xref: /freebsd/sys/netinet6/ip6_input.c (revision 783d3ff6d7fae619db8a7990b8a6387de0c677b5)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. Neither the name of the project nor the names of its contributors
16  *    may be used to endorse or promote products derived from this software
17  *    without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  *
31  *	$KAME: ip6_input.c,v 1.259 2002/01/21 04:58:09 jinmei Exp $
32  */
33 
34 /*-
35  * Copyright (c) 1982, 1986, 1988, 1993
36  *	The Regents of the University of California.  All rights reserved.
37  *
38  * Redistribution and use in source and binary forms, with or without
39  * modification, are permitted provided that the following conditions
40  * are met:
41  * 1. Redistributions of source code must retain the above copyright
42  *    notice, this list of conditions and the following disclaimer.
43  * 2. Redistributions in binary form must reproduce the above copyright
44  *    notice, this list of conditions and the following disclaimer in the
45  *    documentation and/or other materials provided with the distribution.
46  * 3. Neither the name of the University nor the names of its contributors
47  *    may be used to endorse or promote products derived from this software
48  *    without specific prior written permission.
49  *
50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60  * SUCH DAMAGE.
61  */
62 
63 #include <sys/cdefs.h>
64 #include "opt_inet.h"
65 #include "opt_inet6.h"
66 #include "opt_ipsec.h"
67 #include "opt_route.h"
68 #include "opt_rss.h"
69 #include "opt_sctp.h"
70 
71 #include <sys/param.h>
72 #include <sys/systm.h>
73 #include <sys/hhook.h>
74 #include <sys/malloc.h>
75 #include <sys/mbuf.h>
76 #include <sys/proc.h>
77 #include <sys/domain.h>
78 #include <sys/protosw.h>
79 #include <sys/sdt.h>
80 #include <sys/socket.h>
81 #include <sys/socketvar.h>
82 #include <sys/errno.h>
83 #include <sys/time.h>
84 #include <sys/kernel.h>
85 #include <sys/lock.h>
86 #include <sys/rmlock.h>
87 #include <sys/syslog.h>
88 #include <sys/sysctl.h>
89 #include <sys/eventhandler.h>
90 
91 #include <net/if.h>
92 #include <net/if_var.h>
93 #include <net/if_types.h>
94 #include <net/if_private.h>
95 #include <net/if_dl.h>
96 #include <net/route.h>
97 #include <net/netisr.h>
98 #include <net/rss_config.h>
99 #include <net/pfil.h>
100 #include <net/vnet.h>
101 
102 #include <netinet/in.h>
103 #include <netinet/in_kdtrace.h>
104 #include <netinet/ip_var.h>
105 #include <netinet/in_systm.h>
106 #include <net/if_llatbl.h>
107 #ifdef INET
108 #include <netinet/ip.h>
109 #include <netinet/ip_icmp.h>
110 #endif /* INET */
111 #include <netinet/ip6.h>
112 #include <netinet6/in6_var.h>
113 #include <netinet6/ip6_var.h>
114 #include <netinet/ip_encap.h>
115 #include <netinet/in_pcb.h>
116 #include <netinet/icmp6.h>
117 #include <netinet6/scope6_var.h>
118 #include <netinet6/in6_ifattach.h>
119 #include <netinet6/mld6_var.h>
120 #include <netinet6/nd6.h>
121 #include <netinet6/in6_rss.h>
122 #ifdef SCTP
123 #include <netinet/sctp_pcb.h>
124 #include <netinet6/sctp6_var.h>
125 #endif
126 
127 #include <netipsec/ipsec_support.h>
128 
129 ip6proto_input_t	*ip6_protox[IPPROTO_MAX] = {
130 			    [0 ... IPPROTO_MAX - 1] = rip6_input };
131 ip6proto_ctlinput_t	*ip6_ctlprotox[IPPROTO_MAX] = {
132 			    [0 ... IPPROTO_MAX - 1] = rip6_ctlinput };
133 
134 VNET_DEFINE(struct in6_ifaddrhead, in6_ifaddrhead);
135 VNET_DEFINE(struct in6_ifaddrlisthead *, in6_ifaddrhashtbl);
136 VNET_DEFINE(u_long, in6_ifaddrhmask);
137 
138 static struct netisr_handler ip6_nh = {
139 	.nh_name = "ip6",
140 	.nh_handler = ip6_input,
141 	.nh_proto = NETISR_IPV6,
142 #ifdef RSS
143 	.nh_m2cpuid = rss_soft_m2cpuid_v6,
144 	.nh_policy = NETISR_POLICY_CPU,
145 	.nh_dispatch = NETISR_DISPATCH_HYBRID,
146 #else
147 	.nh_policy = NETISR_POLICY_FLOW,
148 #endif
149 };
150 
151 static int
152 sysctl_netinet6_intr_queue_maxlen(SYSCTL_HANDLER_ARGS)
153 {
154 	int error, qlimit;
155 
156 	netisr_getqlimit(&ip6_nh, &qlimit);
157 	error = sysctl_handle_int(oidp, &qlimit, 0, req);
158 	if (error || !req->newptr)
159 		return (error);
160 	if (qlimit < 1)
161 		return (EINVAL);
162 	return (netisr_setqlimit(&ip6_nh, qlimit));
163 }
164 SYSCTL_DECL(_net_inet6_ip6);
165 SYSCTL_PROC(_net_inet6_ip6, IPV6CTL_INTRQMAXLEN, intr_queue_maxlen,
166     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
167     0, 0, sysctl_netinet6_intr_queue_maxlen, "I",
168     "Maximum size of the IPv6 input queue");
169 
170 VNET_DEFINE_STATIC(bool, ip6_sav) = true;
171 #define	V_ip6_sav	VNET(ip6_sav)
172 SYSCTL_BOOL(_net_inet6_ip6, OID_AUTO, source_address_validation,
173     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip6_sav), true,
174     "Drop incoming packets with source address that is a local address");
175 
176 #ifdef RSS
177 static struct netisr_handler ip6_direct_nh = {
178 	.nh_name = "ip6_direct",
179 	.nh_handler = ip6_direct_input,
180 	.nh_proto = NETISR_IPV6_DIRECT,
181 	.nh_m2cpuid = rss_soft_m2cpuid_v6,
182 	.nh_policy = NETISR_POLICY_CPU,
183 	.nh_dispatch = NETISR_DISPATCH_HYBRID,
184 };
185 
186 static int
187 sysctl_netinet6_intr_direct_queue_maxlen(SYSCTL_HANDLER_ARGS)
188 {
189 	int error, qlimit;
190 
191 	netisr_getqlimit(&ip6_direct_nh, &qlimit);
192 	error = sysctl_handle_int(oidp, &qlimit, 0, req);
193 	if (error || !req->newptr)
194 		return (error);
195 	if (qlimit < 1)
196 		return (EINVAL);
197 	return (netisr_setqlimit(&ip6_direct_nh, qlimit));
198 }
199 SYSCTL_PROC(_net_inet6_ip6, IPV6CTL_INTRDQMAXLEN, intr_direct_queue_maxlen,
200     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
201     0, 0, sysctl_netinet6_intr_direct_queue_maxlen, "I",
202     "Maximum size of the IPv6 direct input queue");
203 
204 #endif
205 
206 VNET_DEFINE(pfil_head_t, inet6_pfil_head);
207 VNET_DEFINE(pfil_head_t, inet6_local_pfil_head);
208 
209 VNET_PCPUSTAT_DEFINE(struct ip6stat, ip6stat);
210 VNET_PCPUSTAT_SYSINIT(ip6stat);
211 #ifdef VIMAGE
212 VNET_PCPUSTAT_SYSUNINIT(ip6stat);
213 #endif /* VIMAGE */
214 
215 struct rmlock in6_ifaddr_lock;
216 RM_SYSINIT(in6_ifaddr_lock, &in6_ifaddr_lock, "in6_ifaddr_lock");
217 
218 static int ip6_hopopts_input(u_int32_t *, u_int32_t *, struct mbuf **, int *);
219 
220 /*
221  * IP6 initialization: fill in IP6 protocol switch table.
222  * All protocols not implemented in kernel go to raw IP6 protocol handler.
223  */
224 static void
225 ip6_vnet_init(void *arg __unused)
226 {
227 	struct pfil_head_args args;
228 
229 	TUNABLE_INT_FETCH("net.inet6.ip6.auto_linklocal",
230 	    &V_ip6_auto_linklocal);
231 	TUNABLE_INT_FETCH("net.inet6.ip6.accept_rtadv", &V_ip6_accept_rtadv);
232 	TUNABLE_INT_FETCH("net.inet6.ip6.no_radr", &V_ip6_no_radr);
233 
234 	CK_STAILQ_INIT(&V_in6_ifaddrhead);
235 	V_in6_ifaddrhashtbl = hashinit(IN6ADDR_NHASH, M_IFADDR,
236 	    &V_in6_ifaddrhmask);
237 
238 	/* Initialize packet filter hooks. */
239 	args.pa_version = PFIL_VERSION;
240 	args.pa_flags = PFIL_IN | PFIL_OUT;
241 	args.pa_type = PFIL_TYPE_IP6;
242 	args.pa_headname = PFIL_INET6_NAME;
243 	V_inet6_pfil_head = pfil_head_register(&args);
244 
245 	args.pa_flags = PFIL_OUT;
246 	args.pa_headname = PFIL_INET6_LOCAL_NAME;
247 	V_inet6_local_pfil_head = pfil_head_register(&args);
248 
249 	if (hhook_head_register(HHOOK_TYPE_IPSEC_IN, AF_INET6,
250 	    &V_ipsec_hhh_in[HHOOK_IPSEC_INET6],
251 	    HHOOK_WAITOK | HHOOK_HEADISINVNET) != 0)
252 		printf("%s: WARNING: unable to register input helper hook\n",
253 		    __func__);
254 	if (hhook_head_register(HHOOK_TYPE_IPSEC_OUT, AF_INET6,
255 	    &V_ipsec_hhh_out[HHOOK_IPSEC_INET6],
256 	    HHOOK_WAITOK | HHOOK_HEADISINVNET) != 0)
257 		printf("%s: WARNING: unable to register output helper hook\n",
258 		    __func__);
259 
260 	scope6_init();
261 	addrsel_policy_init();
262 	nd6_init();
263 	frag6_init();
264 
265 	V_ip6_desync_factor = arc4random() % MAX_TEMP_DESYNC_FACTOR;
266 
267 	/* Skip global initialization stuff for non-default instances. */
268 #ifdef VIMAGE
269 	netisr_register_vnet(&ip6_nh);
270 #ifdef RSS
271 	netisr_register_vnet(&ip6_direct_nh);
272 #endif
273 #endif
274 }
275 VNET_SYSINIT(ip6_vnet_init, SI_SUB_PROTO_DOMAIN, SI_ORDER_FOURTH,
276     ip6_vnet_init, NULL);
277 
278 static void
279 ip6_init(void *arg __unused)
280 {
281 
282 	/*
283 	 * Register statically those protocols that are unlikely to ever go
284 	 * dynamic.
285 	 */
286 	IP6PROTO_REGISTER(IPPROTO_ICMPV6, icmp6_input, rip6_ctlinput);
287 	IP6PROTO_REGISTER(IPPROTO_DSTOPTS, dest6_input, NULL);
288 	IP6PROTO_REGISTER(IPPROTO_ROUTING, route6_input, NULL);
289 	IP6PROTO_REGISTER(IPPROTO_FRAGMENT, frag6_input, NULL);
290 	IP6PROTO_REGISTER(IPPROTO_IPV4, encap6_input, NULL);
291 	IP6PROTO_REGISTER(IPPROTO_IPV6, encap6_input, NULL);
292 	IP6PROTO_REGISTER(IPPROTO_ETHERIP, encap6_input, NULL);
293 	IP6PROTO_REGISTER(IPPROTO_GRE, encap6_input, NULL);
294 	IP6PROTO_REGISTER(IPPROTO_PIM, encap6_input, NULL);
295 #ifdef SCTP	/* XXX: has a loadable & static version */
296 	IP6PROTO_REGISTER(IPPROTO_SCTP, sctp6_input, sctp6_ctlinput);
297 #endif
298 
299 	EVENTHANDLER_REGISTER(vm_lowmem, frag6_drain, NULL, LOWMEM_PRI_DEFAULT);
300 	EVENTHANDLER_REGISTER(mbuf_lowmem, frag6_drain, NULL,
301 	    LOWMEM_PRI_DEFAULT);
302 
303 	netisr_register(&ip6_nh);
304 #ifdef RSS
305 	netisr_register(&ip6_direct_nh);
306 #endif
307 }
308 SYSINIT(ip6_init, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD, ip6_init, NULL);
309 
310 int
311 ip6proto_register(uint8_t proto, ip6proto_input_t input,
312     ip6proto_ctlinput_t ctl)
313 {
314 
315 	MPASS(proto > 0);
316 
317 	if (ip6_protox[proto] == rip6_input) {
318 		ip6_protox[proto] = input;
319 		ip6_ctlprotox[proto] = ctl;
320 		return (0);
321 	} else
322 		return (EEXIST);
323 }
324 
325 int
326 ip6proto_unregister(uint8_t proto)
327 {
328 
329 	MPASS(proto > 0);
330 
331 	if (ip6_protox[proto] != rip6_input) {
332 		ip6_protox[proto] = rip6_input;
333 		ip6_ctlprotox[proto] = rip6_ctlinput;
334 		return (0);
335 	} else
336 		return (ENOENT);
337 }
338 
339 #ifdef VIMAGE
340 static void
341 ip6_destroy(void *unused __unused)
342 {
343 	struct ifaddr *ifa, *nifa;
344 	struct ifnet *ifp;
345 	int error;
346 
347 #ifdef RSS
348 	netisr_unregister_vnet(&ip6_direct_nh);
349 #endif
350 	netisr_unregister_vnet(&ip6_nh);
351 
352 	pfil_head_unregister(V_inet6_pfil_head);
353 	error = hhook_head_deregister(V_ipsec_hhh_in[HHOOK_IPSEC_INET6]);
354 	if (error != 0) {
355 		printf("%s: WARNING: unable to deregister input helper hook "
356 		    "type HHOOK_TYPE_IPSEC_IN, id HHOOK_IPSEC_INET6: "
357 		    "error %d returned\n", __func__, error);
358 	}
359 	error = hhook_head_deregister(V_ipsec_hhh_out[HHOOK_IPSEC_INET6]);
360 	if (error != 0) {
361 		printf("%s: WARNING: unable to deregister output helper hook "
362 		    "type HHOOK_TYPE_IPSEC_OUT, id HHOOK_IPSEC_INET6: "
363 		    "error %d returned\n", __func__, error);
364 	}
365 
366 	/* Cleanup addresses. */
367 	IFNET_RLOCK();
368 	CK_STAILQ_FOREACH(ifp, &V_ifnet, if_link) {
369 		/* Cannot lock here - lock recursion. */
370 		/* IF_ADDR_LOCK(ifp); */
371 		CK_STAILQ_FOREACH_SAFE(ifa, &ifp->if_addrhead, ifa_link, nifa) {
372 			if (ifa->ifa_addr->sa_family != AF_INET6)
373 				continue;
374 			in6_purgeaddr(ifa);
375 		}
376 		/* IF_ADDR_UNLOCK(ifp); */
377 		in6_ifdetach_destroy(ifp);
378 		mld_domifdetach(ifp);
379 	}
380 	IFNET_RUNLOCK();
381 
382 	/* Make sure any routes are gone as well. */
383 	rib_flush_routes_family(AF_INET6);
384 
385 	frag6_destroy();
386 	nd6_destroy();
387 	in6_ifattach_destroy();
388 
389 	hashdestroy(V_in6_ifaddrhashtbl, M_IFADDR, V_in6_ifaddrhmask);
390 }
391 
392 VNET_SYSUNINIT(inet6, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD, ip6_destroy, NULL);
393 #endif
394 
395 static int
396 ip6_input_hbh(struct mbuf **mp, uint32_t *plen, uint32_t *rtalert, int *off,
397     int *nxt, int *ours)
398 {
399 	struct mbuf *m;
400 	struct ip6_hdr *ip6;
401 	struct ip6_hbh *hbh;
402 
403 	if (ip6_hopopts_input(plen, rtalert, mp, off)) {
404 #if 0	/*touches NULL pointer*/
405 		in6_ifstat_inc((*mp)->m_pkthdr.rcvif, ifs6_in_discard);
406 #endif
407 		goto out;	/* m have already been freed */
408 	}
409 
410 	/* adjust pointer */
411 	m = *mp;
412 	ip6 = mtod(m, struct ip6_hdr *);
413 
414 	/*
415 	 * if the payload length field is 0 and the next header field
416 	 * indicates Hop-by-Hop Options header, then a Jumbo Payload
417 	 * option MUST be included.
418 	 */
419 	if (ip6->ip6_plen == 0 && *plen == 0) {
420 		/*
421 		 * Note that if a valid jumbo payload option is
422 		 * contained, ip6_hopopts_input() must set a valid
423 		 * (non-zero) payload length to the variable plen.
424 		 */
425 		IP6STAT_INC(ip6s_badoptions);
426 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_discard);
427 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_hdrerr);
428 		icmp6_error(m, ICMP6_PARAM_PROB,
429 			    ICMP6_PARAMPROB_HEADER,
430 			    (caddr_t)&ip6->ip6_plen - (caddr_t)ip6);
431 		goto out;
432 	}
433 	/* ip6_hopopts_input() ensures that mbuf is contiguous */
434 	hbh = (struct ip6_hbh *)(ip6 + 1);
435 	*nxt = hbh->ip6h_nxt;
436 
437 	/*
438 	 * If we are acting as a router and the packet contains a
439 	 * router alert option, see if we know the option value.
440 	 * Currently, we only support the option value for MLD, in which
441 	 * case we should pass the packet to the multicast routing
442 	 * daemon.
443 	 */
444 	if (*rtalert != ~0) {
445 		switch (*rtalert) {
446 		case IP6OPT_RTALERT_MLD:
447 			if (V_ip6_forwarding)
448 				*ours = 1;
449 			break;
450 		default:
451 			/*
452 			 * RFC2711 requires unrecognized values must be
453 			 * silently ignored.
454 			 */
455 			break;
456 		}
457 	}
458 
459 	return (0);
460 
461 out:
462 	return (1);
463 }
464 
465 #ifdef RSS
466 /*
467  * IPv6 direct input routine.
468  *
469  * This is called when reinjecting completed fragments where
470  * all of the previous checking and book-keeping has been done.
471  */
472 void
473 ip6_direct_input(struct mbuf *m)
474 {
475 	int off, nxt;
476 	int nest;
477 	struct m_tag *mtag;
478 	struct ip6_direct_ctx *ip6dc;
479 
480 	mtag = m_tag_locate(m, MTAG_ABI_IPV6, IPV6_TAG_DIRECT, NULL);
481 	KASSERT(mtag != NULL, ("Reinjected packet w/o direct ctx tag!"));
482 
483 	ip6dc = (struct ip6_direct_ctx *)(mtag + 1);
484 	nxt = ip6dc->ip6dc_nxt;
485 	off = ip6dc->ip6dc_off;
486 
487 	nest = 0;
488 
489 	m_tag_delete(m, mtag);
490 
491 	while (nxt != IPPROTO_DONE) {
492 		if (V_ip6_hdrnestlimit && (++nest > V_ip6_hdrnestlimit)) {
493 			IP6STAT_INC(ip6s_toomanyhdr);
494 			goto bad;
495 		}
496 
497 		/*
498 		 * protection against faulty packet - there should be
499 		 * more sanity checks in header chain processing.
500 		 */
501 		if (m->m_pkthdr.len < off) {
502 			IP6STAT_INC(ip6s_tooshort);
503 			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
504 			goto bad;
505 		}
506 
507 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
508 		if (IPSEC_ENABLED(ipv6)) {
509 			if (IPSEC_INPUT(ipv6, m, off, nxt) != 0)
510 				return;
511 		}
512 #endif /* IPSEC */
513 
514 		nxt = ip6_protox[nxt](&m, &off, nxt);
515 	}
516 	return;
517 bad:
518 	m_freem(m);
519 }
520 #endif
521 
522 void
523 ip6_input(struct mbuf *m)
524 {
525 	struct in6_addr odst;
526 	struct ip6_hdr *ip6;
527 	struct in6_ifaddr *ia;
528 	struct ifnet *rcvif;
529 	u_int32_t plen;
530 	u_int32_t rtalert = ~0;
531 	int off = sizeof(struct ip6_hdr), nest;
532 	int nxt, ours = 0;
533 	int srcrt = 0;
534 
535 	/*
536 	 * Drop the packet if IPv6 operation is disabled on the interface.
537 	 */
538 	rcvif = m->m_pkthdr.rcvif;
539 	if ((ND_IFINFO(rcvif)->flags & ND6_IFF_IFDISABLED))
540 		goto bad;
541 
542 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
543 	/*
544 	 * should the inner packet be considered authentic?
545 	 * see comment in ah4_input().
546 	 * NB: m cannot be NULL when passed to the input routine
547 	 */
548 
549 	m->m_flags &= ~M_AUTHIPHDR;
550 	m->m_flags &= ~M_AUTHIPDGM;
551 
552 #endif /* IPSEC */
553 
554 	if (m->m_flags & M_FASTFWD_OURS) {
555 		/*
556 		 * Firewall changed destination to local.
557 		 */
558 		ip6 = mtod(m, struct ip6_hdr *);
559 		goto passin;
560 	}
561 
562 	/*
563 	 * mbuf statistics
564 	 */
565 	if (m->m_flags & M_EXT) {
566 		if (m->m_next)
567 			IP6STAT_INC(ip6s_mext2m);
568 		else
569 			IP6STAT_INC(ip6s_mext1);
570 	} else {
571 		if (m->m_next) {
572 			struct ifnet *ifp = (m->m_flags & M_LOOP) ? V_loif : rcvif;
573 			int ifindex = ifp->if_index;
574 			if (ifindex >= IP6S_M2MMAX)
575 				ifindex = 0;
576 			IP6STAT_INC(ip6s_m2m[ifindex]);
577 		} else
578 			IP6STAT_INC(ip6s_m1);
579 	}
580 
581 	in6_ifstat_inc(rcvif, ifs6_in_receive);
582 	IP6STAT_INC(ip6s_total);
583 
584 	/*
585 	 * L2 bridge code and some other code can return mbuf chain
586 	 * that does not conform to KAME requirement.  too bad.
587 	 * XXX: fails to join if interface MTU > MCLBYTES.  jumbogram?
588 	 */
589 	if (m && m->m_next != NULL && m->m_pkthdr.len < MCLBYTES) {
590 		struct mbuf *n;
591 
592 		if (m->m_pkthdr.len > MHLEN)
593 			n = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR);
594 		else
595 			n = m_gethdr(M_NOWAIT, MT_DATA);
596 		if (n == NULL)
597 			goto bad;
598 
599 		m_move_pkthdr(n, m);
600 		m_copydata(m, 0, n->m_pkthdr.len, mtod(n, caddr_t));
601 		n->m_len = n->m_pkthdr.len;
602 		m_freem(m);
603 		m = n;
604 	}
605 	if (m->m_len < sizeof(struct ip6_hdr)) {
606 		if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
607 			IP6STAT_INC(ip6s_toosmall);
608 			in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
609 			goto bad;
610 		}
611 	}
612 
613 	ip6 = mtod(m, struct ip6_hdr *);
614 	if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
615 		IP6STAT_INC(ip6s_badvers);
616 		in6_ifstat_inc(rcvif, ifs6_in_hdrerr);
617 		goto bad;
618 	}
619 
620 	IP6STAT_INC(ip6s_nxthist[ip6->ip6_nxt]);
621 	IP_PROBE(receive, NULL, NULL, ip6, rcvif, NULL, ip6);
622 
623 	/*
624 	 * Check against address spoofing/corruption.
625 	 */
626 	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
627 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
628 		/*
629 		 * XXX: "badscope" is not very suitable for a multicast source.
630 		 */
631 		IP6STAT_INC(ip6s_badscope);
632 		in6_ifstat_inc(rcvif, ifs6_in_addrerr);
633 		goto bad;
634 	}
635 	if (IN6_IS_ADDR_MC_INTFACELOCAL(&ip6->ip6_dst) &&
636 	    !(m->m_flags & M_LOOP)) {
637 		/*
638 		 * In this case, the packet should come from the loopback
639 		 * interface.  However, we cannot just check the if_flags,
640 		 * because ip6_mloopback() passes the "actual" interface
641 		 * as the outgoing/incoming interface.
642 		 */
643 		IP6STAT_INC(ip6s_badscope);
644 		in6_ifstat_inc(rcvif, ifs6_in_addrerr);
645 		goto bad;
646 	}
647 	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) &&
648 	    IPV6_ADDR_MC_SCOPE(&ip6->ip6_dst) == 0) {
649 		/*
650 		 * RFC4291 2.7:
651 		 * Nodes must not originate a packet to a multicast address
652 		 * whose scop field contains the reserved value 0; if such
653 		 * a packet is received, it must be silently dropped.
654 		 */
655 		IP6STAT_INC(ip6s_badscope);
656 		in6_ifstat_inc(rcvif, ifs6_in_addrerr);
657 		goto bad;
658 	}
659 	/*
660 	 * The following check is not documented in specs.  A malicious
661 	 * party may be able to use IPv4 mapped addr to confuse tcp/udp stack
662 	 * and bypass security checks (act as if it was from 127.0.0.1 by using
663 	 * IPv6 src ::ffff:127.0.0.1).  Be cautious.
664 	 *
665 	 * We have supported IPv6-only kernels for a few years and this issue
666 	 * has not come up.  The world seems to move mostly towards not using
667 	 * v4mapped on the wire, so it makes sense for us to keep rejecting
668 	 * any such packets.
669 	 */
670 	if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
671 	    IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
672 		IP6STAT_INC(ip6s_badscope);
673 		in6_ifstat_inc(rcvif, ifs6_in_addrerr);
674 		goto bad;
675 	}
676 #if 0
677 	/*
678 	 * Reject packets with IPv4 compatible addresses (auto tunnel).
679 	 *
680 	 * The code forbids auto tunnel relay case in RFC1933 (the check is
681 	 * stronger than RFC1933).  We may want to re-enable it if mech-xx
682 	 * is revised to forbid relaying case.
683 	 */
684 	if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
685 	    IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
686 		IP6STAT_INC(ip6s_badscope);
687 		in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_addrerr);
688 		goto bad;
689 	}
690 #endif
691 	/*
692 	 * Try to forward the packet, but if we fail continue.
693 	 * ip6_tryforward() does not generate redirects, so fall
694 	 * through to normal processing if redirects are required.
695 	 * ip6_tryforward() does inbound and outbound packet firewall
696 	 * processing. If firewall has decided that destination becomes
697 	 * our local address, it sets M_FASTFWD_OURS flag. In this
698 	 * case skip another inbound firewall processing and update
699 	 * ip6 pointer.
700 	 */
701 	if (V_ip6_forwarding != 0 && V_ip6_sendredirects == 0
702 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
703 	    && (!IPSEC_ENABLED(ipv6) ||
704 	    IPSEC_CAPS(ipv6, m, IPSEC_CAP_OPERABLE) == 0)
705 #endif
706 	    ) {
707 		if ((m = ip6_tryforward(m)) == NULL)
708 			return;
709 		if (m->m_flags & M_FASTFWD_OURS) {
710 			ip6 = mtod(m, struct ip6_hdr *);
711 			goto passin;
712 		}
713 	}
714 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
715 	/*
716 	 * Bypass packet filtering for packets previously handled by IPsec.
717 	 */
718 	if (IPSEC_ENABLED(ipv6) &&
719 	    IPSEC_CAPS(ipv6, m, IPSEC_CAP_BYPASS_FILTER) != 0)
720 			goto passin;
721 #endif
722 	/*
723 	 * Run through list of hooks for input packets.
724 	 *
725 	 * NB: Beware of the destination address changing
726 	 *     (e.g. by NAT rewriting).  When this happens,
727 	 *     tell ip6_forward to do the right thing.
728 	 */
729 
730 	/* Jump over all PFIL processing if hooks are not active. */
731 	if (!PFIL_HOOKED_IN(V_inet6_pfil_head))
732 		goto passin;
733 
734 	odst = ip6->ip6_dst;
735 	if (pfil_mbuf_in(V_inet6_pfil_head, &m, m->m_pkthdr.rcvif,
736 	    NULL) != PFIL_PASS)
737 		return;
738 	ip6 = mtod(m, struct ip6_hdr *);
739 	srcrt = !IN6_ARE_ADDR_EQUAL(&odst, &ip6->ip6_dst);
740 	if ((m->m_flags & (M_IP6_NEXTHOP | M_FASTFWD_OURS)) == M_IP6_NEXTHOP &&
741 	    m_tag_find(m, PACKET_TAG_IPFORWARD, NULL) != NULL) {
742 		/*
743 		 * Directly ship the packet on.  This allows forwarding
744 		 * packets originally destined to us to some other directly
745 		 * connected host.
746 		 */
747 		ip6_forward(m, 1);
748 		return;
749 	}
750 
751 passin:
752 	/*
753 	 * Disambiguate address scope zones (if there is ambiguity).
754 	 * We first make sure that the original source or destination address
755 	 * is not in our internal form for scoped addresses.  Such addresses
756 	 * are not necessarily invalid spec-wise, but we cannot accept them due
757 	 * to the usage conflict.
758 	 * in6_setscope() then also checks and rejects the cases where src or
759 	 * dst are the loopback address and the receiving interface
760 	 * is not loopback.
761 	 */
762 	if (in6_clearscope(&ip6->ip6_src) || in6_clearscope(&ip6->ip6_dst)) {
763 		IP6STAT_INC(ip6s_badscope); /* XXX */
764 		goto bad;
765 	}
766 	if (in6_setscope(&ip6->ip6_src, rcvif, NULL) ||
767 	    in6_setscope(&ip6->ip6_dst, rcvif, NULL)) {
768 		IP6STAT_INC(ip6s_badscope);
769 		goto bad;
770 	}
771 	if (m->m_flags & M_FASTFWD_OURS) {
772 		m->m_flags &= ~M_FASTFWD_OURS;
773 		ours = 1;
774 		goto hbhcheck;
775 	}
776 	/*
777 	 * Multicast check. Assume packet is for us to avoid
778 	 * prematurely taking locks.
779 	 */
780 	if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
781 		ours = 1;
782 		in6_ifstat_inc(rcvif, ifs6_in_mcast);
783 		goto hbhcheck;
784 	}
785 	/*
786 	 * Unicast check
787 	 * XXX: For now we keep link-local IPv6 addresses with embedded
788 	 *      scope zone id, therefore we use zero zoneid here.
789 	 */
790 	ia = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false);
791 	if (ia != NULL) {
792 		if (ia->ia6_flags & IN6_IFF_NOTREADY) {
793 			char ip6bufs[INET6_ADDRSTRLEN];
794 			char ip6bufd[INET6_ADDRSTRLEN];
795 			/* address is not ready, so discard the packet. */
796 			nd6log((LOG_INFO,
797 			    "ip6_input: packet to an unready address %s->%s\n",
798 			    ip6_sprintf(ip6bufs, &ip6->ip6_src),
799 			    ip6_sprintf(ip6bufd, &ip6->ip6_dst)));
800 			goto bad;
801 		}
802 		if (V_ip6_sav && !(m->m_flags & M_LOOP) &&
803 		    __predict_false(in6_localip_fib(&ip6->ip6_src,
804 			    rcvif->if_fib))) {
805 			IP6STAT_INC(ip6s_badscope); /* XXX */
806 			goto bad;
807 		}
808 		/* Count the packet in the ip address stats */
809 		counter_u64_add(ia->ia_ifa.ifa_ipackets, 1);
810 		counter_u64_add(ia->ia_ifa.ifa_ibytes, m->m_pkthdr.len);
811 		ours = 1;
812 		goto hbhcheck;
813 	}
814 
815 	/*
816 	 * Now there is no reason to process the packet if it's not our own
817 	 * and we're not a router.
818 	 */
819 	if (!V_ip6_forwarding) {
820 		IP6STAT_INC(ip6s_cantforward);
821 		goto bad;
822 	}
823 
824   hbhcheck:
825 	/*
826 	 * Process Hop-by-Hop options header if it's contained.
827 	 * m may be modified in ip6_hopopts_input().
828 	 * If a JumboPayload option is included, plen will also be modified.
829 	 */
830 	plen = (u_int32_t)ntohs(ip6->ip6_plen);
831 	if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
832 		if (ip6_input_hbh(&m, &plen, &rtalert, &off, &nxt, &ours) != 0)
833 			return;
834 	} else
835 		nxt = ip6->ip6_nxt;
836 
837 	/*
838 	 * Use mbuf flags to propagate Router Alert option to
839 	 * ICMPv6 layer, as hop-by-hop options have been stripped.
840 	 */
841 	if (rtalert != ~0)
842 		m->m_flags |= M_RTALERT_MLD;
843 
844 	/*
845 	 * Check that the amount of data in the buffers
846 	 * is as at least much as the IPv6 header would have us expect.
847 	 * Trim mbufs if longer than we expect.
848 	 * Drop packet if shorter than we expect.
849 	 */
850 	if (m->m_pkthdr.len - sizeof(struct ip6_hdr) < plen) {
851 		IP6STAT_INC(ip6s_tooshort);
852 		in6_ifstat_inc(rcvif, ifs6_in_truncated);
853 		goto bad;
854 	}
855 	if (m->m_pkthdr.len > sizeof(struct ip6_hdr) + plen) {
856 		if (m->m_len == m->m_pkthdr.len) {
857 			m->m_len = sizeof(struct ip6_hdr) + plen;
858 			m->m_pkthdr.len = sizeof(struct ip6_hdr) + plen;
859 		} else
860 			m_adj(m, sizeof(struct ip6_hdr) + plen - m->m_pkthdr.len);
861 	}
862 
863 	/*
864 	 * Forward if desirable.
865 	 */
866 	if (V_ip6_mrouter &&
867 	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
868 		/*
869 		 * If we are acting as a multicast router, all
870 		 * incoming multicast packets are passed to the
871 		 * kernel-level multicast forwarding function.
872 		 * The packet is returned (relatively) intact; if
873 		 * ip6_mforward() returns a non-zero value, the packet
874 		 * must be discarded, else it may be accepted below.
875 		 *
876 		 * XXX TODO: Check hlim and multicast scope here to avoid
877 		 * unnecessarily calling into ip6_mforward().
878 		 */
879 		if (ip6_mforward && ip6_mforward(ip6, rcvif, m)) {
880 			IP6STAT_INC(ip6s_cantforward);
881 			goto bad;
882 		}
883 	} else if (!ours) {
884 		ip6_forward(m, srcrt);
885 		return;
886 	}
887 
888 	/*
889 	 * We are going to ship the packet to the local protocol stack. Call the
890 	 * filter again for this 'output' action, allowing redirect-like rules
891 	 * to adjust the source address.
892 	 */
893 	if (PFIL_HOOKED_OUT(V_inet6_local_pfil_head)) {
894 		if (pfil_mbuf_out(V_inet6_local_pfil_head, &m, V_loif, NULL) !=
895 		    PFIL_PASS)
896 			return;
897 		ip6 = mtod(m, struct ip6_hdr *);
898 	}
899 
900 	/*
901 	 * Tell launch routine the next header
902 	 */
903 	IP6STAT_INC(ip6s_delivered);
904 	in6_ifstat_inc(rcvif, ifs6_in_deliver);
905 	nest = 0;
906 
907 	while (nxt != IPPROTO_DONE) {
908 		if (V_ip6_hdrnestlimit && (++nest > V_ip6_hdrnestlimit)) {
909 			IP6STAT_INC(ip6s_toomanyhdr);
910 			goto bad;
911 		}
912 
913 		/*
914 		 * protection against faulty packet - there should be
915 		 * more sanity checks in header chain processing.
916 		 */
917 		if (m->m_pkthdr.len < off) {
918 			IP6STAT_INC(ip6s_tooshort);
919 			in6_ifstat_inc(rcvif, ifs6_in_truncated);
920 			goto bad;
921 		}
922 
923 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
924 		if (IPSEC_ENABLED(ipv6)) {
925 			if (IPSEC_INPUT(ipv6, m, off, nxt) != 0)
926 				return;
927 		}
928 #endif /* IPSEC */
929 
930 		nxt = ip6_protox[nxt](&m, &off, nxt);
931 	}
932 	return;
933 bad:
934 	in6_ifstat_inc(rcvif, ifs6_in_discard);
935 	if (m != NULL)
936 		m_freem(m);
937 }
938 
939 /*
940  * Hop-by-Hop options header processing. If a valid jumbo payload option is
941  * included, the real payload length will be stored in plenp.
942  *
943  * rtalertp - XXX: should be stored more smart way
944  */
945 static int
946 ip6_hopopts_input(u_int32_t *plenp, u_int32_t *rtalertp,
947     struct mbuf **mp, int *offp)
948 {
949 	struct mbuf *m = *mp;
950 	int off = *offp, hbhlen;
951 	struct ip6_hbh *hbh;
952 
953 	/* validation of the length of the header */
954 	if (m->m_len < off + sizeof(*hbh)) {
955 		m = m_pullup(m, off + sizeof(*hbh));
956 		if (m == NULL) {
957 			IP6STAT_INC(ip6s_exthdrtoolong);
958 			*mp = NULL;
959 			return (-1);
960 		}
961 	}
962 	hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
963 	hbhlen = (hbh->ip6h_len + 1) << 3;
964 
965 	if (m->m_len < off + hbhlen) {
966 		m = m_pullup(m, off + hbhlen);
967 		if (m == NULL) {
968 			IP6STAT_INC(ip6s_exthdrtoolong);
969 			*mp = NULL;
970 			return (-1);
971 		}
972 	}
973 	hbh = (struct ip6_hbh *)(mtod(m, caddr_t) + off);
974 	off += hbhlen;
975 	hbhlen -= sizeof(struct ip6_hbh);
976 	if (ip6_process_hopopts(m, (u_int8_t *)hbh + sizeof(struct ip6_hbh),
977 				hbhlen, rtalertp, plenp) < 0) {
978 		*mp = NULL;
979 		return (-1);
980 	}
981 
982 	*offp = off;
983 	*mp = m;
984 	return (0);
985 }
986 
987 /*
988  * Search header for all Hop-by-hop options and process each option.
989  * This function is separate from ip6_hopopts_input() in order to
990  * handle a case where the sending node itself process its hop-by-hop
991  * options header. In such a case, the function is called from ip6_output().
992  *
993  * The function assumes that hbh header is located right after the IPv6 header
994  * (RFC2460 p7), opthead is pointer into data content in m, and opthead to
995  * opthead + hbhlen is located in contiguous memory region.
996  */
997 int
998 ip6_process_hopopts(struct mbuf *m, u_int8_t *opthead, int hbhlen,
999     u_int32_t *rtalertp, u_int32_t *plenp)
1000 {
1001 	struct ip6_hdr *ip6;
1002 	int optlen = 0;
1003 	u_int8_t *opt = opthead;
1004 	u_int16_t rtalert_val;
1005 	u_int32_t jumboplen;
1006 	const int erroff = sizeof(struct ip6_hdr) + sizeof(struct ip6_hbh);
1007 
1008 	for (; hbhlen > 0; hbhlen -= optlen, opt += optlen) {
1009 		switch (*opt) {
1010 		case IP6OPT_PAD1:
1011 			optlen = 1;
1012 			break;
1013 		case IP6OPT_PADN:
1014 			if (hbhlen < IP6OPT_MINLEN) {
1015 				IP6STAT_INC(ip6s_toosmall);
1016 				goto bad;
1017 			}
1018 			optlen = *(opt + 1) + 2;
1019 			break;
1020 		case IP6OPT_ROUTER_ALERT:
1021 			/* XXX may need check for alignment */
1022 			if (hbhlen < IP6OPT_RTALERT_LEN) {
1023 				IP6STAT_INC(ip6s_toosmall);
1024 				goto bad;
1025 			}
1026 			if (*(opt + 1) != IP6OPT_RTALERT_LEN - 2) {
1027 				/* XXX stat */
1028 				icmp6_error(m, ICMP6_PARAM_PROB,
1029 				    ICMP6_PARAMPROB_HEADER,
1030 				    erroff + opt + 1 - opthead);
1031 				return (-1);
1032 			}
1033 			optlen = IP6OPT_RTALERT_LEN;
1034 			bcopy((caddr_t)(opt + 2), (caddr_t)&rtalert_val, 2);
1035 			*rtalertp = ntohs(rtalert_val);
1036 			break;
1037 		case IP6OPT_JUMBO:
1038 			/* XXX may need check for alignment */
1039 			if (hbhlen < IP6OPT_JUMBO_LEN) {
1040 				IP6STAT_INC(ip6s_toosmall);
1041 				goto bad;
1042 			}
1043 			if (*(opt + 1) != IP6OPT_JUMBO_LEN - 2) {
1044 				/* XXX stat */
1045 				icmp6_error(m, ICMP6_PARAM_PROB,
1046 				    ICMP6_PARAMPROB_HEADER,
1047 				    erroff + opt + 1 - opthead);
1048 				return (-1);
1049 			}
1050 			optlen = IP6OPT_JUMBO_LEN;
1051 
1052 			/*
1053 			 * IPv6 packets that have non 0 payload length
1054 			 * must not contain a jumbo payload option.
1055 			 */
1056 			ip6 = mtod(m, struct ip6_hdr *);
1057 			if (ip6->ip6_plen) {
1058 				IP6STAT_INC(ip6s_badoptions);
1059 				icmp6_error(m, ICMP6_PARAM_PROB,
1060 				    ICMP6_PARAMPROB_HEADER,
1061 				    erroff + opt - opthead);
1062 				return (-1);
1063 			}
1064 
1065 			/*
1066 			 * We may see jumbolen in unaligned location, so
1067 			 * we'd need to perform bcopy().
1068 			 */
1069 			bcopy(opt + 2, &jumboplen, sizeof(jumboplen));
1070 			jumboplen = (u_int32_t)htonl(jumboplen);
1071 
1072 #if 1
1073 			/*
1074 			 * if there are multiple jumbo payload options,
1075 			 * *plenp will be non-zero and the packet will be
1076 			 * rejected.
1077 			 * the behavior may need some debate in ipngwg -
1078 			 * multiple options does not make sense, however,
1079 			 * there's no explicit mention in specification.
1080 			 */
1081 			if (*plenp != 0) {
1082 				IP6STAT_INC(ip6s_badoptions);
1083 				icmp6_error(m, ICMP6_PARAM_PROB,
1084 				    ICMP6_PARAMPROB_HEADER,
1085 				    erroff + opt + 2 - opthead);
1086 				return (-1);
1087 			}
1088 #endif
1089 
1090 			/*
1091 			 * jumbo payload length must be larger than 65535.
1092 			 */
1093 			if (jumboplen <= IPV6_MAXPACKET) {
1094 				IP6STAT_INC(ip6s_badoptions);
1095 				icmp6_error(m, ICMP6_PARAM_PROB,
1096 				    ICMP6_PARAMPROB_HEADER,
1097 				    erroff + opt + 2 - opthead);
1098 				return (-1);
1099 			}
1100 			*plenp = jumboplen;
1101 
1102 			break;
1103 		default:		/* unknown option */
1104 			if (hbhlen < IP6OPT_MINLEN) {
1105 				IP6STAT_INC(ip6s_toosmall);
1106 				goto bad;
1107 			}
1108 			optlen = ip6_unknown_opt(opt, m,
1109 			    erroff + opt - opthead);
1110 			if (optlen == -1)
1111 				return (-1);
1112 			optlen += 2;
1113 			break;
1114 		}
1115 	}
1116 
1117 	return (0);
1118 
1119   bad:
1120 	m_freem(m);
1121 	return (-1);
1122 }
1123 
1124 /*
1125  * Unknown option processing.
1126  * The third argument `off' is the offset from the IPv6 header to the option,
1127  * which is necessary if the IPv6 header the and option header and IPv6 header
1128  * is not contiguous in order to return an ICMPv6 error.
1129  */
1130 int
1131 ip6_unknown_opt(u_int8_t *optp, struct mbuf *m, int off)
1132 {
1133 	struct ip6_hdr *ip6;
1134 
1135 	switch (IP6OPT_TYPE(*optp)) {
1136 	case IP6OPT_TYPE_SKIP: /* ignore the option */
1137 		return ((int)*(optp + 1));
1138 	case IP6OPT_TYPE_DISCARD:	/* silently discard */
1139 		m_freem(m);
1140 		return (-1);
1141 	case IP6OPT_TYPE_FORCEICMP: /* send ICMP even if multicasted */
1142 		IP6STAT_INC(ip6s_badoptions);
1143 		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_OPTION, off);
1144 		return (-1);
1145 	case IP6OPT_TYPE_ICMP: /* send ICMP if not multicasted */
1146 		IP6STAT_INC(ip6s_badoptions);
1147 		ip6 = mtod(m, struct ip6_hdr *);
1148 		if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1149 		    (m->m_flags & (M_BCAST|M_MCAST)))
1150 			m_freem(m);
1151 		else
1152 			icmp6_error(m, ICMP6_PARAM_PROB,
1153 				    ICMP6_PARAMPROB_OPTION, off);
1154 		return (-1);
1155 	}
1156 
1157 	m_freem(m);		/* XXX: NOTREACHED */
1158 	return (-1);
1159 }
1160 
1161 /*
1162  * Create the "control" list for this pcb.
1163  * These functions will not modify mbuf chain at all.
1164  *
1165  * The routine will be called from upper layer handlers like tcp6_input().
1166  * Thus the routine assumes that the caller (tcp6_input) have already
1167  * called m_pullup() and all the extension headers are located in the
1168  * very first mbuf on the mbuf chain.
1169  *
1170  * ip6_savecontrol_v4 will handle those options that are possible to be
1171  * set on a v4-mapped socket.
1172  * ip6_savecontrol will directly call ip6_savecontrol_v4 to handle those
1173  * options and handle the v6-only ones itself.
1174  */
1175 struct mbuf **
1176 ip6_savecontrol_v4(struct inpcb *inp, struct mbuf *m, struct mbuf **mp,
1177     int *v4only)
1178 {
1179 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
1180 
1181 #ifdef SO_TIMESTAMP
1182 	if ((inp->inp_socket->so_options & SO_TIMESTAMP) != 0) {
1183 		union {
1184 			struct timeval tv;
1185 			struct bintime bt;
1186 			struct timespec ts;
1187 		} t;
1188 		struct bintime boottimebin, bt1;
1189 		struct timespec ts1;
1190 		bool stamped;
1191 
1192 		stamped = false;
1193 		switch (inp->inp_socket->so_ts_clock) {
1194 		case SO_TS_REALTIME_MICRO:
1195 			if ((m->m_flags & (M_PKTHDR | M_TSTMP)) == (M_PKTHDR |
1196 			    M_TSTMP)) {
1197 				mbuf_tstmp2timespec(m, &ts1);
1198 				timespec2bintime(&ts1, &bt1);
1199 				getboottimebin(&boottimebin);
1200 				bintime_add(&bt1, &boottimebin);
1201 				bintime2timeval(&bt1, &t.tv);
1202 			} else {
1203 				microtime(&t.tv);
1204 			}
1205 			*mp = sbcreatecontrol(&t.tv, sizeof(t.tv),
1206 			    SCM_TIMESTAMP, SOL_SOCKET, M_NOWAIT);
1207 			if (*mp != NULL) {
1208 				mp = &(*mp)->m_next;
1209 				stamped = true;
1210 			}
1211 			break;
1212 
1213 		case SO_TS_BINTIME:
1214 			if ((m->m_flags & (M_PKTHDR | M_TSTMP)) == (M_PKTHDR |
1215 			    M_TSTMP)) {
1216 				mbuf_tstmp2timespec(m, &ts1);
1217 				timespec2bintime(&ts1, &t.bt);
1218 				getboottimebin(&boottimebin);
1219 				bintime_add(&t.bt, &boottimebin);
1220 			} else {
1221 				bintime(&t.bt);
1222 			}
1223 			*mp = sbcreatecontrol(&t.bt, sizeof(t.bt), SCM_BINTIME,
1224 			    SOL_SOCKET, M_NOWAIT);
1225 			if (*mp != NULL) {
1226 				mp = &(*mp)->m_next;
1227 				stamped = true;
1228 			}
1229 			break;
1230 
1231 		case SO_TS_REALTIME:
1232 			if ((m->m_flags & (M_PKTHDR | M_TSTMP)) == (M_PKTHDR |
1233 			    M_TSTMP)) {
1234 				mbuf_tstmp2timespec(m, &t.ts);
1235 				getboottimebin(&boottimebin);
1236 				bintime2timespec(&boottimebin, &ts1);
1237 				timespecadd(&t.ts, &ts1, &t.ts);
1238 			} else {
1239 				nanotime(&t.ts);
1240 			}
1241 			*mp = sbcreatecontrol(&t.ts, sizeof(t.ts),
1242 			    SCM_REALTIME, SOL_SOCKET, M_NOWAIT);
1243 			if (*mp != NULL) {
1244 				mp = &(*mp)->m_next;
1245 				stamped = true;
1246 			}
1247 			break;
1248 
1249 		case SO_TS_MONOTONIC:
1250 			if ((m->m_flags & (M_PKTHDR | M_TSTMP)) == (M_PKTHDR |
1251 			    M_TSTMP))
1252 				mbuf_tstmp2timespec(m, &t.ts);
1253 			else
1254 				nanouptime(&t.ts);
1255 			*mp = sbcreatecontrol(&t.ts, sizeof(t.ts),
1256 			    SCM_MONOTONIC, SOL_SOCKET, M_NOWAIT);
1257 			if (*mp != NULL) {
1258 				mp = &(*mp)->m_next;
1259 				stamped = true;
1260 			}
1261 			break;
1262 
1263 		default:
1264 			panic("unknown (corrupted) so_ts_clock");
1265 		}
1266 		if (stamped && (m->m_flags & (M_PKTHDR | M_TSTMP)) ==
1267 		    (M_PKTHDR | M_TSTMP)) {
1268 			struct sock_timestamp_info sti;
1269 
1270 			bzero(&sti, sizeof(sti));
1271 			sti.st_info_flags = ST_INFO_HW;
1272 			if ((m->m_flags & M_TSTMP_HPREC) != 0)
1273 				sti.st_info_flags |= ST_INFO_HW_HPREC;
1274 			*mp = sbcreatecontrol(&sti, sizeof(sti), SCM_TIME_INFO,
1275 			    SOL_SOCKET, M_NOWAIT);
1276 			if (*mp != NULL)
1277 				mp = &(*mp)->m_next;
1278 		}
1279 	}
1280 #endif
1281 
1282 #define IS2292(inp, x, y)	(((inp)->inp_flags & IN6P_RFC2292) ? (x) : (y))
1283 	/* RFC 2292 sec. 5 */
1284 	if ((inp->inp_flags & IN6P_PKTINFO) != 0) {
1285 		struct in6_pktinfo pi6;
1286 
1287 		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
1288 #ifdef INET
1289 			struct ip *ip;
1290 
1291 			ip = mtod(m, struct ip *);
1292 			pi6.ipi6_addr.s6_addr32[0] = 0;
1293 			pi6.ipi6_addr.s6_addr32[1] = 0;
1294 			pi6.ipi6_addr.s6_addr32[2] = IPV6_ADDR_INT32_SMP;
1295 			pi6.ipi6_addr.s6_addr32[3] = ip->ip_dst.s_addr;
1296 #else
1297 			/* We won't hit this code */
1298 			bzero(&pi6.ipi6_addr, sizeof(struct in6_addr));
1299 #endif
1300 		} else {
1301 			bcopy(&ip6->ip6_dst, &pi6.ipi6_addr, sizeof(struct in6_addr));
1302 			in6_clearscope(&pi6.ipi6_addr);	/* XXX */
1303 		}
1304 		pi6.ipi6_ifindex =
1305 		    (m && m->m_pkthdr.rcvif) ? m->m_pkthdr.rcvif->if_index : 0;
1306 
1307 		*mp = sbcreatecontrol(&pi6, sizeof(struct in6_pktinfo),
1308 		    IS2292(inp, IPV6_2292PKTINFO, IPV6_PKTINFO), IPPROTO_IPV6,
1309 		    M_NOWAIT);
1310 		if (*mp)
1311 			mp = &(*mp)->m_next;
1312 	}
1313 
1314 	if ((inp->inp_flags & IN6P_HOPLIMIT) != 0) {
1315 		int hlim;
1316 
1317 		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
1318 #ifdef INET
1319 			struct ip *ip;
1320 
1321 			ip = mtod(m, struct ip *);
1322 			hlim = ip->ip_ttl;
1323 #else
1324 			/* We won't hit this code */
1325 			hlim = 0;
1326 #endif
1327 		} else {
1328 			hlim = ip6->ip6_hlim & 0xff;
1329 		}
1330 		*mp = sbcreatecontrol(&hlim, sizeof(int),
1331 		    IS2292(inp, IPV6_2292HOPLIMIT, IPV6_HOPLIMIT),
1332 		    IPPROTO_IPV6, M_NOWAIT);
1333 		if (*mp)
1334 			mp = &(*mp)->m_next;
1335 	}
1336 
1337 	if ((inp->inp_flags & IN6P_TCLASS) != 0) {
1338 		int tclass;
1339 
1340 		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
1341 #ifdef INET
1342 			struct ip *ip;
1343 
1344 			ip = mtod(m, struct ip *);
1345 			tclass = ip->ip_tos;
1346 #else
1347 			/* We won't hit this code */
1348 			tclass = 0;
1349 #endif
1350 		} else {
1351 			u_int32_t flowinfo;
1352 
1353 			flowinfo = (u_int32_t)ntohl(ip6->ip6_flow & IPV6_FLOWINFO_MASK);
1354 			flowinfo >>= 20;
1355 			tclass = flowinfo & 0xff;
1356 		}
1357 		*mp = sbcreatecontrol(&tclass, sizeof(int), IPV6_TCLASS,
1358 		    IPPROTO_IPV6, M_NOWAIT);
1359 		if (*mp)
1360 			mp = &(*mp)->m_next;
1361 	}
1362 
1363 	if (v4only != NULL) {
1364 		if ((ip6->ip6_vfc & IPV6_VERSION_MASK) != IPV6_VERSION) {
1365 			*v4only = 1;
1366 		} else {
1367 			*v4only = 0;
1368 		}
1369 	}
1370 
1371 	return (mp);
1372 }
1373 
1374 void
1375 ip6_savecontrol(struct inpcb *inp, struct mbuf *m, struct mbuf **mp)
1376 {
1377 	struct ip6_hdr *ip6;
1378 	int v4only = 0;
1379 
1380 	mp = ip6_savecontrol_v4(inp, m, mp, &v4only);
1381 	if (v4only)
1382 		return;
1383 
1384 	ip6 = mtod(m, struct ip6_hdr *);
1385 	/*
1386 	 * IPV6_HOPOPTS socket option.  Recall that we required super-user
1387 	 * privilege for the option (see ip6_ctloutput), but it might be too
1388 	 * strict, since there might be some hop-by-hop options which can be
1389 	 * returned to normal user.
1390 	 * See also RFC 2292 section 6 (or RFC 3542 section 8).
1391 	 */
1392 	if ((inp->inp_flags & IN6P_HOPOPTS) != 0) {
1393 		/*
1394 		 * Check if a hop-by-hop options header is contatined in the
1395 		 * received packet, and if so, store the options as ancillary
1396 		 * data. Note that a hop-by-hop options header must be
1397 		 * just after the IPv6 header, which is assured through the
1398 		 * IPv6 input processing.
1399 		 */
1400 		if (ip6->ip6_nxt == IPPROTO_HOPOPTS) {
1401 			struct ip6_hbh *hbh;
1402 			u_int hbhlen;
1403 
1404 			hbh = (struct ip6_hbh *)(ip6 + 1);
1405 			hbhlen = (hbh->ip6h_len + 1) << 3;
1406 
1407 			/*
1408 			 * XXX: We copy the whole header even if a
1409 			 * jumbo payload option is included, the option which
1410 			 * is to be removed before returning according to
1411 			 * RFC2292.
1412 			 * Note: this constraint is removed in RFC3542
1413 			 */
1414 			*mp = sbcreatecontrol(hbh, hbhlen,
1415 			    IS2292(inp, IPV6_2292HOPOPTS, IPV6_HOPOPTS),
1416 			    IPPROTO_IPV6, M_NOWAIT);
1417 			if (*mp)
1418 				mp = &(*mp)->m_next;
1419 		}
1420 	}
1421 
1422 	if ((inp->inp_flags & (IN6P_RTHDR | IN6P_DSTOPTS)) != 0) {
1423 		int nxt = ip6->ip6_nxt, off = sizeof(struct ip6_hdr);
1424 
1425 		/*
1426 		 * Search for destination options headers or routing
1427 		 * header(s) through the header chain, and stores each
1428 		 * header as ancillary data.
1429 		 * Note that the order of the headers remains in
1430 		 * the chain of ancillary data.
1431 		 */
1432 		while (1) {	/* is explicit loop prevention necessary? */
1433 			struct ip6_ext *ip6e = NULL;
1434 			u_int elen;
1435 
1436 			/*
1437 			 * if it is not an extension header, don't try to
1438 			 * pull it from the chain.
1439 			 */
1440 			switch (nxt) {
1441 			case IPPROTO_DSTOPTS:
1442 			case IPPROTO_ROUTING:
1443 			case IPPROTO_HOPOPTS:
1444 			case IPPROTO_AH: /* is it possible? */
1445 				break;
1446 			default:
1447 				goto loopend;
1448 			}
1449 
1450 			if (off + sizeof(*ip6e) > m->m_len)
1451 				goto loopend;
1452 			ip6e = (struct ip6_ext *)(mtod(m, caddr_t) + off);
1453 			if (nxt == IPPROTO_AH)
1454 				elen = (ip6e->ip6e_len + 2) << 2;
1455 			else
1456 				elen = (ip6e->ip6e_len + 1) << 3;
1457 			if (off + elen > m->m_len)
1458 				goto loopend;
1459 
1460 			switch (nxt) {
1461 			case IPPROTO_DSTOPTS:
1462 				if (!(inp->inp_flags & IN6P_DSTOPTS))
1463 					break;
1464 
1465 				*mp = sbcreatecontrol(ip6e, elen,
1466 				    IS2292(inp, IPV6_2292DSTOPTS, IPV6_DSTOPTS),
1467 				    IPPROTO_IPV6, M_NOWAIT);
1468 				if (*mp)
1469 					mp = &(*mp)->m_next;
1470 				break;
1471 			case IPPROTO_ROUTING:
1472 				if (!(inp->inp_flags & IN6P_RTHDR))
1473 					break;
1474 
1475 				*mp = sbcreatecontrol(ip6e, elen,
1476 				    IS2292(inp, IPV6_2292RTHDR, IPV6_RTHDR),
1477 				    IPPROTO_IPV6, M_NOWAIT);
1478 				if (*mp)
1479 					mp = &(*mp)->m_next;
1480 				break;
1481 			case IPPROTO_HOPOPTS:
1482 			case IPPROTO_AH: /* is it possible? */
1483 				break;
1484 
1485 			default:
1486 				/*
1487 				 * other cases have been filtered in the above.
1488 				 * none will visit this case.  here we supply
1489 				 * the code just in case (nxt overwritten or
1490 				 * other cases).
1491 				 */
1492 				goto loopend;
1493 			}
1494 
1495 			/* proceed with the next header. */
1496 			off += elen;
1497 			nxt = ip6e->ip6e_nxt;
1498 			ip6e = NULL;
1499 		}
1500 	  loopend:
1501 		;
1502 	}
1503 
1504 	if (inp->inp_flags2 & INP_RECVFLOWID) {
1505 		uint32_t flowid, flow_type;
1506 
1507 		flowid = m->m_pkthdr.flowid;
1508 		flow_type = M_HASHTYPE_GET(m);
1509 
1510 		/*
1511 		 * XXX should handle the failure of one or the
1512 		 * other - don't populate both?
1513 		 */
1514 		*mp = sbcreatecontrol(&flowid, sizeof(uint32_t), IPV6_FLOWID,
1515 		    IPPROTO_IPV6, M_NOWAIT);
1516 		if (*mp)
1517 			mp = &(*mp)->m_next;
1518 		*mp = sbcreatecontrol(&flow_type, sizeof(uint32_t),
1519 		    IPV6_FLOWTYPE, IPPROTO_IPV6, M_NOWAIT);
1520 		if (*mp)
1521 			mp = &(*mp)->m_next;
1522 	}
1523 
1524 #ifdef	RSS
1525 	if (inp->inp_flags2 & INP_RECVRSSBUCKETID) {
1526 		uint32_t flowid, flow_type;
1527 		uint32_t rss_bucketid;
1528 
1529 		flowid = m->m_pkthdr.flowid;
1530 		flow_type = M_HASHTYPE_GET(m);
1531 
1532 		if (rss_hash2bucket(flowid, flow_type, &rss_bucketid) == 0) {
1533 			*mp = sbcreatecontrol(&rss_bucketid, sizeof(uint32_t),
1534 			    IPV6_RSSBUCKETID, IPPROTO_IPV6, M_NOWAIT);
1535 			if (*mp)
1536 				mp = &(*mp)->m_next;
1537 		}
1538 	}
1539 #endif
1540 
1541 }
1542 #undef IS2292
1543 
1544 void
1545 ip6_notify_pmtu(struct inpcb *inp, struct sockaddr_in6 *dst, u_int32_t mtu)
1546 {
1547 	struct socket *so;
1548 	struct mbuf *m_mtu;
1549 	struct ip6_mtuinfo mtuctl;
1550 
1551 	KASSERT(inp != NULL, ("%s: inp == NULL", __func__));
1552 	/*
1553 	 * Notify the error by sending IPV6_PATHMTU ancillary data if
1554 	 * application wanted to know the MTU value.
1555 	 * NOTE: we notify disconnected sockets, because some udp
1556 	 * applications keep sending sockets disconnected.
1557 	 * NOTE: our implementation doesn't notify connected sockets that has
1558 	 * foreign address that is different than given destination addresses
1559 	 * (this is permitted by RFC 3542).
1560 	 */
1561 	if ((inp->inp_flags & IN6P_MTU) == 0 || (
1562 	    !IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
1563 	    !IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &dst->sin6_addr)))
1564 		return;
1565 
1566 	mtuctl.ip6m_mtu = mtu;
1567 	mtuctl.ip6m_addr = *dst;
1568 	if (sa6_recoverscope(&mtuctl.ip6m_addr))
1569 		return;
1570 
1571 	if ((m_mtu = sbcreatecontrol(&mtuctl, sizeof(mtuctl), IPV6_PATHMTU,
1572 	    IPPROTO_IPV6, M_NOWAIT)) == NULL)
1573 		return;
1574 
1575 	so =  inp->inp_socket;
1576 	if (sbappendaddr(&so->so_rcv, (struct sockaddr *)dst, NULL, m_mtu)
1577 	    == 0) {
1578 		soroverflow(so);
1579 		m_freem(m_mtu);
1580 		/* XXX: should count statistics */
1581 	} else
1582 		sorwakeup(so);
1583 }
1584 
1585 /*
1586  * Get pointer to the previous header followed by the header
1587  * currently processed.
1588  */
1589 int
1590 ip6_get_prevhdr(const struct mbuf *m, int off)
1591 {
1592 	struct ip6_ext ip6e;
1593 	struct ip6_hdr *ip6;
1594 	int len, nlen, nxt;
1595 
1596 	if (off == sizeof(struct ip6_hdr))
1597 		return (offsetof(struct ip6_hdr, ip6_nxt));
1598 	if (off < sizeof(struct ip6_hdr))
1599 		panic("%s: off < sizeof(struct ip6_hdr)", __func__);
1600 
1601 	ip6 = mtod(m, struct ip6_hdr *);
1602 	nxt = ip6->ip6_nxt;
1603 	len = sizeof(struct ip6_hdr);
1604 	nlen = 0;
1605 	while (len < off) {
1606 		m_copydata(m, len, sizeof(ip6e), (caddr_t)&ip6e);
1607 		switch (nxt) {
1608 		case IPPROTO_FRAGMENT:
1609 			nlen = sizeof(struct ip6_frag);
1610 			break;
1611 		case IPPROTO_AH:
1612 			nlen = (ip6e.ip6e_len + 2) << 2;
1613 			break;
1614 		default:
1615 			nlen = (ip6e.ip6e_len + 1) << 3;
1616 		}
1617 		len += nlen;
1618 		nxt = ip6e.ip6e_nxt;
1619 	}
1620 	return (len - nlen);
1621 }
1622 
1623 /*
1624  * get next header offset.  m will be retained.
1625  */
1626 int
1627 ip6_nexthdr(const struct mbuf *m, int off, int proto, int *nxtp)
1628 {
1629 	struct ip6_hdr ip6;
1630 	struct ip6_ext ip6e;
1631 	struct ip6_frag fh;
1632 
1633 	/* just in case */
1634 	if (m == NULL)
1635 		panic("ip6_nexthdr: m == NULL");
1636 	if ((m->m_flags & M_PKTHDR) == 0 || m->m_pkthdr.len < off)
1637 		return -1;
1638 
1639 	switch (proto) {
1640 	case IPPROTO_IPV6:
1641 		if (m->m_pkthdr.len < off + sizeof(ip6))
1642 			return -1;
1643 		m_copydata(m, off, sizeof(ip6), (caddr_t)&ip6);
1644 		if (nxtp)
1645 			*nxtp = ip6.ip6_nxt;
1646 		off += sizeof(ip6);
1647 		return off;
1648 
1649 	case IPPROTO_FRAGMENT:
1650 		/*
1651 		 * terminate parsing if it is not the first fragment,
1652 		 * it does not make sense to parse through it.
1653 		 */
1654 		if (m->m_pkthdr.len < off + sizeof(fh))
1655 			return -1;
1656 		m_copydata(m, off, sizeof(fh), (caddr_t)&fh);
1657 		/* IP6F_OFF_MASK = 0xfff8(BigEndian), 0xf8ff(LittleEndian) */
1658 		if (fh.ip6f_offlg & IP6F_OFF_MASK)
1659 			return -1;
1660 		if (nxtp)
1661 			*nxtp = fh.ip6f_nxt;
1662 		off += sizeof(struct ip6_frag);
1663 		return off;
1664 
1665 	case IPPROTO_AH:
1666 		if (m->m_pkthdr.len < off + sizeof(ip6e))
1667 			return -1;
1668 		m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
1669 		if (nxtp)
1670 			*nxtp = ip6e.ip6e_nxt;
1671 		off += (ip6e.ip6e_len + 2) << 2;
1672 		return off;
1673 
1674 	case IPPROTO_HOPOPTS:
1675 	case IPPROTO_ROUTING:
1676 	case IPPROTO_DSTOPTS:
1677 		if (m->m_pkthdr.len < off + sizeof(ip6e))
1678 			return -1;
1679 		m_copydata(m, off, sizeof(ip6e), (caddr_t)&ip6e);
1680 		if (nxtp)
1681 			*nxtp = ip6e.ip6e_nxt;
1682 		off += (ip6e.ip6e_len + 1) << 3;
1683 		return off;
1684 
1685 	case IPPROTO_NONE:
1686 	case IPPROTO_ESP:
1687 	case IPPROTO_IPCOMP:
1688 		/* give up */
1689 		return -1;
1690 
1691 	default:
1692 		return -1;
1693 	}
1694 
1695 	/* NOTREACHED */
1696 }
1697 
1698 /*
1699  * get offset for the last header in the chain.  m will be kept untainted.
1700  */
1701 int
1702 ip6_lasthdr(const struct mbuf *m, int off, int proto, int *nxtp)
1703 {
1704 	int newoff;
1705 	int nxt;
1706 
1707 	if (!nxtp) {
1708 		nxt = -1;
1709 		nxtp = &nxt;
1710 	}
1711 	while (1) {
1712 		newoff = ip6_nexthdr(m, off, proto, nxtp);
1713 		if (newoff < 0)
1714 			return off;
1715 		else if (newoff < off)
1716 			return -1;	/* invalid */
1717 		else if (newoff == off)
1718 			return newoff;
1719 
1720 		off = newoff;
1721 		proto = *nxtp;
1722 	}
1723 }
1724