ip_fastfwd.c revision 167682
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 * $FreeBSD: head/sys/netinet/ip_fastfwd.c 167682 2007-03-18 23:05:20Z bms $ 30 */ 31 32/* 33 * ip_fastforward gets its speed from processing the forwarded packet to 34 * completion (if_output on the other side) without any queues or netisr's. 35 * The receiving interface DMAs the packet into memory, the upper half of 36 * driver calls ip_fastforward, we do our routing table lookup and directly 37 * send it off to the outgoing interface, which DMAs the packet to the 38 * network card. The only part of the packet we touch with the CPU is the 39 * IP header (unless there are complex firewall rules touching other parts 40 * of the packet, but that is up to you). We are essentially limited by bus 41 * bandwidth and how fast the network card/driver can set up receives and 42 * transmits. 43 * 44 * We handle basic errors, IP header errors, checksum errors, 45 * destination unreachable, fragmentation and fragmentation needed and 46 * report them via ICMP to the sender. 47 * 48 * Else if something is not pure IPv4 unicast forwarding we fall back to 49 * the normal ip_input processing path. We should only be called from 50 * interfaces connected to the outside world. 51 * 52 * Firewalling is fully supported including divert, ipfw fwd and ipfilter 53 * ipnat and address rewrite. 54 * 55 * IPSEC is not supported if this host is a tunnel broker. IPSEC is 56 * supported for connections to/from local host. 57 * 58 * We try to do the least expensive (in CPU ops) checks and operations 59 * first to catch junk with as little overhead as possible. 60 * 61 * We take full advantage of hardware support for IP checksum and 62 * fragmentation offloading. 63 * 64 * We don't do ICMP redirect in the fast forwarding path. I have had my own 65 * cases where two core routers with Zebra routing suite would send millions 66 * ICMP redirects to connected hosts if the destination router was not the 67 * default gateway. In one case it was filling the routing table of a host 68 * with approximately 300.000 cloned redirect entries until it ran out of 69 * kernel memory. However the networking code proved very robust and it didn't 70 * crash or fail in other ways. 71 */ 72 73/* 74 * Many thanks to Matt Thomas of NetBSD for basic structure of ip_flow.c which 75 * is being followed here. 76 */ 77 78#include "opt_ipfw.h" 79#include "opt_ipstealth.h" 80 81#include <sys/param.h> 82#include <sys/systm.h> 83#include <sys/kernel.h> 84#include <sys/malloc.h> 85#include <sys/mbuf.h> 86#include <sys/protosw.h> 87#include <sys/socket.h> 88#include <sys/sysctl.h> 89 90#include <net/pfil.h> 91#include <net/if.h> 92#include <net/if_types.h> 93#include <net/if_var.h> 94#include <net/if_dl.h> 95#include <net/route.h> 96 97#include <netinet/in.h> 98#include <netinet/in_systm.h> 99#include <netinet/in_var.h> 100#include <netinet/ip.h> 101#include <netinet/ip_var.h> 102#include <netinet/ip_icmp.h> 103#include <netinet/ip_options.h> 104 105#include <machine/in_cksum.h> 106 107static int ipfastforward_active = 0; 108SYSCTL_INT(_net_inet_ip, OID_AUTO, fastforwarding, CTLFLAG_RW, 109 &ipfastforward_active, 0, "Enable fast IP forwarding"); 110 111static struct sockaddr_in * 112ip_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 rtalloc_ign(ro, RTF_CLONING); 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.ips_noroute++; 138 ipstat.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 1; 151 * otherwise 0 is returned and the packet should be delivered 152 * to ip_input for full processing. 153 */ 154struct mbuf * 155ip_fastforward(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 u_short sum, ip_len; 164 int error = 0; 165 int hlen, mtu; 166#ifdef IPFIREWALL_FORWARD 167 struct m_tag *fwd_tag; 168#endif 169 170 /* 171 * Are we active and forwarding packets? 172 */ 173 if (!ipfastforward_active || !ipforwarding) 174 return m; 175 176 M_ASSERTVALID(m); 177 M_ASSERTPKTHDR(m); 178 179 ro.ro_rt = NULL; 180 181 /* 182 * Step 1: check for packet drop conditions (and sanity checks) 183 */ 184 185 /* 186 * Is entire packet big enough? 187 */ 188 if (m->m_pkthdr.len < sizeof(struct ip)) { 189 ipstat.ips_tooshort++; 190 goto drop; 191 } 192 193 /* 194 * Is first mbuf large enough for ip header and is header present? 195 */ 196 if (m->m_len < sizeof (struct ip) && 197 (m = m_pullup(m, sizeof (struct ip))) == NULL) { 198 ipstat.ips_toosmall++; 199 return NULL; /* mbuf already free'd */ 200 } 201 202 ip = mtod(m, struct ip *); 203 204 /* 205 * Is it IPv4? 206 */ 207 if (ip->ip_v != IPVERSION) { 208 ipstat.ips_badvers++; 209 goto drop; 210 } 211 212 /* 213 * Is IP header length correct and is it in first mbuf? 214 */ 215 hlen = ip->ip_hl << 2; 216 if (hlen < sizeof(struct ip)) { /* minimum header length */ 217 ipstat.ips_badlen++; 218 goto drop; 219 } 220 if (hlen > m->m_len) { 221 if ((m = m_pullup(m, hlen)) == NULL) { 222 ipstat.ips_badhlen++; 223 return NULL; /* mbuf already free'd */ 224 } 225 ip = mtod(m, struct ip *); 226 } 227 228 /* 229 * Checksum correct? 230 */ 231 if (m->m_pkthdr.csum_flags & CSUM_IP_CHECKED) 232 sum = !(m->m_pkthdr.csum_flags & CSUM_IP_VALID); 233 else { 234 if (hlen == sizeof(struct ip)) 235 sum = in_cksum_hdr(ip); 236 else 237 sum = in_cksum(m, hlen); 238 } 239 if (sum) { 240 ipstat.ips_badsum++; 241 goto drop; 242 } 243 244 /* 245 * Remember that we have checked the IP header and found it valid. 246 */ 247 m->m_pkthdr.csum_flags |= (CSUM_IP_CHECKED | CSUM_IP_VALID); 248 249 ip_len = ntohs(ip->ip_len); 250 251 /* 252 * Is IP length longer than packet we have got? 253 */ 254 if (m->m_pkthdr.len < ip_len) { 255 ipstat.ips_tooshort++; 256 goto drop; 257 } 258 259 /* 260 * Is packet longer than IP header tells us? If yes, truncate packet. 261 */ 262 if (m->m_pkthdr.len > ip_len) { 263 if (m->m_len == m->m_pkthdr.len) { 264 m->m_len = ip_len; 265 m->m_pkthdr.len = ip_len; 266 } else 267 m_adj(m, ip_len - m->m_pkthdr.len); 268 } 269 270 /* 271 * Is packet from or to 127/8? 272 */ 273 if ((ntohl(ip->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET || 274 (ntohl(ip->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET) { 275 ipstat.ips_badaddr++; 276 goto drop; 277 } 278 279#ifdef ALTQ 280 /* 281 * Is packet dropped by traffic conditioner? 282 */ 283 if (altq_input != NULL && (*altq_input)(m, AF_INET) == 0) 284 goto drop; 285#endif 286 287 /* 288 * Step 2: fallback conditions to normal ip_input path processing 289 */ 290 291 /* 292 * Only IP packets without options 293 */ 294 if (ip->ip_hl != (sizeof(struct ip) >> 2)) { 295 if (ip_doopts == 1) 296 return m; 297 else if (ip_doopts == 2) { 298 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_FILTER_PROHIB, 299 0, 0); 300 return NULL; /* mbuf already free'd */ 301 } 302 /* else ignore IP options and continue */ 303 } 304 305 /* 306 * Only unicast IP, not from loopback, no L2 or IP broadcast, 307 * no multicast, no INADDR_ANY 308 * 309 * XXX: Probably some of these checks could be direct drop 310 * conditions. However it is not clear whether there are some 311 * hacks or obscure behaviours which make it neccessary to 312 * let ip_input handle it. We play safe here and let ip_input 313 * deal with it until it is proven that we can directly drop it. 314 */ 315 if ((m->m_flags & (M_BCAST|M_MCAST)) || 316 (m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) || 317 ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST || 318 ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST || 319 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 320 IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 321 IN_LINKLOCAL(ntohl(ip->ip_src.s_addr)) || 322 IN_LINKLOCAL(ntohl(ip->ip_dst.s_addr)) || 323 ip->ip_src.s_addr == INADDR_ANY || 324 ip->ip_dst.s_addr == INADDR_ANY ) 325 return m; 326 327 /* 328 * Is it for a local address on this host? 329 */ 330 if (in_localip(ip->ip_dst)) 331 return m; 332 333 ipstat.ips_total++; 334 335 /* 336 * Step 3: incoming packet firewall processing 337 */ 338 339 /* 340 * Convert to host representation 341 */ 342 ip->ip_len = ntohs(ip->ip_len); 343 ip->ip_off = ntohs(ip->ip_off); 344 345 odest.s_addr = dest.s_addr = ip->ip_dst.s_addr; 346 347 /* 348 * Run through list of ipfilter hooks for input packets 349 */ 350 if (!PFIL_HOOKED(&inet_pfil_hook)) 351 goto passin; 352 353 if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN, NULL) || 354 m == NULL) 355 goto drop; 356 357 M_ASSERTVALID(m); 358 M_ASSERTPKTHDR(m); 359 360 ip = mtod(m, struct ip *); /* m may have changed by pfil hook */ 361 dest.s_addr = ip->ip_dst.s_addr; 362 363 /* 364 * Destination address changed? 365 */ 366 if (odest.s_addr != dest.s_addr) { 367 /* 368 * Is it now for a local address on this host? 369 */ 370 if (in_localip(dest)) 371 goto forwardlocal; 372 /* 373 * Go on with new destination address 374 */ 375 } 376#ifdef IPFIREWALL_FORWARD 377 if (m->m_flags & M_FASTFWD_OURS) { 378 /* 379 * ipfw changed it for a local address on this host. 380 */ 381 goto forwardlocal; 382 } 383#endif /* IPFIREWALL_FORWARD */ 384 385passin: 386 /* 387 * Step 4: decrement TTL and look up route 388 */ 389 390 /* 391 * Check TTL 392 */ 393#ifdef IPSTEALTH 394 if (!ipstealth) { 395#endif 396 if (ip->ip_ttl <= IPTTLDEC) { 397 icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, 0); 398 return NULL; /* mbuf already free'd */ 399 } 400 401 /* 402 * Decrement the TTL and incrementally change the IP header checksum. 403 * Don't bother doing this with hw checksum offloading, it's faster 404 * doing it right here. 405 */ 406 ip->ip_ttl -= IPTTLDEC; 407 if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8)) 408 ip->ip_sum -= ~htons(IPTTLDEC << 8); 409 else 410 ip->ip_sum += htons(IPTTLDEC << 8); 411#ifdef IPSTEALTH 412 } 413#endif 414 415 /* 416 * Find route to destination. 417 */ 418 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 419 return NULL; /* icmp unreach already sent */ 420 ifp = ro.ro_rt->rt_ifp; 421 422 /* 423 * Immediately drop blackholed traffic, and directed broadcasts 424 * for either the all-ones or all-zero subnet addresses on 425 * locally attached networks. 426 */ 427 if ((ro.ro_rt->rt_flags & (RTF_BLACKHOLE|RTF_BROADCAST)) != 0) 428 goto drop; 429 430 /* 431 * Step 5: outgoing firewall packet processing 432 */ 433 434 /* 435 * Run through list of hooks for output packets. 436 */ 437 if (!PFIL_HOOKED(&inet_pfil_hook)) 438 goto passout; 439 440 if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT, NULL) || m == NULL) { 441 goto drop; 442 } 443 444 M_ASSERTVALID(m); 445 M_ASSERTPKTHDR(m); 446 447 ip = mtod(m, struct ip *); 448 dest.s_addr = ip->ip_dst.s_addr; 449 450 /* 451 * Destination address changed? 452 */ 453#ifndef IPFIREWALL_FORWARD 454 if (odest.s_addr != dest.s_addr) { 455#else 456 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 457 if (odest.s_addr != dest.s_addr || fwd_tag != NULL) { 458#endif /* IPFIREWALL_FORWARD */ 459 /* 460 * Is it now for a local address on this host? 461 */ 462#ifndef IPFIREWALL_FORWARD 463 if (in_localip(dest)) { 464#else 465 if (m->m_flags & M_FASTFWD_OURS || in_localip(dest)) { 466#endif /* IPFIREWALL_FORWARD */ 467forwardlocal: 468 /* 469 * Return packet for processing by ip_input(). 470 * Keep host byte order as expected at ip_input's 471 * "ours"-label. 472 */ 473 m->m_flags |= M_FASTFWD_OURS; 474 if (ro.ro_rt) 475 RTFREE(ro.ro_rt); 476 return m; 477 } 478 /* 479 * Redo route lookup with new destination address 480 */ 481#ifdef IPFIREWALL_FORWARD 482 if (fwd_tag) { 483 dest.s_addr = ((struct sockaddr_in *) 484 (fwd_tag + 1))->sin_addr.s_addr; 485 m_tag_delete(m, fwd_tag); 486 } 487#endif /* IPFIREWALL_FORWARD */ 488 RTFREE(ro.ro_rt); 489 if ((dst = ip_findroute(&ro, dest, m)) == NULL) 490 return NULL; /* icmp unreach already sent */ 491 ifp = ro.ro_rt->rt_ifp; 492 } 493 494passout: 495 /* 496 * Step 6: send off the packet 497 */ 498 499 /* 500 * Check if route is dampned (when ARP is unable to resolve) 501 */ 502 if ((ro.ro_rt->rt_flags & RTF_REJECT) && 503 (ro.ro_rt->rt_rmx.rmx_expire == 0 || 504 time_uptime < ro.ro_rt->rt_rmx.rmx_expire)) { 505 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 506 goto consumed; 507 } 508 509#ifndef ALTQ 510 /* 511 * Check if there is enough space in the interface queue 512 */ 513 if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= 514 ifp->if_snd.ifq_maxlen) { 515 ipstat.ips_odropped++; 516 /* would send source quench here but that is depreciated */ 517 goto drop; 518 } 519#endif 520 521 /* 522 * Check if media link state of interface is not down 523 */ 524 if (ifp->if_link_state == LINK_STATE_DOWN) { 525 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0); 526 goto consumed; 527 } 528 529 /* 530 * Check if packet fits MTU or if hardware will fragment for us 531 */ 532 if (ro.ro_rt->rt_rmx.rmx_mtu) 533 mtu = min(ro.ro_rt->rt_rmx.rmx_mtu, ifp->if_mtu); 534 else 535 mtu = ifp->if_mtu; 536 537 if (ip->ip_len <= mtu || 538 (ifp->if_hwassist & CSUM_FRAGMENT && (ip->ip_off & IP_DF) == 0)) { 539 /* 540 * Restore packet header fields to original values 541 */ 542 ip->ip_len = htons(ip->ip_len); 543 ip->ip_off = htons(ip->ip_off); 544 /* 545 * Send off the packet via outgoing interface 546 */ 547 error = (*ifp->if_output)(ifp, m, 548 (struct sockaddr *)dst, ro.ro_rt); 549 } else { 550 /* 551 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery 552 */ 553 if (ip->ip_off & IP_DF) { 554 ipstat.ips_cantfrag++; 555 icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, 556 0, mtu); 557 goto consumed; 558 } else { 559 /* 560 * We have to fragment the packet 561 */ 562 m->m_pkthdr.csum_flags |= CSUM_IP; 563 /* 564 * ip_fragment expects ip_len and ip_off in host byte 565 * order but returns all packets in network byte order 566 */ 567 if (ip_fragment(ip, &m, mtu, ifp->if_hwassist, 568 (~ifp->if_hwassist & CSUM_DELAY_IP))) { 569 goto drop; 570 } 571 KASSERT(m != NULL, ("null mbuf and no error")); 572 /* 573 * Send off the fragments via outgoing interface 574 */ 575 error = 0; 576 do { 577 m0 = m->m_nextpkt; 578 m->m_nextpkt = NULL; 579 580 error = (*ifp->if_output)(ifp, m, 581 (struct sockaddr *)dst, ro.ro_rt); 582 if (error) 583 break; 584 } while ((m = m0) != NULL); 585 if (error) { 586 /* Reclaim remaining fragments */ 587 for (m = m0; m; m = m0) { 588 m0 = m->m_nextpkt; 589 m_freem(m); 590 } 591 } else 592 ipstat.ips_fragmented++; 593 } 594 } 595 596 if (error != 0) 597 ipstat.ips_odropped++; 598 else { 599 ro.ro_rt->rt_rmx.rmx_pksent++; 600 ipstat.ips_forward++; 601 ipstat.ips_fastforward++; 602 } 603consumed: 604 RTFREE(ro.ro_rt); 605 return NULL; 606drop: 607 if (m) 608 m_freem(m); 609 if (ro.ro_rt) 610 RTFREE(ro.ro_rt); 611 return NULL; 612} 613