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(net, (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(net, (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: %pI4: fragmentation needed and DF set.\n", 687 &iph->daddr); 688 } else { 689 info = ip_rt_frag_needed(net, iph, 690 ntohs(icmph->un.frag.mtu), 691 skb->dev); 692 if (!info) 693 goto out; 694 } 695 break; 696 case ICMP_SR_FAILED: 697 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: Source Route Failed.\n", 698 &iph->daddr); 699 break; 700 default: 701 break; 702 } 703 if (icmph->code > NR_ICMP_UNREACH) 704 goto out; 705 } else if (icmph->type == ICMP_PARAMETERPROB) 706 info = ntohl(icmph->un.gateway) >> 24; 707 708 /* 709 * Throw it at our lower layers 710 * 711 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 712 * header. 713 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 714 * transport layer. 715 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 716 * transport layer. 717 */ 718 719 /* 720 * Check the other end isnt violating RFC 1122. Some routers send 721 * bogus responses to broadcast frames. If you see this message 722 * first check your netmask matches at both ends, if it does then 723 * get the other vendor to fix their kit. 724 */ 725 726 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 727 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 728 if (net_ratelimit()) 729 printk(KERN_WARNING "%pI4 sent an invalid ICMP " 730 "type %u, code %u " 731 "error to a broadcast: %pI4 on %s\n", 732 &ip_hdr(skb)->saddr, 733 icmph->type, icmph->code, 734 &iph->daddr, 735 skb->dev->name); 736 goto out; 737 } 738 739 /* Checkin full IP header plus 8 bytes of protocol to 740 * avoid additional coding at protocol handlers. 741 */ 742 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 743 goto out; 744 745 iph = (struct iphdr *)skb->data; 746 protocol = iph->protocol; 747 748 /* 749 * Deliver ICMP message to raw sockets. Pretty useless feature? 750 */ 751 raw_icmp_error(skb, protocol, info); 752 753 hash = protocol & (MAX_INET_PROTOS - 1); 754 rcu_read_lock(); 755 ipprot = rcu_dereference(inet_protos[hash]); 756 if (ipprot && ipprot->err_handler) 757 ipprot->err_handler(skb, info); 758 rcu_read_unlock(); 759 760 out: 761 return; 762 out_err: 763 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 764 goto out; 765 } 766 767 768 /* 769 * Handle ICMP_REDIRECT. 770 */ 771 772 static void icmp_redirect(struct sk_buff *skb) 773 { 774 struct iphdr *iph; 775 776 if (skb->len < sizeof(struct iphdr)) 777 goto out_err; 778 779 /* 780 * Get the copied header of the packet that caused the redirect 781 */ 782 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 783 goto out; 784 785 iph = (struct iphdr *)skb->data; 786 787 switch (icmp_hdr(skb)->code & 7) { 788 case ICMP_REDIR_NET: 789 case ICMP_REDIR_NETTOS: 790 /* 791 * As per RFC recommendations now handle it as a host redirect. 792 */ 793 case ICMP_REDIR_HOST: 794 case ICMP_REDIR_HOSTTOS: 795 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 796 icmp_hdr(skb)->un.gateway, 797 iph->saddr, skb->dev); 798 break; 799 } 800 out: 801 return; 802 out_err: 803 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 804 goto out; 805 } 806 807 /* 808 * Handle ICMP_ECHO ("ping") requests. 809 * 810 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 811 * requests. 812 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 813 * included in the reply. 814 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 815 * echo requests, MUST have default=NOT. 816 * See also WRT handling of options once they are done and working. 817 */ 818 819 static void icmp_echo(struct sk_buff *skb) 820 { 821 struct net *net; 822 823 net = dev_net(skb->dst->dev); 824 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 825 struct icmp_bxm icmp_param; 826 827 icmp_param.data.icmph = *icmp_hdr(skb); 828 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 829 icmp_param.skb = skb; 830 icmp_param.offset = 0; 831 icmp_param.data_len = skb->len; 832 icmp_param.head_len = sizeof(struct icmphdr); 833 icmp_reply(&icmp_param, skb); 834 } 835 } 836 837 /* 838 * Handle ICMP Timestamp requests. 839 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 840 * SHOULD be in the kernel for minimum random latency. 841 * MUST be accurate to a few minutes. 842 * MUST be updated at least at 15Hz. 843 */ 844 static void icmp_timestamp(struct sk_buff *skb) 845 { 846 struct timespec tv; 847 struct icmp_bxm icmp_param; 848 /* 849 * Too short. 850 */ 851 if (skb->len < 4) 852 goto out_err; 853 854 /* 855 * Fill in the current time as ms since midnight UT: 856 */ 857 getnstimeofday(&tv); 858 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 859 tv.tv_nsec / NSEC_PER_MSEC); 860 icmp_param.data.times[2] = icmp_param.data.times[1]; 861 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 862 BUG(); 863 icmp_param.data.icmph = *icmp_hdr(skb); 864 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 865 icmp_param.data.icmph.code = 0; 866 icmp_param.skb = skb; 867 icmp_param.offset = 0; 868 icmp_param.data_len = 0; 869 icmp_param.head_len = sizeof(struct icmphdr) + 12; 870 icmp_reply(&icmp_param, skb); 871 out: 872 return; 873 out_err: 874 ICMP_INC_STATS_BH(dev_net(skb->dst->dev), ICMP_MIB_INERRORS); 875 goto out; 876 } 877 878 879 /* 880 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 881 * 882 * RFC1122 (3.2.2.9). A host MUST only send replies to 883 * ADDRESS_MASK requests if it's been configured as an address mask 884 * agent. Receiving a request doesn't constitute implicit permission to 885 * act as one. Of course, implementing this correctly requires (SHOULD) 886 * a way to turn the functionality on and off. Another one for sysctl(), 887 * I guess. -- MS 888 * 889 * RFC1812 (4.3.3.9). A router MUST implement it. 890 * A router SHOULD have switch turning it on/off. 891 * This switch MUST be ON by default. 892 * 893 * Gratuitous replies, zero-source replies are not implemented, 894 * that complies with RFC. DO NOT implement them!!! All the idea 895 * of broadcast addrmask replies as specified in RFC950 is broken. 896 * The problem is that it is not uncommon to have several prefixes 897 * on one physical interface. Moreover, addrmask agent can even be 898 * not aware of existing another prefixes. 899 * If source is zero, addrmask agent cannot choose correct prefix. 900 * Gratuitous mask announcements suffer from the same problem. 901 * RFC1812 explains it, but still allows to use ADDRMASK, 902 * that is pretty silly. --ANK 903 * 904 * All these rules are so bizarre, that I removed kernel addrmask 905 * support at all. It is wrong, it is obsolete, nobody uses it in 906 * any case. --ANK 907 * 908 * Furthermore you can do it with a usermode address agent program 909 * anyway... 910 */ 911 912 static void icmp_address(struct sk_buff *skb) 913 { 914 #if 0 915 if (net_ratelimit()) 916 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 917 #endif 918 } 919 920 /* 921 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 922 * loudly if an inconsistency is found. 923 */ 924 925 static void icmp_address_reply(struct sk_buff *skb) 926 { 927 struct rtable *rt = skb->rtable; 928 struct net_device *dev = skb->dev; 929 struct in_device *in_dev; 930 struct in_ifaddr *ifa; 931 932 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 933 goto out; 934 935 in_dev = in_dev_get(dev); 936 if (!in_dev) 937 goto out; 938 rcu_read_lock(); 939 if (in_dev->ifa_list && 940 IN_DEV_LOG_MARTIANS(in_dev) && 941 IN_DEV_FORWARD(in_dev)) { 942 __be32 _mask, *mp; 943 944 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 945 BUG_ON(mp == NULL); 946 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 947 if (*mp == ifa->ifa_mask && 948 inet_ifa_match(rt->rt_src, ifa)) 949 break; 950 } 951 if (!ifa && net_ratelimit()) { 952 printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n", 953 mp, dev->name, &rt->rt_src); 954 } 955 } 956 rcu_read_unlock(); 957 in_dev_put(in_dev); 958 out:; 959 } 960 961 static void icmp_discard(struct sk_buff *skb) 962 { 963 } 964 965 /* 966 * Deal with incoming ICMP packets. 967 */ 968 int icmp_rcv(struct sk_buff *skb) 969 { 970 struct icmphdr *icmph; 971 struct rtable *rt = skb->rtable; 972 struct net *net = dev_net(rt->u.dst.dev); 973 974 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 975 struct sec_path *sp = skb_sec_path(skb); 976 int nh; 977 978 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 979 XFRM_STATE_ICMP)) 980 goto drop; 981 982 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 983 goto drop; 984 985 nh = skb_network_offset(skb); 986 skb_set_network_header(skb, sizeof(*icmph)); 987 988 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 989 goto drop; 990 991 skb_set_network_header(skb, nh); 992 } 993 994 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 995 996 switch (skb->ip_summed) { 997 case CHECKSUM_COMPLETE: 998 if (!csum_fold(skb->csum)) 999 break; 1000 /* fall through */ 1001 case CHECKSUM_NONE: 1002 skb->csum = 0; 1003 if (__skb_checksum_complete(skb)) 1004 goto error; 1005 } 1006 1007 if (!pskb_pull(skb, sizeof(*icmph))) 1008 goto error; 1009 1010 icmph = icmp_hdr(skb); 1011 1012 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1013 /* 1014 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1015 * 1016 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1017 * discarded. 1018 */ 1019 if (icmph->type > NR_ICMP_TYPES) 1020 goto error; 1021 1022 1023 /* 1024 * Parse the ICMP message 1025 */ 1026 1027 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1028 /* 1029 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1030 * silently ignored (we let user decide with a sysctl). 1031 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1032 * discarded if to broadcast/multicast. 1033 */ 1034 if ((icmph->type == ICMP_ECHO || 1035 icmph->type == ICMP_TIMESTAMP) && 1036 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1037 goto error; 1038 } 1039 if (icmph->type != ICMP_ECHO && 1040 icmph->type != ICMP_TIMESTAMP && 1041 icmph->type != ICMP_ADDRESS && 1042 icmph->type != ICMP_ADDRESSREPLY) { 1043 goto error; 1044 } 1045 } 1046 1047 icmp_pointers[icmph->type].handler(skb); 1048 1049 drop: 1050 kfree_skb(skb); 1051 return 0; 1052 error: 1053 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1054 goto drop; 1055 } 1056 1057 /* 1058 * This table is the definition of how we handle ICMP. 1059 */ 1060 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1061 [ICMP_ECHOREPLY] = { 1062 .handler = icmp_discard, 1063 }, 1064 [1] = { 1065 .handler = icmp_discard, 1066 .error = 1, 1067 }, 1068 [2] = { 1069 .handler = icmp_discard, 1070 .error = 1, 1071 }, 1072 [ICMP_DEST_UNREACH] = { 1073 .handler = icmp_unreach, 1074 .error = 1, 1075 }, 1076 [ICMP_SOURCE_QUENCH] = { 1077 .handler = icmp_unreach, 1078 .error = 1, 1079 }, 1080 [ICMP_REDIRECT] = { 1081 .handler = icmp_redirect, 1082 .error = 1, 1083 }, 1084 [6] = { 1085 .handler = icmp_discard, 1086 .error = 1, 1087 }, 1088 [7] = { 1089 .handler = icmp_discard, 1090 .error = 1, 1091 }, 1092 [ICMP_ECHO] = { 1093 .handler = icmp_echo, 1094 }, 1095 [9] = { 1096 .handler = icmp_discard, 1097 .error = 1, 1098 }, 1099 [10] = { 1100 .handler = icmp_discard, 1101 .error = 1, 1102 }, 1103 [ICMP_TIME_EXCEEDED] = { 1104 .handler = icmp_unreach, 1105 .error = 1, 1106 }, 1107 [ICMP_PARAMETERPROB] = { 1108 .handler = icmp_unreach, 1109 .error = 1, 1110 }, 1111 [ICMP_TIMESTAMP] = { 1112 .handler = icmp_timestamp, 1113 }, 1114 [ICMP_TIMESTAMPREPLY] = { 1115 .handler = icmp_discard, 1116 }, 1117 [ICMP_INFO_REQUEST] = { 1118 .handler = icmp_discard, 1119 }, 1120 [ICMP_INFO_REPLY] = { 1121 .handler = icmp_discard, 1122 }, 1123 [ICMP_ADDRESS] = { 1124 .handler = icmp_address, 1125 }, 1126 [ICMP_ADDRESSREPLY] = { 1127 .handler = icmp_address_reply, 1128 }, 1129 }; 1130 1131 static void __net_exit icmp_sk_exit(struct net *net) 1132 { 1133 int i; 1134 1135 for_each_possible_cpu(i) 1136 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1137 kfree(net->ipv4.icmp_sk); 1138 net->ipv4.icmp_sk = NULL; 1139 } 1140 1141 static int __net_init icmp_sk_init(struct net *net) 1142 { 1143 int i, err; 1144 1145 net->ipv4.icmp_sk = 1146 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1147 if (net->ipv4.icmp_sk == NULL) 1148 return -ENOMEM; 1149 1150 for_each_possible_cpu(i) { 1151 struct sock *sk; 1152 1153 err = inet_ctl_sock_create(&sk, PF_INET, 1154 SOCK_RAW, IPPROTO_ICMP, net); 1155 if (err < 0) 1156 goto fail; 1157 1158 net->ipv4.icmp_sk[i] = sk; 1159 1160 /* Enough space for 2 64K ICMP packets, including 1161 * sk_buff struct overhead. 1162 */ 1163 sk->sk_sndbuf = 1164 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1165 1166 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1167 } 1168 1169 /* Control parameters for ECHO replies. */ 1170 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1171 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1172 1173 /* Control parameter - ignore bogus broadcast responses? */ 1174 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1175 1176 /* 1177 * Configurable global rate limit. 1178 * 1179 * ratelimit defines tokens/packet consumed for dst->rate_token 1180 * bucket ratemask defines which icmp types are ratelimited by 1181 * setting it's bit position. 1182 * 1183 * default: 1184 * dest unreachable (3), source quench (4), 1185 * time exceeded (11), parameter problem (12) 1186 */ 1187 1188 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1189 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1190 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1191 1192 return 0; 1193 1194 fail: 1195 for_each_possible_cpu(i) 1196 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1197 kfree(net->ipv4.icmp_sk); 1198 return err; 1199 } 1200 1201 static struct pernet_operations __net_initdata icmp_sk_ops = { 1202 .init = icmp_sk_init, 1203 .exit = icmp_sk_exit, 1204 }; 1205 1206 int __init icmp_init(void) 1207 { 1208 return register_pernet_device(&icmp_sk_ops); 1209 } 1210 1211 EXPORT_SYMBOL(icmp_err_convert); 1212 EXPORT_SYMBOL(icmp_send); 1213 EXPORT_SYMBOL(xrlim_allow); 1214