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/system.h> 95 #include <asm/uaccess.h> 96 #include <net/checksum.h> 97 #include <net/xfrm.h> 98 #include <net/inet_common.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 if (!rt->peer) 258 rt_bind_peer(rt, fl4->daddr, 1); 259 rc = inet_peer_xrlim_allow(rt->peer, 260 net->ipv4.sysctl_icmp_ratelimit); 261 } 262 out: 263 return rc; 264 } 265 266 /* 267 * Maintain the counters used in the SNMP statistics for outgoing ICMP 268 */ 269 void icmp_out_count(struct net *net, unsigned char type) 270 { 271 ICMPMSGOUT_INC_STATS(net, type); 272 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 273 } 274 275 /* 276 * Checksum each fragment, and on the first include the headers and final 277 * checksum. 278 */ 279 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 280 struct sk_buff *skb) 281 { 282 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 283 __wsum csum; 284 285 csum = skb_copy_and_csum_bits(icmp_param->skb, 286 icmp_param->offset + offset, 287 to, len, 0); 288 289 skb->csum = csum_block_add(skb->csum, csum, odd); 290 if (icmp_pointers[icmp_param->data.icmph.type].error) 291 nf_ct_attach(skb, icmp_param->skb); 292 return 0; 293 } 294 295 static void icmp_push_reply(struct icmp_bxm *icmp_param, 296 struct flowi4 *fl4, 297 struct ipcm_cookie *ipc, struct rtable **rt) 298 { 299 struct sock *sk; 300 struct sk_buff *skb; 301 302 sk = icmp_sk(dev_net((*rt)->dst.dev)); 303 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 304 icmp_param->data_len+icmp_param->head_len, 305 icmp_param->head_len, 306 ipc, rt, MSG_DONTWAIT) < 0) { 307 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 308 ip_flush_pending_frames(sk); 309 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 310 struct icmphdr *icmph = icmp_hdr(skb); 311 __wsum csum = 0; 312 struct sk_buff *skb1; 313 314 skb_queue_walk(&sk->sk_write_queue, skb1) { 315 csum = csum_add(csum, skb1->csum); 316 } 317 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 318 (char *)icmph, 319 icmp_param->head_len, csum); 320 icmph->checksum = csum_fold(csum); 321 skb->ip_summed = CHECKSUM_NONE; 322 ip_push_pending_frames(sk, fl4); 323 } 324 } 325 326 /* 327 * Driving logic for building and sending ICMP messages. 328 */ 329 330 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 331 { 332 struct ipcm_cookie ipc; 333 struct rtable *rt = skb_rtable(skb); 334 struct net *net = dev_net(rt->dst.dev); 335 struct flowi4 fl4; 336 struct sock *sk; 337 struct inet_sock *inet; 338 __be32 daddr; 339 340 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb)) 341 return; 342 343 sk = icmp_xmit_lock(net); 344 if (sk == NULL) 345 return; 346 inet = inet_sk(sk); 347 348 icmp_param->data.icmph.checksum = 0; 349 350 inet->tos = ip_hdr(skb)->tos; 351 daddr = ipc.addr = ip_hdr(skb)->saddr; 352 ipc.opt = NULL; 353 ipc.tx_flags = 0; 354 if (icmp_param->replyopts.opt.opt.optlen) { 355 ipc.opt = &icmp_param->replyopts.opt; 356 if (ipc.opt->opt.srr) 357 daddr = icmp_param->replyopts.opt.opt.faddr; 358 } 359 memset(&fl4, 0, sizeof(fl4)); 360 fl4.daddr = daddr; 361 fl4.saddr = rt->rt_spec_dst; 362 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 363 fl4.flowi4_proto = IPPROTO_ICMP; 364 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 365 rt = ip_route_output_key(net, &fl4); 366 if (IS_ERR(rt)) 367 goto out_unlock; 368 if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type, 369 icmp_param->data.icmph.code)) 370 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 371 ip_rt_put(rt); 372 out_unlock: 373 icmp_xmit_unlock(sk); 374 } 375 376 static struct rtable *icmp_route_lookup(struct net *net, 377 struct flowi4 *fl4, 378 struct sk_buff *skb_in, 379 const struct iphdr *iph, 380 __be32 saddr, u8 tos, 381 int type, int code, 382 struct icmp_bxm *param) 383 { 384 struct rtable *rt, *rt2; 385 struct flowi4 fl4_dec; 386 int err; 387 388 memset(fl4, 0, sizeof(*fl4)); 389 fl4->daddr = (param->replyopts.opt.opt.srr ? 390 param->replyopts.opt.opt.faddr : iph->saddr); 391 fl4->saddr = saddr; 392 fl4->flowi4_tos = RT_TOS(tos); 393 fl4->flowi4_proto = IPPROTO_ICMP; 394 fl4->fl4_icmp_type = type; 395 fl4->fl4_icmp_code = code; 396 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 397 rt = __ip_route_output_key(net, fl4); 398 if (IS_ERR(rt)) 399 return rt; 400 401 /* No need to clone since we're just using its address. */ 402 rt2 = rt; 403 404 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 405 flowi4_to_flowi(fl4), NULL, 0); 406 if (!IS_ERR(rt)) { 407 if (rt != rt2) 408 return rt; 409 } else if (PTR_ERR(rt) == -EPERM) { 410 rt = NULL; 411 } else 412 return rt; 413 414 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 415 if (err) 416 goto relookup_failed; 417 418 if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) { 419 rt2 = __ip_route_output_key(net, &fl4_dec); 420 if (IS_ERR(rt2)) 421 err = PTR_ERR(rt2); 422 } else { 423 struct flowi4 fl4_2 = {}; 424 unsigned long orefdst; 425 426 fl4_2.daddr = fl4_dec.saddr; 427 rt2 = ip_route_output_key(net, &fl4_2); 428 if (IS_ERR(rt2)) { 429 err = PTR_ERR(rt2); 430 goto relookup_failed; 431 } 432 /* Ugh! */ 433 orefdst = skb_in->_skb_refdst; /* save old refdst */ 434 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 435 RT_TOS(tos), rt2->dst.dev); 436 437 dst_release(&rt2->dst); 438 rt2 = skb_rtable(skb_in); 439 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 440 } 441 442 if (err) 443 goto relookup_failed; 444 445 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 446 flowi4_to_flowi(&fl4_dec), NULL, 447 XFRM_LOOKUP_ICMP); 448 if (!IS_ERR(rt2)) { 449 dst_release(&rt->dst); 450 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 451 rt = rt2; 452 } else if (PTR_ERR(rt2) == -EPERM) { 453 if (rt) 454 dst_release(&rt->dst); 455 return rt2; 456 } else { 457 err = PTR_ERR(rt2); 458 goto relookup_failed; 459 } 460 return rt; 461 462 relookup_failed: 463 if (rt) 464 return rt; 465 return ERR_PTR(err); 466 } 467 468 /* 469 * Send an ICMP message in response to a situation 470 * 471 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 472 * MAY send more (we do). 473 * MUST NOT change this header information. 474 * MUST NOT reply to a multicast/broadcast IP address. 475 * MUST NOT reply to a multicast/broadcast MAC address. 476 * MUST reply to only the first fragment. 477 */ 478 479 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 480 { 481 struct iphdr *iph; 482 int room; 483 struct icmp_bxm icmp_param; 484 struct rtable *rt = skb_rtable(skb_in); 485 struct ipcm_cookie ipc; 486 struct flowi4 fl4; 487 __be32 saddr; 488 u8 tos; 489 struct net *net; 490 struct sock *sk; 491 492 if (!rt) 493 goto out; 494 net = dev_net(rt->dst.dev); 495 496 /* 497 * Find the original header. It is expected to be valid, of course. 498 * Check this, icmp_send is called from the most obscure devices 499 * sometimes. 500 */ 501 iph = ip_hdr(skb_in); 502 503 if ((u8 *)iph < skb_in->head || 504 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 505 goto out; 506 507 /* 508 * No replies to physical multicast/broadcast 509 */ 510 if (skb_in->pkt_type != PACKET_HOST) 511 goto out; 512 513 /* 514 * Now check at the protocol level 515 */ 516 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 517 goto out; 518 519 /* 520 * Only reply to fragment 0. We byte re-order the constant 521 * mask for efficiency. 522 */ 523 if (iph->frag_off & htons(IP_OFFSET)) 524 goto out; 525 526 /* 527 * If we send an ICMP error to an ICMP error a mess would result.. 528 */ 529 if (icmp_pointers[type].error) { 530 /* 531 * We are an error, check if we are replying to an 532 * ICMP error 533 */ 534 if (iph->protocol == IPPROTO_ICMP) { 535 u8 _inner_type, *itp; 536 537 itp = skb_header_pointer(skb_in, 538 skb_network_header(skb_in) + 539 (iph->ihl << 2) + 540 offsetof(struct icmphdr, 541 type) - 542 skb_in->data, 543 sizeof(_inner_type), 544 &_inner_type); 545 if (itp == NULL) 546 goto out; 547 548 /* 549 * Assume any unknown ICMP type is an error. This 550 * isn't specified by the RFC, but think about it.. 551 */ 552 if (*itp > NR_ICMP_TYPES || 553 icmp_pointers[*itp].error) 554 goto out; 555 } 556 } 557 558 sk = icmp_xmit_lock(net); 559 if (sk == NULL) 560 return; 561 562 /* 563 * Construct source address and options. 564 */ 565 566 saddr = iph->daddr; 567 if (!(rt->rt_flags & RTCF_LOCAL)) { 568 struct net_device *dev = NULL; 569 570 rcu_read_lock(); 571 if (rt_is_input_route(rt) && 572 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 573 dev = dev_get_by_index_rcu(net, rt->rt_iif); 574 575 if (dev) 576 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 577 else 578 saddr = 0; 579 rcu_read_unlock(); 580 } 581 582 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 583 IPTOS_PREC_INTERNETCONTROL) : 584 iph->tos; 585 586 if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in)) 587 goto out_unlock; 588 589 590 /* 591 * Prepare data for ICMP header. 592 */ 593 594 icmp_param.data.icmph.type = type; 595 icmp_param.data.icmph.code = code; 596 icmp_param.data.icmph.un.gateway = info; 597 icmp_param.data.icmph.checksum = 0; 598 icmp_param.skb = skb_in; 599 icmp_param.offset = skb_network_offset(skb_in); 600 inet_sk(sk)->tos = tos; 601 ipc.addr = iph->saddr; 602 ipc.opt = &icmp_param.replyopts.opt; 603 ipc.tx_flags = 0; 604 605 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, 606 type, code, &icmp_param); 607 if (IS_ERR(rt)) 608 goto out_unlock; 609 610 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 611 goto ende; 612 613 /* RFC says return as much as we can without exceeding 576 bytes. */ 614 615 room = dst_mtu(&rt->dst); 616 if (room > 576) 617 room = 576; 618 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 619 room -= sizeof(struct icmphdr); 620 621 icmp_param.data_len = skb_in->len - icmp_param.offset; 622 if (icmp_param.data_len > room) 623 icmp_param.data_len = room; 624 icmp_param.head_len = sizeof(struct icmphdr); 625 626 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 627 ende: 628 ip_rt_put(rt); 629 out_unlock: 630 icmp_xmit_unlock(sk); 631 out:; 632 } 633 EXPORT_SYMBOL(icmp_send); 634 635 636 /* 637 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 638 */ 639 640 static void icmp_unreach(struct sk_buff *skb) 641 { 642 const struct iphdr *iph; 643 struct icmphdr *icmph; 644 int hash, protocol; 645 const struct net_protocol *ipprot; 646 u32 info = 0; 647 struct net *net; 648 649 net = dev_net(skb_dst(skb)->dev); 650 651 /* 652 * Incomplete header ? 653 * Only checks for the IP header, there should be an 654 * additional check for longer headers in upper levels. 655 */ 656 657 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 658 goto out_err; 659 660 icmph = icmp_hdr(skb); 661 iph = (const struct iphdr *)skb->data; 662 663 if (iph->ihl < 5) /* Mangled header, drop. */ 664 goto out_err; 665 666 if (icmph->type == ICMP_DEST_UNREACH) { 667 switch (icmph->code & 15) { 668 case ICMP_NET_UNREACH: 669 case ICMP_HOST_UNREACH: 670 case ICMP_PROT_UNREACH: 671 case ICMP_PORT_UNREACH: 672 break; 673 case ICMP_FRAG_NEEDED: 674 if (ipv4_config.no_pmtu_disc) { 675 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"), 676 &iph->daddr); 677 } else { 678 info = ip_rt_frag_needed(net, iph, 679 ntohs(icmph->un.frag.mtu), 680 skb->dev); 681 if (!info) 682 goto out; 683 } 684 break; 685 case ICMP_SR_FAILED: 686 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"), 687 &iph->daddr); 688 break; 689 default: 690 break; 691 } 692 if (icmph->code > NR_ICMP_UNREACH) 693 goto out; 694 } else if (icmph->type == ICMP_PARAMETERPROB) 695 info = ntohl(icmph->un.gateway) >> 24; 696 697 /* 698 * Throw it at our lower layers 699 * 700 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 701 * header. 702 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 703 * transport layer. 704 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 705 * transport layer. 706 */ 707 708 /* 709 * Check the other end isn't violating RFC 1122. Some routers send 710 * bogus responses to broadcast frames. If you see this message 711 * first check your netmask matches at both ends, if it does then 712 * get the other vendor to fix their kit. 713 */ 714 715 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 716 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 717 if (net_ratelimit()) 718 pr_warn("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 719 &ip_hdr(skb)->saddr, 720 icmph->type, icmph->code, 721 &iph->daddr, skb->dev->name); 722 goto out; 723 } 724 725 /* Checkin full IP header plus 8 bytes of protocol to 726 * avoid additional coding at protocol handlers. 727 */ 728 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 729 goto out; 730 731 iph = (const struct iphdr *)skb->data; 732 protocol = iph->protocol; 733 734 /* 735 * Deliver ICMP message to raw sockets. Pretty useless feature? 736 */ 737 raw_icmp_error(skb, protocol, info); 738 739 hash = protocol & (MAX_INET_PROTOS - 1); 740 rcu_read_lock(); 741 ipprot = rcu_dereference(inet_protos[hash]); 742 if (ipprot && ipprot->err_handler) 743 ipprot->err_handler(skb, info); 744 rcu_read_unlock(); 745 746 out: 747 return; 748 out_err: 749 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 750 goto out; 751 } 752 753 754 /* 755 * Handle ICMP_REDIRECT. 756 */ 757 758 static void icmp_redirect(struct sk_buff *skb) 759 { 760 const struct iphdr *iph; 761 762 if (skb->len < sizeof(struct iphdr)) 763 goto out_err; 764 765 /* 766 * Get the copied header of the packet that caused the redirect 767 */ 768 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 769 goto out; 770 771 iph = (const struct iphdr *)skb->data; 772 773 switch (icmp_hdr(skb)->code & 7) { 774 case ICMP_REDIR_NET: 775 case ICMP_REDIR_NETTOS: 776 /* 777 * As per RFC recommendations now handle it as a host redirect. 778 */ 779 case ICMP_REDIR_HOST: 780 case ICMP_REDIR_HOSTTOS: 781 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 782 icmp_hdr(skb)->un.gateway, 783 iph->saddr, skb->dev); 784 break; 785 } 786 787 /* Ping wants to see redirects. 788 * Let's pretend they are errors of sorts... */ 789 if (iph->protocol == IPPROTO_ICMP && 790 iph->ihl >= 5 && 791 pskb_may_pull(skb, (iph->ihl<<2)+8)) { 792 ping_err(skb, icmp_hdr(skb)->un.gateway); 793 } 794 795 out: 796 return; 797 out_err: 798 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 799 goto out; 800 } 801 802 /* 803 * Handle ICMP_ECHO ("ping") requests. 804 * 805 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 806 * requests. 807 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 808 * included in the reply. 809 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 810 * echo requests, MUST have default=NOT. 811 * See also WRT handling of options once they are done and working. 812 */ 813 814 static void icmp_echo(struct sk_buff *skb) 815 { 816 struct net *net; 817 818 net = dev_net(skb_dst(skb)->dev); 819 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 820 struct icmp_bxm icmp_param; 821 822 icmp_param.data.icmph = *icmp_hdr(skb); 823 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 824 icmp_param.skb = skb; 825 icmp_param.offset = 0; 826 icmp_param.data_len = skb->len; 827 icmp_param.head_len = sizeof(struct icmphdr); 828 icmp_reply(&icmp_param, skb); 829 } 830 } 831 832 /* 833 * Handle ICMP Timestamp requests. 834 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 835 * SHOULD be in the kernel for minimum random latency. 836 * MUST be accurate to a few minutes. 837 * MUST be updated at least at 15Hz. 838 */ 839 static void icmp_timestamp(struct sk_buff *skb) 840 { 841 struct timespec tv; 842 struct icmp_bxm icmp_param; 843 /* 844 * Too short. 845 */ 846 if (skb->len < 4) 847 goto out_err; 848 849 /* 850 * Fill in the current time as ms since midnight UT: 851 */ 852 getnstimeofday(&tv); 853 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 854 tv.tv_nsec / NSEC_PER_MSEC); 855 icmp_param.data.times[2] = icmp_param.data.times[1]; 856 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 857 BUG(); 858 icmp_param.data.icmph = *icmp_hdr(skb); 859 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 860 icmp_param.data.icmph.code = 0; 861 icmp_param.skb = skb; 862 icmp_param.offset = 0; 863 icmp_param.data_len = 0; 864 icmp_param.head_len = sizeof(struct icmphdr) + 12; 865 icmp_reply(&icmp_param, skb); 866 out: 867 return; 868 out_err: 869 ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 870 goto out; 871 } 872 873 874 /* 875 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 876 * 877 * RFC1122 (3.2.2.9). A host MUST only send replies to 878 * ADDRESS_MASK requests if it's been configured as an address mask 879 * agent. Receiving a request doesn't constitute implicit permission to 880 * act as one. Of course, implementing this correctly requires (SHOULD) 881 * a way to turn the functionality on and off. Another one for sysctl(), 882 * I guess. -- MS 883 * 884 * RFC1812 (4.3.3.9). A router MUST implement it. 885 * A router SHOULD have switch turning it on/off. 886 * This switch MUST be ON by default. 887 * 888 * Gratuitous replies, zero-source replies are not implemented, 889 * that complies with RFC. DO NOT implement them!!! All the idea 890 * of broadcast addrmask replies as specified in RFC950 is broken. 891 * The problem is that it is not uncommon to have several prefixes 892 * on one physical interface. Moreover, addrmask agent can even be 893 * not aware of existing another prefixes. 894 * If source is zero, addrmask agent cannot choose correct prefix. 895 * Gratuitous mask announcements suffer from the same problem. 896 * RFC1812 explains it, but still allows to use ADDRMASK, 897 * that is pretty silly. --ANK 898 * 899 * All these rules are so bizarre, that I removed kernel addrmask 900 * support at all. It is wrong, it is obsolete, nobody uses it in 901 * any case. --ANK 902 * 903 * Furthermore you can do it with a usermode address agent program 904 * anyway... 905 */ 906 907 static void icmp_address(struct sk_buff *skb) 908 { 909 #if 0 910 if (net_ratelimit()) 911 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 912 #endif 913 } 914 915 /* 916 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 917 * loudly if an inconsistency is found. 918 * called with rcu_read_lock() 919 */ 920 921 static void icmp_address_reply(struct sk_buff *skb) 922 { 923 struct rtable *rt = skb_rtable(skb); 924 struct net_device *dev = skb->dev; 925 struct in_device *in_dev; 926 struct in_ifaddr *ifa; 927 928 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 929 return; 930 931 in_dev = __in_dev_get_rcu(dev); 932 if (!in_dev) 933 return; 934 935 if (in_dev->ifa_list && 936 IN_DEV_LOG_MARTIANS(in_dev) && 937 IN_DEV_FORWARD(in_dev)) { 938 __be32 _mask, *mp; 939 940 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 941 BUG_ON(mp == NULL); 942 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 943 if (*mp == ifa->ifa_mask && 944 inet_ifa_match(ip_hdr(skb)->saddr, ifa)) 945 break; 946 } 947 if (!ifa && net_ratelimit()) { 948 pr_info("Wrong address mask %pI4 from %s/%pI4\n", 949 mp, dev->name, &ip_hdr(skb)->saddr); 950 } 951 } 952 } 953 954 static void icmp_discard(struct sk_buff *skb) 955 { 956 } 957 958 /* 959 * Deal with incoming ICMP packets. 960 */ 961 int icmp_rcv(struct sk_buff *skb) 962 { 963 struct icmphdr *icmph; 964 struct rtable *rt = skb_rtable(skb); 965 struct net *net = dev_net(rt->dst.dev); 966 967 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 968 struct sec_path *sp = skb_sec_path(skb); 969 int nh; 970 971 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 972 XFRM_STATE_ICMP)) 973 goto drop; 974 975 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 976 goto drop; 977 978 nh = skb_network_offset(skb); 979 skb_set_network_header(skb, sizeof(*icmph)); 980 981 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 982 goto drop; 983 984 skb_set_network_header(skb, nh); 985 } 986 987 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 988 989 switch (skb->ip_summed) { 990 case CHECKSUM_COMPLETE: 991 if (!csum_fold(skb->csum)) 992 break; 993 /* fall through */ 994 case CHECKSUM_NONE: 995 skb->csum = 0; 996 if (__skb_checksum_complete(skb)) 997 goto error; 998 } 999 1000 if (!pskb_pull(skb, sizeof(*icmph))) 1001 goto error; 1002 1003 icmph = icmp_hdr(skb); 1004 1005 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1006 /* 1007 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1008 * 1009 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1010 * discarded. 1011 */ 1012 if (icmph->type > NR_ICMP_TYPES) 1013 goto error; 1014 1015 1016 /* 1017 * Parse the ICMP message 1018 */ 1019 1020 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1021 /* 1022 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1023 * silently ignored (we let user decide with a sysctl). 1024 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1025 * discarded if to broadcast/multicast. 1026 */ 1027 if ((icmph->type == ICMP_ECHO || 1028 icmph->type == ICMP_TIMESTAMP) && 1029 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1030 goto error; 1031 } 1032 if (icmph->type != ICMP_ECHO && 1033 icmph->type != ICMP_TIMESTAMP && 1034 icmph->type != ICMP_ADDRESS && 1035 icmph->type != ICMP_ADDRESSREPLY) { 1036 goto error; 1037 } 1038 } 1039 1040 icmp_pointers[icmph->type].handler(skb); 1041 1042 drop: 1043 kfree_skb(skb); 1044 return 0; 1045 error: 1046 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1047 goto drop; 1048 } 1049 1050 /* 1051 * This table is the definition of how we handle ICMP. 1052 */ 1053 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1054 [ICMP_ECHOREPLY] = { 1055 .handler = ping_rcv, 1056 }, 1057 [1] = { 1058 .handler = icmp_discard, 1059 .error = 1, 1060 }, 1061 [2] = { 1062 .handler = icmp_discard, 1063 .error = 1, 1064 }, 1065 [ICMP_DEST_UNREACH] = { 1066 .handler = icmp_unreach, 1067 .error = 1, 1068 }, 1069 [ICMP_SOURCE_QUENCH] = { 1070 .handler = icmp_unreach, 1071 .error = 1, 1072 }, 1073 [ICMP_REDIRECT] = { 1074 .handler = icmp_redirect, 1075 .error = 1, 1076 }, 1077 [6] = { 1078 .handler = icmp_discard, 1079 .error = 1, 1080 }, 1081 [7] = { 1082 .handler = icmp_discard, 1083 .error = 1, 1084 }, 1085 [ICMP_ECHO] = { 1086 .handler = icmp_echo, 1087 }, 1088 [9] = { 1089 .handler = icmp_discard, 1090 .error = 1, 1091 }, 1092 [10] = { 1093 .handler = icmp_discard, 1094 .error = 1, 1095 }, 1096 [ICMP_TIME_EXCEEDED] = { 1097 .handler = icmp_unreach, 1098 .error = 1, 1099 }, 1100 [ICMP_PARAMETERPROB] = { 1101 .handler = icmp_unreach, 1102 .error = 1, 1103 }, 1104 [ICMP_TIMESTAMP] = { 1105 .handler = icmp_timestamp, 1106 }, 1107 [ICMP_TIMESTAMPREPLY] = { 1108 .handler = icmp_discard, 1109 }, 1110 [ICMP_INFO_REQUEST] = { 1111 .handler = icmp_discard, 1112 }, 1113 [ICMP_INFO_REPLY] = { 1114 .handler = icmp_discard, 1115 }, 1116 [ICMP_ADDRESS] = { 1117 .handler = icmp_address, 1118 }, 1119 [ICMP_ADDRESSREPLY] = { 1120 .handler = icmp_address_reply, 1121 }, 1122 }; 1123 1124 static void __net_exit icmp_sk_exit(struct net *net) 1125 { 1126 int i; 1127 1128 for_each_possible_cpu(i) 1129 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1130 kfree(net->ipv4.icmp_sk); 1131 net->ipv4.icmp_sk = NULL; 1132 } 1133 1134 static int __net_init icmp_sk_init(struct net *net) 1135 { 1136 int i, err; 1137 1138 net->ipv4.icmp_sk = 1139 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1140 if (net->ipv4.icmp_sk == NULL) 1141 return -ENOMEM; 1142 1143 for_each_possible_cpu(i) { 1144 struct sock *sk; 1145 1146 err = inet_ctl_sock_create(&sk, PF_INET, 1147 SOCK_RAW, IPPROTO_ICMP, net); 1148 if (err < 0) 1149 goto fail; 1150 1151 net->ipv4.icmp_sk[i] = sk; 1152 1153 /* Enough space for 2 64K ICMP packets, including 1154 * sk_buff/skb_shared_info struct overhead. 1155 */ 1156 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1157 1158 /* 1159 * Speedup sock_wfree() 1160 */ 1161 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1162 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1163 } 1164 1165 /* Control parameters for ECHO replies. */ 1166 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1167 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1168 1169 /* Control parameter - ignore bogus broadcast responses? */ 1170 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1171 1172 /* 1173 * Configurable global rate limit. 1174 * 1175 * ratelimit defines tokens/packet consumed for dst->rate_token 1176 * bucket ratemask defines which icmp types are ratelimited by 1177 * setting it's bit position. 1178 * 1179 * default: 1180 * dest unreachable (3), source quench (4), 1181 * time exceeded (11), parameter problem (12) 1182 */ 1183 1184 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1185 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1186 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1187 1188 return 0; 1189 1190 fail: 1191 for_each_possible_cpu(i) 1192 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1193 kfree(net->ipv4.icmp_sk); 1194 return err; 1195 } 1196 1197 static struct pernet_operations __net_initdata icmp_sk_ops = { 1198 .init = icmp_sk_init, 1199 .exit = icmp_sk_exit, 1200 }; 1201 1202 int __init icmp_init(void) 1203 { 1204 return register_pernet_subsys(&icmp_sk_ops); 1205 } 1206