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/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 <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 = 1; 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 const 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 return; 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 } 419 420 421 /* 422 * Send an ICMP message in response to a situation 423 * 424 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 425 * MAY send more (we do). 426 * MUST NOT change this header information. 427 * MUST NOT reply to a multicast/broadcast IP address. 428 * MUST NOT reply to a multicast/broadcast MAC address. 429 * MUST reply to only the first fragment. 430 */ 431 432 void icmp_send(struct sk_buff *skb_in, int type, int code, u32 info) 433 { 434 struct iphdr *iph; 435 int room; 436 struct icmp_bxm icmp_param; 437 struct rtable *rt = (struct rtable *)skb_in->dst; 438 struct ipcm_cookie ipc; 439 u32 saddr; 440 u8 tos; 441 442 if (!rt) 443 goto out; 444 445 /* 446 * Find the original header. It is expected to be valid, of course. 447 * Check this, icmp_send is called from the most obscure devices 448 * sometimes. 449 */ 450 iph = skb_in->nh.iph; 451 452 if ((u8 *)iph < skb_in->head || (u8 *)(iph + 1) > skb_in->tail) 453 goto out; 454 455 /* 456 * No replies to physical multicast/broadcast 457 */ 458 if (skb_in->pkt_type != PACKET_HOST) 459 goto out; 460 461 /* 462 * Now check at the protocol level 463 */ 464 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 465 goto out; 466 467 /* 468 * Only reply to fragment 0. We byte re-order the constant 469 * mask for efficiency. 470 */ 471 if (iph->frag_off & htons(IP_OFFSET)) 472 goto out; 473 474 /* 475 * If we send an ICMP error to an ICMP error a mess would result.. 476 */ 477 if (icmp_pointers[type].error) { 478 /* 479 * We are an error, check if we are replying to an 480 * ICMP error 481 */ 482 if (iph->protocol == IPPROTO_ICMP) { 483 u8 _inner_type, *itp; 484 485 itp = skb_header_pointer(skb_in, 486 skb_in->nh.raw + 487 (iph->ihl << 2) + 488 offsetof(struct icmphdr, 489 type) - 490 skb_in->data, 491 sizeof(_inner_type), 492 &_inner_type); 493 if (itp == NULL) 494 goto out; 495 496 /* 497 * Assume any unknown ICMP type is an error. This 498 * isn't specified by the RFC, but think about it.. 499 */ 500 if (*itp > NR_ICMP_TYPES || 501 icmp_pointers[*itp].error) 502 goto out; 503 } 504 } 505 506 if (icmp_xmit_lock()) 507 return; 508 509 /* 510 * Construct source address and options. 511 */ 512 513 saddr = iph->daddr; 514 if (!(rt->rt_flags & RTCF_LOCAL)) { 515 if (sysctl_icmp_errors_use_inbound_ifaddr) 516 saddr = inet_select_addr(skb_in->dev, 0, RT_SCOPE_LINK); 517 else 518 saddr = 0; 519 } 520 521 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 522 IPTOS_PREC_INTERNETCONTROL) : 523 iph->tos; 524 525 if (ip_options_echo(&icmp_param.replyopts, skb_in)) 526 goto out_unlock; 527 528 529 /* 530 * Prepare data for ICMP header. 531 */ 532 533 icmp_param.data.icmph.type = type; 534 icmp_param.data.icmph.code = code; 535 icmp_param.data.icmph.un.gateway = info; 536 icmp_param.data.icmph.checksum = 0; 537 icmp_param.skb = skb_in; 538 icmp_param.offset = skb_in->nh.raw - skb_in->data; 539 icmp_out_count(icmp_param.data.icmph.type); 540 inet_sk(icmp_socket->sk)->tos = tos; 541 ipc.addr = iph->saddr; 542 ipc.opt = &icmp_param.replyopts; 543 544 { 545 struct flowi fl = { 546 .nl_u = { 547 .ip4_u = { 548 .daddr = icmp_param.replyopts.srr ? 549 icmp_param.replyopts.faddr : 550 iph->saddr, 551 .saddr = saddr, 552 .tos = RT_TOS(tos) 553 } 554 }, 555 .proto = IPPROTO_ICMP, 556 .uli_u = { 557 .icmpt = { 558 .type = type, 559 .code = code 560 } 561 } 562 }; 563 if (ip_route_output_key(&rt, &fl)) 564 goto out_unlock; 565 } 566 567 if (!icmpv4_xrlim_allow(rt, type, code)) 568 goto ende; 569 570 /* RFC says return as much as we can without exceeding 576 bytes. */ 571 572 room = dst_mtu(&rt->u.dst); 573 if (room > 576) 574 room = 576; 575 room -= sizeof(struct iphdr) + icmp_param.replyopts.optlen; 576 room -= sizeof(struct icmphdr); 577 578 icmp_param.data_len = skb_in->len - icmp_param.offset; 579 if (icmp_param.data_len > room) 580 icmp_param.data_len = room; 581 icmp_param.head_len = sizeof(struct icmphdr); 582 583 icmp_push_reply(&icmp_param, &ipc, rt); 584 ende: 585 ip_rt_put(rt); 586 out_unlock: 587 icmp_xmit_unlock(); 588 out:; 589 } 590 591 592 /* 593 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH. 594 */ 595 596 static void icmp_unreach(struct sk_buff *skb) 597 { 598 struct iphdr *iph; 599 struct icmphdr *icmph; 600 int hash, protocol; 601 struct net_protocol *ipprot; 602 struct sock *raw_sk; 603 u32 info = 0; 604 605 /* 606 * Incomplete header ? 607 * Only checks for the IP header, there should be an 608 * additional check for longer headers in upper levels. 609 */ 610 611 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 612 goto out_err; 613 614 icmph = skb->h.icmph; 615 iph = (struct iphdr *)skb->data; 616 617 if (iph->ihl < 5) /* Mangled header, drop. */ 618 goto out_err; 619 620 if (icmph->type == ICMP_DEST_UNREACH) { 621 switch (icmph->code & 15) { 622 case ICMP_NET_UNREACH: 623 case ICMP_HOST_UNREACH: 624 case ICMP_PROT_UNREACH: 625 case ICMP_PORT_UNREACH: 626 break; 627 case ICMP_FRAG_NEEDED: 628 if (ipv4_config.no_pmtu_disc) { 629 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: " 630 "fragmentation needed " 631 "and DF set.\n", 632 NIPQUAD(iph->daddr)); 633 } else { 634 info = ip_rt_frag_needed(iph, 635 ntohs(icmph->un.frag.mtu)); 636 if (!info) 637 goto out; 638 } 639 break; 640 case ICMP_SR_FAILED: 641 LIMIT_NETDEBUG(KERN_INFO "ICMP: %u.%u.%u.%u: Source " 642 "Route Failed.\n", 643 NIPQUAD(iph->daddr)); 644 break; 645 default: 646 break; 647 } 648 if (icmph->code > NR_ICMP_UNREACH) 649 goto out; 650 } else if (icmph->type == ICMP_PARAMETERPROB) 651 info = ntohl(icmph->un.gateway) >> 24; 652 653 /* 654 * Throw it at our lower layers 655 * 656 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 657 * header. 658 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 659 * transport layer. 660 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 661 * transport layer. 662 */ 663 664 /* 665 * Check the other end isnt violating RFC 1122. Some routers send 666 * bogus responses to broadcast frames. If you see this message 667 * first check your netmask matches at both ends, if it does then 668 * get the other vendor to fix their kit. 669 */ 670 671 if (!sysctl_icmp_ignore_bogus_error_responses && 672 inet_addr_type(iph->daddr) == RTN_BROADCAST) { 673 if (net_ratelimit()) 674 printk(KERN_WARNING "%u.%u.%u.%u sent an invalid ICMP " 675 "type %u, code %u " 676 "error to a broadcast: %u.%u.%u.%u on %s\n", 677 NIPQUAD(skb->nh.iph->saddr), 678 icmph->type, icmph->code, 679 NIPQUAD(iph->daddr), 680 skb->dev->name); 681 goto out; 682 } 683 684 /* Checkin full IP header plus 8 bytes of protocol to 685 * avoid additional coding at protocol handlers. 686 */ 687 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) 688 goto out; 689 690 iph = (struct iphdr *)skb->data; 691 protocol = iph->protocol; 692 693 /* 694 * Deliver ICMP message to raw sockets. Pretty useless feature? 695 */ 696 697 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 698 hash = protocol & (MAX_INET_PROTOS - 1); 699 read_lock(&raw_v4_lock); 700 if ((raw_sk = sk_head(&raw_v4_htable[hash])) != NULL) { 701 while ((raw_sk = __raw_v4_lookup(raw_sk, protocol, iph->daddr, 702 iph->saddr, 703 skb->dev->ifindex)) != NULL) { 704 raw_err(raw_sk, skb, info); 705 raw_sk = sk_next(raw_sk); 706 iph = (struct iphdr *)skb->data; 707 } 708 } 709 read_unlock(&raw_v4_lock); 710 711 rcu_read_lock(); 712 ipprot = rcu_dereference(inet_protos[hash]); 713 if (ipprot && ipprot->err_handler) 714 ipprot->err_handler(skb, info); 715 rcu_read_unlock(); 716 717 out: 718 return; 719 out_err: 720 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 721 goto out; 722 } 723 724 725 /* 726 * Handle ICMP_REDIRECT. 727 */ 728 729 static void icmp_redirect(struct sk_buff *skb) 730 { 731 struct iphdr *iph; 732 733 if (skb->len < sizeof(struct iphdr)) 734 goto out_err; 735 736 /* 737 * Get the copied header of the packet that caused the redirect 738 */ 739 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 740 goto out; 741 742 iph = (struct iphdr *)skb->data; 743 744 switch (skb->h.icmph->code & 7) { 745 case ICMP_REDIR_NET: 746 case ICMP_REDIR_NETTOS: 747 /* 748 * As per RFC recommendations now handle it as a host redirect. 749 */ 750 case ICMP_REDIR_HOST: 751 case ICMP_REDIR_HOSTTOS: 752 ip_rt_redirect(skb->nh.iph->saddr, iph->daddr, 753 skb->h.icmph->un.gateway, 754 iph->saddr, skb->dev); 755 break; 756 } 757 out: 758 return; 759 out_err: 760 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 761 goto out; 762 } 763 764 /* 765 * Handle ICMP_ECHO ("ping") requests. 766 * 767 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 768 * requests. 769 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 770 * included in the reply. 771 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 772 * echo requests, MUST have default=NOT. 773 * See also WRT handling of options once they are done and working. 774 */ 775 776 static void icmp_echo(struct sk_buff *skb) 777 { 778 if (!sysctl_icmp_echo_ignore_all) { 779 struct icmp_bxm icmp_param; 780 781 icmp_param.data.icmph = *skb->h.icmph; 782 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 783 icmp_param.skb = skb; 784 icmp_param.offset = 0; 785 icmp_param.data_len = skb->len; 786 icmp_param.head_len = sizeof(struct icmphdr); 787 icmp_reply(&icmp_param, skb); 788 } 789 } 790 791 /* 792 * Handle ICMP Timestamp requests. 793 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 794 * SHOULD be in the kernel for minimum random latency. 795 * MUST be accurate to a few minutes. 796 * MUST be updated at least at 15Hz. 797 */ 798 static void icmp_timestamp(struct sk_buff *skb) 799 { 800 struct timeval tv; 801 struct icmp_bxm icmp_param; 802 /* 803 * Too short. 804 */ 805 if (skb->len < 4) 806 goto out_err; 807 808 /* 809 * Fill in the current time as ms since midnight UT: 810 */ 811 do_gettimeofday(&tv); 812 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * 1000 + 813 tv.tv_usec / 1000); 814 icmp_param.data.times[2] = icmp_param.data.times[1]; 815 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 816 BUG(); 817 icmp_param.data.icmph = *skb->h.icmph; 818 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 819 icmp_param.data.icmph.code = 0; 820 icmp_param.skb = skb; 821 icmp_param.offset = 0; 822 icmp_param.data_len = 0; 823 icmp_param.head_len = sizeof(struct icmphdr) + 12; 824 icmp_reply(&icmp_param, skb); 825 out: 826 return; 827 out_err: 828 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 829 goto out; 830 } 831 832 833 /* 834 * Handle ICMP_ADDRESS_MASK requests. (RFC950) 835 * 836 * RFC1122 (3.2.2.9). A host MUST only send replies to 837 * ADDRESS_MASK requests if it's been configured as an address mask 838 * agent. Receiving a request doesn't constitute implicit permission to 839 * act as one. Of course, implementing this correctly requires (SHOULD) 840 * a way to turn the functionality on and off. Another one for sysctl(), 841 * I guess. -- MS 842 * 843 * RFC1812 (4.3.3.9). A router MUST implement it. 844 * A router SHOULD have switch turning it on/off. 845 * This switch MUST be ON by default. 846 * 847 * Gratuitous replies, zero-source replies are not implemented, 848 * that complies with RFC. DO NOT implement them!!! All the idea 849 * of broadcast addrmask replies as specified in RFC950 is broken. 850 * The problem is that it is not uncommon to have several prefixes 851 * on one physical interface. Moreover, addrmask agent can even be 852 * not aware of existing another prefixes. 853 * If source is zero, addrmask agent cannot choose correct prefix. 854 * Gratuitous mask announcements suffer from the same problem. 855 * RFC1812 explains it, but still allows to use ADDRMASK, 856 * that is pretty silly. --ANK 857 * 858 * All these rules are so bizarre, that I removed kernel addrmask 859 * support at all. It is wrong, it is obsolete, nobody uses it in 860 * any case. --ANK 861 * 862 * Furthermore you can do it with a usermode address agent program 863 * anyway... 864 */ 865 866 static void icmp_address(struct sk_buff *skb) 867 { 868 #if 0 869 if (net_ratelimit()) 870 printk(KERN_DEBUG "a guy asks for address mask. Who is it?\n"); 871 #endif 872 } 873 874 /* 875 * RFC1812 (4.3.3.9). A router SHOULD listen all replies, and complain 876 * loudly if an inconsistency is found. 877 */ 878 879 static void icmp_address_reply(struct sk_buff *skb) 880 { 881 struct rtable *rt = (struct rtable *)skb->dst; 882 struct net_device *dev = skb->dev; 883 struct in_device *in_dev; 884 struct in_ifaddr *ifa; 885 886 if (skb->len < 4 || !(rt->rt_flags&RTCF_DIRECTSRC)) 887 goto out; 888 889 in_dev = in_dev_get(dev); 890 if (!in_dev) 891 goto out; 892 rcu_read_lock(); 893 if (in_dev->ifa_list && 894 IN_DEV_LOG_MARTIANS(in_dev) && 895 IN_DEV_FORWARD(in_dev)) { 896 u32 _mask, *mp; 897 898 mp = skb_header_pointer(skb, 0, sizeof(_mask), &_mask); 899 BUG_ON(mp == NULL); 900 for (ifa = in_dev->ifa_list; ifa; ifa = ifa->ifa_next) { 901 if (*mp == ifa->ifa_mask && 902 inet_ifa_match(rt->rt_src, ifa)) 903 break; 904 } 905 if (!ifa && net_ratelimit()) { 906 printk(KERN_INFO "Wrong address mask %u.%u.%u.%u from " 907 "%s/%u.%u.%u.%u\n", 908 NIPQUAD(*mp), dev->name, NIPQUAD(rt->rt_src)); 909 } 910 } 911 rcu_read_unlock(); 912 in_dev_put(in_dev); 913 out:; 914 } 915 916 static void icmp_discard(struct sk_buff *skb) 917 { 918 } 919 920 /* 921 * Deal with incoming ICMP packets. 922 */ 923 int icmp_rcv(struct sk_buff *skb) 924 { 925 struct icmphdr *icmph; 926 struct rtable *rt = (struct rtable *)skb->dst; 927 928 ICMP_INC_STATS_BH(ICMP_MIB_INMSGS); 929 930 switch (skb->ip_summed) { 931 case CHECKSUM_HW: 932 if (!(u16)csum_fold(skb->csum)) 933 break; 934 /* fall through */ 935 case CHECKSUM_NONE: 936 skb->csum = 0; 937 if (__skb_checksum_complete(skb)) 938 goto error; 939 } 940 941 if (!pskb_pull(skb, sizeof(struct icmphdr))) 942 goto error; 943 944 icmph = skb->h.icmph; 945 946 /* 947 * 18 is the highest 'known' ICMP type. Anything else is a mystery 948 * 949 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 950 * discarded. 951 */ 952 if (icmph->type > NR_ICMP_TYPES) 953 goto error; 954 955 956 /* 957 * Parse the ICMP message 958 */ 959 960 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 961 /* 962 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 963 * silently ignored (we let user decide with a sysctl). 964 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 965 * discarded if to broadcast/multicast. 966 */ 967 if ((icmph->type == ICMP_ECHO || 968 icmph->type == ICMP_TIMESTAMP) && 969 sysctl_icmp_echo_ignore_broadcasts) { 970 goto error; 971 } 972 if (icmph->type != ICMP_ECHO && 973 icmph->type != ICMP_TIMESTAMP && 974 icmph->type != ICMP_ADDRESS && 975 icmph->type != ICMP_ADDRESSREPLY) { 976 goto error; 977 } 978 } 979 980 ICMP_INC_STATS_BH(icmp_pointers[icmph->type].input_entry); 981 icmp_pointers[icmph->type].handler(skb); 982 983 drop: 984 kfree_skb(skb); 985 return 0; 986 error: 987 ICMP_INC_STATS_BH(ICMP_MIB_INERRORS); 988 goto drop; 989 } 990 991 /* 992 * This table is the definition of how we handle ICMP. 993 */ 994 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 995 [ICMP_ECHOREPLY] = { 996 .output_entry = ICMP_MIB_OUTECHOREPS, 997 .input_entry = ICMP_MIB_INECHOREPS, 998 .handler = icmp_discard, 999 }, 1000 [1] = { 1001 .output_entry = ICMP_MIB_DUMMY, 1002 .input_entry = ICMP_MIB_INERRORS, 1003 .handler = icmp_discard, 1004 .error = 1, 1005 }, 1006 [2] = { 1007 .output_entry = ICMP_MIB_DUMMY, 1008 .input_entry = ICMP_MIB_INERRORS, 1009 .handler = icmp_discard, 1010 .error = 1, 1011 }, 1012 [ICMP_DEST_UNREACH] = { 1013 .output_entry = ICMP_MIB_OUTDESTUNREACHS, 1014 .input_entry = ICMP_MIB_INDESTUNREACHS, 1015 .handler = icmp_unreach, 1016 .error = 1, 1017 }, 1018 [ICMP_SOURCE_QUENCH] = { 1019 .output_entry = ICMP_MIB_OUTSRCQUENCHS, 1020 .input_entry = ICMP_MIB_INSRCQUENCHS, 1021 .handler = icmp_unreach, 1022 .error = 1, 1023 }, 1024 [ICMP_REDIRECT] = { 1025 .output_entry = ICMP_MIB_OUTREDIRECTS, 1026 .input_entry = ICMP_MIB_INREDIRECTS, 1027 .handler = icmp_redirect, 1028 .error = 1, 1029 }, 1030 [6] = { 1031 .output_entry = ICMP_MIB_DUMMY, 1032 .input_entry = ICMP_MIB_INERRORS, 1033 .handler = icmp_discard, 1034 .error = 1, 1035 }, 1036 [7] = { 1037 .output_entry = ICMP_MIB_DUMMY, 1038 .input_entry = ICMP_MIB_INERRORS, 1039 .handler = icmp_discard, 1040 .error = 1, 1041 }, 1042 [ICMP_ECHO] = { 1043 .output_entry = ICMP_MIB_OUTECHOS, 1044 .input_entry = ICMP_MIB_INECHOS, 1045 .handler = icmp_echo, 1046 }, 1047 [9] = { 1048 .output_entry = ICMP_MIB_DUMMY, 1049 .input_entry = ICMP_MIB_INERRORS, 1050 .handler = icmp_discard, 1051 .error = 1, 1052 }, 1053 [10] = { 1054 .output_entry = ICMP_MIB_DUMMY, 1055 .input_entry = ICMP_MIB_INERRORS, 1056 .handler = icmp_discard, 1057 .error = 1, 1058 }, 1059 [ICMP_TIME_EXCEEDED] = { 1060 .output_entry = ICMP_MIB_OUTTIMEEXCDS, 1061 .input_entry = ICMP_MIB_INTIMEEXCDS, 1062 .handler = icmp_unreach, 1063 .error = 1, 1064 }, 1065 [ICMP_PARAMETERPROB] = { 1066 .output_entry = ICMP_MIB_OUTPARMPROBS, 1067 .input_entry = ICMP_MIB_INPARMPROBS, 1068 .handler = icmp_unreach, 1069 .error = 1, 1070 }, 1071 [ICMP_TIMESTAMP] = { 1072 .output_entry = ICMP_MIB_OUTTIMESTAMPS, 1073 .input_entry = ICMP_MIB_INTIMESTAMPS, 1074 .handler = icmp_timestamp, 1075 }, 1076 [ICMP_TIMESTAMPREPLY] = { 1077 .output_entry = ICMP_MIB_OUTTIMESTAMPREPS, 1078 .input_entry = ICMP_MIB_INTIMESTAMPREPS, 1079 .handler = icmp_discard, 1080 }, 1081 [ICMP_INFO_REQUEST] = { 1082 .output_entry = ICMP_MIB_DUMMY, 1083 .input_entry = ICMP_MIB_DUMMY, 1084 .handler = icmp_discard, 1085 }, 1086 [ICMP_INFO_REPLY] = { 1087 .output_entry = ICMP_MIB_DUMMY, 1088 .input_entry = ICMP_MIB_DUMMY, 1089 .handler = icmp_discard, 1090 }, 1091 [ICMP_ADDRESS] = { 1092 .output_entry = ICMP_MIB_OUTADDRMASKS, 1093 .input_entry = ICMP_MIB_INADDRMASKS, 1094 .handler = icmp_address, 1095 }, 1096 [ICMP_ADDRESSREPLY] = { 1097 .output_entry = ICMP_MIB_OUTADDRMASKREPS, 1098 .input_entry = ICMP_MIB_INADDRMASKREPS, 1099 .handler = icmp_address_reply, 1100 }, 1101 }; 1102 1103 void __init icmp_init(struct net_proto_family *ops) 1104 { 1105 struct inet_sock *inet; 1106 int i; 1107 1108 for_each_possible_cpu(i) { 1109 int err; 1110 1111 err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP, 1112 &per_cpu(__icmp_socket, i)); 1113 1114 if (err < 0) 1115 panic("Failed to create the ICMP control socket.\n"); 1116 1117 per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC; 1118 1119 /* Enough space for 2 64K ICMP packets, including 1120 * sk_buff struct overhead. 1121 */ 1122 per_cpu(__icmp_socket, i)->sk->sk_sndbuf = 1123 (2 * ((64 * 1024) + sizeof(struct sk_buff))); 1124 1125 inet = inet_sk(per_cpu(__icmp_socket, i)->sk); 1126 inet->uc_ttl = -1; 1127 inet->pmtudisc = IP_PMTUDISC_DONT; 1128 1129 /* Unhash it so that IP input processing does not even 1130 * see it, we do not wish this socket to see incoming 1131 * packets. 1132 */ 1133 per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk); 1134 } 1135 } 1136 1137 EXPORT_SYMBOL(icmp_err_convert); 1138 EXPORT_SYMBOL(icmp_send); 1139 EXPORT_SYMBOL(icmp_statistics); 1140 EXPORT_SYMBOL(xrlim_allow); 1141