xref: /linux/net/ipv4/icmp.c (revision 348f968b89bfeec0bb53dd82dba58b94d97fbd34)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	NET3:	Implementation of the ICMP protocol layer.
4  *
5  *		Alan Cox, <alan@lxorguk.ukuu.org.uk>
6  *
7  *	Some of the function names and the icmp unreach table for this
8  *	module were derived from [icmp.c 1.0.11 06/02/93] by
9  *	Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
10  *	Other than that this module is a complete rewrite.
11  *
12  *	Fixes:
13  *	Clemens Fruhwirth	:	introduce global icmp rate limiting
14  *					with icmp type masking ability instead
15  *					of broken per type icmp timeouts.
16  *		Mike Shaver	:	RFC1122 checks.
17  *		Alan Cox	:	Multicast ping reply as self.
18  *		Alan Cox	:	Fix atomicity lockup in ip_build_xmit
19  *					call.
20  *		Alan Cox	:	Added 216,128 byte paths to the MTU
21  *					code.
22  *		Martin Mares	:	RFC1812 checks.
23  *		Martin Mares	:	Can be configured to follow redirects
24  *					if acting as a router _without_ a
25  *					routing protocol (RFC 1812).
26  *		Martin Mares	:	Echo requests may be configured to
27  *					be ignored (RFC 1812).
28  *		Martin Mares	:	Limitation of ICMP error message
29  *					transmit rate (RFC 1812).
30  *		Martin Mares	:	TOS and Precedence set correctly
31  *					(RFC 1812).
32  *		Martin Mares	:	Now copying as much data from the
33  *					original packet as we can without
34  *					exceeding 576 bytes (RFC 1812).
35  *	Willy Konynenberg	:	Transparent proxying support.
36  *		Keith Owens	:	RFC1191 correction for 4.2BSD based
37  *					path MTU bug.
38  *		Thomas Quinot	:	ICMP Dest Unreach codes up to 15 are
39  *					valid (RFC 1812).
40  *		Andi Kleen	:	Check all packet lengths properly
41  *					and moved all kfree_skb() up to
42  *					icmp_rcv.
43  *		Andi Kleen	:	Move the rate limit bookkeeping
44  *					into the dest entry and use a token
45  *					bucket filter (thanks to ANK). Make
46  *					the rates sysctl configurable.
47  *		Yu Tianli	:	Fixed two ugly bugs in icmp_send
48  *					- IP option length was accounted wrongly
49  *					- ICMP header length was not accounted
50  *					  at all.
51  *              Tristan Greaves :       Added sysctl option to ignore bogus
52  *              			broadcast responses from broken routers.
53  *
54  * To Fix:
55  *
56  *	- Should use skb_pull() instead of all the manual checking.
57  *	  This would also greatly simply some upper layer error handlers. --AK
58  */
59 
60 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
61 
62 #include <linux/module.h>
63 #include <linux/types.h>
64 #include <linux/jiffies.h>
65 #include <linux/kernel.h>
66 #include <linux/fcntl.h>
67 #include <linux/socket.h>
68 #include <linux/in.h>
69 #include <linux/inet.h>
70 #include <linux/inetdevice.h>
71 #include <linux/netdevice.h>
72 #include <linux/string.h>
73 #include <linux/netfilter_ipv4.h>
74 #include <linux/slab.h>
75 #include <net/snmp.h>
76 #include <net/ip.h>
77 #include <net/route.h>
78 #include <net/protocol.h>
79 #include <net/icmp.h>
80 #include <net/tcp.h>
81 #include <net/udp.h>
82 #include <net/raw.h>
83 #include <net/ping.h>
84 #include <linux/skbuff.h>
85 #include <net/sock.h>
86 #include <linux/errno.h>
87 #include <linux/timer.h>
88 #include <linux/init.h>
89 #include <linux/uaccess.h>
90 #include <net/checksum.h>
91 #include <net/xfrm.h>
92 #include <net/inet_common.h>
93 #include <net/ip_fib.h>
94 #include <net/l3mdev.h>
95 #include <net/addrconf.h>
96 #include <net/inet_dscp.h>
97 #define CREATE_TRACE_POINTS
98 #include <trace/events/icmp.h>
99 
100 /*
101  *	Build xmit assembly blocks
102  */
103 
104 struct icmp_bxm {
105 	struct sk_buff *skb;
106 	int offset;
107 	int data_len;
108 
109 	struct {
110 		struct icmphdr icmph;
111 		__be32	       times[3];
112 	} data;
113 	int head_len;
114 	struct ip_options_data replyopts;
115 };
116 
117 /* An array of errno for error messages from dest unreach. */
118 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
119 
120 const struct icmp_err icmp_err_convert[] = {
121 	{
122 		.errno = ENETUNREACH,	/* ICMP_NET_UNREACH */
123 		.fatal = 0,
124 	},
125 	{
126 		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNREACH */
127 		.fatal = 0,
128 	},
129 	{
130 		.errno = ENOPROTOOPT	/* ICMP_PROT_UNREACH */,
131 		.fatal = 1,
132 	},
133 	{
134 		.errno = ECONNREFUSED,	/* ICMP_PORT_UNREACH */
135 		.fatal = 1,
136 	},
137 	{
138 		.errno = EMSGSIZE,	/* ICMP_FRAG_NEEDED */
139 		.fatal = 0,
140 	},
141 	{
142 		.errno = EOPNOTSUPP,	/* ICMP_SR_FAILED */
143 		.fatal = 0,
144 	},
145 	{
146 		.errno = ENETUNREACH,	/* ICMP_NET_UNKNOWN */
147 		.fatal = 1,
148 	},
149 	{
150 		.errno = EHOSTDOWN,	/* ICMP_HOST_UNKNOWN */
151 		.fatal = 1,
152 	},
153 	{
154 		.errno = ENONET,	/* ICMP_HOST_ISOLATED */
155 		.fatal = 1,
156 	},
157 	{
158 		.errno = ENETUNREACH,	/* ICMP_NET_ANO	*/
159 		.fatal = 1,
160 	},
161 	{
162 		.errno = EHOSTUNREACH,	/* ICMP_HOST_ANO */
163 		.fatal = 1,
164 	},
165 	{
166 		.errno = ENETUNREACH,	/* ICMP_NET_UNR_TOS */
167 		.fatal = 0,
168 	},
169 	{
170 		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNR_TOS */
171 		.fatal = 0,
172 	},
173 	{
174 		.errno = EHOSTUNREACH,	/* ICMP_PKT_FILTERED */
175 		.fatal = 1,
176 	},
177 	{
178 		.errno = EHOSTUNREACH,	/* ICMP_PREC_VIOLATION */
179 		.fatal = 1,
180 	},
181 	{
182 		.errno = EHOSTUNREACH,	/* ICMP_PREC_CUTOFF */
183 		.fatal = 1,
184 	},
185 };
186 EXPORT_SYMBOL(icmp_err_convert);
187 
188 /*
189  *	ICMP control array. This specifies what to do with each ICMP.
190  */
191 
192 struct icmp_control {
193 	enum skb_drop_reason (*handler)(struct sk_buff *skb);
194 	short   error;		/* This ICMP is classed as an error message */
195 };
196 
197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
198 
199 static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
200 
201 /* Called with BH disabled */
icmp_xmit_lock(struct net * net)202 static inline struct sock *icmp_xmit_lock(struct net *net)
203 {
204 	struct sock *sk;
205 
206 	sk = this_cpu_read(ipv4_icmp_sk);
207 
208 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
209 		/* This can happen if the output path signals a
210 		 * dst_link_failure() for an outgoing ICMP packet.
211 		 */
212 		return NULL;
213 	}
214 	sock_net_set(sk, net);
215 	return sk;
216 }
217 
icmp_xmit_unlock(struct sock * sk)218 static inline void icmp_xmit_unlock(struct sock *sk)
219 {
220 	sock_net_set(sk, &init_net);
221 	spin_unlock(&sk->sk_lock.slock);
222 }
223 
224 /**
225  * icmp_global_allow - Are we allowed to send one more ICMP message ?
226  * @net: network namespace
227  *
228  * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
229  * Returns false if we reached the limit and can not send another packet.
230  * Works in tandem with icmp_global_consume().
231  */
icmp_global_allow(struct net * net)232 bool icmp_global_allow(struct net *net)
233 {
234 	u32 delta, now, oldstamp;
235 	int incr, new, old;
236 
237 	/* Note: many cpus could find this condition true.
238 	 * Then later icmp_global_consume() could consume more credits,
239 	 * this is an acceptable race.
240 	 */
241 	if (atomic_read(&net->ipv4.icmp_global_credit) > 0)
242 		return true;
243 
244 	now = jiffies;
245 	oldstamp = READ_ONCE(net->ipv4.icmp_global_stamp);
246 	delta = min_t(u32, now - oldstamp, HZ);
247 	if (delta < HZ / 50)
248 		return false;
249 
250 	incr = READ_ONCE(net->ipv4.sysctl_icmp_msgs_per_sec) * delta / HZ;
251 	if (!incr)
252 		return false;
253 
254 	if (cmpxchg(&net->ipv4.icmp_global_stamp, oldstamp, now) == oldstamp) {
255 		old = atomic_read(&net->ipv4.icmp_global_credit);
256 		do {
257 			new = min(old + incr, READ_ONCE(net->ipv4.sysctl_icmp_msgs_burst));
258 		} while (!atomic_try_cmpxchg(&net->ipv4.icmp_global_credit, &old, new));
259 	}
260 	return true;
261 }
262 EXPORT_SYMBOL(icmp_global_allow);
263 
icmp_global_consume(struct net * net)264 void icmp_global_consume(struct net *net)
265 {
266 	int credits = get_random_u32_below(3);
267 
268 	/* Note: this might make icmp_global.credit negative. */
269 	if (credits)
270 		atomic_sub(credits, &net->ipv4.icmp_global_credit);
271 }
272 EXPORT_SYMBOL(icmp_global_consume);
273 
icmpv4_mask_allow(struct net * net,int type,int code)274 static bool icmpv4_mask_allow(struct net *net, int type, int code)
275 {
276 	if (type > NR_ICMP_TYPES)
277 		return true;
278 
279 	/* Don't limit PMTU discovery. */
280 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
281 		return true;
282 
283 	/* Limit if icmp type is enabled in ratemask. */
284 	if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
285 		return true;
286 
287 	return false;
288 }
289 
icmpv4_global_allow(struct net * net,int type,int code,bool * apply_ratelimit)290 static bool icmpv4_global_allow(struct net *net, int type, int code,
291 				bool *apply_ratelimit)
292 {
293 	if (icmpv4_mask_allow(net, type, code))
294 		return true;
295 
296 	if (icmp_global_allow(net)) {
297 		*apply_ratelimit = true;
298 		return true;
299 	}
300 	__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
301 	return false;
302 }
303 
304 /*
305  *	Send an ICMP frame.
306  */
307 
icmpv4_xrlim_allow(struct net * net,struct rtable * rt,struct flowi4 * fl4,int type,int code,bool apply_ratelimit)308 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
309 			       struct flowi4 *fl4, int type, int code,
310 			       bool apply_ratelimit)
311 {
312 	struct dst_entry *dst = &rt->dst;
313 	struct inet_peer *peer;
314 	bool rc = true;
315 
316 	if (!apply_ratelimit)
317 		return true;
318 
319 	/* No rate limit on loopback */
320 	if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
321 		goto out;
322 
323 	rcu_read_lock();
324 	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
325 			       l3mdev_master_ifindex_rcu(dst->dev));
326 	rc = inet_peer_xrlim_allow(peer,
327 				   READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
328 	rcu_read_unlock();
329 out:
330 	if (!rc)
331 		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
332 	else
333 		icmp_global_consume(net);
334 	return rc;
335 }
336 
337 /*
338  *	Maintain the counters used in the SNMP statistics for outgoing ICMP
339  */
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 rtable *rt = skb_rtable(skb);
403 	struct net *net = dev_net_rcu(rt->dst.dev);
404 	bool apply_ratelimit = false;
405 	struct ipcm_cookie ipc;
406 	struct flowi4 fl4;
407 	struct sock *sk;
408 	struct inet_sock *inet;
409 	__be32 daddr, saddr;
410 	u32 mark = IP4_REPLY_MARK(net, skb->mark);
411 	int type = icmp_param->data.icmph.type;
412 	int code = icmp_param->data.icmph.code;
413 
414 	if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
415 		return;
416 
417 	/* Needed by both icmpv4_global_allow and icmp_xmit_lock */
418 	local_bh_disable();
419 
420 	/* is global icmp_msgs_per_sec exhausted ? */
421 	if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
422 		goto out_bh_enable;
423 
424 	sk = icmp_xmit_lock(net);
425 	if (!sk)
426 		goto out_bh_enable;
427 	inet = inet_sk(sk);
428 
429 	icmp_param->data.icmph.checksum = 0;
430 
431 	ipcm_init(&ipc);
432 	inet->tos = ip_hdr(skb)->tos;
433 	ipc.sockc.mark = mark;
434 	daddr = ipc.addr = ip_hdr(skb)->saddr;
435 	saddr = fib_compute_spec_dst(skb);
436 
437 	if (icmp_param->replyopts.opt.opt.optlen) {
438 		ipc.opt = &icmp_param->replyopts.opt;
439 		if (ipc.opt->opt.srr)
440 			daddr = icmp_param->replyopts.opt.opt.faddr;
441 	}
442 	memset(&fl4, 0, sizeof(fl4));
443 	fl4.daddr = daddr;
444 	fl4.saddr = saddr;
445 	fl4.flowi4_mark = mark;
446 	fl4.flowi4_uid = sock_net_uid(net, NULL);
447 	fl4.flowi4_tos = inet_dscp_to_dsfield(ip4h_dscp(ip_hdr(skb)));
448 	fl4.flowi4_proto = IPPROTO_ICMP;
449 	fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
450 	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
451 	rt = ip_route_output_key(net, &fl4);
452 	if (IS_ERR(rt))
453 		goto out_unlock;
454 	if (icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
455 		icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
456 	ip_rt_put(rt);
457 out_unlock:
458 	icmp_xmit_unlock(sk);
459 out_bh_enable:
460 	local_bh_enable();
461 }
462 
463 /*
464  * The device used for looking up which routing table to use for sending an ICMP
465  * error is preferably the source whenever it is set, which should ensure the
466  * icmp error can be sent to the source host, else lookup using the routing
467  * table of the destination device, else use the main routing table (index 0).
468  */
icmp_get_route_lookup_dev(struct sk_buff * skb)469 static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
470 {
471 	struct net_device *route_lookup_dev = NULL;
472 
473 	if (skb->dev)
474 		route_lookup_dev = skb->dev;
475 	else if (skb_dst(skb))
476 		route_lookup_dev = skb_dst(skb)->dev;
477 	return route_lookup_dev;
478 }
479 
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)480 static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
481 					struct sk_buff *skb_in,
482 					const struct iphdr *iph, __be32 saddr,
483 					dscp_t dscp, u32 mark, int type,
484 					int code, struct icmp_bxm *param)
485 {
486 	struct net_device *route_lookup_dev;
487 	struct dst_entry *dst, *dst2;
488 	struct rtable *rt, *rt2;
489 	struct flowi4 fl4_dec;
490 	int err;
491 
492 	memset(fl4, 0, sizeof(*fl4));
493 	fl4->daddr = (param->replyopts.opt.opt.srr ?
494 		      param->replyopts.opt.opt.faddr : iph->saddr);
495 	fl4->saddr = saddr;
496 	fl4->flowi4_mark = mark;
497 	fl4->flowi4_uid = sock_net_uid(net, NULL);
498 	fl4->flowi4_tos = inet_dscp_to_dsfield(dscp);
499 	fl4->flowi4_proto = IPPROTO_ICMP;
500 	fl4->fl4_icmp_type = type;
501 	fl4->fl4_icmp_code = code;
502 	route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
503 	fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
504 
505 	security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
506 	rt = ip_route_output_key_hash(net, fl4, skb_in);
507 	if (IS_ERR(rt))
508 		return rt;
509 
510 	/* No need to clone since we're just using its address. */
511 	rt2 = rt;
512 
513 	dst = xfrm_lookup(net, &rt->dst,
514 			  flowi4_to_flowi(fl4), NULL, 0);
515 	rt = dst_rtable(dst);
516 	if (!IS_ERR(dst)) {
517 		if (rt != rt2)
518 			return rt;
519 		if (inet_addr_type_dev_table(net, route_lookup_dev,
520 					     fl4->daddr) == RTN_LOCAL)
521 			return rt;
522 	} else if (PTR_ERR(dst) == -EPERM) {
523 		rt = NULL;
524 	} else {
525 		return rt;
526 	}
527 	err = xfrm_decode_session_reverse(net, skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
528 	if (err)
529 		goto relookup_failed;
530 
531 	if (inet_addr_type_dev_table(net, route_lookup_dev,
532 				     fl4_dec.saddr) == RTN_LOCAL) {
533 		rt2 = __ip_route_output_key(net, &fl4_dec);
534 		if (IS_ERR(rt2))
535 			err = PTR_ERR(rt2);
536 	} else {
537 		struct flowi4 fl4_2 = {};
538 		unsigned long orefdst;
539 
540 		fl4_2.daddr = fl4_dec.saddr;
541 		rt2 = ip_route_output_key(net, &fl4_2);
542 		if (IS_ERR(rt2)) {
543 			err = PTR_ERR(rt2);
544 			goto relookup_failed;
545 		}
546 		/* Ugh! */
547 		orefdst = skb_in->_skb_refdst; /* save old refdst */
548 		skb_dst_set(skb_in, NULL);
549 		err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
550 				     dscp, rt2->dst.dev) ? -EINVAL : 0;
551 
552 		dst_release(&rt2->dst);
553 		rt2 = skb_rtable(skb_in);
554 		skb_in->_skb_refdst = orefdst; /* restore old refdst */
555 	}
556 
557 	if (err)
558 		goto relookup_failed;
559 
560 	dst2 = xfrm_lookup(net, &rt2->dst, flowi4_to_flowi(&fl4_dec), NULL,
561 			   XFRM_LOOKUP_ICMP);
562 	rt2 = dst_rtable(dst2);
563 	if (!IS_ERR(dst2)) {
564 		dst_release(&rt->dst);
565 		memcpy(fl4, &fl4_dec, sizeof(*fl4));
566 		rt = rt2;
567 	} else if (PTR_ERR(dst2) == -EPERM) {
568 		if (rt)
569 			dst_release(&rt->dst);
570 		return rt2;
571 	} else {
572 		err = PTR_ERR(dst2);
573 		goto relookup_failed;
574 	}
575 	return rt;
576 
577 relookup_failed:
578 	if (rt)
579 		return rt;
580 	return ERR_PTR(err);
581 }
582 
583 /*
584  *	Send an ICMP message in response to a situation
585  *
586  *	RFC 1122: 3.2.2	MUST send at least the IP header and 8 bytes of header.
587  *		  MAY send more (we do).
588  *			MUST NOT change this header information.
589  *			MUST NOT reply to a multicast/broadcast IP address.
590  *			MUST NOT reply to a multicast/broadcast MAC address.
591  *			MUST reply to only the first fragment.
592  */
593 
__icmp_send(struct sk_buff * skb_in,int type,int code,__be32 info,const struct ip_options * opt)594 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
595 		 const struct ip_options *opt)
596 {
597 	struct iphdr *iph;
598 	int room;
599 	struct icmp_bxm icmp_param;
600 	struct rtable *rt = skb_rtable(skb_in);
601 	bool apply_ratelimit = false;
602 	struct ipcm_cookie ipc;
603 	struct flowi4 fl4;
604 	__be32 saddr;
605 	u8  tos;
606 	u32 mark;
607 	struct net *net;
608 	struct sock *sk;
609 
610 	if (!rt)
611 		return;
612 
613 	rcu_read_lock();
614 
615 	if (rt->dst.dev)
616 		net = dev_net_rcu(rt->dst.dev);
617 	else if (skb_in->dev)
618 		net = dev_net_rcu(skb_in->dev);
619 	else
620 		goto out;
621 
622 	/*
623 	 *	Find the original header. It is expected to be valid, of course.
624 	 *	Check this, icmp_send is called from the most obscure devices
625 	 *	sometimes.
626 	 */
627 	iph = ip_hdr(skb_in);
628 
629 	if ((u8 *)iph < skb_in->head ||
630 	    (skb_network_header(skb_in) + sizeof(*iph)) >
631 	    skb_tail_pointer(skb_in))
632 		goto out;
633 
634 	/*
635 	 *	No replies to physical multicast/broadcast
636 	 */
637 	if (skb_in->pkt_type != PACKET_HOST)
638 		goto out;
639 
640 	/*
641 	 *	Now check at the protocol level
642 	 */
643 	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
644 		goto out;
645 
646 	/*
647 	 *	Only reply to fragment 0. We byte re-order the constant
648 	 *	mask for efficiency.
649 	 */
650 	if (iph->frag_off & htons(IP_OFFSET))
651 		goto out;
652 
653 	/*
654 	 *	If we send an ICMP error to an ICMP error a mess would result..
655 	 */
656 	if (icmp_pointers[type].error) {
657 		/*
658 		 *	We are an error, check if we are replying to an
659 		 *	ICMP error
660 		 */
661 		if (iph->protocol == IPPROTO_ICMP) {
662 			u8 _inner_type, *itp;
663 
664 			itp = skb_header_pointer(skb_in,
665 						 skb_network_header(skb_in) +
666 						 (iph->ihl << 2) +
667 						 offsetof(struct icmphdr,
668 							  type) -
669 						 skb_in->data,
670 						 sizeof(_inner_type),
671 						 &_inner_type);
672 			if (!itp)
673 				goto out;
674 
675 			/*
676 			 *	Assume any unknown ICMP type is an error. This
677 			 *	isn't specified by the RFC, but think about it..
678 			 */
679 			if (*itp > NR_ICMP_TYPES ||
680 			    icmp_pointers[*itp].error)
681 				goto out;
682 		}
683 	}
684 
685 	/* Needed by both icmpv4_global_allow and icmp_xmit_lock */
686 	local_bh_disable();
687 
688 	/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
689 	 * incoming dev is loopback.  If outgoing dev change to not be
690 	 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
691 	 */
692 	if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
693 	      !icmpv4_global_allow(net, type, code, &apply_ratelimit))
694 		goto out_bh_enable;
695 
696 	sk = icmp_xmit_lock(net);
697 	if (!sk)
698 		goto out_bh_enable;
699 
700 	/*
701 	 *	Construct source address and options.
702 	 */
703 
704 	saddr = iph->daddr;
705 	if (!(rt->rt_flags & RTCF_LOCAL)) {
706 		struct net_device *dev = NULL;
707 
708 		rcu_read_lock();
709 		if (rt_is_input_route(rt) &&
710 		    READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
711 			dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
712 
713 		if (dev)
714 			saddr = inet_select_addr(dev, iph->saddr,
715 						 RT_SCOPE_LINK);
716 		else
717 			saddr = 0;
718 		rcu_read_unlock();
719 	}
720 
721 	tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
722 					   IPTOS_PREC_INTERNETCONTROL) :
723 					   iph->tos;
724 	mark = IP4_REPLY_MARK(net, skb_in->mark);
725 
726 	if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
727 		goto out_unlock;
728 
729 
730 	/*
731 	 *	Prepare data for ICMP header.
732 	 */
733 
734 	icmp_param.data.icmph.type	 = type;
735 	icmp_param.data.icmph.code	 = code;
736 	icmp_param.data.icmph.un.gateway = info;
737 	icmp_param.data.icmph.checksum	 = 0;
738 	icmp_param.skb	  = skb_in;
739 	icmp_param.offset = skb_network_offset(skb_in);
740 	inet_sk(sk)->tos = tos;
741 	ipcm_init(&ipc);
742 	ipc.addr = iph->saddr;
743 	ipc.opt = &icmp_param.replyopts.opt;
744 	ipc.sockc.mark = mark;
745 
746 	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr,
747 			       inet_dsfield_to_dscp(tos), mark, type, code,
748 			       &icmp_param);
749 	if (IS_ERR(rt))
750 		goto out_unlock;
751 
752 	/* peer icmp_ratelimit */
753 	if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
754 		goto ende;
755 
756 	/* RFC says return as much as we can without exceeding 576 bytes. */
757 
758 	room = dst_mtu(&rt->dst);
759 	if (room > 576)
760 		room = 576;
761 	room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
762 	room -= sizeof(struct icmphdr);
763 	/* Guard against tiny mtu. We need to include at least one
764 	 * IP network header for this message to make any sense.
765 	 */
766 	if (room <= (int)sizeof(struct iphdr))
767 		goto ende;
768 
769 	icmp_param.data_len = skb_in->len - icmp_param.offset;
770 	if (icmp_param.data_len > room)
771 		icmp_param.data_len = room;
772 	icmp_param.head_len = sizeof(struct icmphdr);
773 
774 	/* if we don't have a source address at this point, fall back to the
775 	 * dummy address instead of sending out a packet with a source address
776 	 * of 0.0.0.0
777 	 */
778 	if (!fl4.saddr)
779 		fl4.saddr = htonl(INADDR_DUMMY);
780 
781 	trace_icmp_send(skb_in, type, code);
782 
783 	icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
784 ende:
785 	ip_rt_put(rt);
786 out_unlock:
787 	icmp_xmit_unlock(sk);
788 out_bh_enable:
789 	local_bh_enable();
790 out:
791 	rcu_read_unlock();
792 }
793 EXPORT_SYMBOL(__icmp_send);
794 
795 #if IS_ENABLED(CONFIG_NF_NAT)
796 #include <net/netfilter/nf_conntrack.h>
icmp_ndo_send(struct sk_buff * skb_in,int type,int code,__be32 info)797 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
798 {
799 	struct sk_buff *cloned_skb = NULL;
800 	struct ip_options opts = { 0 };
801 	enum ip_conntrack_info ctinfo;
802 	struct nf_conn *ct;
803 	__be32 orig_ip;
804 
805 	ct = nf_ct_get(skb_in, &ctinfo);
806 	if (!ct || !(ct->status & IPS_SRC_NAT)) {
807 		__icmp_send(skb_in, type, code, info, &opts);
808 		return;
809 	}
810 
811 	if (skb_shared(skb_in))
812 		skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
813 
814 	if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
815 	    (skb_network_header(skb_in) + sizeof(struct iphdr)) >
816 	    skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
817 	    skb_network_offset(skb_in) + sizeof(struct iphdr))))
818 		goto out;
819 
820 	orig_ip = ip_hdr(skb_in)->saddr;
821 	ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
822 	__icmp_send(skb_in, type, code, info, &opts);
823 	ip_hdr(skb_in)->saddr = orig_ip;
824 out:
825 	consume_skb(cloned_skb);
826 }
827 EXPORT_SYMBOL(icmp_ndo_send);
828 #endif
829 
icmp_socket_deliver(struct sk_buff * skb,u32 info)830 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
831 {
832 	const struct iphdr *iph = (const struct iphdr *)skb->data;
833 	const struct net_protocol *ipprot;
834 	int protocol = iph->protocol;
835 
836 	/* Checkin full IP header plus 8 bytes of protocol to
837 	 * avoid additional coding at protocol handlers.
838 	 */
839 	if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
840 		__ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
841 		return;
842 	}
843 
844 	raw_icmp_error(skb, protocol, info);
845 
846 	ipprot = rcu_dereference(inet_protos[protocol]);
847 	if (ipprot && ipprot->err_handler)
848 		ipprot->err_handler(skb, info);
849 }
850 
icmp_tag_validation(int proto)851 static bool icmp_tag_validation(int proto)
852 {
853 	bool ok;
854 
855 	rcu_read_lock();
856 	ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
857 	rcu_read_unlock();
858 	return ok;
859 }
860 
861 /*
862  *	Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
863  *	ICMP_PARAMETERPROB.
864  */
865 
icmp_unreach(struct sk_buff * skb)866 static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
867 {
868 	enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
869 	const struct iphdr *iph;
870 	struct icmphdr *icmph;
871 	struct net *net;
872 	u32 info = 0;
873 
874 	net = dev_net_rcu(skb_dst(skb)->dev);
875 
876 	/*
877 	 *	Incomplete header ?
878 	 * 	Only checks for the IP header, there should be an
879 	 *	additional check for longer headers in upper levels.
880 	 */
881 
882 	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
883 		goto out_err;
884 
885 	icmph = icmp_hdr(skb);
886 	iph   = (const struct iphdr *)skb->data;
887 
888 	if (iph->ihl < 5)  { /* Mangled header, drop. */
889 		reason = SKB_DROP_REASON_IP_INHDR;
890 		goto out_err;
891 	}
892 
893 	switch (icmph->type) {
894 	case ICMP_DEST_UNREACH:
895 		switch (icmph->code & 15) {
896 		case ICMP_NET_UNREACH:
897 		case ICMP_HOST_UNREACH:
898 		case ICMP_PROT_UNREACH:
899 		case ICMP_PORT_UNREACH:
900 			break;
901 		case ICMP_FRAG_NEEDED:
902 			/* for documentation of the ip_no_pmtu_disc
903 			 * values please see
904 			 * Documentation/networking/ip-sysctl.rst
905 			 */
906 			switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
907 			default:
908 				net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
909 						    &iph->daddr);
910 				break;
911 			case 2:
912 				goto out;
913 			case 3:
914 				if (!icmp_tag_validation(iph->protocol))
915 					goto out;
916 				fallthrough;
917 			case 0:
918 				info = ntohs(icmph->un.frag.mtu);
919 			}
920 			break;
921 		case ICMP_SR_FAILED:
922 			net_dbg_ratelimited("%pI4: Source Route Failed\n",
923 					    &iph->daddr);
924 			break;
925 		default:
926 			break;
927 		}
928 		if (icmph->code > NR_ICMP_UNREACH)
929 			goto out;
930 		break;
931 	case ICMP_PARAMETERPROB:
932 		info = ntohl(icmph->un.gateway) >> 24;
933 		break;
934 	case ICMP_TIME_EXCEEDED:
935 		__ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
936 		if (icmph->code == ICMP_EXC_FRAGTIME)
937 			goto out;
938 		break;
939 	}
940 
941 	/*
942 	 *	Throw it at our lower layers
943 	 *
944 	 *	RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
945 	 *		  header.
946 	 *	RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
947 	 *		  transport layer.
948 	 *	RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
949 	 *		  transport layer.
950 	 */
951 
952 	/*
953 	 *	Check the other end isn't violating RFC 1122. Some routers send
954 	 *	bogus responses to broadcast frames. If you see this message
955 	 *	first check your netmask matches at both ends, if it does then
956 	 *	get the other vendor to fix their kit.
957 	 */
958 
959 	if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
960 	    inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
961 		net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
962 				     &ip_hdr(skb)->saddr,
963 				     icmph->type, icmph->code,
964 				     &iph->daddr, skb->dev->name);
965 		goto out;
966 	}
967 
968 	icmp_socket_deliver(skb, info);
969 
970 out:
971 	return reason;
972 out_err:
973 	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
974 	return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
975 }
976 
977 
978 /*
979  *	Handle ICMP_REDIRECT.
980  */
981 
icmp_redirect(struct sk_buff * skb)982 static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
983 {
984 	if (skb->len < sizeof(struct iphdr)) {
985 		__ICMP_INC_STATS(dev_net_rcu(skb->dev), ICMP_MIB_INERRORS);
986 		return SKB_DROP_REASON_PKT_TOO_SMALL;
987 	}
988 
989 	if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
990 		/* there aught to be a stat */
991 		return SKB_DROP_REASON_NOMEM;
992 	}
993 
994 	icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
995 	return SKB_NOT_DROPPED_YET;
996 }
997 
998 /*
999  *	Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
1000  *
1001  *	RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
1002  *		  requests.
1003  *	RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
1004  *		  included in the reply.
1005  *	RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
1006  *		  echo requests, MUST have default=NOT.
1007  *	RFC 8335: 8 MUST have a config option to enable/disable ICMP
1008  *		  Extended Echo Functionality, MUST be disabled by default
1009  *	See also WRT handling of options once they are done and working.
1010  */
1011 
icmp_echo(struct sk_buff * skb)1012 static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
1013 {
1014 	struct icmp_bxm icmp_param;
1015 	struct net *net;
1016 
1017 	net = dev_net_rcu(skb_dst(skb)->dev);
1018 	/* should there be an ICMP stat for ignored echos? */
1019 	if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
1020 		return SKB_NOT_DROPPED_YET;
1021 
1022 	icmp_param.data.icmph	   = *icmp_hdr(skb);
1023 	icmp_param.skb		   = skb;
1024 	icmp_param.offset	   = 0;
1025 	icmp_param.data_len	   = skb->len;
1026 	icmp_param.head_len	   = sizeof(struct icmphdr);
1027 
1028 	if (icmp_param.data.icmph.type == ICMP_ECHO)
1029 		icmp_param.data.icmph.type = ICMP_ECHOREPLY;
1030 	else if (!icmp_build_probe(skb, &icmp_param.data.icmph))
1031 		return SKB_NOT_DROPPED_YET;
1032 
1033 	icmp_reply(&icmp_param, skb);
1034 	return SKB_NOT_DROPPED_YET;
1035 }
1036 
1037 /*	Helper for icmp_echo and icmpv6_echo_reply.
1038  *	Searches for net_device that matches PROBE interface identifier
1039  *		and builds PROBE reply message in icmphdr.
1040  *
1041  *	Returns false if PROBE responses are disabled via sysctl
1042  */
1043 
icmp_build_probe(struct sk_buff * skb,struct icmphdr * icmphdr)1044 bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1045 {
1046 	struct net *net = dev_net_rcu(skb->dev);
1047 	struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1048 	struct icmp_ext_echo_iio *iio, _iio;
1049 	struct inet6_dev *in6_dev;
1050 	struct in_device *in_dev;
1051 	struct net_device *dev;
1052 	char buff[IFNAMSIZ];
1053 	u16 ident_len;
1054 	u8 status;
1055 
1056 	if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
1057 		return false;
1058 
1059 	/* We currently only support probing interfaces on the proxy node
1060 	 * Check to ensure L-bit is set
1061 	 */
1062 	if (!(ntohs(icmphdr->un.echo.sequence) & 1))
1063 		return false;
1064 	/* Clear status bits in reply message */
1065 	icmphdr->un.echo.sequence &= htons(0xFF00);
1066 	if (icmphdr->type == ICMP_EXT_ECHO)
1067 		icmphdr->type = ICMP_EXT_ECHOREPLY;
1068 	else
1069 		icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
1070 	ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
1071 	/* Size of iio is class_type dependent.
1072 	 * Only check header here and assign length based on ctype in the switch statement
1073 	 */
1074 	iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
1075 	if (!ext_hdr || !iio)
1076 		goto send_mal_query;
1077 	if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
1078 	    ntohs(iio->extobj_hdr.length) > sizeof(_iio))
1079 		goto send_mal_query;
1080 	ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
1081 	iio = skb_header_pointer(skb, sizeof(_ext_hdr),
1082 				 sizeof(iio->extobj_hdr) + ident_len, &_iio);
1083 	if (!iio)
1084 		goto send_mal_query;
1085 
1086 	status = 0;
1087 	dev = NULL;
1088 	switch (iio->extobj_hdr.class_type) {
1089 	case ICMP_EXT_ECHO_CTYPE_NAME:
1090 		if (ident_len >= IFNAMSIZ)
1091 			goto send_mal_query;
1092 		memset(buff, 0, sizeof(buff));
1093 		memcpy(buff, &iio->ident.name, ident_len);
1094 		dev = dev_get_by_name(net, buff);
1095 		break;
1096 	case ICMP_EXT_ECHO_CTYPE_INDEX:
1097 		if (ident_len != sizeof(iio->ident.ifindex))
1098 			goto send_mal_query;
1099 		dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
1100 		break;
1101 	case ICMP_EXT_ECHO_CTYPE_ADDR:
1102 		if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
1103 		    ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
1104 				 iio->ident.addr.ctype3_hdr.addrlen)
1105 			goto send_mal_query;
1106 		switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
1107 		case ICMP_AFI_IP:
1108 			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
1109 				goto send_mal_query;
1110 			dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
1111 			break;
1112 #if IS_ENABLED(CONFIG_IPV6)
1113 		case ICMP_AFI_IP6:
1114 			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
1115 				goto send_mal_query;
1116 			dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
1117 			dev_hold(dev);
1118 			break;
1119 #endif
1120 		default:
1121 			goto send_mal_query;
1122 		}
1123 		break;
1124 	default:
1125 		goto send_mal_query;
1126 	}
1127 	if (!dev) {
1128 		icmphdr->code = ICMP_EXT_CODE_NO_IF;
1129 		return true;
1130 	}
1131 	/* Fill bits in reply message */
1132 	if (dev->flags & IFF_UP)
1133 		status |= ICMP_EXT_ECHOREPLY_ACTIVE;
1134 
1135 	in_dev = __in_dev_get_rcu(dev);
1136 	if (in_dev && rcu_access_pointer(in_dev->ifa_list))
1137 		status |= ICMP_EXT_ECHOREPLY_IPV4;
1138 
1139 	in6_dev = __in6_dev_get(dev);
1140 	if (in6_dev && !list_empty(&in6_dev->addr_list))
1141 		status |= ICMP_EXT_ECHOREPLY_IPV6;
1142 
1143 	dev_put(dev);
1144 	icmphdr->un.echo.sequence |= htons(status);
1145 	return true;
1146 send_mal_query:
1147 	icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1148 	return true;
1149 }
1150 EXPORT_SYMBOL_GPL(icmp_build_probe);
1151 
1152 /*
1153  *	Handle ICMP Timestamp requests.
1154  *	RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
1155  *		  SHOULD be in the kernel for minimum random latency.
1156  *		  MUST be accurate to a few minutes.
1157  *		  MUST be updated at least at 15Hz.
1158  */
icmp_timestamp(struct sk_buff * skb)1159 static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
1160 {
1161 	struct icmp_bxm icmp_param;
1162 	/*
1163 	 *	Too short.
1164 	 */
1165 	if (skb->len < 4)
1166 		goto out_err;
1167 
1168 	/*
1169 	 *	Fill in the current time as ms since midnight UT:
1170 	 */
1171 	icmp_param.data.times[1] = inet_current_timestamp();
1172 	icmp_param.data.times[2] = icmp_param.data.times[1];
1173 
1174 	BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
1175 
1176 	icmp_param.data.icmph	   = *icmp_hdr(skb);
1177 	icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
1178 	icmp_param.data.icmph.code = 0;
1179 	icmp_param.skb		   = skb;
1180 	icmp_param.offset	   = 0;
1181 	icmp_param.data_len	   = 0;
1182 	icmp_param.head_len	   = sizeof(struct icmphdr) + 12;
1183 	icmp_reply(&icmp_param, skb);
1184 	return SKB_NOT_DROPPED_YET;
1185 
1186 out_err:
1187 	__ICMP_INC_STATS(dev_net_rcu(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1188 	return SKB_DROP_REASON_PKT_TOO_SMALL;
1189 }
1190 
icmp_discard(struct sk_buff * skb)1191 static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
1192 {
1193 	/* pretend it was a success */
1194 	return SKB_NOT_DROPPED_YET;
1195 }
1196 
1197 /*
1198  *	Deal with incoming ICMP packets.
1199  */
icmp_rcv(struct sk_buff * skb)1200 int icmp_rcv(struct sk_buff *skb)
1201 {
1202 	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
1203 	struct rtable *rt = skb_rtable(skb);
1204 	struct net *net = dev_net_rcu(rt->dst.dev);
1205 	struct icmphdr *icmph;
1206 
1207 	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1208 		struct sec_path *sp = skb_sec_path(skb);
1209 		int nh;
1210 
1211 		if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1212 				 XFRM_STATE_ICMP)) {
1213 			reason = SKB_DROP_REASON_XFRM_POLICY;
1214 			goto drop;
1215 		}
1216 
1217 		if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1218 			goto drop;
1219 
1220 		nh = skb_network_offset(skb);
1221 		skb_set_network_header(skb, sizeof(*icmph));
1222 
1223 		if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
1224 						skb)) {
1225 			reason = SKB_DROP_REASON_XFRM_POLICY;
1226 			goto drop;
1227 		}
1228 
1229 		skb_set_network_header(skb, nh);
1230 	}
1231 
1232 	__ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1233 
1234 	if (skb_checksum_simple_validate(skb))
1235 		goto csum_error;
1236 
1237 	if (!pskb_pull(skb, sizeof(*icmph)))
1238 		goto error;
1239 
1240 	icmph = icmp_hdr(skb);
1241 
1242 	ICMPMSGIN_INC_STATS(net, icmph->type);
1243 
1244 	/* Check for ICMP Extended Echo (PROBE) messages */
1245 	if (icmph->type == ICMP_EXT_ECHO) {
1246 		/* We can't use icmp_pointers[].handler() because it is an array of
1247 		 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
1248 		 */
1249 		reason = icmp_echo(skb);
1250 		goto reason_check;
1251 	}
1252 
1253 	if (icmph->type == ICMP_EXT_ECHOREPLY) {
1254 		reason = ping_rcv(skb);
1255 		goto reason_check;
1256 	}
1257 
1258 	/*
1259 	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
1260 	 *
1261 	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1262 	 *		  discarded.
1263 	 */
1264 	if (icmph->type > NR_ICMP_TYPES) {
1265 		reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1266 		goto error;
1267 	}
1268 
1269 	/*
1270 	 *	Parse the ICMP message
1271 	 */
1272 
1273 	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1274 		/*
1275 		 *	RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1276 		 *	  silently ignored (we let user decide with a sysctl).
1277 		 *	RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1278 		 *	  discarded if to broadcast/multicast.
1279 		 */
1280 		if ((icmph->type == ICMP_ECHO ||
1281 		     icmph->type == ICMP_TIMESTAMP) &&
1282 		    READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1283 			reason = SKB_DROP_REASON_INVALID_PROTO;
1284 			goto error;
1285 		}
1286 		if (icmph->type != ICMP_ECHO &&
1287 		    icmph->type != ICMP_TIMESTAMP &&
1288 		    icmph->type != ICMP_ADDRESS &&
1289 		    icmph->type != ICMP_ADDRESSREPLY) {
1290 			reason = SKB_DROP_REASON_INVALID_PROTO;
1291 			goto error;
1292 		}
1293 	}
1294 
1295 	reason = icmp_pointers[icmph->type].handler(skb);
1296 reason_check:
1297 	if (!reason)  {
1298 		consume_skb(skb);
1299 		return NET_RX_SUCCESS;
1300 	}
1301 
1302 drop:
1303 	kfree_skb_reason(skb, reason);
1304 	return NET_RX_DROP;
1305 csum_error:
1306 	reason = SKB_DROP_REASON_ICMP_CSUM;
1307 	__ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1308 error:
1309 	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1310 	goto drop;
1311 }
1312 
ip_icmp_error_rfc4884_validate(const struct sk_buff * skb,int off)1313 static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1314 {
1315 	struct icmp_extobj_hdr *objh, _objh;
1316 	struct icmp_ext_hdr *exth, _exth;
1317 	u16 olen;
1318 
1319 	exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
1320 	if (!exth)
1321 		return false;
1322 	if (exth->version != 2)
1323 		return true;
1324 
1325 	if (exth->checksum &&
1326 	    csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
1327 		return false;
1328 
1329 	off += sizeof(_exth);
1330 	while (off < skb->len) {
1331 		objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
1332 		if (!objh)
1333 			return false;
1334 
1335 		olen = ntohs(objh->length);
1336 		if (olen < sizeof(_objh))
1337 			return false;
1338 
1339 		off += olen;
1340 		if (off > skb->len)
1341 			return false;
1342 	}
1343 
1344 	return true;
1345 }
1346 
ip_icmp_error_rfc4884(const struct sk_buff * skb,struct sock_ee_data_rfc4884 * out,int thlen,int off)1347 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1348 			   struct sock_ee_data_rfc4884 *out,
1349 			   int thlen, int off)
1350 {
1351 	int hlen;
1352 
1353 	/* original datagram headers: end of icmph to payload (skb->data) */
1354 	hlen = -skb_transport_offset(skb) - thlen;
1355 
1356 	/* per rfc 4884: minimal datagram length of 128 bytes */
1357 	if (off < 128 || off < hlen)
1358 		return;
1359 
1360 	/* kernel has stripped headers: return payload offset in bytes */
1361 	off -= hlen;
1362 	if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1363 		return;
1364 
1365 	out->len = off;
1366 
1367 	if (!ip_icmp_error_rfc4884_validate(skb, off))
1368 		out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1369 }
1370 EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
1371 
icmp_err(struct sk_buff * skb,u32 info)1372 int icmp_err(struct sk_buff *skb, u32 info)
1373 {
1374 	struct iphdr *iph = (struct iphdr *)skb->data;
1375 	int offset = iph->ihl<<2;
1376 	struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1377 	struct net *net = dev_net_rcu(skb->dev);
1378 	int type = icmp_hdr(skb)->type;
1379 	int code = icmp_hdr(skb)->code;
1380 
1381 	/*
1382 	 * Use ping_err to handle all icmp errors except those
1383 	 * triggered by ICMP_ECHOREPLY which sent from kernel.
1384 	 */
1385 	if (icmph->type != ICMP_ECHOREPLY) {
1386 		ping_err(skb, offset, info);
1387 		return 0;
1388 	}
1389 
1390 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1391 		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1392 	else if (type == ICMP_REDIRECT)
1393 		ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1394 
1395 	return 0;
1396 }
1397 
1398 /*
1399  *	This table is the definition of how we handle ICMP.
1400  */
1401 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1402 	[ICMP_ECHOREPLY] = {
1403 		.handler = ping_rcv,
1404 	},
1405 	[1] = {
1406 		.handler = icmp_discard,
1407 		.error = 1,
1408 	},
1409 	[2] = {
1410 		.handler = icmp_discard,
1411 		.error = 1,
1412 	},
1413 	[ICMP_DEST_UNREACH] = {
1414 		.handler = icmp_unreach,
1415 		.error = 1,
1416 	},
1417 	[ICMP_SOURCE_QUENCH] = {
1418 		.handler = icmp_unreach,
1419 		.error = 1,
1420 	},
1421 	[ICMP_REDIRECT] = {
1422 		.handler = icmp_redirect,
1423 		.error = 1,
1424 	},
1425 	[6] = {
1426 		.handler = icmp_discard,
1427 		.error = 1,
1428 	},
1429 	[7] = {
1430 		.handler = icmp_discard,
1431 		.error = 1,
1432 	},
1433 	[ICMP_ECHO] = {
1434 		.handler = icmp_echo,
1435 	},
1436 	[9] = {
1437 		.handler = icmp_discard,
1438 		.error = 1,
1439 	},
1440 	[10] = {
1441 		.handler = icmp_discard,
1442 		.error = 1,
1443 	},
1444 	[ICMP_TIME_EXCEEDED] = {
1445 		.handler = icmp_unreach,
1446 		.error = 1,
1447 	},
1448 	[ICMP_PARAMETERPROB] = {
1449 		.handler = icmp_unreach,
1450 		.error = 1,
1451 	},
1452 	[ICMP_TIMESTAMP] = {
1453 		.handler = icmp_timestamp,
1454 	},
1455 	[ICMP_TIMESTAMPREPLY] = {
1456 		.handler = icmp_discard,
1457 	},
1458 	[ICMP_INFO_REQUEST] = {
1459 		.handler = icmp_discard,
1460 	},
1461 	[ICMP_INFO_REPLY] = {
1462 		.handler = icmp_discard,
1463 	},
1464 	[ICMP_ADDRESS] = {
1465 		.handler = icmp_discard,
1466 	},
1467 	[ICMP_ADDRESSREPLY] = {
1468 		.handler = icmp_discard,
1469 	},
1470 };
1471 
icmp_sk_init(struct net * net)1472 static int __net_init icmp_sk_init(struct net *net)
1473 {
1474 	/* Control parameters for ECHO replies. */
1475 	net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1476 	net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1477 	net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1478 
1479 	/* Control parameter - ignore bogus broadcast responses? */
1480 	net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1481 
1482 	/*
1483 	 * 	Configurable global rate limit.
1484 	 *
1485 	 *	ratelimit defines tokens/packet consumed for dst->rate_token
1486 	 *	bucket ratemask defines which icmp types are ratelimited by
1487 	 *	setting	it's bit position.
1488 	 *
1489 	 *	default:
1490 	 *	dest unreachable (3), source quench (4),
1491 	 *	time exceeded (11), parameter problem (12)
1492 	 */
1493 
1494 	net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1495 	net->ipv4.sysctl_icmp_ratemask = 0x1818;
1496 	net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1497 	net->ipv4.sysctl_icmp_msgs_per_sec = 1000;
1498 	net->ipv4.sysctl_icmp_msgs_burst = 50;
1499 
1500 	return 0;
1501 }
1502 
1503 static struct pernet_operations __net_initdata icmp_sk_ops = {
1504        .init = icmp_sk_init,
1505 };
1506 
icmp_init(void)1507 int __init icmp_init(void)
1508 {
1509 	int err, i;
1510 
1511 	for_each_possible_cpu(i) {
1512 		struct sock *sk;
1513 
1514 		err = inet_ctl_sock_create(&sk, PF_INET,
1515 					   SOCK_RAW, IPPROTO_ICMP, &init_net);
1516 		if (err < 0)
1517 			return err;
1518 
1519 		per_cpu(ipv4_icmp_sk, i) = sk;
1520 
1521 		/* Enough space for 2 64K ICMP packets, including
1522 		 * sk_buff/skb_shared_info struct overhead.
1523 		 */
1524 		sk->sk_sndbuf =	2 * SKB_TRUESIZE(64 * 1024);
1525 
1526 		/*
1527 		 * Speedup sock_wfree()
1528 		 */
1529 		sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1530 		inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1531 	}
1532 	return register_pernet_subsys(&icmp_sk_ops);
1533 }
1534