1 /* $NetBSD: ip6_forward.c,v 1.81 2016/08/31 09:14:47 ozaki-r 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 1.81 2016/08/31 09:14:47 ozaki-r 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/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 #include <sys/percpu.h> 52 53 #include <net/if.h> 54 #include <net/route.h> 55 #include <net/pfil.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_var.h> 59 #include <netinet/ip_var.h> 60 #include <netinet/ip6.h> 61 #include <netinet6/ip6_var.h> 62 #include <netinet6/ip6_private.h> 63 #include <netinet6/scope6_var.h> 64 #include <netinet/icmp6.h> 65 #include <netinet6/nd6.h> 66 67 #ifdef IPSEC 68 #include <netipsec/ipsec.h> 69 #include <netipsec/ipsec6.h> 70 #include <netipsec/key.h> 71 #include <netipsec/xform.h> 72 #endif /* IPSEC */ 73 74 #include <net/net_osdep.h> 75 76 extern percpu_t *ip6_forward_rt_percpu; 77 78 extern pfil_head_t *inet6_pfil_hook; /* XXX */ 79 80 static void __printflike(4, 5) 81 ip6_cantforward(const struct ip6_hdr *ip6, const struct ifnet *srcifp, 82 const struct ifnet *dstifp, const char *fmt, ...) 83 { 84 char sbuf[INET6_ADDRSTRLEN], dbuf[INET6_ADDRSTRLEN]; 85 char reason[256]; 86 va_list ap; 87 uint64_t *ip6s; 88 89 /* update statistics */ 90 ip6s = IP6_STAT_GETREF(); 91 ip6s[IP6_STAT_CANTFORWARD]++; 92 if (dstifp) 93 ip6s[IP6_STAT_BADSCOPE]++; 94 IP6_STAT_PUTREF(); 95 96 if (dstifp) 97 in6_ifstat_inc(dstifp, ifs6_in_discard); 98 99 if (ip6_log_time + ip6_log_interval >= time_uptime) 100 return; 101 ip6_log_time = time_uptime; 102 103 va_start(ap, fmt); 104 vsnprintf(reason, sizeof(reason), fmt, ap); 105 va_end(ap); 106 107 log(LOG_DEBUG, "Cannot forward from %s@%s to %s@%s nxt %d (%s)\n", 108 IN6_PRINT(sbuf, &ip6->ip6_src), srcifp ? if_name(srcifp) : "?", 109 IN6_PRINT(dbuf, &ip6->ip6_dst), dstifp ? if_name(dstifp) : "?", 110 ip6->ip6_nxt, reason); 111 } 112 113 /* 114 * Forward a packet. If some error occurs return the sender 115 * an icmp packet. Note we can't always generate a meaningful 116 * icmp message because icmp doesn't have a large enough repertoire 117 * of codes and types. 118 * 119 * If not forwarding, just drop the packet. This could be confusing 120 * if ipforwarding was zero but some routing protocol was advancing 121 * us as a gateway to somewhere. However, we must let the routing 122 * protocol deal with that. 123 * 124 */ 125 126 void 127 ip6_forward(struct mbuf *m, int srcrt) 128 { 129 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 130 const struct sockaddr_in6 *dst; 131 struct rtentry *rt; 132 int error = 0, type = 0, code = 0; 133 struct mbuf *mcopy = NULL; 134 struct ifnet *origifp; /* maybe unnecessary */ 135 uint32_t inzone, outzone; 136 struct in6_addr src_in6, dst_in6; 137 struct ifnet *rcvif = NULL; 138 struct psref psref; 139 struct route *ro; 140 #ifdef IPSEC 141 int needipsec = 0; 142 struct secpolicy *sp = NULL; 143 #endif 144 145 /* 146 * Clear any in-bound checksum flags for this packet. 147 */ 148 m->m_pkthdr.csum_flags = 0; 149 150 rcvif = m_get_rcvif_psref(m, &psref); 151 if (__predict_false(rcvif == NULL)) 152 goto drop; 153 154 /* 155 * Do not forward packets to multicast destination (should be handled 156 * by ip6_mforward(). 157 * Do not forward packets with unspecified source. It was discussed 158 * in July 2000, on ipngwg mailing list. 159 */ 160 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 161 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 162 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 163 ip6_cantforward(ip6, rcvif, NULL, 164 ((m->m_flags & (M_BCAST|M_MCAST)) != 0) ? "bcast/mcast" : 165 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ? "mcast/dst" : 166 "unspec/src"); 167 goto drop; 168 } 169 170 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 171 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_discard) */ 172 icmp6_error(m, ICMP6_TIME_EXCEEDED, 173 ICMP6_TIME_EXCEED_TRANSIT, 0); 174 goto out; 175 } 176 ip6->ip6_hlim -= IPV6_HLIMDEC; 177 178 /* 179 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 180 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 181 * we need to generate an ICMP6 message to the src. 182 * Thanks to M_EXT, in most cases copy will not occur. 183 * 184 * It is important to save it before IPsec processing as IPsec 185 * processing may modify the mbuf. 186 */ 187 mcopy = m_copy(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN)); 188 189 #ifdef IPSEC 190 if (ipsec_used) { 191 /* Check the security policy (SP) for the packet */ 192 193 sp = ipsec6_check_policy(m, NULL, 0, &needipsec, &error); 194 if (error != 0) { 195 /* 196 * Hack: -EINVAL is used to signal that a packet 197 * should be silently discarded. This is typically 198 * because we asked key management for an SA and 199 * it was delayed (e.g. kicked up to IKE). 200 */ 201 if (error == -EINVAL) 202 error = 0; 203 goto freecopy; 204 } 205 } 206 #endif /* IPSEC */ 207 208 ro = percpu_getref(ip6_forward_rt_percpu); 209 if (srcrt) { 210 union { 211 struct sockaddr dst; 212 struct sockaddr_in6 dst6; 213 } u; 214 215 sockaddr_in6_init(&u.dst6, &ip6->ip6_dst, 0, 0, 0); 216 if ((rt = rtcache_lookup(ro, &u.dst)) == NULL) { 217 IP6_STATINC(IP6_STAT_NOROUTE); 218 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 219 if (mcopy) { 220 icmp6_error(mcopy, ICMP6_DST_UNREACH, 221 ICMP6_DST_UNREACH_NOROUTE, 0); 222 } 223 percpu_putref(ip6_forward_rt_percpu); 224 goto drop; 225 } 226 } else if ((rt = rtcache_validate(ro)) == NULL && 227 (rt = rtcache_update(ro, 1)) == NULL) { 228 /* 229 * rtcache_getdst(ip6_forward_rt)->sin6_addr was equal to 230 * ip6->ip6_dst 231 */ 232 IP6_STATINC(IP6_STAT_NOROUTE); 233 /* XXX in6_ifstat_inc(rt->rt_ifp, ifs6_in_noroute) */ 234 if (mcopy) { 235 icmp6_error(mcopy, ICMP6_DST_UNREACH, 236 ICMP6_DST_UNREACH_NOROUTE, 0); 237 } 238 percpu_putref(ip6_forward_rt_percpu); 239 goto drop; 240 } 241 dst = satocsin6(rtcache_getdst(ro)); 242 percpu_putref(ip6_forward_rt_percpu); 243 244 /* 245 * Source scope check: if a packet can't be delivered to its 246 * destination for the reason that the destination is beyond the scope 247 * of the source address, discard the packet and return an icmp6 248 * destination unreachable error with Code 2 (beyond scope of source 249 * address). We use a local copy of ip6_src, since in6_setscope() 250 * will possibly modify its first argument. 251 * [draft-ietf-ipngwg-icmp-v3-07, Section 3.1] 252 */ 253 src_in6 = ip6->ip6_src; 254 inzone = outzone = ~0; 255 if (in6_setscope(&src_in6, rt->rt_ifp, &outzone) != 0 || 256 in6_setscope(&src_in6, rcvif, &inzone) != 0 || 257 inzone != outzone) { 258 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 259 "src[%s] inzone %d outzone %d", 260 in6_getscopename(&ip6->ip6_src), inzone, outzone); 261 if (mcopy) 262 icmp6_error(mcopy, ICMP6_DST_UNREACH, 263 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 264 goto drop; 265 } 266 267 #ifdef IPSEC 268 /* 269 * If we need to encapsulate the packet, do it here 270 * ipsec6_proces_packet will send the packet using ip6_output 271 */ 272 if (needipsec) { 273 int s = splsoftnet(); 274 error = ipsec6_process_packet(m, sp->req); 275 splx(s); 276 if (mcopy) 277 goto freecopy; 278 } 279 #endif 280 281 /* 282 * Destination scope check: if a packet is going to break the scope 283 * zone of packet's destination address, discard it. This case should 284 * usually be prevented by appropriately-configured routing table, but 285 * we need an explicit check because we may mistakenly forward the 286 * packet to a different zone by (e.g.) a default route. 287 */ 288 dst_in6 = ip6->ip6_dst; 289 inzone = outzone = ~0; 290 if (in6_setscope(&dst_in6, rcvif, &inzone) != 0 || 291 in6_setscope(&dst_in6, rt->rt_ifp, &outzone) != 0 || 292 inzone != outzone) { 293 ip6_cantforward(ip6, rcvif, rt->rt_ifp, 294 "dst[%s] inzone %d outzone %d", 295 in6_getscopename(&ip6->ip6_dst), inzone, outzone); 296 if (mcopy) 297 icmp6_error(mcopy, ICMP6_DST_UNREACH, 298 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 299 goto drop; 300 } 301 302 if (m->m_pkthdr.len > IN6_LINKMTU(rt->rt_ifp)) { 303 in6_ifstat_inc(rt->rt_ifp, ifs6_in_toobig); 304 if (mcopy) { 305 u_long mtu; 306 307 mtu = IN6_LINKMTU(rt->rt_ifp); 308 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, mtu); 309 } 310 goto drop; 311 } 312 313 if (rt->rt_flags & RTF_GATEWAY) 314 dst = (struct sockaddr_in6 *)rt->rt_gateway; 315 316 /* 317 * If we are to forward the packet using the same interface 318 * as one we got the packet from, perhaps we should send a redirect 319 * to sender to shortcut a hop. 320 * Only send redirect if source is sending directly to us, 321 * and if packet was not source routed (or has any options). 322 * Also, don't send redirect if forwarding using a route 323 * modified by a redirect. 324 */ 325 if (rt->rt_ifp == rcvif && !srcrt && ip6_sendredirects && 326 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 327 ro = percpu_getref(ip6_forward_rt_percpu); 328 if ((rt->rt_ifp->if_flags & IFF_POINTOPOINT) && 329 nd6_is_addr_neighbor(satocsin6(rtcache_getdst(ro)), 330 rt->rt_ifp)) { 331 percpu_putref(ip6_forward_rt_percpu); 332 /* 333 * If the incoming interface is equal to the outgoing 334 * one, the link attached to the interface is 335 * point-to-point, and the IPv6 destination is 336 * regarded as on-link on the link, then it will be 337 * highly probable that the destination address does 338 * not exist on the link and that the packet is going 339 * to loop. Thus, we immediately drop the packet and 340 * send an ICMPv6 error message. 341 * For other routing loops, we dare to let the packet 342 * go to the loop, so that a remote diagnosing host 343 * can detect the loop by traceroute. 344 * type/code is based on suggestion by Rich Draves. 345 * not sure if it is the best pick. 346 */ 347 icmp6_error(mcopy, ICMP6_DST_UNREACH, 348 ICMP6_DST_UNREACH_ADDR, 0); 349 goto drop; 350 } 351 percpu_putref(ip6_forward_rt_percpu); 352 type = ND_REDIRECT; 353 } 354 355 /* 356 * Fake scoped addresses. Note that even link-local source or 357 * destinaion can appear, if the originating node just sends the 358 * packet to us (without address resolution for the destination). 359 * Since both icmp6_error and icmp6_redirect_output fill the embedded 360 * link identifiers, we can do this stuff after making a copy for 361 * returning an error. 362 */ 363 if ((rt->rt_ifp->if_flags & IFF_LOOPBACK) != 0) { 364 /* 365 * See corresponding comments in ip6_output. 366 * XXX: but is it possible that ip6_forward() sends a packet 367 * to a loopback interface? I don't think so, and thus 368 * I bark here. (jinmei@kame.net) 369 * XXX: it is common to route invalid packets to loopback. 370 * also, the codepath will be visited on use of ::1 in 371 * rthdr. (itojun) 372 */ 373 #if 1 374 if (0) 375 #else 376 if ((rt->rt_flags & (RTF_BLACKHOLE|RTF_REJECT)) == 0) 377 #endif 378 { 379 printf("ip6_forward: outgoing interface is loopback. " 380 "src %s, dst %s, nxt %d, rcvif %s, outif %s\n", 381 ip6_sprintf(&ip6->ip6_src), 382 ip6_sprintf(&ip6->ip6_dst), 383 ip6->ip6_nxt, if_name(rcvif), 384 if_name(rt->rt_ifp)); 385 } 386 387 /* we can just use rcvif in forwarding. */ 388 origifp = rcvif; 389 } 390 else 391 origifp = rt->rt_ifp; 392 /* 393 * clear embedded scope identifiers if necessary. 394 * in6_clearscope will touch the addresses only when necessary. 395 */ 396 in6_clearscope(&ip6->ip6_src); 397 in6_clearscope(&ip6->ip6_dst); 398 399 /* 400 * Run through list of hooks for output packets. 401 */ 402 if ((error = pfil_run_hooks(inet6_pfil_hook, &m, rt->rt_ifp, 403 PFIL_OUT)) != 0) 404 goto senderr; 405 if (m == NULL) 406 goto freecopy; 407 ip6 = mtod(m, struct ip6_hdr *); 408 409 error = nd6_output(rt->rt_ifp, origifp, m, dst, rt); 410 if (error) { 411 in6_ifstat_inc(rt->rt_ifp, ifs6_out_discard); 412 IP6_STATINC(IP6_STAT_CANTFORWARD); 413 } else { 414 IP6_STATINC(IP6_STAT_FORWARD); 415 in6_ifstat_inc(rt->rt_ifp, ifs6_out_forward); 416 if (type) 417 IP6_STATINC(IP6_STAT_REDIRECTSENT); 418 else { 419 #ifdef GATEWAY 420 ro = percpu_getref(ip6_forward_rt_percpu); 421 if (m->m_flags & M_CANFASTFWD) 422 ip6flow_create(ro, m); 423 percpu_putref(ip6_forward_rt_percpu); 424 #endif 425 if (mcopy) 426 goto freecopy; 427 } 428 } 429 430 senderr: 431 if (mcopy == NULL) 432 goto out; 433 switch (error) { 434 case 0: 435 if (type == ND_REDIRECT) { 436 icmp6_redirect_output(mcopy, rt); 437 goto out; 438 } 439 goto freecopy; 440 441 case EMSGSIZE: 442 /* xxx MTU is constant in PPP? */ 443 goto freecopy; 444 445 case ENOBUFS: 446 /* Tell source to slow down like source quench in IP? */ 447 goto freecopy; 448 449 case ENETUNREACH: /* shouldn't happen, checked above */ 450 case EHOSTUNREACH: 451 case ENETDOWN: 452 case EHOSTDOWN: 453 default: 454 type = ICMP6_DST_UNREACH; 455 code = ICMP6_DST_UNREACH_ADDR; 456 break; 457 } 458 icmp6_error(mcopy, type, code, 0); 459 goto out; 460 461 freecopy: 462 m_freem(mcopy); 463 goto out; 464 drop: 465 m_freem(m); 466 out: 467 if (rcvif != NULL) 468 m_put_rcvif_psref(rcvif, &psref); 469 return; 470 } 471