xref: /freebsd/sys/netipsec/ipsec_input.c (revision 88ba5e8955518c1e032eafbce27d548eaf5a59ea)
1 /*	$OpenBSD: ipsec_input.c,v 1.63 2003/02/20 18:35:43 deraadt Exp $	*/
2 /*-
3  * The authors of this code are John Ioannidis (ji@tla.org),
4  * Angelos D. Keromytis (kermit@csd.uch.gr) and
5  * Niels Provos (provos@physnet.uni-hamburg.de).
6  *
7  * This code was written by John Ioannidis for BSD/OS in Athens, Greece,
8  * in November 1995.
9  *
10  * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
11  * by Angelos D. Keromytis.
12  *
13  * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
14  * and Niels Provos.
15  *
16  * Additional features in 1999 by Angelos D. Keromytis.
17  *
18  * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
19  * Angelos D. Keromytis and Niels Provos.
20  * Copyright (c) 2001, Angelos D. Keromytis.
21  * Copyright (c) 2016 Andrey V. Elsukov <ae@FreeBSD.org>
22  *
23  * Permission to use, copy, and modify this software with or without fee
24  * is hereby granted, provided that this entire notice is included in
25  * all copies of any software which is or includes a copy or
26  * modification of this software.
27  * You may use this code under the GNU public license if you so wish. Please
28  * contribute changes back to the authors under this freer than GPL license
29  * so that we may further the use of strong encryption without limitations to
30  * all.
31  *
32  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
33  * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
34  * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
35  * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
36  * PURPOSE.
37  */
38 
39 /*
40  * IPsec input processing.
41  */
42 
43 #include <sys/cdefs.h>
44 __FBSDID("$FreeBSD$");
45 
46 #include "opt_inet.h"
47 #include "opt_inet6.h"
48 #include "opt_ipsec.h"
49 
50 #include <sys/param.h>
51 #include <sys/systm.h>
52 #include <sys/malloc.h>
53 #include <sys/mbuf.h>
54 #include <sys/domain.h>
55 #include <sys/protosw.h>
56 #include <sys/socket.h>
57 #include <sys/errno.h>
58 #include <sys/hhook.h>
59 #include <sys/syslog.h>
60 
61 #include <net/if.h>
62 #include <net/if_var.h>
63 #include <net/if_enc.h>
64 #include <net/netisr.h>
65 #include <net/vnet.h>
66 
67 #include <netinet/in.h>
68 #include <netinet/in_systm.h>
69 #include <netinet/ip.h>
70 #include <netinet/ip_var.h>
71 #include <netinet/ip_icmp.h>
72 #include <netinet/in_var.h>
73 #include <netinet/tcp_var.h>
74 
75 #include <netinet/ip6.h>
76 #ifdef INET6
77 #include <netinet6/ip6_var.h>
78 #endif
79 #include <netinet/in_pcb.h>
80 #ifdef INET6
81 #include <netinet/icmp6.h>
82 #endif
83 
84 #include <netipsec/ipsec.h>
85 #ifdef INET6
86 #include <netipsec/ipsec6.h>
87 #endif
88 #include <netipsec/ah_var.h>
89 #include <netipsec/esp.h>
90 #include <netipsec/esp_var.h>
91 #include <netipsec/ipcomp_var.h>
92 
93 #include <netipsec/key.h>
94 #include <netipsec/keydb.h>
95 #include <netipsec/key_debug.h>
96 
97 #include <netipsec/xform.h>
98 #include <netinet6/ip6protosw.h>
99 
100 #include <machine/in_cksum.h>
101 #include <machine/stdarg.h>
102 
103 #define	IPSEC_ISTAT(proto, name)	do {	\
104 	if ((proto) == IPPROTO_ESP)		\
105 		ESPSTAT_INC(esps_##name);	\
106 	else if ((proto) == IPPROTO_AH)		\
107 		AHSTAT_INC(ahs_##name);		\
108 	else					\
109 		IPCOMPSTAT_INC(ipcomps_##name);	\
110 } while (0)
111 
112 /*
113  * ipsec_common_input gets called when an IPsec-protected packet
114  * is received by IPv4 or IPv6.  Its job is to find the right SA
115  * and call the appropriate transform.  The transform callback
116  * takes care of further processing (like ingress filtering).
117  */
118 static int
119 ipsec_common_input(struct mbuf *m, int skip, int protoff, int af, int sproto)
120 {
121 	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
122 	union sockaddr_union dst_address;
123 	struct secasvar *sav;
124 	uint32_t spi;
125 	int error;
126 
127 	IPSEC_ISTAT(sproto, input);
128 
129 	IPSEC_ASSERT(m != NULL, ("null packet"));
130 
131 	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
132 		sproto == IPPROTO_IPCOMP,
133 		("unexpected security protocol %u", sproto));
134 
135 	if ((sproto == IPPROTO_ESP && !V_esp_enable) ||
136 	    (sproto == IPPROTO_AH && !V_ah_enable) ||
137 	    (sproto == IPPROTO_IPCOMP && !V_ipcomp_enable)) {
138 		m_freem(m);
139 		IPSEC_ISTAT(sproto, pdrops);
140 		return EOPNOTSUPP;
141 	}
142 
143 	if (m->m_pkthdr.len - skip < 2 * sizeof (u_int32_t)) {
144 		m_freem(m);
145 		IPSEC_ISTAT(sproto, hdrops);
146 		DPRINTF(("%s: packet too small\n", __func__));
147 		return EINVAL;
148 	}
149 
150 	/* Retrieve the SPI from the relevant IPsec header */
151 	if (sproto == IPPROTO_ESP)
152 		m_copydata(m, skip, sizeof(u_int32_t), (caddr_t) &spi);
153 	else if (sproto == IPPROTO_AH)
154 		m_copydata(m, skip + sizeof(u_int32_t), sizeof(u_int32_t),
155 		    (caddr_t) &spi);
156 	else if (sproto == IPPROTO_IPCOMP) {
157 		u_int16_t cpi;
158 		m_copydata(m, skip + sizeof(u_int16_t), sizeof(u_int16_t),
159 		    (caddr_t) &cpi);
160 		spi = ntohl(htons(cpi));
161 	}
162 
163 	/*
164 	 * Find the SA and (indirectly) call the appropriate
165 	 * kernel crypto routine. The resulting mbuf chain is a valid
166 	 * IP packet ready to go through input processing.
167 	 */
168 	bzero(&dst_address, sizeof (dst_address));
169 	dst_address.sa.sa_family = af;
170 	switch (af) {
171 #ifdef INET
172 	case AF_INET:
173 		dst_address.sin.sin_len = sizeof(struct sockaddr_in);
174 		m_copydata(m, offsetof(struct ip, ip_dst),
175 		    sizeof(struct in_addr),
176 		    (caddr_t) &dst_address.sin.sin_addr);
177 		break;
178 #endif /* INET */
179 #ifdef INET6
180 	case AF_INET6:
181 		dst_address.sin6.sin6_len = sizeof(struct sockaddr_in6);
182 		m_copydata(m, offsetof(struct ip6_hdr, ip6_dst),
183 		    sizeof(struct in6_addr),
184 		    (caddr_t) &dst_address.sin6.sin6_addr);
185 		/* We keep addresses in SADB without embedded scope id */
186 		if (IN6_IS_SCOPE_LINKLOCAL(&dst_address.sin6.sin6_addr)) {
187 			/* XXX: sa6_recoverscope() */
188 			dst_address.sin6.sin6_scope_id =
189 			    ntohs(dst_address.sin6.sin6_addr.s6_addr16[1]);
190 			dst_address.sin6.sin6_addr.s6_addr16[1] = 0;
191 		}
192 		break;
193 #endif /* INET6 */
194 	default:
195 		DPRINTF(("%s: unsupported protocol family %u\n", __func__, af));
196 		m_freem(m);
197 		IPSEC_ISTAT(sproto, nopf);
198 		return EPFNOSUPPORT;
199 	}
200 
201 	/* NB: only pass dst since key_allocsa follows RFC2401 */
202 	sav = key_allocsa(&dst_address, sproto, spi);
203 	if (sav == NULL) {
204 		DPRINTF(("%s: no key association found for SA %s/%08lx/%u\n",
205 		    __func__, ipsec_address(&dst_address, buf, sizeof(buf)),
206 		    (u_long) ntohl(spi), sproto));
207 		IPSEC_ISTAT(sproto, notdb);
208 		m_freem(m);
209 		return ENOENT;
210 	}
211 
212 	if (sav->tdb_xform == NULL) {
213 		DPRINTF(("%s: attempted to use uninitialized SA %s/%08lx/%u\n",
214 		    __func__, ipsec_address(&dst_address, buf, sizeof(buf)),
215 		    (u_long) ntohl(spi), sproto));
216 		IPSEC_ISTAT(sproto, noxform);
217 		key_freesav(&sav);
218 		m_freem(m);
219 		return ENXIO;
220 	}
221 
222 	/*
223 	 * Call appropriate transform and return -- callback takes care of
224 	 * everything else.
225 	 */
226 	error = (*sav->tdb_xform->xf_input)(m, sav, skip, protoff);
227 	return (error);
228 }
229 
230 #ifdef INET
231 extern struct protosw inetsw[];
232 
233 /*
234  * IPSEC_INPUT() method implementation for IPv4.
235  *  0 - Permitted by inbound security policy for further processing.
236  *  EACCES - Forbidden by inbound security policy.
237  *  EINPROGRESS - consumed by IPsec.
238  */
239 int
240 ipsec4_input(struct mbuf *m, int offset, int proto)
241 {
242 
243 	switch (proto) {
244 	case IPPROTO_AH:
245 	case IPPROTO_ESP:
246 	case IPPROTO_IPCOMP:
247 		/* Do inbound IPsec processing for AH/ESP/IPCOMP */
248 		ipsec_common_input(m, offset,
249 		    offsetof(struct ip, ip_p), AF_INET, proto);
250 		return (EINPROGRESS); /* mbuf consumed by IPsec */
251 	default:
252 		/*
253 		 * Protocols with further headers get their IPsec treatment
254 		 * within the protocol specific processing.
255 		 */
256 		if ((inetsw[ip_protox[proto]].pr_flags & PR_LASTHDR) == 0)
257 			return (0);
258 		/* FALLTHROUGH */
259 	};
260 	/*
261 	 * Enforce IPsec policy checking if we are seeing last header.
262 	 */
263 	if (ipsec4_in_reject(m, NULL) != 0) {
264 		/* Forbidden by inbound security policy */
265 		m_freem(m);
266 		return (EACCES);
267 	}
268 	return (0);
269 }
270 
271 int
272 ipsec4_ctlinput(int code, struct sockaddr *sa, void *v)
273 {
274 	struct in_conninfo inc;
275 	struct secasvar *sav;
276 	struct icmp *icp;
277 	struct ip *ip = v;
278 	uint32_t pmtu, spi;
279 
280 	if (code != PRC_MSGSIZE || ip == NULL)
281 		return (EINVAL);
282 	if (sa->sa_family != AF_INET ||
283 	    sa->sa_len != sizeof(struct sockaddr_in))
284 		return (EAFNOSUPPORT);
285 
286 	icp = __containerof(ip, struct icmp, icmp_ip);
287 	pmtu = ntohs(icp->icmp_nextmtu);
288 
289 	if (pmtu < V_ip4_ipsec_min_pmtu)
290 		return (EINVAL);
291 
292 	memcpy(&spi, (caddr_t)ip + (ip->ip_hl << 2), sizeof(spi));
293 	sav = key_allocsa((union sockaddr_union *)sa, ip->ip_p, spi);
294 	if (sav == NULL)
295 		return (ENOENT);
296 
297 	key_freesav(&sav);
298 
299 	memset(&inc, 0, sizeof(inc));
300 	inc.inc_faddr = satosin(sa)->sin_addr;
301 	tcp_hc_updatemtu(&inc, pmtu);
302 	return (0);
303 }
304 
305 /*
306  * IPsec input callback for INET protocols.
307  * This routine is called as the transform callback.
308  * Takes care of filtering and other sanity checks on
309  * the processed packet.
310  */
311 int
312 ipsec4_common_input_cb(struct mbuf *m, struct secasvar *sav, int skip,
313     int protoff)
314 {
315 	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
316 	struct epoch_tracker et;
317 	struct ipsec_ctx_data ctx;
318 	struct xform_history *xh;
319 	struct secasindex *saidx;
320 	struct m_tag *mtag;
321 	struct ip *ip;
322 	int error, prot, af, sproto, isr_prot;
323 
324 	IPSEC_ASSERT(sav != NULL, ("null SA"));
325 	IPSEC_ASSERT(sav->sah != NULL, ("null SAH"));
326 	saidx = &sav->sah->saidx;
327 	af = saidx->dst.sa.sa_family;
328 	IPSEC_ASSERT(af == AF_INET, ("unexpected af %u", af));
329 	sproto = saidx->proto;
330 	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
331 		sproto == IPPROTO_IPCOMP,
332 		("unexpected security protocol %u", sproto));
333 
334 	if (skip != 0) {
335 		/*
336 		 * Fix IPv4 header
337 		 */
338 		if (m->m_len < skip && (m = m_pullup(m, skip)) == NULL) {
339 			DPRINTF(("%s: processing failed for SA %s/%08lx\n",
340 			    __func__, ipsec_address(&sav->sah->saidx.dst,
341 			    buf, sizeof(buf)), (u_long) ntohl(sav->spi)));
342 			IPSEC_ISTAT(sproto, hdrops);
343 			error = ENOBUFS;
344 			goto bad;
345 		}
346 
347 		ip = mtod(m, struct ip *);
348 		ip->ip_len = htons(m->m_pkthdr.len);
349 		ip->ip_sum = 0;
350 		ip->ip_sum = in_cksum(m, ip->ip_hl << 2);
351 	} else {
352 		ip = mtod(m, struct ip *);
353 	}
354 	prot = ip->ip_p;
355 	/*
356 	 * Check that we have NAT-T enabled and apply transport mode
357 	 * decapsulation NAT procedure (RFC3948).
358 	 * Do this before invoking into the PFIL.
359 	 */
360 	if (sav->natt != NULL &&
361 	    (prot == IPPROTO_UDP || prot == IPPROTO_TCP))
362 		udp_ipsec_adjust_cksum(m, sav, prot, skip);
363 
364 	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, AF_INET, IPSEC_ENC_BEFORE);
365 	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
366 		goto bad;
367 	ip = mtod(m, struct ip *);	/* update pointer */
368 
369 	/* IP-in-IP encapsulation */
370 	if (prot == IPPROTO_IPIP &&
371 	    saidx->mode != IPSEC_MODE_TRANSPORT) {
372 		if (m->m_pkthdr.len - skip < sizeof(struct ip)) {
373 			IPSEC_ISTAT(sproto, hdrops);
374 			error = EINVAL;
375 			goto bad;
376 		}
377 		/* enc0: strip outer IPv4 header */
378 		m_striphdr(m, 0, ip->ip_hl << 2);
379 	}
380 #ifdef INET6
381 	/* IPv6-in-IP encapsulation. */
382 	else if (prot == IPPROTO_IPV6 &&
383 	    saidx->mode != IPSEC_MODE_TRANSPORT) {
384 		if (m->m_pkthdr.len - skip < sizeof(struct ip6_hdr)) {
385 			IPSEC_ISTAT(sproto, hdrops);
386 			error = EINVAL;
387 			goto bad;
388 		}
389 		/* enc0: strip IPv4 header, keep IPv6 header only */
390 		m_striphdr(m, 0, ip->ip_hl << 2);
391 	}
392 #endif /* INET6 */
393 	else if (prot != IPPROTO_IPV6 && saidx->mode == IPSEC_MODE_ANY) {
394 		/*
395 		 * When mode is wildcard, inner protocol is IPv6 and
396 		 * we have no INET6 support - drop this packet a bit later.
397 		 * In other cases we assume transport mode. Set prot to
398 		 * correctly choose netisr.
399 		 */
400 		prot = IPPROTO_IPIP;
401 	}
402 
403 	/*
404 	 * Record what we've done to the packet (under what SA it was
405 	 * processed).
406 	 */
407 	if (sproto != IPPROTO_IPCOMP) {
408 		mtag = m_tag_get(PACKET_TAG_IPSEC_IN_DONE,
409 		    sizeof(struct xform_history), M_NOWAIT);
410 		if (mtag == NULL) {
411 			DPRINTF(("%s: failed to get tag\n", __func__));
412 			IPSEC_ISTAT(sproto, hdrops);
413 			error = ENOMEM;
414 			goto bad;
415 		}
416 
417 		xh = (struct xform_history *)(mtag + 1);
418 		bcopy(&saidx->dst, &xh->dst, saidx->dst.sa.sa_len);
419 		xh->spi = sav->spi;
420 		xh->proto = sproto;
421 		xh->mode = saidx->mode;
422 		m_tag_prepend(m, mtag);
423 	}
424 
425 	key_sa_recordxfer(sav, m);		/* record data transfer */
426 
427 	/*
428 	 * In transport mode requeue decrypted mbuf back to IPv4 protocol
429 	 * handler. This is necessary to correctly expose rcvif.
430 	 */
431 	if (saidx->mode == IPSEC_MODE_TRANSPORT)
432 		prot = IPPROTO_IPIP;
433 	/*
434 	 * Re-dispatch via software interrupt.
435 	 */
436 	switch (prot) {
437 	case IPPROTO_IPIP:
438 		isr_prot = NETISR_IP;
439 		af = AF_INET;
440 		break;
441 #ifdef INET6
442 	case IPPROTO_IPV6:
443 		isr_prot = NETISR_IPV6;
444 		af = AF_INET6;
445 		break;
446 #endif
447 	default:
448 		DPRINTF(("%s: cannot handle inner ip proto %d\n",
449 			    __func__, prot));
450 		IPSEC_ISTAT(sproto, nopf);
451 		error = EPFNOSUPPORT;
452 		goto bad;
453 	}
454 
455 	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_AFTER);
456 	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
457 		goto bad;
458 
459 	/* Handle virtual tunneling interfaces */
460 	if (saidx->mode == IPSEC_MODE_TUNNEL)
461 		error = ipsec_if_input(m, sav, af);
462 	if (error == 0) {
463 		NET_EPOCH_ENTER(et);
464 		error = netisr_queue_src(isr_prot, (uintptr_t)sav->spi, m);
465 		NET_EPOCH_EXIT(et);
466 		if (error) {
467 			IPSEC_ISTAT(sproto, qfull);
468 			DPRINTF(("%s: queue full; proto %u packet dropped\n",
469 			    __func__, sproto));
470 		}
471 	}
472 	key_freesav(&sav);
473 	return (error);
474 bad:
475 	key_freesav(&sav);
476 	if (m != NULL)
477 		m_freem(m);
478 	return (error);
479 }
480 #endif /* INET */
481 
482 #ifdef INET6
483 /*
484  * IPSEC_INPUT() method implementation for IPv6.
485  *  0 - Permitted by inbound security policy for further processing.
486  *  EACCES - Forbidden by inbound security policy.
487  *  EINPROGRESS - consumed by IPsec.
488  */
489 int
490 ipsec6_input(struct mbuf *m, int offset, int proto)
491 {
492 
493 	switch (proto) {
494 	case IPPROTO_AH:
495 	case IPPROTO_ESP:
496 	case IPPROTO_IPCOMP:
497 		/* Do inbound IPsec processing for AH/ESP/IPCOMP */
498 		ipsec_common_input(m, offset,
499 		    offsetof(struct ip6_hdr, ip6_nxt), AF_INET6, proto);
500 		return (EINPROGRESS); /* mbuf consumed by IPsec */
501 	default:
502 		/*
503 		 * Protocols with further headers get their IPsec treatment
504 		 * within the protocol specific processing.
505 		 */
506 		if ((inet6sw[ip6_protox[proto]].pr_flags & PR_LASTHDR) == 0)
507 			return (0);
508 		/* FALLTHROUGH */
509 	};
510 	/*
511 	 * Enforce IPsec policy checking if we are seeing last header.
512 	 */
513 	if (ipsec6_in_reject(m, NULL) != 0) {
514 		/* Forbidden by inbound security policy */
515 		m_freem(m);
516 		return (EACCES);
517 	}
518 	return (0);
519 }
520 
521 int
522 ipsec6_ctlinput(int code, struct sockaddr *sa, void *v)
523 {
524 	return (0);
525 }
526 
527 /*
528  * IPsec input callback, called by the transform callback. Takes care of
529  * filtering and other sanity checks on the processed packet.
530  */
531 int
532 ipsec6_common_input_cb(struct mbuf *m, struct secasvar *sav, int skip,
533     int protoff)
534 {
535 	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
536 	struct epoch_tracker et;
537 	struct ipsec_ctx_data ctx;
538 	struct xform_history *xh;
539 	struct secasindex *saidx;
540 	struct ip6_hdr *ip6;
541 	struct m_tag *mtag;
542 	int prot, af, sproto;
543 	int nxt, isr_prot;
544 	int error, nest;
545 	uint8_t nxt8;
546 
547 	IPSEC_ASSERT(sav != NULL, ("null SA"));
548 	IPSEC_ASSERT(sav->sah != NULL, ("null SAH"));
549 	saidx = &sav->sah->saidx;
550 	af = saidx->dst.sa.sa_family;
551 	IPSEC_ASSERT(af == AF_INET6, ("unexpected af %u", af));
552 	sproto = saidx->proto;
553 	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
554 		sproto == IPPROTO_IPCOMP,
555 		("unexpected security protocol %u", sproto));
556 
557 	/* Fix IPv6 header */
558 	if (m->m_len < sizeof(struct ip6_hdr) &&
559 	    (m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
560 		DPRINTF(("%s: processing failed for SA %s/%08lx\n",
561 		    __func__, ipsec_address(&sav->sah->saidx.dst, buf,
562 		    sizeof(buf)), (u_long) ntohl(sav->spi)));
563 
564 		IPSEC_ISTAT(sproto, hdrops);
565 		error = EACCES;
566 		goto bad;
567 	}
568 
569 	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_BEFORE);
570 	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
571 		goto bad;
572 
573 	ip6 = mtod(m, struct ip6_hdr *);
574 	ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));
575 
576 	/* Save protocol */
577 	m_copydata(m, protoff, 1, &nxt8);
578 	prot = nxt8;
579 
580 	/* IPv6-in-IP encapsulation */
581 	if (prot == IPPROTO_IPV6 &&
582 	    saidx->mode != IPSEC_MODE_TRANSPORT) {
583 		if (m->m_pkthdr.len - skip < sizeof(struct ip6_hdr)) {
584 			IPSEC_ISTAT(sproto, hdrops);
585 			error = EINVAL;
586 			goto bad;
587 		}
588 		/* ip6n will now contain the inner IPv6 header. */
589 		m_striphdr(m, 0, skip);
590 		skip = 0;
591 	}
592 #ifdef INET
593 	/* IP-in-IP encapsulation */
594 	else if (prot == IPPROTO_IPIP &&
595 	    saidx->mode != IPSEC_MODE_TRANSPORT) {
596 		if (m->m_pkthdr.len - skip < sizeof(struct ip)) {
597 			IPSEC_ISTAT(sproto, hdrops);
598 			error = EINVAL;
599 			goto bad;
600 		}
601 		/* ipn will now contain the inner IPv4 header */
602 		m_striphdr(m, 0, skip);
603 		skip = 0;
604 	}
605 #endif /* INET */
606 	else {
607 		prot = IPPROTO_IPV6; /* for correct BPF processing */
608 	}
609 
610 	/*
611 	 * Record what we've done to the packet (under what SA it was
612 	 * processed).
613 	 */
614 	if (sproto != IPPROTO_IPCOMP) {
615 		mtag = m_tag_get(PACKET_TAG_IPSEC_IN_DONE,
616 		    sizeof(struct xform_history), M_NOWAIT);
617 		if (mtag == NULL) {
618 			DPRINTF(("%s: failed to get tag\n", __func__));
619 			IPSEC_ISTAT(sproto, hdrops);
620 			error = ENOMEM;
621 			goto bad;
622 		}
623 
624 		xh = (struct xform_history *)(mtag + 1);
625 		bcopy(&saidx->dst, &xh->dst, saidx->dst.sa.sa_len);
626 		xh->spi = sav->spi;
627 		xh->proto = sproto;
628 		xh->mode = saidx->mode;
629 		m_tag_prepend(m, mtag);
630 	}
631 
632 	key_sa_recordxfer(sav, m);
633 
634 #ifdef INET
635 	if (prot == IPPROTO_IPIP)
636 		af = AF_INET;
637 	else
638 #endif
639 		af = AF_INET6;
640 	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_AFTER);
641 	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
642 		goto bad;
643 	if (skip == 0) {
644 		/*
645 		 * We stripped outer IPv6 header.
646 		 * Now we should requeue decrypted packet via netisr.
647 		 */
648 		switch (prot) {
649 #ifdef INET
650 		case IPPROTO_IPIP:
651 			isr_prot = NETISR_IP;
652 			break;
653 #endif
654 		case IPPROTO_IPV6:
655 			isr_prot = NETISR_IPV6;
656 			break;
657 		default:
658 			DPRINTF(("%s: cannot handle inner ip proto %d\n",
659 			    __func__, prot));
660 			IPSEC_ISTAT(sproto, nopf);
661 			error = EPFNOSUPPORT;
662 			goto bad;
663 		}
664 		/* Handle virtual tunneling interfaces */
665 		if (saidx->mode == IPSEC_MODE_TUNNEL)
666 			error = ipsec_if_input(m, sav, af);
667 		if (error == 0) {
668 			NET_EPOCH_ENTER(et);
669 			error = netisr_queue_src(isr_prot,
670 			    (uintptr_t)sav->spi, m);
671 			NET_EPOCH_EXIT(et);
672 			if (error) {
673 				IPSEC_ISTAT(sproto, qfull);
674 				DPRINTF(("%s: queue full; proto %u packet"
675 				    " dropped\n", __func__, sproto));
676 			}
677 		}
678 		key_freesav(&sav);
679 		return (error);
680 	}
681 	/*
682 	 * See the end of ip6_input for this logic.
683 	 * IPPROTO_IPV[46] case will be processed just like other ones
684 	 */
685 	nest = 0;
686 	nxt = nxt8;
687 	NET_EPOCH_ENTER(et);
688 	while (nxt != IPPROTO_DONE) {
689 		if (V_ip6_hdrnestlimit && (++nest > V_ip6_hdrnestlimit)) {
690 			IP6STAT_INC(ip6s_toomanyhdr);
691 			error = EINVAL;
692 			goto bad_epoch;
693 		}
694 
695 		/*
696 		 * Protection against faulty packet - there should be
697 		 * more sanity checks in header chain processing.
698 		 */
699 		if (m->m_pkthdr.len < skip) {
700 			IP6STAT_INC(ip6s_tooshort);
701 			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
702 			error = EINVAL;
703 			goto bad_epoch;
704 		}
705 		/*
706 		 * Enforce IPsec policy checking if we are seeing last header.
707 		 * note that we do not visit this with protocols with pcb layer
708 		 * code - like udp/tcp/raw ip.
709 		 */
710 		if ((inet6sw[ip6_protox[nxt]].pr_flags & PR_LASTHDR) != 0 &&
711 		    ipsec6_in_reject(m, NULL)) {
712 			error = EINVAL;
713 			goto bad_epoch;
714 		}
715 		nxt = (*inet6sw[ip6_protox[nxt]].pr_input)(&m, &skip, nxt);
716 	}
717 	NET_EPOCH_EXIT(et);
718 	key_freesav(&sav);
719 	return (0);
720 bad_epoch:
721 	NET_EPOCH_EXIT(et);
722 bad:
723 	key_freesav(&sav);
724 	if (m)
725 		m_freem(m);
726 	return (error);
727 }
728 #endif /* INET6 */
729