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