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 <linux/slab.h> 78 #include <net/snmp.h> 79 #include <net/ip.h> 80 #include <net/route.h> 81 #include <net/protocol.h> 82 #include <net/icmp.h> 83 #include <net/tcp.h> 84 #include <net/udp.h> 85 #include <net/raw.h> 86 #include <linux/skbuff.h> 87 #include <net/sock.h> 88 #include <linux/errno.h> 89 #include <linux/timer.h> 90 #include <linux/init.h> 91 #include <asm/system.h> 92 #include <asm/uaccess.h> 93 #include <net/checksum.h> 94 #include <net/xfrm.h> 95 #include <net/inet_common.h> 96 97 /* 98 * Build xmit assembly blocks 99 */ 100 101 struct icmp_bxm { 102 struct sk_buff *skb; 103 int offset; 104 int data_len; 105 106 struct { 107 struct icmphdr icmph; 108 __be32 times[3]; 109 } data; 110 int head_len; 111 struct ip_options replyopts; 112 unsigned char optbuf[40]; 113 }; 114 115 /* An array of errno for error messages from dest unreach. */ 116 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 117 118 const struct icmp_err icmp_err_convert[] = { 119 { 120 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 121 .fatal = 0, 122 }, 123 { 124 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 125 .fatal = 0, 126 }, 127 { 128 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 129 .fatal = 1, 130 }, 131 { 132 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 133 .fatal = 1, 134 }, 135 { 136 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 137 .fatal = 0, 138 }, 139 { 140 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 141 .fatal = 0, 142 }, 143 { 144 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 145 .fatal = 1, 146 }, 147 { 148 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 149 .fatal = 1, 150 }, 151 { 152 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 153 .fatal = 1, 154 }, 155 { 156 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 157 .fatal = 1, 158 }, 159 { 160 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 161 .fatal = 1, 162 }, 163 { 164 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 165 .fatal = 0, 166 }, 167 { 168 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 169 .fatal = 0, 170 }, 171 { 172 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 173 .fatal = 1, 174 }, 175 { 176 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 177 .fatal = 1, 178 }, 179 { 180 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 181 .fatal = 1, 182 }, 183 }; 184 EXPORT_SYMBOL(icmp_err_convert); 185 186 /* 187 * ICMP control array. This specifies what to do with each ICMP. 188 */ 189 190 struct icmp_control { 191 void (*handler)(struct sk_buff *skb); 192 short error; /* This ICMP is classed as an error message */ 193 }; 194 195 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 196 197 /* 198 * The ICMP socket(s). This is the most convenient way to flow control 199 * our ICMP output as well as maintain a clean interface throughout 200 * all layers. All Socketless IP sends will soon be gone. 201 * 202 * On SMP we have one ICMP socket per-cpu. 203 */ 204 static struct sock *icmp_sk(struct net *net) 205 { 206 return net->ipv4.icmp_sk[smp_processor_id()]; 207 } 208 209 static inline struct sock *icmp_xmit_lock(struct net *net) 210 { 211 struct sock *sk; 212 213 local_bh_disable(); 214 215 sk = icmp_sk(net); 216 217 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 218 /* This can happen if the output path signals a 219 * dst_link_failure() for an outgoing ICMP packet. 220 */ 221 local_bh_enable(); 222 return NULL; 223 } 224 return sk; 225 } 226 227 static inline void icmp_xmit_unlock(struct sock *sk) 228 { 229 spin_unlock_bh(&sk->sk_lock.slock); 230 } 231 232 /* 233 * Send an ICMP frame. 234 */ 235 236 /* 237 * Check transmit rate limitation for given message. 238 * The rate information is held in the destination cache now. 239 * This function is generic and could be used for other purposes 240 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov. 241 * 242 * Note that the same dst_entry fields are modified by functions in 243 * route.c too, but these work for packet destinations while xrlim_allow 244 * works for icmp destinations. This means the rate limiting information 245 * for one "ip object" is shared - and these ICMPs are twice limited: 246 * by source and by destination. 247 * 248 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate 249 * SHOULD allow setting of rate limits 250 * 251 * Shared between ICMPv4 and ICMPv6. 252 */ 253 #define XRLIM_BURST_FACTOR 6 254 int xrlim_allow(struct dst_entry *dst, int timeout) 255 { 256 unsigned long now, token = dst->rate_tokens; 257 int rc = 0; 258 259 now = jiffies; 260 token += now - dst->rate_last; 261 dst->rate_last = now; 262 if (token > XRLIM_BURST_FACTOR * timeout) 263 token = XRLIM_BURST_FACTOR * timeout; 264 if (token >= timeout) { 265 token -= timeout; 266 rc = 1; 267 } 268 dst->rate_tokens = token; 269 return rc; 270 } 271 EXPORT_SYMBOL(xrlim_allow); 272 273 static inline int icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 274 int type, int code) 275 { 276 struct dst_entry *dst = &rt->dst; 277 int rc = 1; 278 279 if (type > NR_ICMP_TYPES) 280 goto out; 281 282 /* Don't limit PMTU discovery. */ 283 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 284 goto out; 285 286 /* No rate limit on loopback */ 287 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 288 goto out; 289 290 /* Limit if icmp type is enabled in ratemask. */ 291 if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) 292 rc = xrlim_allow(dst, net->ipv4.sysctl_icmp_ratelimit); 293 out: 294 return rc; 295 } 296 297 /* 298 * Maintain the counters used in the SNMP statistics for outgoing ICMP 299 */ 300 void icmp_out_count(struct net *net, unsigned char type) 301 { 302 ICMPMSGOUT_INC_STATS(net, type); 303 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 304 } 305 306 /* 307 * Checksum each fragment, and on the first include the headers and final 308 * checksum. 309 */ 310 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 311 struct sk_buff *skb) 312 { 313 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 314 __wsum csum; 315 316 csum = skb_copy_and_csum_bits(icmp_param->skb, 317 icmp_param->offset + offset, 318 to, len, 0); 319 320 skb->csum = csum_block_add(skb->csum, csum, odd); 321 if (icmp_pointers[icmp_param->data.icmph.type].error) 322 nf_ct_attach(skb, icmp_param->skb); 323 return 0; 324 } 325 326 static void icmp_push_reply(struct icmp_bxm *icmp_param, 327 struct ipcm_cookie *ipc, struct rtable **rt) 328 { 329 struct sock *sk; 330 struct sk_buff *skb; 331 332 sk = icmp_sk(dev_net((*rt)->dst.dev)); 333 if (ip_append_data(sk, icmp_glue_bits, icmp_param, 334 icmp_param->data_len+icmp_param->head_len, 335 icmp_param->head_len, 336 ipc, rt, MSG_DONTWAIT) < 0) { 337 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 338 ip_flush_pending_frames(sk); 339 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 340 struct icmphdr *icmph = icmp_hdr(skb); 341 __wsum csum = 0; 342 struct sk_buff *skb1; 343 344 skb_queue_walk(&sk->sk_write_queue, skb1) { 345 csum = csum_add(csum, skb1->csum); 346 } 347 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 348 (char *)icmph, 349 icmp_param->head_len, csum); 350 icmph->checksum = csum_fold(csum); 351 skb->ip_summed = CHECKSUM_NONE; 352 ip_push_pending_frames(sk); 353 } 354 } 355 356 /* 357 * Driving logic for building and sending ICMP messages. 358 */ 359 360 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 361 { 362 struct ipcm_cookie ipc; 363 struct rtable *rt = skb_rtable(skb); 364 struct net *net = dev_net(rt->dst.dev); 365 struct sock *sk; 366 struct inet_sock *inet; 367 __be32 daddr; 368 369 if (ip_options_echo(&icmp_param->replyopts, skb)) 370 return; 371 372 sk = icmp_xmit_lock(net); 373 if (sk == NULL) 374 return; 375 inet = inet_sk(sk); 376 377 icmp_param->data.icmph.checksum = 0; 378 379 inet->tos = ip_hdr(skb)->tos; 380 daddr = ipc.addr = rt->rt_src; 381 ipc.opt = NULL; 382 ipc.tx_flags = 0; 383 if (icmp_param->replyopts.optlen) { 384 ipc.opt = &icmp_param->replyopts; 385 if (ipc.opt->srr) 386 daddr = icmp_param->replyopts.faddr; 387 } 388 { 389 struct flowi fl = { .nl_u = { .ip4_u = 390 { .daddr = daddr, 391 .saddr = rt->rt_spec_dst, 392 .tos = RT_TOS(ip_hdr(skb)->tos) } }, 393 .proto = IPPROTO_ICMP }; 394 security_skb_classify_flow(skb, &fl); 395 if (ip_route_output_key(net, &rt, &fl)) 396 goto out_unlock; 397 } 398 if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type, 399 icmp_param->data.icmph.code)) 400 icmp_push_reply(icmp_param, &ipc, &rt); 401 ip_rt_put(rt); 402 out_unlock: 403 icmp_xmit_unlock(sk); 404 } 405 406 407 /* 408 * Send an ICMP message in response to a situation 409 * 410 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 411 * MAY send more (we do). 412 * MUST NOT change this header information. 413 * MUST NOT reply to a multicast/broadcast IP address. 414 * MUST NOT reply to a multicast/broadcast MAC address. 415 * MUST reply to only the first fragment. 416 */ 417 418 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 419 { 420 struct iphdr *iph; 421 int room; 422 struct icmp_bxm icmp_param; 423 struct rtable *rt = skb_rtable(skb_in); 424 struct ipcm_cookie ipc; 425 __be32 saddr; 426 u8 tos; 427 struct net *net; 428 struct sock *sk; 429 430 if (!rt) 431 goto out; 432 net = dev_net(rt->dst.dev); 433 434 /* 435 * Find the original header. It is expected to be valid, of course. 436 * Check this, icmp_send is called from the most obscure devices 437 * sometimes. 438 */ 439 iph = ip_hdr(skb_in); 440 441 if ((u8 *)iph < skb_in->head || 442 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 443 goto out; 444 445 /* 446 * No replies to physical multicast/broadcast 447 */ 448 if (skb_in->pkt_type != PACKET_HOST) 449 goto out; 450 451 /* 452 * Now check at the protocol level 453 */ 454 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 455 goto out; 456 457 /* 458 * Only reply to fragment 0. We byte re-order the constant 459 * mask for efficiency. 460 */ 461 if (iph->frag_off & htons(IP_OFFSET)) 462 goto out; 463 464 /* 465 * If we send an ICMP error to an ICMP error a mess would result.. 466 */ 467 if (icmp_pointers[type].error) { 468 /* 469 * We are an error, check if we are replying to an 470 * ICMP error 471 */ 472 if (iph->protocol == IPPROTO_ICMP) { 473 u8 _inner_type, *itp; 474 475 itp = skb_header_pointer(skb_in, 476 skb_network_header(skb_in) + 477 (iph->ihl << 2) + 478 offsetof(struct icmphdr, 479 type) - 480 skb_in->data, 481 sizeof(_inner_type), 482 &_inner_type); 483 if (itp == NULL) 484 goto out; 485 486 /* 487 * Assume any unknown ICMP type is an error. This 488 * isn't specified by the RFC, but think about it.. 489 */ 490 if (*itp > NR_ICMP_TYPES || 491 icmp_pointers[*itp].error) 492 goto out; 493 } 494 } 495 496 sk = icmp_xmit_lock(net); 497 if (sk == NULL) 498 return; 499 500 /* 501 * Construct source address and options. 502 */ 503 504 saddr = iph->daddr; 505 if (!(rt->rt_flags & RTCF_LOCAL)) { 506 struct net_device *dev = NULL; 507 508 rcu_read_lock(); 509 if (rt->fl.iif && 510 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 511 dev = dev_get_by_index_rcu(net, rt->fl.iif); 512 513 if (dev) 514 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 515 else 516 saddr = 0; 517 rcu_read_unlock(); 518 } 519 520 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 521 IPTOS_PREC_INTERNETCONTROL) : 522 iph->tos; 523 524 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 525 goto out_unlock; 526 527 528 /* 529 * Prepare data for ICMP header. 530 */ 531 532 icmp_param.data.icmph.type = type; 533 icmp_param.data.icmph.code = code; 534 icmp_param.data.icmph.un.gateway = info; 535 icmp_param.data.icmph.checksum = 0; 536 icmp_param.skb = skb_in; 537 icmp_param.offset = skb_network_offset(skb_in); 538 inet_sk(sk)->tos = tos; 539 ipc.addr = iph->saddr; 540 ipc.opt = &icmp_param.replyopts; 541 ipc.tx_flags = 0; 542 543 { 544 struct flowi fl = { 545 .nl_u = { 546 .ip4_u = { 547 .daddr = icmp_param.replyopts.srr ? 548 icmp_param.replyopts.faddr : 549 iph->saddr, 550 .saddr = saddr, 551 .tos = RT_TOS(tos) 552 } 553 }, 554 .proto = IPPROTO_ICMP, 555 .uli_u = { 556 .icmpt = { 557 .type = type, 558 .code = code 559 } 560 } 561 }; 562 int err; 563 struct rtable *rt2; 564 565 security_skb_classify_flow(skb_in, &fl); 566 if (__ip_route_output_key(net, &rt, &fl)) 567 goto out_unlock; 568 569 /* No need to clone since we're just using its address. */ 570 rt2 = rt; 571 572 if (!fl.nl_u.ip4_u.saddr) 573 fl.nl_u.ip4_u.saddr = rt->rt_src; 574 575 err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0); 576 switch (err) { 577 case 0: 578 if (rt != rt2) 579 goto route_done; 580 break; 581 case -EPERM: 582 rt = NULL; 583 break; 584 default: 585 goto out_unlock; 586 } 587 588 if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET)) 589 goto relookup_failed; 590 591 if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) 592 err = __ip_route_output_key(net, &rt2, &fl); 593 else { 594 struct flowi fl2 = {}; 595 unsigned long orefdst; 596 597 fl2.fl4_dst = fl.fl4_src; 598 if (ip_route_output_key(net, &rt2, &fl2)) 599 goto relookup_failed; 600 601 /* Ugh! */ 602 orefdst = skb_in->_skb_refdst; /* save old refdst */ 603 err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src, 604 RT_TOS(tos), rt2->dst.dev); 605 606 dst_release(&rt2->dst); 607 rt2 = skb_rtable(skb_in); 608 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 609 } 610 611 if (err) 612 goto relookup_failed; 613 614 err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL, 615 XFRM_LOOKUP_ICMP); 616 switch (err) { 617 case 0: 618 dst_release(&rt->dst); 619 rt = rt2; 620 break; 621 case -EPERM: 622 goto ende; 623 default: 624 relookup_failed: 625 if (!rt) 626 goto out_unlock; 627 break; 628 } 629 } 630 631 route_done: 632 if (!icmpv4_xrlim_allow(net, rt, type, code)) 633 goto ende; 634 635 /* RFC says return as much as we can without exceeding 576 bytes. */ 636 637 room = dst_mtu(&rt->dst); 638 if (room > 576) 639 room = 576; 640 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 641 room -= sizeof(struct icmphdr); 642 643 icmp_param.data_len = skb_in->len - icmp_param.offset; 644 if (icmp_param.data_len > room) 645 icmp_param.data_len = room; 646 icmp_param.head_len = sizeof(struct icmphdr); 647 648 icmp_push_reply(&icmp_param, &ipc, &rt); 649 ende: 650 ip_rt_put(rt); 651 out_unlock: 652 icmp_xmit_unlock(sk); 653 out:; 654 } 655 EXPORT_SYMBOL(icmp_send); 656 657 658 /* 659 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 660 */ 661 662 static void icmp_unreach(struct sk_buff *skb) 663 { 664 struct iphdr *iph; 665 struct icmphdr *icmph; 666 int hash, protocol; 667 const struct net_protocol *ipprot; 668 u32 info = 0; 669 struct net *net; 670 671 net = dev_net(skb_dst(skb)->dev); 672 673 /* 674 * Incomplete header ? 675 * Only checks for the IP header, there should be an 676 * additional check for longer headers in upper levels. 677 */ 678 679 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 680 goto out_err; 681 682 icmph = icmp_hdr(skb); 683 iph = (struct iphdr *)skb->data; 684 685 if (iph->ihl < 5) /* Mangled header, drop. */ 686 goto out_err; 687 688 if (icmph->type == ICMP_DEST_UNREACH) { 689 switch (icmph->code & 15) { 690 case ICMP_NET_UNREACH: 691 case ICMP_HOST_UNREACH: 692 case ICMP_PROT_UNREACH: 693 case ICMP_PORT_UNREACH: 694 break; 695 case ICMP_FRAG_NEEDED: 696 if (ipv4_config.no_pmtu_disc) { 697 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: fragmentation needed and DF set.\n", 698 &iph->daddr); 699 } else { 700 info = ip_rt_frag_needed(net, iph, 701 ntohs(icmph->un.frag.mtu), 702 skb->dev); 703 if (!info) 704 goto out; 705 } 706 break; 707 case ICMP_SR_FAILED: 708 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: Source Route Failed.\n", 709 &iph->daddr); 710 break; 711 default: 712 break; 713 } 714 if (icmph->code > NR_ICMP_UNREACH) 715 goto out; 716 } else if (icmph->type == ICMP_PARAMETERPROB) 717 info = ntohl(icmph->un.gateway) >> 24; 718 719 /* 720 * Throw it at our lower layers 721 * 722 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 723 * header. 724 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 725 * transport layer. 726 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 727 * transport layer. 728 */ 729 730 /* 731 * Check the other end isnt violating RFC 1122. Some routers send 732 * bogus responses to broadcast frames. If you see this message 733 * first check your netmask matches at both ends, if it does then 734 * get the other vendor to fix their kit. 735 */ 736 737 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 738 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 739 if (net_ratelimit()) 740 printk(KERN_WARNING "%pI4 sent an invalid ICMP " 741 "type %u, code %u " 742 "error to a broadcast: %pI4 on %s\n", 743 &ip_hdr(skb)->saddr, 744 icmph->type, icmph->code, 745 &iph->daddr, 746 skb->dev->name); 747 goto out; 748 } 749 750 /* Checkin full IP header plus 8 bytes of protocol to 751 * avoid additional coding at protocol handlers. 752 */ 753 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 754 goto out; 755 756 iph = (struct iphdr *)skb->data; 757 protocol = iph->protocol; 758 759 /* 760 * Deliver ICMP message to raw sockets. Pretty useless feature? 761 */ 762 raw_icmp_error(skb, protocol, info); 763 764 hash = protocol & (MAX_INET_PROTOS - 1); 765 rcu_read_lock(); 766 ipprot = rcu_dereference(inet_protos[hash]); 767 if (ipprot && ipprot->err_handler) 768 ipprot->err_handler(skb, info); 769 rcu_read_unlock(); 770 771 out: 772 return; 773 out_err: 774 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 775 goto out; 776 } 777 778 779 /* 780 * Handle ICMP_REDIRECT. 781 */ 782 783 static void icmp_redirect(struct sk_buff *skb) 784 { 785 struct iphdr *iph; 786 787 if (skb->len < sizeof(struct iphdr)) 788 goto out_err; 789 790 /* 791 * Get the copied header of the packet that caused the redirect 792 */ 793 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 794 goto out; 795 796 iph = (struct iphdr *)skb->data; 797 798 switch (icmp_hdr(skb)->code & 7) { 799 case ICMP_REDIR_NET: 800 case ICMP_REDIR_NETTOS: 801 /* 802 * As per RFC recommendations now handle it as a host redirect. 803 */ 804 case ICMP_REDIR_HOST: 805 case ICMP_REDIR_HOSTTOS: 806 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 807 icmp_hdr(skb)->un.gateway, 808 iph->saddr, skb->dev); 809 break; 810 } 811 out: 812 return; 813 out_err: 814 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 815 goto out; 816 } 817 818 /* 819 * Handle ICMP_ECHO ("ping") requests. 820 * 821 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 822 * requests. 823 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 824 * included in the reply. 825 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 826 * echo requests, MUST have default=NOT. 827 * See also WRT handling of options once they are done and working. 828 */ 829 830 static void icmp_echo(struct sk_buff *skb) 831 { 832 struct net *net; 833 834 net = dev_net(skb_dst(skb)->dev); 835 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 836 struct icmp_bxm icmp_param; 837 838 icmp_param.data.icmph = *icmp_hdr(skb); 839 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 840 icmp_param.skb = skb; 841 icmp_param.offset = 0; 842 icmp_param.data_len = skb->len; 843 icmp_param.head_len = sizeof(struct icmphdr); 844 icmp_reply(&icmp_param, skb); 845 } 846 } 847 848 /* 849 * Handle ICMP Timestamp requests. 850 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 851 * SHOULD be in the kernel for minimum random latency. 852 * MUST be accurate to a few minutes. 853 * MUST be updated at least at 15Hz. 854 */ 855 static void icmp_timestamp(struct sk_buff *skb) 856 { 857 struct timespec tv; 858 struct icmp_bxm icmp_param; 859 /* 860 * Too short. 861 */ 862 if (skb->len < 4) 863 goto out_err; 864 865 /* 866 * Fill in the current time as ms since midnight UT: 867 */ 868 getnstimeofday(&tv); 869 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 870 tv.tv_nsec / NSEC_PER_MSEC); 871 icmp_param.data.times[2] = icmp_param.data.times[1]; 872 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 873 BUG(); 874 icmp_param.data.icmph = *icmp_hdr(skb); 875 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 876 icmp_param.data.icmph.code = 0; 877 icmp_param.skb = skb; 878 icmp_param.offset = 0; 879 icmp_param.data_len = 0; 880 icmp_param.head_len = sizeof(struct icmphdr) + 12; 881 icmp_reply(&icmp_param, skb); 882 out: 883 return; 884 out_err: 885 ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 886 goto out; 887 } 888 889 890 /* 891 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 892 * 893 * RFC1122 (3.2.2.9). A host MUST only send replies to 894 * ADDRESS_MASK requests if it's been configured as an address mask 895 * agent. Receiving a request doesn't constitute implicit permission to 896 * act as one. Of course, implementing this correctly requires (SHOULD) 897 * a way to turn the functionality on and off. Another one for sysctl(), 898 * I guess. -- MS 899 * 900 * RFC1812 (4.3.3.9). A router MUST implement it. 901 * A router SHOULD have switch turning it on/off. 902 * This switch MUST be ON by default. 903 * 904 * Gratuitous replies, zero-source replies are not implemented, 905 * that complies with RFC. DO NOT implement them!!! All the idea 906 * of broadcast addrmask replies as specified in RFC950 is broken. 907 * The problem is that it is not uncommon to have several prefixes 908 * on one physical interface. Moreover, addrmask agent can even be 909 * not aware of existing another prefixes. 910 * If source is zero, addrmask agent cannot choose correct prefix. 911 * Gratuitous mask announcements suffer from the same problem. 912 * RFC1812 explains it, but still allows to use ADDRMASK, 913 * that is pretty silly. --ANK 914 * 915 * All these rules are so bizarre, that I removed kernel addrmask 916 * support at all. It is wrong, it is obsolete, nobody uses it in 917 * any case. --ANK 918 * 919 * Furthermore you can do it with a usermode address agent program 920 * anyway... 921 */ 922 923 static void icmp_address(struct sk_buff *skb) 924 { 925 #if 0 926 if (net_ratelimit()) 927 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 928 #endif 929 } 930 931 /* 932 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 933 * loudly if an inconsistency is found. 934 * called with rcu_read_lock() 935 */ 936 937 static void icmp_address_reply(struct sk_buff *skb) 938 { 939 struct rtable *rt = skb_rtable(skb); 940 struct net_device *dev = skb->dev; 941 struct in_device *in_dev; 942 struct in_ifaddr *ifa; 943 944 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 945 return; 946 947 in_dev = __in_dev_get_rcu(dev); 948 if (!in_dev) 949 return; 950 951 if (in_dev->ifa_list && 952 IN_DEV_LOG_MARTIANS(in_dev) && 953 IN_DEV_FORWARD(in_dev)) { 954 __be32 _mask, *mp; 955 956 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 957 BUG_ON(mp == NULL); 958 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 959 if (*mp == ifa->ifa_mask && 960 inet_ifa_match(rt->rt_src, ifa)) 961 break; 962 } 963 if (!ifa && net_ratelimit()) { 964 printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n", 965 mp, dev->name, &rt->rt_src); 966 } 967 } 968 } 969 970 static void icmp_discard(struct sk_buff *skb) 971 { 972 } 973 974 /* 975 * Deal with incoming ICMP packets. 976 */ 977 int icmp_rcv(struct sk_buff *skb) 978 { 979 struct icmphdr *icmph; 980 struct rtable *rt = skb_rtable(skb); 981 struct net *net = dev_net(rt->dst.dev); 982 983 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 984 struct sec_path *sp = skb_sec_path(skb); 985 int nh; 986 987 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 988 XFRM_STATE_ICMP)) 989 goto drop; 990 991 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 992 goto drop; 993 994 nh = skb_network_offset(skb); 995 skb_set_network_header(skb, sizeof(*icmph)); 996 997 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 998 goto drop; 999 1000 skb_set_network_header(skb, nh); 1001 } 1002 1003 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 1004 1005 switch (skb->ip_summed) { 1006 case CHECKSUM_COMPLETE: 1007 if (!csum_fold(skb->csum)) 1008 break; 1009 /* fall through */ 1010 case CHECKSUM_NONE: 1011 skb->csum = 0; 1012 if (__skb_checksum_complete(skb)) 1013 goto error; 1014 } 1015 1016 if (!pskb_pull(skb, sizeof(*icmph))) 1017 goto error; 1018 1019 icmph = icmp_hdr(skb); 1020 1021 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1022 /* 1023 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1024 * 1025 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1026 * discarded. 1027 */ 1028 if (icmph->type > NR_ICMP_TYPES) 1029 goto error; 1030 1031 1032 /* 1033 * Parse the ICMP message 1034 */ 1035 1036 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1037 /* 1038 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1039 * silently ignored (we let user decide with a sysctl). 1040 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1041 * discarded if to broadcast/multicast. 1042 */ 1043 if ((icmph->type == ICMP_ECHO || 1044 icmph->type == ICMP_TIMESTAMP) && 1045 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1046 goto error; 1047 } 1048 if (icmph->type != ICMP_ECHO && 1049 icmph->type != ICMP_TIMESTAMP && 1050 icmph->type != ICMP_ADDRESS && 1051 icmph->type != ICMP_ADDRESSREPLY) { 1052 goto error; 1053 } 1054 } 1055 1056 icmp_pointers[icmph->type].handler(skb); 1057 1058 drop: 1059 kfree_skb(skb); 1060 return 0; 1061 error: 1062 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1063 goto drop; 1064 } 1065 1066 /* 1067 * This table is the definition of how we handle ICMP. 1068 */ 1069 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1070 [ICMP_ECHOREPLY] = { 1071 .handler = icmp_discard, 1072 }, 1073 [1] = { 1074 .handler = icmp_discard, 1075 .error = 1, 1076 }, 1077 [2] = { 1078 .handler = icmp_discard, 1079 .error = 1, 1080 }, 1081 [ICMP_DEST_UNREACH] = { 1082 .handler = icmp_unreach, 1083 .error = 1, 1084 }, 1085 [ICMP_SOURCE_QUENCH] = { 1086 .handler = icmp_unreach, 1087 .error = 1, 1088 }, 1089 [ICMP_REDIRECT] = { 1090 .handler = icmp_redirect, 1091 .error = 1, 1092 }, 1093 [6] = { 1094 .handler = icmp_discard, 1095 .error = 1, 1096 }, 1097 [7] = { 1098 .handler = icmp_discard, 1099 .error = 1, 1100 }, 1101 [ICMP_ECHO] = { 1102 .handler = icmp_echo, 1103 }, 1104 [9] = { 1105 .handler = icmp_discard, 1106 .error = 1, 1107 }, 1108 [10] = { 1109 .handler = icmp_discard, 1110 .error = 1, 1111 }, 1112 [ICMP_TIME_EXCEEDED] = { 1113 .handler = icmp_unreach, 1114 .error = 1, 1115 }, 1116 [ICMP_PARAMETERPROB] = { 1117 .handler = icmp_unreach, 1118 .error = 1, 1119 }, 1120 [ICMP_TIMESTAMP] = { 1121 .handler = icmp_timestamp, 1122 }, 1123 [ICMP_TIMESTAMPREPLY] = { 1124 .handler = icmp_discard, 1125 }, 1126 [ICMP_INFO_REQUEST] = { 1127 .handler = icmp_discard, 1128 }, 1129 [ICMP_INFO_REPLY] = { 1130 .handler = icmp_discard, 1131 }, 1132 [ICMP_ADDRESS] = { 1133 .handler = icmp_address, 1134 }, 1135 [ICMP_ADDRESSREPLY] = { 1136 .handler = icmp_address_reply, 1137 }, 1138 }; 1139 1140 static void __net_exit icmp_sk_exit(struct net *net) 1141 { 1142 int i; 1143 1144 for_each_possible_cpu(i) 1145 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1146 kfree(net->ipv4.icmp_sk); 1147 net->ipv4.icmp_sk = NULL; 1148 } 1149 1150 static int __net_init icmp_sk_init(struct net *net) 1151 { 1152 int i, err; 1153 1154 net->ipv4.icmp_sk = 1155 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1156 if (net->ipv4.icmp_sk == NULL) 1157 return -ENOMEM; 1158 1159 for_each_possible_cpu(i) { 1160 struct sock *sk; 1161 1162 err = inet_ctl_sock_create(&sk, PF_INET, 1163 SOCK_RAW, IPPROTO_ICMP, net); 1164 if (err < 0) 1165 goto fail; 1166 1167 net->ipv4.icmp_sk[i] = sk; 1168 1169 /* Enough space for 2 64K ICMP packets, including 1170 * sk_buff struct overhead. 1171 */ 1172 sk->sk_sndbuf = 1173 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1174 1175 /* 1176 * Speedup sock_wfree() 1177 */ 1178 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1179 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1180 } 1181 1182 /* Control parameters for ECHO replies. */ 1183 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1184 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1185 1186 /* Control parameter - ignore bogus broadcast responses? */ 1187 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1188 1189 /* 1190 * Configurable global rate limit. 1191 * 1192 * ratelimit defines tokens/packet consumed for dst->rate_token 1193 * bucket ratemask defines which icmp types are ratelimited by 1194 * setting it's bit position. 1195 * 1196 * default: 1197 * dest unreachable (3), source quench (4), 1198 * time exceeded (11), parameter problem (12) 1199 */ 1200 1201 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1202 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1203 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1204 1205 return 0; 1206 1207 fail: 1208 for_each_possible_cpu(i) 1209 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1210 kfree(net->ipv4.icmp_sk); 1211 return err; 1212 } 1213 1214 static struct pernet_operations __net_initdata icmp_sk_ops = { 1215 .init = icmp_sk_init, 1216 .exit = icmp_sk_exit, 1217 }; 1218 1219 int __init icmp_init(void) 1220 { 1221 return register_pernet_subsys(&icmp_sk_ops); 1222 } 1223