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 <linux/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 #include <net/l3mdev.h> 100 101 /* 102 * Build xmit assembly blocks 103 */ 104 105 struct icmp_bxm { 106 struct sk_buff *skb; 107 int offset; 108 int data_len; 109 110 struct { 111 struct icmphdr icmph; 112 __be32 times[3]; 113 } data; 114 int head_len; 115 struct ip_options_data replyopts; 116 }; 117 118 /* An array of errno for error messages from dest unreach. */ 119 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 120 121 const struct icmp_err icmp_err_convert[] = { 122 { 123 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 124 .fatal = 0, 125 }, 126 { 127 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 128 .fatal = 0, 129 }, 130 { 131 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 132 .fatal = 1, 133 }, 134 { 135 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 136 .fatal = 1, 137 }, 138 { 139 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 140 .fatal = 0, 141 }, 142 { 143 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 144 .fatal = 0, 145 }, 146 { 147 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 148 .fatal = 1, 149 }, 150 { 151 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 152 .fatal = 1, 153 }, 154 { 155 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 156 .fatal = 1, 157 }, 158 { 159 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 160 .fatal = 1, 161 }, 162 { 163 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 164 .fatal = 1, 165 }, 166 { 167 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 168 .fatal = 0, 169 }, 170 { 171 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 172 .fatal = 0, 173 }, 174 { 175 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 176 .fatal = 1, 177 }, 178 { 179 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 180 .fatal = 1, 181 }, 182 { 183 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 184 .fatal = 1, 185 }, 186 }; 187 EXPORT_SYMBOL(icmp_err_convert); 188 189 /* 190 * ICMP control array. This specifies what to do with each ICMP. 191 */ 192 193 struct icmp_control { 194 bool (*handler)(struct sk_buff *skb); 195 short error; /* This ICMP is classed as an error message */ 196 }; 197 198 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 199 200 /* 201 * The ICMP socket(s). This is the most convenient way to flow control 202 * our ICMP output as well as maintain a clean interface throughout 203 * all layers. All Socketless IP sends will soon be gone. 204 * 205 * On SMP we have one ICMP socket per-cpu. 206 */ 207 static struct sock *icmp_sk(struct net *net) 208 { 209 return *this_cpu_ptr(net->ipv4.icmp_sk); 210 } 211 212 /* Called with BH disabled */ 213 static inline struct sock *icmp_xmit_lock(struct net *net) 214 { 215 struct sock *sk; 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 return NULL; 224 } 225 return sk; 226 } 227 228 static inline void icmp_xmit_unlock(struct sock *sk) 229 { 230 spin_unlock(&sk->sk_lock.slock); 231 } 232 233 int sysctl_icmp_msgs_per_sec __read_mostly = 1000; 234 int sysctl_icmp_msgs_burst __read_mostly = 50; 235 236 static struct { 237 spinlock_t lock; 238 u32 credit; 239 u32 stamp; 240 } icmp_global = { 241 .lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock), 242 }; 243 244 /** 245 * icmp_global_allow - Are we allowed to send one more ICMP message ? 246 * 247 * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. 248 * Returns false if we reached the limit and can not send another packet. 249 * Note: called with BH disabled 250 */ 251 bool icmp_global_allow(void) 252 { 253 u32 credit, delta, incr = 0, now = (u32)jiffies; 254 bool rc = false; 255 256 /* Check if token bucket is empty and cannot be refilled 257 * without taking the spinlock. 258 */ 259 if (!icmp_global.credit) { 260 delta = min_t(u32, now - icmp_global.stamp, HZ); 261 if (delta < HZ / 50) 262 return false; 263 } 264 265 spin_lock(&icmp_global.lock); 266 delta = min_t(u32, now - icmp_global.stamp, HZ); 267 if (delta >= HZ / 50) { 268 incr = sysctl_icmp_msgs_per_sec * delta / HZ ; 269 if (incr) 270 icmp_global.stamp = now; 271 } 272 credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); 273 if (credit) { 274 credit--; 275 rc = true; 276 } 277 icmp_global.credit = credit; 278 spin_unlock(&icmp_global.lock); 279 return rc; 280 } 281 EXPORT_SYMBOL(icmp_global_allow); 282 283 static bool icmpv4_mask_allow(struct net *net, int type, int code) 284 { 285 if (type > NR_ICMP_TYPES) 286 return true; 287 288 /* Don't limit PMTU discovery. */ 289 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 290 return true; 291 292 /* Limit if icmp type is enabled in ratemask. */ 293 if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask)) 294 return true; 295 296 return false; 297 } 298 299 static bool icmpv4_global_allow(struct net *net, int type, int code) 300 { 301 if (icmpv4_mask_allow(net, type, code)) 302 return true; 303 304 if (icmp_global_allow()) 305 return true; 306 307 return false; 308 } 309 310 /* 311 * Send an ICMP frame. 312 */ 313 314 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 315 struct flowi4 *fl4, int type, int code) 316 { 317 struct dst_entry *dst = &rt->dst; 318 struct inet_peer *peer; 319 bool rc = true; 320 int vif; 321 322 if (icmpv4_mask_allow(net, type, code)) 323 goto out; 324 325 /* No rate limit on loopback */ 326 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 327 goto out; 328 329 vif = l3mdev_master_ifindex(dst->dev); 330 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1); 331 rc = inet_peer_xrlim_allow(peer, net->ipv4.sysctl_icmp_ratelimit); 332 if (peer) 333 inet_putpeer(peer); 334 out: 335 return rc; 336 } 337 338 /* 339 * Maintain the counters used in the SNMP statistics for outgoing ICMP 340 */ 341 void icmp_out_count(struct net *net, unsigned char type) 342 { 343 ICMPMSGOUT_INC_STATS(net, type); 344 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 345 } 346 347 /* 348 * Checksum each fragment, and on the first include the headers and final 349 * checksum. 350 */ 351 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 352 struct sk_buff *skb) 353 { 354 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 355 __wsum csum; 356 357 csum = skb_copy_and_csum_bits(icmp_param->skb, 358 icmp_param->offset + offset, 359 to, len, 0); 360 361 skb->csum = csum_block_add(skb->csum, csum, odd); 362 if (icmp_pointers[icmp_param->data.icmph.type].error) 363 nf_ct_attach(skb, icmp_param->skb); 364 return 0; 365 } 366 367 static void icmp_push_reply(struct icmp_bxm *icmp_param, 368 struct flowi4 *fl4, 369 struct ipcm_cookie *ipc, struct rtable **rt) 370 { 371 struct sock *sk; 372 struct sk_buff *skb; 373 374 sk = icmp_sk(dev_net((*rt)->dst.dev)); 375 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 376 icmp_param->data_len+icmp_param->head_len, 377 icmp_param->head_len, 378 ipc, rt, MSG_DONTWAIT) < 0) { 379 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS); 380 ip_flush_pending_frames(sk); 381 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 382 struct icmphdr *icmph = icmp_hdr(skb); 383 __wsum csum = 0; 384 struct sk_buff *skb1; 385 386 skb_queue_walk(&sk->sk_write_queue, skb1) { 387 csum = csum_add(csum, skb1->csum); 388 } 389 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 390 (char *)icmph, 391 icmp_param->head_len, csum); 392 icmph->checksum = csum_fold(csum); 393 skb->ip_summed = CHECKSUM_NONE; 394 ip_push_pending_frames(sk, fl4); 395 } 396 } 397 398 /* 399 * Driving logic for building and sending ICMP messages. 400 */ 401 402 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 403 { 404 struct ipcm_cookie ipc; 405 struct rtable *rt = skb_rtable(skb); 406 struct net *net = dev_net(rt->dst.dev); 407 struct flowi4 fl4; 408 struct sock *sk; 409 struct inet_sock *inet; 410 __be32 daddr, saddr; 411 u32 mark = IP4_REPLY_MARK(net, skb->mark); 412 int type = icmp_param->data.icmph.type; 413 int code = icmp_param->data.icmph.code; 414 415 if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb)) 416 return; 417 418 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 419 local_bh_disable(); 420 421 /* global icmp_msgs_per_sec */ 422 if (!icmpv4_global_allow(net, type, code)) 423 goto out_bh_enable; 424 425 sk = icmp_xmit_lock(net); 426 if (!sk) 427 goto out_bh_enable; 428 inet = inet_sk(sk); 429 430 icmp_param->data.icmph.checksum = 0; 431 432 inet->tos = ip_hdr(skb)->tos; 433 sk->sk_mark = mark; 434 daddr = ipc.addr = ip_hdr(skb)->saddr; 435 saddr = fib_compute_spec_dst(skb); 436 ipc.opt = NULL; 437 ipc.tx_flags = 0; 438 ipc.ttl = 0; 439 ipc.tos = -1; 440 441 if (icmp_param->replyopts.opt.opt.optlen) { 442 ipc.opt = &icmp_param->replyopts.opt; 443 if (ipc.opt->opt.srr) 444 daddr = icmp_param->replyopts.opt.opt.faddr; 445 } 446 memset(&fl4, 0, sizeof(fl4)); 447 fl4.daddr = daddr; 448 fl4.saddr = saddr; 449 fl4.flowi4_mark = mark; 450 fl4.flowi4_uid = sock_net_uid(net, NULL); 451 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 452 fl4.flowi4_proto = IPPROTO_ICMP; 453 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev); 454 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 455 rt = ip_route_output_key(net, &fl4); 456 if (IS_ERR(rt)) 457 goto out_unlock; 458 if (icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 459 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 460 ip_rt_put(rt); 461 out_unlock: 462 icmp_xmit_unlock(sk); 463 out_bh_enable: 464 local_bh_enable(); 465 } 466 467 static struct rtable *icmp_route_lookup(struct net *net, 468 struct flowi4 *fl4, 469 struct sk_buff *skb_in, 470 const struct iphdr *iph, 471 __be32 saddr, u8 tos, u32 mark, 472 int type, int code, 473 struct icmp_bxm *param) 474 { 475 struct rtable *rt, *rt2; 476 struct flowi4 fl4_dec; 477 int err; 478 479 memset(fl4, 0, sizeof(*fl4)); 480 fl4->daddr = (param->replyopts.opt.opt.srr ? 481 param->replyopts.opt.opt.faddr : iph->saddr); 482 fl4->saddr = saddr; 483 fl4->flowi4_mark = mark; 484 fl4->flowi4_uid = sock_net_uid(net, NULL); 485 fl4->flowi4_tos = RT_TOS(tos); 486 fl4->flowi4_proto = IPPROTO_ICMP; 487 fl4->fl4_icmp_type = type; 488 fl4->fl4_icmp_code = code; 489 fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev); 490 491 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 492 rt = ip_route_output_key_hash(net, fl4, skb_in); 493 if (IS_ERR(rt)) 494 return rt; 495 496 /* No need to clone since we're just using its address. */ 497 rt2 = rt; 498 499 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 500 flowi4_to_flowi(fl4), NULL, 0); 501 if (!IS_ERR(rt)) { 502 if (rt != rt2) 503 return rt; 504 } else if (PTR_ERR(rt) == -EPERM) { 505 rt = NULL; 506 } else 507 return rt; 508 509 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 510 if (err) 511 goto relookup_failed; 512 513 if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev, 514 fl4_dec.saddr) == RTN_LOCAL) { 515 rt2 = __ip_route_output_key(net, &fl4_dec); 516 if (IS_ERR(rt2)) 517 err = PTR_ERR(rt2); 518 } else { 519 struct flowi4 fl4_2 = {}; 520 unsigned long orefdst; 521 522 fl4_2.daddr = fl4_dec.saddr; 523 rt2 = ip_route_output_key(net, &fl4_2); 524 if (IS_ERR(rt2)) { 525 err = PTR_ERR(rt2); 526 goto relookup_failed; 527 } 528 /* Ugh! */ 529 orefdst = skb_in->_skb_refdst; /* save old refdst */ 530 skb_dst_set(skb_in, NULL); 531 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 532 RT_TOS(tos), rt2->dst.dev); 533 534 dst_release(&rt2->dst); 535 rt2 = skb_rtable(skb_in); 536 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 537 } 538 539 if (err) 540 goto relookup_failed; 541 542 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 543 flowi4_to_flowi(&fl4_dec), NULL, 544 XFRM_LOOKUP_ICMP); 545 if (!IS_ERR(rt2)) { 546 dst_release(&rt->dst); 547 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 548 rt = rt2; 549 } else if (PTR_ERR(rt2) == -EPERM) { 550 if (rt) 551 dst_release(&rt->dst); 552 return rt2; 553 } else { 554 err = PTR_ERR(rt2); 555 goto relookup_failed; 556 } 557 return rt; 558 559 relookup_failed: 560 if (rt) 561 return rt; 562 return ERR_PTR(err); 563 } 564 565 /* 566 * Send an ICMP message in response to a situation 567 * 568 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 569 * MAY send more (we do). 570 * MUST NOT change this header information. 571 * MUST NOT reply to a multicast/broadcast IP address. 572 * MUST NOT reply to a multicast/broadcast MAC address. 573 * MUST reply to only the first fragment. 574 */ 575 576 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 577 { 578 struct iphdr *iph; 579 int room; 580 struct icmp_bxm icmp_param; 581 struct rtable *rt = skb_rtable(skb_in); 582 struct ipcm_cookie ipc; 583 struct flowi4 fl4; 584 __be32 saddr; 585 u8 tos; 586 u32 mark; 587 struct net *net; 588 struct sock *sk; 589 590 if (!rt) 591 goto out; 592 net = dev_net(rt->dst.dev); 593 594 /* 595 * Find the original header. It is expected to be valid, of course. 596 * Check this, icmp_send is called from the most obscure devices 597 * sometimes. 598 */ 599 iph = ip_hdr(skb_in); 600 601 if ((u8 *)iph < skb_in->head || 602 (skb_network_header(skb_in) + sizeof(*iph)) > 603 skb_tail_pointer(skb_in)) 604 goto out; 605 606 /* 607 * No replies to physical multicast/broadcast 608 */ 609 if (skb_in->pkt_type != PACKET_HOST) 610 goto out; 611 612 /* 613 * Now check at the protocol level 614 */ 615 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 616 goto out; 617 618 /* 619 * Only reply to fragment 0. We byte re-order the constant 620 * mask for efficiency. 621 */ 622 if (iph->frag_off & htons(IP_OFFSET)) 623 goto out; 624 625 /* 626 * If we send an ICMP error to an ICMP error a mess would result.. 627 */ 628 if (icmp_pointers[type].error) { 629 /* 630 * We are an error, check if we are replying to an 631 * ICMP error 632 */ 633 if (iph->protocol == IPPROTO_ICMP) { 634 u8 _inner_type, *itp; 635 636 itp = skb_header_pointer(skb_in, 637 skb_network_header(skb_in) + 638 (iph->ihl << 2) + 639 offsetof(struct icmphdr, 640 type) - 641 skb_in->data, 642 sizeof(_inner_type), 643 &_inner_type); 644 if (!itp) 645 goto out; 646 647 /* 648 * Assume any unknown ICMP type is an error. This 649 * isn't specified by the RFC, but think about it.. 650 */ 651 if (*itp > NR_ICMP_TYPES || 652 icmp_pointers[*itp].error) 653 goto out; 654 } 655 } 656 657 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 658 local_bh_disable(); 659 660 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless 661 * incoming dev is loopback. If outgoing dev change to not be 662 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow) 663 */ 664 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) && 665 !icmpv4_global_allow(net, type, code)) 666 goto out_bh_enable; 667 668 sk = icmp_xmit_lock(net); 669 if (!sk) 670 goto out_bh_enable; 671 672 /* 673 * Construct source address and options. 674 */ 675 676 saddr = iph->daddr; 677 if (!(rt->rt_flags & RTCF_LOCAL)) { 678 struct net_device *dev = NULL; 679 680 rcu_read_lock(); 681 if (rt_is_input_route(rt) && 682 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 683 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 684 685 if (dev) 686 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 687 else 688 saddr = 0; 689 rcu_read_unlock(); 690 } 691 692 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 693 IPTOS_PREC_INTERNETCONTROL) : 694 iph->tos; 695 mark = IP4_REPLY_MARK(net, skb_in->mark); 696 697 if (ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in)) 698 goto out_unlock; 699 700 701 /* 702 * Prepare data for ICMP header. 703 */ 704 705 icmp_param.data.icmph.type = type; 706 icmp_param.data.icmph.code = code; 707 icmp_param.data.icmph.un.gateway = info; 708 icmp_param.data.icmph.checksum = 0; 709 icmp_param.skb = skb_in; 710 icmp_param.offset = skb_network_offset(skb_in); 711 inet_sk(sk)->tos = tos; 712 sk->sk_mark = mark; 713 ipc.addr = iph->saddr; 714 ipc.opt = &icmp_param.replyopts.opt; 715 ipc.tx_flags = 0; 716 ipc.ttl = 0; 717 ipc.tos = -1; 718 719 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 720 type, code, &icmp_param); 721 if (IS_ERR(rt)) 722 goto out_unlock; 723 724 /* peer icmp_ratelimit */ 725 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 726 goto ende; 727 728 /* RFC says return as much as we can without exceeding 576 bytes. */ 729 730 room = dst_mtu(&rt->dst); 731 if (room > 576) 732 room = 576; 733 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 734 room -= sizeof(struct icmphdr); 735 736 icmp_param.data_len = skb_in->len - icmp_param.offset; 737 if (icmp_param.data_len > room) 738 icmp_param.data_len = room; 739 icmp_param.head_len = sizeof(struct icmphdr); 740 741 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 742 ende: 743 ip_rt_put(rt); 744 out_unlock: 745 icmp_xmit_unlock(sk); 746 out_bh_enable: 747 local_bh_enable(); 748 out:; 749 } 750 EXPORT_SYMBOL(icmp_send); 751 752 753 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 754 { 755 const struct iphdr *iph = (const struct iphdr *) skb->data; 756 const struct net_protocol *ipprot; 757 int protocol = iph->protocol; 758 759 /* Checkin full IP header plus 8 bytes of protocol to 760 * avoid additional coding at protocol handlers. 761 */ 762 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 763 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 764 return; 765 } 766 767 raw_icmp_error(skb, protocol, info); 768 769 ipprot = rcu_dereference(inet_protos[protocol]); 770 if (ipprot && ipprot->err_handler) 771 ipprot->err_handler(skb, info); 772 } 773 774 static bool icmp_tag_validation(int proto) 775 { 776 bool ok; 777 778 rcu_read_lock(); 779 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 780 rcu_read_unlock(); 781 return ok; 782 } 783 784 /* 785 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and 786 * ICMP_PARAMETERPROB. 787 */ 788 789 static bool icmp_unreach(struct sk_buff *skb) 790 { 791 const struct iphdr *iph; 792 struct icmphdr *icmph; 793 struct net *net; 794 u32 info = 0; 795 796 net = dev_net(skb_dst(skb)->dev); 797 798 /* 799 * Incomplete header ? 800 * Only checks for the IP header, there should be an 801 * additional check for longer headers in upper levels. 802 */ 803 804 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 805 goto out_err; 806 807 icmph = icmp_hdr(skb); 808 iph = (const struct iphdr *)skb->data; 809 810 if (iph->ihl < 5) /* Mangled header, drop. */ 811 goto out_err; 812 813 if (icmph->type == ICMP_DEST_UNREACH) { 814 switch (icmph->code & 15) { 815 case ICMP_NET_UNREACH: 816 case ICMP_HOST_UNREACH: 817 case ICMP_PROT_UNREACH: 818 case ICMP_PORT_UNREACH: 819 break; 820 case ICMP_FRAG_NEEDED: 821 /* for documentation of the ip_no_pmtu_disc 822 * values please see 823 * Documentation/networking/ip-sysctl.txt 824 */ 825 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 826 default: 827 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 828 &iph->daddr); 829 break; 830 case 2: 831 goto out; 832 case 3: 833 if (!icmp_tag_validation(iph->protocol)) 834 goto out; 835 /* fall through */ 836 case 0: 837 info = ntohs(icmph->un.frag.mtu); 838 } 839 break; 840 case ICMP_SR_FAILED: 841 net_dbg_ratelimited("%pI4: Source Route Failed\n", 842 &iph->daddr); 843 break; 844 default: 845 break; 846 } 847 if (icmph->code > NR_ICMP_UNREACH) 848 goto out; 849 } else if (icmph->type == ICMP_PARAMETERPROB) 850 info = ntohl(icmph->un.gateway) >> 24; 851 852 /* 853 * Throw it at our lower layers 854 * 855 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 856 * header. 857 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 858 * transport layer. 859 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 860 * transport layer. 861 */ 862 863 /* 864 * Check the other end isn't violating RFC 1122. Some routers send 865 * bogus responses to broadcast frames. If you see this message 866 * first check your netmask matches at both ends, if it does then 867 * get the other vendor to fix their kit. 868 */ 869 870 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 871 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) { 872 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 873 &ip_hdr(skb)->saddr, 874 icmph->type, icmph->code, 875 &iph->daddr, skb->dev->name); 876 goto out; 877 } 878 879 icmp_socket_deliver(skb, info); 880 881 out: 882 return true; 883 out_err: 884 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 885 return false; 886 } 887 888 889 /* 890 * Handle ICMP_REDIRECT. 891 */ 892 893 static bool icmp_redirect(struct sk_buff *skb) 894 { 895 if (skb->len < sizeof(struct iphdr)) { 896 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 897 return false; 898 } 899 900 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 901 /* there aught to be a stat */ 902 return false; 903 } 904 905 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 906 return true; 907 } 908 909 /* 910 * Handle ICMP_ECHO ("ping") requests. 911 * 912 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 913 * requests. 914 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 915 * included in the reply. 916 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 917 * echo requests, MUST have default=NOT. 918 * See also WRT handling of options once they are done and working. 919 */ 920 921 static bool icmp_echo(struct sk_buff *skb) 922 { 923 struct net *net; 924 925 net = dev_net(skb_dst(skb)->dev); 926 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 927 struct icmp_bxm icmp_param; 928 929 icmp_param.data.icmph = *icmp_hdr(skb); 930 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 931 icmp_param.skb = skb; 932 icmp_param.offset = 0; 933 icmp_param.data_len = skb->len; 934 icmp_param.head_len = sizeof(struct icmphdr); 935 icmp_reply(&icmp_param, skb); 936 } 937 /* should there be an ICMP stat for ignored echos? */ 938 return true; 939 } 940 941 /* 942 * Handle ICMP Timestamp requests. 943 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 944 * SHOULD be in the kernel for minimum random latency. 945 * MUST be accurate to a few minutes. 946 * MUST be updated at least at 15Hz. 947 */ 948 static bool icmp_timestamp(struct sk_buff *skb) 949 { 950 struct icmp_bxm icmp_param; 951 /* 952 * Too short. 953 */ 954 if (skb->len < 4) 955 goto out_err; 956 957 /* 958 * Fill in the current time as ms since midnight UT: 959 */ 960 icmp_param.data.times[1] = inet_current_timestamp(); 961 icmp_param.data.times[2] = icmp_param.data.times[1]; 962 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 963 BUG(); 964 icmp_param.data.icmph = *icmp_hdr(skb); 965 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 966 icmp_param.data.icmph.code = 0; 967 icmp_param.skb = skb; 968 icmp_param.offset = 0; 969 icmp_param.data_len = 0; 970 icmp_param.head_len = sizeof(struct icmphdr) + 12; 971 icmp_reply(&icmp_param, skb); 972 return true; 973 974 out_err: 975 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 976 return false; 977 } 978 979 static bool icmp_discard(struct sk_buff *skb) 980 { 981 /* pretend it was a success */ 982 return true; 983 } 984 985 /* 986 * Deal with incoming ICMP packets. 987 */ 988 int icmp_rcv(struct sk_buff *skb) 989 { 990 struct icmphdr *icmph; 991 struct rtable *rt = skb_rtable(skb); 992 struct net *net = dev_net(rt->dst.dev); 993 bool success; 994 995 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 996 struct sec_path *sp = skb_sec_path(skb); 997 int nh; 998 999 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 1000 XFRM_STATE_ICMP)) 1001 goto drop; 1002 1003 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 1004 goto drop; 1005 1006 nh = skb_network_offset(skb); 1007 skb_set_network_header(skb, sizeof(*icmph)); 1008 1009 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 1010 goto drop; 1011 1012 skb_set_network_header(skb, nh); 1013 } 1014 1015 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS); 1016 1017 if (skb_checksum_simple_validate(skb)) 1018 goto csum_error; 1019 1020 if (!pskb_pull(skb, sizeof(*icmph))) 1021 goto error; 1022 1023 icmph = icmp_hdr(skb); 1024 1025 ICMPMSGIN_INC_STATS(net, icmph->type); 1026 /* 1027 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1028 * 1029 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1030 * discarded. 1031 */ 1032 if (icmph->type > NR_ICMP_TYPES) 1033 goto error; 1034 1035 1036 /* 1037 * Parse the ICMP message 1038 */ 1039 1040 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1041 /* 1042 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1043 * silently ignored (we let user decide with a sysctl). 1044 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1045 * discarded if to broadcast/multicast. 1046 */ 1047 if ((icmph->type == ICMP_ECHO || 1048 icmph->type == ICMP_TIMESTAMP) && 1049 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1050 goto error; 1051 } 1052 if (icmph->type != ICMP_ECHO && 1053 icmph->type != ICMP_TIMESTAMP && 1054 icmph->type != ICMP_ADDRESS && 1055 icmph->type != ICMP_ADDRESSREPLY) { 1056 goto error; 1057 } 1058 } 1059 1060 success = icmp_pointers[icmph->type].handler(skb); 1061 1062 if (success) { 1063 consume_skb(skb); 1064 return NET_RX_SUCCESS; 1065 } 1066 1067 drop: 1068 kfree_skb(skb); 1069 return NET_RX_DROP; 1070 csum_error: 1071 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS); 1072 error: 1073 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 1074 goto drop; 1075 } 1076 1077 void icmp_err(struct sk_buff *skb, u32 info) 1078 { 1079 struct iphdr *iph = (struct iphdr *)skb->data; 1080 int offset = iph->ihl<<2; 1081 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1082 int type = icmp_hdr(skb)->type; 1083 int code = icmp_hdr(skb)->code; 1084 struct net *net = dev_net(skb->dev); 1085 1086 /* 1087 * Use ping_err to handle all icmp errors except those 1088 * triggered by ICMP_ECHOREPLY which sent from kernel. 1089 */ 1090 if (icmph->type != ICMP_ECHOREPLY) { 1091 ping_err(skb, offset, info); 1092 return; 1093 } 1094 1095 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1096 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 1097 else if (type == ICMP_REDIRECT) 1098 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 1099 } 1100 1101 /* 1102 * This table is the definition of how we handle ICMP. 1103 */ 1104 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1105 [ICMP_ECHOREPLY] = { 1106 .handler = ping_rcv, 1107 }, 1108 [1] = { 1109 .handler = icmp_discard, 1110 .error = 1, 1111 }, 1112 [2] = { 1113 .handler = icmp_discard, 1114 .error = 1, 1115 }, 1116 [ICMP_DEST_UNREACH] = { 1117 .handler = icmp_unreach, 1118 .error = 1, 1119 }, 1120 [ICMP_SOURCE_QUENCH] = { 1121 .handler = icmp_unreach, 1122 .error = 1, 1123 }, 1124 [ICMP_REDIRECT] = { 1125 .handler = icmp_redirect, 1126 .error = 1, 1127 }, 1128 [6] = { 1129 .handler = icmp_discard, 1130 .error = 1, 1131 }, 1132 [7] = { 1133 .handler = icmp_discard, 1134 .error = 1, 1135 }, 1136 [ICMP_ECHO] = { 1137 .handler = icmp_echo, 1138 }, 1139 [9] = { 1140 .handler = icmp_discard, 1141 .error = 1, 1142 }, 1143 [10] = { 1144 .handler = icmp_discard, 1145 .error = 1, 1146 }, 1147 [ICMP_TIME_EXCEEDED] = { 1148 .handler = icmp_unreach, 1149 .error = 1, 1150 }, 1151 [ICMP_PARAMETERPROB] = { 1152 .handler = icmp_unreach, 1153 .error = 1, 1154 }, 1155 [ICMP_TIMESTAMP] = { 1156 .handler = icmp_timestamp, 1157 }, 1158 [ICMP_TIMESTAMPREPLY] = { 1159 .handler = icmp_discard, 1160 }, 1161 [ICMP_INFO_REQUEST] = { 1162 .handler = icmp_discard, 1163 }, 1164 [ICMP_INFO_REPLY] = { 1165 .handler = icmp_discard, 1166 }, 1167 [ICMP_ADDRESS] = { 1168 .handler = icmp_discard, 1169 }, 1170 [ICMP_ADDRESSREPLY] = { 1171 .handler = icmp_discard, 1172 }, 1173 }; 1174 1175 static void __net_exit icmp_sk_exit(struct net *net) 1176 { 1177 int i; 1178 1179 for_each_possible_cpu(i) 1180 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1181 free_percpu(net->ipv4.icmp_sk); 1182 net->ipv4.icmp_sk = NULL; 1183 } 1184 1185 static int __net_init icmp_sk_init(struct net *net) 1186 { 1187 int i, err; 1188 1189 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1190 if (!net->ipv4.icmp_sk) 1191 return -ENOMEM; 1192 1193 for_each_possible_cpu(i) { 1194 struct sock *sk; 1195 1196 err = inet_ctl_sock_create(&sk, PF_INET, 1197 SOCK_RAW, IPPROTO_ICMP, net); 1198 if (err < 0) 1199 goto fail; 1200 1201 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1202 1203 /* Enough space for 2 64K ICMP packets, including 1204 * sk_buff/skb_shared_info struct overhead. 1205 */ 1206 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1207 1208 /* 1209 * Speedup sock_wfree() 1210 */ 1211 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1212 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1213 } 1214 1215 /* Control parameters for ECHO replies. */ 1216 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1217 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1218 1219 /* Control parameter - ignore bogus broadcast responses? */ 1220 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1221 1222 /* 1223 * Configurable global rate limit. 1224 * 1225 * ratelimit defines tokens/packet consumed for dst->rate_token 1226 * bucket ratemask defines which icmp types are ratelimited by 1227 * setting it's bit position. 1228 * 1229 * default: 1230 * dest unreachable (3), source quench (4), 1231 * time exceeded (11), parameter problem (12) 1232 */ 1233 1234 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1235 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1236 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1237 1238 return 0; 1239 1240 fail: 1241 for_each_possible_cpu(i) 1242 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1243 free_percpu(net->ipv4.icmp_sk); 1244 return err; 1245 } 1246 1247 static struct pernet_operations __net_initdata icmp_sk_ops = { 1248 .init = icmp_sk_init, 1249 .exit = icmp_sk_exit, 1250 }; 1251 1252 int __init icmp_init(void) 1253 { 1254 return register_pernet_subsys(&icmp_sk_ops); 1255 } 1256