1 /* $NetBSD: ip6_forward.c,v 1.85 2017/01/16 15:44:47 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 1.85 2017/01/16 15:44:47 christos 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/errno.h> 45 #include <sys/time.h> 46 #include <sys/kernel.h> 47 #include <sys/syslog.h> 48 #include <sys/percpu.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 extern percpu_t *ip6_forward_rt_percpu; 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_uptime) 97 return; 98 ip6_log_time = time_uptime; 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 = NULL; 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 struct ifnet *rcvif = NULL; 135 struct psref psref; 136 struct route *ro = NULL; 137 #ifdef IPSEC 138 int needipsec = 0; 139 struct secpolicy *sp = NULL; 140 #endif 141 142 /* 143 * Clear any in-bound checksum flags for this packet. 144 */ 145 m->m_pkthdr.csum_flags = 0; 146 147 rcvif = m_get_rcvif_psref(m, &psref); 148 if (__predict_false(rcvif == NULL)) 149 goto drop; 150 151 /* 152 * Do not forward packets to multicast destination (should be handled 153 * by ip6_mforward(). 154 * Do not forward packets with unspecified source. It was discussed 155 * in July 2000, on ipngwg mailing list. 156 */ 157 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 158 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 159 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 160 ip6_cantforward(ip6, rcvif, NULL, 161 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : 162 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : 163 "unspec/src"); 164 goto drop; 165 } 166 167 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 168 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 169 icmp6_error(m, ICMP6_TIME_EXCEEDED, 170 ICMP6_TIME_EXCEED_TRANSIT, 0); 171 goto out; 172 } 173 ip6->ip6_hlim -= IPV6_HLIMDEC; 174 175 /* 176 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 177 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 178 * we need to generate an ICMP6 message to the src. 179 * Thanks to M_EXT, in most cases copy will not occur. 180 * 181 * It is important to save it before IPsec processing as IPsec 182 * processing may modify the mbuf. 183 */ 184 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 185 186 #ifdef IPSEC 187 if (ipsec_used) { 188 /* Check the security policy (SP) for the packet */ 189 190 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error); 191 if (error != 0) { 192 /* 193 * Hack: -EINVAL is used to signal that a packet 194 * should be silently discarded. This is typically 195 * because we asked key management for an SA and 196 * it was delayed (e.g. kicked up to IKE). 197 */ 198 if (error == -EINVAL) 199 error = 0; 200 goto freecopy; 201 } 202 } 203 #endif /* IPSEC */ 204 205 ro = percpu_getref(ip6_forward_rt_percpu); 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 rt = rtcache_lookup(ro, &u.dst); 214 if (rt == NULL) { 215 IP6_STATINC(IP6_STAT_NOROUTE); 216 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 217 if (mcopy) { 218 icmp6_error(mcopy, ICMP6_DST_UNREACH, 219 ICMP6_DST_UNREACH_NOROUTE, 0); 220 } 221 goto drop; 222 } 223 } else if ((rt = rtcache_validate(ro)) == NULL && 224 (rt = rtcache_update(ro, 1)) == NULL) { 225 /* 226 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 227 * ip6->ip6_dst 228 */ 229 IP6_STATINC(IP6_STAT_NOROUTE); 230 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 231 if (mcopy) { 232 icmp6_error(mcopy, ICMP6_DST_UNREACH, 233 ICMP6_DST_UNREACH_NOROUTE, 0); 234 } 235 goto drop; 236 } 237 dst = satocsin6(rtcache_getdst(ro)); 238 239 /* 240 * Source scope check: if a packet can't be delivered to its 241 * destination for the reason that the destination is beyond the scope 242 * of the source address, discard the packet and return an icmp6 243 * destination unreachable error with Code 2 (beyond scope of source 244 * address). We use a local copy of ip6_src, since in6_setscope() 245 * will possibly modify its first argument. 246 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 247 */ 248 src_in6 = ip6->ip6_src; 249 inzone = outzone = ~0; 250 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || 251 in6_setscope(&src_in6, rcvif, &inzone) != 0 || 252 inzone != outzone) { 253 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 254 "src[%s] inzone %d outzone %d", 255 in6_getscopename(&ip6->ip6_src), inzone, outzone); 256 if (mcopy) 257 icmp6_error(mcopy, ICMP6_DST_UNREACH, 258 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 259 goto drop; 260 } 261 262 #ifdef IPSEC 263 /* 264 * If we need to encapsulate the packet, do it here 265 * ipsec6_proces_packet will send the packet using ip6_output 266 */ 267 if (needipsec) { 268 int s = splsoftnet(); 269 error = ipsec6_process_packet(m, sp->req); 270 splx(s); 271 if (mcopy) 272 goto freecopy; 273 } 274 #endif 275 276 /* 277 * Destination scope check: if a packet is going to break the scope 278 * zone of packet's destination address, discard it. This case should 279 * usually be prevented by appropriately-configured routing table, but 280 * we need an explicit check because we may mistakenly forward the 281 * packet to a different zone by (e.g.) a default route. 282 */ 283 dst_in6 = ip6->ip6_dst; 284 inzone = outzone = ~0; 285 if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 || 286 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 287 inzone != outzone) { 288 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 289 "dst[%s] inzone %d outzone %d", 290 in6_getscopename(&ip6->ip6_dst), inzone, outzone); 291 if (mcopy) 292 icmp6_error(mcopy, ICMP6_DST_UNREACH, 293 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 294 goto drop; 295 } 296 297 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 298 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 299 if (mcopy) { 300 u_long mtu; 301 302 mtu = IN6_LINKMTU(rt->rt_ifp); 303 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 304 } 305 goto drop; 306 } 307 308 if (rt->rt_flags & RTF_GATEWAY) 309 dst = (struct sockaddr_in6 *)rt->rt_gateway; 310 311 /* 312 * If we are to forward the packet using the same interface 313 * as one we got the packet from, perhaps we should send a redirect 314 * to sender to shortcut a hop. 315 * Only send redirect if source is sending directly to us, 316 * and if packet was not source routed (or has any options). 317 * Also, don't send redirect if forwarding using a route 318 * modified by a redirect. 319 */ 320 if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects && 321 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 322 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 323 nd6_is_addr_neighbor(satocsin6(rtcache_getdst(ro)), 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@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 char ip6bufs[INET6_ADDRSTRLEN]; 372 char ip6bufd[INET6_ADDRSTRLEN]; 373 374 printf("ip6_forward: outgoing interface is loopback. " 375 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 376 IN6_PRINT(ip6bufs, &ip6->ip6_src), 377 IN6_PRINT(ip6bufd, &ip6->ip6_dst), 378 ip6->ip6_nxt, if_name(rcvif), 379 if_name(rt->rt_ifp)); 380 } 381 382 /* we can just use rcvif in forwarding. */ 383 origifp = rcvif; 384 } 385 else 386 origifp = rt->rt_ifp; 387 /* 388 * clear embedded scope identifiers if necessary. 389 * in6_clearscope will touch the addresses only when necessary. 390 */ 391 in6_clearscope(&ip6->ip6_src); 392 in6_clearscope(&ip6->ip6_dst); 393 394 /* 395 * Run through list of hooks for output packets. 396 */ 397 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 398 PFIL_OUT)) != 0) 399 goto senderr; 400 if (m == NULL) 401 goto freecopy; 402 ip6 = mtod(m, struct ip6_hdr *); 403 404 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 405 if (error) { 406 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 407 IP6_STATINC(IP6_STAT_CANTFORWARD); 408 } else { 409 IP6_STATINC(IP6_STAT_FORWARD); 410 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 411 if (type) 412 IP6_STATINC(IP6_STAT_REDIRECTSENT); 413 else { 414 #ifdef GATEWAY 415 /* Need to release rt here */ 416 rtcache_unref(rt, ro); 417 rt = NULL; 418 if (m->m_flags & M_CANFASTFWD) 419 ip6flow_create(ro, m); 420 #endif 421 if (mcopy) 422 goto freecopy; 423 } 424 } 425 426 senderr: 427 if (mcopy == NULL) 428 goto out; 429 switch (error) { 430 case 0: 431 if (type == ND_REDIRECT) { 432 icmp6_redirect_output(mcopy, rt); 433 goto out; 434 } 435 goto freecopy; 436 437 case EMSGSIZE: 438 /* xxx MTU is constant in PPP? */ 439 goto freecopy; 440 441 case ENOBUFS: 442 /* Tell source to slow down like source quench in IP? */ 443 goto freecopy; 444 445 case ENETUNREACH: /* shouldn't happen, checked above */ 446 case EHOSTUNREACH: 447 case ENETDOWN: 448 case EHOSTDOWN: 449 default: 450 type = ICMP6_DST_UNREACH; 451 code = ICMP6_DST_UNREACH_ADDR; 452 break; 453 } 454 icmp6_error(mcopy, type, code, 0); 455 goto out; 456 457 freecopy: 458 m_freem(mcopy); 459 goto out; 460 drop: 461 m_freem(m); 462 out: 463 rtcache_unref(rt, ro); 464 if (ro != NULL) 465 percpu_putref(ip6_forward_rt_percpu); 466 if (rcvif != NULL) 467 m_put_rcvif_psref(rcvif, &psref); 468 return; 469 } 470