1 /* 2 * NET3: Implementation of the ICMP protocol layer. 3 * 4 * Alan Cox, <alan@lxorguk.ukuu.org.uk> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 * Some of the function names and the icmp unreach table for this 12 * module were derived from [icmp.c 1.0.11 06/02/93] by 13 * Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting. 14 * Other than that this module is a complete rewrite. 15 * 16 * Fixes: 17 * Clemens Fruhwirth : introduce global icmp rate limiting 18 * with icmp type masking ability instead 19 * of broken per type icmp timeouts. 20 * Mike Shaver : RFC1122 checks. 21 * Alan Cox : Multicast ping reply as self. 22 * Alan Cox : Fix atomicity lockup in ip_build_xmit 23 * call. 24 * Alan Cox : Added 216,128 byte paths to the MTU 25 * code. 26 * Martin Mares : RFC1812 checks. 27 * Martin Mares : Can be configured to follow redirects 28 * if acting as a router _without_ a 29 * routing protocol (RFC 1812). 30 * Martin Mares : Echo requests may be configured to 31 * be ignored (RFC 1812). 32 * Martin Mares : Limitation of ICMP error message 33 * transmit rate (RFC 1812). 34 * Martin Mares : TOS and Precedence set correctly 35 * (RFC 1812). 36 * Martin Mares : Now copying as much data from the 37 * original packet as we can without 38 * exceeding 576 bytes (RFC 1812). 39 * Willy Konynenberg : Transparent proxying support. 40 * Keith Owens : RFC1191 correction for 4.2BSD based 41 * path MTU bug. 42 * Thomas Quinot : ICMP Dest Unreach codes up to 15 are 43 * valid (RFC 1812). 44 * Andi Kleen : Check all packet lengths properly 45 * and moved all kfree_skb() up to 46 * icmp_rcv. 47 * Andi Kleen : Move the rate limit bookkeeping 48 * into the dest entry and use a token 49 * bucket filter (thanks to ANK). Make 50 * the rates sysctl configurable. 51 * Yu Tianli : Fixed two ugly bugs in icmp_send 52 * - IP option length was accounted wrongly 53 * - ICMP header length was not accounted 54 * at all. 55 * Tristan Greaves : Added sysctl option to ignore bogus 56 * broadcast responses from broken routers. 57 * 58 * To Fix: 59 * 60 * - Should use skb_pull() instead of all the manual checking. 61 * This would also greatly simply some upper layer error handlers. --AK 62 * 63 */ 64 65 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 66 67 #include <linux/module.h> 68 #include <linux/types.h> 69 #include <linux/jiffies.h> 70 #include <linux/kernel.h> 71 #include <linux/fcntl.h> 72 #include <linux/socket.h> 73 #include <linux/in.h> 74 #include <linux/inet.h> 75 #include <linux/inetdevice.h> 76 #include <linux/netdevice.h> 77 #include <linux/string.h> 78 #include <linux/netfilter_ipv4.h> 79 #include <linux/slab.h> 80 #include <net/snmp.h> 81 #include <net/ip.h> 82 #include <net/route.h> 83 #include <net/protocol.h> 84 #include <net/icmp.h> 85 #include <net/tcp.h> 86 #include <net/udp.h> 87 #include <net/raw.h> 88 #include <net/ping.h> 89 #include <linux/skbuff.h> 90 #include <net/sock.h> 91 #include <linux/errno.h> 92 #include <linux/timer.h> 93 #include <linux/init.h> 94 #include <asm/uaccess.h> 95 #include <net/checksum.h> 96 #include <net/xfrm.h> 97 #include <net/inet_common.h> 98 #include <net/ip_fib.h> 99 100 /* 101 * Build xmit assembly blocks 102 */ 103 104 struct icmp_bxm { 105 struct sk_buff *skb; 106 int offset; 107 int data_len; 108 109 struct { 110 struct icmphdr icmph; 111 __be32 times[3]; 112 } data; 113 int head_len; 114 struct ip_options_data replyopts; 115 }; 116 117 /* An array of errno for error messages from dest unreach. */ 118 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 119 120 const struct icmp_err icmp_err_convert[] = { 121 { 122 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 123 .fatal = 0, 124 }, 125 { 126 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 127 .fatal = 0, 128 }, 129 { 130 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 131 .fatal = 1, 132 }, 133 { 134 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 135 .fatal = 1, 136 }, 137 { 138 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 139 .fatal = 0, 140 }, 141 { 142 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 143 .fatal = 0, 144 }, 145 { 146 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 147 .fatal = 1, 148 }, 149 { 150 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 151 .fatal = 1, 152 }, 153 { 154 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 155 .fatal = 1, 156 }, 157 { 158 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 159 .fatal = 1, 160 }, 161 { 162 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 163 .fatal = 1, 164 }, 165 { 166 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 167 .fatal = 0, 168 }, 169 { 170 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 171 .fatal = 0, 172 }, 173 { 174 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 175 .fatal = 1, 176 }, 177 { 178 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 179 .fatal = 1, 180 }, 181 { 182 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 183 .fatal = 1, 184 }, 185 }; 186 EXPORT_SYMBOL(icmp_err_convert); 187 188 /* 189 * ICMP control array. This specifies what to do with each ICMP. 190 */ 191 192 struct icmp_control { 193 bool (*handler)(struct sk_buff *skb); 194 short error; /* This ICMP is classed as an error message */ 195 }; 196 197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 198 199 /* 200 * The ICMP socket(s). This is the most convenient way to flow control 201 * our ICMP output as well as maintain a clean interface throughout 202 * all layers. All Socketless IP sends will soon be gone. 203 * 204 * On SMP we have one ICMP socket per-cpu. 205 */ 206 static struct sock *icmp_sk(struct net *net) 207 { 208 return *this_cpu_ptr(net->ipv4.icmp_sk); 209 } 210 211 static inline struct sock *icmp_xmit_lock(struct net *net) 212 { 213 struct sock *sk; 214 215 local_bh_disable(); 216 217 sk = icmp_sk(net); 218 219 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 220 /* This can happen if the output path signals a 221 * dst_link_failure() for an outgoing ICMP packet. 222 */ 223 local_bh_enable(); 224 return NULL; 225 } 226 return sk; 227 } 228 229 static inline void icmp_xmit_unlock(struct sock *sk) 230 { 231 spin_unlock_bh(&sk->sk_lock.slock); 232 } 233 234 int sysctl_icmp_msgs_per_sec __read_mostly = 1000; 235 int sysctl_icmp_msgs_burst __read_mostly = 50; 236 237 static struct { 238 spinlock_t lock; 239 u32 credit; 240 u32 stamp; 241 } icmp_global = { 242 .lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock), 243 }; 244 245 /** 246 * icmp_global_allow - Are we allowed to send one more ICMP message ? 247 * 248 * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. 249 * Returns false if we reached the limit and can not send another packet. 250 * Note: called with BH disabled 251 */ 252 bool icmp_global_allow(void) 253 { 254 u32 credit, delta, incr = 0, now = (u32)jiffies; 255 bool rc = false; 256 257 /* Check if token bucket is empty and cannot be refilled 258 * without taking the spinlock. 259 */ 260 if (!icmp_global.credit) { 261 delta = min_t(u32, now - icmp_global.stamp, HZ); 262 if (delta < HZ / 50) 263 return false; 264 } 265 266 spin_lock(&icmp_global.lock); 267 delta = min_t(u32, now - icmp_global.stamp, HZ); 268 if (delta >= HZ / 50) { 269 incr = sysctl_icmp_msgs_per_sec * delta / HZ ; 270 if (incr) 271 icmp_global.stamp = now; 272 } 273 credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); 274 if (credit) { 275 credit--; 276 rc = true; 277 } 278 icmp_global.credit = credit; 279 spin_unlock(&icmp_global.lock); 280 return rc; 281 } 282 EXPORT_SYMBOL(icmp_global_allow); 283 284 /* 285 * Send an ICMP frame. 286 */ 287 288 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 289 struct flowi4 *fl4, int type, int code) 290 { 291 struct dst_entry *dst = &rt->dst; 292 bool rc = true; 293 294 if (type > NR_ICMP_TYPES) 295 goto out; 296 297 /* Don't limit PMTU discovery. */ 298 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 299 goto out; 300 301 /* No rate limit on loopback */ 302 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 303 goto out; 304 305 /* Limit if icmp type is enabled in ratemask. */ 306 if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask)) 307 goto out; 308 309 rc = false; 310 if (icmp_global_allow()) { 311 struct inet_peer *peer; 312 313 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, 1); 314 rc = inet_peer_xrlim_allow(peer, 315 net->ipv4.sysctl_icmp_ratelimit); 316 if (peer) 317 inet_putpeer(peer); 318 } 319 out: 320 return rc; 321 } 322 323 /* 324 * Maintain the counters used in the SNMP statistics for outgoing ICMP 325 */ 326 void icmp_out_count(struct net *net, unsigned char type) 327 { 328 ICMPMSGOUT_INC_STATS(net, type); 329 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 330 } 331 332 /* 333 * Checksum each fragment, and on the first include the headers and final 334 * checksum. 335 */ 336 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 337 struct sk_buff *skb) 338 { 339 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 340 __wsum csum; 341 342 csum = skb_copy_and_csum_bits(icmp_param->skb, 343 icmp_param->offset + offset, 344 to, len, 0); 345 346 skb->csum = csum_block_add(skb->csum, csum, odd); 347 if (icmp_pointers[icmp_param->data.icmph.type].error) 348 nf_ct_attach(skb, icmp_param->skb); 349 return 0; 350 } 351 352 static void icmp_push_reply(struct icmp_bxm *icmp_param, 353 struct flowi4 *fl4, 354 struct ipcm_cookie *ipc, struct rtable **rt) 355 { 356 struct sock *sk; 357 struct sk_buff *skb; 358 359 sk = icmp_sk(dev_net((*rt)->dst.dev)); 360 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 361 icmp_param->data_len+icmp_param->head_len, 362 icmp_param->head_len, 363 ipc, rt, MSG_DONTWAIT) < 0) { 364 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS); 365 ip_flush_pending_frames(sk); 366 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 367 struct icmphdr *icmph = icmp_hdr(skb); 368 __wsum csum = 0; 369 struct sk_buff *skb1; 370 371 skb_queue_walk(&sk->sk_write_queue, skb1) { 372 csum = csum_add(csum, skb1->csum); 373 } 374 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 375 (char *)icmph, 376 icmp_param->head_len, csum); 377 icmph->checksum = csum_fold(csum); 378 skb->ip_summed = CHECKSUM_NONE; 379 ip_push_pending_frames(sk, fl4); 380 } 381 } 382 383 /* 384 * Driving logic for building and sending ICMP messages. 385 */ 386 387 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 388 { 389 struct ipcm_cookie ipc; 390 struct rtable *rt = skb_rtable(skb); 391 struct net *net = dev_net(rt->dst.dev); 392 struct flowi4 fl4; 393 struct sock *sk; 394 struct inet_sock *inet; 395 __be32 daddr, saddr; 396 u32 mark = IP4_REPLY_MARK(net, skb->mark); 397 398 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb)) 399 return; 400 401 sk = icmp_xmit_lock(net); 402 if (sk == NULL) 403 return; 404 inet = inet_sk(sk); 405 406 icmp_param->data.icmph.checksum = 0; 407 408 inet->tos = ip_hdr(skb)->tos; 409 sk->sk_mark = mark; 410 daddr = ipc.addr = ip_hdr(skb)->saddr; 411 saddr = fib_compute_spec_dst(skb); 412 ipc.opt = NULL; 413 ipc.tx_flags = 0; 414 ipc.ttl = 0; 415 ipc.tos = -1; 416 417 if (icmp_param->replyopts.opt.opt.optlen) { 418 ipc.opt = &icmp_param->replyopts.opt; 419 if (ipc.opt->opt.srr) 420 daddr = icmp_param->replyopts.opt.opt.faddr; 421 } 422 memset(&fl4, 0, sizeof(fl4)); 423 fl4.daddr = daddr; 424 fl4.saddr = saddr; 425 fl4.flowi4_mark = mark; 426 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 427 fl4.flowi4_proto = IPPROTO_ICMP; 428 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 429 rt = ip_route_output_key(net, &fl4); 430 if (IS_ERR(rt)) 431 goto out_unlock; 432 if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type, 433 icmp_param->data.icmph.code)) 434 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 435 ip_rt_put(rt); 436 out_unlock: 437 icmp_xmit_unlock(sk); 438 } 439 440 static struct rtable *icmp_route_lookup(struct net *net, 441 struct flowi4 *fl4, 442 struct sk_buff *skb_in, 443 const struct iphdr *iph, 444 __be32 saddr, u8 tos, u32 mark, 445 int type, int code, 446 struct icmp_bxm *param) 447 { 448 struct rtable *rt, *rt2; 449 struct flowi4 fl4_dec; 450 int err; 451 452 memset(fl4, 0, sizeof(*fl4)); 453 fl4->daddr = (param->replyopts.opt.opt.srr ? 454 param->replyopts.opt.opt.faddr : iph->saddr); 455 fl4->saddr = saddr; 456 fl4->flowi4_mark = mark; 457 fl4->flowi4_tos = RT_TOS(tos); 458 fl4->flowi4_proto = IPPROTO_ICMP; 459 fl4->fl4_icmp_type = type; 460 fl4->fl4_icmp_code = code; 461 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 462 rt = __ip_route_output_key(net, fl4); 463 if (IS_ERR(rt)) 464 return rt; 465 466 /* No need to clone since we're just using its address. */ 467 rt2 = rt; 468 469 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 470 flowi4_to_flowi(fl4), NULL, 0); 471 if (!IS_ERR(rt)) { 472 if (rt != rt2) 473 return rt; 474 } else if (PTR_ERR(rt) == -EPERM) { 475 rt = NULL; 476 } else 477 return rt; 478 479 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 480 if (err) 481 goto relookup_failed; 482 483 if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) { 484 rt2 = __ip_route_output_key(net, &fl4_dec); 485 if (IS_ERR(rt2)) 486 err = PTR_ERR(rt2); 487 } else { 488 struct flowi4 fl4_2 = {}; 489 unsigned long orefdst; 490 491 fl4_2.daddr = fl4_dec.saddr; 492 rt2 = ip_route_output_key(net, &fl4_2); 493 if (IS_ERR(rt2)) { 494 err = PTR_ERR(rt2); 495 goto relookup_failed; 496 } 497 /* Ugh! */ 498 orefdst = skb_in->_skb_refdst; /* save old refdst */ 499 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 500 RT_TOS(tos), rt2->dst.dev); 501 502 dst_release(&rt2->dst); 503 rt2 = skb_rtable(skb_in); 504 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 505 } 506 507 if (err) 508 goto relookup_failed; 509 510 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 511 flowi4_to_flowi(&fl4_dec), NULL, 512 XFRM_LOOKUP_ICMP); 513 if (!IS_ERR(rt2)) { 514 dst_release(&rt->dst); 515 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 516 rt = rt2; 517 } else if (PTR_ERR(rt2) == -EPERM) { 518 if (rt) 519 dst_release(&rt->dst); 520 return rt2; 521 } else { 522 err = PTR_ERR(rt2); 523 goto relookup_failed; 524 } 525 return rt; 526 527 relookup_failed: 528 if (rt) 529 return rt; 530 return ERR_PTR(err); 531 } 532 533 /* 534 * Send an ICMP message in response to a situation 535 * 536 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 537 * MAY send more (we do). 538 * MUST NOT change this header information. 539 * MUST NOT reply to a multicast/broadcast IP address. 540 * MUST NOT reply to a multicast/broadcast MAC address. 541 * MUST reply to only the first fragment. 542 */ 543 544 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 545 { 546 struct iphdr *iph; 547 int room; 548 struct icmp_bxm *icmp_param; 549 struct rtable *rt = skb_rtable(skb_in); 550 struct ipcm_cookie ipc; 551 struct flowi4 fl4; 552 __be32 saddr; 553 u8 tos; 554 u32 mark; 555 struct net *net; 556 struct sock *sk; 557 558 if (!rt) 559 goto out; 560 net = dev_net(rt->dst.dev); 561 562 /* 563 * Find the original header. It is expected to be valid, of course. 564 * Check this, icmp_send is called from the most obscure devices 565 * sometimes. 566 */ 567 iph = ip_hdr(skb_in); 568 569 if ((u8 *)iph < skb_in->head || 570 (skb_network_header(skb_in) + sizeof(*iph)) > 571 skb_tail_pointer(skb_in)) 572 goto out; 573 574 /* 575 * No replies to physical multicast/broadcast 576 */ 577 if (skb_in->pkt_type != PACKET_HOST) 578 goto out; 579 580 /* 581 * Now check at the protocol level 582 */ 583 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 584 goto out; 585 586 /* 587 * Only reply to fragment 0. We byte re-order the constant 588 * mask for efficiency. 589 */ 590 if (iph->frag_off & htons(IP_OFFSET)) 591 goto out; 592 593 /* 594 * If we send an ICMP error to an ICMP error a mess would result.. 595 */ 596 if (icmp_pointers[type].error) { 597 /* 598 * We are an error, check if we are replying to an 599 * ICMP error 600 */ 601 if (iph->protocol == IPPROTO_ICMP) { 602 u8 _inner_type, *itp; 603 604 itp = skb_header_pointer(skb_in, 605 skb_network_header(skb_in) + 606 (iph->ihl << 2) + 607 offsetof(struct icmphdr, 608 type) - 609 skb_in->data, 610 sizeof(_inner_type), 611 &_inner_type); 612 if (itp == NULL) 613 goto out; 614 615 /* 616 * Assume any unknown ICMP type is an error. This 617 * isn't specified by the RFC, but think about it.. 618 */ 619 if (*itp > NR_ICMP_TYPES || 620 icmp_pointers[*itp].error) 621 goto out; 622 } 623 } 624 625 icmp_param = kmalloc(sizeof(*icmp_param), GFP_ATOMIC); 626 if (!icmp_param) 627 return; 628 629 sk = icmp_xmit_lock(net); 630 if (sk == NULL) 631 goto out_free; 632 633 /* 634 * Construct source address and options. 635 */ 636 637 saddr = iph->daddr; 638 if (!(rt->rt_flags & RTCF_LOCAL)) { 639 struct net_device *dev = NULL; 640 641 rcu_read_lock(); 642 if (rt_is_input_route(rt) && 643 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 644 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 645 646 if (dev) 647 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 648 else 649 saddr = 0; 650 rcu_read_unlock(); 651 } 652 653 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 654 IPTOS_PREC_INTERNETCONTROL) : 655 iph->tos; 656 mark = IP4_REPLY_MARK(net, skb_in->mark); 657 658 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb_in)) 659 goto out_unlock; 660 661 662 /* 663 * Prepare data for ICMP header. 664 */ 665 666 icmp_param->data.icmph.type = type; 667 icmp_param->data.icmph.code = code; 668 icmp_param->data.icmph.un.gateway = info; 669 icmp_param->data.icmph.checksum = 0; 670 icmp_param->skb = skb_in; 671 icmp_param->offset = skb_network_offset(skb_in); 672 inet_sk(sk)->tos = tos; 673 sk->sk_mark = mark; 674 ipc.addr = iph->saddr; 675 ipc.opt = &icmp_param->replyopts.opt; 676 ipc.tx_flags = 0; 677 ipc.ttl = 0; 678 ipc.tos = -1; 679 680 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 681 type, code, icmp_param); 682 if (IS_ERR(rt)) 683 goto out_unlock; 684 685 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 686 goto ende; 687 688 /* RFC says return as much as we can without exceeding 576 bytes. */ 689 690 room = dst_mtu(&rt->dst); 691 if (room > 576) 692 room = 576; 693 room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.opt.optlen; 694 room -= sizeof(struct icmphdr); 695 696 icmp_param->data_len = skb_in->len - icmp_param->offset; 697 if (icmp_param->data_len > room) 698 icmp_param->data_len = room; 699 icmp_param->head_len = sizeof(struct icmphdr); 700 701 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 702 ende: 703 ip_rt_put(rt); 704 out_unlock: 705 icmp_xmit_unlock(sk); 706 out_free: 707 kfree(icmp_param); 708 out:; 709 } 710 EXPORT_SYMBOL(icmp_send); 711 712 713 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 714 { 715 const struct iphdr *iph = (const struct iphdr *) skb->data; 716 const struct net_protocol *ipprot; 717 int protocol = iph->protocol; 718 719 /* Checkin full IP header plus 8 bytes of protocol to 720 * avoid additional coding at protocol handlers. 721 */ 722 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 723 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 724 return; 725 } 726 727 raw_icmp_error(skb, protocol, info); 728 729 ipprot = rcu_dereference(inet_protos[protocol]); 730 if (ipprot && ipprot->err_handler) 731 ipprot->err_handler(skb, info); 732 } 733 734 static bool icmp_tag_validation(int proto) 735 { 736 bool ok; 737 738 rcu_read_lock(); 739 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 740 rcu_read_unlock(); 741 return ok; 742 } 743 744 /* 745 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and 746 * ICMP_PARAMETERPROB. 747 */ 748 749 static bool icmp_unreach(struct sk_buff *skb) 750 { 751 const struct iphdr *iph; 752 struct icmphdr *icmph; 753 struct net *net; 754 u32 info = 0; 755 756 net = dev_net(skb_dst(skb)->dev); 757 758 /* 759 * Incomplete header ? 760 * Only checks for the IP header, there should be an 761 * additional check for longer headers in upper levels. 762 */ 763 764 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 765 goto out_err; 766 767 icmph = icmp_hdr(skb); 768 iph = (const struct iphdr *)skb->data; 769 770 if (iph->ihl < 5) /* Mangled header, drop. */ 771 goto out_err; 772 773 if (icmph->type == ICMP_DEST_UNREACH) { 774 switch (icmph->code & 15) { 775 case ICMP_NET_UNREACH: 776 case ICMP_HOST_UNREACH: 777 case ICMP_PROT_UNREACH: 778 case ICMP_PORT_UNREACH: 779 break; 780 case ICMP_FRAG_NEEDED: 781 /* for documentation of the ip_no_pmtu_disc 782 * values please see 783 * Documentation/networking/ip-sysctl.txt 784 */ 785 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 786 default: 787 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 788 &iph->daddr); 789 break; 790 case 2: 791 goto out; 792 case 3: 793 if (!icmp_tag_validation(iph->protocol)) 794 goto out; 795 /* fall through */ 796 case 0: 797 info = ntohs(icmph->un.frag.mtu); 798 } 799 break; 800 case ICMP_SR_FAILED: 801 net_dbg_ratelimited("%pI4: Source Route Failed\n", 802 &iph->daddr); 803 break; 804 default: 805 break; 806 } 807 if (icmph->code > NR_ICMP_UNREACH) 808 goto out; 809 } else if (icmph->type == ICMP_PARAMETERPROB) 810 info = ntohl(icmph->un.gateway) >> 24; 811 812 /* 813 * Throw it at our lower layers 814 * 815 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 816 * header. 817 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 818 * transport layer. 819 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 820 * transport layer. 821 */ 822 823 /* 824 * Check the other end isn't violating RFC 1122. Some routers send 825 * bogus responses to broadcast frames. If you see this message 826 * first check your netmask matches at both ends, if it does then 827 * get the other vendor to fix their kit. 828 */ 829 830 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 831 inet_addr_type(net, iph->daddr) == RTN_BROADCAST) { 832 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 833 &ip_hdr(skb)->saddr, 834 icmph->type, icmph->code, 835 &iph->daddr, skb->dev->name); 836 goto out; 837 } 838 839 icmp_socket_deliver(skb, info); 840 841 out: 842 return true; 843 out_err: 844 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 845 return false; 846 } 847 848 849 /* 850 * Handle ICMP_REDIRECT. 851 */ 852 853 static bool icmp_redirect(struct sk_buff *skb) 854 { 855 if (skb->len < sizeof(struct iphdr)) { 856 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS); 857 return false; 858 } 859 860 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 861 /* there aught to be a stat */ 862 return false; 863 } 864 865 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 866 return true; 867 } 868 869 /* 870 * Handle ICMP_ECHO ("ping") requests. 871 * 872 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 873 * requests. 874 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 875 * included in the reply. 876 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 877 * echo requests, MUST have default=NOT. 878 * See also WRT handling of options once they are done and working. 879 */ 880 881 static bool icmp_echo(struct sk_buff *skb) 882 { 883 struct net *net; 884 885 net = dev_net(skb_dst(skb)->dev); 886 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 887 struct icmp_bxm icmp_param; 888 889 icmp_param.data.icmph = *icmp_hdr(skb); 890 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 891 icmp_param.skb = skb; 892 icmp_param.offset = 0; 893 icmp_param.data_len = skb->len; 894 icmp_param.head_len = sizeof(struct icmphdr); 895 icmp_reply(&icmp_param, skb); 896 } 897 /* should there be an ICMP stat for ignored echos? */ 898 return true; 899 } 900 901 /* 902 * Handle ICMP Timestamp requests. 903 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 904 * SHOULD be in the kernel for minimum random latency. 905 * MUST be accurate to a few minutes. 906 * MUST be updated at least at 15Hz. 907 */ 908 static bool icmp_timestamp(struct sk_buff *skb) 909 { 910 struct timespec tv; 911 struct icmp_bxm icmp_param; 912 /* 913 * Too short. 914 */ 915 if (skb->len < 4) 916 goto out_err; 917 918 /* 919 * Fill in the current time as ms since midnight UT: 920 */ 921 getnstimeofday(&tv); 922 icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + 923 tv.tv_nsec / NSEC_PER_MSEC); 924 icmp_param.data.times[2] = icmp_param.data.times[1]; 925 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 926 BUG(); 927 icmp_param.data.icmph = *icmp_hdr(skb); 928 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 929 icmp_param.data.icmph.code = 0; 930 icmp_param.skb = skb; 931 icmp_param.offset = 0; 932 icmp_param.data_len = 0; 933 icmp_param.head_len = sizeof(struct icmphdr) + 12; 934 icmp_reply(&icmp_param, skb); 935 return true; 936 937 out_err: 938 ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 939 return false; 940 } 941 942 static bool icmp_discard(struct sk_buff *skb) 943 { 944 /* pretend it was a success */ 945 return true; 946 } 947 948 /* 949 * Deal with incoming ICMP packets. 950 */ 951 int icmp_rcv(struct sk_buff *skb) 952 { 953 struct icmphdr *icmph; 954 struct rtable *rt = skb_rtable(skb); 955 struct net *net = dev_net(rt->dst.dev); 956 bool success; 957 958 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 959 struct sec_path *sp = skb_sec_path(skb); 960 int nh; 961 962 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 963 XFRM_STATE_ICMP)) 964 goto drop; 965 966 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 967 goto drop; 968 969 nh = skb_network_offset(skb); 970 skb_set_network_header(skb, sizeof(*icmph)); 971 972 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 973 goto drop; 974 975 skb_set_network_header(skb, nh); 976 } 977 978 ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS); 979 980 if (skb_checksum_simple_validate(skb)) 981 goto csum_error; 982 983 if (!pskb_pull(skb, sizeof(*icmph))) 984 goto error; 985 986 icmph = icmp_hdr(skb); 987 988 ICMPMSGIN_INC_STATS_BH(net, icmph->type); 989 /* 990 * 18 is the highest 'known' ICMP type. Anything else is a mystery 991 * 992 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 993 * discarded. 994 */ 995 if (icmph->type > NR_ICMP_TYPES) 996 goto error; 997 998 999 /* 1000 * Parse the ICMP message 1001 */ 1002 1003 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1004 /* 1005 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1006 * silently ignored (we let user decide with a sysctl). 1007 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1008 * discarded if to broadcast/multicast. 1009 */ 1010 if ((icmph->type == ICMP_ECHO || 1011 icmph->type == ICMP_TIMESTAMP) && 1012 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1013 goto error; 1014 } 1015 if (icmph->type != ICMP_ECHO && 1016 icmph->type != ICMP_TIMESTAMP && 1017 icmph->type != ICMP_ADDRESS && 1018 icmph->type != ICMP_ADDRESSREPLY) { 1019 goto error; 1020 } 1021 } 1022 1023 success = icmp_pointers[icmph->type].handler(skb); 1024 1025 if (success) { 1026 consume_skb(skb); 1027 return 0; 1028 } 1029 1030 drop: 1031 kfree_skb(skb); 1032 return 0; 1033 csum_error: 1034 ICMP_INC_STATS_BH(net, ICMP_MIB_CSUMERRORS); 1035 error: 1036 ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS); 1037 goto drop; 1038 } 1039 1040 void icmp_err(struct sk_buff *skb, u32 info) 1041 { 1042 struct iphdr *iph = (struct iphdr *)skb->data; 1043 int offset = iph->ihl<<2; 1044 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1045 int type = icmp_hdr(skb)->type; 1046 int code = icmp_hdr(skb)->code; 1047 struct net *net = dev_net(skb->dev); 1048 1049 /* 1050 * Use ping_err to handle all icmp errors except those 1051 * triggered by ICMP_ECHOREPLY which sent from kernel. 1052 */ 1053 if (icmph->type != ICMP_ECHOREPLY) { 1054 ping_err(skb, offset, info); 1055 return; 1056 } 1057 1058 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1059 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 1060 else if (type == ICMP_REDIRECT) 1061 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 1062 } 1063 1064 /* 1065 * This table is the definition of how we handle ICMP. 1066 */ 1067 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1068 [ICMP_ECHOREPLY] = { 1069 .handler = ping_rcv, 1070 }, 1071 [1] = { 1072 .handler = icmp_discard, 1073 .error = 1, 1074 }, 1075 [2] = { 1076 .handler = icmp_discard, 1077 .error = 1, 1078 }, 1079 [ICMP_DEST_UNREACH] = { 1080 .handler = icmp_unreach, 1081 .error = 1, 1082 }, 1083 [ICMP_SOURCE_QUENCH] = { 1084 .handler = icmp_unreach, 1085 .error = 1, 1086 }, 1087 [ICMP_REDIRECT] = { 1088 .handler = icmp_redirect, 1089 .error = 1, 1090 }, 1091 [6] = { 1092 .handler = icmp_discard, 1093 .error = 1, 1094 }, 1095 [7] = { 1096 .handler = icmp_discard, 1097 .error = 1, 1098 }, 1099 [ICMP_ECHO] = { 1100 .handler = icmp_echo, 1101 }, 1102 [9] = { 1103 .handler = icmp_discard, 1104 .error = 1, 1105 }, 1106 [10] = { 1107 .handler = icmp_discard, 1108 .error = 1, 1109 }, 1110 [ICMP_TIME_EXCEEDED] = { 1111 .handler = icmp_unreach, 1112 .error = 1, 1113 }, 1114 [ICMP_PARAMETERPROB] = { 1115 .handler = icmp_unreach, 1116 .error = 1, 1117 }, 1118 [ICMP_TIMESTAMP] = { 1119 .handler = icmp_timestamp, 1120 }, 1121 [ICMP_TIMESTAMPREPLY] = { 1122 .handler = icmp_discard, 1123 }, 1124 [ICMP_INFO_REQUEST] = { 1125 .handler = icmp_discard, 1126 }, 1127 [ICMP_INFO_REPLY] = { 1128 .handler = icmp_discard, 1129 }, 1130 [ICMP_ADDRESS] = { 1131 .handler = icmp_discard, 1132 }, 1133 [ICMP_ADDRESSREPLY] = { 1134 .handler = icmp_discard, 1135 }, 1136 }; 1137 1138 static void __net_exit icmp_sk_exit(struct net *net) 1139 { 1140 int i; 1141 1142 for_each_possible_cpu(i) 1143 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1144 free_percpu(net->ipv4.icmp_sk); 1145 net->ipv4.icmp_sk = NULL; 1146 } 1147 1148 static int __net_init icmp_sk_init(struct net *net) 1149 { 1150 int i, err; 1151 1152 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1153 if (!net->ipv4.icmp_sk) 1154 return -ENOMEM; 1155 1156 for_each_possible_cpu(i) { 1157 struct sock *sk; 1158 1159 err = inet_ctl_sock_create(&sk, PF_INET, 1160 SOCK_RAW, IPPROTO_ICMP, net); 1161 if (err < 0) 1162 goto fail; 1163 1164 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1165 1166 /* Enough space for 2 64K ICMP packets, including 1167 * sk_buff/skb_shared_info struct overhead. 1168 */ 1169 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1170 1171 /* 1172 * Speedup sock_wfree() 1173 */ 1174 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1175 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1176 } 1177 1178 /* Control parameters for ECHO replies. */ 1179 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1180 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1181 1182 /* Control parameter - ignore bogus broadcast responses? */ 1183 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1184 1185 /* 1186 * Configurable global rate limit. 1187 * 1188 * ratelimit defines tokens/packet consumed for dst->rate_token 1189 * bucket ratemask defines which icmp types are ratelimited by 1190 * setting it's bit position. 1191 * 1192 * default: 1193 * dest unreachable (3), source quench (4), 1194 * time exceeded (11), parameter problem (12) 1195 */ 1196 1197 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1198 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1199 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1200 1201 return 0; 1202 1203 fail: 1204 for_each_possible_cpu(i) 1205 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1206 free_percpu(net->ipv4.icmp_sk); 1207 return err; 1208 } 1209 1210 static struct pernet_operations __net_initdata icmp_sk_ops = { 1211 .init = icmp_sk_init, 1212 .exit = icmp_sk_exit, 1213 }; 1214 1215 int __init icmp_init(void) 1216 { 1217 return register_pernet_subsys(&icmp_sk_ops); 1218 } 1219