1 /* $NetBSD: ip6_forward.c,v 1.18 2001/02/10 04:14:28 itojun Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.56 2000/09/22 04:01:37 itojun 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 "opt_ipsec.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/malloc.h> 38 #include <sys/mbuf.h> 39 #include <sys/domain.h> 40 #include <sys/protosw.h> 41 #include <sys/socket.h> 42 #include <sys/errno.h> 43 #include <sys/time.h> 44 #include <sys/kernel.h> 45 #include <sys/syslog.h> 46 47 #include <net/if.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_var.h> 52 #include <netinet/ip_var.h> 53 #include <netinet/ip6.h> 54 #include <netinet6/ip6_var.h> 55 #include <netinet/icmp6.h> 56 #include <netinet6/nd6.h> 57 58 #ifdef IPSEC 59 #include <netinet6/ipsec.h> 60 #include <netkey/key.h> 61 #endif /* IPSEC */ 62 63 #include <net/net_osdep.h> 64 65 struct route_in6 ip6_forward_rt; 66 67 /* 68 * Forward a packet. If some error occurs return the sender 69 * an icmp packet. Note we can't always generate a meaningful 70 * icmp message because icmp doesn't have a large enough repertoire 71 * of codes and types. 72 * 73 * If not forwarding, just drop the packet. This could be confusing 74 * if ipforwarding was zero but some routing protocol was advancing 75 * us as a gateway to somewhere. However, we must let the routing 76 * protocol deal with that. 77 * 78 */ 79 80 void 81 ip6_forward(m, srcrt) 82 struct mbuf *m; 83 int srcrt; 84 { 85 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 86 struct sockaddr_in6 *dst; 87 struct rtentry *rt; 88 int error, type = 0, code = 0; 89 struct mbuf *mcopy = NULL; 90 struct ifnet *origifp; /* maybe unnecessary */ 91 #ifdef IPSEC 92 struct secpolicy *sp = NULL; 93 #endif 94 long time_second = time.tv_sec; 95 96 #ifdef IPSEC 97 /* 98 * Check AH/ESP integrity. 99 */ 100 /* 101 * Don't increment ip6s_cantforward because this is the check 102 * before forwarding packet actually. 103 */ 104 if (ipsec6_in_reject(m, NULL)) { 105 ipsec6stat.in_polvio++; 106 m_freem(m); 107 return; 108 } 109 #endif /*IPSEC*/ 110 111 /* 112 * Do not forward packets to multicast destination (should be handled 113 * by ip6_mforward(). 114 * Do not forward packets with unspecified source. It was discussed 115 * in July 2000, on ipngwg mailing list. 116 */ 117 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 118 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 119 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 120 ip6stat.ip6s_cantforward++; 121 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 122 if (ip6_log_time + ip6_log_interval < time_second) { 123 ip6_log_time = time_second; 124 log(LOG_DEBUG, 125 "cannot forward " 126 "from %s to %s nxt %d received on %s\n", 127 ip6_sprintf(&ip6->ip6_src), 128 ip6_sprintf(&ip6->ip6_dst), 129 ip6->ip6_nxt, 130 if_name(m->m_pkthdr.rcvif)); 131 } 132 m_freem(m); 133 return; 134 } 135 136 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 137 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 138 icmp6_error(m, ICMP6_TIME_EXCEEDED, 139 ICMP6_TIME_EXCEED_TRANSIT, 0); 140 return; 141 } 142 ip6->ip6_hlim -= IPV6_HLIMDEC; 143 144 /* 145 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 146 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 147 * we need to generate an ICMP6 message to the src. 148 * Thanks to M_EXT, in most cases copy will not occur. 149 * 150 * It is important to save it before IPsec processing as IPsec 151 * processing may modify the mbuf. 152 */ 153 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 154 155 #ifdef IPSEC 156 /* get a security policy for this packet */ 157 sp = ipsec6_getpolicybyaddr(m, IPSEC_DIR_OUTBOUND, IP_FORWARDING, 158 &error); 159 if (sp == NULL) { 160 ipsec6stat.out_inval++; 161 ip6stat.ip6s_cantforward++; 162 if (mcopy) { 163 #if 0 164 /* XXX: what icmp ? */ 165 #else 166 m_freem(mcopy); 167 #endif 168 } 169 m_freem(m); 170 return; 171 } 172 173 error = 0; 174 175 /* check policy */ 176 switch (sp->policy) { 177 case IPSEC_POLICY_DISCARD: 178 /* 179 * This packet is just discarded. 180 */ 181 ipsec6stat.out_polvio++; 182 ip6stat.ip6s_cantforward++; 183 key_freesp(sp); 184 if (mcopy) { 185 #if 0 186 /* XXX: what icmp ? */ 187 #else 188 m_freem(mcopy); 189 #endif 190 } 191 m_freem(m); 192 return; 193 194 case IPSEC_POLICY_BYPASS: 195 case IPSEC_POLICY_NONE: 196 /* no need to do IPsec. */ 197 key_freesp(sp); 198 goto skip_ipsec; 199 200 case IPSEC_POLICY_IPSEC: 201 if (sp->req == NULL) { 202 /* XXX should be panic ? */ 203 printf("ip6_forward: No IPsec request specified.\n"); 204 ip6stat.ip6s_cantforward++; 205 key_freesp(sp); 206 if (mcopy) { 207 #if 0 208 /* XXX: what icmp ? */ 209 #else 210 m_freem(mcopy); 211 #endif 212 } 213 m_freem(m); 214 return; 215 } 216 /* do IPsec */ 217 break; 218 219 case IPSEC_POLICY_ENTRUST: 220 default: 221 /* should be panic ?? */ 222 printf("ip6_forward: Invalid policy found. %d\n", sp->policy); 223 key_freesp(sp); 224 goto skip_ipsec; 225 } 226 227 { 228 struct ipsec_output_state state; 229 230 /* 231 * All the extension headers will become inaccessible 232 * (since they can be encrypted). 233 * Don't panic, we need no more updates to extension headers 234 * on inner IPv6 packet (since they are now encapsulated). 235 * 236 * IPv6 [ESP|AH] IPv6 [extension headers] payload 237 */ 238 bzero(&state, sizeof(state)); 239 state.m = m; 240 state.ro = NULL; /* update at ipsec6_output_tunnel() */ 241 state.dst = NULL; /* update at ipsec6_output_tunnel() */ 242 243 error = ipsec6_output_tunnel(&state, sp, 0); 244 245 m = state.m; 246 #if 0 /* XXX allocate a route (ro, dst) again later */ 247 ro = (struct route_in6 *)state.ro; 248 dst = (struct sockaddr_in6 *)state.dst; 249 #endif 250 key_freesp(sp); 251 252 if (error) { 253 /* mbuf is already reclaimed in ipsec6_output_tunnel. */ 254 switch (error) { 255 case EHOSTUNREACH: 256 case ENETUNREACH: 257 case EMSGSIZE: 258 case ENOBUFS: 259 case ENOMEM: 260 break; 261 default: 262 printf("ip6_output (ipsec): error code %d\n", error); 263 /*fall through*/ 264 case ENOENT: 265 /* don't show these error codes to the user */ 266 break; 267 } 268 ip6stat.ip6s_cantforward++; 269 if (mcopy) { 270 #if 0 271 /* XXX: what icmp ? */ 272 #else 273 m_freem(mcopy); 274 #endif 275 } 276 m_freem(m); 277 return; 278 } 279 } 280 skip_ipsec: 281 #endif /* IPSEC */ 282 283 dst = &ip6_forward_rt.ro_dst; 284 if (!srcrt) { 285 /* 286 * ip6_forward_rt.ro_dst.sin6_addr is equal to ip6->ip6_dst 287 */ 288 if (ip6_forward_rt.ro_rt == 0 || 289 (ip6_forward_rt.ro_rt->rt_flags & RTF_UP) == 0) { 290 if (ip6_forward_rt.ro_rt) { 291 RTFREE(ip6_forward_rt.ro_rt); 292 ip6_forward_rt.ro_rt = 0; 293 } 294 /* this probably fails but give it a try again */ 295 rtalloc((struct route *)&ip6_forward_rt); 296 } 297 298 if (ip6_forward_rt.ro_rt == 0) { 299 ip6stat.ip6s_noroute++; 300 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 301 if (mcopy) { 302 icmp6_error(mcopy, ICMP6_DST_UNREACH, 303 ICMP6_DST_UNREACH_NOROUTE, 0); 304 } 305 m_freem(m); 306 return; 307 } 308 } else if ((rt = ip6_forward_rt.ro_rt) == 0 || 309 !IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst->sin6_addr)) { 310 if (ip6_forward_rt.ro_rt) { 311 RTFREE(ip6_forward_rt.ro_rt); 312 ip6_forward_rt.ro_rt = 0; 313 } 314 bzero(dst, sizeof(*dst)); 315 dst->sin6_len = sizeof(struct sockaddr_in6); 316 dst->sin6_family = AF_INET6; 317 dst->sin6_addr = ip6->ip6_dst; 318 319 rtalloc((struct route *)&ip6_forward_rt); 320 if (ip6_forward_rt.ro_rt == 0) { 321 ip6stat.ip6s_noroute++; 322 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 323 if (mcopy) { 324 icmp6_error(mcopy, ICMP6_DST_UNREACH, 325 ICMP6_DST_UNREACH_NOROUTE, 0); 326 } 327 m_freem(m); 328 return; 329 } 330 } 331 rt = ip6_forward_rt.ro_rt; 332 333 /* 334 * Scope check: if a packet can't be delivered to its destination 335 * for the reason that the destination is beyond the scope of the 336 * source address, discard the packet and return an icmp6 destination 337 * unreachable error with Code 2 (beyond scope of source address). 338 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 339 */ 340 if (in6_addr2scopeid(m->m_pkthdr.rcvif, &ip6->ip6_src) != 341 in6_addr2scopeid(rt->rt_ifp, &ip6->ip6_src)) { 342 ip6stat.ip6s_cantforward++; 343 ip6stat.ip6s_badscope++; 344 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 345 346 if (ip6_log_time + ip6_log_interval < time_second) { 347 ip6_log_time = time_second; 348 log(LOG_DEBUG, 349 "cannot forward " 350 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 351 ip6_sprintf(&ip6->ip6_src), 352 ip6_sprintf(&ip6->ip6_dst), 353 ip6->ip6_nxt, 354 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 355 } 356 if (mcopy) 357 icmp6_error(mcopy, ICMP6_DST_UNREACH, 358 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 359 m_freem(m); 360 return; 361 } 362 363 if (m->m_pkthdr.len > rt->rt_ifp->if_mtu) { 364 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 365 if (mcopy) { 366 u_long mtu; 367 #ifdef IPSEC 368 struct secpolicy *sp; 369 int ipsecerror; 370 size_t ipsechdrsiz; 371 #endif 372 373 mtu = rt->rt_ifp->if_mtu; 374 #ifdef IPSEC 375 /* 376 * When we do IPsec tunnel ingress, we need to play 377 * with if_mtu value (decrement IPsec header size 378 * from mtu value). The code is much simpler than v4 379 * case, as we have the outgoing interface for 380 * encapsulated packet as "rt->rt_ifp". 381 */ 382 sp = ipsec6_getpolicybyaddr(mcopy, IPSEC_DIR_OUTBOUND, 383 IP_FORWARDING, &ipsecerror); 384 if (sp) { 385 ipsechdrsiz = ipsec6_hdrsiz(mcopy, 386 IPSEC_DIR_OUTBOUND, NULL); 387 if (ipsechdrsiz < mtu) 388 mtu -= ipsechdrsiz; 389 } 390 391 /* 392 * if mtu becomes less than minimum MTU, 393 * tell minimum MTU (and I'll need to fragment it). 394 */ 395 if (mtu < IPV6_MMTU) 396 mtu = IPV6_MMTU; 397 #endif 398 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 399 } 400 m_freem(m); 401 return; 402 } 403 404 if (rt->rt_flags & RTF_GATEWAY) 405 dst = (struct sockaddr_in6 *)rt->rt_gateway; 406 407 /* 408 * If we are to forward the packet using the same interface 409 * as one we got the packet from, perhaps we should send a redirect 410 * to sender to shortcut a hop. 411 * Only send redirect if source is sending directly to us, 412 * and if packet was not source routed (or has any options). 413 * Also, don't send redirect if forwarding using a route 414 * modified by a redirect. 415 */ 416 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && 417 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) 418 type = ND_REDIRECT; 419 420 /* 421 * Fake scoped addresses. Note that even link-local source or 422 * destinaion can appear, if the originating node just sends the 423 * packet to us (without address resolution for the destination). 424 * Since both icmp6_error and icmp6_redirect_output fill the embedded 425 * link identifiers, we can do this stuff after making a copy for 426 * returning an error. 427 */ 428 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 429 /* 430 * See corresponding comments in ip6_output. 431 * XXX: but is it possible that ip6_forward() sends a packet 432 * to a loopback interface? I don't think so, and thus 433 * I bark here. (jinmei@kame.net) 434 * XXX: it is common to route invalid packets to loopback. 435 * also, the codepath will be visited on use of ::1 in 436 * rthdr. (itojun) 437 */ 438 #if 1 439 if (0) 440 #else 441 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 442 #endif 443 { 444 printf("ip6_forward: outgoing interface is loopback. " 445 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 446 ip6_sprintf(&ip6->ip6_src), 447 ip6_sprintf(&ip6->ip6_dst), 448 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 449 if_name(rt->rt_ifp)); 450 } 451 452 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 453 origifp = ifindex2ifnet[ntohs(ip6->ip6_src.s6_addr16[1])]; 454 else if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 455 origifp = ifindex2ifnet[ntohs(ip6->ip6_dst.s6_addr16[1])]; 456 else 457 origifp = rt->rt_ifp; 458 } 459 else 460 origifp = rt->rt_ifp; 461 #ifndef FAKE_LOOPBACK_IF 462 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) == 0) 463 #else 464 if (1) 465 #endif 466 { 467 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) 468 ip6->ip6_src.s6_addr16[1] = 0; 469 if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) 470 ip6->ip6_dst.s6_addr16[1] = 0; 471 } 472 473 #ifdef OLDIP6OUTPUT 474 error = (*rt->rt_ifp->if_output)(rt->rt_ifp, m, 475 (struct sockaddr *)dst, 476 ip6_forward_rt.ro_rt); 477 #else 478 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 479 #endif 480 if (error) { 481 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 482 ip6stat.ip6s_cantforward++; 483 } else { 484 ip6stat.ip6s_forward++; 485 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 486 if (type) 487 ip6stat.ip6s_redirectsent++; 488 else { 489 if (mcopy) 490 goto freecopy; 491 } 492 } 493 if (mcopy == NULL) 494 return; 495 496 switch (error) { 497 case 0: 498 #if 1 499 if (type == ND_REDIRECT) { 500 icmp6_redirect_output(mcopy, rt); 501 return; 502 } 503 #endif 504 goto freecopy; 505 506 case EMSGSIZE: 507 /* xxx MTU is constant in PPP? */ 508 goto freecopy; 509 510 case ENOBUFS: 511 /* Tell source to slow down like source quench in IP? */ 512 goto freecopy; 513 514 case ENETUNREACH: /* shouldn't happen, checked above */ 515 case EHOSTUNREACH: 516 case ENETDOWN: 517 case EHOSTDOWN: 518 default: 519 type = ICMP6_DST_UNREACH; 520 code = ICMP6_DST_UNREACH_ADDR; 521 break; 522 } 523 icmp6_error(mcopy, type, code, 0); 524 return; 525 526 freecopy: 527 m_freem(mcopy); 528 return; 529 } 530