xnu-2422.90.20.tar.gz

[apple/xnu.git] / bsd / netinet6 / ip6_output.c

/*
 * Copyright (c) 2000-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ip_output.c 8.3 (Berkeley) 1/21/94
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/kauth.h>
#include <sys/mcache.h>
#include <sys/sysctl.h>
#include <kern/zalloc.h>
#include <libkern/OSByteOrder.h>

#include <pexpert/pexpert.h>
#include <mach/sdt.h>

#include <net/if.h>
#include <net/route.h>
#include <net/dlil.h>
#include <net/net_osdep.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet6/in6_var.h>
#include <netinet/ip6.h>
#include <netinet/kpi_ipfilter_var.h>

#include <netinet6/ip6protosw.h>
#include <netinet/icmp6.h>
#include <netinet6/ip6_var.h>
#include <netinet/in_pcb.h>
#include <netinet6/nd6.h>
#include <netinet6/scope6_var.h>
#if IPSEC
#include <netinet6/ipsec.h>
#include <netinet6/ipsec6.h>
#include <netkey/key.h>
extern int ipsec_bypass;
#endif /* IPSEC */

#if CONFIG_MACF_NET
#include <security/mac.h>
#endif /* CONFIG_MACF_NET */

#if DUMMYNET
#include <netinet6/ip6_fw.h>
#include <netinet/ip_fw.h>
#include <netinet/ip_dummynet.h>
#endif /* DUMMYNET */

#if PF
#include <net/pfvar.h>
#endif /* PF */

static int ip6_copyexthdr(struct mbuf **, caddr_t, int);
static void ip6_out_cksum_stats(int, u_int32_t);
static int ip6_insert_jumboopt(struct ip6_exthdrs *, u_int32_t);
static int ip6_insertfraghdr(struct mbuf *, struct mbuf *, int,
    struct ip6_frag **);
static int ip6_getpmtu(struct route_in6 *, struct route_in6 *,
    struct ifnet *, struct in6_addr *, u_int32_t *, boolean_t *);
static int ip6_pcbopts(struct ip6_pktopts **, struct mbuf *, struct socket *,
    struct sockopt *sopt);
static int ip6_pcbopt(int, u_char *, int, struct ip6_pktopts **, int);
static int ip6_getpcbopt(struct ip6_pktopts *, int, struct sockopt *);
static int copypktopts(struct ip6_pktopts *, struct ip6_pktopts *, int);
static void im6o_trace(struct ip6_moptions *, int);
static int ip6_setpktopt(int, u_char *, int, struct ip6_pktopts *, int,
    int, int);
static int ip6_splithdr(struct mbuf *, struct ip6_exthdrs *);
static void ip6_output_checksum(struct ifnet *, uint32_t, struct mbuf *,
    int, uint32_t, uint32_t);

#define IM6O_TRACE_HIST_SIZE    32      /* size of trace history */

/* For gdb */
__private_extern__ unsigned int im6o_trace_hist_size = IM6O_TRACE_HIST_SIZE;

struct ip6_moptions_dbg {
        struct ip6_moptions     im6o;                   /* ip6_moptions */
        u_int16_t               im6o_refhold_cnt;       /* # of IM6O_ADDREF */
        u_int16_t               im6o_refrele_cnt;       /* # of IM6O_REMREF */
        /*
         * Alloc and free callers.
         */
        ctrace_t                im6o_alloc;
        ctrace_t                im6o_free;
        /*
         * Circular lists of IM6O_ADDREF and IM6O_REMREF callers.
         */
        ctrace_t                im6o_refhold[IM6O_TRACE_HIST_SIZE];
        ctrace_t                im6o_refrele[IM6O_TRACE_HIST_SIZE];
};

#if DEBUG
static unsigned int im6o_debug = 1;     /* debugging (enabled) */
#else
static unsigned int im6o_debug;         /* debugging (disabled) */
#endif /* !DEBUG */

static unsigned int im6o_size;          /* size of zone element */
static struct zone *im6o_zone;          /* zone for ip6_moptions */

#define IM6O_ZONE_MAX           64              /* maximum elements in zone */
#define IM6O_ZONE_NAME          "ip6_moptions"  /* zone name */

SYSCTL_DECL(_net_inet6_ip6);

static int ip6_maxchainsent = 0;
SYSCTL_INT(_net_inet6_ip6, OID_AUTO, maxchainsent,
        CTLFLAG_RW | CTLFLAG_LOCKED, &ip6_maxchainsent, 0,
        "use dlil_output_list");

/*
 * XXX we don't handle mbuf chains yet in nd6_output() so ip6_output_list() only
 * walks through the packet chain and sends each mbuf separately.
 */
int
ip6_output_list(struct mbuf *m0, int packetlist, struct ip6_pktopts *opt,
    struct route_in6 *ro, int flags, struct ip6_moptions *im6o,
    struct ifnet **ifpp, struct ip6_out_args *ip6oa)
{
#pragma unused(packetlist)
        struct mbuf *m = m0, *nextpkt;
        int error = 0;

        while (m != NULL) {
                /*
                 * Break the chain before calling ip6_output() and free the
                 * mbufs if there was an error.
                 */
                nextpkt = m->m_nextpkt;
                m->m_nextpkt = NULL;
                error = ip6_output(m, opt, ro, flags, im6o, ifpp, ip6oa);
                if (error != 0) {
                        if (nextpkt != NULL)
                                m_freem_list(nextpkt);
                        return (error);
                }
                m = nextpkt;
        }

        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.
 *
 * If ro is non-NULL and has valid ro->ro_rt, route lookup would be
 * skipped and ro->ro_rt would be used.  Otherwise the result of route
 * lookup is stored in ro->ro_rt.
 *
 * type of "mtu": rt_rmx.rmx_mtu is u_int32_t, ifnet.ifr_mtu is int, and
 * nd_ifinfo.linkmtu is u_int32_t.  so we use u_int32_t to hold largest one,
 * which is rt_rmx.rmx_mtu.
 */
int
ip6_output(struct mbuf *m0, struct ip6_pktopts *opt, struct route_in6 *ro,
    int flags, struct ip6_moptions *im6o, struct ifnet **ifpp,
    struct ip6_out_args *ip6oa)
{
        struct ip6_hdr *ip6;
        u_char *nexthdrp;
        struct ifnet *ifp = NULL, *origifp = NULL;      /* refcnt'd */
        struct mbuf *m, *mprev;
        int hlen, tlen, len, off, nxt0;
        struct route_in6 *ro_pmtu = NULL;
        struct rtentry *rt = NULL;
        struct sockaddr_in6 *dst, src_sa, dst_sa;
        int error = 0;
        struct in6_ifaddr *ia = NULL, *src_ia = NULL;
        u_int32_t mtu;
        boolean_t alwaysfrag = FALSE;
        u_int32_t optlen = 0, plen = 0, unfragpartlen = 0;
        struct ip6_rthdr *rh;
        struct in6_addr finaldst;
        ipfilter_t inject_filter_ref;
        struct ipf_pktopts *ippo = NULL;
        struct flowadv *adv = NULL;
#if DUMMYNET
        struct m_tag *tag;
        struct ip6_out_args saved_ip6oa;
        struct sockaddr_in6 dst_buf;
#endif /* DUMMYNET */
#if IPSEC
        struct socket *so = NULL;
        struct secpolicy *sp = NULL;
        struct route_in6 *ipsec_saved_route = NULL;
        boolean_t needipsectun = FALSE;
#endif /* IPSEC */
        struct {
                struct ipf_pktopts ipf_pktopts;
                struct ip6_exthdrs exthdrs;
                struct route_in6 ip6route;
#if IPSEC
                struct ipsec_output_state ipsec_state;
#endif /* IPSEC */
#if DUMMYNET
                struct route_in6 saved_route;
                struct route_in6 saved_ro_pmtu;
                struct ip_fw_args args;
#endif /* DUMMYNET */
        } ip6obz;
#define ipf_pktopts     ip6obz.ipf_pktopts
#define exthdrs         ip6obz.exthdrs
#define ip6route        ip6obz.ip6route
#define ipsec_state     ip6obz.ipsec_state
#define saved_route     ip6obz.saved_route
#define saved_ro_pmtu   ip6obz.saved_ro_pmtu
#define args            ip6obz.args
        union {
                struct {
                        boolean_t select_srcif : 1;
                        boolean_t hdrsplit : 1;
                        boolean_t dontfrag : 1;
#if IPSEC
                        boolean_t needipsec : 1;
                        boolean_t noipsec : 1;
#endif /* IPSEC */
                };
                uint32_t raw;
        } ip6obf = { .raw = 0 };

        VERIFY(m0->m_flags & M_PKTHDR);

        /* zero out {saved_route, saved_ro_pmtu, ip6route, exthdrs, args} */
        bzero(&ip6obz, sizeof (ip6obz));

#if DUMMYNET
        if (SLIST_EMPTY(&m0->m_pkthdr.tags))
                goto tags_done;

        /* Grab info from mtags prepended to the chain */
        if ((tag = m_tag_locate(m0, KERNEL_MODULE_TAG_ID,
            KERNEL_TAG_TYPE_DUMMYNET, NULL)) != NULL) {
                struct dn_pkt_tag       *dn_tag;

                dn_tag = (struct dn_pkt_tag *)(tag+1);
                args.fwa_pf_rule = dn_tag->dn_pf_rule;

                bcopy(&dn_tag->dn_dst6, &dst_buf, sizeof (dst_buf));
                dst = &dst_buf;
                ifp = dn_tag->dn_ifp;
                if (ifp != NULL)
                        ifnet_reference(ifp);
                flags = dn_tag->dn_flags;
                if (dn_tag->dn_flags & IPV6_OUTARGS) {
                        saved_ip6oa = dn_tag->dn_ip6oa;
                        ip6oa = &saved_ip6oa;
                }

                saved_route = dn_tag->dn_ro6;
                ro = &saved_route;
                saved_ro_pmtu = dn_tag->dn_ro6_pmtu;
                ro_pmtu = &saved_ro_pmtu;
                origifp = dn_tag->dn_origifp;
                if (origifp != NULL)
                        ifnet_reference(origifp);
                mtu = dn_tag->dn_mtu;
                alwaysfrag = (dn_tag->dn_alwaysfrag != 0);
                unfragpartlen = dn_tag->dn_unfragpartlen;

                bcopy(&dn_tag->dn_exthdrs, &exthdrs, sizeof (exthdrs));

                m_tag_delete(m0, tag);
        }

tags_done:
#endif /* DUMMYNET */

        m = m0;
        m->m_pkthdr.pkt_flags &= ~(PKTF_LOOP|PKTF_IFAINFO);

#if IPSEC
        /* for AH processing. stupid to have "socket" variable in IP layer... */
        if (ipsec_bypass == 0) {
                so = ipsec_getsocket(m);
                (void) ipsec_setsocket(m, NULL);

                /* If packet is bound to an interface, check bound policies */
                if ((flags & IPV6_OUTARGS) &&
                    (ip6oa->ip6oa_flags & IPOAF_BOUND_IF) &&
                    ip6oa->ip6oa_boundif != IFSCOPE_NONE) {
                        /* ip6obf.noipsec is a bitfield, use temp integer */
                        int noipsec = 0;

                        if (ipsec6_getpolicybyinterface(m, IPSEC_DIR_OUTBOUND,
                            flags, ip6oa, &noipsec, &sp) != 0)
                                goto bad;

                        ip6obf.noipsec = (noipsec != 0);
                }
        }
#endif /* IPSEC */

        ip6 = mtod(m, struct ip6_hdr *);
        nxt0 = ip6->ip6_nxt;
        finaldst = ip6->ip6_dst;
        inject_filter_ref = ipf_get_inject_filter(m);
        ippo = &ipf_pktopts;

        if (ip6_doscopedroute && (flags & IPV6_OUTARGS)) {
                /*
                 * In the forwarding case, only the ifscope value is used,
                 * as source interface selection doesn't take place.
                 */
                if ((ip6obf.select_srcif = (!(flags & (IPV6_FORWARDING |
                    IPV6_UNSPECSRC | IPV6_FLAG_NOSRCIFSEL)) &&
                    (ip6oa->ip6oa_flags & IP6OAF_SELECT_SRCIF))))
                        ipf_pktopts.ippo_flags |= IPPOF_SELECT_SRCIF;

                if ((ip6oa->ip6oa_flags & IP6OAF_BOUND_IF) &&
                    ip6oa->ip6oa_boundif != IFSCOPE_NONE) {
                        ipf_pktopts.ippo_flags |= (IPPOF_BOUND_IF |
                            (ip6oa->ip6oa_boundif << IPPOF_SHIFT_IFSCOPE));
                }

                if (ip6oa->ip6oa_flags & IP6OAF_BOUND_SRCADDR)
                        ipf_pktopts.ippo_flags |= IPPOF_BOUND_SRCADDR;
        } else {
                ip6obf.select_srcif = FALSE;
                if (flags & IPV6_OUTARGS) {
                        ip6oa->ip6oa_boundif = IFSCOPE_NONE;
                        ip6oa->ip6oa_flags &= ~(IP6OAF_SELECT_SRCIF |
                            IP6OAF_BOUND_IF | IP6OAF_BOUND_SRCADDR);
                }
        }

        if ((flags & IPV6_OUTARGS) && (ip6oa->ip6oa_flags & IP6OAF_NO_CELLULAR))
                ipf_pktopts.ippo_flags |= IPPOF_NO_IFT_CELLULAR;

        if (flags & IPV6_OUTARGS) {
                adv = &ip6oa->ip6oa_flowadv;
                adv->code = FADV_SUCCESS;
                ip6oa->ip6oa_retflags = 0;
        }

#if DUMMYNET
        if (args.fwa_pf_rule) {
                ip6 = mtod(m, struct ip6_hdr *);
                VERIFY(ro != NULL);     /* ro == saved_route */
                goto check_with_pf;
        }
#endif /* DUMMYNET */

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

        if (opt != NULL) {
                /* Hop-by-Hop options header */
                MAKE_EXTHDR(opt->ip6po_hbh, &exthdrs.ip6e_hbh);
                /* Destination options header(1st part) */
                if (opt->ip6po_rthdr) {
                        /*
                         * Destination options header(1st part)
                         * This only makes sense with a routing header.
                         * See Section 9.2 of RFC 3542.
                         * Disabling this part just for MIP6 convenience is
                         * a bad idea.  We need to think carefully about a
                         * way to make the advanced API coexist with MIP6
                         * options, which might automatically be inserted in
                         * the kernel.
                         */
                        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);
        }

#undef MAKE_EXTHDR

#if IPSEC
        if (ipsec_bypass != 0 || ip6obf.noipsec)
                goto skip_ipsec;

        /* May have been set above if packet was bound */
        if (sp == NULL) {
                /* get a security policy for this packet */
                if (so == NULL) {
                        sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
                            0, &error);
                } else {
                        sp = ipsec6_getpolicybysock(m, IPSEC_DIR_OUTBOUND,
                            so, &error);
                }
                if (sp == NULL) {
                        IPSEC_STAT_INCREMENT(ipsec6stat.out_inval);
                        goto freehdrs;
                }
        }

        error = 0;

        /* check policy */
        switch (sp->policy) {
        case IPSEC_POLICY_DISCARD:
        case IPSEC_POLICY_GENERATE:
                /*
                 * This packet is just discarded.
                 */
                IPSEC_STAT_INCREMENT(ipsec6stat.out_polvio);
                goto freehdrs;

        case IPSEC_POLICY_BYPASS:
        case IPSEC_POLICY_NONE:
                /* no need to do IPsec. */
                ip6obf.needipsec = FALSE;
                break;

        case IPSEC_POLICY_IPSEC:
                if (sp->req == NULL) {
                        /* acquire a policy */
                        error = key_spdacquire(sp);
                        goto freehdrs;
                }
                if (sp->ipsec_if) {
                        /* Verify the redirect to ipsec interface */
                        if (sp->ipsec_if == ifp) {
                                /* Set policy for mbuf */
                                m->m_pkthdr.ipsec_policy = sp->id;
                                goto skip_ipsec;
                        }
                        goto bad;
                } else {
                        ip6obf.needipsec = TRUE;
                }
                break;

        case IPSEC_POLICY_ENTRUST:
        default:
                printf("%s: Invalid policy found: %d\n", __func__, sp->policy);
                break;
        }
skip_ipsec:
#endif /* IPSEC */

        /*
         * Calculate the total length of the extension header chain.
         * Keep the length of the unfragmentable part for fragmentation.
         */
        optlen = 0;
        if (exthdrs.ip6e_hbh != NULL)
                optlen += exthdrs.ip6e_hbh->m_len;
        if (exthdrs.ip6e_dest1 != NULL)
                optlen += exthdrs.ip6e_dest1->m_len;
        if (exthdrs.ip6e_rthdr != NULL)
                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 != NULL)
                optlen += exthdrs.ip6e_dest2->m_len;

        /*
         * If we need IPsec, or there is at least one extension header,
         * separate IP6 header from the payload.
         */
        if ((
#if IPSEC
            ip6obf.needipsec ||
#endif /* IPSEC */
            optlen) && !ip6obf.hdrsplit) {
                if ((error = ip6_splithdr(m, &exthdrs)) != 0) {
                        m = NULL;
                        goto freehdrs;
                }
                m = exthdrs.ip6e_ip6;
                ip6obf.hdrsplit = TRUE;
        }

        /* 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 (!ip6obf.hdrsplit) {
                        if ((error = ip6_splithdr(m, &exthdrs)) != 0) {
                                m = NULL;
                                goto freehdrs;
                        }
                        m = exthdrs.ip6e_ip6;
                        ip6obf.hdrsplit = TRUE;
                }
                /* adjust pointer */
                ip6 = mtod(m, struct ip6_hdr *);
                if ((error = ip6_insert_jumboopt(&exthdrs, plen)) != 0)
                        goto freehdrs;
                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.
         */
        nexthdrp = &ip6->ip6_nxt;
        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 != NULL) {
                if (!ip6obf.hdrsplit) {
                        panic("assumption failed: hdr not split");
                        /* NOTREACHED */
                }
                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 != NULL) {                                                \
                if (!ip6obf.hdrsplit) {                                 \
                        panic("assumption failed: hdr not split");      \
                        /* NOTREACHED */                                \
                }                                                       \
                *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 (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);

#undef MAKE_CHAIN

#if IPSEC
        if (ip6obf.needipsec && (m->m_pkthdr.csum_flags & CSUM_DELAY_IPV6_DATA))
                in6_delayed_cksum_offset(m, 0, optlen, nxt0);
#endif /* IPSEC */

        if (!TAILQ_EMPTY(&ipv6_filters)) {
                struct ipfilter *filter;
                int seen = (inject_filter_ref == NULL);
                int fixscope = 0;

                if (im6o != NULL && IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                        ippo->ippo_flags |= IPPOF_MCAST_OPTS;
                        IM6O_LOCK(im6o);
                        ippo->ippo_mcast_ifnet = im6o->im6o_multicast_ifp;
                        ippo->ippo_mcast_ttl = im6o->im6o_multicast_hlim;
                        ippo->ippo_mcast_loop = im6o->im6o_multicast_loop;
                        IM6O_UNLOCK(im6o);
                }

                /* Hack: embed the scope_id in the destination */
                if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst) &&
                    (ip6->ip6_dst.s6_addr16[1] == 0) && (ro != NULL)) {
                        fixscope = 1;
                        ip6->ip6_dst.s6_addr16[1] =
                            htons(ro->ro_dst.sin6_scope_id);
                }

                ipf_ref();
                TAILQ_FOREACH(filter, &ipv6_filters, ipf_link) {
                        /*
                         * Don't process packet twice if we've already seen it.
                         */
                        if (seen == 0) {
                                if ((struct ipfilter *)inject_filter_ref ==
                                    filter)
                                        seen = 1;
                        } else if (filter->ipf_filter.ipf_output != NULL) {
                                errno_t result;

                                result = filter->ipf_filter.ipf_output(
                                    filter->ipf_filter.cookie,
                                    (mbuf_t *)&m, ippo);
                                if (result == EJUSTRETURN) {
                                        ipf_unref();
                                        goto done;
                                }
                                if (result != 0) {
                                        ipf_unref();
                                        goto bad;
                                }
                        }
                }
                ipf_unref();

                ip6 = mtod(m, struct ip6_hdr *);
                /* Hack: cleanup embedded scope_id if we put it there */
                if (fixscope)
                        ip6->ip6_dst.s6_addr16[1] = 0;
        }

#if IPSEC
        if (ip6obf.needipsec) {
                int segleft_org;

                /*
                 * pointers after IPsec headers are not valid any more.
                 * other pointers need a great care too.
                 * (IPsec routines should not mangle mbufs prior to AH/ESP)
                 */
                exthdrs.ip6e_dest2 = NULL;

                if (exthdrs.ip6e_rthdr != NULL) {
                        rh = mtod(exthdrs.ip6e_rthdr, struct ip6_rthdr *);
                        segleft_org = rh->ip6r_segleft;
                        rh->ip6r_segleft = 0;
                } else {
                        rh = NULL;
                        segleft_org = 0;
                }

                ipsec_state.m = m;
                error = ipsec6_output_trans(&ipsec_state, nexthdrp, mprev,
                    sp, flags, &needipsectun);
                m = ipsec_state.m;
                if (error) {
                        /* mbuf is already reclaimed in ipsec6_output_trans. */
                        m = NULL;
                        switch (error) {
                        case EHOSTUNREACH:
                        case ENETUNREACH:
                        case EMSGSIZE:
                        case ENOBUFS:
                        case ENOMEM:
                                break;
                        default:
                                printf("ip6_output (ipsec): error code %d\n",
                                    error);
                                /* FALLTHRU */
                        case ENOENT:
                                /* don't show these error codes to the user */
                                error = 0;
                                break;
                        }
                        goto bad;
                }
                if (exthdrs.ip6e_rthdr != NULL) {
                        /* ah6_output doesn't modify mbuf chain */
                        rh->ip6r_segleft = segleft_org;
                }
        }
#endif /* IPSEC */

        /*
         * If there is a routing header, replace the destination address field
         * with the first hop of the routing header.
         */
        if (exthdrs.ip6e_rthdr != NULL) {
                struct ip6_rthdr0 *rh0;
                struct in6_addr *addr;
                struct sockaddr_in6 sa;

                rh = (struct ip6_rthdr *)
                    (mtod(exthdrs.ip6e_rthdr, struct ip6_rthdr *));
                switch (rh->ip6r_type) {
                case IPV6_RTHDR_TYPE_0:
                        rh0 = (struct ip6_rthdr0 *)rh;
                        addr = (struct in6_addr *)(void *)(rh0 + 1);

                        /*
                         * construct a sockaddr_in6 form of
                         * the first hop.
                         *
                         * XXX: we may not have enough
                         * information about its scope zone;
                         * there is no standard API to pass
                         * the information from the
                         * application.
                         */
                        bzero(&sa, sizeof (sa));
                        sa.sin6_family = AF_INET6;
                        sa.sin6_len = sizeof (sa);
                        sa.sin6_addr = addr[0];
                        if ((error = sa6_embedscope(&sa,
                            ip6_use_defzone)) != 0) {
                                goto bad;
                        }
                        ip6->ip6_dst = sa.sin6_addr;
                        bcopy(&addr[1], &addr[0], sizeof (struct in6_addr) *
                            (rh0->ip6r0_segleft - 1));
                        addr[rh0->ip6r0_segleft - 1] = finaldst;
                        /* XXX */
                        in6_clearscope(addr + rh0->ip6r0_segleft - 1);
                        break;
                default:        /* is it possible? */
                        error = EINVAL;
                        goto bad;
                }
        }

        /* Source address validation */
        if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src) &&
            !(flags & IPV6_UNSPECSRC)) {
                error = EOPNOTSUPP;
                ip6stat.ip6s_badscope++;
                goto bad;
        }
        if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
                error = EOPNOTSUPP;
                ip6stat.ip6s_badscope++;
                goto bad;
        }

        ip6stat.ip6s_localout++;

        /*
         * Route packet.
         */
        if (ro == NULL) {
                ro = &ip6route;
                bzero((caddr_t)ro, sizeof (*ro));
        }
        VERIFY(ro_pmtu == NULL);        /* must not get here if dummynet */
        ro_pmtu = ro;
        if (opt != NULL && opt->ip6po_rthdr)
                ro = &opt->ip6po_route;
        dst = SIN6(&ro->ro_dst);

        if (ro->ro_rt != NULL)
                RT_LOCK_ASSERT_NOTHELD(ro->ro_rt);
        /*
         * 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 != NULL && 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) {
                        IM6O_LOCK(im6o);
                        ip6->ip6_hlim = im6o->im6o_multicast_hlim;
                        IM6O_UNLOCK(im6o);
                } else {
                        ip6->ip6_hlim = ip6_defmcasthlim;
                }
        }

        /*
         * If there is a cached route, check that it is to the same
         * destination and is still up. If not, free it and try again.
         * Test rt_flags without holding rt_lock for performance reasons;
         * if the route is down it will hopefully be caught by the layer
         * below (since it uses this route as a hint) or during the
         * next transmit.
         */
        if (ROUTE_UNUSABLE(ro) || dst->sin6_family != AF_INET6 ||
            !IN6_ARE_ADDR_EQUAL(&dst->sin6_addr, &ip6->ip6_dst))
                ROUTE_RELEASE(ro);

        if (ro->ro_rt == NULL) {
                bzero(dst, sizeof (*dst));
                dst->sin6_family = AF_INET6;
                dst->sin6_len = sizeof (struct sockaddr_in6);
                dst->sin6_addr = ip6->ip6_dst;
        }
#if IPSEC
        if (ip6obf.needipsec && needipsectun) {
#if CONFIG_DTRACE
                struct ifnet *trace_ifp = (ifpp != NULL) ? (*ifpp) : NULL;
#endif /* CONFIG_DTRACE */
                /*
                 * All the extension headers will become inaccessible
                 * (since they can be encrypted).
                 * Don't panic, we need no more updates to extension headers
                 * on inner IPv6 packet (since they are now encapsulated).
                 *
                 * IPv6 [ESP|AH] IPv6 [extension headers] payload
                 */
                bzero(&exthdrs, sizeof (exthdrs));
                exthdrs.ip6e_ip6 = m;

                ipsec_state.m = m;
                route_copyout(&ipsec_state.ro, (struct route *)ro,
                    sizeof (ipsec_state.ro));
                ipsec_state.dst = SA(dst);

                /* So that we can see packets inside the tunnel */
                DTRACE_IP6(send, struct mbuf *, m, struct inpcb *, NULL,
                    struct ip6_hdr *, ip6, struct ifnet *, trace_ifp,
                    struct ip *, NULL, struct ip6_hdr *, ip6);

                error = ipsec6_output_tunnel(&ipsec_state, sp, flags);
                /* tunneled in IPv4? packet is gone */
                if (ipsec_state.tunneled == 4)
                        goto done;
                m = ipsec_state.m;
                ipsec_saved_route = ro;
                ro = (struct route_in6 *)&ipsec_state.ro;
                dst = SIN6(ipsec_state.dst);
                if (error) {
                        /* mbuf is already reclaimed in ipsec6_output_tunnel. */
                        m0 = m = NULL;
                        m = NULL;
                        switch (error) {
                        case EHOSTUNREACH:
                        case ENETUNREACH:
                        case EMSGSIZE:
                        case ENOBUFS:
                        case ENOMEM:
                                break;
                        default:
                                printf("ip6_output (ipsec): error code %d\n",
                                    error);
                                /* FALLTHRU */
                        case ENOENT:
                                /* don't show these error codes to the user */
                                error = 0;
                                break;
                        }
                        goto bad;
                }
                /*
                 * The packet has been encapsulated so the ifscope
                 * is no longer valid since it does not apply to the
                 * outer address: ignore the ifscope.
                 */
                if (flags & IPV6_OUTARGS) {
                        ip6oa->ip6oa_boundif = IFSCOPE_NONE;
                        ip6oa->ip6oa_flags &= ~IP6OAF_BOUND_IF;
                }
                if (opt != NULL && opt->ip6po_pktinfo != NULL) {
                        if (opt->ip6po_pktinfo->ipi6_ifindex != IFSCOPE_NONE)
                                opt->ip6po_pktinfo->ipi6_ifindex = IFSCOPE_NONE;
                }
                exthdrs.ip6e_ip6 = m;
        }
#endif /* IPSEC */

        /* for safety */
        if (ifp != NULL) {
                ifnet_release(ifp);
                ifp = NULL;
        }

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

        if (ip6obf.select_srcif) {
                bzero(&src_sa, sizeof (src_sa));
                src_sa.sin6_family = AF_INET6;
                src_sa.sin6_len = sizeof (src_sa);
                src_sa.sin6_addr = ip6->ip6_src;
        }
        bzero(&dst_sa, sizeof (dst_sa));
        dst_sa.sin6_family = AF_INET6;
        dst_sa.sin6_len = sizeof (dst_sa);
        dst_sa.sin6_addr = ip6->ip6_dst;

        /*
         * in6_selectroute() might return an ifp with its reference held
         * even in the error case, so make sure to release its reference.
         * ip6oa may be NULL if IPV6_OUTARGS isn't set.
         */
        if ((error = in6_selectroute(ip6obf.select_srcif ? &src_sa : NULL,
            &dst_sa, opt, im6o, &src_ia, ro, &ifp, &rt, 0, ip6oa)) != 0) {
                switch (error) {
                case EHOSTUNREACH:
                        ip6stat.ip6s_noroute++;
                        break;
                case EADDRNOTAVAIL:
                default:
                        break; /* XXX statistics? */
                }
                if (ifp != NULL)
                        in6_ifstat_inc(ifp, ifs6_out_discard);
                /* ifp (if non-NULL) will be released at the end */
                goto bad;
        }
        if (rt == NULL) {
                /*
                 * If in6_selectroute() does not return a route entry,
                 * dst may not have been updated.
                 */
                *dst = dst_sa;  /* XXX */
        }

        /*
         * then rt (for unicast) and ifp must be non-NULL valid values.
         */
        if (!(flags & IPV6_FORWARDING)) {
                /* XXX: the FORWARDING flag can be set for mrouting. */
                in6_ifstat_inc_na(ifp, ifs6_out_request);
        }
        if (rt != NULL) {
                RT_LOCK(rt);
                ia = (struct in6_ifaddr *)(rt->rt_ifa);
                if (ia != NULL)
                        IFA_ADDREF(&ia->ia_ifa);
                rt->rt_use++;
                RT_UNLOCK(rt);
        }

        /*
         * The outgoing interface must be in the zone of source and
         * destination addresses (except local/loopback).  We should
         * use ia_ifp to support the case of sending packets to an
         * address of our own.
         */
        if (ia != NULL && ia->ia_ifp) {
                ifnet_reference(ia->ia_ifp);    /* for origifp */
                if (origifp != NULL)
                        ifnet_release(origifp);
                origifp = ia->ia_ifp;
        } else {
                if (ifp != NULL)
                        ifnet_reference(ifp);   /* for origifp */
                if (origifp != NULL)
                        ifnet_release(origifp);
                origifp = ifp;
        }

        /* skip scope enforcements for local/loopback route */
        if (rt == NULL || !(rt->rt_ifp->if_flags & IFF_LOOPBACK)) {
                struct in6_addr src0, dst0;
                u_int32_t zone;

                src0 = ip6->ip6_src;
                if (in6_setscope(&src0, origifp, &zone))
                        goto badscope;
                bzero(&src_sa, sizeof (src_sa));
                src_sa.sin6_family = AF_INET6;
                src_sa.sin6_len = sizeof (src_sa);
                src_sa.sin6_addr = ip6->ip6_src;
                if ((sa6_recoverscope(&src_sa, TRUE) ||
                    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 */
                bzero(&dst_sa, sizeof (dst_sa));
                dst_sa.sin6_family = AF_INET6;
                dst_sa.sin6_len = sizeof (dst_sa);
                dst_sa.sin6_addr = ip6->ip6_dst;
                if ((sa6_recoverscope(&dst_sa, TRUE) ||
                    zone != dst_sa.sin6_scope_id))
                        goto badscope;

                /* scope check is done. */
                goto routefound;

badscope:
                ip6stat.ip6s_badscope++;
                in6_ifstat_inc(origifp, ifs6_out_discard);
                if (error == 0)
                        error = EHOSTUNREACH; /* XXX */
                goto bad;
        }

routefound:
        if (rt != NULL && !IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                if (opt != NULL && opt->ip6po_nextroute.ro_rt) {
                        /*
                         * The nexthop is explicitly specified by the
                         * application.  We assume the next hop is an IPv6
                         * address.
                         */
                        dst = SIN6(opt->ip6po_nexthop);
                } else if ((rt->rt_flags & RTF_GATEWAY)) {
                        dst = SIN6(rt->rt_gateway);
                }
                /*
                 * For packets destined to local/loopback, record the
                 * source the source interface (which owns the source
                 * address), as well as the output interface.  This is
                 * needed to reconstruct the embedded zone for the
                 * link-local address case in ip6_input().
                 */
                if (ia != NULL && (ifp->if_flags & IFF_LOOPBACK)) {
                        uint32_t srcidx;

                        if (src_ia != NULL)
                                srcidx = src_ia->ia_ifp->if_index;
                        else if (ro->ro_srcia != NULL)
                                srcidx = ro->ro_srcia->ifa_ifp->if_index;
                        else
                                srcidx = 0;

                        ip6_setsrcifaddr_info(m, srcidx, NULL);
                        ip6_setdstifaddr_info(m, 0, ia);
                }
        }

        if (!IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
                m->m_flags &= ~(M_BCAST | M_MCAST); /* just in case */
        } else {
                struct  in6_multi *in6m;

                m->m_flags = (m->m_flags & ~M_BCAST) | M_MCAST;
                in6_ifstat_inc_na(ifp, ifs6_out_mcast);

                /*
                 * Confirm that the outgoing interface supports multicast.
                 */
                if (!(ifp->if_flags & IFF_MULTICAST)) {
                        ip6stat.ip6s_noroute++;
                        in6_ifstat_inc(ifp, ifs6_out_discard);
                        error = ENETUNREACH;
                        goto bad;
                }
                in6_multihead_lock_shared();
                IN6_LOOKUP_MULTI(&ip6->ip6_dst, ifp, in6m);
                in6_multihead_lock_done();
                if (im6o != NULL)
                        IM6O_LOCK(im6o);
                if (in6m != NULL &&
                    (im6o == NULL || im6o->im6o_multicast_loop)) {
                        if (im6o != NULL)
                                IM6O_UNLOCK(im6o);
                        /*
                         * If we belong to the destination multicast group
                         * on the outgoing interface, and the caller did not
                         * forbid loopback, loop back a copy.
                         */
                        ip6_mloopback(NULL, ifp, m, dst, optlen, nxt0);
                } else {
                        if (im6o != NULL)
                                IM6O_UNLOCK(im6o);
                        /*
                         * 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 MROUTING
                        if (ip6_mrouter && !(flags & IPV6_FORWARDING)) {
                                /*
                                 * XXX: ip6_mforward expects that rcvif is NULL
                                 * when it is called from the originating path.
                                 * However, it is not always the case, since
                                 * some versions of MGETHDR() does not
                                 * initialize the field.
                                 */
                                m->m_pkthdr.rcvif = NULL;
                                if (ip6_mforward(ip6, ifp, m) != 0) {
                                        m_freem(m);
                                        if (in6m != NULL)
                                                IN6M_REMREF(in6m);
                                        goto done;
                                }
                        }
#endif /* MROUTING */
                }
                if (in6m != NULL)
                        IN6M_REMREF(in6m);
                /*
                 * 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 inteface to tell the upper layer
         * to increment per-interface statistics.
         */
        if (ifpp != NULL) {
                ifnet_reference(ifp);   /* for caller */
                if (*ifpp != NULL)
                        ifnet_release(*ifpp);
                *ifpp = ifp;
        }

        /* Determine path MTU. */
        if ((error = ip6_getpmtu(ro_pmtu, ro, ifp, &finaldst, &mtu,
            &alwaysfrag)) != 0)
                goto bad;

        /*
         * 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 IPFW2
        /*
         * Check with the firewall...
         */
        if (ip6_fw_enable && ip6_fw_chk_ptr) {
                u_short port = 0;
                m->m_pkthdr.rcvif = NULL;       /* XXX */
                /* If ipfw says divert, we have to just drop packet */
                if (ip6_fw_chk_ptr(&ip6, ifp, &port, &m)) {
                        m_freem(m);
                        goto done;
                }
                if (m == NULL) {
                        error = EACCES;
                        goto done;
                }
        }
#endif /* IPFW2 */

        /*
         * 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.)
         */
        if (exthdrs.ip6e_hbh != NULL) {
                struct ip6_hbh *hbh = mtod(exthdrs.ip6e_hbh, struct ip6_hbh *);
                u_int32_t dummy; /* XXX unused */
                uint32_t oplen = 0; /* for ip6_process_hopopts() */
#if DIAGNOSTIC
                if ((hbh->ip6h_len + 1) << 3 > exthdrs.ip6e_hbh->m_len)
                        panic("ip6e_hbh is not continuous");
#endif
                /*
                 * XXX: If we have to send an ICMPv6 error to the sender,
                 * we need the M_LOOP flag since icmp6_error() expects
                 * the IPv6 and the hop-by-hop options header are
                 * continuous unless the flag is set.
                 */
                m->m_flags |= M_LOOP;
                m->m_pkthdr.rcvif = ifp;
                if (ip6_process_hopopts(m, (u_int8_t *)(hbh + 1),
                    ((hbh->ip6h_len + 1) << 3) - sizeof (struct ip6_hbh),
                    &dummy, &oplen) < 0) {
                        /* m was already freed at this point */
                        error = EINVAL; /* better error? */
                        goto done;
                }
                m->m_flags &= ~M_LOOP; /* XXX */
                m->m_pkthdr.rcvif = NULL;
        }

#if DUMMYNET
check_with_pf:
#endif /* DUMMYNET */
#if PF
        if (PF_IS_ENABLED) {
#if DUMMYNET
                /*
                 * TODO: Need to save opt->ip6po_flags for reinjection
                 * rdar://10434993
                 */
                args.fwa_m = m;
                args.fwa_oif = ifp;
                args.fwa_oflags = flags;
                if (flags & IPV6_OUTARGS)
                        args.fwa_ip6oa = ip6oa;
                args.fwa_ro6 = ro;
                args.fwa_dst6 = dst;
                args.fwa_ro6_pmtu = ro_pmtu;
                args.fwa_origifp = origifp;
                args.fwa_mtu = mtu;
                args.fwa_alwaysfrag = alwaysfrag;
                args.fwa_unfragpartlen = unfragpartlen;
                args.fwa_exthdrs = &exthdrs;
                /* Invoke outbound packet filter */
                error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, &args);
#else /* !DUMMYNET */
                error = pf_af_hook(ifp, NULL, &m, AF_INET6, FALSE, NULL);
#endif /* !DUMMYNET */

                if (error != 0 || m == NULL) {
                        /*
                         * Note that if we ever handle packet chain, we will
                         * have to restore the linkage from the previous
                         * packet to the next like in ip_outout_list()
                         */
                        if (m != NULL) {
                                panic("%s: unexpected packet %p\n",
                                    __func__, m);
                                /* NOTREACHED */
                        }
                        /* Already freed by callee */
                        goto done;
                }
                ip6 = mtod(m, struct ip6_hdr *);
        }
#endif /* PF */

        /*
         * 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;

        if (opt != NULL && (opt->ip6po_flags & IP6PO_DONTFRAG))
                ip6obf.dontfrag = TRUE;
        else
                ip6obf.dontfrag = FALSE;
        if (ip6obf.dontfrag && alwaysfrag) {    /* case 4 */
                /* conflicting request - can't transmit */
                error = EMSGSIZE;
                goto bad;
        }

        lck_rw_lock_shared(nd_if_rwlock);
        /* Access without acquiring nd_ifinfo lock for performance */
        if (ip6obf.dontfrag && tlen > IN6_LINKMTU(ifp)) {       /* case 2-b */
                lck_rw_done(nd_if_rwlock);
                /*
                 * 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;
                bzero(&ip6cp, sizeof (ip6cp));
                ip6cp.ip6c_cmdarg = (void *)&mtu32;
                pfctlinput2(PRC_MSGSIZE, SA(&ro_pmtu->ro_dst), (void *)&ip6cp);
                error = EMSGSIZE;
                goto bad;
        } else {
                lck_rw_done(nd_if_rwlock);
        }

        /*
         * transmit packet without fragmentation
         */
        if (ip6obf.dontfrag || (!alwaysfrag &&          /* case 1-a and 2-a */
            (tlen <= mtu || TSO_IPV6_OK(ifp, m) ||
            (ifp->if_hwassist & CSUM_FRAGMENT_IPV6)))) {
#ifdef IPSEC
                /* clean ipsec history once it goes out of the node */
                ipsec_delaux(m);
#endif /* IPSEC */

                ip6_output_checksum(ifp, mtu, m, nxt0, tlen, optlen);

                if (ro->ro_rt)
                        RT_LOCK_ASSERT_NOTHELD(ro->ro_rt);
                error = nd6_output(ifp, origifp, m, dst, ro->ro_rt, adv);
                goto done;
        }

        /*
         * try to fragment the packet.  case 1-b and 3
         */
        if ((m->m_pkthdr.csum_flags & CSUM_TSO_IPV6)) {
                /* TSO and fragment aren't compatible */
                error = EMSGSIZE;
                in6_ifstat_inc(ifp, ifs6_out_fragfail);
                goto bad;
        } else if (mtu < IPV6_MMTU) {
                /* path MTU cannot be less than IPV6_MMTU */
                error = EMSGSIZE;
                in6_ifstat_inc(ifp, ifs6_out_fragfail);
                goto bad;
        } else if (ip6->ip6_plen == 0) {
                /* jumbo payload cannot be fragmented */
                error = EMSGSIZE;
                in6_ifstat_inc(ifp, ifs6_out_fragfail);
                goto bad;
        } else {
                struct mbuf **mnext, *m_frgpart;
                struct ip6_frag *ip6f;
                u_int32_t id = htonl(ip6_randomid());
                u_char nextproto;

                /*
                 * Too large for the destination or interface;
                 * fragment if possible.
                 * Must be able to put at least 8 bytes per fragment.
                 */
                hlen = unfragpartlen;
                if (mtu > IPV6_MAXPACKET)
                        mtu = IPV6_MAXPACKET;

                len = (mtu - hlen - sizeof (struct ip6_frag)) & ~7;
                if (len < 8) {
                        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 != NULL) {
                        nextproto = *mtod(exthdrs.ip6e_rthdr, u_char *);
                        *mtod(exthdrs.ip6e_rthdr, u_char *) = IPPROTO_FRAGMENT;
                } else if (exthdrs.ip6e_dest1 != NULL) {
                        nextproto = *mtod(exthdrs.ip6e_dest1, u_char *);
                        *mtod(exthdrs.ip6e_dest1, u_char *) = IPPROTO_FRAGMENT;
                } else if (exthdrs.ip6e_hbh != NULL) {
                        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 & CSUM_DELAY_IPV6_DATA)
                        in6_delayed_cksum_offset(m, 0, optlen, nxt0);

                /*
                 * 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 ip6_hdr *mhip6;

                        MGETHDR(m, M_DONTWAIT, MT_HEADER);      /* MAC-OK */
                        if (m == NULL) {
                                error = ENOBUFS;
                                ip6stat.ip6s_odropped++;
                                goto sendorfree;
                        }
                        m->m_pkthdr.rcvif = NULL;
                        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);
                        error = ip6_insertfraghdr(m0, m, hlen, &ip6f);
                        if (error) {
                                ip6stat.ip6s_odropped++;
                                goto sendorfree;
                        }
                        ip6f->ip6f_offlg = htons((u_short)((off - hlen) & ~7));
                        if (off + len >= tlen)
                                len = tlen - off;
                        else
                                ip6f->ip6f_offlg |= IP6F_MORE_FRAG;
                        mhip6->ip6_plen = htons((u_short)(len + hlen +
                            sizeof (*ip6f) - sizeof (struct ip6_hdr)));
                        if ((m_frgpart = m_copy(m0, off, len)) == NULL) {
                                error = ENOBUFS;
                                ip6stat.ip6s_odropped++;
                                goto sendorfree;
                        }
                        m_cat(m, m_frgpart);
                        m->m_pkthdr.len = len + hlen + sizeof (*ip6f);
                        m->m_pkthdr.rcvif = NULL;

                        M_COPY_CLASSIFIER(m, m0);
                        M_COPY_PFTAG(m, m0);

#ifdef notyet
#if CONFIG_MACF_NET
                        mac_create_fragment(m0, m);
#endif /* CONFIG_MACF_NET */
#endif /* notyet */

                        ip6f->ip6f_reserved = 0;
                        ip6f->ip6f_ident = id;
                        ip6f->ip6f_nxt = nextproto;
                        ip6stat.ip6s_ofragments++;
                        in6_ifstat_inc(ifp, ifs6_out_fragcreat);
                }

                in6_ifstat_inc(ifp, ifs6_out_fragok);
        }

        /*
         * Remove leading garbages.
         */
sendorfree:
        m = m0->m_nextpkt;
        m0->m_nextpkt = NULL;
        m_freem(m0);
        for (m0 = m; m != NULL; m = m0) {
                m0 = m->m_nextpkt;
                m->m_nextpkt = NULL;
                if (error == 0) {
#if IPSEC
                        /* clean ipsec history once it goes out of the node */
                        ipsec_delaux(m);
#endif /* IPSEC */
                        error = nd6_output(ifp, origifp, m, dst, ro->ro_rt,
                            adv);
                } else {
                        m_freem(m);
                }
        }

        if (error == 0)
                ip6stat.ip6s_fragmented++;

done:
        ROUTE_RELEASE(&ip6route);
#if IPSEC
        ROUTE_RELEASE(&ipsec_state.ro);
        if (sp != NULL)
                key_freesp(sp, KEY_SADB_UNLOCKED);
#endif /* IPSEC */
#if DUMMYNET
        ROUTE_RELEASE(&saved_route);
        ROUTE_RELEASE(&saved_ro_pmtu);
#endif /* DUMMYNET */

        if (ia != NULL)
                IFA_REMREF(&ia->ia_ifa);
        if (src_ia != NULL)
                IFA_REMREF(&src_ia->ia_ifa);
        if (ifp != NULL)
                ifnet_release(ifp);
        if (origifp != NULL)
                ifnet_release(origifp);
        return (error);

freehdrs:
        if (exthdrs.ip6e_hbh != NULL)
                m_freem(exthdrs.ip6e_hbh);
        if (exthdrs.ip6e_dest1 != NULL)
                m_freem(exthdrs.ip6e_dest1);
        if (exthdrs.ip6e_rthdr != NULL)
                m_freem(exthdrs.ip6e_rthdr);
        if (exthdrs.ip6e_dest2 != NULL)
                m_freem(exthdrs.ip6e_dest2);
        /* FALLTHRU */
bad:
        if (m != NULL)
                m_freem(m);
        goto done;

#undef ipf_pktopts
#undef exthdrs
#undef ip6route
#undef ipsec_state
#undef saved_route
#undef saved_ro_pmtu
#undef args
}

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

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

        MGET(m, M_DONTWAIT, MT_DATA);
        if (m == NULL)
                return (ENOBUFS);

        if (hlen > MLEN) {
                MCLGET(m, M_DONTWAIT);
                if (!(m->m_flags & M_EXT)) {
                        m_free(m);
                        return (ENOBUFS);
                }
        }
        m->m_len = hlen;
        if (hdr != NULL)
                bcopy(hdr, mtod(m, caddr_t), hlen);

        *mp = m;
        return (0);
}

static void
ip6_out_cksum_stats(int proto, u_int32_t len)
{
        switch (proto) {
        case IPPROTO_TCP:
                tcp_out6_cksum_stats(len);
                break;
        case IPPROTO_UDP:
                udp_out6_cksum_stats(len);
                break;
        default:
                /* keep only TCP or UDP stats for now */
                break;
        }
}

/*
 * Process a delayed payload checksum calculation (outbound path.)
 *
 * hoff is the number of bytes beyond the mbuf data pointer which
 * points to the IPv6 header.  optlen is the number of bytes, if any,
 * between the end of IPv6 header and the beginning of the ULP payload
 * header, which represents the extension headers.  If optlen is less
 * than zero, this routine will bail when it detects extension headers.
 *
 * Returns a bitmask representing all the work done in software.
 */
uint32_t
in6_finalize_cksum(struct mbuf *m, uint32_t hoff, int32_t optlen,
    int32_t nxt0, uint32_t csum_flags)
{
        unsigned char buf[sizeof (struct ip6_hdr)] __attribute__((aligned(8)));
        struct ip6_hdr *ip6;
        uint32_t offset, mlen, hlen, olen, sw_csum;
        uint16_t csum, ulpoff, plen;
        uint8_t nxt;

        _CASSERT(sizeof (csum) == sizeof (uint16_t));
        VERIFY(m->m_flags & M_PKTHDR);

        sw_csum = (csum_flags & m->m_pkthdr.csum_flags);

        if ((sw_csum &= CSUM_DELAY_IPV6_DATA) == 0)
                goto done;

        mlen = m->m_pkthdr.len;                         /* total mbuf len */
        hlen = sizeof (*ip6);                           /* IPv6 header len */

        /* sanity check (need at least IPv6 header) */
        if (mlen < (hoff + hlen)) {
                panic("%s: mbuf %p pkt len (%u) < hoff+ip6_hdr "
                    "(%u+%u)\n", __func__, m, mlen, hoff, hlen);
                /* NOTREACHED */
        }

        /*
         * In case the IPv6 header is not contiguous, or not 32-bit
         * aligned, copy it to a local buffer.
         */
        if ((hoff + hlen) > m->m_len ||
            !IP6_HDR_ALIGNED_P(mtod(m, caddr_t) + hoff)) {
                m_copydata(m, hoff, hlen, (caddr_t)buf);
                ip6 = (struct ip6_hdr *)(void *)buf;
        } else {
                ip6 = (struct ip6_hdr *)(void *)(m->m_data + hoff);
        }

        nxt = ip6->ip6_nxt;
        plen = ntohs(ip6->ip6_plen);
        if (plen != (mlen - (hoff + hlen))) {
                plen = OSSwapInt16(plen);
                if (plen != (mlen - (hoff + hlen))) {
                        /* Don't complain for jumbograms */
                        if (plen != 0 || nxt != IPPROTO_HOPOPTS) {
                                printf("%s: mbuf 0x%llx proto %d IPv6 "
                                    "plen %d (%x) [swapped %d (%x)] doesn't "
                                    "match actual packet length; %d is used "
                                    "instead\n", __func__,
                                    (uint64_t)VM_KERNEL_ADDRPERM(m), nxt,
                                    ip6->ip6_plen, ip6->ip6_plen, plen, plen,
                                    (mlen - (hoff + hlen)));
                        }
                        plen = mlen - (hoff + hlen);
                }
        }

        if (optlen < 0) {
                /* next header isn't TCP/UDP and we don't know optlen, bail */
                if (nxt != IPPROTO_TCP && nxt != IPPROTO_UDP) {
                        sw_csum = 0;
                        goto done;
                }
                olen = 0;
        } else {
                /* caller supplied the original transport number; use it */
                if (nxt0 >= 0)
                        nxt = nxt0;
                olen = optlen;
        }

        offset = hoff + hlen + olen;                    /* ULP header */

        /* sanity check */
        if (mlen < offset) {
                panic("%s: mbuf %p pkt len (%u) < hoff+ip6_hdr+ext_hdr "
                    "(%u+%u+%u)\n", __func__, m, mlen, hoff, hlen, olen);
                /* NOTREACHED */
        }

        /*
         * offset is added to the lower 16-bit value of csum_data,
         * which is expected to contain the ULP offset; therefore
         * CSUM_PARTIAL offset adjustment must be undone.
         */
        if ((m->m_pkthdr.csum_flags & (CSUM_PARTIAL|CSUM_DATA_VALID)) ==
            (CSUM_PARTIAL|CSUM_DATA_VALID)) {
                /*
                 * Get back the original ULP offset (this will
                 * undo the CSUM_PARTIAL logic in ip6_output.)
                 */
                m->m_pkthdr.csum_data = (m->m_pkthdr.csum_tx_stuff -
                    m->m_pkthdr.csum_tx_start);
        }

        ulpoff = (m->m_pkthdr.csum_data & 0xffff);      /* ULP csum offset */

        if (mlen < (ulpoff + sizeof (csum))) {
                panic("%s: mbuf %p pkt len (%u) proto %d invalid ULP "
                    "cksum offset (%u) cksum flags 0x%x\n", __func__,
                    m, mlen, nxt, ulpoff, m->m_pkthdr.csum_flags);
                /* NOTREACHED */
        }

        csum = inet6_cksum(m, 0, offset, plen - olen);

        /* Update stats */
        ip6_out_cksum_stats(nxt, plen - olen);

        /* RFC1122 4.1.3.4 */
        if (csum == 0 && (m->m_pkthdr.csum_flags & CSUM_UDPIPV6))
                csum = 0xffff;

        /* Insert the checksum in the ULP csum field */
        offset += ulpoff;
        if ((offset + sizeof (csum)) > m->m_len) {
                m_copyback(m, offset, sizeof (csum), &csum);
        } else if (IP6_HDR_ALIGNED_P(mtod(m, char *) + hoff)) {
                *(uint16_t *)(void *)(mtod(m, char *) + offset) = csum;
        } else {
                bcopy(&csum, (mtod(m, char *) + offset), sizeof (csum));
        }
        m->m_pkthdr.csum_flags &=
            ~(CSUM_DELAY_IPV6_DATA | CSUM_DATA_VALID | CSUM_PARTIAL);

done:
        return (sw_csum);
}

/*
 * Insert jumbo payload option.
 */
static int
ip6_insert_jumboopt(struct ip6_exthdrs *exthdrs, u_int32_t plen)
{
        struct mbuf *mopt;
        u_char *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 == NULL)
                        return (ENOBUFS);
                mopt->m_len = JUMBOOPTLEN;
                optbuf = mtod(mopt, u_char *);
                optbuf[1] = 0;  /* = ((JUMBOOPTLEN) >> 3) - 1 */
                exthdrs->ip6e_hbh = mopt;
        } else {
                struct ip6_hbh *hbh;

                mopt = exthdrs->ip6e_hbh;
                if (M_TRAILINGSPACE(mopt) < JUMBOOPTLEN) {
                        /*
                         * XXX assumption:
                         * - exthdrs->ip6e_hbh is not referenced from places
                         *   other than exthdrs.
                         * - exthdrs->ip6e_hbh is not an mbuf chain.
                         */
                        u_int32_t oldoptlen = mopt->m_len;
                        struct mbuf *n;

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

                        /*
                         * As a consequence, we must always prepare a cluster
                         * at this point.
                         */
                        MGET(n, M_DONTWAIT, MT_DATA);
                        if (n != NULL) {
                                MCLGET(n, M_DONTWAIT);
                                if (!(n->m_flags & M_EXT)) {
                                        m_freem(n);
                                        n = NULL;
                                }
                        }
                        if (n == NULL)
                                return (ENOBUFS);
                        n->m_len = oldoptlen + JUMBOOPTLEN;
                        bcopy(mtod(mopt, caddr_t), mtod(n, caddr_t),
                            oldoptlen);
                        optbuf = mtod(n, u_char *) + oldoptlen;
                        m_freem(mopt);
                        mopt = exthdrs->ip6e_hbh = n;
                } else {
                        optbuf = mtod(mopt, u_char *) + mopt->m_len;
                        mopt->m_len += JUMBOOPTLEN;
                }
                optbuf[0] = IP6OPT_PADN;
                optbuf[1] = 1;

                /*
                 * 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);
        bcopy(&v, &optbuf[4], 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.
 */
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) &&
            M_TRAILINGSPACE(mlast) >= sizeof (struct ip6_frag)) {
                /* use the trailing space of the last mbuf for the frag hdr */
                *frghdrp = (struct ip6_frag *)(mtod(mlast, caddr_t) +
                    mlast->m_len);
                mlast->m_len += sizeof (struct ip6_frag);
                m->m_pkthdr.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 route_in6 *ro_pmtu, struct route_in6 *ro,
    struct ifnet *ifp, struct in6_addr *dst, u_int32_t *mtup,
    boolean_t *alwaysfragp)
{
        u_int32_t mtu = 0;
        boolean_t alwaysfrag = FALSE;
        int error = 0;

        if (ro_pmtu != ro) {
                /* The first hop and the final destination may differ. */
                struct sockaddr_in6 *sa6_dst = SIN6(&ro_pmtu->ro_dst);
                if (ROUTE_UNUSABLE(ro_pmtu) ||
                    !IN6_ARE_ADDR_EQUAL(&sa6_dst->sin6_addr, dst))
                        ROUTE_RELEASE(ro_pmtu);

                if (ro_pmtu->ro_rt == NULL) {
                        bzero(sa6_dst, sizeof (*sa6_dst));
                        sa6_dst->sin6_family = AF_INET6;
                        sa6_dst->sin6_len = sizeof (struct sockaddr_in6);
                        sa6_dst->sin6_addr = *dst;

                        rtalloc_scoped((struct route *)ro_pmtu,
                            ifp != NULL ? ifp->if_index : IFSCOPE_NONE);
                }
        }

        if (ro_pmtu->ro_rt != NULL) {
                u_int32_t ifmtu;

                lck_rw_lock_shared(nd_if_rwlock);
                /* Access without acquiring nd_ifinfo lock for performance */
                ifmtu = IN6_LINKMTU(ifp);
                lck_rw_done(nd_if_rwlock);

                /*
                 * Access rmx_mtu without holding the route entry lock,
                 * for performance; this isn't something that changes
                 * often, so optimize.
                 */
                mtu = ro_pmtu->ro_rt->rt_rmx.rmx_mtu;
                if (mtu > ifmtu || mtu == 0) {
                        /*
                         * 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).
                         *
                         * if MTU on the route is 0, we need to fix the MTU.
                         * this case happens with path MTU discovery timeouts.
                         */
                        mtu = ifmtu;
                        if (!(ro_pmtu->ro_rt->rt_rmx.rmx_locks & RTV_MTU))
                                ro_pmtu->ro_rt->rt_rmx.rmx_mtu = mtu; /* XXX */
                } 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 framgent header attached.
                         * (fragment header is needed regardless from the
                         * packet size, for translators to identify packets)
                         */
                        alwaysfrag = TRUE;
                        mtu = IPV6_MMTU;
                }
        } else {
                if (ifp) {
                        lck_rw_lock_shared(nd_if_rwlock);
                        /* Don't hold nd_ifinfo lock for performance */
                        mtu = IN6_LINKMTU(ifp);
                        lck_rw_done(nd_if_rwlock);
                } else {
                        error = EHOSTUNREACH; /* XXX */
                }
        }

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

/*
 * IP6 socket option processing.
 */
int
ip6_ctloutput(struct socket *so, struct sockopt *sopt)
{
        int optdatalen, uproto;
        void *optdata;
        int privileged;
        struct inpcb *in6p = sotoinpcb(so);
        int error = 0, optval = 0;
        int level, op = -1, optname = 0;
        int optlen = 0;
        struct proc *p;

        VERIFY(sopt != NULL);

        level = sopt->sopt_level;
        op = sopt->sopt_dir;
        optname = sopt->sopt_name;
        optlen = sopt->sopt_valsize;
        p = sopt->sopt_p;
        uproto = (int)SOCK_PROTO(so);

        privileged = (proc_suser(p) == 0);

        if (level == IPPROTO_IPV6) {
                switch (op) {
                case SOPT_SET:
                        switch (optname) {
                        case IPV6_2292PKTOPTIONS: {
                                struct mbuf *m;

                                error = soopt_getm(sopt, &m);
                                if (error != 0)
                                        break;
                                error = soopt_mcopyin(sopt, m);
                                if (error != 0)
                                        break;
                                error = ip6_pcbopts(&in6p->in6p_outputopts,
                                    m, so, sopt);
                                m_freem(m);
                                break;
                        }

                        /*
                         * 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:
                                if (!privileged)
                                        break;
                                /* FALLTHROUGH */
                        case IPV6_UNICAST_HOPS:
                        case IPV6_HOPLIMIT:
                        case IPV6_RECVPKTINFO:
                        case IPV6_RECVHOPLIMIT:
                        case IPV6_RECVRTHDR:
                        case IPV6_RECVPATHMTU:
                        case IPV6_RECVTCLASS:
                        case IPV6_V6ONLY:
                        case IPV6_AUTOFLOWLABEL:
                                if (optlen != sizeof (int)) {
                                        error = EINVAL;
                                        break;
                                }
                                error = sooptcopyin(sopt, &optval,
                                    sizeof (optval), sizeof (optval));
                                if (error)
                                        break;

                                switch (optname) {
                                case IPV6_UNICAST_HOPS:
                                        if (optval < -1 || optval >= 256) {
                                                error = EINVAL;
                                        } else {
                                                /* -1 = kernel default */
                                                in6p->in6p_hops = optval;
                                                if (in6p->inp_vflag &
                                                    INP_IPV4) {
                                                        in6p->inp_ip_ttl =
                                                            optval;
                                                }
                                        }
                                        break;
#define OPTSET(bit) do {                                                \
        if (optval)                                                     \
                in6p->inp_flags |= (bit);                               \
        else                                                            \
                in6p->inp_flags &= ~(bit);                              \
} while (0)

#define OPTSET2292(bit) do {                                            \
        in6p->inp_flags |= IN6P_RFC2292;                                \
        if (optval)                                                     \
                in6p->inp_flags |= (bit);                               \
        else                                                            \
                in6p->inp_flags &= ~(bit);                              \
} while (0)

#define OPTBIT(bit) (in6p->inp_flags & (bit) ? 1 : 0)

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

                                case IPV6_HOPLIMIT: {
                                        struct ip6_pktopts **optp;

                                        /* cannot mix with RFC2292 */
                                        if (OPTBIT(IN6P_RFC2292)) {
                                                error = EINVAL;
                                                break;
                                        }
                                        optp = &in6p->in6p_outputopts;
                                        error = ip6_pcbopt(IPV6_HOPLIMIT,
                                            (u_char *)&optval, sizeof (optval),
                                            optp, uproto);
                                        break;
                                }

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

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

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

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

                                case IPV6_RECVRTHDR:
                                        /* cannot mix with RFC2292 */
                                        if (OPTBIT(IN6P_RFC2292)) {
                                                error = EINVAL;
                                                break;
                                        }
                                        OPTSET(IN6P_RTHDR);
                                        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 (in6p->inp_lport ||
                                            !IN6_IS_ADDR_UNSPECIFIED(
                                            &in6p->in6p_laddr)) {
                                                error = EINVAL;
                                                break;
                                        }
                                        OPTSET(IN6P_IPV6_V6ONLY);
                                        if (optval)
                                                in6p->inp_vflag &= ~INP_IPV4;
                                        else
                                                in6p->inp_vflag |= INP_IPV4;
                                        break;

                                case IPV6_RECVTCLASS:
                                        /* we can mix with RFC2292 */
                                        OPTSET(IN6P_TCLASS);
                                        break;

                                case IPV6_AUTOFLOWLABEL:
                                        OPTSET(IN6P_AUTOFLOWLABEL);
                                        break;

                                }
                                break;

                        case IPV6_TCLASS:
                        case IPV6_DONTFRAG:
                        case IPV6_USE_MIN_MTU:
                        case IPV6_PREFER_TEMPADDR: {
                                struct ip6_pktopts **optp;

                                if (optlen != sizeof (optval)) {
                                        error = EINVAL;
                                        break;
                                }
                                error = sooptcopyin(sopt, &optval,
                                    sizeof (optval), sizeof (optval));
                                if (error)
                                        break;

                                optp = &in6p->in6p_outputopts;
                                error = ip6_pcbopt(optname, (u_char *)&optval,
                                    sizeof (optval), optp, uproto);
                                break;
                        }

                        case IPV6_2292PKTINFO:
                        case IPV6_2292HOPLIMIT:
                        case IPV6_2292HOPOPTS:
                        case IPV6_2292DSTOPTS:
                        case IPV6_2292RTHDR:
                                /* RFC 2292 */
                                if (optlen != sizeof (int)) {
                                        error = EINVAL;
                                        break;
                                }
                                error = sooptcopyin(sopt, &optval,
                                    sizeof (optval), sizeof (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.
                                         */
                                        if (!privileged)
                                                return (EPERM);
                                        OPTSET2292(IN6P_HOPOPTS);
                                        break;
                                case IPV6_2292DSTOPTS:
                                        if (!privileged)
                                                return (EPERM);
                                        OPTSET2292(IN6P_DSTOPTS|
                                            IN6P_RTHDRDSTOPTS); /* XXX */
                                        break;
                                case IPV6_2292RTHDR:
                                        OPTSET2292(IN6P_RTHDR);
                                        break;
                                }
                                break;

                        case IPV6_3542PKTINFO:
                        case IPV6_3542HOPOPTS:
                        case IPV6_3542RTHDR:
                        case IPV6_3542DSTOPTS:
                        case IPV6_RTHDRDSTOPTS:
                        case IPV6_3542NEXTHOP: {
                                struct ip6_pktopts **optp;
                                /* new advanced API (RFC3542) */
                                struct mbuf *m;

                                /* cannot mix with RFC2292 */
                                if (OPTBIT(IN6P_RFC2292)) {
                                        error = EINVAL;
                                        break;
                                }
                                error = soopt_getm(sopt, &m);
                                if (error != 0)
                                        break;
                                error = soopt_mcopyin(sopt, m);
                                if (error != 0)
                                        break;

                                optp = &in6p->in6p_outputopts;
                                error = ip6_pcbopt(optname, mtod(m, u_char *),
                                    m->m_len, optp, uproto);
                                m_freem(m);
                                break;
                        }
#undef OPTSET
                        case IPV6_MULTICAST_IF:
                        case IPV6_MULTICAST_HOPS:
                        case IPV6_MULTICAST_LOOP:
                        case IPV6_JOIN_GROUP:
                        case IPV6_LEAVE_GROUP:
                        case IPV6_MSFILTER:
                        case MCAST_BLOCK_SOURCE:
                        case MCAST_UNBLOCK_SOURCE:
                        case MCAST_JOIN_GROUP:
                        case MCAST_LEAVE_GROUP:
                        case MCAST_JOIN_SOURCE_GROUP:
                        case MCAST_LEAVE_SOURCE_GROUP:
                                error = ip6_setmoptions(in6p, sopt);
                                break;

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

                                switch (optval) {
                                case IPV6_PORTRANGE_DEFAULT:
                                        in6p->inp_flags &= ~(INP_LOWPORT);
                                        in6p->inp_flags &= ~(INP_HIGHPORT);
                                        break;

                                case IPV6_PORTRANGE_HIGH:
                                        in6p->inp_flags &= ~(INP_LOWPORT);
                                        in6p->inp_flags |= INP_HIGHPORT;
                                        break;

                                case IPV6_PORTRANGE_LOW:
                                        in6p->inp_flags &= ~(INP_HIGHPORT);
                                        in6p->inp_flags |= INP_LOWPORT;
                                        break;

                                default:
                                        error = EINVAL;
                                        break;
                                }
                                break;
#if IPSEC
                        case IPV6_IPSEC_POLICY: {
                                caddr_t req = NULL;
                                size_t len = 0;
                                struct mbuf *m;

                                if ((error = soopt_getm(sopt, &m)) != 0)
                                        break;
                                if ((error = soopt_mcopyin(sopt, m)) != 0)
                                        break;

                                req = mtod(m, caddr_t);
                                len = m->m_len;
                                error = ipsec6_set_policy(in6p, optname, req,
                                    len, privileged);
                                m_freem(m);
                                break;
                        }
#endif /* IPSEC */
#if IPFIREWALL
                        case IPV6_FW_ADD:
                        case IPV6_FW_DEL:
                        case IPV6_FW_FLUSH:
                        case IPV6_FW_ZERO: {
                                if (ip6_fw_ctl_ptr == NULL)
                                        load_ip6fw();
                                if (ip6_fw_ctl_ptr != NULL)
                                        error = (*ip6_fw_ctl_ptr)(sopt);
                                else
                                        error = ENOPROTOOPT;
                                break;
                        }
#endif /* IPFIREWALL */
                        /*
                         * IPv6 variant of IP_BOUND_IF; for details see
                         * comments on IP_BOUND_IF in ip_ctloutput().
                         */
                        case IPV6_BOUND_IF:
                                /* This option is settable only on IPv6 */
                                if (!(in6p->inp_vflag & INP_IPV6)) {
                                        error = EINVAL;
                                        break;
                                }

                                error = sooptcopyin(sopt, &optval,
                                    sizeof (optval), sizeof (optval));

                                if (error)
                                        break;

                                error = inp_bindif(in6p, optval, NULL);
                                break;

                        case IPV6_NO_IFT_CELLULAR:
                                /* This option is settable only for IPv6 */
                                if (!(in6p->inp_vflag & INP_IPV6)) {
                                        error = EINVAL;
                                        break;
                                }

                                error = sooptcopyin(sopt, &optval,
                                    sizeof (optval), sizeof (optval));

                                if (error)
                                        break;

                                /* once set, it cannot be unset */
                                if (!optval &&
                                    (in6p->inp_flags & INP_NO_IFT_CELLULAR)) {
                                        error = EINVAL;
                                        break;
                                }

                                error = so_set_restrictions(so,
                                    SO_RESTRICT_DENY_CELLULAR);
                                break;

                        case IPV6_OUT_IF:
                                /* This option is not settable */
                                error = EINVAL;
                                break;

                        default:
                                error = ENOPROTOOPT;
                                break;
                        }
                        break;

                case SOPT_GET:
                        switch (optname) {

                        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.
                                 */
                                sopt->sopt_valsize = 0;
                                break;

                        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_V6ONLY:
                        case IPV6_PORTRANGE:
                        case IPV6_RECVTCLASS:
                        case IPV6_AUTOFLOWLABEL:
                                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->in6p_hops;
                                        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_V6ONLY:
                                        optval = OPTBIT(IN6P_IPV6_V6ONLY);
                                        break;

                                case IPV6_PORTRANGE: {
                                        int flags;
                                        flags = in6p->inp_flags;
                                        if (flags & INP_HIGHPORT)
                                                optval = IPV6_PORTRANGE_HIGH;
                                        else if (flags & INP_LOWPORT)
                                                optval = IPV6_PORTRANGE_LOW;
                                        else
                                                optval = 0;
                                        break;
                                }
                                case IPV6_RECVTCLASS:
                                        optval = OPTBIT(IN6P_TCLASS);
                                        break;

                                case IPV6_AUTOFLOWLABEL:
                                        optval = OPTBIT(IN6P_AUTOFLOWLABEL);
                                        break;
                                }
                                if (error)
                                        break;
                                error = sooptcopyout(sopt, &optval,
                                    sizeof (optval));
                                break;

                        case IPV6_PATHMTU: {
                                u_int32_t pmtu = 0;
                                struct ip6_mtuinfo mtuinfo;
                                struct route_in6 sro;

                                bzero(&sro, sizeof (sro));

                                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.
                                 */
                                error = ip6_getpmtu(&sro, NULL, NULL,
                                    &in6p->in6p_faddr, &pmtu, NULL);
                                ROUTE_RELEASE(&sro);
                                if (error)
                                        break;
                                if (pmtu > IPV6_MAXPACKET)
                                        pmtu = IPV6_MAXPACKET;

                                bzero(&mtuinfo, sizeof (mtuinfo));
                                mtuinfo.ip6m_mtu = (u_int32_t)pmtu;
                                optdata = (void *)&mtuinfo;
                                optdatalen = sizeof (mtuinfo);
                                error = sooptcopyout(sopt, optdata,
                                    optdatalen);
                                break;
                        }

                        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 = sooptcopyout(sopt, &optval,
                                    sizeof (optval));
                                break;

                        case IPV6_PKTINFO:
                        case IPV6_HOPOPTS:
                        case IPV6_RTHDR:
                        case IPV6_DSTOPTS:
                        case IPV6_RTHDRDSTOPTS:
                        case IPV6_NEXTHOP:
                        case IPV6_TCLASS:
                        case IPV6_DONTFRAG:
                        case IPV6_USE_MIN_MTU:
                        case IPV6_PREFER_TEMPADDR:
                                error = ip6_getpcbopt(in6p->in6p_outputopts,
                                    optname, sopt);
                                break;

                        case IPV6_MULTICAST_IF:
                        case IPV6_MULTICAST_HOPS:
                        case IPV6_MULTICAST_LOOP:
                        case IPV6_MSFILTER:
                                error = ip6_getmoptions(in6p, sopt);
                                break;
#if IPSEC
                        case IPV6_IPSEC_POLICY: {
                                caddr_t req = NULL;
                                size_t len = 0;
                                struct mbuf *m = NULL;
                                struct mbuf *mp = NULL;

                                error = soopt_getm(sopt, &m);
                                if (error != 0)
                                        break;
                                error = soopt_mcopyin(sopt, m);
                                if (error != 0)
                                        break;

                                req = mtod(m, caddr_t);
                                len = m->m_len;
                                error = ipsec6_get_policy(in6p, req, len, &mp);
                                if (error == 0)
                                        error = soopt_mcopyout(sopt, mp);
                                if (mp != NULL)
                                        m_freem(mp);
                                m_freem(m);
                                break;
                        }
#endif /* IPSEC */
#if IPFIREWALL
                        case IPV6_FW_GET: {
                                if (ip6_fw_ctl_ptr == NULL)
                                        load_ip6fw();
                                if (ip6_fw_ctl_ptr != NULL)
                                        error = (*ip6_fw_ctl_ptr)(sopt);
                                else
                                        error = ENOPROTOOPT;
                                break;
                        }
#endif /* IPFIREWALL */
                        case IPV6_BOUND_IF:
                                if (in6p->inp_flags & INP_BOUND_IF)
                                        optval = in6p->inp_boundifp->if_index;
                                error = sooptcopyout(sopt, &optval,
                                    sizeof (optval));
                                break;

                        case IPV6_NO_IFT_CELLULAR:
                                optval = (in6p->inp_flags & INP_NO_IFT_CELLULAR)
                                    ? 1 : 0;
                                error = sooptcopyout(sopt, &optval,
                                    sizeof (optval));
                                break;

                        case IPV6_OUT_IF:
                                optval = (in6p->in6p_last_outifp != NULL) ?
                                    in6p->in6p_last_outifp->if_index : 0;
                                error = sooptcopyout(sopt, &optval,
                                    sizeof (optval));
                                break;

                        default:
                                error = ENOPROTOOPT;
                                break;
                        }
                        break;
                }
        } else {
                error = EINVAL;
        }
        return (error);
}

int
ip6_raw_ctloutput(struct socket *so, struct sockopt *sopt)
{
        int error = 0, optval, optlen;
        const int icmp6off = offsetof(struct icmp6_hdr, icmp6_cksum);
        struct inpcb *in6p = sotoinpcb(so);
        int level, op, optname;

        level = sopt->sopt_level;
        op = sopt->sopt_dir;
        optname = sopt->sopt_name;
        optlen = sopt->sopt_valsize;

        if (level != IPPROTO_IPV6)
                return (EINVAL);

        switch (optname) {
        case IPV6_CHECKSUM:
                /*
                 * For ICMPv6 sockets, no modification allowed for checksum
                 * offset, permit "no change" values to help existing apps.
                 *
                 * RFC3542 says: "An attempt to set IPV6_CHECKSUM
                 * for an ICMPv6 socket will fail."
                 * The current behavior does not meet RFC3542.
                 */
                switch (op) {
                case SOPT_SET:
                        if (optlen != sizeof (int)) {
                                error = EINVAL;
                                break;
                        }
                        error = sooptcopyin(sopt, &optval, sizeof (optval),
                            sizeof (optval));
                        if (error)
                                break;
                        if ((optval % 2) != 0) {
                                /* the API assumes even offset values */
                                error = EINVAL;
                        } else if (SOCK_PROTO(so) == IPPROTO_ICMPV6) {
                                if (optval != icmp6off)
                                        error = EINVAL;
                        } else {
                                in6p->in6p_cksum = optval;
                        }
                        break;

                case SOPT_GET:
                        if (SOCK_PROTO(so) == IPPROTO_ICMPV6)
                                optval = icmp6off;
                        else
                                optval = in6p->in6p_cksum;

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

                default:
                        error = EINVAL;
                        break;
                }
                break;

        default:
                error = ENOPROTOOPT;
                break;
        }

        return (error);
}

/*
 * 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 mbuf *m, struct socket *so,
    struct sockopt *sopt)
{
#pragma unused(sopt)
        struct ip6_pktopts *opt = *pktopt;
        int error = 0;

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

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

        /*  set options specified by user. */
        if ((error = ip6_setpktopts(m, opt, NULL, SOCK_PROTO(so))) != 0) {
                ip6_clearpktopts(opt, -1); /* XXX: discard all options */
                FREE(opt, M_IP6OPT);
                return (error);
        }
        *pktopt = opt;
        return (0);
}

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

        bzero(opt, 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;
}

static int
ip6_pcbopt(int optname, u_char *buf, int len, struct ip6_pktopts **pktopt,
    int uproto)
{
        struct ip6_pktopts *opt;

        opt = *pktopt;
        if (opt == NULL) {
                opt = _MALLOC(sizeof (*opt), M_IP6OPT, M_WAITOK);
                if (opt == NULL)
                        return (ENOBUFS);
                ip6_initpktopts(opt);
                *pktopt = opt;
        }

        return (ip6_setpktopt(optname, buf, len, opt, 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;
        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... */
                        bzero(&null_pktinfo, sizeof (null_pktinfo));
                        optdata = (void *)&null_pktinfo;
                }
                optdatalen = sizeof (struct in6_pktinfo);
                break;

        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);
        }

        return (sooptcopyout(sopt, optdata, optdatalen));
}

void
ip6_clearpktopts(struct ip6_pktopts *pktopt, int optname)
{
        if (pktopt == NULL)
                return;

        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) {
                ROUTE_RELEASE(&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;
                ROUTE_RELEASE(&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 && canwait == M_NOWAIT)           \
                        goto bad;                                       \
                bcopy(src->type, dst->type, hlen);                      \
        }                                                               \
} while (0)

static int
copypktopts(struct ip6_pktopts *dst, struct ip6_pktopts *src, int canwait)
{
        if (dst == NULL || src == NULL)  {
                printf("copypktopts: invalid argument\n");
                return (EINVAL);
        }

        dst->ip6po_hlim = src->ip6po_hlim;
        dst->ip6po_tclass = src->ip6po_tclass;
        dst->ip6po_flags = src->ip6po_flags;
        if (src->ip6po_pktinfo) {
                dst->ip6po_pktinfo = _MALLOC(sizeof (*dst->ip6po_pktinfo),
                    M_IP6OPT, canwait);
                if (dst->ip6po_pktinfo == NULL && canwait == M_NOWAIT)
                        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 && canwait == M_NOWAIT)
                        goto bad;
                bcopy(src->ip6po_nexthop, dst->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:
        ip6_clearpktopts(dst, -1);
        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);
}

void
ip6_moptions_init(void)
{
        PE_parse_boot_argn("ifa_debug", &im6o_debug, sizeof (im6o_debug));

        im6o_size = (im6o_debug == 0) ? sizeof (struct ip6_moptions) :
            sizeof (struct ip6_moptions_dbg);

        im6o_zone = zinit(im6o_size, IM6O_ZONE_MAX * im6o_size, 0,
            IM6O_ZONE_NAME);
        if (im6o_zone == NULL) {
                panic("%s: failed allocating %s", __func__, IM6O_ZONE_NAME);
                /* NOTREACHED */
        }
        zone_change(im6o_zone, Z_EXPAND, TRUE);
}

void
im6o_addref(struct ip6_moptions *im6o, int locked)
{
        if (!locked)
                IM6O_LOCK(im6o);
        else
                IM6O_LOCK_ASSERT_HELD(im6o);

        if (++im6o->im6o_refcnt == 0) {
                panic("%s: im6o %p wraparound refcnt\n", __func__, im6o);
                /* NOTREACHED */
        } else if (im6o->im6o_trace != NULL) {
                (*im6o->im6o_trace)(im6o, TRUE);
        }

        if (!locked)
                IM6O_UNLOCK(im6o);
}

void
im6o_remref(struct ip6_moptions *im6o)
{
        int i;

        IM6O_LOCK(im6o);
        if (im6o->im6o_refcnt == 0) {
                panic("%s: im6o %p negative refcnt", __func__, im6o);
                /* NOTREACHED */
        } else if (im6o->im6o_trace != NULL) {
                (*im6o->im6o_trace)(im6o, FALSE);
        }

        --im6o->im6o_refcnt;
        if (im6o->im6o_refcnt > 0) {
                IM6O_UNLOCK(im6o);
                return;
        }

        for (i = 0; i < im6o->im6o_num_memberships; ++i) {
                struct in6_mfilter *imf;

                imf = im6o->im6o_mfilters ? &im6o->im6o_mfilters[i] : NULL;
                if (imf != NULL)
                        im6f_leave(imf);

                (void) in6_mc_leave(im6o->im6o_membership[i], imf);

                if (imf != NULL)
                        im6f_purge(imf);

                IN6M_REMREF(im6o->im6o_membership[i]);
                im6o->im6o_membership[i] = NULL;
        }
        im6o->im6o_num_memberships = 0;
        if (im6o->im6o_mfilters != NULL) {
                FREE(im6o->im6o_mfilters, M_IN6MFILTER);
                im6o->im6o_mfilters = NULL;
        }
        if (im6o->im6o_membership != NULL) {
                FREE(im6o->im6o_membership, M_IP6MOPTS);
                im6o->im6o_membership = NULL;
        }
        IM6O_UNLOCK(im6o);

        lck_mtx_destroy(&im6o->im6o_lock, ifa_mtx_grp);

        if (!(im6o->im6o_debug & IFD_ALLOC)) {
                panic("%s: im6o %p cannot be freed", __func__, im6o);
                /* NOTREACHED */
        }
        zfree(im6o_zone, im6o);
}

static void
im6o_trace(struct ip6_moptions *im6o, int refhold)
{
        struct ip6_moptions_dbg *im6o_dbg = (struct ip6_moptions_dbg *)im6o;
        ctrace_t *tr;
        u_int32_t idx;
        u_int16_t *cnt;

        if (!(im6o->im6o_debug & IFD_DEBUG)) {
                panic("%s: im6o %p has no debug structure", __func__, im6o);
                /* NOTREACHED */
        }
        if (refhold) {
                cnt = &im6o_dbg->im6o_refhold_cnt;
                tr = im6o_dbg->im6o_refhold;
        } else {
                cnt = &im6o_dbg->im6o_refrele_cnt;
                tr = im6o_dbg->im6o_refrele;
        }

        idx = atomic_add_16_ov(cnt, 1) % IM6O_TRACE_HIST_SIZE;
        ctrace_record(&tr[idx]);
}

struct ip6_moptions *
ip6_allocmoptions(int how)
{
        struct ip6_moptions *im6o;

        im6o = (how == M_WAITOK) ?
            zalloc(im6o_zone) : zalloc_noblock(im6o_zone);
        if (im6o != NULL) {
                bzero(im6o, im6o_size);
                lck_mtx_init(&im6o->im6o_lock, ifa_mtx_grp, ifa_mtx_attr);
                im6o->im6o_debug |= IFD_ALLOC;
                if (im6o_debug != 0) {
                        im6o->im6o_debug |= IFD_DEBUG;
                        im6o->im6o_trace = im6o_trace;
                }
                IM6O_ADDREF(im6o);
        }

        return (im6o);
}

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

        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);

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

        for (cm = M_FIRST_CMSGHDR(control); cm != NULL;
            cm = M_NXT_CMSGHDR(control, cm)) {
                int error;

                if (cm->cmsg_len < sizeof (struct cmsghdr) ||
                    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, 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,
    int sticky, int cmsg, int uproto)
{
        int minmtupolicy, preftemp;
        int error;

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

        /*
         * Caller must have ensured that the buffer is at least
         * aligned on 32-bit boundary.
         */
        VERIFY(IS_P2ALIGNED(buf, sizeof (u_int32_t)));

        /*
         * 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_TCLASS:
                case IPV6_PREFER_TEMPADDR: /* XXX: not an RFC3542 option */
                        return (ENOPROTOOPT);
                }
        }

        switch (optname) {
        case IPV6_2292PKTINFO:
        case IPV6_PKTINFO: {
                struct ifnet *ifp = NULL;
                struct in6_pktinfo *pktinfo;

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

                pktinfo = (struct in6_pktinfo *)(void *)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. */
                ifnet_head_lock_shared();

                if (pktinfo->ipi6_ifindex > if_index) {
                        ifnet_head_done();
                        return (ENXIO);
                }

                if (pktinfo->ipi6_ifindex) {
                        ifp = ifindex2ifnet[pktinfo->ipi6_ifindex];
                        if (ifp == NULL) {
                                ifnet_head_done();
                                return (ENXIO);
                        }
                }

                ifnet_head_done();

                /*
                 * 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);
                }
                bcopy(pktinfo, opt->ip6po_pktinfo, sizeof (*pktinfo));
                break;
        }

        case IPV6_2292HOPLIMIT:
        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 *)(void *)buf;
                if (*hlimp < -1 || *hlimp > 255)
                        return (EINVAL);

                opt->ip6po_hlim = *hlimp;
                break;
        }

        case IPV6_TCLASS: {
                int tclass;

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

                opt->ip6po_tclass = tclass;
                break;
        }

        case IPV6_2292NEXTHOP:
        case IPV6_NEXTHOP:
                error = suser(kauth_cred_get(), 0);
                if (error)
                        return (EACCES);

                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 (SA(buf)->sa_family) {
                case AF_INET6: {
                        struct sockaddr_in6 *sa6 = SIN6(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:   /* should 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);
                bcopy(buf, opt->ip6po_nexthop, *buf);
                break;

        case IPV6_2292HOPOPTS:
        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 = suser(kauth_cred_get(), 0);
                if (error)
                        return (EACCES);

                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 *)(void *)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);
                bcopy(hbh, opt->ip6po_hbh, hbhlen);

                break;
        }

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

                error = suser(kauth_cred_get(), 0);
                if (error)
                        return (EACCES);

                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 *)(void *)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 advacned 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);
                bcopy(dest, *newdest, destlen);
                break;
        }

        case IPV6_2292RTHDR:
        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 *)(void *)buf;
                rthlen = (rth->ip6r_len + 1) << 3;
                if (len != rthlen)
                        return (EINVAL);

                switch (rth->ip6r_type) {
                case IPV6_RTHDR_TYPE_0:
                        if (rth->ip6r_len == 0) /* must contain one addr */
                                return (EINVAL);
                        if (rth->ip6r_len % 2) /* length must be even */
                                return (EINVAL);
                        if (rth->ip6r_len / 2 != rth->ip6r_segleft)
                                return (EINVAL);
                        break;
                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);
                bcopy(rth, opt->ip6po_rthdr, rthlen);
                break;
        }

        case IPV6_USE_MIN_MTU:
                if (len != sizeof (int))
                        return (EINVAL);
                minmtupolicy = *(int *)(void *)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 *)(void *)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:
                if (len != sizeof (int))
                        return (EINVAL);
                preftemp = *(int *)(void *)buf;
                if (preftemp != IP6PO_TEMPADDR_SYSTEM &&
                    preftemp != IP6PO_TEMPADDR_NOTPREFER &&
                    preftemp != IP6PO_TEMPADDR_PREFER) {
                        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 &loif -- easier than replicating that code here.
 */
void
ip6_mloopback(struct ifnet *srcifp, struct ifnet *origifp, struct mbuf *m,
    struct sockaddr_in6 *dst, uint32_t optlen, int32_t nxt0)
{
        struct mbuf *copym;
        struct ip6_hdr *ip6;
        struct in6_addr src;

        if (lo_ifp == NULL)
                return;

        /*
         * Copy the packet header as it's needed for the checksum.
         * 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.
         */
        copym = m_copym_mode(m, 0, M_COPYALL, M_DONTWAIT, M_COPYM_COPY_HDR);
        if (copym != NULL && ((copym->m_flags & M_EXT) ||
            copym->m_len < sizeof (struct ip6_hdr)))
                copym = m_pullup(copym, sizeof (struct ip6_hdr));

        if (copym == NULL)
                return;

        ip6 = mtod(copym, struct ip6_hdr *);
        src = ip6->ip6_src;
        /*
         * 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 (copym->m_pkthdr.csum_flags & CSUM_DELAY_IPV6_DATA)
                in6_delayed_cksum_offset(copym, 0, optlen, nxt0);

        /*
         * Stuff the 'real' ifp into the pkthdr, to be used in matching
         * in ip6_input(); we need the loopback ifp/dl_tag passed as args
         * to make the loopback driver compliant with the data link
         * requirements.
         */
        copym->m_pkthdr.rcvif = origifp;

        /*
         * Also record the source interface (which owns the source address).
         * This is basically a stripped down version of ifa_foraddr6().
         */
        if (srcifp == NULL) {
                struct in6_ifaddr *ia;

                lck_rw_lock_shared(&in6_ifaddr_rwlock);
                for (ia = in6_ifaddrs; ia != NULL; ia = ia->ia_next) {
                        IFA_LOCK_SPIN(&ia->ia_ifa);
                        /* compare against src addr with embedded scope */
                        if (IN6_ARE_ADDR_EQUAL(&ia->ia_addr.sin6_addr, &src)) {
                                srcifp = ia->ia_ifp;
                                IFA_UNLOCK(&ia->ia_ifa);
                                break;
                        }
                        IFA_UNLOCK(&ia->ia_ifa);
                }
                lck_rw_done(&in6_ifaddr_rwlock);
        }
        if (srcifp != NULL)
                ip6_setsrcifaddr_info(copym, srcifp->if_index, NULL);
        ip6_setdstifaddr_info(copym, origifp->if_index, NULL);

        dlil_output(lo_ifp, PF_INET6, copym, NULL, SA(dst), 0, 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);     /* MAC-OK */
                if (mh == NULL) {
                        m_freem(m);
                        return (ENOBUFS);
                }
                M_COPY_PKTHDR(mh, m);
                MH_ALIGN(mh, sizeof (*ip6));
                m->m_flags &= ~M_PKTHDR;
                m->m_len -= sizeof (*ip6);
                m->m_data += sizeof (*ip6);
                mh->m_next = m;
                m = mh;
                m->m_len = sizeof (*ip6);
                bcopy((caddr_t)ip6, mtod(m, caddr_t), sizeof (*ip6));
        }
        exthdrs->ip6e_ip6 = m;
        return (0);
}

static void
ip6_output_checksum(struct ifnet *ifp, uint32_t mtu, struct mbuf *m,
    int nxt0, uint32_t tlen, uint32_t optlen)
{
        uint32_t sw_csum, hwcap = ifp->if_hwassist;
        int tso = TSO_IPV6_OK(ifp, m);

        if (!hwcksum_tx) {
                /* do all in software; checksum offload is disabled */
                sw_csum = CSUM_DELAY_IPV6_DATA & m->m_pkthdr.csum_flags;
        } else {
                /* do in software what the hardware cannot */
                sw_csum = m->m_pkthdr.csum_flags &
                    ~IF_HWASSIST_CSUM_FLAGS(hwcap);
        }

        if (optlen != 0) {
                sw_csum |= (CSUM_DELAY_IPV6_DATA &
                    m->m_pkthdr.csum_flags);
        } else if (!(sw_csum & CSUM_DELAY_IPV6_DATA) &&
            (hwcap & CSUM_PARTIAL)) {
                /*
                 * Partial checksum offload, ere), if no extension
                 * headers, and TCP only (no UDP support, as the
                 * hardware may not be able to convert +0 to
                 * -0 (0xffff) per RFC1122 4.1.3.4.)
                 */
                if (hwcksum_tx && !tso &&
                    (m->m_pkthdr.csum_flags & CSUM_TCPIPV6) &&
                    tlen <= mtu) {
                        uint16_t start = sizeof (struct ip6_hdr);
                        uint16_t ulpoff =
                            m->m_pkthdr.csum_data & 0xffff;
                        m->m_pkthdr.csum_flags |=
                            (CSUM_DATA_VALID | CSUM_PARTIAL);
                        m->m_pkthdr.csum_tx_stuff = (ulpoff + start);
                        m->m_pkthdr.csum_tx_start = start;
                        sw_csum = 0;
                } else {
                        sw_csum |= (CSUM_DELAY_IPV6_DATA &
                            m->m_pkthdr.csum_flags);
                }
        }

        if (sw_csum & CSUM_DELAY_IPV6_DATA) {
                in6_delayed_cksum_offset(m, 0, optlen, nxt0);
                sw_csum &= ~CSUM_DELAY_IPV6_DATA;
        }

        if (hwcksum_tx) {
                /*
                 * Drop off bits that aren't supported by hardware;
                 * also make sure to preserve non-checksum related bits.
                 */
                m->m_pkthdr.csum_flags =
                    ((m->m_pkthdr.csum_flags &
                    (IF_HWASSIST_CSUM_FLAGS(hwcap) | CSUM_DATA_VALID)) |
                    (m->m_pkthdr.csum_flags & ~IF_HWASSIST_CSUM_MASK));
        } else {
                /* drop all bits; checksum offload is disabled */
                m->m_pkthdr.csum_flags = 0;
        }
}

/*
 * Compute IPv6 extension header length.
 */
int
ip6_optlen(struct in6pcb *in6p)
{
        int len;

        if (!in6p->in6p_outputopts)
                return (0);

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

        len += elen(in6p->in6p_outputopts->ip6po_hbh);
        if (in6p->in6p_outputopts->ip6po_rthdr) {
                /* dest1 is valid with rthdr only */
                len += elen(in6p->in6p_outputopts->ip6po_dest1);
        }
        len += elen(in6p->in6p_outputopts->ip6po_rthdr);
        len += elen(in6p->in6p_outputopts->ip6po_dest2);
        return (len);
#undef elen
}