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 <net/ping.h> 87 #include <linux/skbuff.h> 88 #include <net/sock.h> 89 #include <linux/errno.h> 90 #include <linux/timer.h> 91 #include <linux/init.h> 92 #include <asm/system.h> 93 #include <asm/uaccess.h> 94 #include <net/checksum.h> 95 #include <net/xfrm.h> 96 #include <net/inet_common.h> 97 98 /* 99 * Build xmit assembly blocks 100 */ 101 102 struct icmp_bxm { 103 struct sk_buff *skb; 104 int offset; 105 int data_len; 106 107 struct { 108 struct icmphdr icmph; 109 __be32 times[3]; 110 } data; 111 int head_len; 112 struct ip_options_data replyopts; 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 struct flowi4 *fl4, 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, fl4->daddr, 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 flowi4 *fl4, 295 struct ipcm_cookie *ipc, struct rtable **rt) 296 { 297 struct sock *sk; 298 struct sk_buff *skb; 299 300 sk = icmp_sk(dev_net((*rt)->dst.dev)); 301 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 302 icmp_param->data_len+icmp_param->head_len, 303 icmp_param->head_len, 304 ipc, rt, MSG_DONTWAIT) < 0) { 305 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 306 ip_flush_pending_frames(sk); 307 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 308 struct icmphdr *icmph = icmp_hdr(skb); 309 __wsum csum = 0; 310 struct sk_buff *skb1; 311 312 skb_queue_walk(&sk->sk_write_queue, skb1) { 313 csum = csum_add(csum, skb1->csum); 314 } 315 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 316 (char *)icmph, 317 icmp_param->head_len, csum); 318 icmph->checksum = csum_fold(csum); 319 skb->ip_summed = CHECKSUM_NONE; 320 ip_push_pending_frames(sk, fl4); 321 } 322 } 323 324 /* 325 * Driving logic for building and sending ICMP messages. 326 */ 327 328 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 329 { 330 struct ipcm_cookie ipc; 331 struct rtable *rt = skb_rtable(skb); 332 struct net *net = dev_net(rt->dst.dev); 333 struct flowi4 fl4; 334 struct sock *sk; 335 struct inet_sock *inet; 336 __be32 daddr; 337 338 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb)) 339 return; 340 341 sk = icmp_xmit_lock(net); 342 if (sk == NULL) 343 return; 344 inet = inet_sk(sk); 345 346 icmp_param->data.icmph.checksum = 0; 347 348 inet->tos = ip_hdr(skb)->tos; 349 daddr = ipc.addr = ip_hdr(skb)->saddr; 350 ipc.opt = NULL; 351 ipc.tx_flags = 0; 352 if (icmp_param->replyopts.opt.opt.optlen) { 353 ipc.opt = &icmp_param->replyopts.opt; 354 if (ipc.opt->opt.srr) 355 daddr = icmp_param->replyopts.opt.opt.faddr; 356 } 357 memset(&fl4, 0, sizeof(fl4)); 358 fl4.daddr = daddr; 359 fl4.saddr = rt->rt_spec_dst; 360 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 361 fl4.flowi4_proto = IPPROTO_ICMP; 362 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 363 rt = ip_route_output_key(net, &fl4); 364 if (IS_ERR(rt)) 365 goto out_unlock; 366 if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type, 367 icmp_param->data.icmph.code)) 368 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 369 ip_rt_put(rt); 370 out_unlock: 371 icmp_xmit_unlock(sk); 372 } 373 374 static struct rtable *icmp_route_lookup(struct net *net, 375 struct flowi4 *fl4, 376 struct sk_buff *skb_in, 377 const struct iphdr *iph, 378 __be32 saddr, u8 tos, 379 int type, int code, 380 struct icmp_bxm *param) 381 { 382 struct rtable *rt, *rt2; 383 struct flowi4 fl4_dec; 384 int err; 385 386 memset(fl4, 0, sizeof(*fl4)); 387 fl4->daddr = (param->replyopts.opt.opt.srr ? 388 param->replyopts.opt.opt.faddr : iph->saddr); 389 fl4->saddr = saddr; 390 fl4->flowi4_tos = RT_TOS(tos); 391 fl4->flowi4_proto = IPPROTO_ICMP; 392 fl4->fl4_icmp_type = type; 393 fl4->fl4_icmp_code = code; 394 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 395 rt = __ip_route_output_key(net, fl4); 396 if (IS_ERR(rt)) 397 return rt; 398 399 /* No need to clone since we're just using its address. */ 400 rt2 = rt; 401 402 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 403 flowi4_to_flowi(fl4), NULL, 0); 404 if (!IS_ERR(rt)) { 405 if (rt != rt2) 406 return rt; 407 } else if (PTR_ERR(rt) == -EPERM) { 408 rt = NULL; 409 } else 410 return rt; 411 412 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 413 if (err) 414 goto relookup_failed; 415 416 if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) { 417 rt2 = __ip_route_output_key(net, &fl4_dec); 418 if (IS_ERR(rt2)) 419 err = PTR_ERR(rt2); 420 } else { 421 struct flowi4 fl4_2 = {}; 422 unsigned long orefdst; 423 424 fl4_2.daddr = fl4_dec.saddr; 425 rt2 = ip_route_output_key(net, &fl4_2); 426 if (IS_ERR(rt2)) { 427 err = PTR_ERR(rt2); 428 goto relookup_failed; 429 } 430 /* Ugh! */ 431 orefdst = skb_in->_skb_refdst; /* save old refdst */ 432 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 433 RT_TOS(tos), rt2->dst.dev); 434 435 dst_release(&rt2->dst); 436 rt2 = skb_rtable(skb_in); 437 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 438 } 439 440 if (err) 441 goto relookup_failed; 442 443 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 444 flowi4_to_flowi(&fl4_dec), NULL, 445 XFRM_LOOKUP_ICMP); 446 if (!IS_ERR(rt2)) { 447 dst_release(&rt->dst); 448 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 449 rt = rt2; 450 } else if (PTR_ERR(rt2) == -EPERM) { 451 if (rt) 452 dst_release(&rt->dst); 453 return rt2; 454 } else { 455 err = PTR_ERR(rt2); 456 goto relookup_failed; 457 } 458 return rt; 459 460 relookup_failed: 461 if (rt) 462 return rt; 463 return ERR_PTR(err); 464 } 465 466 /* 467 * Send an ICMP message in response to a situation 468 * 469 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 470 * MAY send more (we do). 471 * MUST NOT change this header information. 472 * MUST NOT reply to a multicast/broadcast IP address. 473 * MUST NOT reply to a multicast/broadcast MAC address. 474 * MUST reply to only the first fragment. 475 */ 476 477 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 478 { 479 struct iphdr *iph; 480 int room; 481 struct icmp_bxm icmp_param; 482 struct rtable *rt = skb_rtable(skb_in); 483 struct ipcm_cookie ipc; 484 struct flowi4 fl4; 485 __be32 saddr; 486 u8 tos; 487 struct net *net; 488 struct sock *sk; 489 490 if (!rt) 491 goto out; 492 net = dev_net(rt->dst.dev); 493 494 /* 495 * Find the original header. It is expected to be valid, of course. 496 * Check this, icmp_send is called from the most obscure devices 497 * sometimes. 498 */ 499 iph = ip_hdr(skb_in); 500 501 if ((u8 *)iph < skb_in->head || 502 (skb_in->network_header + sizeof(*iph)) > skb_in->tail) 503 goto out; 504 505 /* 506 * No replies to physical multicast/broadcast 507 */ 508 if (skb_in->pkt_type != PACKET_HOST) 509 goto out; 510 511 /* 512 * Now check at the protocol level 513 */ 514 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 515 goto out; 516 517 /* 518 * Only reply to fragment 0. We byte re-order the constant 519 * mask for efficiency. 520 */ 521 if (iph->frag_off & htons(IP_OFFSET)) 522 goto out; 523 524 /* 525 * If we send an ICMP error to an ICMP error a mess would result.. 526 */ 527 if (icmp_pointers[type].error) { 528 /* 529 * We are an error, check if we are replying to an 530 * ICMP error 531 */ 532 if (iph->protocol == IPPROTO_ICMP) { 533 u8 _inner_type, *itp; 534 535 itp = skb_header_pointer(skb_in, 536 skb_network_header(skb_in) + 537 (iph->ihl << 2) + 538 offsetof(struct icmphdr, 539 type) - 540 skb_in->data, 541 sizeof(_inner_type), 542 &_inner_type); 543 if (itp == NULL) 544 goto out; 545 546 /* 547 * Assume any unknown ICMP type is an error. This 548 * isn't specified by the RFC, but think about it.. 549 */ 550 if (*itp > NR_ICMP_TYPES || 551 icmp_pointers[*itp].error) 552 goto out; 553 } 554 } 555 556 sk = icmp_xmit_lock(net); 557 if (sk == NULL) 558 return; 559 560 /* 561 * Construct source address and options. 562 */ 563 564 saddr = iph->daddr; 565 if (!(rt->rt_flags & RTCF_LOCAL)) { 566 struct net_device *dev = NULL; 567 568 rcu_read_lock(); 569 if (rt_is_input_route(rt) && 570 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 571 dev = dev_get_by_index_rcu(net, rt->rt_iif); 572 573 if (dev) 574 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 575 else 576 saddr = 0; 577 rcu_read_unlock(); 578 } 579 580 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 581 IPTOS_PREC_INTERNETCONTROL) : 582 iph->tos; 583 584 if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in)) 585 goto out_unlock; 586 587 588 /* 589 * Prepare data for ICMP header. 590 */ 591 592 icmp_param.data.icmph.type = type; 593 icmp_param.data.icmph.code = code; 594 icmp_param.data.icmph.un.gateway = info; 595 icmp_param.data.icmph.checksum = 0; 596 icmp_param.skb = skb_in; 597 icmp_param.offset = skb_network_offset(skb_in); 598 inet_sk(sk)->tos = tos; 599 ipc.addr = iph->saddr; 600 ipc.opt = &icmp_param.replyopts.opt; 601 ipc.tx_flags = 0; 602 603 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, 604 type, code, &icmp_param); 605 if (IS_ERR(rt)) 606 goto out_unlock; 607 608 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 609 goto ende; 610 611 /* RFC says return as much as we can without exceeding 576 bytes. */ 612 613 room = dst_mtu(&rt->dst); 614 if (room > 576) 615 room = 576; 616 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 617 room -= sizeof(struct icmphdr); 618 619 icmp_param.data_len = skb_in->len - icmp_param.offset; 620 if (icmp_param.data_len > room) 621 icmp_param.data_len = room; 622 icmp_param.head_len = sizeof(struct icmphdr); 623 624 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 625 ende: 626 ip_rt_put(rt); 627 out_unlock: 628 icmp_xmit_unlock(sk); 629 out:; 630 } 631 EXPORT_SYMBOL(icmp_send); 632 633 634 /* 635 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 636 */ 637 638 static void icmp_unreach(struct sk_buff *skb) 639 { 640 const struct iphdr *iph; 641 struct icmphdr *icmph; 642 int hash, protocol; 643 const struct net_protocol *ipprot; 644 u32 info = 0; 645 struct net *net; 646 647 net = dev_net(skb_dst(skb)->dev); 648 649 /* 650 * Incomplete header ? 651 * Only checks for the IP header, there should be an 652 * additional check for longer headers in upper levels. 653 */ 654 655 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 656 goto out_err; 657 658 icmph = icmp_hdr(skb); 659 iph = (const struct iphdr *)skb->data; 660 661 if (iph->ihl < 5) /* Mangled header, drop. */ 662 goto out_err; 663 664 if (icmph->type == ICMP_DEST_UNREACH) { 665 switch (icmph->code & 15) { 666 case ICMP_NET_UNREACH: 667 case ICMP_HOST_UNREACH: 668 case ICMP_PROT_UNREACH: 669 case ICMP_PORT_UNREACH: 670 break; 671 case ICMP_FRAG_NEEDED: 672 if (ipv4_config.no_pmtu_disc) { 673 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: fragmentation needed and DF set.\n", 674 &iph->daddr); 675 } else { 676 info = ip_rt_frag_needed(net, iph, 677 ntohs(icmph->un.frag.mtu), 678 skb->dev); 679 if (!info) 680 goto out; 681 } 682 break; 683 case ICMP_SR_FAILED: 684 LIMIT_NETDEBUG(KERN_INFO "ICMP: %pI4: Source Route Failed.\n", 685 &iph->daddr); 686 break; 687 default: 688 break; 689 } 690 if (icmph->code > NR_ICMP_UNREACH) 691 goto out; 692 } else if (icmph->type == ICMP_PARAMETERPROB) 693 info = ntohl(icmph->un.gateway) >> 24; 694 695 /* 696 * Throw it at our lower layers 697 * 698 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 699 * header. 700 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 701 * transport layer. 702 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 703 * transport layer. 704 */ 705 706 /* 707 * Check the other end isn't violating RFC 1122. Some routers send 708 * bogus responses to broadcast frames. If you see this message 709 * first check your netmask matches at both ends, if it does then 710 * get the other vendor to fix their kit. 711 */ 712 713 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 714 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 715 if (net_ratelimit()) 716 printk(KERN_WARNING "%pI4 sent an invalid ICMP " 717 "type %u, code %u " 718 "error to a broadcast: %pI4 on %s\n", 719 &ip_hdr(skb)->saddr, 720 icmph->type, icmph->code, 721 &iph->daddr, 722 skb->dev->name); 723 goto out; 724 } 725 726 /* Checkin full IP header plus 8 bytes of protocol to 727 * avoid additional coding at protocol handlers. 728 */ 729 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 730 goto out; 731 732 iph = (const struct iphdr *)skb->data; 733 protocol = iph->protocol; 734 735 /* 736 * Deliver ICMP message to raw sockets. Pretty useless feature? 737 */ 738 raw_icmp_error(skb, protocol, info); 739 740 hash = protocol & (MAX_INET_PROTOS - 1); 741 rcu_read_lock(); 742 ipprot = rcu_dereference(inet_protos[hash]); 743 if (ipprot && ipprot->err_handler) 744 ipprot->err_handler(skb, info); 745 rcu_read_unlock(); 746 747 out: 748 return; 749 out_err: 750 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 751 goto out; 752 } 753 754 755 /* 756 * Handle ICMP_REDIRECT. 757 */ 758 759 static void icmp_redirect(struct sk_buff *skb) 760 { 761 const struct iphdr *iph; 762 763 if (skb->len < sizeof(struct iphdr)) 764 goto out_err; 765 766 /* 767 * Get the copied header of the packet that caused the redirect 768 */ 769 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 770 goto out; 771 772 iph = (const struct iphdr *)skb->data; 773 774 switch (icmp_hdr(skb)->code & 7) { 775 case ICMP_REDIR_NET: 776 case ICMP_REDIR_NETTOS: 777 /* 778 * As per RFC recommendations now handle it as a host redirect. 779 */ 780 case ICMP_REDIR_HOST: 781 case ICMP_REDIR_HOSTTOS: 782 ip_rt_redirect(ip_hdr(skb)->saddr, iph->daddr, 783 icmp_hdr(skb)->un.gateway, 784 iph->saddr, skb->dev); 785 break; 786 } 787 788 /* Ping wants to see redirects. 789 * Let's pretend they are errors of sorts... */ 790 if (iph->protocol == IPPROTO_ICMP && 791 iph->ihl >= 5 && 792 pskb_may_pull(skb, (iph->ihl<<2)+8)) { 793 ping_err(skb, icmp_hdr(skb)->un.gateway); 794 } 795 796 out: 797 return; 798 out_err: 799 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 800 goto out; 801 } 802 803 /* 804 * Handle ICMP_ECHO ("ping") requests. 805 * 806 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 807 * requests. 808 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 809 * included in the reply. 810 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 811 * echo requests, MUST have default=NOT. 812 * See also WRT handling of options once they are done and working. 813 */ 814 815 static void icmp_echo(struct sk_buff *skb) 816 { 817 struct net *net; 818 819 net = dev_net(skb_dst(skb)->dev); 820 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 821 struct icmp_bxm icmp_param; 822 823 icmp_param.data.icmph = *icmp_hdr(skb); 824 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 825 icmp_param.skb = skb; 826 icmp_param.offset = 0; 827 icmp_param.data_len = skb->len; 828 icmp_param.head_len = sizeof(struct icmphdr); 829 icmp_reply(&icmp_param, skb); 830 } 831 } 832 833 /* 834 * Handle ICMP Timestamp requests. 835 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 836 * SHOULD be in the kernel for minimum random latency. 837 * MUST be accurate to a few minutes. 838 * MUST be updated at least at 15Hz. 839 */ 840 static void icmp_timestamp(struct sk_buff *skb) 841 { 842 struct timespec tv; 843 struct icmp_bxm icmp_param; 844 /* 845 * Too short. 846 */ 847 if (skb->len < 4) 848 goto out_err; 849 850 /* 851 * Fill in the current time as ms since midnight UT: 852 */ 853 getnstimeofday(&tv); 854 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 855 tv.tv_nsec / NSEC_PER_MSEC); 856 icmp_param.data.times[2] = icmp_param.data.times[1]; 857 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 858 BUG(); 859 icmp_param.data.icmph = *icmp_hdr(skb); 860 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 861 icmp_param.data.icmph.code = 0; 862 icmp_param.skb = skb; 863 icmp_param.offset = 0; 864 icmp_param.data_len = 0; 865 icmp_param.head_len = sizeof(struct icmphdr) + 12; 866 icmp_reply(&icmp_param, skb); 867 out: 868 return; 869 out_err: 870 ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 871 goto out; 872 } 873 874 875 /* 876 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 877 * 878 * RFC1122 (3.2.2.9). A host MUST only send replies to 879 * ADDRESS_MASK requests if it's been configured as an address mask 880 * agent. Receiving a request doesn't constitute implicit permission to 881 * act as one. Of course, implementing this correctly requires (SHOULD) 882 * a way to turn the functionality on and off. Another one for sysctl(), 883 * I guess. -- MS 884 * 885 * RFC1812 (4.3.3.9). A router MUST implement it. 886 * A router SHOULD have switch turning it on/off. 887 * This switch MUST be ON by default. 888 * 889 * Gratuitous replies, zero-source replies are not implemented, 890 * that complies with RFC. DO NOT implement them!!! All the idea 891 * of broadcast addrmask replies as specified in RFC950 is broken. 892 * The problem is that it is not uncommon to have several prefixes 893 * on one physical interface. Moreover, addrmask agent can even be 894 * not aware of existing another prefixes. 895 * If source is zero, addrmask agent cannot choose correct prefix. 896 * Gratuitous mask announcements suffer from the same problem. 897 * RFC1812 explains it, but still allows to use ADDRMASK, 898 * that is pretty silly. --ANK 899 * 900 * All these rules are so bizarre, that I removed kernel addrmask 901 * support at all. It is wrong, it is obsolete, nobody uses it in 902 * any case. --ANK 903 * 904 * Furthermore you can do it with a usermode address agent program 905 * anyway... 906 */ 907 908 static void icmp_address(struct sk_buff *skb) 909 { 910 #if 0 911 if (net_ratelimit()) 912 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 913 #endif 914 } 915 916 /* 917 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 918 * loudly if an inconsistency is found. 919 * called with rcu_read_lock() 920 */ 921 922 static void icmp_address_reply(struct sk_buff *skb) 923 { 924 struct rtable *rt = skb_rtable(skb); 925 struct net_device *dev = skb->dev; 926 struct in_device *in_dev; 927 struct in_ifaddr *ifa; 928 929 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 930 return; 931 932 in_dev = __in_dev_get_rcu(dev); 933 if (!in_dev) 934 return; 935 936 if (in_dev->ifa_list && 937 IN_DEV_LOG_MARTIANS(in_dev) && 938 IN_DEV_FORWARD(in_dev)) { 939 __be32 _mask, *mp; 940 941 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 942 BUG_ON(mp == NULL); 943 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 944 if (*mp == ifa->ifa_mask && 945 inet_ifa_match(ip_hdr(skb)->saddr, ifa)) 946 break; 947 } 948 if (!ifa && net_ratelimit()) { 949 printk(KERN_INFO "Wrong address mask %pI4 from %s/%pI4\n", 950 mp, dev->name, &ip_hdr(skb)->saddr); 951 } 952 } 953 } 954 955 static void icmp_discard(struct sk_buff *skb) 956 { 957 } 958 959 /* 960 * Deal with incoming ICMP packets. 961 */ 962 int icmp_rcv(struct sk_buff *skb) 963 { 964 struct icmphdr *icmph; 965 struct rtable *rt = skb_rtable(skb); 966 struct net *net = dev_net(rt->dst.dev); 967 968 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 969 struct sec_path *sp = skb_sec_path(skb); 970 int nh; 971 972 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 973 XFRM_STATE_ICMP)) 974 goto drop; 975 976 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 977 goto drop; 978 979 nh = skb_network_offset(skb); 980 skb_set_network_header(skb, sizeof(*icmph)); 981 982 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 983 goto drop; 984 985 skb_set_network_header(skb, nh); 986 } 987 988 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 989 990 switch (skb->ip_summed) { 991 case CHECKSUM_COMPLETE: 992 if (!csum_fold(skb->csum)) 993 break; 994 /* fall through */ 995 case CHECKSUM_NONE: 996 skb->csum = 0; 997 if (__skb_checksum_complete(skb)) 998 goto error; 999 } 1000 1001 if (!pskb_pull(skb, sizeof(*icmph))) 1002 goto error; 1003 1004 icmph = icmp_hdr(skb); 1005 1006 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 1007 /* 1008 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1009 * 1010 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1011 * discarded. 1012 */ 1013 if (icmph->type > NR_ICMP_TYPES) 1014 goto error; 1015 1016 1017 /* 1018 * Parse the ICMP message 1019 */ 1020 1021 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1022 /* 1023 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1024 * silently ignored (we let user decide with a sysctl). 1025 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1026 * discarded if to broadcast/multicast. 1027 */ 1028 if ((icmph->type == ICMP_ECHO || 1029 icmph->type == ICMP_TIMESTAMP) && 1030 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1031 goto error; 1032 } 1033 if (icmph->type != ICMP_ECHO && 1034 icmph->type != ICMP_TIMESTAMP && 1035 icmph->type != ICMP_ADDRESS && 1036 icmph->type != ICMP_ADDRESSREPLY) { 1037 goto error; 1038 } 1039 } 1040 1041 icmp_pointers[icmph->type].handler(skb); 1042 1043 drop: 1044 kfree_skb(skb); 1045 return 0; 1046 error: 1047 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1048 goto drop; 1049 } 1050 1051 /* 1052 * This table is the definition of how we handle ICMP. 1053 */ 1054 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1055 [ICMP_ECHOREPLY] = { 1056 .handler = ping_rcv, 1057 }, 1058 [1] = { 1059 .handler = icmp_discard, 1060 .error = 1, 1061 }, 1062 [2] = { 1063 .handler = icmp_discard, 1064 .error = 1, 1065 }, 1066 [ICMP_DEST_UNREACH] = { 1067 .handler = icmp_unreach, 1068 .error = 1, 1069 }, 1070 [ICMP_SOURCE_QUENCH] = { 1071 .handler = icmp_unreach, 1072 .error = 1, 1073 }, 1074 [ICMP_REDIRECT] = { 1075 .handler = icmp_redirect, 1076 .error = 1, 1077 }, 1078 [6] = { 1079 .handler = icmp_discard, 1080 .error = 1, 1081 }, 1082 [7] = { 1083 .handler = icmp_discard, 1084 .error = 1, 1085 }, 1086 [ICMP_ECHO] = { 1087 .handler = icmp_echo, 1088 }, 1089 [9] = { 1090 .handler = icmp_discard, 1091 .error = 1, 1092 }, 1093 [10] = { 1094 .handler = icmp_discard, 1095 .error = 1, 1096 }, 1097 [ICMP_TIME_EXCEEDED] = { 1098 .handler = icmp_unreach, 1099 .error = 1, 1100 }, 1101 [ICMP_PARAMETERPROB] = { 1102 .handler = icmp_unreach, 1103 .error = 1, 1104 }, 1105 [ICMP_TIMESTAMP] = { 1106 .handler = icmp_timestamp, 1107 }, 1108 [ICMP_TIMESTAMPREPLY] = { 1109 .handler = icmp_discard, 1110 }, 1111 [ICMP_INFO_REQUEST] = { 1112 .handler = icmp_discard, 1113 }, 1114 [ICMP_INFO_REPLY] = { 1115 .handler = icmp_discard, 1116 }, 1117 [ICMP_ADDRESS] = { 1118 .handler = icmp_address, 1119 }, 1120 [ICMP_ADDRESSREPLY] = { 1121 .handler = icmp_address_reply, 1122 }, 1123 }; 1124 1125 static void __net_exit icmp_sk_exit(struct net *net) 1126 { 1127 int i; 1128 1129 for_each_possible_cpu(i) 1130 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1131 kfree(net->ipv4.icmp_sk); 1132 net->ipv4.icmp_sk = NULL; 1133 } 1134 1135 static int __net_init icmp_sk_init(struct net *net) 1136 { 1137 int i, err; 1138 1139 net->ipv4.icmp_sk = 1140 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL); 1141 if (net->ipv4.icmp_sk == NULL) 1142 return -ENOMEM; 1143 1144 for_each_possible_cpu(i) { 1145 struct sock *sk; 1146 1147 err = inet_ctl_sock_create(&sk, PF_INET, 1148 SOCK_RAW, IPPROTO_ICMP, net); 1149 if (err < 0) 1150 goto fail; 1151 1152 net->ipv4.icmp_sk[i] = sk; 1153 1154 /* Enough space for 2 64K ICMP packets, including 1155 * sk_buff/skb_shared_info struct overhead. 1156 */ 1157 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1158 1159 /* 1160 * Speedup sock_wfree() 1161 */ 1162 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1163 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1164 } 1165 1166 /* Control parameters for ECHO replies. */ 1167 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1168 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1169 1170 /* Control parameter - ignore bogus broadcast responses? */ 1171 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1172 1173 /* 1174 * Configurable global rate limit. 1175 * 1176 * ratelimit defines tokens/packet consumed for dst->rate_token 1177 * bucket ratemask defines which icmp types are ratelimited by 1178 * setting it's bit position. 1179 * 1180 * default: 1181 * dest unreachable (3), source quench (4), 1182 * time exceeded (11), parameter problem (12) 1183 */ 1184 1185 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1186 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1187 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1188 1189 return 0; 1190 1191 fail: 1192 for_each_possible_cpu(i) 1193 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]); 1194 kfree(net->ipv4.icmp_sk); 1195 return err; 1196 } 1197 1198 static struct pernet_operations __net_initdata icmp_sk_ops = { 1199 .init = icmp_sk_init, 1200 .exit = icmp_sk_exit, 1201 }; 1202 1203 int __init icmp_init(void) 1204 { 1205 return register_pernet_subsys(&icmp_sk_ops); 1206 } 1207