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/nospec.h>
68 #include <linux/socket.h>
69 #include <linux/in.h>
70 #include <linux/inet.h>
71 #include <linux/inetdevice.h>
72 #include <linux/netdevice.h>
73 #include <linux/string.h>
74 #include <linux/netfilter_ipv4.h>
75 #include <linux/slab.h>
76 #include <net/flow.h>
77 #include <net/snmp.h>
78 #include <net/ip.h>
79 #include <net/route.h>
80 #include <net/protocol.h>
81 #include <net/icmp.h>
82 #include <net/tcp.h>
83 #include <net/udp.h>
84 #include <net/raw.h>
85 #include <net/ping.h>
86 #include <linux/skbuff.h>
87 #include <net/sock.h>
88 #include <linux/errno.h>
89 #include <linux/timer.h>
90 #include <linux/init.h>
91 #include <linux/uaccess.h>
92 #include <net/checksum.h>
93 #include <net/xfrm.h>
94 #include <net/inet_common.h>
95 #include <net/ip_fib.h>
96 #include <net/l3mdev.h>
97 #include <net/addrconf.h>
98 #include <net/inet_dscp.h>
99 #define CREATE_TRACE_POINTS
100 #include <trace/events/icmp.h>
101
102 /*
103 * Build xmit assembly blocks
104 */
105
106 struct icmp_bxm {
107 struct sk_buff *skb;
108 int offset;
109 int data_len;
110
111 struct {
112 struct icmphdr icmph;
113 __be32 times[3];
114 } data;
115 int head_len;
116
117 /* Must be last as it ends in a flexible-array member. */
118 struct ip_options_rcu replyopts;
119 };
120
121 /* An array of errno for error messages from dest unreach. */
122 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
123
124 const struct icmp_err icmp_err_convert[] = {
125 {
126 .errno = ENETUNREACH, /* ICMP_NET_UNREACH */
127 .fatal = 0,
128 },
129 {
130 .errno = EHOSTUNREACH, /* ICMP_HOST_UNREACH */
131 .fatal = 0,
132 },
133 {
134 .errno = ENOPROTOOPT /* ICMP_PROT_UNREACH */,
135 .fatal = 1,
136 },
137 {
138 .errno = ECONNREFUSED, /* ICMP_PORT_UNREACH */
139 .fatal = 1,
140 },
141 {
142 .errno = EMSGSIZE, /* ICMP_FRAG_NEEDED */
143 .fatal = 0,
144 },
145 {
146 .errno = EOPNOTSUPP, /* ICMP_SR_FAILED */
147 .fatal = 0,
148 },
149 {
150 .errno = ENETUNREACH, /* ICMP_NET_UNKNOWN */
151 .fatal = 1,
152 },
153 {
154 .errno = EHOSTDOWN, /* ICMP_HOST_UNKNOWN */
155 .fatal = 1,
156 },
157 {
158 .errno = ENONET, /* ICMP_HOST_ISOLATED */
159 .fatal = 1,
160 },
161 {
162 .errno = ENETUNREACH, /* ICMP_NET_ANO */
163 .fatal = 1,
164 },
165 {
166 .errno = EHOSTUNREACH, /* ICMP_HOST_ANO */
167 .fatal = 1,
168 },
169 {
170 .errno = ENETUNREACH, /* ICMP_NET_UNR_TOS */
171 .fatal = 0,
172 },
173 {
174 .errno = EHOSTUNREACH, /* ICMP_HOST_UNR_TOS */
175 .fatal = 0,
176 },
177 {
178 .errno = EHOSTUNREACH, /* ICMP_PKT_FILTERED */
179 .fatal = 1,
180 },
181 {
182 .errno = EHOSTUNREACH, /* ICMP_PREC_VIOLATION */
183 .fatal = 1,
184 },
185 {
186 .errno = EHOSTUNREACH, /* ICMP_PREC_CUTOFF */
187 .fatal = 1,
188 },
189 };
190 EXPORT_SYMBOL(icmp_err_convert);
191
192 /*
193 * ICMP control array. This specifies what to do with each ICMP.
194 */
195
196 struct icmp_control {
197 enum skb_drop_reason (*handler)(struct sk_buff *skb);
198 short error; /* This ICMP is classed as an error message */
199 };
200
201 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
202
203 static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
204
205 /* Called with BH disabled */
icmp_xmit_lock(struct net * net)206 static inline struct sock *icmp_xmit_lock(struct net *net)
207 {
208 struct sock *sk;
209
210 sk = this_cpu_read(ipv4_icmp_sk);
211
212 if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
213 /* This can happen if the output path signals a
214 * dst_link_failure() for an outgoing ICMP packet.
215 */
216 return NULL;
217 }
218 sock_net_set(sk, net);
219 return sk;
220 }
221
icmp_xmit_unlock(struct sock * sk)222 static inline void icmp_xmit_unlock(struct sock *sk)
223 {
224 sock_net_set(sk, &init_net);
225 spin_unlock(&sk->sk_lock.slock);
226 }
227
228 /**
229 * icmp_global_allow - Are we allowed to send one more ICMP message ?
230 * @net: network namespace
231 *
232 * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
233 * Returns false if we reached the limit and can not send another packet.
234 * Works in tandem with icmp_global_consume().
235 */
icmp_global_allow(struct net * net)236 bool icmp_global_allow(struct net *net)
237 {
238 u32 delta, now, oldstamp;
239 int incr, new, old;
240
241 /* Note: many cpus could find this condition true.
242 * Then later icmp_global_consume() could consume more credits,
243 * this is an acceptable race.
244 */
245 if (atomic_read(&net->ipv4.icmp_global_credit) > 0)
246 return true;
247
248 now = jiffies;
249 oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
250 delta = min_t(u32, now - oldstamp, HZ);
251 if (delta < HZ / 50)
252 return false;
253
254 incr = READ_ONCE(net->ipv4.sysctl_icmp_msgs_per_sec);
255 incr = div_u64((u64)incr * delta, HZ);
256 if (!incr)
257 return false;
258
259 if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
260 old = atomic_read(&net->ipv4.icmp_global_credit);
261 do {
262 new = min(old + incr, READ_ONCE(net->ipv4.sysctl_icmp_msgs_burst));
263 } while (!atomic_try_cmpxchg(&net->ipv4.icmp_global_credit, &old, new));
264 }
265 return true;
266 }
267
icmp_global_consume(struct net * net)268 void icmp_global_consume(struct net *net)
269 {
270 int credits = get_random_u32_below(3);
271
272 /* Note: this might make icmp_global.credit negative. */
273 if (credits)
274 atomic_sub(credits, &net->ipv4.icmp_global_credit);
275 }
276
icmpv4_mask_allow(struct net * net,int type,int code)277 static bool icmpv4_mask_allow(struct net *net, int type, int code)
278 {
279 if (type > NR_ICMP_TYPES)
280 return true;
281
282 /* Don't limit PMTU discovery. */
283 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
284 return true;
285
286 /* Limit if icmp type is enabled in ratemask. */
287 if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
288 return true;
289
290 return false;
291 }
292
icmpv4_global_allow(struct net * net,int type,int code,bool * apply_ratelimit)293 static bool icmpv4_global_allow(struct net *net, int type, int code,
294 bool *apply_ratelimit)
295 {
296 if (icmpv4_mask_allow(net, type, code))
297 return true;
298
299 if (icmp_global_allow(net)) {
300 *apply_ratelimit = true;
301 return true;
302 }
303 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
304 return false;
305 }
306
307 /*
308 * Send an ICMP frame.
309 */
310
icmpv4_xrlim_allow(struct net * net,struct rtable * rt,struct flowi4 * fl4,int type,int code,bool apply_ratelimit)311 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
312 struct flowi4 *fl4, int type, int code,
313 bool apply_ratelimit)
314 {
315 struct dst_entry *dst = &rt->dst;
316 struct inet_peer *peer;
317 struct net_device *dev;
318 int peer_timeout;
319 bool rc = true;
320
321 if (!apply_ratelimit)
322 return true;
323
324 peer_timeout = READ_ONCE(net->ipv4.sysctl_icmp_ratelimit);
325 if (!peer_timeout)
326 goto out;
327
328 /* No rate limit on loopback */
329 rcu_read_lock();
330 dev = dst_dev_rcu(dst);
331 if (dev && (dev->flags & IFF_LOOPBACK))
332 goto out_unlock;
333
334 peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
335 l3mdev_master_ifindex_rcu(dev));
336 rc = inet_peer_xrlim_allow(peer, peer_timeout);
337
338 out_unlock:
339 rcu_read_unlock();
340 out:
341 if (!rc)
342 __ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
343 else
344 icmp_global_consume(net);
345 return rc;
346 }
347
348 /*
349 * Maintain the counters used in the SNMP statistics for outgoing ICMP
350 */
icmp_out_count(struct net * net,unsigned char type)351 void icmp_out_count(struct net *net, unsigned char type)
352 {
353 ICMPMSGOUT_INC_STATS(net, type);
354 ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
355 }
356
357 /*
358 * Checksum each fragment, and on the first include the headers and final
359 * checksum.
360 */
icmp_glue_bits(void * from,char * to,int offset,int len,int odd,struct sk_buff * skb)361 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
362 struct sk_buff *skb)
363 {
364 DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
365 IP_OPTIONS_DATA_FIXED_SIZE);
366 __wsum csum;
367
368 icmp_param = from;
369
370 csum = skb_copy_and_csum_bits(icmp_param->skb,
371 icmp_param->offset + offset,
372 to, len);
373
374 skb->csum = csum_block_add(skb->csum, csum, odd);
375 if (icmp_param->data.icmph.type <= NR_ICMP_TYPES &&
376 icmp_pointers[array_index_nospec(icmp_param->data.icmph.type,
377 NR_ICMP_TYPES + 1)].error)
378 nf_ct_attach(skb, icmp_param->skb);
379 return 0;
380 }
381
icmp_push_reply(struct sock * sk,struct icmp_bxm * icmp_param,struct flowi4 * fl4,struct ipcm_cookie * ipc,struct rtable ** rt)382 static void icmp_push_reply(struct sock *sk,
383 struct icmp_bxm *icmp_param,
384 struct flowi4 *fl4,
385 struct ipcm_cookie *ipc, struct rtable **rt)
386 {
387 struct sk_buff *skb;
388
389 if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
390 icmp_param->data_len+icmp_param->head_len,
391 icmp_param->head_len,
392 ipc, rt, MSG_DONTWAIT) < 0) {
393 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
394 ip_flush_pending_frames(sk);
395 } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
396 struct icmphdr *icmph = icmp_hdr(skb);
397 __wsum csum;
398 struct sk_buff *skb1;
399
400 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
401 (char *)icmph,
402 icmp_param->head_len);
403 skb_queue_walk(&sk->sk_write_queue, skb1) {
404 csum = csum_add(csum, skb1->csum);
405 }
406 icmph->checksum = csum_fold(csum);
407 skb->ip_summed = CHECKSUM_NONE;
408 ip_push_pending_frames(sk, fl4);
409 }
410 }
411
412 /*
413 * Driving logic for building and sending ICMP messages.
414 */
415
icmp_reply(struct icmp_bxm * icmp_param,struct sk_buff * skb)416 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
417 {
418 struct rtable *rt = skb_rtable(skb);
419 struct net *net = dev_net_rcu(rt->dst.dev);
420 bool apply_ratelimit = false;
421 struct ipcm_cookie ipc;
422 struct flowi4 fl4;
423 struct sock *sk;
424 __be32 daddr, saddr;
425 u32 mark = IP4_REPLY_MARK(net, skb->mark);
426 int type = icmp_param->data.icmph.type;
427 int code = icmp_param->data.icmph.code;
428
429 if (ip_options_echo(net, &icmp_param->replyopts.opt, skb))
430 return;
431
432 /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
433 local_bh_disable();
434
435 /* is global icmp_msgs_per_sec exhausted ? */
436 if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
437 goto out_bh_enable;
438
439 sk = icmp_xmit_lock(net);
440 if (!sk)
441 goto out_bh_enable;
442
443 icmp_param->data.icmph.checksum = 0;
444
445 ipcm_init(&ipc);
446 ipc.tos = ip_hdr(skb)->tos;
447 ipc.sockc.mark = mark;
448 daddr = ipc.addr = ip_hdr(skb)->saddr;
449 saddr = fib_compute_spec_dst(skb);
450
451 if (icmp_param->replyopts.opt.optlen) {
452 ipc.opt = &icmp_param->replyopts;
453 if (ipc.opt->opt.srr)
454 daddr = icmp_param->replyopts.opt.faddr;
455 }
456 memset(&fl4, 0, sizeof(fl4));
457 fl4.daddr = daddr;
458 fl4.saddr = saddr;
459 fl4.flowi4_mark = mark;
460 fl4.flowi4_uid = sock_net_uid(net, NULL);
461 fl4.flowi4_dscp = ip4h_dscp(ip_hdr(skb));
462 fl4.flowi4_proto = IPPROTO_ICMP;
463 fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
464 security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
465 rt = ip_route_output_key(net, &fl4);
466 if (IS_ERR(rt))
467 goto out_unlock;
468 if (icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
469 icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
470 ip_rt_put(rt);
471 out_unlock:
472 icmp_xmit_unlock(sk);
473 out_bh_enable:
474 local_bh_enable();
475 }
476
477 /*
478 * The device used for looking up which routing table to use for sending an ICMP
479 * error is preferably the source whenever it is set, which should ensure the
480 * icmp error can be sent to the source host, else lookup using the routing
481 * table of the destination device, else use the main routing table (index 0).
482 */
icmp_get_route_lookup_dev(struct sk_buff * skb)483 static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
484 {
485 struct net_device *dev = skb->dev;
486 const struct dst_entry *dst;
487
488 if (dev)
489 return dev;
490 dst = skb_dst(skb);
491 return dst ? dst_dev(dst) : NULL;
492 }
493
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)494 static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
495 struct sk_buff *skb_in,
496 const struct iphdr *iph, __be32 saddr,
497 dscp_t dscp, u32 mark, int type,
498 int code, struct icmp_bxm *param)
499 {
500 struct net_device *route_lookup_dev;
501 struct dst_entry *dst, *dst2;
502 struct rtable *rt, *rt2;
503 struct flowi4 fl4_dec;
504 int err;
505
506 memset(fl4, 0, sizeof(*fl4));
507 fl4->daddr = (param->replyopts.opt.srr ?
508 param->replyopts.opt.faddr : iph->saddr);
509 fl4->saddr = saddr;
510 fl4->flowi4_mark = mark;
511 fl4->flowi4_uid = sock_net_uid(net, NULL);
512 fl4->flowi4_dscp = dscp;
513 fl4->flowi4_proto = IPPROTO_ICMP;
514 fl4->fl4_icmp_type = type;
515 fl4->fl4_icmp_code = code;
516 route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
517 fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
518
519 security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
520 rt = ip_route_output_key_hash(net, fl4, skb_in);
521 if (IS_ERR(rt))
522 return rt;
523
524 /* No need to clone since we're just using its address. */
525 rt2 = rt;
526
527 dst = xfrm_lookup(net, &rt->dst,
528 flowi4_to_flowi(fl4), NULL, 0);
529 rt = dst_rtable(dst);
530 if (!IS_ERR(dst)) {
531 if (rt != rt2)
532 return rt;
533 if (inet_addr_type_dev_table(net, route_lookup_dev,
534 fl4->daddr) == RTN_LOCAL)
535 return rt;
536 } else if (PTR_ERR(dst) == -EPERM) {
537 rt = NULL;
538 } else {
539 return rt;
540 }
541 err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
542 if (err)
543 goto relookup_failed;
544
545 if (inet_addr_type_dev_table(net, route_lookup_dev,
546 fl4_dec.saddr) == RTN_LOCAL) {
547 rt2 = __ip_route_output_key(net, &fl4_dec);
548 if (IS_ERR(rt2))
549 err = PTR_ERR(rt2);
550 } else {
551 struct flowi4 fl4_2 = fl4_dec;
552 unsigned long orefdst;
553
554 swap(fl4_2.daddr, fl4_2.saddr);
555 switch (fl4_2.flowi4_proto) {
556 case IPPROTO_TCP:
557 case IPPROTO_UDP:
558 case IPPROTO_SCTP:
559 case IPPROTO_DCCP:
560 swap(fl4_2.fl4_sport, fl4_2.fl4_dport);
561 break;
562 }
563
564 fl4_2.flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
565 fl4_2.flowi4_flags |= FLOWI_FLAG_ANYSRC;
566
567 rt2 = __ip_route_output_key(net, &fl4_2);
568 if (IS_ERR(rt2)) {
569 err = PTR_ERR(rt2);
570 goto relookup_failed;
571 }
572 /* Ugh! */
573 orefdst = skb_dstref_steal(skb_in);
574 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
575 dscp, rt2->dst.dev) ? -EINVAL : 0;
576
577 dst_release(&rt2->dst);
578 rt2 = skb_rtable(skb_in);
579 /* steal dst entry from skb_in, don't drop refcnt */
580 skb_dstref_steal(skb_in);
581 skb_dstref_restore(skb_in, orefdst);
582
583 /*
584 * At this point, fl4_dec.daddr should NOT be local (we
585 * checked fl4_dec.saddr above). However, a race condition
586 * may occur if the address is added to the interface
587 * concurrently. In that case, ip_route_input() returns a
588 * LOCAL route with dst.output=ip_rt_bug, which must not
589 * be used for output.
590 */
591 if (!err && rt2 && rt2->rt_type == RTN_LOCAL) {
592 net_warn_ratelimited("detected local route for %pI4 during ICMP sending, src %pI4\n",
593 &fl4_dec.daddr, &fl4_dec.saddr);
594 dst_release(&rt2->dst);
595 err = -EINVAL;
596 }
597 }
598
599 if (err)
600 goto relookup_failed;
601
602 dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
603 XFRM_LOOKUP_ICMP);
604 rt2 = dst_rtable(dst2);
605 if (!IS_ERR(dst2)) {
606 dst_release(&rt->dst);
607 rt = rt2;
608 } else if (PTR_ERR(dst2) == -EPERM) {
609 if (rt)
610 dst_release(&rt->dst);
611 return rt2;
612 } else {
613 err = PTR_ERR(dst2);
614 goto relookup_failed;
615 }
616 return rt;
617
618 relookup_failed:
619 if (rt)
620 return rt;
621 return ERR_PTR(err);
622 }
623
624 struct icmp_ext_iio_addr4_subobj {
625 __be16 afi;
626 __be16 reserved;
627 __be32 addr4;
628 };
629
icmp_ext_iio_len(void)630 static unsigned int icmp_ext_iio_len(void)
631 {
632 return sizeof(struct icmp_extobj_hdr) +
633 /* ifIndex */
634 sizeof(__be32) +
635 /* Interface Address Sub-Object */
636 sizeof(struct icmp_ext_iio_addr4_subobj) +
637 /* Interface Name Sub-Object. Length must be a multiple of 4
638 * bytes.
639 */
640 ALIGN(sizeof(struct icmp_ext_iio_name_subobj), 4) +
641 /* MTU */
642 sizeof(__be32);
643 }
644
icmp_ext_max_len(u8 ext_objs)645 static unsigned int icmp_ext_max_len(u8 ext_objs)
646 {
647 unsigned int ext_max_len;
648
649 ext_max_len = sizeof(struct icmp_ext_hdr);
650
651 if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
652 ext_max_len += icmp_ext_iio_len();
653
654 return ext_max_len;
655 }
656
icmp_ext_iio_addr4_find(const struct net_device * dev)657 static __be32 icmp_ext_iio_addr4_find(const struct net_device *dev)
658 {
659 struct in_device *in_dev;
660 struct in_ifaddr *ifa;
661
662 in_dev = __in_dev_get_rcu(dev);
663 if (!in_dev)
664 return 0;
665
666 /* It is unclear from RFC 5837 which IP address should be chosen, but
667 * it makes sense to choose a global unicast address.
668 */
669 in_dev_for_each_ifa_rcu(ifa, in_dev) {
670 if (READ_ONCE(ifa->ifa_flags) & IFA_F_SECONDARY)
671 continue;
672 if (ifa->ifa_scope != RT_SCOPE_UNIVERSE ||
673 ipv4_is_multicast(ifa->ifa_address))
674 continue;
675 return ifa->ifa_address;
676 }
677
678 return 0;
679 }
680
icmp_ext_iio_iif_append(struct net * net,struct sk_buff * skb,int iif)681 static void icmp_ext_iio_iif_append(struct net *net, struct sk_buff *skb,
682 int iif)
683 {
684 struct icmp_ext_iio_name_subobj *name_subobj;
685 struct icmp_extobj_hdr *objh;
686 struct net_device *dev;
687 __be32 data;
688
689 if (!iif)
690 return;
691
692 /* Add the fields in the order specified by RFC 5837. */
693 objh = skb_put(skb, sizeof(*objh));
694 objh->class_num = ICMP_EXT_OBJ_CLASS_IIO;
695 objh->class_type = ICMP_EXT_CTYPE_IIO_ROLE(ICMP_EXT_CTYPE_IIO_ROLE_IIF);
696
697 data = htonl(iif);
698 skb_put_data(skb, &data, sizeof(__be32));
699 objh->class_type |= ICMP_EXT_CTYPE_IIO_IFINDEX;
700
701 rcu_read_lock();
702
703 dev = dev_get_by_index_rcu(net, iif);
704 if (!dev)
705 goto out;
706
707 data = icmp_ext_iio_addr4_find(dev);
708 if (data) {
709 struct icmp_ext_iio_addr4_subobj *addr4_subobj;
710
711 addr4_subobj = skb_put_zero(skb, sizeof(*addr4_subobj));
712 addr4_subobj->afi = htons(ICMP_AFI_IP);
713 addr4_subobj->addr4 = data;
714 objh->class_type |= ICMP_EXT_CTYPE_IIO_IPADDR;
715 }
716
717 name_subobj = skb_put_zero(skb, ALIGN(sizeof(*name_subobj), 4));
718 name_subobj->len = ALIGN(sizeof(*name_subobj), 4);
719 netdev_copy_name(dev, name_subobj->name);
720 objh->class_type |= ICMP_EXT_CTYPE_IIO_NAME;
721
722 data = htonl(READ_ONCE(dev->mtu));
723 skb_put_data(skb, &data, sizeof(__be32));
724 objh->class_type |= ICMP_EXT_CTYPE_IIO_MTU;
725
726 out:
727 rcu_read_unlock();
728 objh->length = htons(skb_tail_pointer(skb) - (unsigned char *)objh);
729 }
730
icmp_ext_objs_append(struct net * net,struct sk_buff * skb,u8 ext_objs,int iif)731 static void icmp_ext_objs_append(struct net *net, struct sk_buff *skb,
732 u8 ext_objs, int iif)
733 {
734 if (ext_objs & BIT(ICMP_ERR_EXT_IIO_IIF))
735 icmp_ext_iio_iif_append(net, skb, iif);
736 }
737
738 static struct sk_buff *
icmp_ext_append(struct net * net,struct sk_buff * skb_in,struct icmphdr * icmph,unsigned int room,int iif)739 icmp_ext_append(struct net *net, struct sk_buff *skb_in, struct icmphdr *icmph,
740 unsigned int room, int iif)
741 {
742 unsigned int payload_len, ext_max_len, ext_len;
743 struct icmp_ext_hdr *ext_hdr;
744 struct sk_buff *skb;
745 u8 ext_objs;
746 int nhoff;
747
748 switch (icmph->type) {
749 case ICMP_DEST_UNREACH:
750 case ICMP_TIME_EXCEEDED:
751 case ICMP_PARAMETERPROB:
752 break;
753 default:
754 return NULL;
755 }
756
757 ext_objs = READ_ONCE(net->ipv4.sysctl_icmp_errors_extension_mask);
758 if (!ext_objs)
759 return NULL;
760
761 ext_max_len = icmp_ext_max_len(ext_objs);
762 if (ICMP_EXT_ORIG_DGRAM_MIN_LEN + ext_max_len > room)
763 return NULL;
764
765 skb = skb_clone(skb_in, GFP_ATOMIC);
766 if (!skb)
767 return NULL;
768
769 nhoff = skb_network_offset(skb);
770 payload_len = min(skb->len - nhoff, ICMP_EXT_ORIG_DGRAM_MIN_LEN);
771
772 if (!pskb_network_may_pull(skb, payload_len))
773 goto free_skb;
774
775 if (pskb_trim(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN) ||
776 __skb_put_padto(skb, nhoff + ICMP_EXT_ORIG_DGRAM_MIN_LEN, false))
777 goto free_skb;
778
779 if (pskb_expand_head(skb, 0, ext_max_len, GFP_ATOMIC))
780 goto free_skb;
781
782 ext_hdr = skb_put_zero(skb, sizeof(*ext_hdr));
783 ext_hdr->version = ICMP_EXT_VERSION_2;
784
785 icmp_ext_objs_append(net, skb, ext_objs, iif);
786
787 /* Do not send an empty extension structure. */
788 ext_len = skb_tail_pointer(skb) - (unsigned char *)ext_hdr;
789 if (ext_len == sizeof(*ext_hdr))
790 goto free_skb;
791
792 ext_hdr->checksum = ip_compute_csum(ext_hdr, ext_len);
793 /* The length of the original datagram in 32-bit words (RFC 4884). */
794 icmph->un.reserved[1] = ICMP_EXT_ORIG_DGRAM_MIN_LEN / sizeof(u32);
795
796 return skb;
797
798 free_skb:
799 consume_skb(skb);
800 return NULL;
801 }
802
803 /*
804 * Send an ICMP message in response to a situation
805 *
806 * RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
807 * MAY send more (we do).
808 * MUST NOT change this header information.
809 * MUST NOT reply to a multicast/broadcast IP address.
810 * MUST NOT reply to a multicast/broadcast MAC address.
811 * MUST reply to only the first fragment.
812 */
813
__icmp_send(struct sk_buff * skb_in,int type,int code,__be32 info,const struct inet_skb_parm * parm)814 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
815 const struct inet_skb_parm *parm)
816 {
817 DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
818 IP_OPTIONS_DATA_FIXED_SIZE);
819 struct iphdr *iph;
820 int room;
821 struct rtable *rt = skb_rtable(skb_in);
822 bool apply_ratelimit = false;
823 struct sk_buff *ext_skb;
824 struct ipcm_cookie ipc;
825 struct flowi4 fl4;
826 __be32 saddr;
827 u8 tos;
828 u32 mark;
829 struct net *net;
830 struct sock *sk;
831
832 if (!rt)
833 return;
834
835 rcu_read_lock();
836
837 if (rt->dst.dev)
838 net = dev_net_rcu(rt->dst.dev);
839 else if (skb_in->dev)
840 net = dev_net_rcu(skb_in->dev);
841 else
842 goto out;
843
844 /*
845 * Find the original header. It is expected to be valid, of course.
846 * Check this, icmp_send is called from the most obscure devices
847 * sometimes.
848 */
849 iph = ip_hdr(skb_in);
850
851 if ((u8 *)iph < skb_in->head ||
852 (skb_network_header(skb_in) + sizeof(*iph)) >
853 skb_tail_pointer(skb_in))
854 goto out;
855
856 /*
857 * No replies to physical multicast/broadcast
858 */
859 if (skb_in->pkt_type != PACKET_HOST)
860 goto out;
861
862 /*
863 * Now check at the protocol level
864 */
865 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
866 goto out;
867
868 /*
869 * Only reply to fragment 0. We byte re-order the constant
870 * mask for efficiency.
871 */
872 if (iph->frag_off & htons(IP_OFFSET))
873 goto out;
874
875 /*
876 * If we send an ICMP error to an ICMP error a mess would result..
877 */
878 if (icmp_pointers[type].error) {
879 /*
880 * We are an error, check if we are replying to an
881 * ICMP error
882 */
883 if (iph->protocol == IPPROTO_ICMP) {
884 u8 _inner_type, *itp;
885
886 itp = skb_header_pointer(skb_in,
887 skb_network_header(skb_in) +
888 (iph->ihl << 2) +
889 offsetof(struct icmphdr,
890 type) -
891 skb_in->data,
892 sizeof(_inner_type),
893 &_inner_type);
894 if (!itp)
895 goto out;
896
897 /*
898 * Assume any unknown ICMP type is an error. This
899 * isn't specified by the RFC, but think about it..
900 */
901 if (*itp > NR_ICMP_TYPES ||
902 icmp_pointers[*itp].error)
903 goto out;
904 }
905 }
906
907 /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
908 local_bh_disable();
909
910 /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
911 * incoming dev is loopback. If outgoing dev change to not be
912 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
913 */
914 if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
915 !icmpv4_global_allow(net, type, code, &apply_ratelimit))
916 goto out_bh_enable;
917
918 sk = icmp_xmit_lock(net);
919 if (!sk)
920 goto out_bh_enable;
921
922 /*
923 * Construct source address and options.
924 */
925
926 saddr = iph->daddr;
927 if (!(rt->rt_flags & RTCF_LOCAL)) {
928 struct net_device *dev = NULL;
929
930 rcu_read_lock();
931 if (rt_is_input_route(rt) &&
932 READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
933 dev = dev_get_by_index_rcu(net, parm->iif ? parm->iif :
934 inet_iif(skb_in));
935
936 if (dev)
937 saddr = inet_select_addr(dev, iph->saddr,
938 RT_SCOPE_LINK);
939 else
940 saddr = 0;
941 rcu_read_unlock();
942 }
943
944 tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
945 IPTOS_PREC_INTERNETCONTROL) :
946 iph->tos;
947 mark = IP4_REPLY_MARK(net, skb_in->mark);
948
949 if (__ip_options_echo(net, &icmp_param->replyopts.opt, skb_in,
950 &parm->opt))
951 goto out_unlock;
952
953
954 /*
955 * Prepare data for ICMP header.
956 */
957
958 icmp_param->data.icmph.type = type;
959 icmp_param->data.icmph.code = code;
960 icmp_param->data.icmph.un.gateway = info;
961 icmp_param->data.icmph.checksum = 0;
962 icmp_param->skb = skb_in;
963 icmp_param->offset = skb_network_offset(skb_in);
964 ipcm_init(&ipc);
965 ipc.tos = tos;
966 ipc.addr = iph->saddr;
967 ipc.opt = &icmp_param->replyopts;
968 ipc.sockc.mark = mark;
969
970 rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr,
971 inet_dsfield_to_dscp(tos), mark, type, code,
972 icmp_param);
973 if (IS_ERR(rt))
974 goto out_unlock;
975
976 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
977 goto ende;
978
979 /* peer icmp_ratelimit */
980 if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
981 goto ende;
982
983 /* RFC says return as much as we can without exceeding 576 bytes. */
984
985 room = dst4_mtu(&rt->dst);
986 if (room > 576)
987 room = 576;
988 room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.optlen;
989 room -= sizeof(struct icmphdr);
990 /* Guard against tiny mtu. We need to include at least one
991 * IP network header for this message to make any sense.
992 */
993 if (room <= (int)sizeof(struct iphdr))
994 goto ende;
995
996 ext_skb = icmp_ext_append(net, skb_in, &icmp_param->data.icmph, room,
997 parm->iif);
998 if (ext_skb)
999 icmp_param->skb = ext_skb;
1000
1001 icmp_param->data_len = icmp_param->skb->len - icmp_param->offset;
1002 if (icmp_param->data_len > room)
1003 icmp_param->data_len = room;
1004 icmp_param->head_len = sizeof(struct icmphdr);
1005
1006 /* if we don't have a source address at this point, fall back to the
1007 * dummy address instead of sending out a packet with a source address
1008 * of 0.0.0.0
1009 */
1010 if (!fl4.saddr)
1011 fl4.saddr = htonl(INADDR_DUMMY);
1012
1013 trace_icmp_send(skb_in, type, code);
1014
1015 icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
1016
1017 if (ext_skb)
1018 consume_skb(ext_skb);
1019 ende:
1020 ip_rt_put(rt);
1021 out_unlock:
1022 icmp_xmit_unlock(sk);
1023 out_bh_enable:
1024 local_bh_enable();
1025 out:
1026 rcu_read_unlock();
1027 }
1028 EXPORT_SYMBOL(__icmp_send);
1029
1030 #if IS_ENABLED(CONFIG_NF_NAT)
1031 #include <net/netfilter/nf_conntrack.h>
icmp_ndo_send(struct sk_buff * skb_in,int type,int code,__be32 info)1032 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
1033 {
1034 struct sk_buff *cloned_skb = NULL;
1035 enum ip_conntrack_info ctinfo;
1036 enum ip_conntrack_dir dir;
1037 struct inet_skb_parm parm;
1038 struct nf_conn *ct;
1039 __be32 orig_ip;
1040
1041 memset(&parm, 0, sizeof(parm));
1042 ct = nf_ct_get(skb_in, &ctinfo);
1043 if (!ct || !(READ_ONCE(ct->status) & IPS_NAT_MASK)) {
1044 __icmp_send(skb_in, type, code, info, &parm);
1045 return;
1046 }
1047
1048 if (skb_shared(skb_in))
1049 skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
1050
1051 if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
1052 (skb_network_header(skb_in) + sizeof(struct iphdr)) >
1053 skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
1054 skb_network_offset(skb_in) + sizeof(struct iphdr))))
1055 goto out;
1056
1057 orig_ip = ip_hdr(skb_in)->saddr;
1058 dir = CTINFO2DIR(ctinfo);
1059 ip_hdr(skb_in)->saddr = ct->tuplehash[dir].tuple.src.u3.ip;
1060 __icmp_send(skb_in, type, code, info, &parm);
1061 ip_hdr(skb_in)->saddr = orig_ip;
1062 out:
1063 consume_skb(cloned_skb);
1064 }
1065 EXPORT_SYMBOL(icmp_ndo_send);
1066 #endif
1067
icmp_socket_deliver(struct sk_buff * skb,u32 info)1068 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
1069 {
1070 const struct iphdr *iph = (const struct iphdr *)skb->data;
1071 const struct net_protocol *ipprot;
1072 int protocol = iph->protocol;
1073
1074 /* Checkin full IP header plus 8 bytes of protocol to
1075 * avoid additional coding at protocol handlers.
1076 */
1077 if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
1078 goto out;
1079
1080 /* IPPROTO_RAW sockets are not supposed to receive anything. */
1081 if (protocol == IPPROTO_RAW)
1082 goto out;
1083
1084 raw_icmp_error(skb, protocol, info);
1085
1086 ipprot = rcu_dereference(inet_protos[protocol]);
1087 if (ipprot && ipprot->err_handler)
1088 ipprot->err_handler(skb, info);
1089 return;
1090
1091 out:
1092 __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
1093 }
1094
icmp_tag_validation(int proto)1095 static bool icmp_tag_validation(int proto)
1096 {
1097 const struct net_protocol *ipprot;
1098 bool ok;
1099
1100 rcu_read_lock();
1101 ipprot = rcu_dereference(inet_protos[proto]);
1102 ok = ipprot ? ipprot->icmp_strict_tag_validation : false;
1103 rcu_read_unlock();
1104 return ok;
1105 }
1106
1107 /*
1108 * Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
1109 * ICMP_PARAMETERPROB.
1110 */
1111
icmp_unreach(struct sk_buff * skb)1112 static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
1113 {
1114 enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
1115 const struct iphdr *iph;
1116 struct icmphdr *icmph;
1117 struct net *net;
1118 u32 info = 0;
1119
1120 net = skb_dst_dev_net_rcu(skb);
1121
1122 /*
1123 * Incomplete header ?
1124 * Only checks for the IP header, there should be an
1125 * additional check for longer headers in upper levels.
1126 */
1127
1128 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
1129 goto out_err;
1130
1131 icmph = icmp_hdr(skb);
1132 iph = (const struct iphdr *)skb->data;
1133
1134 if (iph->ihl < 5) { /* Mangled header, drop. */
1135 reason = SKB_DROP_REASON_IP_INHDR;
1136 goto out_err;
1137 }
1138
1139 switch (icmph->type) {
1140 case ICMP_DEST_UNREACH:
1141 switch (icmph->code & 15) {
1142 case ICMP_NET_UNREACH:
1143 case ICMP_HOST_UNREACH:
1144 case ICMP_PROT_UNREACH:
1145 case ICMP_PORT_UNREACH:
1146 break;
1147 case ICMP_FRAG_NEEDED:
1148 /* for documentation of the ip_no_pmtu_disc
1149 * values please see
1150 * Documentation/networking/ip-sysctl.rst
1151 */
1152 switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
1153 default:
1154 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
1155 &iph->daddr);
1156 break;
1157 case 2:
1158 goto out;
1159 case 3:
1160 if (!icmp_tag_validation(iph->protocol))
1161 goto out;
1162 fallthrough;
1163 case 0:
1164 info = ntohs(icmph->un.frag.mtu);
1165 }
1166 break;
1167 case ICMP_SR_FAILED:
1168 net_dbg_ratelimited("%pI4: Source Route Failed\n",
1169 &iph->daddr);
1170 break;
1171 default:
1172 break;
1173 }
1174 if (icmph->code > NR_ICMP_UNREACH)
1175 goto out;
1176 break;
1177 case ICMP_PARAMETERPROB:
1178 info = ntohl(icmph->un.gateway) >> 24;
1179 break;
1180 case ICMP_TIME_EXCEEDED:
1181 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
1182 if (icmph->code == ICMP_EXC_FRAGTIME)
1183 goto out;
1184 break;
1185 }
1186
1187 /*
1188 * Throw it at our lower layers
1189 *
1190 * RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
1191 * header.
1192 * RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
1193 * transport layer.
1194 * RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
1195 * transport layer.
1196 */
1197
1198 /*
1199 * Check the other end isn't violating RFC 1122. Some routers send
1200 * bogus responses to broadcast frames. If you see this message
1201 * first check your netmask matches at both ends, if it does then
1202 * get the other vendor to fix their kit.
1203 */
1204
1205 if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
1206 inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
1207 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
1208 &ip_hdr(skb)->saddr,
1209 icmph->type, icmph->code,
1210 &iph->daddr, skb->dev->name);
1211 goto out;
1212 }
1213
1214 icmp_socket_deliver(skb, info);
1215
1216 out:
1217 return reason;
1218 out_err:
1219 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1220 return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
1221 }
1222
1223
1224 /*
1225 * Handle ICMP_REDIRECT.
1226 */
1227
icmp_redirect(struct sk_buff * skb)1228 static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
1229 {
1230 if (skb->len < sizeof(struct iphdr)) {
1231 __ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
1232 return SKB_DROP_REASON_PKT_TOO_SMALL;
1233 }
1234
1235 if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
1236 /* there aught to be a stat */
1237 return SKB_DROP_REASON_NOMEM;
1238 }
1239
1240 icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
1241 return SKB_NOT_DROPPED_YET;
1242 }
1243
1244 /*
1245 * Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
1246 *
1247 * RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
1248 * requests.
1249 * RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
1250 * included in the reply.
1251 * RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
1252 * echo requests, MUST have default=NOT.
1253 * RFC 8335: 8 MUST have a config option to enable/disable ICMP
1254 * Extended Echo Functionality, MUST be disabled by default
1255 * See also WRT handling of options once they are done and working.
1256 */
1257
icmp_echo(struct sk_buff * skb)1258 static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
1259 {
1260 DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
1261 IP_OPTIONS_DATA_FIXED_SIZE);
1262 struct net *net;
1263
1264 net = skb_dst_dev_net_rcu(skb);
1265 /* should there be an ICMP stat for ignored echos? */
1266 if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
1267 return SKB_NOT_DROPPED_YET;
1268
1269 icmp_param->data.icmph = *icmp_hdr(skb);
1270 icmp_param->skb = skb;
1271 icmp_param->offset = 0;
1272 icmp_param->data_len = skb->len;
1273 icmp_param->head_len = sizeof(struct icmphdr);
1274
1275 if (icmp_param->data.icmph.type == ICMP_ECHO)
1276 icmp_param->data.icmph.type = ICMP_ECHOREPLY;
1277 else if (!icmp_build_probe(skb, &icmp_param->data.icmph))
1278 return SKB_NOT_DROPPED_YET;
1279
1280 icmp_reply(icmp_param, skb);
1281 return SKB_NOT_DROPPED_YET;
1282 }
1283
1284 /* Helper for icmp_echo and icmpv6_echo_reply.
1285 * Searches for net_device that matches PROBE interface identifier
1286 * and builds PROBE reply message in icmphdr.
1287 *
1288 * Returns false if PROBE responses are disabled via sysctl
1289 */
1290
icmp_build_probe(struct sk_buff * skb,struct icmphdr * icmphdr)1291 bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1292 {
1293 struct net *net = dev_net_rcu(skb->dev);
1294 struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1295 struct icmp_ext_echo_iio *iio, _iio;
1296 struct inet6_dev *in6_dev;
1297 struct in_device *in_dev;
1298 struct net_device *dev;
1299 char buff[IFNAMSIZ];
1300 u16 ident_len;
1301 u8 status;
1302
1303 if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
1304 return false;
1305
1306 /* We currently only support probing interfaces on the proxy node
1307 * Check to ensure L-bit is set
1308 */
1309 if (!(ntohs(icmphdr->un.echo.sequence) & 1))
1310 return false;
1311 /* Clear status bits in reply message */
1312 icmphdr->un.echo.sequence &= htons(0xFF00);
1313 if (icmphdr->type == ICMP_EXT_ECHO)
1314 icmphdr->type = ICMP_EXT_ECHOREPLY;
1315 else
1316 icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
1317 ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
1318 /* Size of iio is class_type dependent.
1319 * Only check header here and assign length based on ctype in the switch statement
1320 */
1321 iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
1322 if (!ext_hdr || !iio)
1323 goto send_mal_query;
1324 if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
1325 ntohs(iio->extobj_hdr.length) > sizeof(_iio))
1326 goto send_mal_query;
1327 ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
1328 iio = skb_header_pointer(skb, sizeof(_ext_hdr),
1329 sizeof(iio->extobj_hdr) + ident_len, &_iio);
1330 if (!iio)
1331 goto send_mal_query;
1332
1333 status = 0;
1334 dev = NULL;
1335 switch (iio->extobj_hdr.class_type) {
1336 case ICMP_EXT_ECHO_CTYPE_NAME:
1337 if (ident_len >= IFNAMSIZ)
1338 goto send_mal_query;
1339 memset(buff, 0, sizeof(buff));
1340 memcpy(buff, &iio->ident.name, ident_len);
1341 dev = dev_get_by_name(net, buff);
1342 break;
1343 case ICMP_EXT_ECHO_CTYPE_INDEX:
1344 if (ident_len != sizeof(iio->ident.ifindex))
1345 goto send_mal_query;
1346 dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
1347 break;
1348 case ICMP_EXT_ECHO_CTYPE_ADDR:
1349 if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
1350 ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
1351 iio->ident.addr.ctype3_hdr.addrlen)
1352 goto send_mal_query;
1353 switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
1354 case ICMP_AFI_IP:
1355 if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
1356 goto send_mal_query;
1357 dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
1358 break;
1359 #if IS_ENABLED(CONFIG_IPV6)
1360 case ICMP_AFI_IP6:
1361 if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
1362 goto send_mal_query;
1363 dev = ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
1364 dev_hold(dev);
1365 break;
1366 #endif
1367 default:
1368 goto send_mal_query;
1369 }
1370 break;
1371 default:
1372 goto send_mal_query;
1373 }
1374 if (!dev) {
1375 icmphdr->code = ICMP_EXT_CODE_NO_IF;
1376 return true;
1377 }
1378 /* Fill bits in reply message */
1379 if (dev->flags & IFF_UP)
1380 status |= ICMP_EXT_ECHOREPLY_ACTIVE;
1381
1382 in_dev = __in_dev_get_rcu(dev);
1383 if (in_dev && rcu_access_pointer(in_dev->ifa_list))
1384 status |= ICMP_EXT_ECHOREPLY_IPV4;
1385
1386 in6_dev = __in6_dev_get(dev);
1387 if (in6_dev && !list_empty(&in6_dev->addr_list))
1388 status |= ICMP_EXT_ECHOREPLY_IPV6;
1389
1390 dev_put(dev);
1391 icmphdr->un.echo.sequence |= htons(status);
1392 return true;
1393 send_mal_query:
1394 icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1395 return true;
1396 }
1397
1398 /*
1399 * Handle ICMP Timestamp requests.
1400 * RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
1401 * SHOULD be in the kernel for minimum random latency.
1402 * MUST be accurate to a few minutes.
1403 * MUST be updated at least at 15Hz.
1404 */
icmp_timestamp(struct sk_buff * skb)1405 static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
1406 {
1407 DEFINE_RAW_FLEX(struct icmp_bxm, icmp_param, replyopts.opt.__data,
1408 IP_OPTIONS_DATA_FIXED_SIZE);
1409 /*
1410 * Too short.
1411 */
1412 if (skb->len < 4)
1413 goto out_err;
1414
1415 /*
1416 * Fill in the current time as ms since midnight UT:
1417 */
1418 icmp_param->data.times[1] = inet_current_timestamp();
1419 icmp_param->data.times[2] = icmp_param->data.times[1];
1420
1421 BUG_ON(skb_copy_bits(skb, 0, &icmp_param->data.times[0], 4));
1422
1423 icmp_param->data.icmph = *icmp_hdr(skb);
1424 icmp_param->data.icmph.type = ICMP_TIMESTAMPREPLY;
1425 icmp_param->data.icmph.code = 0;
1426 icmp_param->skb = skb;
1427 icmp_param->offset = 0;
1428 icmp_param->data_len = 0;
1429 icmp_param->head_len = sizeof(struct icmphdr) + 12;
1430 icmp_reply(icmp_param, skb);
1431 return SKB_NOT_DROPPED_YET;
1432
1433 out_err:
1434 __ICMP_INC_STATS(skb_dst_dev_net_rcu(skb), ICMP_MIB_INERRORS);
1435 return SKB_DROP_REASON_PKT_TOO_SMALL;
1436 }
1437
icmp_discard(struct sk_buff * skb)1438 static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
1439 {
1440 /* pretend it was a success */
1441 return SKB_NOT_DROPPED_YET;
1442 }
1443
1444 /*
1445 * Deal with incoming ICMP packets.
1446 */
icmp_rcv(struct sk_buff * skb)1447 int icmp_rcv(struct sk_buff *skb)
1448 {
1449 enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
1450 struct rtable *rt = skb_rtable(skb);
1451 struct net *net = dev_net_rcu(rt->dst.dev);
1452 struct icmphdr *icmph;
1453
1454 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1455 struct sec_path *sp = skb_sec_path(skb);
1456 int nh;
1457
1458 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1459 XFRM_STATE_ICMP)) {
1460 reason = SKB_DROP_REASON_XFRM_POLICY;
1461 goto drop;
1462 }
1463
1464 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1465 goto drop;
1466
1467 nh = skb_network_offset(skb);
1468 skb_set_network_header(skb, sizeof(*icmph));
1469
1470 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
1471 skb)) {
1472 reason = SKB_DROP_REASON_XFRM_POLICY;
1473 goto drop;
1474 }
1475
1476 skb_set_network_header(skb, nh);
1477 }
1478
1479 __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1480
1481 if (skb_checksum_simple_validate(skb))
1482 goto csum_error;
1483
1484 if (!pskb_pull(skb, sizeof(*icmph)))
1485 goto error;
1486
1487 icmph = icmp_hdr(skb);
1488
1489 ICMPMSGIN_INC_STATS(net, icmph->type);
1490
1491 /* Check for ICMP Extended Echo (PROBE) messages */
1492 if (icmph->type == ICMP_EXT_ECHO) {
1493 /* We can't use icmp_pointers[].handler() because it is an array of
1494 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
1495 */
1496 reason = icmp_echo(skb);
1497 goto reason_check;
1498 }
1499
1500 /*
1501 * Parse the ICMP message
1502 */
1503
1504 if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1505 /*
1506 * RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1507 * silently ignored (we let user decide with a sysctl).
1508 * RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1509 * discarded if to broadcast/multicast.
1510 */
1511 if ((icmph->type == ICMP_ECHO ||
1512 icmph->type == ICMP_TIMESTAMP) &&
1513 READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1514 reason = SKB_DROP_REASON_INVALID_PROTO;
1515 goto error;
1516 }
1517 if (icmph->type != ICMP_ECHO &&
1518 icmph->type != ICMP_TIMESTAMP &&
1519 icmph->type != ICMP_ADDRESS &&
1520 icmph->type != ICMP_ADDRESSREPLY) {
1521 reason = SKB_DROP_REASON_INVALID_PROTO;
1522 goto error;
1523 }
1524 }
1525
1526 if (icmph->type == ICMP_EXT_ECHOREPLY ||
1527 icmph->type == ICMP_ECHOREPLY) {
1528 reason = ping_rcv(skb);
1529 return reason ? NET_RX_DROP : NET_RX_SUCCESS;
1530 }
1531
1532 /*
1533 * 18 is the highest 'known' ICMP type. Anything else is a mystery
1534 *
1535 * RFC 1122: 3.2.2 Unknown ICMP messages types MUST be silently
1536 * discarded.
1537 */
1538 if (icmph->type > NR_ICMP_TYPES) {
1539 reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1540 goto error;
1541 }
1542
1543 reason = icmp_pointers[icmph->type].handler(skb);
1544 reason_check:
1545 if (!reason) {
1546 consume_skb(skb);
1547 return NET_RX_SUCCESS;
1548 }
1549
1550 drop:
1551 kfree_skb_reason(skb, reason);
1552 return NET_RX_DROP;
1553 csum_error:
1554 reason = SKB_DROP_REASON_ICMP_CSUM;
1555 __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1556 error:
1557 __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1558 goto drop;
1559 }
1560
ip_icmp_error_rfc4884_validate(const struct sk_buff * skb,int off)1561 static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1562 {
1563 struct icmp_extobj_hdr *objh, _objh;
1564 struct icmp_ext_hdr *exth, _exth;
1565 u16 olen;
1566
1567 exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
1568 if (!exth)
1569 return false;
1570 if (exth->version != 2)
1571 return true;
1572
1573 if (exth->checksum &&
1574 csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
1575 return false;
1576
1577 off += sizeof(_exth);
1578 while (off < skb->len) {
1579 objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
1580 if (!objh)
1581 return false;
1582
1583 olen = ntohs(objh->length);
1584 if (olen < sizeof(_objh))
1585 return false;
1586
1587 off += olen;
1588 if (off > skb->len)
1589 return false;
1590 }
1591
1592 return true;
1593 }
1594
ip_icmp_error_rfc4884(const struct sk_buff * skb,struct sock_ee_data_rfc4884 * out,int thlen,int off)1595 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1596 struct sock_ee_data_rfc4884 *out,
1597 int thlen, int off)
1598 {
1599 int hlen;
1600
1601 /* original datagram headers: end of icmph to payload (skb->data) */
1602 hlen = -skb_transport_offset(skb) - thlen;
1603
1604 /* per rfc 4884: minimal datagram length of 128 bytes */
1605 if (off < 128 || off < hlen)
1606 return;
1607
1608 /* kernel has stripped headers: return payload offset in bytes */
1609 off -= hlen;
1610 if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1611 return;
1612
1613 out->len = off;
1614
1615 if (!ip_icmp_error_rfc4884_validate(skb, off))
1616 out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1617 }
1618
icmp_err(struct sk_buff * skb,u32 info)1619 int icmp_err(struct sk_buff *skb, u32 info)
1620 {
1621 struct iphdr *iph = (struct iphdr *)skb->data;
1622 int offset = iph->ihl<<2;
1623 struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1624 struct net *net = dev_net_rcu(skb->dev);
1625 int type = icmp_hdr(skb)->type;
1626 int code = icmp_hdr(skb)->code;
1627
1628 /*
1629 * Use ping_err to handle all icmp errors except those
1630 * triggered by ICMP_ECHOREPLY which sent from kernel.
1631 */
1632 if (icmph->type != ICMP_ECHOREPLY) {
1633 ping_err(skb, offset, info);
1634 return 0;
1635 }
1636
1637 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1638 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1639 else if (type == ICMP_REDIRECT)
1640 ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1641
1642 return 0;
1643 }
1644
1645 /*
1646 * This table is the definition of how we handle ICMP.
1647 */
1648 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1649 [ICMP_ECHOREPLY] = {
1650 .handler = ping_rcv,
1651 },
1652 [1] = {
1653 .handler = icmp_discard,
1654 .error = 1,
1655 },
1656 [2] = {
1657 .handler = icmp_discard,
1658 .error = 1,
1659 },
1660 [ICMP_DEST_UNREACH] = {
1661 .handler = icmp_unreach,
1662 .error = 1,
1663 },
1664 [ICMP_SOURCE_QUENCH] = {
1665 .handler = icmp_unreach,
1666 .error = 1,
1667 },
1668 [ICMP_REDIRECT] = {
1669 .handler = icmp_redirect,
1670 .error = 1,
1671 },
1672 [6] = {
1673 .handler = icmp_discard,
1674 .error = 1,
1675 },
1676 [7] = {
1677 .handler = icmp_discard,
1678 .error = 1,
1679 },
1680 [ICMP_ECHO] = {
1681 .handler = icmp_echo,
1682 },
1683 [9] = {
1684 .handler = icmp_discard,
1685 .error = 1,
1686 },
1687 [10] = {
1688 .handler = icmp_discard,
1689 .error = 1,
1690 },
1691 [ICMP_TIME_EXCEEDED] = {
1692 .handler = icmp_unreach,
1693 .error = 1,
1694 },
1695 [ICMP_PARAMETERPROB] = {
1696 .handler = icmp_unreach,
1697 .error = 1,
1698 },
1699 [ICMP_TIMESTAMP] = {
1700 .handler = icmp_timestamp,
1701 },
1702 [ICMP_TIMESTAMPREPLY] = {
1703 .handler = icmp_discard,
1704 },
1705 [ICMP_INFO_REQUEST] = {
1706 .handler = icmp_discard,
1707 },
1708 [ICMP_INFO_REPLY] = {
1709 .handler = icmp_discard,
1710 },
1711 [ICMP_ADDRESS] = {
1712 .handler = icmp_discard,
1713 },
1714 [ICMP_ADDRESSREPLY] = {
1715 .handler = icmp_discard,
1716 },
1717 };
1718
icmp_sk_init(struct net * net)1719 static int __net_init icmp_sk_init(struct net *net)
1720 {
1721 /* Control parameters for ECHO replies. */
1722 net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1723 net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1724 net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1725
1726 /* Control parameter - ignore bogus broadcast responses? */
1727 net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1728
1729 /*
1730 * Configurable global rate limit.
1731 *
1732 * ratelimit defines tokens/packet consumed for dst->rate_token
1733 * bucket ratemask defines which icmp types are ratelimited by
1734 * setting it's bit position.
1735 *
1736 * default:
1737 * dest unreachable (3), source quench (4),
1738 * time exceeded (11), parameter problem (12)
1739 */
1740
1741 net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1742 net->ipv4.sysctl_icmp_ratemask = 0x1818;
1743 net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1744 net->ipv4.sysctl_icmp_errors_extension_mask = 0;
1745 net->ipv4.sysctl_icmp_msgs_per_sec = 10000;
1746 net->ipv4.sysctl_icmp_msgs_burst = 10000;
1747
1748 return 0;
1749 }
1750
1751 static struct pernet_operations __net_initdata icmp_sk_ops = {
1752 .init = icmp_sk_init,
1753 };
1754
icmp_init(void)1755 int __init icmp_init(void)
1756 {
1757 int err, i;
1758
1759 for_each_possible_cpu(i) {
1760 struct sock *sk;
1761
1762 err = inet_ctl_sock_create(&sk, PF_INET,
1763 SOCK_RAW, IPPROTO_ICMP, &init_net);
1764 if (err < 0)
1765 return err;
1766
1767 per_cpu(ipv4_icmp_sk, i) = sk;
1768
1769 /* Enough space for 2 64K ICMP packets, including
1770 * sk_buff/skb_shared_info struct overhead.
1771 */
1772 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1773
1774 /*
1775 * Speedup sock_wfree()
1776 */
1777 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1778 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1779 }
1780 return register_pernet_subsys(&icmp_sk_ops);
1781 }
1782