freebsd-skq/sys/netinet6/ip6_input.c

/*-
 * 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: ip6_input.c,v 1.259 2002/01/21 04:58:09 jinmei 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.
 * 4. 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.
 *
 *	@(#)ip_input.c	8.2 (Berkeley) 1/4/94
 */

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

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

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/sdt.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/rmlock.h>
#include <sys/syslog.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/netisr.h>
#include <net/pfil.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/ip_var.h>
#include <netinet/in_systm.h>
#include <net/if_llatbl.h>
#ifdef INET
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#endif /* INET */
#include <netinet/ip6.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet/in_pcb.h>
#include <netinet/icmp6.h>
#include <netinet6/scope6_var.h>
#include <netinet6/in6_ifattach.h>
#include <netinet6/nd6.h>

#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netinet6/ip6_ipsec.h>
#include <netipsec/ipsec6.h>
#endif /* IPSEC */

#include <netinet6/ip6protosw.h>

extern struct domain inet6domain;

u_char ip6_protox[IPPROTO_MAX];
VNET_DEFINE(struct in6_ifaddrhead, in6_ifaddrhead);
VNET_DEFINE(struct in6_ifaddrlisthead *, in6_ifaddrhashtbl);
VNET_DEFINE(u_long, in6_ifaddrhmask);

static struct netisr_handler ip6_nh = {
	.nh_name = "ip6",
	.nh_handler = ip6_input,
	.nh_proto = NETISR_IPV6,
	.nh_policy = NETISR_POLICY_FLOW,
};

VNET_DECLARE(struct callout, in6_tmpaddrtimer_ch);
#define	V_in6_tmpaddrtimer_ch		VNET(in6_tmpaddrtimer_ch)

VNET_DEFINE(struct pfil_head, inet6_pfil_hook);

VNET_PCPUSTAT_DEFINE(struct ip6stat, ip6stat);
VNET_PCPUSTAT_SYSINIT(ip6stat);
#ifdef VIMAGE
VNET_PCPUSTAT_SYSUNINIT(ip6stat);
#endif /* VIMAGE */

struct rmlock in6_ifaddr_lock;
RM_SYSINIT(in6_ifaddr_lock, &in6_ifaddr_lock, "in6_ifaddr_lock");

static void ip6_init2(void *);
static int ip6_hopopts_input(u_int32_t *, u_int32_t *, struct mbuf **, int *);
#ifdef PULLDOWN_TEST
static struct mbuf *ip6_pullexthdr(struct mbuf *, size_t, int);
#endif

/*
 * IP6 initialization: fill in IP6 protocol switch table.
 * All protocols not implemented in kernel go to raw IP6 protocol handler.
 */
void
ip6_init(void)
{
	struct protosw *pr;
	int i;

	TUNABLE_INT_FETCH("net.inet6.ip6.auto_linklocal",
	    &V_ip6_auto_linklocal);
	TUNABLE_INT_FETCH("net.inet6.ip6.accept_rtadv", &V_ip6_accept_rtadv);
	TUNABLE_INT_FETCH("net.inet6.ip6.no_radr", &V_ip6_no_radr);

	TAILQ_INIT(&V_in6_ifaddrhead);
	V_in6_ifaddrhashtbl = hashinit(IN6ADDR_NHASH, M_IFADDR,
	    &V_in6_ifaddrhmask);

	/* Initialize packet filter hooks. */
	V_inet6_pfil_hook.ph_type = PFIL_TYPE_AF;
	V_inet6_pfil_hook.ph_af = AF_INET6;
	if ((i = pfil_head_register(&V_inet6_pfil_hook)) != 0)
		printf("%s: WARNING: unable to register pfil hook, "
			"error %d\n", __func__, i);

	scope6_init();
	addrsel_policy_init();
	nd6_init();
	frag6_init();

	V_ip6_desync_factor = arc4random() % MAX_TEMP_DESYNC_FACTOR;

	/* Skip global initialization stuff for non-default instances. */
	if (!IS_DEFAULT_VNET(curvnet))
		return;

	pr = pffindproto(PF_INET6, IPPROTO_RAW, SOCK_RAW);
	if (pr == NULL)
		panic("ip6_init");

	/* Initialize the entire ip6_protox[] array to IPPROTO_RAW. */
	for (i = 0; i < IPPROTO_MAX; i++)
		ip6_protox[i] = pr - inet6sw;
	/*
	 * Cycle through IP protocols and put them into the appropriate place
	 * in ip6_protox[].
	 */
	for (pr = inet6domain.dom_protosw;
	    pr < inet6domain.dom_protoswNPROTOSW; pr++)
		if (pr->pr_domain->dom_family == PF_INET6 &&
		    pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW) {
			/* Be careful to only index valid IP protocols. */
			if (pr->pr_protocol < IPPROTO_MAX)
				ip6_protox[pr->pr_protocol] = pr - inet6sw;
		}

	netisr_register(&ip6_nh);
}

/*
 * The protocol to be inserted into ip6_protox[] must be already registered
 * in inet6sw[], either statically or through pf_proto_register().
 */
int
ip6proto_register(short ip6proto)
{
	struct protosw *pr;

	/* Sanity checks. */
	if (ip6proto <= 0 || ip6proto >= IPPROTO_MAX)
		return (EPROTONOSUPPORT);

	/*
	 * The protocol slot must not be occupied by another protocol
	 * already.  An index pointing to IPPROTO_RAW is unused.
	 */
	pr = pffindproto(PF_INET6, IPPROTO_RAW, SOCK_RAW);
	if (pr == NULL)
		return (EPFNOSUPPORT);
	if (ip6_protox[ip6proto] != pr - inet6sw)	/* IPPROTO_RAW */
		return (EEXIST);

	/*
	 * Find the protocol position in inet6sw[] and set the index.
	 */
	for (pr = inet6domain.dom_protosw;
	    pr < inet6domain.dom_protoswNPROTOSW; pr++) {
		if (pr->pr_domain->dom_family == PF_INET6 &&
		    pr->pr_protocol && pr->pr_protocol == ip6proto) {
			ip6_protox[pr->pr_protocol] = pr - inet6sw;
			return (0);
		}
	}
	return (EPROTONOSUPPORT);
}

int
ip6proto_unregister(short ip6proto)
{
	struct protosw *pr;

	/* Sanity checks. */
	if (ip6proto <= 0 || ip6proto >= IPPROTO_MAX)
		return (EPROTONOSUPPORT);

	/* Check if the protocol was indeed registered. */
	pr = pffindproto(PF_INET6, IPPROTO_RAW, SOCK_RAW);
	if (pr == NULL)
		return (EPFNOSUPPORT);
	if (ip6_protox[ip6proto] == pr - inet6sw)	/* IPPROTO_RAW */
		return (ENOENT);

	/* Reset the protocol slot to IPPROTO_RAW. */
	ip6_protox[ip6proto] = pr - inet6sw;
	return (0);
}

#ifdef VIMAGE
void
ip6_destroy()
{
	int i;

	if ((i = pfil_head_unregister(&V_inet6_pfil_hook)) != 0)
		printf("%s: WARNING: unable to unregister pfil hook, "
		    "error %d\n", __func__, i);
	hashdestroy(V_in6_ifaddrhashtbl, M_IFADDR, V_in6_ifaddrhmask);
	nd6_destroy();
	callout_drain(&V_in6_tmpaddrtimer_ch);
}
#endif

static int
ip6_init2_vnet(const void *unused __unused)
{

	/* nd6_timer_init */
	callout_init(&V_nd6_timer_ch, 0);
	callout_reset(&V_nd6_timer_ch, hz, nd6_timer, curvnet);

	/* timer for regeneranation of temporary addresses randomize ID */
	callout_init(&V_in6_tmpaddrtimer_ch, 0);
	callout_reset(&V_in6_tmpaddrtimer_ch,
		      (V_ip6_temp_preferred_lifetime - V_ip6_desync_factor -
		       V_ip6_temp_regen_advance) * hz,
		      in6_tmpaddrtimer, curvnet);

	return (0);
}

static void
ip6_init2(void *dummy)
{

	ip6_init2_vnet(NULL);
}

/* cheat */
/* This must be after route_init(), which is now SI_ORDER_THIRD */
SYSINIT(netinet6init2, SI_SUB_PROTO_DOMAIN, SI_ORDER_MIDDLE, ip6_init2, NULL);

static int
ip6_input_hbh(struct mbuf *m, uint32_t *plen, uint32_t *rtalert, int *off,
    int *nxt, int *ours)
{
	struct ip6_hdr *ip6;
	struct ip6_hbh *hbh;

	if (ip6_hopopts_input(plen, rtalert, &m, off)) {
#if 0	/*touches NULL pointer*/
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
#endif
		goto out;	/* m have already been freed */
	}

	/* adjust pointer */
	ip6 = mtod(m, struct ip6_hdr *);

	/*
	 * if the payload length field is 0 and the next header field
	 * indicates Hop-by-Hop Options header, then a Jumbo Payload
	 * option MUST be included.
	 */
	if (ip6->ip6_plen == 0 && *plen == 0) {
		/*
		 * Note that if a valid jumbo payload option is
		 * contained, ip6_hopopts_input() must set a valid
		 * (non-zero) payload length to the variable plen.
		 */
		IP6STAT_INC(ip6s_badoptions);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
		icmp6_error(m, ICMP6_PARAM_PROB,
			    ICMP6_PARAMPROB_HEADER,
			    (caddr_t)&ip6->ip6_plen - (caddr_t)ip6);
		goto out;
	}
#ifndef PULLDOWN_TEST
	/* ip6_hopopts_input() ensures that mbuf is contiguous */
	hbh = (struct ip6_hbh *)(ip6 + 1);
#else
	IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m, sizeof(struct ip6_hdr),
		sizeof(struct ip6_hbh));
	if (hbh == NULL) {
		IP6STAT_INC(ip6s_tooshort);
		goto out;
	}
#endif
	*nxt = hbh->ip6h_nxt;

	/*
	 * If we are acting as a router and the packet contains a
	 * router alert option, see if we know the option value.
	 * Currently, we only support the option value for MLD, in which
	 * case we should pass the packet to the multicast routing
	 * daemon.
	 */
	if (*rtalert != ~0) {
		switch (*rtalert) {
		case IP6OPT_RTALERT_MLD:
			if (V_ip6_forwarding)
				*ours = 1;
			break;
		default:
			/*
			 * RFC2711 requires unrecognized values must be
			 * silently ignored.
			 */
			break;
		}
	}

	return (0);

out:
	return (1);
}

void
ip6_input(struct mbuf *m)
{
	struct in6_addr odst;
	struct ip6_hdr *ip6;
	struct in6_ifaddr *ia;
	u_int32_t plen;
	u_int32_t rtalert = ~0;
	int off = sizeof(struct ip6_hdr), nest;
	int nxt, ours = 0;
	int srcrt = 0;

#ifdef IPSEC
	/*
	 * should the inner packet be considered authentic?
	 * see comment in ah4_input().
	 * NB: m cannot be NULL when passed to the input routine
	 */

	m->m_flags &= ~M_AUTHIPHDR;
	m->m_flags &= ~M_AUTHIPDGM;

#endif /* IPSEC */

	if (m->m_flags & M_FASTFWD_OURS) {
		/*
		 * Firewall changed destination to local.
		 */
		m->m_flags &= ~M_FASTFWD_OURS;
		ours = 1;
		ip6 = mtod(m, struct ip6_hdr *);
		goto hbhcheck;
	}

	/*
	 * mbuf statistics
	 */
	if (m->m_flags & M_EXT) {
		if (m->m_next)
			IP6STAT_INC(ip6s_mext2m);
		else
			IP6STAT_INC(ip6s_mext1);
	} else {
		if (m->m_next) {
			if (m->m_flags & M_LOOP) {
				IP6STAT_INC(ip6s_m2m[V_loif->if_index]);
			} else if (m->m_pkthdr.rcvif->if_index < IP6S_M2MMAX)
				IP6STAT_INC(
				    ip6s_m2m[m->m_pkthdr.rcvif->if_index]);
			else
				IP6STAT_INC(ip6s_m2m[0]);
		} else
			IP6STAT_INC(ip6s_m1);
	}

	/* drop the packet if IPv6 operation is disabled on the IF */
	if ((ND_IFINFO(m->m_pkthdr.rcvif)->flags & ND6_IFF_IFDISABLED))
		goto bad;

	in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_receive);
	IP6STAT_INC(ip6s_total);

#ifndef PULLDOWN_TEST
	/*
	 * L2 bridge code and some other code can return mbuf chain
	 * that does not conform to KAME requirement.  too bad.
	 * XXX: fails to join if interface MTU > MCLBYTES.  jumbogram?
	 */
	if (m && m->m_next != NULL && m->m_pkthdr.len < MCLBYTES) {
		struct mbuf *n;

		if (m->m_pkthdr.len > MHLEN)
			n = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
		else
			n = m_gethdr(M_NOWAIT, MT_DATA);
		if (n == NULL) {
			m_freem(m);
			return;	/* ENOBUFS */
		}

		m_move_pkthdr(n, m);
		m_copydata(m, 0, n->m_pkthdr.len, mtod(n, caddr_t));
		n->m_len = n->m_pkthdr.len;
		m_freem(m);
		m = n;
	}
	IP6_EXTHDR_CHECK(m, 0, sizeof(struct ip6_hdr), /* nothing */);
#endif

	if (m->m_len < sizeof(struct ip6_hdr)) {
		struct ifnet *inifp;
		inifp = m->m_pkthdr.rcvif;
		if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
			IP6STAT_INC(ip6s_toosmall);
			in6_ifstat_inc(inifp, ifs6_in_hdrerr);
			return;
		}
	}

	ip6 = mtod(m, struct ip6_hdr *);

	if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
		IP6STAT_INC(ip6s_badvers);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
		goto bad;
	}

	IP6STAT_INC(ip6s_nxthist[ip6->ip6_nxt]);

	IP_PROBE(receive, NULL, NULL, ip6, m->m_pkthdr.rcvif, NULL, ip6);

	/*
	 * Check against address spoofing/corruption.
	 */
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
		/*
		 * XXX: "badscope" is not very suitable for a multicast source.
		 */
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}
	if (IN6_IS_ADDR_MC_INTFACELOCAL(&ip6->ip6_dst) &&
	    !(m->m_flags & M_LOOP)) {
		/*
		 * In this case, the packet should come from the loopback
		 * interface.  However, we cannot just check the if_flags,
		 * because ip6_mloopback() passes the "actual" interface
		 * as the outgoing/incoming interface.
		 */
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) &&
	    IPV6_ADDR_MC_SCOPE(&ip6->ip6_dst) == 0) {
		/*
		 * RFC4291 2.7:
		 * Nodes must not originate a packet to a multicast address
		 * whose scop field contains the reserved value 0; if such
		 * a packet is received, it must be silently dropped.
		 */
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}
#ifdef ALTQ
	if (altq_input != NULL && (*altq_input)(m, AF_INET6) == 0) {
		/* packet is dropped by traffic conditioner */
		return;
	}
#endif
	/*
	 * The following check is not documented in specs.  A malicious
	 * party may be able to use IPv4 mapped addr to confuse tcp/udp stack
	 * and bypass security checks (act as if it was from 127.0.0.1 by using
	 * IPv6 src ::ffff:127.0.0.1).  Be cautious.
	 *
	 * This check chokes if we are in an SIIT cloud.  As none of BSDs
	 * support IPv4-less kernel compilation, we cannot support SIIT
	 * environment at all.  So, it makes more sense for us to reject any
	 * malicious packets for non-SIIT environment, than try to do a
	 * partial support for SIIT environment.
	 */
	if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
	    IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}
#if 0
	/*
	 * Reject packets with IPv4 compatible addresses (auto tunnel).
	 *
	 * The code forbids auto tunnel relay case in RFC1933 (the check is
	 * stronger than RFC1933).  We may want to re-enable it if mech-xx
	 * is revised to forbid relaying case.
	 */
	if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
	    IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}
#endif
#ifdef IPSEC
	/*
	 * Bypass packet filtering for packets previously handled by IPsec.
	 */
	if (ip6_ipsec_filtertunnel(m))
		goto passin;
#endif /* IPSEC */

	/*
	 * Run through list of hooks for input packets.
	 *
	 * NB: Beware of the destination address changing
	 *     (e.g. by NAT rewriting).  When this happens,
	 *     tell ip6_forward to do the right thing.
	 */
	odst = ip6->ip6_dst;

	/* Jump over all PFIL processing if hooks are not active. */
	if (!PFIL_HOOKED(&V_inet6_pfil_hook))
		goto passin;

	if (pfil_run_hooks(&V_inet6_pfil_hook, &m,
	    m->m_pkthdr.rcvif, PFIL_IN, NULL))
		return;
	if (m == NULL)			/* consumed by filter */
		return;
	ip6 = mtod(m, struct ip6_hdr *);
	srcrt = !IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst);

	if (m->m_flags & M_FASTFWD_OURS) {
		m->m_flags &= ~M_FASTFWD_OURS;
		ours = 1;
		goto hbhcheck;
	}
	if ((m->m_flags & M_IP6_NEXTHOP) &&
	    m_tag_find(m, PACKET_TAG_IPFORWARD, NULL) != NULL) {
		/*
		 * Directly ship the packet on.  This allows forwarding
		 * packets originally destined to us to some other directly
		 * connected host.
		 */
		ip6_forward(m, 1);
		return;
	}

passin:
	/*
	 * Disambiguate address scope zones (if there is ambiguity).
	 * We first make sure that the original source or destination address
	 * is not in our internal form for scoped addresses.  Such addresses
	 * are not necessarily invalid spec-wise, but we cannot accept them due
	 * to the usage conflict.
	 * in6_setscope() then also checks and rejects the cases where src or
	 * dst are the loopback address and the receiving interface
	 * is not loopback.
	 */
	if (in6_clearscope(&ip6->ip6_src) || in6_clearscope(&ip6->ip6_dst)) {
		IP6STAT_INC(ip6s_badscope); /* XXX */
		goto bad;
	}
	if (in6_setscope(&ip6->ip6_src, m->m_pkthdr.rcvif, NULL) ||
	    in6_setscope(&ip6->ip6_dst, m->m_pkthdr.rcvif, NULL)) {
		IP6STAT_INC(ip6s_badscope);
		goto bad;
	}
	/*
	 * Multicast check. Assume packet is for us to avoid
	 * prematurely taking locks.
	 */
	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		ours = 1;
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_mcast);
		goto hbhcheck;
	}
	/*
	 * Unicast check
	 * XXX: For now we keep link-local IPv6 addresses with embedded
	 *      scope zone id, therefore we use zero zoneid here.
	 */
	ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
	if (ia != NULL) {
		if (ia->ia6_flags & IN6_IFF_NOTREADY) {
			char ip6bufs[INET6_ADDRSTRLEN];
			char ip6bufd[INET6_ADDRSTRLEN];
			/* address is not ready, so discard the packet. */
			nd6log((LOG_INFO,
			    "ip6_input: packet to an unready address %s->%s\n",
			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
			    ip6_sprintf(ip6bufd, &ip6->ip6_dst)));
			ifa_free(&ia->ia_ifa);
			goto bad;
		}
		/* Count the packet in the ip address stats */
		counter_u64_add(ia->ia_ifa.ifa_ipackets, 1);
		counter_u64_add(ia->ia_ifa.ifa_ibytes, m->m_pkthdr.len);
		ifa_free(&ia->ia_ifa);
		ours = 1;
		goto hbhcheck;
	}

	/*
	 * Now there is no reason to process the packet if it's not our own
	 * and we're not a router.
	 */
	if (!V_ip6_forwarding) {
		IP6STAT_INC(ip6s_cantforward);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
		goto bad;
	}

  hbhcheck:
	/*
	 * Process Hop-by-Hop options header if it's contained.
	 * m may be modified in ip6_hopopts_input().
	 * If a JumboPayload option is included, plen will also be modified.
	 */
	plen = (u_int32_t)ntohs(ip6->ip6_plen);
	if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
		if (ip6_input_hbh(m, &plen, &rtalert, &off, &nxt, &ours) != 0)
			return;
	} else
		nxt = ip6->ip6_nxt;

	/*
	 * Check that the amount of data in the buffers
	 * is as at least much as the IPv6 header would have us expect.
	 * Trim mbufs if longer than we expect.
	 * Drop packet if shorter than we expect.
	 */
	if (m->m_pkthdr.len - sizeof(struct ip6_hdr) < plen) {
		IP6STAT_INC(ip6s_tooshort);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
		goto bad;
	}
	if (m->m_pkthdr.len > sizeof(struct ip6_hdr) + plen) {
		if (m->m_len == m->m_pkthdr.len) {
			m->m_len = sizeof(struct ip6_hdr) + plen;
			m->m_pkthdr.len = sizeof(struct ip6_hdr) + plen;
		} else
			m_adj(m, sizeof(struct ip6_hdr) + plen - m->m_pkthdr.len);
	}

	/*
	 * Forward if desirable.
	 */
	if (V_ip6_mrouter &&
	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
		/*
		 * If we are acting as a multicast router, all
		 * incoming multicast packets are passed to the
		 * kernel-level multicast forwarding function.
		 * The packet is returned (relatively) intact; if
		 * ip6_mforward() returns a non-zero value, the packet
		 * must be discarded, else it may be accepted below.
		 *
		 * XXX TODO: Check hlim and multicast scope here to avoid
		 * unnecessarily calling into ip6_mforward().
		 */
		if (ip6_mforward &&
		    ip6_mforward(ip6, m->m_pkthdr.rcvif, m)) {
			IP6STAT_INC(ip6s_cantforward);
			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
			goto bad;
		}
	} else if (!ours) {
		ip6_forward(m, srcrt);
		return;
	}

	ip6 = mtod(m, struct ip6_hdr *);

	/*
	 * Malicious party may be able to use IPv4 mapped addr to confuse
	 * tcp/udp stack and bypass security checks (act as if it was from
	 * 127.0.0.1 by using IPv6 src ::ffff:127.0.0.1).  Be cautious.
	 *
	 * For SIIT end node behavior, you may want to disable the check.
	 * However, you will  become vulnerable to attacks using IPv4 mapped
	 * source.
	 */
	if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
	    IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
		IP6STAT_INC(ip6s_badscope);
		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
		goto bad;
	}

	/*
	 * Tell launch routine the next header
	 */
	IP6STAT_INC(ip6s_delivered);
	in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_deliver);
	nest = 0;

	while (nxt != IPPROTO_DONE) {
		if (V_ip6_hdrnestlimit && (++nest > V_ip6_hdrnestlimit)) {
			IP6STAT_INC(ip6s_toomanyhdr);
			goto bad;
		}

		/*
		 * protection against faulty packet - there should be
		 * more sanity checks in header chain processing.
		 */
		if (m->m_pkthdr.len < off) {
			IP6STAT_INC(ip6s_tooshort);
			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
			goto bad;
		}

#ifdef IPSEC
		/*
		 * enforce IPsec policy checking if we are seeing last header.
		 * note that we do not visit this with protocols with pcb layer
		 * code - like udp/tcp/raw ip.
		 */
		if (ip6_ipsec_input(m, nxt))
			goto bad;
#endif /* IPSEC */

		/*
		 * Use mbuf flags to propagate Router Alert option to
		 * ICMPv6 layer, as hop-by-hop options have been stripped.
		 */
		if (nxt == IPPROTO_ICMPV6 && rtalert != ~0)
			m->m_flags |= M_RTALERT_MLD;

		nxt = (*inet6sw[ip6_protox[nxt]].pr_input)(&m, &off, nxt);
	}
	return;
bad:
	m_freem(m);
}

/*
 * Hop-by-Hop options header processing. If a valid jumbo payload option is
 * included, the real payload length will be stored in plenp.
 *
 * rtalertp - XXX: should be stored more smart way
 */
static int
ip6_hopopts_input(u_int32_t *plenp, u_int32_t *rtalertp,
    struct mbuf **mp, int *offp)
{
	struct mbuf *m = *mp;
	int off = *offp, hbhlen;
	struct ip6_hbh *hbh;

	/* validation of the length of the header */
#ifndef PULLDOWN_TEST
	IP6_EXTHDR_CHECK(m, off, sizeof(*hbh), -1);
	hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
	hbhlen = (hbh->ip6h_len + 1) << 3;

	IP6_EXTHDR_CHECK(m, off, hbhlen, -1);
	hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
#else
	IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m,
		sizeof(struct ip6_hdr), sizeof(struct ip6_hbh));
	if (hbh == NULL) {
		IP6STAT_INC(ip6s_tooshort);
		return -1;
	}
	hbhlen = (hbh->ip6h_len + 1) << 3;
	IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m, sizeof(struct ip6_hdr),
		hbhlen);
	if (hbh == NULL) {
		IP6STAT_INC(ip6s_tooshort);
		return -1;
	}
#endif
	off += hbhlen;
	hbhlen -= sizeof(struct ip6_hbh);
	if (ip6_process_hopopts(m, (u_int8_t *)hbh + sizeof(struct ip6_hbh),
				hbhlen, rtalertp, plenp) < 0)
		return (-1);

	*offp = off;
	*mp = m;
	return (0);
}

/*
 * Search header for all Hop-by-hop options and process each option.
 * This function is separate from ip6_hopopts_input() in order to
 * handle a case where the sending node itself process its hop-by-hop
 * options header. In such a case, the function is called from ip6_output().
 *
 * The function assumes that hbh header is located right after the IPv6 header
 * (RFC2460 p7), opthead is pointer into data content in m, and opthead to
 * opthead + hbhlen is located in contiguous memory region.
 */
int
ip6_process_hopopts(struct mbuf *m, u_int8_t *opthead, int hbhlen,
    u_int32_t *rtalertp, u_int32_t *plenp)
{
	struct ip6_hdr *ip6;
	int optlen = 0;
	u_int8_t *opt = opthead;
	u_int16_t rtalert_val;
	u_int32_t jumboplen;
	const int erroff = sizeof(struct ip6_hdr) + sizeof(struct ip6_hbh);

	for (; hbhlen > 0; hbhlen -= optlen, opt += optlen) {
		switch (*opt) {
		case IP6OPT_PAD1:
			optlen = 1;
			break;
		case IP6OPT_PADN:
			if (hbhlen < IP6OPT_MINLEN) {
				IP6STAT_INC(ip6s_toosmall);
				goto bad;
			}
			optlen = *(opt + 1) + 2;
			break;
		case IP6OPT_ROUTER_ALERT:
			/* XXX may need check for alignment */
			if (hbhlen < IP6OPT_RTALERT_LEN) {
				IP6STAT_INC(ip6s_toosmall);
				goto bad;
			}
			if (*(opt + 1) != IP6OPT_RTALERT_LEN - 2) {
				/* XXX stat */
				icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_HEADER,
				    erroff + opt + 1 - opthead);
				return (-1);
			}
			optlen = IP6OPT_RTALERT_LEN;
			bcopy((caddr_t)(opt + 2), (caddr_t)&rtalert_val, 2);
			*rtalertp = ntohs(rtalert_val);
			break;
		case IP6OPT_JUMBO:
			/* XXX may need check for alignment */
			if (hbhlen < IP6OPT_JUMBO_LEN) {
				IP6STAT_INC(ip6s_toosmall);
				goto bad;
			}
			if (*(opt + 1) != IP6OPT_JUMBO_LEN - 2) {
				/* XXX stat */
				icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_HEADER,
				    erroff + opt + 1 - opthead);
				return (-1);
			}
			optlen = IP6OPT_JUMBO_LEN;

			/*
			 * IPv6 packets that have non 0 payload length
			 * must not contain a jumbo payload option.
			 */
			ip6 = mtod(m, struct ip6_hdr *);
			if (ip6->ip6_plen) {
				IP6STAT_INC(ip6s_badoptions);
				icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_HEADER,
				    erroff + opt - opthead);
				return (-1);
			}

			/*
			 * We may see jumbolen in unaligned location, so
			 * we'd need to perform bcopy().
			 */
			bcopy(opt + 2, &jumboplen, sizeof(jumboplen));
			jumboplen = (u_int32_t)htonl(jumboplen);

#if 1
			/*
			 * if there are multiple jumbo payload options,
			 * *plenp will be non-zero and the packet will be
			 * rejected.
			 * the behavior may need some debate in ipngwg -
			 * multiple options does not make sense, however,
			 * there's no explicit mention in specification.
			 */
			if (*plenp != 0) {
				IP6STAT_INC(ip6s_badoptions);
				icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_HEADER,
				    erroff + opt + 2 - opthead);
				return (-1);
			}
#endif

			/*
			 * jumbo payload length must be larger than 65535.
			 */
			if (jumboplen <= IPV6_MAXPACKET) {
				IP6STAT_INC(ip6s_badoptions);
				icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_HEADER,
				    erroff + opt + 2 - opthead);
				return (-1);
			}
			*plenp = jumboplen;

			break;
		default:		/* unknown option */
			if (hbhlen < IP6OPT_MINLEN) {
				IP6STAT_INC(ip6s_toosmall);
				goto bad;
			}
			optlen = ip6_unknown_opt(opt, m,
			    erroff + opt - opthead);
			if (optlen == -1)
				return (-1);
			optlen += 2;
			break;
		}
	}

	return (0);

  bad:
	m_freem(m);
	return (-1);
}

/*
 * Unknown option processing.
 * The third argument `off' is the offset from the IPv6 header to the option,
 * which is necessary if the IPv6 header the and option header and IPv6 header
 * is not contiguous in order to return an ICMPv6 error.
 */
int
ip6_unknown_opt(u_int8_t *optp, struct mbuf *m, int off)
{
	struct ip6_hdr *ip6;

	switch (IP6OPT_TYPE(*optp)) {
	case IP6OPT_TYPE_SKIP: /* ignore the option */
		return ((int)*(optp + 1));
	case IP6OPT_TYPE_DISCARD:	/* silently discard */
		m_freem(m);
		return (-1);
	case IP6OPT_TYPE_FORCEICMP: /* send ICMP even if multicasted */
		IP6STAT_INC(ip6s_badoptions);
		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_OPTION, off);
		return (-1);
	case IP6OPT_TYPE_ICMP: /* send ICMP if not multicasted */
		IP6STAT_INC(ip6s_badoptions);
		ip6 = mtod(m, struct ip6_hdr *);
		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
		    (m->m_flags & (M_BCAST|M_MCAST)))
			m_freem(m);
		else
			icmp6_error(m, ICMP6_PARAM_PROB,
				    ICMP6_PARAMPROB_OPTION, off);
		return (-1);
	}

	m_freem(m);		/* XXX: NOTREACHED */
	return (-1);
}

/*
 * Create the "control" list for this pcb.
 * These functions will not modify mbuf chain at all.
 *
 * With KAME mbuf chain restriction:
 * The routine will be called from upper layer handlers like tcp6_input().
 * Thus the routine assumes that the caller (tcp6_input) have already
 * called IP6_EXTHDR_CHECK() and all the extension headers are located in the
 * very first mbuf on the mbuf chain.
 *
 * ip6_savecontrol_v4 will handle those options that are possible to be
 * set on a v4-mapped socket.
 * ip6_savecontrol will directly call ip6_savecontrol_v4 to handle those
 * options and handle the v6-only ones itself.
 */
struct mbuf **
ip6_savecontrol_v4(struct inpcb *inp, struct mbuf *m, struct mbuf **mp,
    int *v4only)
{
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

#ifdef SO_TIMESTAMP
	if ((inp->inp_socket->so_options & SO_TIMESTAMP) != 0) {
		struct timeval tv;

		microtime(&tv);
		*mp = sbcreatecontrol((caddr_t) &tv, sizeof(tv),
		    SCM_TIMESTAMP, SOL_SOCKET);
		if (*mp)
			mp = &(*mp)->m_next;
	}
#endif

#define IS2292(inp, x, y)	(((inp)->inp_flags & IN6P_RFC2292) ? (x) : (y))
	/* RFC 2292 sec. 5 */
	if ((inp->inp_flags & IN6P_PKTINFO) != 0) {
		struct in6_pktinfo pi6;

		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
#ifdef INET
			struct ip *ip;

			ip = mtod(m, struct ip *);
			pi6.ipi6_addr.s6_addr32[0] = 0;
			pi6.ipi6_addr.s6_addr32[1] = 0;
			pi6.ipi6_addr.s6_addr32[2] = IPV6_ADDR_INT32_SMP;
			pi6.ipi6_addr.s6_addr32[3] = ip->ip_dst.s_addr;
#else
			/* We won't hit this code */
			bzero(&pi6.ipi6_addr, sizeof(struct in6_addr));
#endif
		} else {	
			bcopy(&ip6->ip6_dst, &pi6.ipi6_addr, sizeof(struct in6_addr));
			in6_clearscope(&pi6.ipi6_addr);	/* XXX */
		}
		pi6.ipi6_ifindex =
		    (m && m->m_pkthdr.rcvif) ? m->m_pkthdr.rcvif->if_index : 0;

		*mp = sbcreatecontrol((caddr_t) &pi6,
		    sizeof(struct in6_pktinfo),
		    IS2292(inp, IPV6_2292PKTINFO, IPV6_PKTINFO), IPPROTO_IPV6);
		if (*mp)
			mp = &(*mp)->m_next;
	}

	if ((inp->inp_flags & IN6P_HOPLIMIT) != 0) {
		int hlim;

		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
#ifdef INET
			struct ip *ip;

			ip = mtod(m, struct ip *);
			hlim = ip->ip_ttl;
#else
			/* We won't hit this code */
			hlim = 0;
#endif
		} else {
			hlim = ip6->ip6_hlim & 0xff;
		}
		*mp = sbcreatecontrol((caddr_t) &hlim, sizeof(int),
		    IS2292(inp, IPV6_2292HOPLIMIT, IPV6_HOPLIMIT),
		    IPPROTO_IPV6);
		if (*mp)
			mp = &(*mp)->m_next;
	}

	if ((inp->inp_flags & IN6P_TCLASS) != 0) {
		int tclass;

		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
#ifdef INET
			struct ip *ip;

			ip = mtod(m, struct ip *);
			tclass = ip->ip_tos;
#else
			/* We won't hit this code */
			tclass = 0;
#endif
		} else {
			u_int32_t flowinfo;

			flowinfo = (u_int32_t)ntohl(ip6->ip6_flow & IPV6_FLOWINFO_MASK);
			flowinfo >>= 20;
			tclass = flowinfo & 0xff;
		}
		*mp = sbcreatecontrol((caddr_t) &tclass, sizeof(int),
		    IPV6_TCLASS, IPPROTO_IPV6);
		if (*mp)
			mp = &(*mp)->m_next;
	}

	if (v4only != NULL) {
		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
			*v4only = 1;
		} else {
			*v4only = 0;
		}
	}

	return (mp);
}

void
ip6_savecontrol(struct inpcb *in6p, struct mbuf *m, struct mbuf **mp)
{
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
	int v4only = 0;

	mp = ip6_savecontrol_v4(in6p, m, mp, &v4only);
	if (v4only)
		return;

	/*
	 * IPV6_HOPOPTS socket option.  Recall that we required super-user
	 * privilege for the option (see ip6_ctloutput), but it might be too
	 * strict, since there might be some hop-by-hop options which can be
	 * returned to normal user.
	 * See also RFC 2292 section 6 (or RFC 3542 section 8).
	 */
	if ((in6p->inp_flags & IN6P_HOPOPTS) != 0) {
		/*
		 * Check if a hop-by-hop options header is contatined in the
		 * received packet, and if so, store the options as ancillary
		 * data. Note that a hop-by-hop options header must be
		 * just after the IPv6 header, which is assured through the
		 * IPv6 input processing.
		 */
		if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
			struct ip6_hbh *hbh;
			int hbhlen = 0;
#ifdef PULLDOWN_TEST
			struct mbuf *ext;
#endif

#ifndef PULLDOWN_TEST
			hbh = (struct ip6_hbh *)(ip6 + 1);
			hbhlen = (hbh->ip6h_len + 1) << 3;
#else
			ext = ip6_pullexthdr(m, sizeof(struct ip6_hdr),
			    ip6->ip6_nxt);
			if (ext == NULL) {
				IP6STAT_INC(ip6s_tooshort);
				return;
			}
			hbh = mtod(ext, struct ip6_hbh *);
			hbhlen = (hbh->ip6h_len + 1) << 3;
			if (hbhlen != ext->m_len) {
				m_freem(ext);
				IP6STAT_INC(ip6s_tooshort);
				return;
			}
#endif

			/*
			 * XXX: We copy the whole header even if a
			 * jumbo payload option is included, the option which
			 * is to be removed before returning according to
			 * RFC2292.
			 * Note: this constraint is removed in RFC3542
			 */
			*mp = sbcreatecontrol((caddr_t)hbh, hbhlen,
			    IS2292(in6p, IPV6_2292HOPOPTS, IPV6_HOPOPTS),
			    IPPROTO_IPV6);
			if (*mp)
				mp = &(*mp)->m_next;
#ifdef PULLDOWN_TEST
			m_freem(ext);
#endif
		}
	}

	if ((in6p->inp_flags & (IN6P_RTHDR | IN6P_DSTOPTS)) != 0) {
		int nxt = ip6->ip6_nxt, off = sizeof(struct ip6_hdr);

		/*
		 * Search for destination options headers or routing
		 * header(s) through the header chain, and stores each
		 * header as ancillary data.
		 * Note that the order of the headers remains in
		 * the chain of ancillary data.
		 */
		while (1) {	/* is explicit loop prevention necessary? */
			struct ip6_ext *ip6e = NULL;
			int elen;
#ifdef PULLDOWN_TEST
			struct mbuf *ext = NULL;
#endif

			/*
			 * if it is not an extension header, don't try to
			 * pull it from the chain.
			 */
			switch (nxt) {
			case IPPROTO_DSTOPTS:
			case IPPROTO_ROUTING:
			case IPPROTO_HOPOPTS:
			case IPPROTO_AH: /* is it possible? */
				break;
			default:
				goto loopend;
			}

#ifndef PULLDOWN_TEST
			if (off + sizeof(*ip6e) > m->m_len)
				goto loopend;
			ip6e = (struct ip6_ext *)(mtod(m, caddr_t) + off);
			if (nxt == IPPROTO_AH)
				elen = (ip6e->ip6e_len + 2) << 2;
			else
				elen = (ip6e->ip6e_len + 1) << 3;
			if (off + elen > m->m_len)
				goto loopend;
#else
			ext = ip6_pullexthdr(m, off, nxt);
			if (ext == NULL) {
				IP6STAT_INC(ip6s_tooshort);
				return;
			}
			ip6e = mtod(ext, struct ip6_ext *);
			if (nxt == IPPROTO_AH)
				elen = (ip6e->ip6e_len + 2) << 2;
			else
				elen = (ip6e->ip6e_len + 1) << 3;
			if (elen != ext->m_len) {
				m_freem(ext);
				IP6STAT_INC(ip6s_tooshort);
				return;
			}
#endif

			switch (nxt) {
			case IPPROTO_DSTOPTS:
				if (!(in6p->inp_flags & IN6P_DSTOPTS))
					break;

				*mp = sbcreatecontrol((caddr_t)ip6e, elen,
				    IS2292(in6p,
					IPV6_2292DSTOPTS, IPV6_DSTOPTS),
				    IPPROTO_IPV6);
				if (*mp)
					mp = &(*mp)->m_next;
				break;
			case IPPROTO_ROUTING:
				if (!(in6p->inp_flags & IN6P_RTHDR))
					break;

				*mp = sbcreatecontrol((caddr_t)ip6e, elen,
				    IS2292(in6p, IPV6_2292RTHDR, IPV6_RTHDR),
				    IPPROTO_IPV6);
				if (*mp)
					mp = &(*mp)->m_next;
				break;
			case IPPROTO_HOPOPTS:
			case IPPROTO_AH: /* is it possible? */
				break;

			default:
				/*
				 * other cases have been filtered in the above.
				 * none will visit this case.  here we supply
				 * the code just in case (nxt overwritten or
				 * other cases).
				 */
#ifdef PULLDOWN_TEST
				m_freem(ext);
#endif
				goto loopend;

			}

			/* proceed with the next header. */
			off += elen;
			nxt = ip6e->ip6e_nxt;
			ip6e = NULL;
#ifdef PULLDOWN_TEST
			m_freem(ext);
			ext = NULL;
#endif
		}
	  loopend:
		;
	}
}
#undef IS2292

void
ip6_notify_pmtu(struct inpcb *inp, struct sockaddr_in6 *dst, u_int32_t mtu)
{
	struct socket *so;
	struct mbuf *m_mtu;
	struct ip6_mtuinfo mtuctl;

	KASSERT(inp != NULL, ("%s: inp == NULL", __func__));
	/*
	 * Notify the error by sending IPV6_PATHMTU ancillary data if
	 * application wanted to know the MTU value.
	 * NOTE: we notify disconnected sockets, because some udp
	 * applications keep sending sockets disconnected.
	 * NOTE: our implementation doesn't notify connected sockets that has
	 * foreign address that is different than given destination addresses
	 * (this is permitted by RFC 3542).
	 */
	if ((inp->inp_flags & IN6P_MTU) == 0 || (
	    !IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
	    !IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &dst->sin6_addr)))
		return;

	mtuctl.ip6m_mtu = mtu;
	mtuctl.ip6m_addr = *dst;
	if (sa6_recoverscope(&mtuctl.ip6m_addr))
		return;

	if ((m_mtu = sbcreatecontrol((caddr_t)&mtuctl, sizeof(mtuctl),
	    IPV6_PATHMTU, IPPROTO_IPV6)) == NULL)
		return;

	so =  inp->inp_socket;
	if (sbappendaddr(&so->so_rcv, (struct sockaddr *)dst, NULL, m_mtu)
	    == 0) {
		m_freem(m_mtu);
		/* XXX: should count statistics */
	} else
		sorwakeup(so);
}

#ifdef PULLDOWN_TEST
/*
 * pull single extension header from mbuf chain.  returns single mbuf that
 * contains the result, or NULL on error.
 */
static struct mbuf *
ip6_pullexthdr(struct mbuf *m, size_t off, int nxt)
{
	struct ip6_ext ip6e;
	size_t elen;
	struct mbuf *n;

#ifdef DIAGNOSTIC
	switch (nxt) {
	case IPPROTO_DSTOPTS:
	case IPPROTO_ROUTING:
	case IPPROTO_HOPOPTS:
	case IPPROTO_AH: /* is it possible? */
		break;
	default:
		printf("ip6_pullexthdr: invalid nxt=%d\n", nxt);
	}
#endif

	m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
	if (nxt == IPPROTO_AH)
		elen = (ip6e.ip6e_len + 2) << 2;
	else
		elen = (ip6e.ip6e_len + 1) << 3;

	if (elen > MLEN)
		n = m_getcl(M_NOWAIT, MT_DATA, 0);
	else
		n = m_get(M_NOWAIT, MT_DATA);
	if (n == NULL)
		return NULL;

	m_copydata(m, off, elen, mtod(n, caddr_t));
	n->m_len = elen;
	return n;
}
#endif

/*
 * Get pointer to the previous header followed by the header
 * currently processed.
 * XXX: This function supposes that
 *	M includes all headers,
 *	the next header field and the header length field of each header
 *	are valid, and
 *	the sum of each header length equals to OFF.
 * Because of these assumptions, this function must be called very
 * carefully. Moreover, it will not be used in the near future when
 * we develop `neater' mechanism to process extension headers.
 */
char *
ip6_get_prevhdr(struct mbuf *m, int off)
{
	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

	if (off == sizeof(struct ip6_hdr))
		return (&ip6->ip6_nxt);
	else {
		int len, nxt;
		struct ip6_ext *ip6e = NULL;

		nxt = ip6->ip6_nxt;
		len = sizeof(struct ip6_hdr);
		while (len < off) {
			ip6e = (struct ip6_ext *)(mtod(m, caddr_t) + len);

			switch (nxt) {
			case IPPROTO_FRAGMENT:
				len += sizeof(struct ip6_frag);
				break;
			case IPPROTO_AH:
				len += (ip6e->ip6e_len + 2) << 2;
				break;
			default:
				len += (ip6e->ip6e_len + 1) << 3;
				break;
			}
			nxt = ip6e->ip6e_nxt;
		}
		if (ip6e)
			return (&ip6e->ip6e_nxt);
		else
			return NULL;
	}
}

/*
 * get next header offset.  m will be retained.
 */
int
ip6_nexthdr(struct mbuf *m, int off, int proto, int *nxtp)
{
	struct ip6_hdr ip6;
	struct ip6_ext ip6e;
	struct ip6_frag fh;

	/* just in case */
	if (m == NULL)
		panic("ip6_nexthdr: m == NULL");
	if ((m->m_flags & M_PKTHDR) == 0 || m->m_pkthdr.len < off)
		return -1;

	switch (proto) {
	case IPPROTO_IPV6:
		if (m->m_pkthdr.len < off + sizeof(ip6))
			return -1;
		m_copydata(m, off, sizeof(ip6), (caddr_t)&ip6);
		if (nxtp)
			*nxtp = ip6.ip6_nxt;
		off += sizeof(ip6);
		return off;

	case IPPROTO_FRAGMENT:
		/*
		 * terminate parsing if it is not the first fragment,
		 * it does not make sense to parse through it.
		 */
		if (m->m_pkthdr.len < off + sizeof(fh))
			return -1;
		m_copydata(m, off, sizeof(fh), (caddr_t)&fh);
		/* IP6F_OFF_MASK = 0xfff8(BigEndian), 0xf8ff(LittleEndian) */
		if (fh.ip6f_offlg & IP6F_OFF_MASK)
			return -1;
		if (nxtp)
			*nxtp = fh.ip6f_nxt;
		off += sizeof(struct ip6_frag);
		return off;

	case IPPROTO_AH:
		if (m->m_pkthdr.len < off + sizeof(ip6e))
			return -1;
		m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
		if (nxtp)
			*nxtp = ip6e.ip6e_nxt;
		off += (ip6e.ip6e_len + 2) << 2;
		return off;

	case IPPROTO_HOPOPTS:
	case IPPROTO_ROUTING:
	case IPPROTO_DSTOPTS:
		if (m->m_pkthdr.len < off + sizeof(ip6e))
			return -1;
		m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
		if (nxtp)
			*nxtp = ip6e.ip6e_nxt;
		off += (ip6e.ip6e_len + 1) << 3;
		return off;

	case IPPROTO_NONE:
	case IPPROTO_ESP:
	case IPPROTO_IPCOMP:
		/* give up */
		return -1;

	default:
		return -1;
	}

	return -1;
}

/*
 * get offset for the last header in the chain.  m will be kept untainted.
 */
int
ip6_lasthdr(struct mbuf *m, int off, int proto, int *nxtp)
{
	int newoff;
	int nxt;

	if (!nxtp) {
		nxt = -1;
		nxtp = &nxt;
	}
	while (1) {
		newoff = ip6_nexthdr(m, off, proto, nxtp);
		if (newoff < 0)
			return off;
		else if (newoff < off)
			return -1;	/* invalid */
		else if (newoff == off)
			return newoff;

		off = newoff;
		proto = *nxtp;
	}
}

/*
 * System control for IP6
 */

u_char	inet6ctlerrmap[PRC_NCMDS] = {
	0,		0,		0,		0,
	0,		EMSGSIZE,	EHOSTDOWN,	EHOSTUNREACH,
	EHOSTUNREACH,	EHOSTUNREACH,	ECONNREFUSED,	ECONNREFUSED,
	EMSGSIZE,	EHOSTUNREACH,	0,		0,
	0,		0,		0,		0,
	ENOPROTOOPT
};