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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 66 67 #include <linux/module.h> 68 #include <linux/types.h> 69 #include <linux/jiffies.h> 70 #include <linux/kernel.h> 71 #include <linux/fcntl.h> 72 #include <linux/socket.h> 73 #include <linux/in.h> 74 #include <linux/inet.h> 75 #include <linux/inetdevice.h> 76 #include <linux/netdevice.h> 77 #include <linux/string.h> 78 #include <linux/netfilter_ipv4.h> 79 #include <linux/slab.h> 80 #include <net/snmp.h> 81 #include <net/ip.h> 82 #include <net/route.h> 83 #include <net/protocol.h> 84 #include <net/icmp.h> 85 #include <net/tcp.h> 86 #include <net/udp.h> 87 #include <net/raw.h> 88 #include <net/ping.h> 89 #include <linux/skbuff.h> 90 #include <net/sock.h> 91 #include <linux/errno.h> 92 #include <linux/timer.h> 93 #include <linux/init.h> 94 #include <asm/uaccess.h> 95 #include <net/checksum.h> 96 #include <net/xfrm.h> 97 #include <net/inet_common.h> 98 #include <net/ip_fib.h> 99 100 /* 101 * Build xmit assembly blocks 102 */ 103 104 struct icmp_bxm { 105 struct sk_buff *skb; 106 int offset; 107 int data_len; 108 109 struct { 110 struct icmphdr icmph; 111 __be32 times[3]; 112 } data; 113 int head_len; 114 struct ip_options_data replyopts; 115 }; 116 117 /* An array of errno for error messages from dest unreach. */ 118 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 119 120 const struct icmp_err icmp_err_convert[] = { 121 { 122 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 123 .fatal = 0, 124 }, 125 { 126 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 127 .fatal = 0, 128 }, 129 { 130 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 131 .fatal = 1, 132 }, 133 { 134 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 135 .fatal = 1, 136 }, 137 { 138 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 139 .fatal = 0, 140 }, 141 { 142 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 143 .fatal = 0, 144 }, 145 { 146 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 147 .fatal = 1, 148 }, 149 { 150 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 151 .fatal = 1, 152 }, 153 { 154 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 155 .fatal = 1, 156 }, 157 { 158 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 159 .fatal = 1, 160 }, 161 { 162 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 163 .fatal = 1, 164 }, 165 { 166 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 167 .fatal = 0, 168 }, 169 { 170 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 171 .fatal = 0, 172 }, 173 { 174 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 175 .fatal = 1, 176 }, 177 { 178 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 179 .fatal = 1, 180 }, 181 { 182 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 183 .fatal = 1, 184 }, 185 }; 186 EXPORT_SYMBOL(icmp_err_convert); 187 188 /* 189 * ICMP control array. This specifies what to do with each ICMP. 190 */ 191 192 struct icmp_control { 193 void (*handler)(struct sk_buff *skb); 194 short error; /* This ICMP is classed as an error message */ 195 }; 196 197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 198 199 /* 200 * The ICMP socket(s). This is the most convenient way to flow control 201 * our ICMP output as well as maintain a clean interface throughout 202 * all layers. All Socketless IP sends will soon be gone. 203 * 204 * On SMP we have one ICMP socket per-cpu. 205 */ 206 static struct sock *icmp_sk(struct net *net) 207 { 208 return net->ipv4.icmp_sk[smp_processor_id()]; 209 } 210 211 static inline struct sock *icmp_xmit_lock(struct net *net) 212 { 213 struct sock *sk; 214 215 local_bh_disable(); 216 217 sk = icmp_sk(net); 218 219 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 220 /* This can happen if the output path signals a 221 * dst_link_failure() for an outgoing ICMP packet. 222 */ 223 local_bh_enable(); 224 return NULL; 225 } 226 return sk; 227 } 228 229 static inline void icmp_xmit_unlock(struct sock *sk) 230 { 231 spin_unlock_bh(&sk->sk_lock.slock); 232 } 233 234 /* 235 * Send an ICMP frame. 236 */ 237 238 static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 239 struct flowi4 *fl4, int type, int code) 240 { 241 struct dst_entry *dst = &rt->dst; 242 bool rc = true; 243 244 if (type > NR_ICMP_TYPES) 245 goto out; 246 247 /* Don't limit PMTU discovery. */ 248 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 249 goto out; 250 251 /* No rate limit on loopback */ 252 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 253 goto out; 254 255 /* Limit if icmp type is enabled in ratemask. */ 256 if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) { 257 struct inet_peer *peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, 1); 258 rc = inet_peer_xrlim_allow(peer, 259 net->ipv4.sysctl_icmp_ratelimit); 260 if (peer) 261 inet_putpeer(peer); 262 } 263 out: 264 return rc; 265 } 266 267 /* 268 * Maintain the counters used in the SNMP statistics for outgoing ICMP 269 */ 270 void icmp_out_count(struct net *net, unsigned char type) 271 { 272 ICMPMSGOUT_INC_STATS(net, type); 273 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 274 } 275 276 /* 277 * Checksum each fragment, and on the first include the headers and final 278 * checksum. 279 */ 280 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 281 struct sk_buff *skb) 282 { 283 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 284 __wsum csum; 285 286 csum = skb_copy_and_csum_bits(icmp_param->skb, 287 icmp_param->offset + offset, 288 to, len, 0); 289 290 skb->csum = csum_block_add(skb->csum, csum, odd); 291 if (icmp_pointers[icmp_param->data.icmph.type].error) 292 nf_ct_attach(skb, icmp_param->skb); 293 return 0; 294 } 295 296 static void icmp_push_reply(struct icmp_bxm *icmp_param, 297 struct flowi4 *fl4, 298 struct ipcm_cookie *ipc, struct rtable **rt) 299 { 300 struct sock *sk; 301 struct sk_buff *skb; 302 303 sk = icmp_sk(dev_net((*rt)->dst.dev)); 304 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 305 icmp_param->data_len+icmp_param->head_len, 306 icmp_param->head_len, 307 ipc, rt, MSG_DONTWAIT) < 0) { 308 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 309 ip_flush_pending_frames(sk); 310 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 311 struct icmphdr *icmph = icmp_hdr(skb); 312 __wsum csum = 0; 313 struct sk_buff *skb1; 314 315 skb_queue_walk(&sk->sk_write_queue, skb1) { 316 csum = csum_add(csum, skb1->csum); 317 } 318 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 319 (char *)icmph, 320 icmp_param->head_len, csum); 321 icmph->checksum = csum_fold(csum); 322 skb->ip_summed = CHECKSUM_NONE; 323 ip_push_pending_frames(sk, fl4); 324 } 325 } 326 327 /* 328 * Driving logic for building and sending ICMP messages. 329 */ 330 331 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 332 { 333 struct ipcm_cookie ipc; 334 struct rtable *rt = skb_rtable(skb); 335 struct net *net = dev_net(rt->dst.dev); 336 struct flowi4 fl4; 337 struct sock *sk; 338 struct inet_sock *inet; 339 __be32 daddr, saddr; 340 u32 mark = IP4_REPLY_MARK(net, skb->mark); 341 342 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb)) 343 return; 344 345 sk = icmp_xmit_lock(net); 346 if (sk == NULL) 347 return; 348 inet = inet_sk(sk); 349 350 icmp_param->data.icmph.checksum = 0; 351 352 inet->tos = ip_hdr(skb)->tos; 353 sk->sk_mark = mark; 354 daddr = ipc.addr = ip_hdr(skb)->saddr; 355 saddr = fib_compute_spec_dst(skb); 356 ipc.opt = NULL; 357 ipc.tx_flags = 0; 358 ipc.ttl = 0; 359 ipc.tos = -1; 360 361 if (icmp_param->replyopts.opt.opt.optlen) { 362 ipc.opt = &icmp_param->replyopts.opt; 363 if (ipc.opt->opt.srr) 364 daddr = icmp_param->replyopts.opt.opt.faddr; 365 } 366 memset(&fl4, 0, sizeof(fl4)); 367 fl4.daddr = daddr; 368 fl4.saddr = saddr; 369 fl4.flowi4_mark = mark; 370 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 371 fl4.flowi4_proto = IPPROTO_ICMP; 372 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 373 rt = ip_route_output_key(net, &fl4); 374 if (IS_ERR(rt)) 375 goto out_unlock; 376 if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type, 377 icmp_param->data.icmph.code)) 378 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 379 ip_rt_put(rt); 380 out_unlock: 381 icmp_xmit_unlock(sk); 382 } 383 384 static struct rtable *icmp_route_lookup(struct net *net, 385 struct flowi4 *fl4, 386 struct sk_buff *skb_in, 387 const struct iphdr *iph, 388 __be32 saddr, u8 tos, u32 mark, 389 int type, int code, 390 struct icmp_bxm *param) 391 { 392 struct rtable *rt, *rt2; 393 struct flowi4 fl4_dec; 394 int err; 395 396 memset(fl4, 0, sizeof(*fl4)); 397 fl4->daddr = (param->replyopts.opt.opt.srr ? 398 param->replyopts.opt.opt.faddr : iph->saddr); 399 fl4->saddr = saddr; 400 fl4->flowi4_mark = mark; 401 fl4->flowi4_tos = RT_TOS(tos); 402 fl4->flowi4_proto = IPPROTO_ICMP; 403 fl4->fl4_icmp_type = type; 404 fl4->fl4_icmp_code = code; 405 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 406 rt = __ip_route_output_key(net, fl4); 407 if (IS_ERR(rt)) 408 return rt; 409 410 /* No need to clone since we're just using its address. */ 411 rt2 = rt; 412 413 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 414 flowi4_to_flowi(fl4), NULL, 0); 415 if (!IS_ERR(rt)) { 416 if (rt != rt2) 417 return rt; 418 } else if (PTR_ERR(rt) == -EPERM) { 419 rt = NULL; 420 } else 421 return rt; 422 423 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 424 if (err) 425 goto relookup_failed; 426 427 if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) { 428 rt2 = __ip_route_output_key(net, &fl4_dec); 429 if (IS_ERR(rt2)) 430 err = PTR_ERR(rt2); 431 } else { 432 struct flowi4 fl4_2 = {}; 433 unsigned long orefdst; 434 435 fl4_2.daddr = fl4_dec.saddr; 436 rt2 = ip_route_output_key(net, &fl4_2); 437 if (IS_ERR(rt2)) { 438 err = PTR_ERR(rt2); 439 goto relookup_failed; 440 } 441 /* Ugh! */ 442 orefdst = skb_in->_skb_refdst; /* save old refdst */ 443 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 444 RT_TOS(tos), rt2->dst.dev); 445 446 dst_release(&rt2->dst); 447 rt2 = skb_rtable(skb_in); 448 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 449 } 450 451 if (err) 452 goto relookup_failed; 453 454 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 455 flowi4_to_flowi(&fl4_dec), NULL, 456 XFRM_LOOKUP_ICMP); 457 if (!IS_ERR(rt2)) { 458 dst_release(&rt->dst); 459 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 460 rt = rt2; 461 } else if (PTR_ERR(rt2) == -EPERM) { 462 if (rt) 463 dst_release(&rt->dst); 464 return rt2; 465 } else { 466 err = PTR_ERR(rt2); 467 goto relookup_failed; 468 } 469 return rt; 470 471 relookup_failed: 472 if (rt) 473 return rt; 474 return ERR_PTR(err); 475 } 476 477 /* 478 * Send an ICMP message in response to a situation 479 * 480 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 481 * MAY send more (we do). 482 * MUST NOT change this header information. 483 * MUST NOT reply to a multicast/broadcast IP address. 484 * MUST NOT reply to a multicast/broadcast MAC address. 485 * MUST reply to only the first fragment. 486 */ 487 488 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 489 { 490 struct iphdr *iph; 491 int room; 492 struct icmp_bxm *icmp_param; 493 struct rtable *rt = skb_rtable(skb_in); 494 struct ipcm_cookie ipc; 495 struct flowi4 fl4; 496 __be32 saddr; 497 u8 tos; 498 u32 mark; 499 struct net *net; 500 struct sock *sk; 501 502 if (!rt) 503 goto out; 504 net = dev_net(rt->dst.dev); 505 506 /* 507 * Find the original header. It is expected to be valid, of course. 508 * Check this, icmp_send is called from the most obscure devices 509 * sometimes. 510 */ 511 iph = ip_hdr(skb_in); 512 513 if ((u8 *)iph < skb_in->head || 514 (skb_network_header(skb_in) + sizeof(*iph)) > 515 skb_tail_pointer(skb_in)) 516 goto out; 517 518 /* 519 * No replies to physical multicast/broadcast 520 */ 521 if (skb_in->pkt_type != PACKET_HOST) 522 goto out; 523 524 /* 525 * Now check at the protocol level 526 */ 527 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 528 goto out; 529 530 /* 531 * Only reply to fragment 0. We byte re-order the constant 532 * mask for efficiency. 533 */ 534 if (iph->frag_off & htons(IP_OFFSET)) 535 goto out; 536 537 /* 538 * If we send an ICMP error to an ICMP error a mess would result.. 539 */ 540 if (icmp_pointers[type].error) { 541 /* 542 * We are an error, check if we are replying to an 543 * ICMP error 544 */ 545 if (iph->protocol == IPPROTO_ICMP) { 546 u8 _inner_type, *itp; 547 548 itp = skb_header_pointer(skb_in, 549 skb_network_header(skb_in) + 550 (iph->ihl << 2) + 551 offsetof(struct icmphdr, 552 type) - 553 skb_in->data, 554 sizeof(_inner_type), 555 &_inner_type); 556 if (itp == NULL) 557 goto out; 558 559 /* 560 * Assume any unknown ICMP type is an error. This 561 * isn't specified by the RFC, but think about it.. 562 */ 563 if (*itp > NR_ICMP_TYPES || 564 icmp_pointers[*itp].error) 565 goto out; 566 } 567 } 568 569 icmp_param = kmalloc(sizeof(*icmp_param), GFP_ATOMIC); 570 if (!icmp_param) 571 return; 572 573 sk = icmp_xmit_lock(net); 574 if (sk == NULL) 575 goto out_free; 576 577 /* 578 * Construct source address and options. 579 */ 580 581 saddr = iph->daddr; 582 if (!(rt->rt_flags & RTCF_LOCAL)) { 583 struct net_device *dev = NULL; 584 585 rcu_read_lock(); 586 if (rt_is_input_route(rt) && 587 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 588 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 589 590 if (dev) 591 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 592 else 593 saddr = 0; 594 rcu_read_unlock(); 595 } 596 597 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 598 IPTOS_PREC_INTERNETCONTROL) : 599 iph->tos; 600 mark = IP4_REPLY_MARK(net, skb_in->mark); 601 602 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb_in)) 603 goto out_unlock; 604 605 606 /* 607 * Prepare data for ICMP header. 608 */ 609 610 icmp_param->data.icmph.type = type; 611 icmp_param->data.icmph.code = code; 612 icmp_param->data.icmph.un.gateway = info; 613 icmp_param->data.icmph.checksum = 0; 614 icmp_param->skb = skb_in; 615 icmp_param->offset = skb_network_offset(skb_in); 616 inet_sk(sk)->tos = tos; 617 sk->sk_mark = mark; 618 ipc.addr = iph->saddr; 619 ipc.opt = &icmp_param->replyopts.opt; 620 ipc.tx_flags = 0; 621 ipc.ttl = 0; 622 ipc.tos = -1; 623 624 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 625 type, code, icmp_param); 626 if (IS_ERR(rt)) 627 goto out_unlock; 628 629 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 630 goto ende; 631 632 /* RFC says return as much as we can without exceeding 576 bytes. */ 633 634 room = dst_mtu(&rt->dst); 635 if (room > 576) 636 room = 576; 637 room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.opt.optlen; 638 room -= sizeof(struct icmphdr); 639 640 icmp_param->data_len = skb_in->len - icmp_param->offset; 641 if (icmp_param->data_len > room) 642 icmp_param->data_len = room; 643 icmp_param->head_len = sizeof(struct icmphdr); 644 645 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 646 ende: 647 ip_rt_put(rt); 648 out_unlock: 649 icmp_xmit_unlock(sk); 650 out_free: 651 kfree(icmp_param); 652 out:; 653 } 654 EXPORT_SYMBOL(icmp_send); 655 656 657 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 658 { 659 const struct iphdr *iph = (const struct iphdr *) skb->data; 660 const struct net_protocol *ipprot; 661 int protocol = iph->protocol; 662 663 /* Checkin full IP header plus 8 bytes of protocol to 664 * avoid additional coding at protocol handlers. 665 */ 666 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 667 return; 668 669 raw_icmp_error(skb, protocol, info); 670 671 rcu_read_lock(); 672 ipprot = rcu_dereference(inet_protos[protocol]); 673 if (ipprot && ipprot->err_handler) 674 ipprot->err_handler(skb, info); 675 rcu_read_unlock(); 676 } 677 678 static bool icmp_tag_validation(int proto) 679 { 680 bool ok; 681 682 rcu_read_lock(); 683 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 684 rcu_read_unlock(); 685 return ok; 686 } 687 688 /* 689 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and 690 * ICMP_PARAMETERPROB. 691 */ 692 693 static void icmp_unreach(struct sk_buff *skb) 694 { 695 const struct iphdr *iph; 696 struct icmphdr *icmph; 697 struct net *net; 698 u32 info = 0; 699 700 net = dev_net(skb_dst(skb)->dev); 701 702 /* 703 * Incomplete header ? 704 * Only checks for the IP header, there should be an 705 * additional check for longer headers in upper levels. 706 */ 707 708 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 709 goto out_err; 710 711 icmph = icmp_hdr(skb); 712 iph = (const struct iphdr *)skb->data; 713 714 if (iph->ihl < 5) /* Mangled header, drop. */ 715 goto out_err; 716 717 if (icmph->type == ICMP_DEST_UNREACH) { 718 switch (icmph->code & 15) { 719 case ICMP_NET_UNREACH: 720 case ICMP_HOST_UNREACH: 721 case ICMP_PROT_UNREACH: 722 case ICMP_PORT_UNREACH: 723 break; 724 case ICMP_FRAG_NEEDED: 725 /* for documentation of the ip_no_pmtu_disc 726 * values please see 727 * Documentation/networking/ip-sysctl.txt 728 */ 729 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 730 default: 731 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"), 732 &iph->daddr); 733 break; 734 case 2: 735 goto out; 736 case 3: 737 if (!icmp_tag_validation(iph->protocol)) 738 goto out; 739 /* fall through */ 740 case 0: 741 info = ntohs(icmph->un.frag.mtu); 742 if (!info) 743 goto out; 744 } 745 break; 746 case ICMP_SR_FAILED: 747 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"), 748 &iph->daddr); 749 break; 750 default: 751 break; 752 } 753 if (icmph->code > NR_ICMP_UNREACH) 754 goto out; 755 } else if (icmph->type == ICMP_PARAMETERPROB) 756 info = ntohl(icmph->un.gateway) >> 24; 757 758 /* 759 * Throw it at our lower layers 760 * 761 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 762 * header. 763 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 764 * transport layer. 765 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 766 * transport layer. 767 */ 768 769 /* 770 * Check the other end isn't violating RFC 1122. Some routers send 771 * bogus responses to broadcast frames. If you see this message 772 * first check your netmask matches at both ends, if it does then 773 * get the other vendor to fix their kit. 774 */ 775 776 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 777 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 778 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 779 &ip_hdr(skb)->saddr, 780 icmph->type, icmph->code, 781 &iph->daddr, skb->dev->name); 782 goto out; 783 } 784 785 icmp_socket_deliver(skb, info); 786 787 out: 788 return; 789 out_err: 790 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 791 goto out; 792 } 793 794 795 /* 796 * Handle ICMP_REDIRECT. 797 */ 798 799 static void icmp_redirect(struct sk_buff *skb) 800 { 801 if (skb->len < sizeof(struct iphdr)) { 802 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 803 return; 804 } 805 806 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 807 return; 808 809 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 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 static void icmp_discard(struct sk_buff *skb) 884 { 885 } 886 887 /* 888 * Deal with incoming ICMP packets. 889 */ 890 int icmp_rcv(struct sk_buff *skb) 891 { 892 struct icmphdr *icmph; 893 struct rtable *rt = skb_rtable(skb); 894 struct net *net = dev_net(rt->dst.dev); 895 896 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 897 struct sec_path *sp = skb_sec_path(skb); 898 int nh; 899 900 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 901 XFRM_STATE_ICMP)) 902 goto drop; 903 904 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 905 goto drop; 906 907 nh = skb_network_offset(skb); 908 skb_set_network_header(skb, sizeof(*icmph)); 909 910 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 911 goto drop; 912 913 skb_set_network_header(skb, nh); 914 } 915 916 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 917 918 if (skb_checksum_simple_validate(skb)) 919 goto csum_error; 920 921 if (!pskb_pull(skb, sizeof(*icmph))) 922 goto error; 923 924 icmph = icmp_hdr(skb); 925 926 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 927 /* 928 * 18 is the highest 'known' ICMP type. Anything else is a mystery 929 * 930 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 931 * discarded. 932 */ 933 if (icmph->type > NR_ICMP_TYPES) 934 goto error; 935 936 937 /* 938 * Parse the ICMP message 939 */ 940 941 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 942 /* 943 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 944 * silently ignored (we let user decide with a sysctl). 945 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 946 * discarded if to broadcast/multicast. 947 */ 948 if ((icmph->type == ICMP_ECHO || 949 icmph->type == ICMP_TIMESTAMP) && 950 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 951 goto error; 952 } 953 if (icmph->type != ICMP_ECHO && 954 icmph->type != ICMP_TIMESTAMP && 955 icmph->type != ICMP_ADDRESS && 956 icmph->type != ICMP_ADDRESSREPLY) { 957 goto error; 958 } 959 } 960 961 icmp_pointers[icmph->type].handler(skb); 962 963 drop: 964 kfree_skb(skb); 965 return 0; 966 csum_error: 967 ICMP_INC_STATS_BH(net, ICMP_MIB_CSUMERRORS); 968 error: 969 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 970 goto drop; 971 } 972 973 void icmp_err(struct sk_buff *skb, u32 info) 974 { 975 struct iphdr *iph = (struct iphdr *)skb->data; 976 int offset = iph->ihl<<2; 977 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 978 int type = icmp_hdr(skb)->type; 979 int code = icmp_hdr(skb)->code; 980 struct net *net = dev_net(skb->dev); 981 982 /* 983 * Use ping_err to handle all icmp errors except those 984 * triggered by ICMP_ECHOREPLY which sent from kernel. 985 */ 986 if (icmph->type != ICMP_ECHOREPLY) { 987 ping_err(skb, offset, info); 988 return; 989 } 990 991 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 992 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 993 else if (type == ICMP_REDIRECT) 994 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 995 } 996 997 /* 998 * This table is the definition of how we handle ICMP. 999 */ 1000 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1001 [ICMP_ECHOREPLY] = { 1002 .handler = ping_rcv, 1003 }, 1004 [1] = { 1005 .handler = icmp_discard, 1006 .error = 1, 1007 }, 1008 [2] = { 1009 .handler = icmp_discard, 1010 .error = 1, 1011 }, 1012 [ICMP_DEST_UNREACH] = { 1013 .handler = icmp_unreach, 1014 .error = 1, 1015 }, 1016 [ICMP_SOURCE_QUENCH] = { 1017 .handler = icmp_unreach, 1018 .error = 1, 1019 }, 1020 [ICMP_REDIRECT] = { 1021 .handler = icmp_redirect, 1022 .error = 1, 1023 }, 1024 [6] = { 1025 .handler = icmp_discard, 1026 .error = 1, 1027 }, 1028 [7] = { 1029 .handler = icmp_discard, 1030 .error = 1, 1031 }, 1032 [ICMP_ECHO] = { 1033 .handler = icmp_echo, 1034 }, 1035 [9] = { 1036 .handler = icmp_discard, 1037 .error = 1, 1038 }, 1039 [10] = { 1040 .handler = icmp_discard, 1041 .error = 1, 1042 }, 1043 [ICMP_TIME_EXCEEDED] = { 1044 .handler = icmp_unreach, 1045 .error = 1, 1046 }, 1047 [ICMP_PARAMETERPROB] = { 1048 .handler = icmp_unreach, 1049 .error = 1, 1050 }, 1051 [ICMP_TIMESTAMP] = { 1052 .handler = icmp_timestamp, 1053 }, 1054 [ICMP_TIMESTAMPREPLY] = { 1055 .handler = icmp_discard, 1056 }, 1057 [ICMP_INFO_REQUEST] = { 1058 .handler = icmp_discard, 1059 }, 1060 [ICMP_INFO_REPLY] = { 1061 .handler = icmp_discard, 1062 }, 1063 [ICMP_ADDRESS] = { 1064 .handler = icmp_discard, 1065 }, 1066 [ICMP_ADDRESSREPLY] = { 1067 .handler = icmp_discard, 1068 }, 1069 }; 1070 1071 static void __net_exit icmp_sk_exit(struct net *net) 1072 { 1073 int i; 1074 1075 for_each_possible_cpu(i) 1076 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1077 kfree(net->ipv4.icmp_sk); 1078 net->ipv4.icmp_sk = NULL; 1079 } 1080 1081 static int __net_init icmp_sk_init(struct net *net) 1082 { 1083 int i, err; 1084 1085 net->ipv4.icmp_sk = 1086 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1087 if (net->ipv4.icmp_sk == NULL) 1088 return -ENOMEM; 1089 1090 for_each_possible_cpu(i) { 1091 struct sock *sk; 1092 1093 err = inet_ctl_sock_create(&sk, PF_INET, 1094 SOCK_RAW, IPPROTO_ICMP, net); 1095 if (err < 0) 1096 goto fail; 1097 1098 net->ipv4.icmp_sk[i] = sk; 1099 1100 /* Enough space for 2 64K ICMP packets, including 1101 * sk_buff/skb_shared_info struct overhead. 1102 */ 1103 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1104 1105 /* 1106 * Speedup sock_wfree() 1107 */ 1108 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1109 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1110 } 1111 1112 /* Control parameters for ECHO replies. */ 1113 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1114 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1115 1116 /* Control parameter - ignore bogus broadcast responses? */ 1117 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1118 1119 /* 1120 * Configurable global rate limit. 1121 * 1122 * ratelimit defines tokens/packet consumed for dst->rate_token 1123 * bucket ratemask defines which icmp types are ratelimited by 1124 * setting it's bit position. 1125 * 1126 * default: 1127 * dest unreachable (3), source quench (4), 1128 * time exceeded (11), parameter problem (12) 1129 */ 1130 1131 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1132 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1133 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1134 1135 return 0; 1136 1137 fail: 1138 for_each_possible_cpu(i) 1139 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1140 kfree(net->ipv4.icmp_sk); 1141 return err; 1142 } 1143 1144 static struct pernet_operations __net_initdata icmp_sk_ops = { 1145 .init = icmp_sk_init, 1146 .exit = icmp_sk_exit, 1147 }; 1148 1149 int __init icmp_init(void) 1150 { 1151 return register_pernet_subsys(&icmp_sk_ops); 1152 } 1153