/*      $NetBSD: ip6_input.c,v 1.228 2024/06/29 13:00:44 riastradh Exp $        */
/*      $KAME: ip6_input.c,v 1.188 2001/03/29 05:34:31 itojun Exp $     */

/*
 * 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.
 */

/*
 * 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.
 *
 *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip6_input.c,v 1.228 2024/06/29 13:00:44 riastradh Exp $");

#ifdef _KERNEL_OPT
#include "opt_gateway.h"
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_net_mpsafe.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/cprng.h>
#include <sys/percpu.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/pktqueue.h>
#include <net/pfil.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#ifdef INET
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#endif /* INET */
#include <netinet/ip6.h>
#include <netinet/portalgo.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet6/in6_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 <netipsec/ipsec6.h>
#include <netipsec/key.h>
#endif /* IPSEC */

#include <netinet6/ip6protosw.h>

#include "faith.h"

extern struct domain inet6domain;

u_char ip6_protox[IPPROTO_MAX];
pktqueue_t *ip6_pktq __read_mostly;

pfil_head_t *inet6_pfil_hook;

percpu_t *ip6stat_percpu;

percpu_t *ip6_forward_rt_percpu __cacheline_aligned;

static void ip6intr(void *);
static void ip6_input(struct mbuf *, struct ifnet *);
static bool ip6_badaddr(struct ip6_hdr *);
static struct m_tag *ip6_setdstifaddr(struct mbuf *, const struct in6_ifaddr *);

static struct m_tag *ip6_addaux(struct mbuf *);
static struct m_tag *ip6_findaux(struct mbuf *);
static void ip6_delaux(struct mbuf *);

static int ip6_process_hopopts(struct mbuf *, u_int8_t *, int, u_int32_t *,
    u_int32_t *);
static struct mbuf *ip6_pullexthdr(struct mbuf *, size_t, int);
static void sysctl_net_inet6_ip6_setup(struct sysctllog **);

#ifdef NET_MPSAFE
#define SOFTNET_LOCK()          mutex_enter(softnet_lock)
#define SOFTNET_UNLOCK()        mutex_exit(softnet_lock)
#else
#define SOFTNET_LOCK()          KASSERT(mutex_owned(softnet_lock))
#define SOFTNET_UNLOCK()        KASSERT(mutex_owned(softnet_lock))
#endif

/* Ensure that non packed structures are the desired size. */
__CTASSERT(sizeof(struct ip6_hdr) == 40);
__CTASSERT(sizeof(struct ip6_ext) == 2);
__CTASSERT(sizeof(struct ip6_hbh) == 2);
__CTASSERT(sizeof(struct ip6_dest) == 2);
__CTASSERT(sizeof(struct ip6_opt) == 2);
__CTASSERT(sizeof(struct ip6_opt_jumbo) == 6);
__CTASSERT(sizeof(struct ip6_opt_nsap) == 4);
__CTASSERT(sizeof(struct ip6_opt_tunnel) == 3);
__CTASSERT(sizeof(struct ip6_opt_router) == 4);
__CTASSERT(sizeof(struct ip6_rthdr) == 4);
__CTASSERT(sizeof(struct ip6_rthdr0) == 8);
__CTASSERT(sizeof(struct ip6_frag) == 8);

/*
 * IP6 initialization: fill in IP6 protocol switch table.
 * All protocols not implemented in kernel go to raw IP6 protocol handler.
 */
void
ip6_init(void)
{
        const struct ip6protosw *pr;
        int i;

        in6_init();

        ip6_pktq = pktq_create(IFQ_MAXLEN, ip6intr, NULL);
        KASSERT(ip6_pktq != NULL);

        sysctl_net_inet6_ip6_setup(NULL);
        pr = (const struct ip6protosw *)pffindproto(PF_INET6, IPPROTO_RAW, SOCK_RAW);
        if (pr == 0)
                panic("ip6_init");
        for (i = 0; i < IPPROTO_MAX; i++)
                ip6_protox[i] = pr - inet6sw;
        for (pr = (const struct ip6protosw *)inet6domain.dom_protosw;
            pr < (const struct ip6protosw *)inet6domain.dom_protoswNPROTOSW; pr++)
                if (pr->pr_domain->dom_family == PF_INET6 &&
                    pr->pr_protocol && pr->pr_protocol != IPPROTO_RAW)
                        ip6_protox[pr->pr_protocol] = pr - inet6sw;

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

#ifdef GATEWAY
        ip6flow_init(ip6_hashsize);
#endif
        /* Register our Packet Filter hook. */
        inet6_pfil_hook = pfil_head_create(PFIL_TYPE_AF, (void *)AF_INET6);
        KASSERT(inet6_pfil_hook != NULL);

        ip6stat_percpu = percpu_alloc(sizeof(uint64_t) * IP6_NSTATS);
        ip6_forward_rt_percpu = rtcache_percpu_alloc();
}

/*
 * IP6 input interrupt handling. Just pass the packet to ip6_input.
 */
static void
ip6intr(void *arg __unused)
{
        struct mbuf *m;

        SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
        while ((m = pktq_dequeue(ip6_pktq)) != NULL) {
                struct psref psref;
                struct ifnet *rcvif = m_get_rcvif_psref(m, &psref);

                if (rcvif == NULL) {
                        IP6_STATINC(IP6_STAT_IFDROP);
                        m_freem(m);
                        continue;
                }
                /*
                 * Drop the packet if IPv6 is disabled on the interface.
                 */
                if ((ND_IFINFO(rcvif)->flags & ND6_IFF_IFDISABLED)) {
                        m_put_rcvif_psref(rcvif, &psref);
                        IP6_STATINC(IP6_STAT_IFDROP);
                        m_freem(m);
                        continue;
                }
                ip6_input(m, rcvif);
                m_put_rcvif_psref(rcvif, &psref);
        }
        SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

static void
ip6_input(struct mbuf *m, struct ifnet *rcvif)
{
        struct ip6_hdr *ip6;
        int hit, off = sizeof(struct ip6_hdr), nest;
        u_int32_t plen;
        u_int32_t rtalert = ~0;
        int nxt, ours = 0, rh_present = 0, frg_present;
        struct ifnet *deliverifp = NULL;
        int srcrt = 0;
        struct rtentry *rt = NULL;
        union {
                struct sockaddr         dst;
                struct sockaddr_in6     dst6;
        } u;
        struct route *ro;

        KASSERT(rcvif != NULL);

        /*
         * make sure we don't have onion peering information into m_tag.
         */
        ip6_delaux(m);

        /*
         * mbuf statistics
         */
        if (m->m_flags & M_EXT) {
                if (m->m_next)
                        IP6_STATINC(IP6_STAT_MEXT2M);
                else
                        IP6_STATINC(IP6_STAT_MEXT1);
        } else {
#define M2MMAX  32
                if (m->m_next) {
                        if (m->m_flags & M_LOOP)
                        /*XXX*/ IP6_STATINC(IP6_STAT_M2M + lo0ifp->if_index);
                        else if (rcvif->if_index < M2MMAX)
                                IP6_STATINC(IP6_STAT_M2M + rcvif->if_index);
                        else
                                IP6_STATINC(IP6_STAT_M2M);
                } else
                        IP6_STATINC(IP6_STAT_M1);
#undef M2MMAX
        }

        in6_ifstat_inc(rcvif, ifs6_in_receive);
        IP6_STATINC(IP6_STAT_TOTAL);

        /*
         * If the IPv6 header is not aligned, slurp it up into a new
         * mbuf with space for link headers, in the event we forward
         * it.  Otherwise, if it is aligned, make sure the entire base
         * IPv6 header is in the first mbuf of the chain.
         */
        if (M_GET_ALIGNED_HDR(&m, struct ip6_hdr, true) != 0) {
                /* XXXJRT new stat, please */
                IP6_STATINC(IP6_STAT_TOOSMALL);
                in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                return;
        }

        ip6 = mtod(m, struct ip6_hdr *);

        if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
                IP6_STATINC(IP6_STAT_BADVERS);
                in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                goto bad;
        }

        if (ip6_badaddr(ip6)) {
                IP6_STATINC(IP6_STAT_BADSCOPE);
                in6_ifstat_inc(rcvif, ifs6_in_addrerr);
                goto bad;
        }

        /*
         * Assume that we can create a fast-forward IP flow entry
         * based on this packet.
         */
        m->m_flags |= M_CANFASTFWD;

        /*
         * Run through list of hooks for input packets.  If there are any
         * filters which require that additional packets in the flow are
         * not fast-forwarded, they must clear the M_CANFASTFWD flag.
         * Note that filters must _never_ set this flag, as another filter
         * in the list may have previously cleared it.
         *
         * Don't call hooks if the packet has already been processed by
         * IPsec (encapsulated, tunnel mode).
         */
#if defined(IPSEC)
        if (!ipsec_used || !ipsec_skip_pfil(m))
#else
        if (1)
#endif
        {
                struct in6_addr odst;
                int error;

                odst = ip6->ip6_dst;
                error = pfil_run_hooks(inet6_pfil_hook, &m, rcvif, PFIL_IN);
                if (error != 0 || m == NULL) {
                        IP6_STATINC(IP6_STAT_PFILDROP_IN);
                        return;
                }
                if (m->m_len < sizeof(struct ip6_hdr)) {
                        if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
                                IP6_STATINC(IP6_STAT_TOOSMALL);
                                in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                                return;
                        }
                }
                ip6 = mtod(m, struct ip6_hdr *);
                srcrt = !IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst);
        }

        IP6_STATINC(IP6_STAT_NXTHIST + ip6->ip6_nxt);

#ifdef ALTQ
        if (altq_input != NULL) {
                SOFTNET_LOCK();
                if ((*altq_input)(m, AF_INET6) == 0) {
                        SOFTNET_UNLOCK();
                        /* packet is dropped by traffic conditioner */
                        return;
                }
                SOFTNET_UNLOCK();
        }
#endif

        /*
         * 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 (__predict_false(
            m_makewritable(&m, 0, sizeof(struct ip6_hdr), M_DONTWAIT))) {
                IP6_STATINC(IP6_STAT_IDROPPED);
                goto bad;
        }
        ip6 = mtod(m, struct ip6_hdr *);
        if (in6_clearscope(&ip6->ip6_src) || in6_clearscope(&ip6->ip6_dst)) {
                IP6_STATINC(IP6_STAT_BADSCOPE); /* XXX */
                goto bad;
        }
        if (in6_setscope(&ip6->ip6_src, rcvif, NULL) ||
            in6_setscope(&ip6->ip6_dst, rcvif, NULL)) {
                IP6_STATINC(IP6_STAT_BADSCOPE);
                goto bad;
        }

        ro = rtcache_percpu_getref(ip6_forward_rt_percpu);

        /*
         * Multicast check
         */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                bool ingroup;

                in6_ifstat_inc(rcvif, ifs6_in_mcast);
                /*
                 * See if we belong to the destination multicast group on the
                 * arrival interface.
                 */
                ingroup = in6_multi_group(&ip6->ip6_dst, rcvif);
                if (ingroup) {
                        ours = 1;
                } else if (!ip6_mrouter) {
                        net_stat_ref_t ip6s = IP6_STAT_GETREF();
                        _NET_STATINC_REF(ip6s, IP6_STAT_NOTMEMBER);
                        _NET_STATINC_REF(ip6s, IP6_STAT_CANTFORWARD);
                        IP6_STAT_PUTREF();
                        in6_ifstat_inc(rcvif, ifs6_in_discard);
                        goto bad_unref;
                }
                deliverifp = rcvif;
                goto hbhcheck;
        }

        sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);

        /*
         * Unicast check
         */
        rt = rtcache_lookup2(ro, &u.dst, 1, &hit);
        if (hit)
                IP6_STATINC(IP6_STAT_FORWARD_CACHEHIT);
        else
                IP6_STATINC(IP6_STAT_FORWARD_CACHEMISS);

        /*
         * Accept the packet if the forwarding interface to the destination
         * (according to the routing table) is the loopback interface,
         * unless the associated route has a gateway.
         *
         * We don't explicitly match ip6_dst against an interface here. It
         * is already done in rtcache_lookup2: rt->rt_ifp->if_type will be
         * IFT_LOOP if the packet is for us.
         *
         * Note that this approach causes to accept a packet if there is a
         * route to the loopback interface for the destination of the packet.
         * But we think it's even useful in some situations, e.g. when using
         * a special daemon which wants to intercept the packet.
         */
        if (rt != NULL &&
            (rt->rt_flags & (RTF_HOST|RTF_GATEWAY)) == RTF_HOST &&
            rt->rt_ifp->if_type == IFT_LOOP) {
                struct in6_ifaddr *ia6 = (struct in6_ifaddr *)rt->rt_ifa;
                int addrok;

                if (ia6->ia6_flags & IN6_IFF_ANYCAST)
                        m->m_flags |= M_ANYCAST6;
                /*
                 * packets to a tentative, duplicated, or somehow invalid
                 * address must not be accepted.
                 */
                if (ia6->ia6_flags & IN6_IFF_NOTREADY)
                        addrok = 0;
                else if (ia6->ia6_flags & IN6_IFF_DETACHED &&
                    !IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src))
                {
                        /* Allow internal traffic to DETACHED addresses */
                        struct sockaddr_in6 sin6;
                        int s;

                        memset(&sin6, 0, sizeof(sin6));
                        sin6.sin6_family = AF_INET6;
                        sin6.sin6_len = sizeof(sin6);
                        sin6.sin6_addr = ip6->ip6_src;
                        s = pserialize_read_enter();
                        addrok = (ifa_ifwithaddr(sin6tosa(&sin6)) != NULL);
                        pserialize_read_exit(s);
                } else
                        addrok = 1;
                if (addrok) {
                        /* this address is ready */
                        ours = 1;
                        deliverifp = ia6->ia_ifp;       /* correct? */
                        goto hbhcheck;
                } else {
                        /* address is not ready, so discard the packet. */
                        char ip6bufs[INET6_ADDRSTRLEN];
                        char ip6bufd[INET6_ADDRSTRLEN];
                        nd6log(LOG_INFO, "packet to an unready address %s->%s\n",
                            IN6_PRINT(ip6bufs, &ip6->ip6_src),
                            IN6_PRINT(ip6bufd, &ip6->ip6_dst));

                        IP6_STATINC(IP6_STAT_IDROPPED);
                        goto bad_unref;
                }
        }

        /*
         * FAITH (Firewall Aided Internet Translator)
         */
#if defined(NFAITH) && 0 < NFAITH
        if (ip6_keepfaith) {
                if (rt != NULL && rt->rt_ifp != NULL &&
                    rt->rt_ifp->if_type == IFT_FAITH) {
                        /* XXX do we need more sanity checks? */
                        ours = 1;
                        deliverifp = rt->rt_ifp; /* faith */
                        goto hbhcheck;
                }
        }
#endif

        /*
         * Now there is no reason to process the packet if it's not our own
         * and we're not a router.
         */
        if (!ip6_forwarding) {
                IP6_STATINC(IP6_STAT_CANTFORWARD);
                in6_ifstat_inc(rcvif, ifs6_in_discard);
                goto bad_unref;
        }

hbhcheck:
        /*
         * Record address information into m_tag, if we don't have one yet.
         * Note that we are unable to record it, if the address is not listed
         * as our interface address (e.g. multicast addresses, addresses
         * within FAITH prefixes and such).
         */
        if (deliverifp && ip6_getdstifaddr(m) == NULL) {
                struct in6_ifaddr *ia6;
                int s = pserialize_read_enter();

                ia6 = in6_ifawithifp(deliverifp, &ip6->ip6_dst);
                /* Depends on ip6_setdstifaddr never sleep */
                if (ia6 != NULL && ip6_setdstifaddr(m, ia6) == NULL) {
                        /*
                         * XXX maybe we should drop the packet here,
                         * as we could not provide enough information
                         * to the upper layers.
                         */
                }
                pserialize_read_exit(s);
        }

        /*
         * 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) {
                struct ip6_hbh *hbh;

                if (ip6_hopopts_input(&plen, &rtalert, &m, &off)) {
                        /* m already freed */
                        in6_ifstat_inc(rcvif, ifs6_in_discard);
                        rtcache_unref(rt, ro);
                        rtcache_percpu_putref(ip6_forward_rt_percpu);
                        return;
                }

                /* 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.
                         */
                        IP6_STATINC(IP6_STAT_BADOPTIONS);
                        in6_ifstat_inc(rcvif, ifs6_in_discard);
                        in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                        icmp6_error(m, ICMP6_PARAM_PROB,
                                    ICMP6_PARAMPROB_HEADER,
                                    (char *)&ip6->ip6_plen - (char *)ip6);
                        rtcache_unref(rt, ro);
                        rtcache_percpu_putref(ip6_forward_rt_percpu);
                        return;
                }
                IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m, sizeof(struct ip6_hdr),
                        sizeof(struct ip6_hbh));
                if (hbh == NULL) {
                        IP6_STATINC(IP6_STAT_TOOSHORT);
                        rtcache_unref(rt, ro);
                        rtcache_percpu_putref(ip6_forward_rt_percpu);
                        return;
                }
                KASSERT(ACCESSIBLE_POINTER(hbh, struct ip6_hdr));
                nxt = hbh->ip6h_nxt;

                /*
                 * accept the packet if a router alert option is included
                 * and we act as an IPv6 router.
                 */
                if (rtalert != ~0 && ip6_forwarding)
                        ours = 1;
        } else
                nxt = ip6->ip6_nxt;

        /*
         * Check that the amount of data in the buffers is 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) {
                IP6_STATINC(IP6_STAT_TOOSHORT);
                in6_ifstat_inc(rcvif, ifs6_in_truncated);
                goto bad_unref;
        }
        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 (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.
                 */
                if (ip6_mrouter != NULL) {
                        int error;

                        SOFTNET_LOCK();
                        error = ip6_mforward(ip6, rcvif, m);
                        SOFTNET_UNLOCK();

                        if (error != 0) {
                                rtcache_unref(rt, ro);
                                rtcache_percpu_putref(ip6_forward_rt_percpu);
                                IP6_STATINC(IP6_STAT_CANTFORWARD);
                                goto bad;
                        }
                }
                if (!ours) {
                        IP6_STATINC(IP6_STAT_CANTFORWARD);
                        goto bad_unref;
                }
        } else if (!ours) {
                rtcache_unref(rt, ro);
                rtcache_percpu_putref(ip6_forward_rt_percpu);
                ip6_forward(m, srcrt, rcvif);
                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)) {
                IP6_STATINC(IP6_STAT_BADSCOPE);
                in6_ifstat_inc(rcvif, ifs6_in_addrerr);
                goto bad_unref;
        }

#ifdef IFA_STATS
        if (deliverifp != NULL) {
                struct in6_ifaddr *ia6;
                int s = pserialize_read_enter();
                ia6 = in6_ifawithifp(deliverifp, &ip6->ip6_dst);
                if (ia6)
                        ia6->ia_ifa.ifa_data.ifad_inbytes += m->m_pkthdr.len;
                pserialize_read_exit(s);
        }
#endif
        IP6_STATINC(IP6_STAT_DELIVERED);
        in6_ifstat_inc(deliverifp, ifs6_in_deliver);
        nest = 0;

        if (rt != NULL) {
                rtcache_unref(rt, ro);
                rt = NULL;
        }
        rtcache_percpu_putref(ip6_forward_rt_percpu);

        rh_present = 0;
        frg_present = 0;
        while (nxt != IPPROTO_DONE) {
                if (ip6_hdrnestlimit && (++nest > ip6_hdrnestlimit)) {
                        IP6_STATINC(IP6_STAT_TOOMANYHDR);
                        in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                        goto bad;
                }

                M_VERIFY_PACKET(m);

                /*
                 * protection against faulty packet - there should be
                 * more sanity checks in header chain processing.
                 */
                if (m->m_pkthdr.len < off) {
                        IP6_STATINC(IP6_STAT_TOOSHORT);
                        in6_ifstat_inc(rcvif, ifs6_in_truncated);
                        goto bad;
                }

                if (nxt == IPPROTO_ROUTING) {
                        if (rh_present++) {
                                in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                                IP6_STATINC(IP6_STAT_BADOPTIONS);
                                goto bad;
                        }
                } else if (nxt == IPPROTO_FRAGMENT) {
                        if (frg_present++) {
                                in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
                                IP6_STATINC(IP6_STAT_BADOPTIONS);
                                goto bad;
                        }
                }

#ifdef IPSEC
                if (ipsec_used) {
                        /*
                         * 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 ((inet6sw[ip6_protox[nxt]].pr_flags
                            & PR_LASTHDR) != 0) {
                                int error;

                                error = ipsec_ip_input_checkpolicy(m, false);
                                if (error) {
                                        IP6_STATINC(IP6_STAT_IPSECDROP_IN);
                                        goto bad;
                                }
                        }
                }
#endif

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

bad_unref:
        rtcache_unref(rt, ro);
        rtcache_percpu_putref(ip6_forward_rt_percpu);
bad:
        m_freem(m);
        return;
}

static bool
ip6_badaddr(struct ip6_hdr *ip6)
{
        /* Check against address spoofing/corruption. */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
            IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
                return true;
        }

        /*
         * 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)) {
                return true;
        }

        /*
         * Reject packets with IPv4-compatible IPv6 addresses (RFC4291).
         */
        if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
            IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
                return true;
        }

        return false;
}

/*
 * set/grab in6_ifaddr correspond to IPv6 destination address.
 */
static struct m_tag *
ip6_setdstifaddr(struct mbuf *m, const struct in6_ifaddr *ia)
{
        struct m_tag *mtag;
        struct ip6aux *ip6a;

        mtag = ip6_addaux(m);
        if (mtag == NULL)
                return NULL;

        ip6a = (struct ip6aux *)(mtag + 1);
        if (in6_setscope(&ip6a->ip6a_src, ia->ia_ifp, &ip6a->ip6a_scope_id)) {
                IP6_STATINC(IP6_STAT_BADSCOPE);
                return NULL;
        }

        ip6a->ip6a_src = ia->ia_addr.sin6_addr;
        ip6a->ip6a_flags = ia->ia6_flags;
        return mtag;
}

const struct ip6aux *
ip6_getdstifaddr(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = ip6_findaux(m);
        if (mtag != NULL)
                return (struct ip6aux *)(mtag + 1);
        else
                return NULL;
}

/*
 * 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
 */
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 */
        IP6_EXTHDR_GET(hbh, struct ip6_hbh *, m,
            sizeof(struct ip6_hdr), sizeof(struct ip6_hbh));
        if (hbh == NULL) {
                IP6_STATINC(IP6_STAT_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) {
                IP6_STATINC(IP6_STAT_TOOSHORT);
                return -1;
        }
        KASSERT(ACCESSIBLE_POINTER(hbh, struct ip6_hdr));
        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 continuous memory region.
 */
static 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) {
                                IP6_STATINC(IP6_STAT_TOOSMALL);
                                goto bad;
                        }
                        optlen = *(opt + 1) + 2;
                        break;
                case IP6OPT_RTALERT:
                        /* XXX may need check for alignment */
                        if (hbhlen < IP6OPT_RTALERT_LEN) {
                                IP6_STATINC(IP6_STAT_TOOSMALL);
                                goto bad;
                        }
                        if (*(opt + 1) != IP6OPT_RTALERT_LEN - 2) {
                                IP6_STATINC(IP6_STAT_BADOPTIONS);
                                icmp6_error(m, ICMP6_PARAM_PROB,
                                    ICMP6_PARAMPROB_HEADER,
                                    erroff + opt + 1 - opthead);
                                return (-1);
                        }
                        optlen = IP6OPT_RTALERT_LEN;
                        memcpy((void *)&rtalert_val, (void *)(opt + 2), 2);
                        *rtalertp = ntohs(rtalert_val);
                        break;
                case IP6OPT_JUMBO:
                        /* XXX may need check for alignment */
                        if (hbhlen < IP6OPT_JUMBO_LEN) {
                                IP6_STATINC(IP6_STAT_TOOSMALL);
                                goto bad;
                        }
                        if (*(opt + 1) != IP6OPT_JUMBO_LEN - 2) {
                                IP6_STATINC(IP6_STAT_BADOPTIONS);
                                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) {
                                IP6_STATINC(IP6_STAT_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 memcpy().
                         */
                        memcpy(&jumboplen, opt + 2, 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) {
                                IP6_STATINC(IP6_STAT_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) {
                                IP6_STATINC(IP6_STAT_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) {
                                IP6_STATINC(IP6_STAT_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 continuous 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 */
                IP6_STATINC(IP6_STAT_BADOPTIONS);
                icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_OPTION, off);
                return (-1);
        case IP6OPT_TYPE_ICMP: /* send ICMP if not multicasted */
                IP6_STATINC(IP6_STAT_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);
}

void
ip6_savecontrol(struct inpcb *inp, struct mbuf **mp, 
        struct ip6_hdr *ip6, struct mbuf *m)
{
        struct socket *so = inp->inp_socket;
#ifdef RFC2292
#define IS2292(x, y)    ((inp->inp_flags & IN6P_RFC2292) ? (x) : (y))
#else
#define IS2292(x, y)    (y)
#endif

        KASSERT(m->m_flags & M_PKTHDR);

        if (SOOPT_TIMESTAMP(so->so_options))
                mp = sbsavetimestamp(so->so_options, mp);

        /* some OSes call this logic with IPv4 packet, for SO_TIMESTAMP */
        if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION)
                return;

        /* RFC 2292 sec. 5 */
        if ((inp->inp_flags & IN6P_PKTINFO) != 0) {
                struct in6_pktinfo pi6;

                memcpy(&pi6.ipi6_addr, &ip6->ip6_dst, sizeof(struct in6_addr));
                in6_clearscope(&pi6.ipi6_addr); /* XXX */
                pi6.ipi6_ifindex = m->m_pkthdr.rcvif_index;
                *mp = sbcreatecontrol(&pi6, sizeof(pi6),
                    IS2292(IPV6_2292PKTINFO, IPV6_PKTINFO), IPPROTO_IPV6);
                if (*mp)
                        mp = &(*mp)->m_next;
        }

        if (inp->inp_flags & IN6P_HOPLIMIT) {
                int hlim = ip6->ip6_hlim & 0xff;

                *mp = sbcreatecontrol(&hlim, sizeof(hlim),
                    IS2292(IPV6_2292HOPLIMIT, IPV6_HOPLIMIT), IPPROTO_IPV6);
                if (*mp)
                        mp = &(*mp)->m_next;
        }

        if ((inp->inp_flags & IN6P_TCLASS) != 0) {
                u_int32_t flowinfo;
                int tclass;

                flowinfo = (u_int32_t)ntohl(ip6->ip6_flow & IPV6_FLOWINFO_MASK);
                flowinfo >>= 20;

                tclass = flowinfo & 0xff;
                *mp = sbcreatecontrol(&tclass, sizeof(tclass),
                    IPV6_TCLASS, IPPROTO_IPV6);

                if (*mp)
                        mp = &(*mp)->m_next;
        }

        /*
         * 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 RFC3542 section 8 (or RFC2292 section 6).
         */
        if ((inp->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 fact is assured through
                 * the IPv6 input processing.
                 */
                struct ip6_hdr *xip6 = mtod(m, struct ip6_hdr *);
                if (xip6->ip6_nxt == IPPROTO_HOPOPTS) {
                        struct ip6_hbh *hbh;
                        int hbhlen;
                        struct mbuf *ext;

                        ext = ip6_pullexthdr(m, sizeof(struct ip6_hdr),
                            xip6->ip6_nxt);
                        if (ext == NULL) {
                                IP6_STATINC(IP6_STAT_TOOSHORT);
                                return;
                        }
                        hbh = mtod(ext, struct ip6_hbh *);
                        hbhlen = (hbh->ip6h_len + 1) << 3;
                        if (hbhlen != ext->m_len) {
                                m_freem(ext);
                                IP6_STATINC(IP6_STAT_TOOSHORT);
                                return;
                        }

                        /*
                         * XXX: We copy whole the header even if a jumbo
                         * payload option is included, which option is to
                         * be removed before returning in the RFC 2292.
                         * Note: this constraint is removed in RFC3542.
                         */
                        *mp = sbcreatecontrol(hbh, hbhlen,
                            IS2292(IPV6_2292HOPOPTS, IPV6_HOPOPTS),
                            IPPROTO_IPV6);
                        if (*mp)
                                mp = &(*mp)->m_next;
                        m_freem(ext);
                }
        }

        /* IPV6_DSTOPTS and IPV6_RTHDR socket options */
        if (inp->inp_flags & (IN6P_DSTOPTS | IN6P_RTHDR)) {
                struct ip6_hdr *xip6 = mtod(m, struct ip6_hdr *);
                int nxt = xip6->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.
                 */
                for (;;) {      /* is explicit loop prevention necessary? */
                        struct ip6_ext *ip6e = NULL;
                        int elen;
                        struct mbuf *ext = NULL;

                        /*
                         * 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;
                        }

                        ext = ip6_pullexthdr(m, off, nxt);
                        if (ext == NULL) {
                                IP6_STATINC(IP6_STAT_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);
                                IP6_STATINC(IP6_STAT_TOOSHORT);
                                return;
                        }
                        KASSERT(ACCESSIBLE_POINTER(ip6e, struct ip6_hdr));

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

                                *mp = sbcreatecontrol(ip6e, elen,
                                    IS2292(IPV6_2292DSTOPTS, IPV6_DSTOPTS),
                                    IPPROTO_IPV6);
                                if (*mp)
                                        mp = &(*mp)->m_next;
                                break;

                        case IPPROTO_ROUTING:
                                if (!(inp->inp_flags & IN6P_RTHDR))
                                        break;

                                *mp = sbcreatecontrol(ip6e, elen,
                                    IS2292(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).
                                 */
                                m_freem(ext);
                                goto loopend;

                        }

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


void
ip6_notify_pmtu(struct inpcb *inp, const struct sockaddr_in6 *dst,
    uint32_t *mtu)
{
        struct socket *so;
        struct mbuf *m_mtu;
        struct ip6_mtuinfo mtuctl;

        so = inp->inp_socket;

        if (mtu == NULL)
                return;

        KASSERT(so != NULL);

        memset(&mtuctl, 0, sizeof(mtuctl));     /* zero-clear for safety */
        mtuctl.ip6m_mtu = *mtu;
        mtuctl.ip6m_addr = *dst;
        if (sa6_recoverscope(&mtuctl.ip6m_addr))
                return;

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

        if (sbappendaddr(&so->so_rcv, (const struct sockaddr *)dst, NULL, m_mtu)
            == 0) {
                soroverflow(so);
                m_freem(m_mtu);
        } else
                sorwakeup(so);

        return;
}

/*
 * 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;

        if (off + sizeof(ip6e) > m->m_pkthdr.len)
                return NULL;

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

        if (off + elen > m->m_pkthdr.len)
                return NULL;

        MGET(n, M_DONTWAIT, MT_DATA);
        if (n && elen >= MLEN) {
                MCLGET(n, M_DONTWAIT);
                if ((n->m_flags & M_EXT) == 0) {
                        m_free(n);
                        n = NULL;
                }
        }
        if (!n)
                return NULL;

        n->m_len = 0;
        if (elen >= M_TRAILINGSPACE(n)) {
                m_free(n);
                return NULL;
        }

        m_copydata(m, off, elen, mtod(n, void *));
        n->m_len = elen;
        return n;
}

/*
 * Get offset to the previous header followed by the header
 * currently processed.
 */
int
ip6_get_prevhdr(struct mbuf *m, int off)
{
        struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);

        if (off == sizeof(struct ip6_hdr)) {
                return offsetof(struct ip6_hdr, ip6_nxt);
        } else if (off < sizeof(struct ip6_hdr)) {
                panic("%s: off < sizeof(struct ip6_hdr)", __func__);
        } else {
                int len, nlen, nxt;
                struct ip6_ext ip6e;

                nxt = ip6->ip6_nxt;
                len = sizeof(struct ip6_hdr);
                nlen = 0;
                while (len < off) {
                        m_copydata(m, len, sizeof(ip6e), &ip6e);

                        switch (nxt) {
                        case IPPROTO_FRAGMENT:
                                nlen = sizeof(struct ip6_frag);
                                break;
                        case IPPROTO_AH:
                                nlen = (ip6e.ip6e_len + 2) << 2;
                                break;
                        default:
                                nlen = (ip6e.ip6e_len + 1) << 3;
                                break;
                        }
                        len += nlen;
                        nxt = ip6e.ip6e_nxt;
                }

                return (len - nlen);
        }
}

/*
 * 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("%s: m == NULL", __func__);
        if ((m->m_flags & M_PKTHDR) == 0 || m->m_pkthdr.len < off)
                return -1;

        switch (proto) {
        case IPPROTO_IPV6:
                /* do not chase beyond intermediate IPv6 headers */
                if (off != 0)
                        return -1;
                if (m->m_pkthdr.len < off + sizeof(ip6))
                        return -1;
                m_copydata(m, off, sizeof(ip6), (void *)&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), (void *)&fh);
                if ((fh.ip6f_offlg & IP6F_OFF_MASK) != 0)
                        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), (void *)&ip6e);
                if (nxtp)
                        *nxtp = ip6e.ip6e_nxt;
                off += (ip6e.ip6e_len + 2) << 2;
                if (m->m_pkthdr.len < off)
                        return -1;
                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), (void *)&ip6e);
                if (nxtp)
                        *nxtp = ip6e.ip6e_nxt;
                off += (ip6e.ip6e_len + 1) << 3;
                if (m->m_pkthdr.len < off)
                        return -1;
                return off;

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

        default:
                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;
        }
        for (;;) {
                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;
        }
}

static struct m_tag *
ip6_addaux(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = m_tag_find(m, PACKET_TAG_INET6);
        if (!mtag) {
                mtag = m_tag_get(PACKET_TAG_INET6, sizeof(struct ip6aux),
                    M_NOWAIT);
                if (mtag) {
                        m_tag_prepend(m, mtag);
                        memset(mtag + 1, 0, sizeof(struct ip6aux));
                }
        }
        return mtag;
}

static struct m_tag *
ip6_findaux(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = m_tag_find(m, PACKET_TAG_INET6);
        return mtag;
}

static void
ip6_delaux(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = m_tag_find(m, PACKET_TAG_INET6);
        if (mtag)
                m_tag_delete(m, mtag);
}

/*
 * System control for IP6
 */

const 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
};

extern int sysctl_net_inet6_addrctlpolicy(SYSCTLFN_ARGS);

static int
sysctl_net_inet6_ip6_stats(SYSCTLFN_ARGS)
{

        return (NETSTAT_SYSCTL(ip6stat_percpu, IP6_NSTATS));
}

static void
sysctl_net_inet6_ip6_setup(struct sysctllog **clog)
{
        const struct sysctlnode *ip6_node;

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "inet6",
                       SYSCTL_DESCR("PF_INET6 related settings"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, CTL_EOL);
        sysctl_createv(clog, 0, NULL, &ip6_node,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "ip6",
                       SYSCTL_DESCR("IPv6 related settings"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6, CTL_EOL);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "forwarding",
                       SYSCTL_DESCR("Enable forwarding of INET6 datagrams"),
                       NULL, 0, &ip6_forwarding, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_FORWARDING, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "redirect",
                       SYSCTL_DESCR("Enable sending of ICMPv6 redirect messages"),
                       NULL, 0, &ip6_sendredirects, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_SENDREDIRECTS, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "hlim",
                       SYSCTL_DESCR("Hop limit for an INET6 datagram"),
                       NULL, 0, &ip6_defhlim, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_DEFHLIM, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "maxfragpackets",
                       SYSCTL_DESCR("Maximum number of fragments to buffer "
                                    "for reassembly"),
                       NULL, 0, &ip6_maxfragpackets, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_MAXFRAGPACKETS, CTL_EOL);

        pktq_sysctl_setup(ip6_pktq, clog, ip6_node, IPV6CTL_IFQ);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "keepfaith",
                       SYSCTL_DESCR("Activate faith interface"),
                       NULL, 0, &ip6_keepfaith, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_KEEPFAITH, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "log_interval",
                       SYSCTL_DESCR("Minimum interval between logging "
                                    "unroutable packets"),
                       NULL, 0, &ip6_log_interval, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_LOG_INTERVAL, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "hdrnestlimit",
                       SYSCTL_DESCR("Maximum number of nested IPv6 headers"),
                       NULL, 0, &ip6_hdrnestlimit, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_HDRNESTLIMIT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "dad_count",
                       SYSCTL_DESCR("Number of Duplicate Address Detection "
                                    "probes to send"),
                       NULL, 0, &ip6_dad_count, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_DAD_COUNT, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "auto_flowlabel",
                       SYSCTL_DESCR("Assign random IPv6 flow labels"),
                       NULL, 0, &ip6_auto_flowlabel, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_AUTO_FLOWLABEL, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "defmcasthlim",
                       SYSCTL_DESCR("Default multicast hop limit"),
                       NULL, 0, &ip6_defmcasthlim, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_DEFMCASTHLIM, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRING, "kame_version",
                       SYSCTL_DESCR("KAME Version"),
                       NULL, 0, __UNCONST(__KAME_VERSION), 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_KAME_VERSION, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "use_deprecated",
                       SYSCTL_DESCR("Allow use of deprecated addresses as "
                                    "source addresses"),
                       NULL, 0, &ip6_use_deprecated, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_USE_DEPRECATED, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT
#ifndef INET6_BINDV6ONLY
                       |CTLFLAG_READWRITE,
#endif
                       CTLTYPE_INT, "v6only",
                       SYSCTL_DESCR("Disallow PF_INET6 sockets from connecting "
                                    "to PF_INET sockets"),
                       NULL, 0, &ip6_v6only, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_V6ONLY, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "anonportmin",
                       SYSCTL_DESCR("Lowest ephemeral port number to assign"),
                       sysctl_net_inet_ip_ports, 0, &ip6_anonportmin, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_ANONPORTMIN, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "anonportmax",
                       SYSCTL_DESCR("Highest ephemeral port number to assign"),
                       sysctl_net_inet_ip_ports, 0, &ip6_anonportmax, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_ANONPORTMAX, CTL_EOL);
#ifndef IPNOPRIVPORTS
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "lowportmin",
                       SYSCTL_DESCR("Lowest privileged ephemeral port number "
                                    "to assign"),
                       sysctl_net_inet_ip_ports, 0, &ip6_lowportmin, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_LOWPORTMIN, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "lowportmax",
                       SYSCTL_DESCR("Highest privileged ephemeral port number "
                                    "to assign"),
                       sysctl_net_inet_ip_ports, 0, &ip6_lowportmax, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_LOWPORTMAX, CTL_EOL);
#endif /* IPNOPRIVPORTS */
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "auto_linklocal",
                       SYSCTL_DESCR("Default value of per-interface flag for "
                                    "adding an IPv6 link-local address to "
                                    "interfaces when attached"),
                       NULL, 0, &ip6_auto_linklocal, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_AUTO_LINKLOCAL, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READONLY,
                       CTLTYPE_STRUCT, "addctlpolicy",
                       SYSCTL_DESCR("Return the current address control"
                           " policy"),
                       sysctl_net_inet6_addrctlpolicy, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_ADDRCTLPOLICY, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "prefer_tempaddr",
                       SYSCTL_DESCR("Prefer temporary address as source "
                                    "address"),
                       NULL, 0, &ip6_prefer_tempaddr, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "maxfrags",
                       SYSCTL_DESCR("Maximum fragments in reassembly queue"),
                       NULL, 0, &ip6_maxfrags, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_MAXFRAGS, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRUCT, "stats",
                       SYSCTL_DESCR("IPv6 statistics"),
                       sysctl_net_inet6_ip6_stats, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_STATS, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "use_defaultzone",
                       SYSCTL_DESCR("Whether to use the default scope zones"),
                       NULL, 0, &ip6_use_defzone, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       IPV6CTL_USE_DEFAULTZONE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "mcast_pmtu",
                       SYSCTL_DESCR("Enable pMTU discovery for multicast packet"),
                       NULL, 0, &ip6_mcast_pmtu, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       CTL_CREATE, CTL_EOL);
        /* anonportalgo RFC6056 subtree */
        const struct sysctlnode *portalgo_node;
        sysctl_createv(clog, 0, NULL, &portalgo_node,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "anonportalgo",
                       SYSCTL_DESCR("Anonymous port algorithm selection (RFC 6056)"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6, CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, &portalgo_node, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRING, "available",
                       SYSCTL_DESCR("available algorithms"),
                       sysctl_portalgo_available, 0, NULL, PORTALGO_MAXLEN,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, &portalgo_node, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_STRING, "selected",
                       SYSCTL_DESCR("selected algorithm"),
                       sysctl_portalgo_selected6, 0, NULL, PORTALGO_MAXLEN,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, &portalgo_node, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_STRUCT, "reserve",
                       SYSCTL_DESCR("bitmap of reserved ports"),
                       sysctl_portalgo_reserve6, 0, NULL, 0,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "neighborgcthresh",
                       SYSCTL_DESCR("Maximum number of entries in neighbor"
                        " cache"),
                       NULL, 1, &ip6_neighborgcthresh, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "maxdynroutes",
                       SYSCTL_DESCR("Maximum number of routes created via"
                           " redirect"),
                       NULL, 1, &ip6_maxdynroutes, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       CTL_CREATE, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "param_rt_msg",
                       SYSCTL_DESCR("How to send parameter changing"
                           " routing message"),
                       NULL, 0, &ip6_param_rt_msg, 0,
                       CTL_NET, PF_INET6, IPPROTO_IPV6,
                       CTL_CREATE, CTL_EOL);
}

void
ip6_statinc(u_int stat)
{

        KASSERT(stat < IP6_NSTATS);
        IP6_STATINC(stat);
}