path: root/sys/netinet/ipsec_input.c

/*	$OpenBSD: ipsec_input.c,v 1.46 2001/06/24 18:22:47 provos 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.
 *
 * Permission to use, copy, and modify this software 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/protosw.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/kernel.h>

#include <net/if.h>
#include <net/netisr.h>
#include <net/bpf.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/in_var.h>
#include <netinet/ip_icmp.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>

#ifdef INET6
#ifndef INET
#include <netinet/in.h>
#endif
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6protosw.h>
#endif /* INET6 */

#include <netinet/ip_ipsp.h>
#include <netinet/ip_esp.h>
#include <netinet/ip_ah.h>

#include <net/if_enc.h>

#include "bpfilter.h"

int ipsec_common_input(struct mbuf *, int, int, int, int);
void *ipsec_common_ctlinput(int, struct sockaddr *, void *, int);

#ifdef ENCDEBUG
#define DPRINTF(x)	if (encdebug) printf x
#else
#define DPRINTF(x)
#endif

/* sysctl variables */
int esp_enable = 0;
int ah_enable = 0;

#ifdef INET6
extern struct ip6protosw inet6sw[];
extern u_char ip6_protox[];
#endif

/*
 * ipsec_common_input() gets called when we receive an IPsec-protected packet
 * in IPv4 or IPv6. All it does is find the right TDB and call the appropriate
 * transform. The callback takes care of further processing (like ingress
 * filtering).
 */
int
ipsec_common_input(struct mbuf *m, int skip, int protoff, int af, int sproto)
{
#define IPSEC_ISTAT(y,z) (sproto == IPPROTO_ESP ? (y)++ : (z)++)

    union sockaddr_union dst_address;
    struct tdb *tdbp;
    u_int32_t spi;
    int s;

    IPSEC_ISTAT(espstat.esps_input, ahstat.ahs_input);

    if (m == 0)
    {
	DPRINTF(("ipsec_common_input(): NULL packet received\n"));
        IPSEC_ISTAT(espstat.esps_hdrops, ahstat.ahs_hdrops);
        return EINVAL;
    }

    if ((sproto == IPPROTO_ESP && !esp_enable) ||
	(sproto == IPPROTO_AH && !ah_enable))
    {
        m_freem(m);
        IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
        return EOPNOTSUPP;
    }

    if (m->m_pkthdr.len - skip < 2 * sizeof(u_int32_t))
    {
        m_freem(m);
        IPSEC_ISTAT(espstat.esps_hdrops, ahstat.ahs_hdrops);
	DPRINTF(("ipsec_common_input(): packet too small\n"));
        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
      m_copydata(m, skip + sizeof(u_int32_t), sizeof(u_int32_t),
		 (caddr_t) &spi);

    /*
     * Find tunnel control block 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));
	    break;
#endif /* INET6 */

	default:
	    DPRINTF(("ipsec_common_input(): unsupported protocol family %d\n",
		     af));
	    m_freem(m);
	    IPSEC_ISTAT(espstat.esps_nopf, ahstat.ahs_nopf);
	    return EPFNOSUPPORT;
    }

    s = spltdb();
    tdbp = gettdb(spi, &dst_address, sproto);
    if (tdbp == NULL)
    {
	splx(s);
	DPRINTF(("ipsec_common_input(): could not find SA for packet to %s, spi %08x\n", ipsp_address(dst_address), ntohl(spi)));
	m_freem(m);
	IPSEC_ISTAT(espstat.esps_notdb, ahstat.ahs_notdb);
	return ENOENT;
    }

    if (tdbp->tdb_flags & TDBF_INVALID)
    {
	splx(s);
	DPRINTF(("ipsec_common_input(): attempted to use invalid SA %s/%08x/%u\n", ipsp_address(dst_address), ntohl(spi), tdbp->tdb_sproto));
	m_freem(m);
	IPSEC_ISTAT(espstat.esps_invalid, ahstat.ahs_invalid);
	return EINVAL;
    }

    if (tdbp->tdb_xform == NULL)
    {
	splx(s);
	DPRINTF(("ipsec_common_input(): attempted to use uninitialized SA %s/%08x/%u\n", ipsp_address(dst_address), ntohl(spi), tdbp->tdb_sproto));
	m_freem(m);
	IPSEC_ISTAT(espstat.esps_noxform, ahstat.ahs_noxform);
	return ENXIO;
    }

    if (tdbp->tdb_dst.sa.sa_family == AF_INET)
    {
	/*
	 * XXX The fragment conflicts with scoped nature of IPv6, so do it for
	 * only for IPv4 for now.
	 */
	m->m_pkthdr.rcvif = &encif[0].sc_if;
    }

    /* Register first use, setup expiration timer */
    if (tdbp->tdb_first_use == 0)
    {
	tdbp->tdb_first_use = time.tv_sec;
	if (tdbp->tdb_flags & TDBF_FIRSTUSE)
	    timeout_add(&tdbp->tdb_first_tmo, hz * tdbp->tdb_exp_first_use);
	if (tdbp->tdb_flags & TDBF_SOFT_FIRSTUSE)
	    timeout_add(&tdbp->tdb_sfirst_tmo, hz * tdbp->tdb_soft_first_use);
    }

    /*
     * Call appropriate transform and return -- callback takes care of
     * everything else.
     */
    if ((*(tdbp->tdb_xform->xf_input))(m, tdbp, skip, protoff) == NULL)
    {
	splx(s);
	return EINVAL;
    }
    else
    {
	splx(s);
	return 0;
    }
}

/*
 * IPsec input callback, called by the transform callback. Takes care of
 * filtering and other sanity checks on the processed packet.
 */
int
ipsec_common_input_cb(struct mbuf *m, struct tdb *tdbp, int skip, int protoff,
		      struct m_tag *mt)
{
    int prot, af, sproto;

#if NBPFILTER > 0
    struct ifnet *bpfif;
#endif

#ifdef INET
    struct ip *ip, ipn;
#endif /* INET */

#ifdef INET6
    struct ip6_hdr *ip6, ip6n;
#endif /* INET6 */
    struct m_tag *mtag;
    struct tdb_ident *tdbi;

    af = tdbp->tdb_dst.sa.sa_family;
    sproto = tdbp->tdb_sproto;

    tdbp->tdb_last_used = time.tv_sec;

    /* Sanity check */
    if (m == NULL)
    {
	/* The called routine will print a message if necessary */
	IPSEC_ISTAT(espstat.esps_badkcr, ahstat.ahs_badkcr);
	return EINVAL;
    }

#ifdef INET
    /* Fix IPv4 header */
    if (tdbp->tdb_dst.sa.sa_family == AF_INET)
    {
        if ((m->m_len < skip) && ((m = m_pullup(m, skip)) == NULL))
        {
	    DPRINTF(("ipsec_common_input_cb(): processing failed for SA %s/%08x\n", ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
            IPSEC_ISTAT(espstat.esps_hdrops, ahstat.ahs_hdrops);
            return ENOBUFS;
        }

	ip = mtod(m, struct ip *);
	ip->ip_len = htons(m->m_pkthdr.len);
	HTONS(ip->ip_off);
	ip->ip_sum = 0;
	ip->ip_sum = in_cksum(m, ip->ip_hl << 2);
	prot = ip->ip_p;

	/* IP-in-IP encapsulation */
	if (prot == IPPROTO_IPIP)
	{
	    /* ipn will now contain the inner IPv4 header */
	    m_copydata(m, ip->ip_hl << 2, sizeof(struct ip), (caddr_t) &ipn);

	    /*
	     * Check that the inner source address is the same as
	     * the proxy address, if available.
	     */
	    if (((tdbp->tdb_proxy.sa.sa_family == AF_INET) &&
		 (tdbp->tdb_proxy.sin.sin_addr.s_addr != INADDR_ANY) &&
		 (ipn.ip_src.s_addr != tdbp->tdb_proxy.sin.sin_addr.s_addr)) ||
		((tdbp->tdb_proxy.sa.sa_family != AF_INET) &&
		 (tdbp->tdb_proxy.sa.sa_family != 0)))
	    {
		DPRINTF(("ipsec_common_input_cb(): inner source address %s doesn't correspond to expected proxy source %s, SA %s/%08x\n", inet_ntoa4(ipn.ip_src), ipsp_address(tdbp->tdb_proxy), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
		m_freem(m);
                IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
		return EACCES;
	    }
	}

#if INET6
	/* IPv6-in-IP encapsulation */
	if (prot == IPPROTO_IPV6)
	{
	    /* ip6n will now contain the inner IPv6 header */
	    m_copydata(m, ip->ip_hl << 2, sizeof(struct ip6_hdr),
		       (caddr_t) &ip6n);

	    /*
	     * Check that the inner source address is the same as
	     * the proxy address, if available.
	     */
	    if (((tdbp->tdb_proxy.sa.sa_family == AF_INET6) &&
		 !IN6_IS_ADDR_UNSPECIFIED(&tdbp->tdb_proxy.sin6.sin6_addr) &&
		 !IN6_ARE_ADDR_EQUAL(&ip6n.ip6_src,
				     &tdbp->tdb_proxy.sin6.sin6_addr)) ||
		((tdbp->tdb_proxy.sa.sa_family != AF_INET6) &&
		 (tdbp->tdb_proxy.sa.sa_family != 0)))
	    {
		DPRINTF(("ipsec_common_input_cb(): inner source address %s doesn't correspond to expected proxy source %s, SA %s/%08x\n", ip6_sprintf(&ip6n.ip6_src), ipsp_address(tdbp->tdb_proxy), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
		m_freem(m);
		IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
		return EACCES;
	    }
	}
#endif /* INET6 */

	/*
	 * Check that the source address is an expected one, if we know what
	 * it's supposed to be. This avoids source address spoofing.
	 */
	if (((tdbp->tdb_src.sa.sa_family == AF_INET) &&
	     (tdbp->tdb_src.sin.sin_addr.s_addr != INADDR_ANY) &&
	     (ip->ip_src.s_addr != tdbp->tdb_src.sin.sin_addr.s_addr)) ||
	    ((tdbp->tdb_src.sa.sa_family != AF_INET) &&
	     (tdbp->tdb_src.sa.sa_family != 0)))
	{
	    DPRINTF(("ipsec_common_input_cb(): source address %s doesn't correspond to expected source %s, SA %s/%08x\n", inet_ntoa4(ip->ip_src), ipsp_address(tdbp->tdb_src), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
	    m_freem(m);
	    IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
	    return EACCES;
	}
    }
#endif /* INET */

#ifdef INET6
    /* Fix IPv6 header */
    if (af == INET6)
    {
        if ((m->m_len < sizeof(struct ip6_hdr)) &&
            ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL))
        {
	    DPRINTF(("ipsec_common_input_cb(): processing failed for SA %s/%08x\n", ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
            IPSEC_ISTAT(espstat.esps_hdrops, ahstat.ahs_hdrops);
            return EACCES;
        }

	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, (unsigned char *) &prot);

#ifdef INET
	/* IP-in-IP encapsulation */
	if (prot == IPPROTO_IPIP)
	{
	    /* ipn will now contain the inner IPv4 header */
	    m_copydata(m, skip, sizeof(struct ip), (caddr_t) &ipn);

	    /*
	     * Check that the inner source address is the same as
	     * the proxy address, if available.
	     */
	    if (((tdbp->tdb_proxy.sa.sa_family == AF_INET) &&
		 (tdbp->tdb_proxy.sin.sin_addr.s_addr != INADDR_ANY) &&
		 (ipn.ip_src.s_addr != tdbp->tdb_proxy.sin.sin_addr.s_addr)) ||
		((tdbp->tdb_proxy.sa.sa_family != AF_INET) &&
		 (tdbp->tdb_proxy.sa.sa_family != 0)))
	    {
		DPRINTF(("ipsec_common_input_cb(): inner source address %s doesn't correspond to expected proxy source %s, SA %s/%08x\n", inet_ntoa4(ipn.ip_src), ipsp_address(tdbp->tdb_proxy), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
		m_freem(m);
		IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
		return EACCES;
	    }
	}
#endif /* INET */

	/* IPv6-in-IP encapsulation */
	if (prot == IPPROTO_IPV6)
	{
	    /* ip6n will now contain the inner IPv6 header */
	    m_copydata(m, skip, sizeof(struct ip6_hdr), (caddr_t) &ip6n);

	    /*
	     * Check that the inner source address is the same as
	     * the proxy address, if available.
	     */
	    if (((tdbp->tdb_proxy.sa.sa_family == AF_INET6) &&
		 !IN6_IS_ADDR_UNSPECIFIED(&tdbp->tdb_proxy.sin6.sin6_addr) &&
		 !IN6_ARE_ADDR_EQUAL(&ip6n.ip6_src,
				     &tdbp->tdb_proxy.sin6.sin6_addr)) ||
		((tdbp->tdb_proxy.sa.sa_family != AF_INET6) &&
		 (tdbp->tdb_proxy.sa.sa_family != 0)))
	    {
		DPRINTF(("ipsec_common_input_cb(): inner source address %s doesn't correspond to expected proxy source %s, SA %s/%08x\n", ip6_sprintf(&ip6n.ip6_src), ipsp_address(tdbp->tdb_proxy), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
		m_freem(m);
		IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
		return EACCES;
	    }
	}

	/*
	 * Check that the source address is an expected one, if we know what
	 * it's supposed to be. This avoids source address spoofing.
	 */
	if (((tdbp->tdb_src.sa.sa_family == AF_INET6) &&
	     !IN6_IS_ADDR_UNSPECIFIED(&tdbp->tdb_src.sin6.sin6_addr) &&
	     !IN6_ARE_ADDR_EQUAL(&ip6->ip6_src,
				 &tdbp->tdb_src.sin6.sin6_addr)) ||
	    ((tdbp->tdb_src.sa.sa_family != AF_INET6) &&
	     (tdbp->tdb_src.sa.sa_family != 0)))
	{
	    DPRINTF(("ipsec_common_input_cb(): packet %s to %s does not match any ACL entries, SA %s/%08x\n", ip6_sprintf(&ip6->ip6_src), ip6_sprintf(&ip6->ip6_dst), ipsp_address(tdbp->tdb_src), ipsp_address(tdbp->tdb_dst), ntohl(tdbp->tdb_spi)));
	    m_freem(m);
	    IPSEC_ISTAT(espstat.esps_pdrops, ahstat.ahs_pdrops);
	    return EACCES;
	}
    }
#endif /* INET6 */

    /*
     * Record what we've done to the packet (under what SA it was
     * processed). If we've been passed an mtag, it means the packet
     * was already processed by an ethernet/crypto combo card and
     * thus has a tag attached with all the right information, but
     * with a PACKET_TAG_IPSEC_IN_CRYPTO_DONE as opposed to
     * PACKET_TAG_IPSEC_IN_DONE type; in that case, just change the type.
     */
    if (mt == NULL)
    {
	mtag = m_tag_get(PACKET_TAG_IPSEC_IN_DONE, sizeof(struct tdb_ident),
			 M_NOWAIT);
	if (mtag == NULL)
	{
	    m_freem(m);
	    DPRINTF(("ipsec_common_input_cb(): failed to get tag\n"));
	    IPSEC_ISTAT(espstat.esps_hdrops, ahstat.ahs_hdrops);
	    return ENOMEM;
	}

	tdbi = (struct tdb_ident *)(mtag + 1);
	bcopy(&tdbp->tdb_dst, &tdbi->dst, sizeof(union sockaddr_union));
	tdbi->proto = tdbp->tdb_sproto;
	tdbi->spi = tdbp->tdb_spi;

	m_tag_prepend(m, mtag);
    }
    else
      mt->m_tag_id = PACKET_TAG_IPSEC_IN_DONE;

    if (sproto == IPPROTO_ESP)
    {
	/* Packet is confidential ? */
	if (tdbp->tdb_encalgxform)
	  m->m_flags |= M_CONF;

	/* Check if we had authenticated ESP */
	if (tdbp->tdb_authalgxform)
	  m->m_flags |= M_AUTH;
    }
    else
      m->m_flags |= M_AUTH;

#if NBPFILTER > 0
    bpfif = &encif[0].sc_if;
    if (bpfif->if_bpf)
    {
        /*
         * We need to prepend the address family as
         * a four byte field.  Cons up a dummy header
         * to pacify bpf.  This is safe because bpf
         * will only read from the mbuf (i.e., it won't
         * try to free it or keep a pointer a to it).
         */
        struct mbuf m1;
        struct enchdr hdr;

	hdr.af = af;
	hdr.spi = tdbp->tdb_spi;
	hdr.flags = m->m_flags & (M_AUTH|M_CONF);

        m1.m_next = m;
        m1.m_len = ENC_HDRLEN;
        m1.m_data = (char *) &hdr;

        bpf_mtap(bpfif->if_bpf, &m1);
    }
#endif

    /* Call the appropriate IPsec transform callback */
    switch (af)
    {
#ifdef INET
	case AF_INET:
	    switch (sproto)
	    {
		case IPPROTO_ESP:
		    return esp4_input_cb(m);

		case IPPROTO_AH:
		    return ah4_input_cb(m);

		default:
		    DPRINTF(("ipsec_common_input_cb(): unknown/unsupported security protocol %d\n", sproto));
		    m_freem(m);
		    return EPFNOSUPPORT;
	    }
	    break;
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    switch (sproto)
	    {
		case IPPROTO_ESP:
		    return esp6_input_cb(m, skip, protoff);

		case IPPROTO_AH:
		    return ah6_input_cb(m, skip, protoff);

		default:
		    DPRINTF(("ipsec_common_input_cb(): unknown/unsupported security protocol %d\n", sproto));
		    m_freem(m);
		    return EPFNOSUPPORT;
	    }
	    break;
#endif /* INET6 */

	default:
	    DPRINTF(("ipsec_common_input_cb(): unknown/unsupported protocol family %d\n", af));
	    m_freem(m);
	    return EPFNOSUPPORT;
    }
#undef IPSEC_ISTAT
}

int
esp_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlen, void *newp,
	   size_t newlen)
{
    /* All sysctl names at this level are terminal. */
    if (namelen != 1)
      return ENOTDIR;

    switch (name[0])
    {
	case ESPCTL_ENABLE:
	    return sysctl_int(oldp, oldlen, newp, newlen, &esp_enable);
	default:
	    return ENOPROTOOPT;
    }
    /* NOTREACHED */
}

int
ah_sysctl(int *name, u_int namelen, void *oldp, size_t *oldlen, void *newp,
	  size_t newlen)
{
    /* All sysctl names at this level are terminal. */
    if (namelen != 1)
      return ENOTDIR;

    switch (name[0])
    {
	case AHCTL_ENABLE:
	    return sysctl_int(oldp, oldlen, newp, newlen, &ah_enable);
	default:
	    return ENOPROTOOPT;
    }
    /* NOTREACHED */
}

#ifdef INET
/* IPv4 AH wrapper */
void
ah4_input(struct mbuf *m, ...)
{
    int skip;

    va_list ap;
    va_start(ap, m);
    skip = va_arg(ap, int);
    va_end(ap);

    ipsec_common_input(m, skip, offsetof(struct ip, ip_p), AF_INET,
		       IPPROTO_AH);
    return;
}

/* IPv4 AH callback */
int
ah4_input_cb(struct mbuf *m, ...)
{
    struct ifqueue *ifq = &ipintrq;
    int s = splimp();

    /*
     * Interface pointer is already in first mbuf; chop off the
     * `outer' header and reschedule.
     */

    if (IF_QFULL(ifq))
    {
	IF_DROP(ifq);
	ahstat.ahs_qfull++;
	splx(s);

	m_freem(m);
	DPRINTF(("ah4_input_cb(): dropped packet because of full IP queue\n"));
	return ENOBUFS;
    }

    IF_ENQUEUE(ifq, m);
    schednetisr(NETISR_IP);
    splx(s);

    return 0;
}


void *
ah4_ctlinput(int cmd, struct sockaddr *sa, void *v)
{
	if (sa->sa_family != AF_INET ||
	    sa->sa_len != sizeof(struct sockaddr_in))
		return (NULL);

	return (ipsec_common_ctlinput(cmd, sa, v, IPPROTO_AH));
}

/* IPv4 ESP wrapper */
void
esp4_input(struct mbuf *m, ...)
{
    int skip;

    va_list ap;
    va_start(ap, m);
    skip = va_arg(ap, int);
    va_end(ap);

    ipsec_common_input(m, skip, offsetof(struct ip, ip_p), AF_INET,
		       IPPROTO_ESP);
}

/* IPv4 ESP callback */
int
esp4_input_cb(struct mbuf *m, ...)
{
    struct ifqueue *ifq = &ipintrq;
    int s = splimp();

    /*
     * Interface pointer is already in first mbuf; chop off the
     * `outer' header and reschedule.
     */
    if (IF_QFULL(ifq))
    {
	IF_DROP(ifq);
	espstat.esps_qfull++;
	splx(s);

	m_freem(m);
	DPRINTF(("esp4_input_cb(): dropped packet because of full IP queue\n"));
	return ENOBUFS;
    }

    IF_ENQUEUE(ifq, m);
    schednetisr(NETISR_IP);
    splx(s);

    return 0;
}

void *
ipsec_common_ctlinput(int cmd, struct sockaddr *sa, void *v, int proto)
{
	extern u_int ip_mtudisc_timeout;
	struct ip *ip = v;
	int s;

	if (cmd == PRC_MSGSIZE && ip && ip->ip_v == 4) {
		struct tdb *tdbp;
		struct sockaddr_in dst;
		struct icmp *icp;
		int hlen = ip->ip_hl << 2;
		u_int32_t spi, mtu;
		ssize_t adjust;
	
		/* Find the right MTU */
		icp = (struct icmp *)((caddr_t) ip -
				      offsetof(struct icmp, icmp_ip));
		mtu = ntohs(icp->icmp_nextmtu);

		/* Ignore the packet, if we do not receive a MTU
		 * or the MTU is too small to be acceptable.
		 */
		if (mtu < 296)
			return (NULL);

		bzero(&dst, sizeof(struct sockaddr_in));
		dst.sin_family = AF_INET;
		dst.sin_len = sizeof(struct sockaddr_in);
		dst.sin_addr.s_addr = ip->ip_dst.s_addr;

		bcopy((caddr_t)ip + hlen, &spi, sizeof(u_int32_t));

		s = spltdb();
		tdbp = gettdb(spi, (union sockaddr_union *)&dst, proto);
		if (tdbp == NULL || tdbp->tdb_flags & TDBF_INVALID) {
			splx(s);
			return (NULL);
		}

		/* Walk the chain backswards to the first tdb */
		for (; tdbp; tdbp = tdbp->tdb_inext) {
			if (tdbp->tdb_flags & TDBF_INVALID ||
			    (adjust = ipsec_hdrsz(tdbp)) == -1) {
				splx(s);
				return (NULL);
			}

			mtu -= adjust;

			/* Store adjusted MTU in tdb */
			tdbp->tdb_mtu = mtu;
			tdbp->tdb_mtutimeout = time.tv_sec +
				ip_mtudisc_timeout;
		}
		splx(s);

		return (NULL);
	}

	return (NULL);
}

void *
esp4_ctlinput(int cmd, struct sockaddr *sa, void *v)
{
	if (sa->sa_family != AF_INET ||
	    sa->sa_len != sizeof(struct sockaddr_in))
		return (NULL);

	return (ipsec_common_ctlinput(cmd, sa, v, IPPROTO_ESP));
}
#endif /* INET */

#ifdef INET6
/* IPv6 AH wrapper */
int
ah6_input(struct mbuf **mp, int *offp, int proto)
{
    int l = 0;
    int protoff;
    struct ip6_ext ip6e;

    if (*offp < sizeof(struct ip6_hdr))
    {
	DPRINTF(("ah6_input(): bad offset\n"));
	return IPPROTO_DONE;
    }
    else if (*offp == sizeof(struct ip6_hdr))
    {
	protoff = offsetof(struct ip6_hdr, ip6_nxt);
    }
    else
    {
	/* Chase down the header chain... */
	protoff = sizeof(struct ip6_hdr);

	do
	{
	    protoff += l;
	    m_copydata(*mp, protoff, sizeof(ip6e), (caddr_t) &ip6e);
	    if (ip6e.ip6e_nxt == IPPROTO_AH)
		l = (ip6e.ip6e_len + 2) << 2;
	    else
		l = (ip6e.ip6e_len + 1) << 3;
#ifdef DIAGNOSTIC
	    if (l <= 0)
		panic("ah6_input: l went zero or negative");
#endif
	} while (protoff + l < *offp);

	/* Malformed packet check */
	if (protoff + l != *offp)
	{
	    DPRINTF(("ah6_input(): bad packet header chain\n"));
	    ahstat.ahs_hdrops++;
	    m_freem(*mp);
	    *mp = NULL;
	    return IPPROTO_DONE;
	}

	protoff += offsetof(struct ip6_ext, ip6e_nxt);
    }

    ipsec_common_input(*mp, *offp, protoff, AF_INET6, proto);
    return IPPROTO_DONE;
}

/* IPv6 AH callback */
int
ah6_input_cb(struct mbuf *m, int off, int protoff)
{
    int nxt;
    u_int8_t nxt8;
    int nest = 0;

    /* Retrieve new protocol */
    m_copydata(m, protoff, sizeof(u_int8_t), (caddr_t) &nxt8);
    nxt = nxt8;

    /*
     * see the end of ip6_input for this logic.
     * IPPROTO_IPV[46] case will be processed just like other ones
     */
    while (nxt != IPPROTO_DONE) {
	if (ip6_hdrnestlimit && (++nest > ip6_hdrnestlimit)) {
	    ip6stat.ip6s_toomanyhdr++;
	    goto bad;
	}

	/*
	 * protection against faulty packet - there should be
	 * more sanity checks in header chain processing.
	 */
	if (m->m_pkthdr.len < off) {
	    ip6stat.ip6s_tooshort++;
	    in6_ifstat_inc(m->m_pkthdr.rcvif, ifs6_in_truncated);
	    goto bad;
	}

	nxt = (*inet6sw[ip6_protox[nxt]].pr_input)(&m, &off, nxt);
    }

    return 0;

bad:
    m_freem(m);
    return EINVAL;
}

/* IPv6 ESP wrapper */
int
esp6_input(struct mbuf **mp, int *offp, int proto)
{
    int l = 0;
    int protoff;
    struct ip6_ext ip6e;

    if (*offp < sizeof(struct ip6_hdr))
    {
	DPRINTF(("esp6_input(): bad offset\n"));
	return IPPROTO_DONE;
    }
    else if (*offp == sizeof(struct ip6_hdr))
    {
	protoff = offsetof(struct ip6_hdr, ip6_nxt);
    }
    else
    {
	/* Chase down the header chain... */
	protoff = sizeof(struct ip6_hdr);

	do
	{
	    protoff += l;
	    m_copydata(*mp, protoff, sizeof(ip6e), (caddr_t) &ip6e);
	    if (ip6e.ip6e_nxt == IPPROTO_AH)
		l = (ip6e.ip6e_len + 2) << 2;
	    else
		l = (ip6e.ip6e_len + 1) << 3;
#ifdef DIAGNOSTIC
	    if (l <= 0)
		panic("esp6_input: l went zero or negative");
#endif
	} while (protoff + l < *offp);

	/* Malformed packet check */
	if (protoff + l != *offp)
	{
	    DPRINTF(("esp6_input(): bad packet header chain\n"));
	    espstat.esps_hdrops++;
	    m_freem(*mp);
	    *mp = NULL;
	    return IPPROTO_DONE;
	}

	protoff += offsetof(struct ip6_ext, ip6e_nxt);
    }

    ipsec_common_input(*mp, *offp, protoff, AF_INET6, proto);
    return IPPROTO_DONE;
}

/* IPv6 ESP callback */
int
esp6_input_cb(struct mbuf *m, int skip, int protoff)
{
    return ah6_input_cb(m, skip, protoff);
}
#endif /* INET6 */