/*      $NetBSD: ip6_output.c,v 1.235 2024/04/19 00:55:35 riastradh Exp $       */
/*      $KAME: ip6_output.c,v 1.172 2001/03/25 09:55:56 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, 1990, 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_output.c 8.3 (Berkeley) 1/21/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.235 2024/04/19 00:55:35 riastradh Exp $");

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

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/kauth.h>

#include <net/if.h>
#include <net/route.h>
#include <net/pfil.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip6.h>
#include <netinet/ip_var.h>
#include <netinet/icmp6.h>
#include <netinet/in_offload.h>
#include <netinet/portalgo.h>
#include <netinet6/in6_offload.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/nd6.h>
#include <netinet6/ip6protosw.h>
#include <netinet6/scope6_var.h>

#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#include <netipsec/key.h>
#endif

extern pfil_head_t *inet6_pfil_hook;    /* XXX */

struct ip6_exthdrs {
        struct mbuf *ip6e_ip6;
        struct mbuf *ip6e_hbh;
        struct mbuf *ip6e_dest1;
        struct mbuf *ip6e_rthdr;
        struct mbuf *ip6e_dest2;
};

static int ip6_pcbopt(int, u_char *, int, struct ip6_pktopts **,
        kauth_cred_t, int);
static int ip6_getpcbopt(struct ip6_pktopts *, int, struct sockopt *);
static int ip6_setpktopt(int, u_char *, int, struct ip6_pktopts *, kauth_cred_t,
        int, int, int);
static int ip6_setmoptions(const struct sockopt *, struct inpcb *);
static int ip6_getmoptions(struct sockopt *, struct inpcb *);
static int ip6_copyexthdr(struct mbuf **, void *, int);
static int ip6_insertfraghdr(struct mbuf *, struct mbuf *, int,
        struct ip6_frag **);
static int ip6_insert_jumboopt(struct ip6_exthdrs *, u_int32_t);
static int ip6_splithdr(struct mbuf *, struct ip6_exthdrs *);
static int ip6_getpmtu(struct rtentry *, struct ifnet *, u_long *, int *);
static int copypktopts(struct ip6_pktopts *, struct ip6_pktopts *, int);
static int ip6_ifaddrvalid(const struct in6_addr *, const struct in6_addr *);
static int ip6_handle_rthdr(struct ip6_rthdr *, struct ip6_hdr *);

#ifdef RFC2292
static int ip6_pcbopts(struct ip6_pktopts **, struct socket *, struct sockopt *);
#endif

static int
ip6_handle_rthdr(struct ip6_rthdr *rh, struct ip6_hdr *ip6)
{
        int error = 0;

        switch (rh->ip6r_type) {
        case IPV6_RTHDR_TYPE_0:
                /* Dropped, RFC5095. */
        default:        /* is it possible? */
                error = EINVAL;
        }

        return error;
}

/*
 * Send an IP packet to a host.
 */
int
ip6_if_output(struct ifnet * const ifp, struct ifnet * const origifp,
    struct mbuf * const m, const struct sockaddr_in6 * const dst,
    const struct rtentry *rt)
{
        int error = 0;

        if (rt != NULL) {
                error = rt_check_reject_route(rt, ifp);
                if (error != 0) {
                        IP6_STATINC(IP6_STAT_RTREJECT);
                        m_freem(m);
                        return error;
                }
        }

        /* discard the packet if IPv6 operation is disabled on the interface */
        if ((ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED)) {
                m_freem(m);
                return ENETDOWN; /* better error? */
        }

        if ((ifp->if_flags & IFF_LOOPBACK) != 0)
                error = if_output_lock(ifp, origifp, m, sin6tocsa(dst), rt);
        else
                error = if_output_lock(ifp, ifp, m, sin6tocsa(dst), rt);
        return error;
}

/*
 * IP6 output. The packet in mbuf chain m contains a skeletal IP6
 * header (with pri, len, nxt, hlim, src, dst).
 *
 * This function may modify ver and hlim only. The mbuf chain containing the
 * packet will be freed. The mbuf opt, if present, will not be freed.
 *
 * Type of "mtu": rt_rmx.rmx_mtu is u_long, ifnet.ifr_mtu is int, and
 * nd_ifinfo.linkmtu is u_int32_t. So we use u_long to hold largest one,
 * which is rt_rmx.rmx_mtu.
 */
int
ip6_output(
    struct mbuf *m0,
    struct ip6_pktopts *opt,
    struct route *ro,
    int flags,
    struct ip6_moptions *im6o,
    struct inpcb *inp,
    struct ifnet **ifpp         /* XXX: just for statistics */
)
{
        struct ip6_hdr *ip6, *mhip6;
        struct ifnet *ifp = NULL, *origifp = NULL;
        struct mbuf *m = m0;
        int tlen, len, off;
        bool tso;
        struct route ip6route;
        struct rtentry *rt = NULL, *rt_pmtu;
        const struct sockaddr_in6 *dst;
        struct sockaddr_in6 src_sa, dst_sa;
        int error = 0;
        struct in6_ifaddr *ia = NULL;
        u_long mtu;
        int alwaysfrag, dontfrag;
        u_int32_t optlen = 0, plen = 0, unfragpartlen = 0;
        struct ip6_exthdrs exthdrs;
        struct in6_addr finaldst, src0, dst0;
        u_int32_t zone;
        struct route *ro_pmtu = NULL;
        int hdrsplit = 0;
        int needipsec = 0;
#ifdef IPSEC
        struct secpolicy *sp = NULL;
#endif
        struct psref psref, psref_ia;
        int bound = curlwp_bind();
        bool release_psref_ia = false;

#ifdef DIAGNOSTIC
        if ((m->m_flags & M_PKTHDR) == 0)
                panic("ip6_output: no HDR");
        if ((m->m_pkthdr.csum_flags &
            (M_CSUM_TCPv4|M_CSUM_UDPv4|M_CSUM_TSOv4)) != 0) {
                panic("ip6_output: IPv4 checksum offload flags: %d",
                    m->m_pkthdr.csum_flags);
        }
        if ((m->m_pkthdr.csum_flags & (M_CSUM_TCPv6|M_CSUM_UDPv6)) ==
            (M_CSUM_TCPv6|M_CSUM_UDPv6)) {
                panic("ip6_output: conflicting checksum offload flags: %d",
                    m->m_pkthdr.csum_flags);
        }
#endif

        M_CSUM_DATA_IPv6_SET(m->m_pkthdr.csum_data, sizeof(struct ip6_hdr));

#define MAKE_EXTHDR(hp, mp)                                             \
    do {                                                                \
        if (hp) {                                                       \
                struct ip6_ext *eh = (struct ip6_ext *)(hp);            \
                error = ip6_copyexthdr((mp), (void *)(hp),              \
                    ((eh)->ip6e_len + 1) << 3);                         \
                if (error)                                              \
                        goto freehdrs;                                  \
        }                                                               \
    } while (/*CONSTCOND*/ 0)

        memset(&exthdrs, 0, sizeof(exthdrs));
        if (opt) {
                /* Hop-by-Hop options header */
                MAKE_EXTHDR(opt->ip6po_hbh, &exthdrs.ip6e_hbh);
                /* Destination options header (1st part) */
                MAKE_EXTHDR(opt->ip6po_dest1, &exthdrs.ip6e_dest1);
                /* Routing header */
                MAKE_EXTHDR(opt->ip6po_rthdr, &exthdrs.ip6e_rthdr);
                /* Destination options header (2nd part) */
                MAKE_EXTHDR(opt->ip6po_dest2, &exthdrs.ip6e_dest2);
        }

        /*
         * Calculate the total length of the extension header chain.
         * Keep the length of the unfragmentable part for fragmentation.
         */
        optlen = 0;
        if (exthdrs.ip6e_hbh)
                optlen += exthdrs.ip6e_hbh->m_len;
        if (exthdrs.ip6e_dest1)
                optlen += exthdrs.ip6e_dest1->m_len;
        if (exthdrs.ip6e_rthdr)
                optlen += exthdrs.ip6e_rthdr->m_len;
        unfragpartlen = optlen + sizeof(struct ip6_hdr);
        /* NOTE: we don't add AH/ESP length here. do that later. */
        if (exthdrs.ip6e_dest2)
                optlen += exthdrs.ip6e_dest2->m_len;

#ifdef IPSEC
        if (ipsec_used) {
                /* Check the security policy (SP) for the packet */
                sp = ipsec6_check_policy(m, inp, flags, &needipsec, &error);
                if (error != 0) {
                        /*
                         * Hack: -EINVAL is used to signal that a packet
                         * should be silently discarded.  This is typically
                         * because we asked key management for an SA and
                         * it was delayed (e.g. kicked up to IKE).
                         */
                        if (error == -EINVAL)
                                error = 0;
                        IP6_STATINC(IP6_STAT_IPSECDROP_OUT);
                        goto freehdrs;
                }
        }
#endif

        if (needipsec &&
            (m->m_pkthdr.csum_flags & (M_CSUM_UDPv6|M_CSUM_TCPv6)) != 0) {
                in6_undefer_cksum_tcpudp(m);
                m->m_pkthdr.csum_flags &= ~(M_CSUM_UDPv6|M_CSUM_TCPv6);
        }

        /*
         * If we need IPsec, or there is at least one extension header,
         * separate IP6 header from the payload.
         */
        if ((needipsec || optlen) && !hdrsplit) {
                if ((error = ip6_splithdr(m, &exthdrs)) != 0) {
                        IP6_STATINC(IP6_STAT_ODROPPED);
                        m = NULL;
                        goto freehdrs;
                }
                m = exthdrs.ip6e_ip6;
                hdrsplit++;
        }

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

        /* adjust mbuf packet header length */
        m->m_pkthdr.len += optlen;
        plen = m->m_pkthdr.len - sizeof(*ip6);

        /* If this is a jumbo payload, insert a jumbo payload option. */
        if (plen > IPV6_MAXPACKET) {
                if (!hdrsplit) {
                        if ((error = ip6_splithdr(m, &exthdrs)) != 0) {
                                IP6_STATINC(IP6_STAT_ODROPPED);
                                m = NULL;
                                goto freehdrs;
                        }
                        m = exthdrs.ip6e_ip6;
                        hdrsplit++;
                }
                /* adjust pointer */
                ip6 = mtod(m, struct ip6_hdr *);
                if ((error = ip6_insert_jumboopt(&exthdrs, plen)) != 0) {
                        IP6_STATINC(IP6_STAT_ODROPPED);
                        goto freehdrs;
                }
                optlen += 8; /* XXX JUMBOOPTLEN */
                ip6->ip6_plen = 0;
        } else
                ip6->ip6_plen = htons(plen);

        /*
         * Concatenate headers and fill in next header fields.
         * Here we have, on "m"
         *      IPv6 payload
         * and we insert headers accordingly.  Finally, we should be getting:
         *      IPv6 hbh dest1 rthdr ah* [esp* dest2 payload]
         *
         * during the header composing process, "m" points to IPv6 header.
         * "mprev" points to an extension header prior to esp.
         */
        {
                u_char *nexthdrp = &ip6->ip6_nxt;
                struct mbuf *mprev = m;

                /*
                 * we treat dest2 specially.  this makes IPsec processing
                 * much easier.  the goal here is to make mprev point the
                 * mbuf prior to dest2.
                 *
                 * result: IPv6 dest2 payload
                 * m and mprev will point to IPv6 header.
                 */
                if (exthdrs.ip6e_dest2) {
                        if (!hdrsplit)
                                panic("assumption failed: hdr not split");
                        exthdrs.ip6e_dest2->m_next = m->m_next;
                        m->m_next = exthdrs.ip6e_dest2;
                        *mtod(exthdrs.ip6e_dest2, u_char *) = ip6->ip6_nxt;
                        ip6->ip6_nxt = IPPROTO_DSTOPTS;
                }

#define MAKE_CHAIN(m, mp, p, i)\
    do {\
        if (m) {\
                if (!hdrsplit) \
                        panic("assumption failed: hdr not split"); \
                *mtod((m), u_char *) = *(p);\
                *(p) = (i);\
                p = mtod((m), u_char *);\
                (m)->m_next = (mp)->m_next;\
                (mp)->m_next = (m);\
                (mp) = (m);\
        }\
    } while (/*CONSTCOND*/ 0)
                /*
                 * result: IPv6 hbh dest1 rthdr dest2 payload
                 * m will point to IPv6 header.  mprev will point to the
                 * extension header prior to dest2 (rthdr in the above case).
                 */
                MAKE_CHAIN(exthdrs.ip6e_hbh, mprev, nexthdrp, IPPROTO_HOPOPTS);
                MAKE_CHAIN(exthdrs.ip6e_dest1, mprev, nexthdrp,
                    IPPROTO_DSTOPTS);
                MAKE_CHAIN(exthdrs.ip6e_rthdr, mprev, nexthdrp,
                    IPPROTO_ROUTING);

                M_CSUM_DATA_IPv6_SET(m->m_pkthdr.csum_data,
                    sizeof(struct ip6_hdr) + optlen);
        }

        /* Need to save for pmtu */
        finaldst = ip6->ip6_dst;

        /*
         * If there is a routing header, replace destination address field
         * with the first hop of the routing header.
         */
        if (exthdrs.ip6e_rthdr) {
                struct ip6_rthdr *rh;

                rh = mtod(exthdrs.ip6e_rthdr, struct ip6_rthdr *);

                error = ip6_handle_rthdr(rh, ip6);
                if (error != 0) {
                        IP6_STATINC(IP6_STAT_ODROPPED);
                        goto bad;
                }
        }

        /* Source address validation */
        if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) &&
            (flags & IPV6_UNSPECSRC) == 0) {
                error = EOPNOTSUPP;
                IP6_STATINC(IP6_STAT_BADSCOPE);
                goto bad;
        }
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
                error = EOPNOTSUPP;
                IP6_STATINC(IP6_STAT_BADSCOPE);
                goto bad;
        }

        IP6_STATINC(IP6_STAT_LOCALOUT);

        /*
         * Route packet.
         */
        /* initialize cached route */
        if (ro == NULL) {
                memset(&ip6route, 0, sizeof(ip6route));
                ro = &ip6route;
        }
        ro_pmtu = ro;
        if (opt && opt->ip6po_rthdr)
                ro = &opt->ip6po_route;

        /*
         * if specified, try to fill in the traffic class field.
         * do not override if a non-zero value is already set.
         * we check the diffserv field and the ecn field separately.
         */
        if (opt && opt->ip6po_tclass >= 0) {
                int mask = 0;

                if ((ip6->ip6_flow & htonl(0xfc << 20)) == 0)
                        mask |= 0xfc;
                if ((ip6->ip6_flow & htonl(0x03 << 20)) == 0)
                        mask |= 0x03;
                if (mask != 0)
                        ip6->ip6_flow |= htonl((opt->ip6po_tclass & mask) << 20);
        }

        /* fill in or override the hop limit field, if necessary. */
        if (opt && opt->ip6po_hlim != -1)
                ip6->ip6_hlim = opt->ip6po_hlim & 0xff;
        else if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                if (im6o != NULL)
                        ip6->ip6_hlim = im6o->im6o_multicast_hlim;
                else
                        ip6->ip6_hlim = ip6_defmcasthlim;
        }

#ifdef IPSEC
        if (needipsec) {
                error = ipsec6_process_packet(m, sp->req, flags);

                /*
                 * Preserve KAME behaviour: ENOENT can be returned
                 * when an SA acquire is in progress.  Don't propagate
                 * this to user-level; it confuses applications.
                 * XXX this will go away when the SADB is redone.
                 */
                if (error == ENOENT)
                        error = 0;

                goto done;
        }
#endif

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

        sockaddr_in6_init(&dst_sa, &ip6->ip6_dst, 0, 0, 0);

        /* We do not need a route for multicast */
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                struct in6_pktinfo *pi = NULL;

                /*
                 * If the outgoing interface for the address is specified by
                 * the caller, use it.
                 */
                if (opt && (pi = opt->ip6po_pktinfo) != NULL) {
                        /* XXX boundary check is assumed to be already done. */
                        ifp = if_get_byindex(pi->ipi6_ifindex, &psref);
                } else if (im6o != NULL) {
                        ifp = if_get_byindex(im6o->im6o_multicast_if_index,
                            &psref);
                }
        }

        if (ifp == NULL) {
                error = in6_selectroute(&dst_sa, opt, &ro, &rt, true);
                if (error != 0)
                        goto bad;
                ifp = if_get_byindex(rt->rt_ifp->if_index, &psref);
        }

        if (rt == NULL) {
                /*
                 * If in6_selectroute() does not return a route entry,
                 * dst may not have been updated.
                 */
                error = rtcache_setdst(ro, sin6tosa(&dst_sa));
                if (error) {
                        IP6_STATINC(IP6_STAT_ODROPPED);
                        goto bad;
                }
        }

        /*
         * then rt (for unicast) and ifp must be non-NULL valid values.
         */
        if ((flags & IPV6_FORWARDING) == 0) {
                /* XXX: the FORWARDING flag can be set for mrouting. */
                in6_ifstat_inc(ifp, ifs6_out_request);
        }
        if (rt != NULL) {
                ia = (struct in6_ifaddr *)(rt->rt_ifa);
                rt->rt_use++;
        }

        /*
         * The outgoing interface must be in the zone of source and
         * destination addresses.  We should use ia_ifp to support the
         * case of sending packets to an address of our own.
         */
        if (ia != NULL) {
                origifp = ia->ia_ifp;
                if (if_is_deactivated(origifp)) {
                        IP6_STATINC(IP6_STAT_ODROPPED);
                        goto bad;
                }
                if_acquire(origifp, &psref_ia);
                release_psref_ia = true;
        } else
                origifp = ifp;

        src0 = ip6->ip6_src;
        if (in6_setscope(&src0, origifp, &zone))
                goto badscope;
        sockaddr_in6_init(&src_sa, &ip6->ip6_src, 0, 0, 0);
        if (sa6_recoverscope(&src_sa) || zone != src_sa.sin6_scope_id)
                goto badscope;

        dst0 = ip6->ip6_dst;
        if (in6_setscope(&dst0, origifp, &zone))
                goto badscope;
        /* re-initialize to be sure */
        sockaddr_in6_init(&dst_sa, &ip6->ip6_dst, 0, 0, 0);
        if (sa6_recoverscope(&dst_sa) || zone != dst_sa.sin6_scope_id)
                goto badscope;

        /* scope check is done. */

        /* Ensure we only send from a valid address. */
        if ((ifp->if_flags & IFF_LOOPBACK) == 0 &&
            (flags & IPV6_FORWARDING) == 0 &&
            (error = ip6_ifaddrvalid(&src0, &dst0)) != 0)
        {
                char ip6buf[INET6_ADDRSTRLEN];
                nd6log(LOG_ERR,
                    "refusing to send from invalid address %s (pid %d)\n",
                    IN6_PRINT(ip6buf, &src0), curproc->p_pid);
                IP6_STATINC(IP6_STAT_ODROPPED);
                in6_ifstat_inc(origifp, ifs6_out_discard);
                if (error == 1)
                        /*
                         * Address exists, but is tentative or detached.
                         * We can't send from it because it's invalid,
                         * so we drop the packet.
                         */
                        error = 0;
                else
                        error = EADDRNOTAVAIL;
                goto bad;
        }

        if (rt != NULL && (rt->rt_flags & RTF_GATEWAY) &&
            !IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst))
                dst = satocsin6(rt->rt_gateway);
        else
                dst = satocsin6(rtcache_getdst(ro));

        /*
         * XXXXXX: original code follows:
         */
        if (!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst))
                m->m_flags &= ~(M_BCAST | M_MCAST);     /* just in case */
        else {
                bool ingroup;

                m->m_flags = (m->m_flags & ~M_BCAST) | M_MCAST;

                in6_ifstat_inc(ifp, ifs6_out_mcast);

                /*
                 * Confirm that the outgoing interface supports multicast.
                 */
                if (!(ifp->if_flags & IFF_MULTICAST)) {
                        IP6_STATINC(IP6_STAT_NOROUTE);
                        in6_ifstat_inc(ifp, ifs6_out_discard);
                        error = ENETUNREACH;
                        goto bad;
                }

                ingroup = in6_multi_group(&ip6->ip6_dst, ifp);
                if (ingroup && (im6o == NULL || im6o->im6o_multicast_loop)) {
                        /*
                         * If we belong to the destination multicast group
                         * on the outgoing interface, and the caller did not
                         * forbid loopback, loop back a copy.
                         */
                        KASSERT(dst != NULL);
                        ip6_mloopback(ifp, m, dst);
                } else {
                        /*
                         * If we are acting as a multicast router, perform
                         * multicast forwarding as if the packet had just
                         * arrived on the interface to which we are about
                         * to send.  The multicast forwarding function
                         * recursively calls this function, using the
                         * IPV6_FORWARDING flag to prevent infinite recursion.
                         *
                         * Multicasts that are looped back by ip6_mloopback(),
                         * above, will be forwarded by the ip6_input() routine,
                         * if necessary.
                         */
                        if (ip6_mrouter && (flags & IPV6_FORWARDING) == 0) {
                                if (ip6_mforward(ip6, ifp, m) != 0) {
                                        m_freem(m);
                                        goto done;
                                }
                        }
                }
                /*
                 * Multicasts with a hoplimit of zero may be looped back,
                 * above, but must not be transmitted on a network.
                 * Also, multicasts addressed to the loopback interface
                 * are not sent -- the above call to ip6_mloopback() will
                 * loop back a copy if this host actually belongs to the
                 * destination group on the loopback interface.
                 */
                if (ip6->ip6_hlim == 0 || (ifp->if_flags & IFF_LOOPBACK) ||
                    IN6_IS_ADDR_MC_INTFACELOCAL(&ip6->ip6_dst)) {
                        m_freem(m);
                        goto done;
                }
        }

        /*
         * Fill the outgoing interface to tell the upper layer
         * to increment per-interface statistics.
         */
        if (ifpp)
                *ifpp = ifp;

        /* Determine path MTU. */
        /*
         * ro_pmtu represent final destination while
         * ro might represent immediate destination.
         * Use ro_pmtu destination since MTU might differ.
         */
        if (ro_pmtu != ro) {
                union {
                        struct sockaddr         dst;
                        struct sockaddr_in6     dst6;
                } u;

                /* ro_pmtu may not have a cache */
                sockaddr_in6_init(&u.dst6, &finaldst, 0, 0, 0);
                rt_pmtu = rtcache_lookup(ro_pmtu, &u.dst);
        } else
                rt_pmtu = rt;
        error = ip6_getpmtu(rt_pmtu, ifp, &mtu, &alwaysfrag);
        if (rt_pmtu != NULL && rt_pmtu != rt)
                rtcache_unref(rt_pmtu, ro_pmtu);
        KASSERT(error == 0); /* ip6_getpmtu never fail if ifp is passed */

        /*
         * The caller of this function may specify to use the minimum MTU
         * in some cases.
         * An advanced API option (IPV6_USE_MIN_MTU) can also override MTU
         * setting.  The logic is a bit complicated; by default, unicast
         * packets will follow path MTU while multicast packets will be sent at
         * the minimum MTU.  If IP6PO_MINMTU_ALL is specified, all packets
         * including unicast ones will be sent at the minimum MTU.  Multicast
         * packets will always be sent at the minimum MTU unless
         * IP6PO_MINMTU_DISABLE is explicitly specified.
         * See RFC 3542 for more details.
         */
        if (mtu > IPV6_MMTU) {
                if ((flags & IPV6_MINMTU))
                        mtu = IPV6_MMTU;
                else if (opt && opt->ip6po_minmtu == IP6PO_MINMTU_ALL)
                        mtu = IPV6_MMTU;
                else if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) &&
                         (opt == NULL ||
                          opt->ip6po_minmtu != IP6PO_MINMTU_DISABLE)) {
                        mtu = IPV6_MMTU;
                }
        }

        /*
         * clear embedded scope identifiers if necessary.
         * in6_clearscope will touch the addresses only when necessary.
         */
        in6_clearscope(&ip6->ip6_src);
        in6_clearscope(&ip6->ip6_dst);

        /*
         * If the outgoing packet contains a hop-by-hop options header,
         * it must be examined and processed even by the source node.
         * (RFC 2460, section 4.)
         *
         * XXX Is this really necessary?
         */
        if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
                u_int32_t dummy1 = 0; /* XXX unused */
                u_int32_t dummy2; /* XXX unused */
                int hoff = sizeof(struct ip6_hdr);

                if (ip6_hopopts_input(&dummy1, &dummy2, &m, &hoff)) {
                        /* m was already freed at this point */
                        error = EINVAL;
                        goto done;
                }

                ip6 = mtod(m, struct ip6_hdr *);
        }

        /*
         * Run through list of hooks for output packets.
         */
        error = pfil_run_hooks(inet6_pfil_hook, &m, ifp, PFIL_OUT);
        if (error != 0 || m == NULL) {
                IP6_STATINC(IP6_STAT_PFILDROP_OUT);
                goto done;
        }
        ip6 = mtod(m, struct ip6_hdr *);

        /*
         * Send the packet to the outgoing interface.
         * If necessary, do IPv6 fragmentation before sending.
         *
         * the logic here is rather complex:
         * 1: normal case (dontfrag == 0, alwaysfrag == 0)
         * 1-a: send as is if tlen <= path mtu
         * 1-b: fragment if tlen > path mtu
         *
         * 2: if user asks us not to fragment (dontfrag == 1)
         * 2-a: send as is if tlen <= interface mtu
         * 2-b: error if tlen > interface mtu
         *
         * 3: if we always need to attach fragment header (alwaysfrag == 1)
         *      always fragment
         *
         * 4: if dontfrag == 1 && alwaysfrag == 1
         *      error, as we cannot handle this conflicting request
         */
        tlen = m->m_pkthdr.len;
        tso = (m->m_pkthdr.csum_flags & M_CSUM_TSOv6) != 0;
        if (opt && (opt->ip6po_flags & IP6PO_DONTFRAG))
                dontfrag = 1;
        else
                dontfrag = 0;

        if (dontfrag && alwaysfrag) {   /* case 4 */
                /* conflicting request - can't transmit */
                IP6_STATINC(IP6_STAT_CANTFRAG);
                error = EMSGSIZE;
                goto bad;
        }
        if (dontfrag && (!tso && tlen > ifp->if_mtu)) { /* case 2-b */
                /*
                 * Even if the DONTFRAG option is specified, we cannot send the
                 * packet when the data length is larger than the MTU of the
                 * outgoing interface.
                 * Notify the error by sending IPV6_PATHMTU ancillary data as
                 * well as returning an error code (the latter is not described
                 * in the API spec.)
                 */
                u_int32_t mtu32;
                struct ip6ctlparam ip6cp;

                mtu32 = (u_int32_t)mtu;
                memset(&ip6cp, 0, sizeof(ip6cp));
                ip6cp.ip6c_cmdarg = (void *)&mtu32;
                pfctlinput2(PRC_MSGSIZE,
                    rtcache_getdst(ro_pmtu), &ip6cp);

                IP6_STATINC(IP6_STAT_CANTFRAG);
                error = EMSGSIZE;
                goto bad;
        }

        /*
         * transmit packet without fragmentation
         */
        if (dontfrag || (!alwaysfrag && (tlen <= mtu || tso))) {
                /* case 1-a and 2-a */
                struct in6_ifaddr *ia6;
                int sw_csum;
                int s;

                ip6 = mtod(m, struct ip6_hdr *);
                s = pserialize_read_enter();
                ia6 = in6_ifawithifp(ifp, &ip6->ip6_src);
                if (ia6) {
                        /* Record statistics for this interface address. */
                        ia6->ia_ifa.ifa_data.ifad_outbytes += m->m_pkthdr.len;
                }
                pserialize_read_exit(s);

                sw_csum = m->m_pkthdr.csum_flags & ~ifp->if_csum_flags_tx;
                if ((sw_csum & (M_CSUM_UDPv6|M_CSUM_TCPv6)) != 0) {
                        if (IN6_NEED_CHECKSUM(ifp,
                            sw_csum & (M_CSUM_UDPv6|M_CSUM_TCPv6))) {
                                in6_undefer_cksum_tcpudp(m);
                        }
                        m->m_pkthdr.csum_flags &= ~(M_CSUM_UDPv6|M_CSUM_TCPv6);
                }

                KASSERT(dst != NULL);
                if (__predict_false(sw_csum & M_CSUM_TSOv6)) {
                        /*
                         * TSO6 is required by a packet, but disabled for
                         * the interface.
                         */
                        error = ip6_tso_output(ifp, origifp, m, dst, rt);
                } else
                        error = ip6_if_output(ifp, origifp, m, dst, rt);
                goto done;
        }

        if (tso) {
                IP6_STATINC(IP6_STAT_CANTFRAG); /* XXX */
                error = EINVAL; /* XXX */
                goto bad;
        }

        /*
         * try to fragment the packet.  case 1-b and 3
         */
        if (mtu < IPV6_MMTU) {
                /* path MTU cannot be less than IPV6_MMTU */
                IP6_STATINC(IP6_STAT_CANTFRAG);
                error = EMSGSIZE;
                in6_ifstat_inc(ifp, ifs6_out_fragfail);
                goto bad;
        } else if (ip6->ip6_plen == 0) {
                /* jumbo payload cannot be fragmented */
                IP6_STATINC(IP6_STAT_CANTFRAG);
                error = EMSGSIZE;
                in6_ifstat_inc(ifp, ifs6_out_fragfail);
                goto bad;
        } else {
                const uint32_t id = ip6_randomid();
                struct mbuf **mnext, *m_frgpart;
                const int hlen = unfragpartlen;
                struct ip6_frag *ip6f;
                u_char nextproto;

                if (mtu > IPV6_MAXPACKET)
                        mtu = IPV6_MAXPACKET;

                /*
                 * Must be able to put at least 8 bytes per fragment.
                 */
                len = (mtu - hlen - sizeof(struct ip6_frag)) & ~7;
                if (len < 8) {
                        IP6_STATINC(IP6_STAT_CANTFRAG);
                        error = EMSGSIZE;
                        in6_ifstat_inc(ifp, ifs6_out_fragfail);
                        goto bad;
                }

                mnext = &m->m_nextpkt;

                /*
                 * Change the next header field of the last header in the
                 * unfragmentable part.
                 */
                if (exthdrs.ip6e_rthdr) {
                        nextproto = *mtod(exthdrs.ip6e_rthdr, u_char *);
                        *mtod(exthdrs.ip6e_rthdr, u_char *) = IPPROTO_FRAGMENT;
                } else if (exthdrs.ip6e_dest1) {
                        nextproto = *mtod(exthdrs.ip6e_dest1, u_char *);
                        *mtod(exthdrs.ip6e_dest1, u_char *) = IPPROTO_FRAGMENT;
                } else if (exthdrs.ip6e_hbh) {
                        nextproto = *mtod(exthdrs.ip6e_hbh, u_char *);
                        *mtod(exthdrs.ip6e_hbh, u_char *) = IPPROTO_FRAGMENT;
                } else {
                        nextproto = ip6->ip6_nxt;
                        ip6->ip6_nxt = IPPROTO_FRAGMENT;
                }

                if ((m->m_pkthdr.csum_flags & (M_CSUM_UDPv6|M_CSUM_TCPv6))
                    != 0) {
                        if (IN6_NEED_CHECKSUM(ifp,
                            m->m_pkthdr.csum_flags &
                            (M_CSUM_UDPv6|M_CSUM_TCPv6))) {
                                in6_undefer_cksum_tcpudp(m);
                        }
                        m->m_pkthdr.csum_flags &= ~(M_CSUM_UDPv6|M_CSUM_TCPv6);
                }

                /*
                 * Loop through length of segment after first fragment,
                 * make new header and copy data of each part and link onto
                 * chain.
                 */
                m0 = m;
                for (off = hlen; off < tlen; off += len) {
                        struct mbuf *mlast;

                        MGETHDR(m, M_DONTWAIT, MT_HEADER);
                        if (!m) {
                                error = ENOBUFS;
                                IP6_STATINC(IP6_STAT_ODROPPED);
                                goto sendorfree;
                        }
                        m_reset_rcvif(m);
                        m->m_flags = m0->m_flags & M_COPYFLAGS;
                        *mnext = m;
                        mnext = &m->m_nextpkt;
                        m->m_data += max_linkhdr;
                        mhip6 = mtod(m, struct ip6_hdr *);
                        *mhip6 = *ip6;
                        m->m_len = sizeof(*mhip6);

                        ip6f = NULL;
                        error = ip6_insertfraghdr(m0, m, hlen, &ip6f);
                        if (error) {
                                IP6_STATINC(IP6_STAT_ODROPPED);
                                goto sendorfree;
                        }

                        /* Fill in the Frag6 Header */
                        ip6f->ip6f_offlg = htons((u_int16_t)((off - hlen) & ~7));
                        if (off + len >= tlen)
                                len = tlen - off;
                        else
                                ip6f->ip6f_offlg |= IP6F_MORE_FRAG;
                        ip6f->ip6f_reserved = 0;
                        ip6f->ip6f_ident = id;
                        ip6f->ip6f_nxt = nextproto;

                        mhip6->ip6_plen = htons((u_int16_t)(len + hlen +
                            sizeof(*ip6f) - sizeof(struct ip6_hdr)));
                        if ((m_frgpart = m_copym(m0, off, len, M_DONTWAIT)) == NULL) {
                                error = ENOBUFS;
                                IP6_STATINC(IP6_STAT_ODROPPED);
                                goto sendorfree;
                        }
                        for (mlast = m; mlast->m_next; mlast = mlast->m_next)
                                ;
                        mlast->m_next = m_frgpart;

                        m->m_pkthdr.len = len + hlen + sizeof(*ip6f);
                        m_reset_rcvif(m);
                        IP6_STATINC(IP6_STAT_OFRAGMENTS);
                        in6_ifstat_inc(ifp, ifs6_out_fragcreat);
                }

                in6_ifstat_inc(ifp, ifs6_out_fragok);
        }

sendorfree:
        m = m0->m_nextpkt;
        m0->m_nextpkt = 0;
        m_freem(m0);
        for (m0 = m; m; m = m0) {
                m0 = m->m_nextpkt;
                m->m_nextpkt = 0;
                if (error == 0) {
                        struct in6_ifaddr *ia6;
                        int s;
                        ip6 = mtod(m, struct ip6_hdr *);
                        s = pserialize_read_enter();
                        ia6 = in6_ifawithifp(ifp, &ip6->ip6_src);
                        if (ia6) {
                                /*
                                 * Record statistics for this interface
                                 * address.
                                 */
                                ia6->ia_ifa.ifa_data.ifad_outbytes +=
                                    m->m_pkthdr.len;
                        }
                        pserialize_read_exit(s);
                        KASSERT(dst != NULL);
                        error = ip6_if_output(ifp, origifp, m, dst, rt);
                } else
                        m_freem(m);
        }

        if (error == 0)
                IP6_STATINC(IP6_STAT_FRAGMENTED);

done:
        rtcache_unref(rt, ro);
        if (ro == &ip6route)
                rtcache_free(&ip6route);
#ifdef IPSEC
        if (sp != NULL)
                KEY_SP_UNREF(&sp);
#endif
        if_put(ifp, &psref);
        if (release_psref_ia)
                if_put(origifp, &psref_ia);
        curlwp_bindx(bound);

        return error;

freehdrs:
        m_freem(exthdrs.ip6e_hbh);
        m_freem(exthdrs.ip6e_dest1);
        m_freem(exthdrs.ip6e_rthdr);
        m_freem(exthdrs.ip6e_dest2);
        /* FALLTHROUGH */
bad:
        m_freem(m);
        goto done;

badscope:
        IP6_STATINC(IP6_STAT_BADSCOPE);
        in6_ifstat_inc(origifp, ifs6_out_discard);
        if (error == 0)
                error = EHOSTUNREACH; /* XXX */
        goto bad;
}

static int
ip6_copyexthdr(struct mbuf **mp, void *hdr, int hlen)
{
        struct mbuf *m;

        if (hlen > MCLBYTES)
                return ENOBUFS; /* XXX */

        MGET(m, M_DONTWAIT, MT_DATA);
        if (!m)
                return ENOBUFS;

        if (hlen > MLEN) {
                MCLGET(m, M_DONTWAIT);
                if ((m->m_flags & M_EXT) == 0) {
                        m_free(m);
                        return ENOBUFS;
                }
        }
        m->m_len = hlen;
        if (hdr)
                memcpy(mtod(m, void *), hdr, hlen);

        *mp = m;
        return 0;
}

/*
 * Insert jumbo payload option.
 */
static int
ip6_insert_jumboopt(struct ip6_exthdrs *exthdrs, u_int32_t plen)
{
        struct mbuf *mopt;
        u_int8_t *optbuf;
        u_int32_t v;

#define JUMBOOPTLEN     8       /* length of jumbo payload option and padding */

        /*
         * If there is no hop-by-hop options header, allocate new one.
         * If there is one but it doesn't have enough space to store the
         * jumbo payload option, allocate a cluster to store the whole options.
         * Otherwise, use it to store the options.
         */
        if (exthdrs->ip6e_hbh == NULL) {
                MGET(mopt, M_DONTWAIT, MT_DATA);
                if (mopt == 0)
                        return (ENOBUFS);
                mopt->m_len = JUMBOOPTLEN;
                optbuf = mtod(mopt, u_int8_t *);
                optbuf[1] = 0;  /* = ((JUMBOOPTLEN) >> 3) - 1 */
                exthdrs->ip6e_hbh = mopt;
        } else {
                struct ip6_hbh *hbh;

                mopt = exthdrs->ip6e_hbh;
                if (M_TRAILINGSPACE(mopt) < JUMBOOPTLEN) {
                        const int oldoptlen = mopt->m_len;
                        struct mbuf *n;

                        /*
                         * Assumptions:
                         * - exthdrs->ip6e_hbh is not referenced from places
                         *   other than exthdrs.
                         * - exthdrs->ip6e_hbh is not an mbuf chain.
                         */
                        KASSERT(mopt->m_next == NULL);

                        /*
                         * Give up if the whole (new) hbh header does not fit
                         * even in an mbuf cluster.
                         */
                        if (oldoptlen + JUMBOOPTLEN > MCLBYTES)
                                return ENOBUFS;

                        /*
                         * At this point, we must always prepare a cluster.
                         */
                        MGET(n, M_DONTWAIT, MT_DATA);
                        if (n) {
                                MCLGET(n, M_DONTWAIT);
                                if ((n->m_flags & M_EXT) == 0) {
                                        m_freem(n);
                                        n = NULL;
                                }
                        }
                        if (!n)
                                return ENOBUFS;

                        n->m_len = oldoptlen + JUMBOOPTLEN;
                        bcopy(mtod(mopt, void *), mtod(n, void *),
                            oldoptlen);
                        optbuf = mtod(n, u_int8_t *) + oldoptlen;
                        m_freem(mopt);
                        mopt = exthdrs->ip6e_hbh = n;
                } else {
                        optbuf = mtod(mopt, u_int8_t *) + mopt->m_len;
                        mopt->m_len += JUMBOOPTLEN;
                }
                optbuf[0] = IP6OPT_PADN;
                optbuf[1] = 0;

                /*
                 * Adjust the header length according to the pad and
                 * the jumbo payload option.
                 */
                hbh = mtod(mopt, struct ip6_hbh *);
                hbh->ip6h_len += (JUMBOOPTLEN >> 3);
        }

        /* fill in the option. */
        optbuf[2] = IP6OPT_JUMBO;
        optbuf[3] = 4;
        v = (u_int32_t)htonl(plen + JUMBOOPTLEN);
        memcpy(&optbuf[4], &v, sizeof(u_int32_t));

        /* finally, adjust the packet header length */
        exthdrs->ip6e_ip6->m_pkthdr.len += JUMBOOPTLEN;

        return 0;
#undef JUMBOOPTLEN
}

/*
 * Insert fragment header and copy unfragmentable header portions.
 *
 * *frghdrp will not be read, and it is guaranteed that either an
 * error is returned or that *frghdrp will point to space allocated
 * for the fragment header.
 *
 * On entry, m contains:
 *     IPv6 Header
 * On exit, it contains:
 *     IPv6 Header -> Unfragmentable Part -> Frag6 Header
 */
static int
ip6_insertfraghdr(struct mbuf *m0, struct mbuf *m, int hlen,
        struct ip6_frag **frghdrp)
{
        struct mbuf *n, *mlast;

        if (hlen > sizeof(struct ip6_hdr)) {
                n = m_copym(m0, sizeof(struct ip6_hdr),
                    hlen - sizeof(struct ip6_hdr), M_DONTWAIT);
                if (n == NULL)
                        return ENOBUFS;
                m->m_next = n;
        } else
                n = m;

        /* Search for the last mbuf of unfragmentable part. */
        for (mlast = n; mlast->m_next; mlast = mlast->m_next)
                ;

        if ((mlast->m_flags & M_EXT) == 0 &&
            M_TRAILINGSPACE(mlast) >= sizeof(struct ip6_frag)) {
                /* use the trailing space of the last mbuf for the fragment hdr */
                *frghdrp = (struct ip6_frag *)(mtod(mlast, char *) +
                    mlast->m_len);
                mlast->m_len += sizeof(struct ip6_frag);
        } else {
                /* allocate a new mbuf for the fragment header */
                struct mbuf *mfrg;

                MGET(mfrg, M_DONTWAIT, MT_DATA);
                if (mfrg == NULL)
                        return ENOBUFS;
                mfrg->m_len = sizeof(struct ip6_frag);
                *frghdrp = mtod(mfrg, struct ip6_frag *);
                mlast->m_next = mfrg;
        }

        return 0;
}

static int
ip6_getpmtu(struct rtentry *rt, struct ifnet *ifp, u_long *mtup,
    int *alwaysfragp)
{
        u_int32_t mtu = 0;
        int alwaysfrag = 0;
        int error = 0;

        if (rt != NULL) {
                if (ifp == NULL)
                        ifp = rt->rt_ifp;
                mtu = rt->rt_rmx.rmx_mtu;
                if (mtu == 0)
                        mtu = ifp->if_mtu;
                else if (mtu < IPV6_MMTU) {
                        /*
                         * RFC2460 section 5, last paragraph:
                         * if we record ICMPv6 too big message with
                         * mtu < IPV6_MMTU, transmit packets sized IPV6_MMTU
                         * or smaller, with fragment header attached.
                         * (fragment header is needed regardless from the
                         * packet size, for translators to identify packets)
                         */
                        alwaysfrag = 1;
                        mtu = IPV6_MMTU;
                } else if (mtu > ifp->if_mtu) {
                        /*
                         * The MTU on the route is larger than the MTU on
                         * the interface!  This shouldn't happen, unless the
                         * MTU of the interface has been changed after the
                         * interface was brought up.  Change the MTU in the
                         * route to match the interface MTU (as long as the
                         * field isn't locked).
                         */
                        mtu = ifp->if_mtu;
                        if (!(rt->rt_rmx.rmx_locks & RTV_MTU))
                                rt->rt_rmx.rmx_mtu = mtu;
                }
        } else if (ifp) {
                mtu = ifp->if_mtu;
        } else
                error = EHOSTUNREACH; /* XXX */

        *mtup = mtu;
        if (alwaysfragp)
                *alwaysfragp = alwaysfrag;
        return (error);
}

/*
 * IP6 socket option processing.
 */
int
ip6_ctloutput(int op, struct socket *so, struct sockopt *sopt)
{
        int optdatalen, uproto;
        void *optdata;
        struct inpcb *inp = sotoinpcb(so);
        struct ip_moptions **mopts;
        int error, optval;
        int level, optname;

        KASSERT(solocked(so));
        KASSERT(sopt != NULL);

        level = sopt->sopt_level;
        optname = sopt->sopt_name;

        error = optval = 0;
        uproto = (int)so->so_proto->pr_protocol;

        switch (level) {
        case IPPROTO_IP:
                switch (optname) {
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                case IP_MULTICAST_IF:
                case IP_MULTICAST_LOOP:
                case IP_MULTICAST_TTL:
                        mopts = &inp->inp_moptions;
                        switch (op) {
                        case PRCO_GETOPT:
                                return ip_getmoptions(*mopts, sopt);
                        case PRCO_SETOPT:
                                return ip_setmoptions(mopts, sopt);
                        default:
                                return EINVAL;
                        }
                default:
                        return ENOPROTOOPT;
                }
        case IPPROTO_IPV6:
                break;
        default:
                return ENOPROTOOPT;
        }
        switch (op) {
        case PRCO_SETOPT:
                switch (optname) {
#ifdef RFC2292
                case IPV6_2292PKTOPTIONS:
                        error = ip6_pcbopts(&in6p_outputopts(inp), so, sopt);
                        break;
#endif

                /*
                 * Use of some Hop-by-Hop options or some
                 * Destination options, might require special
                 * privilege.  That is, normal applications
                 * (without special privilege) might be forbidden
                 * from setting certain options in outgoing packets,
                 * and might never see certain options in received
                 * packets. [RFC 2292 Section 6]
                 * KAME specific note:
                 *  KAME prevents non-privileged users from sending or
                 *  receiving ANY hbh/dst options in order to avoid
                 *  overhead of parsing options in the kernel.
                 */
                case IPV6_RECVHOPOPTS:
                case IPV6_RECVDSTOPTS:
                case IPV6_RECVRTHDRDSTOPTS:
                        error = kauth_authorize_network(
                            kauth_cred_get(),
                            KAUTH_NETWORK_IPV6, KAUTH_REQ_NETWORK_IPV6_HOPBYHOP,
                            NULL, NULL, NULL);
                        if (error)
                                break;
                        /* FALLTHROUGH */
                case IPV6_UNICAST_HOPS:
                case IPV6_HOPLIMIT:
                case IPV6_FAITH:

                case IPV6_RECVPKTINFO:
                case IPV6_RECVHOPLIMIT:
                case IPV6_RECVRTHDR:
                case IPV6_RECVPATHMTU:
                case IPV6_RECVTCLASS:
                case IPV6_V6ONLY:
                case IPV6_BINDANY:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;
                        switch (optname) {
                        case IPV6_UNICAST_HOPS:
                                if (optval < -1 || optval >= 256)
                                        error = EINVAL;
                                else {
                                        /* -1 = kernel default */
                                        in6p_hops6(inp) = optval;
                                }
                                break;
#define OPTSET(bit) \
do { \
if (optval) \
        inp->inp_flags |= (bit); \
else \
        inp->inp_flags &= ~(bit); \
} while (/*CONSTCOND*/ 0)

#ifdef RFC2292
#define OPTSET2292(bit)                         \
do {                                            \
inp->inp_flags |= IN6P_RFC2292;         \
if (optval)                             \
        inp->inp_flags |= (bit);        \
else                                    \
        inp->inp_flags &= ~(bit);       \
} while (/*CONSTCOND*/ 0)
#endif

#define OPTBIT(bit) (inp->inp_flags & (bit) ? 1 : 0)

                        case IPV6_RECVPKTINFO:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_PKTINFO);
                                break;

                        case IPV6_HOPLIMIT:
                        {
                                struct ip6_pktopts **optp;

#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                optp = &in6p_outputopts(inp);
                                error = ip6_pcbopt(IPV6_HOPLIMIT,
                                                   (u_char *)&optval,
                                                   sizeof(optval),
                                                   optp,
                                                   kauth_cred_get(), uproto);
                                break;
                        }

                        case IPV6_RECVHOPLIMIT:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_HOPLIMIT);
                                break;

                        case IPV6_RECVHOPOPTS:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_HOPOPTS);
                                break;

                        case IPV6_RECVDSTOPTS:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_DSTOPTS);
                                break;

                        case IPV6_RECVRTHDRDSTOPTS:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_RTHDRDSTOPTS);
                                break;

                        case IPV6_RECVRTHDR:
#ifdef RFC2292
                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_RTHDR);
                                break;

                        case IPV6_FAITH:
                                OPTSET(IN6P_FAITH);
                                break;

                        case IPV6_RECVPATHMTU:
                                /*
                                 * We ignore this option for TCP
                                 * sockets.
                                 * (RFC3542 leaves this case
                                 * unspecified.)
                                 */
                                if (uproto != IPPROTO_TCP)
                                        OPTSET(IN6P_MTU);
                                break;

                        case IPV6_V6ONLY:
                                /*
                                 * make setsockopt(IPV6_V6ONLY)
                                 * available only prior to bind(2).
                                 * see ipng mailing list, Jun 22 2001.
                                 */
                                if (inp->inp_lport ||
                                    !IN6_IS_ADDR_UNSPECIFIED(&in6p_laddr(inp))) {
                                        error = EINVAL;
                                        break;
                                }
#ifdef INET6_BINDV6ONLY
                                if (!optval)
                                        error = EINVAL;
#else
                                OPTSET(IN6P_IPV6_V6ONLY);
#endif
                                break;

                        case IPV6_RECVTCLASS:
#ifdef RFC2292
                                /* cannot mix with RFC2292 XXX */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
#endif
                                OPTSET(IN6P_TCLASS);
                                break;

                        case IPV6_BINDANY:
                                error = kauth_authorize_network(
                                    kauth_cred_get(), KAUTH_NETWORK_BIND,
                                    KAUTH_REQ_NETWORK_BIND_ANYADDR, so, NULL,
                                    NULL);
                                if (error)
                                        break;
                                OPTSET(IN6P_BINDANY);
                                break;
                        }
                        break;

                case IPV6_OTCLASS:
                {
                        struct ip6_pktopts **optp;
                        u_int8_t tclass;

                        error = sockopt_get(sopt, &tclass, sizeof(tclass));
                        if (error)
                                break;
                        optp = &in6p_outputopts(inp);
                        error = ip6_pcbopt(optname,
                                           (u_char *)&tclass,
                                           sizeof(tclass),
                                           optp,
                                           kauth_cred_get(), uproto);
                        break;
                }

                case IPV6_TCLASS:
                case IPV6_DONTFRAG:
                case IPV6_USE_MIN_MTU:
                case IPV6_PREFER_TEMPADDR:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;
                        {
                                struct ip6_pktopts **optp;
                                optp = &in6p_outputopts(inp);
                                error = ip6_pcbopt(optname,
                                                   (u_char *)&optval,
                                                   sizeof(optval),
                                                   optp,
                                                   kauth_cred_get(), uproto);
                                break;
                        }

#ifdef RFC2292
                case IPV6_2292PKTINFO:
                case IPV6_2292HOPLIMIT:
                case IPV6_2292HOPOPTS:
                case IPV6_2292DSTOPTS:
                case IPV6_2292RTHDR:
                        /* RFC 2292 */
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        switch (optname) {
                        case IPV6_2292PKTINFO:
                                OPTSET2292(IN6P_PKTINFO);
                                break;
                        case IPV6_2292HOPLIMIT:
                                OPTSET2292(IN6P_HOPLIMIT);
                                break;
                        case IPV6_2292HOPOPTS:
                                /*
                                 * Check super-user privilege.
                                 * See comments for IPV6_RECVHOPOPTS.
                                 */
                                error = kauth_authorize_network(
                                    kauth_cred_get(),
                                    KAUTH_NETWORK_IPV6,
                                    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP, NULL,
                                    NULL, NULL);
                                if (error)
                                        return (error);
                                OPTSET2292(IN6P_HOPOPTS);
                                break;
                        case IPV6_2292DSTOPTS:
                                error = kauth_authorize_network(
                                    kauth_cred_get(),
                                    KAUTH_NETWORK_IPV6,
                                    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP, NULL,
                                    NULL, NULL);
                                if (error)
                                        return (error);
                                OPTSET2292(IN6P_DSTOPTS|IN6P_RTHDRDSTOPTS); /* XXX */
                                break;
                        case IPV6_2292RTHDR:
                                OPTSET2292(IN6P_RTHDR);
                                break;
                        }
                        break;
#endif
                case IPV6_PKTINFO:
                case IPV6_HOPOPTS:
                case IPV6_RTHDR:
                case IPV6_DSTOPTS:
                case IPV6_RTHDRDSTOPTS:
                case IPV6_NEXTHOP: {
                        /* new advanced API (RFC3542) */
                        void *optbuf;
                        int optbuflen;
                        struct ip6_pktopts **optp;

#ifdef RFC2292
                        /* cannot mix with RFC2292 */
                        if (OPTBIT(IN6P_RFC2292)) {
                                error = EINVAL;
                                break;
                        }
#endif

                        optbuflen = sopt->sopt_size;
                        optbuf = malloc(optbuflen, M_IP6OPT, M_NOWAIT);
                        if (optbuf == NULL) {
                                error = ENOBUFS;
                                break;
                        }

                        error = sockopt_get(sopt, optbuf, optbuflen);
                        if (error) {
                                free(optbuf, M_IP6OPT);
                                break;
                        }
                        optp = &in6p_outputopts(inp);
                        error = ip6_pcbopt(optname, optbuf, optbuflen,
                            optp, kauth_cred_get(), uproto);

                        free(optbuf, M_IP6OPT);
                        break;
                        }
#undef OPTSET

                case IPV6_MULTICAST_IF:
                case IPV6_MULTICAST_HOPS:
                case IPV6_MULTICAST_LOOP:
                case IPV6_JOIN_GROUP:
                case IPV6_LEAVE_GROUP:
                        error = ip6_setmoptions(sopt, inp);
                        break;

                case IPV6_PORTRANGE:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        switch (optval) {
                        case IPV6_PORTRANGE_DEFAULT:
                                inp->inp_flags &= ~(IN6P_LOWPORT);
                                inp->inp_flags &= ~(IN6P_HIGHPORT);
                                break;

                        case IPV6_PORTRANGE_HIGH:
                                inp->inp_flags &= ~(IN6P_LOWPORT);
                                inp->inp_flags |= IN6P_HIGHPORT;
                                break;

                        case IPV6_PORTRANGE_LOW:
                                inp->inp_flags &= ~(IN6P_HIGHPORT);
                                inp->inp_flags |= IN6P_LOWPORT;
                                break;

                        default:
                                error = EINVAL;
                                break;
                        }
                        break;

                case IPV6_PORTALGO:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        error = portalgo_algo_index_select(inp, optval);
                        break;

#if defined(IPSEC)
                case IPV6_IPSEC_POLICY:
                        if (ipsec_enabled) {
                                error = ipsec_set_policy(inp,
                                    sopt->sopt_data, sopt->sopt_size,
                                    kauth_cred_get());
                        } else
                                error = ENOPROTOOPT;
                        break;
#endif /* IPSEC */

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case PRCO_GETOPT:
                switch (optname) {
#ifdef RFC2292
                case IPV6_2292PKTOPTIONS:
                        /*
                         * RFC3542 (effectively) deprecated the
                         * semantics of the 2292-style pktoptions.
                         * Since it was not reliable in nature (i.e.,
                         * applications had to expect the lack of some
                         * information after all), it would make sense
                         * to simplify this part by always returning
                         * empty data.
                         */
                        break;
#endif

                case IPV6_RECVHOPOPTS:
                case IPV6_RECVDSTOPTS:
                case IPV6_RECVRTHDRDSTOPTS:
                case IPV6_UNICAST_HOPS:
                case IPV6_RECVPKTINFO:
                case IPV6_RECVHOPLIMIT:
                case IPV6_RECVRTHDR:
                case IPV6_RECVPATHMTU:

                case IPV6_FAITH:
                case IPV6_V6ONLY:
                case IPV6_PORTRANGE:
                case IPV6_RECVTCLASS:
                case IPV6_BINDANY:
                        switch (optname) {

                        case IPV6_RECVHOPOPTS:
                                optval = OPTBIT(IN6P_HOPOPTS);
                                break;

                        case IPV6_RECVDSTOPTS:
                                optval = OPTBIT(IN6P_DSTOPTS);
                                break;

                        case IPV6_RECVRTHDRDSTOPTS:
                                optval = OPTBIT(IN6P_RTHDRDSTOPTS);
                                break;

                        case IPV6_UNICAST_HOPS:
                                optval = in6p_hops6(inp);
                                break;

                        case IPV6_RECVPKTINFO:
                                optval = OPTBIT(IN6P_PKTINFO);
                                break;

                        case IPV6_RECVHOPLIMIT:
                                optval = OPTBIT(IN6P_HOPLIMIT);
                                break;

                        case IPV6_RECVRTHDR:
                                optval = OPTBIT(IN6P_RTHDR);
                                break;

                        case IPV6_RECVPATHMTU:
                                optval = OPTBIT(IN6P_MTU);
                                break;

                        case IPV6_FAITH:
                                optval = OPTBIT(IN6P_FAITH);
                                break;

                        case IPV6_V6ONLY:
                                optval = OPTBIT(IN6P_IPV6_V6ONLY);
                                break;

                        case IPV6_PORTRANGE:
                            {
                                int flags;
                                flags = inp->inp_flags;
                                if (flags & IN6P_HIGHPORT)
                                        optval = IPV6_PORTRANGE_HIGH;
                                else if (flags & IN6P_LOWPORT)
                                        optval = IPV6_PORTRANGE_LOW;
                                else
                                        optval = 0;
                                break;
                            }
                        case IPV6_RECVTCLASS:
                                optval = OPTBIT(IN6P_TCLASS);
                                break;

                        case IPV6_BINDANY:
                                optval = OPTBIT(IN6P_BINDANY);
                                break;
                        }

                        if (error)
                                break;
                        error = sockopt_setint(sopt, optval);
                        break;

                case IPV6_PATHMTU:
                    {
                        u_long pmtu = 0;
                        struct ip6_mtuinfo mtuinfo;
                        struct route *ro = &inp->inp_route;
                        struct rtentry *rt;
                        union {
                                struct sockaddr         dst;
                                struct sockaddr_in6     dst6;
                        } u;

                        if (!(so->so_state & SS_ISCONNECTED))
                                return (ENOTCONN);
                        /*
                         * XXX: we dot not consider the case of source
                         * routing, or optional information to specify
                         * the outgoing interface.
                         */
                        sockaddr_in6_init(&u.dst6, &in6p_faddr(inp), 0, 0, 0);
                        rt = rtcache_lookup(ro, &u.dst);
                        error = ip6_getpmtu(rt, NULL, &pmtu, NULL);
                        rtcache_unref(rt, ro);
                        if (error)
                                break;
                        if (pmtu > IPV6_MAXPACKET)
                                pmtu = IPV6_MAXPACKET;

                        memset(&mtuinfo, 0, sizeof(mtuinfo));
                        mtuinfo.ip6m_mtu = (u_int32_t)pmtu;
                        optdata = (void *)&mtuinfo;
                        optdatalen = sizeof(mtuinfo);
                        if (optdatalen > MCLBYTES)
                                return (EMSGSIZE); /* XXX */
                        error = sockopt_set(sopt, optdata, optdatalen);
                        break;
                    }

#ifdef RFC2292
                case IPV6_2292PKTINFO:
                case IPV6_2292HOPLIMIT:
                case IPV6_2292HOPOPTS:
                case IPV6_2292RTHDR:
                case IPV6_2292DSTOPTS:
                        switch (optname) {
                        case IPV6_2292PKTINFO:
                                optval = OPTBIT(IN6P_PKTINFO);
                                break;
                        case IPV6_2292HOPLIMIT:
                                optval = OPTBIT(IN6P_HOPLIMIT);
                                break;
                        case IPV6_2292HOPOPTS:
                                optval = OPTBIT(IN6P_HOPOPTS);
                                break;
                        case IPV6_2292RTHDR:
                                optval = OPTBIT(IN6P_RTHDR);
                                break;
                        case IPV6_2292DSTOPTS:
                                optval = OPTBIT(IN6P_DSTOPTS|IN6P_RTHDRDSTOPTS);
                                break;
                        }
                        error = sockopt_setint(sopt, optval);
                        break;
#endif
                case IPV6_PKTINFO:
                case IPV6_HOPOPTS:
                case IPV6_RTHDR:
                case IPV6_DSTOPTS:
                case IPV6_RTHDRDSTOPTS:
                case IPV6_NEXTHOP:
                case IPV6_OTCLASS:
                case IPV6_TCLASS:
                case IPV6_DONTFRAG:
                case IPV6_USE_MIN_MTU:
                case IPV6_PREFER_TEMPADDR:
                        error = ip6_getpcbopt(in6p_outputopts(inp),
                            optname, sopt);
                        break;

                case IPV6_MULTICAST_IF:
                case IPV6_MULTICAST_HOPS:
                case IPV6_MULTICAST_LOOP:
                case IPV6_JOIN_GROUP:
                case IPV6_LEAVE_GROUP:
                        error = ip6_getmoptions(sopt, inp);
                        break;

                case IPV6_PORTALGO:
                        optval = inp->inp_portalgo;
                        error = sockopt_setint(sopt, optval);
                        break;

#if defined(IPSEC)
                case IPV6_IPSEC_POLICY:
                        if (ipsec_used) {
                                struct mbuf *m = NULL;

                                /*
                                 * XXX: this will return EINVAL as sopt is
                                 * empty
                                 */
                                error = ipsec_get_policy(inp, sopt->sopt_data,
                                    sopt->sopt_size, &m);
                                if (!error)
                                        error = sockopt_setmbuf(sopt, m);
                        } else
                                error = ENOPROTOOPT;
                        break;
#endif /* IPSEC */

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;
        }
        return (error);
}

int
ip6_raw_ctloutput(int op, struct socket *so, struct sockopt *sopt)
{
        int error = 0, optval;
        const int icmp6off = offsetof(struct icmp6_hdr, icmp6_cksum);
        struct inpcb *inp = sotoinpcb(so);
        int level, optname;

        KASSERT(sopt != NULL);

        level = sopt->sopt_level;
        optname = sopt->sopt_name;

        if (level != IPPROTO_IPV6) {
                return ENOPROTOOPT;
        }

        switch (optname) {
        case IPV6_CHECKSUM:
                /*
                 * For ICMPv6 sockets, no modification allowed for checksum
                 * offset, permit "no change" values to help existing apps.
                 *
                 * XXX RFC3542 says: "An attempt to set IPV6_CHECKSUM
                 * for an ICMPv6 socket will fail."  The current
                 * behavior does not meet RFC3542.
                 */
                switch (op) {
                case PRCO_SETOPT:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;
                        if (optval < -1 ||
                            (optval > 0 && (optval % 2) != 0)) {
                                /*
                                 * The API assumes non-negative even offset
                                 * values or -1 as a special value.
                                 */
                                error = EINVAL;
                        } else if (so->so_proto->pr_protocol ==
                            IPPROTO_ICMPV6) {
                                if (optval != icmp6off)
                                        error = EINVAL;
                        } else
                                in6p_cksum(inp) = optval;
                        break;

                case PRCO_GETOPT:
                        if (so->so_proto->pr_protocol == IPPROTO_ICMPV6)
                                optval = icmp6off;
                        else
                                optval = in6p_cksum(inp);

                        error = sockopt_setint(sopt, optval);
                        break;

                default:
                        error = EINVAL;
                        break;
                }
                break;

        default:
                error = ENOPROTOOPT;
                break;
        }

        return (error);
}

#ifdef RFC2292
/*
 * Set up IP6 options in pcb for insertion in output packets or
 * specifying behavior of outgoing packets.
 */
static int
ip6_pcbopts(struct ip6_pktopts **pktopt, struct socket *so,
    struct sockopt *sopt)
{
        struct ip6_pktopts *opt = *pktopt;
        struct mbuf *m;
        int error = 0;

        KASSERT(solocked(so));

        /* turn off any old options. */
        if (opt) {
#ifdef DIAGNOSTIC
            if (opt->ip6po_pktinfo || opt->ip6po_nexthop ||
                opt->ip6po_hbh || opt->ip6po_dest1 || opt->ip6po_dest2 ||
                opt->ip6po_rhinfo.ip6po_rhi_rthdr)
                    printf("ip6_pcbopts: all specified options are cleared.\n");
#endif
                ip6_clearpktopts(opt, -1);
        } else {
                opt = malloc(sizeof(*opt), M_IP6OPT, M_NOWAIT);
                if (opt == NULL)
                        return (ENOBUFS);
        }
        *pktopt = NULL;

        if (sopt == NULL || sopt->sopt_size == 0) {
                /*
                 * Only turning off any previous options, regardless of
                 * whether the opt is just created or given.
                 */
                free(opt, M_IP6OPT);
                return (0);
        }

        /*  set options specified by user. */
        m = sockopt_getmbuf(sopt);
        if (m == NULL) {
                free(opt, M_IP6OPT);
                return (ENOBUFS);
        }

        error = ip6_setpktopts(m, opt, NULL, kauth_cred_get(),
            so->so_proto->pr_protocol);
        m_freem(m);
        if (error != 0) {
                ip6_clearpktopts(opt, -1); /* XXX: discard all options */
                free(opt, M_IP6OPT);
                return (error);
        }
        *pktopt = opt;
        return (0);
}
#endif

/*
 * initialize ip6_pktopts.  beware that there are non-zero default values in
 * the struct.
 */
void
ip6_initpktopts(struct ip6_pktopts *opt)
{

        memset(opt, 0, sizeof(*opt));
        opt->ip6po_hlim = -1;   /* -1 means default hop limit */
        opt->ip6po_tclass = -1; /* -1 means default traffic class */
        opt->ip6po_minmtu = IP6PO_MINMTU_MCASTONLY;
        opt->ip6po_prefer_tempaddr = IP6PO_TEMPADDR_SYSTEM;
}

#define sin6tosa(sin6)  ((struct sockaddr *)(sin6)) /* XXX */
static int
ip6_pcbopt(int optname, u_char *buf, int len, struct ip6_pktopts **pktopt,
    kauth_cred_t cred, int uproto)
{
        struct ip6_pktopts *opt;

        if (*pktopt == NULL) {
                *pktopt = malloc(sizeof(struct ip6_pktopts), M_IP6OPT,
                    M_NOWAIT);
                if (*pktopt == NULL)
                        return (ENOBUFS);

                ip6_initpktopts(*pktopt);
        }
        opt = *pktopt;

        return (ip6_setpktopt(optname, buf, len, opt, cred, 1, 0, uproto));
}

static int
ip6_getpcbopt(struct ip6_pktopts *pktopt, int optname, struct sockopt *sopt)
{
        void *optdata = NULL;
        int optdatalen = 0;
        struct ip6_ext *ip6e;
        int error = 0;
        struct in6_pktinfo null_pktinfo;
        int deftclass = 0, on;
        int defminmtu = IP6PO_MINMTU_MCASTONLY;
        int defpreftemp = IP6PO_TEMPADDR_SYSTEM;

        switch (optname) {
        case IPV6_PKTINFO:
                if (pktopt && pktopt->ip6po_pktinfo)
                        optdata = (void *)pktopt->ip6po_pktinfo;
                else {
                        /* XXX: we don't have to do this every time... */
                        memset(&null_pktinfo, 0, sizeof(null_pktinfo));
                        optdata = (void *)&null_pktinfo;
                }
                optdatalen = sizeof(struct in6_pktinfo);
                break;
        case IPV6_OTCLASS:
                /* XXX */
                return (EINVAL);
        case IPV6_TCLASS:
                if (pktopt && pktopt->ip6po_tclass >= 0)
                        optdata = (void *)&pktopt->ip6po_tclass;
                else
                        optdata = (void *)&deftclass;
                optdatalen = sizeof(int);
                break;
        case IPV6_HOPOPTS:
                if (pktopt && pktopt->ip6po_hbh) {
                        optdata = (void *)pktopt->ip6po_hbh;
                        ip6e = (struct ip6_ext *)pktopt->ip6po_hbh;
                        optdatalen = (ip6e->ip6e_len + 1) << 3;
                }
                break;
        case IPV6_RTHDR:
                if (pktopt && pktopt->ip6po_rthdr) {
                        optdata = (void *)pktopt->ip6po_rthdr;
                        ip6e = (struct ip6_ext *)pktopt->ip6po_rthdr;
                        optdatalen = (ip6e->ip6e_len + 1) << 3;
                }
                break;
        case IPV6_RTHDRDSTOPTS:
                if (pktopt && pktopt->ip6po_dest1) {
                        optdata = (void *)pktopt->ip6po_dest1;
                        ip6e = (struct ip6_ext *)pktopt->ip6po_dest1;
                        optdatalen = (ip6e->ip6e_len + 1) << 3;
                }
                break;
        case IPV6_DSTOPTS:
                if (pktopt && pktopt->ip6po_dest2) {
                        optdata = (void *)pktopt->ip6po_dest2;
                        ip6e = (struct ip6_ext *)pktopt->ip6po_dest2;
                        optdatalen = (ip6e->ip6e_len + 1) << 3;
                }
                break;
        case IPV6_NEXTHOP:
                if (pktopt && pktopt->ip6po_nexthop) {
                        optdata = (void *)pktopt->ip6po_nexthop;
                        optdatalen = pktopt->ip6po_nexthop->sa_len;
                }
                break;
        case IPV6_USE_MIN_MTU:
                if (pktopt)
                        optdata = (void *)&pktopt->ip6po_minmtu;
                else
                        optdata = (void *)&defminmtu;
                optdatalen = sizeof(int);
                break;
        case IPV6_DONTFRAG:
                if (pktopt && ((pktopt->ip6po_flags) & IP6PO_DONTFRAG))
                        on = 1;
                else
                        on = 0;
                optdata = (void *)&on;
                optdatalen = sizeof(on);
                break;
        case IPV6_PREFER_TEMPADDR:
                if (pktopt)
                        optdata = (void *)&pktopt->ip6po_prefer_tempaddr;
                else
                        optdata = (void *)&defpreftemp;
                optdatalen = sizeof(int);
                break;
        default:                /* should not happen */
#ifdef DIAGNOSTIC
                panic("ip6_getpcbopt: unexpected option\n");
#endif
                return (ENOPROTOOPT);
        }

        error = sockopt_set(sopt, optdata, optdatalen);

        return (error);
}

void
ip6_clearpktopts(struct ip6_pktopts *pktopt, int optname)
{
        if (optname == -1 || optname == IPV6_PKTINFO) {
                if (pktopt->ip6po_pktinfo)
                        free(pktopt->ip6po_pktinfo, M_IP6OPT);
                pktopt->ip6po_pktinfo = NULL;
        }
        if (optname == -1 || optname == IPV6_HOPLIMIT)
                pktopt->ip6po_hlim = -1;
        if (optname == -1 || optname == IPV6_TCLASS)
                pktopt->ip6po_tclass = -1;
        if (optname == -1 || optname == IPV6_NEXTHOP) {
                rtcache_free(&pktopt->ip6po_nextroute);
                if (pktopt->ip6po_nexthop)
                        free(pktopt->ip6po_nexthop, M_IP6OPT);
                pktopt->ip6po_nexthop = NULL;
        }
        if (optname == -1 || optname == IPV6_HOPOPTS) {
                if (pktopt->ip6po_hbh)
                        free(pktopt->ip6po_hbh, M_IP6OPT);
                pktopt->ip6po_hbh = NULL;
        }
        if (optname == -1 || optname == IPV6_RTHDRDSTOPTS) {
                if (pktopt->ip6po_dest1)
                        free(pktopt->ip6po_dest1, M_IP6OPT);
                pktopt->ip6po_dest1 = NULL;
        }
        if (optname == -1 || optname == IPV6_RTHDR) {
                if (pktopt->ip6po_rhinfo.ip6po_rhi_rthdr)
                        free(pktopt->ip6po_rhinfo.ip6po_rhi_rthdr, M_IP6OPT);
                pktopt->ip6po_rhinfo.ip6po_rhi_rthdr = NULL;
                rtcache_free(&pktopt->ip6po_route);
        }
        if (optname == -1 || optname == IPV6_DSTOPTS) {
                if (pktopt->ip6po_dest2)
                        free(pktopt->ip6po_dest2, M_IP6OPT);
                pktopt->ip6po_dest2 = NULL;
        }
}

#define PKTOPT_EXTHDRCPY(type)                                  \
do {                                                            \
        if (src->type) {                                        \
                int hlen = (((struct ip6_ext *)src->type)->ip6e_len + 1) << 3;\
                dst->type = malloc(hlen, M_IP6OPT, canwait);    \
                if (dst->type == NULL)                          \
                        goto bad;                               \
                memcpy(dst->type, src->type, hlen);             \
        }                                                       \
} while (/*CONSTCOND*/ 0)

static int
copypktopts(struct ip6_pktopts *dst, struct ip6_pktopts *src, int canwait)
{
        dst->ip6po_hlim = src->ip6po_hlim;
        dst->ip6po_tclass = src->ip6po_tclass;
        dst->ip6po_flags = src->ip6po_flags;
        dst->ip6po_minmtu = src->ip6po_minmtu;
        dst->ip6po_prefer_tempaddr = src->ip6po_prefer_tempaddr;
        if (src->ip6po_pktinfo) {
                dst->ip6po_pktinfo = malloc(sizeof(*dst->ip6po_pktinfo),
                    M_IP6OPT, canwait);
                if (dst->ip6po_pktinfo == NULL)
                        goto bad;
                *dst->ip6po_pktinfo = *src->ip6po_pktinfo;
        }
        if (src->ip6po_nexthop) {
                dst->ip6po_nexthop = malloc(src->ip6po_nexthop->sa_len,
                    M_IP6OPT, canwait);
                if (dst->ip6po_nexthop == NULL)
                        goto bad;
                memcpy(dst->ip6po_nexthop, src->ip6po_nexthop,
                    src->ip6po_nexthop->sa_len);
        }
        PKTOPT_EXTHDRCPY(ip6po_hbh);
        PKTOPT_EXTHDRCPY(ip6po_dest1);
        PKTOPT_EXTHDRCPY(ip6po_dest2);
        PKTOPT_EXTHDRCPY(ip6po_rthdr); /* not copy the cached route */
        return (0);

  bad:
        if (dst->ip6po_pktinfo) free(dst->ip6po_pktinfo, M_IP6OPT);
        if (dst->ip6po_nexthop) free(dst->ip6po_nexthop, M_IP6OPT);
        if (dst->ip6po_hbh) free(dst->ip6po_hbh, M_IP6OPT);
        if (dst->ip6po_dest1) free(dst->ip6po_dest1, M_IP6OPT);
        if (dst->ip6po_dest2) free(dst->ip6po_dest2, M_IP6OPT);
        if (dst->ip6po_rthdr) free(dst->ip6po_rthdr, M_IP6OPT);

        return (ENOBUFS);
}
#undef PKTOPT_EXTHDRCPY

struct ip6_pktopts *
ip6_copypktopts(struct ip6_pktopts *src, int canwait)
{
        int error;
        struct ip6_pktopts *dst;

        dst = malloc(sizeof(*dst), M_IP6OPT, canwait);
        if (dst == NULL)
                return (NULL);
        ip6_initpktopts(dst);

        if ((error = copypktopts(dst, src, canwait)) != 0) {
                free(dst, M_IP6OPT);
                return (NULL);
        }

        return (dst);
}

void
ip6_freepcbopts(struct ip6_pktopts *pktopt)
{
        if (pktopt == NULL)
                return;

        ip6_clearpktopts(pktopt, -1);

        free(pktopt, M_IP6OPT);
}

int
ip6_get_membership(const struct sockopt *sopt, struct ifnet **ifp,
    struct psref *psref, void *v, size_t l)
{
        struct ipv6_mreq mreq;
        int error;
        struct in6_addr *ia = &mreq.ipv6mr_multiaddr;
        struct in_addr *ia4 = (void *)&ia->s6_addr32[3];

        error = sockopt_get(sopt, &mreq, sizeof(mreq));
        if (error != 0)
                return error;

        if (IN6_IS_ADDR_UNSPECIFIED(ia)) {
                /*
                 * We use the unspecified address to specify to accept
                 * all multicast addresses. Only super user is allowed
                 * to do this.
                 */
                if (kauth_authorize_network(kauth_cred_get(),
                    KAUTH_NETWORK_IPV6,
                    KAUTH_REQ_NETWORK_IPV6_JOIN_MULTICAST, NULL, NULL, NULL))
                        return EACCES;
        } else if (IN6_IS_ADDR_V4MAPPED(ia)) {
                // Don't bother if we are not going to use ifp.
                if (l == sizeof(*ia)) {
                        memcpy(v, ia, l);
                        return 0;
                }
        } else if (!IN6_IS_ADDR_MULTICAST(ia)) {
                return EINVAL;
        }

        /*
         * If no interface was explicitly specified, choose an
         * appropriate one according to the given multicast address.
         */
        if (mreq.ipv6mr_interface == 0) {
                struct rtentry *rt;
                union {
                        struct sockaddr         dst;
                        struct sockaddr_in      dst4;
                        struct sockaddr_in6     dst6;
                } u;
                struct route ro;

                /*
                 * Look up the routing table for the
                 * address, and choose the outgoing interface.
                 *   XXX: is it a good approach?
                 */
                memset(&ro, 0, sizeof(ro));
                if (IN6_IS_ADDR_V4MAPPED(ia))
                        sockaddr_in_init(&u.dst4, ia4, 0);
                else
                        sockaddr_in6_init(&u.dst6, ia, 0, 0, 0);
                error = rtcache_setdst(&ro, &u.dst);
                if (error != 0)
                        return error;
                rt = rtcache_init(&ro);
                *ifp = rt != NULL ?
                    if_get_byindex(rt->rt_ifp->if_index, psref) : NULL;
                rtcache_unref(rt, &ro);
                rtcache_free(&ro);
        } else {
                /*
                 * If the interface is specified, validate it.
                 */
                *ifp = if_get_byindex(mreq.ipv6mr_interface, psref);
                if (*ifp == NULL)
                        return ENXIO;   /* XXX EINVAL? */
        }
        if (sizeof(*ia) == l)
                memcpy(v, ia, l);
        else
                memcpy(v, ia4, l);
        return 0;
}

/*
 * Set the IP6 multicast options in response to user setsockopt().
 */
static int
ip6_setmoptions(const struct sockopt *sopt, struct inpcb *inp)
{
        int error = 0;
        u_int loop, ifindex;
        struct ipv6_mreq mreq;
        struct in6_addr ia;
        struct ifnet *ifp;
        struct ip6_moptions *im6o = in6p_moptions(inp);
        struct in6_multi_mship *imm;

        KASSERT(inp_locked(inp));

        if (im6o == NULL) {
                /*
                 * No multicast option buffer attached to the pcb;
                 * allocate one and initialize to default values.
                 */
                im6o = malloc(sizeof(*im6o), M_IPMOPTS, M_NOWAIT);
                if (im6o == NULL)
                        return (ENOBUFS);
                in6p_moptions(inp) = im6o;
                im6o->im6o_multicast_if_index = 0;
                im6o->im6o_multicast_hlim = ip6_defmcasthlim;
                im6o->im6o_multicast_loop = IPV6_DEFAULT_MULTICAST_LOOP;
                LIST_INIT(&im6o->im6o_memberships);
        }

        switch (sopt->sopt_name) {

        case IPV6_MULTICAST_IF: {
                int s;
                /*
                 * Select the interface for outgoing multicast packets.
                 */
                error = sockopt_get(sopt, &ifindex, sizeof(ifindex));
                if (error != 0)
                        break;

                s = pserialize_read_enter();
                if (ifindex != 0) {
                        if ((ifp = if_byindex(ifindex)) == NULL) {
                                pserialize_read_exit(s);
                                error = ENXIO;  /* XXX EINVAL? */
                                break;
                        }
                        if ((ifp->if_flags & IFF_MULTICAST) == 0) {
                                pserialize_read_exit(s);
                                error = EADDRNOTAVAIL;
                                break;
                        }
                } else
                        ifp = NULL;
                im6o->im6o_multicast_if_index = if_get_index(ifp);
                pserialize_read_exit(s);
                break;
            }

        case IPV6_MULTICAST_HOPS:
            {
                /*
                 * Set the IP6 hoplimit for outgoing multicast packets.
                 */
                int optval;

                error = sockopt_getint(sopt, &optval);
                if (error != 0)
                        break;

                if (optval < -1 || optval >= 256)
                        error = EINVAL;
                else if (optval == -1)
                        im6o->im6o_multicast_hlim = ip6_defmcasthlim;
                else
                        im6o->im6o_multicast_hlim = optval;
                break;
            }

        case IPV6_MULTICAST_LOOP:
                /*
                 * Set the loopback flag for outgoing multicast packets.
                 * Must be zero or one.
                 */
                error = sockopt_get(sopt, &loop, sizeof(loop));
                if (error != 0)
                        break;
                if (loop > 1) {
                        error = EINVAL;
                        break;
                }
                im6o->im6o_multicast_loop = loop;
                break;

        case IPV6_JOIN_GROUP: {
                int bound;
                struct psref psref;
                /*
                 * Add a multicast group membership.
                 * Group must be a valid IP6 multicast address.
                 */
                bound = curlwp_bind();
                ifp = NULL;
                error = ip6_get_membership(sopt, &ifp, &psref, &ia, sizeof(ia));
                if (error != 0) {
                        KASSERT(ifp == NULL);
                        curlwp_bindx(bound);
                        return error;
                }

                if (IN6_IS_ADDR_V4MAPPED(&ia)) {
                        error = ip_setmoptions(&inp->inp_moptions, sopt);
                        goto put_break;
                }
                /*
                 * See if we found an interface, and confirm that it
                 * supports multicast
                 */
                if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                        error = EADDRNOTAVAIL;
                        goto put_break;
                }

                if (in6_setscope(&ia, ifp, NULL)) {
                        error = EADDRNOTAVAIL; /* XXX: should not happen */
                        goto put_break;
                }

                /*
                 * See if the membership already exists.
                 */
                LIST_FOREACH(imm, &im6o->im6o_memberships, i6mm_chain) {
                        if (imm->i6mm_maddr->in6m_ifp == ifp &&
                            IN6_ARE_ADDR_EQUAL(&imm->i6mm_maddr->in6m_addr,
                            &ia))
                                goto put_break;
                }
                if (imm != NULL) {
                        error = EADDRINUSE;
                        goto put_break;
                }
                /*
                 * Everything looks good; add a new record to the multicast
                 * address list for the given interface.
                 */
                imm = in6_joingroup(ifp, &ia, &error, 0);
                if (imm == NULL)
                        goto put_break;
                LIST_INSERT_HEAD(&im6o->im6o_memberships, imm, i6mm_chain);
            put_break:
                if_put(ifp, &psref);
                curlwp_bindx(bound);
                break;
            }

        case IPV6_LEAVE_GROUP: {
                /*
                 * Drop a multicast group membership.
                 * Group must be a valid IP6 multicast address.
                 */
                error = sockopt_get(sopt, &mreq, sizeof(mreq));
                if (error != 0)
                        break;

                if (IN6_IS_ADDR_V4MAPPED(&mreq.ipv6mr_multiaddr)) {
                        error = ip_setmoptions(&inp->inp_moptions, sopt);
                        break;
                }
                /*
                 * If an interface address was specified, get a pointer
                 * to its ifnet structure.
                 */
                if (mreq.ipv6mr_interface != 0) {
                        if ((ifp = if_byindex(mreq.ipv6mr_interface)) == NULL) {
                                error = ENXIO;  /* XXX EINVAL? */
                                break;
                        }
                } else
                        ifp = NULL;

                /* Fill in the scope zone ID */
                if (ifp) {
                        if (in6_setscope(&mreq.ipv6mr_multiaddr, ifp, NULL)) {
                                /* XXX: should not happen */
                                error = EADDRNOTAVAIL;
                                break;
                        }
                } else if (mreq.ipv6mr_interface != 0) {
                        /*
                         * XXX: This case would happens when the (positive)
                         * index is in the valid range, but the corresponding
                         * interface has been detached dynamically.  The above
                         * check probably avoids such case to happen here, but
                         * we check it explicitly for safety.
                         */
                        error = EADDRNOTAVAIL;
                        break;
                } else {        /* ipv6mr_interface == 0 */
                        struct sockaddr_in6 sa6_mc;

                        /*
                         * The API spec says as follows:
                         *  If the interface index is specified as 0, the
                         *  system may choose a multicast group membership to
                         *  drop by matching the multicast address only.
                         * On the other hand, we cannot disambiguate the scope
                         * zone unless an interface is provided.  Thus, we
                         * check if there's ambiguity with the default scope
                         * zone as the last resort.
                         */
                        sockaddr_in6_init(&sa6_mc, &mreq.ipv6mr_multiaddr,
                            0, 0, 0);
                        error = sa6_embedscope(&sa6_mc, ip6_use_defzone);
                        if (error != 0)
                                break;
                        mreq.ipv6mr_multiaddr = sa6_mc.sin6_addr;
                }

                /*
                 * Find the membership in the membership list.
                 */
                LIST_FOREACH(imm, &im6o->im6o_memberships, i6mm_chain) {
                        if ((ifp == NULL || imm->i6mm_maddr->in6m_ifp == ifp) &&
                            IN6_ARE_ADDR_EQUAL(&imm->i6mm_maddr->in6m_addr,
                            &mreq.ipv6mr_multiaddr))
                                break;
                }
                if (imm == NULL) {
                        /* Unable to resolve interface */
                        error = EADDRNOTAVAIL;
                        break;
                }
                /*
                 * Give up the multicast address record to which the
                 * membership points.
                 */
                LIST_REMOVE(imm, i6mm_chain);
                in6_leavegroup(imm);
                /* in6m_ifp should not leave thanks to inp_lock */
                break;
            }

        default:
                error = EOPNOTSUPP;
                break;
        }

        /*
         * If all options have default values, no need to keep the mbuf.
         */
        if (im6o->im6o_multicast_if_index == 0 &&
            im6o->im6o_multicast_hlim == ip6_defmcasthlim &&
            im6o->im6o_multicast_loop == IPV6_DEFAULT_MULTICAST_LOOP &&
            LIST_EMPTY(&im6o->im6o_memberships)) {
                free(in6p_moptions(inp), M_IPMOPTS);
                in6p_moptions(inp) = NULL;
        }

        return (error);
}

/*
 * Return the IP6 multicast options in response to user getsockopt().
 */
static int
ip6_getmoptions(struct sockopt *sopt, struct inpcb *inp)
{
        u_int optval;
        int error;
        struct ip6_moptions *im6o = in6p_moptions(inp);

        switch (sopt->sopt_name) {
        case IPV6_MULTICAST_IF:
                if (im6o == NULL || im6o->im6o_multicast_if_index == 0)
                        optval = 0;
                else
                        optval = im6o->im6o_multicast_if_index;

                error = sockopt_set(sopt, &optval, sizeof(optval));
                break;

        case IPV6_MULTICAST_HOPS:
                if (im6o == NULL)
                        optval = ip6_defmcasthlim;
                else
                        optval = im6o->im6o_multicast_hlim;

                error = sockopt_set(sopt, &optval, sizeof(optval));
                break;

        case IPV6_MULTICAST_LOOP:
                if (im6o == NULL)
                        optval = IPV6_DEFAULT_MULTICAST_LOOP;
                else
                        optval = im6o->im6o_multicast_loop;

                error = sockopt_set(sopt, &optval, sizeof(optval));
                break;

        default:
                error = EOPNOTSUPP;
        }

        return (error);
}

/*
 * Discard the IP6 multicast options.
 */
void
ip6_freemoptions(struct ip6_moptions *im6o)
{
        struct in6_multi_mship *imm, *nimm;

        if (im6o == NULL)
                return;

        /* The owner of im6o (inp) should be protected by solock */
        LIST_FOREACH_SAFE(imm, &im6o->im6o_memberships, i6mm_chain, nimm) {
                LIST_REMOVE(imm, i6mm_chain);
                in6_leavegroup(imm);
        }
        free(im6o, M_IPMOPTS);
}

/*
 * Set IPv6 outgoing packet options based on advanced API.
 */
int
ip6_setpktopts(struct mbuf *control, struct ip6_pktopts *opt,
        struct ip6_pktopts *stickyopt, kauth_cred_t cred, int uproto)
{
        struct cmsghdr *cm = 0;

        if (control == NULL || opt == NULL)
                return (EINVAL);

        ip6_initpktopts(opt);
        if (stickyopt) {
                int error;

                /*
                 * If stickyopt is provided, make a local copy of the options
                 * for this particular packet, then override them by ancillary
                 * objects.
                 * XXX: copypktopts() does not copy the cached route to a next
                 * hop (if any).  This is not very good in terms of efficiency,
                 * but we can allow this since this option should be rarely
                 * used.
                 */
                if ((error = copypktopts(opt, stickyopt, M_NOWAIT)) != 0)
                        return (error);
        }

        /*
         * XXX: Currently, we assume all the optional information is stored
         * in a single mbuf.
         */
        if (control->m_next)
                return (EINVAL);

        /* XXX if cm->cmsg_len is not aligned, control->m_len can become <0 */
        for (; control->m_len > 0; control->m_data += CMSG_ALIGN(cm->cmsg_len),
            control->m_len -= CMSG_ALIGN(cm->cmsg_len)) {
                int error;

                if (control->m_len < CMSG_LEN(0))
                        return (EINVAL);

                cm = mtod(control, struct cmsghdr *);
                if (cm->cmsg_len < CMSG_LEN(0) || cm->cmsg_len > control->m_len)
                        return (EINVAL);
                if (cm->cmsg_level != IPPROTO_IPV6)
                        continue;

                error = ip6_setpktopt(cm->cmsg_type, CMSG_DATA(cm),
                    cm->cmsg_len - CMSG_LEN(0), opt, cred, 0, 1, uproto);
                if (error)
                        return (error);
        }

        return (0);
}

/*
 * Set a particular packet option, as a sticky option or an ancillary data
 * item.  "len" can be 0 only when it's a sticky option.
 * We have 4 cases of combination of "sticky" and "cmsg":
 * "sticky=0, cmsg=0": impossible
 * "sticky=0, cmsg=1": RFC2292 or RFC3542 ancillary data
 * "sticky=1, cmsg=0": RFC3542 socket option
 * "sticky=1, cmsg=1": RFC2292 socket option
 */
static int
ip6_setpktopt(int optname, u_char *buf, int len, struct ip6_pktopts *opt,
    kauth_cred_t cred, int sticky, int cmsg, int uproto)
{
        int minmtupolicy;
        int error;

        if (!sticky && !cmsg) {
#ifdef DIAGNOSTIC
                printf("ip6_setpktopt: impossible case\n");
#endif
                return (EINVAL);
        }

        /*
         * IPV6_2292xxx is for backward compatibility to RFC2292, and should
         * not be specified in the context of RFC3542.  Conversely,
         * RFC3542 types should not be specified in the context of RFC2292.
         */
        if (!cmsg) {
                switch (optname) {
                case IPV6_2292PKTINFO:
                case IPV6_2292HOPLIMIT:
                case IPV6_2292NEXTHOP:
                case IPV6_2292HOPOPTS:
                case IPV6_2292DSTOPTS:
                case IPV6_2292RTHDR:
                case IPV6_2292PKTOPTIONS:
                        return (ENOPROTOOPT);
                }
        }
        if (sticky && cmsg) {
                switch (optname) {
                case IPV6_PKTINFO:
                case IPV6_HOPLIMIT:
                case IPV6_NEXTHOP:
                case IPV6_HOPOPTS:
                case IPV6_DSTOPTS:
                case IPV6_RTHDRDSTOPTS:
                case IPV6_RTHDR:
                case IPV6_USE_MIN_MTU:
                case IPV6_DONTFRAG:
                case IPV6_OTCLASS:
                case IPV6_TCLASS:
                case IPV6_PREFER_TEMPADDR: /* XXX not an RFC3542 option */
                        return (ENOPROTOOPT);
                }
        }

        switch (optname) {
#ifdef RFC2292
        case IPV6_2292PKTINFO:
#endif
        case IPV6_PKTINFO:
        {
                struct in6_pktinfo *pktinfo;

                if (len != sizeof(struct in6_pktinfo))
                        return (EINVAL);

                pktinfo = (struct in6_pktinfo *)buf;

                /*
                 * An application can clear any sticky IPV6_PKTINFO option by
                 * doing a "regular" setsockopt with ipi6_addr being
                 * in6addr_any and ipi6_ifindex being zero.
                 * [RFC 3542, Section 6]
                 */
                if (optname == IPV6_PKTINFO && opt->ip6po_pktinfo &&
                    pktinfo->ipi6_ifindex == 0 &&
                    IN6_IS_ADDR_UNSPECIFIED(&pktinfo->ipi6_addr)) {
                        ip6_clearpktopts(opt, optname);
                        break;
                }

                if (uproto == IPPROTO_TCP && optname == IPV6_PKTINFO &&
                    sticky && !IN6_IS_ADDR_UNSPECIFIED(&pktinfo->ipi6_addr)) {
                        return (EINVAL);
                }

                /* Validate the interface index if specified. */
                if (pktinfo->ipi6_ifindex) {
                        struct ifnet *ifp;
                        int s = pserialize_read_enter();
                        ifp = if_byindex(pktinfo->ipi6_ifindex);
                        if (ifp == NULL) {
                                pserialize_read_exit(s);
                                return ENXIO;
                        }
                        pserialize_read_exit(s);
                }

                /*
                 * We store the address anyway, and let in6_selectsrc()
                 * validate the specified address.  This is because ipi6_addr
                 * may not have enough information about its scope zone, and
                 * we may need additional information (such as outgoing
                 * interface or the scope zone of a destination address) to
                 * disambiguate the scope.
                 * XXX: the delay of the validation may confuse the
                 * application when it is used as a sticky option.
                 */
                if (opt->ip6po_pktinfo == NULL) {
                        opt->ip6po_pktinfo = malloc(sizeof(*pktinfo),
                            M_IP6OPT, M_NOWAIT);
                        if (opt->ip6po_pktinfo == NULL)
                                return (ENOBUFS);
                }
                memcpy(opt->ip6po_pktinfo, pktinfo, sizeof(*pktinfo));
                break;
        }

#ifdef RFC2292
        case IPV6_2292HOPLIMIT:
#endif
        case IPV6_HOPLIMIT:
        {
                int *hlimp;

                /*
                 * RFC 3542 deprecated the usage of sticky IPV6_HOPLIMIT
                 * to simplify the ordering among hoplimit options.
                 */
                if (optname == IPV6_HOPLIMIT && sticky)
                        return (ENOPROTOOPT);

                if (len != sizeof(int))
                        return (EINVAL);
                hlimp = (int *)buf;
                if (*hlimp < -1 || *hlimp > 255)
                        return (EINVAL);

                opt->ip6po_hlim = *hlimp;
                break;
        }

        case IPV6_OTCLASS:
                if (len != sizeof(u_int8_t))
                        return (EINVAL);

                opt->ip6po_tclass = *(u_int8_t *)buf;
                break;

        case IPV6_TCLASS:
        {
                int tclass;

                if (len != sizeof(int))
                        return (EINVAL);
                tclass = *(int *)buf;
                if (tclass < -1 || tclass > 255)
                        return (EINVAL);

                opt->ip6po_tclass = tclass;
                break;
        }

#ifdef RFC2292
        case IPV6_2292NEXTHOP:
#endif
        case IPV6_NEXTHOP:
                error = kauth_authorize_network(cred,
                    KAUTH_NETWORK_IPV6,
                    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP, NULL, NULL, NULL);
                if (error)
                        return (error);

                if (len == 0) { /* just remove the option */
                        ip6_clearpktopts(opt, IPV6_NEXTHOP);
                        break;
                }

                /* check if cmsg_len is large enough for sa_len */
                if (len < sizeof(struct sockaddr) || len < *buf)
                        return (EINVAL);

                switch (((struct sockaddr *)buf)->sa_family) {
                case AF_INET6:
                {
                        struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *)buf;

                        if (sa6->sin6_len != sizeof(struct sockaddr_in6))
                                return (EINVAL);

                        if (IN6_IS_ADDR_UNSPECIFIED(&sa6->sin6_addr) ||
                            IN6_IS_ADDR_MULTICAST(&sa6->sin6_addr)) {
                                return (EINVAL);
                        }
                        if ((error = sa6_embedscope(sa6, ip6_use_defzone))
                            != 0) {
                                return (error);
                        }
                        break;
                }
                case AF_LINK:   /* eventually be supported? */
                default:
                        return (EAFNOSUPPORT);
                }

                /* turn off the previous option, then set the new option. */
                ip6_clearpktopts(opt, IPV6_NEXTHOP);
                opt->ip6po_nexthop = malloc(*buf, M_IP6OPT, M_NOWAIT);
                if (opt->ip6po_nexthop == NULL)
                        return (ENOBUFS);
                memcpy(opt->ip6po_nexthop, buf, *buf);
                break;

#ifdef RFC2292
        case IPV6_2292HOPOPTS:
#endif
        case IPV6_HOPOPTS:
        {
                struct ip6_hbh *hbh;
                int hbhlen;

                /*
                 * XXX: We don't allow a non-privileged user to set ANY HbH
                 * options, since per-option restriction has too much
                 * overhead.
                 */
                error = kauth_authorize_network(cred,
                    KAUTH_NETWORK_IPV6,
                    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP, NULL, NULL, NULL);
                if (error)
                        return (error);

                if (len == 0) {
                        ip6_clearpktopts(opt, IPV6_HOPOPTS);
                        break;  /* just remove the option */
                }

                /* message length validation */
                if (len < sizeof(struct ip6_hbh))
                        return (EINVAL);
                hbh = (struct ip6_hbh *)buf;
                hbhlen = (hbh->ip6h_len + 1) << 3;
                if (len != hbhlen)
                        return (EINVAL);

                /* turn off the previous option, then set the new option. */
                ip6_clearpktopts(opt, IPV6_HOPOPTS);
                opt->ip6po_hbh = malloc(hbhlen, M_IP6OPT, M_NOWAIT);
                if (opt->ip6po_hbh == NULL)
                        return (ENOBUFS);
                memcpy(opt->ip6po_hbh, hbh, hbhlen);

                break;
        }

#ifdef RFC2292
        case IPV6_2292DSTOPTS:
#endif
        case IPV6_DSTOPTS:
        case IPV6_RTHDRDSTOPTS:
        {
                struct ip6_dest *dest, **newdest = NULL;
                int destlen;

                /* XXX: see the comment for IPV6_HOPOPTS */
                error = kauth_authorize_network(cred,
                    KAUTH_NETWORK_IPV6,
                    KAUTH_REQ_NETWORK_IPV6_HOPBYHOP, NULL, NULL, NULL);
                if (error)
                        return (error);

                if (len == 0) {
                        ip6_clearpktopts(opt, optname);
                        break;  /* just remove the option */
                }

                /* message length validation */
                if (len < sizeof(struct ip6_dest))
                        return (EINVAL);
                dest = (struct ip6_dest *)buf;
                destlen = (dest->ip6d_len + 1) << 3;
                if (len != destlen)
                        return (EINVAL);
                /*
                 * Determine the position that the destination options header
                 * should be inserted; before or after the routing header.
                 */
                switch (optname) {
                case IPV6_2292DSTOPTS:
                        /*
                         * The old advanced API is ambiguous on this point.
                         * Our approach is to determine the position based
                         * according to the existence of a routing header.
                         * Note, however, that this depends on the order of the
                         * extension headers in the ancillary data; the 1st
                         * part of the destination options header must appear
                         * before the routing header in the ancillary data,
                         * too.
                         * RFC3542 solved the ambiguity by introducing
                         * separate ancillary data or option types.
                         */
                        if (opt->ip6po_rthdr == NULL)
                                newdest = &opt->ip6po_dest1;
                        else
                                newdest = &opt->ip6po_dest2;
                        break;
                case IPV6_RTHDRDSTOPTS:
                        newdest = &opt->ip6po_dest1;
                        break;
                case IPV6_DSTOPTS:
                        newdest = &opt->ip6po_dest2;
                        break;
                }

                /* turn off the previous option, then set the new option. */
                ip6_clearpktopts(opt, optname);
                *newdest = malloc(destlen, M_IP6OPT, M_NOWAIT);
                if (*newdest == NULL)
                        return (ENOBUFS);
                memcpy(*newdest, dest, destlen);

                break;
        }

#ifdef RFC2292
        case IPV6_2292RTHDR:
#endif
        case IPV6_RTHDR:
        {
                struct ip6_rthdr *rth;
                int rthlen;

                if (len == 0) {
                        ip6_clearpktopts(opt, IPV6_RTHDR);
                        break;  /* just remove the option */
                }

                /* message length validation */
                if (len < sizeof(struct ip6_rthdr))
                        return (EINVAL);
                rth = (struct ip6_rthdr *)buf;
                rthlen = (rth->ip6r_len + 1) << 3;
                if (len != rthlen)
                        return (EINVAL);
                switch (rth->ip6r_type) {
                case IPV6_RTHDR_TYPE_0:
                        /* Dropped, RFC5095. */
                default:
                        return (EINVAL);        /* not supported */
                }
                /* turn off the previous option */
                ip6_clearpktopts(opt, IPV6_RTHDR);
                opt->ip6po_rthdr = malloc(rthlen, M_IP6OPT, M_NOWAIT);
                if (opt->ip6po_rthdr == NULL)
                        return (ENOBUFS);
                memcpy(opt->ip6po_rthdr, rth, rthlen);
                break;
        }

        case IPV6_USE_MIN_MTU:
                if (len != sizeof(int))
                        return (EINVAL);
                minmtupolicy = *(int *)buf;
                if (minmtupolicy != IP6PO_MINMTU_MCASTONLY &&
                    minmtupolicy != IP6PO_MINMTU_DISABLE &&
                    minmtupolicy != IP6PO_MINMTU_ALL) {
                        return (EINVAL);
                }
                opt->ip6po_minmtu = minmtupolicy;
                break;

        case IPV6_DONTFRAG:
                if (len != sizeof(int))
                        return (EINVAL);

                if (uproto == IPPROTO_TCP || *(int *)buf == 0) {
                        /*
                         * we ignore this option for TCP sockets.
                         * (RFC3542 leaves this case unspecified.)
                         */
                        opt->ip6po_flags &= ~IP6PO_DONTFRAG;
                } else
                        opt->ip6po_flags |= IP6PO_DONTFRAG;
                break;

        case IPV6_PREFER_TEMPADDR:
        {
                int preftemp;

                if (len != sizeof(int))
                        return (EINVAL);
                preftemp = *(int *)buf;
                switch (preftemp) {
                case IP6PO_TEMPADDR_SYSTEM:
                case IP6PO_TEMPADDR_NOTPREFER:
                case IP6PO_TEMPADDR_PREFER:
                        break;
                default:
                        return (EINVAL);
                }
                opt->ip6po_prefer_tempaddr = preftemp;
                break;
        }

        default:
                return (ENOPROTOOPT);
        } /* end of switch */

        return (0);
}

/*
 * Routine called from ip6_output() to loop back a copy of an IP6 multicast
 * packet to the input queue of a specified interface.  Note that this
 * calls the output routine of the loopback "driver", but with an interface
 * pointer that might NOT be lo0ifp -- easier than replicating that code here.
 */
void
ip6_mloopback(struct ifnet *ifp, struct mbuf *m,
        const struct sockaddr_in6 *dst)
{
        struct mbuf *copym;
        struct ip6_hdr *ip6;

        copym = m_copypacket(m, M_DONTWAIT);
        if (copym == NULL)
                return;

        /*
         * Make sure to deep-copy IPv6 header portion in case the data
         * is in an mbuf cluster, so that we can safely override the IPv6
         * header portion later.
         */
        if ((copym->m_flags & M_EXT) != 0 ||
            copym->m_len < sizeof(struct ip6_hdr)) {
                copym = m_pullup(copym, sizeof(struct ip6_hdr));
                if (copym == NULL)
                        return;
        }

#ifdef DIAGNOSTIC
        if (copym->m_len < sizeof(*ip6)) {
                m_freem(copym);
                return;
        }
#endif

        ip6 = mtod(copym, struct ip6_hdr *);
        /*
         * clear embedded scope identifiers if necessary.
         * in6_clearscope will touch the addresses only when necessary.
         */
        in6_clearscope(&ip6->ip6_src);
        in6_clearscope(&ip6->ip6_dst);

        (void)looutput(ifp, copym, (const struct sockaddr *)dst, NULL);
}

/*
 * Chop IPv6 header off from the payload.
 */
static int
ip6_splithdr(struct mbuf *m, struct ip6_exthdrs *exthdrs)
{
        struct mbuf *mh;
        struct ip6_hdr *ip6;

        ip6 = mtod(m, struct ip6_hdr *);
        if (m->m_len > sizeof(*ip6)) {
                MGETHDR(mh, M_DONTWAIT, MT_HEADER);
                if (mh == NULL) {
                        m_freem(m);
                        return ENOBUFS;
                }
                m_move_pkthdr(mh, m);
                m_align(mh, sizeof(*ip6));
                m->m_len -= sizeof(*ip6);
                m->m_data += sizeof(*ip6);
                mh->m_next = m;
                mh->m_len = sizeof(*ip6);
                memcpy(mtod(mh, void *), (void *)ip6, sizeof(*ip6));
                m = mh;
        }
        exthdrs->ip6e_ip6 = m;
        return 0;
}

/*
 * Compute IPv6 extension header length.
 */
int
ip6_optlen(struct inpcb *inp)
{
        int len;

        if (!in6p_outputopts(inp))
                return 0;

        len = 0;
#define elen(x) \
    (((struct ip6_ext *)(x)) ? (((struct ip6_ext *)(x))->ip6e_len + 1) << 3 : 0)

        len += elen(in6p_outputopts(inp)->ip6po_hbh);
        len += elen(in6p_outputopts(inp)->ip6po_dest1);
        len += elen(in6p_outputopts(inp)->ip6po_rthdr);
        len += elen(in6p_outputopts(inp)->ip6po_dest2);
        return len;
#undef elen
}

/*
 * Ensure sending address is valid.
 * Returns 0 on success, -1 if an error should be sent back or 1
 * if the packet could be dropped without error (protocol dependent).
 */
static int
ip6_ifaddrvalid(const struct in6_addr *src, const struct in6_addr *dst)
{
        struct sockaddr_in6 sin6;
        int s, error;
        struct ifaddr *ifa;
        struct in6_ifaddr *ia6;

        if (IN6_IS_ADDR_UNSPECIFIED(src))
                return 0;

        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_family = AF_INET6;
        sin6.sin6_len = sizeof(sin6);
        sin6.sin6_addr = *src;

        s = pserialize_read_enter();
        ifa = ifa_ifwithaddr(sin6tosa(&sin6));
        if ((ia6 = ifatoia6(ifa)) == NULL ||
            ia6->ia6_flags & (IN6_IFF_ANYCAST | IN6_IFF_DUPLICATED))
                error = -1;
        else if (ia6->ia6_flags & IN6_IFF_TENTATIVE)
                error = 1;
        else if (ia6->ia6_flags & IN6_IFF_DETACHED &&
            (sin6.sin6_addr = *dst, ifa_ifwithaddr(sin6tosa(&sin6)) == NULL))
                /* Allow internal traffic to DETACHED addresses */
                error = 1;
        else
                error = 0;
        pserialize_read_exit(s);

        return error;
}