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