xref: /xnu-12377.1.9/bsd/netinet6/nd6_rtr.c (revision f6217f891ac0bb64f3d375211650a4c1ff8ca1ea)

/*
 * Copyright (c) 2003-2025 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/queue.h>
#include <sys/mcache.h>
#include <sys/protosw.h>

#include <dev/random/randomdev.h>

#include <kern/locks.h>
#include <kern/uipc_domain.h>
#include <kern/zalloc.h>
#include <machine/machine_routines.h>

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

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

#include <net/net_osdep.h>

#include <net/sockaddr_utils.h>

static void defrouter_addreq(struct nd_defrouter *, struct nd_route_info *, boolean_t);
static struct nd_defrouter *defrtrlist_update_common(struct nd_defrouter *,
    struct nd_drhead *, boolean_t);
static void pfxrtr_add(struct nd_prefix *, struct nd_defrouter *);
static void pfxrtr_del(struct nd_pfxrouter *, struct nd_prefix *);
static struct nd_pfxrouter *find_pfxlist_reachable_router(struct nd_prefix *);
static void nd6_rtmsg(u_char, struct rtentry *);

static int nd6_prefix_onlink_common(struct nd_prefix *, boolean_t,
    unsigned int);
static struct nd_prefix *nd6_prefix_equal_lookup(struct nd_prefix *, boolean_t);
static void nd6_prefix_sync(struct ifnet *);

static void in6_init_address_ltimes(struct in6_addrlifetime *);
static int rt6_deleteroute(struct radix_node *, void *);

static struct nd_defrouter *nddr_alloc(zalloc_flags_t);
static void nddr_free(struct nd_defrouter *);
static void nddr_trace(struct nd_defrouter *, int);

static struct nd_prefix *ndpr_alloc(int);
static void ndpr_free(struct nd_prefix *);
static void ndpr_trace(struct nd_prefix *, int);

extern int nd6_recalc_reachtm_interval;

static struct ifnet *nd6_defifp = NULL;
int nd6_defifindex = 0;
static unsigned int nd6_defrouter_genid;

int ip6_use_tempaddr = IP6_USE_TMPADDR_DEFAULT; /* use temp addr by default for testing now */
int ip6_ula_use_tempaddr = IP6_ULA_USE_TMPADDR_DEFAULT;

int nd6_accept_6to4 = 1;

int ip6_desync_factor;
u_int32_t ip6_temp_preferred_lifetime = DEF_TEMP_PREFERRED_LIFETIME;
u_int32_t ip6_temp_valid_lifetime = DEF_TEMP_VALID_LIFETIME;
/*
 * shorter lifetimes for debugging purposes.
 *	u_int32_t ip6_temp_preferred_lifetime = 800;
 *	static u_int32_t ip6_temp_valid_lifetime = 1800;
 */
int ip6_temp_regen_advance = TEMPADDR_REGEN_ADVANCE;

/* Serialization variables for single thread access to nd_prefix */
static boolean_t nd_prefix_busy;
static void *nd_prefix_waitchan = &nd_prefix_busy;
static int nd_prefix_waiters = 0;

/* Serialization variables for single thread access to nd_defrouter */
static boolean_t nd_defrouter_busy;
static void *nd_defrouter_waitchan = &nd_defrouter_busy;
static int nd_defrouter_waiters = 0;

#define equal(a1, a2) (bcmp((caddr_t)(a1), (caddr_t)(a2), (a1)->sa_len) == 0)
/* RTPREF_MEDIUM has to be 0! */
#define RTPREF_HIGH     1
#define RTPREF_MEDIUM   0
#define RTPREF_LOW      (-1)
#define RTPREF_RESERVED (-2)
#define RTPREF_INVALID  (-3)    /* internal */

#define NDPR_TRACE_HIST_SIZE    32              /* size of trace history */

/* For gdb */
__private_extern__ unsigned int ndpr_trace_hist_size = NDPR_TRACE_HIST_SIZE;

struct nd_prefix_dbg {
	struct nd_prefix        ndpr_pr;                /* nd_prefix */
	u_int16_t               ndpr_refhold_cnt;       /* # of ref */
	u_int16_t               ndpr_refrele_cnt;       /* # of rele */
	/*
	 * Circular lists of ndpr_addref and ndpr_remref callers.
	 */
	ctrace_t                ndpr_refhold[NDPR_TRACE_HIST_SIZE];
	ctrace_t                ndpr_refrele[NDPR_TRACE_HIST_SIZE];
};

static unsigned int ndpr_debug;                 /* debug flags */
ZONE_DECLARE(ndpr_zone, struct nd_prefix);
#define NDPR_ZONE_NAME  "nd6_prefix"            /* zone name */
zone_t ndpr_zone;                               /* zone for nd_prefix */

#define NDDR_TRACE_HIST_SIZE    32              /* size of trace history */

/* For gdb */
__private_extern__ unsigned int nddr_trace_hist_size = NDDR_TRACE_HIST_SIZE;

struct nd_defrouter_dbg {
	struct nd_defrouter     nddr_dr;                /* nd_defrouter */
	uint16_t                nddr_refhold_cnt;       /* # of ref */
	uint16_t                nddr_refrele_cnt;       /* # of rele */
	/*
	 * Circular lists of nddr_addref and nddr_remref callers.
	 */
	ctrace_t                nddr_refhold[NDDR_TRACE_HIST_SIZE];
	ctrace_t                nddr_refrele[NDDR_TRACE_HIST_SIZE];
};

static unsigned int nddr_debug;                 /* debug flags */
ZONE_DECLARE(nddr_zone, struct nd_defrouter);
#define NDDR_ZONE_NAME  "nd6_defrouter"         /* zone name */
zone_t nddr_zone;                               /* zone for nd_defrouter */

static KALLOC_TYPE_DEFINE(ndprtr_zone, struct nd_pfxrouter, NET_KT_DEFAULT);

#define TWOHOUR         (120*60)
extern int nd6_process_rti;                     /* Default to 0 for now */


static void
nd6_prefix_glb_init(void)
{
	PE_parse_boot_argn("ifa_debug", &ndpr_debug, sizeof(ndpr_debug));
	vm_size_t ndpr_size = (ndpr_debug == 0) ? sizeof(struct nd_prefix) :
	    sizeof(struct nd_prefix_dbg);
	ndpr_zone = zone_create(NDPR_ZONE_NAME, ndpr_size, ZC_ZFREE_CLEARMEM);
}

static void
nd6_defrouter_glb_init(void)
{
	PE_parse_boot_argn("ifa_debug", &nddr_debug, sizeof(nddr_debug));
	vm_size_t nddr_size = (nddr_debug == 0) ? sizeof(struct nd_defrouter) :
	    sizeof(struct nd_defrouter_dbg);
	nddr_zone = zone_create(NDDR_ZONE_NAME, nddr_size, ZC_ZFREE_CLEARMEM);
}

void
nd6_rtr_init(void)
{
	nd6_prefix_glb_init();
	nd6_defrouter_glb_init();
}

/*
 * Receive Router Solicitation Message - just for routers.
 * Router solicitation/advertisement is mostly managed by userland program
 * (rtadvd) so here we have no function like nd6_ra_output().
 *
 * Based on RFC 2461
 */
void
nd6_rs_input(
	struct  mbuf *m,
	int off,
	int icmp6len)
{
	struct ifnet *ifp = m->m_pkthdr.rcvif;
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
	struct nd_router_solicit *nd_rs = NULL;
	struct in6_addr saddr6 = ip6->ip6_src;
	char *lladdr = NULL;
	int lladdrlen = 0;
	union nd_opts ndopts = {};
	drop_reason_t drop_reason = DROP_REASON_UNSPECIFIED;

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

	/* If I'm not a router, ignore it. */
	if (!ip6_forwarding || ifp->if_ipv6_router_mode == IPV6_ROUTER_MODE_DISABLED) {
		goto freeit;
	}

	/* Sanity checks */
	if (ip6->ip6_hlim != IPV6_MAXHLIM) {
		nd6log0(error,
		    "nd6_rs_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));
		drop_reason = DROP_REASON_IP6_BAD_HLIM;
		goto bad;
	}

	/*
	 * Don't update the neighbor cache, if src = :: or a non-neighbor.
	 * The former case indicates that the src has no IP address assigned
	 * yet.  See nd6_ns_input() for the latter case.
	 */
	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
		goto freeit;
	} else {
		struct sockaddr_in6 src_sa6;

		SOCKADDR_ZERO(&src_sa6, sizeof(src_sa6));
		src_sa6.sin6_family = AF_INET6;
		src_sa6.sin6_len = sizeof(src_sa6);
		src_sa6.sin6_addr = ip6->ip6_src;
		src_sa6.sin6_scope_id = (!in6_embedded_scope && IN6_IS_SCOPE_EMBED(&src_sa6.sin6_addr)) ? ip6_input_getsrcifscope(m) : IFSCOPE_NONE;
		if (!nd6_is_addr_neighbor(&src_sa6, ifp, 0)) {
			nd6log(info, "nd6_rs_input: "
			    "RS packet from non-neighbor\n");
			goto freeit;
		}
	}

	IP6_EXTHDR_CHECK(m, off, icmp6len, return );
	ip6 = mtod(m, struct ip6_hdr *);
	nd_rs = (struct nd_router_solicit *)((caddr_t)ip6 + off);

	icmp6len -= sizeof(*nd_rs);

	nd6_option_init(nd_rs + 1, icmp6len, &ndopts);
	if (nd6_options(&ndopts) < 0) {
		nd6log(info,
		    "nd6_rs_input: invalid ND option, ignored\n");
		/* nd6_options have incremented stats */
		goto freeit;
	}

	if (ndopts.nd_opts_src_lladdr) {
		ND_OPT_LLADDR(ndopts.nd_opts_src_lladdr, nd_opt_len, lladdr, lladdrlen);
	}

	if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
		nd6log(info,
		    "nd6_rs_input: lladdrlen mismatch for %s "
		    "(if %d, RS packet %d)\n",
		    ip6_sprintf(&saddr6), ifp->if_addrlen, lladdrlen - 2);
		drop_reason = DROP_REASON_IP6_RS_BAD_LLADDR_LEN;
		goto bad;
	}

	nd6_cache_lladdr(ifp, &saddr6, lladdr, lladdrlen, ND_ROUTER_SOLICIT, 0, NULL);

freeit:
	m_freem(m);
	return;

bad:
	icmp6stat.icp6s_badrs++;
	m_drop(m, DROPTAP_FLAG_DIR_IN | DROPTAP_FLAG_L2_MISSING, drop_reason, NULL, 0);
}

#define ND_OPT_LEN_TO_BYTE_SCALE        3 /* ND opt len is in units of 8 octets */

#define ND_OPT_LEN_RTI_MIN              1
#define ND_OPT_LEN_RTI_MAX              3
#define ND_OPT_RTI_PFXLEN_MAX           128
/*
 * Receive Router Advertisement Message.
 *
 * Based on RFC 2461
 * TODO: on-link bit on prefix information
 * TODO: ND_RA_FLAG_{OTHER,MANAGED} processing
 */
void
nd6_ra_input(
	struct mbuf *m,
	int off,
	int icmp6len)
{
	ifnet_ref_t ifp = m->m_pkthdr.rcvif;
	struct nd_ifinfo *ndi = NULL;
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
	struct nd_router_advert *nd_ra;
	struct in6_addr saddr6 = ip6->ip6_src;
	int mcast = 0;
	union nd_opts ndopts;
	struct nd_defrouter *dr = NULL;
	u_int32_t mtu = 0;
	char *lladdr = NULL;
	u_int32_t lladdrlen = 0;
	struct nd_prefix_list *nd_prefix_list_head = NULL;
	u_int32_t nd_prefix_list_length = 0;
	struct in6_ifaddr *ia6 = NULL;
	struct nd_prefix_list *__single prfl;
	struct nd_defrouter dr0 = {0};
	u_int32_t advreachable;
	boolean_t rti_defrtr_processed = FALSE;
	boolean_t is_local_ra = FALSE;
	drop_reason_t drop_reason = DROP_REASON_UNSPECIFIED;

#if (DEVELOPMENT || DEBUG)
	if (ip6_accept_rtadv == 0) {
		goto freeit;
	}
#endif /* (DEVELOPMENT || DEBUG) */
	/* Expect 32-bit aligned data pointer on strict-align platforms */
	MBUF_STRICT_DATA_ALIGNMENT_CHECK_32(m);

	/*
	 * Accept the RA if IFEF_ACCEPT_RTADV is set, or when
	 * the RA is locally generated.
	 *
	 * For convenience, we allow locally generated (rtadvd)
	 * RAs to be processed on the advertising interface, as a router.
	 *
	 * Note that we don't test against ip6_forwarding as we could be
	 * both a host and a router on different interfaces, hence the
	 * check against the per-interface flags.
	 */

	is_local_ra = (ia6 = ifa_foraddr6(&saddr6)) != NULL;
	if (ia6 != NULL) {
		ifa_remref(&ia6->ia_ifa);
		ia6 = NULL;
	}

	if ((ifp->if_eflags & IFEF_ACCEPT_RTADV) == 0) {
		if (is_local_ra) {
			/* accept locally generated RA */
		} else {
			nd6log(debug,
			    "%s: skipping RA from %s to %s on %s, accept RA: %d local RA=%d\n",
			    __func__,
			    ip6_sprintf(&ip6->ip6_src),
			    ip6_sprintf(&ip6->ip6_dst), if_name(ifp),
			    (ifp->if_eflags & IFEF_ACCEPT_RTADV) == 0, is_local_ra);
			goto freeit;
		}
	}

	if (ip6->ip6_hlim != IPV6_MAXHLIM) {
		nd6log0(error,
		    "nd6_ra_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));
		drop_reason = DROP_REASON_IP6_BAD_HLIM;
		goto bad;
	}

	if (!IN6_IS_ADDR_LINKLOCAL(&saddr6)) {
		nd6log0(error,
		    "nd6_ra_input: src %s is not link-local\n",
		    ip6_sprintf(&saddr6));
		drop_reason = DROP_REASON_IP6_RA_NOT_LL;
		goto bad;
	}

	nd6log(debug, "%s: accepting RA from %s to %s on %s, local RA=%d\n",
	    __func__,
	    ip6_sprintf(&ip6->ip6_src),
	    ip6_sprintf(&ip6->ip6_dst), if_name(ifp), is_local_ra);

	IP6_EXTHDR_CHECK(m, off, icmp6len, return );
	ip6 = mtod(m, struct ip6_hdr *);
	nd_ra = (struct nd_router_advert *)((caddr_t)ip6 + off);

	icmp6len -= sizeof(*nd_ra);

	nd6_option_init(nd_ra + 1, icmp6len, &ndopts);
	if (nd6_options(&ndopts) < 0) {
		nd6log(info,
		    "nd6_ra_input: invalid ND option, ignored\n");
		/* nd6_options have incremented stats */
		goto freeit;
	}

	advreachable = nd_ra->nd_ra_reachable;

	/* remember if this is a multicasted advertisement */
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		mcast = 1;
	}

	ndi = ND_IFINFO(ifp);
	VERIFY(NULL != ndi && TRUE == ndi->initialized);
	lck_mtx_lock(&ndi->lock);
	/* unspecified or not? (RFC 2461 6.3.4) */
	if (advreachable) {
		advreachable = ntohl(advreachable);
		if (advreachable <= MAX_REACHABLE_TIME &&
		    ndi->basereachable != advreachable) {
			ndi->basereachable = advreachable;
			ndi->reachable = ND_COMPUTE_RTIME(ndi->basereachable);
			ndi->recalctm = nd6_recalc_reachtm_interval; /* reset */
		}
	}
	if (nd_ra->nd_ra_retransmit) {
		u_int32_t retrans = ntohl(nd_ra->nd_ra_retransmit);
		if (retrans < MAX_RA_RETRANS_TIMER) {
			ndi->retrans = retrans;
		} else {
			nd6log0(info, "%s: ignoring retrans time of %u in RA from %s ;"
			    " Using default of %u",
			    __func__,
			    retrans, ip6_sprintf(&ip6->ip6_src), ndi->retrans);
		}
	}
	if (nd_ra->nd_ra_curhoplimit) {
		if (ndi->chlim < nd_ra->nd_ra_curhoplimit) {
			ndi->chlim = nd_ra->nd_ra_curhoplimit;
		} else if (ndi->chlim != nd_ra->nd_ra_curhoplimit) {
			nd6log0(error,
			    "RA with a lower CurHopLimit sent from "
			    "%s on %s (current = %d, received = %d). "
			    "Ignored.\n", ip6_sprintf(&ip6->ip6_src),
			    if_name(ifp), ndi->chlim,
			    nd_ra->nd_ra_curhoplimit);
		}
	}
	lck_mtx_unlock(&ndi->lock);

	/* Initialize nd_defrouter invariants for RA processing */
	bzero(&dr0, sizeof(dr0));
	dr0.rtaddr = saddr6;
	dr0.ifp = ifp;
	if (is_local_ra == TRUE) {
		dr0.stateflags |= NDDRF_LOCAL;
	}

	/*
	 * Route Information Option (RIO)
	 */
	if (ndopts.nd_opts_rti && IFNET_IS_ETHERNET(ifp)) {
		struct nd_opt_hdr *rt = NULL;
		struct sockaddr_in6 rti_gateway = {0};

		rti_gateway.sin6_family = AF_INET6;
		rti_gateway.sin6_len = sizeof(rti_gateway);
		memcpy(&rti_gateway.sin6_addr, &saddr6, sizeof(rti_gateway.sin6_addr));

		for (rt = TAKE_ND_NEXT_OPT(ndopts.nd_opts_rti, nd_opts_rti, nd_opts_last);
		    rt <= (struct nd_opt_hdr *)ndopts.nd_opts_rti_end;
		    rt = (struct nd_opt_hdr *)((caddr_t)rt +
		    (rt->nd_opt_len << ND_OPT_LEN_TO_BYTE_SCALE))) {
			struct sockaddr_in6 rti_prefix = {};
			struct nd_route_info rti = {};
			struct nd_opt_route_info *rti_opt = NULL;
			u_int32_t rounded_prefix_bytes = 0;

			if (rt->nd_opt_type != ND_OPT_ROUTE_INFO) {
				continue;
			}

			rti_opt = (struct nd_opt_route_info *)rt;
			if ((rti_opt->nd_opt_rti_len < ND_OPT_LEN_RTI_MIN) ||
			    (rti_opt->nd_opt_rti_len > ND_OPT_LEN_RTI_MAX)) {
				nd6log(info,
				    "%s: invalid option "
				    "len %d for route information option, "
				    "ignored\n", __func__,
				    rti_opt->nd_opt_rti_len);
				continue;
			}

			if (rti_opt->nd_opt_rti_prefixlen > ND_OPT_RTI_PFXLEN_MAX) {
				nd6log(info,
				    "%s: invalid prefix length %d "
				    "in the route information option, "
				    "ignored\n", __func__, rti_opt->nd_opt_rti_prefixlen);
				continue;
			}

			if (rti_opt->nd_opt_rti_prefixlen != 0 &&
			    rti_opt->nd_opt_rti_prefixlen <= 64 &&
			    rti_opt->nd_opt_rti_len == ND_OPT_LEN_RTI_MIN) {
				nd6log(info,
				    "%s: invalid prefix "
				    "len %d is OOB for route information option, "
				    "with total option length of %d. Ignored.\n",
				    __func__, rti_opt->nd_opt_rti_prefixlen,
				    rti_opt->nd_opt_rti_len);
				continue;
			}

			if (rti_opt->nd_opt_rti_prefixlen > 64 &&
			    rti_opt->nd_opt_rti_len != ND_OPT_LEN_RTI_MAX) {
				nd6log(info,
				    "%s: invalid prefix "
				    "len %d is OOB for route information option, "
				    "with total option length of %d. Ignored.\n",
				    __func__, rti_opt->nd_opt_rti_prefixlen,
				    rti_opt->nd_opt_rti_len);
				continue;
			}

			if ((rti_opt->nd_opt_rti_flags & ND_RA_FLAG_RTPREF_MASK) ==
			    ND_RA_FLAG_RTPREF_RSV) {
				nd6log(info,
				    "%s: using reserved preference mask, "
				    "ignored\n", __func__);
				continue;
			}

			rti_prefix.sin6_family = AF_INET6;
			rti_prefix.sin6_len = sizeof(rti_prefix);

			rounded_prefix_bytes = rti_opt->nd_opt_rti_prefixlen >> 3;
			if (rti_opt->nd_opt_rti_prefixlen & 0x7) {
				rounded_prefix_bytes++;
			}
			memcpy(&rti_prefix.sin6_addr, rti_opt + 1, rounded_prefix_bytes);

			nd6log(info, "%s: received RA with route opt, "
			    "prefix %s/%u pref %u lifetime %u\n", __func__,
			    ip6_sprintf(&rti_prefix.sin6_addr),
			    rti_opt->nd_opt_rti_prefixlen,
			    rti_opt->nd_opt_rti_flags,
			    ntohl(rti_opt->nd_opt_rti_lifetime));

			dr0.flags  = rti_opt->nd_opt_rti_flags;

			/*
			 * https://tools.ietf.org/html/rfc4191#section-3.1
			 * Type C Host requirements:
			 * The Router Preference and Lifetime values in a
			 * ::/0 Route Information Option override the
			 * preference and lifetime values in the Router
			 * Advertisement header.
			 */
			if (IN6_IS_ADDR_UNSPECIFIED(&rti_prefix.sin6_addr)
			    && rti_opt->nd_opt_rti_prefixlen == 0) {
				rti_defrtr_processed = TRUE;
				/*
				 * If the router lifetime is 0, set the state flag
				 * to dummy, so that it is skipped and not used as a
				 * default router.
				 * Set the lifetime to 2 hrs to make sure we get rid
				 * of the router eventually if this was indeed for a router
				 * going away.
				 *
				 * We partly have to do this to ensure advertised prefixes
				 * stay onlink.
				 * A periodic RA would also keep refreshing the cached
				 * neighbor cache entry if it contains source link layer
				 * information.
				 */
				if (rti_opt->nd_opt_rti_lifetime == 0) {
					dr0.rtlifetime = TWOHOUR;
					dr0.stateflags |= NDDRF_INELIGIBLE;
				} else {
					dr0.rtlifetime = ntohl(rti_opt->nd_opt_rti_lifetime);
				}
				dr0.expire = net_uptime() + dr0.rtlifetime;

				lck_mtx_lock(nd6_mutex);
				dr = defrtrlist_update(&dr0, NULL);
				if (dr != NULL) {
					dr->is_reachable = TRUE;
				}
				lck_mtx_unlock(nd6_mutex);
				continue;
			}

			dr0.rtlifetime = ntohl(rti_opt->nd_opt_rti_lifetime);
			dr0.expire = net_uptime() + dr0.rtlifetime;
			bzero(&rti, sizeof(rti));
			rti.nd_rti_prefixlen = rti_opt->nd_opt_rti_prefixlen;
			rti.nd_rti_prefix = rti_prefix.sin6_addr;
			nd6_rtilist_update(&rti, &dr0);
		}
	}

	if (!rti_defrtr_processed) {
		dr0.flags = nd_ra->nd_ra_flags_reserved;

		/*
		 * If the router lifetime is 0, set the state flag
		 * to dummy, so that it is skipped and not used as a
		 * default router.
		 * Set the lifetime to 2 hrs to make sure we get rid
		 * of the router eventually if this was indeed for a router
		 * going away.
		 *
		 * We partly have to do this to ensure advertised prefixes
		 * stay onlink.
		 * A periodic RA would also keep refreshing the cached
		 * neighbor cache entry if it contains source link layer
		 * information.
		 */
		if (nd_ra->nd_ra_router_lifetime == 0) {
			dr0.rtlifetime = TWOHOUR;
			dr0.stateflags |= NDDRF_INELIGIBLE;
		} else {
			dr0.rtlifetime = ntohs(nd_ra->nd_ra_router_lifetime);
		}
		dr0.expire = net_uptime() + dr0.rtlifetime;
		lck_mtx_lock(nd6_mutex);
		dr = defrtrlist_update(&dr0, NULL);
		if (dr != NULL) {
			dr->is_reachable = TRUE;
		}
		lck_mtx_unlock(nd6_mutex);
	}

	/*
	 * prefix (PIO)
	 */
	if (ndopts.nd_opts_pi) {
		struct nd_opt_hdr *pt;
		struct nd_opt_prefix_info *__single pi = NULL;
		struct nd_prefix pr;

		for (pt = TAKE_ND_NEXT_OPT(ndopts.nd_opts_pi, nd_opts_pi, nd_opts_last);
		    pt <= (struct nd_opt_hdr *)ndopts.nd_opts_pi_end;
		    pt = (struct nd_opt_hdr *)((caddr_t)pt +
		    (pt->nd_opt_len << ND_OPT_LEN_TO_BYTE_SCALE))) {
			struct in6_addr pi_mask;
			bzero(&pi_mask, sizeof(pi_mask));

			if (pt->nd_opt_type != ND_OPT_PREFIX_INFORMATION) {
				continue;
			}
			pi = (struct nd_opt_prefix_info *)pt;

			if (pi->nd_opt_pi_len != 4) {
				nd6log(info,
				    "nd6_ra_input: invalid option "
				    "len %d for prefix information option, "
				    "ignored\n", pi->nd_opt_pi_len);
				continue;
			}

			if (128 < pi->nd_opt_pi_prefix_len) {
				nd6log(info,
				    "nd6_ra_input: invalid prefix "
				    "len %d for prefix information option, "
				    "ignored\n", pi->nd_opt_pi_prefix_len);
				continue;
			}

			/*
			 * To ignore ::/64 make sure bits beyond prefixlen
			 * are set to zero
			 */
			in6_prefixlen2mask(&pi_mask, pi->nd_opt_pi_prefix_len);
			pi->nd_opt_pi_prefix.s6_addr32[0] &= pi_mask.s6_addr32[0];
			pi->nd_opt_pi_prefix.s6_addr32[1] &= pi_mask.s6_addr32[1];
			pi->nd_opt_pi_prefix.s6_addr32[2] &= pi_mask.s6_addr32[2];
			pi->nd_opt_pi_prefix.s6_addr32[3] &= pi_mask.s6_addr32[3];

			if (IN6_IS_ADDR_UNSPECIFIED(&pi->nd_opt_pi_prefix) ||
			    IN6_IS_ADDR_MULTICAST(&pi->nd_opt_pi_prefix) ||
			    IN6_IS_ADDR_LINKLOCAL(&pi->nd_opt_pi_prefix)) {
				nd6log(info,
				    "%s: invalid prefix %s, ignored\n",
				    __func__,
				    ip6_sprintf(&pi->nd_opt_pi_prefix));
				continue;
			}

			bzero(&pr, sizeof(pr));
			lck_mtx_init(&pr.ndpr_lock, &ifa_mtx_grp, &ifa_mtx_attr);
			NDPR_LOCK(&pr);
			pr.ndpr_prefix.sin6_family = AF_INET6;
			pr.ndpr_prefix.sin6_len = sizeof(pr.ndpr_prefix);
			pr.ndpr_prefix.sin6_addr = pi->nd_opt_pi_prefix;
			pr.ndpr_ifp = m->m_pkthdr.rcvif;

			pr.ndpr_raf_onlink = (pi->nd_opt_pi_flags_reserved &
			    ND_OPT_PI_FLAG_ONLINK) ? 1 : 0;
			pr.ndpr_raf_auto = (pi->nd_opt_pi_flags_reserved &
			    ND_OPT_PI_FLAG_AUTO) ? 1 : 0;
			pr.ndpr_plen = pi->nd_opt_pi_prefix_len;
			pr.ndpr_vltime = ntohl(pi->nd_opt_pi_valid_time);
			pr.ndpr_pltime =
			    ntohl(pi->nd_opt_pi_preferred_time);

			/*
			 * Exceptions to stateless autoconfiguration processing:
			 * + nd6_accept_6to4 == 0 && address has 6to4 prefix
			 * + ip6_only_allow_rfc4193_prefix != 0 &&
			 * address not RFC 4193
			 */
			if (ip6_only_allow_rfc4193_prefix &&
			    !IN6_IS_ADDR_UNIQUE_LOCAL(&pi->nd_opt_pi_prefix)) {
				nd6log(info,
				    "nd6_ra_input: no SLAAC on prefix %s "
				    "[not RFC 4193]\n",
				    ip6_sprintf(&pi->nd_opt_pi_prefix));
				pr.ndpr_raf_auto = 0;
			} else if (!nd6_accept_6to4 &&
			    IN6_IS_ADDR_6TO4(&pi->nd_opt_pi_prefix)) {
				nd6log(info,
				    "%s: no SLAAC on prefix %s "
				    "[6to4]\n", __func__,
				    ip6_sprintf(&pi->nd_opt_pi_prefix));
				pr.ndpr_raf_auto = 0;
			}

			if (in6_init_prefix_ltimes(&pr)) {
				NDPR_UNLOCK(&pr);
				lck_mtx_destroy(&pr.ndpr_lock, &ifa_mtx_grp);
				continue; /* prefix lifetime init failed */
			} else {
				NDPR_UNLOCK(&pr);
			}
			(void) prelist_update(&pr, dr, m, mcast);
			lck_mtx_destroy(&pr.ndpr_lock, &ifa_mtx_grp);

			/*
			 * We have to copy the values out after the
			 * prelist_update call since some of these values won't
			 * be properly set until after the router advertisement
			 * updating can vet the values.
			 */
			prfl = kalloc_type(struct nd_prefix_list,
			    Z_WAITOK | Z_ZERO | Z_NOFAIL);

			/* this is only for nd6_post_msg(), otherwise unused */
			SOCKADDR_COPY(&pr.ndpr_prefix, &prfl->pr.ndpr_prefix,
			    sizeof(prfl->pr.ndpr_prefix));
			prfl->pr.ndpr_raf = pr.ndpr_raf;
			prfl->pr.ndpr_plen = pr.ndpr_plen;
			prfl->pr.ndpr_vltime = pr.ndpr_vltime;
			prfl->pr.ndpr_pltime = pr.ndpr_pltime;
			prfl->pr.ndpr_expire = pr.ndpr_expire;
			prfl->pr.ndpr_base_calendartime =
			    pr.ndpr_base_calendartime;
			prfl->pr.ndpr_base_uptime = pr.ndpr_base_uptime;
			prfl->pr.ndpr_stateflags = pr.ndpr_stateflags;
			prfl->pr.ndpr_addrcnt = pr.ndpr_addrcnt;
			prfl->pr.ndpr_ifp = pr.ndpr_ifp;

			prfl->next = nd_prefix_list_head;
			nd_prefix_list_head = prfl;
			nd_prefix_list_length++;
		}
	}


	/*
	 * MTU
	 */
	if (ndopts.nd_opts_mtu && ndopts.nd_opts_mtu->nd_opt_mtu_len == 1) {
		mtu = ntohl(ndopts.nd_opts_mtu->nd_opt_mtu_mtu);
		/* lower bound */
		if (mtu < IPV6_MMTU) {
			nd6log(info, "nd6_ra_input: bogus mtu option "
			    "mtu=%d sent from %s, ignoring\n",
			    mtu, ip6_sprintf(&ip6->ip6_src));
			goto skip;
		}

		lck_mtx_lock(&ndi->lock);
		/* upper bound */
		if (ndi->maxmtu) {
			if (mtu <= ndi->maxmtu) {
				int change = (ndi->linkmtu != mtu);

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

skip:

	/*
	 * Source link layer address
	 */
	if (ndopts.nd_opts_src_lladdr) {
		ND_OPT_LLADDR(ndopts.nd_opts_src_lladdr, nd_opt_len, lladdr, lladdrlen);
	}

	if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
		nd6log(info,
		    "nd6_ra_input: lladdrlen mismatch for %s "
		    "(if %d, RA packet %d)\n",
		    ip6_sprintf(&saddr6), ifp->if_addrlen, lladdrlen - 2);
		drop_reason = DROP_REASON_IP6_RA_BAD_LLADDR_LEN;
		goto bad;
	}

	if (dr && dr->stateflags & NDDRF_MAPPED) {
		saddr6 = dr->rtaddr_mapped;
	}

	nd6_cache_lladdr(ifp, &saddr6, lladdr, (int)lladdrlen,
	    ND_ROUTER_ADVERT, 0, NULL);

	/* Post message */
	nd6_post_msg(KEV_ND6_RA, nd_prefix_list_head, nd_prefix_list_length,
	    mtu);

	/*
	 * Installing a link-layer address might change the state of the
	 * router's neighbor cache, which might also affect our on-link
	 * detection of adveritsed prefixes.
	 */
	lck_mtx_lock(nd6_mutex);
	pfxlist_onlink_check();
	lck_mtx_unlock(nd6_mutex);

freeit:
	if (m) {
		m_freem(m);
	}
	if (dr) {
		NDDR_REMREF(dr);
	}

	prfl = NULL;
	while ((prfl = nd_prefix_list_head) != NULL) {
		nd_prefix_list_head = prfl->next;
		kfree_type(struct nd_prefix_list, prfl);
	}

	return;

bad:
	m_drop(m, DROPTAP_FLAG_DIR_IN | DROPTAP_FLAG_L2_MISSING, drop_reason, NULL, 0);
	m = NULL;

	icmp6stat.icp6s_badra++;
	goto freeit;
}

/*
 * default router list processing sub routines
 */

/* tell the change to user processes watching the routing socket. */
static void
nd6_rtmsg(u_char cmd, struct rtentry *rt)
{
	struct rt_addrinfo info;
	struct ifnet *ifp = rt->rt_ifp;

	RT_LOCK_ASSERT_HELD(rt);

	bzero((caddr_t)&info, sizeof(info));
	/* It's not necessary to lock ifp for if_lladdr */
	info.rti_info[RTAX_DST] = rt_key(rt);
	info.rti_info[RTAX_GATEWAY] = rt->rt_gateway;
	info.rti_info[RTAX_NETMASK] = rt_mask(rt);
	/*
	 * ifa_addr pointers for both should always be valid
	 * in this context; no need to hold locks.
	 */
	info.rti_info[RTAX_IFP] = ifp->if_lladdr->ifa_addr;
	info.rti_info[RTAX_IFA] = rt->rt_ifa->ifa_addr;

	rt_missmsg(cmd, &info, rt->rt_flags, 0);
}

static void
defrouter_addreq(struct nd_defrouter *new, struct nd_route_info *rti, boolean_t scoped)
{
	struct sockaddr_in6 key, mask, gate;
	struct rtentry *newrt __single = NULL;
	unsigned int ifscope;
	int err;
	struct nd_ifinfo *ndi = ND_IFINFO(new->ifp);
	int rtflags = RTF_GATEWAY;
	if (rti) {
		nd6log(info, "%s: defrouter_addreq prefix %s scoped=%d", __func__, ip6_sprintf(&rti->nd_rti_prefix), scoped);
	} else {
		nd6log(info, "%s: defrouter_addreq scoped=%d", __func__, scoped);
	}

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);
	NDDR_LOCK_ASSERT_NOTHELD(new);
	/*
	 * We're free to lock and unlock NDDR because our callers
	 * are holding an extra reference for us.
	 */

	NDDR_LOCK(new);
	if (new->stateflags & NDDRF_INSTALLED) {
		nd6log(info, "%s: defrouter_addreq already installed", __func__);
		goto out;
	}
	if (new->ifp->if_ipv6_router_mode == IPV6_ROUTER_MODE_EXCLUSIVE) {
		nd6log2(info, "%s: ignoring router %s, scoped=%d, "
		    "static=%d on advertising interface\n", if_name(new->ifp),
		    ip6_sprintf(&new->rtaddr), scoped,
		    (new->stateflags & NDDRF_STATIC) ? 1 : 0);
		goto out;
	}

	nd6log2(info, "%s: adding default router %s, scoped=%d, "
	    "static=%d\n", if_name(new->ifp), ip6_sprintf(&new->rtaddr),
	    scoped, (new->stateflags & NDDRF_STATIC) ? 1 : 0);

	Bzero(&key, sizeof(key));
	Bzero(&mask, sizeof(mask));
	Bzero(&gate, sizeof(gate));

	key.sin6_len = mask.sin6_len = gate.sin6_len
	            = sizeof(struct sockaddr_in6);
	key.sin6_family = mask.sin6_family = gate.sin6_family = AF_INET6;

	if (rti != NULL) {
		key.sin6_addr = rti->nd_rti_prefix;
		in6_len2mask(&mask.sin6_addr, rti->nd_rti_prefixlen);
		if (rti->nd_rti_prefixlen == ND_OPT_RTI_PFXLEN_MAX) {
			rtflags |= RTF_HOST;
		} else {
			rtflags |= RTF_PRCLONING;
		}

		if (IN6_IS_SCOPE_EMBED(&key.sin6_addr) ||
		    IN6_IS_ADDR_LOOPBACK(&key.sin6_addr)) {
			nd6log2(info, "%s: ignoring router %s, rti prefix %s, scoped=%d, "
			    "static=%d on advertising interface\n", if_name(new->ifp),
			    ip6_sprintf(&new->rtaddr), ip6_sprintf(&rti->nd_rti_prefix), scoped,
			    (new->stateflags & NDDRF_STATIC) ? 1 : 0);
			goto out;
		}
	}

	if (new->stateflags & NDDRF_MAPPED) {
		gate.sin6_addr = new->rtaddr_mapped;
	} else {
		gate.sin6_addr = new->rtaddr;
	}
	if (!in6_embedded_scope && IN6_IS_SCOPE_EMBED(&gate.sin6_addr)) {
		gate.sin6_scope_id = new->ifp->if_index;
	}

	ifscope = scoped ? new->ifp->if_index : IFSCOPE_NONE;
	NDDR_UNLOCK(new);

	/*
	 * Cellular networks may have buggy deployments
	 * with gateway IPv6 link local address with same
	 * interface identifier as the one that has been
	 * assigned for the cellular context.
	 * If gateway is same as locally configured link local
	 * interface on cellular interface, generated a different one
	 * and store it in the nd_defrouter entry and use it to work
	 * on routing table
	 */
	if (new->ifp->if_type == IFT_CELLULAR &&
	    !(new->stateflags & NDDRF_STATIC) &&
	    !(new->stateflags & NDDRF_MAPPED) &&
	    IN6_IS_ADDR_LINKLOCAL(&gate.sin6_addr) &&
	    ndi && !(ndi->flags & ND6_IFF_PERFORMNUD)) {
		struct in6_ifaddr *tmp_ia6 = in6ifa_ifpforlinklocal(new->ifp, 0);

		if (tmp_ia6 != NULL &&
		    !(tmp_ia6->ia6_flags & IN6_IFF_NOTMANUAL) &&
		    IN6_ARE_ADDR_EQUAL(&tmp_ia6->ia_addr.sin6_addr,
		    &gate.sin6_addr)) {
			gate.sin6_addr.s6_addr8[15] += 1;
			new->rtaddr_mapped = gate.sin6_addr;
			new->stateflags |= NDDRF_MAPPED;

			nd6log(info, "%s: %s Default router %s mapped "
			    "to ", __func__, if_name(new->ifp), ip6_sprintf(&new->rtaddr));
			nd6log(info, "%s\n", ip6_sprintf(&new->rtaddr_mapped));
			nd6log(info, "%s\n", ip6_sprintf(&new->rtaddr_mapped));
		}
	}

	err = rtrequest_scoped(RTM_ADD, SA(&key), SA(&gate), SA(&mask),
	    rtflags, &newrt, ifscope);

	if (newrt) {
		RT_LOCK(newrt);
		nd6_rtmsg(RTM_ADD, newrt);      /* tell user process */
		RT_REMREF_LOCKED(newrt);
		RT_UNLOCK(newrt);
		NDDR_LOCK(new);
		new->stateflags |= NDDRF_INSTALLED;
		if (ifscope != IFSCOPE_NONE) {
			new->stateflags |= NDDRF_IFSCOPE;
		}
	} else {
		nd6log0(error, "%s: failed to add default router "
		    "%s on %s scoped %d (errno = %d)\n", __func__,
		    ip6_sprintf(&gate.sin6_addr), if_name(new->ifp),
		    (ifscope != IFSCOPE_NONE), err);
		NDDR_LOCK(new);
	}
	new->err = err;

out:
	NDDR_UNLOCK(new);
}

void
defrouter_set_reachability(
	struct in6_addr *addr,
	struct ifnet *ifp,
	boolean_t is_reachable)
{
	struct nd_defrouter *dr = NULL;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

	lck_mtx_lock(nd6_mutex);
	dr = defrouter_lookup(NULL, addr, ifp);
	if (dr != NULL) {
		dr->is_reachable = is_reachable;
		NDDR_REMREF(dr);
	}
	lck_mtx_unlock(nd6_mutex);
}

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

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	if (nd_router_listp == NULL) {
		nd_router_listp = &nd_defrouter_list;
	}

	for (dr = TAILQ_FIRST(nd_router_listp); dr;
	    dr = TAILQ_NEXT(dr, dr_entry)) {
		NDDR_LOCK(dr);
		if (dr->ifp == ifp && IN6_ARE_ADDR_EQUAL(addr, &dr->rtaddr)) {
			NDDR_ADDREF(dr);
			NDDR_UNLOCK(dr);
			return dr;
		}
		NDDR_UNLOCK(dr);
	}

	return NULL;          /* search failed */
}

/* Remove the default route for a given router */
void
defrouter_delreq(struct nd_defrouter *dr, struct nd_route_info *rti)
{
	struct sockaddr_in6 key, mask, gate;
	struct rtentry *oldrt __single = NULL;
	unsigned int ifscope;
	int err;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);
	NDDR_LOCK_ASSERT_NOTHELD(dr);
	/*
	 * We're free to lock and unlock NDDR because our callers
	 * are holding an extra reference for us.
	 */
	NDDR_LOCK(dr);
	/* ifp would be NULL for the "drany" case */
	if (dr->ifp != NULL && !(dr->stateflags & NDDRF_INSTALLED)) {
		goto out;
	}

	nd6log2(info, "%s: removing default router %s, scoped=%d, "
	    "static=%d\n", dr->ifp != NULL ? if_name(dr->ifp) : "ANY",
	    ip6_sprintf(&dr->rtaddr), (dr->stateflags & NDDRF_IFSCOPE) ? 1 : 0,
	    (dr->stateflags & NDDRF_STATIC) ? 1 : 0);

	Bzero(&key, sizeof(key));
	Bzero(&mask, sizeof(mask));
	Bzero(&gate, sizeof(gate));

	key.sin6_len = mask.sin6_len = gate.sin6_len
	            = sizeof(struct sockaddr_in6);
	key.sin6_family = mask.sin6_family = gate.sin6_family = AF_INET6;


	if (rti != NULL) {
		key.sin6_addr = rti->nd_rti_prefix;
		in6_len2mask(&mask.sin6_addr, rti->nd_rti_prefixlen);
	}
	/*
	 * The router entry may be mapped to a different address.
	 * If that is the case, use the mapped address as gateway
	 * to do operation on the routing table.
	 * To get more context, read the related comment in
	 * defrouter_addreq
	 */
	if (dr->stateflags & NDDRF_MAPPED) {
		gate.sin6_addr = dr->rtaddr_mapped;
	} else {
		gate.sin6_addr = dr->rtaddr;
	}

	if (dr->ifp != NULL) {
		ifscope = (dr->stateflags & NDDRF_IFSCOPE) ?
		    dr->ifp->if_index : IFSCOPE_NONE;
	} else {
		ifscope = IFSCOPE_NONE;
	}
	NDDR_UNLOCK(dr);

	err = rtrequest_scoped(RTM_DELETE, SA(&key), SA(&gate), SA(&mask),
	    RTF_GATEWAY, &oldrt, ifscope);

	if (oldrt) {
		RT_LOCK(oldrt);
		nd6_rtmsg(RTM_DELETE, oldrt);
		RT_UNLOCK(oldrt);
		rtfree(oldrt);
	} else if (err != ESRCH) {
		nd6log0(error, "%s: failed to delete default router "
		    "%s on %s scoped %d (errno = %d)\n", __func__,
		    ip6_sprintf(&gate.sin6_addr), dr->ifp != NULL ?
		    if_name(dr->ifp) : "ANY", (ifscope != IFSCOPE_NONE), err);
	}
	NDDR_LOCK(dr);
	/* ESRCH means it's no longer in the routing table; ignore it */
	if (oldrt != NULL || err == ESRCH) {
		dr->stateflags &= ~NDDRF_INSTALLED;
		if (ifscope != IFSCOPE_NONE) {
			dr->stateflags &= ~NDDRF_IFSCOPE;
		}
	}
	dr->err = 0;
out:
	NDDR_UNLOCK(dr);
}


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

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	dr = TAILQ_FIRST(&nd_defrouter_list);
	while (dr) {
		NDDR_LOCK(dr);
		if (dr->stateflags & NDDRF_INSTALLED) {
			NDDR_ADDREF(dr);
			NDDR_UNLOCK(dr);
			lck_mtx_unlock(nd6_mutex);
			defrouter_delreq(dr, NULL);
			lck_mtx_lock(nd6_mutex);
			NDDR_REMREF(dr);
			dr = TAILQ_FIRST(&nd_defrouter_list);
		} else {
			NDDR_UNLOCK(dr);
			dr = TAILQ_NEXT(dr, dr_entry);
		}
	}

	/* Nuke primary (non-scoped) default router */
	bzero(&drany, sizeof(drany));
	lck_mtx_init(&drany.nddr_lock, &ifa_mtx_grp, &ifa_mtx_attr);
	lck_mtx_unlock(nd6_mutex);
	defrouter_delreq(&drany, NULL);
	lck_mtx_destroy(&drany.nddr_lock, &ifa_mtx_grp);
	lck_mtx_lock(nd6_mutex);
}

int
defrtrlist_ioctl(u_long cmd, caddr_t __sized_by(IOCPARM_LEN(cmd)) data)
{
	struct nd_defrouter dr0;
	unsigned int ifindex;
	struct ifnet *dr_ifp;
	int error = 0, add = 0;

	/* XXX Handle mapped default router entries */
	switch (cmd) {
	case SIOCDRADD_IN6_32:          /* struct in6_defrouter_32 */
	case SIOCDRADD_IN6_64:          /* struct in6_defrouter_64 */
		++add;
		OS_FALLTHROUGH;
	case SIOCDRDEL_IN6_32:          /* struct in6_defrouter_32 */
	case SIOCDRDEL_IN6_64:          /* struct in6_defrouter_64 */
		bzero(&dr0, sizeof(dr0));
		if (cmd == SIOCDRADD_IN6_64 || cmd == SIOCDRDEL_IN6_64) {
			struct in6_defrouter_64 *r_64 =
			    (struct in6_defrouter_64 *)(void *)data;
			u_int16_t i;

			bcopy(&r_64->rtaddr.sin6_addr, &dr0.rtaddr,
			    sizeof(dr0.rtaddr));
			dr0.flags = r_64->flags;
			bcopy(&r_64->if_index, &i, sizeof(i));
			ifindex = i;
		} else {
			struct in6_defrouter_32 *__single r_32 =
			    (struct in6_defrouter_32 *)(void *)data;
			u_int16_t i;

			bcopy(&r_32->rtaddr.sin6_addr, &dr0.rtaddr,
			    sizeof(dr0.rtaddr));
			dr0.flags = r_32->flags;
			bcopy(&r_32->if_index, &i, sizeof(i));
			ifindex = i;
		}
		ifnet_head_lock_shared();
		/* Don't need to check is ifindex is < 0 since it's unsigned */
		if (!IF_INDEX_IN_RANGE(ifindex) ||
		    (dr_ifp = ifindex2ifnet[ifindex]) == NULL) {
			ifnet_head_done();
			error = EINVAL;
			break;
		}
		dr0.ifp = dr_ifp;
		ifnet_head_done();

		if (ND_IFINFO(dr_ifp) == NULL ||
		    !ND_IFINFO(dr_ifp)->initialized) {
			error = ENXIO;
			break;
		}

		if (IN6_IS_SCOPE_EMBED(&dr0.rtaddr) && in6_embedded_scope) {
			uint16_t *scope = &dr0.rtaddr.s6_addr16[1];

			if (*scope == 0) {
				*scope = htons(dr_ifp->if_index);
			} else if (*scope != htons(dr_ifp->if_index)) {
				error = EINVAL;
				break;
			}
		}
		if (add) {
			error = defrtrlist_add_static(&dr0);
		}
		if (!add || error != 0) {
			int err = defrtrlist_del_static(&dr0);
			if (!add) {
				error = err;
			}
		}
		break;

	default:
		error = EOPNOTSUPP; /* check for safety */
		break;
	}

	return error;
}

/*
 * XXX Please make sure to remove dr from the
 * global default router tailq list before this
 * function call.
 * Also ensure that you release the list reference
 * only after calling this routine.
 */
void
defrtrlist_del(struct nd_defrouter *dr, struct nd_drhead *nd_router_listp)
{
#if (DEVELOPMENT || DEBUG)
	struct nd_defrouter *dr_itr = NULL;
#endif
	struct nd_prefix *pr;
	struct ifnet *ifp = dr->ifp;
	struct nd_ifinfo *ndi = NULL;
	boolean_t resetmtu = FALSE;
	struct nd_route_info *rti = NULL;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	if (nd_router_listp == NULL) {
		nd_router_listp = &nd_defrouter_list;
	}

	if (nd_router_listp != &nd_defrouter_list) {
		rti = (struct nd_route_info *)nd_router_listp;
	}

#if (DEVELOPMENT || DEBUG)
	/*
	 * Verify that the router is not in the global default
	 * router list.
	 * Can't use defrouter_lookup here because that just works
	 * with address and ifp pointer.
	 * We have to compare the memory here.
	 * Also we can't use ASSERT here as that is not defined
	 * for development builds.
	 */
	TAILQ_FOREACH(dr_itr, nd_router_listp, dr_entry)
	VERIFY(dr != dr_itr);
#endif
	++nd6_defrouter_genid;
	/*
	 * Flush all the routing table entries that use the router
	 * as a next hop.
	 *
	 * XXX Note that for a router advertising itself as default router
	 * and also advertising route information option, the following
	 * code will have the default router entry and router entry of
	 * RTI step over each other.
	 * The following therefore may not be efficient but won't be
	 * causing blocking issues.
	 */
	NDDR_ADDREF(dr);
	lck_mtx_unlock(nd6_mutex);
	if (dr->stateflags & NDDRF_MAPPED) {
		rt6_flush(&dr->rtaddr_mapped, ifp);
	} else {
		rt6_flush(&dr->rtaddr, ifp);
	}
	lck_mtx_lock(nd6_mutex);
	NDDR_REMREF(dr);
	nd6log2(info, "%s: freeing route to %s with gateway %s\n", if_name(dr->ifp),
	    (rti == NULL)? "::" : ip6_sprintf(&rti->nd_rti_prefix),
	    ip6_sprintf(&dr->rtaddr));
	/*
	 * Delete it from the routing table.
	 */
	NDDR_ADDREF(dr);
	lck_mtx_unlock(nd6_mutex);
	defrouter_delreq(dr, rti);
	lck_mtx_lock(nd6_mutex);
	NDDR_REMREF(dr);

	/*
	 * The following should mostly be limited to when we are working
	 * with a default router entry and not a router entry from
	 * rti router list.
	 */
	if (rti == NULL) {
		/*
		 * Also delete all the pointers to the router in each prefix lists.
		 */
		for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
			struct nd_pfxrouter *__single pfxrtr;

			NDPR_LOCK(pr);
			if ((pfxrtr = pfxrtr_lookup(pr, dr)) != NULL) {
				pfxrtr_del(pfxrtr, pr);
			}
			NDPR_UNLOCK(pr);
		}
		pfxlist_onlink_check();
	}
	ndi = ND_IFINFO(ifp);
	VERIFY(NULL != ndi && TRUE == ndi->initialized);
	lck_mtx_lock(&ndi->lock);
	VERIFY(ndi->ndefrouters >= 0);
	if (ndi->ndefrouters > 0 && --ndi->ndefrouters == 0) {
		nd6_ifreset(ifp);
		resetmtu = TRUE;
	}
	lck_mtx_unlock(&ndi->lock);
	/*
	 * If the router is the primary one, choose a new one.
	 * We always try to pick another eligible router
	 * on this interface as we do scoped routing
	 */
	defrouter_select(ifp, nd_router_listp);

	if (resetmtu) {
		nd6_setmtu(ifp);
	}
}

int
defrtrlist_add_static(struct nd_defrouter *new)
{
	struct nd_defrouter *dr;
	int err = 0;

	new->rtlifetime = -1;
	new->stateflags |= NDDRF_STATIC;

	/* we only want the preference level */
	new->flags &= ND_RA_FLAG_RTPREF_MASK;

	lck_mtx_lock(nd6_mutex);
	dr = defrouter_lookup(NULL, &new->rtaddr, new->ifp);
	if (dr != NULL && !(dr->stateflags & NDDRF_STATIC)) {
		err = EINVAL;
	} else {
		if (dr != NULL) {
			NDDR_REMREF(dr);
		}
		dr = defrtrlist_update(new, NULL);
		if (dr != NULL) {
			err = dr->err;
		} else {
			err = ENOMEM;
		}
	}
	if (dr != NULL) {
		NDDR_REMREF(dr);
	}
	lck_mtx_unlock(nd6_mutex);

	return err;
}

int
defrtrlist_del_static(struct nd_defrouter *new)
{
	struct nd_defrouter *dr;

	lck_mtx_lock(nd6_mutex);
	dr = defrouter_lookup(NULL, &new->rtaddr, new->ifp);
	if (dr == NULL || !(dr->stateflags & NDDRF_STATIC)) {
		if (dr != NULL) {
			NDDR_REMREF(dr);
		}
		dr = NULL;
	} else {
		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);

	return dr != NULL ? 0 : EINVAL;
}

/*
 * for default router selection
 * regards router-preference field as a 2-bit signed integer
 */
static int
rtpref(struct nd_defrouter *dr)
{
	switch (dr->flags & ND_RA_FLAG_RTPREF_MASK) {
	case ND_RA_FLAG_RTPREF_HIGH:
		return RTPREF_HIGH;
	case ND_RA_FLAG_RTPREF_MEDIUM:
	case ND_RA_FLAG_RTPREF_RSV:
		return RTPREF_MEDIUM;
	case ND_RA_FLAG_RTPREF_LOW:
		return RTPREF_LOW;
	default:
		/*
		 * This case should never happen.  If it did, it would mean a
		 * serious bug of kernel internal.  We thus always bark here.
		 * Or, can we even panic?
		 */
		log(LOG_ERR, "rtpref: impossible RA flag %x\n", dr->flags);
		return RTPREF_INVALID;
	}
	/* NOTREACHED */
}

/*
 * Default Router Selection according to Section 6.3.6 of RFC 2461 and RFC 4191:
 *
 * 1) Routers that are reachable or probably reachable should be preferred.
 *    If we have more than one (probably) reachable router, prefer ones
 *    with the highest router preference.
 * 2) When no routers on the list are known to be reachable or
 *    probably reachable, routers SHOULD be selected in a round-robin
 *    fashion, regardless of router preference values.
 * 3) If the Default Router List is empty, assume that all
 *    destinations are on-link.
 *
 * When Scoped Routing is enabled, the selection logic is amended as follows:
 *
 * a) When a default interface is specified, the primary/non-scoped default
 *    router will be set to the reachable router on that link (if any) with
 *    the highest router preference.
 * b) When there are more than one routers on the same link, the one with
 *    the highest router preference will be installed, either as scoped or
 *    non-scoped route entry.  If they all share the same preference value,
 *    the one installed will be the static or the first encountered reachable
 *    router, i.e. static one wins over dynamic.
 * c) When no routers on the list are known to be reachable, or probably
 *    reachable, no round-robin selection will take place when the default
 *    interface is set.
 *
 * We assume nd_defrouter is sorted by router preference value.
 * Since the code below covers both with and without router preference cases,
 * we do not need to classify the cases by ifdef.
 */
void
defrouter_select(struct ifnet *ifp, struct nd_drhead *nd_router_listp)
{
	struct nd_defrouter *dr = NULL;
	struct nd_defrouter *selected_dr = NULL;
	struct nd_defrouter *installed_dr = NULL;
	struct llinfo_nd6 *__single ln = NULL;
	struct rtentry *rt = NULL;
	struct nd_ifinfo *ndi = NULL;
	unsigned int genid = 0;
	boolean_t is_installed_reachable = FALSE;
	struct nd_route_info *rti = NULL;
	boolean_t scoped = TRUE;
	boolean_t is_rti_rtrlist = FALSE;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	if (nd_router_listp == NULL) {
		nd_router_listp = &nd_defrouter_list;
	}

	if (nd_router_listp != &nd_defrouter_list) {
		rti = (struct nd_route_info *)nd_router_listp;
		/* XXX For now we treat RTI routes as un-scoped */
		scoped = FALSE;
		is_rti_rtrlist = TRUE;
	}


	if (ifp == NULL) {
		ifp = nd6_defifp;
		if (ifp == NULL) {
			nd6log2(info,
			    "%s:%d: Return early. NULL interface",
			    __func__, __LINE__);
			return;
		}
		nd6log2(info,
		    "%s:%d: NULL interface passed. Setting to default interface %s.\n",
		    __func__, __LINE__, if_name(ifp));
	}

	/*
	 * When we are working with RTI router list, the nd6_defifp may be
	 * NULL. That is the scenario when the network may not have WAN
	 * v6 connectivity and the only RAs we may be getting are with lifetime
	 * 0.
	 */
	if (ifp == lo_ifp && !is_rti_rtrlist) {
		nd6log2(info,
		    "%s:%d: Return early. "
		    "Default router select called for loopback.\n",
		    __func__, __LINE__);
		return;
	}

	if (ifp->if_ipv6_router_mode == IPV6_ROUTER_MODE_EXCLUSIVE) {
		nd6log2(info,
		    "%s:%d: Return early. "
		    "Default router select called for interface"
		    " %s in IPV6_ROUTER_MODE_EXCLUSIVE\n",
		    __func__, __LINE__, if_name(ifp));
		return;
	}

	/*
	 * Let's handle easy case (3) first:
	 * If default router list is empty, there's nothing to be done.
	 */
	if (!TAILQ_FIRST(nd_router_listp)) {
		nd6log2(info,
		    "%s:%d: Return early. "
		    "Default router is empty.\n", __func__, __LINE__);
		return;
	}

	/*
	 * Take an early exit if number of routers in nd_ifinfo is
	 * 0 for the interface.
	 */
	ndi = ND_IFINFO(ifp);
	if (!ndi || !ndi->initialized) {
		nd6log2(info,
		    "%s:%d: Return early. "
		    "Interface %s's nd_ifinfo not initialized.\n",
		    __func__, __LINE__, if_name(ifp));
		return;
	}

	/*
	 * RTI router list routes are installed as unscoped.
	 * Since there can be only one unscoped route, we need to
	 * go through the entire list and consider all interfaces.
	 * Further, for now, RTI option is only processed on Ethernet
	 * type interfaces only.
	 */
	if (ndi->ndefrouters == 0 && !is_rti_rtrlist) {
		nd6log2(info,
		    "%s:%d: Return early. "
		    "%s does not have any default routers.\n",
		    __func__, __LINE__, if_name(ifp));
		return;
	}

	/*
	 * Due to the number of times we drop nd6_mutex, we need to
	 * serialize this function.
	 */
	while (nd_defrouter_busy) {
		nd_defrouter_waiters++;
		msleep(nd_defrouter_waitchan, nd6_mutex, (PZERO - 1),
		    __func__, NULL);
		LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	}
	nd_defrouter_busy = TRUE;

	/*
	 * Search for a (probably) reachable router from the list.
	 * We just pick up the first reachable one (if any), assuming that
	 * the ordering rule of the list described in defrtrlist_update().
	 *
	 * For all intents and purposes of Scoped Routing:
	 *	selected_dr	= candidate for primary router
	 *	installed_dr	= currently installed primary router
	 */
	genid = nd6_defrouter_genid;
	dr = TAILQ_FIRST(nd_router_listp);

	while (dr != NULL) {
		struct in6_addr rtaddr;
		ifnet_ref_t drifp = NULL;
		struct nd_defrouter *__single drrele = NULL;
		boolean_t nd6_mutex_unlocked = FALSE;

		NDDR_LOCK(dr);
		drifp = dr->ifp;
		if (drifp != ifp && !is_rti_rtrlist) {
			NDDR_UNLOCK(dr);
			dr = TAILQ_NEXT(dr, dr_entry);
			continue;
		}

		if (dr->stateflags & NDDRF_INELIGIBLE) {
			NDDR_UNLOCK(dr);
			dr = TAILQ_NEXT(dr, dr_entry);
			nd6log(info, "Ignoring dummy entry for default router.");
			continue;
		}

		if (dr->ifp->if_type != IFT_CELLULAR &&
		    dr->stateflags & NDDRF_LOCAL) {
			NDDR_UNLOCK(dr);
			nd6log(info, "%s: Ignoring router %s that has locally hosted address.\n",
			    if_name(dr->ifp),
			    ip6_sprintf(&dr->rtaddr));
			dr = TAILQ_NEXT(dr, dr_entry);
			continue;
		}

		/*
		 * Optimize for the common case.
		 * When the interface has only one default router
		 * there's no point checking for reachability as
		 * there's nothing else to choose from.
		 */
		if (ndi->ndefrouters == 1 && !is_rti_rtrlist) {
			nd6log2(info,
			    "%s:%d: Fast forward default router selection "
			    "as interface %s has learned only one default "
			    "router and there's nothing else to choose from.\n",
			    __func__, __LINE__, if_name(ifp));
			VERIFY(selected_dr == NULL && installed_dr == NULL);
			selected_dr = dr;
			if (dr->stateflags & NDDRF_INSTALLED) {
				installed_dr = dr;
			}
			NDDR_ADDREF(selected_dr);
			NDDR_UNLOCK(dr);
			goto install_route;
		}

		if (dr->stateflags & NDDRF_MAPPED) {
			rtaddr = dr->rtaddr_mapped;
		} else {
			rtaddr = dr->rtaddr;
		}

		NDDR_ADDREF(dr); /* for this for loop */
		NDDR_UNLOCK(dr);

		/* Callee returns a locked route upon success */
		if (selected_dr == NULL) {
			nd6_mutex_unlocked = TRUE;
			lck_mtx_unlock(nd6_mutex);
			if ((rt = nd6_lookup(&rtaddr, 0, drifp, 0)) != NULL &&
			    (ln = rt->rt_llinfo) != NULL &&
			    ND6_IS_LLINFO_PROBREACH(ln)) {
				RT_LOCK_ASSERT_HELD(rt);
				selected_dr = dr;
				NDDR_ADDREF(selected_dr);
			}
		}

		if (rt) {
			RT_REMREF_LOCKED(rt);
			RT_UNLOCK(rt);
			rt = NULL;
		}

		if (nd6_mutex_unlocked) {
			lck_mtx_lock(nd6_mutex);
		}

		/*
		 * Handle case (b)
		 * When there are more than one routers on the same link, the one with
		 * the highest router preference will be installed.
		 * Since the list is in decreasing order of preference:
		 * 1) If selected_dr is not NULL, only use dr if it is static and has
		 *    equal preference and selected_dr is not static.
		 * 2) Else if selected_dr is NULL, and dr is static make selected_dr = dr
		 */
		NDDR_LOCK(dr);
		if (((selected_dr && (rtpref(dr) >= rtpref(selected_dr)) &&
		    !(selected_dr->stateflags & NDDRF_STATIC)) ||
		    (selected_dr == NULL)) &&
		    (dr->stateflags & NDDRF_STATIC)) {
			if (selected_dr) {
				/* Release it later on */
				VERIFY(drrele == NULL);
				drrele = selected_dr;
			}
			selected_dr = dr;
			NDDR_ADDREF(selected_dr);
		}

		/* Record the currently installed router */
		if (dr->stateflags & NDDRF_INSTALLED) {
			if (installed_dr == NULL) {
				installed_dr = dr;
				NDDR_ADDREF(installed_dr);
				if (dr->stateflags & NDDRF_MAPPED) {
					rtaddr = installed_dr->rtaddr_mapped;
				} else {
					rtaddr = installed_dr->rtaddr;
				}
				NDDR_UNLOCK(dr);
				lck_mtx_unlock(nd6_mutex);
				/* Callee returns a locked route upon success */
				if ((rt = nd6_lookup(&rtaddr, 0, installed_dr->ifp, 0)) != NULL) {
					RT_LOCK_ASSERT_HELD(rt);
					if ((ln = rt->rt_llinfo) != NULL &&
					    ND6_IS_LLINFO_PROBREACH(ln)) {
						is_installed_reachable = TRUE;
					}

					RT_REMREF_LOCKED(rt);
					RT_UNLOCK(rt);
					rt = NULL;
				}
				lck_mtx_lock(nd6_mutex);
			} else {
				/* this should not happen; warn for diagnosis */
				nd6log0(error, "%s: more than one "
				    "default router is installed for interface: %s\n",
				    __func__, if_name(installed_dr->ifp));
				NDDR_UNLOCK(dr);
			}
		} else {
			NDDR_UNLOCK(dr);
		}

		NDDR_REMREF(dr);        /* for this for loop */
		if (drrele != NULL) {
			NDDR_REMREF(drrele);
		}

		/*
		 * Check if the list changed when we gave up
		 * the nd6_mutex lock
		 */
		if (genid != nd6_defrouter_genid) {
			if (selected_dr) {
				NDDR_REMREF(selected_dr);
				selected_dr = NULL;
			}

			if (installed_dr) {
				NDDR_REMREF(installed_dr);
				installed_dr = NULL;
			}

			if (ndi->ndefrouters == 0 && !is_rti_rtrlist) {
				nd6log2(info,
				    "%s:%d: Interface %s no longer "
				    "has any default routers. Abort.\n",
				    __func__, __LINE__, if_name(ifp));
				goto out;
			}
			nd6log2(info,
			    "%s:%d: Iterate default router list again "
			    "for interface %s, as the list seems to have "
			    "changed during release-reaquire of global "
			    "nd6_mutex lock.\n",
			    __func__, __LINE__, if_name(ifp));

			is_installed_reachable = FALSE;
			genid = nd6_defrouter_genid;
			dr = TAILQ_FIRST(nd_router_listp);
		} else {
			dr = TAILQ_NEXT(dr, dr_entry);
		}
	}

	/*
	 * If none of the default routers was found to be reachable,
	 * round-robin the list regardless of preference.
	 * Please note selected_dr equal to NULL implies that even
	 * installed default router is not reachable
	 */
	if (selected_dr == NULL) {
		if (installed_dr) {
			for (dr = TAILQ_NEXT(installed_dr, dr_entry); dr;
			    dr = TAILQ_NEXT(dr, dr_entry)) {
				if (installed_dr->ifp != dr->ifp && !is_rti_rtrlist) {
					continue;
				}
				if (dr->stateflags & NDDRF_INELIGIBLE) {
					continue;
				}
				selected_dr = dr;
				break;
			}
		}

		/*
		 * If none was installed or the installed one if the last
		 * one on the list, select the first one from the list
		 */
		if ((installed_dr == NULL) || (selected_dr == NULL)) {
			for (dr = TAILQ_FIRST(nd_router_listp); dr;
			    dr = TAILQ_NEXT(dr, dr_entry)) {
				if (dr->stateflags & NDDRF_INELIGIBLE) {
					continue;
				}
				if (dr->ifp == ifp || is_rti_rtrlist) {
					selected_dr = dr;
					break;
				}
			}
		}

		if ((selected_dr == NULL) && (installed_dr == NULL)) {
			nd6log2(info,
			    "%s:%d: Between release and re-acquire of global "
			    "nd6_mutex lock, the list seems to have changed "
			    "and it does not have any default routers for "
			    "interface %s.\n",
			    __func__, __LINE__, if_name(ifp));
			goto out;
		}

		if (selected_dr != installed_dr) {
			NDDR_ADDREF(selected_dr);
		}
	} else if (installed_dr != NULL) {
		if (installed_dr != selected_dr) {
			/*
			 * This means that selected default router is reachable
			 * while installed one may or may not be.
			 * Static router should always be considered as reachable
			 * for router selection process.
			 */
			if ((installed_dr->stateflags & NDDRF_STATIC) &&
			    rtpref(installed_dr) >= rtpref(selected_dr)) {
				NDDR_REMREF(selected_dr);
				selected_dr = installed_dr;
			} else if (is_installed_reachable) {
				if (rtpref(selected_dr) <= rtpref(installed_dr)) {
					NDDR_REMREF(selected_dr);
					selected_dr = installed_dr;
				}
			}
		} else {
			NDDR_REMREF(selected_dr);
		}
	}

install_route:
	/*
	 * If the selected router is different than the installed one,
	 * remove the installed router and install the selected one.
	 * Note that the selected router is never NULL here.
	 * Else check if the route entry scope has to be changed.
	 */
	lck_mtx_unlock(nd6_mutex);
	if (installed_dr != selected_dr) {
		if (rti) {
			nd6log(info,
			    "%s:%d: Found a better router for interface "
			    "%s. Installing new default route: %s/%p\n",
			    __func__, __LINE__, if_name(ifp),
			    ip6_sprintf(&rti->nd_rti_prefix), &rti->nd_rti_prefix);
		} else {
			nd6log(info,
			    "%s:%d: Found a better router for interface "
			    "%s. Installing new default route. NO RTI\n",
			    __func__, __LINE__, if_name(ifp));
		}
		if (installed_dr != NULL) {
			defrouter_delreq(installed_dr, rti);
		}
		/*
		 * Install scoped route if the interface is not
		 * the default nd6 interface.
		 */
		defrouter_addreq(selected_dr, rti,
		    scoped && (selected_dr->ifp != nd6_defifp));
	} else if (((installed_dr->stateflags & NDDRF_IFSCOPE) &&
	    (installed_dr->ifp == nd6_defifp)) ||
	    (scoped && !(installed_dr->stateflags & NDDRF_IFSCOPE) &&
	    (installed_dr->ifp != nd6_defifp))) {
		nd6log(info,
		    "%s:%d: Need to reinstall default route for interface "
		    "%s as its scope has changed.\n",
		    __func__, __LINE__, if_name(ifp));
		defrouter_delreq(installed_dr, rti);
		defrouter_addreq(installed_dr, rti,
		    scoped && (installed_dr->ifp != nd6_defifp));
	} else {
		nd6log2(info,
		    "%s:%d: No need to change the default "
		    "route for interface %s.\n",
		    __func__, __LINE__, if_name(ifp));
	}
	lck_mtx_lock(nd6_mutex);
out:
	if (selected_dr && (selected_dr != installed_dr)) {
		NDDR_REMREF(selected_dr);
	}
	if (installed_dr) {
		NDDR_REMREF(installed_dr);
	}
	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	VERIFY(nd_defrouter_busy);
	nd_defrouter_busy = FALSE;
	if (nd_defrouter_waiters > 0) {
		nd_defrouter_waiters = 0;
		wakeup(nd_defrouter_waitchan);
	}
}

static struct nd_defrouter *
defrtrlist_update_common(struct nd_defrouter *new, struct nd_drhead *nd_router_listp, boolean_t scoped)
{
	struct nd_defrouter *dr, *n;
	struct ifnet *ifp = new->ifp;
	struct nd_ifinfo *ndi = NULL;
	struct timeval caltime;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	if (nd_router_listp == NULL) {
		nd_router_listp = &nd_defrouter_list;
	}

	/*
	 * If we are not operating on default router list,
	 * it implies we are operating on RTI's router list.
	 * XXX For now we manage RTI routes un-scoped.
	 */
	if (nd_router_listp != &nd_defrouter_list) {
		scoped = FALSE;
	}

	if ((dr = defrouter_lookup(nd_router_listp, &new->rtaddr, ifp)) != NULL) {
		/* entry exists */
		/*
		 * 1. If previous entry was not dummy and new is,
		 * delete it and return NULL.
		 * 2. If previous entry was dummy and the new one
		 * is also dummy, simply return dr.
		 * 3. If previous was dummy but new one is not,
		 * make sure we perform default router selection again.
		 */
		/* If the router was not added as a dummy and there's
		 * been a change (lifetime advertised was 0, communicated
		 * as NDDRF_INELIGIBLE flag), remove the entry.
		 */
		if ((new->stateflags & NDDRF_INELIGIBLE) != 0 &&
		    (dr->stateflags & NDDRF_INELIGIBLE) == 0) {
			TAILQ_REMOVE(nd_router_listp, dr, dr_entry);
			defrtrlist_del(dr, nd_router_listp);
			NDDR_REMREF(dr);        /* remove list reference */
			NDDR_REMREF(dr);
			dr = NULL;
			return NULL;
		} else {
			int oldpref = rtpref(dr);
			struct nd_defrouter *__single p = NULL;
			boolean_t dummy_change = FALSE;
			/*
			 * If new one is not dummy but the old one was,
			 * reset the stateflag.
			 */
			if ((new->stateflags & NDDRF_INELIGIBLE) == 0 &&
			    (dr->stateflags & NDDRF_INELIGIBLE) != 0) {
				dummy_change = TRUE;
				dr->stateflags &= ~NDDRF_INELIGIBLE;
			}

			/* override */
			dr->flags = new->flags; /* xxx flag check */
			dr->rtlifetime = new->rtlifetime;
			dr->expire = new->expire;

			/*
			 * If the preference does not change, there's no need
			 * to sort the entries.  If Scoped Routing is enabled,
			 * put the primary/non-scoped router at the top of the
			 * list of routers in the same preference band, unless
			 * it's already at that position.
			 */
			/* same preference and scoped; just return */
			if (rtpref(new) == oldpref && scoped && dummy_change == FALSE) {
				return dr;
			}

			n = TAILQ_FIRST(nd_router_listp);
			while (n != NULL) {
				/* preference changed; sort it */
				if (rtpref(new) != oldpref) {
					break;
				}

				/* not at the top of band; sort it */
				if (n != dr && rtpref(n) == oldpref &&
				    (!p || rtpref(p) > rtpref(n))) {
					break;
				}

				p = n;
				n = TAILQ_NEXT(n, dr_entry);
			}

			/* nothing has changed, just return */
			if (n == NULL && (scoped ||
			    !(dr->stateflags & NDDRF_IFSCOPE)) && dummy_change == FALSE) {
				return dr;
			}

			/*
			 * preferred router may be changed, so relocate
			 * this router.
			 * XXX: calling TAILQ_REMOVE directly is bad manners.
			 * However, since defrtrlist_del() has many side
			 * effects, we intentionally do so here.
			 * defrouter_select() below will handle routing
			 * changes later.
			 */
			TAILQ_REMOVE(nd_router_listp, dr, dr_entry);
			new->stateflags = dr->stateflags;

			n = dr;
			goto insert;
		}
	}

	VERIFY(dr == NULL);
	n = nddr_alloc(Z_WAITOK);

	ndi = ND_IFINFO(ifp);
	VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
	lck_mtx_lock(&ndi->lock);

	if (ip6_maxifdefrouters >= 0 &&
	    ndi->ndefrouters >= ip6_maxifdefrouters) {
		lck_mtx_unlock(&ndi->lock);
		nddr_free(n);
		nd6log0(error, "%s: ignoring router addition as we have hit the "
		    "max limit of %d for max default routers.\n", __func__,
		    ip6_maxifdefrouters);
		return NULL;
	}

	NDDR_ADDREF(n); /* for the nd_defrouter list */
	NDDR_ADDREF(n); /* for the caller */

	++nd6_defrouter_genid;
	ndi->ndefrouters++;
	VERIFY(ndi->ndefrouters != 0);
	lck_mtx_unlock(&ndi->lock);

	nd6log2(info, "%s: allocating defrouter %s\n", if_name(ifp),
	    ip6_sprintf(&new->rtaddr));

	getmicrotime(&caltime);
	NDDR_LOCK(n);
	memcpy(&n->rtaddr, &new->rtaddr, sizeof(n->rtaddr));
	n->flags = new->flags;
	n->stateflags = new->stateflags;
	n->rtlifetime = new->rtlifetime;
	n->expire = new->expire;
	n->base_calendartime = caltime.tv_sec;
	n->base_uptime = net_uptime();
	n->ifp = new->ifp;
	n->err = new->err;
	n->is_reachable = TRUE;
	NDDR_UNLOCK(n);
insert:
	/* get nd6_service() to be scheduled as soon as it's convenient */
	++nd6_sched_timeout_want;

	/*
	 * Insert the new router in the Default Router List;
	 * The Default Router List should be in the descending order
	 * of router-preferece.  When Scoped Routing is disabled, routers
	 * with the same preference are sorted in the arriving time order;
	 * otherwise, the first entry in the list of routers having the same
	 * preference is the primary default router, when the interface used
	 * by the entry is the default interface.
	 */

	/* insert at the end of the group */
	for (dr = TAILQ_FIRST(nd_router_listp); dr;
	    dr = TAILQ_NEXT(dr, dr_entry)) {
		if (rtpref(n) > rtpref(dr) ||
		    (!scoped && rtpref(n) == rtpref(dr))) {
			break;
		}
	}
	if (dr) {
		TAILQ_INSERT_BEFORE(dr, n, dr_entry);
	} else {
		TAILQ_INSERT_TAIL(nd_router_listp, n, dr_entry);
	}

	defrouter_select(ifp, nd_router_listp);

	return n;
}

struct nd_defrouter *
defrtrlist_update(struct nd_defrouter *new, struct nd_drhead *nd_router_list)
{
	struct nd_defrouter *dr;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	dr = defrtrlist_update_common(new, nd_router_list,
	    (nd6_defifp != NULL && new->ifp != nd6_defifp));

	return dr;
}

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

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	NDPR_LOCK_ASSERT_HELD(pr);

	for (search = pr->ndpr_advrtrs.lh_first; search;
	    search = search->pfr_next) {
		if (search->router == dr) {
			break;
		}
	}

	return search;
}

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

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	NDPR_LOCK_ASSERT_NOTHELD(pr);

	new = zalloc_flags(ndprtr_zone, Z_WAITOK | Z_ZERO | Z_NOFAIL);
	new->router = dr;

	NDPR_LOCK(pr);
	LIST_INSERT_HEAD(&pr->ndpr_advrtrs, new, pfr_entry);
	pr->ndpr_genid++;
	NDPR_UNLOCK(pr);

	pfxlist_onlink_check();
}

static void
pfxrtr_del(struct nd_pfxrouter *pfr, struct nd_prefix *pr)
{
	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	NDPR_LOCK_ASSERT_HELD(pr);
	pr->ndpr_genid++;
	LIST_REMOVE(pfr, pfr_entry);
	zfree(ndprtr_zone, pfr);
}

/*
 * The routine has been modified to atomically refresh expiry
 * time for nd6 prefix as the part of lookup.
 * There's a corner case where a system going
 * in sleep gets rid of manual addresses configured in the system
 * and then schedules the prefix for deletion.
 * However before the prefix gets deleted, if system comes out
 * from sleep and configures same address before prefix deletion
 * , the later prefix deletion will remove the prefix route and
 * the system will not be able to communicate with other IPv6
 * neighbor nodes in the same subnet.
 */
struct nd_prefix *
nd6_prefix_lookup(struct nd_prefix *pr, int nd6_prefix_expiry)
{
	struct nd_prefix *__single search;

	lck_mtx_lock(nd6_mutex);
	for (search = nd_prefix.lh_first; search; search = search->ndpr_next) {
		NDPR_LOCK(search);
		if (pr->ndpr_ifp == search->ndpr_ifp &&
		    pr->ndpr_plen == search->ndpr_plen &&
		    in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr, pr->ndpr_prefix.sin6_scope_id,
		    &search->ndpr_prefix.sin6_addr, search->ndpr_prefix.sin6_scope_id, pr->ndpr_plen)) {
			if (nd6_prefix_expiry != ND6_PREFIX_EXPIRY_UNSPEC) {
				search->ndpr_expire = nd6_prefix_expiry;
			}
			NDPR_ADDREF(search);
			NDPR_UNLOCK(search);
			break;
		}
		NDPR_UNLOCK(search);
	}
	lck_mtx_unlock(nd6_mutex);

	return search;
}

int
nd6_prelist_add(struct nd_prefix *pr, struct nd_defrouter *dr,
    struct nd_prefix **newp, boolean_t force_scoped)
{
	struct nd_prefix *__single new = NULL;
	ifnet_ref_t ifp = pr->ndpr_ifp;
	struct nd_ifinfo *__single ndi = NULL;
	int i, error;

	if (ip6_maxifprefixes >= 0) {
		ndi = ND_IFINFO(ifp);
		VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
		lck_mtx_lock(&ndi->lock);
		if (ndi->nprefixes >= ip6_maxifprefixes) {
			lck_mtx_unlock(&ndi->lock);
			return ENOMEM;
		}
		lck_mtx_unlock(&ndi->lock);
	}

	new = ndpr_alloc(M_WAITOK);
	if (new == NULL) {
		return ENOMEM;
	}

	NDPR_LOCK(new);
	NDPR_LOCK(pr);
	new->ndpr_ifp = pr->ndpr_ifp;
	new->ndpr_prefix = pr->ndpr_prefix;
	new->ndpr_plen = pr->ndpr_plen;
	new->ndpr_vltime = pr->ndpr_vltime;
	new->ndpr_pltime = pr->ndpr_pltime;
	new->ndpr_flags = pr->ndpr_flags;
	if (pr->ndpr_stateflags & NDPRF_STATIC) {
		new->ndpr_stateflags |= NDPRF_STATIC;
	}
	NDPR_UNLOCK(pr);
	if ((error = in6_init_prefix_ltimes(new)) != 0) {
		NDPR_UNLOCK(new);
		ndpr_free(new);
		return error;
	}
	new->ndpr_lastupdate = net_uptime();
	if (newp != NULL) {
		*newp = new;
		NDPR_ADDREF(new);        /* for caller */
	}
	/* initialization */
	LIST_INIT(&new->ndpr_advrtrs);
	in6_prefixlen2mask(&new->ndpr_mask, new->ndpr_plen);
	/* make prefix in the canonical form */
	for (i = 0; i < 4; i++) {
		new->ndpr_prefix.sin6_addr.s6_addr32[i] &=
		    new->ndpr_mask.s6_addr32[i];
	}

	NDPR_UNLOCK(new);

	/* get nd6_service() to be scheduled as soon as it's convenient */
	++nd6_sched_timeout_want;

	lck_mtx_lock(nd6_mutex);
	/* link ndpr_entry to nd_prefix list */
	LIST_INSERT_HEAD(&nd_prefix, new, ndpr_entry);
	new->ndpr_debug |= IFD_ATTACHED;
	NDPR_ADDREF(new);       /* for nd_prefix list */

	lck_mtx_lock(&ndi->lock);
	ndi->nprefixes++;
	VERIFY(ndi->nprefixes != 0);
	lck_mtx_unlock(&ndi->lock);

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

		if ((e = nd6_prefix_onlink_common(new, force_scoped,
		    new->ndpr_ifp->if_index)) != 0) {
			nd6log0(error, "nd6_prelist_add: failed to make "
			    "the prefix %s/%d on-link %s on %s (errno=%d)\n",
			    ip6_sprintf(&new->ndpr_prefix.sin6_addr),
			    new->ndpr_plen, force_scoped ? "scoped" :
			    "non-scoped", if_name(ifp), e);
			/* proceed anyway. XXX: is it correct? */
		}
	}

	if (dr) {
		pfxrtr_add(new, dr);
	}

	lck_mtx_unlock(nd6_mutex);

	return 0;
}

/*
 * Caller must have held an extra reference on nd_prefix.
 */
void
prelist_remove(struct nd_prefix *pr)
{
	struct nd_pfxrouter *__single pfr = NULL, *__single next = NULL;
	ifnet_ref_t ifp = pr->ndpr_ifp;
	struct nd_ifinfo *__single ndi = NULL;
	struct nd_prefix *__single tmp_pr = NULL;
	boolean_t pr_scoped;
	int err;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	NDPR_LOCK_ASSERT_HELD(pr);

	if (pr->ndpr_stateflags & NDPRF_DEFUNCT) {
		return;
	}

	pr_scoped = (pr->ndpr_stateflags & NDPRF_IFSCOPE) != 0;
	/*
	 * If there are no more addresses, defunct the prefix.  This is needed
	 * because we don't want multiple threads calling prelist_remove() for
	 * the same prefix and this might happen because we unlock nd6_mutex
	 * down below.
	 */
	if (pr->ndpr_addrcnt == 0) {
		pr->ndpr_stateflags |= NDPRF_DEFUNCT;
	}

	/* make sure to invalidate the prefix until it is really freed. */
	pr->ndpr_vltime = 0;
	pr->ndpr_pltime = 0;

	/*
	 * Though these flags are now meaningless, we'd rather keep the value
	 * of pr->ndpr_raf_onlink and pr->ndpr_raf_auto not to confuse users
	 * when executing "ndp -p".
	 */
	if (pr->ndpr_stateflags & NDPRF_ONLINK) {
		int error = 0;
		NDPR_ADDREF(pr);
		NDPR_UNLOCK(pr);
		lck_mtx_unlock(nd6_mutex);
		if ((error = nd6_prefix_offlink(pr)) != 0) {
			nd6log0(error, "prelist_remove: failed to make "
			    "%s/%d offlink on %s, errno=%d\n",
			    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
			    pr->ndpr_plen, if_name(ifp), error);
			/* what should we do? */
		}
		lck_mtx_lock(nd6_mutex);
		NDPR_LOCK(pr);
		if (NDPR_REMREF(pr) == NULL) {
			return;
		}
	}

	/*
	 * Check if there is a scoped version of this PR, if so
	 * make it unscoped.
	 */
	if (!pr_scoped && IN6_IS_ADDR_UNIQUE_LOCAL(&pr->ndpr_prefix.sin6_addr)) {
		tmp_pr = nd6_prefix_equal_lookup(pr, FALSE);
		if (tmp_pr != NULL) {
			NDPR_ADDREF(pr);
			NDPR_UNLOCK(pr);

			lck_mtx_unlock(nd6_mutex);
			err = nd6_prefix_offlink(tmp_pr);
			lck_mtx_lock(nd6_mutex);
			if (err != 0) {
				nd6log0(error,
				    "%s: failed to make %s/%d offlink on %s, "
				    "errno=%d\n", __func__,
				    ip6_sprintf(&tmp_pr->ndpr_prefix.sin6_addr),
				    tmp_pr->ndpr_plen, if_name(tmp_pr->ndpr_ifp), err);
			}

			err = nd6_prefix_onlink_scoped(tmp_pr, IFSCOPE_NONE);
			if (err != 0) {
				nd6log0(error,
				    "%s: failed to make %s/%d onlink on %s, errno=%d\n",
				    __func__, ip6_sprintf(&tmp_pr->ndpr_prefix.sin6_addr),
				    tmp_pr->ndpr_plen, if_name(tmp_pr->ndpr_ifp), err);
			}

			if (err != 0) {
				nd6log0(error,
				    "%s: error unscoping %s/%d from %s\n",
				    __func__, ip6_sprintf(&tmp_pr->ndpr_prefix.sin6_addr),
				    tmp_pr->ndpr_plen, if_name(tmp_pr->ndpr_ifp));
			} else {
				nd6log2(info,
				    "%s: %s/%d unscoped, previously on %s\n",
				    __func__, ip6_sprintf(&tmp_pr->ndpr_prefix.sin6_addr),
				    tmp_pr->ndpr_plen, if_name(tmp_pr->ndpr_ifp));
			}

			NDPR_REMREF(tmp_pr);

			NDPR_LOCK(pr);
			if (NDPR_REMREF(pr) == NULL) {
				return;
			}
		}
	}

	if (pr->ndpr_addrcnt > 0) {
		/*
		 * The state might have changed if we called
		 * nd6_prefix_offlink().
		 */
		pr->ndpr_stateflags &= ~NDPRF_DEFUNCT;
		return; /* notice here? */
	}

	/* unlink ndpr_entry from nd_prefix list */
	LIST_REMOVE(pr, ndpr_entry);
	pr->ndpr_debug &= ~IFD_ATTACHED;

	/* free list of routers that adversed the prefix */
	for (pfr = pr->ndpr_advrtrs.lh_first; pfr; pfr = next) {
		next = pfr->pfr_next;
		pfxrtr_del(pfr, pr);
	}

	ndi = ND_IFINFO(ifp);
	VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
	lck_mtx_lock(&ndi->lock);
	VERIFY(ndi->nprefixes > 0);
	ndi->nprefixes--;
	lck_mtx_unlock(&ndi->lock);

	/* This must not be the last reference to the nd_prefix */
	if (NDPR_REMREF(pr) == NULL) {
		panic("%s: unexpected (missing) refcnt ndpr=%p", __func__, pr);
		/* NOTREACHED */
	}

	/*
	 * Don't call pfxlist_onlink_check() here because we are
	 * holding the NDPR lock and this could cause a deadlock when
	 * there are multiple threads executing pfxlist_onlink_check().
	 */
}

int
prelist_update(
	struct nd_prefix *new,
	struct nd_defrouter *dr, /* may be NULL */
	struct mbuf *m,
	int mcast)
{
	struct in6_ifaddr *__single ia6 = NULL, *__single ia6_match = NULL;
	struct ifaddr *__single ifa;
	ifnet_ref_t ifp = new->ndpr_ifp;
	struct nd_prefix *__single pr;
	int error = 0;
	int newprefix = 0;
	int auth;
	uint64_t timenow = net_uptime();

	/* no need to lock "new" here, as it is local to the caller */
	NDPR_LOCK_ASSERT_NOTHELD(new);

	auth = 0;
	if (m) {
		/*
		 * Authenticity for NA consists authentication for
		 * both IP header and IP datagrams, doesn't it ?
		 */
#if defined(M_AUTHIPHDR) && defined(M_AUTHIPDGM)
		auth = (m->m_flags & M_AUTHIPHDR) && (m->m_flags & M_AUTHIPDGM);
#endif
	}

	if ((pr = nd6_prefix_lookup(new, ND6_PREFIX_EXPIRY_UNSPEC)) != NULL) {
		/*
		 * nd6_prefix_lookup() ensures that pr and new have the same
		 * prefix on a same interface.
		 */

		/*
		 * Update prefix information.  Note that the on-link (L) bit
		 * and the autonomous (A) bit should NOT be changed from 1
		 * to 0.
		 */
		lck_mtx_lock(nd6_mutex);
		NDPR_LOCK(pr);
		if (new->ndpr_raf_onlink == 1) {
			pr->ndpr_raf_onlink = 1;
		}
		if (new->ndpr_raf_auto == 1) {
			pr->ndpr_raf_auto = 1;
		}
		if (new->ndpr_raf_onlink) {
			pr->ndpr_vltime = new->ndpr_vltime;
			pr->ndpr_pltime = new->ndpr_pltime;
			(void) in6_init_prefix_ltimes(pr); /* XXX error case? */
			pr->ndpr_lastupdate = net_uptime();
		}

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

			NDPR_UNLOCK(pr);
			if ((e = nd6_prefix_onlink(pr)) != 0) {
				nd6log0(error,
				    "prelist_update: failed to make "
				    "the prefix %s/%d on-link on %s "
				    "(errno=%d)\n",
				    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
				    pr->ndpr_plen, if_name(pr->ndpr_ifp), e);
				/* proceed anyway. XXX: is it correct? */
			}
			NDPR_LOCK(pr);
		}

		if (dr && pfxrtr_lookup(pr, dr) == NULL) {
			NDPR_UNLOCK(pr);
			pfxrtr_add(pr, dr);
		} else {
			NDPR_UNLOCK(pr);
		}
		NDPR_REMREF(pr);
		lck_mtx_unlock(nd6_mutex);
	} else {
		newprefix = 1;

		if (new->ndpr_vltime == 0) {
			goto end;
		}
		if (new->ndpr_raf_onlink == 0 && new->ndpr_raf_auto == 0) {
			goto end;
		}

		bzero(&new->ndpr_addr, sizeof(struct in6_addr));

		error = nd6_prelist_add(new, dr, &pr, FALSE);
		if (error != 0 || pr == NULL) {
			nd6log(info, "prelist_update: "
			    "nd6_prelist_add failed for %s/%d on %s "
			    "errno=%d, returnpr=0x%llx\n",
			    ip6_sprintf(&new->ndpr_prefix.sin6_addr),
			    new->ndpr_plen, if_name(new->ndpr_ifp),
			    error, (uint64_t)VM_KERNEL_ADDRPERM(pr));
			goto end; /* we should just give up in this case. */
		}
	}

	/*
	 * Address autoconfiguration based on Section 5.5.3 of RFC 4862.
	 * Note that pr must be non NULL at this point.
	 */

	/* 5.5.3 (a). Ignore the prefix without the A bit set. */
	if (!new->ndpr_raf_auto) {
		goto end;
	}

	/*
	 * 5.5.3 (b). the link-local prefix should have been ignored in
	 * nd6_ra_input.
	 */

	/* 5.5.3 (c). Consistency check on lifetimes: pltime <= vltime. */
	if (new->ndpr_pltime > new->ndpr_vltime) {
		error = EINVAL; /* XXX: won't be used */
		goto end;
	}

	/*
	 * 5.5.3 (d).  If the prefix advertised is not equal to the prefix of
	 * an address configured by stateless autoconfiguration already in the
	 * list of addresses associated with the interface, and the Valid
	 * Lifetime is not 0, form an address.  We first check if we have
	 * a matching prefix.
	 */
	ifnet_lock_shared(ifp);
	TAILQ_FOREACH(ifa, &ifp->if_addrlist, ifa_list) {
		struct in6_ifaddr *__single ifa6 = NULL;
		u_int32_t remaininglifetime = 0;
		struct in6_addrlifetime lt6_tmp = {};

		IFA_LOCK(ifa);
		if (ifa->ifa_addr->sa_family != AF_INET6) {
			IFA_UNLOCK(ifa);
			continue;
		}
		ifa6 = ifatoia6(ifa);

		/*
		 * We only consider autoconfigured addresses as per RFC 4862.
		 */
		if (!(ifa6->ia6_flags & IN6_IFF_AUTOCONF)) {
			IFA_UNLOCK(ifa);
			continue;
		}
		/*
		 * Spec is not clear here, but I believe we should concentrate
		 * on unicast (i.e. not anycast) addresses.
		 * XXX: other ia6_flags? detached or duplicated?
		 */
		if ((ifa6->ia6_flags & IN6_IFF_ANYCAST) != 0) {
			IFA_UNLOCK(ifa);
			continue;
		}
		/*
		 * Ignore the address if it is not associated with a prefix
		 * or is associated with a prefix that is different from this
		 * one.  (pr is never NULL here)
		 */
		if (ifa6->ia6_ndpr != pr) {
			IFA_UNLOCK(ifa);
			continue;
		}

		if (ia6_match == NULL) { /* remember the first one */
			ia6_match = ifa6;
			ifa_addref(ifa); /* for ia6_match */
		}

		/*
		 * An already autoconfigured address matched.  Now that we
		 * are sure there is at least one matched address, we can
		 * proceed to 5.5.3. (e): update the lifetimes according to the
		 * "two hours" rule and the privacy extension.
		 */
		/* retrieve time as uptime (last arg is 0) */
		in6ifa_getlifetime(ifa6, &lt6_tmp, 0);

		if (lt6_tmp.ia6t_vltime == ND6_INFINITE_LIFETIME) {
			remaininglifetime = ND6_INFINITE_LIFETIME;
		} else if (timenow - ifa6->ia6_updatetime > lt6_tmp.ia6t_vltime) {
			/*
			 * The case of "invalid" address.  We should usually
			 * not see this case.
			 */
			remaininglifetime = 0;
		} else {
			remaininglifetime = lt6_tmp.ia6t_vltime -
			    (uint32_t)(timenow - ifa6->ia6_updatetime);
		}
		/* when not updating, keep the current stored lifetime. */
		lt6_tmp.ia6t_vltime = remaininglifetime;

		if (TWOHOUR < new->ndpr_vltime ||
		    remaininglifetime < new->ndpr_vltime) {
			lt6_tmp.ia6t_vltime = new->ndpr_vltime;
		} else if (remaininglifetime <= TWOHOUR) {
			if (auth) {
				lt6_tmp.ia6t_vltime = new->ndpr_vltime;
			}
		} else {
			/*
			 * new->ndpr_vltime <= TWOHOUR &&
			 * TWOHOUR < remaininglifetime
			 */
			lt6_tmp.ia6t_vltime = TWOHOUR;
		}

		/* The 2 hour rule is not imposed for preferred lifetime. */
		lt6_tmp.ia6t_pltime = new->ndpr_pltime;

		/* Special handling for lifetimes of temporary addresses. */
		if ((ifa6->ia6_flags & IN6_IFF_TEMPORARY) != 0) {
			u_int32_t maxvltime, maxpltime;

			/* Constrain lifetimes to system limits. */
			if (lt6_tmp.ia6t_vltime > ip6_temp_valid_lifetime) {
				lt6_tmp.ia6t_vltime = ip6_temp_valid_lifetime;
			}
			if (lt6_tmp.ia6t_pltime > ip6_temp_preferred_lifetime) {
				lt6_tmp.ia6t_pltime =
				    ip6_temp_preferred_lifetime -
				    ip6_desync_factor;
			}

			/*
			 * According to RFC 4941, section 3.3 (1), we only
			 * update the lifetimes when they are in the maximum
			 * intervals.
			 */
			if (ip6_temp_valid_lifetime >
			    (u_int32_t)((timenow - ifa6->ia6_createtime) +
			    ip6_desync_factor)) {
				maxvltime = ip6_temp_valid_lifetime -
				    (uint32_t)((timenow - ifa6->ia6_createtime) +
				    ip6_desync_factor);
			} else {
				maxvltime = 0;
			}
			if (ip6_temp_preferred_lifetime >
			    (u_int32_t)((timenow - ifa6->ia6_createtime) +
			    ip6_desync_factor)) {
				maxpltime = ip6_temp_preferred_lifetime -
				    (uint32_t)((timenow - ifa6->ia6_createtime) +
				    ip6_desync_factor);
			} else {
				maxpltime = 0;
			}

			if (lt6_tmp.ia6t_vltime == ND6_INFINITE_LIFETIME ||
			    lt6_tmp.ia6t_vltime > maxvltime) {
				lt6_tmp.ia6t_vltime = maxvltime;
			}

			if (lt6_tmp.ia6t_pltime == ND6_INFINITE_LIFETIME ||
			    lt6_tmp.ia6t_pltime > maxpltime) {
				lt6_tmp.ia6t_pltime = maxpltime;
			}
		}

		in6_init_address_ltimes(&lt6_tmp);
		in6ifa_setlifetime(ifa6, &lt6_tmp);
		ifa6->ia6_updatetime = timenow;
		IFA_UNLOCK(ifa);
	}
	ifnet_lock_done(ifp);
	if (ia6_match == NULL && new->ndpr_vltime) {
		/*
		 * 5.5.3 (d) (continued)
		 * No address matched and the valid lifetime is non-zero.
		 * Create a new address.
		 */
		if ((ia6 = in6_pfx_newpersistaddr(new, mcast, &error, FALSE, 0))
		    != NULL) {
			/*
			 * note that we should use pr (not new) for reference.
			 */
			IFA_LOCK(&ia6->ia_ifa);
			NDPR_LOCK(pr);
			ia6->ia6_ndpr = pr;
			NDPR_ADDREF(pr); /* for addr reference */
			pr->ndpr_addrcnt++;
			VERIFY(pr->ndpr_addrcnt != 0);
			NDPR_UNLOCK(pr);
			IFA_UNLOCK(&ia6->ia_ifa);

			/*
			 * RFC 4941 3.3 (2).
			 * When a new public address is created as described
			 * in RFC 4862, also create a new temporary address.
			 *
			 * RFC 4941 3.5.
			 * When an interface connects to a new link, a new
			 * randomized interface identifier should be generated
			 * immediately together with a new set of temporary
			 * addresses.  Thus, we specify 1 as the 2nd arg of
			 * in6_tmpifadd().
			 */
			if (ip6_use_tempaddr &&
			    (!IN6_IS_ADDR_UNIQUE_LOCAL(&new->ndpr_prefix.sin6_addr)
			    || ip6_ula_use_tempaddr)) {
				int e;
				if ((e = in6_tmpifadd(ia6, 1)) != 0) {
					nd6log(info, "prelist_update: "
					    "failed to create a temporary "
					    "address, errno=%d\n",
					    e);
				}
			}
			ifa_remref(&ia6->ia_ifa);
			ia6 = NULL;

			/*
			 * If the interface is marked for CLAT46 configuration
			 * try and configure the reserved IPv6 address for
			 * stateless translation.
			 */
			if (IS_INTF_CLAT46(ifp)) {
				if ((ia6 = in6_pfx_newpersistaddr(new, mcast,
				    &error, TRUE, CLAT46_COLLISION_COUNT_OFFSET))
				    != NULL) {
					IFA_LOCK(&ia6->ia_ifa);
					NDPR_LOCK(pr);
					ia6->ia6_ndpr = pr;
					NDPR_ADDREF(pr); /* for addr reference */
					pr->ndpr_addrcnt++;
					VERIFY(pr->ndpr_addrcnt != 0);
					pr->ndpr_stateflags |= NDPRF_CLAT46;
					NDPR_UNLOCK(pr);
					IFA_UNLOCK(&ia6->ia_ifa);
					ifa_remref(&ia6->ia_ifa);
					ia6 = NULL;
				} else if (error != EEXIST) {
					uuid_t tmp_uuid = {};
					/*
					 * Only report the error if it is not
					 * EEXIST.
					 */
					ip6stat.ip6s_clat464_v6addr_conffail++;
					in6_clat46_event_enqueue_nwk_wq_entry(
						IN6_CLAT46_EVENT_V6_ADDR_CONFFAIL,
						0,
						tmp_uuid);
					nd6log0(error, "Could not configure CLAT46 address on interface %s.\n", ifp->if_xname);
				}
				/*
				 * Reset the error as we do not want to
				 * treat failure of CLAT46 address configuration
				 * as complete failure in prelist update path.
				 */
				error = 0;
			}

			/*
			 * A newly added address might affect the status
			 * of other addresses, so we check and update it.
			 * XXX: what if address duplication happens?
			 */
			lck_mtx_lock(nd6_mutex);
			pfxlist_onlink_check();
			lck_mtx_unlock(nd6_mutex);
		}
	}
end:
	if (pr != NULL) {
		NDPR_REMREF(pr);
	}
	if (ia6_match != NULL) {
		ifa_remref(&ia6_match->ia_ifa);
	}
	return error;
}

/*
 * Neighbor Discover Default Router structure reference counting routines.
 */
static struct nd_defrouter *
nddr_alloc(zalloc_flags_t how)
{
	struct nd_defrouter *__single dr;

	dr = zalloc_flags(nddr_zone, how | Z_ZERO);
	if (dr) {
		lck_mtx_init(&dr->nddr_lock, &ifa_mtx_grp, &ifa_mtx_attr);
		lck_mtx_init(&dr->nddr_ref_lock, &ifa_mtx_grp, &ifa_mtx_attr);
		dr->nddr_debug |= IFD_ALLOC;
		if (nddr_debug != 0) {
			dr->nddr_debug |= IFD_DEBUG;
			dr->nddr_trace = nddr_trace;
		}
	}
	return dr;
}

static void
nddr_free(struct nd_defrouter *dr)
{
	if (dr->nddr_debug & IFD_ATTACHED) {
		panic("%s: attached nddr %p is being freed", __func__, dr);
		/* NOTREACHED */
	} else if (!(dr->nddr_debug & IFD_ALLOC)) {
		panic("%s: nddr %p cannot be freed", __func__, dr);
		/* NOTREACHED */
	}
	dr->nddr_debug &= ~IFD_ALLOC;
	lck_mtx_destroy(&dr->nddr_lock, &ifa_mtx_grp);
	lck_mtx_destroy(&dr->nddr_ref_lock, &ifa_mtx_grp);
	zfree(nddr_zone, dr);
}

static void
nddr_trace(struct nd_defrouter *dr, int refhold)
{
	struct nd_defrouter_dbg *__single dr_dbg = (struct nd_defrouter_dbg *)dr;
	ctrace_t *tr;
	uint32_t idx;
	uint16_t *cnt;

	if (!(dr->nddr_debug & IFD_DEBUG)) {
		panic("%s: nddr %p has no debug structure", __func__, dr);
		/* NOTREACHED */
	}
	if (refhold) {
		cnt = &dr_dbg->nddr_refhold_cnt;
		tr = dr_dbg->nddr_refhold;
	} else {
		cnt = &dr_dbg->nddr_refrele_cnt;
		tr = dr_dbg->nddr_refrele;
	}

	idx = os_atomic_inc_orig(cnt, relaxed) % NDDR_TRACE_HIST_SIZE;
	ctrace_record(&tr[idx]);
}

void
nddr_addref(struct nd_defrouter *nddr)
{
	NDDR_REF_LOCK_SPIN(nddr);
	if (++nddr->nddr_refcount == 0) {
		panic("%s: nddr %p wraparound refcnt", __func__, nddr);
		/* NOTREACHED */
	} else if (nddr->nddr_trace != NULL) {
		(*nddr->nddr_trace)(nddr, TRUE);
	}
	NDDR_REF_UNLOCK(nddr);
}

struct nd_defrouter *
nddr_remref(struct nd_defrouter *nddr)
{
	NDDR_REF_LOCK_SPIN(nddr);
	if (nddr->nddr_refcount == 0) {
		panic("%s: nddr %p negative refcnt", __func__, nddr);
		/* NOTREACHED */
	} else if (nddr->nddr_trace != NULL) {
		(*nddr->nddr_trace)(nddr, FALSE);
	}

	if (--nddr->nddr_refcount == 0) {
		NDDR_REF_UNLOCK(nddr);
		nddr_free(nddr);
		nddr = NULL;
	} else {
		NDDR_REF_UNLOCK(nddr);
	}
	return nddr;
}

uint64_t
nddr_getexpire(struct nd_defrouter *dr)
{
	struct timeval caltime;
	uint64_t expiry;

	if (dr->expire != 0) {
		/* account for system time change */
		getmicrotime(&caltime);

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

		expiry = dr->base_calendartime +
		    dr->expire - dr->base_uptime;
	} else {
		expiry = 0;
	}
	return expiry;
}

/*
 * Neighbor Discover Prefix structure reference counting routines.
 */
static struct nd_prefix *
ndpr_alloc(int how)
{
	struct nd_prefix *__single pr;

	pr = zalloc_flags(ndpr_zone, how | Z_ZERO);
	if (pr != NULL) {
		lck_mtx_init(&pr->ndpr_lock, &ifa_mtx_grp, &ifa_mtx_attr);
		lck_mtx_init(&pr->ndpr_ref_lock, &ifa_mtx_grp, &ifa_mtx_attr);
		RB_INIT(&pr->ndpr_prproxy_sols);
		pr->ndpr_debug |= IFD_ALLOC;
		if (ndpr_debug != 0) {
			pr->ndpr_debug |= IFD_DEBUG;
			pr->ndpr_trace = ndpr_trace;
		}
	}
	return pr;
}

static void
ndpr_free(struct nd_prefix *pr)
{
	if (pr->ndpr_debug & IFD_ATTACHED) {
		panic("%s: attached ndpr %p is being freed", __func__, pr);
		/* NOTREACHED */
	} else if (!(pr->ndpr_debug & IFD_ALLOC)) {
		panic("%s: ndpr %p cannot be freed", __func__, pr);
		/* NOTREACHED */
	} else if (pr->ndpr_rt != NULL) {
		panic("%s: ndpr %p route %p not freed", __func__, pr,
		    pr->ndpr_rt);
		/* NOTREACHED */
	} else if (pr->ndpr_prproxy_sols_cnt != 0) {
		panic("%s: ndpr %p non-zero solicitors count (%d)",
		    __func__, pr, pr->ndpr_prproxy_sols_cnt);
		/* NOTREACHED */
	} else if (!RB_EMPTY(&pr->ndpr_prproxy_sols)) {
		panic("%s: ndpr %p non-empty solicitors tree", __func__, pr);
		/* NOTREACHED */
	}
	pr->ndpr_debug &= ~IFD_ALLOC;
	lck_mtx_destroy(&pr->ndpr_lock, &ifa_mtx_grp);
	lck_mtx_destroy(&pr->ndpr_ref_lock, &ifa_mtx_grp);
	zfree(ndpr_zone, pr);
}

static void
ndpr_trace(struct nd_prefix *pr, int refhold)
{
	struct nd_prefix_dbg *__single pr_dbg = (struct nd_prefix_dbg *)pr;
	ctrace_t *tr;
	u_int32_t idx;
	u_int16_t *cnt;

	if (!(pr->ndpr_debug & IFD_DEBUG)) {
		panic("%s: ndpr %p has no debug structure", __func__, pr);
		/* NOTREACHED */
	}
	if (refhold) {
		cnt = &pr_dbg->ndpr_refhold_cnt;
		tr = pr_dbg->ndpr_refhold;
	} else {
		cnt = &pr_dbg->ndpr_refrele_cnt;
		tr = pr_dbg->ndpr_refrele;
	}

	idx = os_atomic_inc_orig(cnt, relaxed) % NDPR_TRACE_HIST_SIZE;
	ctrace_record(&tr[idx]);
}

void
ndpr_addref(struct nd_prefix *ndpr)
{
	NDPR_REF_LOCK_SPIN(ndpr);
	if (++ndpr->ndpr_refcount == 0) {
		panic("%s: ndpr %p wraparound refcnt", __func__, ndpr);
		/* NOTREACHED */
	} else if (ndpr->ndpr_trace != NULL) {
		(*ndpr->ndpr_trace)(ndpr, TRUE);
	}
	NDPR_REF_UNLOCK(ndpr);
}

struct nd_prefix *
ndpr_remref(struct nd_prefix *ndpr)
{
	NDPR_REF_LOCK_SPIN(ndpr);
	if (ndpr->ndpr_refcount == 0) {
		panic("%s: ndpr %p negative refcnt", __func__, ndpr);
		/* NOTREACHED */
	} else if (ndpr->ndpr_trace != NULL) {
		(*ndpr->ndpr_trace)(ndpr, FALSE);
	}

	if (--ndpr->ndpr_refcount == 0) {
		if (ndpr->ndpr_addrcnt != 0) {
			panic("%s: freeing ndpr %p with outstanding address "
			    "reference (%d)", __func__, ndpr,
			    ndpr->ndpr_addrcnt);
			/* NOTREACHED */
		}
		NDPR_REF_UNLOCK(ndpr);
		ndpr_free(ndpr);
		ndpr = NULL;
	} else {
		NDPR_REF_UNLOCK(ndpr);
	}
	return ndpr;
}

uint64_t
ndpr_getexpire(struct nd_prefix *pr)
{
	struct timeval caltime;
	uint64_t expiry;

	if (pr->ndpr_expire != 0 && pr->ndpr_vltime != ND6_INFINITE_LIFETIME) {
		/* account for system time change */
		getmicrotime(&caltime);

		pr->ndpr_base_calendartime +=
		    NET_CALCULATE_CLOCKSKEW(caltime,
		    pr->ndpr_base_calendartime, net_uptime(),
		    pr->ndpr_base_uptime);

		expiry = pr->ndpr_base_calendartime +
		    pr->ndpr_expire - pr->ndpr_base_uptime;
	} else {
		expiry = 0;
	}
	return expiry;
}

/*
 * A supplement function used in the on-link detection below;
 * detect if a given prefix has a (probably) reachable advertising router.
 * XXX: lengthy function name...
 */
static struct nd_pfxrouter *
find_pfxlist_reachable_router(struct nd_prefix *pr)
{
	struct nd_pfxrouter *__single pfxrtr = NULL;
	ifnet_ref_t ifp = NULL;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	NDPR_LOCK_ASSERT_HELD(pr);

	pfxrtr = LIST_FIRST(&pr->ndpr_advrtrs);
	while (pfxrtr) {
		/* XXX This should be same as prefixes interface. */
		ifp = pfxrtr->router->ifp;

		/*
		 * As long as there's a router advertisting this prefix
		 * on cellular (for that matter any interface that is point
		 * to point really), we treat the router as reachable.
		 */
		if (ifp != NULL && ifp->if_type == IFT_CELLULAR) {
			break;
		}

		if (pfxrtr->router->is_reachable) {
			break;
		}
		pfxrtr = LIST_NEXT(pfxrtr, pfr_entry);
	}
	return pfxrtr;
}

/*
 * Check if each prefix in the prefix list has at least one available router
 * that advertised the prefix (a router is "available" if its neighbor cache
 * entry is reachable or probably reachable).
 * If the check fails, the prefix may be off-link, because, for example,
 * we have moved from the network but the lifetime of the prefix has not
 * expired yet.  So we should not use the prefix if there is another prefix
 * that has an available router.
 * But, if there is no prefix that has an available router, we still regards
 * all the prefixes as on-link.  This is because we can't tell if all the
 * routers are simply dead or if we really moved from the network and there
 * is no router around us.
 */
void
pfxlist_onlink_check(void)
{
	struct nd_prefix *__single pr, *__single prclear;
	struct in6_ifaddr *__single ifa;
	struct nd_defrouter *__single dr;
	struct nd_pfxrouter *__single pfxrtr = NULL;
	int err, i, found = 0;
	u_int16_t addresses_count;
	struct ifaddr **__single __counted_by(addresses_count) ifap = NULL;
	struct nd_prefix *__single ndpr;
	u_int64_t timenow = net_uptime();

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	while (nd_prefix_busy) {
		nd_prefix_waiters++;
		msleep(nd_prefix_waitchan, nd6_mutex, (PZERO - 1),
		    __func__, NULL);
		LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);
	}
	nd_prefix_busy = TRUE;

	/*
	 * Check if there is a prefix that has a reachable advertising
	 * router.
	 */
	pr = nd_prefix.lh_first;
	while (pr) {
		NDPR_LOCK(pr);
		if (pr->ndpr_raf_onlink && find_pfxlist_reachable_router(pr) &&
		    (pr->ndpr_debug & IFD_ATTACHED)) {
			NDPR_UNLOCK(pr);
			break;
		}
		NDPR_UNLOCK(pr);
		pr = pr->ndpr_next;
	}
	/*
	 * If we have no such prefix, check whether we still have a router
	 * that does not advertise any prefixes.
	 */
	if (pr == NULL) {
		for (dr = TAILQ_FIRST(&nd_defrouter_list); dr;
		    dr = TAILQ_NEXT(dr, dr_entry)) {
			struct nd_prefix *__single pr0;

			for (pr0 = nd_prefix.lh_first; pr0;
			    pr0 = pr0->ndpr_next) {
				NDPR_LOCK(pr0);
				if ((pfxrtr = pfxrtr_lookup(pr0, dr)) != NULL) {
					NDPR_UNLOCK(pr0);
					break;
				}
				NDPR_UNLOCK(pr0);
			}
			if (pfxrtr != NULL) {
				break;
			}
		}
	}
	if (pr != NULL || (TAILQ_FIRST(&nd_defrouter_list) && pfxrtr == NULL)) {
		/*
		 * There is at least one prefix that has a reachable router,
		 * or at least a router which probably does not advertise
		 * any prefixes.  The latter would be the case when we move
		 * to a new link where we have a router that does not provide
		 * prefixes and we configure an address by hand.
		 * Detach prefixes which have no reachable advertising
		 * router, and attach other prefixes.
		 */
		pr = nd_prefix.lh_first;
		while (pr) {
			NDPR_LOCK(pr);
			/*
			 * We aren't interested prefixes already processed,
			 * nor in prefixes without the L bit
			 * set nor in static prefixes
			 */
			if (pr->ndpr_raf_onlink == 0 ||
			    pr->ndpr_stateflags & NDPRF_STATIC) {
				NDPR_UNLOCK(pr);
				pr = pr->ndpr_next;
				continue;
			}
			if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
			    find_pfxlist_reachable_router(pr) == NULL &&
			    (pr->ndpr_debug & IFD_ATTACHED)) {
				pr->ndpr_stateflags |= NDPRF_DETACHED;
			}
			if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0 &&
			    find_pfxlist_reachable_router(pr) != NULL &&
			    (pr->ndpr_debug & IFD_ATTACHED)) {
				pr->ndpr_stateflags &= ~NDPRF_DETACHED;
			}
			NDPR_UNLOCK(pr);
			pr = pr->ndpr_next;
		}
	} else {
		/* there is no prefix that has a reachable router */
		for (pr = nd_prefix.lh_first; pr; pr = pr->ndpr_next) {
			NDPR_LOCK(pr);
			if (pr->ndpr_raf_onlink == 0 ||
			    pr->ndpr_stateflags & NDPRF_STATIC) {
				NDPR_UNLOCK(pr);
				continue;
			}
			if ((pr->ndpr_stateflags & NDPRF_DETACHED) != 0) {
				pr->ndpr_stateflags &= ~NDPRF_DETACHED;
			}
			NDPR_UNLOCK(pr);
		}
	}
	/*
	 * Instead of removing interface route for detached prefix,
	 * keep the route and treat unreachability similar to the processing
	 * of an RA that has just deprecated the prefix.
	 * Keep around the detached flag just to be able to be able
	 * to differentiate the scenario from explicit RA deprecation
	 * of prefix.
	 * Keep the logic to install the interface route for a (just) attached
	 * prefix. Note that all attempt of reinstallation does not
	 * necessarily success, when a same prefix is shared among multiple
	 * interfaces.  Such cases will be handled in nd6_prefix_onlink,
	 * so we don't have to care about them.
	 */
	pr = nd_prefix.lh_first;
	while (pr) {
		int error;

		NDPR_LOCK(pr);
		if (pr->ndpr_raf_onlink == 0 ||
		    pr->ndpr_stateflags & NDPRF_STATIC ||
		    pr->ndpr_stateflags & NDPRF_PROCESSED_ONLINK ||
		    pr->ndpr_stateflags & NDPRF_DEFUNCT) {
			NDPR_UNLOCK(pr);
			pr = pr->ndpr_next;
			continue;
		}
		pr->ndpr_stateflags |= NDPRF_PROCESSED_ONLINK;
		NDPR_ADDREF(pr);
		if (pr->ndpr_stateflags & NDPRF_DETACHED) {
			/*
			 * When a prefix is detached, make it deprecated by setting pltime
			 * to 0, and let it expire according to its advertised vltime.
			 * If its original vltime is infinite or longer than 2hr,
			 * set it to 2hr.
			 */
			pr->ndpr_pltime = 0;
			uint32_t pr_remaining_lifetime;
			uint32_t original_lifetime = (uint32_t)(timenow - pr->ndpr_base_uptime);
			if (pr->ndpr_vltime > original_lifetime) {
				pr_remaining_lifetime = pr->ndpr_vltime - original_lifetime;
			} else {
				pr_remaining_lifetime = 0;
			}
			if (pr->ndpr_vltime == ND6_INFINITE_LIFETIME ||
			    pr_remaining_lifetime >= TWOHOUR) {
				pr->ndpr_vltime = TWOHOUR;
			} else {
				pr->ndpr_vltime = pr_remaining_lifetime;
			}
			in6_init_prefix_ltimes(pr);
			NDPR_UNLOCK(pr);
		} else if ((pr->ndpr_stateflags & NDPRF_DETACHED) == 0 &&
		    (pr->ndpr_stateflags & NDPRF_ONLINK) == 0 &&
		    pr->ndpr_raf_onlink) {
			NDPR_UNLOCK(pr);
			if ((error = nd6_prefix_onlink(pr)) != 0) {
				nd6log0(error,
				    "pfxlist_onlink_check: failed to "
				    "make %s/%d offlink, errno=%d\n",
				    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
				    pr->ndpr_plen, error);
			}
			NDPR_REMREF(pr);
			pr = nd_prefix.lh_first;
			continue;
		} else {
			NDPR_UNLOCK(pr);
		}
		NDPR_REMREF(pr);
		pr = pr->ndpr_next;
	}
	LIST_FOREACH(prclear, &nd_prefix, ndpr_entry) {
		NDPR_LOCK(prclear);
		prclear->ndpr_stateflags &= ~NDPRF_PROCESSED_ONLINK;
		NDPR_UNLOCK(prclear);
	}
	VERIFY(nd_prefix_busy);
	nd_prefix_busy = FALSE;
	if (nd_prefix_waiters > 0) {
		nd_prefix_waiters = 0;
		wakeup(nd_prefix_waitchan);
	}

	/*
	 * Changes on the prefix status might affect address status as well.
	 * Make sure that all addresses derived from an attached prefix are
	 * attached, and that all addresses derived from a detached prefix are
	 * detached.  Note, however, that a manually configured address should
	 * always be attached.
	 * The precise detection logic is same as the one for prefixes.
	 *
	 * ifnet_get_address_list_family_internal() may fail due to memory
	 * pressure, but we will eventually be called again when we receive
	 * another NA, RA, or when the link status changes.
	 */
	err = ifnet_get_address_list_family_internal(NULL, &ifap, &addresses_count,
	    AF_INET6, 0, M_NOWAIT, 0);
	if (err != 0 || ifap == NULL) {
		nd6log0(error, "%s: ifnet_get_address_list_family_internal "
		    "failed. err=%d", __func__, err);
		return;
	}
	for (i = 0; ifap[i]; i++) {
		ifa = ifatoia6(ifap[i]);
		IFA_LOCK(&ifa->ia_ifa);
		if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0 ||
		    (ifap[i]->ifa_debug & IFD_ATTACHED) == 0) {
			IFA_UNLOCK(&ifa->ia_ifa);
			continue;
		}
		if ((ndpr = ifa->ia6_ndpr) == NULL) {
			/*
			 * This can happen when we first configure the address
			 * (i.e. the address exists, but the prefix does not).
			 * XXX: complicated relationships...
			 */
			IFA_UNLOCK(&ifa->ia_ifa);
			continue;
		}
		IFA_UNLOCK(&ifa->ia_ifa);

		NDPR_LOCK(ndpr);
		if (find_pfxlist_reachable_router(ndpr)) {
			NDPR_UNLOCK(ndpr);
			found = 1;
			break;
		}
		NDPR_UNLOCK(ndpr);
	}
	if (found) {
		for (i = 0; ifap[i]; i++) {
			struct in6_addrlifetime lt6_tmp = {};

			ifa = ifatoia6(ifap[i]);
			IFA_LOCK(&ifa->ia_ifa);
			if ((ifa->ia6_flags & IN6_IFF_AUTOCONF) == 0 ||
			    (ifap[i]->ifa_debug & IFD_ATTACHED) == 0) {
				IFA_UNLOCK(&ifa->ia_ifa);
				continue;
			}
			if ((ndpr = ifa->ia6_ndpr) == NULL) {
				/* XXX: see above. */
				IFA_UNLOCK(&ifa->ia_ifa);
				continue;
			}
			IFA_UNLOCK(&ifa->ia_ifa);
			NDPR_LOCK(ndpr);
			if (find_pfxlist_reachable_router(ndpr) == NULL) {
				/*
				 * When the prefix of an addr is detached, make the address
				 * deprecated by setting pltime to 0, and let it expire according
				 * to its advertised vltime. If its original vltime is infinite
				 * or longer than 2hr, set it to 2hr.
				 */
				NDPR_UNLOCK(ndpr);
				IFA_LOCK(&ifa->ia_ifa);
				in6ifa_getlifetime(ifa, &lt6_tmp, 0);
				/* We want to immediately deprecate the address */
				lt6_tmp.ia6t_pltime = 0;
				/* Do not extend its valid lifetime */
				uint32_t remaining_lifetime;
				uint32_t original_lifetime = (uint32_t)(timenow - ifa->ia6_updatetime);
				if (lt6_tmp.ia6t_vltime > original_lifetime) {
					remaining_lifetime = lt6_tmp.ia6t_vltime - original_lifetime;
				} else {
					remaining_lifetime = 0;
				}
				if (lt6_tmp.ia6t_vltime == ND6_INFINITE_LIFETIME || remaining_lifetime >= TWOHOUR) {
					lt6_tmp.ia6t_vltime = TWOHOUR;
				} else {
					lt6_tmp.ia6t_vltime = remaining_lifetime;
				}

				in6_init_address_ltimes(&lt6_tmp);
				in6ifa_setlifetime(ifa, &lt6_tmp);
				ifa->ia6_updatetime = timenow;

				/*
				 * The next nd6 service timer expiry will take
				 * care of marking the addresses as deprecated
				 * and issuing the notifications as well.
				 */
				IFA_UNLOCK(&ifa->ia_ifa);
			} else {
				NDPR_UNLOCK(ndpr);
			}
		}
	}
	ifnet_address_list_free_counted_by(ifap, addresses_count);
}

static struct nd_prefix *
nd6_prefix_equal_lookup(struct nd_prefix *pr, boolean_t primary_only)
{
	struct nd_prefix *__single opr;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	for (opr = nd_prefix.lh_first; opr; opr = opr->ndpr_next) {
		if (opr == pr) {
			continue;
		}

		NDPR_LOCK(opr);
		if ((opr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
			NDPR_UNLOCK(opr);
			continue;
		}
		if (opr->ndpr_plen == pr->ndpr_plen &&
		    in6_are_prefix_equal(&pr->ndpr_prefix.sin6_addr, pr->ndpr_prefix.sin6_scope_id,
		    &opr->ndpr_prefix.sin6_addr, opr->ndpr_prefix.sin6_scope_id, pr->ndpr_plen) &&
		    (!primary_only ||
		    !(opr->ndpr_stateflags & NDPRF_IFSCOPE))) {
			NDPR_ADDREF(opr);
			NDPR_UNLOCK(opr);
			return opr;
		}
		NDPR_UNLOCK(opr);
	}
	return NULL;
}

/*
 * Synchronize the interface routes of similar prefixes on different
 * interfaces; the one using the default interface would be (re)installed
 * as a primary/non-scoped entry, and the rest as scoped entri(es).
 */
static void
nd6_prefix_sync(struct ifnet *ifp)
{
	struct nd_prefix *__single pr, *__single opr;
	int err = 0;
	uint64_t timenow;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	if (ifp == NULL) {
		return;
	}


	net_update_uptime();
	timenow = net_uptime();

	LIST_FOREACH(pr, &nd_prefix, ndpr_entry) {
		NDPR_LOCK(pr);
		if ((pr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
			NDPR_UNLOCK(pr);
			continue;
		}
		if (pr->ndpr_expire != 0 && pr->ndpr_expire < timenow) {
			NDPR_UNLOCK(pr);
			continue;
		}
		if (pr->ndpr_ifp == ifp &&
		    (pr->ndpr_stateflags & NDPRF_IFSCOPE) &&
		    !IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr)) {
			NDPR_UNLOCK(pr);
			break;
		}
		NDPR_UNLOCK(pr);
	}

	if (pr == NULL) {
		return;
	}

	/* Remove conflicting entries */
	opr = nd6_prefix_equal_lookup(pr, TRUE);
	if (opr != NULL) {
		lck_mtx_unlock(nd6_mutex);
		err = nd6_prefix_offlink(opr);
		lck_mtx_lock(nd6_mutex);
		if (err != 0) {
			nd6log0(error,
			    "%s: failed to make %s/%d offlink on %s, "
			    "errno=%d\n", __func__,
			    ip6_sprintf(&opr->ndpr_prefix.sin6_addr),
			    opr->ndpr_plen, if_name(opr->ndpr_ifp), err);
		}
	} else {
		nd6log0(error,
		    "%s: scoped %s/%d on %s has no matching unscoped prefix\n",
		    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp));
	}

	lck_mtx_unlock(nd6_mutex);
	err = nd6_prefix_offlink(pr);
	lck_mtx_lock(nd6_mutex);
	if (err != 0) {
		nd6log0(error,
		    "%s: failed to make %s/%d offlink on %s, errno=%d\n",
		    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp), err);
	}

	/* Add the entries back */
	if (opr != NULL) {
		err = nd6_prefix_onlink_scoped(opr, opr->ndpr_ifp->if_index);
		if (err != 0) {
			nd6log0(error,
			    "%s: failed to make %s/%d scoped onlink on %s, "
			    "errno=%d\n", __func__,
			    ip6_sprintf(&opr->ndpr_prefix.sin6_addr),
			    opr->ndpr_plen, if_name(opr->ndpr_ifp), err);
		}
	}

	err = nd6_prefix_onlink_scoped(pr, IFSCOPE_NONE);
	if (err != 0) {
		nd6log0(error,
		    "%s: failed to make %s/%d onlink on %s, errno=%d\n",
		    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp), err);
	}

	if (err != 0) {
		nd6log0(error,
		    "%s: error promoting %s/%d to %s from %s\n",
		    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp),
		    (opr != NULL) ? if_name(opr->ndpr_ifp) : "NONE");
	} else {
		nd6log2(info,
		    "%s: %s/%d promoted, previously on %s\n",
		    if_name(pr->ndpr_ifp),
		    ip6_sprintf(&pr->ndpr_prefix.sin6_addr), pr->ndpr_plen,
		    (opr != NULL) ? if_name(opr->ndpr_ifp) : "NONE");
	}

	if (opr != NULL) {
		NDPR_REMREF(opr);
	}
}

static int
nd6_prefix_onlink_common(struct nd_prefix *pr, boolean_t force_scoped,
    unsigned int ifscope)
{
	struct ifaddr *__single ifa;
	ifnet_ref_t ifp = pr->ndpr_ifp;
	struct sockaddr_in6 mask6, prefix;
	struct nd_prefix *__single opr;
	u_int32_t rtflags;
	int error = 0, prproxy = 0;
	rtentry_ref_t rt = NULL;
	u_char prefix_len = 0;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_OWNED);

	/* sanity check */
	NDPR_LOCK(pr);
	if ((pr->ndpr_stateflags & NDPRF_ONLINK) != 0) {
		nd6log0(error,
		    "%s: %s/%d on %s scoped=%d is already on-link\n",
		    __func__, ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp),
		    (pr->ndpr_stateflags & NDPRF_IFSCOPE) ? 1 : 0);
		NDPR_UNLOCK(pr);
		return EEXIST;
	}
	NDPR_UNLOCK(pr);

	/*
	 * Add the interface route associated with the prefix.  Before
	 * installing the route, check if there's the same prefix on another
	 * interface, and the prefix has already installed the interface route.
	 */
	opr = nd6_prefix_equal_lookup(pr, FALSE);
	if (opr != NULL) {
		NDPR_REMREF(opr);
	}

	if (!force_scoped) {
		/*
		 * If a primary/non-scoped interface route already exists,
		 * install the new one as a scoped entry.  If the existing
		 * interface route is scoped, install new as non-scoped.
		 */
		ifscope = (opr != NULL) ? ifp->if_index : IFSCOPE_NONE;
		opr = nd6_prefix_equal_lookup(pr, TRUE);
		if (opr != NULL) {
			NDPR_REMREF(opr);
		} else if (ifscope != IFSCOPE_NONE) {
			ifscope = IFSCOPE_NONE;
		}
	}

	/*
	 * We prefer link-local addresses as the associated interface address.
	 */
	/* search for a link-local addr */
	ifa = (struct ifaddr *)in6ifa_ifpforlinklocal(ifp,
	    IN6_IFF_NOTREADY | IN6_IFF_ANYCAST);
	if (ifa == NULL) {
		struct in6_ifaddr *__single ia6;
		ifnet_lock_shared(ifp);
		IFP_TO_IA6(ifp, ia6);
		ifnet_lock_done(ifp);
		if (ia6 != NULL) {
			ifa = &ia6->ia_ifa;
		}
		/* should we care about ia6_flags? */
	}
	NDPR_LOCK(pr);
	if (ifa == NULL) {
		/*
		 * This can still happen, when, for example, we receive an RA
		 * containing a prefix with the L bit set and the A bit clear,
		 * after removing all IPv6 addresses on the receiving
		 * interface.  This should, of course, be rare though.
		 */
		nd6log(info,
		    "nd6_prefix_onlink: failed to find any ifaddr"
		    " to add route for a prefix(%s/%d) on %s\n",
		    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(ifp));
		NDPR_UNLOCK(pr);
		return 0;
	}

	/*
	 * in6_ifinit() sets nd6_rtrequest to ifa_rtrequest for all ifaddrs.
	 * ifa->ifa_rtrequest = nd6_rtrequest;
	 */
	SOCKADDR_ZERO(&mask6, sizeof(mask6));
	mask6.sin6_len = sizeof(mask6);
	mask6.sin6_addr = pr->ndpr_mask;
	prefix = pr->ndpr_prefix;
	prefix_len = pr->ndpr_plen;
	if ((rt = pr->ndpr_rt) != NULL) {
		pr->ndpr_rt = NULL;
	}
	NDPR_ADDREF(pr);         /* keep reference for this routine */
	NDPR_UNLOCK(pr);

	IFA_LOCK_SPIN(ifa);
	rtflags = ifa->ifa_flags | RTF_CLONING | RTF_UP;
	IFA_UNLOCK(ifa);
	if (nd6_need_cache(ifp)) {
		/* explicitly set in case ifa_flags does not set the flag. */
		rtflags |= RTF_CLONING;
	} else {
		/*
		 * explicitly clear the cloning bit in case ifa_flags sets it.
		 */
		rtflags &= ~RTF_CLONING;
	}

	lck_mtx_unlock(nd6_mutex);

	/*
	 * check if it conflicts with a indirect prefix route added by RIO
	 * if so, remove the rti entry.
	 */
	if (ifscope == IFSCOPE_NONE) {
		rtentry_ref_t temp_route = NULL;
		LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
		lck_mtx_lock(rnh_lock);
		temp_route = rt_lookup(TRUE, SA(&prefix), SA(&mask6), rt_tables[AF_INET6], IFSCOPE_NONE);
		lck_mtx_unlock(rnh_lock);

		if (temp_route != NULL && temp_route->rt_flags & RTF_GATEWAY && temp_route->rt_ifp != NULL) {
			struct nd_route_info rti = {};
			bzero(&rti, sizeof(rti));
			rti.nd_rti_prefixlen = prefix_len;
			rti.nd_rti_prefix = prefix.sin6_addr;
			lck_mtx_lock(nd6_mutex);
			nd6_rti_delreq(&rti);
			lck_mtx_unlock(nd6_mutex);
		}
		if (temp_route != NULL) {
			rtfree(temp_route);
		}
	}

	if (rt != NULL) {
		rtfree(rt);
		rt = NULL;
	}

	error = rtrequest_scoped(RTM_ADD, SA(&prefix), ifa->ifa_addr, SA(&mask6),
	    rtflags, &rt, ifscope);

	/*
	 * Serialize the setting of NDPRF_PRPROXY.
	 */
	lck_mtx_lock(&proxy6_lock);

	if (rt != NULL) {
		RT_LOCK(rt);
		nd6_rtmsg(RTM_ADD, rt);
		RT_UNLOCK(rt);
		NDPR_LOCK(pr);
	} else {
		NDPR_LOCK(pr);
		nd6log0(error, "nd6_prefix_onlink: failed to add route for a"
		    " prefix (%s/%d) on %s, gw=%s, mask=%s, flags=%x,"
		    " scoped=%d, errno = %d\n",
		    ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(ifp),
		    ip6_sprintf(&SIN6(ifa->ifa_addr)->sin6_addr),
		    ip6_sprintf(&mask6.sin6_addr), rtflags,
		    (ifscope != IFSCOPE_NONE), error);
	}
	NDPR_LOCK_ASSERT_HELD(pr);

	pr->ndpr_stateflags &= ~(NDPRF_IFSCOPE | NDPRF_PRPROXY);

	/*
	 * TODO: If the prefix route exists, we should really find it and
	 * refer the prefix to it; otherwise ndpr_rt is NULL.
	 */
	if (!(pr->ndpr_stateflags & NDPRF_DEFUNCT) &&
	    (rt != NULL || error == EEXIST)) {
		struct nd_ifinfo *__single ndi = NULL;

		VERIFY(pr->ndpr_prproxy_sols_cnt == 0);
		VERIFY(RB_EMPTY(&pr->ndpr_prproxy_sols));

		ndi = ND_IFINFO(ifp);
		VERIFY((NULL != ndi) && (TRUE == ndi->initialized));
		lck_mtx_lock(&ndi->lock);

		pr->ndpr_rt = rt;       /* keep reference from rtrequest */
		pr->ndpr_stateflags |= NDPRF_ONLINK;
		if (ifscope != IFSCOPE_NONE) {
			pr->ndpr_stateflags |= NDPRF_IFSCOPE;
		} else if ((rtflags & RTF_CLONING) &&
		    (ndi->flags & ND6_IFF_PROXY_PREFIXES) &&
		    !IN6_IS_ADDR_LINKLOCAL(&pr->ndpr_prefix.sin6_addr)) {
			/*
			 * At present, in order for the prefix to be eligible
			 * as a proxying/proxied prefix, we require that the
			 * prefix route entry be marked as a cloning route with
			 * RTF_PROXY; i.e. nd6_need_cache() needs to return
			 * true for the interface type, hence the test for
			 * RTF_CLONING above.
			 */
			pr->ndpr_stateflags |= NDPRF_PRPROXY;
		}

		lck_mtx_unlock(&ndi->lock);
	} else if (rt != NULL && pr->ndpr_stateflags & NDPRF_DEFUNCT) {
		rtfree(rt);
	}

	prproxy = (pr->ndpr_stateflags & NDPRF_PRPROXY);
	VERIFY(!prproxy || !(pr->ndpr_stateflags & NDPRF_IFSCOPE));
	NDPR_UNLOCK(pr);

	ifa_remref(ifa);

	/*
	 * If this is an upstream prefix, find the downstream ones (if any)
	 * and re-configure their prefix routes accordingly.  Otherwise,
	 * this could be potentially be a downstream prefix, and so find the
	 * upstream prefix, if any.
	 */
	nd6_prproxy_prelist_update(pr, prproxy ? pr : NULL);

	NDPR_REMREF(pr);        /* release reference for this routine */
	lck_mtx_unlock(&proxy6_lock);

	lck_mtx_lock(nd6_mutex);

	return error;
}

int
nd6_prefix_onlink(struct nd_prefix *pr)
{
	return nd6_prefix_onlink_common(pr, FALSE, IFSCOPE_NONE);
}

int
nd6_prefix_onlink_scoped(struct nd_prefix *pr, unsigned int ifscope)
{
	return nd6_prefix_onlink_common(pr, TRUE, ifscope);
}

int
nd6_prefix_offlink(struct nd_prefix *pr)
{
	int error = 0, prproxy;
	ifnet_ref_t ifp = pr->ndpr_ifp;
	struct sockaddr_in6 sa6, mask6, prefix;
	rtentry_ref_t rt = NULL, ndpr_rt = NULL;
	unsigned int ifscope;
	u_char prefix_len = 0;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

	/* sanity check */
	NDPR_LOCK(pr);
	if ((pr->ndpr_stateflags & NDPRF_ONLINK) == 0) {
		nd6log0(error,
		    "nd6_prefix_offlink: %s/%d on %s scoped=%d is already "
		    "off-link\n", ip6_sprintf(&pr->ndpr_prefix.sin6_addr),
		    pr->ndpr_plen, if_name(pr->ndpr_ifp),
		    (pr->ndpr_stateflags & NDPRF_IFSCOPE) ? 1 : 0);
		NDPR_UNLOCK(pr);
		return EEXIST;
	}

	SOCKADDR_ZERO(&sa6, sizeof(sa6));
	sa6.sin6_family = AF_INET6;
	sa6.sin6_len = sizeof(sa6);
	bcopy(&pr->ndpr_prefix.sin6_addr, &sa6.sin6_addr,
	    sizeof(struct in6_addr));
	SOCKADDR_ZERO(&mask6, sizeof(mask6));
	mask6.sin6_family = AF_INET6;
	mask6.sin6_len = sizeof(sa6);
	bcopy(&pr->ndpr_mask, &mask6.sin6_addr, sizeof(struct in6_addr));
	prefix = pr->ndpr_prefix;
	prefix_len = pr->ndpr_plen;
	if ((ndpr_rt = pr->ndpr_rt) != NULL) {
		pr->ndpr_rt = NULL;
	}
	NDPR_ADDREF(pr);         /* keep reference for this routine */
	NDPR_UNLOCK(pr);

	ifscope = (pr->ndpr_stateflags & NDPRF_IFSCOPE) ?
	    ifp->if_index : IFSCOPE_NONE;

	error = rtrequest_scoped(RTM_DELETE, SA(&sa6), NULL, SA(&mask6),
	    0, &rt, ifscope);

	if (rt != NULL) {
		/* report the route deletion to the routing socket. */
		RT_LOCK(rt);
		nd6_rtmsg(RTM_DELETE, rt);
		RT_UNLOCK(rt);
		rtfree(rt);
	} else {
		nd6log0(error,
		    "nd6_prefix_offlink: failed to delete route: "
		    "%s/%d on %s, scoped %d, (errno = %d)\n",
		    ip6_sprintf(&sa6.sin6_addr), prefix_len, if_name(ifp),
		    (ifscope != IFSCOPE_NONE), error);
	}

	struct nd_route_info rti = {};
	bzero(&rti, sizeof(rti));
	rti.nd_rti_prefixlen = prefix_len;
	rti.nd_rti_prefix = prefix.sin6_addr;

	lck_mtx_lock(nd6_mutex);
	nd6_rti_select(&rti, ifp);
	lck_mtx_unlock(nd6_mutex);

	if (ndpr_rt != NULL) {
		rtfree(ndpr_rt);
	}

	lck_mtx_lock(&proxy6_lock);

	NDPR_LOCK(pr);
	prproxy = (pr->ndpr_stateflags & NDPRF_PRPROXY);
	VERIFY(!prproxy || !(pr->ndpr_stateflags & NDPRF_IFSCOPE));
	pr->ndpr_stateflags &= ~(NDPRF_ONLINK | NDPRF_IFSCOPE | NDPRF_PRPROXY);
	if (pr->ndpr_prproxy_sols_cnt > 0) {
		VERIFY(prproxy);
		nd6_prproxy_sols_reap(pr);
		VERIFY(pr->ndpr_prproxy_sols_cnt == 0);
		VERIFY(RB_EMPTY(&pr->ndpr_prproxy_sols));
	}
	NDPR_UNLOCK(pr);

	/*
	 * If this was an upstream prefix, find the downstream ones and do
	 * some cleanups.  If this was a downstream prefix, the prefix route
	 * has been removed from the routing table above, but there may be
	 * other tasks to perform.
	 */
	nd6_prproxy_prelist_update(pr, prproxy ? pr : NULL);

	NDPR_REMREF(pr);        /* release reference for this routine */
	lck_mtx_unlock(&proxy6_lock);

	return error;
}

struct in6_ifaddr *
in6_pfx_newpersistaddr(struct nd_prefix *pr, int mcast, int *errorp,
    boolean_t is_clat46, uint8_t collision_count)
{
	struct in6_ifaddr *__single ia6 = NULL;
	ifnet_ref_t ifp = NULL;
	struct nd_ifinfo *__single ndi = NULL;
	struct in6_addr mask;
	struct in6_aliasreq ifra;
	int error, ifaupdate, iidlen, notcga;

	VERIFY(pr != NULL);
	VERIFY(errorp != NULL);

	NDPR_LOCK(pr);
	ifp = pr->ndpr_ifp;
	ia6 = NULL;
	error = 0;

	/*
	 * Prefix Length check:
	 * If the sum of the prefix length and interface identifier
	 * length does not equal 128 bits, the Prefix Information
	 * option MUST be ignored.  The length of the interface
	 * identifier is defined in a separate link-type specific
	 * document.
	 */
	iidlen = in6_if2idlen(ifp);
	if (iidlen < 0) {
		error = EADDRNOTAVAIL;
		/* this should not happen, so we always log it. */
		log(LOG_ERR, "%s: IID length undefined (%s)\n",
		    __func__, if_name(ifp));
		goto unlock1;
	} else if (iidlen != 64) {
		error = EADDRNOTAVAIL;
		/*
		 * stateless autoconfiguration not yet well-defined for IID
		 * lengths other than 64 octets. Just give up for now.
		 */
		nd6log(info, "%s: IID length not 64 octets (%s)\n",
		    __func__, if_name(ifp));
		goto unlock1;
	}

	if (iidlen + pr->ndpr_plen != 128) {
		error = EADDRNOTAVAIL;
		nd6log(info,
		    "%s: invalid prefix length %d for %s, ignored\n",
		    __func__, pr->ndpr_plen, if_name(ifp));
		goto unlock1;
	}

	bzero(&ifra, sizeof(ifra));
	strlcpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
	ifra.ifra_addr.sin6_family = AF_INET6;
	ifra.ifra_addr.sin6_len = sizeof(struct sockaddr_in6);

	/* prefix */
	bcopy(&pr->ndpr_prefix.sin6_addr, &ifra.ifra_addr.sin6_addr,
	    sizeof(ifra.ifra_addr.sin6_addr));
	in6_len2mask(&mask, pr->ndpr_plen);
	ifra.ifra_addr.sin6_addr.s6_addr32[0] &= mask.s6_addr32[0];
	ifra.ifra_addr.sin6_addr.s6_addr32[1] &= mask.s6_addr32[1];
	ifra.ifra_addr.sin6_addr.s6_addr32[2] &= mask.s6_addr32[2];
	ifra.ifra_addr.sin6_addr.s6_addr32[3] &= mask.s6_addr32[3];

	ndi = ND_IFINFO(ifp);
	VERIFY(ndi->initialized);
	lck_mtx_lock(&ndi->lock);

	notcga = nd6_send_opstate == ND6_SEND_OPMODE_DISABLED ||
	    (ndi->flags & ND6_IFF_INSECURE) != 0;

	lck_mtx_unlock(&ndi->lock);
	NDPR_UNLOCK(pr);

	if (notcga && !is_clat46) {
		ia6 = in6ifa_ifpforlinklocal(ifp, 0);
		if (ia6 == NULL) {
			error = EADDRNOTAVAIL;
			nd6log(info, "%s: no link-local address (%s)\n",
			    __func__, if_name(ifp));
			goto done;
		}

		IFA_LOCK(&ia6->ia_ifa);
		ifra.ifra_addr.sin6_addr.s6_addr32[0] |=
		    (ia6->ia_addr.sin6_addr.s6_addr32[0] & ~mask.s6_addr32[0]);
		ifra.ifra_addr.sin6_addr.s6_addr32[1] |=
		    (ia6->ia_addr.sin6_addr.s6_addr32[1] & ~mask.s6_addr32[1]);
		ifra.ifra_addr.sin6_addr.s6_addr32[2] |=
		    (ia6->ia_addr.sin6_addr.s6_addr32[2] & ~mask.s6_addr32[2]);
		ifra.ifra_addr.sin6_addr.s6_addr32[3] |=
		    (ia6->ia_addr.sin6_addr.s6_addr32[3] & ~mask.s6_addr32[3]);
		IFA_UNLOCK(&ia6->ia_ifa);
		ifa_remref(&ia6->ia_ifa);
		ia6 = NULL;
	} else {
		struct in6_cga_prepare local_cga_prepare;
		struct in6_cga_prepare *__single prepare_p;


		in6_cga_node_lock();

		if (ndi->cga_initialized) {
			bcopy(&(ndi->local_cga_modifier),
			    &(local_cga_prepare.cga_modifier),
			    sizeof(local_cga_prepare.cga_modifier));
			prepare_p = &local_cga_prepare;
		} else {
			prepare_p = NULL;
		}
		error = in6_cga_generate(prepare_p, collision_count,
		    &ifra.ifra_addr.sin6_addr, ifp);
		in6_cga_node_unlock();
		if (error == 0) {
			ifra.ifra_flags |= IN6_IFF_SECURED;
			if (is_clat46) {
				ifra.ifra_flags |= IN6_IFF_CLAT46;
			}
		} else {
			if (!is_clat46) {
				nd6log0(error, "%s: no CGA available (%s) err=%d\n",
				    __func__, if_name(ifp), error);
			} else {
				nd6log0(error, "%s: no CLAT46 available (%s) err=%d\n",
				    __func__, if_name(ifp), error);
			}
			goto done;
		}
	}

	VERIFY(ia6 == NULL);

	/* new prefix mask. */
	ifra.ifra_prefixmask.sin6_len = sizeof(struct sockaddr_in6);
	ifra.ifra_prefixmask.sin6_family = AF_INET6;
	bcopy(&mask, &ifra.ifra_prefixmask.sin6_addr,
	    sizeof(ifra.ifra_prefixmask.sin6_addr));

	/* lifetimes. */
	ifra.ifra_lifetime.ia6t_vltime = pr->ndpr_vltime;
	ifra.ifra_lifetime.ia6t_pltime = pr->ndpr_pltime;

	/* address flags */
	ifra.ifra_flags |= IN6_IFF_AUTOCONF; /* obey autoconf */

	/*
	 * Make sure that we do not have this address already.  This should
	 * usually not happen, but we can still see this case, e.g., if we
	 * have manually configured the exact address to be configured.
	 */
	if ((ia6 = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr))
	    != NULL) {
		error = EEXIST;
		ifa_remref(&ia6->ia_ifa);
		ia6 = NULL;

		/* this should be rare enough to make an explicit log */
		log(LOG_INFO, "%s: %s is already configured!\n",
		    __func__, ip6_sprintf(&ifra.ifra_addr.sin6_addr));
		goto done;
	}

	/*
	 * Allocate ifaddr structure, link into chain, etc.
	 * If we are going to create a new address upon receiving a multicasted
	 * RA, we need to impose a random delay before starting DAD.
	 * [RFC 4862, Section 5.4.2]
	 */
	ifaupdate = IN6_IFAUPDATE_NOWAIT;
	if (mcast) {
		ifaupdate |= IN6_IFAUPDATE_DADDELAY;
	}
	error = in6_update_ifa(ifp, &ifra, ifaupdate, &ia6);
	if (error != 0) {
		nd6log0(error,
		    "%s: failed to make ifaddr %s on %s (errno=%d)\n",
		    __func__, ip6_sprintf(&ifra.ifra_addr.sin6_addr),
		    if_name(ifp), error);
		error = EADDRNOTAVAIL;
		goto done;
	} else {
		/* remember the collision count */
		ia6->ia6_cga_collision_count = collision_count;
	}

	VERIFY(ia6 != NULL);
	in6_post_msg(ifp, KEV_INET6_NEW_RTADV_ADDR, ia6, NULL, 0);
	goto done;

unlock1:
	NDPR_UNLOCK(pr);

done:
	*errorp = error;
	return ia6;
}

#define IA6_NONCONST(ifa) __DECONST(struct in6_ifaddr *, (ifa))

int
in6_tmpifadd(const struct in6_ifaddr *ia0, int forcegen)
{
	ifnet_ref_t ifp = ia0->ia_ifa.ifa_ifp;
	struct in6_ifaddr *__single ia, *__single newia;
	struct in6_aliasreq ifra;
	int i, error, ifaupdate;
	int trylimit = 3;       /* XXX: adhoc value */
	u_int32_t randid[2];
	uint32_t vltime0, pltime0;
	uint64_t timenow = net_uptime();
	struct in6_addr addr;
	struct nd_prefix *__single ndpr;

	bzero(&ifra, sizeof(ifra));
	strlcpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
	IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
	ifra.ifra_addr = ia0->ia_addr;
	/* copy prefix mask */
	ifra.ifra_prefixmask = ia0->ia_prefixmask;
	/* clear the old IFID */
	for (i = 0; i < 4; i++) {
		ifra.ifra_addr.sin6_addr.s6_addr32[i]
		        &= ifra.ifra_prefixmask.sin6_addr.s6_addr32[i];
	}
	addr = ia0->ia_addr.sin6_addr;
	IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);

again:
	in6_iid_mktmp(ifp, (u_int8_t *)randid,
	    (const u_int8_t *)&addr.s6_addr[8], forcegen);

	ifra.ifra_addr.sin6_addr.s6_addr32[2] |=
	    (randid[0] & ~(ifra.ifra_prefixmask.sin6_addr.s6_addr32[2]));
	ifra.ifra_addr.sin6_addr.s6_addr32[3] |=
	    (randid[1] & ~(ifra.ifra_prefixmask.sin6_addr.s6_addr32[3]));

	/*
	 * in6_iid_mktmp() quite likely provided a unique interface ID.
	 * However, we may still have a chance to see collision, because
	 * there may be a time lag between generation of the ID and generation
	 * of the address.  So, we'll do one more sanity check.
	 */
	if ((ia = in6ifa_ifpwithaddr(ifp, &ifra.ifra_addr.sin6_addr)) != NULL) {
		ifa_remref(&ia->ia_ifa);
		if (trylimit-- == 0) {
			nd6log(info, "in6_tmpifadd: failed to find "
			    "a unique random IFID\n");
			return EEXIST;
		}
		forcegen = 1;
		goto again;
	}

	/*
	 * The Valid Lifetime is the lower of the Valid Lifetime of the
	 * public address or TEMP_VALID_LIFETIME.
	 * The Preferred Lifetime is the lower of the Preferred Lifetime
	 * of the public address or TEMP_PREFERRED_LIFETIME -
	 * DESYNC_FACTOR.
	 */
	IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
	if (ia0->ia6_lifetime.ia6ti_vltime != ND6_INFINITE_LIFETIME) {
		vltime0 = IFA6_IS_INVALID(ia0, timenow) ? 0 :
		    (ia0->ia6_lifetime.ia6ti_vltime -
		    (uint32_t)(timenow - ia0->ia6_updatetime));
		if (vltime0 > ip6_temp_valid_lifetime) {
			vltime0 = ip6_temp_valid_lifetime;
		}
	} else {
		vltime0 = ip6_temp_valid_lifetime;
	}
	if (ia0->ia6_lifetime.ia6ti_pltime != ND6_INFINITE_LIFETIME) {
		pltime0 = IFA6_IS_DEPRECATED(ia0, timenow) ? 0 :
		    (ia0->ia6_lifetime.ia6ti_pltime -
		    (uint32_t)(timenow - ia0->ia6_updatetime));
		if (pltime0 > ip6_temp_preferred_lifetime - ip6_desync_factor) {
			pltime0 = ip6_temp_preferred_lifetime -
			    ip6_desync_factor;
		}
	} else {
		pltime0 = ip6_temp_preferred_lifetime - ip6_desync_factor;
	}
	ifra.ifra_lifetime.ia6t_vltime = vltime0;
	ifra.ifra_lifetime.ia6t_pltime = pltime0;
	IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
	/*
	 * A temporary address is created only if this calculated Preferred
	 * Lifetime is greater than REGEN_ADVANCE time units.
	 */
	if (ifra.ifra_lifetime.ia6t_pltime <= ip6_temp_regen_advance) {
		return 0;
	}

	/* XXX: scope zone ID? */

	ifra.ifra_flags |= (IN6_IFF_AUTOCONF | IN6_IFF_TEMPORARY);

	/* allocate ifaddr structure, link into chain, etc. */
	ifaupdate = IN6_IFAUPDATE_NOWAIT | IN6_IFAUPDATE_DADDELAY;
	error = in6_update_ifa(ifp, &ifra, ifaupdate, &newia);
	if (error != 0) {
		nd6log0(error, "%s: failed to add address. err=%d\n",
		    __func__, error);
		return error;
	}
	VERIFY(newia != NULL);

	IFA_LOCK(&IA6_NONCONST(ia0)->ia_ifa);
	ndpr = ia0->ia6_ndpr;
	if (ndpr == NULL) {
		/*
		 * We lost the race with another thread that has purged
		 * ia0 address; in this case, purge the tmp addr as well.
		 */
		nd6log0(error, "in6_tmpifadd: no public address\n");
		VERIFY(!(ia0->ia6_flags & IN6_IFF_AUTOCONF));
		IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
		in6_purgeaddr(&newia->ia_ifa);
		ifa_remref(&newia->ia_ifa);
		return EADDRNOTAVAIL;
	}
	NDPR_ADDREF(ndpr);      /* for us */
	IFA_UNLOCK(&IA6_NONCONST(ia0)->ia_ifa);
	IFA_LOCK(&newia->ia_ifa);
	if (newia->ia6_ndpr != NULL) {
		NDPR_LOCK(newia->ia6_ndpr);
		VERIFY(newia->ia6_ndpr->ndpr_addrcnt != 0);
		newia->ia6_ndpr->ndpr_addrcnt--;
		NDPR_UNLOCK(newia->ia6_ndpr);
		NDPR_REMREF(newia->ia6_ndpr);   /* release addr reference */
	}
	newia->ia6_ndpr = ndpr;
	NDPR_LOCK(newia->ia6_ndpr);
	newia->ia6_ndpr->ndpr_addrcnt++;
	VERIFY(newia->ia6_ndpr->ndpr_addrcnt != 0);
	NDPR_ADDREF(newia->ia6_ndpr);    /* for addr reference */
	NDPR_UNLOCK(newia->ia6_ndpr);
	IFA_UNLOCK(&newia->ia_ifa);
	/*
	 * A newly added address might affect the status of other addresses.
	 * XXX: when the temporary address is generated with a new public
	 * address, the onlink check is redundant.  However, it would be safe
	 * to do the check explicitly everywhere a new address is generated,
	 * and, in fact, we surely need the check when we create a new
	 * temporary address due to deprecation of an old temporary address.
	 */
	lck_mtx_lock(nd6_mutex);
	pfxlist_onlink_check();
	lck_mtx_unlock(nd6_mutex);
	ifa_remref(&newia->ia_ifa);

	/* remove our reference */
	NDPR_REMREF(ndpr);

	return 0;
}
#undef IA6_NONCONST

int
in6_init_prefix_ltimes(struct nd_prefix *ndpr)
{
	struct timeval caltime;
	u_int64_t timenow = net_uptime();

	NDPR_LOCK_ASSERT_HELD(ndpr);

	getmicrotime(&caltime);
	ndpr->ndpr_base_calendartime = caltime.tv_sec;
	ndpr->ndpr_base_uptime = timenow;

	/* check if preferred lifetime > valid lifetime.  RFC 4862 5.5.3 (c) */
	if (ndpr->ndpr_pltime > ndpr->ndpr_vltime) {
		nd6log(info, "in6_init_prefix_ltimes: preferred lifetime"
		    "(%d) is greater than valid lifetime(%d)\n",
		    (u_int)ndpr->ndpr_pltime, (u_int)ndpr->ndpr_vltime);
		return EINVAL;
	}
	if (ndpr->ndpr_pltime == ND6_INFINITE_LIFETIME) {
		ndpr->ndpr_preferred = 0;
	} else {
		ndpr->ndpr_preferred = timenow + ndpr->ndpr_pltime;
	}
	if (ndpr->ndpr_vltime == ND6_INFINITE_LIFETIME) {
		ndpr->ndpr_expire = 0;
	} else {
		ndpr->ndpr_expire = timenow + ndpr->ndpr_vltime;
	}

	return 0;
}

static void
in6_init_address_ltimes(struct in6_addrlifetime *lt6)
{
	uint64_t timenow = net_uptime();

	/* Valid lifetime must not be updated unless explicitly specified. */
	/* init ia6t_expire */
	if (lt6->ia6t_vltime == ND6_INFINITE_LIFETIME) {
		lt6->ia6t_expire = 0;
	} else {
		lt6->ia6t_expire = timenow;
		lt6->ia6t_expire += lt6->ia6t_vltime;
	}

	/* init ia6t_preferred */
	if (lt6->ia6t_pltime == ND6_INFINITE_LIFETIME) {
		lt6->ia6t_preferred = 0;
	} else {
		lt6->ia6t_preferred = timenow;
		lt6->ia6t_preferred += lt6->ia6t_pltime;
	}
}

/*
 * Delete all the routing table entries that use the specified gateway.
 * XXX: this function causes search through all entries of routing table, so
 * it shouldn't be called when acting as a router.
 *
 * This should really be working on entries that have a specific
 * parent route.
 */
void
rt6_flush(
	struct in6_addr *gateway,
	struct ifnet *ifp)
{
	radix_node_head_ref_t rnh = rt_tables[AF_INET6];

	/* We'll care only link-local addresses */
	if (!IN6_IS_ADDR_LINKLOCAL(gateway)) {
		return;
	}
	lck_mtx_lock(rnh_lock);
	/* XXX: hack for KAME's link-local address kludge */
	if (in6_embedded_scope) {
		gateway->s6_addr16[1] = htons(ifp->if_index);
	}

	rnh->rnh_walktree(rnh, rt6_deleteroute, (void *)gateway);
	lck_mtx_unlock(rnh_lock);
}

static int
rt6_deleteroute(
	struct radix_node *rn,
	void *arg)
{
	rtentry_ref_t rt = (struct rtentry *)rn;
	struct in6_addr *__single gate = (struct in6_addr *)arg;

	LCK_MTX_ASSERT(rnh_lock, LCK_MTX_ASSERT_OWNED);

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

	if (!IN6_ARE_ADDR_EQUAL(gate, &SIN6(rt->rt_gateway)->sin6_addr)) {
		RT_UNLOCK(rt);
		return 0;
	}
	/*
	 * Do not delete a static route.
	 * XXX: this seems to be a bit ad-hoc. Should we consider the
	 * 'cloned' bit instead?
	 */
	if ((rt->rt_flags & RTF_STATIC) != 0) {
		RT_UNLOCK(rt);
		return 0;
	}
	/*
	 * We delete only host route. This means, in particular, we don't
	 * delete default route.
	 */
	if ((rt->rt_flags & RTF_HOST) == 0) {
		RT_UNLOCK(rt);
		return 0;
	}

	/*
	 * Safe to drop rt_lock and use rt_key, rt_gateway, since holding
	 * rnh_lock here prevents another thread from calling rt_setgate()
	 * on this route.
	 */
	RT_UNLOCK(rt);
	return rtrequest_locked(RTM_DELETE, rt_key(rt), rt->rt_gateway,
	           rt_mask(rt), rt->rt_flags, 0);
}

int
nd6_setdefaultiface(
	int ifindex)
{
	int error = 0;
	ifnet_t def_ifp = NULL;

	LCK_MTX_ASSERT(nd6_mutex, LCK_MTX_ASSERT_NOTOWNED);

	ifnet_head_lock_shared();
	if (!IF_INDEX_IN_RANGE(ifindex)) {
		ifnet_head_done();
		return EINVAL;
	}
	def_ifp = ifindex2ifnet[ifindex];
	ifnet_head_done();

	lck_mtx_lock(nd6_mutex);
	if (nd6_defifindex != ifindex) {
		ifnet_ref_t odef_ifp = nd6_defifp;

		nd6_defifindex = ifindex;
		if (nd6_defifindex > 0) {
			nd6_defifp = def_ifp;
		} else {
			nd6_defifp = NULL;
		}

		if (nd6_defifp != NULL) {
			nd6log(info, "%s: is now the default "
			    "interface (was %s)\n", if_name(nd6_defifp),
			    odef_ifp != NULL ? if_name(odef_ifp) : "NONE");
		} else {
			nd6log(info, "No default interface set\n");
		}

		/*
		 * If the Default Router List is empty, install a route
		 * to the specified interface as default or remove the default
		 * route when the default interface becomes canceled.
		 * The check for the queue is actually redundant, but
		 * we do this here to avoid re-install the default route
		 * if the list is NOT empty.
		 */
		if (odef_ifp != NULL) {
			defrouter_select(odef_ifp, NULL);
		}

		if (nd6_defifp != NULL) {
			defrouter_select(nd6_defifp, NULL);
			nd6_prefix_sync(nd6_defifp);
		}

		/*
		 * XXX For now we managed RTI routes as un-scoped.
		 * Therefore we ignore the change in nd6_defifindex
		 * for RTI routes for now.
		 */
		/*
		 * Our current implementation assumes one-to-one mapping between
		 * interfaces and links, so it would be natural to use the
		 * default interface as the default link.
		 */
		scope6_setdefault(nd6_defifp);
	}
	lck_mtx_unlock(nd6_mutex);
	return error;
}