1 /* $NetBSD: ip6_forward.c,v 1.70 2012/03/22 20:34:40 drochner 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 1.70 2012/03/22 20:34:40 drochner Exp $"); 35 36 #include "opt_gateway.h" 37 #include "opt_ipsec.h" 38 #include "opt_pfil_hooks.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/malloc.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 55 #include <netinet/in.h> 56 #include <netinet/in_var.h> 57 #include <netinet/ip_var.h> 58 #include <netinet/ip6.h> 59 #include <netinet6/ip6_var.h> 60 #include <netinet6/ip6_private.h> 61 #include <netinet6/scope6_var.h> 62 #include <netinet/icmp6.h> 63 #include <netinet6/nd6.h> 64 65 #ifdef FAST_IPSEC 66 #include <netipsec/ipsec.h> 67 #include <netipsec/ipsec6.h> 68 #include <netipsec/key.h> 69 #include <netipsec/xform.h> 70 #endif /* FAST_IPSEC */ 71 72 #ifdef PFIL_HOOKS 73 #include <net/pfil.h> 74 #endif 75 76 #include <net/net_osdep.h> 77 78 struct route ip6_forward_rt; 79 80 #ifdef PFIL_HOOKS 81 extern struct pfil_head inet6_pfil_hook; /* XXX */ 82 #endif 83 84 /* 85 * Forward a packet. If some error occurs return the sender 86 * an icmp packet. Note we can't always generate a meaningful 87 * icmp message because icmp doesn't have a large enough repertoire 88 * of codes and types. 89 * 90 * If not forwarding, just drop the packet. This could be confusing 91 * if ipforwarding was zero but some routing protocol was advancing 92 * us as a gateway to somewhere. However, we must let the routing 93 * protocol deal with that. 94 * 95 */ 96 97 void 98 ip6_forward(struct mbuf *m, int srcrt) 99 { 100 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 101 const struct sockaddr_in6 *dst; 102 struct rtentry *rt; 103 int error = 0, type = 0, code = 0; 104 struct mbuf *mcopy = NULL; 105 struct ifnet *origifp; /* maybe unnecessary */ 106 u_int32_t inzone, outzone; 107 struct in6_addr src_in6, dst_in6; 108 #ifdef FAST_IPSEC 109 struct secpolicy *sp = NULL; 110 int needipsec = 0; 111 int s; 112 #endif 113 114 /* 115 * Clear any in-bound checksum flags for this packet. 116 */ 117 m->m_pkthdr.csum_flags = 0; 118 119 /* 120 * Do not forward packets to multicast destination (should be handled 121 * by ip6_mforward(). 122 * Do not forward packets with unspecified source. It was discussed 123 * in July 2000, on ipngwg mailing list. 124 */ 125 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 126 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 127 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 128 IP6_STATINC(IP6_STAT_CANTFORWARD); 129 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 130 if (ip6_log_time + ip6_log_interval < time_second) { 131 ip6_log_time = time_second; 132 log(LOG_DEBUG, 133 "cannot forward " 134 "from %s to %s nxt %d received on %s\n", 135 ip6_sprintf(&ip6->ip6_src), 136 ip6_sprintf(&ip6->ip6_dst), 137 ip6->ip6_nxt, 138 if_name(m->m_pkthdr.rcvif)); 139 } 140 m_freem(m); 141 return; 142 } 143 144 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 145 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 146 icmp6_error(m, ICMP6_TIME_EXCEEDED, 147 ICMP6_TIME_EXCEED_TRANSIT, 0); 148 return; 149 } 150 ip6->ip6_hlim -= IPV6_HLIMDEC; 151 152 /* 153 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 154 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 155 * we need to generate an ICMP6 message to the src. 156 * Thanks to M_EXT, in most cases copy will not occur. 157 * 158 * It is important to save it before IPsec processing as IPsec 159 * processing may modify the mbuf. 160 */ 161 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 162 163 #ifdef FAST_IPSEC 164 /* Check the security policy (SP) for the packet */ 165 166 sp = ipsec6_check_policy(m,NULL,0,&needipsec,&error); 167 if (error != 0) { 168 /* 169 * Hack: -EINVAL is used to signal that a packet 170 * should be silently discarded. This is typically 171 * because we asked key management for an SA and 172 * it was delayed (e.g. kicked up to IKE). 173 */ 174 if (error == -EINVAL) 175 error = 0; 176 goto freecopy; 177 } 178 #endif /* FAST_IPSEC */ 179 180 if (srcrt) { 181 union { 182 struct sockaddr dst; 183 struct sockaddr_in6 dst6; 184 } u; 185 186 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 187 if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) { 188 IP6_STATINC(IP6_STAT_NOROUTE); 189 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 190 if (mcopy) { 191 icmp6_error(mcopy, ICMP6_DST_UNREACH, 192 ICMP6_DST_UNREACH_NOROUTE, 0); 193 } 194 m_freem(m); 195 return; 196 } 197 } else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL && 198 (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) { 199 /* 200 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 201 * ip6->ip6_dst 202 */ 203 IP6_STATINC(IP6_STAT_NOROUTE); 204 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 205 if (mcopy) { 206 icmp6_error(mcopy, ICMP6_DST_UNREACH, 207 ICMP6_DST_UNREACH_NOROUTE, 0); 208 } 209 m_freem(m); 210 return; 211 } 212 dst = satocsin6(rtcache_getdst(&ip6_forward_rt)); 213 214 /* 215 * Source scope check: if a packet can't be delivered to its 216 * destination for the reason that the destination is beyond the scope 217 * of the source address, discard the packet and return an icmp6 218 * destination unreachable error with Code 2 (beyond scope of source 219 * address). We use a local copy of ip6_src, since in6_setscope() 220 * will possibly modify its first argument. 221 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 222 */ 223 src_in6 = ip6->ip6_src; 224 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) { 225 /* XXX: this should not happen */ 226 uint64_t *ip6s = IP6_STAT_GETREF(); 227 ip6s[IP6_STAT_CANTFORWARD]++; 228 ip6s[IP6_STAT_BADSCOPE]++; 229 IP6_STAT_PUTREF(); 230 m_freem(m); 231 return; 232 } 233 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) { 234 uint64_t *ip6s = IP6_STAT_GETREF(); 235 ip6s[IP6_STAT_CANTFORWARD]++; 236 ip6s[IP6_STAT_BADSCOPE]++; 237 IP6_STAT_PUTREF(); 238 m_freem(m); 239 return; 240 } 241 if (inzone != outzone) { 242 uint64_t *ip6s = IP6_STAT_GETREF(); 243 ip6s[IP6_STAT_CANTFORWARD]++; 244 ip6s[IP6_STAT_BADSCOPE]++; 245 IP6_STAT_PUTREF(); 246 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 247 248 if (ip6_log_time + ip6_log_interval < time_second) { 249 ip6_log_time = time_second; 250 log(LOG_DEBUG, 251 "cannot forward " 252 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 253 ip6_sprintf(&ip6->ip6_src), 254 ip6_sprintf(&ip6->ip6_dst), 255 ip6->ip6_nxt, 256 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 257 } 258 if (mcopy) 259 icmp6_error(mcopy, ICMP6_DST_UNREACH, 260 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 261 m_freem(m); 262 return; 263 } 264 #ifdef FAST_IPSEC 265 /* 266 * If we need to encapsulate the packet, do it here 267 * ipsec6_proces_packet will send the packet using ip6_output 268 */ 269 if (needipsec) { 270 s = splsoftnet(); 271 error = ipsec6_process_packet(m,sp->req); 272 splx(s); 273 if (mcopy) 274 goto freecopy; 275 } 276 #endif 277 278 279 280 /* 281 * Destination scope check: if a packet is going to break the scope 282 * zone of packet's destination address, discard it. This case should 283 * usually be prevented by appropriately-configured routing table, but 284 * we need an explicit check because we may mistakenly forward the 285 * packet to a different zone by (e.g.) a default route. 286 */ 287 dst_in6 = ip6->ip6_dst; 288 if (in6_setscope(&dst_in6, m->m_pkthdr.rcvif, &inzone) != 0 || 289 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 290 inzone != outzone) { 291 uint64_t *ip6s = IP6_STAT_GETREF(); 292 ip6s[IP6_STAT_CANTFORWARD]++; 293 ip6s[IP6_STAT_BADSCOPE]++; 294 IP6_STAT_PUTREF(); 295 m_freem(m); 296 return; 297 } 298 299 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 300 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 301 if (mcopy) { 302 u_long mtu; 303 304 mtu = IN6_LINKMTU(rt->rt_ifp); 305 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 306 } 307 m_freem(m); 308 return; 309 } 310 311 if (rt->rt_flags & RTF_GATEWAY) 312 dst = (struct sockaddr_in6 *)rt->rt_gateway; 313 314 /* 315 * If we are to forward the packet using the same interface 316 * as one we got the packet from, perhaps we should send a redirect 317 * to sender to shortcut a hop. 318 * Only send redirect if source is sending directly to us, 319 * and if packet was not source routed (or has any options). 320 * Also, don't send redirect if forwarding using a route 321 * modified by a redirect. 322 */ 323 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects && 324 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 325 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 326 nd6_is_addr_neighbor( 327 satocsin6(rtcache_getdst(&ip6_forward_rt)), 328 rt->rt_ifp)) { 329 /* 330 * If the incoming interface is equal to the outgoing 331 * one, the link attached to the interface is 332 * point-to-point, and the IPv6 destination is 333 * regarded as on-link on the link, then it will be 334 * highly probable that the destination address does 335 * not exist on the link and that the packet is going 336 * to loop. Thus, we immediately drop the packet and 337 * send an ICMPv6 error message. 338 * For other routing loops, we dare to let the packet 339 * go to the loop, so that a remote diagnosing host 340 * can detect the loop by traceroute. 341 * type/code is based on suggestion by Rich Draves. 342 * not sure if it is the best pick. 343 */ 344 icmp6_error(mcopy, ICMP6_DST_UNREACH, 345 ICMP6_DST_UNREACH_ADDR, 0); 346 m_freem(m); 347 return; 348 } 349 type = ND_REDIRECT; 350 } 351 352 /* 353 * Fake scoped addresses. Note that even link-local source or 354 * destinaion can appear, if the originating node just sends the 355 * packet to us (without address resolution for the destination). 356 * Since both icmp6_error and icmp6_redirect_output fill the embedded 357 * link identifiers, we can do this stuff after making a copy for 358 * returning an error. 359 */ 360 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 361 /* 362 * See corresponding comments in ip6_output. 363 * XXX: but is it possible that ip6_forward() sends a packet 364 * to a loopback interface? I don't think so, and thus 365 * I bark here. (jinmei@kame.net) 366 * XXX: it is common to route invalid packets to loopback. 367 * also, the codepath will be visited on use of ::1 in 368 * rthdr. (itojun) 369 */ 370 #if 1 371 if (0) 372 #else 373 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 374 #endif 375 { 376 printf("ip6_forward: outgoing interface is loopback. " 377 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 378 ip6_sprintf(&ip6->ip6_src), 379 ip6_sprintf(&ip6->ip6_dst), 380 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 381 if_name(rt->rt_ifp)); 382 } 383 384 /* we can just use rcvif in forwarding. */ 385 origifp = m->m_pkthdr.rcvif; 386 } 387 else 388 origifp = rt->rt_ifp; 389 /* 390 * clear embedded scope identifiers if necessary. 391 * in6_clearscope will touch the addresses only when necessary. 392 */ 393 in6_clearscope(&ip6->ip6_src); 394 in6_clearscope(&ip6->ip6_dst); 395 396 #ifdef PFIL_HOOKS 397 /* 398 * Run through list of hooks for output packets. 399 */ 400 if ((error = pfil_run_hooks(&inet6_pfil_hook, &m, rt->rt_ifp, 401 PFIL_OUT)) != 0) 402 goto senderr; 403 if (m == NULL) 404 goto freecopy; 405 ip6 = mtod(m, struct ip6_hdr *); 406 #endif /* PFIL_HOOKS */ 407 408 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 409 if (error) { 410 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 411 IP6_STATINC(IP6_STAT_CANTFORWARD); 412 } else { 413 IP6_STATINC(IP6_STAT_FORWARD); 414 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 415 if (type) 416 IP6_STATINC(IP6_STAT_REDIRECTSENT); 417 else { 418 #ifdef GATEWAY 419 if (m->m_flags & M_CANFASTFWD) 420 ip6flow_create(&ip6_forward_rt, m); 421 #endif 422 if (mcopy) 423 goto freecopy; 424 } 425 } 426 427 #ifdef PFIL_HOOKS 428 senderr: 429 #endif 430 if (mcopy == NULL) 431 return; 432 switch (error) { 433 case 0: 434 if (type == ND_REDIRECT) { 435 icmp6_redirect_output(mcopy, rt); 436 return; 437 } 438 goto freecopy; 439 440 case EMSGSIZE: 441 /* xxx MTU is constant in PPP? */ 442 goto freecopy; 443 444 case ENOBUFS: 445 /* Tell source to slow down like source quench in IP? */ 446 goto freecopy; 447 448 case ENETUNREACH: /* shouldn't happen, checked above */ 449 case EHOSTUNREACH: 450 case ENETDOWN: 451 case EHOSTDOWN: 452 default: 453 type = ICMP6_DST_UNREACH; 454 code = ICMP6_DST_UNREACH_ADDR; 455 break; 456 } 457 icmp6_error(mcopy, type, code, 0); 458 return; 459 460 freecopy: 461 m_freem(mcopy); 462 return; 463 } 464