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 ipc.sockc.transmit_time = 0; 441 442 if (icmp_param->replyopts.opt.opt.optlen) { 443 ipc.opt = &icmp_param->replyopts.opt; 444 if (ipc.opt->opt.srr) 445 daddr = icmp_param->replyopts.opt.opt.faddr; 446 } 447 memset(&fl4, 0, sizeof(fl4)); 448 fl4.daddr = daddr; 449 fl4.saddr = saddr; 450 fl4.flowi4_mark = mark; 451 fl4.flowi4_uid = sock_net_uid(net, NULL); 452 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 453 fl4.flowi4_proto = IPPROTO_ICMP; 454 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev); 455 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 456 rt = ip_route_output_key(net, &fl4); 457 if (IS_ERR(rt)) 458 goto out_unlock; 459 if (icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 460 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 461 ip_rt_put(rt); 462 out_unlock: 463 icmp_xmit_unlock(sk); 464 out_bh_enable: 465 local_bh_enable(); 466 } 467 468 static struct rtable *icmp_route_lookup(struct net *net, 469 struct flowi4 *fl4, 470 struct sk_buff *skb_in, 471 const struct iphdr *iph, 472 __be32 saddr, u8 tos, u32 mark, 473 int type, int code, 474 struct icmp_bxm *param) 475 { 476 struct rtable *rt, *rt2; 477 struct flowi4 fl4_dec; 478 int err; 479 480 memset(fl4, 0, sizeof(*fl4)); 481 fl4->daddr = (param->replyopts.opt.opt.srr ? 482 param->replyopts.opt.opt.faddr : iph->saddr); 483 fl4->saddr = saddr; 484 fl4->flowi4_mark = mark; 485 fl4->flowi4_uid = sock_net_uid(net, NULL); 486 fl4->flowi4_tos = RT_TOS(tos); 487 fl4->flowi4_proto = IPPROTO_ICMP; 488 fl4->fl4_icmp_type = type; 489 fl4->fl4_icmp_code = code; 490 fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev); 491 492 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 493 rt = ip_route_output_key_hash(net, fl4, skb_in); 494 if (IS_ERR(rt)) 495 return rt; 496 497 /* No need to clone since we're just using its address. */ 498 rt2 = rt; 499 500 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 501 flowi4_to_flowi(fl4), NULL, 0); 502 if (!IS_ERR(rt)) { 503 if (rt != rt2) 504 return rt; 505 } else if (PTR_ERR(rt) == -EPERM) { 506 rt = NULL; 507 } else 508 return rt; 509 510 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 511 if (err) 512 goto relookup_failed; 513 514 if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev, 515 fl4_dec.saddr) == RTN_LOCAL) { 516 rt2 = __ip_route_output_key(net, &fl4_dec); 517 if (IS_ERR(rt2)) 518 err = PTR_ERR(rt2); 519 } else { 520 struct flowi4 fl4_2 = {}; 521 unsigned long orefdst; 522 523 fl4_2.daddr = fl4_dec.saddr; 524 rt2 = ip_route_output_key(net, &fl4_2); 525 if (IS_ERR(rt2)) { 526 err = PTR_ERR(rt2); 527 goto relookup_failed; 528 } 529 /* Ugh! */ 530 orefdst = skb_in->_skb_refdst; /* save old refdst */ 531 skb_dst_set(skb_in, NULL); 532 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 533 RT_TOS(tos), rt2->dst.dev); 534 535 dst_release(&rt2->dst); 536 rt2 = skb_rtable(skb_in); 537 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 538 } 539 540 if (err) 541 goto relookup_failed; 542 543 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 544 flowi4_to_flowi(&fl4_dec), NULL, 545 XFRM_LOOKUP_ICMP); 546 if (!IS_ERR(rt2)) { 547 dst_release(&rt->dst); 548 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 549 rt = rt2; 550 } else if (PTR_ERR(rt2) == -EPERM) { 551 if (rt) 552 dst_release(&rt->dst); 553 return rt2; 554 } else { 555 err = PTR_ERR(rt2); 556 goto relookup_failed; 557 } 558 return rt; 559 560 relookup_failed: 561 if (rt) 562 return rt; 563 return ERR_PTR(err); 564 } 565 566 /* 567 * Send an ICMP message in response to a situation 568 * 569 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 570 * MAY send more (we do). 571 * MUST NOT change this header information. 572 * MUST NOT reply to a multicast/broadcast IP address. 573 * MUST NOT reply to a multicast/broadcast MAC address. 574 * MUST reply to only the first fragment. 575 */ 576 577 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 578 { 579 struct iphdr *iph; 580 int room; 581 struct icmp_bxm icmp_param; 582 struct rtable *rt = skb_rtable(skb_in); 583 struct ipcm_cookie ipc; 584 struct flowi4 fl4; 585 __be32 saddr; 586 u8 tos; 587 u32 mark; 588 struct net *net; 589 struct sock *sk; 590 591 if (!rt) 592 goto out; 593 net = dev_net(rt->dst.dev); 594 595 /* 596 * Find the original header. It is expected to be valid, of course. 597 * Check this, icmp_send is called from the most obscure devices 598 * sometimes. 599 */ 600 iph = ip_hdr(skb_in); 601 602 if ((u8 *)iph < skb_in->head || 603 (skb_network_header(skb_in) + sizeof(*iph)) > 604 skb_tail_pointer(skb_in)) 605 goto out; 606 607 /* 608 * No replies to physical multicast/broadcast 609 */ 610 if (skb_in->pkt_type != PACKET_HOST) 611 goto out; 612 613 /* 614 * Now check at the protocol level 615 */ 616 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 617 goto out; 618 619 /* 620 * Only reply to fragment 0. We byte re-order the constant 621 * mask for efficiency. 622 */ 623 if (iph->frag_off & htons(IP_OFFSET)) 624 goto out; 625 626 /* 627 * If we send an ICMP error to an ICMP error a mess would result.. 628 */ 629 if (icmp_pointers[type].error) { 630 /* 631 * We are an error, check if we are replying to an 632 * ICMP error 633 */ 634 if (iph->protocol == IPPROTO_ICMP) { 635 u8 _inner_type, *itp; 636 637 itp = skb_header_pointer(skb_in, 638 skb_network_header(skb_in) + 639 (iph->ihl << 2) + 640 offsetof(struct icmphdr, 641 type) - 642 skb_in->data, 643 sizeof(_inner_type), 644 &_inner_type); 645 if (!itp) 646 goto out; 647 648 /* 649 * Assume any unknown ICMP type is an error. This 650 * isn't specified by the RFC, but think about it.. 651 */ 652 if (*itp > NR_ICMP_TYPES || 653 icmp_pointers[*itp].error) 654 goto out; 655 } 656 } 657 658 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 659 local_bh_disable(); 660 661 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless 662 * incoming dev is loopback. If outgoing dev change to not be 663 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow) 664 */ 665 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) && 666 !icmpv4_global_allow(net, type, code)) 667 goto out_bh_enable; 668 669 sk = icmp_xmit_lock(net); 670 if (!sk) 671 goto out_bh_enable; 672 673 /* 674 * Construct source address and options. 675 */ 676 677 saddr = iph->daddr; 678 if (!(rt->rt_flags & RTCF_LOCAL)) { 679 struct net_device *dev = NULL; 680 681 rcu_read_lock(); 682 if (rt_is_input_route(rt) && 683 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 684 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 685 686 if (dev) 687 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 688 else 689 saddr = 0; 690 rcu_read_unlock(); 691 } 692 693 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 694 IPTOS_PREC_INTERNETCONTROL) : 695 iph->tos; 696 mark = IP4_REPLY_MARK(net, skb_in->mark); 697 698 if (ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in)) 699 goto out_unlock; 700 701 702 /* 703 * Prepare data for ICMP header. 704 */ 705 706 icmp_param.data.icmph.type = type; 707 icmp_param.data.icmph.code = code; 708 icmp_param.data.icmph.un.gateway = info; 709 icmp_param.data.icmph.checksum = 0; 710 icmp_param.skb = skb_in; 711 icmp_param.offset = skb_network_offset(skb_in); 712 inet_sk(sk)->tos = tos; 713 sk->sk_mark = mark; 714 ipc.addr = iph->saddr; 715 ipc.opt = &icmp_param.replyopts.opt; 716 ipc.tx_flags = 0; 717 ipc.ttl = 0; 718 ipc.tos = -1; 719 ipc.sockc.transmit_time = 0; 720 721 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 722 type, code, &icmp_param); 723 if (IS_ERR(rt)) 724 goto out_unlock; 725 726 /* peer icmp_ratelimit */ 727 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 728 goto ende; 729 730 /* RFC says return as much as we can without exceeding 576 bytes. */ 731 732 room = dst_mtu(&rt->dst); 733 if (room > 576) 734 room = 576; 735 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 736 room -= sizeof(struct icmphdr); 737 738 icmp_param.data_len = skb_in->len - icmp_param.offset; 739 if (icmp_param.data_len > room) 740 icmp_param.data_len = room; 741 icmp_param.head_len = sizeof(struct icmphdr); 742 743 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 744 ende: 745 ip_rt_put(rt); 746 out_unlock: 747 icmp_xmit_unlock(sk); 748 out_bh_enable: 749 local_bh_enable(); 750 out:; 751 } 752 EXPORT_SYMBOL(icmp_send); 753 754 755 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 756 { 757 const struct iphdr *iph = (const struct iphdr *) skb->data; 758 const struct net_protocol *ipprot; 759 int protocol = iph->protocol; 760 761 /* Checkin full IP header plus 8 bytes of protocol to 762 * avoid additional coding at protocol handlers. 763 */ 764 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 765 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 766 return; 767 } 768 769 raw_icmp_error(skb, protocol, info); 770 771 ipprot = rcu_dereference(inet_protos[protocol]); 772 if (ipprot && ipprot->err_handler) 773 ipprot->err_handler(skb, info); 774 } 775 776 static bool icmp_tag_validation(int proto) 777 { 778 bool ok; 779 780 rcu_read_lock(); 781 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 782 rcu_read_unlock(); 783 return ok; 784 } 785 786 /* 787 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and 788 * ICMP_PARAMETERPROB. 789 */ 790 791 static bool icmp_unreach(struct sk_buff *skb) 792 { 793 const struct iphdr *iph; 794 struct icmphdr *icmph; 795 struct net *net; 796 u32 info = 0; 797 798 net = dev_net(skb_dst(skb)->dev); 799 800 /* 801 * Incomplete header ? 802 * Only checks for the IP header, there should be an 803 * additional check for longer headers in upper levels. 804 */ 805 806 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 807 goto out_err; 808 809 icmph = icmp_hdr(skb); 810 iph = (const struct iphdr *)skb->data; 811 812 if (iph->ihl < 5) /* Mangled header, drop. */ 813 goto out_err; 814 815 switch (icmph->type) { 816 case ICMP_DEST_UNREACH: 817 switch (icmph->code & 15) { 818 case ICMP_NET_UNREACH: 819 case ICMP_HOST_UNREACH: 820 case ICMP_PROT_UNREACH: 821 case ICMP_PORT_UNREACH: 822 break; 823 case ICMP_FRAG_NEEDED: 824 /* for documentation of the ip_no_pmtu_disc 825 * values please see 826 * Documentation/networking/ip-sysctl.txt 827 */ 828 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 829 default: 830 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 831 &iph->daddr); 832 break; 833 case 2: 834 goto out; 835 case 3: 836 if (!icmp_tag_validation(iph->protocol)) 837 goto out; 838 /* fall through */ 839 case 0: 840 info = ntohs(icmph->un.frag.mtu); 841 } 842 break; 843 case ICMP_SR_FAILED: 844 net_dbg_ratelimited("%pI4: Source Route Failed\n", 845 &iph->daddr); 846 break; 847 default: 848 break; 849 } 850 if (icmph->code > NR_ICMP_UNREACH) 851 goto out; 852 break; 853 case ICMP_PARAMETERPROB: 854 info = ntohl(icmph->un.gateway) >> 24; 855 break; 856 case ICMP_TIME_EXCEEDED: 857 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS); 858 if (icmph->code == ICMP_EXC_FRAGTIME) 859 goto out; 860 break; 861 } 862 863 /* 864 * Throw it at our lower layers 865 * 866 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 867 * header. 868 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 869 * transport layer. 870 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 871 * transport layer. 872 */ 873 874 /* 875 * Check the other end isn't violating RFC 1122. Some routers send 876 * bogus responses to broadcast frames. If you see this message 877 * first check your netmask matches at both ends, if it does then 878 * get the other vendor to fix their kit. 879 */ 880 881 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 882 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) { 883 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 884 &ip_hdr(skb)->saddr, 885 icmph->type, icmph->code, 886 &iph->daddr, skb->dev->name); 887 goto out; 888 } 889 890 icmp_socket_deliver(skb, info); 891 892 out: 893 return true; 894 out_err: 895 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 896 return false; 897 } 898 899 900 /* 901 * Handle ICMP_REDIRECT. 902 */ 903 904 static bool icmp_redirect(struct sk_buff *skb) 905 { 906 if (skb->len < sizeof(struct iphdr)) { 907 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 908 return false; 909 } 910 911 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 912 /* there aught to be a stat */ 913 return false; 914 } 915 916 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 917 return true; 918 } 919 920 /* 921 * Handle ICMP_ECHO ("ping") requests. 922 * 923 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 924 * requests. 925 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 926 * included in the reply. 927 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 928 * echo requests, MUST have default=NOT. 929 * See also WRT handling of options once they are done and working. 930 */ 931 932 static bool icmp_echo(struct sk_buff *skb) 933 { 934 struct net *net; 935 936 net = dev_net(skb_dst(skb)->dev); 937 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 938 struct icmp_bxm icmp_param; 939 940 icmp_param.data.icmph = *icmp_hdr(skb); 941 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 942 icmp_param.skb = skb; 943 icmp_param.offset = 0; 944 icmp_param.data_len = skb->len; 945 icmp_param.head_len = sizeof(struct icmphdr); 946 icmp_reply(&icmp_param, skb); 947 } 948 /* should there be an ICMP stat for ignored echos? */ 949 return true; 950 } 951 952 /* 953 * Handle ICMP Timestamp requests. 954 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 955 * SHOULD be in the kernel for minimum random latency. 956 * MUST be accurate to a few minutes. 957 * MUST be updated at least at 15Hz. 958 */ 959 static bool icmp_timestamp(struct sk_buff *skb) 960 { 961 struct icmp_bxm icmp_param; 962 /* 963 * Too short. 964 */ 965 if (skb->len < 4) 966 goto out_err; 967 968 /* 969 * Fill in the current time as ms since midnight UT: 970 */ 971 icmp_param.data.times[1] = inet_current_timestamp(); 972 icmp_param.data.times[2] = icmp_param.data.times[1]; 973 974 BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)); 975 976 icmp_param.data.icmph = *icmp_hdr(skb); 977 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 978 icmp_param.data.icmph.code = 0; 979 icmp_param.skb = skb; 980 icmp_param.offset = 0; 981 icmp_param.data_len = 0; 982 icmp_param.head_len = sizeof(struct icmphdr) + 12; 983 icmp_reply(&icmp_param, skb); 984 return true; 985 986 out_err: 987 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 988 return false; 989 } 990 991 static bool icmp_discard(struct sk_buff *skb) 992 { 993 /* pretend it was a success */ 994 return true; 995 } 996 997 /* 998 * Deal with incoming ICMP packets. 999 */ 1000 int icmp_rcv(struct sk_buff *skb) 1001 { 1002 struct icmphdr *icmph; 1003 struct rtable *rt = skb_rtable(skb); 1004 struct net *net = dev_net(rt->dst.dev); 1005 bool success; 1006 1007 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 1008 struct sec_path *sp = skb_sec_path(skb); 1009 int nh; 1010 1011 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 1012 XFRM_STATE_ICMP)) 1013 goto drop; 1014 1015 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 1016 goto drop; 1017 1018 nh = skb_network_offset(skb); 1019 skb_set_network_header(skb, sizeof(*icmph)); 1020 1021 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 1022 goto drop; 1023 1024 skb_set_network_header(skb, nh); 1025 } 1026 1027 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS); 1028 1029 if (skb_checksum_simple_validate(skb)) 1030 goto csum_error; 1031 1032 if (!pskb_pull(skb, sizeof(*icmph))) 1033 goto error; 1034 1035 icmph = icmp_hdr(skb); 1036 1037 ICMPMSGIN_INC_STATS(net, icmph->type); 1038 /* 1039 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1040 * 1041 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1042 * discarded. 1043 */ 1044 if (icmph->type > NR_ICMP_TYPES) 1045 goto error; 1046 1047 1048 /* 1049 * Parse the ICMP message 1050 */ 1051 1052 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1053 /* 1054 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1055 * silently ignored (we let user decide with a sysctl). 1056 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1057 * discarded if to broadcast/multicast. 1058 */ 1059 if ((icmph->type == ICMP_ECHO || 1060 icmph->type == ICMP_TIMESTAMP) && 1061 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1062 goto error; 1063 } 1064 if (icmph->type != ICMP_ECHO && 1065 icmph->type != ICMP_TIMESTAMP && 1066 icmph->type != ICMP_ADDRESS && 1067 icmph->type != ICMP_ADDRESSREPLY) { 1068 goto error; 1069 } 1070 } 1071 1072 success = icmp_pointers[icmph->type].handler(skb); 1073 1074 if (success) { 1075 consume_skb(skb); 1076 return NET_RX_SUCCESS; 1077 } 1078 1079 drop: 1080 kfree_skb(skb); 1081 return NET_RX_DROP; 1082 csum_error: 1083 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS); 1084 error: 1085 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 1086 goto drop; 1087 } 1088 1089 void icmp_err(struct sk_buff *skb, u32 info) 1090 { 1091 struct iphdr *iph = (struct iphdr *)skb->data; 1092 int offset = iph->ihl<<2; 1093 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1094 int type = icmp_hdr(skb)->type; 1095 int code = icmp_hdr(skb)->code; 1096 struct net *net = dev_net(skb->dev); 1097 1098 /* 1099 * Use ping_err to handle all icmp errors except those 1100 * triggered by ICMP_ECHOREPLY which sent from kernel. 1101 */ 1102 if (icmph->type != ICMP_ECHOREPLY) { 1103 ping_err(skb, offset, info); 1104 return; 1105 } 1106 1107 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1108 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 1109 else if (type == ICMP_REDIRECT) 1110 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 1111 } 1112 1113 /* 1114 * This table is the definition of how we handle ICMP. 1115 */ 1116 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1117 [ICMP_ECHOREPLY] = { 1118 .handler = ping_rcv, 1119 }, 1120 [1] = { 1121 .handler = icmp_discard, 1122 .error = 1, 1123 }, 1124 [2] = { 1125 .handler = icmp_discard, 1126 .error = 1, 1127 }, 1128 [ICMP_DEST_UNREACH] = { 1129 .handler = icmp_unreach, 1130 .error = 1, 1131 }, 1132 [ICMP_SOURCE_QUENCH] = { 1133 .handler = icmp_unreach, 1134 .error = 1, 1135 }, 1136 [ICMP_REDIRECT] = { 1137 .handler = icmp_redirect, 1138 .error = 1, 1139 }, 1140 [6] = { 1141 .handler = icmp_discard, 1142 .error = 1, 1143 }, 1144 [7] = { 1145 .handler = icmp_discard, 1146 .error = 1, 1147 }, 1148 [ICMP_ECHO] = { 1149 .handler = icmp_echo, 1150 }, 1151 [9] = { 1152 .handler = icmp_discard, 1153 .error = 1, 1154 }, 1155 [10] = { 1156 .handler = icmp_discard, 1157 .error = 1, 1158 }, 1159 [ICMP_TIME_EXCEEDED] = { 1160 .handler = icmp_unreach, 1161 .error = 1, 1162 }, 1163 [ICMP_PARAMETERPROB] = { 1164 .handler = icmp_unreach, 1165 .error = 1, 1166 }, 1167 [ICMP_TIMESTAMP] = { 1168 .handler = icmp_timestamp, 1169 }, 1170 [ICMP_TIMESTAMPREPLY] = { 1171 .handler = icmp_discard, 1172 }, 1173 [ICMP_INFO_REQUEST] = { 1174 .handler = icmp_discard, 1175 }, 1176 [ICMP_INFO_REPLY] = { 1177 .handler = icmp_discard, 1178 }, 1179 [ICMP_ADDRESS] = { 1180 .handler = icmp_discard, 1181 }, 1182 [ICMP_ADDRESSREPLY] = { 1183 .handler = icmp_discard, 1184 }, 1185 }; 1186 1187 static void __net_exit icmp_sk_exit(struct net *net) 1188 { 1189 int i; 1190 1191 for_each_possible_cpu(i) 1192 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1193 free_percpu(net->ipv4.icmp_sk); 1194 net->ipv4.icmp_sk = NULL; 1195 } 1196 1197 static int __net_init icmp_sk_init(struct net *net) 1198 { 1199 int i, err; 1200 1201 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1202 if (!net->ipv4.icmp_sk) 1203 return -ENOMEM; 1204 1205 for_each_possible_cpu(i) { 1206 struct sock *sk; 1207 1208 err = inet_ctl_sock_create(&sk, PF_INET, 1209 SOCK_RAW, IPPROTO_ICMP, net); 1210 if (err < 0) 1211 goto fail; 1212 1213 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1214 1215 /* Enough space for 2 64K ICMP packets, including 1216 * sk_buff/skb_shared_info struct overhead. 1217 */ 1218 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1219 1220 /* 1221 * Speedup sock_wfree() 1222 */ 1223 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1224 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1225 } 1226 1227 /* Control parameters for ECHO replies. */ 1228 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1229 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1230 1231 /* Control parameter - ignore bogus broadcast responses? */ 1232 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1233 1234 /* 1235 * Configurable global rate limit. 1236 * 1237 * ratelimit defines tokens/packet consumed for dst->rate_token 1238 * bucket ratemask defines which icmp types are ratelimited by 1239 * setting it's bit position. 1240 * 1241 * default: 1242 * dest unreachable (3), source quench (4), 1243 * time exceeded (11), parameter problem (12) 1244 */ 1245 1246 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1247 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1248 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1249 1250 return 0; 1251 1252 fail: 1253 for_each_possible_cpu(i) 1254 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1255 free_percpu(net->ipv4.icmp_sk); 1256 return err; 1257 } 1258 1259 static struct pernet_operations __net_initdata icmp_sk_ops = { 1260 .init = icmp_sk_init, 1261 .exit = icmp_sk_exit, 1262 }; 1263 1264 int __init icmp_init(void) 1265 { 1266 return register_pernet_subsys(&icmp_sk_ops); 1267 } 1268