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 ipcm_init(&ipc); 433 inet->tos = ip_hdr(skb)->tos; 434 sk->sk_mark = mark; 435 daddr = ipc.addr = ip_hdr(skb)->saddr; 436 saddr = fib_compute_spec_dst(skb); 437 438 if (icmp_param->replyopts.opt.opt.optlen) { 439 ipc.opt = &icmp_param->replyopts.opt; 440 if (ipc.opt->opt.srr) 441 daddr = icmp_param->replyopts.opt.opt.faddr; 442 } 443 memset(&fl4, 0, sizeof(fl4)); 444 fl4.daddr = daddr; 445 fl4.saddr = saddr; 446 fl4.flowi4_mark = mark; 447 fl4.flowi4_uid = sock_net_uid(net, NULL); 448 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 449 fl4.flowi4_proto = IPPROTO_ICMP; 450 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev); 451 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 452 rt = ip_route_output_key(net, &fl4); 453 if (IS_ERR(rt)) 454 goto out_unlock; 455 if (icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 456 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 457 ip_rt_put(rt); 458 out_unlock: 459 icmp_xmit_unlock(sk); 460 out_bh_enable: 461 local_bh_enable(); 462 } 463 464 static struct rtable *icmp_route_lookup(struct net *net, 465 struct flowi4 *fl4, 466 struct sk_buff *skb_in, 467 const struct iphdr *iph, 468 __be32 saddr, u8 tos, u32 mark, 469 int type, int code, 470 struct icmp_bxm *param) 471 { 472 struct rtable *rt, *rt2; 473 struct flowi4 fl4_dec; 474 int err; 475 476 memset(fl4, 0, sizeof(*fl4)); 477 fl4->daddr = (param->replyopts.opt.opt.srr ? 478 param->replyopts.opt.opt.faddr : iph->saddr); 479 fl4->saddr = saddr; 480 fl4->flowi4_mark = mark; 481 fl4->flowi4_uid = sock_net_uid(net, NULL); 482 fl4->flowi4_tos = RT_TOS(tos); 483 fl4->flowi4_proto = IPPROTO_ICMP; 484 fl4->fl4_icmp_type = type; 485 fl4->fl4_icmp_code = code; 486 fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev); 487 488 security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4)); 489 rt = ip_route_output_key_hash(net, fl4, skb_in); 490 if (IS_ERR(rt)) 491 return rt; 492 493 /* No need to clone since we're just using its address. */ 494 rt2 = rt; 495 496 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 497 flowi4_to_flowi(fl4), NULL, 0); 498 if (!IS_ERR(rt)) { 499 if (rt != rt2) 500 return rt; 501 } else if (PTR_ERR(rt) == -EPERM) { 502 rt = NULL; 503 } else 504 return rt; 505 506 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 507 if (err) 508 goto relookup_failed; 509 510 if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev, 511 fl4_dec.saddr) == RTN_LOCAL) { 512 rt2 = __ip_route_output_key(net, &fl4_dec); 513 if (IS_ERR(rt2)) 514 err = PTR_ERR(rt2); 515 } else { 516 struct flowi4 fl4_2 = {}; 517 unsigned long orefdst; 518 519 fl4_2.daddr = fl4_dec.saddr; 520 rt2 = ip_route_output_key(net, &fl4_2); 521 if (IS_ERR(rt2)) { 522 err = PTR_ERR(rt2); 523 goto relookup_failed; 524 } 525 /* Ugh! */ 526 orefdst = skb_in->_skb_refdst; /* save old refdst */ 527 skb_dst_set(skb_in, NULL); 528 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 529 RT_TOS(tos), rt2->dst.dev); 530 531 dst_release(&rt2->dst); 532 rt2 = skb_rtable(skb_in); 533 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 534 } 535 536 if (err) 537 goto relookup_failed; 538 539 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 540 flowi4_to_flowi(&fl4_dec), NULL, 541 XFRM_LOOKUP_ICMP); 542 if (!IS_ERR(rt2)) { 543 dst_release(&rt->dst); 544 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 545 rt = rt2; 546 } else if (PTR_ERR(rt2) == -EPERM) { 547 if (rt) 548 dst_release(&rt->dst); 549 return rt2; 550 } else { 551 err = PTR_ERR(rt2); 552 goto relookup_failed; 553 } 554 return rt; 555 556 relookup_failed: 557 if (rt) 558 return rt; 559 return ERR_PTR(err); 560 } 561 562 /* 563 * Send an ICMP message in response to a situation 564 * 565 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 566 * MAY send more (we do). 567 * MUST NOT change this header information. 568 * MUST NOT reply to a multicast/broadcast IP address. 569 * MUST NOT reply to a multicast/broadcast MAC address. 570 * MUST reply to only the first fragment. 571 */ 572 573 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 574 { 575 struct iphdr *iph; 576 int room; 577 struct icmp_bxm icmp_param; 578 struct rtable *rt = skb_rtable(skb_in); 579 struct ipcm_cookie ipc; 580 struct flowi4 fl4; 581 __be32 saddr; 582 u8 tos; 583 u32 mark; 584 struct net *net; 585 struct sock *sk; 586 587 if (!rt) 588 goto out; 589 net = dev_net(rt->dst.dev); 590 591 /* 592 * Find the original header. It is expected to be valid, of course. 593 * Check this, icmp_send is called from the most obscure devices 594 * sometimes. 595 */ 596 iph = ip_hdr(skb_in); 597 598 if ((u8 *)iph < skb_in->head || 599 (skb_network_header(skb_in) + sizeof(*iph)) > 600 skb_tail_pointer(skb_in)) 601 goto out; 602 603 /* 604 * No replies to physical multicast/broadcast 605 */ 606 if (skb_in->pkt_type != PACKET_HOST) 607 goto out; 608 609 /* 610 * Now check at the protocol level 611 */ 612 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 613 goto out; 614 615 /* 616 * Only reply to fragment 0. We byte re-order the constant 617 * mask for efficiency. 618 */ 619 if (iph->frag_off & htons(IP_OFFSET)) 620 goto out; 621 622 /* 623 * If we send an ICMP error to an ICMP error a mess would result.. 624 */ 625 if (icmp_pointers[type].error) { 626 /* 627 * We are an error, check if we are replying to an 628 * ICMP error 629 */ 630 if (iph->protocol == IPPROTO_ICMP) { 631 u8 _inner_type, *itp; 632 633 itp = skb_header_pointer(skb_in, 634 skb_network_header(skb_in) + 635 (iph->ihl << 2) + 636 offsetof(struct icmphdr, 637 type) - 638 skb_in->data, 639 sizeof(_inner_type), 640 &_inner_type); 641 if (!itp) 642 goto out; 643 644 /* 645 * Assume any unknown ICMP type is an error. This 646 * isn't specified by the RFC, but think about it.. 647 */ 648 if (*itp > NR_ICMP_TYPES || 649 icmp_pointers[*itp].error) 650 goto out; 651 } 652 } 653 654 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 655 local_bh_disable(); 656 657 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless 658 * incoming dev is loopback. If outgoing dev change to not be 659 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow) 660 */ 661 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) && 662 !icmpv4_global_allow(net, type, code)) 663 goto out_bh_enable; 664 665 sk = icmp_xmit_lock(net); 666 if (!sk) 667 goto out_bh_enable; 668 669 /* 670 * Construct source address and options. 671 */ 672 673 saddr = iph->daddr; 674 if (!(rt->rt_flags & RTCF_LOCAL)) { 675 struct net_device *dev = NULL; 676 677 rcu_read_lock(); 678 if (rt_is_input_route(rt) && 679 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 680 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 681 682 if (dev) 683 saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK); 684 else 685 saddr = 0; 686 rcu_read_unlock(); 687 } 688 689 tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) | 690 IPTOS_PREC_INTERNETCONTROL) : 691 iph->tos; 692 mark = IP4_REPLY_MARK(net, skb_in->mark); 693 694 if (ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in)) 695 goto out_unlock; 696 697 698 /* 699 * Prepare data for ICMP header. 700 */ 701 702 icmp_param.data.icmph.type = type; 703 icmp_param.data.icmph.code = code; 704 icmp_param.data.icmph.un.gateway = info; 705 icmp_param.data.icmph.checksum = 0; 706 icmp_param.skb = skb_in; 707 icmp_param.offset = skb_network_offset(skb_in); 708 inet_sk(sk)->tos = tos; 709 sk->sk_mark = mark; 710 ipcm_init(&ipc); 711 ipc.addr = iph->saddr; 712 ipc.opt = &icmp_param.replyopts.opt; 713 714 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 715 type, code, &icmp_param); 716 if (IS_ERR(rt)) 717 goto out_unlock; 718 719 /* peer icmp_ratelimit */ 720 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 721 goto ende; 722 723 /* RFC says return as much as we can without exceeding 576 bytes. */ 724 725 room = dst_mtu(&rt->dst); 726 if (room > 576) 727 room = 576; 728 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 729 room -= sizeof(struct icmphdr); 730 731 icmp_param.data_len = skb_in->len - icmp_param.offset; 732 if (icmp_param.data_len > room) 733 icmp_param.data_len = room; 734 icmp_param.head_len = sizeof(struct icmphdr); 735 736 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 737 ende: 738 ip_rt_put(rt); 739 out_unlock: 740 icmp_xmit_unlock(sk); 741 out_bh_enable: 742 local_bh_enable(); 743 out:; 744 } 745 EXPORT_SYMBOL(icmp_send); 746 747 748 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 749 { 750 const struct iphdr *iph = (const struct iphdr *) skb->data; 751 const struct net_protocol *ipprot; 752 int protocol = iph->protocol; 753 754 /* Checkin full IP header plus 8 bytes of protocol to 755 * avoid additional coding at protocol handlers. 756 */ 757 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 758 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 759 return; 760 } 761 762 raw_icmp_error(skb, protocol, info); 763 764 ipprot = rcu_dereference(inet_protos[protocol]); 765 if (ipprot && ipprot->err_handler) 766 ipprot->err_handler(skb, info); 767 } 768 769 static bool icmp_tag_validation(int proto) 770 { 771 bool ok; 772 773 rcu_read_lock(); 774 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 775 rcu_read_unlock(); 776 return ok; 777 } 778 779 /* 780 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and 781 * ICMP_PARAMETERPROB. 782 */ 783 784 static bool icmp_unreach(struct sk_buff *skb) 785 { 786 const struct iphdr *iph; 787 struct icmphdr *icmph; 788 struct net *net; 789 u32 info = 0; 790 791 net = dev_net(skb_dst(skb)->dev); 792 793 /* 794 * Incomplete header ? 795 * Only checks for the IP header, there should be an 796 * additional check for longer headers in upper levels. 797 */ 798 799 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 800 goto out_err; 801 802 icmph = icmp_hdr(skb); 803 iph = (const struct iphdr *)skb->data; 804 805 if (iph->ihl < 5) /* Mangled header, drop. */ 806 goto out_err; 807 808 switch (icmph->type) { 809 case ICMP_DEST_UNREACH: 810 switch (icmph->code & 15) { 811 case ICMP_NET_UNREACH: 812 case ICMP_HOST_UNREACH: 813 case ICMP_PROT_UNREACH: 814 case ICMP_PORT_UNREACH: 815 break; 816 case ICMP_FRAG_NEEDED: 817 /* for documentation of the ip_no_pmtu_disc 818 * values please see 819 * Documentation/networking/ip-sysctl.txt 820 */ 821 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 822 default: 823 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 824 &iph->daddr); 825 break; 826 case 2: 827 goto out; 828 case 3: 829 if (!icmp_tag_validation(iph->protocol)) 830 goto out; 831 /* fall through */ 832 case 0: 833 info = ntohs(icmph->un.frag.mtu); 834 } 835 break; 836 case ICMP_SR_FAILED: 837 net_dbg_ratelimited("%pI4: Source Route Failed\n", 838 &iph->daddr); 839 break; 840 default: 841 break; 842 } 843 if (icmph->code > NR_ICMP_UNREACH) 844 goto out; 845 break; 846 case ICMP_PARAMETERPROB: 847 info = ntohl(icmph->un.gateway) >> 24; 848 break; 849 case ICMP_TIME_EXCEEDED: 850 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS); 851 if (icmph->code == ICMP_EXC_FRAGTIME) 852 goto out; 853 break; 854 } 855 856 /* 857 * Throw it at our lower layers 858 * 859 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 860 * header. 861 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 862 * transport layer. 863 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 864 * transport layer. 865 */ 866 867 /* 868 * Check the other end isn't violating RFC 1122. Some routers send 869 * bogus responses to broadcast frames. If you see this message 870 * first check your netmask matches at both ends, if it does then 871 * get the other vendor to fix their kit. 872 */ 873 874 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 875 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) { 876 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 877 &ip_hdr(skb)->saddr, 878 icmph->type, icmph->code, 879 &iph->daddr, skb->dev->name); 880 goto out; 881 } 882 883 icmp_socket_deliver(skb, info); 884 885 out: 886 return true; 887 out_err: 888 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 889 return false; 890 } 891 892 893 /* 894 * Handle ICMP_REDIRECT. 895 */ 896 897 static bool icmp_redirect(struct sk_buff *skb) 898 { 899 if (skb->len < sizeof(struct iphdr)) { 900 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 901 return false; 902 } 903 904 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 905 /* there aught to be a stat */ 906 return false; 907 } 908 909 icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway); 910 return true; 911 } 912 913 /* 914 * Handle ICMP_ECHO ("ping") requests. 915 * 916 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 917 * requests. 918 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 919 * included in the reply. 920 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 921 * echo requests, MUST have default=NOT. 922 * See also WRT handling of options once they are done and working. 923 */ 924 925 static bool icmp_echo(struct sk_buff *skb) 926 { 927 struct net *net; 928 929 net = dev_net(skb_dst(skb)->dev); 930 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 931 struct icmp_bxm icmp_param; 932 933 icmp_param.data.icmph = *icmp_hdr(skb); 934 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 935 icmp_param.skb = skb; 936 icmp_param.offset = 0; 937 icmp_param.data_len = skb->len; 938 icmp_param.head_len = sizeof(struct icmphdr); 939 icmp_reply(&icmp_param, skb); 940 } 941 /* should there be an ICMP stat for ignored echos? */ 942 return true; 943 } 944 945 /* 946 * Handle ICMP Timestamp requests. 947 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 948 * SHOULD be in the kernel for minimum random latency. 949 * MUST be accurate to a few minutes. 950 * MUST be updated at least at 15Hz. 951 */ 952 static bool icmp_timestamp(struct sk_buff *skb) 953 { 954 struct icmp_bxm icmp_param; 955 /* 956 * Too short. 957 */ 958 if (skb->len < 4) 959 goto out_err; 960 961 /* 962 * Fill in the current time as ms since midnight UT: 963 */ 964 icmp_param.data.times[1] = inet_current_timestamp(); 965 icmp_param.data.times[2] = icmp_param.data.times[1]; 966 967 BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)); 968 969 icmp_param.data.icmph = *icmp_hdr(skb); 970 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 971 icmp_param.data.icmph.code = 0; 972 icmp_param.skb = skb; 973 icmp_param.offset = 0; 974 icmp_param.data_len = 0; 975 icmp_param.head_len = sizeof(struct icmphdr) + 12; 976 icmp_reply(&icmp_param, skb); 977 return true; 978 979 out_err: 980 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 981 return false; 982 } 983 984 static bool icmp_discard(struct sk_buff *skb) 985 { 986 /* pretend it was a success */ 987 return true; 988 } 989 990 /* 991 * Deal with incoming ICMP packets. 992 */ 993 int icmp_rcv(struct sk_buff *skb) 994 { 995 struct icmphdr *icmph; 996 struct rtable *rt = skb_rtable(skb); 997 struct net *net = dev_net(rt->dst.dev); 998 bool success; 999 1000 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 1001 struct sec_path *sp = skb_sec_path(skb); 1002 int nh; 1003 1004 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 1005 XFRM_STATE_ICMP)) 1006 goto drop; 1007 1008 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 1009 goto drop; 1010 1011 nh = skb_network_offset(skb); 1012 skb_set_network_header(skb, sizeof(*icmph)); 1013 1014 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 1015 goto drop; 1016 1017 skb_set_network_header(skb, nh); 1018 } 1019 1020 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS); 1021 1022 if (skb_checksum_simple_validate(skb)) 1023 goto csum_error; 1024 1025 if (!pskb_pull(skb, sizeof(*icmph))) 1026 goto error; 1027 1028 icmph = icmp_hdr(skb); 1029 1030 ICMPMSGIN_INC_STATS(net, icmph->type); 1031 /* 1032 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1033 * 1034 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1035 * discarded. 1036 */ 1037 if (icmph->type > NR_ICMP_TYPES) 1038 goto error; 1039 1040 1041 /* 1042 * Parse the ICMP message 1043 */ 1044 1045 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1046 /* 1047 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1048 * silently ignored (we let user decide with a sysctl). 1049 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1050 * discarded if to broadcast/multicast. 1051 */ 1052 if ((icmph->type == ICMP_ECHO || 1053 icmph->type == ICMP_TIMESTAMP) && 1054 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1055 goto error; 1056 } 1057 if (icmph->type != ICMP_ECHO && 1058 icmph->type != ICMP_TIMESTAMP && 1059 icmph->type != ICMP_ADDRESS && 1060 icmph->type != ICMP_ADDRESSREPLY) { 1061 goto error; 1062 } 1063 } 1064 1065 success = icmp_pointers[icmph->type].handler(skb); 1066 1067 if (success) { 1068 consume_skb(skb); 1069 return NET_RX_SUCCESS; 1070 } 1071 1072 drop: 1073 kfree_skb(skb); 1074 return NET_RX_DROP; 1075 csum_error: 1076 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS); 1077 error: 1078 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 1079 goto drop; 1080 } 1081 1082 void icmp_err(struct sk_buff *skb, u32 info) 1083 { 1084 struct iphdr *iph = (struct iphdr *)skb->data; 1085 int offset = iph->ihl<<2; 1086 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1087 int type = icmp_hdr(skb)->type; 1088 int code = icmp_hdr(skb)->code; 1089 struct net *net = dev_net(skb->dev); 1090 1091 /* 1092 * Use ping_err to handle all icmp errors except those 1093 * triggered by ICMP_ECHOREPLY which sent from kernel. 1094 */ 1095 if (icmph->type != ICMP_ECHOREPLY) { 1096 ping_err(skb, offset, info); 1097 return; 1098 } 1099 1100 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1101 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0); 1102 else if (type == ICMP_REDIRECT) 1103 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0); 1104 } 1105 1106 /* 1107 * This table is the definition of how we handle ICMP. 1108 */ 1109 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1110 [ICMP_ECHOREPLY] = { 1111 .handler = ping_rcv, 1112 }, 1113 [1] = { 1114 .handler = icmp_discard, 1115 .error = 1, 1116 }, 1117 [2] = { 1118 .handler = icmp_discard, 1119 .error = 1, 1120 }, 1121 [ICMP_DEST_UNREACH] = { 1122 .handler = icmp_unreach, 1123 .error = 1, 1124 }, 1125 [ICMP_SOURCE_QUENCH] = { 1126 .handler = icmp_unreach, 1127 .error = 1, 1128 }, 1129 [ICMP_REDIRECT] = { 1130 .handler = icmp_redirect, 1131 .error = 1, 1132 }, 1133 [6] = { 1134 .handler = icmp_discard, 1135 .error = 1, 1136 }, 1137 [7] = { 1138 .handler = icmp_discard, 1139 .error = 1, 1140 }, 1141 [ICMP_ECHO] = { 1142 .handler = icmp_echo, 1143 }, 1144 [9] = { 1145 .handler = icmp_discard, 1146 .error = 1, 1147 }, 1148 [10] = { 1149 .handler = icmp_discard, 1150 .error = 1, 1151 }, 1152 [ICMP_TIME_EXCEEDED] = { 1153 .handler = icmp_unreach, 1154 .error = 1, 1155 }, 1156 [ICMP_PARAMETERPROB] = { 1157 .handler = icmp_unreach, 1158 .error = 1, 1159 }, 1160 [ICMP_TIMESTAMP] = { 1161 .handler = icmp_timestamp, 1162 }, 1163 [ICMP_TIMESTAMPREPLY] = { 1164 .handler = icmp_discard, 1165 }, 1166 [ICMP_INFO_REQUEST] = { 1167 .handler = icmp_discard, 1168 }, 1169 [ICMP_INFO_REPLY] = { 1170 .handler = icmp_discard, 1171 }, 1172 [ICMP_ADDRESS] = { 1173 .handler = icmp_discard, 1174 }, 1175 [ICMP_ADDRESSREPLY] = { 1176 .handler = icmp_discard, 1177 }, 1178 }; 1179 1180 static void __net_exit icmp_sk_exit(struct net *net) 1181 { 1182 int i; 1183 1184 for_each_possible_cpu(i) 1185 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1186 free_percpu(net->ipv4.icmp_sk); 1187 net->ipv4.icmp_sk = NULL; 1188 } 1189 1190 static int __net_init icmp_sk_init(struct net *net) 1191 { 1192 int i, err; 1193 1194 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1195 if (!net->ipv4.icmp_sk) 1196 return -ENOMEM; 1197 1198 for_each_possible_cpu(i) { 1199 struct sock *sk; 1200 1201 err = inet_ctl_sock_create(&sk, PF_INET, 1202 SOCK_RAW, IPPROTO_ICMP, net); 1203 if (err < 0) 1204 goto fail; 1205 1206 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1207 1208 /* Enough space for 2 64K ICMP packets, including 1209 * sk_buff/skb_shared_info struct overhead. 1210 */ 1211 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1212 1213 /* 1214 * Speedup sock_wfree() 1215 */ 1216 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1217 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1218 } 1219 1220 /* Control parameters for ECHO replies. */ 1221 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1222 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1223 1224 /* Control parameter - ignore bogus broadcast responses? */ 1225 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1226 1227 /* 1228 * Configurable global rate limit. 1229 * 1230 * ratelimit defines tokens/packet consumed for dst->rate_token 1231 * bucket ratemask defines which icmp types are ratelimited by 1232 * setting it's bit position. 1233 * 1234 * default: 1235 * dest unreachable (3), source quench (4), 1236 * time exceeded (11), parameter problem (12) 1237 */ 1238 1239 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1240 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1241 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1242 1243 return 0; 1244 1245 fail: 1246 for_each_possible_cpu(i) 1247 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1248 free_percpu(net->ipv4.icmp_sk); 1249 return err; 1250 } 1251 1252 static struct pernet_operations __net_initdata icmp_sk_ops = { 1253 .init = icmp_sk_init, 1254 .exit = icmp_sk_exit, 1255 }; 1256 1257 int __init icmp_init(void) 1258 { 1259 return register_pernet_subsys(&icmp_sk_ops); 1260 } 1261