1 /*- 2 * Copyright (c) 2003 Andre Oppermann, Internet Business Solutions AG 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 /* 31 * ip_fastforward gets its speed from processing the forwarded packet to 32 * completion (if_output on the other side) without any queues or netisr's. 33 * The receiving interface DMAs the packet into memory, the upper half of 34 * driver calls ip_fastforward, we do our routing table lookup and directly 35 * send it off to the outgoing interface, which DMAs the packet to the 36 * network card. The only part of the packet we touch with the CPU is the 37 * IP header (unless there are complex firewall rules touching other parts 38 * of the packet, but that is up to you). We are essentially limited by bus 39 * bandwidth and how fast the network card/driver can set up receives and 40 * transmits. 41 * 42 * We handle basic errors, IP header errors, checksum errors, 43 * destination unreachable, fragmentation and fragmentation needed and 44 * report them via ICMP to the sender. 45 * 46 * Else if something is not pure IPv4 unicast forwarding we fall back to 47 * the normal ip_input processing path. We should only be called from 48 * interfaces connected to the outside world. 49 * 50 * Firewalling is fully supported including divert, ipfw fwd and ipfilter 51 * ipnat and address rewrite. 52 * 53 * IPSEC is not supported if this host is a tunnel broker. IPSEC is 54 * supported for connections to/from local host. 55 * 56 * We try to do the least expensive (in CPU ops) checks and operations 57 * first to catch junk with as little overhead as possible. 58 * 59 * We take full advantage of hardware support for IP checksum and 60 * fragmentation offloading. 61 * 62 * We don't do ICMP redirect in the fast forwarding path. I have had my own 63 * cases where two core routers with Zebra routing suite would send millions 64 * ICMP redirects to connected hosts if the destination router was not the 65 * default gateway. In one case it was filling the routing table of a host 66 * with approximately 300.000 cloned redirect entries until it ran out of 67 * kernel memory. However the networking code proved very robust and it didn't 68 * crash or fail in other ways. 69 */ 70 71 /* 72 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which 73 * is being followed here. 74 */ 75 76 #include <sys/cdefs.h> 77 __FBSDID("$FreeBSD$"); 78 79 #include "opt_ipfw.h" 80 #include "opt_ipstealth.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/malloc.h> 86 #include <sys/mbuf.h> 87 #include <sys/protosw.h> 88 #include <sys/sdt.h> 89 #include <sys/socket.h> 90 #include <sys/sysctl.h> 91 92 #include <net/pfil.h> 93 #include <net/if.h> 94 #include <net/if_types.h> 95 #include <net/if_var.h> 96 #include <net/if_dl.h> 97 #include <net/route.h> 98 #include <net/vnet.h> 99 100 #include <netinet/in.h> 101 #include <netinet/in_kdtrace.h> 102 #include <netinet/in_systm.h> 103 #include <netinet/in_var.h> 104 #include <netinet/ip.h> 105 #include <netinet/ip_var.h> 106 #include <netinet/ip_icmp.h> 107 #include <netinet/ip_options.h> 108 109 #include <machine/in_cksum.h> 110 111 static struct sockaddr_in * 112 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) 113 { 114 struct sockaddr_in *dst; 115 struct rtentry *rt; 116 117 /* 118 * Find route to destination. 119 */ 120 bzero(ro, sizeof(*ro)); 121 dst = (struct sockaddr_in *)&ro->ro_dst; 122 dst->sin_family = AF_INET; 123 dst->sin_len = sizeof(*dst); 124 dst->sin_addr.s_addr = dest.s_addr; 125 in_rtalloc_ign(ro, 0, M_GETFIB(m)); 126 127 /* 128 * Route there and interface still up? 129 */ 130 rt = ro->ro_rt; 131 if (rt && (rt->rt_flags & RTF_UP) && 132 (rt->rt_ifp->if_flags & IFF_UP) && 133 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { 134 if (rt->rt_flags & RTF_GATEWAY) 135 dst = (struct sockaddr_in *)rt->rt_gateway; 136 } else { 137 IPSTAT_INC(ips_noroute); 138 IPSTAT_INC(ips_cantforward); 139 if (rt) 140 RTFREE(rt); 141 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 142 return NULL; 143 } 144 return dst; 145 } 146 147 /* 148 * Try to forward a packet based on the destination address. 149 * This is a fast path optimized for the plain forwarding case. 150 * If the packet is handled (and consumed) here then we return NULL; 151 * otherwise mbuf is returned and the packet should be delivered 152 * to ip_input for full processing. 153 */ 154 struct mbuf * 155 ip_tryforward(struct mbuf *m) 156 { 157 struct ip *ip; 158 struct mbuf *m0 = NULL; 159 struct route ro; 160 struct sockaddr_in *dst = NULL; 161 struct ifnet *ifp; 162 struct in_addr odest, dest; 163 uint16_t ip_len, ip_off; 164 int error = 0; 165 int mtu; 166 struct m_tag *fwd_tag = NULL; 167 168 /* 169 * Are we active and forwarding packets? 170 */ 171 172 M_ASSERTVALID(m); 173 M_ASSERTPKTHDR(m); 174 175 bzero(&ro, sizeof(ro)); 176 177 178 #ifdef ALTQ 179 /* 180 * Is packet dropped by traffic conditioner? 181 */ 182 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 183 goto drop; 184 #endif 185 186 /* 187 * Only IP packets without options 188 */ 189 ip = mtod(m, struct ip *); 190 191 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 192 if (V_ip_doopts == 1) 193 return m; 194 else if (V_ip_doopts == 2) { 195 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 196 0, 0); 197 return NULL; /* mbuf already free'd */ 198 } 199 /* else ignore IP options and continue */ 200 } 201 202 /* 203 * Only unicast IP, not from loopback, no L2 or IP broadcast, 204 * no multicast, no INADDR_ANY 205 * 206 * XXX: Probably some of these checks could be direct drop 207 * conditions. However it is not clear whether there are some 208 * hacks or obscure behaviours which make it neccessary to 209 * let ip_input handle it. We play safe here and let ip_input 210 * deal with it until it is proven that we can directly drop it. 211 */ 212 if ((m->m_flags & (M_BCAST|M_MCAST)) || 213 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 214 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 215 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 216 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 217 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 218 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || 219 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 220 ip->ip_src.s_addr == INADDR_ANY || 221 ip->ip_dst.s_addr == INADDR_ANY ) 222 return m; 223 224 /* 225 * Is it for a local address on this host? 226 */ 227 if (in_localip(ip->ip_dst)) 228 return m; 229 230 IPSTAT_INC(ips_total); 231 232 /* 233 * Step 3: incoming packet firewall processing 234 */ 235 236 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 237 238 /* 239 * Run through list of ipfilter hooks for input packets 240 */ 241 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 242 goto passin; 243 244 if (pfil_run_hooks( 245 &V_inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 246 m == NULL) 247 goto drop; 248 249 M_ASSERTVALID(m); 250 M_ASSERTPKTHDR(m); 251 252 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 253 dest.s_addr = ip->ip_dst.s_addr; 254 255 /* 256 * Destination address changed? 257 */ 258 if (odest.s_addr != dest.s_addr) { 259 /* 260 * Is it now for a local address on this host? 261 */ 262 if (in_localip(dest)) 263 goto forwardlocal; 264 /* 265 * Go on with new destination address 266 */ 267 } 268 269 if (m->m_flags & M_FASTFWD_OURS) { 270 /* 271 * ipfw changed it for a local address on this host. 272 */ 273 goto forwardlocal; 274 } 275 276 passin: 277 /* 278 * Step 4: decrement TTL and look up route 279 */ 280 281 /* 282 * Check TTL 283 */ 284 #ifdef IPSTEALTH 285 if (!V_ipstealth) { 286 #endif 287 if (ip->ip_ttl <= IPTTLDEC) { 288 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 289 return NULL; /* mbuf already free'd */ 290 } 291 292 /* 293 * Decrement the TTL and incrementally change the IP header checksum. 294 * Don't bother doing this with hw checksum offloading, it's faster 295 * doing it right here. 296 */ 297 ip->ip_ttl -= IPTTLDEC; 298 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 299 ip->ip_sum -= ~htons(IPTTLDEC << 8); 300 else 301 ip->ip_sum += htons(IPTTLDEC << 8); 302 #ifdef IPSTEALTH 303 } 304 #endif 305 306 /* 307 * Find route to destination. 308 */ 309 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 310 return NULL; /* icmp unreach already sent */ 311 ifp = ro.ro_rt->rt_ifp; 312 313 /* 314 * Immediately drop blackholed traffic, and directed broadcasts 315 * for either the all-ones or all-zero subnet addresses on 316 * locally attached networks. 317 */ 318 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 319 goto drop; 320 321 /* 322 * Step 5: outgoing firewall packet processing 323 */ 324 325 /* 326 * Run through list of hooks for output packets. 327 */ 328 if (!PFIL_HOOKED(&V_inet_pfil_hook)) 329 goto passout; 330 331 if (pfil_run_hooks(&V_inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 332 goto drop; 333 } 334 335 M_ASSERTVALID(m); 336 M_ASSERTPKTHDR(m); 337 338 ip = mtod(m, struct ip *); 339 dest.s_addr = ip->ip_dst.s_addr; 340 341 /* 342 * Destination address changed? 343 */ 344 if (m->m_flags & M_IP_NEXTHOP) 345 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 346 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 347 /* 348 * Is it now for a local address on this host? 349 */ 350 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 351 forwardlocal: 352 /* 353 * Return packet for processing by ip_input(). 354 */ 355 m->m_flags |= M_FASTFWD_OURS; 356 if (ro.ro_rt) 357 RTFREE(ro.ro_rt); 358 return m; 359 } 360 /* 361 * Redo route lookup with new destination address 362 */ 363 if (fwd_tag) { 364 dest.s_addr = ((struct sockaddr_in *) 365 (fwd_tag + 1))->sin_addr.s_addr; 366 m_tag_delete(m, fwd_tag); 367 m->m_flags &= ~M_IP_NEXTHOP; 368 } 369 RTFREE(ro.ro_rt); 370 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 371 return NULL; /* icmp unreach already sent */ 372 ifp = ro.ro_rt->rt_ifp; 373 } 374 375 passout: 376 /* 377 * Step 6: send off the packet 378 */ 379 ip_len = ntohs(ip->ip_len); 380 ip_off = ntohs(ip->ip_off); 381 382 /* 383 * Check if route is dampned (when ARP is unable to resolve) 384 */ 385 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 386 (ro.ro_rt->rt_expire == 0 || time_uptime < ro.ro_rt->rt_expire)) { 387 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 388 goto consumed; 389 } 390 391 /* 392 * Check if media link state of interface is not down 393 */ 394 if (ifp->if_link_state == LINK_STATE_DOWN) { 395 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 396 goto consumed; 397 } 398 399 /* 400 * Check if packet fits MTU or if hardware will fragment for us 401 */ 402 if (ro.ro_rt->rt_mtu) 403 mtu = min(ro.ro_rt->rt_mtu, ifp->if_mtu); 404 else 405 mtu = ifp->if_mtu; 406 407 if (ip_len <= mtu) { 408 /* 409 * Avoid confusing lower layers. 410 */ 411 m_clrprotoflags(m); 412 /* 413 * Send off the packet via outgoing interface 414 */ 415 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL); 416 error = (*ifp->if_output)(ifp, m, 417 (struct sockaddr *)dst, &ro); 418 } else { 419 /* 420 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 421 */ 422 if (ip_off & IP_DF) { 423 IPSTAT_INC(ips_cantfrag); 424 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 425 0, mtu); 426 goto consumed; 427 } else { 428 /* 429 * We have to fragment the packet 430 */ 431 m->m_pkthdr.csum_flags |= CSUM_IP; 432 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist)) 433 goto drop; 434 KASSERT(m != NULL, ("null mbuf and no error")); 435 /* 436 * Send off the fragments via outgoing interface 437 */ 438 error = 0; 439 do { 440 m0 = m->m_nextpkt; 441 m->m_nextpkt = NULL; 442 /* 443 * Avoid confusing lower layers. 444 */ 445 m_clrprotoflags(m); 446 447 IP_PROBE(send, NULL, NULL, ip, ifp, ip, NULL); 448 error = (*ifp->if_output)(ifp, m, 449 (struct sockaddr *)dst, &ro); 450 if (error) 451 break; 452 } while ((m = m0) != NULL); 453 if (error) { 454 /* Reclaim remaining fragments */ 455 for (m = m0; m; m = m0) { 456 m0 = m->m_nextpkt; 457 m_freem(m); 458 } 459 } else 460 IPSTAT_INC(ips_fragmented); 461 } 462 } 463 464 if (error != 0) 465 IPSTAT_INC(ips_odropped); 466 else { 467 counter_u64_add(ro.ro_rt->rt_pksent, 1); 468 IPSTAT_INC(ips_forward); 469 IPSTAT_INC(ips_fastforward); 470 } 471 consumed: 472 RTFREE(ro.ro_rt); 473 return NULL; 474 drop: 475 if (m) 476 m_freem(m); 477 if (ro.ro_rt) 478 RTFREE(ro.ro_rt); 479 return NULL; 480 } 481