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#include <net/addrconf.h>
96#include <net/inet_dscp.h>
97#define CREATE_TRACE_POINTS
98#include <trace/events/icmp.h>
99
100/*
101 * Build xmit assembly blocks
102 */
103
104struct icmp_bxm {
105 struct sk_buff *skb;
106 int offset;
107 int data_len;
108
109 struct {
110 struct icmphdr icmph;
111 __be32 times[3];
112 } data;
113 int head_len;
114 struct ip_options_data replyopts;
115};
116
117/* An array of errno for error messages from dest unreach. */
118/* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
119
120const struct icmp_err icmp_err_convert[] = {
121 {
122 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */
123 .fatal = 0,
124 },
125 {
126 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */
127 .fatal = 0,
128 },
129 {
130 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */,
131 .fatal = 1,
132 },
133 {
134 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */
135 .fatal = 1,
136 },
137 {
138 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */
139 .fatal = 0,
140 },
141 {
142 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */
143 .fatal = 0,
144 },
145 {
146 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */
147 .fatal = 1,
148 },
149 {
150 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */
151 .fatal = 1,
152 },
153 {
154 .errno = ENONET, /* ICMP_HOST_ISOLATED */
155 .fatal = 1,
156 },
157 {
158 .errno = ENETUNREACH, /* ICMP_NET_ANO */
159 .fatal = 1,
160 },
161 {
162 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */
163 .fatal = 1,
164 },
165 {
166 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */
167 .fatal = 0,
168 },
169 {
170 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */
171 .fatal = 0,
172 },
173 {
174 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */
175 .fatal = 1,
176 },
177 {
178 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */
179 .fatal = 1,
180 },
181 {
182 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */
183 .fatal = 1,
184 },
185};
186EXPORT_SYMBOL(icmp_err_convert);
187
188/*
189 * ICMP control array. This specifies what to do with each ICMP.
190 */
191
192struct icmp_control {
193 enum skb_drop_reason (*handler)(struct sk_buff *skb);
194 short error; /* This ICMP is classed as an error message */
195};
196
197static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
198
199static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
200
201/* Called with BH disabled */
202static inline struct sock *icmp_xmit_lock(struct net *net)
203{
204 struct sock *sk;
205
206 sk = this_cpu_read(ipv4_icmp_sk);
207
208 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
209 /* This can happen if the output path signals a
210 * dst_link_failure() for an outgoing ICMP packet.
211 */
212 return NULL;
213 }
214 sock_net_set(sk, net);
215 return sk;
216}
217
218static inline void icmp_xmit_unlock(struct sock *sk)
219{
220 sock_net_set(sk, net: &init_net);
221 spin_unlock(lock: &sk->sk_lock.slock);
222}
223
224/**
225 * icmp_global_allow - Are we allowed to send one more ICMP message ?
226 * @net: network namespace
227 *
228 * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
229 * Returns false if we reached the limit and can not send another packet.
230 * Works in tandem with icmp_global_consume().
231 */
232bool icmp_global_allow(struct net *net)
233{
234 u32 delta, now, oldstamp;
235 int incr, new, old;
236
237 /* Note: many cpus could find this condition true.
238 * Then later icmp_global_consume() could consume more credits,
239 * this is an acceptable race.
240 */
241 if (atomic_read(v: &net->ipv4.icmp_global_credit) > 0)
242 return true;
243
244 now = jiffies;
245 oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
246 delta = min_t(u32, now - oldstamp, HZ);
247 if (delta < HZ / 50)
248 return false;
249
250 incr = READ_ONCE(net->ipv4.sysctl_icmp_msgs_per_sec) * delta / HZ;
251 if (!incr)
252 return false;
253
254 if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
255 old = atomic_read(v: &net->ipv4.icmp_global_credit);
256 do {
257 new = min(old + incr, READ_ONCE(net->ipv4.sysctl_icmp_msgs_burst));
258 } while (!atomic_try_cmpxchg(v: &net->ipv4.icmp_global_credit, old: &old, new));
259 }
260 return true;
261}
262EXPORT_SYMBOL(icmp_global_allow);
263
264void icmp_global_consume(struct net *net)
265{
266 int credits = get_random_u32_below(ceil: 3);
267
268 /* Note: this might make icmp_global.credit negative. */
269 if (credits)
270 atomic_sub(i: credits, v: &net->ipv4.icmp_global_credit);
271}
272EXPORT_SYMBOL(icmp_global_consume);
273
274static bool icmpv4_mask_allow(struct net *net, int type, int code)
275{
276 if (type > NR_ICMP_TYPES)
277 return true;
278
279 /* Don't limit PMTU discovery. */
280 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
281 return true;
282
283 /* Limit if icmp type is enabled in ratemask. */
284 if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
285 return true;
286
287 return false;
288}
289
290static bool icmpv4_global_allow(struct net *net, int type, int code,
291 bool *apply_ratelimit)
292{
293 if (icmpv4_mask_allow(net, type, code))
294 return true;
295
296 if (icmp_global_allow(net)) {
297 *apply_ratelimit = true;
298 return true;
299 }
300 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
301 return false;
302}
303
304/*
305 * Send an ICMP frame.
306 */
307
308static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
309 struct flowi4 *fl4, int type, int code,
310 bool apply_ratelimit)
311{
312 struct dst_entry *dst = &rt->dst;
313 struct inet_peer *peer;
314 bool rc = true;
315
316 if (!apply_ratelimit)
317 return true;
318
319 /* No rate limit on loopback */
320 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
321 goto out;
322
323 rcu_read_lock();
324 peer = inet_getpeer_v4(base: net->ipv4.peers, v4daddr: fl4->daddr,
325 vif: l3mdev_master_ifindex_rcu(dev: dst->dev));
326 rc = inet_peer_xrlim_allow(peer,
327 READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
328 rcu_read_unlock();
329out:
330 if (!rc)
331 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
332 else
333 icmp_global_consume(net);
334 return rc;
335}
336
337/*
338 * Maintain the counters used in the SNMP statistics for outgoing ICMP
339 */
340void icmp_out_count(struct net *net, unsigned char type)
341{
342 ICMPMSGOUT_INC_STATS(net, type);
343 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
344}
345
346/*
347 * Checksum each fragment, and on the first include the headers and final
348 * checksum.
349 */
350static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
351 struct sk_buff *skb)
352{
353 struct icmp_bxm *icmp_param = from;
354 __wsum csum;
355
356 csum = skb_copy_and_csum_bits(skb: icmp_param->skb,
357 offset: icmp_param->offset + offset,
358 to, len);
359
360 skb->csum = csum_block_add(csum: skb->csum, csum2: csum, offset: odd);
361 if (icmp_pointers[icmp_param->data.icmph.type].error)
362 nf_ct_attach(skb, icmp_param->skb);
363 return 0;
364}
365
366static void icmp_push_reply(struct sock *sk,
367 struct icmp_bxm *icmp_param,
368 struct flowi4 *fl4,
369 struct ipcm_cookie *ipc, struct rtable **rt)
370{
371 struct sk_buff *skb;
372
373 if (ip_append_data(sk, fl4, getfrag: icmp_glue_bits, from: icmp_param,
374 len: icmp_param->data_len+icmp_param->head_len,
375 protolen: icmp_param->head_len,
376 ipc, rt, MSG_DONTWAIT) < 0) {
377 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
378 ip_flush_pending_frames(sk);
379 } else if ((skb = skb_peek(list_: &sk->sk_write_queue)) != NULL) {
380 struct icmphdr *icmph = icmp_hdr(skb);
381 __wsum csum;
382 struct sk_buff *skb1;
383
384 csum = csum_partial_copy_nocheck(src: (void *)&icmp_param->data,
385 dst: (char *)icmph,
386 len: icmp_param->head_len);
387 skb_queue_walk(&sk->sk_write_queue, skb1) {
388 csum = csum_add(csum, addend: skb1->csum);
389 }
390 icmph->checksum = csum_fold(csum);
391 skb->ip_summed = CHECKSUM_NONE;
392 ip_push_pending_frames(sk, fl4);
393 }
394}
395
396/*
397 * Driving logic for building and sending ICMP messages.
398 */
399
400static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
401{
402 struct rtable *rt = skb_rtable(skb);
403 struct net *net = dev_net_rcu(dev: rt->dst.dev);
404 bool apply_ratelimit = false;
405 struct ipcm_cookie ipc;
406 struct flowi4 fl4;
407 struct sock *sk;
408 __be32 daddr, saddr;
409 u32 mark = IP4_REPLY_MARK(net, skb->mark);
410 int type = icmp_param->data.icmph.type;
411 int code = icmp_param->data.icmph.code;
412
413 if (ip_options_echo(net, dopt: &icmp_param->replyopts.opt.opt, skb))
414 return;
415
416 /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
417 local_bh_disable();
418
419 /* is global icmp_msgs_per_sec exhausted ? */
420 if (!icmpv4_global_allow(net, type, code, apply_ratelimit: &apply_ratelimit))
421 goto out_bh_enable;
422
423 sk = icmp_xmit_lock(net);
424 if (!sk)
425 goto out_bh_enable;
426
427 icmp_param->data.icmph.checksum = 0;
428
429 ipcm_init(ipcm: &ipc);
430 ipc.tos = ip_hdr(skb)->tos;
431 ipc.sockc.mark = mark;
432 daddr = ipc.addr = ip_hdr(skb)->saddr;
433 saddr = fib_compute_spec_dst(skb);
434
435 if (icmp_param->replyopts.opt.opt.optlen) {
436 ipc.opt = &icmp_param->replyopts.opt;
437 if (ipc.opt->opt.srr)
438 daddr = icmp_param->replyopts.opt.opt.faddr;
439 }
440 memset(&fl4, 0, sizeof(fl4));
441 fl4.daddr = daddr;
442 fl4.saddr = saddr;
443 fl4.flowi4_mark = mark;
444 fl4.flowi4_uid = sock_net_uid(net, NULL);
445 fl4.flowi4_tos = inet_dscp_to_dsfield(dscp: ip4h_dscp(ip4h: ip_hdr(skb)));
446 fl4.flowi4_proto = IPPROTO_ICMP;
447 fl4.flowi4_oif = l3mdev_master_ifindex(dev: skb->dev);
448 security_skb_classify_flow(skb, flic: flowi4_to_flowi_common(fl4: &fl4));
449 rt = ip_route_output_key(net, flp: &fl4);
450 if (IS_ERR(ptr: rt))
451 goto out_unlock;
452 if (icmpv4_xrlim_allow(net, rt, fl4: &fl4, type, code, apply_ratelimit))
453 icmp_push_reply(sk, icmp_param, fl4: &fl4, ipc: &ipc, rt: &rt);
454 ip_rt_put(rt);
455out_unlock:
456 icmp_xmit_unlock(sk);
457out_bh_enable:
458 local_bh_enable();
459}
460
461/*
462 * The device used for looking up which routing table to use for sending an ICMP
463 * error is preferably the source whenever it is set, which should ensure the
464 * icmp error can be sent to the source host, else lookup using the routing
465 * table of the destination device, else use the main routing table (index 0).
466 */
467static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
468{
469 struct net_device *route_lookup_dev = NULL;
470
471 if (skb->dev)
472 route_lookup_dev = skb->dev;
473 else if (skb_dst(skb))
474 route_lookup_dev = skb_dst(skb)->dev;
475 return route_lookup_dev;
476}
477
478static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
479 struct sk_buff *skb_in,
480 const struct iphdr *iph, __be32 saddr,
481 dscp_t dscp, u32 mark, int type,
482 int code, struct icmp_bxm *param)
483{
484 struct net_device *route_lookup_dev;
485 struct dst_entry *dst, *dst2;
486 struct rtable *rt, *rt2;
487 struct flowi4 fl4_dec;
488 int err;
489
490 memset(fl4, 0, sizeof(*fl4));
491 fl4->daddr = (param->replyopts.opt.opt.srr ?
492 param->replyopts.opt.opt.faddr : iph->saddr);
493 fl4->saddr = saddr;
494 fl4->flowi4_mark = mark;
495 fl4->flowi4_uid = sock_net_uid(net, NULL);
496 fl4->flowi4_tos = inet_dscp_to_dsfield(dscp);
497 fl4->flowi4_proto = IPPROTO_ICMP;
498 fl4->fl4_icmp_type = type;
499 fl4->fl4_icmp_code = code;
500 route_lookup_dev = icmp_get_route_lookup_dev(skb: skb_in);
501 fl4->flowi4_oif = l3mdev_master_ifindex(dev: route_lookup_dev);
502
503 security_skb_classify_flow(skb: skb_in, flic: flowi4_to_flowi_common(fl4));
504 rt = ip_route_output_key_hash(net, flp: fl4, skb: skb_in);
505 if (IS_ERR(ptr: rt))
506 return rt;
507
508 /* No need to clone since we're just using its address. */
509 rt2 = rt;
510
511 dst = xfrm_lookup(net, dst_orig: &rt->dst,
512 fl: flowi4_to_flowi(fl4), NULL, flags: 0);
513 rt = dst_rtable(dst);
514 if (!IS_ERR(ptr: dst)) {
515 if (rt != rt2)
516 return rt;
517 if (inet_addr_type_dev_table(net, dev: route_lookup_dev,
518 addr: fl4->daddr) == RTN_LOCAL)
519 return rt;
520 } else if (PTR_ERR(ptr: dst) == -EPERM) {
521 rt = NULL;
522 } else {
523 return rt;
524 }
525 err = xfrm_decode_session_reverse(net, skb: skb_in, fl: flowi4_to_flowi(fl4: &fl4_dec), AF_INET);
526 if (err)
527 goto relookup_failed;
528
529 if (inet_addr_type_dev_table(net, dev: route_lookup_dev,
530 addr: fl4_dec.saddr) == RTN_LOCAL) {
531 rt2 = __ip_route_output_key(net, flp: &fl4_dec);
532 if (IS_ERR(ptr: rt2))
533 err = PTR_ERR(ptr: rt2);
534 } else {
535 struct flowi4 fl4_2 = {};
536 unsigned long orefdst;
537
538 fl4_2.daddr = fl4_dec.saddr;
539 rt2 = ip_route_output_key(net, flp: &fl4_2);
540 if (IS_ERR(ptr: rt2)) {
541 err = PTR_ERR(ptr: rt2);
542 goto relookup_failed;
543 }
544 /* Ugh! */
545 orefdst = skb_in->_skb_refdst; /* save old refdst */
546 skb_dst_set(skb: skb_in, NULL);
547 err = ip_route_input(skb: skb_in, dst: fl4_dec.daddr, src: fl4_dec.saddr,
548 dscp, devin: rt2->dst.dev) ? -EINVAL : 0;
549
550 dst_release(dst: &rt2->dst);
551 rt2 = skb_rtable(skb: skb_in);
552 skb_in->_skb_refdst = orefdst; /* restore old refdst */
553 }
554
555 if (err)
556 goto relookup_failed;
557
558 dst2 = xfrm_lookup(net, dst_orig: &rt2->dst, fl: flowi4_to_flowi(fl4: &fl4_dec), NULL,
559 flags: XFRM_LOOKUP_ICMP);
560 rt2 = dst_rtable(dst2);
561 if (!IS_ERR(ptr: dst2)) {
562 dst_release(dst: &rt->dst);
563 memcpy(fl4, &fl4_dec, sizeof(*fl4));
564 rt = rt2;
565 } else if (PTR_ERR(ptr: dst2) == -EPERM) {
566 if (rt)
567 dst_release(dst: &rt->dst);
568 return rt2;
569 } else {
570 err = PTR_ERR(ptr: dst2);
571 goto relookup_failed;
572 }
573 return rt;
574
575relookup_failed:
576 if (rt)
577 return rt;
578 return ERR_PTR(error: err);
579}
580
581/*
582 * Send an ICMP message in response to a situation
583 *
584 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
585 * MAY send more (we do).
586 * MUST NOT change this header information.
587 * MUST NOT reply to a multicast/broadcast IP address.
588 * MUST NOT reply to a multicast/broadcast MAC address.
589 * MUST reply to only the first fragment.
590 */
591
592void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
593 const struct ip_options *opt)
594{
595 struct iphdr *iph;
596 int room;
597 struct icmp_bxm icmp_param;
598 struct rtable *rt = skb_rtable(skb: skb_in);
599 bool apply_ratelimit = false;
600 struct ipcm_cookie ipc;
601 struct flowi4 fl4;
602 __be32 saddr;
603 u8 tos;
604 u32 mark;
605 struct net *net;
606 struct sock *sk;
607
608 if (!rt)
609 return;
610
611 rcu_read_lock();
612
613 if (rt->dst.dev)
614 net = dev_net_rcu(dev: rt->dst.dev);
615 else if (skb_in->dev)
616 net = dev_net_rcu(dev: skb_in->dev);
617 else
618 goto out;
619
620 /*
621 * Find the original header. It is expected to be valid, of course.
622 * Check this, icmp_send is called from the most obscure devices
623 * sometimes.
624 */
625 iph = ip_hdr(skb: skb_in);
626
627 if ((u8 *)iph < skb_in->head ||
628 (skb_network_header(skb: skb_in) + sizeof(*iph)) >
629 skb_tail_pointer(skb: skb_in))
630 goto out;
631
632 /*
633 * No replies to physical multicast/broadcast
634 */
635 if (skb_in->pkt_type != PACKET_HOST)
636 goto out;
637
638 /*
639 * Now check at the protocol level
640 */
641 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
642 goto out;
643
644 /*
645 * Only reply to fragment 0. We byte re-order the constant
646 * mask for efficiency.
647 */
648 if (iph->frag_off & htons(IP_OFFSET))
649 goto out;
650
651 /*
652 * If we send an ICMP error to an ICMP error a mess would result..
653 */
654 if (icmp_pointers[type].error) {
655 /*
656 * We are an error, check if we are replying to an
657 * ICMP error
658 */
659 if (iph->protocol == IPPROTO_ICMP) {
660 u8 _inner_type, *itp;
661
662 itp = skb_header_pointer(skb: skb_in,
663 offset: skb_network_header(skb: skb_in) +
664 (iph->ihl << 2) +
665 offsetof(struct icmphdr,
666 type) -
667 skb_in->data,
668 len: sizeof(_inner_type),
669 buffer: &_inner_type);
670 if (!itp)
671 goto out;
672
673 /*
674 * Assume any unknown ICMP type is an error. This
675 * isn't specified by the RFC, but think about it..
676 */
677 if (*itp > NR_ICMP_TYPES ||
678 icmp_pointers[*itp].error)
679 goto out;
680 }
681 }
682
683 /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
684 local_bh_disable();
685
686 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
687 * incoming dev is loopback. If outgoing dev change to not be
688 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
689 */
690 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
691 !icmpv4_global_allow(net, type, code, apply_ratelimit: &apply_ratelimit))
692 goto out_bh_enable;
693
694 sk = icmp_xmit_lock(net);
695 if (!sk)
696 goto out_bh_enable;
697
698 /*
699 * Construct source address and options.
700 */
701
702 saddr = iph->daddr;
703 if (!(rt->rt_flags & RTCF_LOCAL)) {
704 struct net_device *dev = NULL;
705
706 rcu_read_lock();
707 if (rt_is_input_route(rt) &&
708 READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
709 dev = dev_get_by_index_rcu(net, ifindex: inet_iif(skb: skb_in));
710
711 if (dev)
712 saddr = inet_select_addr(dev, dst: iph->saddr,
713 scope: RT_SCOPE_LINK);
714 else
715 saddr = 0;
716 rcu_read_unlock();
717 }
718
719 tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
720 IPTOS_PREC_INTERNETCONTROL) :
721 iph->tos;
722 mark = IP4_REPLY_MARK(net, skb_in->mark);
723
724 if (__ip_options_echo(net, dopt: &icmp_param.replyopts.opt.opt, skb: skb_in, sopt: opt))
725 goto out_unlock;
726
727
728 /*
729 * Prepare data for ICMP header.
730 */
731
732 icmp_param.data.icmph.type = type;
733 icmp_param.data.icmph.code = code;
734 icmp_param.data.icmph.un.gateway = info;
735 icmp_param.data.icmph.checksum = 0;
736 icmp_param.skb = skb_in;
737 icmp_param.offset = skb_network_offset(skb: skb_in);
738 ipcm_init(ipcm: &ipc);
739 ipc.tos = tos;
740 ipc.addr = iph->saddr;
741 ipc.opt = &icmp_param.replyopts.opt;
742 ipc.sockc.mark = mark;
743
744 rt = icmp_route_lookup(net, fl4: &fl4, skb_in, iph, saddr,
745 dscp: inet_dsfield_to_dscp(dsfield: tos), mark, type, code,
746 param: &icmp_param);
747 if (IS_ERR(ptr: rt))
748 goto out_unlock;
749
750 /* peer icmp_ratelimit */
751 if (!icmpv4_xrlim_allow(net, rt, fl4: &fl4, type, code, apply_ratelimit))
752 goto ende;
753
754 /* RFC says return as much as we can without exceeding 576 bytes. */
755
756 room = dst_mtu(dst: &rt->dst);
757 if (room > 576)
758 room = 576;
759 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
760 room -= sizeof(struct icmphdr);
761 /* Guard against tiny mtu. We need to include at least one
762 * IP network header for this message to make any sense.
763 */
764 if (room <= (int)sizeof(struct iphdr))
765 goto ende;
766
767 icmp_param.data_len = skb_in->len - icmp_param.offset;
768 if (icmp_param.data_len > room)
769 icmp_param.data_len = room;
770 icmp_param.head_len = sizeof(struct icmphdr);
771
772 /* if we don't have a source address at this point, fall back to the
773 * dummy address instead of sending out a packet with a source address
774 * of 0.0.0.0
775 */
776 if (!fl4.saddr)
777 fl4.saddr = htonl(INADDR_DUMMY);
778
779 trace_icmp_send(skb: skb_in, type, code);
780
781 icmp_push_reply(sk, icmp_param: &icmp_param, fl4: &fl4, ipc: &ipc, rt: &rt);
782ende:
783 ip_rt_put(rt);
784out_unlock:
785 icmp_xmit_unlock(sk);
786out_bh_enable:
787 local_bh_enable();
788out:
789 rcu_read_unlock();
790}
791EXPORT_SYMBOL(__icmp_send);
792
793#if IS_ENABLED(CONFIG_NF_NAT)
794#include <net/netfilter/nf_conntrack.h>
795void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
796{
797 struct sk_buff *cloned_skb = NULL;
798 struct ip_options opts = { 0 };
799 enum ip_conntrack_info ctinfo;
800 struct nf_conn *ct;
801 __be32 orig_ip;
802
803 ct = nf_ct_get(skb: skb_in, ctinfo: &ctinfo);
804 if (!ct || !(ct->status & IPS_SRC_NAT)) {
805 __icmp_send(skb_in, type, code, info, &opts);
806 return;
807 }
808
809 if (skb_shared(skb: skb_in))
810 skb_in = cloned_skb = skb_clone(skb: skb_in, GFP_ATOMIC);
811
812 if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
813 (skb_network_header(skb_in) + sizeof(struct iphdr)) >
814 skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
815 skb_network_offset(skb_in) + sizeof(struct iphdr))))
816 goto out;
817
818 orig_ip = ip_hdr(skb: skb_in)->saddr;
819 ip_hdr(skb: skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
820 __icmp_send(skb_in, type, code, info, &opts);
821 ip_hdr(skb: skb_in)->saddr = orig_ip;
822out:
823 consume_skb(skb: cloned_skb);
824}
825EXPORT_SYMBOL(icmp_ndo_send);
826#endif
827
828static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
829{
830 const struct iphdr *iph = (const struct iphdr *)skb->data;
831 const struct net_protocol *ipprot;
832 int protocol = iph->protocol;
833
834 /* Checkin full IP header plus 8 bytes of protocol to
835 * avoid additional coding at protocol handlers.
836 */
837 if (!pskb_may_pull(skb, len: iph->ihl * 4 + 8)) {
838 __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
839 return;
840 }
841
842 raw_icmp_error(skb, protocol, info);
843
844 ipprot = rcu_dereference(inet_protos[protocol]);
845 if (ipprot && ipprot->err_handler)
846 ipprot->err_handler(skb, info);
847}
848
849static bool icmp_tag_validation(int proto)
850{
851 bool ok;
852
853 rcu_read_lock();
854 ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
855 rcu_read_unlock();
856 return ok;
857}
858
859/*
860 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
861 * ICMP_PARAMETERPROB.
862 */
863
864static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
865{
866 enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
867 const struct iphdr *iph;
868 struct icmphdr *icmph;
869 struct net *net;
870 u32 info = 0;
871
872 net = dev_net_rcu(dev: skb_dst(skb)->dev);
873
874 /*
875 * Incomplete header ?
876 * Only checks for the IP header, there should be an
877 * additional check for longer headers in upper levels.
878 */
879
880 if (!pskb_may_pull(skb, len: sizeof(struct iphdr)))
881 goto out_err;
882
883 icmph = icmp_hdr(skb);
884 iph = (const struct iphdr *)skb->data;
885
886 if (iph->ihl < 5) { /* Mangled header, drop. */
887 reason = SKB_DROP_REASON_IP_INHDR;
888 goto out_err;
889 }
890
891 switch (icmph->type) {
892 case ICMP_DEST_UNREACH:
893 switch (icmph->code & 15) {
894 case ICMP_NET_UNREACH:
895 case ICMP_HOST_UNREACH:
896 case ICMP_PROT_UNREACH:
897 case ICMP_PORT_UNREACH:
898 break;
899 case ICMP_FRAG_NEEDED:
900 /* for documentation of the ip_no_pmtu_disc
901 * values please see
902 * Documentation/networking/ip-sysctl.rst
903 */
904 switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
905 default:
906 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
907 &iph->daddr);
908 break;
909 case 2:
910 goto out;
911 case 3:
912 if (!icmp_tag_validation(proto: iph->protocol))
913 goto out;
914 fallthrough;
915 case 0:
916 info = ntohs(icmph->un.frag.mtu);
917 }
918 break;
919 case ICMP_SR_FAILED:
920 net_dbg_ratelimited("%pI4: Source Route Failed\n",
921 &iph->daddr);
922 break;
923 default:
924 break;
925 }
926 if (icmph->code > NR_ICMP_UNREACH)
927 goto out;
928 break;
929 case ICMP_PARAMETERPROB:
930 info = ntohl(icmph->un.gateway) >> 24;
931 break;
932 case ICMP_TIME_EXCEEDED:
933 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
934 if (icmph->code == ICMP_EXC_FRAGTIME)
935 goto out;
936 break;
937 }
938
939 /*
940 * Throw it at our lower layers
941 *
942 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
943 * header.
944 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
945 * transport layer.
946 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
947 * transport layer.
948 */
949
950 /*
951 * Check the other end isn't violating RFC 1122. Some routers send
952 * bogus responses to broadcast frames. If you see this message
953 * first check your netmask matches at both ends, if it does then
954 * get the other vendor to fix their kit.
955 */
956
957 if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
958 inet_addr_type_dev_table(net, dev: skb->dev, addr: iph->daddr) == RTN_BROADCAST) {
959 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
960 &ip_hdr(skb)->saddr,
961 icmph->type, icmph->code,
962 &iph->daddr, skb->dev->name);
963 goto out;
964 }
965
966 icmp_socket_deliver(skb, info);
967
968out:
969 return reason;
970out_err:
971 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
972 return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
973}
974
975
976/*
977 * Handle ICMP_REDIRECT.
978 */
979
980static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
981{
982 if (skb->len < sizeof(struct iphdr)) {
983 __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
984 return SKB_DROP_REASON_PKT_TOO_SMALL;
985 }
986
987 if (!pskb_may_pull(skb, len: sizeof(struct iphdr))) {
988 /* there aught to be a stat */
989 return SKB_DROP_REASON_NOMEM;
990 }
991
992 icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
993 return SKB_NOT_DROPPED_YET;
994}
995
996/*
997 * Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
998 *
999 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
1000 * requests.
1001 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
1002 * included in the reply.
1003 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
1004 * echo requests, MUST have default=NOT.
1005 * RFC 8335: 8 MUST have a config option to enable/disable ICMP
1006 * Extended Echo Functionality, MUST be disabled by default
1007 * See also WRT handling of options once they are done and working.
1008 */
1009
1010static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
1011{
1012 struct icmp_bxm icmp_param;
1013 struct net *net;
1014
1015 net = dev_net_rcu(dev: skb_dst(skb)->dev);
1016 /* should there be an ICMP stat for ignored echos? */
1017 if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
1018 return SKB_NOT_DROPPED_YET;
1019
1020 icmp_param.data.icmph = *icmp_hdr(skb);
1021 icmp_param.skb = skb;
1022 icmp_param.offset = 0;
1023 icmp_param.data_len = skb->len;
1024 icmp_param.head_len = sizeof(struct icmphdr);
1025
1026 if (icmp_param.data.icmph.type == ICMP_ECHO)
1027 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
1028 else if (!icmp_build_probe(skb, icmphdr: &icmp_param.data.icmph))
1029 return SKB_NOT_DROPPED_YET;
1030
1031 icmp_reply(icmp_param: &icmp_param, skb);
1032 return SKB_NOT_DROPPED_YET;
1033}
1034
1035/* Helper for icmp_echo and icmpv6_echo_reply.
1036 * Searches for net_device that matches PROBE interface identifier
1037 * and builds PROBE reply message in icmphdr.
1038 *
1039 * Returns false if PROBE responses are disabled via sysctl
1040 */
1041
1042bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1043{
1044 struct net *net = dev_net_rcu(dev: skb->dev);
1045 struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1046 struct icmp_ext_echo_iio *iio, _iio;
1047 struct inet6_dev *in6_dev;
1048 struct in_device *in_dev;
1049 struct net_device *dev;
1050 char buff[IFNAMSIZ];
1051 u16 ident_len;
1052 u8 status;
1053
1054 if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
1055 return false;
1056
1057 /* We currently only support probing interfaces on the proxy node
1058 * Check to ensure L-bit is set
1059 */
1060 if (!(ntohs(icmphdr->un.echo.sequence) & 1))
1061 return false;
1062 /* Clear status bits in reply message */
1063 icmphdr->un.echo.sequence &= htons(0xFF00);
1064 if (icmphdr->type == ICMP_EXT_ECHO)
1065 icmphdr->type = ICMP_EXT_ECHOREPLY;
1066 else
1067 icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
1068 ext_hdr = skb_header_pointer(skb, offset: 0, len: sizeof(_ext_hdr), buffer: &_ext_hdr);
1069 /* Size of iio is class_type dependent.
1070 * Only check header here and assign length based on ctype in the switch statement
1071 */
1072 iio = skb_header_pointer(skb, offset: sizeof(_ext_hdr), len: sizeof(iio->extobj_hdr), buffer: &_iio);
1073 if (!ext_hdr || !iio)
1074 goto send_mal_query;
1075 if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
1076 ntohs(iio->extobj_hdr.length) > sizeof(_iio))
1077 goto send_mal_query;
1078 ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
1079 iio = skb_header_pointer(skb, offset: sizeof(_ext_hdr),
1080 len: sizeof(iio->extobj_hdr) + ident_len, buffer: &_iio);
1081 if (!iio)
1082 goto send_mal_query;
1083
1084 status = 0;
1085 dev = NULL;
1086 switch (iio->extobj_hdr.class_type) {
1087 case ICMP_EXT_ECHO_CTYPE_NAME:
1088 if (ident_len >= IFNAMSIZ)
1089 goto send_mal_query;
1090 memset(buff, 0, sizeof(buff));
1091 memcpy(buff, &iio->ident.name, ident_len);
1092 dev = dev_get_by_name(net, name: buff);
1093 break;
1094 case ICMP_EXT_ECHO_CTYPE_INDEX:
1095 if (ident_len != sizeof(iio->ident.ifindex))
1096 goto send_mal_query;
1097 dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
1098 break;
1099 case ICMP_EXT_ECHO_CTYPE_ADDR:
1100 if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
1101 ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
1102 iio->ident.addr.ctype3_hdr.addrlen)
1103 goto send_mal_query;
1104 switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
1105 case ICMP_AFI_IP:
1106 if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
1107 goto send_mal_query;
1108 dev = ip_dev_find(net, addr: iio->ident.addr.ip_addr.ipv4_addr);
1109 break;
1110#if IS_ENABLED(CONFIG_IPV6)
1111 case ICMP_AFI_IP6:
1112 if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
1113 goto send_mal_query;
1114 dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
1115 dev_hold(dev);
1116 break;
1117#endif
1118 default:
1119 goto send_mal_query;
1120 }
1121 break;
1122 default:
1123 goto send_mal_query;
1124 }
1125 if (!dev) {
1126 icmphdr->code = ICMP_EXT_CODE_NO_IF;
1127 return true;
1128 }
1129 /* Fill bits in reply message */
1130 if (dev->flags & IFF_UP)
1131 status |= ICMP_EXT_ECHOREPLY_ACTIVE;
1132
1133 in_dev = __in_dev_get_rcu(dev);
1134 if (in_dev && rcu_access_pointer(in_dev->ifa_list))
1135 status |= ICMP_EXT_ECHOREPLY_IPV4;
1136
1137 in6_dev = __in6_dev_get(dev);
1138 if (in6_dev && !list_empty(head: &in6_dev->addr_list))
1139 status |= ICMP_EXT_ECHOREPLY_IPV6;
1140
1141 dev_put(dev);
1142 icmphdr->un.echo.sequence |= htons(status);
1143 return true;
1144send_mal_query:
1145 icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1146 return true;
1147}
1148EXPORT_SYMBOL_GPL(icmp_build_probe);
1149
1150/*
1151 * Handle ICMP Timestamp requests.
1152 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
1153 * SHOULD be in the kernel for minimum random latency.
1154 * MUST be accurate to a few minutes.
1155 * MUST be updated at least at 15Hz.
1156 */
1157static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
1158{
1159 struct icmp_bxm icmp_param;
1160 /*
1161 * Too short.
1162 */
1163 if (skb->len < 4)
1164 goto out_err;
1165
1166 /*
1167 * Fill in the current time as ms since midnight UT:
1168 */
1169 icmp_param.data.times[1] = inet_current_timestamp();
1170 icmp_param.data.times[2] = icmp_param.data.times[1];
1171
1172 BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
1173
1174 icmp_param.data.icmph = *icmp_hdr(skb);
1175 icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
1176 icmp_param.data.icmph.code = 0;
1177 icmp_param.skb = skb;
1178 icmp_param.offset = 0;
1179 icmp_param.data_len = 0;
1180 icmp_param.head_len = sizeof(struct icmphdr) + 12;
1181 icmp_reply(icmp_param: &icmp_param, skb);
1182 return SKB_NOT_DROPPED_YET;
1183
1184out_err:
1185 __ICMP_INC_STATS(dev_net_rcu(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1186 return SKB_DROP_REASON_PKT_TOO_SMALL;
1187}
1188
1189static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
1190{
1191 /* pretend it was a success */
1192 return SKB_NOT_DROPPED_YET;
1193}
1194
1195/*
1196 * Deal with incoming ICMP packets.
1197 */
1198int icmp_rcv(struct sk_buff *skb)
1199{
1200 enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
1201 struct rtable *rt = skb_rtable(skb);
1202 struct net *net = dev_net_rcu(dev: rt->dst.dev);
1203 struct icmphdr *icmph;
1204
1205 if (!xfrm4_policy_check(NULL, dir: XFRM_POLICY_IN, skb)) {
1206 struct sec_path *sp = skb_sec_path(skb);
1207 int nh;
1208
1209 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1210 XFRM_STATE_ICMP)) {
1211 reason = SKB_DROP_REASON_XFRM_POLICY;
1212 goto drop;
1213 }
1214
1215 if (!pskb_may_pull(skb, len: sizeof(*icmph) + sizeof(struct iphdr)))
1216 goto drop;
1217
1218 nh = skb_network_offset(skb);
1219 skb_set_network_header(skb, offset: sizeof(*icmph));
1220
1221 if (!xfrm4_policy_check_reverse(NULL, dir: XFRM_POLICY_IN,
1222 skb)) {
1223 reason = SKB_DROP_REASON_XFRM_POLICY;
1224 goto drop;
1225 }
1226
1227 skb_set_network_header(skb, offset: nh);
1228 }
1229
1230 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1231
1232 if (skb_checksum_simple_validate(skb))
1233 goto csum_error;
1234
1235 if (!pskb_pull(skb, len: sizeof(*icmph)))
1236 goto error;
1237
1238 icmph = icmp_hdr(skb);
1239
1240 ICMPMSGIN_INC_STATS(net, icmph->type);
1241
1242 /* Check for ICMP Extended Echo (PROBE) messages */
1243 if (icmph->type == ICMP_EXT_ECHO) {
1244 /* We can't use icmp_pointers[].handler() because it is an array of
1245 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
1246 */
1247 reason = icmp_echo(skb);
1248 goto reason_check;
1249 }
1250
1251 /*
1252 * Parse the ICMP message
1253 */
1254
1255 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1256 /*
1257 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1258 * silently ignored (we let user decide with a sysctl).
1259 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1260 * discarded if to broadcast/multicast.
1261 */
1262 if ((icmph->type == ICMP_ECHO ||
1263 icmph->type == ICMP_TIMESTAMP) &&
1264 READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1265 reason = SKB_DROP_REASON_INVALID_PROTO;
1266 goto error;
1267 }
1268 if (icmph->type != ICMP_ECHO &&
1269 icmph->type != ICMP_TIMESTAMP &&
1270 icmph->type != ICMP_ADDRESS &&
1271 icmph->type != ICMP_ADDRESSREPLY) {
1272 reason = SKB_DROP_REASON_INVALID_PROTO;
1273 goto error;
1274 }
1275 }
1276
1277 if (icmph->type == ICMP_EXT_ECHOREPLY ||
1278 icmph->type == ICMP_ECHOREPLY) {
1279 reason = ping_rcv(skb);
1280 return reason ? NET_RX_DROP : NET_RX_SUCCESS;
1281 }
1282
1283 /*
1284 * 18 is the highest 'known' ICMP type. Anything else is a mystery
1285 *
1286 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
1287 * discarded.
1288 */
1289 if (icmph->type > NR_ICMP_TYPES) {
1290 reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1291 goto error;
1292 }
1293
1294 reason = icmp_pointers[icmph->type].handler(skb);
1295reason_check:
1296 if (!reason) {
1297 consume_skb(skb);
1298 return NET_RX_SUCCESS;
1299 }
1300
1301drop:
1302 kfree_skb_reason(skb, reason);
1303 return NET_RX_DROP;
1304csum_error:
1305 reason = SKB_DROP_REASON_ICMP_CSUM;
1306 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1307error:
1308 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1309 goto drop;
1310}
1311
1312static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1313{
1314 struct icmp_extobj_hdr *objh, _objh;
1315 struct icmp_ext_hdr *exth, _exth;
1316 u16 olen;
1317
1318 exth = skb_header_pointer(skb, offset: off, len: sizeof(_exth), buffer: &_exth);
1319 if (!exth)
1320 return false;
1321 if (exth->version != 2)
1322 return true;
1323
1324 if (exth->checksum &&
1325 csum_fold(csum: skb_checksum(skb, offset: off, len: skb->len - off, csum: 0)))
1326 return false;
1327
1328 off += sizeof(_exth);
1329 while (off < skb->len) {
1330 objh = skb_header_pointer(skb, offset: off, len: sizeof(_objh), buffer: &_objh);
1331 if (!objh)
1332 return false;
1333
1334 olen = ntohs(objh->length);
1335 if (olen < sizeof(_objh))
1336 return false;
1337
1338 off += olen;
1339 if (off > skb->len)
1340 return false;
1341 }
1342
1343 return true;
1344}
1345
1346void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1347 struct sock_ee_data_rfc4884 *out,
1348 int thlen, int off)
1349{
1350 int hlen;
1351
1352 /* original datagram headers: end of icmph to payload (skb->data) */
1353 hlen = -skb_transport_offset(skb) - thlen;
1354
1355 /* per rfc 4884: minimal datagram length of 128 bytes */
1356 if (off < 128 || off < hlen)
1357 return;
1358
1359 /* kernel has stripped headers: return payload offset in bytes */
1360 off -= hlen;
1361 if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1362 return;
1363
1364 out->len = off;
1365
1366 if (!ip_icmp_error_rfc4884_validate(skb, off))
1367 out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1368}
1369EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
1370
1371int icmp_err(struct sk_buff *skb, u32 info)
1372{
1373 struct iphdr *iph = (struct iphdr *)skb->data;
1374 int offset = iph->ihl<<2;
1375 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1376 struct net *net = dev_net_rcu(dev: skb->dev);
1377 int type = icmp_hdr(skb)->type;
1378 int code = icmp_hdr(skb)->code;
1379
1380 /*
1381 * Use ping_err to handle all icmp errors except those
1382 * triggered by ICMP_ECHOREPLY which sent from kernel.
1383 */
1384 if (icmph->type != ICMP_ECHOREPLY) {
1385 ping_err(skb, offset, info);
1386 return 0;
1387 }
1388
1389 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1390 ipv4_update_pmtu(skb, net, mtu: info, oif: 0, IPPROTO_ICMP);
1391 else if (type == ICMP_REDIRECT)
1392 ipv4_redirect(skb, net, oif: 0, IPPROTO_ICMP);
1393
1394 return 0;
1395}
1396
1397/*
1398 * This table is the definition of how we handle ICMP.
1399 */
1400static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1401 [ICMP_ECHOREPLY] = {
1402 .handler = ping_rcv,
1403 },
1404 [1] = {
1405 .handler = icmp_discard,
1406 .error = 1,
1407 },
1408 [2] = {
1409 .handler = icmp_discard,
1410 .error = 1,
1411 },
1412 [ICMP_DEST_UNREACH] = {
1413 .handler = icmp_unreach,
1414 .error = 1,
1415 },
1416 [ICMP_SOURCE_QUENCH] = {
1417 .handler = icmp_unreach,
1418 .error = 1,
1419 },
1420 [ICMP_REDIRECT] = {
1421 .handler = icmp_redirect,
1422 .error = 1,
1423 },
1424 [6] = {
1425 .handler = icmp_discard,
1426 .error = 1,
1427 },
1428 [7] = {
1429 .handler = icmp_discard,
1430 .error = 1,
1431 },
1432 [ICMP_ECHO] = {
1433 .handler = icmp_echo,
1434 },
1435 [9] = {
1436 .handler = icmp_discard,
1437 .error = 1,
1438 },
1439 [10] = {
1440 .handler = icmp_discard,
1441 .error = 1,
1442 },
1443 [ICMP_TIME_EXCEEDED] = {
1444 .handler = icmp_unreach,
1445 .error = 1,
1446 },
1447 [ICMP_PARAMETERPROB] = {
1448 .handler = icmp_unreach,
1449 .error = 1,
1450 },
1451 [ICMP_TIMESTAMP] = {
1452 .handler = icmp_timestamp,
1453 },
1454 [ICMP_TIMESTAMPREPLY] = {
1455 .handler = icmp_discard,
1456 },
1457 [ICMP_INFO_REQUEST] = {
1458 .handler = icmp_discard,
1459 },
1460 [ICMP_INFO_REPLY] = {
1461 .handler = icmp_discard,
1462 },
1463 [ICMP_ADDRESS] = {
1464 .handler = icmp_discard,
1465 },
1466 [ICMP_ADDRESSREPLY] = {
1467 .handler = icmp_discard,
1468 },
1469};
1470
1471static int __net_init icmp_sk_init(struct net *net)
1472{
1473 /* Control parameters for ECHO replies. */
1474 net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1475 net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1476 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1477
1478 /* Control parameter - ignore bogus broadcast responses? */
1479 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1480
1481 /*
1482 * Configurable global rate limit.
1483 *
1484 * ratelimit defines tokens/packet consumed for dst->rate_token
1485 * bucket ratemask defines which icmp types are ratelimited by
1486 * setting it's bit position.
1487 *
1488 * default:
1489 * dest unreachable (3), source quench (4),
1490 * time exceeded (11), parameter problem (12)
1491 */
1492
1493 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1494 net->ipv4.sysctl_icmp_ratemask = 0x1818;
1495 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1496 net->ipv4.sysctl_icmp_msgs_per_sec = 1000;
1497 net->ipv4.sysctl_icmp_msgs_burst = 50;
1498
1499 return 0;
1500}
1501
1502static struct pernet_operations __net_initdata icmp_sk_ops = {
1503 .init = icmp_sk_init,
1504};
1505
1506int __init icmp_init(void)
1507{
1508 int err, i;
1509
1510 for_each_possible_cpu(i) {
1511 struct sock *sk;
1512
1513 err = inet_ctl_sock_create(sk: &sk, PF_INET,
1514 type: SOCK_RAW, IPPROTO_ICMP, net: &init_net);
1515 if (err < 0)
1516 return err;
1517
1518 per_cpu(ipv4_icmp_sk, i) = sk;
1519
1520 /* Enough space for 2 64K ICMP packets, including
1521 * sk_buff/skb_shared_info struct overhead.
1522 */
1523 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1524
1525 /*
1526 * Speedup sock_wfree()
1527 */
1528 sock_set_flag(sk, flag: SOCK_USE_WRITE_QUEUE);
1529 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1530 }
1531 return register_pernet_subsys(&icmp_sk_ops);
1532}
1533

source code of linux/net/ipv4/icmp.c