/* $OpenBSD: ip6_forward.c,v 1.39 2007/06/01 00:52:38 henning Exp $ */
/* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "pf.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/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet/icmp6.h>
#include <netinet6/nd6.h>
#if NPF > 0
#include <net/pfvar.h>
#endif
#ifdef IPSEC
#include <netinet/ip_ipsp.h>
#include <netinet/ip_ah.h>
#include <netinet/ip_esp.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <net/pfkeyv2.h>
#endif
struct route_in6 ip6_forward_rt;
int ip6_forward_rtableid;
/*
* Forward a packet. If some error occurs return the sender
* an icmp packet. Note we can't always generate a meaningful
* icmp message because icmp doesn't have a large enough repertoire
* of codes and types.
*
* If not forwarding, just drop the packet. This could be confusing
* if ipforwarding was zero but some routing protocol was advancing
* us as a gateway to somewhere. However, we must let the routing
* protocol deal with that.
*
*/
void
ip6_forward(m, srcrt)
struct mbuf *m;
int srcrt;
{
struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
struct sockaddr_in6 *dst;
struct rtentry *rt;
int error = 0, type = 0, code = 0;
struct mbuf *mcopy = NULL;
struct ifnet *origifp; /* maybe unnecessary */
#ifdef IPSEC
u_int8_t sproto = 0;
struct m_tag *mtag;
union sockaddr_union sdst;
struct tdb_ident *tdbi;
u_int32_t sspi;
struct tdb *tdb;
int s;
#endif /* IPSEC */
int rtableid = 0;
/*
* Do not forward packets to multicast destination (should be handled
* by ip6_mforward().
* Do not forward packets with unspecified source. It was discussed
* in July 2000, on ipngwg mailing list.
*/
if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
ip6stat.ip6s_cantforward++;
/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
if (ip6_log_time + ip6_log_interval < time_second) {
ip6_log_time = time_second;
log(LOG_DEBUG,
"cannot forward "
"from %s to %s nxt %d received on %s\n",
ip6_sprintf(&ip6->ip6_src),
ip6_sprintf(&ip6->ip6_dst),
ip6->ip6_nxt,
m->m_pkthdr.rcvif->if_xname);
}
m_freem(m);
return;
}
if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
icmp6_error(m, ICMP6_TIME_EXCEEDED,
ICMP6_TIME_EXCEED_TRANSIT, 0);
return;
}
ip6->ip6_hlim -= IPV6_HLIMDEC;
#ifdef IPSEC
if (!ipsec_in_use)
goto done_spd;
s = splnet();
/*
* Check if there was an outgoing SA bound to the flow
* from a transport protocol.
*/
/* Do we have any pending SAs to apply ? */
mtag = m_tag_find(m, PACKET_TAG_IPSEC_PENDING_TDB, NULL);
if (mtag != NULL) {
#ifdef DIAGNOSTIC
if (mtag->m_tag_len != sizeof (struct tdb_ident))
panic("ip6_forward: tag of length %d (should be %d",
mtag->m_tag_len, sizeof (struct tdb_ident));
#endif
tdbi = (struct tdb_ident *)(mtag + 1);
tdb = gettdb(tdbi->spi, &tdbi->dst, tdbi->proto);
if (tdb == NULL)
error = -EINVAL;
m_tag_delete(m, mtag);
} else
tdb = ipsp_spd_lookup(m, AF_INET6, sizeof(struct ip6_hdr),
&error, IPSP_DIRECTION_OUT, NULL, NULL);
if (tdb == NULL) {
splx(s);
if (error == 0) {
/*
* No IPsec processing required, we'll just send the
* packet out.
*/
sproto = 0;
/* Fall through to routing/multicast handling */
} else {
/*
* -EINVAL is used to indicate that the packet should
* be silently dropped, typically because we've asked
* key management for an SA.
*/
if (error == -EINVAL) /* Should silently drop packet */
error = 0;
goto freecopy;
}
} else {
/* Loop detection */
for (mtag = m_tag_first(m); mtag != NULL;
mtag = m_tag_next(m, mtag)) {
if (mtag->m_tag_id != PACKET_TAG_IPSEC_OUT_DONE &&
mtag->m_tag_id !=
PACKET_TAG_IPSEC_OUT_CRYPTO_NEEDED)
continue;
tdbi = (struct tdb_ident *)(mtag + 1);
if (tdbi->spi == tdb->tdb_spi &&
tdbi->proto == tdb->tdb_sproto &&
!bcmp(&tdbi->dst, &tdb->tdb_dst,
sizeof(union sockaddr_union))) {
splx(s);
sproto = 0; /* mark as no-IPsec-needed */
goto done_spd;
}
}
/* We need to do IPsec */
bcopy(&tdb->tdb_dst, &sdst, sizeof(sdst));
sspi = tdb->tdb_spi;
sproto = tdb->tdb_sproto;
splx(s);
}
/* Fall through to the routing/multicast handling code */
done_spd:
#endif /* IPSEC */
#if NPF > 0
rtableid = m->m_pkthdr.pf.rtableid;
#endif
/*
* Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
* size of IPv6 + ICMPv6 headers) bytes of the packet in case
* we need to generate an ICMP6 message to the src.
* Thanks to M_EXT, in most cases copy will not occur.
*
* It is important to save it before IPsec processing as IPsec
* processing may modify the mbuf.
*/
mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
dst = &ip6_forward_rt.ro_dst;
if (!srcrt) {
/*
* ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst
*/
if (ip6_forward_rt.ro_rt == 0 ||
(ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0 ||
ip6_forward_rtableid != rtableid) {
if (ip6_forward_rt.ro_rt) {
RTFREE(ip6_forward_rt.ro_rt);
ip6_forward_rt.ro_rt = 0;
}
/* this probably fails but give it a try again */
rtalloc_mpath((struct route *)&ip6_forward_rt,
&ip6->ip6_src.s6_addr32[0], rtableid);
ip6_forward_rtableid = rtableid;
}
if (ip6_forward_rt.ro_rt == 0) {
ip6stat.ip6s_noroute++;
/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
if (mcopy) {
icmp6_error(mcopy, ICMP6_DST_UNREACH,
ICMP6_DST_UNREACH_NOROUTE, 0);
}
m_freem(m);
return;
}
} else if ((rt = ip6_forward_rt.ro_rt) == 0 ||
!IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) {
if (ip6_forward_rt.ro_rt) {
RTFREE(ip6_forward_rt.ro_rt);
ip6_forward_rt.ro_rt = 0;
}
bzero(dst, sizeof(*dst));
dst->sin6_len = sizeof(struct sockaddr_in6);
dst->sin6_family = AF_INET6;
dst->sin6_addr = ip6->ip6_dst;
rtalloc_mpath((struct route *)&ip6_forward_rt,
&ip6->ip6_src.s6_addr32[0], 0);
if (ip6_forward_rt.ro_rt == 0) {
ip6stat.ip6s_noroute++;
/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
if (mcopy) {
icmp6_error(mcopy, ICMP6_DST_UNREACH,
ICMP6_DST_UNREACH_NOROUTE, 0);
}
m_freem(m);
return;
}
}
rt = ip6_forward_rt.ro_rt;
/*
* Scope check: if a packet can't be delivered to its destination
* for the reason that the destination is beyond the scope of the
* source address, discard the packet and return an icmp6 destination
* unreachable error with Code 2 (beyond scope of source address).
* [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1]
*/
if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) !=
in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) {
ip6stat.ip6s_cantforward++;
ip6stat.ip6s_badscope++;
in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard);
if (ip6_log_time + ip6_log_interval < time_second) {
ip6_log_time = time_second;
log(LOG_DEBUG,
"cannot forward "
"src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
ip6_sprintf(&ip6->ip6_src),
ip6_sprintf(&ip6->ip6_dst),
ip6->ip6_nxt,
m->m_pkthdr.rcvif->if_xname, rt->rt_ifp->if_xname);
}
if (mcopy)
icmp6_error(mcopy, ICMP6_DST_UNREACH,
ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
m_freem(m);
goto freert;
}
#ifdef IPSEC
/*
* Check if the packet needs encapsulation.
* ipsp_process_packet will never come back to here.
* XXX ipsp_process_packet() calls ip6_output(), and there'll be no
* PMTU notification. is it okay?
*/
if (sproto != 0) {
s = splnet();
tdb = gettdb(sspi, &sdst, sproto);
if (tdb == NULL) {
splx(s);
error = EHOSTUNREACH;
m_freem(m);
goto senderr; /*XXX*/
}
m->m_flags &= ~(M_BCAST | M_MCAST); /* just in case */
/* Callee frees mbuf */
error = ipsp_process_packet(m, tdb, AF_INET6, 0);
splx(s);
m_freem(mcopy);
goto freert;
}
#endif /* IPSEC */
if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
if (mcopy) {
u_long mtu;
mtu = IN6_LINKMTU(rt->rt_ifp);
icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
}
m_freem(m);
goto freert;
}
if (rt->rt_flags & RTF_GATEWAY)
dst = (struct sockaddr_in6 *)rt->rt_gateway;
/*
* If we are to forward the packet using the same interface
* as one we got the packet from, perhaps we should send a redirect
* to sender to shortcut a hop.
* Only send redirect if source is sending directly to us,
* and if packet was not source routed (or has any options).
* Also, don't send redirect if forwarding using a route
* modified by a redirect.
*/
if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects &&
(rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
nd6_is_addr_neighbor((struct sockaddr_in6 *)&ip6_forward_rt.ro_dst, rt->rt_ifp)) {
/*
* If the incoming interface is equal to the outgoing
* one, the link attached to the interface is
* point-to-point, and the IPv6 destination is
* regarded as on-link on the link, then it will be
* highly probable that the destination address does
* not exist on the link and that the packet is going
* to loop. Thus, we immediately drop the packet and
* send an ICMPv6 error message.
* For other routing loops, we dare to let the packet
* go to the loop, so that a remote diagnosing host
* can detect the loop by traceroute.
* type/code is based on suggestion by Rich Draves.
* not sure if it is the best pick.
*/
icmp6_error(mcopy, ICMP6_DST_UNREACH,
ICMP6_DST_UNREACH_ADDR, 0);
m_freem(m);
goto freert;
}
type = ND_REDIRECT;
}
/*
* Fake scoped addresses. Note that even link-local source or
* destinaion can appear, if the originating node just sends the
* packet to us (without address resolution for the destination).
* Since both icmp6_error and icmp6_redirect_output fill the embedded
* link identifiers, we can do this stuff after making a copy for
* returning an error.
*/
if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
/*
* See corresponding comments in ip6_output.
* XXX: but is it possible that ip6_forward() sends a packet
* to a loopback interface? I don't think so, and thus
* I bark here. (jinmei@kame.net)
* XXX: it is common to route invalid packets to loopback.
* also, the codepath will be visited on use of ::1 in
* rthdr. (itojun)
*/
#if 1
if (0)
#else
if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
#endif
{
printf("ip6_forward: outgoing interface is loopback. "
"src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
ip6_sprintf(&ip6->ip6_src),
ip6_sprintf(&ip6->ip6_dst),
ip6->ip6_nxt, m->m_pkthdr.rcvif->if_xname,
rt->rt_ifp->if_xname);
}
/* we can just use rcvif in forwarding. */
origifp = m->m_pkthdr.rcvif;
}
else
origifp = rt->rt_ifp;
if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src))
ip6->ip6_src.s6_addr16[1] = 0;
if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
ip6->ip6_dst.s6_addr16[1] = 0;
#if NPF > 0
if (pf_test6(PF_OUT, rt->rt_ifp, &m, NULL) != PF_PASS) {
m_freem(m);
goto senderr;
}
if (m == NULL)
goto senderr;
ip6 = mtod(m, struct ip6_hdr *);
#endif
error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
if (error) {
in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
ip6stat.ip6s_cantforward++;
} else {
ip6stat.ip6s_forward++;
in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
if (type)
ip6stat.ip6s_redirectsent++;
else {
if (mcopy)
goto freecopy;
}
}
#if NPF > 0 || defined(IPSEC)
senderr:
#endif
if (mcopy == NULL)
goto freert;
switch (error) {
case 0:
if (type == ND_REDIRECT) {
icmp6_redirect_output(mcopy, rt);
goto freert;
}
goto freecopy;
case EMSGSIZE:
/* xxx MTU is constant in PPP? */
goto freecopy;
case ENOBUFS:
/* Tell source to slow down like source quench in IP? */
goto freecopy;
case ENETUNREACH: /* shouldn't happen, checked above */
case EHOSTUNREACH:
case ENETDOWN:
case EHOSTDOWN:
default:
type = ICMP6_DST_UNREACH;
code = ICMP6_DST_UNREACH_ADDR;
break;
}
icmp6_error(mcopy, type, code, 0);
goto freert;
freecopy:
m_freem(mcopy);
freert:
#ifndef SMALL_KERNEL
if (ip6_multipath && ip6_forward_rt.ro_rt &&
(ip6_forward_rt.ro_rt->rt_flags & RTF_MPATH)) {
RTFREE(ip6_forward_rt.ro_rt);
ip6_forward_rt.ro_rt = 0;
}
#endif
return;
}