_INET6;
                        dst_sa.sin6_len = sizeof(dst_sa);
                        dst_sa.sin6_addr = ip6->ip6_dst;

                        src = in6_selectsrc(&dst_sa, NULL,
                            NULL, &ro, NULL, &src_storage, ip6oa.ip6oa_boundif,
                            &error);
                        if (src == NULL) {
                                nd6log(debug,
                                    "nd6_ns_output: source can't be "
                                    "determined: dst=%s, error=%d\n",
                                    ip6_sprintf(&dst_sa.sin6_addr),
                                    error);
                                goto bad;
                        }

                        if (ia != NULL) {
                                IFA_REMREF(&ia->ia_ifa);
                                ia = NULL;
                        }
                        /*
                         * RFC 4429 section 3.2:
                         * When a node has a unicast packet to send
                         * from an Optimistic Address to a neighbor,
                         * but does not know the neighbor's link-layer
                         * address, it MUST NOT perform Address
                         * Resolution.
                         */
                        ia = in6ifa_ifpwithaddr(ifp, src);
                        if (ia == NULL) {
                                nd6log(debug,
                                    "nd6_ns_output: no preferred source "
                                    "available: dst=%s\n",
                                    ip6_sprintf(&dst_sa.sin6_addr));
                                goto bad;
                        }
                        if (ia->ia6_flags & IN6_IFF_OPTIMISTIC) {
                                is_optimistic = TRUE;
                                nd6log(debug,
                                    "nd6_ns_output: preferred source "
                                    "available is optimistic: dst=%s\n",
                                    ip6_sprintf(&dst_sa.sin6_addr));
                        }
                }
        } else {
                /*
                 * Source address for DAD packet must always be IPv6
                 * unspecified address. (0::0)
                 * We actually don't have to 0-clear the address (we did it
                 * above), but we do so here explicitly to make the intention
                 * clearer.
                 */
                bzero(&src_in, sizeof(src_in));
                src = &src_in;
                ip6oa.ip6oa_flags &= ~IP6OAF_BOUND_SRCADDR;
        }
        ip6->ip6_src = *src;
        nd_ns = (struct nd_neighbor_solicit *)(ip6 + 1);
        nd_ns->nd_ns_type = ND_NEIGHBOR_SOLICIT;
        nd_ns->nd_ns_code = 0;
        nd_ns->nd_ns_reserved = 0;
        nd_ns->nd_ns_target = *taddr6;
        in6_clearscope(&nd_ns->nd_ns_target); /* XXX */

        /*
         * Add source link-layer address option.
         *
         *                              spec            implementation
         *                              ---             ---
         * DAD packet                   MUST NOT        do not add the option
         * Source is optimistic         MUST NOT        do not add the option
         * there's no link layer address:
         *                              impossible      do not add the option
         * there's link layer address:
         *      Multicast NS            MUST add one    add the option
         *      Unicast NS              SHOULD add one  add the option
         *
         * XXX We deviate from RFC 4429 and still use optimistic DAD as source
         * for address resolution. However to ensure that we do not interfere
         * with neighbor cache entries of other neighbors, we MUST ensure
         * that SLLAO is not sent. Also note, sending multicast NS without SLLAO
         * is also a deviation from RFC 4861.
         */
        if (nonce == NULL && (mac = nd6_ifptomac(ifp)) && !is_optimistic) {
                int optlen = sizeof(struct nd_opt_hdr) + ifp->if_addrlen;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_ns + 1);
                /* 8 byte alignments... */
                optlen = (optlen + 7) & ~7;

                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                bzero((caddr_t)nd_opt, optlen);
                nd_opt->nd_opt_type = ND_OPT_SOURCE_LINKADDR;
                nd_opt->nd_opt_len = (uint8_t)(optlen >> 3);
                bcopy(mac, (caddr_t)(nd_opt + 1), ifp->if_addrlen);
        }
        /*
         * Add a Nonce option (RFC 3971) to detect looped back NS messages.
         * This behavior is documented as Enhanced Duplicate Address
         * Detection in draft-ietf-6man-enhanced-dad-13.
         * net.inet6.ip6.dad_enhanced=0 disables this.
         */
        if (dad_enhanced != 0 && nonce != NULL && !(ifp->if_flags & IFF_POINTOPOINT)) {
                int optlen = sizeof(struct nd_opt_hdr) + ND_OPT_NONCE_LEN;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_ns + 1);
                /* 8-byte alignment is required. */
                optlen = (optlen + 7) & ~7;

                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                bzero((caddr_t)nd_opt, optlen);
                nd_opt->nd_opt_type = ND_OPT_NONCE;
                nd_opt->nd_opt_len = (uint8_t)(optlen >> 3);
                bcopy(nonce, (caddr_t)(nd_opt + 1), ND_OPT_NONCE_LEN);
        }
        ip6->ip6_plen = htons((u_short)icmp6len);
        nd_ns->nd_ns_cksum = 0;
        nd_ns->nd_ns_cksum
                = in6_cksum(m, IPPROTO_ICMPV6, sizeof(*ip6), icmp6len);

        flags = nonce ? IPV6_UNSPECSRC : 0;
        flags |= IPV6_OUTARGS;

        /*
         * PKTF_{INET,INET6}_RESOLVE_RTR are mutually exclusive, so make
         * sure only one of them is set (just in case.)
         */
        m->m_pkthdr.pkt_flags &= ~(PKTF_INET_RESOLVE | PKTF_RESOLVE_RTR);
        m->m_pkthdr.pkt_flags |= PKTF_INET6_RESOLVE;
        /*
         * If this is a NS for resolving the (default) router, mark
         * the packet accordingly so that the driver can find out,
         * in case it needs to perform driver-specific action(s).
         */
        if (rtflags & RTF_ROUTER) {
                m->m_pkthdr.pkt_flags |= PKTF_RESOLVE_RTR;
        }

        if (ifp->if_eflags & IFEF_TXSTART) {
                /*
                 * Use control service class if the interface
                 * supports transmit-start model
                 */
                (void) m_set_service_class(m, MBUF_SC_CTL);
        }

        ip6oa.ip6oa_flags |= IP6OAF_SKIP_PF;
        ip6oa.ip6oa_flags |= IP6OAF_DONT_FRAG;
        ip6_output(m, NULL, NULL, flags, im6o, &outif, &ip6oa);
        if (outif) {
                icmp6_ifstat_inc(outif, ifs6_out_msg);
                icmp6_ifstat_inc(outif, ifs6_out_neighborsolicit);
                ifnet_release(outif);
        }
        icmp6stat.icp6s_outhist[ND_NEIGHBOR_SOLICIT]++;

exit:
        if (im6o != NULL) {
                IM6O_REMREF(im6o);
        }

        ROUTE_RELEASE(&ro);     /* we don't cache this route. */

        if (ia != NULL) {
                IFA_REMREF(&ia->ia_ifa);
        }
        return;

bad:
        m_freem(m);
        goto exit;
}

/*
 * Neighbor advertisement input handling.
 *
 * Based on RFC 4861
 * Based on RFC 4862 (duplicate address detection)
 *
 * the following items are not implemented yet:
 * - anycast advertisement delay rule (RFC 4861 7.2.7, SHOULD)
 * - proxy advertisement delay rule (RFC 4861 7.2.8, last paragraph, "should")
 */
void
nd6_na_input(struct mbuf *m, int off, int icmp6len)
{
        struct ifnet *ifp = m->m_pkthdr.rcvif;
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
        struct nd_neighbor_advert *nd_na;
        struct in6_addr saddr6 = ip6->ip6_src;
        struct in6_addr daddr6 = ip6->ip6_dst;
        struct in6_addr taddr6;
        int flags;
        int is_router;
        int is_solicited;
        int is_override;
        char *lladdr = NULL;
        int lladdrlen = 0;
        struct llinfo_nd6 *ln;
        struct rtentry *rt;
        struct sockaddr_dl *sdl;
        union nd_opts ndopts;
        uint64_t timenow;
        bool send_nc_alive_kev = false;

        if ((ifp->if_eflags & IFEF_IPV6_ND6ALT) != 0) {
                nd6log(info, "nd6_na_input: on ND6ALT interface!\n");
                goto freeit;
        }

        /* Expect 32-bit aligned data pointer on strict-align platforms */
        MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);

        if (ip6->ip6_hlim != IPV6_MAXHLIM) {
                nd6log(error,
                    "nd6_na_input: invalid hlim (%d) from %s to %s on %s\n",
                    ip6->ip6_hlim, ip6_sprintf(&ip6->ip6_src),
                    ip6_sprintf(&ip6->ip6_dst), if_name(ifp));
                goto bad;
        }

        IP6_EXTHDR_CHECK(m, off, icmp6len, return );
        ip6 = mtod(m, struct ip6_hdr *);
        nd_na = (struct nd_neighbor_advert *)((caddr_t)ip6 + off);
        m->m_pkthdr.pkt_flags |= PKTF_INET6_RESOLVE;

        flags = nd_na->nd_na_flags_reserved;
        is_router = ((flags & ND_NA_FLAG_ROUTER) != 0);
        is_solicited = ((flags & ND_NA_FLAG_SOLICITED) != 0);
        is_override = ((flags & ND_NA_FLAG_OVERRIDE) != 0);

        taddr6 = nd_na->nd_na_target;
        if (in6_setscope(&taddr6, ifp, NULL)) {
                goto bad;       /* XXX: impossible */
        }
        if (IN6_IS_ADDR_MULTICAST(&taddr6)) {
                nd6log(error,
                    "nd6_na_input: invalid target address %s\n",
                    ip6_sprintf(&taddr6));
                goto bad;
        }
        if (IN6_IS_ADDR_MULTICAST(&daddr6)) {
                if (is_solicited) {
                        nd6log(error,
                            "nd6_na_input: a solicited adv is multicasted\n");
                        goto bad;
                }
        }

        icmp6len -= sizeof(*nd_na);
        nd6_option_init(nd_na + 1, icmp6len, &ndopts);
        if (nd6_options(&ndopts) < 0) {
                nd6log(info,
                    "nd6_na_input: invalid ND option, ignored\n");
                /* nd6_options have incremented stats */
                goto freeit;
        }

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

                if (((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
                        nd6log(info,
                            "nd6_na_input: lladdrlen mismatch for %s "
                            "(if %d, NA packet %d)\n",
                            ip6_sprintf(&taddr6), ifp->if_addrlen,
                            lladdrlen - 2);
                        goto bad;
                }
        }

        m = nd6_dad_na_input(m, ifp, &taddr6, lladdr, lladdrlen);
        if (m == NULL) {
                return;
        }

        /* Forwarding associated with NDPRF_PRPROXY may apply. */
        if (ip6_forwarding && nd6_prproxy) {
                nd6_prproxy_na_input(ifp, &saddr6, &daddr6, &taddr6, flags);
        }

        /*
         * If no neighbor cache entry is found, NA SHOULD silently be
         * discarded.  If we are forwarding (and Scoped Routing is in
         * effect), try to see if there is a neighbor cache entry on
         * another interface (in case we are doing prefix proxying.)
         */
        if ((rt = nd6_lookup(&taddr6, 0, ifp, 0)) == NULL) {
                if (!ip6_forwarding || !nd6_prproxy) {
                        goto freeit;
                }

                if ((rt = nd6_lookup(&taddr6, 0, NULL, 0)) == NULL) {
                        goto freeit;
                }

                RT_LOCK_ASSERT_HELD(rt);
                if (rt->rt_ifp != 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(ifp, 1);
                                rt->rt_if_ref_fn(rt->rt_ifp, -1);
                        }

                        /* Change the interface when the existing route is on */
                        rt->rt_ifp = 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;
                        }
                }
        }

        RT_LOCK_ASSERT_HELD(rt);
        if ((ln = rt->rt_llinfo) == NULL ||
            (sdl = SDL(rt->rt_gateway)) == NULL) {
                RT_REMREF_LOCKED(rt);
                RT_UNLOCK(rt);
                goto freeit;
        }

        timenow = net_uptime();

        if (ln->ln_state == ND6_LLINFO_INCOMPLETE) {
                /*
                 * If the link-layer has address, and no lladdr option came,
                 * discard the packet.
                 */
                if (ifp->if_addrlen && !lladdr) {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        goto freeit;
                }

                /*
                 * Record link-layer address, and update the state.
                 */
                sdl->sdl_alen = ifp->if_addrlen;
                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
                if (is_solicited) {
                        send_nc_alive_kev = (rt->rt_flags & RTF_ROUTER) ? true : false;
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                        if (ln->ln_expire != 0) {
                                struct nd_ifinfo *ndi = NULL;

                                ndi = ND_IFINFO(rt->rt_ifp);
                                VERIFY(ndi != NULL && ndi->initialized);
                                lck_mtx_lock(&ndi->lock);
                                ln_setexpire(ln, timenow + ndi->reachable);
                                lck_mtx_unlock(&ndi->lock);
                                RT_UNLOCK(rt);
                                lck_mtx_lock(rnh_lock);
                                nd6_sched_timeout(NULL, NULL);
                                lck_mtx_unlock(rnh_lock);
                                RT_LOCK(rt);
                        }
                } else {
                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                        ln_setexpire(ln, timenow + nd6_gctimer);
                }


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

                if ((ln->ln_router = (short)is_router) != 0) {
                        struct radix_node_head  *rnh = NULL;
                        struct route_event rt_ev;
                        route_event_init(&rt_ev, rt, NULL, ROUTE_LLENTRY_RESOLVED);
                        /*
                         * This means a router's state has changed from
                         * non-reachable to probably reachable, and might
                         * affect the status of associated prefixes..
                         * We already have a reference on rt. Don't need to
                         * take one for the unlock/lock.
                         */
                        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);
                        lck_mtx_lock(nd6_mutex);
                        pfxlist_onlink_check();
                        lck_mtx_unlock(nd6_mutex);
                        RT_LOCK(rt);
                }
        } else {
                int llchange = 0;

                /*
                 * Check if the link-layer address has changed or not.
                 */
                if (lladdr == NULL) {
                        llchange = 0;
                } else {
                        if (sdl->sdl_alen) {
                                if (bcmp(lladdr, LLADDR(sdl), ifp->if_addrlen)) {
                                        llchange = 1;
                                } else {
                                        llchange = 0;
                                }
                        } else {
                                llchange = 1;
                        }
                }

                /*
                 * This is VERY complex. Look at it with care.
                 *
                 * override solicit lladdr llchange     action
                 *                                      (L: record lladdr)
                 *
                 *      0       0       n       --      (2c)
                 *      0       0       y       n       (2b) L
                 *      0       0       y       y       (1)    REACHABLE->STALE
                 *      0       1       n       --      (2c)   *->REACHABLE
                 *      0       1       y       n       (2b) L *->REACHABLE
                 *      0       1       y       y       (1)    REACHABLE->STALE
                 *      1       0       n       --      (2a)
                 *      1       0       y       n       (2a) L
                 *      1       0       y       y       (2a) L *->STALE
                 *      1       1       n       --      (2a)   *->REACHABLE
                 *      1       1       y       n       (2a) L *->REACHABLE
                 *      1       1       y       y       (2a) L *->REACHABLE
                 */
                if (!is_override && (lladdr != NULL && llchange)) {  /* (1) */
                        /*
                         * If state is REACHABLE, make it STALE.
                         * no other updates should be done.
                         */
                        if (ln->ln_state == ND6_LLINFO_REACHABLE) {
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                                ln_setexpire(ln, timenow + nd6_gctimer);
                        }
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                        goto freeit;
                } else if (is_override                             /* (2a) */
                    || (!is_override && (lladdr && !llchange))     /* (2b) */
                    || !lladdr) {                                  /* (2c) */
                        /*
                         * Update link-local address, if any.
                         */
                        if (lladdr) {
                                sdl->sdl_alen = ifp->if_addrlen;
                                bcopy(lladdr, LLADDR(sdl), ifp->if_addrlen);
                        }

                        /*
                         * If solicited, make the state REACHABLE.
                         * If not solicited and the link-layer address was
                         * changed, make it STALE.
                         */
                        if (is_solicited) {
                                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                                if (ln->ln_expire != 0) {
                                        struct nd_ifinfo *ndi = NULL;

                                        ndi = ND_IFINFO(ifp);
                                        VERIFY(ndi != NULL && ndi->initialized);
                                        lck_mtx_lock(&ndi->lock);
                                        ln_setexpire(ln,
                                            timenow + ndi->reachable);
                                        lck_mtx_unlock(&ndi->lock);
                                        RT_UNLOCK(rt);
                                        lck_mtx_lock(rnh_lock);
                                        nd6_sched_timeout(NULL, NULL);
                                        lck_mtx_unlock(rnh_lock);
                                        RT_LOCK(rt);
                                }
                        } else {
                                if (lladdr && llchange) {
                                        ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_STALE);
                                        ln_setexpire(ln, timenow + nd6_gctimer);
                                }
                        }

                        /*
                         * XXX
                         * The above is somewhat convoluted, for now just
                         * issue a callback for LLENTRY changed.
                         */
                        /* Enqueue work item to invoke callback for this route entry */
                        if (llchange) {
                                route_event_enqueue_nwk_wq_entry(rt, NULL,
                                    ROUTE_LLENTRY_CHANGED, NULL, TRUE);
                        }

                        /*
                         * If the router's link-layer address has changed,
                         * notify routes using this as gateway so they can
                         * update any cached information.
                         */
                        if (ln->ln_router && is_router && llchange) {
                                struct radix_node_head  *rnh = NULL;
                                struct route_event rt_ev;
                                route_event_init(&rt_ev, rt, NULL, ROUTE_LLENTRY_CHANGED);
                                /*
                                 * This means a router's state has changed from
                                 * non-reachable to probably reachable, and might
                                 * affect the status of associated prefixes..
                                 *
                                 * We already have a valid rt reference here.
                                 * We don't need to take another one for unlock/lock.
                                 */
                                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);
                        }
                }

                if (ln->ln_router && !is_router) {
                        /*
                         * The peer dropped the router flag.
                         * Remove the sender from the Default Router List and
                         * update the Destination Cache entries.
                         */
                        struct nd_defrouter *dr;
                        struct in6_addr *in6;
                        struct ifnet *rt_ifp = rt->rt_ifp;

                        in6 = &((struct sockaddr_in6 *)
                            (void *)rt_key(rt))->sin6_addr;

                        RT_UNLOCK(rt);
                        lck_mtx_lock(nd6_mutex);
                        /*
                         * XXX Handle router lists for route information option
                         * as well.
                         */
                        dr = defrouter_lookup(NULL, in6, rt_ifp);
                        if (dr) {
                                TAILQ_REMOVE(&nd_defrouter_list, dr, dr_entry);
                                defrtrlist_del(dr, NULL);
                                NDDR_REMREF(dr);        /* remove list reference */
                                NDDR_REMREF(dr);
                                lck_mtx_unlock(nd6_mutex);
                        } else {
                                lck_mtx_unlock(nd6_mutex);
                                /*
                                 * Even if the neighbor is not in the
                                 * default router list, the neighbor
                                 * may be used as a next hop for some
                                 * destinations (e.g. redirect case).
                                 * So we must call rt6_flush explicitly.
                                 */
                                rt6_flush(&ip6->ip6_src, rt_ifp);
                        }
                        RT_LOCK(rt);
                }
                ln->ln_router = (short)is_router;
        }

        if (send_nc_alive_kev && (ifp->if_addrlen == IF_LLREACH_MAXLEN)) {
                struct kev_msg ev_msg;
                struct kev_nd6_ndalive nd6_ndalive;
                bzero(&ev_msg, sizeof(ev_msg));
                bzero(&nd6_ndalive, sizeof(nd6_ndalive));
                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_NDALIVE;

                nd6_ndalive.link_data.if_family = ifp->if_family;
                nd6_ndalive.link_data.if_unit = ifp->if_unit;
                strlcpy(nd6_ndalive.link_data.if_name,
                    ifp->if_name,
                    sizeof(nd6_ndalive.link_data.if_name));
                ev_msg.dv[0].data_ptr = &nd6_ndalive;
                ev_msg.dv[0].data_length =
                    sizeof(nd6_ndalive);
                dlil_post_complete_msg(NULL, &ev_msg);
        }

        RT_LOCK_ASSERT_HELD(rt);
        rt->rt_flags &= ~RTF_REJECT;

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

        /* update the llinfo, send a queued packet if there is one */
        ln->ln_asked = 0;
        if (ln->ln_hold != NULL) {
                struct mbuf *m_hold, *m_hold_next;
                struct sockaddr_in6 sin6;

                rtkey_to_sa6(rt, &sin6);
                /*
                 * reset the ln_hold in advance, to explicitly
                 * prevent a ln_hold lookup in nd6_output()
                 * (wouldn't happen, though...)
                 */
                m_hold = ln->ln_hold;
                ln->ln_hold = NULL;
                for (; m_hold; m_hold = m_hold_next) {
                        m_hold_next = m_hold->m_nextpkt;
                        m_hold->m_nextpkt = NULL;
                        /*
                         * we assume ifp is not a loopback here, so just set
                         * the 2nd argument as the 1st one.
                         */
                        RT_UNLOCK(rt);
                        nd6_output(ifp, ifp, m_hold, &sin6, rt, NULL);
                        RT_LOCK_SPIN(rt);
                }
        }
        RT_REMREF_LOCKED(rt);
        RT_UNLOCK(rt);
        m_freem(m);
        return;

bad:
        icmp6stat.icp6s_badna++;
        /* fall through */
freeit:
        m_freem(m);
        return;
}

/*
 * Neighbor advertisement output handling.
 *
 * Based on RFC 2461
 *
 * the following items are not implemented yet:
 * - proxy advertisement delay rule (RFC2461 7.2.8, last paragraph, SHOULD)
 * - anycast advertisement delay rule (RFC2461 7.2.7, SHOULD)
 *
 * tlladdr - 1 if include target link-layer address
 * sdl0 - sockaddr_dl (= proxy NA) or NULL
 */
void
nd6_na_output(
        struct ifnet *ifp,
        const struct in6_addr *daddr6_0,
        const struct in6_addr *taddr6,
        uint32_t flags,
        int tlladdr,            /* 1 if include target link-layer address */
        struct sockaddr *sdl0)  /* sockaddr_dl (= proxy NA) or NULL */
{
        struct mbuf *m;
        struct ip6_hdr *ip6;
        struct nd_neighbor_advert *nd_na;
        struct ip6_moptions *im6o = NULL;
        caddr_t mac = NULL;
        struct route_in6 ro;
        struct in6_addr *src, src_storage, daddr6;
        struct in6_ifaddr *ia;
        struct sockaddr_in6 dst_sa;
        int icmp6len, maxlen, error;
        struct ifnet *outif = NULL;

        struct ip6_out_args ip6oa;
        bzero(&ro, sizeof(ro));

        daddr6 = *daddr6_0;     /* make a local copy for modification */

        bzero(&ip6oa, sizeof(ip6oa));
        ip6oa.ip6oa_boundif = ifp->if_index;
        ip6oa.ip6oa_flags = IP6OAF_SELECT_SRCIF | IP6OAF_BOUND_SRCADDR |
            IP6OAF_AWDL_UNRESTRICTED | IP6OAF_INTCOPROC_ALLOWED;
        ip6oa.ip6oa_sotc = SO_TC_UNSPEC;
        ip6oa.ip6oa_netsvctype = _NET_SERVICE_TYPE_UNSPEC;

        ip6oa.ip6oa_flags |= IP6OAF_BOUND_IF;

        /* estimate the size of message */
        maxlen = sizeof(*ip6) + sizeof(*nd_na);
        maxlen += (sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7;
        if (max_linkhdr + maxlen >= MCLBYTES) {
#if DIAGNOSTIC
                printf("nd6_na_output: max_linkhdr + maxlen >= MCLBYTES "
                    "(%d + %d > %d)\n", max_linkhdr, maxlen, MCLBYTES);
#endif
                return;
        }

        MGETHDR(m, M_DONTWAIT, MT_DATA);        /* XXXMAC: mac_create_mbuf_linklayer() probably */
        if (m && max_linkhdr + maxlen >= MHLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0) {
                        m_free(m);
                        m = NULL;
                }
        }
        if (m == NULL) {
                return;
        }
        m->m_pkthdr.rcvif = NULL;

        if (IN6_IS_ADDR_MULTICAST(&daddr6)) {
                m->m_flags |= M_MCAST;

                im6o = ip6_allocmoptions(Z_NOWAIT);
                if (im6o == NULL) {
                        m_freem(m);
                        return;
                }

                im6o->im6o_multicast_ifp = ifp;
                im6o->im6o_multicast_hlim = IPV6_MAXHLIM;
                im6o->im6o_multicast_loop = 0;
        }

        icmp6len = sizeof(*nd_na);
        m->m_pkthdr.len = m->m_len = sizeof(struct ip6_hdr) + icmp6len;
        m->m_data += max_linkhdr;       /* or MH_ALIGN() equivalent? */

        /* fill neighbor advertisement packet */
        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_flow = 0;
        ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc |= IPV6_VERSION;
        ip6->ip6_nxt = IPPROTO_ICMPV6;
        ip6->ip6_hlim = IPV6_MAXHLIM;
        if (IN6_IS_ADDR_UNSPECIFIED(&daddr6)) {
                /* reply to DAD */
                daddr6.s6_addr16[0] = IPV6_ADDR_INT16_MLL;
                daddr6.s6_addr16[1] = 0;
                daddr6.s6_addr32[1] = 0;
                daddr6.s6_addr32[2] = 0;
                daddr6.s6_addr32[3] = IPV6_ADDR_INT32_ONE;
                if (in6_setscope(&daddr6, ifp, NULL)) {
                        goto bad;
                }

                flags &= ~ND_NA_FLAG_SOLICITED;
        } else {
                ip6->ip6_dst = daddr6;
        }

        bzero(&dst_sa, sizeof(struct sockaddr_in6));
        dst_sa.sin6_family = AF_INET6;
        dst_sa.sin6_len = sizeof(struct sockaddr_in6);
        dst_sa.sin6_addr = daddr6;

        /*
         * Select a source whose scope is the same as that of the dest.
         */
        bcopy(&dst_sa, &ro.ro_dst, sizeof(dst_sa));
        src = in6_selectsrc(&dst_sa, NULL, NULL, &ro, NULL, &src_storage,
            ip6oa.ip6oa_boundif, &error);
        if (src == NULL) {
                nd6log(debug, "nd6_na_output: source can't be "
                    "determined: dst=%s, error=%d\n",
                    ip6_sprintf(&dst_sa.sin6_addr), error);
                goto bad;
        }
        ip6->ip6_src = *src;

        /*
         * RFC 4429 requires not setting "override" flag on NA packets sent
         * from optimistic addresses.
         */
        ia = in6ifa_ifpwithaddr(ifp, src);
        if (ia != NULL) {
                if (ia->ia6_flags & IN6_IFF_OPTIMISTIC) {
                        flags &= ~ND_NA_FLAG_OVERRIDE;
                }
                IFA_REMREF(&ia->ia_ifa);
        }

        nd_na = (struct nd_neighbor_advert *)(ip6 + 1);
        nd_na->nd_na_type = ND_NEIGHBOR_ADVERT;
        nd_na->nd_na_code = 0;
        nd_na->nd_na_target = *taddr6;
        in6_clearscope(&nd_na->nd_na_target); /* XXX */

        /*
         * "tlladdr" indicates NS's condition for adding tlladdr or not.
         * see nd6_ns_input() for details.
         * Basically, if NS packet is sent to unicast/anycast addr,
         * target lladdr option SHOULD NOT be included.
         */
        if (tlladdr) {
                /*
                 * sdl0 != NULL indicates proxy NA.  If we do proxy, use
                 * lladdr in sdl0.  If we are not proxying (sending NA for
                 * my address) use lladdr configured for the interface.
                 */
                if (sdl0 == NULL) {
                        mac = nd6_ifptomac(ifp);
                } else if (sdl0->sa_family == AF_LINK) {
                        struct sockaddr_dl *sdl;
                        sdl = (struct sockaddr_dl *)(void *)sdl0;
                        if (sdl->sdl_alen == ifp->if_addrlen) {
                                mac = LLADDR(sdl);
                        }
                }
        }
        if (tlladdr && mac) {
                int optlen = sizeof(struct nd_opt_hdr) + ifp->if_addrlen;
                struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)(nd_na + 1);

                /* roundup to 8 bytes alignment! */
                optlen = (optlen + 7) & ~7;

                m->m_pkthdr.len += optlen;
                m->m_len += optlen;
                icmp6len += optlen;
                bzero((caddr_t)nd_opt, optlen);
                nd_opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;
                nd_opt->nd_opt_len = (uint8_t)(optlen >> 3);
                bcopy(mac, (caddr_t)(nd_opt + 1), ifp->if_addrlen);
        } else {
                flags &= ~ND_NA_FLAG_OVERRIDE;
        }

        ip6->ip6_plen = htons((u_short)icmp6len);
        nd_na->nd_na_flags_reserved = flags;
        nd_na->nd_na_cksum = 0;
        nd_na->nd_na_cksum =
            in6_cksum(m, IPPROTO_ICMPV6, sizeof(struct ip6_hdr), icmp6len);

        m->m_pkthdr.pkt_flags |= PKTF_INET6_RESOLVE;

        if (ifp->if_eflags & IFEF_TXSTART) {
                /* Use control service class if the interface supports
                 * transmit-start model.
                 */
                (void) m_set_service_class(m, MBUF_SC_CTL);
        }

        ip6oa.ip6oa_flags |= IP6OAF_SKIP_PF;
        ip6oa.ip6oa_flags |= IP6OAF_DONT_FRAG;
        ip6_output(m, NULL, NULL, IPV6_OUTARGS, im6o, &outif, &ip6oa);
        if (outif) {
                icmp6_ifstat_inc(outif, ifs6_out_msg);
                icmp6_ifstat_inc(outif, ifs6_out_neighboradvert);
                ifnet_release(outif);
        }
        icmp6stat.icp6s_outhist[ND_NEIGHBOR_ADVERT]++;

exit:
        if (im6o != NULL) {
                IM6O_REMREF(im6o);
        }

        ROUTE_RELEASE(&ro);
        return;

bad:
        m_freem(m);
        goto exit;
}

caddr_t
nd6_ifptomac(
        struct ifnet *ifp)
{
        switch (ifp->if_type) {
        case IFT_ARCNET:
        case IFT_ETHER:
        case IFT_IEEE8023ADLAG:
        case IFT_FDDI:
        case IFT_IEEE1394:
#ifdef IFT_L2VLAN
        case IFT_L2VLAN:
#endif
#ifdef IFT_IEEE80211
        case IFT_IEEE80211:
#endif
#ifdef IFT_CARP
        case IFT_CARP:
#endif
        case IFT_BRIDGE:
        case IFT_ISO88025:
        case IFT_6LOWPAN:
                return (caddr_t)IF_LLADDR(ifp);
        default:
                return NULL;
        }
}

TAILQ_HEAD(dadq_head, dadq);
struct dadq {
        decl_lck_mtx_data(, dad_lock);
        u_int32_t dad_refcount; /* reference count */
        int dad_attached;
        TAILQ_ENTRY(dadq) dad_list;
        struct ifaddr *dad_ifa;
        int dad_count;          /* max NS to send */
        int dad_ns_tcount;      /* # of trials to send NS */
        int dad_ns_ocount;      /* NS sent so far */
        int dad_ns_icount;
        int dad_na_icount;
        int dad_ns_lcount;      /* looped back NS */
        int dad_loopbackprobe;  /* probing state for loopback detection */
        uint8_t dad_lladdr[ETHER_ADDR_LEN];
        uint8_t dad_lladdrlen;
#define ND_OPT_NONCE_LEN32 \
    ((ND_OPT_NONCE_LEN + sizeof(uint32_t) - 1)/sizeof(uint32_t))
        uint32_t dad_nonce[ND_OPT_NONCE_LEN32];
};

static ZONE_DECLARE(dad_zone, "nd6_dad", sizeof(struct dadq), ZC_ZFREE_CLEARMEM);
static struct dadq_head dadq;

void
nd6_nbr_init(void)
{
        int i;

        TAILQ_INIT(&dadq);

        bzero(&hostrtmask, sizeof hostrtmask);
        hostrtmask.sin6_family = AF_INET6;
        hostrtmask.sin6_len = sizeof hostrtmask;
        for (i = 0; i < sizeof hostrtmask.sin6_addr; ++i) {
                hostrtmask.sin6_addr.s6_addr[i] = 0xff;
        }
}

static struct dadq *
nd6_dad_find(struct ifaddr *ifa, struct nd_opt_nonce *nonce)
{
        struct dadq *dp;

        lck_mtx_lock(dad6_mutex);
        for (dp = dadq.tqh_first; dp; dp = dp->dad_list.tqe_next) {
                DAD_LOCK_SPIN(dp);
                if (dp->dad_ifa != ifa) {
                        DAD_UNLOCK(dp);
                        continue;
                }

                /*
                 * Skip if the nonce matches the received one.
                 * +2 in the length is required because of type and
                 * length fields are included in a header.
                 */
                if (nonce != NULL &&
                    nonce->nd_opt_nonce_len == (ND_OPT_NONCE_LEN + 2) / 8 &&
                    memcmp(&nonce->nd_opt_nonce[0], &dp->dad_nonce[0],
                    ND_OPT_NONCE_LEN) == 0) {
                        nd6log(error, "%s: a looped back NS message is "
                            "detected during DAD for %s. Ignoring.\n",
                            if_name(ifa->ifa_ifp),
                            ip6_sprintf(IFA_IN6(ifa)));
                        dp->dad_ns_lcount++;
                        ++ip6stat.ip6s_dad_loopcount;
                        DAD_UNLOCK(dp);
                        continue;
                }

                DAD_ADDREF_LOCKED(dp);
                DAD_UNLOCK(dp);
                break;
        }
        lck_mtx_unlock(dad6_mutex);
        return dp;
}

void
nd6_dad_stoptimer(
        struct ifaddr *ifa)
{
        untimeout((void (*)(void *))nd6_dad_timer, (void *)ifa);
}

/*
 * Start Duplicate Address Detection (DAD) for specified interface address.
 */
void
nd6_dad_start(
        struct ifaddr *ifa,
        int *tick_delay)        /* minimum delay ticks for IFF_UP event */
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;

        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);

        /*
         * If we don't need DAD, don't do it.
         * There are several cases:
         * - DAD is disabled (ip6_dad_count == 0)
         * - the interface address is anycast
         */
        IFA_LOCK(&ia->ia_ifa);
        if (!(ia->ia6_flags & IN6_IFF_DADPROGRESS)) {
                nd6log0(debug,
                    "nd6_dad_start: not a tentative or optimistic address "
                    "%s(%s)\n",
                    ip6_sprintf(&ia->ia_addr.sin6_addr),
                    ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                IFA_UNLOCK(&ia->ia_ifa);
                return;
        }
        if (!ip6_dad_count || (ia->ia6_flags & IN6_IFF_ANYCAST) != 0) {
                ia->ia6_flags &= ~IN6_IFF_DADPROGRESS;
                IFA_UNLOCK(&ia->ia_ifa);
                return;
        }
        IFA_UNLOCK(&ia->ia_ifa);
        if (ifa->ifa_ifp == NULL) {
                panic("nd6_dad_start: ifa->ifa_ifp == NULL");
        }
        if (!(ifa->ifa_ifp->if_flags & IFF_UP) ||
            (ifa->ifa_ifp->if_eflags & IFEF_IPV6_ND6ALT)) {
                return;
        }
        if ((dp = nd6_dad_find(ifa, NULL)) != NULL) {
                DAD_REMREF(dp);
                /* DAD already in progress */
                return;
        }

        dp = zalloc_flags(dad_zone, Z_WAITOK | Z_ZERO);
        lck_mtx_init(&dp->dad_lock, ifa_mtx_grp, ifa_mtx_attr);

        /* Callee adds one reference for us */
        dp = nd6_dad_attach(dp, ifa);

        nd6log0(debug, "%s: starting %sDAD %sfor %s\n",
            if_name(ifa->ifa_ifp),
            (ia->ia6_flags & IN6_IFF_OPTIMISTIC) ? "optimistic " : "",
            (tick_delay == NULL) ? "immediately " : "",
            ip6_sprintf(&ia->ia_addr.sin6_addr));

        /*
         * Send NS packet for DAD, ip6_dad_count times.
         * Note that we must delay the first transmission, if this is the
         * first packet to be sent from the interface after interface
         * (re)initialization.
         */
        if (tick_delay == NULL) {
                u_int32_t retrans;
                struct nd_ifinfo *ndi = NULL;

                nd6_dad_ns_output(dp, ifa);
                ndi = ND_IFINFO(ifa->ifa_ifp);
                VERIFY(ndi != NULL && ndi->initialized);
                lck_mtx_lock(&ndi->lock);
                retrans = ndi->retrans * hz / 1000;
                lck_mtx_unlock(&ndi->lock);
                timeout((void (*)(void *))nd6_dad_timer, (void *)ifa, retrans);
        } else {
                int ntick;

                if (*tick_delay == 0) {
                        ntick = random() % (MAX_RTR_SOLICITATION_DELAY * hz);
                } else {
                        ntick = *tick_delay + random() % (hz / 2);
                }
                *tick_delay = ntick;
                timeout((void (*)(void *))nd6_dad_timer, (void *)ifa,
                    ntick);
        }

        DAD_REMREF(dp);         /* drop our reference */
}

static struct dadq *
nd6_dad_attach(struct dadq *dp, struct ifaddr *ifa)
{
        lck_mtx_lock(dad6_mutex);
        DAD_LOCK(dp);
        dp->dad_ifa = ifa;
        IFA_ADDREF(ifa);        /* for dad_ifa */
        dp->dad_count = ip6_dad_count;
        dp->dad_ns_icount = dp->dad_na_icount = 0;
        dp->dad_ns_ocount = dp->dad_ns_tcount = 0;
        dp->dad_ns_lcount = dp->dad_loopbackprobe = 0;
        VERIFY(!dp->dad_attached);
        dp->dad_attached = 1;
        dp->dad_lladdrlen = 0;
        DAD_ADDREF_LOCKED(dp);  /* for caller */
        DAD_ADDREF_LOCKED(dp);  /* for dadq_head list */
        TAILQ_INSERT_TAIL(&dadq, (struct dadq *)dp, dad_list);
        DAD_UNLOCK(dp);
        lck_mtx_unlock(dad6_mutex);

        return dp;
}

static void
nd6_dad_detach(struct dadq *dp, struct ifaddr *ifa)
{
        int detached;

        lck_mtx_lock(dad6_mutex);
        DAD_LOCK(dp);
        if ((detached = dp->dad_attached)) {
                VERIFY(dp->dad_ifa == ifa);
                TAILQ_REMOVE(&dadq, (struct dadq *)dp, dad_list);
                dp->dad_list.tqe_next = NULL;
                dp->dad_list.tqe_prev = NULL;
                dp->dad_attached = 0;
        }
        DAD_UNLOCK(dp);
        lck_mtx_unlock(dad6_mutex);
        if (detached) {
                DAD_REMREF(dp);         /* drop dadq_head reference */
        }
}

/*
 * terminate DAD unconditionally.  used for address removals.
 */
void
nd6_dad_stop(struct ifaddr *ifa)
{
        struct dadq *dp;

        dp = nd6_dad_find(ifa, NULL);
        if (!dp) {
                /* DAD wasn't started yet */
                return;
        }

        untimeout((void (*)(void *))nd6_dad_timer, (void *)ifa);

        nd6_dad_detach(dp, ifa);
        DAD_REMREF(dp);         /* drop our reference */
}

static void
nd6_unsol_na_output(struct ifaddr *ifa)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct ifnet *ifp = ifa->ifa_ifp;
        struct in6_addr saddr6, taddr6;

        if ((ifp->if_flags & IFF_UP) == 0 ||
            (ifp->if_flags & IFF_RUNNING) == 0 ||
            (ifp->if_eflags & IFEF_IPV6_ND6ALT) != 0) {
                return;
        }

        IFA_LOCK_SPIN(&ia->ia_ifa);
        taddr6 = ia->ia_addr.sin6_addr;
        IFA_UNLOCK(&ia->ia_ifa);
        if (in6_setscope(&taddr6, ifp, NULL) != 0) {
                return;
        }
        saddr6 = in6addr_linklocal_allnodes;
        if (in6_setscope(&saddr6, ifp, NULL) != 0) {
                return;
        }

        nd6log(info, "%s: sending unsolicited NA\n",
            if_name(ifa->ifa_ifp));

        nd6_na_output(ifp, &saddr6, &taddr6, ND_NA_FLAG_OVERRIDE, 1, NULL);
}

static void
nd6_dad_timer(struct ifaddr *ifa)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp = NULL;
        struct nd_ifinfo *ndi = NULL;
        u_int32_t retrans;

        /* Sanity check */
        if (ia == NULL) {
                nd6log0(error, "nd6_dad_timer: called with null parameter\n");
                goto done;
        }

        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);

        dp = nd6_dad_find(ifa, NULL);
        if (dp == NULL) {
                nd6log0(error, "nd6_dad_timer: DAD structure not found\n");
                goto done;
        }
        IFA_LOCK(&ia->ia_ifa);
        if (ia->ia6_flags & IN6_IFF_DUPLICATED) {
                nd6log0(error, "nd6_dad_timer: called with duplicated address "
                    "%s(%s)\n",
                    ip6_sprintf(&ia->ia_addr.sin6_addr),
                    ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                IFA_UNLOCK(&ia->ia_ifa);
                goto done;
        }
        if ((ia->ia6_flags & IN6_IFF_DADPROGRESS) == 0) {
                nd6log0(error, "nd6_dad_timer: not a tentative or optimistic "
                    "address %s(%s)\n",
                    ip6_sprintf(&ia->ia_addr.sin6_addr),
                    ifa->ifa_ifp ? if_name(ifa->ifa_ifp) : "???");
                IFA_UNLOCK(&ia->ia_ifa);
                goto done;
        }
        IFA_UNLOCK(&ia->ia_ifa);

        /* timeouted with IFF_{RUNNING,UP} check */
        DAD_LOCK(dp);
        if (dp->dad_ns_tcount > dad_maxtry) {
                DAD_UNLOCK(dp);
                nd6log0(info, "%s: could not run DAD, driver problem?\n",
                    if_name(ifa->ifa_ifp));

                nd6_dad_detach(dp, ifa);
                goto done;
        }

        /* Need more checks? */
        if (dp->dad_ns_ocount < dp->dad_count) {
                DAD_UNLOCK(dp);
                /*
                 * We have more NS to go.  Send NS packet for DAD.
                 */
                nd6_dad_ns_output(dp, ifa);
                ndi = ND_IFINFO(ifa->ifa_ifp);
                VERIFY(ndi != NULL && ndi->initialized);
                lck_mtx_lock(&ndi->lock);
                retrans = ndi->retrans * hz / 1000;
                lck_mtx_unlock(&ndi->lock);
                timeout((void (*)(void *))nd6_dad_timer, (void *)ifa, retrans);
        } else {
                /*
                 * We have transmitted sufficient number of DAD packets.
                 * See what we've got.
                 */
                if (dp->dad_na_icount > 0 || dp->dad_ns_icount) {
                        /* We've seen NS or NA, means DAD has failed. */
                        DAD_UNLOCK(dp);
                        nd6log0(info,
                            "%s: duplicate IPv6 address %s if:%s [timer]\n",
                            __func__, ip6_sprintf(&ia->ia_addr.sin6_addr),
                            if_name(ia->ia_ifp));
                        nd6_dad_duplicated(ifa);
                        /* (*dp) will be freed in nd6_dad_duplicated() */
                } else if (dad_enhanced != 0 &&
                    dp->dad_ns_lcount > 0 &&
                    dp->dad_ns_lcount > dp->dad_loopbackprobe) {
                        dp->dad_loopbackprobe = dp->dad_ns_lcount;
                        dp->dad_count =
                            dp->dad_ns_ocount + dad_maxtry - 1;
                        DAD_UNLOCK(dp);
                        ndi = ND_IFINFO(ifa->ifa_ifp);
                        VERIFY(ndi != NULL && ndi->initialized);
                        lck_mtx_lock(&ndi->lock);
                        retrans = ndi->retrans * hz / 1000;
                        lck_mtx_unlock(&ndi->lock);

                        /*
                         * Sec. 4.1 in RFC 7527 requires transmission of
                         * additional probes until the loopback condition
                         * becomes clear when a looped back probe is detected.
                         */
                        nd6log0(info,
                            "%s: a looped back NS message is detected during DAD for %s. Another DAD probe is being sent on interface %s.\n",
                            __func__, ip6_sprintf(&ia->ia_addr.sin6_addr),
                            if_name(ia->ia_ifp));
                        /*
                         * Send an NS immediately and increase dad_count by
                         * nd6_mmaxtries - 1.
                         */
                        nd6_dad_ns_output(dp, ifa);
                        timeout((void (*)(void *))nd6_dad_timer, (void *)ifa, retrans);
                        goto done;
                } else {
                        boolean_t txunsolna;
                        DAD_UNLOCK(dp);
                        /*
                         * We are done with DAD.  No NA came, no NS came.
                         * No duplicate address found.
                         */
                        IFA_LOCK_SPIN(&ia->ia_ifa);
                        ia->ia6_flags &= ~IN6_IFF_DADPROGRESS;
                        IFA_UNLOCK(&ia->ia_ifa);

                        ndi = ND_IFINFO(ifa->ifa_ifp);
                        VERIFY(ndi != NULL && ndi->initialized);
                        lck_mtx_lock(&ndi->lock);
                        txunsolna = (ndi->flags & ND6_IFF_REPLICATED) != 0;
                        lck_mtx_unlock(&ndi->lock);

                        if (txunsolna) {
                                nd6_unsol_na_output(ifa);
                        }

                        nd6log0(debug,
                            "%s: DAD complete for %s - no duplicates found %s\n",
                            if_name(ifa->ifa_ifp),
                            ip6_sprintf(&ia->ia_addr.sin6_addr),
                            txunsolna ? ", tx unsolicited NA with O=1" : ".");

                        if (dp->dad_ns_lcount > 0) {
                                nd6log0(debug,
                                    "%s: DAD completed while "
                                    "a looped back NS message is detected "
                                    "during DAD for %s om interface %s\n",
                                    __func__,
                                    ip6_sprintf(&ia->ia_addr.sin6_addr),
                                    if_name(ia->ia_ifp));
                        }

                        in6_post_msg(ia->ia_ifp, KEV_INET6_NEW_USER_ADDR, ia,
                            dp->dad_lladdr);
                        nd6_dad_detach(dp, ifa);
                }
        }

done:
        if (dp != NULL) {
                DAD_REMREF(dp);         /* drop our reference */
        }
}

static void
nd6_dad_duplicated(struct ifaddr *ifa)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct dadq *dp;
        struct ifnet *ifp = ifa->ifa_ifp;
        boolean_t candisable;

        dp = nd6_dad_find(ifa, NULL);
        if (dp == NULL) {
                log(LOG_ERR, "%s: DAD structure not found.\n", __func__);
                return;
        }
        IFA_LOCK(&ia->ia_ifa);
        DAD_LOCK(dp);
        nd6log(error, "%s: NS in/out/loopback=%d/%d/%d, NA in=%d\n",
            __func__, dp->dad_ns_icount, dp->dad_ns_ocount, dp->dad_ns_lcount,
            dp->dad_na_icount);
        candisable = FALSE;

        if (IN6_IS_ADDR_LINKLOCAL(&ia->ia_addr.sin6_addr) &&
            !(ia->ia6_flags & IN6_IFF_SECURED)) {
                struct in6_addr in6;
                struct ifaddr *llifa = NULL;
                struct sockaddr_dl *sdl = NULL;
                uint8_t *lladdr = dp->dad_lladdr;
                uint8_t lladdrlen = dp->dad_lladdrlen;

                /*
                 * To avoid over-reaction, we only apply this logic when we are
                 * very sure that hardware addresses are supposed to be unique.
                 */
                switch (ifp->if_type) {
                case IFT_BRIDGE:
                case IFT_ETHER:
                case IFT_FDDI:
                case IFT_ATM:
                case IFT_IEEE1394:
#ifdef IFT_IEEE80211
                case IFT_IEEE80211:
#endif
                        /*
                         * Check if our hardware address matches the
                         * link layer information received in the
                         * NS/NA
                         */
                        llifa = ifp->if_lladdr;
                        IFA_LOCK(llifa);
                        sdl = (struct sockaddr_dl *)(void *)
                            llifa->ifa_addr;
                        if (lladdrlen == sdl->sdl_alen &&
                            bcmp(lladdr, LLADDR(sdl), lladdrlen) == 0) {
                                candisable = TRUE;
                        }
                        IFA_UNLOCK(llifa);

                        in6 = ia->ia_addr.sin6_addr;
                        if (in6_iid_from_hw(ifp, &in6) != 0) {
                                break;
                        }

                        /* Refine decision about whether IPv6 can be disabled */
                        if (candisable &&
                            !IN6_ARE_ADDR_EQUAL(&ia->ia_addr.sin6_addr, &in6)) {
                                /*
                                 * Apply this logic only to the embedded MAC
                                 * address form of link-local IPv6 address.
                                 */
                                candisable = FALSE;
                        } else if (lladdr == NULL &&
                            IN6_ARE_ADDR_EQUAL(&ia->ia_addr.sin6_addr, &in6)) {
                                /*
                                 * We received a NA with no target link-layer
                                 * address option. This means that someone else
                                 * has our address. Mark it as a hardware
                                 * duplicate so we disable IPv6 later on.
                                 */
                                candisable = TRUE;
                        }
                        break;
                default:
                        break;
                }
        }
        DAD_UNLOCK(dp);

        ia->ia6_flags &= ~IN6_IFF_DADPROGRESS;
        ia->ia6_flags |= IN6_IFF_DUPLICATED;
        in6_event_enqueue_nwk_wq_entry(IN6_ADDR_MARKED_DUPLICATED,
            ia->ia_ifa.ifa_ifp, &ia->ia_addr.sin6_addr,
            0);
        IFA_UNLOCK(&ia->ia_ifa);

        /* increment DAD collision counter */
        ++ip6stat.ip6s_dad_collide;

        /* We are done with DAD, with duplicated address found. (failure) */
        untimeout((void (*)(void *))nd6_dad_timer, (void *)ifa);

        IFA_LOCK(&ia->ia_ifa);
        log(LOG_ERR, "%s: DAD complete for %s - duplicate found.\n",
            if_name(ifp), ip6_sprintf(&ia->ia_addr.sin6_addr));
        IFA_UNLOCK(&ia->ia_ifa);

        if (candisable) {
                struct nd_ifinfo *ndi =  ND_IFINFO(ifp);
                log(LOG_ERR, "%s: possible hardware address duplication "
                    "detected, disabling IPv6 for interface.\n", if_name(ifp));

                VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
                ndi->flags |= ND6_IFF_IFDISABLED;
                /* Make sure to set IFEF_IPV6_DISABLED too */
                nd6_if_disable(ifp, TRUE);
        }

        log(LOG_ERR,
            "%s: manual intervention may be required.\n",
            if_name(ifp));

        /* Send an event to the configuration agent so that the
         * duplicate address will be notified to the user and will
         * be removed.
         */
        in6_post_msg(ifp, KEV_INET6_NEW_USER_ADDR, ia, dp->dad_lladdr);
        nd6_dad_detach(dp, ifa);
        DAD_REMREF(dp);         /* drop our reference */
}

static void
nd6_dad_ns_output(struct dadq *dp, struct ifaddr *ifa)
{
        struct in6_ifaddr *ia = (struct in6_ifaddr *)ifa;
        struct ifnet *ifp = ifa->ifa_ifp;
        int i = 0;
        struct in6_addr taddr6;

        DAD_LOCK(dp);
        dp->dad_ns_tcount++;
        if ((ifp->if_flags & IFF_UP) == 0) {
                DAD_UNLOCK(dp);
                return;
        }
        if ((ifp->if_flags & IFF_RUNNING) == 0) {
                DAD_UNLOCK(dp);
                return;
        }

        dp->dad_ns_ocount++;
        DAD_UNLOCK(dp);
        IFA_LOCK_SPIN(&ia->ia_ifa);
        taddr6 = ia->ia_addr.sin6_addr;
        IFA_UNLOCK(&ia->ia_ifa);
        if (dad_enhanced != 0 && !(ifp->if_flags & IFF_POINTOPOINT)) {
                for (i = 0; i < ND_OPT_NONCE_LEN32; i++) {
                        dp->dad_nonce[i] = RandomULong();
                }
                /*
                 * XXXHRS: Note that in the case that
                 * DupAddrDetectTransmits > 1, multiple NS messages with
                 * different nonces can be looped back in an unexpected
                 * order.  The current implementation recognizes only
                 * the latest nonce on the sender side.  Practically it
                 * should work well in almost all cases.
                 */
        }
        nd6_ns_output(ifp, NULL, &taddr6, NULL,
            (uint8_t *)&dp->dad_nonce[0]);
}

/*
 * @brief       Called to process DAD NS
 *
 * @param       ifa is the pointer to the interface's address
 * @param       lladdr is source link layer information
 * @param       lladdrlen is source's linklayer length
 *
 * @return      void
 */
static void
nd6_dad_ns_input(struct ifaddr *ifa, char *lladdr,
    int lladdrlen, struct nd_opt_nonce *ndopt_nonce)
{
        struct dadq *dp;
        VERIFY(ifa != NULL);

        /* Ignore Nonce option when Enhanced DAD is disabled. */
        if (dad_enhanced == 0) {
                ndopt_nonce = NULL;
        }

        dp = nd6_dad_find(ifa, ndopt_nonce);
        if (dp == NULL) {
                return;
        }

        DAD_LOCK(dp);
        ++dp->dad_ns_icount;
        if (lladdr && lladdrlen >= ETHER_ADDR_LEN) {
                memcpy(dp->dad_lladdr, lladdr, ETHER_ADDR_LEN);
                /* fine to truncate as it is compared against sdl_alen */
                dp->dad_lladdrlen = (uint8_t)lladdrlen;
        }
        DAD_UNLOCK(dp);
        DAD_REMREF(dp);
}

/*
 * @brief       Called to process received NA for DAD
 *
 * @param       m is the pointer to the packet's mbuf
 * @param       ifp is the pointer to the interface on which packet
 *              was receicved.
 * @param       taddr is pointer to target's IPv6 address
 * @param       lladdr is target's link layer information
 * @param       lladdrlen is target's linklayer length
 *
 * @return      NULL if the packet is consumed by DAD processing, else
 *              pointer to the mbuf.
 */
static struct mbuf *
nd6_dad_na_input(struct mbuf *m, struct ifnet *ifp, struct in6_addr *taddr,
    caddr_t lladdr, int lladdrlen)
{
        struct ifaddr *ifa = NULL;
        struct in6_ifaddr *ia = NULL;
        struct dadq *dp = NULL;
        struct nd_ifinfo *ndi = NULL;
        boolean_t replicated;

        ifa = (struct ifaddr *) in6ifa_ifpwithaddr(ifp, taddr);
        if (ifa == NULL) {
                return m;
        }

        replicated = FALSE;

        /* Get the ND6_IFF_REPLICATED flag. */
        ndi = ND_IFINFO(ifp);
        if (ndi != NULL && ndi->initialized) {
                lck_mtx_lock(&ndi->lock);
                replicated = !!(ndi->flags & ND6_IFF_REPLICATED);
                lck_mtx_unlock(&ndi->lock);
        }

        if (replicated) {
                nd6log(info, "%s: ignoring duplicate NA on "
                    "replicated interface %s\n", __func__, if_name(ifp));
                goto done;
        }

        /* Lock the interface address until done (see label below). */
        IFA_LOCK(ifa);
        ia = (struct in6_ifaddr *) ifa;

        if (!(ia->ia6_flags & IN6_IFF_DADPROGRESS)) {
                IFA_UNLOCK(ifa);
                nd6log(info, "%s: ignoring duplicate NA on "
                    "%s [DAD not in progress]\n", __func__,
                    if_name(ifp));
                goto done;
        }

        /* Some sleep proxies improperly send the client's Ethernet address in
         * the target link-layer address option, so detect this by comparing
         * the L2-header source address, if we have seen it, with the target
         * address, and ignoring the NA if they don't match.
         */
        if (lladdr != NULL && lladdrlen >= ETHER_ADDR_LEN) {
                struct ip6aux *ip6a = ip6_findaux(m);
                if (ip6a && (ip6a->ip6a_flags & IP6A_HASEEN) != 0 &&
                    bcmp(ip6a->ip6a_ehsrc, lladdr, ETHER_ADDR_LEN) != 0) {
                        IFA_UNLOCK(ifa);
                        nd6log(error, "%s: ignoring duplicate NA on %s "
                            "[eh_src != tgtlladdr]\n", __func__, if_name(ifp));
                        goto done;
                }
        }

        IFA_UNLOCK(ifa);

        dp = nd6_dad_find(ifa, NULL);
        if (dp == NULL) {
                nd6log(info, "%s: no DAD structure for %s on %s.\n",
                    __func__, ip6_sprintf(taddr), if_name(ifp));
                goto done;
        }

        DAD_LOCK_SPIN(dp);
        if (lladdr != NULL && lladdrlen >= ETHER_ADDR_LEN) {
                memcpy(dp->dad_lladdr, lladdr, ETHER_ADDR_LEN);
                dp->dad_lladdrlen = (uint8_t)lladdrlen;
        }
        dp->dad_na_icount++;
        DAD_UNLOCK(dp);
        DAD_REMREF(dp);

        /* remove the address. */
        nd6log(info,
            "%s: duplicate IPv6 address %s [processing NA on %s]\n", __func__,
            ip6_sprintf(taddr), if_name(ifp));
done:
        IFA_LOCK_ASSERT_NOTHELD(ifa);
        IFA_REMREF(ifa);
        m_freem(m);
        return NULL;
}

static void
dad_addref(struct dadq *dp, int locked)
{
        if (!locked) {
                DAD_LOCK_SPIN(dp);
        } else {
                DAD_LOCK_ASSERT_HELD(dp);
        }

        if (++dp->dad_refcount == 0) {
                panic("%s: dad %p wraparound refcnt\n", __func__, dp);
                /* NOTREACHED */
        }
        if (!locked) {
                DAD_UNLOCK(dp);
        }
}

static void
dad_remref(struct dadq *dp)
{
        struct ifaddr *ifa;

        DAD_LOCK_SPIN(dp);
        if (dp->dad_refcount == 0) {
                panic("%s: dad %p negative refcnt\n", __func__, dp);
        }
        --dp->dad_refcount;
        if (dp->dad_refcount > 0) {
                DAD_UNLOCK(dp);
                return;
        }
        DAD_UNLOCK(dp);

        if (dp->dad_attached ||
            dp->dad_list.tqe_next != NULL || dp->dad_list.tqe_prev != NULL) {
                panic("%s: attached dad=%p is being freed", __func__, dp);
                /* NOTREACHED */
        }

        if ((ifa = dp->dad_ifa) != NULL) {
                IFA_REMREF(ifa);        /* drop dad_ifa reference */
                dp->dad_ifa = NULL;
        }

        lck_mtx_destroy(&dp->dad_lock, ifa_mtx_grp);
        zfree(dad_zone, dp);
}

void
nd6_llreach_set_reachable(struct ifnet *ifp, void *addr, unsigned int alen)
{
        /* Nothing more to do if it's disabled */
        if (nd6_llreach_base == 0) {
                return;
        }

        ifnet_llreach_set_reachable(ifp, ETHERTYPE_IPV6, addr, alen);
}

void
nd6_alt_node_addr_decompose(struct ifnet *ifp, struct sockaddr *sa,
    struct sockaddr_dl* sdl, struct sockaddr_in6 *sin6)
{
        static const size_t EUI64_LENGTH = 8;

        VERIFY(nd6_need_cache(ifp));
        VERIFY(sa);
        VERIFY(sdl && (void *)sa != (void *)sdl);
        VERIFY(sin6 && (void *)sa != (void *)sin6);

        bzero(sin6, sizeof(*sin6));
        sin6->sin6_len = sizeof *sin6;
        sin6->sin6_family = AF_INET6;

        bzero(sdl, sizeof(*sdl));
        sdl->sdl_len = sizeof *sdl;
        sdl->sdl_family = AF_LINK;
        sdl->sdl_type = ifp->if_type;
        sdl->sdl_index = ifp->if_index;

        switch (sa->sa_family) {
        case AF_INET6: {
                struct sockaddr_in6 *sin6a = (struct sockaddr_in6 *)(void *)sa;
                struct in6_addr *in6 = &sin6a->sin6_addr;

                VERIFY(sa->sa_len == sizeof *sin6);
                VERIFY(strlen(ifp->if_name) <= IFNAMSIZ);

                sdl->sdl_nlen = (u_char)strlen(ifp->if_name);
                bcopy(ifp->if_name, sdl->sdl_data, sdl->sdl_nlen);
                if (in6->s6_addr[11] == 0xff && in6->s6_addr[12] == 0xfe) {
                        sdl->sdl_alen = ETHER_ADDR_LEN;
                        LLADDR(sdl)[0] = (in6->s6_addr[8] ^ ND6_EUI64_UBIT);
                        LLADDR(sdl)[1] = in6->s6_addr[9];
                        LLADDR(sdl)[2] = in6->s6_addr[10];
                        LLADDR(sdl)[3] = in6->s6_addr[13];
                        LLADDR(sdl)[4] = in6->s6_addr[14];
                        LLADDR(sdl)[5] = in6->s6_addr[15];
                } else {
                        sdl->sdl_alen = EUI64_LENGTH;
                        bcopy(&in6->s6_addr[8], LLADDR(sdl), EUI64_LENGTH);
                }

                sdl->sdl_slen = 0;
                break;
        }
        case AF_LINK: {
                struct sockaddr_dl *sdla = (struct sockaddr_dl *)(void *)sa;
                struct in6_addr *in6 = &sin6->sin6_addr;
                caddr_t lla = LLADDR(sdla);

                VERIFY(sa->sa_len <= sizeof(*sdl));
                bcopy(sa, sdl, sa->sa_len);

                sin6->sin6_scope_id = sdla->sdl_index;
                if (sin6->sin6_scope_id == 0) {
                        sin6->sin6_scope_id = ifp->if_index;
                }
                in6->s6_addr[0] = 0xfe;
                in6->s6_addr[1] = 0x80;
                if (sdla->sdl_alen == EUI64_LENGTH) {
                        bcopy(lla, &in6->s6_addr[8], EUI64_LENGTH);
                } else {
                        VERIFY(sdla->sdl_alen == ETHER_ADDR_LEN);

                        in6->s6_addr[8] = ((uint8_t) lla[0] ^ ND6_EUI64_UBIT);
                        in6->s6_addr[9] = (uint8_t) lla[1];
                        in6->s6_addr[10] = (uint8_t) lla[2];
                        in6->s6_addr[11] = 0xff;
                        in6->s6_addr[12] = 0xfe;
                        in6->s6_addr[13] = (uint8_t) lla[3];
                        in6->s6_addr[14] = (uint8_t) lla[4];
                        in6->s6_addr[15] = (uint8_t) lla[5];
                }

                break;
        }
        default:
                VERIFY(false);
                break;
        }
}

int
nd6_alt_node_present(struct ifnet *ifp, struct sockaddr_in6 *sin6,
    struct sockaddr_dl *sdl, int32_t rssi, int lqm, int npm)
{
        struct rtentry *rt;
        struct llinfo_nd6 *ln;
        struct  if_llreach *lr = NULL;
        const uint16_t temp_embedded_id = sin6->sin6_addr.s6_addr16[1];

        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr) &&
            (temp_embedded_id == 0)) {
                sin6->sin6_addr.s6_addr16[1] = htons(ifp->if_index);
        }

        nd6_cache_lladdr(ifp, &sin6->sin6_addr, LLADDR(sdl), sdl->sdl_alen,
            ND_NEIGHBOR_ADVERT, 0);

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
        lck_mtx_lock(rnh_lock);

        rt = rtalloc1_scoped_locked((struct sockaddr *)sin6, 1, 0,
            ifp->if_index);

        /* Restore the address that was passed to us */
        if (temp_embedded_id == 0) {
                sin6->sin6_addr.s6_addr16[1] = 0;
        }

        if (rt != NULL) {
                RT_LOCK(rt);
                VERIFY(rt->rt_flags & RTF_LLINFO);
                VERIFY(rt->rt_llinfo);

                ln = rt->rt_llinfo;
                ND6_CACHE_STATE_TRANSITION(ln, ND6_LLINFO_REACHABLE);
                ln_setexpire(ln, 0);

                lr = ln->ln_llreach;
                if (lr) {
                        IFLR_LOCK(lr);
                        lr->lr_rssi = rssi;
                        lr->lr_lqm = (int32_t) lqm;
                        lr->lr_npm = (int32_t) npm;
                        IFLR_UNLOCK(lr);
                }

                RT_UNLOCK(rt);
                RT_REMREF(rt);
        }

        lck_mtx_unlock(rnh_lock);

        if (rt == NULL) {
                log(LOG_ERR, "%s: failed to add/update host route to %s.\n",
                    __func__, ip6_sprintf(&sin6->sin6_addr));
                return EHOSTUNREACH;
        } else {
                nd6log(debug, "%s: host route to %s [lr=0x%llx]\n",
                    __func__, ip6_sprintf(&sin6->sin6_addr),
                    (uint64_t)VM_KERNEL_ADDRPERM(lr));
                return 0;
        }
}

void
nd6_alt_node_absent(struct ifnet *ifp, struct sockaddr_in6 *sin6, struct sockaddr_dl *sdl)
{
        struct rtentry *rt;
        const uint16_t temp_embedded_id = sin6->sin6_addr.s6_addr16[1];

        nd6log(debug, "%s: host route to %s\n", __func__,
            ip6_sprintf(&sin6->sin6_addr));

        if (IN6_IS_SCOPE_LINKLOCAL(&sin6->sin6_addr) &&
            (temp_embedded_id == 0)) {
                sin6->sin6_addr.s6_addr16[1] = htons(ifp->if_index);
        }

        LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
        lck_mtx_lock(rnh_lock);

        rt = rtalloc1_scoped_locked((struct sockaddr *)sin6, 0, 0,
            ifp->if_index);

        /* Restore the address that was passed to us */
        if (temp_embedded_id == 0) {
                sin6->sin6_addr.s6_addr16[1] = 0;
        }

        if (rt != NULL) {
                RT_LOCK(rt);

                if (!(rt->rt_flags & (RTF_CLONING | RTF_PRCLONING)) &&
                    (rt->rt_flags & (RTF_HOST | RTF_LLINFO | RTF_WASCLONED)) ==
                    (RTF_HOST | RTF_LLINFO | RTF_WASCLONED)) {
                        /*
                         * Copy the link layer information in SDL when present
                         * as it later gets used to issue the kernel event for
                         * node absence.
                         */
                        if (sdl != NULL && rt->rt_gateway != NULL &&
                            rt->rt_gateway->sa_family == AF_LINK &&
                            SDL(rt->rt_gateway)->sdl_len <= sizeof(*sdl)) {
                                bcopy(rt->rt_gateway, sdl, SDL(rt->rt_gateway)->sdl_len);
                        }

                        rt->rt_flags |= RTF_CONDEMNED;
                        RT_UNLOCK(rt);

                        (void) rtrequest_locked(RTM_DELETE, rt_key(rt),
                            (struct sockaddr *)NULL, rt_mask(rt), 0,
                            (struct rtentry **)NULL);

                        rtfree_locked(rt);
                } else {
                        RT_REMREF_LOCKED(rt);
                        RT_UNLOCK(rt);
                }
        }

        lck_mtx_unlock(rnh_lock);
}