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Minor changes, preparing for real socket-attached TDBs; also, more
information will be stored in the TDB. ok ho@ provos@

/*	$OpenBSD: ip_ipip.c,v 1.13 2001/04/14 00:30:59 angelos 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).
 *
 * The original version of 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.
 */

/*
 * IP-inside-IP processing
 */


#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/time.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <machine/cpu.h>

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

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

#ifdef MROUTING
#include <netinet/ip_mroute.h>
#endif

#include <sys/socketvar.h>
#include <net/raw_cb.h>

#include <netinet/ip_ipsp.h>
#include <netinet/ip_ipip.h>
#include <dev/rndvar.h>

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

/*
 * We can control the acceptance of IP4 packets by altering the sysctl
 * net.inet.ipip.allow value.  Zero means drop them, all else is acceptance.
 */
int ipip_allow = 0;

struct ipipstat ipipstat;

#ifdef INET6
/*
 * Really only a wrapper for ipip_input(), for use with IPv6.
 */
int
ip4_input6(struct mbuf **m, int *offp, int proto)
{
    /* If we do not accept IPv4 explicitly, drop.  */
    if (!ipip_allow && ((*m)->m_flags & (M_AUTH|M_CONF)) == 0)
    {
	DPRINTF(("ip4_input6(): dropped due to policy\n"));
	ipipstat.ipips_pdrops++;
	m_freem(*m);
	return IPPROTO_DONE;
    }

    ipip_input(*m, *offp);
    return IPPROTO_DONE;
}
#endif /* INET6 */

#ifdef INET
/*
 * Really only a wrapper for ipip_input(), for use with IPv4.
 */
void
ip4_input(struct mbuf *m, ...)
{
    va_list ap;
    int iphlen;

    /* If we do not accept IPv4 explicitly, drop.  */
    if (!ipip_allow && (m->m_flags & (M_AUTH|M_CONF)) == 0)
    {
	DPRINTF(("ip4_input(): dropped due to policy\n"));
	ipipstat.ipips_pdrops++;
	m_freem(m);
	return;
    }

    va_start(ap, m);
    iphlen = va_arg(ap, int);
    va_end(ap);

    ipip_input(m, iphlen);
}
#endif /* INET */

/*
 * ipip_input gets called when we receive an IP{46} encapsulated packet,
 * either because we got it at a real interface, or because AH or ESP
 * were being used in tunnel mode (in which case the rcvif element will 
 * contain the address of the encX interface associated with the tunnel.
 */

void
ipip_input(struct mbuf *m, int iphlen)
{
    register struct sockaddr_in *sin;
    register struct ifnet *ifp;
    register struct ifaddr *ifa;
    struct ifqueue *ifq = NULL;
    struct ip *ipo;
#ifdef INET6
    register struct sockaddr_in6 *sin6;
    struct ip6_hdr *ip6 = NULL;
    u_int8_t itos;
#endif
    u_int8_t nxt;
    int isr;
    u_int8_t otos;
    u_int8_t v;
    int hlen, s;

    ipipstat.ipips_ipackets++;

    m_copydata(m, 0, 1, &v);

    switch (v >> 4)
    {
#ifdef INET
        case 4:
            hlen = sizeof(struct ip);
            break;
#endif /* INET */

#ifdef INET6   
        case 6:
            hlen = sizeof(struct ip6_hdr);
            break;
#endif
        default:
            m_freem(m);
            return /* EAFNOSUPPORT */;
    }

    /* Bring the IP header in the first mbuf, if not there already */
    if (m->m_len < hlen)
    {
	if ((m = m_pullup(m, hlen)) == 0)
	{
	    DPRINTF(("ipip_input(): m_pullup() failed\n"));
	    ipipstat.ipips_hdrops++;
	    return;
	}
    }

    ipo = mtod(m, struct ip *);

#ifdef MROUTING
    if (ipo->ip_v == IPVERSION && ipo->ip_p == IPPROTO_IPV4)
    {
	if (IN_MULTICAST(((struct ip *)((char *) ipo + iphlen))->ip_dst.s_addr))
	{
	    ipip_mroute_input (m, iphlen);
	    return;
	}
    }
#endif MROUTING

    /* keep outer ecn field */

#ifdef INET
    if ((v >> 4) == 4)
      otos = ipo->ip_tos;
#endif /* INET */

#ifdef INET6
    if ((v >> 4) == 6)
      otos = (ntohl(mtod(m, struct ip6_hdr *)->ip6_flow) >> 20) & 0xff;
#endif

    /* Remove outer IP header */
    m_adj(m, iphlen);

    m_copydata(m, 0, 1, &v);

    switch (v >> 4)
    {
#ifdef INET
        case 4:
            hlen = sizeof(struct ip);
            break;
#endif /* INET */

#ifdef INET6
        case 6:
            hlen = sizeof(struct ip6_hdr);
            break;
#endif

        default:
            m_freem(m);
            return /* EAFNOSUPPORT */;
    }

    /* Bring the inner IP header in the first mbuf, if not there already */
    if (m->m_len < hlen)
    {
	if ((m = m_pullup(m, hlen)) == 0)
	{
	    DPRINTF(("ipip_input(): m_pullup() failed\n"));
	    ipipstat.ipips_hdrops++;
	    return;
	}
    }

    /*
     * RFC 1853 specifies that the inner TTL should not be touched on
     * decapsulation. There's no reason this comment should be here, but
     * this is as good as any a position.
     */

    /* Some sanity checks in the inner IPv4 header */
    switch (v >> 4)
    {
#ifdef INET
    	case 4:
                ipo = mtod(m, struct ip *);
                nxt = ipo->ip_p;
		ip_ecn_egress(ECN_ALLOWED, &otos, &ipo->ip_tos);
                break;
#endif /* INET */

#ifdef INET6
    	case 6:
                ip6 = (struct ip6_hdr *) ipo;
                nxt = ip6->ip6_nxt;
		itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
		ip_ecn_egress(ECN_ALLOWED, &otos, &itos);
		ip6->ip6_flow &= ~htonl(0xff << 20);
		ip6->ip6_flow |= htonl((u_int32_t) itos << 20);
                break;
#endif
    }

    /* Check for local address spoofing. */
    if ((m->m_pkthdr.rcvif == NULL ||
	!(m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK)) &&
	ipip_allow != 2)
    {
        for (ifp = ifnet.tqh_first; ifp != 0; ifp = ifp->if_list.tqe_next)
	{
	    for (ifa = ifp->if_addrlist.tqh_first;
		 ifa != 0;
		 ifa = ifa->ifa_list.tqe_next)
	    {
#ifdef INET
		if (ipo)
		{
		    if (ifa->ifa_addr->sa_family != AF_INET)
		      continue;

		    sin = (struct sockaddr_in *) ifa->ifa_addr;

		    if (sin->sin_addr.s_addr == ipo->ip_src.s_addr)
		    {
			DPRINTF(("ipip_input(): possible local address spoofing detected on packet from %s to %s (%s->%s)\n", inet_ntoa4(ipo->ip_src), inet_ntoa4(ipo->ip_dst), inet_ntoa4(ipo->ip_src), inet_ntoa4(ipo->ip_dst)));
			ipipstat.ipips_spoof++;
			m_freem(m);
			return;
		    }
		}
#endif /* INET */

#ifdef INET6
		if (ip6)
		{
		    if (ifa->ifa_addr->sa_family != AF_INET6)
		      continue;

		    sin6 = (struct sockaddr_in6 *) ifa->ifa_addr;

		    if (IN6_ARE_ADDR_EQUAL(&sin6->sin6_addr, &ip6->ip6_src))
		    {
			DPRINTF(("ipip_input(): possible local address spoofing detected on packet\n"));
			m_freem(m);
			return;
		    }

		}
#endif /* INET6 */
	    }
	}
    }
    
    /* Statistics */
    ipipstat.ipips_ibytes += m->m_pkthdr.len - iphlen;

    /*
     * Interface pointer stays the same; if no IPsec processing has
     * been done (or will be done), this will point to a normal 
     * interface. Otherwise, it'll point to an enc interface, which
     * will allow a packet filter to distinguish between secure and
     * untrusted packets.
     */

#ifdef INET
    if (ipo)
    {
	ifq = &ipintrq;
	isr = NETISR_IP;
    }
#endif /* INET */

#ifdef INET6
    if (ip6)
    {
	ifq = &ip6intrq;
	isr = NETISR_IPV6;
    }
#endif /* INET6 */

    s = splimp();			/* isn't it already? */
    if (IF_QFULL(ifq))
    {
	IF_DROP(ifq);
	m_freem(m);
	ipipstat.ipips_qfull++;

	splx(s);

	DPRINTF(("ipip_input(): packet dropped because of full queue\n"));
	return;
    }

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

    return;
}

int
ipip_output(struct mbuf *m, struct tdb *tdb, struct mbuf **mp, int skip,
	    int protoff, struct tdb *tdb2)
{
    u_int8_t tp, otos;

#ifdef INET
    u_int8_t itos;
    struct ip *ipo;
#endif /* INET */

#ifdef INET6    
    struct ip6_hdr *ip6, *ip6o;
#endif /* INET6 */

    /* Deal with empty TDB source/destination addresses */
    /* XXX */

    m_copydata(m, 0, 1, &tp);
    tp = (tp >> 4) & 0xff;  /* Get the IP version number */

    switch (tdb->tdb_dst.sa.sa_family)
    {
#ifdef INET
	case AF_INET:
	    if ((tdb->tdb_src.sa.sa_family != AF_INET) ||
		(tdb->tdb_src.sin.sin_addr.s_addr == INADDR_ANY) ||
		(tdb->tdb_dst.sin.sin_addr.s_addr == INADDR_ANY))
	    {
		DPRINTF(("ipip_output(): unspecified tunnel endpoind address in SA %s/%08x\n", ipsp_address(tdb->tdb_dst), ntohl(tdb->tdb_spi)));
		ipipstat.ipips_unspec++;
		m_freem(m);
		*mp = NULL;
		return EINVAL;
	    }

	    M_PREPEND(m, sizeof(struct ip), M_DONTWAIT);
	    if (m == 0)
	    {
		DPRINTF(("ipip_output(): M_PREPEND failed\n"));
		ipipstat.ipips_hdrops++;
		*mp = NULL;
		return ENOBUFS;
	    }

	    ipo = mtod(m, struct ip *);

	    ipo->ip_v = IPVERSION;
	    ipo->ip_hl = 5;
	    ipo->ip_len = htons(m->m_pkthdr.len);
	    ipo->ip_ttl = ip_defttl;
	    ipo->ip_sum = 0;
	    ipo->ip_src = tdb->tdb_src.sin.sin_addr;
	    ipo->ip_dst = tdb->tdb_dst.sin.sin_addr;

	    /*
	     * We do the htons() to prevent snoopers from determining our
	     * endianness.
	     */
	    ipo->ip_id = htons(ip_randomid());

	    /* If the inner protocol is IP */
	    if (tp == IPVERSION)
	    {
		/* Save ECN notification */
		m_copydata(m, sizeof(struct ip) + offsetof(struct ip, ip_tos),
			   sizeof(u_int8_t), (caddr_t) &itos);

		ipo->ip_p = IPPROTO_IPIP;

		/*
		 * We should be keeping tunnel soft-state and send back ICMPs
		 * if needed.
		 */
		m_copydata(m, sizeof(struct ip) + offsetof(struct ip, ip_off),
			   sizeof(u_int16_t), (caddr_t) &ipo->ip_off);
                NTOHS(ipo->ip_off);
                ipo->ip_off &= ~(IP_DF | IP_MF | IP_OFFMASK);
                HTONS(ipo->ip_off);
	    }
#ifdef INET6
	    else if (tp == (IPV6_VERSION >> 4))
	    {
		u_int32_t itos32;
		/* Save ECN notification */
		m_copydata(m, sizeof(struct ip) +
			   offsetof(struct ip6_hdr, ip6_flow),
			   sizeof(u_int32_t), (caddr_t) &itos32);
		itos = ntohl(itos32) >> 20;

		ipo->ip_p = IPPROTO_IPV6;
		ipo->ip_off = 0;
	    }
#endif /* INET6 */
	    else
	    {
		m_freem(m);
		*mp = NULL;
		return EAFNOSUPPORT;
	    }

	    otos = 0;
	    ip_ecn_ingress(ECN_ALLOWED, &otos, &itos);
	    ipo->ip_tos = otos;
	    break;
#endif /* INET */

#ifdef INET6
	case AF_INET6:
	    if (IN6_IS_ADDR_UNSPECIFIED(&tdb->tdb_dst.sin6.sin6_addr) ||
		(tdb->tdb_src.sa.sa_family != AF_INET6) ||
		IN6_IS_ADDR_UNSPECIFIED(&tdb->tdb_src.sin6.sin6_addr))
	    {
		DPRINTF(("ipip_output(): unspecified tunnel endpoind address in SA %s/%08x\n", ipsp_address(tdb->tdb_dst), ntohl(tdb->tdb_spi)));
		ipipstat.ipips_unspec++;
		m_freem(m);
		*mp = NULL;
		return ENOBUFS;
	    }

	    /* scoped address handling */
	    ip6 = mtod(m, struct ip6_hdr *);
	    if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
		ip6->ip6_src.s6_addr16[1] = 0;
	    if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst))
		ip6->ip6_dst.s6_addr16[1] = 0;

	    M_PREPEND(m, sizeof(struct ip6_hdr), M_DONTWAIT);
	    if (m == 0)
	    {
		DPRINTF(("ipip_output(): M_PREPEND failed\n"));
		ipipstat.ipips_hdrops++;
		*mp = NULL;
		return ENOBUFS;
	    }

	    /* Initialize IPv6 header */
	    ip6o = mtod(m, struct ip6_hdr *);
	    ip6o->ip6_flow = 0;
	    ip6o->ip6_vfc &= ~IPV6_VERSION_MASK;
	    ip6o->ip6_vfc |= IPV6_VERSION;
	    ip6o->ip6_plen = htons(m->m_pkthdr.len);
	    ip6o->ip6_hlim = ip_defttl;
	    ip6o->ip6_dst = tdb->tdb_dst.sin6.sin6_addr;
	    ip6o->ip6_src = tdb->tdb_src.sin6.sin6_addr;

#ifdef INET
	    if (tp == IPVERSION)
	    {
		/* Save ECN notification */
		m_copydata(m, sizeof(struct ip6_hdr) +
			   offsetof(struct ip, ip_tos), sizeof(u_int8_t),
			   (caddr_t) &itos);

		ip6o->ip6_nxt = IPPROTO_IPIP; /* This is really IPVERSION */
	    }
	    else
#endif /* INET */
	    if (tp == (IPV6_VERSION >> 4))
	    {
		u_int32_t itos32;
		/* Save ECN notification */
		m_copydata(m, sizeof(struct ip6_hdr) +
			   offsetof(struct ip6_hdr, ip6_flow),
			   sizeof(u_int32_t), (caddr_t) &itos32);
		itos = ntohl(itos32) >> 20;

		ip6o->ip6_nxt = IPPROTO_IPV6;
	    }
	    else
	    {
		m_freem(m);
		*mp = NULL;
		return EAFNOSUPPORT;
	    }

	    otos = 0;
	    ip_ecn_ingress(ECN_ALLOWED, &otos, &itos);
	    ip6o->ip6_flow |= htonl((u_int32_t) otos << 20);
	    break;
#endif /* INET6 */

	default:
	    DPRINTF(("ipip_output(): unsupported protocol family %d\n",
		     tdb->tdb_dst.sa.sa_family));
	    m_freem(m);
	    *mp = NULL;
	    ipipstat.ipips_family++;
	    return ENOBUFS;
    }

    ipipstat.ipips_opackets++;

    *mp = m;

#ifdef INET
    if (tdb->tdb_dst.sa.sa_family == AF_INET)
    {
	if (tdb->tdb_xform->xf_type == XF_IP4)
	  tdb->tdb_cur_bytes += m->m_pkthdr.len - sizeof(struct ip);

	ipipstat.ipips_obytes += m->m_pkthdr.len - sizeof(struct ip);
    }
#endif /* INET */

#ifdef INET6
    if (tdb->tdb_dst.sa.sa_family == AF_INET6)
    {
	if (tdb->tdb_xform->xf_type == XF_IP4)
	  tdb->tdb_cur_bytes += m->m_pkthdr.len - sizeof(struct ip6_hdr);

	ipipstat.ipips_obytes += m->m_pkthdr.len - sizeof(struct ip6_hdr);
    }
#endif /* INET6 */

    return 0;
}

#ifdef IPSEC

int
ipe4_attach()
{
    return 0;
}

int
ipe4_init(struct tdb *tdbp, struct xformsw *xsp, struct ipsecinit *ii)
{
    tdbp->tdb_xform = xsp;
    return 0;
}

int
ipe4_zeroize(struct tdb *tdbp)
{
    return 0;
}

void
ipe4_input(struct mbuf *m, ...)
{
    /* This is a rather serious mistake, so no conditional printing */
    printf("ipe4_input(): should never be called\n");
    if (m)
      m_freem(m);
}
#endif	/* IPSEC */

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

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