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 static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 237 int type, int code) 238 { 239 struct dst_entry *dst = &rt->dst; 240 bool rc = true; 241 242 if (type > NR_ICMP_TYPES) 243 goto out; 244 245 /* Don't limit PMTU discovery. */ 246 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 247 goto out; 248 249 /* No rate limit on loopback */ 250 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 251 goto out; 252 253 /* Limit if icmp type is enabled in ratemask. */ 254 if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) { 255 if (!rt->peer) 256 rt_bind_peer(rt, 1); 257 rc = inet_peer_xrlim_allow(rt->peer, 258 net->ipv4.sysctl_icmp_ratelimit); 259 } 260 out: 261 return rc; 262 } 263 264 /* 265 * Maintain the counters used in the SNMP statistics for outgoing ICMP 266 */ 267 void icmp_out_count(struct net *net, unsigned char type) 268 { 269 ICMPMSGOUT_INC_STATS(net, type); 270 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 271 } 272 273 /* 274 * Checksum each fragment, and on the first include the headers and final 275 * checksum. 276 */ 277 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 278 struct sk_buff *skb) 279 { 280 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 281 __wsum csum; 282 283 csum = skb_copy_and_csum_bits(icmp_param->skb, 284 icmp_param->offset + offset, 285 to, len, 0); 286 287 skb->csum = csum_block_add(skb->csum, csum, odd); 288 if (icmp_pointers[icmp_param->data.icmph.type].error) 289 nf_ct_attach(skb, icmp_param->skb); 290 return 0; 291 } 292 293 static void icmp_push_reply(struct icmp_bxm *icmp_param, 294 struct ipcm_cookie *ipc, struct rtable **rt) 295 { 296 struct sock *sk; 297 struct sk_buff *skb; 298 299 sk = icmp_sk(dev_net((*rt)->dst.dev)); 300 if (ip_append_data(sk, icmp_glue_bits, icmp_param, 301 icmp_param->data_len+icmp_param->head_len, 302 icmp_param->head_len, 303 ipc, rt, MSG_DONTWAIT) < 0) { 304 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 305 ip_flush_pending_frames(sk); 306 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 307 struct icmphdr *icmph = icmp_hdr(skb); 308 __wsum csum = 0; 309 struct sk_buff *skb1; 310 311 skb_queue_walk(&sk->sk_write_queue, skb1) { 312 csum = csum_add(csum, skb1->csum); 313 } 314 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 315 (char *)icmph, 316 icmp_param->head_len, csum); 317 icmph->checksum = csum_fold(csum); 318 skb->ip_summed = CHECKSUM_NONE; 319 ip_push_pending_frames(sk); 320 } 321 } 322 323 /* 324 * Driving logic for building and sending ICMP messages. 325 */ 326 327 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 328 { 329 struct ipcm_cookie ipc; 330 struct rtable *rt = skb_rtable(skb); 331 struct net *net = dev_net(rt->dst.dev); 332 struct sock *sk; 333 struct inet_sock *inet; 334 __be32 daddr; 335 336 if (ip_options_echo(&icmp_param->replyopts, skb)) 337 return; 338 339 sk = icmp_xmit_lock(net); 340 if (sk == NULL) 341 return; 342 inet = inet_sk(sk); 343 344 icmp_param->data.icmph.checksum = 0; 345 346 inet->tos = ip_hdr(skb)->tos; 347 daddr = ipc.addr = rt->rt_src; 348 ipc.opt = NULL; 349 ipc.tx_flags = 0; 350 if (icmp_param->replyopts.optlen) { 351 ipc.opt = &icmp_param->replyopts; 352 if (ipc.opt->srr) 353 daddr = icmp_param->replyopts.faddr; 354 } 355 { 356 struct flowi fl = { .fl4_dst= daddr, 357 .fl4_src = rt->rt_spec_dst, 358 .fl4_tos = RT_TOS(ip_hdr(skb)->tos), 359 .proto = IPPROTO_ICMP }; 360 security_skb_classify_flow(skb, &fl); 361 rt = ip_route_output_key(net, &fl); 362 if (IS_ERR(rt)) 363 goto out_unlock; 364 } 365 if (icmpv4_xrlim_allow(net, rt, icmp_param->data.icmph.type, 366 icmp_param->data.icmph.code)) 367 icmp_push_reply(icmp_param, &ipc, &rt); 368 ip_rt_put(rt); 369 out_unlock: 370 icmp_xmit_unlock(sk); 371 } 372 373 static struct rtable *icmp_route_lookup(struct net *net, struct sk_buff *skb_in, 374 struct iphdr *iph, 375 __be32 saddr, u8 tos, 376 int type, int code, 377 struct icmp_bxm *param) 378 { 379 struct flowi fl = { 380 .fl4_dst = (param->replyopts.srr ? 381 param->replyopts.faddr : iph->saddr), 382 .fl4_src = saddr, 383 .fl4_tos = RT_TOS(tos), 384 .proto = IPPROTO_ICMP, 385 .fl_icmp_type = type, 386 .fl_icmp_code = code, 387 }; 388 struct rtable *rt, *rt2; 389 int err; 390 391 security_skb_classify_flow(skb_in, &fl); 392 rt = __ip_route_output_key(net, &fl); 393 if (IS_ERR(rt)) 394 return rt; 395 396 /* No need to clone since we're just using its address. */ 397 rt2 = rt; 398 399 if (!fl.fl4_src) 400 fl.fl4_src = rt->rt_src; 401 402 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, &fl, NULL, 0); 403 if (!IS_ERR(rt)) { 404 if (rt != rt2) 405 return rt; 406 } else if (PTR_ERR(rt) == -EPERM) { 407 rt = NULL; 408 } else 409 return rt; 410 411 err = xfrm_decode_session_reverse(skb_in, &fl, AF_INET); 412 if (err) 413 goto relookup_failed; 414 415 if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) { 416 rt2 = __ip_route_output_key(net, &fl); 417 if (IS_ERR(rt2)) 418 err = PTR_ERR(rt2); 419 } else { 420 struct flowi fl2 = {}; 421 unsigned long orefdst; 422 423 fl2.fl4_dst = fl.fl4_src; 424 rt2 = ip_route_output_key(net, &fl2); 425 if (IS_ERR(rt2)) { 426 err = PTR_ERR(rt2); 427 goto relookup_failed; 428 } 429 /* Ugh! */ 430 orefdst = skb_in->_skb_refdst; /* save old refdst */ 431 err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src, 432 RT_TOS(tos), rt2->dst.dev); 433 434 dst_release(&rt2->dst); 435 rt2 = skb_rtable(skb_in); 436 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 437 } 438 439 if (err) 440 goto relookup_failed; 441 442 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, &fl, NULL, XFRM_LOOKUP_ICMP); 443 if (!IS_ERR(rt2)) { 444 dst_release(&rt->dst); 445 rt = rt2; 446 } else if (PTR_ERR(rt2) == -EPERM) { 447 if (rt) 448 dst_release(&rt->dst); 449 return rt2; 450 } else { 451 err = PTR_ERR(rt2); 452 goto relookup_failed; 453 } 454 return rt; 455 456 relookup_failed: 457 if (rt) 458 return rt; 459 return ERR_PTR(err); 460 } 461 462 /* 463 * Send an ICMP message in response to a situation 464 * 465 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 466 * MAY send more (we do). 467 * MUST NOT change this header information. 468 * MUST NOT reply to a multicast/broadcast IP address. 469 * MUST NOT reply to a multicast/broadcast MAC address. 470 * MUST reply to only the first fragment. 471 */ 472 473 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 474 { 475 struct iphdr *iph; 476 int room; 477 struct icmp_bxm icmp_param; 478 struct rtable *rt = skb_rtable(skb_in); 479 struct ipcm_cookie ipc; 480 __be32 saddr; 481 u8 tos; 482 struct net *net; 483 struct sock *sk; 484 485 if (!rt) 486 goto out; 487 net = dev_net(rt->dst.dev); 488 489 /* 490 * Find the original header. It is expected to be valid, of course. 491 * Check this, icmp_send is called from the most obscure devices 492 * sometimes. 493 */ 494 iph = ip_hdr(skb_in); 495 496 if ((u8 *)iph < skb_in->head || 497 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 498 goto out; 499 500 /* 501 * No replies to physical multicast/broadcast 502 */ 503 if (skb_in->pkt_type != PACKET_HOST) 504 goto out; 505 506 /* 507 * Now check at the protocol level 508 */ 509 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 510 goto out; 511 512 /* 513 * Only reply to fragment 0. We byte re-order the constant 514 * mask for efficiency. 515 */ 516 if (iph->frag_off & htons(IP_OFFSET)) 517 goto out; 518 519 /* 520 * If we send an ICMP error to an ICMP error a mess would result.. 521 */ 522 if (icmp_pointers[type].error) { 523 /* 524 * We are an error, check if we are replying to an 525 * ICMP error 526 */ 527 if (iph->protocol == IPPROTO_ICMP) { 528 u8 _inner_type, *itp; 529 530 itp = skb_header_pointer(skb_in, 531 skb_network_header(skb_in) + 532 (iph->ihl << 2) + 533 offsetof(struct icmphdr, 534 type) - 535 skb_in->data, 536 sizeof(_inner_type), 537 &_inner_type); 538 if (itp == NULL) 539 goto out; 540 541 /* 542 * Assume any unknown ICMP type is an error. This 543 * isn't specified by the RFC, but think about it.. 544 */ 545 if (*itp > NR_ICMP_TYPES || 546 icmp_pointers[*itp].error) 547 goto out; 548 } 549 } 550 551 sk = icmp_xmit_lock(net); 552 if (sk == NULL) 553 return; 554 555 /* 556 * Construct source address and options. 557 */ 558 559 saddr = iph->daddr; 560 if (!(rt->rt_flags & RTCF_LOCAL)) { 561 struct net_device *dev = NULL; 562 563 rcu_read_lock(); 564 if (rt_is_input_route(rt) && 565 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 566 dev = dev_get_by_index_rcu(net, rt->rt_iif); 567 568 if (dev) 569 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 570 else 571 saddr = 0; 572 rcu_read_unlock(); 573 } 574 575 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 576 IPTOS_PREC_INTERNETCONTROL) : 577 iph->tos; 578 579 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 580 goto out_unlock; 581 582 583 /* 584 * Prepare data for ICMP header. 585 */ 586 587 icmp_param.data.icmph.type = type; 588 icmp_param.data.icmph.code = code; 589 icmp_param.data.icmph.un.gateway = info; 590 icmp_param.data.icmph.checksum = 0; 591 icmp_param.skb = skb_in; 592 icmp_param.offset = skb_network_offset(skb_in); 593 inet_sk(sk)->tos = tos; 594 ipc.addr = iph->saddr; 595 ipc.opt = &icmp_param.replyopts; 596 ipc.tx_flags = 0; 597 598 rt = icmp_route_lookup(net, skb_in, iph, saddr, tos, 599 type, code, &icmp_param); 600 if (IS_ERR(rt)) 601 goto out_unlock; 602 603 if (!icmpv4_xrlim_allow(net, rt, type, code)) 604 goto ende; 605 606 /* RFC says return as much as we can without exceeding 576 bytes. */ 607 608 room = dst_mtu(&rt->dst); 609 if (room > 576) 610 room = 576; 611 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 612 room -= sizeof(struct icmphdr); 613 614 icmp_param.data_len = skb_in->len - icmp_param.offset; 615 if (icmp_param.data_len > room) 616 icmp_param.data_len = room; 617 icmp_param.head_len = sizeof(struct icmphdr); 618 619 icmp_push_reply(&icmp_param, &ipc, &rt); 620 ende: 621 ip_rt_put(rt); 622 out_unlock: 623 icmp_xmit_unlock(sk); 624 out:; 625 } 626 EXPORT_SYMBOL(icmp_send); 627 628 629 /* 630 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 631 */ 632 633 static void icmp_unreach(struct sk_buff *skb) 634 { 635 struct iphdr *iph; 636 struct icmphdr *icmph; 637 int hash, protocol; 638 const struct net_protocol *ipprot; 639 u32 info = 0; 640 struct net *net; 641 642 net = dev_net(skb_dst(skb)->dev); 643 644 /* 645 * Incomplete header ? 646 * Only checks for the IP header, there should be an 647 * additional check for longer headers in upper levels. 648 */ 649 650 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 651 goto out_err; 652 653 icmph = icmp_hdr(skb); 654 iph = (struct iphdr *)skb->data; 655 656 if (iph->ihl < 5) /* Mangled header, drop. */ 657 goto out_err; 658 659 if (icmph->type == ICMP_DEST_UNREACH) { 660 switch (icmph->code & 15) { 661 case ICMP_NET_UNREACH: 662 case ICMP_HOST_UNREACH: 663 case ICMP_PROT_UNREACH: 664 case ICMP_PORT_UNREACH: 665 break; 666 case ICMP_FRAG_NEEDED: 667 if (ipv4_config.no_pmtu_disc) { 668 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: fragmentation needed and DF set.\n", 669 &iph->daddr); 670 } else { 671 info = ip_rt_frag_needed(net, iph, 672 ntohs(icmph->un.frag.mtu), 673 skb->dev); 674 if (!info) 675 goto out; 676 } 677 break; 678 case ICMP_SR_FAILED: 679 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: Source Route Failed.\n", 680 &iph->daddr); 681 break; 682 default: 683 break; 684 } 685 if (icmph->code > NR_ICMP_UNREACH) 686 goto out; 687 } else if (icmph->type == ICMP_PARAMETERPROB) 688 info = ntohl(icmph->un.gateway) >> 24; 689 690 /* 691 * Throw it at our lower layers 692 * 693 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 694 * header. 695 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 696 * transport layer. 697 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 698 * transport layer. 699 */ 700 701 /* 702 * Check the other end isnt violating RFC 1122. Some routers send 703 * bogus responses to broadcast frames. If you see this message 704 * first check your netmask matches at both ends, if it does then 705 * get the other vendor to fix their kit. 706 */ 707 708 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 709 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 710 if (net_ratelimit()) 711 printk(KERN_WARNING "%pI4 sent an invalid ICMP " 712 "type %u, code %u " 713 "error to a broadcast: %pI4 on %s\n", 714 &ip_hdr(skb)->saddr, 715 icmph->type, icmph->code, 716 &iph->daddr, 717 skb->dev->name); 718 goto out; 719 } 720 721 /* Checkin full IP header plus 8 bytes of protocol to 722 * avoid additional coding at protocol handlers. 723 */ 724 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 725 goto out; 726 727 iph = (struct iphdr *)skb->data; 728 protocol = iph->protocol; 729 730 /* 731 * Deliver ICMP message to raw sockets. Pretty useless feature? 732 */ 733 raw_icmp_error(skb, protocol, info); 734 735 hash = protocol & (MAX_INET_PROTOS - 1); 736 rcu_read_lock(); 737 ipprot = rcu_dereference(inet_protos[hash]); 738 if (ipprot && ipprot->err_handler) 739 ipprot->err_handler(skb, info); 740 rcu_read_unlock(); 741 742 out: 743 return; 744 out_err: 745 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 746 goto out; 747 } 748 749 750 /* 751 * Handle ICMP_REDIRECT. 752 */ 753 754 static void icmp_redirect(struct sk_buff *skb) 755 { 756 struct iphdr *iph; 757 758 if (skb->len < sizeof(struct iphdr)) 759 goto out_err; 760 761 /* 762 * Get the copied header of the packet that caused the redirect 763 */ 764 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 765 goto out; 766 767 iph = (struct iphdr *)skb->data; 768 769 switch (icmp_hdr(skb)->code & 7) { 770 case ICMP_REDIR_NET: 771 case ICMP_REDIR_NETTOS: 772 /* 773 * As per RFC recommendations now handle it as a host redirect. 774 */ 775 case ICMP_REDIR_HOST: 776 case ICMP_REDIR_HOSTTOS: 777 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 778 icmp_hdr(skb)->un.gateway, 779 iph->saddr, skb->dev); 780 break; 781 } 782 out: 783 return; 784 out_err: 785 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 786 goto out; 787 } 788 789 /* 790 * Handle ICMP_ECHO ("ping") requests. 791 * 792 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 793 * requests. 794 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 795 * included in the reply. 796 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 797 * echo requests, MUST have default=NOT. 798 * See also WRT handling of options once they are done and working. 799 */ 800 801 static void icmp_echo(struct sk_buff *skb) 802 { 803 struct net *net; 804 805 net = dev_net(skb_dst(skb)->dev); 806 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 807 struct icmp_bxm icmp_param; 808 809 icmp_param.data.icmph = *icmp_hdr(skb); 810 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 811 icmp_param.skb = skb; 812 icmp_param.offset = 0; 813 icmp_param.data_len = skb->len; 814 icmp_param.head_len = sizeof(struct icmphdr); 815 icmp_reply(&icmp_param, skb); 816 } 817 } 818 819 /* 820 * Handle ICMP Timestamp requests. 821 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 822 * SHOULD be in the kernel for minimum random latency. 823 * MUST be accurate to a few minutes. 824 * MUST be updated at least at 15Hz. 825 */ 826 static void icmp_timestamp(struct sk_buff *skb) 827 { 828 struct timespec tv; 829 struct icmp_bxm icmp_param; 830 /* 831 * Too short. 832 */ 833 if (skb->len < 4) 834 goto out_err; 835 836 /* 837 * Fill in the current time as ms since midnight UT: 838 */ 839 getnstimeofday(&tv); 840 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 841 tv.tv_nsec / NSEC_PER_MSEC); 842 icmp_param.data.times[2] = icmp_param.data.times[1]; 843 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 844 BUG(); 845 icmp_param.data.icmph = *icmp_hdr(skb); 846 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 847 icmp_param.data.icmph.code = 0; 848 icmp_param.skb = skb; 849 icmp_param.offset = 0; 850 icmp_param.data_len = 0; 851 icmp_param.head_len = sizeof(struct icmphdr) + 12; 852 icmp_reply(&icmp_param, skb); 853 out: 854 return; 855 out_err: 856 ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 857 goto out; 858 } 859 860 861 /* 862 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 863 * 864 * RFC1122 (3.2.2.9). A host MUST only send replies to 865 * ADDRESS_MASK requests if it's been configured as an address mask 866 * agent. Receiving a request doesn't constitute implicit permission to 867 * act as one. Of course, implementing this correctly requires (SHOULD) 868 * a way to turn the functionality on and off. Another one for sysctl(), 869 * I guess. -- MS 870 * 871 * RFC1812 (4.3.3.9). A router MUST implement it. 872 * A router SHOULD have switch turning it on/off. 873 * This switch MUST be ON by default. 874 * 875 * Gratuitous replies, zero-source replies are not implemented, 876 * that complies with RFC. DO NOT implement them!!! All the idea 877 * of broadcast addrmask replies as specified in RFC950 is broken. 878 * The problem is that it is not uncommon to have several prefixes 879 * on one physical interface. Moreover, addrmask agent can even be 880 * not aware of existing another prefixes. 881 * If source is zero, addrmask agent cannot choose correct prefix. 882 * Gratuitous mask announcements suffer from the same problem. 883 * RFC1812 explains it, but still allows to use ADDRMASK, 884 * that is pretty silly. --ANK 885 * 886 * All these rules are so bizarre, that I removed kernel addrmask 887 * support at all. It is wrong, it is obsolete, nobody uses it in 888 * any case. --ANK 889 * 890 * Furthermore you can do it with a usermode address agent program 891 * anyway... 892 */ 893 894 static void icmp_address(struct sk_buff *skb) 895 { 896 #if 0 897 if (net_ratelimit()) 898 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 899 #endif 900 } 901 902 /* 903 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 904 * loudly if an inconsistency is found. 905 * called with rcu_read_lock() 906 */ 907 908 static void icmp_address_reply(struct sk_buff *skb) 909 { 910 struct rtable *rt = skb_rtable(skb); 911 struct net_device *dev = skb->dev; 912 struct in_device *in_dev; 913 struct in_ifaddr *ifa; 914 915 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 916 return; 917 918 in_dev = __in_dev_get_rcu(dev); 919 if (!in_dev) 920 return; 921 922 if (in_dev->ifa_list && 923 IN_DEV_LOG_MARTIANS(in_dev) && 924 IN_DEV_FORWARD(in_dev)) { 925 __be32 _mask, *mp; 926 927 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 928 BUG_ON(mp == NULL); 929 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 930 if (*mp == ifa->ifa_mask && 931 inet_ifa_match(rt->rt_src, ifa)) 932 break; 933 } 934 if (!ifa && net_ratelimit()) { 935 printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n", 936 mp, dev->name, &rt->rt_src); 937 } 938 } 939 } 940 941 static void icmp_discard(struct sk_buff *skb) 942 { 943 } 944 945 /* 946 * Deal with incoming ICMP packets. 947 */ 948 int icmp_rcv(struct sk_buff *skb) 949 { 950 struct icmphdr *icmph; 951 struct rtable *rt = skb_rtable(skb); 952 struct net *net = dev_net(rt->dst.dev); 953 954 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 955 struct sec_path *sp = skb_sec_path(skb); 956 int nh; 957 958 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 959 XFRM_STATE_ICMP)) 960 goto drop; 961 962 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 963 goto drop; 964 965 nh = skb_network_offset(skb); 966 skb_set_network_header(skb, sizeof(*icmph)); 967 968 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 969 goto drop; 970 971 skb_set_network_header(skb, nh); 972 } 973 974 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 975 976 switch (skb->ip_summed) { 977 case CHECKSUM_COMPLETE: 978 if (!csum_fold(skb->csum)) 979 break; 980 /* fall through */ 981 case CHECKSUM_NONE: 982 skb->csum = 0; 983 if (__skb_checksum_complete(skb)) 984 goto error; 985 } 986 987 if (!pskb_pull(skb, sizeof(*icmph))) 988 goto error; 989 990 icmph = icmp_hdr(skb); 991 992 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 993 /* 994 * 18 is the highest 'known' ICMP type. Anything else is a mystery 995 * 996 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 997 * discarded. 998 */ 999 if (icmph->type > NR_ICMP_TYPES) 1000 goto error; 1001 1002 1003 /* 1004 * Parse the ICMP message 1005 */ 1006 1007 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1008 /* 1009 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1010 * silently ignored (we let user decide with a sysctl). 1011 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1012 * discarded if to broadcast/multicast. 1013 */ 1014 if ((icmph->type == ICMP_ECHO || 1015 icmph->type == ICMP_TIMESTAMP) && 1016 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1017 goto error; 1018 } 1019 if (icmph->type != ICMP_ECHO && 1020 icmph->type != ICMP_TIMESTAMP && 1021 icmph->type != ICMP_ADDRESS && 1022 icmph->type != ICMP_ADDRESSREPLY) { 1023 goto error; 1024 } 1025 } 1026 1027 icmp_pointers[icmph->type].handler(skb); 1028 1029 drop: 1030 kfree_skb(skb); 1031 return 0; 1032 error: 1033 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1034 goto drop; 1035 } 1036 1037 /* 1038 * This table is the definition of how we handle ICMP. 1039 */ 1040 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1041 [ICMP_ECHOREPLY] = { 1042 .handler = icmp_discard, 1043 }, 1044 [1] = { 1045 .handler = icmp_discard, 1046 .error = 1, 1047 }, 1048 [2] = { 1049 .handler = icmp_discard, 1050 .error = 1, 1051 }, 1052 [ICMP_DEST_UNREACH] = { 1053 .handler = icmp_unreach, 1054 .error = 1, 1055 }, 1056 [ICMP_SOURCE_QUENCH] = { 1057 .handler = icmp_unreach, 1058 .error = 1, 1059 }, 1060 [ICMP_REDIRECT] = { 1061 .handler = icmp_redirect, 1062 .error = 1, 1063 }, 1064 [6] = { 1065 .handler = icmp_discard, 1066 .error = 1, 1067 }, 1068 [7] = { 1069 .handler = icmp_discard, 1070 .error = 1, 1071 }, 1072 [ICMP_ECHO] = { 1073 .handler = icmp_echo, 1074 }, 1075 [9] = { 1076 .handler = icmp_discard, 1077 .error = 1, 1078 }, 1079 [10] = { 1080 .handler = icmp_discard, 1081 .error = 1, 1082 }, 1083 [ICMP_TIME_EXCEEDED] = { 1084 .handler = icmp_unreach, 1085 .error = 1, 1086 }, 1087 [ICMP_PARAMETERPROB] = { 1088 .handler = icmp_unreach, 1089 .error = 1, 1090 }, 1091 [ICMP_TIMESTAMP] = { 1092 .handler = icmp_timestamp, 1093 }, 1094 [ICMP_TIMESTAMPREPLY] = { 1095 .handler = icmp_discard, 1096 }, 1097 [ICMP_INFO_REQUEST] = { 1098 .handler = icmp_discard, 1099 }, 1100 [ICMP_INFO_REPLY] = { 1101 .handler = icmp_discard, 1102 }, 1103 [ICMP_ADDRESS] = { 1104 .handler = icmp_address, 1105 }, 1106 [ICMP_ADDRESSREPLY] = { 1107 .handler = icmp_address_reply, 1108 }, 1109 }; 1110 1111 static void __net_exit icmp_sk_exit(struct net *net) 1112 { 1113 int i; 1114 1115 for_each_possible_cpu(i) 1116 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1117 kfree(net->ipv4.icmp_sk); 1118 net->ipv4.icmp_sk = NULL; 1119 } 1120 1121 static int __net_init icmp_sk_init(struct net *net) 1122 { 1123 int i, err; 1124 1125 net->ipv4.icmp_sk = 1126 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1127 if (net->ipv4.icmp_sk == NULL) 1128 return -ENOMEM; 1129 1130 for_each_possible_cpu(i) { 1131 struct sock *sk; 1132 1133 err = inet_ctl_sock_create(&sk, PF_INET, 1134 SOCK_RAW, IPPROTO_ICMP, net); 1135 if (err < 0) 1136 goto fail; 1137 1138 net->ipv4.icmp_sk[i] = sk; 1139 1140 /* Enough space for 2 64K ICMP packets, including 1141 * sk_buff struct overhead. 1142 */ 1143 sk->sk_sndbuf = 1144 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1145 1146 /* 1147 * Speedup sock_wfree() 1148 */ 1149 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1150 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1151 } 1152 1153 /* Control parameters for ECHO replies. */ 1154 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1155 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1156 1157 /* Control parameter - ignore bogus broadcast responses? */ 1158 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1159 1160 /* 1161 * Configurable global rate limit. 1162 * 1163 * ratelimit defines tokens/packet consumed for dst->rate_token 1164 * bucket ratemask defines which icmp types are ratelimited by 1165 * setting it's bit position. 1166 * 1167 * default: 1168 * dest unreachable (3), source quench (4), 1169 * time exceeded (11), parameter problem (12) 1170 */ 1171 1172 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1173 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1174 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1175 1176 return 0; 1177 1178 fail: 1179 for_each_possible_cpu(i) 1180 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1181 kfree(net->ipv4.icmp_sk); 1182 return err; 1183 } 1184 1185 static struct pernet_operations __net_initdata icmp_sk_ops = { 1186 .init = icmp_sk_init, 1187 .exit = icmp_sk_exit, 1188 }; 1189 1190 int __init icmp_init(void) 1191 { 1192 return register_pernet_subsys(&icmp_sk_ops); 1193 } 1194