source: rtems-libbsd/freebsd/sys/netinet6/ip6_input.c @ 2017a6d

#include <machine/rtems-bsd-kernel-space.h>

/*-
 * 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 <rtems/bsd/local/opt_inet.h>
#include <rtems/bsd/local/opt_inet6.h>
#include <rtems/bsd/local/opt_ipfw.h>
#include <rtems/bsd/local/opt_ipsec.h>
#include <rtems/bsd/local/opt_route.h>

#include <rtems/bsd/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/socket.h>
#include <sys/socketvar.h>
#include <rtems/bsd/sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>

#include <net/if.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/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>

#ifdef FLOWTABLE
#include <net/flowtable.h>
VNET_DECLARE(int, ip6_output_flowtable_size);
#define V_ip6_output_flowtable_size     VNET(ip6_output_flowtable_size)
#endif

extern struct domain inet6domain;

u_char ip6_protox[IPPROTO_MAX];
VNET_DEFINE(struct in6_ifaddrhead, in6_ifaddrhead);

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_DEFINE(struct ip6stat, ip6stat);

struct rwlock in6_ifaddr_lock;
RW_SYSINIT(in6_ifaddr_lock, &in6_ifaddr_lock, "in6_ifaddr_lock");

static void ip6_init2(void *);
static struct ip6aux *ip6_setdstifaddr(struct mbuf *, struct in6_ifaddr *);
static struct ip6aux *ip6_addaux(struct mbuf *);
static struct ip6aux *ip6_findaux(struct mbuf *m);
static void ip6_delaux (struct mbuf *);
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 ip6protosw *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);

        /* 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();

#ifdef FLOWTABLE
        if (TUNABLE_INT_FETCH("net.inet6.ip6.output_flowtable_size",
                &V_ip6_output_flowtable_size)) {
                if (V_ip6_output_flowtable_size < 256)
                        V_ip6_output_flowtable_size = 256;
                if (!powerof2(V_ip6_output_flowtable_size)) {
                        printf("flowtable must be power of 2 size\n");
                        V_ip6_output_flowtable_size = 2048;
                }
        } else {
                /*
                 * round up to the next power of 2
                 */
                V_ip6_output_flowtable_size = 1 << fls((1024 + maxusers * 64)-1);
        }
        V_ip6_ft = flowtable_alloc("ipv6", V_ip6_output_flowtable_size, FL_IPV6|FL_PCPU);
#endif  
        
        V_ip6_desync_factor = arc4random() % MAX_TEMP_DESYNC_FACTOR;

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

#ifdef DIAGNOSTIC
        if (sizeof(struct protosw) != sizeof(struct ip6protosw))
                panic("sizeof(protosw) != sizeof(ip6protosw)");
#endif
        pr = (struct ip6protosw *)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 = (struct ip6protosw *)inet6domain.dom_protosw;
            pr < (struct ip6protosw *)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 ip6protosw *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 = (struct ip6protosw *)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 = (struct ip6protosw *)inet6domain.dom_protosw;
            pr < (struct ip6protosw *)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 ip6protosw *pr;

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

        /* Check if the protocol was indeed registered. */
        pr = (struct ip6protosw *)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()
{

        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 ip6_hdr *ip6;
        int off = sizeof(struct ip6_hdr), nest;
        u_int32_t plen;
        u_int32_t rtalert = ~0;
        int nxt, ours = 0;
        struct ifnet *deliverifp = NULL, *ifp = NULL;
        struct in6_addr odst;
        struct route_in6 rin6;
        int srcrt = 0;
        struct llentry *lle = NULL;
        struct sockaddr_in6 dst6, *dst;

        bzero(&rin6, sizeof(struct route_in6));
#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 */

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

        if (m->m_flags & M_FASTFWD_OURS) {
                /*
                 * Firewall changed destination to local.
                 */
                m->m_flags &= ~M_FASTFWD_OURS;
                ours = 1;
                deliverifp = m->m_pkthdr.rcvif;
                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)) {
                m_freem(m);
                return;
        }

        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;

                MGETHDR(n, M_DONTWAIT, MT_HEADER);
                if (n)
                        M_MOVE_PKTHDR(n, m);
                if (n && n->m_pkthdr.len > MHLEN) {
                        MCLGET(n, M_DONTWAIT);
                        if ((n->m_flags & M_EXT) == 0) {
                                m_freem(n);
                                n = NULL;
                        }
                }
                if (n == NULL) {
                        m_freem(m);
                        return; /* ENOBUFS */
                }

                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]);

        /*
         * 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;
                deliverifp = m->m_pkthdr.rcvif;
                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);
                goto out;
        }

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);
                deliverifp = m->m_pkthdr.rcvif;
                goto hbhcheck;
        }

        /*
         *  Unicast check
         */

        bzero(&dst6, sizeof(dst6));
        dst6.sin6_family = AF_INET6;
        dst6.sin6_len = sizeof(struct sockaddr_in6);
        dst6.sin6_addr = ip6->ip6_dst;
        ifp = m->m_pkthdr.rcvif;
        IF_AFDATA_RLOCK(ifp);
        lle = lla_lookup(LLTABLE6(ifp), 0,
             (struct sockaddr *)&dst6);
        IF_AFDATA_RUNLOCK(ifp);
        if ((lle != NULL) && (lle->la_flags & LLE_IFADDR)) {
                struct ifaddr *ifa;
                struct in6_ifaddr *ia6;
                int bad;

                bad = 1;
#define sa_equal(a1, a2)                                                \
        (bcmp((a1), (a2), ((a1))->sin6_len) == 0)
                IF_ADDR_RLOCK(ifp);
                TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
                        if (ifa->ifa_addr->sa_family != dst6.sin6_family)
                                continue;
                        if (sa_equal(&dst6, ifa->ifa_addr))
                                break;
                }
                KASSERT(ifa != NULL, ("%s: ifa not found for lle %p",
                    __func__, lle));
#undef sa_equal

                ia6 = (struct in6_ifaddr *)ifa;
                if (!(ia6->ia6_flags & IN6_IFF_NOTREADY)) {
                        /* Count the packet in the ip address stats */
                        ia6->ia_ifa.if_ipackets++;
                        ia6->ia_ifa.if_ibytes += m->m_pkthdr.len;

                        /*
                         * record address information into m_tag.
                         */
                        (void)ip6_setdstifaddr(m, ia6);

                        bad = 0;
                } else {
                        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)));
                }
                IF_ADDR_RUNLOCK(ifp);
                LLE_RUNLOCK(lle);
                if (bad)
                        goto bad;
                else {
                        ours = 1;
                        deliverifp = ifp;
                        goto hbhcheck;
                }
        }
        if (lle != NULL)
                LLE_RUNLOCK(lle);

        dst = &rin6.ro_dst;
        dst->sin6_len = sizeof(struct sockaddr_in6);
        dst->sin6_family = AF_INET6;
        dst->sin6_addr = ip6->ip6_dst;
        rin6.ro_rt = in6_rtalloc1((struct sockaddr *)dst, 0, 0, M_GETFIB(m));
        if (rin6.ro_rt)
                RT_UNLOCK(rin6.ro_rt);

#define rt6_key(r) ((struct sockaddr_in6 *)((r)->rt_nodes->rn_key))

        /*
         * 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.
         * 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.
         *
         * XXX: some OSes automatically make a cloned route for the destination
         * of an outgoing packet.  If the outgoing interface of the packet
         * is a loopback one, the kernel would consider the packet to be
         * accepted, even if we have no such address assinged on the interface.
         * We check the cloned flag of the route entry to reject such cases,
         * assuming that route entries for our own addresses are not made by
         * cloning (it should be true because in6_addloop explicitly installs
         * the host route).  However, we might have to do an explicit check
         * while it would be less efficient.  Or, should we rather install a
         * reject route for such a case?
         */
        if (rin6.ro_rt &&
            (rin6.ro_rt->rt_flags &
             (RTF_HOST|RTF_GATEWAY)) == RTF_HOST &&
#ifdef RTF_WASCLONED
            !(rin6.ro_rt->rt_flags & RTF_WASCLONED) &&
#endif
#ifdef RTF_CLONED
            !(rin6.ro_rt->rt_flags & RTF_CLONED) &&
#endif
#if 0
            /*
             * The check below is redundant since the comparison of
             * the destination and the key of the rtentry has
             * already done through looking up the routing table.
             */
            IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
            &rt6_key(rin6.ro_rt)->sin6_addr)
#endif
            rin6.ro_rt->rt_ifp->if_type == IFT_LOOP) {
                int free_ia6 = 0;
                struct in6_ifaddr *ia6;

                /*
                 * found the loopback route to the interface address
                 */
                if (rin6.ro_rt->rt_gateway->sa_family == AF_LINK) {
                        struct sockaddr_in6 dest6;

                        bzero(&dest6, sizeof(dest6));
                        dest6.sin6_family = AF_INET6;
                        dest6.sin6_len = sizeof(dest6);
                        dest6.sin6_addr = ip6->ip6_dst;
                        ia6 = (struct in6_ifaddr *)
                            ifa_ifwithaddr((struct sockaddr *)&dest6);
                        if (ia6 == NULL)
                                goto bad;
                        free_ia6 = 1;
                }
                else
                        ia6 = (struct in6_ifaddr *)rin6.ro_rt->rt_ifa;

                /*
                 * record address information into m_tag.
                 */
                (void)ip6_setdstifaddr(m, ia6);

                /*
                 * packets to a tentative, duplicated, or somehow invalid
                 * address must not be accepted.
                 */
                if (!(ia6->ia6_flags & IN6_IFF_NOTREADY)) {
                        /* this address is ready */
                        ours = 1;
                        deliverifp = ia6->ia_ifp;       /* correct? */
                        /* Count the packet in the ip address stats */
                        ia6->ia_ifa.if_ipackets++;
                        ia6->ia_ifa.if_ibytes += m->m_pkthdr.len;
                        if (ia6 != NULL && free_ia6 != 0)
                                ifa_free(&ia6->ia_ifa);
                        goto hbhcheck;
                } else {
                        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)));

                        if (ia6 != NULL && free_ia6 != 0)
                                ifa_free(&ia6->ia_ifa);
                        goto bad;
                }
        }

        /*
         * FAITH (Firewall Aided Internet Translator)
         */
        if (V_ip6_keepfaith) {
                if (rin6.ro_rt && rin6.ro_rt->rt_ifp &&
                    rin6.ro_rt->rt_ifp->if_type == IFT_FAITH) {
                        /* XXX do we need more sanity checks? */
                        ours = 1;
                        deliverifp = rin6.ro_rt->rt_ifp; /* faith */
                        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:
        /*
         * 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) {
                struct in6_ifaddr *ia6;

                if ((ia6 = ip6_getdstifaddr(m)) != NULL) {
                        ifa_free(&ia6->ia_ifa);
                } else {
                        ia6 = in6_ifawithifp(deliverifp, &ip6->ip6_dst);
                        if (ia6) {
                                if (!ip6_setdstifaddr(m, ia6)) {
                                        /*
                                         * XXX maybe we should drop the packet here,
                                         * as we could not provide enough information
                                         * to the upper layers.
                                         */
                                }
                                ifa_free(&ia6->ia_ifa);
                        }
                }
        }

        /*
         * 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) {
                int error;

                error = ip6_input_hbh(m, &plen, &rtalert, &off, &nxt, &ours);
                if (error != 0)
                        goto out;
        } 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);
                goto out;
        }

        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(deliverifp, 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);
        }
        goto out;
bad:
        m_freem(m);
out:
        if (rin6.ro_rt)
                RTFREE(rin6.ro_rt);
}

/*
 * set/grab in6_ifaddr correspond to IPv6 destination address.
 * XXX backward compatibility wrapper
 *
 * XXXRW: We should bump the refcount on ia6 before sticking it in the m_tag,
 * and then bump it when the tag is copied, and release it when the tag is
 * freed.  Unfortunately, m_tags don't support deep copies (yet), so instead
 * we just bump the ia refcount when we receive it.  This should be fixed.
 */
static struct ip6aux *
ip6_setdstifaddr(struct mbuf *m, struct in6_ifaddr *ia6)
{
        struct ip6aux *ip6a;

        ip6a = ip6_addaux(m);
        if (ip6a)
                ip6a->ip6a_dstia6 = ia6;
        return ip6a;    /* NULL if failed to set */
}

struct in6_ifaddr *
ip6_getdstifaddr(struct mbuf *m)
{
        struct ip6aux *ip6a;
        struct in6_ifaddr *ia;

        ip6a = ip6_findaux(m);
        if (ip6a) {
                ia = ip6a->ip6a_dstia6;
                ifa_ref(&ia->ia_ifa);
                return ia;
        } 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
 */
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;

        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, 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;
        }
}

static struct ip6aux *
ip6_addaux(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = m_tag_find(m, PACKET_TAG_IPV6_INPUT, NULL);
        if (!mtag) {
                mtag = m_tag_get(PACKET_TAG_IPV6_INPUT, sizeof(struct ip6aux),
                    M_NOWAIT);
                if (mtag) {
                        m_tag_prepend(m, mtag);
                        bzero(mtag + 1, sizeof(struct ip6aux));
                }
        }
        return mtag ? (struct ip6aux *)(mtag + 1) : NULL;
}

static struct ip6aux *
ip6_findaux(struct mbuf *m)
{
        struct m_tag *mtag;

        mtag = m_tag_find(m, PACKET_TAG_IPV6_INPUT, NULL);
        return mtag ? (struct ip6aux *)(mtag + 1) : NULL;
}

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

        mtag = m_tag_find(m, PACKET_TAG_IPV6_INPUT, NULL);
        if (mtag)
                m_tag_delete(m, mtag);
}

/*
 * 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
};