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 
96 /*
97  *	Build xmit assembly blocks
98  */
99 
100 struct icmp_bxm {
101 	struct sk_buff *skb;
102 	int offset;
103 	int data_len;
104 
105 	struct {
106 		struct icmphdr icmph;
107 		__be32	       times[3];
108 	} data;
109 	int head_len;
110 	struct ip_options_data replyopts;
111 };
112 
113 /* An array of errno for error messages from dest unreach. */
114 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
115 
116 const struct icmp_err icmp_err_convert[] = {
117 	{
118 		.errno = ENETUNREACH,	/* ICMP_NET_UNREACH */
119 		.fatal = 0,
120 	},
121 	{
122 		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNREACH */
123 		.fatal = 0,
124 	},
125 	{
126 		.errno = ENOPROTOOPT	/* ICMP_PROT_UNREACH */,
127 		.fatal = 1,
128 	},
129 	{
130 		.errno = ECONNREFUSED,	/* ICMP_PORT_UNREACH */
131 		.fatal = 1,
132 	},
133 	{
134 		.errno = EMSGSIZE,	/* ICMP_FRAG_NEEDED */
135 		.fatal = 0,
136 	},
137 	{
138 		.errno = EOPNOTSUPP,	/* ICMP_SR_FAILED */
139 		.fatal = 0,
140 	},
141 	{
142 		.errno = ENETUNREACH,	/* ICMP_NET_UNKNOWN */
143 		.fatal = 1,
144 	},
145 	{
146 		.errno = EHOSTDOWN,	/* ICMP_HOST_UNKNOWN */
147 		.fatal = 1,
148 	},
149 	{
150 		.errno = ENONET,	/* ICMP_HOST_ISOLATED */
151 		.fatal = 1,
152 	},
153 	{
154 		.errno = ENETUNREACH,	/* ICMP_NET_ANO	*/
155 		.fatal = 1,
156 	},
157 	{
158 		.errno = EHOSTUNREACH,	/* ICMP_HOST_ANO */
159 		.fatal = 1,
160 	},
161 	{
162 		.errno = ENETUNREACH,	/* ICMP_NET_UNR_TOS */
163 		.fatal = 0,
164 	},
165 	{
166 		.errno = EHOSTUNREACH,	/* ICMP_HOST_UNR_TOS */
167 		.fatal = 0,
168 	},
169 	{
170 		.errno = EHOSTUNREACH,	/* ICMP_PKT_FILTERED */
171 		.fatal = 1,
172 	},
173 	{
174 		.errno = EHOSTUNREACH,	/* ICMP_PREC_VIOLATION */
175 		.fatal = 1,
176 	},
177 	{
178 		.errno = EHOSTUNREACH,	/* ICMP_PREC_CUTOFF */
179 		.fatal = 1,
180 	},
181 };
182 EXPORT_SYMBOL(icmp_err_convert);
183 
184 /*
185  *	ICMP control array. This specifies what to do with each ICMP.
186  */
187 
188 struct icmp_control {
189 	enum skb_drop_reason (*handler)(struct sk_buff *skb);
190 	short   error;		/* This ICMP is classed as an error message */
191 };
192 
193 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
194 
195 static DEFINE_PER_CPU(struct sock *, ipv4_icmp_sk);
196 
197 /* Called with BH disabled */
icmp_xmit_lock(struct net * net)198 static inline struct sock *icmp_xmit_lock(struct net *net)
199 {
200 	struct sock *sk;
201 
202 	sk = this_cpu_read(ipv4_icmp_sk);
203 
204 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
205 		/* This can happen if the output path signals a
206 		 * dst_link_failure() for an outgoing ICMP packet.
207 		 */
208 		return NULL;
209 	}
210 	sock_net_set(sk, net);
211 	return sk;
212 }
213 
icmp_xmit_unlock(struct sock * sk)214 static inline void icmp_xmit_unlock(struct sock *sk)
215 {
216 	sock_net_set(sk, &init_net);
217 	spin_unlock(&sk->sk_lock.slock);
218 }
219 
220 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
221 int sysctl_icmp_msgs_burst __read_mostly = 50;
222 
223 static struct {
224 	spinlock_t	lock;
225 	u32		credit;
226 	u32		stamp;
227 } icmp_global = {
228 	.lock		= __SPIN_LOCK_UNLOCKED(icmp_global.lock),
229 };
230 
231 /**
232  * icmp_global_allow - Are we allowed to send one more ICMP message ?
233  *
234  * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
235  * Returns false if we reached the limit and can not send another packet.
236  * Note: called with BH disabled
237  */
icmp_global_allow(void)238 bool icmp_global_allow(void)
239 {
240 	u32 credit, delta, incr = 0, now = (u32)jiffies;
241 	bool rc = false;
242 
243 	/* Check if token bucket is empty and cannot be refilled
244 	 * without taking the spinlock. The READ_ONCE() are paired
245 	 * with the following WRITE_ONCE() in this same function.
246 	 */
247 	if (!READ_ONCE(icmp_global.credit)) {
248 		delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
249 		if (delta < HZ / 50)
250 			return false;
251 	}
252 
253 	spin_lock(&icmp_global.lock);
254 	delta = min_t(u32, now - icmp_global.stamp, HZ);
255 	if (delta >= HZ / 50) {
256 		incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
257 		if (incr)
258 			WRITE_ONCE(icmp_global.stamp, now);
259 	}
260 	credit = min_t(u32, icmp_global.credit + incr,
261 		       READ_ONCE(sysctl_icmp_msgs_burst));
262 	if (credit) {
263 		/* We want to use a credit of one in average, but need to randomize
264 		 * it for security reasons.
265 		 */
266 		credit = max_t(int, credit - prandom_u32_max(3), 0);
267 		rc = true;
268 	}
269 	WRITE_ONCE(icmp_global.credit, credit);
270 	spin_unlock(&icmp_global.lock);
271 	return rc;
272 }
273 EXPORT_SYMBOL(icmp_global_allow);
274 
icmpv4_mask_allow(struct net * net,int type,int code)275 static bool icmpv4_mask_allow(struct net *net, int type, int code)
276 {
277 	if (type > NR_ICMP_TYPES)
278 		return true;
279 
280 	/* Don't limit PMTU discovery. */
281 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
282 		return true;
283 
284 	/* Limit if icmp type is enabled in ratemask. */
285 	if (!((1 << type) & READ_ONCE(net->ipv4.sysctl_icmp_ratemask)))
286 		return true;
287 
288 	return false;
289 }
290 
icmpv4_global_allow(struct net * net,int type,int code)291 static bool icmpv4_global_allow(struct net *net, int type, int code)
292 {
293 	if (icmpv4_mask_allow(net, type, code))
294 		return true;
295 
296 	if (icmp_global_allow())
297 		return true;
298 
299 	return false;
300 }
301 
302 /*
303  *	Send an ICMP frame.
304  */
305 
icmpv4_xrlim_allow(struct net * net,struct rtable * rt,struct flowi4 * fl4,int type,int code)306 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
307 			       struct flowi4 *fl4, int type, int code)
308 {
309 	struct dst_entry *dst = &rt->dst;
310 	struct inet_peer *peer;
311 	bool rc = true;
312 	int vif;
313 
314 	if (icmpv4_mask_allow(net, type, code))
315 		goto out;
316 
317 	/* No rate limit on loopback */
318 	if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
319 		goto out;
320 
321 	vif = l3mdev_master_ifindex(dst->dev);
322 	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
323 	rc = inet_peer_xrlim_allow(peer,
324 				   READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
325 	if (peer)
326 		inet_putpeer(peer);
327 out:
328 	return rc;
329 }
330 
331 /*
332  *	Maintain the counters used in the SNMP statistics for outgoing ICMP
333  */
icmp_out_count(struct net * net,unsigned char type)334 void icmp_out_count(struct net *net, unsigned char type)
335 {
336 	ICMPMSGOUT_INC_STATS(net, type);
337 	ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
338 }
339 
340 /*
341  *	Checksum each fragment, and on the first include the headers and final
342  *	checksum.
343  */
icmp_glue_bits(void * from,char * to,int offset,int len,int odd,struct sk_buff * skb)344 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
345 			  struct sk_buff *skb)
346 {
347 	struct icmp_bxm *icmp_param = from;
348 	__wsum csum;
349 
350 	csum = skb_copy_and_csum_bits(icmp_param->skb,
351 				      icmp_param->offset + offset,
352 				      to, len);
353 
354 	skb->csum = csum_block_add(skb->csum, csum, odd);
355 	if (icmp_pointers[icmp_param->data.icmph.type].error)
356 		nf_ct_attach(skb, icmp_param->skb);
357 	return 0;
358 }
359 
icmp_push_reply(struct sock * sk,struct icmp_bxm * icmp_param,struct flowi4 * fl4,struct ipcm_cookie * ipc,struct rtable ** rt)360 static void icmp_push_reply(struct sock *sk,
361 			    struct icmp_bxm *icmp_param,
362 			    struct flowi4 *fl4,
363 			    struct ipcm_cookie *ipc, struct rtable **rt)
364 {
365 	struct sk_buff *skb;
366 
367 	if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
368 			   icmp_param->data_len+icmp_param->head_len,
369 			   icmp_param->head_len,
370 			   ipc, rt, MSG_DONTWAIT) < 0) {
371 		__ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
372 		ip_flush_pending_frames(sk);
373 	} else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
374 		struct icmphdr *icmph = icmp_hdr(skb);
375 		__wsum csum;
376 		struct sk_buff *skb1;
377 
378 		csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
379 						 (char *)icmph,
380 						 icmp_param->head_len);
381 		skb_queue_walk(&sk->sk_write_queue, skb1) {
382 			csum = csum_add(csum, skb1->csum);
383 		}
384 		icmph->checksum = csum_fold(csum);
385 		skb->ip_summed = CHECKSUM_NONE;
386 		ip_push_pending_frames(sk, fl4);
387 	}
388 }
389 
390 /*
391  *	Driving logic for building and sending ICMP messages.
392  */
393 
icmp_reply(struct icmp_bxm * icmp_param,struct sk_buff * skb)394 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
395 {
396 	struct ipcm_cookie ipc;
397 	struct rtable *rt = skb_rtable(skb);
398 	struct net *net = dev_net(rt->dst.dev);
399 	struct flowi4 fl4;
400 	struct sock *sk;
401 	struct inet_sock *inet;
402 	__be32 daddr, saddr;
403 	u32 mark = IP4_REPLY_MARK(net, skb->mark);
404 	int type = icmp_param->data.icmph.type;
405 	int code = icmp_param->data.icmph.code;
406 
407 	if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
408 		return;
409 
410 	/* Needed by both icmp_global_allow and icmp_xmit_lock */
411 	local_bh_disable();
412 
413 	/* global icmp_msgs_per_sec */
414 	if (!icmpv4_global_allow(net, type, code))
415 		goto out_bh_enable;
416 
417 	sk = icmp_xmit_lock(net);
418 	if (!sk)
419 		goto out_bh_enable;
420 	inet = inet_sk(sk);
421 
422 	icmp_param->data.icmph.checksum = 0;
423 
424 	ipcm_init(&ipc);
425 	inet->tos = ip_hdr(skb)->tos;
426 	ipc.sockc.mark = mark;
427 	daddr = ipc.addr = ip_hdr(skb)->saddr;
428 	saddr = fib_compute_spec_dst(skb);
429 
430 	if (icmp_param->replyopts.opt.opt.optlen) {
431 		ipc.opt = &icmp_param->replyopts.opt;
432 		if (ipc.opt->opt.srr)
433 			daddr = icmp_param->replyopts.opt.opt.faddr;
434 	}
435 	memset(&fl4, 0, sizeof(fl4));
436 	fl4.daddr = daddr;
437 	fl4.saddr = saddr;
438 	fl4.flowi4_mark = mark;
439 	fl4.flowi4_uid = sock_net_uid(net, NULL);
440 	fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
441 	fl4.flowi4_proto = IPPROTO_ICMP;
442 	fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
443 	security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4));
444 	rt = ip_route_output_key(net, &fl4);
445 	if (IS_ERR(rt))
446 		goto out_unlock;
447 	if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
448 		icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
449 	ip_rt_put(rt);
450 out_unlock:
451 	icmp_xmit_unlock(sk);
452 out_bh_enable:
453 	local_bh_enable();
454 }
455 
456 /*
457  * The device used for looking up which routing table to use for sending an ICMP
458  * error is preferably the source whenever it is set, which should ensure the
459  * icmp error can be sent to the source host, else lookup using the routing
460  * table of the destination device, else use the main routing table (index 0).
461  */
icmp_get_route_lookup_dev(struct sk_buff * skb)462 static struct net_device *icmp_get_route_lookup_dev(struct sk_buff *skb)
463 {
464 	struct net_device *route_lookup_dev = NULL;
465 
466 	if (skb->dev)
467 		route_lookup_dev = skb->dev;
468 	else if (skb_dst(skb))
469 		route_lookup_dev = skb_dst(skb)->dev;
470 	return route_lookup_dev;
471 }
472 
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)473 static struct rtable *icmp_route_lookup(struct net *net,
474 					struct flowi4 *fl4,
475 					struct sk_buff *skb_in,
476 					const struct iphdr *iph,
477 					__be32 saddr, u8 tos, u32 mark,
478 					int type, int code,
479 					struct icmp_bxm *param)
480 {
481 	struct net_device *route_lookup_dev;
482 	struct rtable *rt, *rt2;
483 	struct flowi4 fl4_dec;
484 	int err;
485 
486 	memset(fl4, 0, sizeof(*fl4));
487 	fl4->daddr = (param->replyopts.opt.opt.srr ?
488 		      param->replyopts.opt.opt.faddr : iph->saddr);
489 	fl4->saddr = saddr;
490 	fl4->flowi4_mark = mark;
491 	fl4->flowi4_uid = sock_net_uid(net, NULL);
492 	fl4->flowi4_tos = RT_TOS(tos);
493 	fl4->flowi4_proto = IPPROTO_ICMP;
494 	fl4->fl4_icmp_type = type;
495 	fl4->fl4_icmp_code = code;
496 	route_lookup_dev = icmp_get_route_lookup_dev(skb_in);
497 	fl4->flowi4_oif = l3mdev_master_ifindex(route_lookup_dev);
498 
499 	security_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));
500 	rt = ip_route_output_key_hash(net, fl4, skb_in);
501 	if (IS_ERR(rt))
502 		return rt;
503 
504 	/* No need to clone since we're just using its address. */
505 	rt2 = rt;
506 
507 	rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
508 					   flowi4_to_flowi(fl4), NULL, 0);
509 	if (!IS_ERR(rt)) {
510 		if (rt != rt2)
511 			return rt;
512 	} else if (PTR_ERR(rt) == -EPERM) {
513 		rt = NULL;
514 	} else
515 		return rt;
516 
517 	err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
518 	if (err)
519 		goto relookup_failed;
520 
521 	if (inet_addr_type_dev_table(net, route_lookup_dev,
522 				     fl4_dec.saddr) == RTN_LOCAL) {
523 		rt2 = __ip_route_output_key(net, &fl4_dec);
524 		if (IS_ERR(rt2))
525 			err = PTR_ERR(rt2);
526 	} else {
527 		struct flowi4 fl4_2 = {};
528 		unsigned long orefdst;
529 
530 		fl4_2.daddr = fl4_dec.saddr;
531 		rt2 = ip_route_output_key(net, &fl4_2);
532 		if (IS_ERR(rt2)) {
533 			err = PTR_ERR(rt2);
534 			goto relookup_failed;
535 		}
536 		/* Ugh! */
537 		orefdst = skb_in->_skb_refdst; /* save old refdst */
538 		skb_dst_set(skb_in, NULL);
539 		err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
540 				     RT_TOS(tos), rt2->dst.dev);
541 
542 		dst_release(&rt2->dst);
543 		rt2 = skb_rtable(skb_in);
544 		skb_in->_skb_refdst = orefdst; /* restore old refdst */
545 	}
546 
547 	if (err)
548 		goto relookup_failed;
549 
550 	rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
551 					    flowi4_to_flowi(&fl4_dec), NULL,
552 					    XFRM_LOOKUP_ICMP);
553 	if (!IS_ERR(rt2)) {
554 		dst_release(&rt->dst);
555 		memcpy(fl4, &fl4_dec, sizeof(*fl4));
556 		rt = rt2;
557 	} else if (PTR_ERR(rt2) == -EPERM) {
558 		if (rt)
559 			dst_release(&rt->dst);
560 		return rt2;
561 	} else {
562 		err = PTR_ERR(rt2);
563 		goto relookup_failed;
564 	}
565 	return rt;
566 
567 relookup_failed:
568 	if (rt)
569 		return rt;
570 	return ERR_PTR(err);
571 }
572 
573 /*
574  *	Send an ICMP message in response to a situation
575  *
576  *	RFC 1122: 3.2.2	MUST send at least the IP header and 8 bytes of header.
577  *		  MAY send more (we do).
578  *			MUST NOT change this header information.
579  *			MUST NOT reply to a multicast/broadcast IP address.
580  *			MUST NOT reply to a multicast/broadcast MAC address.
581  *			MUST reply to only the first fragment.
582  */
583 
__icmp_send(struct sk_buff * skb_in,int type,int code,__be32 info,const struct ip_options * opt)584 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
585 		 const struct ip_options *opt)
586 {
587 	struct iphdr *iph;
588 	int room;
589 	struct icmp_bxm icmp_param;
590 	struct rtable *rt = skb_rtable(skb_in);
591 	struct ipcm_cookie ipc;
592 	struct flowi4 fl4;
593 	__be32 saddr;
594 	u8  tos;
595 	u32 mark;
596 	struct net *net;
597 	struct sock *sk;
598 
599 	if (!rt)
600 		goto out;
601 
602 	if (rt->dst.dev)
603 		net = dev_net(rt->dst.dev);
604 	else if (skb_in->dev)
605 		net = dev_net(skb_in->dev);
606 	else
607 		goto out;
608 
609 	/*
610 	 *	Find the original header. It is expected to be valid, of course.
611 	 *	Check this, icmp_send is called from the most obscure devices
612 	 *	sometimes.
613 	 */
614 	iph = ip_hdr(skb_in);
615 
616 	if ((u8 *)iph < skb_in->head ||
617 	    (skb_network_header(skb_in) + sizeof(*iph)) >
618 	    skb_tail_pointer(skb_in))
619 		goto out;
620 
621 	/*
622 	 *	No replies to physical multicast/broadcast
623 	 */
624 	if (skb_in->pkt_type != PACKET_HOST)
625 		goto out;
626 
627 	/*
628 	 *	Now check at the protocol level
629 	 */
630 	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
631 		goto out;
632 
633 	/*
634 	 *	Only reply to fragment 0. We byte re-order the constant
635 	 *	mask for efficiency.
636 	 */
637 	if (iph->frag_off & htons(IP_OFFSET))
638 		goto out;
639 
640 	/*
641 	 *	If we send an ICMP error to an ICMP error a mess would result..
642 	 */
643 	if (icmp_pointers[type].error) {
644 		/*
645 		 *	We are an error, check if we are replying to an
646 		 *	ICMP error
647 		 */
648 		if (iph->protocol == IPPROTO_ICMP) {
649 			u8 _inner_type, *itp;
650 
651 			itp = skb_header_pointer(skb_in,
652 						 skb_network_header(skb_in) +
653 						 (iph->ihl << 2) +
654 						 offsetof(struct icmphdr,
655 							  type) -
656 						 skb_in->data,
657 						 sizeof(_inner_type),
658 						 &_inner_type);
659 			if (!itp)
660 				goto out;
661 
662 			/*
663 			 *	Assume any unknown ICMP type is an error. This
664 			 *	isn't specified by the RFC, but think about it..
665 			 */
666 			if (*itp > NR_ICMP_TYPES ||
667 			    icmp_pointers[*itp].error)
668 				goto out;
669 		}
670 	}
671 
672 	/* Needed by both icmp_global_allow and icmp_xmit_lock */
673 	local_bh_disable();
674 
675 	/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
676 	 * incoming dev is loopback.  If outgoing dev change to not be
677 	 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
678 	 */
679 	if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
680 	      !icmpv4_global_allow(net, type, code))
681 		goto out_bh_enable;
682 
683 	sk = icmp_xmit_lock(net);
684 	if (!sk)
685 		goto out_bh_enable;
686 
687 	/*
688 	 *	Construct source address and options.
689 	 */
690 
691 	saddr = iph->daddr;
692 	if (!(rt->rt_flags & RTCF_LOCAL)) {
693 		struct net_device *dev = NULL;
694 
695 		rcu_read_lock();
696 		if (rt_is_input_route(rt) &&
697 		    READ_ONCE(net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr))
698 			dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
699 
700 		if (dev)
701 			saddr = inet_select_addr(dev, iph->saddr,
702 						 RT_SCOPE_LINK);
703 		else
704 			saddr = 0;
705 		rcu_read_unlock();
706 	}
707 
708 	tos = icmp_pointers[type].error ? (RT_TOS(iph->tos) |
709 					   IPTOS_PREC_INTERNETCONTROL) :
710 					   iph->tos;
711 	mark = IP4_REPLY_MARK(net, skb_in->mark);
712 
713 	if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
714 		goto out_unlock;
715 
716 
717 	/*
718 	 *	Prepare data for ICMP header.
719 	 */
720 
721 	icmp_param.data.icmph.type	 = type;
722 	icmp_param.data.icmph.code	 = code;
723 	icmp_param.data.icmph.un.gateway = info;
724 	icmp_param.data.icmph.checksum	 = 0;
725 	icmp_param.skb	  = skb_in;
726 	icmp_param.offset = skb_network_offset(skb_in);
727 	inet_sk(sk)->tos = tos;
728 	ipcm_init(&ipc);
729 	ipc.addr = iph->saddr;
730 	ipc.opt = &icmp_param.replyopts.opt;
731 	ipc.sockc.mark = mark;
732 
733 	rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
734 			       type, code, &icmp_param);
735 	if (IS_ERR(rt))
736 		goto out_unlock;
737 
738 	/* peer icmp_ratelimit */
739 	if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
740 		goto ende;
741 
742 	/* RFC says return as much as we can without exceeding 576 bytes. */
743 
744 	room = dst_mtu(&rt->dst);
745 	if (room > 576)
746 		room = 576;
747 	room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
748 	room -= sizeof(struct icmphdr);
749 
750 	icmp_param.data_len = skb_in->len - icmp_param.offset;
751 	if (icmp_param.data_len > room)
752 		icmp_param.data_len = room;
753 	icmp_param.head_len = sizeof(struct icmphdr);
754 
755 	/* if we don't have a source address at this point, fall back to the
756 	 * dummy address instead of sending out a packet with a source address
757 	 * of 0.0.0.0
758 	 */
759 	if (!fl4.saddr)
760 		fl4.saddr = htonl(INADDR_DUMMY);
761 
762 	icmp_push_reply(sk, &icmp_param, &fl4, &ipc, &rt);
763 ende:
764 	ip_rt_put(rt);
765 out_unlock:
766 	icmp_xmit_unlock(sk);
767 out_bh_enable:
768 	local_bh_enable();
769 out:;
770 }
771 EXPORT_SYMBOL(__icmp_send);
772 
773 #if IS_ENABLED(CONFIG_NF_NAT)
774 #include <net/netfilter/nf_conntrack.h>
icmp_ndo_send(struct sk_buff * skb_in,int type,int code,__be32 info)775 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
776 {
777 	struct sk_buff *cloned_skb = NULL;
778 	struct ip_options opts = { 0 };
779 	enum ip_conntrack_info ctinfo;
780 	struct nf_conn *ct;
781 	__be32 orig_ip;
782 
783 	ct = nf_ct_get(skb_in, &ctinfo);
784 	if (!ct || !(ct->status & IPS_SRC_NAT)) {
785 		__icmp_send(skb_in, type, code, info, &opts);
786 		return;
787 	}
788 
789 	if (skb_shared(skb_in))
790 		skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
791 
792 	if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
793 	    (skb_network_header(skb_in) + sizeof(struct iphdr)) >
794 	    skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
795 	    skb_network_offset(skb_in) + sizeof(struct iphdr))))
796 		goto out;
797 
798 	orig_ip = ip_hdr(skb_in)->saddr;
799 	ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
800 	__icmp_send(skb_in, type, code, info, &opts);
801 	ip_hdr(skb_in)->saddr = orig_ip;
802 out:
803 	consume_skb(cloned_skb);
804 }
805 EXPORT_SYMBOL(icmp_ndo_send);
806 #endif
807 
icmp_socket_deliver(struct sk_buff * skb,u32 info)808 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
809 {
810 	const struct iphdr *iph = (const struct iphdr *)skb->data;
811 	const struct net_protocol *ipprot;
812 	int protocol = iph->protocol;
813 
814 	/* Checkin full IP header plus 8 bytes of protocol to
815 	 * avoid additional coding at protocol handlers.
816 	 */
817 	if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
818 		__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
819 		return;
820 	}
821 
822 	raw_icmp_error(skb, protocol, info);
823 
824 	ipprot = rcu_dereference(inet_protos[protocol]);
825 	if (ipprot && ipprot->err_handler)
826 		ipprot->err_handler(skb, info);
827 }
828 
icmp_tag_validation(int proto)829 static bool icmp_tag_validation(int proto)
830 {
831 	bool ok;
832 
833 	rcu_read_lock();
834 	ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
835 	rcu_read_unlock();
836 	return ok;
837 }
838 
839 /*
840  *	Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
841  *	ICMP_PARAMETERPROB.
842  */
843 
icmp_unreach(struct sk_buff * skb)844 static enum skb_drop_reason icmp_unreach(struct sk_buff *skb)
845 {
846 	enum skb_drop_reason reason = SKB_NOT_DROPPED_YET;
847 	const struct iphdr *iph;
848 	struct icmphdr *icmph;
849 	struct net *net;
850 	u32 info = 0;
851 
852 	net = dev_net(skb_dst(skb)->dev);
853 
854 	/*
855 	 *	Incomplete header ?
856 	 * 	Only checks for the IP header, there should be an
857 	 *	additional check for longer headers in upper levels.
858 	 */
859 
860 	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
861 		goto out_err;
862 
863 	icmph = icmp_hdr(skb);
864 	iph   = (const struct iphdr *)skb->data;
865 
866 	if (iph->ihl < 5)  { /* Mangled header, drop. */
867 		reason = SKB_DROP_REASON_IP_INHDR;
868 		goto out_err;
869 	}
870 
871 	switch (icmph->type) {
872 	case ICMP_DEST_UNREACH:
873 		switch (icmph->code & 15) {
874 		case ICMP_NET_UNREACH:
875 		case ICMP_HOST_UNREACH:
876 		case ICMP_PROT_UNREACH:
877 		case ICMP_PORT_UNREACH:
878 			break;
879 		case ICMP_FRAG_NEEDED:
880 			/* for documentation of the ip_no_pmtu_disc
881 			 * values please see
882 			 * Documentation/networking/ip-sysctl.rst
883 			 */
884 			switch (READ_ONCE(net->ipv4.sysctl_ip_no_pmtu_disc)) {
885 			default:
886 				net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
887 						    &iph->daddr);
888 				break;
889 			case 2:
890 				goto out;
891 			case 3:
892 				if (!icmp_tag_validation(iph->protocol))
893 					goto out;
894 				fallthrough;
895 			case 0:
896 				info = ntohs(icmph->un.frag.mtu);
897 			}
898 			break;
899 		case ICMP_SR_FAILED:
900 			net_dbg_ratelimited("%pI4: Source Route Failed\n",
901 					    &iph->daddr);
902 			break;
903 		default:
904 			break;
905 		}
906 		if (icmph->code > NR_ICMP_UNREACH)
907 			goto out;
908 		break;
909 	case ICMP_PARAMETERPROB:
910 		info = ntohl(icmph->un.gateway) >> 24;
911 		break;
912 	case ICMP_TIME_EXCEEDED:
913 		__ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
914 		if (icmph->code == ICMP_EXC_FRAGTIME)
915 			goto out;
916 		break;
917 	}
918 
919 	/*
920 	 *	Throw it at our lower layers
921 	 *
922 	 *	RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
923 	 *		  header.
924 	 *	RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
925 	 *		  transport layer.
926 	 *	RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
927 	 *		  transport layer.
928 	 */
929 
930 	/*
931 	 *	Check the other end isn't violating RFC 1122. Some routers send
932 	 *	bogus responses to broadcast frames. If you see this message
933 	 *	first check your netmask matches at both ends, if it does then
934 	 *	get the other vendor to fix their kit.
935 	 */
936 
937 	if (!READ_ONCE(net->ipv4.sysctl_icmp_ignore_bogus_error_responses) &&
938 	    inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
939 		net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
940 				     &ip_hdr(skb)->saddr,
941 				     icmph->type, icmph->code,
942 				     &iph->daddr, skb->dev->name);
943 		goto out;
944 	}
945 
946 	icmp_socket_deliver(skb, info);
947 
948 out:
949 	return reason;
950 out_err:
951 	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
952 	return reason ?: SKB_DROP_REASON_NOT_SPECIFIED;
953 }
954 
955 
956 /*
957  *	Handle ICMP_REDIRECT.
958  */
959 
icmp_redirect(struct sk_buff * skb)960 static enum skb_drop_reason icmp_redirect(struct sk_buff *skb)
961 {
962 	if (skb->len < sizeof(struct iphdr)) {
963 		__ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
964 		return SKB_DROP_REASON_PKT_TOO_SMALL;
965 	}
966 
967 	if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
968 		/* there aught to be a stat */
969 		return SKB_DROP_REASON_NOMEM;
970 	}
971 
972 	icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
973 	return SKB_NOT_DROPPED_YET;
974 }
975 
976 /*
977  *	Handle ICMP_ECHO ("ping") and ICMP_EXT_ECHO ("PROBE") requests.
978  *
979  *	RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
980  *		  requests.
981  *	RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
982  *		  included in the reply.
983  *	RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
984  *		  echo requests, MUST have default=NOT.
985  *	RFC 8335: 8 MUST have a config option to enable/disable ICMP
986  *		  Extended Echo Functionality, MUST be disabled by default
987  *	See also WRT handling of options once they are done and working.
988  */
989 
icmp_echo(struct sk_buff * skb)990 static enum skb_drop_reason icmp_echo(struct sk_buff *skb)
991 {
992 	struct icmp_bxm icmp_param;
993 	struct net *net;
994 
995 	net = dev_net(skb_dst(skb)->dev);
996 	/* should there be an ICMP stat for ignored echos? */
997 	if (READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_all))
998 		return SKB_NOT_DROPPED_YET;
999 
1000 	icmp_param.data.icmph	   = *icmp_hdr(skb);
1001 	icmp_param.skb		   = skb;
1002 	icmp_param.offset	   = 0;
1003 	icmp_param.data_len	   = skb->len;
1004 	icmp_param.head_len	   = sizeof(struct icmphdr);
1005 
1006 	if (icmp_param.data.icmph.type == ICMP_ECHO)
1007 		icmp_param.data.icmph.type = ICMP_ECHOREPLY;
1008 	else if (!icmp_build_probe(skb, &icmp_param.data.icmph))
1009 		return SKB_NOT_DROPPED_YET;
1010 
1011 	icmp_reply(&icmp_param, skb);
1012 	return SKB_NOT_DROPPED_YET;
1013 }
1014 
1015 /*	Helper for icmp_echo and icmpv6_echo_reply.
1016  *	Searches for net_device that matches PROBE interface identifier
1017  *		and builds PROBE reply message in icmphdr.
1018  *
1019  *	Returns false if PROBE responses are disabled via sysctl
1020  */
1021 
icmp_build_probe(struct sk_buff * skb,struct icmphdr * icmphdr)1022 bool icmp_build_probe(struct sk_buff *skb, struct icmphdr *icmphdr)
1023 {
1024 	struct icmp_ext_hdr *ext_hdr, _ext_hdr;
1025 	struct icmp_ext_echo_iio *iio, _iio;
1026 	struct net *net = dev_net(skb->dev);
1027 	struct net_device *dev;
1028 	char buff[IFNAMSIZ];
1029 	u16 ident_len;
1030 	u8 status;
1031 
1032 	if (!READ_ONCE(net->ipv4.sysctl_icmp_echo_enable_probe))
1033 		return false;
1034 
1035 	/* We currently only support probing interfaces on the proxy node
1036 	 * Check to ensure L-bit is set
1037 	 */
1038 	if (!(ntohs(icmphdr->un.echo.sequence) & 1))
1039 		return false;
1040 	/* Clear status bits in reply message */
1041 	icmphdr->un.echo.sequence &= htons(0xFF00);
1042 	if (icmphdr->type == ICMP_EXT_ECHO)
1043 		icmphdr->type = ICMP_EXT_ECHOREPLY;
1044 	else
1045 		icmphdr->type = ICMPV6_EXT_ECHO_REPLY;
1046 	ext_hdr = skb_header_pointer(skb, 0, sizeof(_ext_hdr), &_ext_hdr);
1047 	/* Size of iio is class_type dependent.
1048 	 * Only check header here and assign length based on ctype in the switch statement
1049 	 */
1050 	iio = skb_header_pointer(skb, sizeof(_ext_hdr), sizeof(iio->extobj_hdr), &_iio);
1051 	if (!ext_hdr || !iio)
1052 		goto send_mal_query;
1053 	if (ntohs(iio->extobj_hdr.length) <= sizeof(iio->extobj_hdr) ||
1054 	    ntohs(iio->extobj_hdr.length) > sizeof(_iio))
1055 		goto send_mal_query;
1056 	ident_len = ntohs(iio->extobj_hdr.length) - sizeof(iio->extobj_hdr);
1057 	iio = skb_header_pointer(skb, sizeof(_ext_hdr),
1058 				 sizeof(iio->extobj_hdr) + ident_len, &_iio);
1059 	if (!iio)
1060 		goto send_mal_query;
1061 
1062 	status = 0;
1063 	dev = NULL;
1064 	switch (iio->extobj_hdr.class_type) {
1065 	case ICMP_EXT_ECHO_CTYPE_NAME:
1066 		if (ident_len >= IFNAMSIZ)
1067 			goto send_mal_query;
1068 		memset(buff, 0, sizeof(buff));
1069 		memcpy(buff, &iio->ident.name, ident_len);
1070 		dev = dev_get_by_name(net, buff);
1071 		break;
1072 	case ICMP_EXT_ECHO_CTYPE_INDEX:
1073 		if (ident_len != sizeof(iio->ident.ifindex))
1074 			goto send_mal_query;
1075 		dev = dev_get_by_index(net, ntohl(iio->ident.ifindex));
1076 		break;
1077 	case ICMP_EXT_ECHO_CTYPE_ADDR:
1078 		if (ident_len < sizeof(iio->ident.addr.ctype3_hdr) ||
1079 		    ident_len != sizeof(iio->ident.addr.ctype3_hdr) +
1080 				 iio->ident.addr.ctype3_hdr.addrlen)
1081 			goto send_mal_query;
1082 		switch (ntohs(iio->ident.addr.ctype3_hdr.afi)) {
1083 		case ICMP_AFI_IP:
1084 			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in_addr))
1085 				goto send_mal_query;
1086 			dev = ip_dev_find(net, iio->ident.addr.ip_addr.ipv4_addr);
1087 			break;
1088 #if IS_ENABLED(CONFIG_IPV6)
1089 		case ICMP_AFI_IP6:
1090 			if (iio->ident.addr.ctype3_hdr.addrlen != sizeof(struct in6_addr))
1091 				goto send_mal_query;
1092 			dev = ipv6_stub->ipv6_dev_find(net, &iio->ident.addr.ip_addr.ipv6_addr, dev);
1093 			dev_hold(dev);
1094 			break;
1095 #endif
1096 		default:
1097 			goto send_mal_query;
1098 		}
1099 		break;
1100 	default:
1101 		goto send_mal_query;
1102 	}
1103 	if (!dev) {
1104 		icmphdr->code = ICMP_EXT_CODE_NO_IF;
1105 		return true;
1106 	}
1107 	/* Fill bits in reply message */
1108 	if (dev->flags & IFF_UP)
1109 		status |= ICMP_EXT_ECHOREPLY_ACTIVE;
1110 	if (__in_dev_get_rcu(dev) && __in_dev_get_rcu(dev)->ifa_list)
1111 		status |= ICMP_EXT_ECHOREPLY_IPV4;
1112 	if (!list_empty(&rcu_dereference(dev->ip6_ptr)->addr_list))
1113 		status |= ICMP_EXT_ECHOREPLY_IPV6;
1114 	dev_put(dev);
1115 	icmphdr->un.echo.sequence |= htons(status);
1116 	return true;
1117 send_mal_query:
1118 	icmphdr->code = ICMP_EXT_CODE_MAL_QUERY;
1119 	return true;
1120 }
1121 EXPORT_SYMBOL_GPL(icmp_build_probe);
1122 
1123 /*
1124  *	Handle ICMP Timestamp requests.
1125  *	RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
1126  *		  SHOULD be in the kernel for minimum random latency.
1127  *		  MUST be accurate to a few minutes.
1128  *		  MUST be updated at least at 15Hz.
1129  */
icmp_timestamp(struct sk_buff * skb)1130 static enum skb_drop_reason icmp_timestamp(struct sk_buff *skb)
1131 {
1132 	struct icmp_bxm icmp_param;
1133 	/*
1134 	 *	Too short.
1135 	 */
1136 	if (skb->len < 4)
1137 		goto out_err;
1138 
1139 	/*
1140 	 *	Fill in the current time as ms since midnight UT:
1141 	 */
1142 	icmp_param.data.times[1] = inet_current_timestamp();
1143 	icmp_param.data.times[2] = icmp_param.data.times[1];
1144 
1145 	BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
1146 
1147 	icmp_param.data.icmph	   = *icmp_hdr(skb);
1148 	icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
1149 	icmp_param.data.icmph.code = 0;
1150 	icmp_param.skb		   = skb;
1151 	icmp_param.offset	   = 0;
1152 	icmp_param.data_len	   = 0;
1153 	icmp_param.head_len	   = sizeof(struct icmphdr) + 12;
1154 	icmp_reply(&icmp_param, skb);
1155 	return SKB_NOT_DROPPED_YET;
1156 
1157 out_err:
1158 	__ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1159 	return SKB_DROP_REASON_PKT_TOO_SMALL;
1160 }
1161 
icmp_discard(struct sk_buff * skb)1162 static enum skb_drop_reason icmp_discard(struct sk_buff *skb)
1163 {
1164 	/* pretend it was a success */
1165 	return SKB_NOT_DROPPED_YET;
1166 }
1167 
1168 /*
1169  *	Deal with incoming ICMP packets.
1170  */
icmp_rcv(struct sk_buff * skb)1171 int icmp_rcv(struct sk_buff *skb)
1172 {
1173 	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
1174 	struct rtable *rt = skb_rtable(skb);
1175 	struct net *net = dev_net(rt->dst.dev);
1176 	struct icmphdr *icmph;
1177 
1178 	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1179 		struct sec_path *sp = skb_sec_path(skb);
1180 		int nh;
1181 
1182 		if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1183 				 XFRM_STATE_ICMP)) {
1184 			reason = SKB_DROP_REASON_XFRM_POLICY;
1185 			goto drop;
1186 		}
1187 
1188 		if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1189 			goto drop;
1190 
1191 		nh = skb_network_offset(skb);
1192 		skb_set_network_header(skb, sizeof(*icmph));
1193 
1194 		if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN,
1195 						skb)) {
1196 			reason = SKB_DROP_REASON_XFRM_POLICY;
1197 			goto drop;
1198 		}
1199 
1200 		skb_set_network_header(skb, nh);
1201 	}
1202 
1203 	__ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1204 
1205 	if (skb_checksum_simple_validate(skb))
1206 		goto csum_error;
1207 
1208 	if (!pskb_pull(skb, sizeof(*icmph)))
1209 		goto error;
1210 
1211 	icmph = icmp_hdr(skb);
1212 
1213 	ICMPMSGIN_INC_STATS(net, icmph->type);
1214 
1215 	/* Check for ICMP Extended Echo (PROBE) messages */
1216 	if (icmph->type == ICMP_EXT_ECHO) {
1217 		/* We can't use icmp_pointers[].handler() because it is an array of
1218 		 * size NR_ICMP_TYPES + 1 (19 elements) and PROBE has code 42.
1219 		 */
1220 		reason = icmp_echo(skb);
1221 		goto reason_check;
1222 	}
1223 
1224 	if (icmph->type == ICMP_EXT_ECHOREPLY) {
1225 		reason = ping_rcv(skb);
1226 		goto reason_check;
1227 	}
1228 
1229 	/*
1230 	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
1231 	 *
1232 	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1233 	 *		  discarded.
1234 	 */
1235 	if (icmph->type > NR_ICMP_TYPES) {
1236 		reason = SKB_DROP_REASON_UNHANDLED_PROTO;
1237 		goto error;
1238 	}
1239 
1240 	/*
1241 	 *	Parse the ICMP message
1242 	 */
1243 
1244 	if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1245 		/*
1246 		 *	RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1247 		 *	  silently ignored (we let user decide with a sysctl).
1248 		 *	RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1249 		 *	  discarded if to broadcast/multicast.
1250 		 */
1251 		if ((icmph->type == ICMP_ECHO ||
1252 		     icmph->type == ICMP_TIMESTAMP) &&
1253 		    READ_ONCE(net->ipv4.sysctl_icmp_echo_ignore_broadcasts)) {
1254 			reason = SKB_DROP_REASON_INVALID_PROTO;
1255 			goto error;
1256 		}
1257 		if (icmph->type != ICMP_ECHO &&
1258 		    icmph->type != ICMP_TIMESTAMP &&
1259 		    icmph->type != ICMP_ADDRESS &&
1260 		    icmph->type != ICMP_ADDRESSREPLY) {
1261 			reason = SKB_DROP_REASON_INVALID_PROTO;
1262 			goto error;
1263 		}
1264 	}
1265 
1266 	reason = icmp_pointers[icmph->type].handler(skb);
1267 reason_check:
1268 	if (!reason)  {
1269 		consume_skb(skb);
1270 		return NET_RX_SUCCESS;
1271 	}
1272 
1273 drop:
1274 	kfree_skb_reason(skb, reason);
1275 	return NET_RX_DROP;
1276 csum_error:
1277 	reason = SKB_DROP_REASON_ICMP_CSUM;
1278 	__ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1279 error:
1280 	__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1281 	goto drop;
1282 }
1283 
ip_icmp_error_rfc4884_validate(const struct sk_buff * skb,int off)1284 static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
1285 {
1286 	struct icmp_extobj_hdr *objh, _objh;
1287 	struct icmp_ext_hdr *exth, _exth;
1288 	u16 olen;
1289 
1290 	exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
1291 	if (!exth)
1292 		return false;
1293 	if (exth->version != 2)
1294 		return true;
1295 
1296 	if (exth->checksum &&
1297 	    csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
1298 		return false;
1299 
1300 	off += sizeof(_exth);
1301 	while (off < skb->len) {
1302 		objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
1303 		if (!objh)
1304 			return false;
1305 
1306 		olen = ntohs(objh->length);
1307 		if (olen < sizeof(_objh))
1308 			return false;
1309 
1310 		off += olen;
1311 		if (off > skb->len)
1312 			return false;
1313 	}
1314 
1315 	return true;
1316 }
1317 
ip_icmp_error_rfc4884(const struct sk_buff * skb,struct sock_ee_data_rfc4884 * out,int thlen,int off)1318 void ip_icmp_error_rfc4884(const struct sk_buff *skb,
1319 			   struct sock_ee_data_rfc4884 *out,
1320 			   int thlen, int off)
1321 {
1322 	int hlen;
1323 
1324 	/* original datagram headers: end of icmph to payload (skb->data) */
1325 	hlen = -skb_transport_offset(skb) - thlen;
1326 
1327 	/* per rfc 4884: minimal datagram length of 128 bytes */
1328 	if (off < 128 || off < hlen)
1329 		return;
1330 
1331 	/* kernel has stripped headers: return payload offset in bytes */
1332 	off -= hlen;
1333 	if (off + sizeof(struct icmp_ext_hdr) > skb->len)
1334 		return;
1335 
1336 	out->len = off;
1337 
1338 	if (!ip_icmp_error_rfc4884_validate(skb, off))
1339 		out->flags |= SO_EE_RFC4884_FLAG_INVALID;
1340 }
1341 EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
1342 
icmp_err(struct sk_buff * skb,u32 info)1343 int icmp_err(struct sk_buff *skb, u32 info)
1344 {
1345 	struct iphdr *iph = (struct iphdr *)skb->data;
1346 	int offset = iph->ihl<<2;
1347 	struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1348 	int type = icmp_hdr(skb)->type;
1349 	int code = icmp_hdr(skb)->code;
1350 	struct net *net = dev_net(skb->dev);
1351 
1352 	/*
1353 	 * Use ping_err to handle all icmp errors except those
1354 	 * triggered by ICMP_ECHOREPLY which sent from kernel.
1355 	 */
1356 	if (icmph->type != ICMP_ECHOREPLY) {
1357 		ping_err(skb, offset, info);
1358 		return 0;
1359 	}
1360 
1361 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1362 		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1363 	else if (type == ICMP_REDIRECT)
1364 		ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1365 
1366 	return 0;
1367 }
1368 
1369 /*
1370  *	This table is the definition of how we handle ICMP.
1371  */
1372 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1373 	[ICMP_ECHOREPLY] = {
1374 		.handler = ping_rcv,
1375 	},
1376 	[1] = {
1377 		.handler = icmp_discard,
1378 		.error = 1,
1379 	},
1380 	[2] = {
1381 		.handler = icmp_discard,
1382 		.error = 1,
1383 	},
1384 	[ICMP_DEST_UNREACH] = {
1385 		.handler = icmp_unreach,
1386 		.error = 1,
1387 	},
1388 	[ICMP_SOURCE_QUENCH] = {
1389 		.handler = icmp_unreach,
1390 		.error = 1,
1391 	},
1392 	[ICMP_REDIRECT] = {
1393 		.handler = icmp_redirect,
1394 		.error = 1,
1395 	},
1396 	[6] = {
1397 		.handler = icmp_discard,
1398 		.error = 1,
1399 	},
1400 	[7] = {
1401 		.handler = icmp_discard,
1402 		.error = 1,
1403 	},
1404 	[ICMP_ECHO] = {
1405 		.handler = icmp_echo,
1406 	},
1407 	[9] = {
1408 		.handler = icmp_discard,
1409 		.error = 1,
1410 	},
1411 	[10] = {
1412 		.handler = icmp_discard,
1413 		.error = 1,
1414 	},
1415 	[ICMP_TIME_EXCEEDED] = {
1416 		.handler = icmp_unreach,
1417 		.error = 1,
1418 	},
1419 	[ICMP_PARAMETERPROB] = {
1420 		.handler = icmp_unreach,
1421 		.error = 1,
1422 	},
1423 	[ICMP_TIMESTAMP] = {
1424 		.handler = icmp_timestamp,
1425 	},
1426 	[ICMP_TIMESTAMPREPLY] = {
1427 		.handler = icmp_discard,
1428 	},
1429 	[ICMP_INFO_REQUEST] = {
1430 		.handler = icmp_discard,
1431 	},
1432 	[ICMP_INFO_REPLY] = {
1433 		.handler = icmp_discard,
1434 	},
1435 	[ICMP_ADDRESS] = {
1436 		.handler = icmp_discard,
1437 	},
1438 	[ICMP_ADDRESSREPLY] = {
1439 		.handler = icmp_discard,
1440 	},
1441 };
1442 
icmp_sk_init(struct net * net)1443 static int __net_init icmp_sk_init(struct net *net)
1444 {
1445 	/* Control parameters for ECHO replies. */
1446 	net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1447 	net->ipv4.sysctl_icmp_echo_enable_probe = 0;
1448 	net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1449 
1450 	/* Control parameter - ignore bogus broadcast responses? */
1451 	net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1452 
1453 	/*
1454 	 * 	Configurable global rate limit.
1455 	 *
1456 	 *	ratelimit defines tokens/packet consumed for dst->rate_token
1457 	 *	bucket ratemask defines which icmp types are ratelimited by
1458 	 *	setting	it's bit position.
1459 	 *
1460 	 *	default:
1461 	 *	dest unreachable (3), source quench (4),
1462 	 *	time exceeded (11), parameter problem (12)
1463 	 */
1464 
1465 	net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1466 	net->ipv4.sysctl_icmp_ratemask = 0x1818;
1467 	net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1468 
1469 	return 0;
1470 }
1471 
1472 static struct pernet_operations __net_initdata icmp_sk_ops = {
1473        .init = icmp_sk_init,
1474 };
1475 
icmp_init(void)1476 int __init icmp_init(void)
1477 {
1478 	int err, i;
1479 
1480 	for_each_possible_cpu(i) {
1481 		struct sock *sk;
1482 
1483 		err = inet_ctl_sock_create(&sk, PF_INET,
1484 					   SOCK_RAW, IPPROTO_ICMP, &init_net);
1485 		if (err < 0)
1486 			return err;
1487 
1488 		per_cpu(ipv4_icmp_sk, i) = sk;
1489 
1490 		/* Enough space for 2 64K ICMP packets, including
1491 		 * sk_buff/skb_shared_info struct overhead.
1492 		 */
1493 		sk->sk_sndbuf =	2 * SKB_TRUESIZE(64 * 1024);
1494 
1495 		/*
1496 		 * Speedup sock_wfree()
1497 		 */
1498 		sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1499 		inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1500 	}
1501 	return register_pernet_subsys(&icmp_sk_ops);
1502 }
1503