1 /* $OpenBSD: ip6_forward.c,v 1.108 2022/08/09 21:10:02 kn Exp $ */ 2 /* $KAME: ip6_forward.c,v 1.75 2001/06/29 12:42:13 jinmei 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 "pf.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/mbuf.h> 38 #include <sys/socket.h> 39 #include <sys/errno.h> 40 #include <sys/time.h> 41 #include <sys/kernel.h> 42 #include <sys/syslog.h> 43 44 #include <net/if.h> 45 #include <net/if_var.h> 46 #include <net/if_enc.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/ip_var.h> 51 #include <netinet6/in6_var.h> 52 #include <netinet/ip6.h> 53 #include <netinet6/ip6_var.h> 54 #include <netinet/icmp6.h> 55 #include <netinet6/nd6.h> 56 57 #if NPF > 0 58 #include <net/pfvar.h> 59 #endif 60 61 #ifdef IPSEC 62 #include <netinet/ip_ipsp.h> 63 #include <netinet/ip_ah.h> 64 #include <netinet/ip_esp.h> 65 #include <netinet/udp.h> 66 #include <netinet/tcp.h> 67 #endif 68 69 /* 70 * Forward a packet. If some error occurs return the sender 71 * an icmp packet. Note we can't always generate a meaningful 72 * icmp message because icmp doesn't have a large enough repertoire 73 * of codes and types. 74 * 75 * If not forwarding, just drop the packet. This could be confusing 76 * if ipforwarding was zero but some routing protocol was advancing 77 * us as a gateway to somewhere. However, we must let the routing 78 * protocol deal with that. 79 * 80 */ 81 82 void 83 ip6_forward(struct mbuf *m, struct rtentry *rt, int srcrt) 84 { 85 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); 86 struct sockaddr_in6 *sin6; 87 struct route_in6 ro; 88 struct ifnet *ifp = NULL; 89 int error = 0, type = 0, code = 0, destmtu = 0; 90 struct mbuf *mcopy = NULL; 91 #ifdef IPSEC 92 struct tdb *tdb = NULL; 93 #endif /* IPSEC */ 94 char src6[INET6_ADDRSTRLEN], dst6[INET6_ADDRSTRLEN]; 95 96 /* 97 * Do not forward packets to multicast destination (should be handled 98 * by ip6_mforward(). 99 * Do not forward packets with unspecified source. It was discussed 100 * in July 2000, on ipngwg mailing list. 101 */ 102 if ((m->m_flags & (M_BCAST|M_MCAST)) != 0 || 103 IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 104 IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 105 ip6stat_inc(ip6s_cantforward); 106 if (ip6_log_time + ip6_log_interval < getuptime()) { 107 ip6_log_time = getuptime(); 108 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 109 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 110 log(LOG_DEBUG, 111 "cannot forward " 112 "from %s to %s nxt %d received on interface %u\n", 113 src6, dst6, 114 ip6->ip6_nxt, 115 m->m_pkthdr.ph_ifidx); 116 } 117 m_freem(m); 118 goto out; 119 } 120 121 if (ip6->ip6_hlim <= IPV6_HLIMDEC) { 122 icmp6_error(m, ICMP6_TIME_EXCEEDED, 123 ICMP6_TIME_EXCEED_TRANSIT, 0); 124 goto out; 125 } 126 ip6->ip6_hlim -= IPV6_HLIMDEC; 127 128 /* 129 * Save at most ICMPV6_PLD_MAXLEN (= the min IPv6 MTU - 130 * size of IPv6 + ICMPv6 headers) bytes of the packet in case 131 * we need to generate an ICMP6 message to the src. 132 * Thanks to M_EXT, in most cases copy will not occur. 133 * 134 * It is important to save it before IPsec processing as IPsec 135 * processing may modify the mbuf. 136 */ 137 mcopy = m_copym(m, 0, imin(m->m_pkthdr.len, ICMPV6_PLD_MAXLEN), 138 M_NOWAIT); 139 140 #if NPF > 0 141 reroute: 142 #endif 143 144 #ifdef IPSEC 145 if (ipsec_in_use) { 146 error = ip6_output_ipsec_lookup(m, NULL, &tdb); 147 if (error) { 148 /* 149 * -EINVAL is used to indicate that the packet should 150 * be silently dropped, typically because we've asked 151 * key management for an SA. 152 */ 153 if (error == -EINVAL) /* Should silently drop packet */ 154 error = 0; 155 156 m_freem(m); 157 goto freecopy; 158 } 159 } 160 #endif /* IPSEC */ 161 162 memset(&ro, 0, sizeof(ro)); 163 sin6 = &ro.ro_dst; 164 sin6->sin6_family = AF_INET6; 165 sin6->sin6_len = sizeof(*sin6); 166 sin6->sin6_addr = ip6->ip6_dst; 167 168 if (!rtisvalid(rt)) { 169 rtfree(rt); 170 rt = rtalloc_mpath(sin6tosa(sin6), &ip6->ip6_src.s6_addr32[0], 171 m->m_pkthdr.ph_rtableid); 172 if (rt == NULL) { 173 ip6stat_inc(ip6s_noroute); 174 if (mcopy) { 175 icmp6_error(mcopy, ICMP6_DST_UNREACH, 176 ICMP6_DST_UNREACH_NOROUTE, 0); 177 } 178 m_freem(m); 179 goto out; 180 } 181 } 182 183 /* 184 * Scope check: if a packet can't be delivered to its destination 185 * for the reason that the destination is beyond the scope of the 186 * source address, discard the packet and return an icmp6 destination 187 * unreachable error with Code 2 (beyond scope of source address). 188 * [draft-ietf-ipngwg-icmp-v3-00.txt, Section 3.1] 189 */ 190 if (in6_addr2scopeid(m->m_pkthdr.ph_ifidx, &ip6->ip6_src) != 191 in6_addr2scopeid(rt->rt_ifidx, &ip6->ip6_src)) { 192 ip6stat_inc(ip6s_cantforward); 193 ip6stat_inc(ip6s_badscope); 194 195 if (ip6_log_time + ip6_log_interval < getuptime()) { 196 ip6_log_time = getuptime(); 197 inet_ntop(AF_INET6, &ip6->ip6_src, src6, sizeof(src6)); 198 inet_ntop(AF_INET6, &ip6->ip6_dst, dst6, sizeof(dst6)); 199 log(LOG_DEBUG, 200 "cannot forward " 201 "src %s, dst %s, nxt %d, rcvif %u, outif %u\n", 202 src6, dst6, 203 ip6->ip6_nxt, 204 m->m_pkthdr.ph_ifidx, rt->rt_ifidx); 205 } 206 if (mcopy) 207 icmp6_error(mcopy, ICMP6_DST_UNREACH, 208 ICMP6_DST_UNREACH_BEYONDSCOPE, 0); 209 m_freem(m); 210 goto out; 211 } 212 213 #ifdef IPSEC 214 /* 215 * Check if the packet needs encapsulation. 216 * ipsp_process_packet will never come back to here. 217 */ 218 if (tdb != NULL) { 219 /* Callee frees mbuf */ 220 ro.ro_rt = rt; 221 ro.ro_tableid = m->m_pkthdr.ph_rtableid; 222 error = ip6_output_ipsec_send(tdb, m, &ro, 0, 1); 223 rt = ro.ro_rt; 224 if (error) 225 goto senderr; 226 goto freecopy; 227 } 228 #endif /* IPSEC */ 229 230 if (rt->rt_flags & RTF_GATEWAY) 231 sin6 = satosin6(rt->rt_gateway); 232 233 /* 234 * If we are to forward the packet using the same interface 235 * as one we got the packet from, perhaps we should send a redirect 236 * to sender to shortcut a hop. 237 * Only send redirect if source is sending directly to us, 238 * and if packet was not source routed (or has any options). 239 * Also, don't send redirect if forwarding using a route 240 * modified by a redirect. 241 */ 242 ifp = if_get(rt->rt_ifidx); 243 if (ifp == NULL) { 244 m_freem(m); 245 goto freecopy; 246 } 247 if (rt->rt_ifidx == m->m_pkthdr.ph_ifidx && !srcrt && 248 ip6_sendredirects && 249 (rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0) { 250 if ((ifp->if_flags & IFF_POINTOPOINT) && 251 nd6_is_addr_neighbor(&ro.ro_dst, ifp)) { 252 /* 253 * If the incoming interface is equal to the outgoing 254 * one, the link attached to the interface is 255 * point-to-point, and the IPv6 destination is 256 * regarded as on-link on the link, then it will be 257 * highly probable that the destination address does 258 * not exist on the link and that the packet is going 259 * to loop. Thus, we immediately drop the packet and 260 * send an ICMPv6 error message. 261 * For other routing loops, we dare to let the packet 262 * go to the loop, so that a remote diagnosing host 263 * can detect the loop by traceroute. 264 * type/code is based on suggestion by Rich Draves. 265 * not sure if it is the best pick. 266 */ 267 if (mcopy) 268 icmp6_error(mcopy, ICMP6_DST_UNREACH, 269 ICMP6_DST_UNREACH_ADDR, 0); 270 m_freem(m); 271 goto out; 272 } 273 type = ND_REDIRECT; 274 } 275 276 /* 277 * Fake scoped addresses. Note that even link-local source or 278 * destination can appear, if the originating node just sends the 279 * packet to us (without address resolution for the destination). 280 * Since both icmp6_error and icmp6_redirect_output fill the embedded 281 * link identifiers, we can do this stuff after making a copy for 282 * returning an error. 283 */ 284 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_src)) 285 ip6->ip6_src.s6_addr16[1] = 0; 286 if (IN6_IS_SCOPE_EMBED(&ip6->ip6_dst)) 287 ip6->ip6_dst.s6_addr16[1] = 0; 288 289 #if NPF > 0 290 if (pf_test(AF_INET6, PF_FWD, ifp, &m) != PF_PASS) { 291 m_freem(m); 292 goto senderr; 293 } 294 if (m == NULL) 295 goto senderr; 296 ip6 = mtod(m, struct ip6_hdr *); 297 if ((m->m_pkthdr.pf.flags & (PF_TAG_REROUTE | PF_TAG_GENERATED)) == 298 (PF_TAG_REROUTE | PF_TAG_GENERATED)) { 299 /* already rerun the route lookup, go on */ 300 m->m_pkthdr.pf.flags &= ~(PF_TAG_GENERATED | PF_TAG_REROUTE); 301 } else if (m->m_pkthdr.pf.flags & PF_TAG_REROUTE) { 302 /* tag as generated to skip over pf_test on rerun */ 303 m->m_pkthdr.pf.flags |= PF_TAG_GENERATED; 304 srcrt = 1; 305 rtfree(rt); 306 rt = NULL; 307 if_put(ifp); 308 ifp = NULL; 309 goto reroute; 310 } 311 #endif 312 in6_proto_cksum_out(m, ifp); 313 314 /* Check the size after pf_test to give pf a chance to refragment. */ 315 if (m->m_pkthdr.len > ifp->if_mtu) { 316 if (mcopy) 317 icmp6_error(mcopy, ICMP6_PACKET_TOO_BIG, 0, 318 ifp->if_mtu); 319 m_freem(m); 320 goto out; 321 } 322 323 error = ifp->if_output(ifp, m, sin6tosa(sin6), rt); 324 if (error) { 325 ip6stat_inc(ip6s_cantforward); 326 } else { 327 ip6stat_inc(ip6s_forward); 328 if (type) 329 ip6stat_inc(ip6s_redirectsent); 330 else { 331 if (mcopy) 332 goto freecopy; 333 } 334 } 335 336 #if NPF > 0 || defined(IPSEC) 337 senderr: 338 #endif 339 if (mcopy == NULL) 340 goto out; 341 342 switch (error) { 343 case 0: 344 if (type == ND_REDIRECT) { 345 icmp6_redirect_output(mcopy, rt); 346 goto out; 347 } 348 goto freecopy; 349 350 case EMSGSIZE: 351 type = ICMP6_PACKET_TOO_BIG; 352 code = 0; 353 if (rt != NULL) { 354 if (rt->rt_mtu) { 355 destmtu = rt->rt_mtu; 356 } else { 357 struct ifnet *destifp; 358 359 destifp = if_get(rt->rt_ifidx); 360 if (destifp != NULL) 361 destmtu = destifp->if_mtu; 362 if_put(destifp); 363 } 364 } 365 ip6stat_inc(ip6s_cantfrag); 366 if (destmtu == 0) 367 goto freecopy; 368 break; 369 370 case EACCES: 371 /* 372 * pf(4) blocked the packet. There is no need to send an ICMP 373 * packet back since pf(4) takes care of it. 374 */ 375 goto freecopy; 376 377 case ENOBUFS: 378 /* Tell source to slow down like source quench in IP? */ 379 goto freecopy; 380 381 case ENETUNREACH: /* shouldn't happen, checked above */ 382 case EHOSTUNREACH: 383 case ENETDOWN: 384 case EHOSTDOWN: 385 default: 386 type = ICMP6_DST_UNREACH; 387 code = ICMP6_DST_UNREACH_ADDR; 388 break; 389 } 390 icmp6_error(mcopy, type, code, destmtu); 391 goto out; 392 393 freecopy: 394 m_freem(mcopy); 395 out: 396 rtfree(rt); 397 if_put(ifp); 398 #ifdef IPSEC 399 tdb_unref(tdb); 400 #endif /* IPSEC */ 401 } 402