xnu-2782.1.97.tar.gz

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

/*
 * Copyright (c) 2000-2014 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 NECP
#include <net/necp.h>
#endif /* NECP */

#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 */
#if NECP
	necp_kernel_policy_result necp_result = 0;
	necp_kernel_policy_result_parameter necp_result_parameter;
	necp_kernel_policy_id necp_matched_policy_id = 0;
#endif /* NECP */
	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 NECP
		struct route_in6 necp_route;
#endif /* NECP */
#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	necp_route	ip6obz.necp_route
#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
	if (ipsec_bypass == 0) {
		so = ipsec_getsocket(m);
		if (so != NULL) {
			(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) {
		if (ip6oa->ip6oa_flags & IP6OAF_NO_CELLULAR)
			ipf_pktopts.ippo_flags |= IPPOF_NO_IFT_CELLULAR;
		if (ip6oa->ip6oa_flags & IP6OAF_NO_EXPENSIVE)
			ipf_pktopts.ippo_flags |= IPPOF_NO_IFF_EXPENSIVE;
		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 NECP
	necp_matched_policy_id = necp_ip6_output_find_policy_match (m, flags, (flags & IPV6_OUTARGS) ? ip6oa : NULL,
										   &necp_result, &necp_result_parameter);
	if (necp_matched_policy_id) {
		necp_mark_packet_from_ip(m, necp_matched_policy_id);
		switch (necp_result) {
			case NECP_KERNEL_POLICY_RESULT_PASS:
				goto skip_ipsec;
			case NECP_KERNEL_POLICY_RESULT_DROP:
			case NECP_KERNEL_POLICY_RESULT_SOCKET_DIVERT:
				/* Flow divert packets should be blocked at the IP layer */
				error = EHOSTUNREACH;
				goto bad;
			case NECP_KERNEL_POLICY_RESULT_IP_TUNNEL: {
				/* Verify that the packet is being routed to the tunnel */
				struct ifnet *policy_ifp = necp_get_ifnet_from_result_parameter(&necp_result_parameter);
				if (policy_ifp == ifp) {
					goto skip_ipsec;
				} else {
					if (necp_packet_can_rebind_to_ifnet(m, policy_ifp, (struct route *)&necp_route, AF_INET6)) {
						/* Set scoped index to the tunnel interface, since it is compatible with the packet */
						/* This will only work for callers who pass IPV6_OUTARGS, but that covers all of the
						   clients we care about today */
						if (flags & IPV6_OUTARGS) {
							ip6oa->ip6oa_boundif = policy_ifp->if_index;
							ip6oa->ip6oa_flags |= IP6OAF_BOUND_IF;
						}
						if (opt != NULL && opt->ip6po_pktinfo != NULL) {
							opt->ip6po_pktinfo->ipi6_ifindex = policy_ifp->if_index;
						}
						ro = &necp_route;
						goto skip_ipsec;
					} else {
						error = ENETUNREACH;
						goto bad;
					}
				}
				break;
			}
			default:
				break;
		}
	}
#endif /* NECP */
	
#if IPSEC
	if (ipsec_bypass != 0 || ip6obf.noipsec)
		goto skip_ipsec;

	if (sp == NULL) {
		/* get a security policy for this packet */
		if (so != NULL) {
			sp = ipsec6_getpolicybysock(m, IPSEC_DIR_OUTBOUND,
				so, &error);
		} else {
			sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND,
				0, &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) {
			goto skip_ipsec;
		} 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)) {
		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 (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 NECP
	ROUTE_RELEASE(&necp_route);
#endif /* NECP */
#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;

		if (ifp == NULL)
			ifp = ro_pmtu->ro_rt->rt_ifp;
		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 && INP_NO_CELLULAR(in6p)) {
					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: {
				error = 0; /* This option is no longer supported */
				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 = INP_NO_CELLULAR(in6p) ? 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
}