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
104 struct 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
120 const 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 };
186 EXPORT_SYMBOL(icmp_err_convert);
187
188 /*
189 * ICMP control array. This specifies what to do with each ICMP.
190 */
191
192 struct 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
197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
198
199 static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
200
201 /* Called with BH disabled */
icmp_xmit_lock(struct net * net)202 static 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
icmp_xmit_unlock(struct sock * sk)218 static inline void icmp_xmit_unlock(struct sock *sk)
219 {
220 sock_net_set(sk, &init_net);
221 spin_unlock(&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 */
icmp_global_allow(struct net * net)232 bool 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(&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(&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(&net->ipv4.icmp_global_credit, &old, new));
259 }
260 return true;
261 }
262 EXPORT_SYMBOL(icmp_global_allow);
263
icmp_global_consume(struct net * net)264 void icmp_global_consume(struct net *net)
265 {
266 int credits = get_random_u32_below(3);
267
268 /* Note: this might make icmp_global.credit negative. */
269 if (credits)
270 atomic_sub(credits, &net->ipv4.icmp_global_credit);
271 }
272 EXPORT_SYMBOL(icmp_global_consume);
273
icmpv4_mask_allow(struct net * net,int type,int code)274 static 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
icmpv4_global_allow(struct net * net,int type,int code,bool * apply_ratelimit)290 static 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
icmpv4_xrlim_allow(struct net * net,struct rtable * rt,struct flowi4 * fl4,int type,int code,bool apply_ratelimit)308 static 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 int vif;
316
317 if (!apply_ratelimit)
318 return true;
319
320 /* No rate limit on loopback */
321 if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
322 goto out;
323
324 vif = l3mdev_master_ifindex(dst->dev);
325 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
326 rc = inet_peer_xrlim_allow(peer,
327 READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
328 if (peer)
329 inet_putpeer(peer);
330 out:
331 if (!rc)
332 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
333 else
334 icmp_global_consume(net);
335 return rc;
336 }
337
338 /*
339 * Maintain the counters used in the SNMP statistics for outgoing ICMP
340 */
icmp_out_count(struct net * net,unsigned char type)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 */
icmp_glue_bits(void * from,char * to,int offset,int len,int odd,struct sk_buff * skb)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 = from;
355 __wsum csum;
356
357 csum = skb_copy_and_csum_bits(icmp_param->skb,
358 icmp_param->offset + offset,
359 to, len);
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
icmp_push_reply(struct sock * sk,struct icmp_bxm * icmp_param,struct flowi4 * fl4,struct ipcm_cookie * ipc,struct rtable ** rt)367 static void icmp_push_reply(struct sock *sk,
368 struct icmp_bxm *icmp_param,
369 struct flowi4 *fl4,
370 struct ipcm_cookie *ipc, struct rtable **rt)
371 {
372 struct sk_buff *skb;
373
374 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
375 icmp_param->data_len+icmp_param->head_len,
376 icmp_param->head_len,
377 ipc, rt, MSG_DONTWAIT) < 0) {
378 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
379 ip_flush_pending_frames(sk);
380 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
381 struct icmphdr *icmph = icmp_hdr(skb);
382 __wsum csum;
383 struct sk_buff *skb1;
384
385 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
386 (char *)icmph,
387 icmp_param->head_len);
388 skb_queue_walk(&sk->sk_write_queue, skb1) {
389 csum = csum_add(csum, skb1->csum);
390 }
391 icmph->checksum = csum_fold(csum);
392 skb->ip_summed = CHECKSUM_NONE;
393 ip_push_pending_frames(sk, fl4);
394 }
395 }
396
397 /*
398 * Driving logic for building and sending ICMP messages.
399 */
400
icmp_reply(struct icmp_bxm * icmp_param,struct sk_buff * skb)401 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
402 {
403 struct ipcm_cookie ipc;
404 struct rtable *rt = skb_rtable(skb);
405 struct net *net = dev_net(rt->dst.dev);
406 bool apply_ratelimit = false;
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 icmpv4_global_allow and icmp_xmit_lock */
419 local_bh_disable();
420
421 /* is global icmp_msgs_per_sec exhausted ? */
422 if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
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 ipc.sockc.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 = inet_dscp_to_dsfield(ip4h_dscp(ip_hdr(skb)));
449 fl4.flowi4_proto = IPPROTO_ICMP;
450 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
451 security_skb_classify_flow(skb, flowi4_to_flowi_common(&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, apply_ratelimit))
456 icmp_push_reply(sk, 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 /*
465 * The device used for looking up which routing table to use for sending an ICMP
466 * error is preferably the source whenever it is set, which should ensure the
467 * icmp error can be sent to the source host, else lookup using the routing
468 * table of the destination device, else use the main routing table (index 0).
469 */
icmp_get_route_lookup_dev(struct sk_buff * skb)470 static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
471 {
472 struct net_device *route_lookup_dev = NULL;
473
474 if (skb->dev)
475 route_lookup_dev = skb->dev;
476 else if (skb_dst(skb))
477 route_lookup_dev = skb_dst(skb)->dev;
478 return route_lookup_dev;
479 }
480
icmp_route_lookup(struct net * net,struct flowi4 * fl4,struct sk_buff * skb_in,const struct iphdr * iph,__be32 saddr,dscp_t dscp,u32 mark,int type,int code,struct icmp_bxm * param)481 static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
482 struct sk_buff *skb_in,
483 const struct iphdr *iph, __be32 saddr,
484 dscp_t dscp, u32 mark, int type,
485 int code, struct icmp_bxm *param)
486 {
487 struct net_device *route_lookup_dev;
488 struct dst_entry *dst, *dst2;
489 struct rtable *rt, *rt2;
490 struct flowi4 fl4_dec;
491 int err;
492
493 memset(fl4, 0, sizeof(*fl4));
494 fl4->daddr = (param->replyopts.opt.opt.srr ?
495 param->replyopts.opt.opt.faddr : iph->saddr);
496 fl4->saddr = saddr;
497 fl4->flowi4_mark = mark;
498 fl4->flowi4_uid = sock_net_uid(net, NULL);
499 fl4->flowi4_tos = inet_dscp_to_dsfield(dscp);
500 fl4->flowi4_proto = IPPROTO_ICMP;
501 fl4->fl4_icmp_type = type;
502 fl4->fl4_icmp_code = code;
503 route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
504 fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
505
506 security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
507 rt = ip_route_output_key_hash(net, fl4, skb_in);
508 if (IS_ERR(rt))
509 return rt;
510
511 /* No need to clone since we're just using its address. */
512 rt2 = rt;
513
514 dst = xfrm_lookup(net, &rt->dst,
515 flowi4_to_flowi(fl4), NULL, 0);
516 rt = dst_rtable(dst);
517 if (!IS_ERR(dst)) {
518 if (rt != rt2)
519 return rt;
520 if (inet_addr_type_dev_table(net, route_lookup_dev,
521 fl4->daddr) == RTN_LOCAL)
522 return rt;
523 } else if (PTR_ERR(dst) == -EPERM) {
524 rt = NULL;
525 } else {
526 return rt;
527 }
528 err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
529 if (err)
530 goto relookup_failed;
531
532 if (inet_addr_type_dev_table(net, route_lookup_dev,
533 fl4_dec.saddr) == RTN_LOCAL) {
534 rt2 = __ip_route_output_key(net, &fl4_dec);
535 if (IS_ERR(rt2))
536 err = PTR_ERR(rt2);
537 } else {
538 struct flowi4 fl4_2 = {};
539 unsigned long orefdst;
540
541 fl4_2.daddr = fl4_dec.saddr;
542 rt2 = ip_route_output_key(net, &fl4_2);
543 if (IS_ERR(rt2)) {
544 err = PTR_ERR(rt2);
545 goto relookup_failed;
546 }
547 /* Ugh! */
548 orefdst = skb_in->_skb_refdst; /* save old refdst */
549 skb_dst_set(skb_in, NULL);
550 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
551 dscp, rt2->dst.dev) ? -EINVAL : 0;
552
553 dst_release(&rt2->dst);
554 rt2 = skb_rtable(skb_in);
555 skb_in->_skb_refdst = orefdst; /* restore old refdst */
556 }
557
558 if (err)
559 goto relookup_failed;
560
561 dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
562 XFRM_LOOKUP_ICMP);
563 rt2 = dst_rtable(dst2);
564 if (!IS_ERR(dst2)) {
565 dst_release(&rt->dst);
566 memcpy(fl4, &fl4_dec, sizeof(*fl4));
567 rt = rt2;
568 } else if (PTR_ERR(dst2) == -EPERM) {
569 if (rt)
570 dst_release(&rt->dst);
571 return rt2;
572 } else {
573 err = PTR_ERR(dst2);
574 goto relookup_failed;
575 }
576 return rt;
577
578 relookup_failed:
579 if (rt)
580 return rt;
581 return ERR_PTR(err);
582 }
583
584 /*
585 * Send an ICMP message in response to a situation
586 *
587 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
588 * MAY send more (we do).
589 * MUST NOT change this header information.
590 * MUST NOT reply to a multicast/broadcast IP address.
591 * MUST NOT reply to a multicast/broadcast MAC address.
592 * MUST reply to only the first fragment.
593 */
594
__icmp_send(struct sk_buff * skb_in,int type,int code,__be32 info,const struct ip_options * opt)595 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
596 const struct ip_options *opt)
597 {
598 struct iphdr *iph;
599 int room;
600 struct icmp_bxm icmp_param;
601 struct rtable *rt = skb_rtable(skb_in);
602 bool apply_ratelimit = false;
603 struct ipcm_cookie ipc;
604 struct flowi4 fl4;
605 __be32 saddr;
606 u8 tos;
607 u32 mark;
608 struct net *net;
609 struct sock *sk;
610
611 if (!rt)
612 goto out;
613
614 if (rt->dst.dev)
615 net = dev_net(rt->dst.dev);
616 else if (skb_in->dev)
617 net = dev_net(skb_in->dev);
618 else
619 goto out;
620
621 /*
622 * Find the original header. It is expected to be valid, of course.
623 * Check this, icmp_send is called from the most obscure devices
624 * sometimes.
625 */
626 iph = ip_hdr(skb_in);
627
628 if ((u8 *)iph < skb_in->head ||
629 (skb_network_header(skb_in) + sizeof(*iph)) >
630 skb_tail_pointer(skb_in))
631 goto out;
632
633 /*
634 * No replies to physical multicast/broadcast
635 */
636 if (skb_in->pkt_type != PACKET_HOST)
637 goto out;
638
639 /*
640 * Now check at the protocol level
641 */
642 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
643 goto out;
644
645 /*
646 * Only reply to fragment 0. We byte re-order the constant
647 * mask for efficiency.
648 */
649 if (iph->frag_off & htons(IP_OFFSET))
650 goto out;
651
652 /*
653 * If we send an ICMP error to an ICMP error a mess would result..
654 */
655 if (icmp_pointers[type].error) {
656 /*
657 * We are an error, check if we are replying to an
658 * ICMP error
659 */
660 if (iph->protocol == IPPROTO_ICMP) {
661 u8 _inner_type, *itp;
662
663 itp = skb_header_pointer(skb_in,
664 skb_network_header(skb_in) +
665 (iph->ihl << 2) +
666 offsetof(struct icmphdr,
667 type) -
668 skb_in->data,
669 sizeof(_inner_type),
670 &_inner_type);
671 if (!itp)
672 goto out;
673
674 /*
675 * Assume any unknown ICMP type is an error. This
676 * isn't specified by the RFC, but think about it..
677 */
678 if (*itp > NR_ICMP_TYPES ||
679 icmp_pointers[*itp].error)
680 goto out;
681 }
682 }
683
684 /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
685 local_bh_disable();
686
687 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
688 * incoming dev is loopback. If outgoing dev change to not be
689 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
690 */
691 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
692 !icmpv4_global_allow(net, type, code, &apply_ratelimit))
693 goto out_bh_enable;
694
695 sk = icmp_xmit_lock(net);
696 if (!sk)
697 goto out_bh_enable;
698
699 /*
700 * Construct source address and options.
701 */
702
703 saddr = iph->daddr;
704 if (!(rt->rt_flags & RTCF_LOCAL)) {
705 struct net_device *dev = NULL;
706
707 rcu_read_lock();
708 if (rt_is_input_route(rt) &&
709 READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
710 dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
711
712 if (dev)
713 saddr = inet_select_addr(dev, iph->saddr,
714 RT_SCOPE_LINK);
715 else
716 saddr = 0;
717 rcu_read_unlock();
718 }
719
720 tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
721 IPTOS_PREC_INTERNETCONTROL) :
722 iph->tos;
723 mark = IP4_REPLY_MARK(net, skb_in->mark);
724
725 if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
726 goto out_unlock;
727
728
729 /*
730 * Prepare data for ICMP header.
731 */
732
733 icmp_param.data.icmph.type = type;
734 icmp_param.data.icmph.code = code;
735 icmp_param.data.icmph.un.gateway = info;
736 icmp_param.data.icmph.checksum = 0;
737 icmp_param.skb = skb_in;
738 icmp_param.offset = skb_network_offset(skb_in);
739 inet_sk(sk)->tos = tos;
740 ipcm_init(&ipc);
741 ipc.addr = iph->saddr;
742 ipc.opt = &icmp_param.replyopts.opt;
743 ipc.sockc.mark = mark;
744
745 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr,
746 inet_dsfield_to_dscp(tos), mark, type, code,
747 &icmp_param);
748 if (IS_ERR(rt))
749 goto out_unlock;
750
751 /* peer icmp_ratelimit */
752 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
753 goto ende;
754
755 /* RFC says return as much as we can without exceeding 576 bytes. */
756
757 room = dst_mtu(&rt->dst);
758 if (room > 576)
759 room = 576;
760 room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
761 room -= sizeof(struct icmphdr);
762 /* Guard against tiny mtu. We need to include at least one
763 * IP network header for this message to make any sense.
764 */
765 if (room <= (int)sizeof(struct iphdr))
766 goto ende;
767
768 icmp_param.data_len = skb_in->len - icmp_param.offset;
769 if (icmp_param.data_len > room)
770 icmp_param.data_len = room;
771 icmp_param.head_len = sizeof(struct icmphdr);
772
773 /* if we don't have a source address at this point, fall back to the
774 * dummy address instead of sending out a packet with a source address
775 * of 0.0.0.0
776 */
777 if (!fl4.saddr)
778 fl4.saddr = htonl(INADDR_DUMMY);
779
780 trace_icmp_send(skb_in, type, code);
781
782 icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
783 ende:
784 ip_rt_put(rt);
785 out_unlock:
786 icmp_xmit_unlock(sk);
787 out_bh_enable:
788 local_bh_enable();
789 out:;
790 }
791 EXPORT_SYMBOL(__icmp_send);
792
793 #if IS_ENABLED(CONFIG_NF_NAT)
794 #include <net/netfilter/nf_conntrack.h>
icmp_ndo_send(struct sk_buff * skb_in,int type,int code,__be32 info)795 void 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_in, &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_in))
810 skb_in = cloned_skb = skb_clone(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_in)->saddr;
819 ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
820 __icmp_send(skb_in, type, code, info, &opts);
821 ip_hdr(skb_in)->saddr = orig_ip;
822 out:
823 consume_skb(cloned_skb);
824 }
825 EXPORT_SYMBOL(icmp_ndo_send);
826 #endif
827
icmp_socket_deliver(struct sk_buff * skb,u32 info)828 static 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, iph->ihl * 4 + 8)) {
838 __ICMP_INC_STATS(dev_net(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
icmp_tag_validation(int proto)849 static 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
icmp_unreach(struct sk_buff * skb)864 static 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(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, 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(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, skb->dev, 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
968 out:
969 return reason;
970 out_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
icmp_redirect(struct sk_buff * skb)980 static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
981 {
982 if (skb->len < sizeof(struct iphdr)) {
983 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
984 return SKB_DROP_REASON_PKT_TOO_SMALL;
985 }
986
987 if (!pskb_may_pull(skb, 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
icmp_echo(struct sk_buff * skb)1010 static 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(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, &icmp_param.data.icmph))
1029 return SKB_NOT_DROPPED_YET;
1030
1031 icmp_reply(&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
icmp_build_probe(struct sk_buff * skb,struct icmphdr * icmphdr)1042 bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1043 {
1044 struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1045 struct icmp_ext_echo_iio *iio, _iio;
1046 struct net *net = dev_net(skb->dev);
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, 0, sizeof(_ext_hdr), &_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, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_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, sizeof(_ext_hdr),
1080 sizeof(iio->extobj_hdr) + ident_len, &_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, 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, 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(&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;
1144 send_mal_query:
1145 icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1146 return true;
1147 }
1148 EXPORT_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 */
icmp_timestamp(struct sk_buff * skb)1157 static 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, skb);
1182 return SKB_NOT_DROPPED_YET;
1183
1184 out_err:
1185 __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1186 return SKB_DROP_REASON_PKT_TOO_SMALL;
1187 }
1188
icmp_discard(struct sk_buff * skb)1189 static 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 */
icmp_rcv(struct sk_buff * skb)1198 int 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(rt->dst.dev);
1203 struct icmphdr *icmph;
1204
1205 if (!xfrm4_policy_check(NULL, 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, sizeof(*icmph) + sizeof(struct iphdr)))
1216 goto drop;
1217
1218 nh = skb_network_offset(skb);
1219 skb_set_network_header(skb, sizeof(*icmph));
1220
1221 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
1222 skb)) {
1223 reason = SKB_DROP_REASON_XFRM_POLICY;
1224 goto drop;
1225 }
1226
1227 skb_set_network_header(skb, 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, 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 if (icmph->type == ICMP_EXT_ECHOREPLY) {
1252 reason = ping_rcv(skb);
1253 goto reason_check;
1254 }
1255
1256 /*
1257 * 18 is the highest 'known' ICMP type. Anything else is a mystery
1258 *
1259 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
1260 * discarded.
1261 */
1262 if (icmph->type > NR_ICMP_TYPES) {
1263 reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1264 goto error;
1265 }
1266
1267 /*
1268 * Parse the ICMP message
1269 */
1270
1271 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1272 /*
1273 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1274 * silently ignored (we let user decide with a sysctl).
1275 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1276 * discarded if to broadcast/multicast.
1277 */
1278 if ((icmph->type == ICMP_ECHO ||
1279 icmph->type == ICMP_TIMESTAMP) &&
1280 READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1281 reason = SKB_DROP_REASON_INVALID_PROTO;
1282 goto error;
1283 }
1284 if (icmph->type != ICMP_ECHO &&
1285 icmph->type != ICMP_TIMESTAMP &&
1286 icmph->type != ICMP_ADDRESS &&
1287 icmph->type != ICMP_ADDRESSREPLY) {
1288 reason = SKB_DROP_REASON_INVALID_PROTO;
1289 goto error;
1290 }
1291 }
1292
1293 reason = icmp_pointers[icmph->type].handler(skb);
1294 reason_check:
1295 if (!reason) {
1296 consume_skb(skb);
1297 return NET_RX_SUCCESS;
1298 }
1299
1300 drop:
1301 kfree_skb_reason(skb, reason);
1302 return NET_RX_DROP;
1303 csum_error:
1304 reason = SKB_DROP_REASON_ICMP_CSUM;
1305 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1306 error:
1307 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1308 goto drop;
1309 }
1310
ip_icmp_error_rfc4884_validate(const struct sk_buff * skb,int off)1311 static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1312 {
1313 struct icmp_extobj_hdr *objh, _objh;
1314 struct icmp_ext_hdr *exth, _exth;
1315 u16 olen;
1316
1317 exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
1318 if (!exth)
1319 return false;
1320 if (exth->version != 2)
1321 return true;
1322
1323 if (exth->checksum &&
1324 csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
1325 return false;
1326
1327 off += sizeof(_exth);
1328 while (off < skb->len) {
1329 objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
1330 if (!objh)
1331 return false;
1332
1333 olen = ntohs(objh->length);
1334 if (olen < sizeof(_objh))
1335 return false;
1336
1337 off += olen;
1338 if (off > skb->len)
1339 return false;
1340 }
1341
1342 return true;
1343 }
1344
ip_icmp_error_rfc4884(const struct sk_buff * skb,struct sock_ee_data_rfc4884 * out,int thlen,int off)1345 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1346 struct sock_ee_data_rfc4884 *out,
1347 int thlen, int off)
1348 {
1349 int hlen;
1350
1351 /* original datagram headers: end of icmph to payload (skb->data) */
1352 hlen = -skb_transport_offset(skb) - thlen;
1353
1354 /* per rfc 4884: minimal datagram length of 128 bytes */
1355 if (off < 128 || off < hlen)
1356 return;
1357
1358 /* kernel has stripped headers: return payload offset in bytes */
1359 off -= hlen;
1360 if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1361 return;
1362
1363 out->len = off;
1364
1365 if (!ip_icmp_error_rfc4884_validate(skb, off))
1366 out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1367 }
1368 EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
1369
icmp_err(struct sk_buff * skb,u32 info)1370 int icmp_err(struct sk_buff *skb, u32 info)
1371 {
1372 struct iphdr *iph = (struct iphdr *)skb->data;
1373 int offset = iph->ihl<<2;
1374 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1375 int type = icmp_hdr(skb)->type;
1376 int code = icmp_hdr(skb)->code;
1377 struct net *net = dev_net(skb->dev);
1378
1379 /*
1380 * Use ping_err to handle all icmp errors except those
1381 * triggered by ICMP_ECHOREPLY which sent from kernel.
1382 */
1383 if (icmph->type != ICMP_ECHOREPLY) {
1384 ping_err(skb, offset, info);
1385 return 0;
1386 }
1387
1388 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1389 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1390 else if (type == ICMP_REDIRECT)
1391 ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1392
1393 return 0;
1394 }
1395
1396 /*
1397 * This table is the definition of how we handle ICMP.
1398 */
1399 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1400 [ICMP_ECHOREPLY] = {
1401 .handler = ping_rcv,
1402 },
1403 [1] = {
1404 .handler = icmp_discard,
1405 .error = 1,
1406 },
1407 [2] = {
1408 .handler = icmp_discard,
1409 .error = 1,
1410 },
1411 [ICMP_DEST_UNREACH] = {
1412 .handler = icmp_unreach,
1413 .error = 1,
1414 },
1415 [ICMP_SOURCE_QUENCH] = {
1416 .handler = icmp_unreach,
1417 .error = 1,
1418 },
1419 [ICMP_REDIRECT] = {
1420 .handler = icmp_redirect,
1421 .error = 1,
1422 },
1423 [6] = {
1424 .handler = icmp_discard,
1425 .error = 1,
1426 },
1427 [7] = {
1428 .handler = icmp_discard,
1429 .error = 1,
1430 },
1431 [ICMP_ECHO] = {
1432 .handler = icmp_echo,
1433 },
1434 [9] = {
1435 .handler = icmp_discard,
1436 .error = 1,
1437 },
1438 [10] = {
1439 .handler = icmp_discard,
1440 .error = 1,
1441 },
1442 [ICMP_TIME_EXCEEDED] = {
1443 .handler = icmp_unreach,
1444 .error = 1,
1445 },
1446 [ICMP_PARAMETERPROB] = {
1447 .handler = icmp_unreach,
1448 .error = 1,
1449 },
1450 [ICMP_TIMESTAMP] = {
1451 .handler = icmp_timestamp,
1452 },
1453 [ICMP_TIMESTAMPREPLY] = {
1454 .handler = icmp_discard,
1455 },
1456 [ICMP_INFO_REQUEST] = {
1457 .handler = icmp_discard,
1458 },
1459 [ICMP_INFO_REPLY] = {
1460 .handler = icmp_discard,
1461 },
1462 [ICMP_ADDRESS] = {
1463 .handler = icmp_discard,
1464 },
1465 [ICMP_ADDRESSREPLY] = {
1466 .handler = icmp_discard,
1467 },
1468 };
1469
icmp_sk_init(struct net * net)1470 static int __net_init icmp_sk_init(struct net *net)
1471 {
1472 /* Control parameters for ECHO replies. */
1473 net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1474 net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1475 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1476
1477 /* Control parameter - ignore bogus broadcast responses? */
1478 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1479
1480 /*
1481 * Configurable global rate limit.
1482 *
1483 * ratelimit defines tokens/packet consumed for dst->rate_token
1484 * bucket ratemask defines which icmp types are ratelimited by
1485 * setting it's bit position.
1486 *
1487 * default:
1488 * dest unreachable (3), source quench (4),
1489 * time exceeded (11), parameter problem (12)
1490 */
1491
1492 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1493 net->ipv4.sysctl_icmp_ratemask = 0x1818;
1494 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1495 net->ipv4.sysctl_icmp_msgs_per_sec = 1000;
1496 net->ipv4.sysctl_icmp_msgs_burst = 50;
1497
1498 return 0;
1499 }
1500
1501 static struct pernet_operations __net_initdata icmp_sk_ops = {
1502 .init = icmp_sk_init,
1503 };
1504
icmp_init(void)1505 int __init icmp_init(void)
1506 {
1507 int err, i;
1508
1509 for_each_possible_cpu(i) {
1510 struct sock *sk;
1511
1512 err = inet_ctl_sock_create(&sk, PF_INET,
1513 SOCK_RAW, IPPROTO_ICMP, &init_net);
1514 if (err < 0)
1515 return err;
1516
1517 per_cpu(ipv4_icmp_sk, i) = sk;
1518
1519 /* Enough space for 2 64K ICMP packets, including
1520 * sk_buff/skb_shared_info struct overhead.
1521 */
1522 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1523
1524 /*
1525 * Speedup sock_wfree()
1526 */
1527 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1528 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1529 }
1530 return register_pernet_subsys(&icmp_sk_ops);
1531 }
1532