1 /* $NetBSD: ip6_forward.c,v 1.72 2013/06/29 21:06:58 rmind 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 1.72 2013/06/29 21:06:58 rmind 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/malloc.h> 42 #include <sys/mbuf.h> 43 #include <sys/domain.h> 44 #include <sys/protosw.h> 45 #include <sys/socket.h> 46 #include <sys/errno.h> 47 #include <sys/time.h> 48 #include <sys/kernel.h> 49 #include <sys/syslog.h> 50 51 #include <net/if.h> 52 #include <net/route.h> 53 #include <net/pfil.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 IPSEC 66 #include <netipsec/ipsec.h> 67 #include <netipsec/ipsec6.h> 68 #include <netipsec/key.h> 69 #include <netipsec/xform.h> 70 #endif /* IPSEC */ 71 72 #include <net/net_osdep.h> 73 74 struct route ip6_forward_rt; 75 76 extern pfil_head_t *inet6_pfil_hook; /* XXX */ 77 78 /* 79 * Forward a packet. If some error occurs return the sender 80 * an icmp packet. Note we can't always generate a meaningful 81 * icmp message because icmp doesn't have a large enough repertoire 82 * of codes and types. 83 * 84 * If not forwarding, just drop the packet. This could be confusing 85 * if ipforwarding was zero but some routing protocol was advancing 86 * us as a gateway to somewhere. However, we must let the routing 87 * protocol deal with that. 88 * 89 */ 90 91 void 92 ip6_forward(struct mbuf *m, int srcrt) 93 { 94 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 95 const struct sockaddr_in6 *dst; 96 struct rtentry *rt; 97 int error = 0, type = 0, code = 0; 98 struct mbuf *mcopy = NULL; 99 struct ifnet *origifp; /* maybe unnecessary */ 100 u_int32_t inzone, outzone; 101 struct in6_addr src_in6, dst_in6; 102 #ifdef IPSEC 103 struct secpolicy *sp = NULL; 104 int needipsec = 0; 105 int s; 106 #endif 107 108 /* 109 * Clear any in-bound checksum flags for this packet. 110 */ 111 m->m_pkthdr.csum_flags = 0; 112 113 /* 114 * Do not forward packets to multicast destination (should be handled 115 * by ip6_mforward(). 116 * Do not forward packets with unspecified source. It was discussed 117 * in July 2000, on ipngwg mailing list. 118 */ 119 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 120 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 121 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 122 IP6_STATINC(IP6_STAT_CANTFORWARD); 123 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 124 if (ip6_log_time + ip6_log_interval < time_second) { 125 ip6_log_time = time_second; 126 log(LOG_DEBUG, 127 "cannot forward " 128 "from %s to %s nxt %d received on %s\n", 129 ip6_sprintf(&ip6->ip6_src), 130 ip6_sprintf(&ip6->ip6_dst), 131 ip6->ip6_nxt, 132 if_name(m->m_pkthdr.rcvif)); 133 } 134 m_freem(m); 135 return; 136 } 137 138 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 139 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 140 icmp6_error(m, ICMP6_TIME_EXCEEDED, 141 ICMP6_TIME_EXCEED_TRANSIT, 0); 142 return; 143 } 144 ip6->ip6_hlim -= IPV6_HLIMDEC; 145 146 /* 147 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 148 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 149 * we need to generate an ICMP6 message to the src. 150 * Thanks to M_EXT, in most cases copy will not occur. 151 * 152 * It is important to save it before IPsec processing as IPsec 153 * processing may modify the mbuf. 154 */ 155 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 156 157 #ifdef IPSEC 158 /* Check the security policy (SP) for the packet */ 159 160 sp = ipsec6_check_policy(m,NULL,0,&needipsec,&error); 161 if (error != 0) { 162 /* 163 * Hack: -EINVAL is used to signal that a packet 164 * should be silently discarded. This is typically 165 * because we asked key management for an SA and 166 * it was delayed (e.g. kicked up to IKE). 167 */ 168 if (error == -EINVAL) 169 error = 0; 170 goto freecopy; 171 } 172 #endif /* IPSEC */ 173 174 if (srcrt) { 175 union { 176 struct sockaddr dst; 177 struct sockaddr_in6 dst6; 178 } u; 179 180 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 181 if ((rt = rtcache_lookup(&ip6_forward_rt, &u.dst)) == NULL) { 182 IP6_STATINC(IP6_STAT_NOROUTE); 183 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 184 if (mcopy) { 185 icmp6_error(mcopy, ICMP6_DST_UNREACH, 186 ICMP6_DST_UNREACH_NOROUTE, 0); 187 } 188 m_freem(m); 189 return; 190 } 191 } else if ((rt = rtcache_validate(&ip6_forward_rt)) == NULL && 192 (rt = rtcache_update(&ip6_forward_rt, 1)) == NULL) { 193 /* 194 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 195 * ip6->ip6_dst 196 */ 197 IP6_STATINC(IP6_STAT_NOROUTE); 198 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 199 if (mcopy) { 200 icmp6_error(mcopy, ICMP6_DST_UNREACH, 201 ICMP6_DST_UNREACH_NOROUTE, 0); 202 } 203 m_freem(m); 204 return; 205 } 206 dst = satocsin6(rtcache_getdst(&ip6_forward_rt)); 207 208 /* 209 * Source scope check: if a packet can't be delivered to its 210 * destination for the reason that the destination is beyond the scope 211 * of the source address, discard the packet and return an icmp6 212 * destination unreachable error with Code 2 (beyond scope of source 213 * address). We use a local copy of ip6_src, since in6_setscope() 214 * will possibly modify its first argument. 215 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 216 */ 217 src_in6 = ip6->ip6_src; 218 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone)) { 219 /* XXX: this should not happen */ 220 uint64_t *ip6s = IP6_STAT_GETREF(); 221 ip6s[IP6_STAT_CANTFORWARD]++; 222 ip6s[IP6_STAT_BADSCOPE]++; 223 IP6_STAT_PUTREF(); 224 m_freem(m); 225 return; 226 } 227 if (in6_setscope(&src_in6, m->m_pkthdr.rcvif, &inzone)) { 228 uint64_t *ip6s = IP6_STAT_GETREF(); 229 ip6s[IP6_STAT_CANTFORWARD]++; 230 ip6s[IP6_STAT_BADSCOPE]++; 231 IP6_STAT_PUTREF(); 232 m_freem(m); 233 return; 234 } 235 if (inzone != outzone) { 236 uint64_t *ip6s = IP6_STAT_GETREF(); 237 ip6s[IP6_STAT_CANTFORWARD]++; 238 ip6s[IP6_STAT_BADSCOPE]++; 239 IP6_STAT_PUTREF(); 240 in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard); 241 242 if (ip6_log_time + ip6_log_interval < time_second) { 243 ip6_log_time = time_second; 244 log(LOG_DEBUG, 245 "cannot forward " 246 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 247 ip6_sprintf(&ip6->ip6_src), 248 ip6_sprintf(&ip6->ip6_dst), 249 ip6->ip6_nxt, 250 if_name(m->m_pkthdr.rcvif), if_name(rt->rt_ifp)); 251 } 252 if (mcopy) 253 icmp6_error(mcopy, ICMP6_DST_UNREACH, 254 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 255 m_freem(m); 256 return; 257 } 258 #ifdef IPSEC 259 /* 260 * If we need to encapsulate the packet, do it here 261 * ipsec6_proces_packet will send the packet using ip6_output 262 */ 263 if (needipsec) { 264 s = splsoftnet(); 265 error = ipsec6_process_packet(m,sp->req); 266 splx(s); 267 if (mcopy) 268 goto freecopy; 269 } 270 #endif 271 272 /* 273 * Destination scope check: if a packet is going to break the scope 274 * zone of packet's destination address, discard it. This case should 275 * usually be prevented by appropriately-configured routing table, but 276 * we need an explicit check because we may mistakenly forward the 277 * packet to a different zone by (e.g.) a default route. 278 */ 279 dst_in6 = ip6->ip6_dst; 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 uint64_t *ip6s = IP6_STAT_GETREF(); 284 ip6s[IP6_STAT_CANTFORWARD]++; 285 ip6s[IP6_STAT_BADSCOPE]++; 286 IP6_STAT_PUTREF(); 287 m_freem(m); 288 return; 289 } 290 291 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 292 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 293 if (mcopy) { 294 u_long mtu; 295 296 mtu = IN6_LINKMTU(rt->rt_ifp); 297 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 298 } 299 m_freem(m); 300 return; 301 } 302 303 if (rt->rt_flags & RTF_GATEWAY) 304 dst = (struct sockaddr_in6 *)rt->rt_gateway; 305 306 /* 307 * If we are to forward the packet using the same interface 308 * as one we got the packet from, perhaps we should send a redirect 309 * to sender to shortcut a hop. 310 * Only send redirect if source is sending directly to us, 311 * and if packet was not source routed (or has any options). 312 * Also, don't send redirect if forwarding using a route 313 * modified by a redirect. 314 */ 315 if (rt->rt_ifp == m->m_pkthdr.rcvif && !srcrt && ip6_sendredirects && 316 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 317 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 318 nd6_is_addr_neighbor( 319 satocsin6(rtcache_getdst(&ip6_forward_rt)), 320 rt->rt_ifp)) { 321 /* 322 * If the incoming interface is equal to the outgoing 323 * one, the link attached to the interface is 324 * point-to-point, and the IPv6 destination is 325 * regarded as on-link on the link, then it will be 326 * highly probable that the destination address does 327 * not exist on the link and that the packet is going 328 * to loop. Thus, we immediately drop the packet and 329 * send an ICMPv6 error message. 330 * For other routing loops, we dare to let the packet 331 * go to the loop, so that a remote diagnosing host 332 * can detect the loop by traceroute. 333 * type/code is based on suggestion by Rich Draves. 334 * not sure if it is the best pick. 335 */ 336 icmp6_error(mcopy, ICMP6_DST_UNREACH, 337 ICMP6_DST_UNREACH_ADDR, 0); 338 m_freem(m); 339 return; 340 } 341 type = ND_REDIRECT; 342 } 343 344 /* 345 * Fake scoped addresses. Note that even link-local source or 346 * destinaion can appear, if the originating node just sends the 347 * packet to us (without address resolution for the destination). 348 * Since both icmp6_error and icmp6_redirect_output fill the embedded 349 * link identifiers, we can do this stuff after making a copy for 350 * returning an error. 351 */ 352 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 353 /* 354 * See corresponding comments in ip6_output. 355 * XXX: but is it possible that ip6_forward() sends a packet 356 * to a loopback interface? I don't think so, and thus 357 * I bark here. (jinmei@kame.net) 358 * XXX: it is common to route invalid packets to loopback. 359 * also, the codepath will be visited on use of ::1 in 360 * rthdr. (itojun) 361 */ 362 #if 1 363 if (0) 364 #else 365 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 366 #endif 367 { 368 printf("ip6_forward: outgoing interface is loopback. " 369 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 370 ip6_sprintf(&ip6->ip6_src), 371 ip6_sprintf(&ip6->ip6_dst), 372 ip6->ip6_nxt, if_name(m->m_pkthdr.rcvif), 373 if_name(rt->rt_ifp)); 374 } 375 376 /* we can just use rcvif in forwarding. */ 377 origifp = m->m_pkthdr.rcvif; 378 } 379 else 380 origifp = rt->rt_ifp; 381 /* 382 * clear embedded scope identifiers if necessary. 383 * in6_clearscope will touch the addresses only when necessary. 384 */ 385 in6_clearscope(&ip6->ip6_src); 386 in6_clearscope(&ip6->ip6_dst); 387 388 /* 389 * Run through list of hooks for output packets. 390 */ 391 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 392 PFIL_OUT)) != 0) 393 goto senderr; 394 if (m == NULL) 395 goto freecopy; 396 ip6 = mtod(m, struct ip6_hdr *); 397 398 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 399 if (error) { 400 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 401 IP6_STATINC(IP6_STAT_CANTFORWARD); 402 } else { 403 IP6_STATINC(IP6_STAT_FORWARD); 404 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 405 if (type) 406 IP6_STATINC(IP6_STAT_REDIRECTSENT); 407 else { 408 #ifdef GATEWAY 409 if (m->m_flags & M_CANFASTFWD) 410 ip6flow_create(&ip6_forward_rt, m); 411 #endif 412 if (mcopy) 413 goto freecopy; 414 } 415 } 416 417 senderr: 418 if (mcopy == NULL) 419 return; 420 switch (error) { 421 case 0: 422 if (type == ND_REDIRECT) { 423 icmp6_redirect_output(mcopy, rt); 424 return; 425 } 426 goto freecopy; 427 428 case EMSGSIZE: 429 /* xxx MTU is constant in PPP? */ 430 goto freecopy; 431 432 case ENOBUFS: 433 /* Tell source to slow down like source quench in IP? */ 434 goto freecopy; 435 436 case ENETUNREACH: /* shouldn't happen, checked above */ 437 case EHOSTUNREACH: 438 case ENETDOWN: 439 case EHOSTDOWN: 440 default: 441 type = ICMP6_DST_UNREACH; 442 code = ICMP6_DST_UNREACH_ADDR; 443 break; 444 } 445 icmp6_error(mcopy, type, code, 0); 446 return; 447 448 freecopy: 449 m_freem(mcopy); 450 return; 451 } 452