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 static inline struct sock *icmp_xmit_lock(struct net *net) 213 { 214 struct sock *sk; 215 216 local_bh_disable(); 217 218 sk = icmp_sk(net); 219 220 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 221 /* This can happen if the output path signals a 222 * dst_link_failure() for an outgoing ICMP packet. 223 */ 224 local_bh_enable(); 225 return NULL; 226 } 227 return sk; 228 } 229 230 static inline void icmp_xmit_unlock(struct sock *sk) 231 { 232 spin_unlock_bh(&sk->sk_lock.slock); 233 } 234 235 int sysctl_icmp_msgs_per_sec __read_mostly = 1000; 236 int sysctl_icmp_msgs_burst __read_mostly = 50; 237 238 static struct { 239 spinlock_t lock; 240 u32 credit; 241 u32 stamp; 242 } icmp_global = { 243 .lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock), 244 }; 245 246 /** 247 * icmp_global_allow - Are we allowed to send one more ICMP message ? 248 * 249 * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. 250 * Returns false if we reached the limit and can not send another packet. 251 * Note: called with BH disabled 252 */ 253 bool icmp_global_allow(void) 254 { 255 u32 credit, delta, incr = 0, now = (u32)jiffies; 256 bool rc = false; 257 258 /* Check if token bucket is empty and cannot be refilled 259 * without taking the spinlock. 260 */ 261 if (!icmp_global.credit) { 262 delta = min_t(u32, now - icmp_global.stamp, HZ); 263 if (delta < HZ / 50) 264 return false; 265 } 266 267 spin_lock(&icmp_global.lock); 268 delta = min_t(u32, now - icmp_global.stamp, HZ); 269 if (delta >= HZ / 50) { 270 incr = sysctl_icmp_msgs_per_sec * delta / HZ ; 271 if (incr) 272 icmp_global.stamp = now; 273 } 274 credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); 275 if (credit) { 276 credit--; 277 rc = true; 278 } 279 icmp_global.credit = credit; 280 spin_unlock(&icmp_global.lock); 281 return rc; 282 } 283 EXPORT_SYMBOL(icmp_global_allow); 284 285 /* 286 * Send an ICMP frame. 287 */ 288 289 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 290 struct flowi4 *fl4, int type, int code) 291 { 292 struct dst_entry *dst = &rt->dst; 293 bool rc = true; 294 295 if (type > NR_ICMP_TYPES) 296 goto out; 297 298 /* Don't limit PMTU discovery. */ 299 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 300 goto out; 301 302 /* No rate limit on loopback */ 303 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 304 goto out; 305 306 /* Limit if icmp type is enabled in ratemask. */ 307 if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask)) 308 goto out; 309 310 rc = false; 311 if (icmp_global_allow()) { 312 int vif = l3mdev_master_ifindex(dst->dev); 313 struct inet_peer *peer; 314 315 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1); 316 rc = inet_peer_xrlim_allow(peer, 317 net->ipv4.sysctl_icmp_ratelimit); 318 if (peer) 319 inet_putpeer(peer); 320 } 321 out: 322 return rc; 323 } 324 325 /* 326 * Maintain the counters used in the SNMP statistics for outgoing ICMP 327 */ 328 void icmp_out_count(struct net *net, unsigned char type) 329 { 330 ICMPMSGOUT_INC_STATS(net, type); 331 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 332 } 333 334 /* 335 * Checksum each fragment, and on the first include the headers and final 336 * checksum. 337 */ 338 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 339 struct sk_buff *skb) 340 { 341 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 342 __wsum csum; 343 344 csum = skb_copy_and_csum_bits(icmp_param->skb, 345 icmp_param->offset + offset, 346 to, len, 0); 347 348 skb->csum = csum_block_add(skb->csum, csum, odd); 349 if (icmp_pointers[icmp_param->data.icmph.type].error) 350 nf_ct_attach(skb, icmp_param->skb); 351 return 0; 352 } 353 354 static void icmp_push_reply(struct icmp_bxm *icmp_param, 355 struct flowi4 *fl4, 356 struct ipcm_cookie *ipc, struct rtable **rt) 357 { 358 struct sock *sk; 359 struct sk_buff *skb; 360 361 sk = icmp_sk(dev_net((*rt)->dst.dev)); 362 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 363 icmp_param->data_len+icmp_param->head_len, 364 icmp_param->head_len, 365 ipc, rt, MSG_DONTWAIT) < 0) { 366 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS); 367 ip_flush_pending_frames(sk); 368 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 369 struct icmphdr *icmph = icmp_hdr(skb); 370 __wsum csum = 0; 371 struct sk_buff *skb1; 372 373 skb_queue_walk(&sk->sk_write_queue, skb1) { 374 csum = csum_add(csum, skb1->csum); 375 } 376 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 377 (char *)icmph, 378 icmp_param->head_len, csum); 379 icmph->checksum = csum_fold(csum); 380 skb->ip_summed = CHECKSUM_NONE; 381 ip_push_pending_frames(sk, fl4); 382 } 383 } 384 385 /* 386 * Driving logic for building and sending ICMP messages. 387 */ 388 389 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 390 { 391 struct ipcm_cookie ipc; 392 struct rtable *rt = skb_rtable(skb); 393 struct net *net = dev_net(rt->dst.dev); 394 struct flowi4 fl4; 395 struct sock *sk; 396 struct inet_sock *inet; 397 __be32 daddr, saddr; 398 u32 mark = IP4_REPLY_MARK(net, skb->mark); 399 400 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb)) 401 return; 402 403 sk = icmp_xmit_lock(net); 404 if (!sk) 405 return; 406 inet = inet_sk(sk); 407 408 icmp_param->data.icmph.checksum = 0; 409 410 inet->tos = ip_hdr(skb)->tos; 411 sk->sk_mark = mark; 412 daddr = ipc.addr = ip_hdr(skb)->saddr; 413 saddr = fib_compute_spec_dst(skb); 414 ipc.opt = NULL; 415 ipc.tx_flags = 0; 416 ipc.ttl = 0; 417 ipc.tos = -1; 418 419 if (icmp_param->replyopts.opt.opt.optlen) { 420 ipc.opt = &icmp_param->replyopts.opt; 421 if (ipc.opt->opt.srr) 422 daddr = icmp_param->replyopts.opt.opt.faddr; 423 } 424 memset(&fl4, 0, sizeof(fl4)); 425 fl4.daddr = daddr; 426 fl4.saddr = saddr; 427 fl4.flowi4_mark = mark; 428 fl4.flowi4_uid = sock_net_uid(net, NULL); 429 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 430 fl4.flowi4_proto = IPPROTO_ICMP; 431 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev); 432 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 433 rt = ip_route_output_key(net, &fl4); 434 if (IS_ERR(rt)) 435 goto out_unlock; 436 if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type, 437 icmp_param->data.icmph.code)) 438 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 439 ip_rt_put(rt); 440 out_unlock: 441 icmp_xmit_unlock(sk); 442 } 443 444 #ifdef CONFIG_IP_ROUTE_MULTIPATH 445 446 /* Source and destination is swapped. See ip_multipath_icmp_hash */ 447 static int icmp_multipath_hash_skb(const struct sk_buff *skb) 448 { 449 const struct iphdr *iph = ip_hdr(skb); 450 451 return fib_multipath_hash(iph->daddr, iph->saddr); 452 } 453 454 #else 455 456 #define icmp_multipath_hash_skb(skb) (-1) 457 458 #endif 459 460 static struct rtable *icmp_route_lookup(struct net *net, 461 struct flowi4 *fl4, 462 struct sk_buff *skb_in, 463 const struct iphdr *iph, 464 __be32 saddr, u8 tos, u32 mark, 465 int type, int code, 466 struct icmp_bxm *param) 467 { 468 struct rtable *rt, *rt2; 469 struct flowi4 fl4_dec; 470 int err; 471 472 memset(fl4, 0, sizeof(*fl4)); 473 fl4->daddr = (param->replyopts.opt.opt.srr ? 474 param->replyopts.opt.opt.faddr : iph->saddr); 475 fl4->saddr = saddr; 476 fl4->flowi4_mark = mark; 477 fl4->flowi4_uid = sock_net_uid(net, NULL); 478 fl4->flowi4_tos = RT_TOS(tos); 479 fl4->flowi4_proto = IPPROTO_ICMP; 480 fl4->fl4_icmp_type = type; 481 fl4->fl4_icmp_code = code; 482 fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev); 483 484 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 485 rt = __ip_route_output_key_hash(net, fl4, 486 icmp_multipath_hash_skb(skb_in)); 487 if (IS_ERR(rt)) 488 return rt; 489 490 /* No need to clone since we're just using its address. */ 491 rt2 = rt; 492 493 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 494 flowi4_to_flowi(fl4), NULL, 0); 495 if (!IS_ERR(rt)) { 496 if (rt != rt2) 497 return rt; 498 } else if (PTR_ERR(rt) == -EPERM) { 499 rt = NULL; 500 } else 501 return rt; 502 503 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 504 if (err) 505 goto relookup_failed; 506 507 if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev, 508 fl4_dec.saddr) == RTN_LOCAL) { 509 rt2 = __ip_route_output_key(net, &fl4_dec); 510 if (IS_ERR(rt2)) 511 err = PTR_ERR(rt2); 512 } else { 513 struct flowi4 fl4_2 = {}; 514 unsigned long orefdst; 515 516 fl4_2.daddr = fl4_dec.saddr; 517 rt2 = ip_route_output_key(net, &fl4_2); 518 if (IS_ERR(rt2)) { 519 err = PTR_ERR(rt2); 520 goto relookup_failed; 521 } 522 /* Ugh! */ 523 orefdst = skb_in->_skb_refdst; /* save old refdst */ 524 skb_dst_set(skb_in, NULL); 525 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 526 RT_TOS(tos), rt2->dst.dev); 527 528 dst_release(&rt2->dst); 529 rt2 = skb_rtable(skb_in); 530 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 531 } 532 533 if (err) 534 goto relookup_failed; 535 536 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 537 flowi4_to_flowi(&fl4_dec), NULL, 538 XFRM_LOOKUP_ICMP); 539 if (!IS_ERR(rt2)) { 540 dst_release(&rt->dst); 541 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 542 rt = rt2; 543 } else if (PTR_ERR(rt2) == -EPERM) { 544 if (rt) 545 dst_release(&rt->dst); 546 return rt2; 547 } else { 548 err = PTR_ERR(rt2); 549 goto relookup_failed; 550 } 551 return rt; 552 553 relookup_failed: 554 if (rt) 555 return rt; 556 return ERR_PTR(err); 557 } 558 559 /* 560 * Send an ICMP message in response to a situation 561 * 562 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 563 * MAY send more (we do). 564 * MUST NOT change this header information. 565 * MUST NOT reply to a multicast/broadcast IP address. 566 * MUST NOT reply to a multicast/broadcast MAC address. 567 * MUST reply to only the first fragment. 568 */ 569 570 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 571 { 572 struct iphdr *iph; 573 int room; 574 struct icmp_bxm *icmp_param; 575 struct rtable *rt = skb_rtable(skb_in); 576 struct ipcm_cookie ipc; 577 struct flowi4 fl4; 578 __be32 saddr; 579 u8 tos; 580 u32 mark; 581 struct net *net; 582 struct sock *sk; 583 584 if (!rt) 585 goto out; 586 net = dev_net(rt->dst.dev); 587 588 /* 589 * Find the original header. It is expected to be valid, of course. 590 * Check this, icmp_send is called from the most obscure devices 591 * sometimes. 592 */ 593 iph = ip_hdr(skb_in); 594 595 if ((u8 *)iph < skb_in->head || 596 (skb_network_header(skb_in) + sizeof(*iph)) > 597 skb_tail_pointer(skb_in)) 598 goto out; 599 600 /* 601 * No replies to physical multicast/broadcast 602 */ 603 if (skb_in->pkt_type != PACKET_HOST) 604 goto out; 605 606 /* 607 * Now check at the protocol level 608 */ 609 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 610 goto out; 611 612 /* 613 * Only reply to fragment 0. We byte re-order the constant 614 * mask for efficiency. 615 */ 616 if (iph->frag_off & htons(IP_OFFSET)) 617 goto out; 618 619 /* 620 * If we send an ICMP error to an ICMP error a mess would result.. 621 */ 622 if (icmp_pointers[type].error) { 623 /* 624 * We are an error, check if we are replying to an 625 * ICMP error 626 */ 627 if (iph->protocol == IPPROTO_ICMP) { 628 u8 _inner_type, *itp; 629 630 itp = skb_header_pointer(skb_in, 631 skb_network_header(skb_in) + 632 (iph->ihl << 2) + 633 offsetof(struct icmphdr, 634 type) - 635 skb_in->data, 636 sizeof(_inner_type), 637 &_inner_type); 638 if (!itp) 639 goto out; 640 641 /* 642 * Assume any unknown ICMP type is an error. This 643 * isn't specified by the RFC, but think about it.. 644 */ 645 if (*itp > NR_ICMP_TYPES || 646 icmp_pointers[*itp].error) 647 goto out; 648 } 649 } 650 651 icmp_param = kmalloc(sizeof(*icmp_param), GFP_ATOMIC); 652 if (!icmp_param) 653 return; 654 655 sk = icmp_xmit_lock(net); 656 if (!sk) 657 goto out_free; 658 659 /* 660 * Construct source address and options. 661 */ 662 663 saddr = iph->daddr; 664 if (!(rt->rt_flags & RTCF_LOCAL)) { 665 struct net_device *dev = NULL; 666 667 rcu_read_lock(); 668 if (rt_is_input_route(rt) && 669 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 670 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 671 672 if (dev) 673 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 674 else 675 saddr = 0; 676 rcu_read_unlock(); 677 } 678 679 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 680 IPTOS_PREC_INTERNETCONTROL) : 681 iph->tos; 682 mark = IP4_REPLY_MARK(net, skb_in->mark); 683 684 if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb_in)) 685 goto out_unlock; 686 687 688 /* 689 * Prepare data for ICMP header. 690 */ 691 692 icmp_param->data.icmph.type = type; 693 icmp_param->data.icmph.code = code; 694 icmp_param->data.icmph.un.gateway = info; 695 icmp_param->data.icmph.checksum = 0; 696 icmp_param->skb = skb_in; 697 icmp_param->offset = skb_network_offset(skb_in); 698 inet_sk(sk)->tos = tos; 699 sk->sk_mark = mark; 700 ipc.addr = iph->saddr; 701 ipc.opt = &icmp_param->replyopts.opt; 702 ipc.tx_flags = 0; 703 ipc.ttl = 0; 704 ipc.tos = -1; 705 706 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 707 type, code, icmp_param); 708 if (IS_ERR(rt)) 709 goto out_unlock; 710 711 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 712 goto ende; 713 714 /* RFC says return as much as we can without exceeding 576 bytes. */ 715 716 room = dst_mtu(&rt->dst); 717 if (room > 576) 718 room = 576; 719 room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.opt.optlen; 720 room -= sizeof(struct icmphdr); 721 722 icmp_param->data_len = skb_in->len - icmp_param->offset; 723 if (icmp_param->data_len > room) 724 icmp_param->data_len = room; 725 icmp_param->head_len = sizeof(struct icmphdr); 726 727 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 728 ende: 729 ip_rt_put(rt); 730 out_unlock: 731 icmp_xmit_unlock(sk); 732 out_free: 733 kfree(icmp_param); 734 out:; 735 } 736 EXPORT_SYMBOL(icmp_send); 737 738 739 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 740 { 741 const struct iphdr *iph = (const struct iphdr *) skb->data; 742 const struct net_protocol *ipprot; 743 int protocol = iph->protocol; 744 745 /* Checkin full IP header plus 8 bytes of protocol to 746 * avoid additional coding at protocol handlers. 747 */ 748 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 749 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 750 return; 751 } 752 753 raw_icmp_error(skb, protocol, info); 754 755 ipprot = rcu_dereference(inet_protos[protocol]); 756 if (ipprot && ipprot->err_handler) 757 ipprot->err_handler(skb, info); 758 } 759 760 static bool icmp_tag_validation(int proto) 761 { 762 bool ok; 763 764 rcu_read_lock(); 765 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 766 rcu_read_unlock(); 767 return ok; 768 } 769 770 /* 771 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, ICMP_QUENCH, and 772 * ICMP_PARAMETERPROB. 773 */ 774 775 static bool icmp_unreach(struct sk_buff *skb) 776 { 777 const struct iphdr *iph; 778 struct icmphdr *icmph; 779 struct net *net; 780 u32 info = 0; 781 782 net = dev_net(skb_dst(skb)->dev); 783 784 /* 785 * Incomplete header ? 786 * Only checks for the IP header, there should be an 787 * additional check for longer headers in upper levels. 788 */ 789 790 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 791 goto out_err; 792 793 icmph = icmp_hdr(skb); 794 iph = (const struct iphdr *)skb->data; 795 796 if (iph->ihl < 5) /* Mangled header, drop. */ 797 goto out_err; 798 799 if (icmph->type == ICMP_DEST_UNREACH) { 800 switch (icmph->code & 15) { 801 case ICMP_NET_UNREACH: 802 case ICMP_HOST_UNREACH: 803 case ICMP_PROT_UNREACH: 804 case ICMP_PORT_UNREACH: 805 break; 806 case ICMP_FRAG_NEEDED: 807 /* for documentation of the ip_no_pmtu_disc 808 * values please see 809 * Documentation/networking/ip-sysctl.txt 810 */ 811 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 812 default: 813 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 814 &iph->daddr); 815 break; 816 case 2: 817 goto out; 818 case 3: 819 if (!icmp_tag_validation(iph->protocol)) 820 goto out; 821 /* fall through */ 822 case 0: 823 info = ntohs(icmph->un.frag.mtu); 824 } 825 break; 826 case ICMP_SR_FAILED: 827 net_dbg_ratelimited("%pI4: Source Route Failed\n", 828 &iph->daddr); 829 break; 830 default: 831 break; 832 } 833 if (icmph->code > NR_ICMP_UNREACH) 834 goto out; 835 } else if (icmph->type == ICMP_PARAMETERPROB) 836 info = ntohl(icmph->un.gateway) >> 24; 837 838 /* 839 * Throw it at our lower layers 840 * 841 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 842 * header. 843 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 844 * transport layer. 845 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 846 * transport layer. 847 */ 848 849 /* 850 * Check the other end isn't violating RFC 1122. Some routers send 851 * bogus responses to broadcast frames. If you see this message 852 * first check your netmask matches at both ends, if it does then 853 * get the other vendor to fix their kit. 854 */ 855 856 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 857 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) { 858 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 859 &ip_hdr(skb)->saddr, 860 icmph->type, icmph->code, 861 &iph->daddr, skb->dev->name); 862 goto out; 863 } 864 865 icmp_socket_deliver(skb, info); 866 867 out: 868 return true; 869 out_err: 870 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 871 return false; 872 } 873 874 875 /* 876 * Handle ICMP_REDIRECT. 877 */ 878 879 static bool icmp_redirect(struct sk_buff *skb) 880 { 881 if (skb->len < sizeof(struct iphdr)) { 882 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 883 return false; 884 } 885 886 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 887 /* there aught to be a stat */ 888 return false; 889 } 890 891 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 892 return true; 893 } 894 895 /* 896 * Handle ICMP_ECHO ("ping") requests. 897 * 898 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 899 * requests. 900 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 901 * included in the reply. 902 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 903 * echo requests, MUST have default=NOT. 904 * See also WRT handling of options once they are done and working. 905 */ 906 907 static bool icmp_echo(struct sk_buff *skb) 908 { 909 struct net *net; 910 911 net = dev_net(skb_dst(skb)->dev); 912 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 913 struct icmp_bxm icmp_param; 914 915 icmp_param.data.icmph = *icmp_hdr(skb); 916 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 917 icmp_param.skb = skb; 918 icmp_param.offset = 0; 919 icmp_param.data_len = skb->len; 920 icmp_param.head_len = sizeof(struct icmphdr); 921 icmp_reply(&icmp_param, skb); 922 } 923 /* should there be an ICMP stat for ignored echos? */ 924 return true; 925 } 926 927 /* 928 * Handle ICMP Timestamp requests. 929 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 930 * SHOULD be in the kernel for minimum random latency. 931 * MUST be accurate to a few minutes. 932 * MUST be updated at least at 15Hz. 933 */ 934 static bool icmp_timestamp(struct sk_buff *skb) 935 { 936 struct icmp_bxm icmp_param; 937 /* 938 * Too short. 939 */ 940 if (skb->len < 4) 941 goto out_err; 942 943 /* 944 * Fill in the current time as ms since midnight UT: 945 */ 946 icmp_param.data.times[1] = inet_current_timestamp(); 947 icmp_param.data.times[2] = icmp_param.data.times[1]; 948 if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)) 949 BUG(); 950 icmp_param.data.icmph = *icmp_hdr(skb); 951 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 952 icmp_param.data.icmph.code = 0; 953 icmp_param.skb = skb; 954 icmp_param.offset = 0; 955 icmp_param.data_len = 0; 956 icmp_param.head_len = sizeof(struct icmphdr) + 12; 957 icmp_reply(&icmp_param, skb); 958 return true; 959 960 out_err: 961 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 962 return false; 963 } 964 965 static bool icmp_discard(struct sk_buff *skb) 966 { 967 /* pretend it was a success */ 968 return true; 969 } 970 971 /* 972 * Deal with incoming ICMP packets. 973 */ 974 int icmp_rcv(struct sk_buff *skb) 975 { 976 struct icmphdr *icmph; 977 struct rtable *rt = skb_rtable(skb); 978 struct net *net = dev_net(rt->dst.dev); 979 bool success; 980 981 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 982 struct sec_path *sp = skb_sec_path(skb); 983 int nh; 984 985 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 986 XFRM_STATE_ICMP)) 987 goto drop; 988 989 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 990 goto drop; 991 992 nh = skb_network_offset(skb); 993 skb_set_network_header(skb, sizeof(*icmph)); 994 995 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 996 goto drop; 997 998 skb_set_network_header(skb, nh); 999 } 1000 1001 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS); 1002 1003 if (skb_checksum_simple_validate(skb)) 1004 goto csum_error; 1005 1006 if (!pskb_pull(skb, sizeof(*icmph))) 1007 goto error; 1008 1009 icmph = icmp_hdr(skb); 1010 1011 ICMPMSGIN_INC_STATS(net, icmph->type); 1012 /* 1013 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1014 * 1015 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1016 * discarded. 1017 */ 1018 if (icmph->type > NR_ICMP_TYPES) 1019 goto error; 1020 1021 1022 /* 1023 * Parse the ICMP message 1024 */ 1025 1026 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1027 /* 1028 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1029 * silently ignored (we let user decide with a sysctl). 1030 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1031 * discarded if to broadcast/multicast. 1032 */ 1033 if ((icmph->type == ICMP_ECHO || 1034 icmph->type == ICMP_TIMESTAMP) && 1035 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1036 goto error; 1037 } 1038 if (icmph->type != ICMP_ECHO && 1039 icmph->type != ICMP_TIMESTAMP && 1040 icmph->type != ICMP_ADDRESS && 1041 icmph->type != ICMP_ADDRESSREPLY) { 1042 goto error; 1043 } 1044 } 1045 1046 success = icmp_pointers[icmph->type].handler(skb); 1047 1048 if (success) { 1049 consume_skb(skb); 1050 return NET_RX_SUCCESS; 1051 } 1052 1053 drop: 1054 kfree_skb(skb); 1055 return NET_RX_DROP; 1056 csum_error: 1057 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS); 1058 error: 1059 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 1060 goto drop; 1061 } 1062 1063 void icmp_err(struct sk_buff *skb, u32 info) 1064 { 1065 struct iphdr *iph = (struct iphdr *)skb->data; 1066 int offset = iph->ihl<<2; 1067 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1068 int type = icmp_hdr(skb)->type; 1069 int code = icmp_hdr(skb)->code; 1070 struct net *net = dev_net(skb->dev); 1071 1072 /* 1073 * Use ping_err to handle all icmp errors except those 1074 * triggered by ICMP_ECHOREPLY which sent from kernel. 1075 */ 1076 if (icmph->type != ICMP_ECHOREPLY) { 1077 ping_err(skb, offset, info); 1078 return; 1079 } 1080 1081 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1082 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 1083 else if (type == ICMP_REDIRECT) 1084 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 1085 } 1086 1087 /* 1088 * This table is the definition of how we handle ICMP. 1089 */ 1090 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1091 [ICMP_ECHOREPLY] = { 1092 .handler = ping_rcv, 1093 }, 1094 [1] = { 1095 .handler = icmp_discard, 1096 .error = 1, 1097 }, 1098 [2] = { 1099 .handler = icmp_discard, 1100 .error = 1, 1101 }, 1102 [ICMP_DEST_UNREACH] = { 1103 .handler = icmp_unreach, 1104 .error = 1, 1105 }, 1106 [ICMP_SOURCE_QUENCH] = { 1107 .handler = icmp_unreach, 1108 .error = 1, 1109 }, 1110 [ICMP_REDIRECT] = { 1111 .handler = icmp_redirect, 1112 .error = 1, 1113 }, 1114 [6] = { 1115 .handler = icmp_discard, 1116 .error = 1, 1117 }, 1118 [7] = { 1119 .handler = icmp_discard, 1120 .error = 1, 1121 }, 1122 [ICMP_ECHO] = { 1123 .handler = icmp_echo, 1124 }, 1125 [9] = { 1126 .handler = icmp_discard, 1127 .error = 1, 1128 }, 1129 [10] = { 1130 .handler = icmp_discard, 1131 .error = 1, 1132 }, 1133 [ICMP_TIME_EXCEEDED] = { 1134 .handler = icmp_unreach, 1135 .error = 1, 1136 }, 1137 [ICMP_PARAMETERPROB] = { 1138 .handler = icmp_unreach, 1139 .error = 1, 1140 }, 1141 [ICMP_TIMESTAMP] = { 1142 .handler = icmp_timestamp, 1143 }, 1144 [ICMP_TIMESTAMPREPLY] = { 1145 .handler = icmp_discard, 1146 }, 1147 [ICMP_INFO_REQUEST] = { 1148 .handler = icmp_discard, 1149 }, 1150 [ICMP_INFO_REPLY] = { 1151 .handler = icmp_discard, 1152 }, 1153 [ICMP_ADDRESS] = { 1154 .handler = icmp_discard, 1155 }, 1156 [ICMP_ADDRESSREPLY] = { 1157 .handler = icmp_discard, 1158 }, 1159 }; 1160 1161 static void __net_exit icmp_sk_exit(struct net *net) 1162 { 1163 int i; 1164 1165 for_each_possible_cpu(i) 1166 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1167 free_percpu(net->ipv4.icmp_sk); 1168 net->ipv4.icmp_sk = NULL; 1169 } 1170 1171 static int __net_init icmp_sk_init(struct net *net) 1172 { 1173 int i, err; 1174 1175 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1176 if (!net->ipv4.icmp_sk) 1177 return -ENOMEM; 1178 1179 for_each_possible_cpu(i) { 1180 struct sock *sk; 1181 1182 err = inet_ctl_sock_create(&sk, PF_INET, 1183 SOCK_RAW, IPPROTO_ICMP, net); 1184 if (err < 0) 1185 goto fail; 1186 1187 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1188 1189 /* Enough space for 2 64K ICMP packets, including 1190 * sk_buff/skb_shared_info struct overhead. 1191 */ 1192 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1193 1194 /* 1195 * Speedup sock_wfree() 1196 */ 1197 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1198 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1199 } 1200 1201 /* Control parameters for ECHO replies. */ 1202 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1203 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1204 1205 /* Control parameter - ignore bogus broadcast responses? */ 1206 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1207 1208 /* 1209 * Configurable global rate limit. 1210 * 1211 * ratelimit defines tokens/packet consumed for dst->rate_token 1212 * bucket ratemask defines which icmp types are ratelimited by 1213 * setting it's bit position. 1214 * 1215 * default: 1216 * dest unreachable (3), source quench (4), 1217 * time exceeded (11), parameter problem (12) 1218 */ 1219 1220 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1221 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1222 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1223 1224 return 0; 1225 1226 fail: 1227 for_each_possible_cpu(i) 1228 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1229 free_percpu(net->ipv4.icmp_sk); 1230 return err; 1231 } 1232 1233 static struct pernet_operations __net_initdata icmp_sk_ops = { 1234 .init = icmp_sk_init, 1235 .exit = icmp_sk_exit, 1236 }; 1237 1238 int __init icmp_init(void) 1239 { 1240 return register_pernet_subsys(&icmp_sk_ops); 1241 } 1242