1 /* 2 * NET3: Implementation of the ICMP protocol layer. 3 * 4 * Alan Cox, <alan@redhat.com> 5 * 6 * Version: $Id: icmp.c,v 1.85 2002/02/01 22:01:03 davem Exp $ 7 * 8 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License 10 * as published by the Free Software Foundation; either version 11 * 2 of the License, or (at your option) any later version. 12 * 13 * Some of the function names and the icmp unreach table for this 14 * module were derived from [icmp.c 1.0.11 06/02/93] by 15 * Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting. 16 * Other than that this module is a complete rewrite. 17 * 18 * Fixes: 19 * Clemens Fruhwirth : introduce global icmp rate limiting 20 * with icmp type masking ability instead 21 * of broken per type icmp timeouts. 22 * Mike Shaver : RFC1122 checks. 23 * Alan Cox : Multicast ping reply as self. 24 * Alan Cox : Fix atomicity lockup in ip_build_xmit 25 * call. 26 * Alan Cox : Added 216,128 byte paths to the MTU 27 * code. 28 * Martin Mares : RFC1812 checks. 29 * Martin Mares : Can be configured to follow redirects 30 * if acting as a router _without_ a 31 * routing protocol (RFC 1812). 32 * Martin Mares : Echo requests may be configured to 33 * be ignored (RFC 1812). 34 * Martin Mares : Limitation of ICMP error message 35 * transmit rate (RFC 1812). 36 * Martin Mares : TOS and Precedence set correctly 37 * (RFC 1812). 38 * Martin Mares : Now copying as much data from the 39 * original packet as we can without 40 * exceeding 576 bytes (RFC 1812). 41 * Willy Konynenberg : Transparent proxying support. 42 * Keith Owens : RFC1191 correction for 4.2BSD based 43 * path MTU bug. 44 * Thomas Quinot : ICMP Dest Unreach codes up to 15 are 45 * valid (RFC 1812). 46 * Andi Kleen : Check all packet lengths properly 47 * and moved all kfree_skb() up to 48 * icmp_rcv. 49 * Andi Kleen : Move the rate limit bookkeeping 50 * into the dest entry and use a token 51 * bucket filter (thanks to ANK). Make 52 * the rates sysctl configurable. 53 * Yu Tianli : Fixed two ugly bugs in icmp_send 54 * - IP option length was accounted wrongly 55 * - ICMP header length was not accounted 56 * at all. 57 * Tristan Greaves : Added sysctl option to ignore bogus 58 * broadcast responses from broken routers. 59 * 60 * To Fix: 61 * 62 * - Should use skb_pull() instead of all the manual checking. 63 * This would also greatly simply some upper layer error handlers. --AK 64 * 65 */ 66 67 #include <linux/module.h> 68 #include <linux/types.h> 69 #include <linux/jiffies.h> 70 #include <linux/kernel.h> 71 #include <linux/fcntl.h> 72 #include <linux/socket.h> 73 #include <linux/in.h> 74 #include <linux/inet.h> 75 #include <linux/inetdevice.h> 76 #include <linux/netdevice.h> 77 #include <linux/string.h> 78 #include <linux/netfilter_ipv4.h> 79 #include <net/snmp.h> 80 #include <net/ip.h> 81 #include <net/route.h> 82 #include <net/protocol.h> 83 #include <net/icmp.h> 84 #include <net/tcp.h> 85 #include <net/udp.h> 86 #include <net/raw.h> 87 #include <linux/skbuff.h> 88 #include <net/sock.h> 89 #include <linux/errno.h> 90 #include <linux/timer.h> 91 #include <linux/init.h> 92 #include <asm/system.h> 93 #include <asm/uaccess.h> 94 #include <net/checksum.h> 95 #include <net/xfrm.h> 96 97 /* 98 * Build xmit assembly blocks 99 */ 100 101 struct icmp_bxm { 102 struct sk_buff *skb; 103 int offset; 104 int data_len; 105 106 struct { 107 struct icmphdr icmph; 108 __be32 times[3]; 109 } data; 110 int head_len; 111 struct ip_options replyopts; 112 unsigned char optbuf[40]; 113 }; 114 115 /* 116 * Statistics 117 */ 118 DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics) __read_mostly; 119 DEFINE_SNMP_STAT(struct icmpmsg_mib, icmpmsg_statistics) __read_mostly; 120 121 /* An array of errno for error messages from dest unreach. */ 122 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 123 124 struct icmp_err icmp_err_convert[] = { 125 { 126 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 127 .fatal = 0, 128 }, 129 { 130 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 131 .fatal = 0, 132 }, 133 { 134 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 135 .fatal = 1, 136 }, 137 { 138 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 139 .fatal = 1, 140 }, 141 { 142 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 143 .fatal = 0, 144 }, 145 { 146 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 147 .fatal = 0, 148 }, 149 { 150 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 151 .fatal = 1, 152 }, 153 { 154 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 155 .fatal = 1, 156 }, 157 { 158 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 159 .fatal = 1, 160 }, 161 { 162 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 163 .fatal = 1, 164 }, 165 { 166 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 167 .fatal = 1, 168 }, 169 { 170 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 171 .fatal = 0, 172 }, 173 { 174 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 175 .fatal = 0, 176 }, 177 { 178 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 179 .fatal = 1, 180 }, 181 { 182 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 183 .fatal = 1, 184 }, 185 { 186 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 187 .fatal = 1, 188 }, 189 }; 190 191 /* Control parameters for ECHO replies. */ 192 int sysctl_icmp_echo_ignore_all __read_mostly; 193 int sysctl_icmp_echo_ignore_broadcasts __read_mostly = 1; 194 195 /* Control parameter - ignore bogus broadcast responses? */ 196 int sysctl_icmp_ignore_bogus_error_responses __read_mostly = 1; 197 198 /* 199 * Configurable global rate limit. 200 * 201 * ratelimit defines tokens/packet consumed for dst->rate_token bucket 202 * ratemask defines which icmp types are ratelimited by setting 203 * it's bit position. 204 * 205 * default: 206 * dest unreachable (3), source quench (4), 207 * time exceeded (11), parameter problem (12) 208 */ 209 210 int sysctl_icmp_ratelimit __read_mostly = 1 * HZ; 211 int sysctl_icmp_ratemask __read_mostly = 0x1818; 212 int sysctl_icmp_errors_use_inbound_ifaddr __read_mostly; 213 214 /* 215 * ICMP control array. This specifies what to do with each ICMP. 216 */ 217 218 struct icmp_control { 219 void (*handler)(struct sk_buff *skb); 220 short error; /* This ICMP is classed as an error message */ 221 }; 222 223 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 224 225 /* 226 * The ICMP socket(s). This is the most convenient way to flow control 227 * our ICMP output as well as maintain a clean interface throughout 228 * all layers. All Socketless IP sends will soon be gone. 229 * 230 * On SMP we have one ICMP socket per-cpu. 231 */ 232 static DEFINE_PER_CPU(struct socket *, __icmp_socket) = NULL; 233 #define icmp_socket __get_cpu_var(__icmp_socket) 234 235 static inline int icmp_xmit_lock(void) 236 { 237 local_bh_disable(); 238 239 if (unlikely(!spin_trylock(&icmp_socket->sk->sk_lock.slock))) { 240 /* This can happen if the output path signals a 241 * dst_link_failure() for an outgoing ICMP packet. 242 */ 243 local_bh_enable(); 244 return 1; 245 } 246 return 0; 247 } 248 249 static inline void icmp_xmit_unlock(void) 250 { 251 spin_unlock_bh(&icmp_socket->sk->sk_lock.slock); 252 } 253 254 /* 255 * Send an ICMP frame. 256 */ 257 258 /* 259 * Check transmit rate limitation for given message. 260 * The rate information is held in the destination cache now. 261 * This function is generic and could be used for other purposes 262 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov. 263 * 264 * Note that the same dst_entry fields are modified by functions in 265 * route.c too, but these work for packet destinations while xrlim_allow 266 * works for icmp destinations. This means the rate limiting information 267 * for one "ip object" is shared - and these ICMPs are twice limited: 268 * by source and by destination. 269 * 270 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate 271 * SHOULD allow setting of rate limits 272 * 273 * Shared between ICMPv4 and ICMPv6. 274 */ 275 #define XRLIM_BURST_FACTOR 6 276 int xrlim_allow(struct dst_entry *dst, int timeout) 277 { 278 unsigned long now, token = dst->rate_tokens; 279 int rc = 0; 280 281 now = jiffies; 282 token += now - dst->rate_last; 283 dst->rate_last = now; 284 if (token > XRLIM_BURST_FACTOR * timeout) 285 token = XRLIM_BURST_FACTOR * timeout; 286 if (token >= timeout) { 287 token -= timeout; 288 rc = 1; 289 } 290 dst->rate_tokens = token; 291 return rc; 292 } 293 294 static inline int icmpv4_xrlim_allow(struct rtable *rt, int type, int code) 295 { 296 struct dst_entry *dst = &rt->u.dst; 297 int rc = 1; 298 299 if (type > NR_ICMP_TYPES) 300 goto out; 301 302 /* Don't limit PMTU discovery. */ 303 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 304 goto out; 305 306 /* No rate limit on loopback */ 307 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 308 goto out; 309 310 /* Limit if icmp type is enabled in ratemask. */ 311 if ((1 << type) & sysctl_icmp_ratemask) 312 rc = xrlim_allow(dst, sysctl_icmp_ratelimit); 313 out: 314 return rc; 315 } 316 317 /* 318 * Maintain the counters used in the SNMP statistics for outgoing ICMP 319 */ 320 void icmp_out_count(unsigned char type) 321 { 322 ICMPMSGOUT_INC_STATS(type); 323 ICMP_INC_STATS(ICMP_MIB_OUTMSGS); 324 } 325 326 /* 327 * Checksum each fragment, and on the first include the headers and final 328 * checksum. 329 */ 330 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 331 struct sk_buff *skb) 332 { 333 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 334 __wsum csum; 335 336 csum = skb_copy_and_csum_bits(icmp_param->skb, 337 icmp_param->offset + offset, 338 to, len, 0); 339 340 skb->csum = csum_block_add(skb->csum, csum, odd); 341 if (icmp_pointers[icmp_param->data.icmph.type].error) 342 nf_ct_attach(skb, icmp_param->skb); 343 return 0; 344 } 345 346 static void icmp_push_reply(struct icmp_bxm *icmp_param, 347 struct ipcm_cookie *ipc, struct rtable *rt) 348 { 349 struct sk_buff *skb; 350 351 if (ip_append_data(icmp_socket->sk, icmp_glue_bits, icmp_param, 352 icmp_param->data_len+icmp_param->head_len, 353 icmp_param->head_len, 354 ipc, rt, MSG_DONTWAIT) < 0) 355 ip_flush_pending_frames(icmp_socket->sk); 356 else if ((skb = skb_peek(&icmp_socket->sk->sk_write_queue)) != NULL) { 357 struct icmphdr *icmph = icmp_hdr(skb); 358 __wsum csum = 0; 359 struct sk_buff *skb1; 360 361 skb_queue_walk(&icmp_socket->sk->sk_write_queue, skb1) { 362 csum = csum_add(csum, skb1->csum); 363 } 364 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 365 (char *)icmph, 366 icmp_param->head_len, csum); 367 icmph->checksum = csum_fold(csum); 368 skb->ip_summed = CHECKSUM_NONE; 369 ip_push_pending_frames(icmp_socket->sk); 370 } 371 } 372 373 /* 374 * Driving logic for building and sending ICMP messages. 375 */ 376 377 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 378 { 379 struct sock *sk = icmp_socket->sk; 380 struct inet_sock *inet = inet_sk(sk); 381 struct ipcm_cookie ipc; 382 struct rtable *rt = (struct rtable *)skb->dst; 383 __be32 daddr; 384 385 if (ip_options_echo(&icmp_param->replyopts, skb)) 386 return; 387 388 if (icmp_xmit_lock()) 389 return; 390 391 icmp_param->data.icmph.checksum = 0; 392 393 inet->tos = ip_hdr(skb)->tos; 394 daddr = ipc.addr = rt->rt_src; 395 ipc.opt = NULL; 396 if (icmp_param->replyopts.optlen) { 397 ipc.opt = &icmp_param->replyopts; 398 if (ipc.opt->srr) 399 daddr = icmp_param->replyopts.faddr; 400 } 401 { 402 struct flowi fl = { .nl_u = { .ip4_u = 403 { .daddr = daddr, 404 .saddr = rt->rt_spec_dst, 405 .tos = RT_TOS(ip_hdr(skb)->tos) } }, 406 .proto = IPPROTO_ICMP }; 407 security_skb_classify_flow(skb, &fl); 408 if (ip_route_output_key(rt->u.dst.dev->nd_net, &rt, &fl)) 409 goto out_unlock; 410 } 411 if (icmpv4_xrlim_allow(rt, icmp_param->data.icmph.type, 412 icmp_param->data.icmph.code)) 413 icmp_push_reply(icmp_param, &ipc, rt); 414 ip_rt_put(rt); 415 out_unlock: 416 icmp_xmit_unlock(); 417 } 418 419 420 /* 421 * Send an ICMP message in response to a situation 422 * 423 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 424 * MAY send more (we do). 425 * MUST NOT change this header information. 426 * MUST NOT reply to a multicast/broadcast IP address. 427 * MUST NOT reply to a multicast/broadcast MAC address. 428 * MUST reply to only the first fragment. 429 */ 430 431 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 432 { 433 struct iphdr *iph; 434 int room; 435 struct icmp_bxm icmp_param; 436 struct rtable *rt = (struct rtable *)skb_in->dst; 437 struct ipcm_cookie ipc; 438 __be32 saddr; 439 u8 tos; 440 struct net *net; 441 442 if (!rt) 443 goto out; 444 net = rt->u.dst.dev->nd_net; 445 446 /* 447 * Find the original header. It is expected to be valid, of course. 448 * Check this, icmp_send is called from the most obscure devices 449 * sometimes. 450 */ 451 iph = ip_hdr(skb_in); 452 453 if ((u8 *)iph < skb_in->head || 454 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 455 goto out; 456 457 /* 458 * No replies to physical multicast/broadcast 459 */ 460 if (skb_in->pkt_type != PACKET_HOST) 461 goto out; 462 463 /* 464 * Now check at the protocol level 465 */ 466 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 467 goto out; 468 469 /* 470 * Only reply to fragment 0. We byte re-order the constant 471 * mask for efficiency. 472 */ 473 if (iph->frag_off & htons(IP_OFFSET)) 474 goto out; 475 476 /* 477 * If we send an ICMP error to an ICMP error a mess would result.. 478 */ 479 if (icmp_pointers[type].error) { 480 /* 481 * We are an error, check if we are replying to an 482 * ICMP error 483 */ 484 if (iph->protocol == IPPROTO_ICMP) { 485 u8 _inner_type, *itp; 486 487 itp = skb_header_pointer(skb_in, 488 skb_network_header(skb_in) + 489 (iph->ihl << 2) + 490 offsetof(struct icmphdr, 491 type) - 492 skb_in->data, 493 sizeof(_inner_type), 494 &_inner_type); 495 if (itp == NULL) 496 goto out; 497 498 /* 499 * Assume any unknown ICMP type is an error. This 500 * isn't specified by the RFC, but think about it.. 501 */ 502 if (*itp > NR_ICMP_TYPES || 503 icmp_pointers[*itp].error) 504 goto out; 505 } 506 } 507 508 if (icmp_xmit_lock()) 509 return; 510 511 /* 512 * Construct source address and options. 513 */ 514 515 saddr = iph->daddr; 516 if (!(rt->rt_flags & RTCF_LOCAL)) { 517 struct net_device *dev = NULL; 518 519 if (rt->fl.iif && sysctl_icmp_errors_use_inbound_ifaddr) 520 dev = dev_get_by_index(net, rt->fl.iif); 521 522 if (dev) { 523 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 524 dev_put(dev); 525 } else 526 saddr = 0; 527 } 528 529 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 530 IPTOS_PREC_INTERNETCONTROL) : 531 iph->tos; 532 533 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 534 goto out_unlock; 535 536 537 /* 538 * Prepare data for ICMP header. 539 */ 540 541 icmp_param.data.icmph.type = type; 542 icmp_param.data.icmph.code = code; 543 icmp_param.data.icmph.un.gateway = info; 544 icmp_param.data.icmph.checksum = 0; 545 icmp_param.skb = skb_in; 546 icmp_param.offset = skb_network_offset(skb_in); 547 inet_sk(icmp_socket->sk)->tos = tos; 548 ipc.addr = iph->saddr; 549 ipc.opt = &icmp_param.replyopts; 550 551 { 552 struct flowi fl = { 553 .nl_u = { 554 .ip4_u = { 555 .daddr = icmp_param.replyopts.srr ? 556 icmp_param.replyopts.faddr : 557 iph->saddr, 558 .saddr = saddr, 559 .tos = RT_TOS(tos) 560 } 561 }, 562 .proto = IPPROTO_ICMP, 563 .uli_u = { 564 .icmpt = { 565 .type = type, 566 .code = code 567 } 568 } 569 }; 570 int err; 571 struct rtable *rt2; 572 573 security_skb_classify_flow(skb_in, &fl); 574 if (__ip_route_output_key(net, &rt, &fl)) 575 goto out_unlock; 576 577 /* No need to clone since we're just using its address. */ 578 rt2 = rt; 579 580 err = xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0); 581 switch (err) { 582 case 0: 583 if (rt != rt2) 584 goto route_done; 585 break; 586 case -EPERM: 587 rt = NULL; 588 break; 589 default: 590 goto out_unlock; 591 } 592 593 if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET)) 594 goto out_unlock; 595 596 if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) 597 err = __ip_route_output_key(net, &rt2, &fl); 598 else { 599 struct flowi fl2 = {}; 600 struct dst_entry *odst; 601 602 fl2.fl4_dst = fl.fl4_src; 603 if (ip_route_output_key(net, &rt2, &fl2)) 604 goto out_unlock; 605 606 /* Ugh! */ 607 odst = skb_in->dst; 608 err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src, 609 RT_TOS(tos), rt2->u.dst.dev); 610 611 dst_release(&rt2->u.dst); 612 rt2 = (struct rtable *)skb_in->dst; 613 skb_in->dst = odst; 614 } 615 616 if (err) 617 goto out_unlock; 618 619 err = xfrm_lookup((struct dst_entry **)&rt2, &fl, NULL, 620 XFRM_LOOKUP_ICMP); 621 if (err == -ENOENT) { 622 if (!rt) 623 goto out_unlock; 624 goto route_done; 625 } 626 627 dst_release(&rt->u.dst); 628 rt = rt2; 629 630 if (err) 631 goto out_unlock; 632 } 633 634 route_done: 635 if (!icmpv4_xrlim_allow(rt, type, code)) 636 goto ende; 637 638 /* RFC says return as much as we can without exceeding 576 bytes. */ 639 640 room = dst_mtu(&rt->u.dst); 641 if (room > 576) 642 room = 576; 643 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 644 room -= sizeof(struct icmphdr); 645 646 icmp_param.data_len = skb_in->len - icmp_param.offset; 647 if (icmp_param.data_len > room) 648 icmp_param.data_len = room; 649 icmp_param.head_len = sizeof(struct icmphdr); 650 651 icmp_push_reply(&icmp_param, &ipc, rt); 652 ende: 653 ip_rt_put(rt); 654 out_unlock: 655 icmp_xmit_unlock(); 656 out:; 657 } 658 659 660 /* 661 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 662 */ 663 664 static void icmp_unreach(struct sk_buff *skb) 665 { 666 struct iphdr *iph; 667 struct icmphdr *icmph; 668 int hash, protocol; 669 struct net_protocol *ipprot; 670 u32 info = 0; 671 struct net *net; 672 673 net = skb->dst->dev->nd_net; 674 675 /* 676 * Incomplete header ? 677 * Only checks for the IP header, there should be an 678 * additional check for longer headers in upper levels. 679 */ 680 681 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 682 goto out_err; 683 684 icmph = icmp_hdr(skb); 685 iph = (struct iphdr *)skb->data; 686 687 if (iph->ihl < 5) /* Mangled header, drop. */ 688 goto out_err; 689 690 if (icmph->type == ICMP_DEST_UNREACH) { 691 switch (icmph->code & 15) { 692 case ICMP_NET_UNREACH: 693 case ICMP_HOST_UNREACH: 694 case ICMP_PROT_UNREACH: 695 case ICMP_PORT_UNREACH: 696 break; 697 case ICMP_FRAG_NEEDED: 698 if (ipv4_config.no_pmtu_disc) { 699 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: " 700 "fragmentation needed " 701 "and DF set.\n", 702 NIPQUAD(iph->daddr)); 703 } else { 704 info = ip_rt_frag_needed(net, iph, 705 ntohs(icmph->un.frag.mtu)); 706 if (!info) 707 goto out; 708 } 709 break; 710 case ICMP_SR_FAILED: 711 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: Source " 712 "Route Failed.\n", 713 NIPQUAD(iph->daddr)); 714 break; 715 default: 716 break; 717 } 718 if (icmph->code > NR_ICMP_UNREACH) 719 goto out; 720 } else if (icmph->type == ICMP_PARAMETERPROB) 721 info = ntohl(icmph->un.gateway) >> 24; 722 723 /* 724 * Throw it at our lower layers 725 * 726 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 727 * header. 728 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 729 * transport layer. 730 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 731 * transport layer. 732 */ 733 734 /* 735 * Check the other end isnt violating RFC 1122. Some routers send 736 * bogus responses to broadcast frames. If you see this message 737 * first check your netmask matches at both ends, if it does then 738 * get the other vendor to fix their kit. 739 */ 740 741 if (!sysctl_icmp_ignore_bogus_error_responses && 742 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 743 if (net_ratelimit()) 744 printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP " 745 "type %u, code %u " 746 "error to a broadcast: %u.%u.%u.%u on %s\n", 747 NIPQUAD(ip_hdr(skb)->saddr), 748 icmph->type, icmph->code, 749 NIPQUAD(iph->daddr), 750 skb->dev->name); 751 goto out; 752 } 753 754 /* Checkin full IP header plus 8 bytes of protocol to 755 * avoid additional coding at protocol handlers. 756 */ 757 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 758 goto out; 759 760 iph = (struct iphdr *)skb->data; 761 protocol = iph->protocol; 762 763 /* 764 * Deliver ICMP message to raw sockets. Pretty useless feature? 765 */ 766 raw_icmp_error(skb, protocol, info); 767 768 hash = protocol & (MAX_INET_PROTOS - 1); 769 rcu_read_lock(); 770 ipprot = rcu_dereference(inet_protos[hash]); 771 if (ipprot && ipprot->err_handler) 772 ipprot->err_handler(skb, info); 773 rcu_read_unlock(); 774 775 out: 776 return; 777 out_err: 778 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 779 goto out; 780 } 781 782 783 /* 784 * Handle ICMP_REDIRECT. 785 */ 786 787 static void icmp_redirect(struct sk_buff *skb) 788 { 789 struct iphdr *iph; 790 791 if (skb->len < sizeof(struct iphdr)) 792 goto out_err; 793 794 /* 795 * Get the copied header of the packet that caused the redirect 796 */ 797 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 798 goto out; 799 800 iph = (struct iphdr *)skb->data; 801 802 switch (icmp_hdr(skb)->code & 7) { 803 case ICMP_REDIR_NET: 804 case ICMP_REDIR_NETTOS: 805 /* 806 * As per RFC recommendations now handle it as a host redirect. 807 */ 808 case ICMP_REDIR_HOST: 809 case ICMP_REDIR_HOSTTOS: 810 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 811 icmp_hdr(skb)->un.gateway, 812 iph->saddr, skb->dev); 813 break; 814 } 815 out: 816 return; 817 out_err: 818 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 819 goto out; 820 } 821 822 /* 823 * Handle ICMP_ECHO ("ping") requests. 824 * 825 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 826 * requests. 827 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 828 * included in the reply. 829 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 830 * echo requests, MUST have default=NOT. 831 * See also WRT handling of options once they are done and working. 832 */ 833 834 static void icmp_echo(struct sk_buff *skb) 835 { 836 if (!sysctl_icmp_echo_ignore_all) { 837 struct icmp_bxm icmp_param; 838 839 icmp_param.data.icmph = *icmp_hdr(skb); 840 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 841 icmp_param.skb = skb; 842 icmp_param.offset = 0; 843 icmp_param.data_len = skb->len; 844 icmp_param.head_len = sizeof(struct icmphdr); 845 icmp_reply(&icmp_param, skb); 846 } 847 } 848 849 /* 850 * Handle ICMP Timestamp requests. 851 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 852 * SHOULD be in the kernel for minimum random latency. 853 * MUST be accurate to a few minutes. 854 * MUST be updated at least at 15Hz. 855 */ 856 static void icmp_timestamp(struct sk_buff *skb) 857 { 858 struct timeval tv; 859 struct icmp_bxm icmp_param; 860 /* 861 * Too short. 862 */ 863 if (skb->len < 4) 864 goto out_err; 865 866 /* 867 * Fill in the current time as ms since midnight UT: 868 */ 869 do_gettimeofday(&tv); 870 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * 1000 + 871 tv.tv_usec / 1000); 872 icmp_param.data.times[2] = icmp_param.data.times[1]; 873 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 874 BUG(); 875 icmp_param.data.icmph = *icmp_hdr(skb); 876 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 877 icmp_param.data.icmph.code = 0; 878 icmp_param.skb = skb; 879 icmp_param.offset = 0; 880 icmp_param.data_len = 0; 881 icmp_param.head_len = sizeof(struct icmphdr) + 12; 882 icmp_reply(&icmp_param, skb); 883 out: 884 return; 885 out_err: 886 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 887 goto out; 888 } 889 890 891 /* 892 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 893 * 894 * RFC1122 (3.2.2.9). A host MUST only send replies to 895 * ADDRESS_MASK requests if it's been configured as an address mask 896 * agent. Receiving a request doesn't constitute implicit permission to 897 * act as one. Of course, implementing this correctly requires (SHOULD) 898 * a way to turn the functionality on and off. Another one for sysctl(), 899 * I guess. -- MS 900 * 901 * RFC1812 (4.3.3.9). A router MUST implement it. 902 * A router SHOULD have switch turning it on/off. 903 * This switch MUST be ON by default. 904 * 905 * Gratuitous replies, zero-source replies are not implemented, 906 * that complies with RFC. DO NOT implement them!!! All the idea 907 * of broadcast addrmask replies as specified in RFC950 is broken. 908 * The problem is that it is not uncommon to have several prefixes 909 * on one physical interface. Moreover, addrmask agent can even be 910 * not aware of existing another prefixes. 911 * If source is zero, addrmask agent cannot choose correct prefix. 912 * Gratuitous mask announcements suffer from the same problem. 913 * RFC1812 explains it, but still allows to use ADDRMASK, 914 * that is pretty silly. --ANK 915 * 916 * All these rules are so bizarre, that I removed kernel addrmask 917 * support at all. It is wrong, it is obsolete, nobody uses it in 918 * any case. --ANK 919 * 920 * Furthermore you can do it with a usermode address agent program 921 * anyway... 922 */ 923 924 static void icmp_address(struct sk_buff *skb) 925 { 926 #if 0 927 if (net_ratelimit()) 928 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 929 #endif 930 } 931 932 /* 933 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 934 * loudly if an inconsistency is found. 935 */ 936 937 static void icmp_address_reply(struct sk_buff *skb) 938 { 939 struct rtable *rt = (struct rtable *)skb->dst; 940 struct net_device *dev = skb->dev; 941 struct in_device *in_dev; 942 struct in_ifaddr *ifa; 943 944 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 945 goto out; 946 947 in_dev = in_dev_get(dev); 948 if (!in_dev) 949 goto out; 950 rcu_read_lock(); 951 if (in_dev->ifa_list && 952 IN_DEV_LOG_MARTIANS(in_dev) && 953 IN_DEV_FORWARD(in_dev)) { 954 __be32 _mask, *mp; 955 956 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 957 BUG_ON(mp == NULL); 958 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 959 if (*mp == ifa->ifa_mask && 960 inet_ifa_match(rt->rt_src, ifa)) 961 break; 962 } 963 if (!ifa && net_ratelimit()) { 964 printk(KERN_INFO "Wrong address mask %u.%u.%u.%u from " 965 "%s/%u.%u.%u.%u\n", 966 NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src)); 967 } 968 } 969 rcu_read_unlock(); 970 in_dev_put(in_dev); 971 out:; 972 } 973 974 static void icmp_discard(struct sk_buff *skb) 975 { 976 } 977 978 /* 979 * Deal with incoming ICMP packets. 980 */ 981 int icmp_rcv(struct sk_buff *skb) 982 { 983 struct icmphdr *icmph; 984 struct rtable *rt = (struct rtable *)skb->dst; 985 986 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 987 int nh; 988 989 if (!(skb->sp && skb->sp->xvec[skb->sp->len - 1]->props.flags & 990 XFRM_STATE_ICMP)) 991 goto drop; 992 993 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 994 goto drop; 995 996 nh = skb_network_offset(skb); 997 skb_set_network_header(skb, sizeof(*icmph)); 998 999 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 1000 goto drop; 1001 1002 skb_set_network_header(skb, nh); 1003 } 1004 1005 ICMP_INC_STATS_BH(ICMP_MIB_INMSGS); 1006 1007 switch (skb->ip_summed) { 1008 case CHECKSUM_COMPLETE: 1009 if (!csum_fold(skb->csum)) 1010 break; 1011 /* fall through */ 1012 case CHECKSUM_NONE: 1013 skb->csum = 0; 1014 if (__skb_checksum_complete(skb)) 1015 goto error; 1016 } 1017 1018 if (!pskb_pull(skb, sizeof(*icmph))) 1019 goto error; 1020 1021 icmph = icmp_hdr(skb); 1022 1023 ICMPMSGIN_INC_STATS_BH(icmph->type); 1024 /* 1025 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1026 * 1027 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1028 * discarded. 1029 */ 1030 if (icmph->type > NR_ICMP_TYPES) 1031 goto error; 1032 1033 1034 /* 1035 * Parse the ICMP message 1036 */ 1037 1038 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1039 /* 1040 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1041 * silently ignored (we let user decide with a sysctl). 1042 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1043 * discarded if to broadcast/multicast. 1044 */ 1045 if ((icmph->type == ICMP_ECHO || 1046 icmph->type == ICMP_TIMESTAMP) && 1047 sysctl_icmp_echo_ignore_broadcasts) { 1048 goto error; 1049 } 1050 if (icmph->type != ICMP_ECHO && 1051 icmph->type != ICMP_TIMESTAMP && 1052 icmph->type != ICMP_ADDRESS && 1053 icmph->type != ICMP_ADDRESSREPLY) { 1054 goto error; 1055 } 1056 } 1057 1058 icmp_pointers[icmph->type].handler(skb); 1059 1060 drop: 1061 kfree_skb(skb); 1062 return 0; 1063 error: 1064 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 1065 goto drop; 1066 } 1067 1068 /* 1069 * This table is the definition of how we handle ICMP. 1070 */ 1071 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1072 [ICMP_ECHOREPLY] = { 1073 .handler = icmp_discard, 1074 }, 1075 [1] = { 1076 .handler = icmp_discard, 1077 .error = 1, 1078 }, 1079 [2] = { 1080 .handler = icmp_discard, 1081 .error = 1, 1082 }, 1083 [ICMP_DEST_UNREACH] = { 1084 .handler = icmp_unreach, 1085 .error = 1, 1086 }, 1087 [ICMP_SOURCE_QUENCH] = { 1088 .handler = icmp_unreach, 1089 .error = 1, 1090 }, 1091 [ICMP_REDIRECT] = { 1092 .handler = icmp_redirect, 1093 .error = 1, 1094 }, 1095 [6] = { 1096 .handler = icmp_discard, 1097 .error = 1, 1098 }, 1099 [7] = { 1100 .handler = icmp_discard, 1101 .error = 1, 1102 }, 1103 [ICMP_ECHO] = { 1104 .handler = icmp_echo, 1105 }, 1106 [9] = { 1107 .handler = icmp_discard, 1108 .error = 1, 1109 }, 1110 [10] = { 1111 .handler = icmp_discard, 1112 .error = 1, 1113 }, 1114 [ICMP_TIME_EXCEEDED] = { 1115 .handler = icmp_unreach, 1116 .error = 1, 1117 }, 1118 [ICMP_PARAMETERPROB] = { 1119 .handler = icmp_unreach, 1120 .error = 1, 1121 }, 1122 [ICMP_TIMESTAMP] = { 1123 .handler = icmp_timestamp, 1124 }, 1125 [ICMP_TIMESTAMPREPLY] = { 1126 .handler = icmp_discard, 1127 }, 1128 [ICMP_INFO_REQUEST] = { 1129 .handler = icmp_discard, 1130 }, 1131 [ICMP_INFO_REPLY] = { 1132 .handler = icmp_discard, 1133 }, 1134 [ICMP_ADDRESS] = { 1135 .handler = icmp_address, 1136 }, 1137 [ICMP_ADDRESSREPLY] = { 1138 .handler = icmp_address_reply, 1139 }, 1140 }; 1141 1142 void __init icmp_init(struct net_proto_family *ops) 1143 { 1144 struct inet_sock *inet; 1145 int i; 1146 1147 for_each_possible_cpu(i) { 1148 int err; 1149 1150 err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP, 1151 &per_cpu(__icmp_socket, i)); 1152 1153 if (err < 0) 1154 panic("Failed to create the ICMP control socket.\n"); 1155 1156 per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC; 1157 1158 /* Enough space for 2 64K ICMP packets, including 1159 * sk_buff struct overhead. 1160 */ 1161 per_cpu(__icmp_socket, i)->sk->sk_sndbuf = 1162 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1163 1164 inet = inet_sk(per_cpu(__icmp_socket, i)->sk); 1165 inet->uc_ttl = -1; 1166 inet->pmtudisc = IP_PMTUDISC_DONT; 1167 1168 /* Unhash it so that IP input processing does not even 1169 * see it, we do not wish this socket to see incoming 1170 * packets. 1171 */ 1172 per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk); 1173 } 1174 } 1175 1176 EXPORT_SYMBOL(icmp_err_convert); 1177 EXPORT_SYMBOL(icmp_send); 1178 EXPORT_SYMBOL(icmp_statistics); 1179 EXPORT_SYMBOL(xrlim_allow); 1180