1 /* 2 * NET3: Implementation of the ICMP protocol layer. 3 * 4 * Alan Cox, <alan@redhat.com> 5 * 6 * Version: $Id: icmp.c,v 1.85 2002/02/01 22:01:03 davem Exp $ 7 * 8 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License 10 * as published by the Free Software Foundation; either version 11 * 2 of the License, or (at your option) any later version. 12 * 13 * Some of the function names and the icmp unreach table for this 14 * module were derived from [icmp.c 1.0.11 06/02/93] by 15 * Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting. 16 * Other than that this module is a complete rewrite. 17 * 18 * Fixes: 19 * Clemens Fruhwirth : introduce global icmp rate limiting 20 * with icmp type masking ability instead 21 * of broken per type icmp timeouts. 22 * Mike Shaver : RFC1122 checks. 23 * Alan Cox : Multicast ping reply as self. 24 * Alan Cox : Fix atomicity lockup in ip_build_xmit 25 * call. 26 * Alan Cox : Added 216,128 byte paths to the MTU 27 * code. 28 * Martin Mares : RFC1812 checks. 29 * Martin Mares : Can be configured to follow redirects 30 * if acting as a router _without_ a 31 * routing protocol (RFC 1812). 32 * Martin Mares : Echo requests may be configured to 33 * be ignored (RFC 1812). 34 * Martin Mares : Limitation of ICMP error message 35 * transmit rate (RFC 1812). 36 * Martin Mares : TOS and Precedence set correctly 37 * (RFC 1812). 38 * Martin Mares : Now copying as much data from the 39 * original packet as we can without 40 * exceeding 576 bytes (RFC 1812). 41 * Willy Konynenberg : Transparent proxying support. 42 * Keith Owens : RFC1191 correction for 4.2BSD based 43 * path MTU bug. 44 * Thomas Quinot : ICMP Dest Unreach codes up to 15 are 45 * valid (RFC 1812). 46 * Andi Kleen : Check all packet lengths properly 47 * and moved all kfree_skb() up to 48 * icmp_rcv. 49 * Andi Kleen : Move the rate limit bookkeeping 50 * into the dest entry and use a token 51 * bucket filter (thanks to ANK). Make 52 * the rates sysctl configurable. 53 * Yu Tianli : Fixed two ugly bugs in icmp_send 54 * - IP option length was accounted wrongly 55 * - ICMP header length was not accounted 56 * at all. 57 * Tristan Greaves : Added sysctl option to ignore bogus 58 * broadcast responses from broken routers. 59 * 60 * To Fix: 61 * 62 * - Should use skb_pull() instead of all the manual checking. 63 * This would also greatly simply some upper layer error handlers. --AK 64 * 65 */ 66 67 #include <linux/config.h> 68 #include <linux/module.h> 69 #include <linux/types.h> 70 #include <linux/jiffies.h> 71 #include <linux/kernel.h> 72 #include <linux/fcntl.h> 73 #include <linux/socket.h> 74 #include <linux/in.h> 75 #include <linux/inet.h> 76 #include <linux/netdevice.h> 77 #include <linux/string.h> 78 #include <linux/netfilter_ipv4.h> 79 #include <net/snmp.h> 80 #include <net/ip.h> 81 #include <net/route.h> 82 #include <net/protocol.h> 83 #include <net/icmp.h> 84 #include <net/tcp.h> 85 #include <net/udp.h> 86 #include <net/raw.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 96 /* 97 * Build xmit assembly blocks 98 */ 99 100 struct icmp_bxm { 101 struct sk_buff *skb; 102 int offset; 103 int data_len; 104 105 struct { 106 struct icmphdr icmph; 107 __u32 times[3]; 108 } data; 109 int head_len; 110 struct ip_options replyopts; 111 unsigned char optbuf[40]; 112 }; 113 114 /* 115 * Statistics 116 */ 117 DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics) __read_mostly; 118 119 /* An array of errno for error messages from dest unreach. */ 120 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 121 122 struct icmp_err icmp_err_convert[] = { 123 { 124 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 125 .fatal = 0, 126 }, 127 { 128 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 129 .fatal = 0, 130 }, 131 { 132 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 133 .fatal = 1, 134 }, 135 { 136 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 137 .fatal = 1, 138 }, 139 { 140 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 141 .fatal = 0, 142 }, 143 { 144 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 145 .fatal = 0, 146 }, 147 { 148 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 149 .fatal = 1, 150 }, 151 { 152 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 153 .fatal = 1, 154 }, 155 { 156 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 157 .fatal = 1, 158 }, 159 { 160 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 161 .fatal = 1, 162 }, 163 { 164 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 165 .fatal = 1, 166 }, 167 { 168 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 169 .fatal = 0, 170 }, 171 { 172 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 173 .fatal = 0, 174 }, 175 { 176 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 177 .fatal = 1, 178 }, 179 { 180 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 181 .fatal = 1, 182 }, 183 { 184 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 185 .fatal = 1, 186 }, 187 }; 188 189 /* Control parameters for ECHO replies. */ 190 int sysctl_icmp_echo_ignore_all; 191 int sysctl_icmp_echo_ignore_broadcasts = 1; 192 193 /* Control parameter - ignore bogus broadcast responses? */ 194 int sysctl_icmp_ignore_bogus_error_responses; 195 196 /* 197 * Configurable global rate limit. 198 * 199 * ratelimit defines tokens/packet consumed for dst->rate_token bucket 200 * ratemask defines which icmp types are ratelimited by setting 201 * it's bit position. 202 * 203 * default: 204 * dest unreachable (3), source quench (4), 205 * time exceeded (11), parameter problem (12) 206 */ 207 208 int sysctl_icmp_ratelimit = 1 * HZ; 209 int sysctl_icmp_ratemask = 0x1818; 210 int sysctl_icmp_errors_use_inbound_ifaddr; 211 212 /* 213 * ICMP control array. This specifies what to do with each ICMP. 214 */ 215 216 struct icmp_control { 217 int output_entry; /* Field for increment on output */ 218 int input_entry; /* Field for increment on input */ 219 void (*handler)(struct sk_buff *skb); 220 short error; /* This ICMP is classed as an error message */ 221 }; 222 223 static struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 224 225 /* 226 * The ICMP socket(s). This is the most convenient way to flow control 227 * our ICMP output as well as maintain a clean interface throughout 228 * all layers. All Socketless IP sends will soon be gone. 229 * 230 * On SMP we have one ICMP socket per-cpu. 231 */ 232 static DEFINE_PER_CPU(struct socket *, __icmp_socket) = NULL; 233 #define icmp_socket __get_cpu_var(__icmp_socket) 234 235 static __inline__ int icmp_xmit_lock(void) 236 { 237 local_bh_disable(); 238 239 if (unlikely(!spin_trylock(&icmp_socket->sk->sk_lock.slock))) { 240 /* This can happen if the output path signals a 241 * dst_link_failure() for an outgoing ICMP packet. 242 */ 243 local_bh_enable(); 244 return 1; 245 } 246 return 0; 247 } 248 249 static void icmp_xmit_unlock(void) 250 { 251 spin_unlock_bh(&icmp_socket->sk->sk_lock.slock); 252 } 253 254 /* 255 * Send an ICMP frame. 256 */ 257 258 /* 259 * Check transmit rate limitation for given message. 260 * The rate information is held in the destination cache now. 261 * This function is generic and could be used for other purposes 262 * too. It uses a Token bucket filter as suggested by Alexey Kuznetsov. 263 * 264 * Note that the same dst_entry fields are modified by functions in 265 * route.c too, but these work for packet destinations while xrlim_allow 266 * works for icmp destinations. This means the rate limiting information 267 * for one "ip object" is shared - and these ICMPs are twice limited: 268 * by source and by destination. 269 * 270 * RFC 1812: 4.3.2.8 SHOULD be able to limit error message rate 271 * SHOULD allow setting of rate limits 272 * 273 * Shared between ICMPv4 and ICMPv6. 274 */ 275 #define XRLIM_BURST_FACTOR 6 276 int xrlim_allow(struct dst_entry *dst, int timeout) 277 { 278 unsigned long now; 279 int rc = 0; 280 281 now = jiffies; 282 dst->rate_tokens += now - dst->rate_last; 283 dst->rate_last = now; 284 if (dst->rate_tokens > XRLIM_BURST_FACTOR * timeout) 285 dst->rate_tokens = XRLIM_BURST_FACTOR * timeout; 286 if (dst->rate_tokens >= timeout) { 287 dst->rate_tokens -= timeout; 288 rc = 1; 289 } 290 return rc; 291 } 292 293 static inline int icmpv4_xrlim_allow(struct rtable *rt, int type, int code) 294 { 295 struct dst_entry *dst = &rt->u.dst; 296 int rc = 1; 297 298 if (type > NR_ICMP_TYPES) 299 goto out; 300 301 /* Don't limit PMTU discovery. */ 302 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 303 goto out; 304 305 /* No rate limit on loopback */ 306 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 307 goto out; 308 309 /* Limit if icmp type is enabled in ratemask. */ 310 if ((1 << type) & sysctl_icmp_ratemask) 311 rc = xrlim_allow(dst, sysctl_icmp_ratelimit); 312 out: 313 return rc; 314 } 315 316 /* 317 * Maintain the counters used in the SNMP statistics for outgoing ICMP 318 */ 319 static void icmp_out_count(int type) 320 { 321 if (type <= NR_ICMP_TYPES) { 322 ICMP_INC_STATS(icmp_pointers[type].output_entry); 323 ICMP_INC_STATS(ICMP_MIB_OUTMSGS); 324 } 325 } 326 327 /* 328 * Checksum each fragment, and on the first include the headers and final 329 * checksum. 330 */ 331 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 332 struct sk_buff *skb) 333 { 334 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 335 unsigned int csum; 336 337 csum = skb_copy_and_csum_bits(icmp_param->skb, 338 icmp_param->offset + offset, 339 to, len, 0); 340 341 skb->csum = csum_block_add(skb->csum, csum, odd); 342 if (icmp_pointers[icmp_param->data.icmph.type].error) 343 nf_ct_attach(skb, icmp_param->skb); 344 return 0; 345 } 346 347 static void icmp_push_reply(struct icmp_bxm *icmp_param, 348 struct ipcm_cookie *ipc, struct rtable *rt) 349 { 350 struct sk_buff *skb; 351 352 if (ip_append_data(icmp_socket->sk, icmp_glue_bits, icmp_param, 353 icmp_param->data_len+icmp_param->head_len, 354 icmp_param->head_len, 355 ipc, rt, MSG_DONTWAIT) < 0) 356 ip_flush_pending_frames(icmp_socket->sk); 357 else if ((skb = skb_peek(&icmp_socket->sk->sk_write_queue)) != NULL) { 358 struct icmphdr *icmph = skb->h.icmph; 359 unsigned int csum = 0; 360 struct sk_buff *skb1; 361 362 skb_queue_walk(&icmp_socket->sk->sk_write_queue, skb1) { 363 csum = csum_add(csum, skb1->csum); 364 } 365 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 366 (char *)icmph, 367 icmp_param->head_len, csum); 368 icmph->checksum = csum_fold(csum); 369 skb->ip_summed = CHECKSUM_NONE; 370 ip_push_pending_frames(icmp_socket->sk); 371 } 372 } 373 374 /* 375 * Driving logic for building and sending ICMP messages. 376 */ 377 378 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 379 { 380 struct sock *sk = icmp_socket->sk; 381 struct inet_sock *inet = inet_sk(sk); 382 struct ipcm_cookie ipc; 383 struct rtable *rt = (struct rtable *)skb->dst; 384 u32 daddr; 385 386 if (ip_options_echo(&icmp_param->replyopts, skb)) 387 goto out; 388 389 if (icmp_xmit_lock()) 390 return; 391 392 icmp_param->data.icmph.checksum = 0; 393 icmp_out_count(icmp_param->data.icmph.type); 394 395 inet->tos = skb->nh.iph->tos; 396 daddr = ipc.addr = rt->rt_src; 397 ipc.opt = NULL; 398 if (icmp_param->replyopts.optlen) { 399 ipc.opt = &icmp_param->replyopts; 400 if (ipc.opt->srr) 401 daddr = icmp_param->replyopts.faddr; 402 } 403 { 404 struct flowi fl = { .nl_u = { .ip4_u = 405 { .daddr = daddr, 406 .saddr = rt->rt_spec_dst, 407 .tos = RT_TOS(skb->nh.iph->tos) } }, 408 .proto = IPPROTO_ICMP }; 409 if (ip_route_output_key(&rt, &fl)) 410 goto out_unlock; 411 } 412 if (icmpv4_xrlim_allow(rt, icmp_param->data.icmph.type, 413 icmp_param->data.icmph.code)) 414 icmp_push_reply(icmp_param, &ipc, rt); 415 ip_rt_put(rt); 416 out_unlock: 417 icmp_xmit_unlock(); 418 out:; 419 } 420 421 422 /* 423 * Send an ICMP message in response to a situation 424 * 425 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 426 * MAY send more (we do). 427 * MUST NOT change this header information. 428 * MUST NOT reply to a multicast/broadcast IP address. 429 * MUST NOT reply to a multicast/broadcast MAC address. 430 * MUST reply to only the first fragment. 431 */ 432 433 void icmp_send(struct sk_buff *skb_in, int type, int code, u32 info) 434 { 435 struct iphdr *iph; 436 int room; 437 struct icmp_bxm icmp_param; 438 struct rtable *rt = (struct rtable *)skb_in->dst; 439 struct ipcm_cookie ipc; 440 u32 saddr; 441 u8 tos; 442 443 if (!rt) 444 goto out; 445 446 /* 447 * Find the original header. It is expected to be valid, of course. 448 * Check this, icmp_send is called from the most obscure devices 449 * sometimes. 450 */ 451 iph = skb_in->nh.iph; 452 453 if ((u8 *)iph < skb_in->head || (u8 *)(iph + 1) > skb_in->tail) 454 goto out; 455 456 /* 457 * No replies to physical multicast/broadcast 458 */ 459 if (skb_in->pkt_type != PACKET_HOST) 460 goto out; 461 462 /* 463 * Now check at the protocol level 464 */ 465 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 466 goto out; 467 468 /* 469 * Only reply to fragment 0. We byte re-order the constant 470 * mask for efficiency. 471 */ 472 if (iph->frag_off & htons(IP_OFFSET)) 473 goto out; 474 475 /* 476 * If we send an ICMP error to an ICMP error a mess would result.. 477 */ 478 if (icmp_pointers[type].error) { 479 /* 480 * We are an error, check if we are replying to an 481 * ICMP error 482 */ 483 if (iph->protocol == IPPROTO_ICMP) { 484 u8 _inner_type, *itp; 485 486 itp = skb_header_pointer(skb_in, 487 skb_in->nh.raw + 488 (iph->ihl << 2) + 489 offsetof(struct icmphdr, 490 type) - 491 skb_in->data, 492 sizeof(_inner_type), 493 &_inner_type); 494 if (itp == NULL) 495 goto out; 496 497 /* 498 * Assume any unknown ICMP type is an error. This 499 * isn't specified by the RFC, but think about it.. 500 */ 501 if (*itp > NR_ICMP_TYPES || 502 icmp_pointers[*itp].error) 503 goto out; 504 } 505 } 506 507 if (icmp_xmit_lock()) 508 return; 509 510 /* 511 * Construct source address and options. 512 */ 513 514 saddr = iph->daddr; 515 if (!(rt->rt_flags & RTCF_LOCAL)) { 516 if (sysctl_icmp_errors_use_inbound_ifaddr) 517 saddr = inet_select_addr(skb_in->dev, 0, RT_SCOPE_LINK); 518 else 519 saddr = 0; 520 } 521 522 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 523 IPTOS_PREC_INTERNETCONTROL) : 524 iph->tos; 525 526 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 527 goto ende; 528 529 530 /* 531 * Prepare data for ICMP header. 532 */ 533 534 icmp_param.data.icmph.type = type; 535 icmp_param.data.icmph.code = code; 536 icmp_param.data.icmph.un.gateway = info; 537 icmp_param.data.icmph.checksum = 0; 538 icmp_param.skb = skb_in; 539 icmp_param.offset = skb_in->nh.raw - skb_in->data; 540 icmp_out_count(icmp_param.data.icmph.type); 541 inet_sk(icmp_socket->sk)->tos = tos; 542 ipc.addr = iph->saddr; 543 ipc.opt = &icmp_param.replyopts; 544 545 { 546 struct flowi fl = { 547 .nl_u = { 548 .ip4_u = { 549 .daddr = icmp_param.replyopts.srr ? 550 icmp_param.replyopts.faddr : 551 iph->saddr, 552 .saddr = saddr, 553 .tos = RT_TOS(tos) 554 } 555 }, 556 .proto = IPPROTO_ICMP, 557 .uli_u = { 558 .icmpt = { 559 .type = type, 560 .code = code 561 } 562 } 563 }; 564 if (ip_route_output_key(&rt, &fl)) 565 goto out_unlock; 566 } 567 568 if (!icmpv4_xrlim_allow(rt, type, code)) 569 goto ende; 570 571 /* RFC says return as much as we can without exceeding 576 bytes. */ 572 573 room = dst_mtu(&rt->u.dst); 574 if (room > 576) 575 room = 576; 576 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 577 room -= sizeof(struct icmphdr); 578 579 icmp_param.data_len = skb_in->len - icmp_param.offset; 580 if (icmp_param.data_len > room) 581 icmp_param.data_len = room; 582 icmp_param.head_len = sizeof(struct icmphdr); 583 584 icmp_push_reply(&icmp_param, &ipc, rt); 585 ende: 586 ip_rt_put(rt); 587 out_unlock: 588 icmp_xmit_unlock(); 589 out:; 590 } 591 592 593 /* 594 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 595 */ 596 597 static void icmp_unreach(struct sk_buff *skb) 598 { 599 struct iphdr *iph; 600 struct icmphdr *icmph; 601 int hash, protocol; 602 struct net_protocol *ipprot; 603 struct sock *raw_sk; 604 u32 info = 0; 605 606 /* 607 * Incomplete header ? 608 * Only checks for the IP header, there should be an 609 * additional check for longer headers in upper levels. 610 */ 611 612 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 613 goto out_err; 614 615 icmph = skb->h.icmph; 616 iph = (struct iphdr *)skb->data; 617 618 if (iph->ihl < 5) /* Mangled header, drop. */ 619 goto out_err; 620 621 if (icmph->type == ICMP_DEST_UNREACH) { 622 switch (icmph->code & 15) { 623 case ICMP_NET_UNREACH: 624 case ICMP_HOST_UNREACH: 625 case ICMP_PROT_UNREACH: 626 case ICMP_PORT_UNREACH: 627 break; 628 case ICMP_FRAG_NEEDED: 629 if (ipv4_config.no_pmtu_disc) { 630 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: " 631 "fragmentation needed " 632 "and DF set.\n", 633 NIPQUAD(iph->daddr)); 634 } else { 635 info = ip_rt_frag_needed(iph, 636 ntohs(icmph->un.frag.mtu)); 637 if (!info) 638 goto out; 639 } 640 break; 641 case ICMP_SR_FAILED: 642 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: Source " 643 "Route Failed.\n", 644 NIPQUAD(iph->daddr)); 645 break; 646 default: 647 break; 648 } 649 if (icmph->code > NR_ICMP_UNREACH) 650 goto out; 651 } else if (icmph->type == ICMP_PARAMETERPROB) 652 info = ntohl(icmph->un.gateway) >> 24; 653 654 /* 655 * Throw it at our lower layers 656 * 657 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 658 * header. 659 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 660 * transport layer. 661 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 662 * transport layer. 663 */ 664 665 /* 666 * Check the other end isnt violating RFC 1122. Some routers send 667 * bogus responses to broadcast frames. If you see this message 668 * first check your netmask matches at both ends, if it does then 669 * get the other vendor to fix their kit. 670 */ 671 672 if (!sysctl_icmp_ignore_bogus_error_responses && 673 inet_addr_type(iph->daddr) == RTN_BROADCAST) { 674 if (net_ratelimit()) 675 printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP " 676 "type %u, code %u " 677 "error to a broadcast: %u.%u.%u.%u on %s\n", 678 NIPQUAD(skb->nh.iph->saddr), 679 icmph->type, icmph->code, 680 NIPQUAD(iph->daddr), 681 skb->dev->name); 682 goto out; 683 } 684 685 /* Checkin full IP header plus 8 bytes of protocol to 686 * avoid additional coding at protocol handlers. 687 */ 688 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 689 goto out; 690 691 iph = (struct iphdr *)skb->data; 692 protocol = iph->protocol; 693 694 /* 695 * Deliver ICMP message to raw sockets. Pretty useless feature? 696 */ 697 698 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 699 hash = protocol & (MAX_INET_PROTOS - 1); 700 read_lock(&raw_v4_lock); 701 if ((raw_sk = sk_head(&raw_v4_htable[hash])) != NULL) { 702 while ((raw_sk = __raw_v4_lookup(raw_sk, protocol, iph->daddr, 703 iph->saddr, 704 skb->dev->ifindex)) != NULL) { 705 raw_err(raw_sk, skb, info); 706 raw_sk = sk_next(raw_sk); 707 iph = (struct iphdr *)skb->data; 708 } 709 } 710 read_unlock(&raw_v4_lock); 711 712 rcu_read_lock(); 713 ipprot = rcu_dereference(inet_protos[hash]); 714 if (ipprot && ipprot->err_handler) 715 ipprot->err_handler(skb, info); 716 rcu_read_unlock(); 717 718 out: 719 return; 720 out_err: 721 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 722 goto out; 723 } 724 725 726 /* 727 * Handle ICMP_REDIRECT. 728 */ 729 730 static void icmp_redirect(struct sk_buff *skb) 731 { 732 struct iphdr *iph; 733 unsigned long ip; 734 735 if (skb->len < sizeof(struct iphdr)) 736 goto out_err; 737 738 /* 739 * Get the copied header of the packet that caused the redirect 740 */ 741 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 742 goto out; 743 744 iph = (struct iphdr *)skb->data; 745 ip = iph->daddr; 746 747 switch (skb->h.icmph->code & 7) { 748 case ICMP_REDIR_NET: 749 case ICMP_REDIR_NETTOS: 750 /* 751 * As per RFC recommendations now handle it as a host redirect. 752 */ 753 case ICMP_REDIR_HOST: 754 case ICMP_REDIR_HOSTTOS: 755 ip_rt_redirect(skb->nh.iph->saddr, ip, skb->h.icmph->un.gateway, 756 iph->saddr, iph->tos, skb->dev); 757 break; 758 } 759 out: 760 return; 761 out_err: 762 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 763 goto out; 764 } 765 766 /* 767 * Handle ICMP_ECHO ("ping") requests. 768 * 769 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 770 * requests. 771 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 772 * included in the reply. 773 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 774 * echo requests, MUST have default=NOT. 775 * See also WRT handling of options once they are done and working. 776 */ 777 778 static void icmp_echo(struct sk_buff *skb) 779 { 780 if (!sysctl_icmp_echo_ignore_all) { 781 struct icmp_bxm icmp_param; 782 783 icmp_param.data.icmph = *skb->h.icmph; 784 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 785 icmp_param.skb = skb; 786 icmp_param.offset = 0; 787 icmp_param.data_len = skb->len; 788 icmp_param.head_len = sizeof(struct icmphdr); 789 icmp_reply(&icmp_param, skb); 790 } 791 } 792 793 /* 794 * Handle ICMP Timestamp requests. 795 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 796 * SHOULD be in the kernel for minimum random latency. 797 * MUST be accurate to a few minutes. 798 * MUST be updated at least at 15Hz. 799 */ 800 static void icmp_timestamp(struct sk_buff *skb) 801 { 802 struct timeval tv; 803 struct icmp_bxm icmp_param; 804 /* 805 * Too short. 806 */ 807 if (skb->len < 4) 808 goto out_err; 809 810 /* 811 * Fill in the current time as ms since midnight UT: 812 */ 813 do_gettimeofday(&tv); 814 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * 1000 + 815 tv.tv_usec / 1000); 816 icmp_param.data.times[2] = icmp_param.data.times[1]; 817 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 818 BUG(); 819 icmp_param.data.icmph = *skb->h.icmph; 820 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 821 icmp_param.data.icmph.code = 0; 822 icmp_param.skb = skb; 823 icmp_param.offset = 0; 824 icmp_param.data_len = 0; 825 icmp_param.head_len = sizeof(struct icmphdr) + 12; 826 icmp_reply(&icmp_param, skb); 827 out: 828 return; 829 out_err: 830 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 831 goto out; 832 } 833 834 835 /* 836 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 837 * 838 * RFC1122 (3.2.2.9). A host MUST only send replies to 839 * ADDRESS_MASK requests if it's been configured as an address mask 840 * agent. Receiving a request doesn't constitute implicit permission to 841 * act as one. Of course, implementing this correctly requires (SHOULD) 842 * a way to turn the functionality on and off. Another one for sysctl(), 843 * I guess. -- MS 844 * 845 * RFC1812 (4.3.3.9). A router MUST implement it. 846 * A router SHOULD have switch turning it on/off. 847 * This switch MUST be ON by default. 848 * 849 * Gratuitous replies, zero-source replies are not implemented, 850 * that complies with RFC. DO NOT implement them!!! All the idea 851 * of broadcast addrmask replies as specified in RFC950 is broken. 852 * The problem is that it is not uncommon to have several prefixes 853 * on one physical interface. Moreover, addrmask agent can even be 854 * not aware of existing another prefixes. 855 * If source is zero, addrmask agent cannot choose correct prefix. 856 * Gratuitous mask announcements suffer from the same problem. 857 * RFC1812 explains it, but still allows to use ADDRMASK, 858 * that is pretty silly. --ANK 859 * 860 * All these rules are so bizarre, that I removed kernel addrmask 861 * support at all. It is wrong, it is obsolete, nobody uses it in 862 * any case. --ANK 863 * 864 * Furthermore you can do it with a usermode address agent program 865 * anyway... 866 */ 867 868 static void icmp_address(struct sk_buff *skb) 869 { 870 #if 0 871 if (net_ratelimit()) 872 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 873 #endif 874 } 875 876 /* 877 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 878 * loudly if an inconsistency is found. 879 */ 880 881 static void icmp_address_reply(struct sk_buff *skb) 882 { 883 struct rtable *rt = (struct rtable *)skb->dst; 884 struct net_device *dev = skb->dev; 885 struct in_device *in_dev; 886 struct in_ifaddr *ifa; 887 888 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 889 goto out; 890 891 in_dev = in_dev_get(dev); 892 if (!in_dev) 893 goto out; 894 rcu_read_lock(); 895 if (in_dev->ifa_list && 896 IN_DEV_LOG_MARTIANS(in_dev) && 897 IN_DEV_FORWARD(in_dev)) { 898 u32 _mask, *mp; 899 900 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 901 if (mp == NULL) 902 BUG(); 903 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 904 if (*mp == ifa->ifa_mask && 905 inet_ifa_match(rt->rt_src, ifa)) 906 break; 907 } 908 if (!ifa && net_ratelimit()) { 909 printk(KERN_INFO "Wrong address mask %u.%u.%u.%u from " 910 "%s/%u.%u.%u.%u\n", 911 NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src)); 912 } 913 } 914 rcu_read_unlock(); 915 in_dev_put(in_dev); 916 out:; 917 } 918 919 static void icmp_discard(struct sk_buff *skb) 920 { 921 } 922 923 /* 924 * Deal with incoming ICMP packets. 925 */ 926 int icmp_rcv(struct sk_buff *skb) 927 { 928 struct icmphdr *icmph; 929 struct rtable *rt = (struct rtable *)skb->dst; 930 931 ICMP_INC_STATS_BH(ICMP_MIB_INMSGS); 932 933 switch (skb->ip_summed) { 934 case CHECKSUM_HW: 935 if (!(u16)csum_fold(skb->csum)) 936 break; 937 LIMIT_NETDEBUG(KERN_DEBUG "icmp v4 hw csum failure\n"); 938 case CHECKSUM_NONE: 939 if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) 940 goto error; 941 default:; 942 } 943 944 if (!pskb_pull(skb, sizeof(struct icmphdr))) 945 goto error; 946 947 icmph = skb->h.icmph; 948 949 /* 950 * 18 is the highest 'known' ICMP type. Anything else is a mystery 951 * 952 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 953 * discarded. 954 */ 955 if (icmph->type > NR_ICMP_TYPES) 956 goto error; 957 958 959 /* 960 * Parse the ICMP message 961 */ 962 963 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 964 /* 965 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 966 * silently ignored (we let user decide with a sysctl). 967 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 968 * discarded if to broadcast/multicast. 969 */ 970 if ((icmph->type == ICMP_ECHO || 971 icmph->type == ICMP_TIMESTAMP) && 972 sysctl_icmp_echo_ignore_broadcasts) { 973 goto error; 974 } 975 if (icmph->type != ICMP_ECHO && 976 icmph->type != ICMP_TIMESTAMP && 977 icmph->type != ICMP_ADDRESS && 978 icmph->type != ICMP_ADDRESSREPLY) { 979 goto error; 980 } 981 } 982 983 ICMP_INC_STATS_BH(icmp_pointers[icmph->type].input_entry); 984 icmp_pointers[icmph->type].handler(skb); 985 986 drop: 987 kfree_skb(skb); 988 return 0; 989 error: 990 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 991 goto drop; 992 } 993 994 /* 995 * This table is the definition of how we handle ICMP. 996 */ 997 static struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 998 [ICMP_ECHOREPLY] = { 999 .output_entry = ICMP_MIB_OUTECHOREPS, 1000 .input_entry = ICMP_MIB_INECHOREPS, 1001 .handler = icmp_discard, 1002 }, 1003 [1] = { 1004 .output_entry = ICMP_MIB_DUMMY, 1005 .input_entry = ICMP_MIB_INERRORS, 1006 .handler = icmp_discard, 1007 .error = 1, 1008 }, 1009 [2] = { 1010 .output_entry = ICMP_MIB_DUMMY, 1011 .input_entry = ICMP_MIB_INERRORS, 1012 .handler = icmp_discard, 1013 .error = 1, 1014 }, 1015 [ICMP_DEST_UNREACH] = { 1016 .output_entry = ICMP_MIB_OUTDESTUNREACHS, 1017 .input_entry = ICMP_MIB_INDESTUNREACHS, 1018 .handler = icmp_unreach, 1019 .error = 1, 1020 }, 1021 [ICMP_SOURCE_QUENCH] = { 1022 .output_entry = ICMP_MIB_OUTSRCQUENCHS, 1023 .input_entry = ICMP_MIB_INSRCQUENCHS, 1024 .handler = icmp_unreach, 1025 .error = 1, 1026 }, 1027 [ICMP_REDIRECT] = { 1028 .output_entry = ICMP_MIB_OUTREDIRECTS, 1029 .input_entry = ICMP_MIB_INREDIRECTS, 1030 .handler = icmp_redirect, 1031 .error = 1, 1032 }, 1033 [6] = { 1034 .output_entry = ICMP_MIB_DUMMY, 1035 .input_entry = ICMP_MIB_INERRORS, 1036 .handler = icmp_discard, 1037 .error = 1, 1038 }, 1039 [7] = { 1040 .output_entry = ICMP_MIB_DUMMY, 1041 .input_entry = ICMP_MIB_INERRORS, 1042 .handler = icmp_discard, 1043 .error = 1, 1044 }, 1045 [ICMP_ECHO] = { 1046 .output_entry = ICMP_MIB_OUTECHOS, 1047 .input_entry = ICMP_MIB_INECHOS, 1048 .handler = icmp_echo, 1049 }, 1050 [9] = { 1051 .output_entry = ICMP_MIB_DUMMY, 1052 .input_entry = ICMP_MIB_INERRORS, 1053 .handler = icmp_discard, 1054 .error = 1, 1055 }, 1056 [10] = { 1057 .output_entry = ICMP_MIB_DUMMY, 1058 .input_entry = ICMP_MIB_INERRORS, 1059 .handler = icmp_discard, 1060 .error = 1, 1061 }, 1062 [ICMP_TIME_EXCEEDED] = { 1063 .output_entry = ICMP_MIB_OUTTIMEEXCDS, 1064 .input_entry = ICMP_MIB_INTIMEEXCDS, 1065 .handler = icmp_unreach, 1066 .error = 1, 1067 }, 1068 [ICMP_PARAMETERPROB] = { 1069 .output_entry = ICMP_MIB_OUTPARMPROBS, 1070 .input_entry = ICMP_MIB_INPARMPROBS, 1071 .handler = icmp_unreach, 1072 .error = 1, 1073 }, 1074 [ICMP_TIMESTAMP] = { 1075 .output_entry = ICMP_MIB_OUTTIMESTAMPS, 1076 .input_entry = ICMP_MIB_INTIMESTAMPS, 1077 .handler = icmp_timestamp, 1078 }, 1079 [ICMP_TIMESTAMPREPLY] = { 1080 .output_entry = ICMP_MIB_OUTTIMESTAMPREPS, 1081 .input_entry = ICMP_MIB_INTIMESTAMPREPS, 1082 .handler = icmp_discard, 1083 }, 1084 [ICMP_INFO_REQUEST] = { 1085 .output_entry = ICMP_MIB_DUMMY, 1086 .input_entry = ICMP_MIB_DUMMY, 1087 .handler = icmp_discard, 1088 }, 1089 [ICMP_INFO_REPLY] = { 1090 .output_entry = ICMP_MIB_DUMMY, 1091 .input_entry = ICMP_MIB_DUMMY, 1092 .handler = icmp_discard, 1093 }, 1094 [ICMP_ADDRESS] = { 1095 .output_entry = ICMP_MIB_OUTADDRMASKS, 1096 .input_entry = ICMP_MIB_INADDRMASKS, 1097 .handler = icmp_address, 1098 }, 1099 [ICMP_ADDRESSREPLY] = { 1100 .output_entry = ICMP_MIB_OUTADDRMASKREPS, 1101 .input_entry = ICMP_MIB_INADDRMASKREPS, 1102 .handler = icmp_address_reply, 1103 }, 1104 }; 1105 1106 void __init icmp_init(struct net_proto_family *ops) 1107 { 1108 struct inet_sock *inet; 1109 int i; 1110 1111 for_each_cpu(i) { 1112 int err; 1113 1114 err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP, 1115 &per_cpu(__icmp_socket, i)); 1116 1117 if (err < 0) 1118 panic("Failed to create the ICMP control socket.\n"); 1119 1120 per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC; 1121 1122 /* Enough space for 2 64K ICMP packets, including 1123 * sk_buff struct overhead. 1124 */ 1125 per_cpu(__icmp_socket, i)->sk->sk_sndbuf = 1126 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1127 1128 inet = inet_sk(per_cpu(__icmp_socket, i)->sk); 1129 inet->uc_ttl = -1; 1130 inet->pmtudisc = IP_PMTUDISC_DONT; 1131 1132 /* Unhash it so that IP input processing does not even 1133 * see it, we do not wish this socket to see incoming 1134 * packets. 1135 */ 1136 per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk); 1137 } 1138 } 1139 1140 EXPORT_SYMBOL(icmp_err_convert); 1141 EXPORT_SYMBOL(icmp_send); 1142 EXPORT_SYMBOL(icmp_statistics); 1143 EXPORT_SYMBOL(xrlim_allow); 1144