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ip6_forward.c revision 1.74.2.3
      1 /*	$NetBSD: ip6_forward.c,v 1.74.2.3 2016/07/09 20:25:22 skrll Exp $	*/
      2 /*	$KAME: ip6_forward.c,v 1.109 2002/09/11 08:10:17 sakane Exp $	*/
      3 
      4 /*
      5  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. Neither the name of the project nor the names of its contributors
     17  *    may be used to endorse or promote products derived from this software
     18  *    without specific prior written permission.
     19  *
     20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
     21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
     24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     30  * SUCH DAMAGE.
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: ip6_forward.c,v 1.74.2.3 2016/07/09 20:25:22 skrll Exp $");
     35 
     36 #ifdef _KERNEL_OPT
     37 #include "opt_gateway.h"
     38 #include "opt_ipsec.h"
     39 #endif
     40 
     41 #include <sys/param.h>
     42 #include <sys/systm.h>
     43 #include <sys/mbuf.h>
     44 #include <sys/domain.h>
     45 #include <sys/protosw.h>
     46 #include <sys/socket.h>
     47 #include <sys/errno.h>
     48 #include <sys/time.h>
     49 #include <sys/kernel.h>
     50 #include <sys/syslog.h>
     51 
     52 #include <net/if.h>
     53 #include <net/route.h>
     54 #include <net/pfil.h>
     55 
     56 #include <netinet/in.h>
     57 #include <netinet/in_var.h>
     58 #include <netinet/ip_var.h>
     59 #include <netinet/ip6.h>
     60 #include <netinet6/ip6_var.h>
     61 #include <netinet6/ip6_private.h>
     62 #include <netinet6/scope6_var.h>
     63 #include <netinet/icmp6.h>
     64 #include <netinet6/nd6.h>
     65 
     66 #ifdef IPSEC
     67 #include <netipsec/ipsec.h>
     68 #include <netipsec/ipsec6.h>
     69 #include <netipsec/key.h>
     70 #include <netipsec/xform.h>
     71 #endif /* IPSEC */
     72 
     73 #include <net/net_osdep.h>
     74 
     75 struct	route ip6_forward_rt;
     76 
     77 extern pfil_head_t *inet6_pfil_hook;	/* XXX */
     78 
     79 static void __printflike(4, 5)
     80 ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp,
     81     const struct ifnet *dstifp, const char *fmt, ...)
     82 {
     83 	char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN];
     84 	char reason[256];
     85 	va_list ap;
     86 	uint64_t *ip6s;
     87 
     88 	/* update statistics */
     89 	ip6s = IP6_STAT_GETREF();
     90 	ip6s[IP6_STAT_CANTFORWARD]++;
     91 	if (dstifp)
     92 		ip6s[IP6_STAT_BADSCOPE]++;
     93 	IP6_STAT_PUTREF();
     94 
     95 	if (dstifp)
     96 		in6_ifstat_inc(dstifp, ifs6_in_discard);
     97 
     98 	if (ip6_log_time + ip6_log_interval >= time_uptime)
     99 		return;
    100 	ip6_log_time = time_uptime;
    101 
    102 	va_start(ap, fmt);
    103 	vsnprintf(reason, sizeof(reason), fmt, ap);
    104 	va_end(ap);
    105 
    106 	log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n",
    107 	    IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?",
    108 	    IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?",
    109 	    ip6->ip6_nxt, reason);
    110 }
    111 
    112 /*
    113  * Forward a packet.  If some error occurs return the sender
    114  * an icmp packet.  Note we can't always generate a meaningful
    115  * icmp message because icmp doesn't have a large enough repertoire
    116  * of codes and types.
    117  *
    118  * If not forwarding, just drop the packet.  This could be confusing
    119  * if ipforwarding was zero but some routing protocol was advancing
    120  * us as a gateway to somewhere.  However, we must let the routing
    121  * protocol deal with that.
    122  *
    123  */
    124 
    125 void
    126 ip6_forward(struct mbuf *m, int srcrt)
    127 {
    128 	struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
    129 	const struct sockaddr_in6 *dst;
    130 	struct rtentry *rt;
    131 	int error = 0, type = 0, code = 0;
    132 	struct mbuf *mcopy = NULL;
    133 	struct ifnet *origifp;	/* maybe unnecessary */
    134 	uint32_t inzone, outzone;
    135 	struct in6_addr src_in6, dst_in6;
    136 	struct ifnet *rcvif = NULL;
    137 	struct psref psref;
    138 #ifdef IPSEC
    139 	int needipsec = 0;
    140 	struct secpolicy *sp = NULL;
    141 #endif
    142 
    143 	/*
    144 	 * Clear any in-bound checksum flags for this packet.
    145 	 */
    146 	m->m_pkthdr.csum_flags = 0;
    147 
    148 	rcvif = m_get_rcvif_psref(m, &psref);
    149 	if (__predict_false(rcvif == NULL))
    150 		goto drop;
    151 
    152 	/*
    153 	 * Do not forward packets to multicast destination (should be handled
    154 	 * by ip6_mforward().
    155 	 * Do not forward packets with unspecified source.  It was discussed
    156 	 * in July 2000, on ipngwg mailing list.
    157 	 */
    158 	if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 ||
    159 	    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
    160 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
    161 		ip6_cantforward(ip6, rcvif, NULL,
    162 		    ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" :
    163 		    IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" :
    164 		    "unspec/src");
    165 		goto drop;
    166 	}
    167 
    168 	if (ip6->ip6_hlim <= IPV6_HLIMDEC) {
    169 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */
    170 		icmp6_error(m, ICMP6_TIME_EXCEEDED,
    171 				ICMP6_TIME_EXCEED_TRANSIT, 0);
    172 		goto out;
    173 	}
    174 	ip6->ip6_hlim -= IPV6_HLIMDEC;
    175 
    176 	/*
    177 	 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU -
    178 	 * size of IPv6 + ICMPv6 headers) bytes of the packet in case
    179 	 * we need to generate an ICMP6 message to the src.
    180 	 * Thanks to M_EXT, in most cases copy will not occur.
    181 	 *
    182 	 * It is important to save it before IPsec processing as IPsec
    183 	 * processing may modify the mbuf.
    184 	 */
    185 	mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN));
    186 
    187 #ifdef IPSEC
    188 	if (ipsec_used) {
    189 		/* Check the security policy (SP) for the packet */
    190 
    191 		sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error);
    192 		if (error != 0) {
    193 			/*
    194 			 * Hack: -EINVAL is used to signal that a packet
    195 			 * should be silently discarded.  This is typically
    196 			 * because we asked key management for an SA and
    197 			 * it was delayed (e.g. kicked up to IKE).
    198 			 */
    199 			if (error == -EINVAL)
    200 				error = 0;
    201 			goto freecopy;
    202 		}
    203 	}
    204 #endif /* IPSEC */
    205 
    206 	if (srcrt) {
    207 		union {
    208 			struct sockaddr		dst;
    209 			struct sockaddr_in6	dst6;
    210 		} u;
    211 
    212 		sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0);
    213 		if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) {
    214 			IP6_STATINC(IP6_STAT_NOROUTE);
    215 			/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
    216 			if (mcopy) {
    217 				icmp6_error(mcopy, ICMP6_DST_UNREACH,
    218 					    ICMP6_DST_UNREACH_NOROUTE, 0);
    219 			}
    220 			goto drop;
    221 		}
    222 	} else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL &&
    223 	           (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) {
    224 		/*
    225 		 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to
    226 		 * ip6->ip6_dst
    227 		 */
    228 		IP6_STATINC(IP6_STAT_NOROUTE);
    229 		/* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */
    230 		if (mcopy) {
    231 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
    232 			    ICMP6_DST_UNREACH_NOROUTE, 0);
    233 		}
    234 		goto drop;
    235 	}
    236 	dst = satocsin6(rtcache_getdst(&ip6_forward_rt));
    237 
    238 	/*
    239 	 * Source scope check: if a packet can't be delivered to its
    240 	 * destination for the reason that the destination is beyond the scope
    241 	 * of the source address, discard the packet and return an icmp6
    242 	 * destination unreachable error with Code 2 (beyond scope of source
    243 	 * address).  We use a local copy of ip6_src, since in6_setscope()
    244 	 * will possibly modify its first argument.
    245 	 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1]
    246 	 */
    247 	src_in6 = ip6->ip6_src;
    248 	inzone = outzone = ~0;
    249 	if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 ||
    250 	    in6_setscope(&src_in6, rcvif, &inzone) != 0 ||
    251 	    inzone != outzone) {
    252 		ip6_cantforward(ip6, rcvif, rt->rt_ifp,
    253 		    "src[%s] inzone %d outzone %d",
    254 		    in6_getscopename(&ip6->ip6_src), inzone, outzone);
    255 		if (mcopy)
    256 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
    257 				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
    258 		goto drop;
    259 	}
    260 
    261 #ifdef IPSEC
    262 	/*
    263 	 * If we need to encapsulate the packet, do it here
    264 	 * ipsec6_proces_packet will send the packet using ip6_output
    265 	 */
    266 	if (needipsec) {
    267 		int s = splsoftnet();
    268 		error = ipsec6_process_packet(m, sp->req);
    269 		splx(s);
    270 		if (mcopy)
    271 			goto freecopy;
    272 	}
    273 #endif
    274 
    275 	/*
    276 	 * Destination scope check: if a packet is going to break the scope
    277 	 * zone of packet's destination address, discard it.  This case should
    278 	 * usually be prevented by appropriately-configured routing table, but
    279 	 * we need an explicit check because we may mistakenly forward the
    280 	 * packet to a different zone by (e.g.) a default route.
    281 	 */
    282 	dst_in6 = ip6->ip6_dst;
    283 	inzone = outzone = ~0;
    284 	if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 ||
    285 	    in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 ||
    286 	    inzone != outzone) {
    287 		ip6_cantforward(ip6, rcvif, rt->rt_ifp,
    288 		    "dst[%s] inzone %d outzone %d",
    289 		    in6_getscopename(&ip6->ip6_dst), inzone, outzone);
    290 		if (mcopy)
    291 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
    292 				    ICMP6_DST_UNREACH_BEYONDSCOPE, 0);
    293 		goto drop;
    294 	}
    295 
    296 	if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) {
    297 		in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig);
    298 		if (mcopy) {
    299 			u_long mtu;
    300 
    301 			mtu = IN6_LINKMTU(rt->rt_ifp);
    302 			icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu);
    303 		}
    304 		goto drop;
    305 	}
    306 
    307 	if (rt->rt_flags & RTF_GATEWAY)
    308 		dst = (struct sockaddr_in6 *)rt->rt_gateway;
    309 
    310 	/*
    311 	 * If we are to forward the packet using the same interface
    312 	 * as one we got the packet from, perhaps we should send a redirect
    313 	 * to sender to shortcut a hop.
    314 	 * Only send redirect if source is sending directly to us,
    315 	 * and if packet was not source routed (or has any options).
    316 	 * Also, don't send redirect if forwarding using a route
    317 	 * modified by a redirect.
    318 	 */
    319 	if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects &&
    320 	    (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) {
    321 		if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) &&
    322 		    nd6_is_addr_neighbor(
    323 		        satocsin6(rtcache_getdst(&ip6_forward_rt)),
    324 			rt->rt_ifp)) {
    325 			/*
    326 			 * If the incoming interface is equal to the outgoing
    327 			 * one, the link attached to the interface is
    328 			 * point-to-point, and the IPv6 destination is
    329 			 * regarded as on-link on the link, then it will be
    330 			 * highly probable that the destination address does
    331 			 * not exist on the link and that the packet is going
    332 			 * to loop.  Thus, we immediately drop the packet and
    333 			 * send an ICMPv6 error message.
    334 			 * For other routing loops, we dare to let the packet
    335 			 * go to the loop, so that a remote diagnosing host
    336 			 * can detect the loop by traceroute.
    337 			 * type/code is based on suggestion by Rich Draves.
    338 			 * not sure if it is the best pick.
    339 			 */
    340 			icmp6_error(mcopy, ICMP6_DST_UNREACH,
    341 				    ICMP6_DST_UNREACH_ADDR, 0);
    342 			goto drop;
    343 		}
    344 		type = ND_REDIRECT;
    345 	}
    346 
    347 	/*
    348 	 * Fake scoped addresses. Note that even link-local source or
    349 	 * destinaion can appear, if the originating node just sends the
    350 	 * packet to us (without address resolution for the destination).
    351 	 * Since both icmp6_error and icmp6_redirect_output fill the embedded
    352 	 * link identifiers, we can do this stuff after making a copy for
    353 	 * returning an error.
    354 	 */
    355 	if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) {
    356 		/*
    357 		 * See corresponding comments in ip6_output.
    358 		 * XXX: but is it possible that ip6_forward() sends a packet
    359 		 *      to a loopback interface? I don't think so, and thus
    360 		 *      I bark here. (jinmei (at) kame.net)
    361 		 * XXX: it is common to route invalid packets to loopback.
    362 		 *	also, the codepath will be visited on use of ::1 in
    363 		 *	rthdr. (itojun)
    364 		 */
    365 #if 1
    366 		if (0)
    367 #else
    368 		if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0)
    369 #endif
    370 		{
    371 			printf("ip6_forward: outgoing interface is loopback. "
    372 			       "src %s, dst %s, nxt %d, rcvif %s, outif %s\n",
    373 			       ip6_sprintf(&ip6->ip6_src),
    374 			       ip6_sprintf(&ip6->ip6_dst),
    375 			       ip6->ip6_nxt, if_name(rcvif),
    376 			       if_name(rt->rt_ifp));
    377 		}
    378 
    379 		/* we can just use rcvif in forwarding. */
    380 		origifp = rcvif;
    381 	}
    382 	else
    383 		origifp = rt->rt_ifp;
    384 	/*
    385 	 * clear embedded scope identifiers if necessary.
    386 	 * in6_clearscope will touch the addresses only when necessary.
    387 	 */
    388 	in6_clearscope(&ip6->ip6_src);
    389 	in6_clearscope(&ip6->ip6_dst);
    390 
    391 	/*
    392 	 * Run through list of hooks for output packets.
    393 	 */
    394 	if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp,
    395 	    PFIL_OUT)) != 0)
    396 		goto senderr;
    397 	if (m == NULL)
    398 		goto freecopy;
    399 	ip6 = mtod(m, struct ip6_hdr *);
    400 
    401 	error = nd6_output(rt->rt_ifp, origifp, m, dst, rt);
    402 	if (error) {
    403 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard);
    404 		IP6_STATINC(IP6_STAT_CANTFORWARD);
    405 	} else {
    406 		IP6_STATINC(IP6_STAT_FORWARD);
    407 		in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward);
    408 		if (type)
    409 			IP6_STATINC(IP6_STAT_REDIRECTSENT);
    410 		else {
    411 #ifdef GATEWAY
    412 			if (m->m_flags & M_CANFASTFWD)
    413 				ip6flow_create(&ip6_forward_rt, m);
    414 #endif
    415 			if (mcopy)
    416 				goto freecopy;
    417 		}
    418 	}
    419 
    420  senderr:
    421 	if (mcopy == NULL)
    422 		goto out;
    423 	switch (error) {
    424 	case 0:
    425 		if (type == ND_REDIRECT) {
    426 			icmp6_redirect_output(mcopy, rt);
    427 			goto out;
    428 		}
    429 		goto freecopy;
    430 
    431 	case EMSGSIZE:
    432 		/* xxx MTU is constant in PPP? */
    433 		goto freecopy;
    434 
    435 	case ENOBUFS:
    436 		/* Tell source to slow down like source quench in IP? */
    437 		goto freecopy;
    438 
    439 	case ENETUNREACH:	/* shouldn't happen, checked above */
    440 	case EHOSTUNREACH:
    441 	case ENETDOWN:
    442 	case EHOSTDOWN:
    443 	default:
    444 		type = ICMP6_DST_UNREACH;
    445 		code = ICMP6_DST_UNREACH_ADDR;
    446 		break;
    447 	}
    448 	icmp6_error(mcopy, type, code, 0);
    449 	goto out;
    450 
    451  freecopy:
    452 	m_freem(mcopy);
    453 	goto out;
    454  drop:
    455  	m_freem(m);
    456  out:
    457 	if (rcvif != NULL)
    458 		m_put_rcvif_psref(rcvif, &psref);
    459 	return;
    460 }
    461