1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * NET3: Implementation of the ICMP protocol layer. 4 * 5 * Alan Cox, <alan@lxorguk.ukuu.org.uk> 6 * 7 * Some of the function names and the icmp unreach table for this 8 * module were derived from [icmp.c 1.0.11 06/02/93] by 9 * Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting. 10 * Other than that this module is a complete rewrite. 11 * 12 * Fixes: 13 * Clemens Fruhwirth : introduce global icmp rate limiting 14 * with icmp type masking ability instead 15 * of broken per type icmp timeouts. 16 * Mike Shaver : RFC1122 checks. 17 * Alan Cox : Multicast ping reply as self. 18 * Alan Cox : Fix atomicity lockup in ip_build_xmit 19 * call. 20 * Alan Cox : Added 216,128 byte paths to the MTU 21 * code. 22 * Martin Mares : RFC1812 checks. 23 * Martin Mares : Can be configured to follow redirects 24 * if acting as a router _without_ a 25 * routing protocol (RFC 1812). 26 * Martin Mares : Echo requests may be configured to 27 * be ignored (RFC 1812). 28 * Martin Mares : Limitation of ICMP error message 29 * transmit rate (RFC 1812). 30 * Martin Mares : TOS and Precedence set correctly 31 * (RFC 1812). 32 * Martin Mares : Now copying as much data from the 33 * original packet as we can without 34 * exceeding 576 bytes (RFC 1812). 35 * Willy Konynenberg : Transparent proxying support. 36 * Keith Owens : RFC1191 correction for 4.2BSD based 37 * path MTU bug. 38 * Thomas Quinot : ICMP Dest Unreach codes up to 15 are 39 * valid (RFC 1812). 40 * Andi Kleen : Check all packet lengths properly 41 * and moved all kfree_skb() up to 42 * icmp_rcv. 43 * Andi Kleen : Move the rate limit bookkeeping 44 * into the dest entry and use a token 45 * bucket filter (thanks to ANK). Make 46 * the rates sysctl configurable. 47 * Yu Tianli : Fixed two ugly bugs in icmp_send 48 * - IP option length was accounted wrongly 49 * - ICMP header length was not accounted 50 * at all. 51 * Tristan Greaves : Added sysctl option to ignore bogus 52 * broadcast responses from broken routers. 53 * 54 * To Fix: 55 * 56 * - Should use skb_pull() instead of all the manual checking. 57 * This would also greatly simply some upper layer error handlers. --AK 58 */ 59 60 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 61 62 #include <linux/module.h> 63 #include <linux/types.h> 64 #include <linux/jiffies.h> 65 #include <linux/kernel.h> 66 #include <linux/fcntl.h> 67 #include <linux/socket.h> 68 #include <linux/in.h> 69 #include <linux/inet.h> 70 #include <linux/inetdevice.h> 71 #include <linux/netdevice.h> 72 #include <linux/string.h> 73 #include <linux/netfilter_ipv4.h> 74 #include <linux/slab.h> 75 #include <net/snmp.h> 76 #include <net/ip.h> 77 #include <net/route.h> 78 #include <net/protocol.h> 79 #include <net/icmp.h> 80 #include <net/tcp.h> 81 #include <net/udp.h> 82 #include <net/raw.h> 83 #include <net/ping.h> 84 #include <linux/skbuff.h> 85 #include <net/sock.h> 86 #include <linux/errno.h> 87 #include <linux/timer.h> 88 #include <linux/init.h> 89 #include <linux/uaccess.h> 90 #include <net/checksum.h> 91 #include <net/xfrm.h> 92 #include <net/inet_common.h> 93 #include <net/ip_fib.h> 94 #include <net/l3mdev.h> 95 96 /* 97 * Build xmit assembly blocks 98 */ 99 100 struct icmp_bxm { 101 struct sk_buff *skb; 102 int offset; 103 int data_len; 104 105 struct { 106 struct icmphdr icmph; 107 __be32 times[3]; 108 } data; 109 int head_len; 110 struct ip_options_data replyopts; 111 }; 112 113 /* An array of errno for error messages from dest unreach. */ 114 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */ 115 116 const struct icmp_err icmp_err_convert[] = { 117 { 118 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */ 119 .fatal = 0, 120 }, 121 { 122 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */ 123 .fatal = 0, 124 }, 125 { 126 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */, 127 .fatal = 1, 128 }, 129 { 130 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */ 131 .fatal = 1, 132 }, 133 { 134 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */ 135 .fatal = 0, 136 }, 137 { 138 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */ 139 .fatal = 0, 140 }, 141 { 142 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */ 143 .fatal = 1, 144 }, 145 { 146 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */ 147 .fatal = 1, 148 }, 149 { 150 .errno = ENONET, /* ICMP_HOST_ISOLATED */ 151 .fatal = 1, 152 }, 153 { 154 .errno = ENETUNREACH, /* ICMP_NET_ANO */ 155 .fatal = 1, 156 }, 157 { 158 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */ 159 .fatal = 1, 160 }, 161 { 162 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */ 163 .fatal = 0, 164 }, 165 { 166 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */ 167 .fatal = 0, 168 }, 169 { 170 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */ 171 .fatal = 1, 172 }, 173 { 174 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */ 175 .fatal = 1, 176 }, 177 { 178 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */ 179 .fatal = 1, 180 }, 181 }; 182 EXPORT_SYMBOL(icmp_err_convert); 183 184 /* 185 * ICMP control array. This specifies what to do with each ICMP. 186 */ 187 188 struct icmp_control { 189 bool (*handler)(struct sk_buff *skb); 190 short error; /* This ICMP is classed as an error message */ 191 }; 192 193 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1]; 194 195 /* 196 * The ICMP socket(s). This is the most convenient way to flow control 197 * our ICMP output as well as maintain a clean interface throughout 198 * all layers. All Socketless IP sends will soon be gone. 199 * 200 * On SMP we have one ICMP socket per-cpu. 201 */ 202 static struct sock *icmp_sk(struct net *net) 203 { 204 return this_cpu_read(*net->ipv4.icmp_sk); 205 } 206 207 /* Called with BH disabled */ 208 static inline struct sock *icmp_xmit_lock(struct net *net) 209 { 210 struct sock *sk; 211 212 sk = icmp_sk(net); 213 214 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) { 215 /* This can happen if the output path signals a 216 * dst_link_failure() for an outgoing ICMP packet. 217 */ 218 return NULL; 219 } 220 return sk; 221 } 222 223 static inline void icmp_xmit_unlock(struct sock *sk) 224 { 225 spin_unlock(&sk->sk_lock.slock); 226 } 227 228 int sysctl_icmp_msgs_per_sec __read_mostly = 1000; 229 int sysctl_icmp_msgs_burst __read_mostly = 50; 230 231 static struct { 232 spinlock_t lock; 233 u32 credit; 234 u32 stamp; 235 } icmp_global = { 236 .lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock), 237 }; 238 239 /** 240 * icmp_global_allow - Are we allowed to send one more ICMP message ? 241 * 242 * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. 243 * Returns false if we reached the limit and can not send another packet. 244 * Note: called with BH disabled 245 */ 246 bool icmp_global_allow(void) 247 { 248 u32 credit, delta, incr = 0, now = (u32)jiffies; 249 bool rc = false; 250 251 /* Check if token bucket is empty and cannot be refilled 252 * without taking the spinlock. The READ_ONCE() are paired 253 * with the following WRITE_ONCE() in this same function. 254 */ 255 if (!READ_ONCE(icmp_global.credit)) { 256 delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ); 257 if (delta < HZ / 50) 258 return false; 259 } 260 261 spin_lock(&icmp_global.lock); 262 delta = min_t(u32, now - icmp_global.stamp, HZ); 263 if (delta >= HZ / 50) { 264 incr = sysctl_icmp_msgs_per_sec * delta / HZ ; 265 if (incr) 266 WRITE_ONCE(icmp_global.stamp, now); 267 } 268 credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); 269 if (credit) { 270 credit--; 271 rc = true; 272 } 273 WRITE_ONCE(icmp_global.credit, credit); 274 spin_unlock(&icmp_global.lock); 275 return rc; 276 } 277 EXPORT_SYMBOL(icmp_global_allow); 278 279 static bool icmpv4_mask_allow(struct net *net, int type, int code) 280 { 281 if (type > NR_ICMP_TYPES) 282 return true; 283 284 /* Don't limit PMTU discovery. */ 285 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 286 return true; 287 288 /* Limit if icmp type is enabled in ratemask. */ 289 if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask)) 290 return true; 291 292 return false; 293 } 294 295 static bool icmpv4_global_allow(struct net *net, int type, int code) 296 { 297 if (icmpv4_mask_allow(net, type, code)) 298 return true; 299 300 if (icmp_global_allow()) 301 return true; 302 303 return false; 304 } 305 306 /* 307 * Send an ICMP frame. 308 */ 309 310 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt, 311 struct flowi4 *fl4, int type, int code) 312 { 313 struct dst_entry *dst = &rt->dst; 314 struct inet_peer *peer; 315 bool rc = true; 316 int vif; 317 318 if (icmpv4_mask_allow(net, type, code)) 319 goto out; 320 321 /* No rate limit on loopback */ 322 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK)) 323 goto out; 324 325 vif = l3mdev_master_ifindex(dst->dev); 326 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1); 327 rc = inet_peer_xrlim_allow(peer, net->ipv4.sysctl_icmp_ratelimit); 328 if (peer) 329 inet_putpeer(peer); 330 out: 331 return rc; 332 } 333 334 /* 335 * Maintain the counters used in the SNMP statistics for outgoing ICMP 336 */ 337 void icmp_out_count(struct net *net, unsigned char type) 338 { 339 ICMPMSGOUT_INC_STATS(net, type); 340 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS); 341 } 342 343 /* 344 * Checksum each fragment, and on the first include the headers and final 345 * checksum. 346 */ 347 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd, 348 struct sk_buff *skb) 349 { 350 struct icmp_bxm *icmp_param = (struct icmp_bxm *)from; 351 __wsum csum; 352 353 csum = skb_copy_and_csum_bits(icmp_param->skb, 354 icmp_param->offset + offset, 355 to, len, 0); 356 357 skb->csum = csum_block_add(skb->csum, csum, odd); 358 if (icmp_pointers[icmp_param->data.icmph.type].error) 359 nf_ct_attach(skb, icmp_param->skb); 360 return 0; 361 } 362 363 static void icmp_push_reply(struct icmp_bxm *icmp_param, 364 struct flowi4 *fl4, 365 struct ipcm_cookie *ipc, struct rtable **rt) 366 { 367 struct sock *sk; 368 struct sk_buff *skb; 369 370 sk = icmp_sk(dev_net((*rt)->dst.dev)); 371 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param, 372 icmp_param->data_len+icmp_param->head_len, 373 icmp_param->head_len, 374 ipc, rt, MSG_DONTWAIT) < 0) { 375 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS); 376 ip_flush_pending_frames(sk); 377 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) { 378 struct icmphdr *icmph = icmp_hdr(skb); 379 __wsum csum = 0; 380 struct sk_buff *skb1; 381 382 skb_queue_walk(&sk->sk_write_queue, skb1) { 383 csum = csum_add(csum, skb1->csum); 384 } 385 csum = csum_partial_copy_nocheck((void *)&icmp_param->data, 386 (char *)icmph, 387 icmp_param->head_len, csum); 388 icmph->checksum = csum_fold(csum); 389 skb->ip_summed = CHECKSUM_NONE; 390 ip_push_pending_frames(sk, fl4); 391 } 392 } 393 394 /* 395 * Driving logic for building and sending ICMP messages. 396 */ 397 398 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 399 { 400 struct ipcm_cookie ipc; 401 struct rtable *rt = skb_rtable(skb); 402 struct net *net = dev_net(rt->dst.dev); 403 struct flowi4 fl4; 404 struct sock *sk; 405 struct inet_sock *inet; 406 __be32 daddr, saddr; 407 u32 mark = IP4_REPLY_MARK(net, skb->mark); 408 int type = icmp_param->data.icmph.type; 409 int code = icmp_param->data.icmph.code; 410 411 if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb)) 412 return; 413 414 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 415 local_bh_disable(); 416 417 /* global icmp_msgs_per_sec */ 418 if (!icmpv4_global_allow(net, type, code)) 419 goto out_bh_enable; 420 421 sk = icmp_xmit_lock(net); 422 if (!sk) 423 goto out_bh_enable; 424 inet = inet_sk(sk); 425 426 icmp_param->data.icmph.checksum = 0; 427 428 ipcm_init(&ipc); 429 inet->tos = ip_hdr(skb)->tos; 430 sk->sk_mark = mark; 431 daddr = ipc.addr = ip_hdr(skb)->saddr; 432 saddr = fib_compute_spec_dst(skb); 433 434 if (icmp_param->replyopts.opt.opt.optlen) { 435 ipc.opt = &icmp_param->replyopts.opt; 436 if (ipc.opt->opt.srr) 437 daddr = icmp_param->replyopts.opt.opt.faddr; 438 } 439 memset(&fl4, 0, sizeof(fl4)); 440 fl4.daddr = daddr; 441 fl4.saddr = saddr; 442 fl4.flowi4_mark = mark; 443 fl4.flowi4_uid = sock_net_uid(net, NULL); 444 fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos); 445 fl4.flowi4_proto = IPPROTO_ICMP; 446 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev); 447 security_skb_classify_flow(skb, flowi4_to_flowi(&fl4)); 448 rt = ip_route_output_key(net, &fl4); 449 if (IS_ERR(rt)) 450 goto out_unlock; 451 if (icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 452 icmp_push_reply(icmp_param, &fl4, &ipc, &rt); 453 ip_rt_put(rt); 454 out_unlock: 455 icmp_xmit_unlock(sk); 456 out_bh_enable: 457 local_bh_enable(); 458 } 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, skb_in); 486 if (IS_ERR(rt)) 487 return rt; 488 489 /* No need to clone since we're just using its address. */ 490 rt2 = rt; 491 492 rt = (struct rtable *) xfrm_lookup(net, &rt->dst, 493 flowi4_to_flowi(fl4), NULL, 0); 494 if (!IS_ERR(rt)) { 495 if (rt != rt2) 496 return rt; 497 } else if (PTR_ERR(rt) == -EPERM) { 498 rt = NULL; 499 } else 500 return rt; 501 502 err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET); 503 if (err) 504 goto relookup_failed; 505 506 if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev, 507 fl4_dec.saddr) == RTN_LOCAL) { 508 rt2 = __ip_route_output_key(net, &fl4_dec); 509 if (IS_ERR(rt2)) 510 err = PTR_ERR(rt2); 511 } else { 512 struct flowi4 fl4_2 = {}; 513 unsigned long orefdst; 514 515 fl4_2.daddr = fl4_dec.saddr; 516 rt2 = ip_route_output_key(net, &fl4_2); 517 if (IS_ERR(rt2)) { 518 err = PTR_ERR(rt2); 519 goto relookup_failed; 520 } 521 /* Ugh! */ 522 orefdst = skb_in->_skb_refdst; /* save old refdst */ 523 skb_dst_set(skb_in, NULL); 524 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr, 525 RT_TOS(tos), rt2->dst.dev); 526 527 dst_release(&rt2->dst); 528 rt2 = skb_rtable(skb_in); 529 skb_in->_skb_refdst = orefdst; /* restore old refdst */ 530 } 531 532 if (err) 533 goto relookup_failed; 534 535 rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst, 536 flowi4_to_flowi(&fl4_dec), NULL, 537 XFRM_LOOKUP_ICMP); 538 if (!IS_ERR(rt2)) { 539 dst_release(&rt->dst); 540 memcpy(fl4, &fl4_dec, sizeof(*fl4)); 541 rt = rt2; 542 } else if (PTR_ERR(rt2) == -EPERM) { 543 if (rt) 544 dst_release(&rt->dst); 545 return rt2; 546 } else { 547 err = PTR_ERR(rt2); 548 goto relookup_failed; 549 } 550 return rt; 551 552 relookup_failed: 553 if (rt) 554 return rt; 555 return ERR_PTR(err); 556 } 557 558 /* 559 * Send an ICMP message in response to a situation 560 * 561 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header. 562 * MAY send more (we do). 563 * MUST NOT change this header information. 564 * MUST NOT reply to a multicast/broadcast IP address. 565 * MUST NOT reply to a multicast/broadcast MAC address. 566 * MUST reply to only the first fragment. 567 */ 568 569 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info, 570 const struct ip_options *opt) 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; 586 587 if (rt->dst.dev) 588 net = dev_net(rt->dst.dev); 589 else if (skb_in->dev) 590 net = dev_net(skb_in->dev); 591 else 592 goto out; 593 594 /* 595 * Find the original header. It is expected to be valid, of course. 596 * Check this, icmp_send is called from the most obscure devices 597 * sometimes. 598 */ 599 iph = ip_hdr(skb_in); 600 601 if ((u8 *)iph < skb_in->head || 602 (skb_network_header(skb_in) + sizeof(*iph)) > 603 skb_tail_pointer(skb_in)) 604 goto out; 605 606 /* 607 * No replies to physical multicast/broadcast 608 */ 609 if (skb_in->pkt_type != PACKET_HOST) 610 goto out; 611 612 /* 613 * Now check at the protocol level 614 */ 615 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) 616 goto out; 617 618 /* 619 * Only reply to fragment 0. We byte re-order the constant 620 * mask for efficiency. 621 */ 622 if (iph->frag_off & htons(IP_OFFSET)) 623 goto out; 624 625 /* 626 * If we send an ICMP error to an ICMP error a mess would result.. 627 */ 628 if (icmp_pointers[type].error) { 629 /* 630 * We are an error, check if we are replying to an 631 * ICMP error 632 */ 633 if (iph->protocol == IPPROTO_ICMP) { 634 u8 _inner_type, *itp; 635 636 itp = skb_header_pointer(skb_in, 637 skb_network_header(skb_in) + 638 (iph->ihl << 2) + 639 offsetof(struct icmphdr, 640 type) - 641 skb_in->data, 642 sizeof(_inner_type), 643 &_inner_type); 644 if (!itp) 645 goto out; 646 647 /* 648 * Assume any unknown ICMP type is an error. This 649 * isn't specified by the RFC, but think about it.. 650 */ 651 if (*itp > NR_ICMP_TYPES || 652 icmp_pointers[*itp].error) 653 goto out; 654 } 655 } 656 657 /* Needed by both icmp_global_allow and icmp_xmit_lock */ 658 local_bh_disable(); 659 660 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless 661 * incoming dev is loopback. If outgoing dev change to not be 662 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow) 663 */ 664 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) && 665 !icmpv4_global_allow(net, type, code)) 666 goto out_bh_enable; 667 668 sk = icmp_xmit_lock(net); 669 if (!sk) 670 goto out_bh_enable; 671 672 /* 673 * Construct source address and options. 674 */ 675 676 saddr = iph->daddr; 677 if (!(rt->rt_flags & RTCF_LOCAL)) { 678 struct net_device *dev = NULL; 679 680 rcu_read_lock(); 681 if (rt_is_input_route(rt) && 682 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr) 683 dev = dev_get_by_index_rcu(net, inet_iif(skb_in)); 684 685 if (dev) 686 saddr = inet_select_addr(dev, iph->saddr, 687 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, opt)) 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 ipcm_init(&ipc); 715 ipc.addr = iph->saddr; 716 ipc.opt = &icmp_param.replyopts.opt; 717 718 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark, 719 type, code, &icmp_param); 720 if (IS_ERR(rt)) 721 goto out_unlock; 722 723 /* peer icmp_ratelimit */ 724 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code)) 725 goto ende; 726 727 /* RFC says return as much as we can without exceeding 576 bytes. */ 728 729 room = dst_mtu(&rt->dst); 730 if (room > 576) 731 room = 576; 732 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen; 733 room -= sizeof(struct icmphdr); 734 735 icmp_param.data_len = skb_in->len - icmp_param.offset; 736 if (icmp_param.data_len > room) 737 icmp_param.data_len = room; 738 icmp_param.head_len = sizeof(struct icmphdr); 739 740 icmp_push_reply(&icmp_param, &fl4, &ipc, &rt); 741 ende: 742 ip_rt_put(rt); 743 out_unlock: 744 icmp_xmit_unlock(sk); 745 out_bh_enable: 746 local_bh_enable(); 747 out:; 748 } 749 EXPORT_SYMBOL(__icmp_send); 750 751 #if IS_ENABLED(CONFIG_NF_NAT) 752 #include <net/netfilter/nf_conntrack.h> 753 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info) 754 { 755 struct sk_buff *cloned_skb = NULL; 756 enum ip_conntrack_info ctinfo; 757 struct nf_conn *ct; 758 __be32 orig_ip; 759 760 ct = nf_ct_get(skb_in, &ctinfo); 761 if (!ct || !(ct->status & IPS_SRC_NAT)) { 762 icmp_send(skb_in, type, code, info); 763 return; 764 } 765 766 if (skb_shared(skb_in)) 767 skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC); 768 769 if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head || 770 (skb_network_header(skb_in) + sizeof(struct iphdr)) > 771 skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in, 772 skb_network_offset(skb_in) + sizeof(struct iphdr)))) 773 goto out; 774 775 orig_ip = ip_hdr(skb_in)->saddr; 776 ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip; 777 icmp_send(skb_in, type, code, info); 778 ip_hdr(skb_in)->saddr = orig_ip; 779 out: 780 consume_skb(cloned_skb); 781 } 782 EXPORT_SYMBOL(icmp_ndo_send); 783 #endif 784 785 static void icmp_socket_deliver(struct sk_buff *skb, u32 info) 786 { 787 const struct iphdr *iph = (const struct iphdr *) skb->data; 788 const struct net_protocol *ipprot; 789 int protocol = iph->protocol; 790 791 /* Checkin full IP header plus 8 bytes of protocol to 792 * avoid additional coding at protocol handlers. 793 */ 794 if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) { 795 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 796 return; 797 } 798 799 raw_icmp_error(skb, protocol, info); 800 801 ipprot = rcu_dereference(inet_protos[protocol]); 802 if (ipprot && ipprot->err_handler) 803 ipprot->err_handler(skb, info); 804 } 805 806 static bool icmp_tag_validation(int proto) 807 { 808 bool ok; 809 810 rcu_read_lock(); 811 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation; 812 rcu_read_unlock(); 813 return ok; 814 } 815 816 /* 817 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and 818 * ICMP_PARAMETERPROB. 819 */ 820 821 static bool icmp_unreach(struct sk_buff *skb) 822 { 823 const struct iphdr *iph; 824 struct icmphdr *icmph; 825 struct net *net; 826 u32 info = 0; 827 828 net = dev_net(skb_dst(skb)->dev); 829 830 /* 831 * Incomplete header ? 832 * Only checks for the IP header, there should be an 833 * additional check for longer headers in upper levels. 834 */ 835 836 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 837 goto out_err; 838 839 icmph = icmp_hdr(skb); 840 iph = (const struct iphdr *)skb->data; 841 842 if (iph->ihl < 5) /* Mangled header, drop. */ 843 goto out_err; 844 845 switch (icmph->type) { 846 case ICMP_DEST_UNREACH: 847 switch (icmph->code & 15) { 848 case ICMP_NET_UNREACH: 849 case ICMP_HOST_UNREACH: 850 case ICMP_PROT_UNREACH: 851 case ICMP_PORT_UNREACH: 852 break; 853 case ICMP_FRAG_NEEDED: 854 /* for documentation of the ip_no_pmtu_disc 855 * values please see 856 * Documentation/networking/ip-sysctl.rst 857 */ 858 switch (net->ipv4.sysctl_ip_no_pmtu_disc) { 859 default: 860 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n", 861 &iph->daddr); 862 break; 863 case 2: 864 goto out; 865 case 3: 866 if (!icmp_tag_validation(iph->protocol)) 867 goto out; 868 fallthrough; 869 case 0: 870 info = ntohs(icmph->un.frag.mtu); 871 } 872 break; 873 case ICMP_SR_FAILED: 874 net_dbg_ratelimited("%pI4: Source Route Failed\n", 875 &iph->daddr); 876 break; 877 default: 878 break; 879 } 880 if (icmph->code > NR_ICMP_UNREACH) 881 goto out; 882 break; 883 case ICMP_PARAMETERPROB: 884 info = ntohl(icmph->un.gateway) >> 24; 885 break; 886 case ICMP_TIME_EXCEEDED: 887 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS); 888 if (icmph->code == ICMP_EXC_FRAGTIME) 889 goto out; 890 break; 891 } 892 893 /* 894 * Throw it at our lower layers 895 * 896 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed 897 * header. 898 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the 899 * transport layer. 900 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to 901 * transport layer. 902 */ 903 904 /* 905 * Check the other end isn't violating RFC 1122. Some routers send 906 * bogus responses to broadcast frames. If you see this message 907 * first check your netmask matches at both ends, if it does then 908 * get the other vendor to fix their kit. 909 */ 910 911 if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses && 912 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) { 913 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n", 914 &ip_hdr(skb)->saddr, 915 icmph->type, icmph->code, 916 &iph->daddr, skb->dev->name); 917 goto out; 918 } 919 920 icmp_socket_deliver(skb, info); 921 922 out: 923 return true; 924 out_err: 925 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 926 return false; 927 } 928 929 930 /* 931 * Handle ICMP_REDIRECT. 932 */ 933 934 static bool icmp_redirect(struct sk_buff *skb) 935 { 936 if (skb->len < sizeof(struct iphdr)) { 937 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS); 938 return false; 939 } 940 941 if (!pskb_may_pull(skb, sizeof(struct iphdr))) { 942 /* there aught to be a stat */ 943 return false; 944 } 945 946 icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway)); 947 return true; 948 } 949 950 /* 951 * Handle ICMP_ECHO ("ping") requests. 952 * 953 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo 954 * requests. 955 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be 956 * included in the reply. 957 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring 958 * echo requests, MUST have default=NOT. 959 * See also WRT handling of options once they are done and working. 960 */ 961 962 static bool icmp_echo(struct sk_buff *skb) 963 { 964 struct net *net; 965 966 net = dev_net(skb_dst(skb)->dev); 967 if (!net->ipv4.sysctl_icmp_echo_ignore_all) { 968 struct icmp_bxm icmp_param; 969 970 icmp_param.data.icmph = *icmp_hdr(skb); 971 icmp_param.data.icmph.type = ICMP_ECHOREPLY; 972 icmp_param.skb = skb; 973 icmp_param.offset = 0; 974 icmp_param.data_len = skb->len; 975 icmp_param.head_len = sizeof(struct icmphdr); 976 icmp_reply(&icmp_param, skb); 977 } 978 /* should there be an ICMP stat for ignored echos? */ 979 return true; 980 } 981 982 /* 983 * Handle ICMP Timestamp requests. 984 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests. 985 * SHOULD be in the kernel for minimum random latency. 986 * MUST be accurate to a few minutes. 987 * MUST be updated at least at 15Hz. 988 */ 989 static bool icmp_timestamp(struct sk_buff *skb) 990 { 991 struct icmp_bxm icmp_param; 992 /* 993 * Too short. 994 */ 995 if (skb->len < 4) 996 goto out_err; 997 998 /* 999 * Fill in the current time as ms since midnight UT: 1000 */ 1001 icmp_param.data.times[1] = inet_current_timestamp(); 1002 icmp_param.data.times[2] = icmp_param.data.times[1]; 1003 1004 BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4)); 1005 1006 icmp_param.data.icmph = *icmp_hdr(skb); 1007 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY; 1008 icmp_param.data.icmph.code = 0; 1009 icmp_param.skb = skb; 1010 icmp_param.offset = 0; 1011 icmp_param.data_len = 0; 1012 icmp_param.head_len = sizeof(struct icmphdr) + 12; 1013 icmp_reply(&icmp_param, skb); 1014 return true; 1015 1016 out_err: 1017 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS); 1018 return false; 1019 } 1020 1021 static bool icmp_discard(struct sk_buff *skb) 1022 { 1023 /* pretend it was a success */ 1024 return true; 1025 } 1026 1027 /* 1028 * Deal with incoming ICMP packets. 1029 */ 1030 int icmp_rcv(struct sk_buff *skb) 1031 { 1032 struct icmphdr *icmph; 1033 struct rtable *rt = skb_rtable(skb); 1034 struct net *net = dev_net(rt->dst.dev); 1035 bool success; 1036 1037 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 1038 struct sec_path *sp = skb_sec_path(skb); 1039 int nh; 1040 1041 if (!(sp && sp->xvec[sp->len - 1]->props.flags & 1042 XFRM_STATE_ICMP)) 1043 goto drop; 1044 1045 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr))) 1046 goto drop; 1047 1048 nh = skb_network_offset(skb); 1049 skb_set_network_header(skb, sizeof(*icmph)); 1050 1051 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb)) 1052 goto drop; 1053 1054 skb_set_network_header(skb, nh); 1055 } 1056 1057 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS); 1058 1059 if (skb_checksum_simple_validate(skb)) 1060 goto csum_error; 1061 1062 if (!pskb_pull(skb, sizeof(*icmph))) 1063 goto error; 1064 1065 icmph = icmp_hdr(skb); 1066 1067 ICMPMSGIN_INC_STATS(net, icmph->type); 1068 /* 1069 * 18 is the highest 'known' ICMP type. Anything else is a mystery 1070 * 1071 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently 1072 * discarded. 1073 */ 1074 if (icmph->type > NR_ICMP_TYPES) 1075 goto error; 1076 1077 1078 /* 1079 * Parse the ICMP message 1080 */ 1081 1082 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) { 1083 /* 1084 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be 1085 * silently ignored (we let user decide with a sysctl). 1086 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently 1087 * discarded if to broadcast/multicast. 1088 */ 1089 if ((icmph->type == ICMP_ECHO || 1090 icmph->type == ICMP_TIMESTAMP) && 1091 net->ipv4.sysctl_icmp_echo_ignore_broadcasts) { 1092 goto error; 1093 } 1094 if (icmph->type != ICMP_ECHO && 1095 icmph->type != ICMP_TIMESTAMP && 1096 icmph->type != ICMP_ADDRESS && 1097 icmph->type != ICMP_ADDRESSREPLY) { 1098 goto error; 1099 } 1100 } 1101 1102 success = icmp_pointers[icmph->type].handler(skb); 1103 1104 if (success) { 1105 consume_skb(skb); 1106 return NET_RX_SUCCESS; 1107 } 1108 1109 drop: 1110 kfree_skb(skb); 1111 return NET_RX_DROP; 1112 csum_error: 1113 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS); 1114 error: 1115 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS); 1116 goto drop; 1117 } 1118 1119 int icmp_err(struct sk_buff *skb, u32 info) 1120 { 1121 struct iphdr *iph = (struct iphdr *)skb->data; 1122 int offset = iph->ihl<<2; 1123 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset); 1124 int type = icmp_hdr(skb)->type; 1125 int code = icmp_hdr(skb)->code; 1126 struct net *net = dev_net(skb->dev); 1127 1128 /* 1129 * Use ping_err to handle all icmp errors except those 1130 * triggered by ICMP_ECHOREPLY which sent from kernel. 1131 */ 1132 if (icmph->type != ICMP_ECHOREPLY) { 1133 ping_err(skb, offset, info); 1134 return 0; 1135 } 1136 1137 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) 1138 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP); 1139 else if (type == ICMP_REDIRECT) 1140 ipv4_redirect(skb, net, 0, IPPROTO_ICMP); 1141 1142 return 0; 1143 } 1144 1145 /* 1146 * This table is the definition of how we handle ICMP. 1147 */ 1148 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = { 1149 [ICMP_ECHOREPLY] = { 1150 .handler = ping_rcv, 1151 }, 1152 [1] = { 1153 .handler = icmp_discard, 1154 .error = 1, 1155 }, 1156 [2] = { 1157 .handler = icmp_discard, 1158 .error = 1, 1159 }, 1160 [ICMP_DEST_UNREACH] = { 1161 .handler = icmp_unreach, 1162 .error = 1, 1163 }, 1164 [ICMP_SOURCE_QUENCH] = { 1165 .handler = icmp_unreach, 1166 .error = 1, 1167 }, 1168 [ICMP_REDIRECT] = { 1169 .handler = icmp_redirect, 1170 .error = 1, 1171 }, 1172 [6] = { 1173 .handler = icmp_discard, 1174 .error = 1, 1175 }, 1176 [7] = { 1177 .handler = icmp_discard, 1178 .error = 1, 1179 }, 1180 [ICMP_ECHO] = { 1181 .handler = icmp_echo, 1182 }, 1183 [9] = { 1184 .handler = icmp_discard, 1185 .error = 1, 1186 }, 1187 [10] = { 1188 .handler = icmp_discard, 1189 .error = 1, 1190 }, 1191 [ICMP_TIME_EXCEEDED] = { 1192 .handler = icmp_unreach, 1193 .error = 1, 1194 }, 1195 [ICMP_PARAMETERPROB] = { 1196 .handler = icmp_unreach, 1197 .error = 1, 1198 }, 1199 [ICMP_TIMESTAMP] = { 1200 .handler = icmp_timestamp, 1201 }, 1202 [ICMP_TIMESTAMPREPLY] = { 1203 .handler = icmp_discard, 1204 }, 1205 [ICMP_INFO_REQUEST] = { 1206 .handler = icmp_discard, 1207 }, 1208 [ICMP_INFO_REPLY] = { 1209 .handler = icmp_discard, 1210 }, 1211 [ICMP_ADDRESS] = { 1212 .handler = icmp_discard, 1213 }, 1214 [ICMP_ADDRESSREPLY] = { 1215 .handler = icmp_discard, 1216 }, 1217 }; 1218 1219 static void __net_exit icmp_sk_exit(struct net *net) 1220 { 1221 int i; 1222 1223 for_each_possible_cpu(i) 1224 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i)); 1225 free_percpu(net->ipv4.icmp_sk); 1226 net->ipv4.icmp_sk = NULL; 1227 } 1228 1229 static int __net_init icmp_sk_init(struct net *net) 1230 { 1231 int i, err; 1232 1233 net->ipv4.icmp_sk = alloc_percpu(struct sock *); 1234 if (!net->ipv4.icmp_sk) 1235 return -ENOMEM; 1236 1237 for_each_possible_cpu(i) { 1238 struct sock *sk; 1239 1240 err = inet_ctl_sock_create(&sk, PF_INET, 1241 SOCK_RAW, IPPROTO_ICMP, net); 1242 if (err < 0) 1243 goto fail; 1244 1245 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk; 1246 1247 /* Enough space for 2 64K ICMP packets, including 1248 * sk_buff/skb_shared_info struct overhead. 1249 */ 1250 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024); 1251 1252 /* 1253 * Speedup sock_wfree() 1254 */ 1255 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE); 1256 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT; 1257 } 1258 1259 /* Control parameters for ECHO replies. */ 1260 net->ipv4.sysctl_icmp_echo_ignore_all = 0; 1261 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1; 1262 1263 /* Control parameter - ignore bogus broadcast responses? */ 1264 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1; 1265 1266 /* 1267 * Configurable global rate limit. 1268 * 1269 * ratelimit defines tokens/packet consumed for dst->rate_token 1270 * bucket ratemask defines which icmp types are ratelimited by 1271 * setting it's bit position. 1272 * 1273 * default: 1274 * dest unreachable (3), source quench (4), 1275 * time exceeded (11), parameter problem (12) 1276 */ 1277 1278 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ; 1279 net->ipv4.sysctl_icmp_ratemask = 0x1818; 1280 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; 1281 1282 return 0; 1283 1284 fail: 1285 icmp_sk_exit(net); 1286 return err; 1287 } 1288 1289 static struct pernet_operations __net_initdata icmp_sk_ops = { 1290 .init = icmp_sk_init, 1291 .exit = icmp_sk_exit, 1292 }; 1293 1294 int __init icmp_init(void) 1295 { 1296 return register_pernet_subsys(&icmp_sk_ops); 1297 } 1298