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/socket.h> 89 #include <sys/sysctl.h> 90 91 #include <net/pfil.h> 92 #include <net/if.h> 93 #include <net/if_types.h> 94 #include <net/if_var.h> 95 #include <net/if_dl.h> 96 #include <net/route.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/in_var.h> 101 #include <netinet/ip.h> 102 #include <netinet/ip_var.h> 103 #include <netinet/ip_icmp.h> 104 #include <netinet/ip_options.h> 105 106 #include <machine/in_cksum.h> 107 108 static int ipfastforward_active = 0; 109 SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, 110 &ipfastforward_active, 0, "Enable fast IP forwarding"); 111 112 static struct sockaddr_in * 113 ip_findroute(struct route *ro, struct in_addr dest, struct mbuf *m) 114 { 115 struct sockaddr_in *dst; 116 struct rtentry *rt; 117 118 /* 119 * Find route to destination. 120 */ 121 bzero(ro, sizeof(*ro)); 122 dst = (struct sockaddr_in *)&ro->ro_dst; 123 dst->sin_family = AF_INET; 124 dst->sin_len = sizeof(*dst); 125 dst->sin_addr.s_addr = dest.s_addr; 126 rtalloc_ign(ro, RTF_CLONING); 127 128 /* 129 * Route there and interface still up? 130 */ 131 rt = ro->ro_rt; 132 if (rt && (rt->rt_flags & RTF_UP) && 133 (rt->rt_ifp->if_flags & IFF_UP) && 134 (rt->rt_ifp->if_drv_flags & IFF_DRV_RUNNING)) { 135 if (rt->rt_flags & RTF_GATEWAY) 136 dst = (struct sockaddr_in *)rt->rt_gateway; 137 } else { 138 ipstat.ips_noroute++; 139 ipstat.ips_cantforward++; 140 if (rt) 141 RTFREE(rt); 142 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 143 return NULL; 144 } 145 return dst; 146 } 147 148 /* 149 * Try to forward a packet based on the destination address. 150 * This is a fast path optimized for the plain forwarding case. 151 * If the packet is handled (and consumed) here then we return 1; 152 * otherwise 0 is returned and the packet should be delivered 153 * to ip_input for full processing. 154 */ 155 struct mbuf * 156 ip_fastforward(struct mbuf *m) 157 { 158 struct ip *ip; 159 struct mbuf *m0 = NULL; 160 struct route ro; 161 struct sockaddr_in *dst = NULL; 162 struct ifnet *ifp; 163 struct in_addr odest, dest; 164 u_short sum, ip_len; 165 int error = 0; 166 int hlen, mtu; 167 #ifdef IPFIREWALL_FORWARD 168 struct m_tag *fwd_tag; 169 #endif 170 171 /* 172 * Are we active and forwarding packets? 173 */ 174 if (!ipfastforward_active || !ipforwarding) 175 return m; 176 177 M_ASSERTVALID(m); 178 M_ASSERTPKTHDR(m); 179 180 ro.ro_rt = NULL; 181 182 /* 183 * Step 1: check for packet drop conditions (and sanity checks) 184 */ 185 186 /* 187 * Is entire packet big enough? 188 */ 189 if (m->m_pkthdr.len < sizeof(struct ip)) { 190 ipstat.ips_tooshort++; 191 goto drop; 192 } 193 194 /* 195 * Is first mbuf large enough for ip header and is header present? 196 */ 197 if (m->m_len < sizeof (struct ip) && 198 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 199 ipstat.ips_toosmall++; 200 return NULL; /* mbuf already free'd */ 201 } 202 203 ip = mtod(m, struct ip *); 204 205 /* 206 * Is it IPv4? 207 */ 208 if (ip->ip_v != IPVERSION) { 209 ipstat.ips_badvers++; 210 goto drop; 211 } 212 213 /* 214 * Is IP header length correct and is it in first mbuf? 215 */ 216 hlen = ip->ip_hl << 2; 217 if (hlen < sizeof(struct ip)) { /* minimum header length */ 218 ipstat.ips_badlen++; 219 goto drop; 220 } 221 if (hlen > m->m_len) { 222 if ((m = m_pullup(m, hlen)) == NULL) { 223 ipstat.ips_badhlen++; 224 return NULL; /* mbuf already free'd */ 225 } 226 ip = mtod(m, struct ip *); 227 } 228 229 /* 230 * Checksum correct? 231 */ 232 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) 233 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); 234 else { 235 if (hlen == sizeof(struct ip)) 236 sum = in_cksum_hdr(ip); 237 else 238 sum = in_cksum(m, hlen); 239 } 240 if (sum) { 241 ipstat.ips_badsum++; 242 goto drop; 243 } 244 245 /* 246 * Remember that we have checked the IP header and found it valid. 247 */ 248 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID); 249 250 ip_len = ntohs(ip->ip_len); 251 252 /* 253 * Is IP length longer than packet we have got? 254 */ 255 if (m->m_pkthdr.len < ip_len) { 256 ipstat.ips_tooshort++; 257 goto drop; 258 } 259 260 /* 261 * Is packet longer than IP header tells us? If yes, truncate packet. 262 */ 263 if (m->m_pkthdr.len > ip_len) { 264 if (m->m_len == m->m_pkthdr.len) { 265 m->m_len = ip_len; 266 m->m_pkthdr.len = ip_len; 267 } else 268 m_adj(m, ip_len - m->m_pkthdr.len); 269 } 270 271 /* 272 * Is packet from or to 127/8? 273 */ 274 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET || 275 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) { 276 ipstat.ips_badaddr++; 277 goto drop; 278 } 279 280 #ifdef ALTQ 281 /* 282 * Is packet dropped by traffic conditioner? 283 */ 284 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 285 goto drop; 286 #endif 287 288 /* 289 * Step 2: fallback conditions to normal ip_input path processing 290 */ 291 292 /* 293 * Only IP packets without options 294 */ 295 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 296 if (ip_doopts == 1) 297 return m; 298 else if (ip_doopts == 2) { 299 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 300 0, 0); 301 return NULL; /* mbuf already free'd */ 302 } 303 /* else ignore IP options and continue */ 304 } 305 306 /* 307 * Only unicast IP, not from loopback, no L2 or IP broadcast, 308 * no multicast, no INADDR_ANY 309 * 310 * XXX: Probably some of these checks could be direct drop 311 * conditions. However it is not clear whether there are some 312 * hacks or obscure behaviours which make it neccessary to 313 * let ip_input handle it. We play safe here and let ip_input 314 * deal with it until it is proven that we can directly drop it. 315 */ 316 if ((m->m_flags & (M_BCAST|M_MCAST)) || 317 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 318 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 319 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 320 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 321 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 322 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || 323 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 324 ip->ip_src.s_addr == INADDR_ANY || 325 ip->ip_dst.s_addr == INADDR_ANY ) 326 return m; 327 328 /* 329 * Is it for a local address on this host? 330 */ 331 if (in_localip(ip->ip_dst)) 332 return m; 333 334 ipstat.ips_total++; 335 336 /* 337 * Step 3: incoming packet firewall processing 338 */ 339 340 /* 341 * Convert to host representation 342 */ 343 ip->ip_len = ntohs(ip->ip_len); 344 ip->ip_off = ntohs(ip->ip_off); 345 346 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 347 348 /* 349 * Run through list of ipfilter hooks for input packets 350 */ 351 if (!PFIL_HOOKED(&inet_pfil_hook)) 352 goto passin; 353 354 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 355 m == NULL) 356 goto drop; 357 358 M_ASSERTVALID(m); 359 M_ASSERTPKTHDR(m); 360 361 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 362 dest.s_addr = ip->ip_dst.s_addr; 363 364 /* 365 * Destination address changed? 366 */ 367 if (odest.s_addr != dest.s_addr) { 368 /* 369 * Is it now for a local address on this host? 370 */ 371 if (in_localip(dest)) 372 goto forwardlocal; 373 /* 374 * Go on with new destination address 375 */ 376 } 377 #ifdef IPFIREWALL_FORWARD 378 if (m->m_flags & M_FASTFWD_OURS) { 379 /* 380 * ipfw changed it for a local address on this host. 381 */ 382 goto forwardlocal; 383 } 384 #endif /* IPFIREWALL_FORWARD */ 385 386 passin: 387 /* 388 * Step 4: decrement TTL and look up route 389 */ 390 391 /* 392 * Check TTL 393 */ 394 #ifdef IPSTEALTH 395 if (!ipstealth) { 396 #endif 397 if (ip->ip_ttl <= IPTTLDEC) { 398 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 399 return NULL; /* mbuf already free'd */ 400 } 401 402 /* 403 * Decrement the TTL and incrementally change the IP header checksum. 404 * Don't bother doing this with hw checksum offloading, it's faster 405 * doing it right here. 406 */ 407 ip->ip_ttl -= IPTTLDEC; 408 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 409 ip->ip_sum -= ~htons(IPTTLDEC << 8); 410 else 411 ip->ip_sum += htons(IPTTLDEC << 8); 412 #ifdef IPSTEALTH 413 } 414 #endif 415 416 /* 417 * Find route to destination. 418 */ 419 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 420 return NULL; /* icmp unreach already sent */ 421 ifp = ro.ro_rt->rt_ifp; 422 423 /* 424 * Immediately drop blackholed traffic, and directed broadcasts 425 * for either the all-ones or all-zero subnet addresses on 426 * locally attached networks. 427 */ 428 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 429 goto drop; 430 431 /* 432 * Step 5: outgoing firewall packet processing 433 */ 434 435 /* 436 * Run through list of hooks for output packets. 437 */ 438 if (!PFIL_HOOKED(&inet_pfil_hook)) 439 goto passout; 440 441 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 442 goto drop; 443 } 444 445 M_ASSERTVALID(m); 446 M_ASSERTPKTHDR(m); 447 448 ip = mtod(m, struct ip *); 449 dest.s_addr = ip->ip_dst.s_addr; 450 451 /* 452 * Destination address changed? 453 */ 454 #ifndef IPFIREWALL_FORWARD 455 if (odest.s_addr != dest.s_addr) { 456 #else 457 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 458 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 459 #endif /* IPFIREWALL_FORWARD */ 460 /* 461 * Is it now for a local address on this host? 462 */ 463 #ifndef IPFIREWALL_FORWARD 464 if (in_localip(dest)) { 465 #else 466 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 467 #endif /* IPFIREWALL_FORWARD */ 468 forwardlocal: 469 /* 470 * Return packet for processing by ip_input(). 471 * Keep host byte order as expected at ip_input's 472 * "ours"-label. 473 */ 474 m->m_flags |= M_FASTFWD_OURS; 475 if (ro.ro_rt) 476 RTFREE(ro.ro_rt); 477 return m; 478 } 479 /* 480 * Redo route lookup with new destination address 481 */ 482 #ifdef IPFIREWALL_FORWARD 483 if (fwd_tag) { 484 dest.s_addr = ((struct sockaddr_in *) 485 (fwd_tag + 1))->sin_addr.s_addr; 486 m_tag_delete(m, fwd_tag); 487 } 488 #endif /* IPFIREWALL_FORWARD */ 489 RTFREE(ro.ro_rt); 490 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 491 return NULL; /* icmp unreach already sent */ 492 ifp = ro.ro_rt->rt_ifp; 493 } 494 495 passout: 496 /* 497 * Step 6: send off the packet 498 */ 499 500 /* 501 * Check if route is dampned (when ARP is unable to resolve) 502 */ 503 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 504 (ro.ro_rt->rt_rmx.rmx_expire == 0 || 505 time_uptime < ro.ro_rt->rt_rmx.rmx_expire)) { 506 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 507 goto consumed; 508 } 509 510 #ifndef ALTQ 511 /* 512 * Check if there is enough space in the interface queue 513 */ 514 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= 515 ifp->if_snd.ifq_maxlen) { 516 ipstat.ips_odropped++; 517 /* would send source quench here but that is depreciated */ 518 goto drop; 519 } 520 #endif 521 522 /* 523 * Check if media link state of interface is not down 524 */ 525 if (ifp->if_link_state == LINK_STATE_DOWN) { 526 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 527 goto consumed; 528 } 529 530 /* 531 * Check if packet fits MTU or if hardware will fragment for us 532 */ 533 if (ro.ro_rt->rt_rmx.rmx_mtu) 534 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); 535 else 536 mtu = ifp->if_mtu; 537 538 if (ip->ip_len <= mtu || 539 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) { 540 /* 541 * Restore packet header fields to original values 542 */ 543 ip->ip_len = htons(ip->ip_len); 544 ip->ip_off = htons(ip->ip_off); 545 /* 546 * Send off the packet via outgoing interface 547 */ 548 error = (*ifp->if_output)(ifp, m, 549 (struct sockaddr *)dst, ro.ro_rt); 550 } else { 551 /* 552 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 553 */ 554 if (ip->ip_off & IP_DF) { 555 ipstat.ips_cantfrag++; 556 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 557 0, mtu); 558 goto consumed; 559 } else { 560 /* 561 * We have to fragment the packet 562 */ 563 m->m_pkthdr.csum_flags |= CSUM_IP; 564 /* 565 * ip_fragment expects ip_len and ip_off in host byte 566 * order but returns all packets in network byte order 567 */ 568 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist, 569 (~ifp->if_hwassist & CSUM_DELAY_IP))) { 570 goto drop; 571 } 572 KASSERT(m != NULL, ("null mbuf and no error")); 573 /* 574 * Send off the fragments via outgoing interface 575 */ 576 error = 0; 577 do { 578 m0 = m->m_nextpkt; 579 m->m_nextpkt = NULL; 580 581 error = (*ifp->if_output)(ifp, m, 582 (struct sockaddr *)dst, ro.ro_rt); 583 if (error) 584 break; 585 } while ((m = m0) != NULL); 586 if (error) { 587 /* Reclaim remaining fragments */ 588 for (m = m0; m; m = m0) { 589 m0 = m->m_nextpkt; 590 m_freem(m); 591 } 592 } else 593 ipstat.ips_fragmented++; 594 } 595 } 596 597 if (error != 0) 598 ipstat.ips_odropped++; 599 else { 600 ro.ro_rt->rt_rmx.rmx_pksent++; 601 ipstat.ips_forward++; 602 ipstat.ips_fastforward++; 603 } 604 consumed: 605 RTFREE(ro.ro_rt); 606 return NULL; 607 drop: 608 if (m) 609 m_freem(m); 610 if (ro.ro_rt) 611 RTFREE(ro.ro_rt); 612 return NULL; 613 } 614