xref: /src/sys/netipsec/ipsec_input.c (revision 183513d15f2290a42b542753aaffe9de2152575b)

/*	$OpenBSD: ipsec_input.c,v 1.63 2003/02/20 18:35:43 deraadt Exp $	*/
/*-
 * The authors of this code are John Ioannidis (ji@tla.org),
 * Angelos D. Keromytis (kermit@csd.uch.gr) and
 * Niels Provos (provos@physnet.uni-hamburg.de).
 *
 * This code was written by John Ioannidis for BSD/OS in Athens, Greece,
 * in November 1995.
 *
 * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
 * by Angelos D. Keromytis.
 *
 * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
 * and Niels Provos.
 *
 * Additional features in 1999 by Angelos D. Keromytis.
 *
 * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
 * Angelos D. Keromytis and Niels Provos.
 * Copyright (c) 2001, Angelos D. Keromytis.
 * Copyright (c) 2016 Andrey V. Elsukov <ae@FreeBSD.org>
 *
 * Permission to use, copy, and modify this software with or without fee
 * is hereby granted, provided that this entire notice is included in
 * all copies of any software which is or includes a copy or
 * modification of this software.
 * You may use this code under the GNU public license if you so wish. Please
 * contribute changes back to the authors under this freer than GPL license
 * so that we may further the use of strong encryption without limitations to
 * all.
 *
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
 * PURPOSE.
 */

/*
 * IPsec input processing.
 */

#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/errno.h>
#include <sys/hhook.h>
#include <sys/stdarg.h>
#include <sys/syslog.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_enc.h>
#include <net/if_private.h>
#include <net/netisr.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/in_var.h>
#include <netinet/tcp_var.h>

#include <netinet/ip6.h>
#ifdef INET6
#include <netinet6/ip6_var.h>
#endif
#include <netinet/in_pcb.h>
#ifdef INET6
#include <netinet/icmp6.h>
#endif

#include <netipsec/ipsec.h>
#ifdef INET6
#include <netipsec/ipsec6.h>
#endif
#include <netipsec/ipsec_support.h>
#include <netipsec/ah_var.h>
#include <netipsec/esp.h>
#include <netipsec/esp_var.h>
#include <netipsec/ipcomp_var.h>
#include <netipsec/ipsec_offload.h>

#include <netipsec/key.h>
#include <netipsec/keydb.h>
#include <netipsec/key_debug.h>

#include <netipsec/xform.h>

#include <machine/in_cksum.h>

#define	IPSEC_ISTAT(proto, name)	do {	\
	if ((proto) == IPPROTO_ESP)		\
		ESPSTAT_INC(esps_##name);	\
	else if ((proto) == IPPROTO_AH)		\
		AHSTAT_INC(ahs_##name);		\
	else					\
		IPCOMPSTAT_INC(ipcomps_##name);	\
} while (0)

/*
 * ipsec_common_input gets called when an IPsec-protected packet
 * is received by IPv4 or IPv6.  Its job is to find the right SA
 * and call the appropriate transform.  The transform callback
 * takes care of further processing (like ingress filtering).
 */
static int
ipsec_common_input(struct mbuf *m, int skip, int protoff, int af, int sproto)
{
	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
	union sockaddr_union dst_address;
	struct secasvar *sav;
	uint32_t spi;
	int error;

	IPSEC_ISTAT(sproto, input);

	IPSEC_ASSERT(m != NULL, ("null packet"));

	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
		sproto == IPPROTO_IPCOMP,
		("unexpected security protocol %u", sproto));

	if ((sproto == IPPROTO_ESP && !V_esp_enable) ||
	    (sproto == IPPROTO_AH && !V_ah_enable) ||
	    (sproto == IPPROTO_IPCOMP && !V_ipcomp_enable)) {
		m_freem(m);
		IPSEC_ISTAT(sproto, pdrops);
		return EOPNOTSUPP;
	}

	if (m->m_pkthdr.len - skip < 2 * sizeof (u_int32_t)) {
		m_freem(m);
		IPSEC_ISTAT(sproto, hdrops);
		DPRINTF(("%s: packet too small\n", __func__));
		return EINVAL;
	}

	/* Retrieve the SPI from the relevant IPsec header */
	if (sproto == IPPROTO_ESP)
		m_copydata(m, skip, sizeof(u_int32_t), (caddr_t) &spi);
	else if (sproto == IPPROTO_AH)
		m_copydata(m, skip + sizeof(u_int32_t), sizeof(u_int32_t),
		    (caddr_t) &spi);
	else if (sproto == IPPROTO_IPCOMP) {
		u_int16_t cpi;
		m_copydata(m, skip + sizeof(u_int16_t), sizeof(u_int16_t),
		    (caddr_t) &cpi);
		spi = ntohl(htons(cpi));
	}

	/*
	 * Find the SA and (indirectly) call the appropriate
	 * kernel crypto routine. The resulting mbuf chain is a valid
	 * IP packet ready to go through input processing.
	 */
	bzero(&dst_address, sizeof (dst_address));
	dst_address.sa.sa_family = af;
	switch (af) {
#ifdef INET
	case AF_INET:
		dst_address.sin.sin_len = sizeof(struct sockaddr_in);
		m_copydata(m, offsetof(struct ip, ip_dst),
		    sizeof(struct in_addr),
		    (caddr_t) &dst_address.sin.sin_addr);
		break;
#endif /* INET */
#ifdef INET6
	case AF_INET6:
		dst_address.sin6.sin6_len = sizeof(struct sockaddr_in6);
		m_copydata(m, offsetof(struct ip6_hdr, ip6_dst),
		    sizeof(struct in6_addr),
		    (caddr_t) &dst_address.sin6.sin6_addr);
		/* We keep addresses in SADB without embedded scope id */
		if (IN6_IS_SCOPE_LINKLOCAL(&dst_address.sin6.sin6_addr)) {
			/* XXX: sa6_recoverscope() */
			dst_address.sin6.sin6_scope_id =
			    ntohs(dst_address.sin6.sin6_addr.s6_addr16[1]);
			dst_address.sin6.sin6_addr.s6_addr16[1] = 0;
		}
		break;
#endif /* INET6 */
	default:
		DPRINTF(("%s: unsupported protocol family %u\n", __func__, af));
		m_freem(m);
		IPSEC_ISTAT(sproto, nopf);
		return EPFNOSUPPORT;
	}

	/* NB: only pass dst since key_allocsa follows RFC2401 */
	sav = key_allocsa(&dst_address, sproto, spi);
	if (sav == NULL) {
		DPRINTF(("%s: no key association found for SA %s/%08lx/%u\n",
		    __func__, ipsec_address(&dst_address, buf, sizeof(buf)),
		    (u_long) ntohl(spi), sproto));
		IPSEC_ISTAT(sproto, notdb);
		m_freem(m);
		return ENOENT;
	}

	if (sav->tdb_xform == NULL) {
		DPRINTF(("%s: attempted to use uninitialized SA %s/%08lx/%u\n",
		    __func__, ipsec_address(&dst_address, buf, sizeof(buf)),
		    (u_long) ntohl(spi), sproto));
		IPSEC_ISTAT(sproto, noxform);
		key_freesav(&sav);
		m_freem(m);
		return ENXIO;
	}

	/*
	 * Call appropriate transform and return -- callback takes care of
	 * everything else.
	 */
	error = (*sav->tdb_xform->xf_input)(m, sav, skip, protoff);
	return (error);
}

#ifdef INET
/*
 * IPSEC_INPUT() method implementation for IPv4.
 *  0 - Permitted by inbound security policy for further processing.
 *  EACCES - Forbidden by inbound security policy.
 *  EINPROGRESS - consumed by IPsec.
 */
int
ipsec4_input(struct mbuf *m, int offset, int proto)
{
	int error;

	error = ipsec_accel_input(m, offset, proto);
	if (error != ENXIO)
		return (error);

	switch (proto) {
	case IPPROTO_AH:
	case IPPROTO_ESP:
	case IPPROTO_IPCOMP:
		/* Do inbound IPsec processing for AH/ESP/IPCOMP */
		ipsec_common_input(m, offset,
		    offsetof(struct ip, ip_p), AF_INET, proto);
		return (EINPROGRESS); /* mbuf consumed by IPsec */
	default:
		/*
		 * Protocols with further headers get their IPsec treatment
		 * within the protocol specific processing.
		 */
		switch (proto) {
		case IPPROTO_ICMP:
		case IPPROTO_IGMP:
		case IPPROTO_IPV4:
		case IPPROTO_IPV6:
		case IPPROTO_RSVP:
		case IPPROTO_GRE:
		case IPPROTO_MOBILE:
		case IPPROTO_ETHERIP:
		case IPPROTO_PIM:
		case IPPROTO_SCTP:
			break;
		default:
			return (0);
		}
	};
	/*
	 * Enforce IPsec policy checking if we are seeing last header.
	 */
	if (ipsec4_in_reject(m, NULL) != 0) {
		/* Forbidden by inbound security policy */
		m_freem(m);
		return (EACCES);
	}
	return (0);
}

int
ipsec4_ctlinput(ipsec_ctlinput_param_t param)
{
	struct icmp *icp = param.icmp;
	struct ip *ip = &icp->icmp_ip;
	struct sockaddr_in icmpsrc = {
		.sin_len = sizeof(struct sockaddr_in),
		.sin_family = AF_INET,
		.sin_addr = ip->ip_dst,
	};
	struct in_conninfo inc;
	struct secasvar *sav;
	uint32_t pmtu, spi;
	uint32_t max_pmtu;
	uint8_t proto;

	pmtu = ntohs(icp->icmp_nextmtu);

	if (pmtu < V_ip4_ipsec_min_pmtu)
		return (EINVAL);

	proto = ip->ip_p;
	if (proto != IPPROTO_ESP && proto != IPPROTO_AH &&
	    proto != IPPROTO_IPCOMP)
		return (EINVAL);

	memcpy(&spi, (caddr_t)ip + (ip->ip_hl << 2), sizeof(spi));
	sav = key_allocsa((union sockaddr_union *)&icmpsrc, proto, spi);
	if (sav == NULL)
		return (ENOENT);

	key_freesav(&sav);

	memset(&inc, 0, sizeof(inc));
	inc.inc_faddr = ip->ip_dst;

	/* Update pmtu only if its smaller than the current one. */
	max_pmtu = tcp_hc_getmtu(&inc);
	if (max_pmtu == 0)
		max_pmtu = tcp_maxmtu(&inc, NULL);

	if (pmtu < max_pmtu)
		tcp_hc_updatemtu(&inc, pmtu);

	return (0);
}

/*
 * IPsec input callback for INET protocols.
 * This routine is called as the transform callback.
 * Takes care of filtering and other sanity checks on
 * the processed packet.
 */
int
ipsec4_common_input_cb(struct mbuf *m, struct secasvar *sav, int skip,
    int protoff, struct rm_priotracker *sahtree_tracker)
{
	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
	struct epoch_tracker et;
	struct ipsec_ctx_data ctx;
	struct xform_history *xh;
	struct secasindex *saidx;
	struct m_tag *mtag;
	struct ip *ip;
	int error, prot, af, sproto, isr_prot;

	IPSEC_ASSERT(sav != NULL, ("null SA"));
	IPSEC_ASSERT(sav->sah != NULL, ("null SAH"));
	saidx = &sav->sah->saidx;
	af = saidx->dst.sa.sa_family;
	IPSEC_ASSERT(af == AF_INET, ("unexpected af %u", af));
	sproto = saidx->proto;
	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
		sproto == IPPROTO_IPCOMP,
		("unexpected security protocol %u", sproto));

	if (skip != 0) {
		/*
		 * Fix IPv4 header
		 */
		if (m->m_len < skip && (m = m_pullup(m, skip)) == NULL) {
			DPRINTF(("%s: processing failed for SA %s/%08lx\n",
			    __func__, ipsec_address(&sav->sah->saidx.dst,
			    buf, sizeof(buf)), (u_long) ntohl(sav->spi)));
			IPSEC_ISTAT(sproto, hdrops);
			error = ENOBUFS;
			goto bad_noepoch;
		}

		ip = mtod(m, struct ip *);
		ip->ip_len = htons(m->m_pkthdr.len);
		ip->ip_sum = 0;
		ip->ip_sum = in_cksum(m, ip->ip_hl << 2);
	} else {
		ip = mtod(m, struct ip *);
	}
	prot = ip->ip_p;
	/*
	 * Check that we have NAT-T enabled and apply transport mode
	 * decapsulation NAT procedure (RFC3948).
	 * Do this before invoking into the PFIL.
	 */
	if (sav->natt != NULL &&
	    (prot == IPPROTO_UDP || prot == IPPROTO_TCP))
		udp_ipsec_adjust_cksum(m, sav, prot, skip);

	/*
	 * Needed for ipsec_run_hooks and netisr_queue_src
	 */
	NET_EPOCH_ENTER(et);

	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, AF_INET, IPSEC_ENC_BEFORE);
	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
		goto bad;
	ip = mtod(m, struct ip *);	/* update pointer */

	/* IP-in-IP encapsulation */
	if (prot == IPPROTO_IPIP &&
	    saidx->mode != IPSEC_MODE_TRANSPORT) {
		if (m->m_pkthdr.len - skip < sizeof(struct ip)) {
			IPSEC_ISTAT(sproto, hdrops);
			error = EINVAL;
			goto bad;
		}
		/* enc0: strip outer IPv4 header */
		m_striphdr(m, 0, ip->ip_hl << 2);
	}
#ifdef INET6
	/* IPv6-in-IP encapsulation. */
	else if (prot == IPPROTO_IPV6 &&
	    saidx->mode != IPSEC_MODE_TRANSPORT) {
		if (m->m_pkthdr.len - skip < sizeof(struct ip6_hdr)) {
			IPSEC_ISTAT(sproto, hdrops);
			error = EINVAL;
			goto bad;
		}
		/* enc0: strip IPv4 header, keep IPv6 header only */
		m_striphdr(m, 0, ip->ip_hl << 2);
	}
#endif /* INET6 */
	else if (prot != IPPROTO_IPV6 && saidx->mode == IPSEC_MODE_ANY) {
		/*
		 * When mode is wildcard, inner protocol is IPv6 and
		 * we have no INET6 support - drop this packet a bit later.
		 * In other cases we assume transport mode. Set prot to
		 * correctly choose netisr.
		 */
		prot = IPPROTO_IPIP;
	}

	/*
	 * Record what we've done to the packet (under what SA it was
	 * processed).
	 */
	if (sproto != IPPROTO_IPCOMP) {
		mtag = m_tag_get(PACKET_TAG_IPSEC_IN_DONE,
		    sizeof(struct xform_history), M_NOWAIT);
		if (mtag == NULL) {
			DPRINTF(("%s: failed to get tag\n", __func__));
			IPSEC_ISTAT(sproto, hdrops);
			error = ENOMEM;
			goto bad;
		}

		xh = (struct xform_history *)(mtag + 1);
		bcopy(&saidx->dst, &xh->dst, saidx->dst.sa.sa_len);
		xh->spi = sav->spi;
		xh->proto = sproto;
		xh->mode = saidx->mode;
		m_tag_prepend(m, mtag);
	}

	key_sa_recordxfer(sav, m);		/* record data transfer */

	/*
	 * In transport mode requeue decrypted mbuf back to IPv4 protocol
	 * handler. This is necessary to correctly expose rcvif.
	 */
	if (saidx->mode == IPSEC_MODE_TRANSPORT)
		prot = IPPROTO_IPIP;
	/*
	 * Re-dispatch via software interrupt.
	 */
	switch (prot) {
	case IPPROTO_IPIP:
		isr_prot = NETISR_IP;
		af = AF_INET;
		break;
#ifdef INET6
	case IPPROTO_IPV6:
		isr_prot = NETISR_IPV6;
		af = AF_INET6;
		break;
#endif
	default:
		DPRINTF(("%s: cannot handle inner ip proto %d\n",
			    __func__, prot));
		IPSEC_ISTAT(sproto, nopf);
		error = EPFNOSUPPORT;
		goto bad;
	}

	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_AFTER);
	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
		goto bad;

	/* Handle virtual tunneling interfaces */
	if (saidx->mode == IPSEC_MODE_TUNNEL)
		error = ipsec_if_input(m, sav, af, sahtree_tracker);
	else
		ipsec_sahtree_runlock(sahtree_tracker);
	if (error == 0) {
		error = netisr_queue_src(isr_prot, (uintptr_t)sav->spi, m);
		if (error) {
			IPSEC_ISTAT(sproto, qfull);
			DPRINTF(("%s: queue full; proto %u packet dropped\n",
			    __func__, sproto));
		}
	}
	NET_EPOCH_EXIT(et);
	key_freesav(&sav);
	return (error);
bad:
	NET_EPOCH_EXIT(et);
bad_noepoch:
	ipsec_sahtree_runlock(sahtree_tracker);
	key_freesav(&sav);
	if (m != NULL)
		m_freem(m);
	return (error);
}
#endif /* INET */

#ifdef INET6
static bool
ipsec6_lasthdr(int proto)
{

	switch (proto) {
	case IPPROTO_IPV4:
	case IPPROTO_IPV6:
	case IPPROTO_GRE:
	case IPPROTO_ICMPV6:
	case IPPROTO_ETHERIP:
	case IPPROTO_PIM:
	case IPPROTO_SCTP:
		return (true);
	default:
		return (false);
	};
}

/*
 * IPSEC_INPUT() method implementation for IPv6.
 *  0 - Permitted by inbound security policy for further processing.
 *  EACCES - Forbidden by inbound security policy.
 *  EINPROGRESS - consumed by IPsec.
 */
int
ipsec6_input(struct mbuf *m, int offset, int proto)
{
	int error;

	error = ipsec_accel_input(m, offset, proto);
	if (error != ENXIO)
		return (error);

	switch (proto) {
	case IPPROTO_AH:
	case IPPROTO_ESP:
	case IPPROTO_IPCOMP:
		/* Do inbound IPsec processing for AH/ESP/IPCOMP */
		ipsec_common_input(m, offset,
		    offsetof(struct ip6_hdr, ip6_nxt), AF_INET6, proto);
		return (EINPROGRESS); /* mbuf consumed by IPsec */
	default:
		/*
		 * Protocols with further headers get their IPsec treatment
		 * within the protocol specific processing.
		 */
		if (!ipsec6_lasthdr(proto))
			return (0);
		/* FALLTHROUGH */
	};
	/*
	 * Enforce IPsec policy checking if we are seeing last header.
	 */
	if (ipsec6_in_reject(m, NULL) != 0) {
		/* Forbidden by inbound security policy */
		m_freem(m);
		return (EACCES);
	}
	return (0);
}

int
ipsec6_ctlinput(ipsec_ctlinput_param_t param)
{
	return (0);
}

extern ipproto_input_t	*ip6_protox[];

/*
 * IPsec input callback, called by the transform callback. Takes care of
 * filtering and other sanity checks on the processed packet.
 */
int
ipsec6_common_input_cb(struct mbuf *m, struct secasvar *sav, int skip,
    int protoff, struct rm_priotracker *sahtree_tracker)
{
	IPSEC_DEBUG_DECLARE(char buf[IPSEC_ADDRSTRLEN]);
	struct epoch_tracker et;
	struct ipsec_ctx_data ctx;
	struct xform_history *xh;
	struct secasindex *saidx;
	struct ip6_hdr *ip6;
	struct m_tag *mtag;
	int prot, af, sproto;
	int nxt, isr_prot;
	int error, nest;
	uint8_t nxt8;

	IPSEC_ASSERT(sav != NULL, ("null SA"));
	IPSEC_ASSERT(sav->sah != NULL, ("null SAH"));
	saidx = &sav->sah->saidx;
	af = saidx->dst.sa.sa_family;
	IPSEC_ASSERT(af == AF_INET6, ("unexpected af %u", af));
	sproto = saidx->proto;
	IPSEC_ASSERT(sproto == IPPROTO_ESP || sproto == IPPROTO_AH ||
		sproto == IPPROTO_IPCOMP,
		("unexpected security protocol %u", sproto));

	NET_EPOCH_ENTER(et);

	/* Fix IPv6 header */
	if (m->m_len < sizeof(struct ip6_hdr) &&
	    (m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) {
		DPRINTF(("%s: processing failed for SA %s/%08lx\n",
		    __func__, ipsec_address(&sav->sah->saidx.dst, buf,
		    sizeof(buf)), (u_long) ntohl(sav->spi)));

		IPSEC_ISTAT(sproto, hdrops);
		error = EACCES;
		goto bad;
	}

	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_BEFORE);
	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
		goto bad;

	ip6 = mtod(m, struct ip6_hdr *);
	ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(struct ip6_hdr));

	/* Save protocol */
	m_copydata(m, protoff, 1, &nxt8);
	prot = nxt8;

	/*
	 * Check that we have NAT-T enabled and apply transport mode
	 * decapsulation NAT procedure (RFC3948).
	 * Do this before invoking into the PFIL.
	 */
	if (sav->natt != NULL &&
	    (prot == IPPROTO_UDP || prot == IPPROTO_TCP))
		udp_ipsec_adjust_cksum(m, sav, prot, skip);

	/* IPv6-in-IP encapsulation */
	if (prot == IPPROTO_IPV6 &&
	    saidx->mode != IPSEC_MODE_TRANSPORT) {
		if (m->m_pkthdr.len - skip < sizeof(struct ip6_hdr)) {
			IPSEC_ISTAT(sproto, hdrops);
			error = EINVAL;
			goto bad;
		}
		/* ip6n will now contain the inner IPv6 header. */
		m_striphdr(m, 0, skip);
		skip = 0;
	}
#ifdef INET
	/* IP-in-IP encapsulation */
	else if (prot == IPPROTO_IPIP &&
	    saidx->mode != IPSEC_MODE_TRANSPORT) {
		if (m->m_pkthdr.len - skip < sizeof(struct ip)) {
			IPSEC_ISTAT(sproto, hdrops);
			error = EINVAL;
			goto bad;
		}
		/* ipn will now contain the inner IPv4 header */
		m_striphdr(m, 0, skip);
		skip = 0;
	}
#endif /* INET */
	else {
		prot = IPPROTO_IPV6; /* for correct BPF processing */
	}

	/*
	 * Record what we've done to the packet (under what SA it was
	 * processed).
	 */
	if (sproto != IPPROTO_IPCOMP) {
		mtag = m_tag_get(PACKET_TAG_IPSEC_IN_DONE,
		    sizeof(struct xform_history), M_NOWAIT);
		if (mtag == NULL) {
			DPRINTF(("%s: failed to get tag\n", __func__));
			IPSEC_ISTAT(sproto, hdrops);
			error = ENOMEM;
			goto bad;
		}

		xh = (struct xform_history *)(mtag + 1);
		bcopy(&saidx->dst, &xh->dst, saidx->dst.sa.sa_len);
		xh->spi = sav->spi;
		xh->proto = sproto;
		xh->mode = saidx->mode;
		m_tag_prepend(m, mtag);
	}

	key_sa_recordxfer(sav, m);

#ifdef INET
	if (prot == IPPROTO_IPIP)
		af = AF_INET;
	else
#endif
		af = AF_INET6;
	IPSEC_INIT_CTX(&ctx, &m, NULL, sav, af, IPSEC_ENC_AFTER);
	if ((error = ipsec_run_hhooks(&ctx, HHOOK_TYPE_IPSEC_IN)) != 0)
		goto bad;
	if (skip == 0) {
		/*
		 * We stripped outer IPv6 header.
		 * Now we should requeue decrypted packet via netisr.
		 */
		switch (prot) {
#ifdef INET
		case IPPROTO_IPIP:
			isr_prot = NETISR_IP;
			break;
#endif
		case IPPROTO_IPV6:
			isr_prot = NETISR_IPV6;
			break;
		default:
			DPRINTF(("%s: cannot handle inner ip proto %d\n",
			    __func__, prot));
			IPSEC_ISTAT(sproto, nopf);
			error = EPFNOSUPPORT;
			goto bad;
		}
		/* Handle virtual tunneling interfaces */
		if (saidx->mode == IPSEC_MODE_TUNNEL)
			error = ipsec_if_input(m, sav, af, sahtree_tracker);
		else
			ipsec_sahtree_runlock(sahtree_tracker);
		if (error == 0) {
			error = netisr_queue_src(isr_prot,
			    (uintptr_t)sav->spi, m);
			if (error) {
				IPSEC_ISTAT(sproto, qfull);
				DPRINTF(("%s: queue full; proto %u packet"
				    " dropped\n", __func__, sproto));
			}
		}
		NET_EPOCH_EXIT(et);
		key_freesav(&sav);
		return (error);
	}

	ipsec_sahtree_runlock(sahtree_tracker);

	/*
	 * See the end of ip6_input for this logic.
	 * IPPROTO_IPV[46] case will be processed just like other ones
	 */
	nest = 0;
	nxt = nxt8;
	while (nxt != IPPROTO_DONE) {
		if (V_ip6_hdrnestlimit && (++nest > V_ip6_hdrnestlimit)) {
			IP6STAT_INC(ip6s_toomanyhdr);
			error = EINVAL;
			goto bad;
		}

		/*
		 * Protection against faulty packet - there should be
		 * more sanity checks in header chain processing.
		 */
		if (m->m_pkthdr.len < skip) {
			IP6STAT_INC(ip6s_tooshort);
			in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
			error = EINVAL;
			goto bad;
		}
		/*
		 * Enforce IPsec policy checking if we are seeing last header.
		 * note that we do not visit this with protocols with pcb layer
		 * code - like udp/tcp/raw ip.
		 */
		if (ipsec6_lasthdr(nxt) && ipsec6_in_reject(m, NULL)) {
			error = EINVAL;
			goto bad;
		}
		nxt = ip6_protox[nxt](&m, &skip, nxt);
	}
	NET_EPOCH_EXIT(et);
	key_freesav(&sav);
	return (0);
bad:
	NET_EPOCH_EXIT(et);
	ipsec_sahtree_runlock(sahtree_tracker);
	key_freesav(&sav);
	if (m)
		m_freem(m);
	return (error);
}
#endif /* INET6 */