icmp6.c (revision b925d719678210b76adeb105f5f4b41550eb6bb4) - OpenGrok cross reference for /freebsd/sys/netinet6/icmp6.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	$KAME: icmp6.c,v 1.211 2001/04/04 05:56:20 itojun Exp $
 */

/*-
 * Copyright (c) 1982, 1986, 1988, 1993
 *	The Regents of the University of California.  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 University 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 REGENTS 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 REGENTS 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/cdefs.h>
#define	MBUF_PRIVATE	/* XXXRW: Optimisation tries to avoid M_EXT mbufs */

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

#include <sys/param.h>
#include <sys/domain.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/signalvar.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sx.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/time.h>

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

#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet/tcp_var.h>

#include <netinet6/in6_fib.h>
#include <netinet6/in6_ifattach.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/mld6_var.h>
#include <netinet6/nd6.h>
#include <netinet6/send.h>

extern ip6proto_ctlinput_t	*ip6_ctlprotox[];

VNET_PCPUSTAT_DEFINE(struct icmp6stat, icmp6stat);
VNET_PCPUSTAT_SYSINIT(icmp6stat);
SYSCTL_VNET_PCPUSTAT(_net_inet6_icmp6, ICMPV6CTL_STATS, stats,
    struct icmp6stat, icmp6stat,
    "ICMPv6 statistics (struct icmp6stat, netinet/icmp6.h)");

#ifdef VIMAGE
VNET_PCPUSTAT_SYSUNINIT(icmp6stat);
#endif /* VIMAGE */

VNET_DEFINE_STATIC(int, icmp6_rediraccept) = 1;
#define	V_icmp6_rediraccept	VNET(icmp6_rediraccept)
SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_REDIRACCEPT, rediraccept,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6_rediraccept), 0,
    "Accept ICMPv6 redirect messages");

VNET_DEFINE_STATIC(int, icmp6_redirtimeout) = 10 * 60;	/* 10 minutes */
#define	V_icmp6_redirtimeout	VNET(icmp6_redirtimeout)
SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_REDIRTIMEOUT, redirtimeout,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6_redirtimeout), 0,
    "Delay in seconds before expiring redirect route");

VNET_DEFINE_STATIC(int, icmp6_nodeinfo) = 0;
#define	V_icmp6_nodeinfo	VNET(icmp6_nodeinfo)
SYSCTL_INT(_net_inet6_icmp6, ICMPV6CTL_NODEINFO, nodeinfo,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6_nodeinfo), 0,
    "Mask of enabled RFC4620 node information query types");

VNET_DECLARE(struct inpcbinfo, ripcbinfo);
#define	V_ripcbinfo		VNET(ripcbinfo)

static void icmp6_errcount(int, int);
static int icmp6_rip6_input(struct mbuf **, int);
static void icmp6_reflect(struct mbuf *, size_t);
static const char *icmp6_redirect_diag(struct in6_addr *,
	struct in6_addr *, struct in6_addr *);
static struct mbuf *ni6_input(struct mbuf *, int, struct prison *);
static struct mbuf *ni6_nametodns(const char *, int, int);
static int ni6_dnsmatch(const char *, int, const char *, int);
static int ni6_addrs(struct icmp6_nodeinfo *, struct mbuf *,
			  struct ifnet **, struct in6_addr *);
static int ni6_store_addrs(struct icmp6_nodeinfo *, struct icmp6_nodeinfo *,
				struct ifnet *, int);
static int icmp6_notify_error(struct mbuf **, int, int);

/*
 * Kernel module interface for updating icmp6stat.  The argument is an index
 * into icmp6stat treated as an array of u_quad_t.  While this encodes the
 * general layout of icmp6stat into the caller, it doesn't encode its
 * location, so that future changes to add, for example, per-CPU stats
 * support won't cause binary compatibility problems for kernel modules.
 */
void
kmod_icmp6stat_inc(int statnum)
{

	counter_u64_add(VNET(icmp6stat)[statnum], 1);
}

static void
icmp6_errcount(int type, int code)
{
	switch (type) {
	case ICMP6_DST_UNREACH:
		switch (code) {
		case ICMP6_DST_UNREACH_NOROUTE:
			ICMP6STAT_INC(icp6s_odst_unreach_noroute);
			return;
		case ICMP6_DST_UNREACH_ADMIN:
			ICMP6STAT_INC(icp6s_odst_unreach_admin);
			return;
		case ICMP6_DST_UNREACH_BEYONDSCOPE:
			ICMP6STAT_INC(icp6s_odst_unreach_beyondscope);
			return;
		case ICMP6_DST_UNREACH_ADDR:
			ICMP6STAT_INC(icp6s_odst_unreach_addr);
			return;
		case ICMP6_DST_UNREACH_NOPORT:
			ICMP6STAT_INC(icp6s_odst_unreach_noport);
			return;
		}
		break;
	case ICMP6_PACKET_TOO_BIG:
		ICMP6STAT_INC(icp6s_opacket_too_big);
		return;
	case ICMP6_TIME_EXCEEDED:
		switch (code) {
		case ICMP6_TIME_EXCEED_TRANSIT:
			ICMP6STAT_INC(icp6s_otime_exceed_transit);
			return;
		case ICMP6_TIME_EXCEED_REASSEMBLY:
			ICMP6STAT_INC(icp6s_otime_exceed_reassembly);
			return;
		}
		break;
	case ICMP6_PARAM_PROB:
		switch (code) {
		case ICMP6_PARAMPROB_HEADER:
			ICMP6STAT_INC(icp6s_oparamprob_header);
			return;
		case ICMP6_PARAMPROB_NEXTHEADER:
			ICMP6STAT_INC(icp6s_oparamprob_nextheader);
			return;
		case ICMP6_PARAMPROB_OPTION:
			ICMP6STAT_INC(icp6s_oparamprob_option);
			return;
		}
		break;
	case ND_REDIRECT:
		ICMP6STAT_INC(icp6s_oredirect);
		return;
	}
	ICMP6STAT_INC(icp6s_ounknown);
}

/*
 * A wrapper function for icmp6_error() necessary when the erroneous packet
 * may not contain enough scope zone information.
 */
void
icmp6_error2(struct mbuf *m, int type, int code, int param,
    struct ifnet *ifp)
{
	struct ip6_hdr *ip6;

	if (ifp == NULL)
		return;

	if (m->m_len < sizeof(struct ip6_hdr)) {
		m = m_pullup(m, sizeof(struct ip6_hdr));
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			return;
		}
	}
	ip6 = mtod(m, struct ip6_hdr *);

	if (in6_setscope(&ip6->ip6_src, ifp, NULL) != 0)
		return;
	if (in6_setscope(&ip6->ip6_dst, ifp, NULL) != 0)
		return;

	icmp6_error(m, type, code, param);
}

/*
 * Generate an error packet of type error in response to bad IP6 packet.
 */
void
icmp6_error(struct mbuf *m, int type, int code, int param)
{
	struct ip6_hdr *oip6, *nip6;
	struct icmp6_hdr *icmp6;
	struct epoch_tracker et;
	u_int preplen;
	int off;
	int nxt;

	ICMP6STAT_INC(icp6s_error);

	/* count per-type-code statistics */
	icmp6_errcount(type, code);

#ifdef M_DECRYPTED	/*not openbsd*/
	if (m->m_flags & M_DECRYPTED) {
		ICMP6STAT_INC(icp6s_canterror);
		goto freeit;
	}
#endif

	if (m->m_len < sizeof(struct ip6_hdr)) {
		m = m_pullup(m, sizeof(struct ip6_hdr));
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			return;
		}
	}
	oip6 = mtod(m, struct ip6_hdr *);

	/*
	 * If the destination address of the erroneous packet is a multicast
	 * address, or the packet was sent using link-layer multicast,
	 * we should basically suppress sending an error (RFC 2463, Section
	 * 2.4).
	 * We have two exceptions (the item e.2 in that section):
	 * - the Packet Too Big message can be sent for path MTU discovery.
	 * - the Parameter Problem Message that can be allowed an icmp6 error
	 *   in the option type field.  This check has been done in
	 *   ip6_unknown_opt(), so we can just check the type and code.
	 */
	if ((m->m_flags & (M_BCAST|M_MCAST) ||
	     IN6_IS_ADDR_MULTICAST(&oip6->ip6_dst)) &&
	    (type != ICMP6_PACKET_TOO_BIG &&
	     (type != ICMP6_PARAM_PROB ||
	      code != ICMP6_PARAMPROB_OPTION)))
		goto freeit;

	/*
	 * RFC 2463, 2.4 (e.5): source address check.
	 * XXX: the case of anycast source?
	 */
	if (IN6_IS_ADDR_UNSPECIFIED(&oip6->ip6_src) ||
	    IN6_IS_ADDR_MULTICAST(&oip6->ip6_src))
		goto freeit;

	/*
	 * If we are about to send ICMPv6 against ICMPv6 error/redirect,
	 * don't do it.
	 */
	nxt = -1;
	off = ip6_lasthdr(m, 0, IPPROTO_IPV6, &nxt);
	if (off >= 0 && nxt == IPPROTO_ICMPV6) {
		struct icmp6_hdr *icp;

		if (m->m_len < off + sizeof(struct icmp6_hdr)) {
			m = m_pullup(m, off + sizeof(struct icmp6_hdr));
			if (m == NULL) {
				IP6STAT_INC(ip6s_exthdrtoolong);
				return;
			}
		}
		oip6 = mtod(m, struct ip6_hdr *);
		icp = (struct icmp6_hdr *)(mtod(m, caddr_t) + off);

		if (icp->icmp6_type < ICMP6_ECHO_REQUEST ||
		    icp->icmp6_type == ND_REDIRECT) {
			/*
			 * ICMPv6 error
			 * Special case: for redirect (which is
			 * informational) we must not send icmp6 error.
			 */
			ICMP6STAT_INC(icp6s_canterror);
			goto freeit;
		} else {
			/* ICMPv6 informational - send the error */
		}
	} else {
		/* non-ICMPv6 - send the error */
	}

	/* Finally, do rate limitation check. */
	if (icmp6_ratelimit(&oip6->ip6_src, type, code))
		goto freeit;

	/*
	 * OK, ICMP6 can be generated.
	 */

	if (m->m_pkthdr.len >= ICMPV6_PLD_MAXLEN)
		m_adj(m, ICMPV6_PLD_MAXLEN - m->m_pkthdr.len);

	preplen = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
	M_PREPEND(m, preplen, M_NOWAIT);	/* FIB is also copied over. */
	if (m == NULL) {
		nd6log((LOG_DEBUG, "ENOBUFS in icmp6_error %d\n", __LINE__));
		return;
	}

	nip6 = mtod(m, struct ip6_hdr *);
	nip6->ip6_src  = oip6->ip6_src;
	nip6->ip6_dst  = oip6->ip6_dst;

	in6_clearscope(&oip6->ip6_src);
	in6_clearscope(&oip6->ip6_dst);

	icmp6 = (struct icmp6_hdr *)(nip6 + 1);
	icmp6->icmp6_type = type;
	icmp6->icmp6_code = code;
	icmp6->icmp6_pptr = htonl((u_int32_t)param);

	ICMP6STAT_INC2(icp6s_outhist, type);
	NET_EPOCH_ENTER(et);
	icmp6_reflect(m, sizeof(struct ip6_hdr)); /* header order: IPv6 - ICMPv6 */
	NET_EPOCH_EXIT(et);

	return;

  freeit:
	/*
	 * If we can't tell whether or not we can generate ICMP6, free it.
	 */
	m_freem(m);
}

int
icmp6_errmap(const struct icmp6_hdr *icmp6)
{

	switch (icmp6->icmp6_type) {
	case ICMP6_DST_UNREACH:
		switch (icmp6->icmp6_code) {
		case ICMP6_DST_UNREACH_NOROUTE:
		case ICMP6_DST_UNREACH_ADDR:
			return (EHOSTUNREACH);
		case ICMP6_DST_UNREACH_NOPORT:
		case ICMP6_DST_UNREACH_ADMIN:
			return (ECONNREFUSED);
		case ICMP6_DST_UNREACH_BEYONDSCOPE:
			return (ENOPROTOOPT);
		default:
			return (0);	/* Shouldn't happen. */
		}
	case ICMP6_PACKET_TOO_BIG:
		return (EMSGSIZE);
	case ICMP6_TIME_EXCEEDED:
		switch (icmp6->icmp6_code) {
		case ICMP6_TIME_EXCEED_TRANSIT:
			return (EHOSTUNREACH);
		case ICMP6_TIME_EXCEED_REASSEMBLY:
			return (0);
		default:
			return (0);	/* Shouldn't happen. */
		}
	case ICMP6_PARAM_PROB:
		switch (icmp6->icmp6_code) {
		case ICMP6_PARAMPROB_NEXTHEADER:
			return (ECONNREFUSED);
		case ICMP6_PARAMPROB_HEADER:
		case ICMP6_PARAMPROB_OPTION:
			return (ENOPROTOOPT);
		default:
			return (0);	/* Shouldn't happen. */
		}
	default:
		return (0);
	}
}

/*
 * Process a received ICMP6 message.
 */
int
icmp6_input(struct mbuf **mp, int *offp, int proto)
{
	struct mbuf *m, *n;
	struct ifnet *ifp;
	struct ip6_hdr *ip6, *nip6;
	struct icmp6_hdr *icmp6, *nicmp6;
	char ip6bufs[INET6_ADDRSTRLEN], ip6bufd[INET6_ADDRSTRLEN];
	int code, error, icmp6len, ip6len, noff, off, sum;

	NET_EPOCH_ASSERT();

	m = *mp;
	off = *offp;

	if (m->m_len < off + sizeof(struct icmp6_hdr)) {
		m = m_pullup(m, off + sizeof(struct icmp6_hdr));
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			*mp = m;
			return (IPPROTO_DONE);
		}
	}

	/*
	 * Locate icmp6 structure in mbuf, and check
	 * that not corrupted and of at least minimum length
	 */

	icmp6len = m->m_pkthdr.len - off;
	if (icmp6len < sizeof(struct icmp6_hdr)) {
		ICMP6STAT_INC(icp6s_tooshort);
		goto freeit;
	}

	ip6 = mtod(m, struct ip6_hdr *);
	ifp = m->m_pkthdr.rcvif;
	/*
	 * Check multicast group membership.
	 * Note: SSM filters are not applied for ICMPv6 traffic.
	 */
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		struct in6_multi	*inm;

		inm = in6m_lookup(ifp, &ip6->ip6_dst);
		if (inm == NULL) {
			IP6STAT_INC(ip6s_notmember);
			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
			goto freeit;
		}
	}

	/* Calculate the checksum. */
	icmp6 = (struct icmp6_hdr *)((caddr_t)ip6 + off);
	code = icmp6->icmp6_code;
	if ((sum = in6_cksum(m, IPPROTO_ICMPV6, off, icmp6len)) != 0) {
		nd6log((LOG_ERR,
		    "ICMP6 checksum error(%d|%x) %s\n",
		    icmp6->icmp6_type, sum,
		    ip6_sprintf(ip6bufs, &ip6->ip6_src)));
		ICMP6STAT_INC(icp6s_checksum);
		goto freeit;
	}

	ICMP6STAT_INC2(icp6s_inhist, icmp6->icmp6_type);
	icmp6_ifstat_inc(ifp, ifs6_in_msg);
	if (icmp6->icmp6_type < ICMP6_INFOMSG_MASK)
		icmp6_ifstat_inc(ifp, ifs6_in_error);

	ip6len = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen);
	switch (icmp6->icmp6_type) {
	case ICMP6_DST_UNREACH:
		icmp6_ifstat_inc(ifp, ifs6_in_dstunreach);
		switch (code) {
		case ICMP6_DST_UNREACH_ADMIN:
			icmp6_ifstat_inc(ifp, ifs6_in_adminprohib);
		case ICMP6_DST_UNREACH_NOROUTE:
		case ICMP6_DST_UNREACH_ADDR:
		case ICMP6_DST_UNREACH_BEYONDSCOPE:
		case ICMP6_DST_UNREACH_NOPORT:
			goto deliver;
		default:
			goto badcode;
		}
	case ICMP6_PACKET_TOO_BIG:
		icmp6_ifstat_inc(ifp, ifs6_in_pkttoobig);
		/*
		 * Validation is made in icmp6_mtudisc_update.
		 * Updating the path MTU will be done after examining
		 * intermediate extension headers.
		 */
		goto deliver;
	case ICMP6_TIME_EXCEEDED:
		icmp6_ifstat_inc(ifp, ifs6_in_timeexceed);
		switch (code) {
		case ICMP6_TIME_EXCEED_TRANSIT:
		case ICMP6_TIME_EXCEED_REASSEMBLY:
			goto deliver;
		default:
			goto badcode;
		}
	case ICMP6_PARAM_PROB:
		icmp6_ifstat_inc(ifp, ifs6_in_paramprob);
		switch (code) {
		case ICMP6_PARAMPROB_NEXTHEADER:
		case ICMP6_PARAMPROB_HEADER:
		case ICMP6_PARAMPROB_OPTION:
			goto deliver;
		default:
			goto badcode;
		}
	case ICMP6_ECHO_REQUEST:
		icmp6_ifstat_inc(ifp, ifs6_in_echo);
		if (code != 0)
			goto badcode;
		if (icmp6_ratelimit(&ip6->ip6_src, ICMP6_ECHO_REPLY, 0))
			break;
		if ((n = m_copym(m, 0, M_COPYALL, M_NOWAIT)) == NULL) {
			/* Give up remote */
			break;
		}
		if (!M_WRITABLE(n)
		 || n->m_len < off + sizeof(struct icmp6_hdr)) {
			struct mbuf *n0 = n;
			int n0len;

			CTASSERT(sizeof(*nip6) + sizeof(*nicmp6) <= MHLEN);
			n = m_gethdr(M_NOWAIT, n0->m_type);
			if (n == NULL) {
				/* Give up remote */
				m_freem(n0);
				break;
			}

			m_move_pkthdr(n, n0);	/* FIB copied. */
			n0len = n0->m_pkthdr.len;	/* save for use below */
			/*
			 * Copy IPv6 and ICMPv6 only.
			 */
			nip6 = mtod(n, struct ip6_hdr *);
			bcopy(ip6, nip6, sizeof(struct ip6_hdr));
			nicmp6 = (struct icmp6_hdr *)(nip6 + 1);
			bcopy(icmp6, nicmp6, sizeof(struct icmp6_hdr));
			noff = sizeof(struct ip6_hdr);
			/* new mbuf contains only ipv6+icmpv6 headers */
			n->m_len = noff + sizeof(struct icmp6_hdr);
			/*
			 * Adjust mbuf.  ip6_plen will be adjusted in
			 * ip6_output().
			 */
			m_adj(n0, off + sizeof(struct icmp6_hdr));
			/* recalculate complete packet size */
			n->m_pkthdr.len = n0len + (noff - off);
			n->m_next = n0;
		} else {
			if (n->m_len < off + sizeof(*nicmp6)) {
				n = m_pullup(n, off + sizeof(*nicmp6));
				if (n == NULL) {
					IP6STAT_INC(ip6s_exthdrtoolong);
					break;
				}
			}
			nicmp6 = (struct icmp6_hdr *)(mtod(n, caddr_t) + off);
			noff = off;
		}
		if (n) {
			nicmp6->icmp6_type = ICMP6_ECHO_REPLY;
			nicmp6->icmp6_code = 0;
			ICMP6STAT_INC(icp6s_reflect);
			ICMP6STAT_INC2(icp6s_outhist, ICMP6_ECHO_REPLY);
			icmp6_reflect(n, noff);
		}
		break;

	case ICMP6_ECHO_REPLY:
		icmp6_ifstat_inc(ifp, ifs6_in_echoreply);
		if (code != 0)
			goto badcode;
		break;

	case MLD_LISTENER_QUERY:
	case MLD_LISTENER_REPORT:
	case MLD_LISTENER_DONE:
	case MLDV2_LISTENER_REPORT:
		/*
		 * Drop MLD traffic which is not link-local, has a hop limit
		 * of greater than 1 hop, or which does not have the
		 * IPv6 HBH Router Alert option.
		 * As IPv6 HBH options are stripped in ip6_input() we must
		 * check an mbuf header flag.
		 * XXX Should we also sanity check that these messages
		 * were directed to a link-local multicast prefix?
		 */
		if ((ip6->ip6_hlim != 1) || (m->m_flags & M_RTALERT_MLD) == 0)
			goto freeit;
		if (mld_input(&m, off, icmp6len) != 0) {
			*mp = NULL;
			return (IPPROTO_DONE);
		}
		/* m stays. */
		break;

	case ICMP6_WRUREQUEST:	/* ICMP6_FQDN_QUERY */
	    {
		enum { WRU, FQDN } mode;
		struct prison *pr;

		if (!V_icmp6_nodeinfo)
			break;

		if (icmp6len == sizeof(struct icmp6_hdr) + 4)
			mode = WRU;
		else if (icmp6len >= sizeof(struct icmp6_nodeinfo))
			mode = FQDN;
		else
			goto badlen;

		pr = NULL;
		sx_slock(&allprison_lock);
		TAILQ_FOREACH(pr, &allprison, pr_list)
			if (pr->pr_vnet == ifp->if_vnet)
				break;
		sx_sunlock(&allprison_lock);
		if (pr == NULL)
			pr = curthread->td_ucred->cr_prison;
		if (mode == FQDN) {
			if (m->m_len < off + sizeof(struct icmp6_nodeinfo)) {
				m = m_pullup(m, off +
				    sizeof(struct icmp6_nodeinfo));
				if (m == NULL) {
					IP6STAT_INC(ip6s_exthdrtoolong);
					*mp = m;
					return (IPPROTO_DONE);
				}
			}
			n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
			if (n)
				n = ni6_input(n, off, pr);
			/* XXX meaningless if n == NULL */
			noff = sizeof(struct ip6_hdr);
		} else {
			u_char *p;
			int maxhlen, hlen;

			/*
			 * XXX: this combination of flags is pointless,
			 * but should we keep this for compatibility?
			 */
			if ((V_icmp6_nodeinfo & (ICMP6_NODEINFO_FQDNOK |
			    ICMP6_NODEINFO_TMPADDROK)) !=
			    (ICMP6_NODEINFO_FQDNOK | ICMP6_NODEINFO_TMPADDROK))
				break;

			if (code != 0)
				goto badcode;

			CTASSERT(sizeof(*nip6) + sizeof(*nicmp6) + 4 <= MHLEN);
			n = m_gethdr(M_NOWAIT, m->m_type);
			if (n == NULL) {
				/* Give up remote */
				break;
			}
			if (!m_dup_pkthdr(n, m, M_NOWAIT)) {
				/*
				 * Previous code did a blind M_COPY_PKTHDR
				 * and said "just for rcvif".  If true, then
				 * we could tolerate the dup failing (due to
				 * the deep copy of the tag chain).  For now
				 * be conservative and just fail.
				 */
				m_free(n);
				n = NULL;
				break;
			}
			/*
			 * Copy IPv6 and ICMPv6 only.
			 */
			nip6 = mtod(n, struct ip6_hdr *);
			bcopy(ip6, nip6, sizeof(struct ip6_hdr));
			nicmp6 = (struct icmp6_hdr *)(nip6 + 1);
			bcopy(icmp6, nicmp6, sizeof(struct icmp6_hdr));
			p = (u_char *)(nicmp6 + 1);
			bzero(p, 4);

			maxhlen = M_TRAILINGSPACE(n) -
			    (sizeof(*nip6) + sizeof(*nicmp6) + 4);
			mtx_lock(&pr->pr_mtx);
			hlen = strlen(pr->pr_hostname);
			if (maxhlen > hlen)
				maxhlen = hlen;
			/* meaningless TTL */
			bcopy(pr->pr_hostname, p + 4, maxhlen);
			mtx_unlock(&pr->pr_mtx);
			noff = sizeof(struct ip6_hdr);
			n->m_pkthdr.len = n->m_len = sizeof(struct ip6_hdr) +
				sizeof(struct icmp6_hdr) + 4 + maxhlen;
			nicmp6->icmp6_type = ICMP6_WRUREPLY;
			nicmp6->icmp6_code = 0;
		}
		if (n) {
			ICMP6STAT_INC(icp6s_reflect);
			ICMP6STAT_INC2(icp6s_outhist, ICMP6_WRUREPLY);
			icmp6_reflect(n, noff);
		}
		break;
	    }

	case ICMP6_WRUREPLY:
		if (code != 0)
			goto badcode;
		break;

	case ND_ROUTER_SOLICIT:
		icmp6_ifstat_inc(ifp, ifs6_in_routersolicit);
		if (code != 0)
			goto badcode;
		if (icmp6len < sizeof(struct nd_router_solicit))
			goto badlen;
		if (send_sendso_input_hook != NULL) {
			if (m->m_len < off + icmp6len) {
				m = m_pullup(m, off + icmp6len);
				if (m == NULL) {
					IP6STAT_INC(ip6s_exthdrtoolong);
					*mp = NULL;
					return (IPPROTO_DONE);
				}
			}
			error = send_sendso_input_hook(m, ifp, SND_IN, ip6len);
			if (error == 0) {
				m = NULL;
				goto freeit;
			}
		}
		n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		nd6_rs_input(m, off, icmp6len);
		m = n;
		if (m == NULL)
			goto freeit;
		break;

	case ND_ROUTER_ADVERT:
		icmp6_ifstat_inc(ifp, ifs6_in_routeradvert);
		if (code != 0)
			goto badcode;
		if (icmp6len < sizeof(struct nd_router_advert))
			goto badlen;
		if (send_sendso_input_hook != NULL) {
			error = send_sendso_input_hook(m, ifp, SND_IN, ip6len);
			if (error == 0) {
				m = NULL;
				goto freeit;
			}
		}
		n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		nd6_ra_input(m, off, icmp6len);
		m = n;
		if (m == NULL)
			goto freeit;
		break;

	case ND_NEIGHBOR_SOLICIT:
		icmp6_ifstat_inc(ifp, ifs6_in_neighborsolicit);
		if (code != 0)
			goto badcode;
		if (icmp6len < sizeof(struct nd_neighbor_solicit))
			goto badlen;
		if (send_sendso_input_hook != NULL) {
			error = send_sendso_input_hook(m, ifp, SND_IN, ip6len);
			if (error == 0) {
				m = NULL;
				goto freeit;
			}
		}
		n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		nd6_ns_input(m, off, icmp6len);
		m = n;
		if (m == NULL)
			goto freeit;
		break;

	case ND_NEIGHBOR_ADVERT:
		icmp6_ifstat_inc(ifp, ifs6_in_neighboradvert);
		if (code != 0)
			goto badcode;
		if (icmp6len < sizeof(struct nd_neighbor_advert))
			goto badlen;
		if (send_sendso_input_hook != NULL) {
			error = send_sendso_input_hook(m, ifp, SND_IN, ip6len);
			if (error == 0) {
				m = NULL;
				goto freeit;
			}
		}
		n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		nd6_na_input(m, off, icmp6len);
		m = n;
		if (m == NULL)
			goto freeit;
		break;

	case ND_REDIRECT:
		icmp6_ifstat_inc(ifp, ifs6_in_redirect);
		if (code != 0)
			goto badcode;
		if (icmp6len < sizeof(struct nd_redirect))
			goto badlen;
		if (send_sendso_input_hook != NULL) {
			error = send_sendso_input_hook(m, ifp, SND_IN, ip6len);
			if (error == 0) {
				m = NULL;
				goto freeit;
			}
		}
		n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		icmp6_redirect_input(m, off);
		m = n;
		if (m == NULL)
			goto freeit;
		break;

	case ICMP6_ROUTER_RENUMBERING:
		if (code != ICMP6_ROUTER_RENUMBERING_COMMAND &&
		    code != ICMP6_ROUTER_RENUMBERING_RESULT)
			goto badcode;
		if (icmp6len < sizeof(struct icmp6_router_renum))
			goto badlen;
		break;

	default:
		nd6log((LOG_DEBUG,
		    "icmp6_input: unknown type %d(src=%s, dst=%s, ifid=%d)\n",
		    icmp6->icmp6_type, ip6_sprintf(ip6bufs, &ip6->ip6_src),
		    ip6_sprintf(ip6bufd, &ip6->ip6_dst),
		    ifp ? ifp->if_index : 0));
		if (icmp6->icmp6_type < ICMP6_ECHO_REQUEST) {
			/* ICMPv6 error: MUST deliver it by spec... */
			goto deliver;
		} else {
			/* ICMPv6 informational: MUST not deliver */
			break;
		}
	deliver:
		if (icmp6_notify_error(&m, off, icmp6len) != 0) {
			/* In this case, m should've been freed. */
			*mp = NULL;
			return (IPPROTO_DONE);
		}
		break;

	badcode:
		ICMP6STAT_INC(icp6s_badcode);
		break;

	badlen:
		ICMP6STAT_INC(icp6s_badlen);
		break;
	}

	/* deliver the packet to appropriate sockets */
	icmp6_rip6_input(&m, *offp);

	*mp = m;
	return (IPPROTO_DONE);

 freeit:
	m_freem(m);
	*mp = NULL;
	return (IPPROTO_DONE);
}

static int
icmp6_notify_error(struct mbuf **mp, int off, int icmp6len)
{
	struct mbuf *m;
	struct icmp6_hdr *icmp6;
	struct ip6_hdr *eip6;
	u_int32_t notifymtu;
	struct sockaddr_in6 icmp6src, icmp6dst;

	m = *mp;

	if (icmp6len < sizeof(struct icmp6_hdr) + sizeof(struct ip6_hdr)) {
		ICMP6STAT_INC(icp6s_tooshort);
		goto freeit;
	}

	if (m->m_len < off + sizeof(*icmp6) + sizeof(struct ip6_hdr)) {
		m = m_pullup(m, off + sizeof(*icmp6) + sizeof(struct ip6_hdr));
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			*mp = m;
			return (-1);
		}
	}
	icmp6 = (struct icmp6_hdr *)(mtod(m, caddr_t) + off);
	eip6 = (struct ip6_hdr *)(icmp6 + 1);
	bzero(&icmp6dst, sizeof(icmp6dst));

	/* Detect the upper level protocol */
	{
		u_int8_t nxt = eip6->ip6_nxt;
		int eoff = off + sizeof(struct icmp6_hdr) +
		    sizeof(struct ip6_hdr);
		struct ip6ctlparam ip6cp;
		int icmp6type = icmp6->icmp6_type;
		struct ip6_frag *fh;
		struct ip6_rthdr *rth;
		struct ip6_rthdr0 *rth0;
		int rthlen;

		while (1) { /* XXX: should avoid infinite loop explicitly? */
			struct ip6_ext *eh;

			switch (nxt) {
			case IPPROTO_HOPOPTS:
			case IPPROTO_DSTOPTS:
			case IPPROTO_AH:
				if (m->m_len < eoff + sizeof(struct ip6_ext)) {
					m = m_pullup(m, eoff +
					    sizeof(struct ip6_ext));
					if (m == NULL) {
						IP6STAT_INC(ip6s_exthdrtoolong);
						*mp = m;
						return (-1);
					}
				}
				eh = (struct ip6_ext *)
				    (mtod(m, caddr_t) + eoff);
				if (nxt == IPPROTO_AH)
					eoff += (eh->ip6e_len + 2) << 2;
				else
					eoff += (eh->ip6e_len + 1) << 3;
				nxt = eh->ip6e_nxt;
				break;
			case IPPROTO_ROUTING:
				/*
				 * When the erroneous packet contains a
				 * routing header, we should examine the
				 * header to determine the final destination.
				 * Otherwise, we can't properly update
				 * information that depends on the final
				 * destination (e.g. path MTU).
				 */
				if (m->m_len < eoff + sizeof(*rth)) {
					m = m_pullup(m, eoff + sizeof(*rth));
					if (m == NULL) {
						IP6STAT_INC(ip6s_exthdrtoolong);
						*mp = m;
						return (-1);
					}
				}
				rth = (struct ip6_rthdr *)
				    (mtod(m, caddr_t) + eoff);
				rthlen = (rth->ip6r_len + 1) << 3;
				/*
				 * XXX: currently there is no
				 * officially defined type other
				 * than type-0.
				 * Note that if the segment left field
				 * is 0, all intermediate hops must
				 * have been passed.
				 */
				if (rth->ip6r_segleft &&
				    rth->ip6r_type == IPV6_RTHDR_TYPE_0) {
					int hops;

					if (m->m_len < eoff + rthlen) {
						m = m_pullup(m, eoff + rthlen);
						if (m == NULL) {
							IP6STAT_INC(
							    ip6s_exthdrtoolong);
							*mp = m;
							return (-1);
						}
					}
					rth0 = (struct ip6_rthdr0 *)
					    (mtod(m, caddr_t) + eoff);

					/* just ignore a bogus header */
					if ((rth0->ip6r0_len % 2) == 0 &&
					    (hops = rth0->ip6r0_len/2))
						icmp6dst.sin6_addr = *((struct in6_addr *)(rth0 + 1) + (hops - 1));
				}
				eoff += rthlen;
				nxt = rth->ip6r_nxt;
				break;
			case IPPROTO_FRAGMENT:
				if (m->m_len < eoff + sizeof(struct ip6_frag)) {
					m = m_pullup(m, eoff +
					    sizeof(struct ip6_frag));
					if (m == NULL) {
						IP6STAT_INC(ip6s_exthdrtoolong);
						*mp = m;
						return (-1);
					}
				}
				fh = (struct ip6_frag *)(mtod(m, caddr_t) +
				    eoff);
				/*
				 * Data after a fragment header is meaningless
				 * unless it is the first fragment, but
				 * we'll go to the notify label for path MTU
				 * discovery.
				 */
				if (fh->ip6f_offlg & IP6F_OFF_MASK)
					goto notify;

				eoff += sizeof(struct ip6_frag);
				nxt = fh->ip6f_nxt;
				break;
			default:
				/*
				 * This case includes ESP and the No Next
				 * Header.  In such cases going to the notify
				 * label does not have any meaning
				 * (i.e. ctlfunc will be NULL), but we go
				 * anyway since we might have to update
				 * path MTU information.
				 */
				goto notify;
			}
		}
	  notify:
		icmp6 = (struct icmp6_hdr *)(mtod(m, caddr_t) + off);

		/*
		 * retrieve parameters from the inner IPv6 header, and convert
		 * them into sockaddr structures.
		 * XXX: there is no guarantee that the source or destination
		 * addresses of the inner packet are in the same scope as
		 * the addresses of the icmp packet.  But there is no other
		 * way to determine the zone.
		 */
		eip6 = (struct ip6_hdr *)(icmp6 + 1);

		/*
		 * Protocol layers can't do anything useful with unspecified
		 * addresses.
		 */
		if (IN6_IS_ADDR_UNSPECIFIED(&eip6->ip6_src) ||
		    IN6_IS_ADDR_UNSPECIFIED(&eip6->ip6_dst))
			goto freeit;

		icmp6dst.sin6_len = sizeof(struct sockaddr_in6);
		icmp6dst.sin6_family = AF_INET6;
		if (IN6_IS_ADDR_UNSPECIFIED(&icmp6dst.sin6_addr))
			icmp6dst.sin6_addr = eip6->ip6_dst;
		if (in6_setscope(&icmp6dst.sin6_addr, m->m_pkthdr.rcvif, NULL))
			goto freeit;
		bzero(&icmp6src, sizeof(icmp6src));
		icmp6src.sin6_len = sizeof(struct sockaddr_in6);
		icmp6src.sin6_family = AF_INET6;
		icmp6src.sin6_addr = eip6->ip6_src;
		if (in6_setscope(&icmp6src.sin6_addr, m->m_pkthdr.rcvif, NULL))
			goto freeit;
		icmp6src.sin6_flowinfo =
		    (eip6->ip6_flow & IPV6_FLOWLABEL_MASK);

		ip6cp.ip6c_m = m;
		ip6cp.ip6c_icmp6 = icmp6;
		ip6cp.ip6c_ip6 = (struct ip6_hdr *)(icmp6 + 1);
		ip6cp.ip6c_off = eoff;
		ip6cp.ip6c_finaldst = &icmp6dst;
		ip6cp.ip6c_src = &icmp6src;
		ip6cp.ip6c_nxt = nxt;

		if (icmp6type == ICMP6_PACKET_TOO_BIG) {
			notifymtu = ntohl(icmp6->icmp6_mtu);
			ip6cp.ip6c_cmdarg = (void *)&notifymtu;
			icmp6_mtudisc_update(&ip6cp, 1);	/*XXX*/
		}

		if (ip6_ctlprotox[nxt] != NULL)
			ip6_ctlprotox[nxt](&ip6cp);
	}
	*mp = m;
	return (0);

  freeit:
	m_freem(m);
	*mp = NULL;
	return (-1);
}

void
icmp6_mtudisc_update(struct ip6ctlparam *ip6cp, int validated)
{
	struct in6_addr *dst = &ip6cp->ip6c_finaldst->sin6_addr;
	struct icmp6_hdr *icmp6 = ip6cp->ip6c_icmp6;
	struct mbuf *m = ip6cp->ip6c_m;	/* will be necessary for scope issue */
	u_int mtu = ntohl(icmp6->icmp6_mtu);
	struct in_conninfo inc;
	uint32_t max_mtu;

#if 0
	/*
	 * RFC2460 section 5, last paragraph.
	 * even though minimum link MTU for IPv6 is IPV6_MMTU,
	 * we may see ICMPv6 too big with mtu < IPV6_MMTU
	 * due to packet translator in the middle.
	 * see ip6_output() and ip6_getpmtu() "alwaysfrag" case for
	 * special handling.
	 */
	if (mtu < IPV6_MMTU)
		return;
#endif

	/*
	 * we reject ICMPv6 too big with abnormally small value.
	 * XXX what is the good definition of "abnormally small"?
	 */
	if (mtu < sizeof(struct ip6_hdr) + sizeof(struct ip6_frag) + 8)
		return;

	if (!validated)
		return;

	/*
	 * In case the suggested mtu is less than IPV6_MMTU, we
	 * only need to remember that it was for above mentioned
	 * "alwaysfrag" case.
	 * Try to be as close to the spec as possible.
	 */
	if (mtu < IPV6_MMTU)
		mtu = IPV6_MMTU - 8;

	bzero(&inc, sizeof(inc));
	inc.inc_fibnum = M_GETFIB(m);
	inc.inc_flags |= INC_ISIPV6;
	inc.inc6_faddr = *dst;
	if (in6_setscope(&inc.inc6_faddr, m->m_pkthdr.rcvif, NULL))
		return;

	max_mtu = tcp_hc_getmtu(&inc);
	if (max_mtu == 0)
		max_mtu = tcp_maxmtu6(&inc, NULL);

	if (mtu < max_mtu) {
		tcp_hc_updatemtu(&inc, mtu);
		ICMP6STAT_INC(icp6s_pmtuchg);
	}
}

/*
 * Process a Node Information Query packet, based on
 * draft-ietf-ipngwg-icmp-name-lookups-07.
 *
 * Spec incompatibilities:
 * - IPv6 Subject address handling
 * - IPv4 Subject address handling support missing
 * - Proxy reply (answer even if it's not for me)
 * - joins NI group address at in6_ifattach() time only, does not cope
 *   with hostname changes by sethostname(3)
 */
static struct mbuf *
ni6_input(struct mbuf *m, int off, struct prison *pr)
{
	struct icmp6_nodeinfo *ni6, *nni6;
	struct mbuf *n = NULL;
	u_int16_t qtype;
	int subjlen;
	int replylen = sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo);
	struct ni_reply_fqdn *fqdn;
	int addrs;		/* for NI_QTYPE_NODEADDR */
	struct ifnet *ifp = NULL; /* for NI_QTYPE_NODEADDR */
	struct in6_addr in6_subj; /* subject address */
	struct ip6_hdr *ip6;
	int oldfqdn = 0;	/* if 1, return pascal string (03 draft) */
	char *subj = NULL;
	struct in6_ifaddr *ia6 = NULL;

	ip6 = mtod(m, struct ip6_hdr *);
	ni6 = (struct icmp6_nodeinfo *)(mtod(m, caddr_t) + off);

	/*
	 * Validate IPv6 source address.
	 * The default configuration MUST be to refuse answering queries from
	 * global-scope addresses according to RFC4602.
	 * Notes:
	 *  - it's not very clear what "refuse" means; this implementation
	 *    simply drops it.
	 *  - it's not very easy to identify global-scope (unicast) addresses
	 *    since there are many prefixes for them.  It should be safer
	 *    and in practice sufficient to check "all" but loopback and
	 *    link-local (note that site-local unicast was deprecated and
	 *    ULA is defined as global scope-wise)
	 */
	if ((V_icmp6_nodeinfo & ICMP6_NODEINFO_GLOBALOK) == 0 &&
	    !IN6_IS_ADDR_LOOPBACK(&ip6->ip6_src) &&
	    !IN6_IS_ADDR_LINKLOCAL(&ip6->ip6_src))
		goto bad;

	/*
	 * Validate IPv6 destination address.
	 *
	 * The Responder must discard the Query without further processing
	 * unless it is one of the Responder's unicast or anycast addresses, or
	 * a link-local scope multicast address which the Responder has joined.
	 * [RFC4602, Section 5.]
	 */
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		if (!IN6_IS_ADDR_MC_LINKLOCAL(&ip6->ip6_dst))
			goto bad;
		/* else it's a link-local multicast, fine */
	} else {		/* unicast or anycast */
		ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false);
		if (ia6 == NULL)
			goto bad; /* XXX impossible */

		if ((ia6->ia6_flags & IN6_IFF_TEMPORARY) &&
		    !(V_icmp6_nodeinfo & ICMP6_NODEINFO_TMPADDROK)) {
			nd6log((LOG_DEBUG, "ni6_input: ignore node info to "
				"a temporary address in %s:%d",
			       __FILE__, __LINE__));
			goto bad;
		}
	}

	/* validate query Subject field. */
	qtype = ntohs(ni6->ni_qtype);
	subjlen = m->m_pkthdr.len - off - sizeof(struct icmp6_nodeinfo);
	switch (qtype) {
	case NI_QTYPE_NOOP:
	case NI_QTYPE_SUPTYPES:
		/* 07 draft */
		if (ni6->ni_code == ICMP6_NI_SUBJ_FQDN && subjlen == 0)
			break;
		/* FALLTHROUGH */
	case NI_QTYPE_FQDN:
	case NI_QTYPE_NODEADDR:
	case NI_QTYPE_IPV4ADDR:
		switch (ni6->ni_code) {
		case ICMP6_NI_SUBJ_IPV6:
#if ICMP6_NI_SUBJ_IPV6 != 0
		case 0:
#endif
			/*
			 * backward compatibility - try to accept 03 draft
			 * format, where no Subject is present.
			 */
			if (qtype == NI_QTYPE_FQDN && ni6->ni_code == 0 &&
			    subjlen == 0) {
				oldfqdn++;
				break;
			}
#if ICMP6_NI_SUBJ_IPV6 != 0
			if (ni6->ni_code != ICMP6_NI_SUBJ_IPV6)
				goto bad;
#endif

			if (subjlen != sizeof(struct in6_addr))
				goto bad;

			/*
			 * Validate Subject address.
			 *
			 * Not sure what exactly "address belongs to the node"
			 * means in the spec, is it just unicast, or what?
			 *
			 * At this moment we consider Subject address as
			 * "belong to the node" if the Subject address equals
			 * to the IPv6 destination address; validation for
			 * IPv6 destination address should have done enough
			 * check for us.
			 *
			 * We do not do proxy at this moment.
			 */
			m_copydata(m, off + sizeof(struct icmp6_nodeinfo),
			    subjlen, (caddr_t)&in6_subj);
			if (in6_setscope(&in6_subj, m->m_pkthdr.rcvif, NULL))
				goto bad;

			subj = (char *)&in6_subj;
			if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &in6_subj))
				break;

			/*
			 * XXX if we are to allow other cases, we should really
			 * be careful about scope here.
			 * basically, we should disallow queries toward IPv6
			 * destination X with subject Y,
			 * if scope(X) > scope(Y).
			 * if we allow scope(X) > scope(Y), it will result in
			 * information leakage across scope boundary.
			 */
			goto bad;

		case ICMP6_NI_SUBJ_FQDN:
			/*
			 * Validate Subject name with gethostname(3).
			 *
			 * The behavior may need some debate, since:
			 * - we are not sure if the node has FQDN as
			 *   hostname (returned by gethostname(3)).
			 * - the code does wildcard match for truncated names.
			 *   however, we are not sure if we want to perform
			 *   wildcard match, if gethostname(3) side has
			 *   truncated hostname.
			 */
			mtx_lock(&pr->pr_mtx);
			n = ni6_nametodns(pr->pr_hostname,
			    strlen(pr->pr_hostname), 0);
			mtx_unlock(&pr->pr_mtx);
			if (!n || n->m_next || n->m_len == 0)
				goto bad;
			if (m->m_len < off + sizeof(struct icmp6_nodeinfo) +
			    subjlen) {
				m = m_pullup(m, off +
				    sizeof(struct icmp6_nodeinfo) + subjlen);
				if (m == NULL) {
					IP6STAT_INC(ip6s_exthdrtoolong);
					goto bad;
				}
			}
			/* ip6 possibly invalid but not used after. */
			ni6 = (struct icmp6_nodeinfo *)(mtod(m, caddr_t) + off);
			subj = (char *)(mtod(m, caddr_t) + off +
			    sizeof(struct icmp6_nodeinfo));
			if (!ni6_dnsmatch(subj, subjlen, mtod(n, const char *),
			    n->m_len)) {
				goto bad;
			}
			m_freem(n);
			n = NULL;
			break;

		case ICMP6_NI_SUBJ_IPV4:	/* XXX: to be implemented? */
		default:
			goto bad;
		}
		break;
	}

	/* refuse based on configuration.  XXX ICMP6_NI_REFUSED? */
	switch (qtype) {
	case NI_QTYPE_FQDN:
		if ((V_icmp6_nodeinfo & ICMP6_NODEINFO_FQDNOK) == 0)
			goto bad;
		break;
	case NI_QTYPE_NODEADDR:
	case NI_QTYPE_IPV4ADDR:
		if ((V_icmp6_nodeinfo & ICMP6_NODEINFO_NODEADDROK) == 0)
			goto bad;
		break;
	}

	/* guess reply length */
	switch (qtype) {
	case NI_QTYPE_NOOP:
		break;		/* no reply data */
	case NI_QTYPE_SUPTYPES:
		replylen += sizeof(u_int32_t);
		break;
	case NI_QTYPE_FQDN:
		/* XXX will append an mbuf */
		replylen += offsetof(struct ni_reply_fqdn, ni_fqdn_namelen);
		break;
	case NI_QTYPE_NODEADDR:
		addrs = ni6_addrs(ni6, m, &ifp, (struct in6_addr *)subj);
		if ((replylen += addrs * (sizeof(struct in6_addr) +
		    sizeof(u_int32_t))) > MCLBYTES)
			replylen = MCLBYTES; /* XXX: will truncate pkt later */
		break;
	case NI_QTYPE_IPV4ADDR:
		/* unsupported - should respond with unknown Qtype? */
		break;
	default:
		/*
		 * XXX: We must return a reply with the ICMP6 code
		 * `unknown Qtype' in this case.  However we regard the case
		 * as an FQDN query for backward compatibility.
		 * Older versions set a random value to this field,
		 * so it rarely varies in the defined qtypes.
		 * But the mechanism is not reliable...
		 * maybe we should obsolete older versions.
		 */
		qtype = NI_QTYPE_FQDN;
		/* XXX will append an mbuf */
		replylen += offsetof(struct ni_reply_fqdn, ni_fqdn_namelen);
		oldfqdn++;
		break;
	}

	/* Allocate an mbuf to reply. */
	if (replylen > MCLBYTES) {
		/*
		 * XXX: should we try to allocate more? But MCLBYTES
		 * is probably much larger than IPV6_MMTU...
		 */
		goto bad;
	}
	if (replylen > MHLEN)
		n = m_getcl(M_NOWAIT, m->m_type, M_PKTHDR);
	else
		n = m_gethdr(M_NOWAIT, m->m_type);
	if (n == NULL) {
		m_freem(m);
		return (NULL);
	}
	m_move_pkthdr(n, m); /* just for recvif and FIB */
	n->m_pkthdr.len = n->m_len = replylen;

	/* copy mbuf header and IPv6 + Node Information base headers */
	bcopy(mtod(m, caddr_t), mtod(n, caddr_t), sizeof(struct ip6_hdr));
	nni6 = (struct icmp6_nodeinfo *)(mtod(n, struct ip6_hdr *) + 1);
	bcopy((caddr_t)ni6, (caddr_t)nni6, sizeof(struct icmp6_nodeinfo));

	/* qtype dependent procedure */
	switch (qtype) {
	case NI_QTYPE_NOOP:
		nni6->ni_code = ICMP6_NI_SUCCESS;
		nni6->ni_flags = 0;
		break;
	case NI_QTYPE_SUPTYPES:
	{
		u_int32_t v;
		nni6->ni_code = ICMP6_NI_SUCCESS;
		nni6->ni_flags = htons(0x0000);	/* raw bitmap */
		/* supports NOOP, SUPTYPES, FQDN, and NODEADDR */
		v = (u_int32_t)htonl(0x0000000f);
		bcopy(&v, nni6 + 1, sizeof(u_int32_t));
		break;
	}
	case NI_QTYPE_FQDN:
		nni6->ni_code = ICMP6_NI_SUCCESS;
		fqdn = (struct ni_reply_fqdn *)(mtod(n, caddr_t) +
		    sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo));
		nni6->ni_flags = 0; /* XXX: meaningless TTL */
		fqdn->ni_fqdn_ttl = 0;	/* ditto. */
		/*
		 * XXX do we really have FQDN in hostname?
		 */
		mtx_lock(&pr->pr_mtx);
		n->m_next = ni6_nametodns(pr->pr_hostname,
		    strlen(pr->pr_hostname), oldfqdn);
		mtx_unlock(&pr->pr_mtx);
		if (n->m_next == NULL)
			goto bad;
		/* XXX we assume that n->m_next is not a chain */
		if (n->m_next->m_next != NULL)
			goto bad;
		n->m_pkthdr.len += n->m_next->m_len;
		break;
	case NI_QTYPE_NODEADDR:
	{
		int lenlim, copied;

		nni6->ni_code = ICMP6_NI_SUCCESS;
		n->m_pkthdr.len = n->m_len =
		    sizeof(struct ip6_hdr) + sizeof(struct icmp6_nodeinfo);
		lenlim = M_TRAILINGSPACE(n);
		copied = ni6_store_addrs(ni6, nni6, ifp, lenlim);
		/* XXX: reset mbuf length */
		n->m_pkthdr.len = n->m_len = sizeof(struct ip6_hdr) +
		    sizeof(struct icmp6_nodeinfo) + copied;
		break;
	}
	default:
		break;		/* XXX impossible! */
	}

	nni6->ni_type = ICMP6_NI_REPLY;
	m_freem(m);
	return (n);

  bad:
	m_freem(m);
	if (n)
		m_freem(n);
	return (NULL);
}

/*
 * make a mbuf with DNS-encoded string.  no compression support.
 *
 * XXX names with less than 2 dots (like "foo" or "foo.section") will be
 * treated as truncated name (two \0 at the end).  this is a wild guess.
 *
 * old - return pascal string if non-zero
 */
static struct mbuf *
ni6_nametodns(const char *name, int namelen, int old)
{
	struct mbuf *m;
	char *cp, *ep;
	const char *p, *q;
	int i, len, nterm;

	if (old)
		len = namelen + 1;
	else
		len = MCLBYTES;

	/* Because MAXHOSTNAMELEN is usually 256, we use cluster mbuf. */
	if (len > MLEN)
		m = m_getcl(M_NOWAIT, MT_DATA, 0);
	else
		m = m_get(M_NOWAIT, MT_DATA);
	if (m == NULL)
		goto fail;

	if (old) {
		m->m_len = len;
		*mtod(m, char *) = namelen;
		bcopy(name, mtod(m, char *) + 1, namelen);
		return m;
	} else {
		m->m_len = 0;
		cp = mtod(m, char *);
		ep = mtod(m, char *) + M_TRAILINGSPACE(m);

		/* if not certain about my name, return empty buffer */
		if (namelen == 0)
			return m;

		/*
		 * guess if it looks like shortened hostname, or FQDN.
		 * shortened hostname needs two trailing "\0".
		 */
		i = 0;
		for (p = name; p < name + namelen; p++) {
			if (*p && *p == '.')
				i++;
		}
		if (i < 2)
			nterm = 2;
		else
			nterm = 1;

		p = name;
		while (cp < ep && p < name + namelen) {
			i = 0;
			for (q = p; q < name + namelen && *q && *q != '.'; q++)
				i++;
			/* result does not fit into mbuf */
			if (cp + i + 1 >= ep)
				goto fail;
			/*
			 * DNS label length restriction, RFC1035 page 8.
			 * "i == 0" case is included here to avoid returning
			 * 0-length label on "foo..bar".
			 */
			if (i <= 0 || i >= 64)
				goto fail;
			*cp++ = i;
			bcopy(p, cp, i);
			cp += i;
			p = q;
			if (p < name + namelen && *p == '.')
				p++;
		}
		/* termination */
		if (cp + nterm >= ep)
			goto fail;
		while (nterm-- > 0)
			*cp++ = '\0';
		m->m_len = cp - mtod(m, char *);
		return m;
	}

	panic("should not reach here");
	/* NOTREACHED */

 fail:
	if (m)
		m_freem(m);
	return NULL;
}

/*
 * check if two DNS-encoded string matches.  takes care of truncated
 * form (with \0\0 at the end).  no compression support.
 * XXX upper/lowercase match (see RFC2065)
 */
static int
ni6_dnsmatch(const char *a, int alen, const char *b, int blen)
{
	const char *a0, *b0;
	int l;

	/* simplest case - need validation? */
	if (alen == blen && bcmp(a, b, alen) == 0)
		return 1;

	a0 = a;
	b0 = b;

	/* termination is mandatory */
	if (alen < 2 || blen < 2)
		return 0;
	if (a0[alen - 1] != '\0' || b0[blen - 1] != '\0')
		return 0;
	alen--;
	blen--;

	while (a - a0 < alen && b - b0 < blen) {
		if (a - a0 + 1 > alen || b - b0 + 1 > blen)
			return 0;

		if ((signed char)a[0] < 0 || (signed char)b[0] < 0)
			return 0;
		/* we don't support compression yet */
		if (a[0] >= 64 || b[0] >= 64)
			return 0;

		/* truncated case */
		if (a[0] == 0 && a - a0 == alen - 1)
			return 1;
		if (b[0] == 0 && b - b0 == blen - 1)
			return 1;
		if (a[0] == 0 || b[0] == 0)
			return 0;

		if (a[0] != b[0])
			return 0;
		l = a[0];
		if (a - a0 + 1 + l > alen || b - b0 + 1 + l > blen)
			return 0;
		if (bcmp(a + 1, b + 1, l) != 0)
			return 0;

		a += 1 + l;
		b += 1 + l;
	}

	if (a - a0 == alen && b - b0 == blen)
		return 1;
	else
		return 0;
}

/*
 * calculate the number of addresses to be returned in the node info reply.
 */
static int
ni6_addrs(struct icmp6_nodeinfo *ni6, struct mbuf *m, struct ifnet **ifpp,
    struct in6_addr *subj)
{
	struct ifnet *ifp;
	struct in6_ifaddr *ifa6;
	struct ifaddr *ifa;
	int addrs = 0, addrsofif, iffound = 0;
	int niflags = ni6->ni_flags;

	NET_EPOCH_ASSERT();

	if ((niflags & NI_NODEADDR_FLAG_ALL) == 0) {
		switch (ni6->ni_code) {
		case ICMP6_NI_SUBJ_IPV6:
			if (subj == NULL) /* must be impossible... */
				return (0);
			break;
		default:
			/*
			 * XXX: we only support IPv6 subject address for
			 * this Qtype.
			 */
			return (0);
		}
	}

	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
		addrsofif = 0;
		CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
			if (ifa->ifa_addr->sa_family != AF_INET6)
				continue;
			ifa6 = (struct in6_ifaddr *)ifa;

			if ((niflags & NI_NODEADDR_FLAG_ALL) == 0 &&
			    IN6_ARE_ADDR_EQUAL(subj, &ifa6->ia_addr.sin6_addr))
				iffound = 1;

			/*
			 * IPv4-mapped addresses can only be returned by a
			 * Node Information proxy, since they represent
			 * addresses of IPv4-only nodes, which perforce do
			 * not implement this protocol.
			 * [icmp-name-lookups-07, Section 5.4]
			 * So we don't support NI_NODEADDR_FLAG_COMPAT in
			 * this function at this moment.
			 */

			/* What do we have to do about ::1? */
			switch (in6_addrscope(&ifa6->ia_addr.sin6_addr)) {
			case IPV6_ADDR_SCOPE_LINKLOCAL:
				if ((niflags & NI_NODEADDR_FLAG_LINKLOCAL) == 0)
					continue;
				break;
			case IPV6_ADDR_SCOPE_SITELOCAL:
				if ((niflags & NI_NODEADDR_FLAG_SITELOCAL) == 0)
					continue;
				break;
			case IPV6_ADDR_SCOPE_GLOBAL:
				if ((niflags & NI_NODEADDR_FLAG_GLOBAL) == 0)
					continue;
				break;
			default:
				continue;
			}

			/*
			 * check if anycast is okay.
			 * XXX: just experimental.  not in the spec.
			 */
			if ((ifa6->ia6_flags & IN6_IFF_ANYCAST) != 0 &&
			    (niflags & NI_NODEADDR_FLAG_ANYCAST) == 0)
				continue; /* we need only unicast addresses */
			if ((ifa6->ia6_flags & IN6_IFF_TEMPORARY) != 0 &&
			    (V_icmp6_nodeinfo & ICMP6_NODEINFO_TMPADDROK) == 0) {
				continue;
			}
			addrsofif++; /* count the address */
		}
		if (iffound) {
			*ifpp = ifp;
			return (addrsofif);
		}

		addrs += addrsofif;
	}

	return (addrs);
}

static int
ni6_store_addrs(struct icmp6_nodeinfo *ni6, struct icmp6_nodeinfo *nni6,
    struct ifnet *ifp0, int resid)
{
	struct ifnet *ifp;
	struct in6_ifaddr *ifa6;
	struct ifaddr *ifa;
	struct ifnet *ifp_dep = NULL;
	int copied = 0, allow_deprecated = 0;
	u_char *cp = (u_char *)(nni6 + 1);
	int niflags = ni6->ni_flags;
	u_int32_t ltime;

	NET_EPOCH_ASSERT();

	if (ifp0 == NULL && !(niflags & NI_NODEADDR_FLAG_ALL))
		return (0);	/* needless to copy */

	ifp = ifp0 ? ifp0 : CK_STAILQ_FIRST(&V_ifnet);
  again:

	for (; ifp; ifp = CK_STAILQ_NEXT(ifp, if_link)) {
		CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
			if (ifa->ifa_addr->sa_family != AF_INET6)
				continue;
			ifa6 = (struct in6_ifaddr *)ifa;

			if ((ifa6->ia6_flags & IN6_IFF_DEPRECATED) != 0 &&
			    allow_deprecated == 0) {
				/*
				 * prefererred address should be put before
				 * deprecated addresses.
				 */

				/* record the interface for later search */
				if (ifp_dep == NULL)
					ifp_dep = ifp;

				continue;
			} else if ((ifa6->ia6_flags & IN6_IFF_DEPRECATED) == 0 &&
			    allow_deprecated != 0)
				continue; /* we now collect deprecated addrs */

			/* What do we have to do about ::1? */
			switch (in6_addrscope(&ifa6->ia_addr.sin6_addr)) {
			case IPV6_ADDR_SCOPE_LINKLOCAL:
				if ((niflags & NI_NODEADDR_FLAG_LINKLOCAL) == 0)
					continue;
				break;
			case IPV6_ADDR_SCOPE_SITELOCAL:
				if ((niflags & NI_NODEADDR_FLAG_SITELOCAL) == 0)
					continue;
				break;
			case IPV6_ADDR_SCOPE_GLOBAL:
				if ((niflags & NI_NODEADDR_FLAG_GLOBAL) == 0)
					continue;
				break;
			default:
				continue;
			}

			/*
			 * check if anycast is okay.
			 * XXX: just experimental.  not in the spec.
			 */
			if ((ifa6->ia6_flags & IN6_IFF_ANYCAST) != 0 &&
			    (niflags & NI_NODEADDR_FLAG_ANYCAST) == 0)
				continue;
			if ((ifa6->ia6_flags & IN6_IFF_TEMPORARY) != 0 &&
			    (V_icmp6_nodeinfo & ICMP6_NODEINFO_TMPADDROK) == 0) {
				continue;
			}

			/* now we can copy the address */
			if (resid < sizeof(struct in6_addr) +
			    sizeof(u_int32_t)) {
				/*
				 * We give up much more copy.
				 * Set the truncate flag and return.
				 */
				nni6->ni_flags |= NI_NODEADDR_FLAG_TRUNCATE;
				return (copied);
			}

			/*
			 * Set the TTL of the address.
			 * The TTL value should be one of the following
			 * according to the specification:
			 *
			 * 1. The remaining lifetime of a DHCP lease on the
			 *    address, or
			 * 2. The remaining Valid Lifetime of a prefix from
			 *    which the address was derived through Stateless
			 *    Autoconfiguration.
			 *
			 * Note that we currently do not support stateful
			 * address configuration by DHCPv6, so the former
			 * case can't happen.
			 */
			if (ifa6->ia6_lifetime.ia6t_expire == 0)
				ltime = ND6_INFINITE_LIFETIME;
			else {
				if (ifa6->ia6_lifetime.ia6t_expire >
				    time_uptime)
					ltime = htonl(ifa6->ia6_lifetime.ia6t_expire - time_uptime);
				else
					ltime = 0;
			}

			bcopy(&ltime, cp, sizeof(u_int32_t));
			cp += sizeof(u_int32_t);

			/* copy the address itself */
			bcopy(&ifa6->ia_addr.sin6_addr, cp,
			    sizeof(struct in6_addr));
			in6_clearscope((struct in6_addr *)cp); /* XXX */
			cp += sizeof(struct in6_addr);

			resid -= (sizeof(struct in6_addr) + sizeof(u_int32_t));
			copied += (sizeof(struct in6_addr) + sizeof(u_int32_t));
		}
		if (ifp0)	/* we need search only on the specified IF */
			break;
	}

	if (allow_deprecated == 0 && ifp_dep != NULL) {
		ifp = ifp_dep;
		allow_deprecated = 1;

		goto again;
	}

	return (copied);
}

static bool
icmp6_rip6_match(const struct inpcb *inp, void *v)
{
	struct ip6_hdr *ip6 = v;

	if ((inp->inp_vflag & INP_IPV6) == 0)
		return (false);
	if (inp->inp_ip_p != IPPROTO_ICMPV6)
		return (false);
	if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr) &&
	   !IN6_ARE_ADDR_EQUAL(&inp->in6p_laddr, &ip6->ip6_dst))
		return (false);
	if (!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
	   !IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &ip6->ip6_src))
		return (false);
	return (true);
}

/*
 * XXX almost dup'ed code with rip6_input.
 */
static int
icmp6_rip6_input(struct mbuf **mp, int off)
{
	struct mbuf *n, *m = *mp;
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
	struct inpcb_iterator inpi = INP_ITERATOR(&V_ripcbinfo,
	    INPLOOKUP_RLOCKPCB, icmp6_rip6_match, ip6);
	struct inpcb *inp;
	struct sockaddr_in6 fromsa;
	struct icmp6_hdr *icmp6;
	struct mbuf *opts = NULL;
	int delivered = 0;

	/* This is assumed to be safe; icmp6_input() does a pullup. */
	icmp6 = (struct icmp6_hdr *)((caddr_t)ip6 + off);

	/*
	 * XXX: the address may have embedded scope zone ID, which should be
	 * hidden from applications.
	 */
	bzero(&fromsa, sizeof(fromsa));
	fromsa.sin6_family = AF_INET6;
	fromsa.sin6_len = sizeof(struct sockaddr_in6);
	fromsa.sin6_addr = ip6->ip6_src;
	if (sa6_recoverscope(&fromsa)) {
		m_freem(m);
		*mp = NULL;
		return (IPPROTO_DONE);
	}

	while ((inp = inp_next(&inpi)) != NULL) {
		if (ICMP6_FILTER_WILLBLOCK(icmp6->icmp6_type,
		    inp->in6p_icmp6filt))
			continue;
		/*
		 * Recent network drivers tend to allocate a single
		 * mbuf cluster, rather than to make a couple of
		 * mbufs without clusters.  Also, since the IPv6 code
		 * path tries to avoid m_pullup(), it is highly
		 * probable that we still have an mbuf cluster here
		 * even though the necessary length can be stored in an
		 * mbuf's internal buffer.
		 * Meanwhile, the default size of the receive socket
		 * buffer for raw sockets is not so large.  This means
		 * the possibility of packet loss is relatively higher
		 * than before.  To avoid this scenario, we copy the
		 * received data to a separate mbuf that does not use
		 * a cluster, if possible.
		 * XXX: it is better to copy the data after stripping
		 * intermediate headers.
		 */
		if ((m->m_flags & M_EXT) && m->m_next == NULL &&
		    m->m_len <= MHLEN) {
			n = m_get(M_NOWAIT, m->m_type);
			if (n != NULL) {
				if (m_dup_pkthdr(n, m, M_NOWAIT)) {
					bcopy(m->m_data, n->m_data, m->m_len);
					n->m_len = m->m_len;
				} else {
					m_free(n);
					n = NULL;
				}
			}
		} else
			n = m_copym(m, 0, M_COPYALL, M_NOWAIT);
		if (n == NULL)
			continue;
		if (inp->inp_flags & INP_CONTROLOPTS)
			ip6_savecontrol(inp, n, &opts);
		/* strip intermediate headers */
		m_adj(n, off);
		SOCKBUF_LOCK(&inp->inp_socket->so_rcv);
		if (sbappendaddr_locked(&inp->inp_socket->so_rcv,
		    (struct sockaddr *)&fromsa, n, opts) == 0) {
			soroverflow_locked(inp->inp_socket);
			m_freem(n);
			if (opts)
				m_freem(opts);
		} else {
			sorwakeup_locked(inp->inp_socket);
			delivered++;
		}
		opts = NULL;
	}
	m_freem(m);
	*mp = NULL;
	if (delivered == 0)
		IP6STAT_DEC(ip6s_delivered);
	return (IPPROTO_DONE);
}

/*
 * Reflect the ip6 packet back to the source.
 * OFF points to the icmp6 header, counted from the top of the mbuf.
 */
static void
icmp6_reflect(struct mbuf *m, size_t off)
{
	struct in6_addr src6, *srcp;
	struct ip6_hdr *ip6;
	struct icmp6_hdr *icmp6;
	struct in6_ifaddr *ia = NULL;
	struct ifnet *outif = NULL;
	int plen;
	int type, code, hlim;

	/* too short to reflect */
	if (off < sizeof(struct ip6_hdr)) {
		nd6log((LOG_DEBUG,
		    "sanity fail: off=%lx, sizeof(ip6)=%lx in %s:%d\n",
		    (u_long)off, (u_long)sizeof(struct ip6_hdr),
		    __FILE__, __LINE__));
		goto bad;
	}

	/*
	 * If there are extra headers between IPv6 and ICMPv6, strip
	 * off that header first.
	 */
#ifdef DIAGNOSTIC
	if (sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) > MHLEN)
		panic("assumption failed in icmp6_reflect");
#endif
	if (off > sizeof(struct ip6_hdr)) {
		size_t l;
		struct ip6_hdr nip6;

		l = off - sizeof(struct ip6_hdr);
		m_copydata(m, 0, sizeof(nip6), (caddr_t)&nip6);
		m_adj(m, l);
		l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
		if (m->m_len < l) {
			if ((m = m_pullup(m, l)) == NULL)
				return;
		}
		bcopy((caddr_t)&nip6, mtod(m, caddr_t), sizeof(nip6));
	} else /* off == sizeof(struct ip6_hdr) */ {
		size_t l;
		l = sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr);
		if (m->m_len < l) {
			if ((m = m_pullup(m, l)) == NULL)
				return;
		}
	}
	plen = m->m_pkthdr.len - sizeof(struct ip6_hdr);
	ip6 = mtod(m, struct ip6_hdr *);
	ip6->ip6_nxt = IPPROTO_ICMPV6;
	icmp6 = (struct icmp6_hdr *)(ip6 + 1);
	type = icmp6->icmp6_type; /* keep type for statistics */
	code = icmp6->icmp6_code; /* ditto. */
	hlim = 0;
	srcp = NULL;

	/*
	 * If the incoming packet was addressed directly to us (i.e. unicast),
	 * use dst as the src for the reply.
	 * The IN6_IFF_NOTREADY case should be VERY rare, but is possible
	 * (for example) when we encounter an error while forwarding procedure
	 * destined to a duplicated address of ours.
	 */
	if (!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false);
		if (ia != NULL && !(ia->ia6_flags &
		    (IN6_IFF_ANYCAST|IN6_IFF_NOTREADY))) {
			src6 = ia->ia_addr.sin6_addr;
			srcp = &src6;

			if (m->m_pkthdr.rcvif != NULL) {
				/* XXX: This may not be the outgoing interface */
				hlim = ND_IFINFO(m->m_pkthdr.rcvif)->chlim;
			} else
				hlim = V_ip6_defhlim;
		}
	}

	if (srcp == NULL) {
		int error;
		struct in6_addr dst6;
		uint32_t scopeid;

		/*
		 * This case matches to multicasts, our anycast, or unicasts
		 * that we do not own.  Select a source address based on the
		 * source address of the erroneous packet.
		 */
		in6_splitscope(&ip6->ip6_src, &dst6, &scopeid);
		error = in6_selectsrc_addr(M_GETFIB(m), &dst6,
		    scopeid, NULL, &src6, &hlim);

		if (error) {
			char ip6buf[INET6_ADDRSTRLEN];
			nd6log((LOG_DEBUG,
			    "icmp6_reflect: source can't be determined: "
			    "dst=%s, error=%d\n",
			    ip6_sprintf(ip6buf, &ip6->ip6_dst), error));
			goto bad;
		}
		srcp = &src6;
	}
	/*
	 * ip6_input() drops a packet if its src is multicast.
	 * So, the src is never multicast.
	 */
	ip6->ip6_dst = ip6->ip6_src;
	ip6->ip6_src = *srcp;
	ip6->ip6_flow = 0;
	ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
	ip6->ip6_vfc |= IPV6_VERSION;
	ip6->ip6_nxt = IPPROTO_ICMPV6;
	ip6->ip6_hlim = hlim;

	icmp6->icmp6_cksum = 0;
	icmp6->icmp6_cksum = in6_cksum(m, IPPROTO_ICMPV6,
	    sizeof(struct ip6_hdr), plen);

	/*
	 * XXX option handling
	 */

	m->m_flags &= ~(M_BCAST|M_MCAST);
	m->m_pkthdr.rcvif = NULL;
	ip6_output(m, NULL, NULL, 0, NULL, &outif, NULL);
	if (outif)
		icmp6_ifoutstat_inc(outif, type, code);

	return;

 bad:
	m_freem(m);
	return;
}

static const char *
icmp6_redirect_diag(struct in6_addr *src6, struct in6_addr *dst6,
    struct in6_addr *tgt6)
{
	static char buf[1024];
	char ip6bufs[INET6_ADDRSTRLEN];
	char ip6bufd[INET6_ADDRSTRLEN];
	char ip6buft[INET6_ADDRSTRLEN];
	snprintf(buf, sizeof(buf), "(src=%s dst=%s tgt=%s)",
	    ip6_sprintf(ip6bufs, src6), ip6_sprintf(ip6bufd, dst6),
	    ip6_sprintf(ip6buft, tgt6));
	return buf;
}

void
icmp6_redirect_input(struct mbuf *m, int off)
{
	struct ifnet *ifp;
	struct ip6_hdr *ip6;
	struct nd_redirect *nd_rd;
	struct in6_addr src6, redtgt6, reddst6;
	union nd_opts ndopts;
	char ip6buf[INET6_ADDRSTRLEN];
	char *lladdr;
	int icmp6len, is_onlink, is_router, lladdrlen;

	M_ASSERTPKTHDR(m);
	KASSERT(m->m_pkthdr.rcvif != NULL, ("%s: no rcvif", __func__));

	/* XXX if we are router, we don't update route by icmp6 redirect */
	if (V_ip6_forwarding)
		goto freeit;
	if (!V_icmp6_rediraccept)
		goto freeit;

	/* RFC 6980: Nodes MUST silently ignore fragments */
	if(m->m_flags & M_FRAGMENTED)
		goto freeit;

	ip6 = mtod(m, struct ip6_hdr *);
	icmp6len = ntohs(ip6->ip6_plen);
	if (m->m_len < off + icmp6len) {
		m = m_pullup(m, off + icmp6len);
		if (m == NULL) {
			IP6STAT_INC(ip6s_exthdrtoolong);
			return;
		}
	}
	ip6 = mtod(m, struct ip6_hdr *);
	nd_rd = (struct nd_redirect *)((caddr_t)ip6 + off);

	ifp = m->m_pkthdr.rcvif;
	redtgt6 = nd_rd->nd_rd_target;
	reddst6 = nd_rd->nd_rd_dst;

	if (in6_setscope(&redtgt6, ifp, NULL) ||
	    in6_setscope(&reddst6, ifp, NULL)) {
		goto freeit;
	}

	/* validation */
	src6 = ip6->ip6_src;
	if (!IN6_IS_ADDR_LINKLOCAL(&src6)) {
		nd6log((LOG_ERR,
		    "ICMP6 redirect sent from %s rejected; "
		    "must be from linklocal\n",
		    ip6_sprintf(ip6buf, &src6)));
		goto bad;
	}
	if (__predict_false(ip6->ip6_hlim != 255)) {
		ICMP6STAT_INC(icp6s_invlhlim);
		nd6log((LOG_ERR,
		    "ICMP6 redirect sent from %s rejected; "
		    "hlim=%d (must be 255)\n",
		    ip6_sprintf(ip6buf, &src6), ip6->ip6_hlim));
		goto bad;
	}
    {
	/* ip6->ip6_src must be equal to gw for icmp6->icmp6_reddst */
	struct nhop_object *nh;
	struct in6_addr kdst;
	uint32_t scopeid;

	in6_splitscope(&reddst6, &kdst, &scopeid);
	NET_EPOCH_ASSERT();
	nh = fib6_lookup(ifp->if_fib, &kdst, scopeid, 0, 0);
	if (nh != NULL) {
		struct in6_addr nh_addr;
		nh_addr = ifatoia6(nh->nh_ifa)->ia_addr.sin6_addr;
		if ((nh->nh_flags & NHF_GATEWAY) == 0) {
			nd6log((LOG_ERR,
			    "ICMP6 redirect rejected; no route "
			    "with inet6 gateway found for redirect dst: %s\n",
			    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
			goto bad;
		}

		/*
		 * Embed scope zone id into next hop address.
		 */
		nh_addr = nh->gw6_sa.sin6_addr;

		if (IN6_ARE_ADDR_EQUAL(&src6, &nh_addr) == 0) {
			nd6log((LOG_ERR,
			    "ICMP6 redirect rejected; "
			    "not equal to gw-for-src=%s (must be same): "
			    "%s\n",
			    ip6_sprintf(ip6buf, &nh_addr),
			    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
			goto bad;
		}
	} else {
		nd6log((LOG_ERR,
		    "ICMP6 redirect rejected; "
		    "no route found for redirect dst: %s\n",
		    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
		goto bad;
	}
    }
	if (IN6_IS_ADDR_MULTICAST(&reddst6)) {
		nd6log((LOG_ERR,
		    "ICMP6 redirect rejected; "
		    "redirect dst must be unicast: %s\n",
		    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
		goto bad;
	}

	is_router = is_onlink = 0;
	if (IN6_IS_ADDR_LINKLOCAL(&redtgt6))
		is_router = 1;	/* router case */
	if (bcmp(&redtgt6, &reddst6, sizeof(redtgt6)) == 0)
		is_onlink = 1;	/* on-link destination case */
	if (!is_router && !is_onlink) {
		nd6log((LOG_ERR,
		    "ICMP6 redirect rejected; "
		    "neither router case nor onlink case: %s\n",
		    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
		goto bad;
	}

	icmp6len -= sizeof(*nd_rd);
	nd6_option_init(nd_rd + 1, icmp6len, &ndopts);
	if (nd6_options(&ndopts) < 0) {
		nd6log((LOG_INFO, "%s: invalid ND option, rejected: %s\n",
		    __func__, icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
		/* nd6_options have incremented stats */
		goto freeit;
	}

	lladdr = NULL;
	lladdrlen = 0;
	if (ndopts.nd_opts_tgt_lladdr) {
		lladdr = (char *)(ndopts.nd_opts_tgt_lladdr + 1);
		lladdrlen = ndopts.nd_opts_tgt_lladdr->nd_opt_len << 3;
	}

	if (lladdr && ((ifp->if_addrlen + 2 + 7) & ~7) != lladdrlen) {
		nd6log((LOG_INFO, "%s: lladdrlen mismatch for %s "
		    "(if %d, icmp6 packet %d): %s\n",
		    __func__, ip6_sprintf(ip6buf, &redtgt6),
		    ifp->if_addrlen, lladdrlen - 2,
		    icmp6_redirect_diag(&src6, &reddst6, &redtgt6)));
		goto bad;
	}

	/* Validation passed. */

	/* RFC 2461 8.3 */
	nd6_cache_lladdr(ifp, &redtgt6, lladdr, lladdrlen, ND_REDIRECT,
	    is_onlink ? ND_REDIRECT_ONLINK : ND_REDIRECT_ROUTER);

	/*
	 * Install a gateway route in the better-router case or an interface
	 * route in the on-link-destination case.
	 */
	{
		struct sockaddr_in6 sdst;
		struct sockaddr_in6 sgw;
		struct sockaddr_in6 ssrc;
		struct sockaddr *gw;
		int rt_flags;
		u_int fibnum;

		bzero(&sdst, sizeof(sdst));
		bzero(&ssrc, sizeof(ssrc));
		sdst.sin6_family = ssrc.sin6_family = AF_INET6;
		sdst.sin6_len = ssrc.sin6_len = sizeof(struct sockaddr_in6);
		bcopy(&reddst6, &sdst.sin6_addr, sizeof(struct in6_addr));
		bcopy(&src6, &ssrc.sin6_addr, sizeof(struct in6_addr));
		rt_flags = 0;
		if (is_router) {
			bzero(&sgw, sizeof(sgw));
			sgw.sin6_family = AF_INET6;
			sgw.sin6_len = sizeof(struct sockaddr_in6);
			bcopy(&redtgt6, &sgw.sin6_addr,
				sizeof(struct in6_addr));
			gw = (struct sockaddr *)&sgw;
			rt_flags |= RTF_GATEWAY;
		} else
			gw = ifp->if_addr->ifa_addr;
		for (fibnum = 0; fibnum < rt_numfibs; fibnum++)
			rib_add_redirect(fibnum, (struct sockaddr *)&sdst, gw,
			    (struct sockaddr *)&ssrc, ifp, rt_flags,
			    V_icmp6_redirtimeout);
	}

 freeit:
	m_freem(m);
	return;

 bad:
	ICMP6STAT_INC(icp6s_badredirect);
	m_freem(m);
}

void
icmp6_redirect_output(struct mbuf *m0, struct nhop_object *nh)
{
	struct ifnet *ifp;	/* my outgoing interface */
	struct in6_addr *ifp_ll6;
	struct in6_addr *router_ll6;
	struct ip6_hdr *sip6;	/* m0 as struct ip6_hdr */
	struct mbuf *m = NULL;	/* newly allocated one */
	struct m_tag *mtag;
	struct ip6_hdr *ip6;	/* m as struct ip6_hdr */
	struct nd_redirect *nd_rd;
	struct llentry *ln = NULL;
	size_t maxlen;
	u_char *p;
	struct ifnet *outif = NULL;
	struct sockaddr_in6 src_sa;

	icmp6_errcount(ND_REDIRECT, 0);

	/* if we are not router, we don't send icmp6 redirect */
	if (!V_ip6_forwarding)
		goto fail;

	/* sanity check */
	if (!m0 || !nh || !(NH_IS_VALID(nh)) || !(ifp = nh->nh_ifp))
		goto fail;

	/*
	 * Address check:
	 *  the source address must identify a neighbor, and
	 *  the destination address must not be a multicast address
	 *  [RFC 2461, sec 8.2]
	 */
	sip6 = mtod(m0, struct ip6_hdr *);
	bzero(&src_sa, sizeof(src_sa));
	src_sa.sin6_family = AF_INET6;
	src_sa.sin6_len = sizeof(src_sa);
	src_sa.sin6_addr = sip6->ip6_src;
	if (nd6_is_addr_neighbor(&src_sa, ifp) == 0)
		goto fail;
	if (IN6_IS_ADDR_MULTICAST(&sip6->ip6_dst))
		goto fail;	/* what should we do here? */

	/* rate limit */
	if (icmp6_ratelimit(&sip6->ip6_src, ND_REDIRECT, 0))
		goto fail;

	/*
	 * Since we are going to append up to 1280 bytes (= IPV6_MMTU),
	 * we almost always ask for an mbuf cluster for simplicity.
	 * (MHLEN < IPV6_MMTU is almost always true)
	 */
#if IPV6_MMTU >= MCLBYTES
# error assumption failed about IPV6_MMTU and MCLBYTES
#endif
	m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
	if (m == NULL)
		goto fail;
	M_SETFIB(m, M_GETFIB(m0));
	maxlen = M_TRAILINGSPACE(m);
	maxlen = min(IPV6_MMTU, maxlen);
	/* just for safety */
	if (maxlen < sizeof(struct ip6_hdr) + sizeof(struct icmp6_hdr) +
	    ((sizeof(struct nd_opt_hdr) + ifp->if_addrlen + 7) & ~7)) {
		goto fail;
	}

	{
		/* get ip6 linklocal address for ifp(my outgoing interface). */
		struct in6_ifaddr *ia;
		if ((ia = in6ifa_ifpforlinklocal(ifp,
						 IN6_IFF_NOTREADY|
						 IN6_IFF_ANYCAST)) == NULL)
			goto fail;
		ifp_ll6 = &ia->ia_addr.sin6_addr;
		/* XXXRW: reference released prematurely. */
		ifa_free(&ia->ia_ifa);
	}

	/* get ip6 linklocal address for the router. */
	if (nh->nh_flags & NHF_GATEWAY) {
		struct sockaddr_in6 *sin6;
		sin6 = &nh->gw6_sa;
		router_ll6 = &sin6->sin6_addr;
		if (!IN6_IS_ADDR_LINKLOCAL(router_ll6))
			router_ll6 = (struct in6_addr *)NULL;
	} else
		router_ll6 = (struct in6_addr *)NULL;

	/* ip6 */
	ip6 = mtod(m, struct ip6_hdr *);
	ip6->ip6_flow = 0;
	ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
	ip6->ip6_vfc |= IPV6_VERSION;
	/* ip6->ip6_plen will be set later */
	ip6->ip6_nxt = IPPROTO_ICMPV6;
	ip6->ip6_hlim = 255;
	/* ip6->ip6_src must be linklocal addr for my outgoing if. */
	bcopy(ifp_ll6, &ip6->ip6_src, sizeof(struct in6_addr));
	bcopy(&sip6->ip6_src, &ip6->ip6_dst, sizeof(struct in6_addr));

	/* ND Redirect */
	nd_rd = (struct nd_redirect *)(ip6 + 1);
	nd_rd->nd_rd_type = ND_REDIRECT;
	nd_rd->nd_rd_code = 0;
	nd_rd->nd_rd_reserved = 0;
	if (nh->nh_flags & NHF_GATEWAY) {
		/*
		 * nd_rd->nd_rd_target must be a link-local address in
		 * better router cases.
		 */
		if (!router_ll6)
			goto fail;
		bcopy(router_ll6, &nd_rd->nd_rd_target,
		    sizeof(nd_rd->nd_rd_target));
		bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_dst,
		    sizeof(nd_rd->nd_rd_dst));
	} else {
		/* make sure redtgt == reddst */
		bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_target,
		    sizeof(nd_rd->nd_rd_target));
		bcopy(&sip6->ip6_dst, &nd_rd->nd_rd_dst,
		    sizeof(nd_rd->nd_rd_dst));
	}

	p = (u_char *)(nd_rd + 1);

	if (!router_ll6)
		goto nolladdropt;

	{
		/* target lladdr option */
		int len;
		struct nd_opt_hdr *nd_opt;
		char *lladdr;

		ln = nd6_lookup(router_ll6, LLE_SF(AF_INET6,  0), ifp);
		if (ln == NULL)
			goto nolladdropt;

		len = sizeof(*nd_opt) + ifp->if_addrlen;
		len = (len + 7) & ~7;	/* round by 8 */
		/* safety check */
		if (len + (p - (u_char *)ip6) > maxlen)
			goto nolladdropt;

		if (ln->la_flags & LLE_VALID) {
			nd_opt = (struct nd_opt_hdr *)p;
			nd_opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;
			nd_opt->nd_opt_len = len >> 3;
			lladdr = (char *)(nd_opt + 1);
			bcopy(ln->ll_addr, lladdr, ifp->if_addrlen);
			p += len;
		}
	}
nolladdropt:
	if (ln != NULL)
		LLE_RUNLOCK(ln);

	m->m_pkthdr.len = m->m_len = p - (u_char *)ip6;

	/* just to be safe */
#ifdef M_DECRYPTED	/*not openbsd*/
	if (m0->m_flags & M_DECRYPTED)
		goto noredhdropt;
#endif
	if (p - (u_char *)ip6 > maxlen)
		goto noredhdropt;

	{
		/* redirected header option */
		int len;
		struct nd_opt_rd_hdr *nd_opt_rh;

		/*
		 * compute the maximum size for icmp6 redirect header option.
		 * XXX room for auth header?
		 */
		len = maxlen - (p - (u_char *)ip6);
		len &= ~7;

		/* This is just for simplicity. */
		if (m0->m_pkthdr.len != m0->m_len) {
			if (m0->m_next) {
				m_freem(m0->m_next);
				m0->m_next = NULL;
			}
			m0->m_pkthdr.len = m0->m_len;
		}

		/*
		 * Redirected header option spec (RFC2461 4.6.3) talks nothing
		 * about padding/truncate rule for the original IP packet.
		 * From the discussion on IPv6imp in Feb 1999,
		 * the consensus was:
		 * - "attach as much as possible" is the goal
		 * - pad if not aligned (original size can be guessed by
		 *   original ip6 header)
		 * Following code adds the padding if it is simple enough,
		 * and truncates if not.
		 */
		if (m0->m_next || m0->m_pkthdr.len != m0->m_len)
			panic("assumption failed in %s:%d", __FILE__,
			    __LINE__);

		if (len - sizeof(*nd_opt_rh) < m0->m_pkthdr.len) {
			/* not enough room, truncate */
			m0->m_pkthdr.len = m0->m_len = len -
			    sizeof(*nd_opt_rh);
		} else {
			/* enough room, pad or truncate */
			size_t extra;

			extra = m0->m_pkthdr.len % 8;
			if (extra) {
				/* pad if easy enough, truncate if not */
				if (8 - extra <= M_TRAILINGSPACE(m0)) {
					/* pad */
					m0->m_len += (8 - extra);
					m0->m_pkthdr.len += (8 - extra);
				} else {
					/* truncate */
					m0->m_pkthdr.len -= extra;
					m0->m_len -= extra;
				}
			}
			len = m0->m_pkthdr.len + sizeof(*nd_opt_rh);
			m0->m_pkthdr.len = m0->m_len = len -
			    sizeof(*nd_opt_rh);
		}

		nd_opt_rh = (struct nd_opt_rd_hdr *)p;
		bzero(nd_opt_rh, sizeof(*nd_opt_rh));
		nd_opt_rh->nd_opt_rh_type = ND_OPT_REDIRECTED_HEADER;
		nd_opt_rh->nd_opt_rh_len = len >> 3;
		p += sizeof(*nd_opt_rh);
		m->m_pkthdr.len = m->m_len = p - (u_char *)ip6;

		/* connect m0 to m */
		m_tag_delete_chain(m0, NULL);
		m0->m_flags &= ~M_PKTHDR;
		m->m_next = m0;
		m->m_pkthdr.len = m->m_len + m0->m_len;
		m0 = NULL;
	}
noredhdropt:;
	if (m0) {
		m_freem(m0);
		m0 = NULL;
	}

	/* XXX: clear embedded link IDs in the inner header */
	in6_clearscope(&sip6->ip6_src);
	in6_clearscope(&sip6->ip6_dst);
	in6_clearscope(&nd_rd->nd_rd_target);
	in6_clearscope(&nd_rd->nd_rd_dst);

	ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));

	nd_rd->nd_rd_cksum = 0;
	nd_rd->nd_rd_cksum = in6_cksum(m, IPPROTO_ICMPV6,
	    sizeof(*ip6), ntohs(ip6->ip6_plen));

        if (send_sendso_input_hook != NULL) {
		mtag = m_tag_get(PACKET_TAG_ND_OUTGOING, sizeof(unsigned short),
			M_NOWAIT);
		if (mtag == NULL)
			goto fail;
		*(unsigned short *)(mtag + 1) = nd_rd->nd_rd_type;
		m_tag_prepend(m, mtag);
	}

	/* send the packet to outside... */
	ip6_output(m, NULL, NULL, 0, NULL, &outif, NULL);
	if (outif) {
		icmp6_ifstat_inc(outif, ifs6_out_msg);
		icmp6_ifstat_inc(outif, ifs6_out_redirect);
	}
	ICMP6STAT_INC2(icp6s_outhist, ND_REDIRECT);

	return;

fail:
	if (m)
		m_freem(m);
	if (m0)
		m_freem(m0);
}

/*
 * ICMPv6 socket option processing.
 */
int
icmp6_ctloutput(struct socket *so, struct sockopt *sopt)
{
	int error = 0;
	int optlen;
	struct inpcb *inp = sotoinpcb(so);
	int level, op, optname;

	if (sopt) {
		level = sopt->sopt_level;
		op = sopt->sopt_dir;
		optname = sopt->sopt_name;
		optlen = sopt->sopt_valsize;
	} else
		level = op = optname = optlen = 0;

	if (level != IPPROTO_ICMPV6) {
		return EINVAL;
	}

	switch (op) {
	case SOPT_SET:
		switch (optname) {
		case ICMP6_FILTER:
		    {
			struct icmp6_filter ic6f;

			if (optlen != sizeof(ic6f)) {
				error = EMSGSIZE;
				break;
			}
			error = sooptcopyin(sopt, &ic6f, optlen, optlen);
			if (error == 0) {
				INP_WLOCK(inp);
				*inp->in6p_icmp6filt = ic6f;
				INP_WUNLOCK(inp);
			}
			break;
		    }

		default:
			error = ENOPROTOOPT;
			break;
		}
		break;

	case SOPT_GET:
		switch (optname) {
		case ICMP6_FILTER:
		    {
			struct icmp6_filter ic6f;

			INP_RLOCK(inp);
			ic6f = *inp->in6p_icmp6filt;
			INP_RUNLOCK(inp);
			error = sooptcopyout(sopt, &ic6f, sizeof(ic6f));
			break;
		    }

		default:
			error = ENOPROTOOPT;
			break;
		}
		break;
	}

	return (error);
}

static int sysctl_icmp6lim_and_jitter(SYSCTL_HANDLER_ARGS);
VNET_DEFINE_STATIC(u_int, icmp6errppslim) = 100;
#define	V_icmp6errppslim	VNET(icmp6errppslim)
SYSCTL_PROC(_net_inet6_icmp6, ICMPV6CTL_ERRPPSLIMIT, errppslimit,
    CTLTYPE_UINT | CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6errppslim), 0,
    &sysctl_icmp6lim_and_jitter, "IU",
    "Maximum number of ICMPv6 error/reply messages per second");

VNET_DEFINE_STATIC(int, icmp6lim_curr_jitter) = 0;
#define	V_icmp6lim_curr_jitter	VNET(icmp6lim_curr_jitter)

VNET_DEFINE_STATIC(u_int, icmp6lim_jitter) = 8;
#define	V_icmp6lim_jitter	VNET(icmp6lim_jitter)
SYSCTL_PROC(_net_inet6_icmp6, OID_AUTO, icmp6lim_jitter, CTLTYPE_UINT |
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_jitter), 0,
    &sysctl_icmp6lim_and_jitter, "IU",
    "Random errppslimit jitter adjustment limit");

VNET_DEFINE_STATIC(int, icmp6lim_output) = 1;
#define	V_icmp6lim_output	VNET(icmp6lim_output)
SYSCTL_INT(_net_inet6_icmp6, OID_AUTO, icmp6lim_output,
    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_output), 0,
    "Enable logging of ICMPv6 response rate limiting");

typedef enum {
	RATELIM_PARAM_PROB = 0,
	RATELIM_TOO_BIG,
	RATELIM_UNREACH,
	RATELIM_TEXCEED,
	RATELIM_REDIR,
	RATELIM_REPLY,
	RATELIM_OTHER,
	RATELIM_MAX
} ratelim_which;

static const char *icmp6_rate_descrs[RATELIM_MAX] = {
	[RATELIM_PARAM_PROB] = "bad IPv6 header",
	[RATELIM_TOO_BIG] = "packet too big",
	[RATELIM_UNREACH] = "destination unreachable",
	[RATELIM_TEXCEED] = "time exceeded",
	[RATELIM_REPLY] = "echo reply",
	[RATELIM_REDIR] = "neighbor discovery redirect",
	[RATELIM_OTHER] = "(other)",
};

static void
icmp6lim_new_jitter(void)
{
	/*
	 * Adjust limit +/- to jitter the measurement to deny a side-channel
	 * port scan as in https://dl.acm.org/doi/10.1145/3372297.3417280
	 */
	if (V_icmp6lim_jitter > 0)
		V_icmp6lim_curr_jitter =
		    arc4random_uniform(V_icmp6lim_jitter * 2 + 1) -
		    V_icmp6lim_jitter;
}

static int
sysctl_icmp6lim_and_jitter(SYSCTL_HANDLER_ARGS)
{
	uint32_t new;
	int error;
	bool lim;

	MPASS(oidp->oid_arg1 == &VNET_NAME(icmp6errppslim) ||
	    oidp->oid_arg1 == &VNET_NAME(icmp6lim_jitter));

	lim = (oidp->oid_arg1 == &VNET_NAME(icmp6errppslim));
	new = lim ? V_icmp6errppslim : V_icmp6lim_jitter;
	error = sysctl_handle_int(oidp, &new, 0, req);
	if (error == 0 && req->newptr) {
		if (lim) {
			if (new != 0 && new <= V_icmp6lim_jitter)
				error = EINVAL;
			else
				V_icmp6errppslim = new;
		} else {
			if (new >= V_icmp6errppslim)
				error = EINVAL;
			else {
				V_icmp6lim_jitter = new;
				icmp6lim_new_jitter();
			}
		}
	}
	MPASS(V_icmp6errppslim + V_icmp6lim_curr_jitter >= 0);

	return (error);
}


VNET_DEFINE_STATIC(struct counter_rate, icmp6_rates[RATELIM_MAX]);
#define	V_icmp6_rates	VNET(icmp6_rates)

static void
icmp6_ratelimit_init(void)
{

	for (int i = 0; i < RATELIM_MAX; i++) {
		V_icmp6_rates[i].cr_rate = counter_u64_alloc(M_WAITOK);
		V_icmp6_rates[i].cr_ticks = ticks;
	}
	icmp6lim_new_jitter();
}
VNET_SYSINIT(icmp6_ratelimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY,
    icmp6_ratelimit_init, NULL);

#ifdef VIMAGE
static void
icmp6_ratelimit_uninit(void)
{

	for (int i = 0; i < RATELIM_MAX; i++)
		counter_u64_free(V_icmp6_rates[i].cr_rate);
}
VNET_SYSUNINIT(icmp6_ratelimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD,
    icmp6_ratelimit_uninit, NULL);
#endif

/*
 * Perform rate limit check.
 * Returns 0 if it is okay to send the icmp6 packet.
 * Returns 1 if the router SHOULD NOT send this icmp6 packet due to rate
 * limitation.
 *
 * XXX per-destination/type check necessary?
 *
 * dst - not used at this moment
 * code - not used at this moment
 */
int
icmp6_ratelimit(const struct in6_addr *dst, const int type, const int code)
{
	ratelim_which which;
	int64_t pps;

	if (V_icmp6errppslim == 0)
		return (0);

	switch (type) {
	case ICMP6_PARAM_PROB:
		which = RATELIM_PARAM_PROB;
		break;
	case ICMP6_PACKET_TOO_BIG:
		which = RATELIM_TOO_BIG;
		break;
	case ICMP6_DST_UNREACH:
		which = RATELIM_UNREACH;
		break;
	case ICMP6_TIME_EXCEEDED:
		which = RATELIM_TEXCEED;
		break;
	case ND_REDIRECT:
		which = RATELIM_REDIR;
		break;
	case ICMP6_ECHO_REPLY:
		which = RATELIM_REPLY;
		break;
	default:
		which = RATELIM_OTHER;
		break;
	};

	pps = counter_ratecheck(&V_icmp6_rates[which], V_icmp6errppslim +
	    V_icmp6lim_curr_jitter);
	if (pps > 0) {
		if (V_icmp6lim_output)
			log(LOG_NOTICE, "Limiting ICMPv6 %s output from %jd "
			    "to %d packets/sec\n", icmp6_rate_descrs[which],
			    (intmax_t )pps, V_icmp6errppslim +
			    V_icmp6lim_curr_jitter);
		icmp6lim_new_jitter();
	}
	if (pps == -1) {
		ICMP6STAT_INC(icp6s_toofreq);
		return (-1);
	}

	return (0);
}