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