1 /* 2 * NET3: Implementation of the ICMP protocol layer. 3 * 4 * Alan Cox, <alan@lxorguk.ukuu.org.uk> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 * Some of the function names and the icmp unreach table for this 12 * module were derived from [icmp.c 1.0.11 06/02/93] by 13 * Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting. 14 * Other than that this module is a complete rewrite. 15 * 16 * Fixes: 17 * Clemens Fruhwirth : introduce global icmp rate limiting 18 * with icmp type masking ability instead 19 * of broken per type icmp timeouts. 20 * Mike Shaver : RFC1122 checks. 21 * Alan Cox : Multicast ping reply as self. 22 * Alan Cox : Fix atomicity lockup in ip_build_xmit 23 * call. 24 * Alan Cox : Added 216,128 byte paths to the MTU 25 * code. 26 * Martin Mares : RFC1812 checks. 27 * Martin Mares : Can be configured to follow redirects 28 * if acting as a router _without_ a 29 * routing protocol (RFC 1812). 30 * Martin Mares : Echo requests may be configured to 31 * be ignored (RFC 1812). 32 * Martin Mares : Limitation of ICMP error message 33 * transmit rate (RFC 1812). 34 * Martin Mares : TOS and Precedence set correctly 35 * (RFC 1812). 36 * Martin Mares : Now copying as much data from the 37 * original packet as we can without 38 * exceeding 576 bytes (RFC 1812). 39 * Willy Konynenberg : Transparent proxying support. 40 * Keith Owens : RFC1191 correction for 4.2BSD based 41 * path MTU bug. 42 * Thomas Quinot : ICMP Dest Unreach codes up to 15 are 43 * valid (RFC 1812). 44 * Andi Kleen : Check all packet lengths properly 45 * and moved all kfree_skb() up to 46 * icmp_rcv. 47 * Andi Kleen : Move the rate limit bookkeeping 48 * into the dest entry and use a token 49 * bucket filter (thanks to ANK). Make 50 * the rates sysctl configurable. 51 * Yu Tianli : Fixed two ugly bugs in icmp_send 52 * - IP option length was accounted wrongly 53 * - ICMP header length was not accounted 54 * at all. 55 * Tristan Greaves : Added sysctl option to ignore bogus 56 * broadcast responses from broken routers. 57 * 58 * To Fix: 59 * 60 * - Should use skb_pull() instead of all the manual checking. 61 * This would also greatly simply some upper layer error handlers. --AK 62 * 63 */ 64 65 #include <linux/module.h> 66 #include <linux/types.h> 67 #include <linux/jiffies.h> 68 #include <linux/kernel.h> 69 #include <linux/fcntl.h> 70 #include <linux/socket.h> 71 #include <linux/in.h> 72 #include <linux/inet.h> 73 #include <linux/inetdevice.h> 74 #include <linux/netdevice.h> 75 #include <linux/string.h> 76 #include <linux/netfilter_ipv4.h> 77 #include <net/snmp.h> 78 #include <net/ip.h> 79 #include <net/route.h> 80 #include <net/protocol.h> 81 #include <net/icmp.h> 82 #include <net/tcp.h> 83 #include <net/udp.h> 84 #include <net/raw.h> 85 #include <linux/skbuff.h> 86 #include <net/sock.h> 87 #include <linux/errno.h> 88 #include <linux/timer.h> 89 #include <linux/init.h> 90 #include <asm/system.h> 91 #include <asm/uaccess.h> 92 #include <net/checksum.h> 93 #include <net/xfrm.h> 94 #include <net/inet_common.h> 95 96 /* 97 * Build xmit assembly blocks 98 */ 99 100 struct icmp_bxm { 101 struct sk_buff *skb; 102 int offset; 103 int data_len; 104 105 struct { 106 struct icmphdr icmph; 107 __be32 times[3]; 108 } data; 109 int head_len; 110 struct ip_options replyopts; 111 unsigned char optbuf[40]; 112 }; 113 114 /* An array of errno for error messages from dest unreach. */ 115 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 116 117 struct icmp_err icmp_err_convert[] = { 118 { 119 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 120 .fatal = 0, 121 }, 122 { 123 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 124 .fatal = 0, 125 }, 126 { 127 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 128 .fatal = 1, 129 }, 130 { 131 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 132 .fatal = 1, 133 }, 134 { 135 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 136 .fatal = 0, 137 }, 138 { 139 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 140 .fatal = 0, 141 }, 142 { 143 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 144 .fatal = 1, 145 }, 146 { 147 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 148 .fatal = 1, 149 }, 150 { 151 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 152 .fatal = 1, 153 }, 154 { 155 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 156 .fatal = 1, 157 }, 158 { 159 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 160 .fatal = 1, 161 }, 162 { 163 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 164 .fatal = 0, 165 }, 166 { 167 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 168 .fatal = 0, 169 }, 170 { 171 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 172 .fatal = 1, 173 }, 174 { 175 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 176 .fatal = 1, 177 }, 178 { 179 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 180 .fatal = 1, 181 }, 182 }; 183 184 /* 185 * ICMP control array. This specifies what to do with each ICMP. 186 */ 187 188 struct icmp_control { 189 void (*handler)(struct sk_buff *skb); 190 short error; /* This ICMP is classed as an error message */ 191 }; 192 193 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 194 195 /* 196 * The ICMP socket(s). This is the most convenient way to flow control 197 * our ICMP output as well as maintain a clean interface throughout 198 * all layers. All Socketless IP sends will soon be gone. 199 * 200 * On SMP we have one ICMP socket per-cpu. 201 */ 202 static struct sock *icmp_sk(struct net *net) 203 { 204 return net->ipv4.icmp_sk[smp_processor_id()]; 205 } 206 207 static inline struct sock *icmp_xmit_lock(struct net *net) 208 { 209 struct sock *sk; 210 211 local_bh_disable(); 212 213 sk = icmp_sk(net); 214 215 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 216 /* This can happen if the output path signals a 217 * dst_link_failure() for an outgoing ICMP packet. 218 */ 219 local_bh_enable(); 220 return NULL; 221 } 222 return sk; 223 } 224 225 static inline void icmp_xmit_unlock(struct sock *sk) 226 { 227 spin_unlock_bh(&sk->sk_lock.slock); 228 } 229 230 /* 231 * Send an ICMP frame. 232 */ 233 234 /* 235 * Check transmit rate limitation for given message. 236 * The rate information is held in the destination cache now. 237 * This function is generic and could be used for other purposes 238 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov. 239 * 240 * Note that the same dst_entry fields are modified by functions in 241 * route.c too, but these work for packet destinations while xrlim_allow 242 * works for icmp destinations. This means the rate limiting information 243 * for one "ip object" is shared - and these ICMPs are twice limited: 244 * by source and by destination. 245 * 246 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate 247 * SHOULD allow setting of rate limits 248 * 249 * Shared between ICMPv4 and ICMPv6. 250 */ 251 #define XRLIM_BURST_FACTOR 6 252 int xrlim_allow(struct dst_entry *dst, int timeout) 253 { 254 unsigned long now, token = dst->rate_tokens; 255 int rc = 0; 256 257 now = jiffies; 258 token += now - dst->rate_last; 259 dst->rate_last = now; 260 if (token > XRLIM_BURST_FACTOR * timeout) 261 token = XRLIM_BURST_FACTOR * timeout; 262 if (token >= timeout) { 263 token -= timeout; 264 rc = 1; 265 } 266 dst->rate_tokens = token; 267 return rc; 268 } 269 270 static inline int icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 271 int type, int code) 272 { 273 struct dst_entry *dst = &rt->u.dst; 274 int rc = 1; 275 276 if (type > NR_ICMP_TYPES) 277 goto out; 278 279 /* Don't limit PMTU discovery. */ 280 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 281 goto out; 282 283 /* No rate limit on loopback */ 284 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 285 goto out; 286 287 /* Limit if icmp type is enabled in ratemask. */ 288 if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) 289 rc = xrlim_allow(dst, net->ipv4.sysctl_icmp_ratelimit); 290 out: 291 return rc; 292 } 293 294 /* 295 * Maintain the counters used in the SNMP statistics for outgoing ICMP 296 */ 297 void icmp_out_count(struct net *net, unsigned char type) 298 { 299 ICMPMSGOUT_INC_STATS(net, type); 300 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 301 } 302 303 /* 304 * Checksum each fragment, and on the first include the headers and final 305 * checksum. 306 */ 307 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 308 struct sk_buff *skb) 309 { 310 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 311 __wsum csum; 312 313 csum = skb_copy_and_csum_bits(icmp_param->skb, 314 icmp_param->offset + offset, 315 to, len, 0); 316 317 skb->csum = csum_block_add(skb->csum, csum, odd); 318 if (icmp_pointers[icmp_param->data.icmph.type].error) 319 nf_ct_attach(skb, icmp_param->skb); 320 return 0; 321 } 322 323 static void icmp_push_reply(struct icmp_bxm *icmp_param, 324 struct ipcm_cookie *ipc, struct rtable *rt) 325 { 326 struct sock *sk; 327 struct sk_buff *skb; 328 329 sk = icmp_sk(dev_net(rt->u.dst.dev)); 330 if (ip_append_data(sk, icmp_glue_bits, icmp_param, 331 icmp_param->data_len+icmp_param->head_len, 332 icmp_param->head_len, 333 ipc, rt, MSG_DONTWAIT) < 0) 334 ip_flush_pending_frames(sk); 335 else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 336 struct icmphdr *icmph = icmp_hdr(skb); 337 __wsum csum = 0; 338 struct sk_buff *skb1; 339 340 skb_queue_walk(&sk->sk_write_queue, skb1) { 341 csum = csum_add(csum, skb1->csum); 342 } 343 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 344 (char *)icmph, 345 icmp_param->head_len, csum); 346 icmph->checksum = csum_fold(csum); 347 skb->ip_summed = CHECKSUM_NONE; 348 ip_push_pending_frames(sk); 349 } 350 } 351 352 /* 353 * Driving logic for building and sending ICMP messages. 354 */ 355 356 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 357 { 358 struct ipcm_cookie ipc; 359 struct rtable *rt = skb->rtable; 360 struct net *net = dev_net(rt->u.dst.dev); 361 struct sock *sk; 362 struct inet_sock *inet; 363 __be32 daddr; 364 365 if (ip_options_echo(&icmp_param->replyopts, skb)) 366 return; 367 368 sk = icmp_xmit_lock(net); 369 if (sk == NULL) 370 return; 371 inet = inet_sk(sk); 372 373 icmp_param->data.icmph.checksum = 0; 374 375 inet->tos = ip_hdr(skb)->tos; 376 daddr = ipc.addr = rt->rt_src; 377 ipc.opt = NULL; 378 if (icmp_param->replyopts.optlen) { 379 ipc.opt = &icmp_param->replyopts; 380 if (ipc.opt->srr) 381 daddr = icmp_param->replyopts.faddr; 382 } 383 { 384 struct flowi fl = { .nl_u = { .ip4_u = 385 { .daddr = daddr, 386 .saddr = rt->rt_spec_dst, 387 .tos = RT_TOS(ip_hdr(skb)->tos) } }, 388 .proto = IPPROTO_ICMP }; 389 security_skb_classify_flow(skb, &fl); 390 if (ip_route_output_key(net, &rt, &fl)) 391 goto out_unlock; 392 } 393 if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type, 394 icmp_param->data.icmph.code)) 395 icmp_push_reply(icmp_param, &ipc, rt); 396 ip_rt_put(rt); 397 out_unlock: 398 icmp_xmit_unlock(sk); 399 } 400 401 402 /* 403 * Send an ICMP message in response to a situation 404 * 405 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 406 * MAY send more (we do). 407 * MUST NOT change this header information. 408 * MUST NOT reply to a multicast/broadcast IP address. 409 * MUST NOT reply to a multicast/broadcast MAC address. 410 * MUST reply to only the first fragment. 411 */ 412 413 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 414 { 415 struct iphdr *iph; 416 int room; 417 struct icmp_bxm icmp_param; 418 struct rtable *rt = skb_in->rtable; 419 struct ipcm_cookie ipc; 420 __be32 saddr; 421 u8 tos; 422 struct net *net; 423 struct sock *sk; 424 425 if (!rt) 426 goto out; 427 net = dev_net(rt->u.dst.dev); 428 429 /* 430 * Find the original header. It is expected to be valid, of course. 431 * Check this, icmp_send is called from the most obscure devices 432 * sometimes. 433 */ 434 iph = ip_hdr(skb_in); 435 436 if ((u8 *)iph < skb_in->head || 437 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 438 goto out; 439 440 /* 441 * No replies to physical multicast/broadcast 442 */ 443 if (skb_in->pkt_type != PACKET_HOST) 444 goto out; 445 446 /* 447 * Now check at the protocol level 448 */ 449 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 450 goto out; 451 452 /* 453 * Only reply to fragment 0. We byte re-order the constant 454 * mask for efficiency. 455 */ 456 if (iph->frag_off & htons(IP_OFFSET)) 457 goto out; 458 459 /* 460 * If we send an ICMP error to an ICMP error a mess would result.. 461 */ 462 if (icmp_pointers[type].error) { 463 /* 464 * We are an error, check if we are replying to an 465 * ICMP error 466 */ 467 if (iph->protocol == IPPROTO_ICMP) { 468 u8 _inner_type, *itp; 469 470 itp = skb_header_pointer(skb_in, 471 skb_network_header(skb_in) + 472 (iph->ihl << 2) + 473 offsetof(struct icmphdr, 474 type) - 475 skb_in->data, 476 sizeof(_inner_type), 477 &_inner_type); 478 if (itp == NULL) 479 goto out; 480 481 /* 482 * Assume any unknown ICMP type is an error. This 483 * isn't specified by the RFC, but think about it.. 484 */ 485 if (*itp > NR_ICMP_TYPES || 486 icmp_pointers[*itp].error) 487 goto out; 488 } 489 } 490 491 sk = icmp_xmit_lock(net); 492 if (sk == NULL) 493 return; 494 495 /* 496 * Construct source address and options. 497 */ 498 499 saddr = iph->daddr; 500 if (!(rt->rt_flags & RTCF_LOCAL)) { 501 struct net_device *dev = NULL; 502 503 if (rt->fl.iif && 504 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 505 dev = dev_get_by_index(net, rt->fl.iif); 506 507 if (dev) { 508 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 509 dev_put(dev); 510 } else 511 saddr = 0; 512 } 513 514 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 515 IPTOS_PREC_INTERNETCONTROL) : 516 iph->tos; 517 518 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 519 goto out_unlock; 520 521 522 /* 523 * Prepare data for ICMP header. 524 */ 525 526 icmp_param.data.icmph.type = type; 527 icmp_param.data.icmph.code = code; 528 icmp_param.data.icmph.un.gateway = info; 529 icmp_param.data.icmph.checksum = 0; 530 icmp_param.skb = skb_in; 531 icmp_param.offset = skb_network_offset(skb_in); 532 inet_sk(sk)->tos = tos; 533 ipc.addr = iph->saddr; 534 ipc.opt = &icmp_param.replyopts; 535 536 { 537 struct flowi fl = { 538 .nl_u = { 539 .ip4_u = { 540 .daddr = icmp_param.replyopts.srr ? 541 icmp_param.replyopts.faddr : 542 iph->saddr, 543 .saddr = saddr, 544 .tos = RT_TOS(tos) 545 } 546 }, 547 .proto = IPPROTO_ICMP, 548 .uli_u = { 549 .icmpt = { 550 .type = type, 551 .code = code 552 } 553 } 554 }; 555 int err; 556 struct rtable *rt2; 557 558 security_skb_classify_flow(skb_in, &fl); 559 if (__ip_route_output_key(net, &rt, &fl)) 560 goto out_unlock; 561 562 /* No need to clone since we're just using its address. */ 563 rt2 = rt; 564 565 err = xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0); 566 switch (err) { 567 case 0: 568 if (rt != rt2) 569 goto route_done; 570 break; 571 case -EPERM: 572 rt = NULL; 573 break; 574 default: 575 goto out_unlock; 576 } 577 578 if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET)) 579 goto relookup_failed; 580 581 if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) 582 err = __ip_route_output_key(net, &rt2, &fl); 583 else { 584 struct flowi fl2 = {}; 585 struct dst_entry *odst; 586 587 fl2.fl4_dst = fl.fl4_src; 588 if (ip_route_output_key(net, &rt2, &fl2)) 589 goto relookup_failed; 590 591 /* Ugh! */ 592 odst = skb_in->dst; 593 err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src, 594 RT_TOS(tos), rt2->u.dst.dev); 595 596 dst_release(&rt2->u.dst); 597 rt2 = skb_in->rtable; 598 skb_in->dst = odst; 599 } 600 601 if (err) 602 goto relookup_failed; 603 604 err = xfrm_lookup((struct dst_entry **)&rt2, &fl, NULL, 605 XFRM_LOOKUP_ICMP); 606 switch (err) { 607 case 0: 608 dst_release(&rt->u.dst); 609 rt = rt2; 610 break; 611 case -EPERM: 612 goto ende; 613 default: 614 relookup_failed: 615 if (!rt) 616 goto out_unlock; 617 break; 618 } 619 } 620 621 route_done: 622 if (!icmpv4_xrlim_allow(net, rt, type, code)) 623 goto ende; 624 625 /* RFC says return as much as we can without exceeding 576 bytes. */ 626 627 room = dst_mtu(&rt->u.dst); 628 if (room > 576) 629 room = 576; 630 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 631 room -= sizeof(struct icmphdr); 632 633 icmp_param.data_len = skb_in->len - icmp_param.offset; 634 if (icmp_param.data_len > room) 635 icmp_param.data_len = room; 636 icmp_param.head_len = sizeof(struct icmphdr); 637 638 icmp_push_reply(&icmp_param, &ipc, rt); 639 ende: 640 ip_rt_put(rt); 641 out_unlock: 642 icmp_xmit_unlock(sk); 643 out:; 644 } 645 646 647 /* 648 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 649 */ 650 651 static void icmp_unreach(struct sk_buff *skb) 652 { 653 struct iphdr *iph; 654 struct icmphdr *icmph; 655 int hash, protocol; 656 struct net_protocol *ipprot; 657 u32 info = 0; 658 struct net *net; 659 660 net = dev_net(skb->dst->dev); 661 662 /* 663 * Incomplete header ? 664 * Only checks for the IP header, there should be an 665 * additional check for longer headers in upper levels. 666 */ 667 668 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 669 goto out_err; 670 671 icmph = icmp_hdr(skb); 672 iph = (struct iphdr *)skb->data; 673 674 if (iph->ihl < 5) /* Mangled header, drop. */ 675 goto out_err; 676 677 if (icmph->type == ICMP_DEST_UNREACH) { 678 switch (icmph->code & 15) { 679 case ICMP_NET_UNREACH: 680 case ICMP_HOST_UNREACH: 681 case ICMP_PROT_UNREACH: 682 case ICMP_PORT_UNREACH: 683 break; 684 case ICMP_FRAG_NEEDED: 685 if (ipv4_config.no_pmtu_disc) { 686 LIMIT_NETDEBUG(KERN_INFO "ICMP: " NIPQUAD_FMT ": " 687 "fragmentation needed " 688 "and DF set.\n", 689 NIPQUAD(iph->daddr)); 690 } else { 691 info = ip_rt_frag_needed(net, iph, 692 ntohs(icmph->un.frag.mtu), 693 skb->dev); 694 if (!info) 695 goto out; 696 } 697 break; 698 case ICMP_SR_FAILED: 699 LIMIT_NETDEBUG(KERN_INFO "ICMP: " NIPQUAD_FMT ": Source " 700 "Route Failed.\n", 701 NIPQUAD(iph->daddr)); 702 break; 703 default: 704 break; 705 } 706 if (icmph->code > NR_ICMP_UNREACH) 707 goto out; 708 } else if (icmph->type == ICMP_PARAMETERPROB) 709 info = ntohl(icmph->un.gateway) >> 24; 710 711 /* 712 * Throw it at our lower layers 713 * 714 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 715 * header. 716 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 717 * transport layer. 718 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 719 * transport layer. 720 */ 721 722 /* 723 * Check the other end isnt violating RFC 1122. Some routers send 724 * bogus responses to broadcast frames. If you see this message 725 * first check your netmask matches at both ends, if it does then 726 * get the other vendor to fix their kit. 727 */ 728 729 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 730 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 731 if (net_ratelimit()) 732 printk(KERN_WARNING NIPQUAD_FMT " sent an invalid ICMP " 733 "type %u, code %u " 734 "error to a broadcast: " NIPQUAD_FMT " on %s\n", 735 NIPQUAD(ip_hdr(skb)->saddr), 736 icmph->type, icmph->code, 737 NIPQUAD(iph->daddr), 738 skb->dev->name); 739 goto out; 740 } 741 742 /* Checkin full IP header plus 8 bytes of protocol to 743 * avoid additional coding at protocol handlers. 744 */ 745 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 746 goto out; 747 748 iph = (struct iphdr *)skb->data; 749 protocol = iph->protocol; 750 751 /* 752 * Deliver ICMP message to raw sockets. Pretty useless feature? 753 */ 754 raw_icmp_error(skb, protocol, info); 755 756 hash = protocol & (MAX_INET_PROTOS - 1); 757 rcu_read_lock(); 758 ipprot = rcu_dereference(inet_protos[hash]); 759 if (ipprot && ipprot->err_handler) 760 ipprot->err_handler(skb, info); 761 rcu_read_unlock(); 762 763 out: 764 return; 765 out_err: 766 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 767 goto out; 768 } 769 770 771 /* 772 * Handle ICMP_REDIRECT. 773 */ 774 775 static void icmp_redirect(struct sk_buff *skb) 776 { 777 struct iphdr *iph; 778 779 if (skb->len < sizeof(struct iphdr)) 780 goto out_err; 781 782 /* 783 * Get the copied header of the packet that caused the redirect 784 */ 785 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 786 goto out; 787 788 iph = (struct iphdr *)skb->data; 789 790 switch (icmp_hdr(skb)->code & 7) { 791 case ICMP_REDIR_NET: 792 case ICMP_REDIR_NETTOS: 793 /* 794 * As per RFC recommendations now handle it as a host redirect. 795 */ 796 case ICMP_REDIR_HOST: 797 case ICMP_REDIR_HOSTTOS: 798 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 799 icmp_hdr(skb)->un.gateway, 800 iph->saddr, skb->dev); 801 break; 802 } 803 out: 804 return; 805 out_err: 806 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 807 goto out; 808 } 809 810 /* 811 * Handle ICMP_ECHO ("ping") requests. 812 * 813 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 814 * requests. 815 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 816 * included in the reply. 817 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 818 * echo requests, MUST have default=NOT. 819 * See also WRT handling of options once they are done and working. 820 */ 821 822 static void icmp_echo(struct sk_buff *skb) 823 { 824 struct net *net; 825 826 net = dev_net(skb->dst->dev); 827 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 828 struct icmp_bxm icmp_param; 829 830 icmp_param.data.icmph = *icmp_hdr(skb); 831 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 832 icmp_param.skb = skb; 833 icmp_param.offset = 0; 834 icmp_param.data_len = skb->len; 835 icmp_param.head_len = sizeof(struct icmphdr); 836 icmp_reply(&icmp_param, skb); 837 } 838 } 839 840 /* 841 * Handle ICMP Timestamp requests. 842 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 843 * SHOULD be in the kernel for minimum random latency. 844 * MUST be accurate to a few minutes. 845 * MUST be updated at least at 15Hz. 846 */ 847 static void icmp_timestamp(struct sk_buff *skb) 848 { 849 struct timespec tv; 850 struct icmp_bxm icmp_param; 851 /* 852 * Too short. 853 */ 854 if (skb->len < 4) 855 goto out_err; 856 857 /* 858 * Fill in the current time as ms since midnight UT: 859 */ 860 getnstimeofday(&tv); 861 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 862 tv.tv_nsec / NSEC_PER_MSEC); 863 icmp_param.data.times[2] = icmp_param.data.times[1]; 864 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 865 BUG(); 866 icmp_param.data.icmph = *icmp_hdr(skb); 867 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 868 icmp_param.data.icmph.code = 0; 869 icmp_param.skb = skb; 870 icmp_param.offset = 0; 871 icmp_param.data_len = 0; 872 icmp_param.head_len = sizeof(struct icmphdr) + 12; 873 icmp_reply(&icmp_param, skb); 874 out: 875 return; 876 out_err: 877 ICMP_INC_STATS_BH(dev_net(skb->dst->dev), ICMP_MIB_INERRORS); 878 goto out; 879 } 880 881 882 /* 883 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 884 * 885 * RFC1122 (3.2.2.9). A host MUST only send replies to 886 * ADDRESS_MASK requests if it's been configured as an address mask 887 * agent. Receiving a request doesn't constitute implicit permission to 888 * act as one. Of course, implementing this correctly requires (SHOULD) 889 * a way to turn the functionality on and off. Another one for sysctl(), 890 * I guess. -- MS 891 * 892 * RFC1812 (4.3.3.9). A router MUST implement it. 893 * A router SHOULD have switch turning it on/off. 894 * This switch MUST be ON by default. 895 * 896 * Gratuitous replies, zero-source replies are not implemented, 897 * that complies with RFC. DO NOT implement them!!! All the idea 898 * of broadcast addrmask replies as specified in RFC950 is broken. 899 * The problem is that it is not uncommon to have several prefixes 900 * on one physical interface. Moreover, addrmask agent can even be 901 * not aware of existing another prefixes. 902 * If source is zero, addrmask agent cannot choose correct prefix. 903 * Gratuitous mask announcements suffer from the same problem. 904 * RFC1812 explains it, but still allows to use ADDRMASK, 905 * that is pretty silly. --ANK 906 * 907 * All these rules are so bizarre, that I removed kernel addrmask 908 * support at all. It is wrong, it is obsolete, nobody uses it in 909 * any case. --ANK 910 * 911 * Furthermore you can do it with a usermode address agent program 912 * anyway... 913 */ 914 915 static void icmp_address(struct sk_buff *skb) 916 { 917 #if 0 918 if (net_ratelimit()) 919 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 920 #endif 921 } 922 923 /* 924 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 925 * loudly if an inconsistency is found. 926 */ 927 928 static void icmp_address_reply(struct sk_buff *skb) 929 { 930 struct rtable *rt = skb->rtable; 931 struct net_device *dev = skb->dev; 932 struct in_device *in_dev; 933 struct in_ifaddr *ifa; 934 935 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 936 goto out; 937 938 in_dev = in_dev_get(dev); 939 if (!in_dev) 940 goto out; 941 rcu_read_lock(); 942 if (in_dev->ifa_list && 943 IN_DEV_LOG_MARTIANS(in_dev) && 944 IN_DEV_FORWARD(in_dev)) { 945 __be32 _mask, *mp; 946 947 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 948 BUG_ON(mp == NULL); 949 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 950 if (*mp == ifa->ifa_mask && 951 inet_ifa_match(rt->rt_src, ifa)) 952 break; 953 } 954 if (!ifa && net_ratelimit()) { 955 printk(KERN_INFO "Wrong address mask " NIPQUAD_FMT " from " 956 "%s/" NIPQUAD_FMT "\n", 957 NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src)); 958 } 959 } 960 rcu_read_unlock(); 961 in_dev_put(in_dev); 962 out:; 963 } 964 965 static void icmp_discard(struct sk_buff *skb) 966 { 967 } 968 969 /* 970 * Deal with incoming ICMP packets. 971 */ 972 int icmp_rcv(struct sk_buff *skb) 973 { 974 struct icmphdr *icmph; 975 struct rtable *rt = skb->rtable; 976 struct net *net = dev_net(rt->u.dst.dev); 977 978 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 979 int nh; 980 981 if (!(skb->sp && skb->sp->xvec[skb->sp->len - 1]->props.flags & 982 XFRM_STATE_ICMP)) 983 goto drop; 984 985 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 986 goto drop; 987 988 nh = skb_network_offset(skb); 989 skb_set_network_header(skb, sizeof(*icmph)); 990 991 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 992 goto drop; 993 994 skb_set_network_header(skb, nh); 995 } 996 997 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 998 999 switch (skb->ip_summed) { 1000 case CHECKSUM_COMPLETE: 1001 if (!csum_fold(skb->csum)) 1002 break; 1003 /* fall through */ 1004 case CHECKSUM_NONE: 1005 skb->csum = 0; 1006 if (__skb_checksum_complete(skb)) 1007 goto error; 1008 } 1009 1010 if (!pskb_pull(skb, sizeof(*icmph))) 1011 goto error; 1012 1013 icmph = icmp_hdr(skb); 1014 1015 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1016 /* 1017 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1018 * 1019 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1020 * discarded. 1021 */ 1022 if (icmph->type > NR_ICMP_TYPES) 1023 goto error; 1024 1025 1026 /* 1027 * Parse the ICMP message 1028 */ 1029 1030 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1031 /* 1032 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1033 * silently ignored (we let user decide with a sysctl). 1034 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1035 * discarded if to broadcast/multicast. 1036 */ 1037 if ((icmph->type == ICMP_ECHO || 1038 icmph->type == ICMP_TIMESTAMP) && 1039 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1040 goto error; 1041 } 1042 if (icmph->type != ICMP_ECHO && 1043 icmph->type != ICMP_TIMESTAMP && 1044 icmph->type != ICMP_ADDRESS && 1045 icmph->type != ICMP_ADDRESSREPLY) { 1046 goto error; 1047 } 1048 } 1049 1050 icmp_pointers[icmph->type].handler(skb); 1051 1052 drop: 1053 kfree_skb(skb); 1054 return 0; 1055 error: 1056 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1057 goto drop; 1058 } 1059 1060 /* 1061 * This table is the definition of how we handle ICMP. 1062 */ 1063 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1064 [ICMP_ECHOREPLY] = { 1065 .handler = icmp_discard, 1066 }, 1067 [1] = { 1068 .handler = icmp_discard, 1069 .error = 1, 1070 }, 1071 [2] = { 1072 .handler = icmp_discard, 1073 .error = 1, 1074 }, 1075 [ICMP_DEST_UNREACH] = { 1076 .handler = icmp_unreach, 1077 .error = 1, 1078 }, 1079 [ICMP_SOURCE_QUENCH] = { 1080 .handler = icmp_unreach, 1081 .error = 1, 1082 }, 1083 [ICMP_REDIRECT] = { 1084 .handler = icmp_redirect, 1085 .error = 1, 1086 }, 1087 [6] = { 1088 .handler = icmp_discard, 1089 .error = 1, 1090 }, 1091 [7] = { 1092 .handler = icmp_discard, 1093 .error = 1, 1094 }, 1095 [ICMP_ECHO] = { 1096 .handler = icmp_echo, 1097 }, 1098 [9] = { 1099 .handler = icmp_discard, 1100 .error = 1, 1101 }, 1102 [10] = { 1103 .handler = icmp_discard, 1104 .error = 1, 1105 }, 1106 [ICMP_TIME_EXCEEDED] = { 1107 .handler = icmp_unreach, 1108 .error = 1, 1109 }, 1110 [ICMP_PARAMETERPROB] = { 1111 .handler = icmp_unreach, 1112 .error = 1, 1113 }, 1114 [ICMP_TIMESTAMP] = { 1115 .handler = icmp_timestamp, 1116 }, 1117 [ICMP_TIMESTAMPREPLY] = { 1118 .handler = icmp_discard, 1119 }, 1120 [ICMP_INFO_REQUEST] = { 1121 .handler = icmp_discard, 1122 }, 1123 [ICMP_INFO_REPLY] = { 1124 .handler = icmp_discard, 1125 }, 1126 [ICMP_ADDRESS] = { 1127 .handler = icmp_address, 1128 }, 1129 [ICMP_ADDRESSREPLY] = { 1130 .handler = icmp_address_reply, 1131 }, 1132 }; 1133 1134 static void __net_exit icmp_sk_exit(struct net *net) 1135 { 1136 int i; 1137 1138 for_each_possible_cpu(i) 1139 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1140 kfree(net->ipv4.icmp_sk); 1141 net->ipv4.icmp_sk = NULL; 1142 } 1143 1144 static int __net_init icmp_sk_init(struct net *net) 1145 { 1146 int i, err; 1147 1148 net->ipv4.icmp_sk = 1149 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1150 if (net->ipv4.icmp_sk == NULL) 1151 return -ENOMEM; 1152 1153 for_each_possible_cpu(i) { 1154 struct sock *sk; 1155 1156 err = inet_ctl_sock_create(&sk, PF_INET, 1157 SOCK_RAW, IPPROTO_ICMP, net); 1158 if (err < 0) 1159 goto fail; 1160 1161 net->ipv4.icmp_sk[i] = sk; 1162 1163 /* Enough space for 2 64K ICMP packets, including 1164 * sk_buff struct overhead. 1165 */ 1166 sk->sk_sndbuf = 1167 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1168 1169 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1170 } 1171 1172 /* Control parameters for ECHO replies. */ 1173 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1174 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1175 1176 /* Control parameter - ignore bogus broadcast responses? */ 1177 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1178 1179 /* 1180 * Configurable global rate limit. 1181 * 1182 * ratelimit defines tokens/packet consumed for dst->rate_token 1183 * bucket ratemask defines which icmp types are ratelimited by 1184 * setting it's bit position. 1185 * 1186 * default: 1187 * dest unreachable (3), source quench (4), 1188 * time exceeded (11), parameter problem (12) 1189 */ 1190 1191 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1192 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1193 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1194 1195 return 0; 1196 1197 fail: 1198 for_each_possible_cpu(i) 1199 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1200 kfree(net->ipv4.icmp_sk); 1201 return err; 1202 } 1203 1204 static struct pernet_operations __net_initdata icmp_sk_ops = { 1205 .init = icmp_sk_init, 1206 .exit = icmp_sk_exit, 1207 }; 1208 1209 int __init icmp_init(void) 1210 { 1211 return register_pernet_device(&icmp_sk_ops); 1212 } 1213 1214 EXPORT_SYMBOL(icmp_err_convert); 1215 EXPORT_SYMBOL(icmp_send); 1216 EXPORT_SYMBOL(xrlim_allow); 1217