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 ipc.shtx.flags = 0; 379 if (icmp_param->replyopts.optlen) { 380 ipc.opt = &icmp_param->replyopts; 381 if (ipc.opt->srr) 382 daddr = icmp_param->replyopts.faddr; 383 } 384 { 385 struct flowi fl = { .nl_u = { .ip4_u = 386 { .daddr = daddr, 387 .saddr = rt->rt_spec_dst, 388 .tos = RT_TOS(ip_hdr(skb)->tos) } }, 389 .proto = IPPROTO_ICMP }; 390 security_skb_classify_flow(skb, &fl); 391 if (ip_route_output_key(net, &rt, &fl)) 392 goto out_unlock; 393 } 394 if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type, 395 icmp_param->data.icmph.code)) 396 icmp_push_reply(icmp_param, &ipc, &rt); 397 ip_rt_put(rt); 398 out_unlock: 399 icmp_xmit_unlock(sk); 400 } 401 402 403 /* 404 * Send an ICMP message in response to a situation 405 * 406 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 407 * MAY send more (we do). 408 * MUST NOT change this header information. 409 * MUST NOT reply to a multicast/broadcast IP address. 410 * MUST NOT reply to a multicast/broadcast MAC address. 411 * MUST reply to only the first fragment. 412 */ 413 414 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 415 { 416 struct iphdr *iph; 417 int room; 418 struct icmp_bxm icmp_param; 419 struct rtable *rt = skb_in->rtable; 420 struct ipcm_cookie ipc; 421 __be32 saddr; 422 u8 tos; 423 struct net *net; 424 struct sock *sk; 425 426 if (!rt) 427 goto out; 428 net = dev_net(rt->u.dst.dev); 429 430 /* 431 * Find the original header. It is expected to be valid, of course. 432 * Check this, icmp_send is called from the most obscure devices 433 * sometimes. 434 */ 435 iph = ip_hdr(skb_in); 436 437 if ((u8 *)iph < skb_in->head || 438 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 439 goto out; 440 441 /* 442 * No replies to physical multicast/broadcast 443 */ 444 if (skb_in->pkt_type != PACKET_HOST) 445 goto out; 446 447 /* 448 * Now check at the protocol level 449 */ 450 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 451 goto out; 452 453 /* 454 * Only reply to fragment 0. We byte re-order the constant 455 * mask for efficiency. 456 */ 457 if (iph->frag_off & htons(IP_OFFSET)) 458 goto out; 459 460 /* 461 * If we send an ICMP error to an ICMP error a mess would result.. 462 */ 463 if (icmp_pointers[type].error) { 464 /* 465 * We are an error, check if we are replying to an 466 * ICMP error 467 */ 468 if (iph->protocol == IPPROTO_ICMP) { 469 u8 _inner_type, *itp; 470 471 itp = skb_header_pointer(skb_in, 472 skb_network_header(skb_in) + 473 (iph->ihl << 2) + 474 offsetof(struct icmphdr, 475 type) - 476 skb_in->data, 477 sizeof(_inner_type), 478 &_inner_type); 479 if (itp == NULL) 480 goto out; 481 482 /* 483 * Assume any unknown ICMP type is an error. This 484 * isn't specified by the RFC, but think about it.. 485 */ 486 if (*itp > NR_ICMP_TYPES || 487 icmp_pointers[*itp].error) 488 goto out; 489 } 490 } 491 492 sk = icmp_xmit_lock(net); 493 if (sk == NULL) 494 return; 495 496 /* 497 * Construct source address and options. 498 */ 499 500 saddr = iph->daddr; 501 if (!(rt->rt_flags & RTCF_LOCAL)) { 502 struct net_device *dev = NULL; 503 504 if (rt->fl.iif && 505 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 506 dev = dev_get_by_index(net, rt->fl.iif); 507 508 if (dev) { 509 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 510 dev_put(dev); 511 } else 512 saddr = 0; 513 } 514 515 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 516 IPTOS_PREC_INTERNETCONTROL) : 517 iph->tos; 518 519 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 520 goto out_unlock; 521 522 523 /* 524 * Prepare data for ICMP header. 525 */ 526 527 icmp_param.data.icmph.type = type; 528 icmp_param.data.icmph.code = code; 529 icmp_param.data.icmph.un.gateway = info; 530 icmp_param.data.icmph.checksum = 0; 531 icmp_param.skb = skb_in; 532 icmp_param.offset = skb_network_offset(skb_in); 533 inet_sk(sk)->tos = tos; 534 ipc.addr = iph->saddr; 535 ipc.opt = &icmp_param.replyopts; 536 ipc.shtx.flags = 0; 537 538 { 539 struct flowi fl = { 540 .nl_u = { 541 .ip4_u = { 542 .daddr = icmp_param.replyopts.srr ? 543 icmp_param.replyopts.faddr : 544 iph->saddr, 545 .saddr = saddr, 546 .tos = RT_TOS(tos) 547 } 548 }, 549 .proto = IPPROTO_ICMP, 550 .uli_u = { 551 .icmpt = { 552 .type = type, 553 .code = code 554 } 555 } 556 }; 557 int err; 558 struct rtable *rt2; 559 560 security_skb_classify_flow(skb_in, &fl); 561 if (__ip_route_output_key(net, &rt, &fl)) 562 goto out_unlock; 563 564 /* No need to clone since we're just using its address. */ 565 rt2 = rt; 566 567 err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0); 568 switch (err) { 569 case 0: 570 if (rt != rt2) 571 goto route_done; 572 break; 573 case -EPERM: 574 rt = NULL; 575 break; 576 default: 577 goto out_unlock; 578 } 579 580 if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET)) 581 goto relookup_failed; 582 583 if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) 584 err = __ip_route_output_key(net, &rt2, &fl); 585 else { 586 struct flowi fl2 = {}; 587 struct dst_entry *odst; 588 589 fl2.fl4_dst = fl.fl4_src; 590 if (ip_route_output_key(net, &rt2, &fl2)) 591 goto relookup_failed; 592 593 /* Ugh! */ 594 odst = skb_in->dst; 595 err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src, 596 RT_TOS(tos), rt2->u.dst.dev); 597 598 dst_release(&rt2->u.dst); 599 rt2 = skb_in->rtable; 600 skb_in->dst = odst; 601 } 602 603 if (err) 604 goto relookup_failed; 605 606 err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL, 607 XFRM_LOOKUP_ICMP); 608 switch (err) { 609 case 0: 610 dst_release(&rt->u.dst); 611 rt = rt2; 612 break; 613 case -EPERM: 614 goto ende; 615 default: 616 relookup_failed: 617 if (!rt) 618 goto out_unlock; 619 break; 620 } 621 } 622 623 route_done: 624 if (!icmpv4_xrlim_allow(net, rt, type, code)) 625 goto ende; 626 627 /* RFC says return as much as we can without exceeding 576 bytes. */ 628 629 room = dst_mtu(&rt->u.dst); 630 if (room > 576) 631 room = 576; 632 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 633 room -= sizeof(struct icmphdr); 634 635 icmp_param.data_len = skb_in->len - icmp_param.offset; 636 if (icmp_param.data_len > room) 637 icmp_param.data_len = room; 638 icmp_param.head_len = sizeof(struct icmphdr); 639 640 icmp_push_reply(&icmp_param, &ipc, &rt); 641 ende: 642 ip_rt_put(rt); 643 out_unlock: 644 icmp_xmit_unlock(sk); 645 out:; 646 } 647 648 649 /* 650 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 651 */ 652 653 static void icmp_unreach(struct sk_buff *skb) 654 { 655 struct iphdr *iph; 656 struct icmphdr *icmph; 657 int hash, protocol; 658 struct net_protocol *ipprot; 659 u32 info = 0; 660 struct net *net; 661 662 net = dev_net(skb->dst->dev); 663 664 /* 665 * Incomplete header ? 666 * Only checks for the IP header, there should be an 667 * additional check for longer headers in upper levels. 668 */ 669 670 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 671 goto out_err; 672 673 icmph = icmp_hdr(skb); 674 iph = (struct iphdr *)skb->data; 675 676 if (iph->ihl < 5) /* Mangled header, drop. */ 677 goto out_err; 678 679 if (icmph->type == ICMP_DEST_UNREACH) { 680 switch (icmph->code & 15) { 681 case ICMP_NET_UNREACH: 682 case ICMP_HOST_UNREACH: 683 case ICMP_PROT_UNREACH: 684 case ICMP_PORT_UNREACH: 685 break; 686 case ICMP_FRAG_NEEDED: 687 if (ipv4_config.no_pmtu_disc) { 688 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: fragmentation needed and DF set.\n", 689 &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: %pI4: Source Route Failed.\n", 700 &iph->daddr); 701 break; 702 default: 703 break; 704 } 705 if (icmph->code > NR_ICMP_UNREACH) 706 goto out; 707 } else if (icmph->type == ICMP_PARAMETERPROB) 708 info = ntohl(icmph->un.gateway) >> 24; 709 710 /* 711 * Throw it at our lower layers 712 * 713 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 714 * header. 715 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 716 * transport layer. 717 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 718 * transport layer. 719 */ 720 721 /* 722 * Check the other end isnt violating RFC 1122. Some routers send 723 * bogus responses to broadcast frames. If you see this message 724 * first check your netmask matches at both ends, if it does then 725 * get the other vendor to fix their kit. 726 */ 727 728 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 729 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 730 if (net_ratelimit()) 731 printk(KERN_WARNING "%pI4 sent an invalid ICMP " 732 "type %u, code %u " 733 "error to a broadcast: %pI4 on %s\n", 734 &ip_hdr(skb)->saddr, 735 icmph->type, icmph->code, 736 &iph->daddr, 737 skb->dev->name); 738 goto out; 739 } 740 741 /* Checkin full IP header plus 8 bytes of protocol to 742 * avoid additional coding at protocol handlers. 743 */ 744 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 745 goto out; 746 747 iph = (struct iphdr *)skb->data; 748 protocol = iph->protocol; 749 750 /* 751 * Deliver ICMP message to raw sockets. Pretty useless feature? 752 */ 753 raw_icmp_error(skb, protocol, info); 754 755 hash = protocol & (MAX_INET_PROTOS - 1); 756 rcu_read_lock(); 757 ipprot = rcu_dereference(inet_protos[hash]); 758 if (ipprot && ipprot->err_handler) 759 ipprot->err_handler(skb, info); 760 rcu_read_unlock(); 761 762 out: 763 return; 764 out_err: 765 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 766 goto out; 767 } 768 769 770 /* 771 * Handle ICMP_REDIRECT. 772 */ 773 774 static void icmp_redirect(struct sk_buff *skb) 775 { 776 struct iphdr *iph; 777 778 if (skb->len < sizeof(struct iphdr)) 779 goto out_err; 780 781 /* 782 * Get the copied header of the packet that caused the redirect 783 */ 784 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 785 goto out; 786 787 iph = (struct iphdr *)skb->data; 788 789 switch (icmp_hdr(skb)->code & 7) { 790 case ICMP_REDIR_NET: 791 case ICMP_REDIR_NETTOS: 792 /* 793 * As per RFC recommendations now handle it as a host redirect. 794 */ 795 case ICMP_REDIR_HOST: 796 case ICMP_REDIR_HOSTTOS: 797 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 798 icmp_hdr(skb)->un.gateway, 799 iph->saddr, skb->dev); 800 break; 801 } 802 out: 803 return; 804 out_err: 805 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 806 goto out; 807 } 808 809 /* 810 * Handle ICMP_ECHO ("ping") requests. 811 * 812 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 813 * requests. 814 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 815 * included in the reply. 816 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 817 * echo requests, MUST have default=NOT. 818 * See also WRT handling of options once they are done and working. 819 */ 820 821 static void icmp_echo(struct sk_buff *skb) 822 { 823 struct net *net; 824 825 net = dev_net(skb->dst->dev); 826 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 827 struct icmp_bxm icmp_param; 828 829 icmp_param.data.icmph = *icmp_hdr(skb); 830 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 831 icmp_param.skb = skb; 832 icmp_param.offset = 0; 833 icmp_param.data_len = skb->len; 834 icmp_param.head_len = sizeof(struct icmphdr); 835 icmp_reply(&icmp_param, skb); 836 } 837 } 838 839 /* 840 * Handle ICMP Timestamp requests. 841 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 842 * SHOULD be in the kernel for minimum random latency. 843 * MUST be accurate to a few minutes. 844 * MUST be updated at least at 15Hz. 845 */ 846 static void icmp_timestamp(struct sk_buff *skb) 847 { 848 struct timespec tv; 849 struct icmp_bxm icmp_param; 850 /* 851 * Too short. 852 */ 853 if (skb->len < 4) 854 goto out_err; 855 856 /* 857 * Fill in the current time as ms since midnight UT: 858 */ 859 getnstimeofday(&tv); 860 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 861 tv.tv_nsec / NSEC_PER_MSEC); 862 icmp_param.data.times[2] = icmp_param.data.times[1]; 863 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 864 BUG(); 865 icmp_param.data.icmph = *icmp_hdr(skb); 866 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 867 icmp_param.data.icmph.code = 0; 868 icmp_param.skb = skb; 869 icmp_param.offset = 0; 870 icmp_param.data_len = 0; 871 icmp_param.head_len = sizeof(struct icmphdr) + 12; 872 icmp_reply(&icmp_param, skb); 873 out: 874 return; 875 out_err: 876 ICMP_INC_STATS_BH(dev_net(skb->dst->dev), ICMP_MIB_INERRORS); 877 goto out; 878 } 879 880 881 /* 882 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 883 * 884 * RFC1122 (3.2.2.9). A host MUST only send replies to 885 * ADDRESS_MASK requests if it's been configured as an address mask 886 * agent. Receiving a request doesn't constitute implicit permission to 887 * act as one. Of course, implementing this correctly requires (SHOULD) 888 * a way to turn the functionality on and off. Another one for sysctl(), 889 * I guess. -- MS 890 * 891 * RFC1812 (4.3.3.9). A router MUST implement it. 892 * A router SHOULD have switch turning it on/off. 893 * This switch MUST be ON by default. 894 * 895 * Gratuitous replies, zero-source replies are not implemented, 896 * that complies with RFC. DO NOT implement them!!! All the idea 897 * of broadcast addrmask replies as specified in RFC950 is broken. 898 * The problem is that it is not uncommon to have several prefixes 899 * on one physical interface. Moreover, addrmask agent can even be 900 * not aware of existing another prefixes. 901 * If source is zero, addrmask agent cannot choose correct prefix. 902 * Gratuitous mask announcements suffer from the same problem. 903 * RFC1812 explains it, but still allows to use ADDRMASK, 904 * that is pretty silly. --ANK 905 * 906 * All these rules are so bizarre, that I removed kernel addrmask 907 * support at all. It is wrong, it is obsolete, nobody uses it in 908 * any case. --ANK 909 * 910 * Furthermore you can do it with a usermode address agent program 911 * anyway... 912 */ 913 914 static void icmp_address(struct sk_buff *skb) 915 { 916 #if 0 917 if (net_ratelimit()) 918 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 919 #endif 920 } 921 922 /* 923 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 924 * loudly if an inconsistency is found. 925 */ 926 927 static void icmp_address_reply(struct sk_buff *skb) 928 { 929 struct rtable *rt = skb->rtable; 930 struct net_device *dev = skb->dev; 931 struct in_device *in_dev; 932 struct in_ifaddr *ifa; 933 934 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 935 goto out; 936 937 in_dev = in_dev_get(dev); 938 if (!in_dev) 939 goto out; 940 rcu_read_lock(); 941 if (in_dev->ifa_list && 942 IN_DEV_LOG_MARTIANS(in_dev) && 943 IN_DEV_FORWARD(in_dev)) { 944 __be32 _mask, *mp; 945 946 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 947 BUG_ON(mp == NULL); 948 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 949 if (*mp == ifa->ifa_mask && 950 inet_ifa_match(rt->rt_src, ifa)) 951 break; 952 } 953 if (!ifa && net_ratelimit()) { 954 printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n", 955 mp, dev->name, &rt->rt_src); 956 } 957 } 958 rcu_read_unlock(); 959 in_dev_put(in_dev); 960 out:; 961 } 962 963 static void icmp_discard(struct sk_buff *skb) 964 { 965 } 966 967 /* 968 * Deal with incoming ICMP packets. 969 */ 970 int icmp_rcv(struct sk_buff *skb) 971 { 972 struct icmphdr *icmph; 973 struct rtable *rt = skb->rtable; 974 struct net *net = dev_net(rt->u.dst.dev); 975 976 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 977 struct sec_path *sp = skb_sec_path(skb); 978 int nh; 979 980 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 981 XFRM_STATE_ICMP)) 982 goto drop; 983 984 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 985 goto drop; 986 987 nh = skb_network_offset(skb); 988 skb_set_network_header(skb, sizeof(*icmph)); 989 990 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 991 goto drop; 992 993 skb_set_network_header(skb, nh); 994 } 995 996 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 997 998 switch (skb->ip_summed) { 999 case CHECKSUM_COMPLETE: 1000 if (!csum_fold(skb->csum)) 1001 break; 1002 /* fall through */ 1003 case CHECKSUM_NONE: 1004 skb->csum = 0; 1005 if (__skb_checksum_complete(skb)) 1006 goto error; 1007 } 1008 1009 if (!pskb_pull(skb, sizeof(*icmph))) 1010 goto error; 1011 1012 icmph = icmp_hdr(skb); 1013 1014 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1015 /* 1016 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1017 * 1018 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1019 * discarded. 1020 */ 1021 if (icmph->type > NR_ICMP_TYPES) 1022 goto error; 1023 1024 1025 /* 1026 * Parse the ICMP message 1027 */ 1028 1029 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1030 /* 1031 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1032 * silently ignored (we let user decide with a sysctl). 1033 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1034 * discarded if to broadcast/multicast. 1035 */ 1036 if ((icmph->type == ICMP_ECHO || 1037 icmph->type == ICMP_TIMESTAMP) && 1038 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1039 goto error; 1040 } 1041 if (icmph->type != ICMP_ECHO && 1042 icmph->type != ICMP_TIMESTAMP && 1043 icmph->type != ICMP_ADDRESS && 1044 icmph->type != ICMP_ADDRESSREPLY) { 1045 goto error; 1046 } 1047 } 1048 1049 icmp_pointers[icmph->type].handler(skb); 1050 1051 drop: 1052 kfree_skb(skb); 1053 return 0; 1054 error: 1055 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1056 goto drop; 1057 } 1058 1059 /* 1060 * This table is the definition of how we handle ICMP. 1061 */ 1062 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1063 [ICMP_ECHOREPLY] = { 1064 .handler = icmp_discard, 1065 }, 1066 [1] = { 1067 .handler = icmp_discard, 1068 .error = 1, 1069 }, 1070 [2] = { 1071 .handler = icmp_discard, 1072 .error = 1, 1073 }, 1074 [ICMP_DEST_UNREACH] = { 1075 .handler = icmp_unreach, 1076 .error = 1, 1077 }, 1078 [ICMP_SOURCE_QUENCH] = { 1079 .handler = icmp_unreach, 1080 .error = 1, 1081 }, 1082 [ICMP_REDIRECT] = { 1083 .handler = icmp_redirect, 1084 .error = 1, 1085 }, 1086 [6] = { 1087 .handler = icmp_discard, 1088 .error = 1, 1089 }, 1090 [7] = { 1091 .handler = icmp_discard, 1092 .error = 1, 1093 }, 1094 [ICMP_ECHO] = { 1095 .handler = icmp_echo, 1096 }, 1097 [9] = { 1098 .handler = icmp_discard, 1099 .error = 1, 1100 }, 1101 [10] = { 1102 .handler = icmp_discard, 1103 .error = 1, 1104 }, 1105 [ICMP_TIME_EXCEEDED] = { 1106 .handler = icmp_unreach, 1107 .error = 1, 1108 }, 1109 [ICMP_PARAMETERPROB] = { 1110 .handler = icmp_unreach, 1111 .error = 1, 1112 }, 1113 [ICMP_TIMESTAMP] = { 1114 .handler = icmp_timestamp, 1115 }, 1116 [ICMP_TIMESTAMPREPLY] = { 1117 .handler = icmp_discard, 1118 }, 1119 [ICMP_INFO_REQUEST] = { 1120 .handler = icmp_discard, 1121 }, 1122 [ICMP_INFO_REPLY] = { 1123 .handler = icmp_discard, 1124 }, 1125 [ICMP_ADDRESS] = { 1126 .handler = icmp_address, 1127 }, 1128 [ICMP_ADDRESSREPLY] = { 1129 .handler = icmp_address_reply, 1130 }, 1131 }; 1132 1133 static void __net_exit icmp_sk_exit(struct net *net) 1134 { 1135 int i; 1136 1137 for_each_possible_cpu(i) 1138 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1139 kfree(net->ipv4.icmp_sk); 1140 net->ipv4.icmp_sk = NULL; 1141 } 1142 1143 static int __net_init icmp_sk_init(struct net *net) 1144 { 1145 int i, err; 1146 1147 net->ipv4.icmp_sk = 1148 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1149 if (net->ipv4.icmp_sk == NULL) 1150 return -ENOMEM; 1151 1152 for_each_possible_cpu(i) { 1153 struct sock *sk; 1154 1155 err = inet_ctl_sock_create(&sk, PF_INET, 1156 SOCK_RAW, IPPROTO_ICMP, net); 1157 if (err < 0) 1158 goto fail; 1159 1160 net->ipv4.icmp_sk[i] = sk; 1161 1162 /* Enough space for 2 64K ICMP packets, including 1163 * sk_buff struct overhead. 1164 */ 1165 sk->sk_sndbuf = 1166 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1167 1168 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1169 } 1170 1171 /* Control parameters for ECHO replies. */ 1172 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1173 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1174 1175 /* Control parameter - ignore bogus broadcast responses? */ 1176 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1177 1178 /* 1179 * Configurable global rate limit. 1180 * 1181 * ratelimit defines tokens/packet consumed for dst->rate_token 1182 * bucket ratemask defines which icmp types are ratelimited by 1183 * setting it's bit position. 1184 * 1185 * default: 1186 * dest unreachable (3), source quench (4), 1187 * time exceeded (11), parameter problem (12) 1188 */ 1189 1190 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1191 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1192 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1193 1194 return 0; 1195 1196 fail: 1197 for_each_possible_cpu(i) 1198 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1199 kfree(net->ipv4.icmp_sk); 1200 return err; 1201 } 1202 1203 static struct pernet_operations __net_initdata icmp_sk_ops = { 1204 .init = icmp_sk_init, 1205 .exit = icmp_sk_exit, 1206 }; 1207 1208 int __init icmp_init(void) 1209 { 1210 return register_pernet_subsys(&icmp_sk_ops); 1211 } 1212 1213 EXPORT_SYMBOL(icmp_err_convert); 1214 EXPORT_SYMBOL(icmp_send); 1215 EXPORT_SYMBOL(xrlim_allow); 1216