1 /* $NetBSD: ip6_forward.c,v 1.76 2014/12/10 01:10:14 christos 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 1.76 2014/12/10 01:10:14 christos Exp $"); 35 36 #include "opt_gateway.h" 37 #include "opt_ipsec.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/mbuf.h> 42 #include <sys/domain.h> 43 #include <sys/protosw.h> 44 #include <sys/socket.h> 45 #include <sys/errno.h> 46 #include <sys/time.h> 47 #include <sys/kernel.h> 48 #include <sys/syslog.h> 49 50 #include <net/if.h> 51 #include <net/route.h> 52 #include <net/pfil.h> 53 54 #include <netinet/in.h> 55 #include <netinet/in_var.h> 56 #include <netinet/ip_var.h> 57 #include <netinet/ip6.h> 58 #include <netinet6/ip6_var.h> 59 #include <netinet6/ip6_private.h> 60 #include <netinet6/scope6_var.h> 61 #include <netinet/icmp6.h> 62 #include <netinet6/nd6.h> 63 64 #ifdef IPSEC 65 #include <netipsec/ipsec.h> 66 #include <netipsec/ipsec6.h> 67 #include <netipsec/key.h> 68 #include <netipsec/xform.h> 69 #endif /* IPSEC */ 70 71 #include <net/net_osdep.h> 72 73 struct route ip6_forward_rt; 74 75 extern pfil_head_t *inet6_pfil_hook; /* XXX */ 76 77 static void __printflike(4, 5) 78 ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp, 79 const struct ifnet *dstifp, const char *fmt, ...) 80 { 81 char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN]; 82 char reason[256]; 83 va_list ap; 84 uint64_t *ip6s; 85 86 /* update statistics */ 87 ip6s = IP6_STAT_GETREF(); 88 ip6s[IP6_STAT_CANTFORWARD]++; 89 if (dstifp) 90 ip6s[IP6_STAT_BADSCOPE]++; 91 IP6_STAT_PUTREF(); 92 93 if (dstifp) 94 in6_ifstat_inc(dstifp, ifs6_in_discard); 95 96 if (ip6_log_time + ip6_log_interval >= time_second) 97 return; 98 ip6_log_time = time_second; 99 100 va_start(ap, fmt); 101 vsnprintf(reason, sizeof(reason), fmt, ap); 102 va_end(ap); 103 104 log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n", 105 IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?", 106 IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?", 107 ip6->ip6_nxt, reason); 108 } 109 110 /* 111 * Forward a packet. If some error occurs return the sender 112 * an icmp packet. Note we can't always generate a meaningful 113 * icmp message because icmp doesn't have a large enough repertoire 114 * of codes and types. 115 * 116 * If not forwarding, just drop the packet. This could be confusing 117 * if ipforwarding was zero but some routing protocol was advancing 118 * us as a gateway to somewhere. However, we must let the routing 119 * protocol deal with that. 120 * 121 */ 122 123 void 124 ip6_forward(struct mbuf *m, int srcrt) 125 { 126 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 127 const struct sockaddr_in6 *dst; 128 struct rtentry *rt; 129 int error = 0, type = 0, code = 0; 130 struct mbuf *mcopy = NULL; 131 struct ifnet *origifp; /* maybe unnecessary */ 132 uint32_t inzone, outzone; 133 struct in6_addr src_in6, dst_in6; 134 #ifdef IPSEC 135 int needipsec = 0; 136 struct secpolicy *sp = NULL; 137 #endif 138 139 /* 140 * Clear any in-bound checksum flags for this packet. 141 */ 142 m->m_pkthdr.csum_flags = 0; 143 144 /* 145 * Do not forward packets to multicast destination (should be handled 146 * by ip6_mforward(). 147 * Do not forward packets with unspecified source. It was discussed 148 * in July 2000, on ipngwg mailing list. 149 */ 150 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 151 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 152 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 153 ip6_cantforward(ip6, m->m_pkthdr.rcvif, NULL, 154 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : 155 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : 156 "unspec/src"); 157 m_freem(m); 158 return; 159 } 160 161 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 162 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 163 icmp6_error(m, ICMP6_TIME_EXCEEDED, 164 ICMP6_TIME_EXCEED_TRANSIT, 0); 165 return; 166 } 167 ip6->ip6_hlim -= IPV6_HLIMDEC; 168 169 /* 170 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 171 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 172 * we need to generate an ICMP6 message to the src. 173 * Thanks to M_EXT, in most cases copy will not occur. 174 * 175 * It is important to save it before IPsec processing as IPsec 176 * processing may modify the mbuf. 177 */ 178 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 179 180 #ifdef IPSEC 181 if (ipsec_used) { 182 /* Check the security policy (SP) for the packet */ 183 184 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error); 185 if (error != 0) { 186 /* 187 * Hack: -EINVAL is used to signal that a packet 188 * should be silently discarded. This is typically 189 * because we asked key management for an SA and 190 * it was delayed (e.g. kicked up to IKE). 191 */ 192 if (error == -EINVAL) 193 error = 0; 194 goto freecopy; 195 } 196 } 197 #endif /* IPSEC */ 198 199 if (srcrt) { 200 union { 201 struct sockaddr dst; 202 struct sockaddr_in6 dst6; 203 } u; 204 205 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 206 if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) { 207 IP6_STATINC(IP6_STAT_NOROUTE); 208 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 209 if (mcopy) { 210 icmp6_error(mcopy, ICMP6_DST_UNREACH, 211 ICMP6_DST_UNREACH_NOROUTE, 0); 212 } 213 m_freem(m); 214 return; 215 } 216 } else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL && 217 (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) { 218 /* 219 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 220 * ip6->ip6_dst 221 */ 222 IP6_STATINC(IP6_STAT_NOROUTE); 223 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 224 if (mcopy) { 225 icmp6_error(mcopy, ICMP6_DST_UNREACH, 226 ICMP6_DST_UNREACH_NOROUTE, 0); 227 } 228 m_freem(m); 229 return; 230 } 231 dst = satocsin6(rtcache_getdst(&ip6_forward_rt)); 232 233 /* 234 * Source scope check: if a packet can't be delivered to its 235 * destination for the reason that the destination is beyond the scope 236 * of the source address, discard the packet and return an icmp6 237 * destination unreachable error with Code 2 (beyond scope of source 238 * address). We use a local copy of ip6_src, since in6_setscope() 239 * will possibly modify its first argument. 240 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 241 */ 242 src_in6 = ip6->ip6_src; 243 inzone = outzone = ~0; 244 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || 245 in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 246 inzone != outzone) { 247 ip6_cantforward(ip6, m->m_pkthdr.rcvif, rt->rt_ifp, 248 "src[%s] inzone %d outzone %d", 249 in6_getscopename(&ip6->ip6_src), inzone, outzone); 250 if (mcopy) 251 icmp6_error(mcopy, ICMP6_DST_UNREACH, 252 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 253 m_freem(m); 254 return; 255 } 256 257 #ifdef IPSEC 258 /* 259 * If we need to encapsulate the packet, do it here 260 * ipsec6_proces_packet will send the packet using ip6_output 261 */ 262 if (needipsec) { 263 int s = splsoftnet(); 264 error = ipsec6_process_packet(m, sp->req); 265 splx(s); 266 if (mcopy) 267 goto freecopy; 268 } 269 #endif 270 271 /* 272 * Destination scope check: if a packet is going to break the scope 273 * zone of packet's destination address, discard it. This case should 274 * usually be prevented by appropriately-configured routing table, but 275 * we need an explicit check because we may mistakenly forward the 276 * packet to a different zone by (e.g.) a default route. 277 */ 278 dst_in6 = ip6->ip6_dst; 279 inzone = outzone = ~0; 280 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 281 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 282 inzone != outzone) { 283 ip6_cantforward(ip6, m->m_pkthdr.rcvif, rt->rt_ifp, 284 "dst[%s] inzone %d outzone %d", 285 in6_getscopename(&ip6->ip6_dst), inzone, outzone); 286 if (mcopy) 287 icmp6_error(mcopy, ICMP6_DST_UNREACH, 288 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 289 m_freem(m); 290 return; 291 } 292 293 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 294 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 295 if (mcopy) { 296 u_long mtu; 297 298 mtu = IN6_LINKMTU(rt->rt_ifp); 299 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 300 } 301 m_freem(m); 302 return; 303 } 304 305 if (rt->rt_flags & RTF_GATEWAY) 306 dst = (struct sockaddr_in6 *)rt->rt_gateway; 307 308 /* 309 * If we are to forward the packet using the same interface 310 * as one we got the packet from, perhaps we should send a redirect 311 * to sender to shortcut a hop. 312 * Only send redirect if source is sending directly to us, 313 * and if packet was not source routed (or has any options). 314 * Also, don't send redirect if forwarding using a route 315 * modified by a redirect. 316 */ 317 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects && 318 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 319 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 320 nd6_is_addr_neighbor( 321 satocsin6(rtcache_getdst(&ip6_forward_rt)), 322 rt->rt_ifp)) { 323 /* 324 * If the incoming interface is equal to the outgoing 325 * one, the link attached to the interface is 326 * point-to-point, and the IPv6 destination is 327 * regarded as on-link on the link, then it will be 328 * highly probable that the destination address does 329 * not exist on the link and that the packet is going 330 * to loop. Thus, we immediately drop the packet and 331 * send an ICMPv6 error message. 332 * For other routing loops, we dare to let the packet 333 * go to the loop, so that a remote diagnosing host 334 * can detect the loop by traceroute. 335 * type/code is based on suggestion by Rich Draves. 336 * not sure if it is the best pick. 337 */ 338 icmp6_error(mcopy, ICMP6_DST_UNREACH, 339 ICMP6_DST_UNREACH_ADDR, 0); 340 m_freem(m); 341 return; 342 } 343 type = ND_REDIRECT; 344 } 345 346 /* 347 * Fake scoped addresses. Note that even link-local source or 348 * destinaion can appear, if the originating node just sends the 349 * packet to us (without address resolution for the destination). 350 * Since both icmp6_error and icmp6_redirect_output fill the embedded 351 * link identifiers, we can do this stuff after making a copy for 352 * returning an error. 353 */ 354 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 355 /* 356 * See corresponding comments in ip6_output. 357 * XXX: but is it possible that ip6_forward() sends a packet 358 * to a loopback interface? I don't think so, and thus 359 * I bark here. (jinmei@kame.net) 360 * XXX: it is common to route invalid packets to loopback. 361 * also, the codepath will be visited on use of ::1 in 362 * rthdr. (itojun) 363 */ 364 #if 1 365 if (0) 366 #else 367 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 368 #endif 369 { 370 printf("ip6_forward: outgoing interface is loopback. " 371 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 372 ip6_sprintf(&ip6->ip6_src), 373 ip6_sprintf(&ip6->ip6_dst), 374 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 375 if_name(rt->rt_ifp)); 376 } 377 378 /* we can just use rcvif in forwarding. */ 379 origifp = m->m_pkthdr.rcvif; 380 } 381 else 382 origifp = rt->rt_ifp; 383 /* 384 * clear embedded scope identifiers if necessary. 385 * in6_clearscope will touch the addresses only when necessary. 386 */ 387 in6_clearscope(&ip6->ip6_src); 388 in6_clearscope(&ip6->ip6_dst); 389 390 /* 391 * Run through list of hooks for output packets. 392 */ 393 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 394 PFIL_OUT)) != 0) 395 goto senderr; 396 if (m == NULL) 397 goto freecopy; 398 ip6 = mtod(m, struct ip6_hdr *); 399 400 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 401 if (error) { 402 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 403 IP6_STATINC(IP6_STAT_CANTFORWARD); 404 } else { 405 IP6_STATINC(IP6_STAT_FORWARD); 406 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 407 if (type) 408 IP6_STATINC(IP6_STAT_REDIRECTSENT); 409 else { 410 #ifdef GATEWAY 411 if (m->m_flags & M_CANFASTFWD) 412 ip6flow_create(&ip6_forward_rt, m); 413 #endif 414 if (mcopy) 415 goto freecopy; 416 } 417 } 418 419 senderr: 420 if (mcopy == NULL) 421 return; 422 switch (error) { 423 case 0: 424 if (type == ND_REDIRECT) { 425 icmp6_redirect_output(mcopy, rt); 426 return; 427 } 428 goto freecopy; 429 430 case EMSGSIZE: 431 /* xxx MTU is constant in PPP? */ 432 goto freecopy; 433 434 case ENOBUFS: 435 /* Tell source to slow down like source quench in IP? */ 436 goto freecopy; 437 438 case ENETUNREACH: /* shouldn't happen, checked above */ 439 case EHOSTUNREACH: 440 case ENETDOWN: 441 case EHOSTDOWN: 442 default: 443 type = ICMP6_DST_UNREACH; 444 code = ICMP6_DST_UNREACH_ADDR; 445 break; 446 } 447 icmp6_error(mcopy, type, code, 0); 448 return; 449 450 freecopy: 451 m_freem(mcopy); 452 return; 453 } 454