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Linux/net/ipv4/icmp.c

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  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         bool (*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 /*
196  *      The ICMP socket(s). This is the most convenient way to flow control
197  *      our ICMP output as well as maintain a clean interface throughout
198  *      all layers. All Socketless IP sends will soon be gone.
199  *
200  *      On SMP we have one ICMP socket per-cpu.
201  */
202 static struct sock *icmp_sk(struct net *net)
203 {
204         return this_cpu_read(*net->ipv4.icmp_sk);
205 }
206 
207 /* Called with BH disabled */
208 static inline struct sock *icmp_xmit_lock(struct net *net)
209 {
210         struct sock *sk;
211 
212         sk = icmp_sk(net);
213 
214         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
215                 /* This can happen if the output path signals a
216                  * dst_link_failure() for an outgoing ICMP packet.
217                  */
218                 return NULL;
219         }
220         return sk;
221 }
222 
223 static inline void icmp_xmit_unlock(struct sock *sk)
224 {
225         spin_unlock(&sk->sk_lock.slock);
226 }
227 
228 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
229 int sysctl_icmp_msgs_burst __read_mostly = 50;
230 
231 static struct {
232         spinlock_t      lock;
233         u32             credit;
234         u32             stamp;
235 } icmp_global = {
236         .lock           = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
237 };
238 
239 /**
240  * icmp_global_allow - Are we allowed to send one more ICMP message ?
241  *
242  * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec.
243  * Returns false if we reached the limit and can not send another packet.
244  * Note: called with BH disabled
245  */
246 bool icmp_global_allow(void)
247 {
248         u32 credit, delta, incr = 0, now = (u32)jiffies;
249         bool rc = false;
250 
251         /* Check if token bucket is empty and cannot be refilled
252          * without taking the spinlock. The READ_ONCE() are paired
253          * with the following WRITE_ONCE() in this same function.
254          */
255         if (!READ_ONCE(icmp_global.credit)) {
256                 delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
257                 if (delta < HZ / 50)
258                         return false;
259         }
260 
261         spin_lock(&icmp_global.lock);
262         delta = min_t(u32, now - icmp_global.stamp, HZ);
263         if (delta >= HZ / 50) {
264                 incr = sysctl_icmp_msgs_per_sec * delta / HZ ;
265                 if (incr)
266                         WRITE_ONCE(icmp_global.stamp, now);
267         }
268         credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst);
269         if (credit) {
270                 credit--;
271                 rc = true;
272         }
273         WRITE_ONCE(icmp_global.credit, credit);
274         spin_unlock(&icmp_global.lock);
275         return rc;
276 }
277 EXPORT_SYMBOL(icmp_global_allow);
278 
279 static bool icmpv4_mask_allow(struct net *net, int type, int code)
280 {
281         if (type > NR_ICMP_TYPES)
282                 return true;
283 
284         /* Don't limit PMTU discovery. */
285         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
286                 return true;
287 
288         /* Limit if icmp type is enabled in ratemask. */
289         if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask))
290                 return true;
291 
292         return false;
293 }
294 
295 static bool icmpv4_global_allow(struct net *net, int type, int code)
296 {
297         if (icmpv4_mask_allow(net, type, code))
298                 return true;
299 
300         if (icmp_global_allow())
301                 return true;
302 
303         return false;
304 }
305 
306 /*
307  *      Send an ICMP frame.
308  */
309 
310 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
311                                struct flowi4 *fl4, int type, int code)
312 {
313         struct dst_entry *dst = &rt->dst;
314         struct inet_peer *peer;
315         bool rc = true;
316         int vif;
317 
318         if (icmpv4_mask_allow(net, type, code))
319                 goto out;
320 
321         /* No rate limit on loopback */
322         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
323                 goto out;
324 
325         vif = l3mdev_master_ifindex(dst->dev);
326         peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
327         rc = inet_peer_xrlim_allow(peer, net->ipv4.sysctl_icmp_ratelimit);
328         if (peer)
329                 inet_putpeer(peer);
330 out:
331         return rc;
332 }
333 
334 /*
335  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
336  */
337 void icmp_out_count(struct net *net, unsigned char type)
338 {
339         ICMPMSGOUT_INC_STATS(net, type);
340         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
341 }
342 
343 /*
344  *      Checksum each fragment, and on the first include the headers and final
345  *      checksum.
346  */
347 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
348                           struct sk_buff *skb)
349 {
350         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
351         __wsum csum;
352 
353         csum = skb_copy_and_csum_bits(icmp_param->skb,
354                                       icmp_param->offset + offset,
355                                       to, len, 0);
356 
357         skb->csum = csum_block_add(skb->csum, csum, odd);
358         if (icmp_pointers[icmp_param->data.icmph.type].error)
359                 nf_ct_attach(skb, icmp_param->skb);
360         return 0;
361 }
362 
363 static void icmp_push_reply(struct icmp_bxm *icmp_param,
364                             struct flowi4 *fl4,
365                             struct ipcm_cookie *ipc, struct rtable **rt)
366 {
367         struct sock *sk;
368         struct sk_buff *skb;
369 
370         sk = icmp_sk(dev_net((*rt)->dst.dev));
371         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
372                            icmp_param->data_len+icmp_param->head_len,
373                            icmp_param->head_len,
374                            ipc, rt, MSG_DONTWAIT) < 0) {
375                 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
376                 ip_flush_pending_frames(sk);
377         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
378                 struct icmphdr *icmph = icmp_hdr(skb);
379                 __wsum csum = 0;
380                 struct sk_buff *skb1;
381 
382                 skb_queue_walk(&sk->sk_write_queue, skb1) {
383                         csum = csum_add(csum, skb1->csum);
384                 }
385                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
386                                                  (char *)icmph,
387                                                  icmp_param->head_len, csum);
388                 icmph->checksum = csum_fold(csum);
389                 skb->ip_summed = CHECKSUM_NONE;
390                 ip_push_pending_frames(sk, fl4);
391         }
392 }
393 
394 /*
395  *      Driving logic for building and sending ICMP messages.
396  */
397 
398 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
399 {
400         struct ipcm_cookie ipc;
401         struct rtable *rt = skb_rtable(skb);
402         struct net *net = dev_net(rt->dst.dev);
403         struct flowi4 fl4;
404         struct sock *sk;
405         struct inet_sock *inet;
406         __be32 daddr, saddr;
407         u32 mark = IP4_REPLY_MARK(net, skb->mark);
408         int type = icmp_param->data.icmph.type;
409         int code = icmp_param->data.icmph.code;
410 
411         if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
412                 return;
413 
414         /* Needed by both icmp_global_allow and icmp_xmit_lock */
415         local_bh_disable();
416 
417         /* global icmp_msgs_per_sec */
418         if (!icmpv4_global_allow(net, type, code))
419                 goto out_bh_enable;
420 
421         sk = icmp_xmit_lock(net);
422         if (!sk)
423                 goto out_bh_enable;
424         inet = inet_sk(sk);
425 
426         icmp_param->data.icmph.checksum = 0;
427 
428         ipcm_init(&ipc);
429         inet->tos = ip_hdr(skb)->tos;
430         ipc.sockc.mark = mark;
431         daddr = ipc.addr = ip_hdr(skb)->saddr;
432         saddr = fib_compute_spec_dst(skb);
433 
434         if (icmp_param->replyopts.opt.opt.optlen) {
435                 ipc.opt = &icmp_param->replyopts.opt;
436                 if (ipc.opt->opt.srr)
437                         daddr = icmp_param->replyopts.opt.opt.faddr;
438         }
439         memset(&fl4, 0, sizeof(fl4));
440         fl4.daddr = daddr;
441         fl4.saddr = saddr;
442         fl4.flowi4_mark = mark;
443         fl4.flowi4_uid = sock_net_uid(net, NULL);
444         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
445         fl4.flowi4_proto = IPPROTO_ICMP;
446         fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
447         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
448         rt = ip_route_output_key(net, &fl4);
449         if (IS_ERR(rt))
450                 goto out_unlock;
451         if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
452                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
453         ip_rt_put(rt);
454 out_unlock:
455         icmp_xmit_unlock(sk);
456 out_bh_enable:
457         local_bh_enable();
458 }
459 
460 static struct rtable *icmp_route_lookup(struct net *net,
461                                         struct flowi4 *fl4,
462                                         struct sk_buff *skb_in,
463                                         const struct iphdr *iph,
464                                         __be32 saddr, u8 tos, u32 mark,
465                                         int type, int code,
466                                         struct icmp_bxm *param)
467 {
468         struct rtable *rt, *rt2;
469         struct flowi4 fl4_dec;
470         int err;
471 
472         memset(fl4, 0, sizeof(*fl4));
473         fl4->daddr = (param->replyopts.opt.opt.srr ?
474                       param->replyopts.opt.opt.faddr : iph->saddr);
475         fl4->saddr = saddr;
476         fl4->flowi4_mark = mark;
477         fl4->flowi4_uid = sock_net_uid(net, NULL);
478         fl4->flowi4_tos = RT_TOS(tos);
479         fl4->flowi4_proto = IPPROTO_ICMP;
480         fl4->fl4_icmp_type = type;
481         fl4->fl4_icmp_code = code;
482         fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev);
483 
484         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
485         rt = ip_route_output_key_hash(net, fl4, skb_in);
486         if (IS_ERR(rt))
487                 return rt;
488 
489         /* No need to clone since we're just using its address. */
490         rt2 = rt;
491 
492         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
493                                            flowi4_to_flowi(fl4), NULL, 0);
494         if (!IS_ERR(rt)) {
495                 if (rt != rt2)
496                         return rt;
497         } else if (PTR_ERR(rt) == -EPERM) {
498                 rt = NULL;
499         } else
500                 return rt;
501 
502         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
503         if (err)
504                 goto relookup_failed;
505 
506         if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev,
507                                      fl4_dec.saddr) == RTN_LOCAL) {
508                 rt2 = __ip_route_output_key(net, &fl4_dec);
509                 if (IS_ERR(rt2))
510                         err = PTR_ERR(rt2);
511         } else {
512                 struct flowi4 fl4_2 = {};
513                 unsigned long orefdst;
514 
515                 fl4_2.daddr = fl4_dec.saddr;
516                 rt2 = ip_route_output_key(net, &fl4_2);
517                 if (IS_ERR(rt2)) {
518                         err = PTR_ERR(rt2);
519                         goto relookup_failed;
520                 }
521                 /* Ugh! */
522                 orefdst = skb_in->_skb_refdst; /* save old refdst */
523                 skb_dst_set(skb_in, NULL);
524                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
525                                      RT_TOS(tos), rt2->dst.dev);
526 
527                 dst_release(&rt2->dst);
528                 rt2 = skb_rtable(skb_in);
529                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
530         }
531 
532         if (err)
533                 goto relookup_failed;
534 
535         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
536                                             flowi4_to_flowi(&fl4_dec), NULL,
537                                             XFRM_LOOKUP_ICMP);
538         if (!IS_ERR(rt2)) {
539                 dst_release(&rt->dst);
540                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
541                 rt = rt2;
542         } else if (PTR_ERR(rt2) == -EPERM) {
543                 if (rt)
544                         dst_release(&rt->dst);
545                 return rt2;
546         } else {
547                 err = PTR_ERR(rt2);
548                 goto relookup_failed;
549         }
550         return rt;
551 
552 relookup_failed:
553         if (rt)
554                 return rt;
555         return ERR_PTR(err);
556 }
557 
558 /*
559  *      Send an ICMP message in response to a situation
560  *
561  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
562  *                MAY send more (we do).
563  *                      MUST NOT change this header information.
564  *                      MUST NOT reply to a multicast/broadcast IP address.
565  *                      MUST NOT reply to a multicast/broadcast MAC address.
566  *                      MUST reply to only the first fragment.
567  */
568 
569 void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
570                  const struct ip_options *opt)
571 {
572         struct iphdr *iph;
573         int room;
574         struct icmp_bxm icmp_param;
575         struct rtable *rt = skb_rtable(skb_in);
576         struct ipcm_cookie ipc;
577         struct flowi4 fl4;
578         __be32 saddr;
579         u8  tos;
580         u32 mark;
581         struct net *net;
582         struct sock *sk;
583 
584         if (!rt)
585                 goto out;
586 
587         if (rt->dst.dev)
588                 net = dev_net(rt->dst.dev);
589         else if (skb_in->dev)
590                 net = dev_net(skb_in->dev);
591         else
592                 goto out;
593 
594         /*
595          *      Find the original header. It is expected to be valid, of course.
596          *      Check this, icmp_send is called from the most obscure devices
597          *      sometimes.
598          */
599         iph = ip_hdr(skb_in);
600 
601         if ((u8 *)iph < skb_in->head ||
602             (skb_network_header(skb_in) + sizeof(*iph)) >
603             skb_tail_pointer(skb_in))
604                 goto out;
605 
606         /*
607          *      No replies to physical multicast/broadcast
608          */
609         if (skb_in->pkt_type != PACKET_HOST)
610                 goto out;
611 
612         /*
613          *      Now check at the protocol level
614          */
615         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
616                 goto out;
617 
618         /*
619          *      Only reply to fragment 0. We byte re-order the constant
620          *      mask for efficiency.
621          */
622         if (iph->frag_off & htons(IP_OFFSET))
623                 goto out;
624 
625         /*
626          *      If we send an ICMP error to an ICMP error a mess would result..
627          */
628         if (icmp_pointers[type].error) {
629                 /*
630                  *      We are an error, check if we are replying to an
631                  *      ICMP error
632                  */
633                 if (iph->protocol == IPPROTO_ICMP) {
634                         u8 _inner_type, *itp;
635 
636                         itp = skb_header_pointer(skb_in,
637                                                  skb_network_header(skb_in) +
638                                                  (iph->ihl << 2) +
639                                                  offsetof(struct icmphdr,
640                                                           type) -
641                                                  skb_in->data,
642                                                  sizeof(_inner_type),
643                                                  &_inner_type);
644                         if (!itp)
645                                 goto out;
646 
647                         /*
648                          *      Assume any unknown ICMP type is an error. This
649                          *      isn't specified by the RFC, but think about it..
650                          */
651                         if (*itp > NR_ICMP_TYPES ||
652                             icmp_pointers[*itp].error)
653                                 goto out;
654                 }
655         }
656 
657         /* Needed by both icmp_global_allow and icmp_xmit_lock */
658         local_bh_disable();
659 
660         /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
661          * incoming dev is loopback.  If outgoing dev change to not be
662          * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
663          */
664         if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
665               !icmpv4_global_allow(net, type, code))
666                 goto out_bh_enable;
667 
668         sk = icmp_xmit_lock(net);
669         if (!sk)
670                 goto out_bh_enable;
671 
672         /*
673          *      Construct source address and options.
674          */
675 
676         saddr = iph->daddr;
677         if (!(rt->rt_flags & RTCF_LOCAL)) {
678                 struct net_device *dev = NULL;
679 
680                 rcu_read_lock();
681                 if (rt_is_input_route(rt) &&
682                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
683                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
684 
685                 if (dev)
686                         saddr = inet_select_addr(dev, iph->saddr,
687                                                  RT_SCOPE_LINK);
688                 else
689                         saddr = 0;
690                 rcu_read_unlock();
691         }
692 
693         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
694                                            IPTOS_PREC_INTERNETCONTROL) :
695                                           iph->tos;
696         mark = IP4_REPLY_MARK(net, skb_in->mark);
697 
698         if (__ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in, opt))
699                 goto out_unlock;
700 
701 
702         /*
703          *      Prepare data for ICMP header.
704          */
705 
706         icmp_param.data.icmph.type       = type;
707         icmp_param.data.icmph.code       = code;
708         icmp_param.data.icmph.un.gateway = info;
709         icmp_param.data.icmph.checksum   = 0;
710         icmp_param.skb    = skb_in;
711         icmp_param.offset = skb_network_offset(skb_in);
712         inet_sk(sk)->tos = tos;
713         ipcm_init(&ipc);
714         ipc.addr = iph->saddr;
715         ipc.opt = &icmp_param.replyopts.opt;
716         ipc.sockc.mark = mark;
717 
718         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
719                                type, code, &icmp_param);
720         if (IS_ERR(rt))
721                 goto out_unlock;
722 
723         /* peer icmp_ratelimit */
724         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
725                 goto ende;
726 
727         /* RFC says return as much as we can without exceeding 576 bytes. */
728 
729         room = dst_mtu(&rt->dst);
730         if (room > 576)
731                 room = 576;
732         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
733         room -= sizeof(struct icmphdr);
734 
735         icmp_param.data_len = skb_in->len - icmp_param.offset;
736         if (icmp_param.data_len > room)
737                 icmp_param.data_len = room;
738         icmp_param.head_len = sizeof(struct icmphdr);
739 
740         icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
741 ende:
742         ip_rt_put(rt);
743 out_unlock:
744         icmp_xmit_unlock(sk);
745 out_bh_enable:
746         local_bh_enable();
747 out:;
748 }
749 EXPORT_SYMBOL(__icmp_send);
750 
751 #if IS_ENABLED(CONFIG_NF_NAT)
752 #include <net/netfilter/nf_conntrack.h>
753 void icmp_ndo_send(struct sk_buff *skb_in, int type, int code, __be32 info)
754 {
755         struct sk_buff *cloned_skb = NULL;
756         enum ip_conntrack_info ctinfo;
757         struct nf_conn *ct;
758         __be32 orig_ip;
759 
760         ct = nf_ct_get(skb_in, &ctinfo);
761         if (!ct || !(ct->status & IPS_SRC_NAT)) {
762                 icmp_send(skb_in, type, code, info);
763                 return;
764         }
765 
766         if (skb_shared(skb_in))
767                 skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
768 
769         if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
770             (skb_network_header(skb_in) + sizeof(struct iphdr)) >
771             skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
772             skb_network_offset(skb_in) + sizeof(struct iphdr))))
773                 goto out;
774 
775         orig_ip = ip_hdr(skb_in)->saddr;
776         ip_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.ip;
777         icmp_send(skb_in, type, code, info);
778         ip_hdr(skb_in)->saddr = orig_ip;
779 out:
780         consume_skb(cloned_skb);
781 }
782 EXPORT_SYMBOL(icmp_ndo_send);
783 #endif
784 
785 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
786 {
787         const struct iphdr *iph = (const struct iphdr *) skb->data;
788         const struct net_protocol *ipprot;
789         int protocol = iph->protocol;
790 
791         /* Checkin full IP header plus 8 bytes of protocol to
792          * avoid additional coding at protocol handlers.
793          */
794         if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
795                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
796                 return;
797         }
798 
799         raw_icmp_error(skb, protocol, info);
800 
801         ipprot = rcu_dereference(inet_protos[protocol]);
802         if (ipprot && ipprot->err_handler)
803                 ipprot->err_handler(skb, info);
804 }
805 
806 static bool icmp_tag_validation(int proto)
807 {
808         bool ok;
809 
810         rcu_read_lock();
811         ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
812         rcu_read_unlock();
813         return ok;
814 }
815 
816 /*
817  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
818  *      ICMP_PARAMETERPROB.
819  */
820 
821 static bool icmp_unreach(struct sk_buff *skb)
822 {
823         const struct iphdr *iph;
824         struct icmphdr *icmph;
825         struct net *net;
826         u32 info = 0;
827 
828         net = dev_net(skb_dst(skb)->dev);
829 
830         /*
831          *      Incomplete header ?
832          *      Only checks for the IP header, there should be an
833          *      additional check for longer headers in upper levels.
834          */
835 
836         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
837                 goto out_err;
838 
839         icmph = icmp_hdr(skb);
840         iph   = (const struct iphdr *)skb->data;
841 
842         if (iph->ihl < 5) /* Mangled header, drop. */
843                 goto out_err;
844 
845         switch (icmph->type) {
846         case ICMP_DEST_UNREACH:
847                 switch (icmph->code & 15) {
848                 case ICMP_NET_UNREACH:
849                 case ICMP_HOST_UNREACH:
850                 case ICMP_PROT_UNREACH:
851                 case ICMP_PORT_UNREACH:
852                         break;
853                 case ICMP_FRAG_NEEDED:
854                         /* for documentation of the ip_no_pmtu_disc
855                          * values please see
856                          * Documentation/networking/ip-sysctl.txt
857                          */
858                         switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
859                         default:
860                                 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
861                                                     &iph->daddr);
862                                 break;
863                         case 2:
864                                 goto out;
865                         case 3:
866                                 if (!icmp_tag_validation(iph->protocol))
867                                         goto out;
868                                 fallthrough;
869                         case 0:
870                                 info = ntohs(icmph->un.frag.mtu);
871                         }
872                         break;
873                 case ICMP_SR_FAILED:
874                         net_dbg_ratelimited("%pI4: Source Route Failed\n",
875                                             &iph->daddr);
876                         break;
877                 default:
878                         break;
879                 }
880                 if (icmph->code > NR_ICMP_UNREACH)
881                         goto out;
882                 break;
883         case ICMP_PARAMETERPROB:
884                 info = ntohl(icmph->un.gateway) >> 24;
885                 break;
886         case ICMP_TIME_EXCEEDED:
887                 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
888                 if (icmph->code == ICMP_EXC_FRAGTIME)
889                         goto out;
890                 break;
891         }
892 
893         /*
894          *      Throw it at our lower layers
895          *
896          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
897          *                header.
898          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
899          *                transport layer.
900          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
901          *                transport layer.
902          */
903 
904         /*
905          *      Check the other end isn't violating RFC 1122. Some routers send
906          *      bogus responses to broadcast frames. If you see this message
907          *      first check your netmask matches at both ends, if it does then
908          *      get the other vendor to fix their kit.
909          */
910 
911         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
912             inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
913                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
914                                      &ip_hdr(skb)->saddr,
915                                      icmph->type, icmph->code,
916                                      &iph->daddr, skb->dev->name);
917                 goto out;
918         }
919 
920         icmp_socket_deliver(skb, info);
921 
922 out:
923         return true;
924 out_err:
925         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
926         return false;
927 }
928 
929 
930 /*
931  *      Handle ICMP_REDIRECT.
932  */
933 
934 static bool icmp_redirect(struct sk_buff *skb)
935 {
936         if (skb->len < sizeof(struct iphdr)) {
937                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
938                 return false;
939         }
940 
941         if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
942                 /* there aught to be a stat */
943                 return false;
944         }
945 
946         icmp_socket_deliver(skb, ntohl(icmp_hdr(skb)->un.gateway));
947         return true;
948 }
949 
950 /*
951  *      Handle ICMP_ECHO ("ping") requests.
952  *
953  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
954  *                requests.
955  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
956  *                included in the reply.
957  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
958  *                echo requests, MUST have default=NOT.
959  *      See also WRT handling of options once they are done and working.
960  */
961 
962 static bool icmp_echo(struct sk_buff *skb)
963 {
964         struct net *net;
965 
966         net = dev_net(skb_dst(skb)->dev);
967         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
968                 struct icmp_bxm icmp_param;
969 
970                 icmp_param.data.icmph      = *icmp_hdr(skb);
971                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
972                 icmp_param.skb             = skb;
973                 icmp_param.offset          = 0;
974                 icmp_param.data_len        = skb->len;
975                 icmp_param.head_len        = sizeof(struct icmphdr);
976                 icmp_reply(&icmp_param, skb);
977         }
978         /* should there be an ICMP stat for ignored echos? */
979         return true;
980 }
981 
982 /*
983  *      Handle ICMP Timestamp requests.
984  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
985  *                SHOULD be in the kernel for minimum random latency.
986  *                MUST be accurate to a few minutes.
987  *                MUST be updated at least at 15Hz.
988  */
989 static bool icmp_timestamp(struct sk_buff *skb)
990 {
991         struct icmp_bxm icmp_param;
992         /*
993          *      Too short.
994          */
995         if (skb->len < 4)
996                 goto out_err;
997 
998         /*
999          *      Fill in the current time as ms since midnight UT:
1000          */
1001         icmp_param.data.times[1] = inet_current_timestamp();
1002         icmp_param.data.times[2] = icmp_param.data.times[1];
1003 
1004         BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
1005 
1006         icmp_param.data.icmph      = *icmp_hdr(skb);
1007         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
1008         icmp_param.data.icmph.code = 0;
1009         icmp_param.skb             = skb;
1010         icmp_param.offset          = 0;
1011         icmp_param.data_len        = 0;
1012         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
1013         icmp_reply(&icmp_param, skb);
1014         return true;
1015 
1016 out_err:
1017         __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
1018         return false;
1019 }
1020 
1021 static bool icmp_discard(struct sk_buff *skb)
1022 {
1023         /* pretend it was a success */
1024         return true;
1025 }
1026 
1027 /*
1028  *      Deal with incoming ICMP packets.
1029  */
1030 int icmp_rcv(struct sk_buff *skb)
1031 {
1032         struct icmphdr *icmph;
1033         struct rtable *rt = skb_rtable(skb);
1034         struct net *net = dev_net(rt->dst.dev);
1035         bool success;
1036 
1037         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1038                 struct sec_path *sp = skb_sec_path(skb);
1039                 int nh;
1040 
1041                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1042                                  XFRM_STATE_ICMP))
1043                         goto drop;
1044 
1045                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1046                         goto drop;
1047 
1048                 nh = skb_network_offset(skb);
1049                 skb_set_network_header(skb, sizeof(*icmph));
1050 
1051                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
1052                         goto drop;
1053 
1054                 skb_set_network_header(skb, nh);
1055         }
1056 
1057         __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1058 
1059         if (skb_checksum_simple_validate(skb))
1060                 goto csum_error;
1061 
1062         if (!pskb_pull(skb, sizeof(*icmph)))
1063                 goto error;
1064 
1065         icmph = icmp_hdr(skb);
1066 
1067         ICMPMSGIN_INC_STATS(net, icmph->type);
1068         /*
1069          *      18 is the highest 'known' ICMP type. Anything else is a mystery
1070          *
1071          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1072          *                discarded.
1073          */
1074         if (icmph->type > NR_ICMP_TYPES)
1075                 goto error;
1076 
1077 
1078         /*
1079          *      Parse the ICMP message
1080          */
1081 
1082         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1083                 /*
1084                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1085                  *        silently ignored (we let user decide with a sysctl).
1086                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1087                  *        discarded if to broadcast/multicast.
1088                  */
1089                 if ((icmph->type == ICMP_ECHO ||
1090                      icmph->type == ICMP_TIMESTAMP) &&
1091                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
1092                         goto error;
1093                 }
1094                 if (icmph->type != ICMP_ECHO &&
1095                     icmph->type != ICMP_TIMESTAMP &&
1096                     icmph->type != ICMP_ADDRESS &&
1097                     icmph->type != ICMP_ADDRESSREPLY) {
1098                         goto error;
1099                 }
1100         }
1101 
1102         success = icmp_pointers[icmph->type].handler(skb);
1103 
1104         if (success)  {
1105                 consume_skb(skb);
1106                 return NET_RX_SUCCESS;
1107         }
1108 
1109 drop:
1110         kfree_skb(skb);
1111         return NET_RX_DROP;
1112 csum_error:
1113         __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1114 error:
1115         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1116         goto drop;
1117 }
1118 
1119 int icmp_err(struct sk_buff *skb, u32 info)
1120 {
1121         struct iphdr *iph = (struct iphdr *)skb->data;
1122         int offset = iph->ihl<<2;
1123         struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1124         int type = icmp_hdr(skb)->type;
1125         int code = icmp_hdr(skb)->code;
1126         struct net *net = dev_net(skb->dev);
1127 
1128         /*
1129          * Use ping_err to handle all icmp errors except those
1130          * triggered by ICMP_ECHOREPLY which sent from kernel.
1131          */
1132         if (icmph->type != ICMP_ECHOREPLY) {
1133                 ping_err(skb, offset, info);
1134                 return 0;
1135         }
1136 
1137         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1138                 ipv4_update_pmtu(skb, net, info, 0, IPPROTO_ICMP);
1139         else if (type == ICMP_REDIRECT)
1140                 ipv4_redirect(skb, net, 0, IPPROTO_ICMP);
1141 
1142         return 0;
1143 }
1144 
1145 /*
1146  *      This table is the definition of how we handle ICMP.
1147  */
1148 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1149         [ICMP_ECHOREPLY] = {
1150                 .handler = ping_rcv,
1151         },
1152         [1] = {
1153                 .handler = icmp_discard,
1154                 .error = 1,
1155         },
1156         [2] = {
1157                 .handler = icmp_discard,
1158                 .error = 1,
1159         },
1160         [ICMP_DEST_UNREACH] = {
1161                 .handler = icmp_unreach,
1162                 .error = 1,
1163         },
1164         [ICMP_SOURCE_QUENCH] = {
1165                 .handler = icmp_unreach,
1166                 .error = 1,
1167         },
1168         [ICMP_REDIRECT] = {
1169                 .handler = icmp_redirect,
1170                 .error = 1,
1171         },
1172         [6] = {
1173                 .handler = icmp_discard,
1174                 .error = 1,
1175         },
1176         [7] = {
1177                 .handler = icmp_discard,
1178                 .error = 1,
1179         },
1180         [ICMP_ECHO] = {
1181                 .handler = icmp_echo,
1182         },
1183         [9] = {
1184                 .handler = icmp_discard,
1185                 .error = 1,
1186         },
1187         [10] = {
1188                 .handler = icmp_discard,
1189                 .error = 1,
1190         },
1191         [ICMP_TIME_EXCEEDED] = {
1192                 .handler = icmp_unreach,
1193                 .error = 1,
1194         },
1195         [ICMP_PARAMETERPROB] = {
1196                 .handler = icmp_unreach,
1197                 .error = 1,
1198         },
1199         [ICMP_TIMESTAMP] = {
1200                 .handler = icmp_timestamp,
1201         },
1202         [ICMP_TIMESTAMPREPLY] = {
1203                 .handler = icmp_discard,
1204         },
1205         [ICMP_INFO_REQUEST] = {
1206                 .handler = icmp_discard,
1207         },
1208         [ICMP_INFO_REPLY] = {
1209                 .handler = icmp_discard,
1210         },
1211         [ICMP_ADDRESS] = {
1212                 .handler = icmp_discard,
1213         },
1214         [ICMP_ADDRESSREPLY] = {
1215                 .handler = icmp_discard,
1216         },
1217 };
1218 
1219 static void __net_exit icmp_sk_exit(struct net *net)
1220 {
1221         int i;
1222 
1223         for_each_possible_cpu(i)
1224                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
1225         free_percpu(net->ipv4.icmp_sk);
1226         net->ipv4.icmp_sk = NULL;
1227 }
1228 
1229 static int __net_init icmp_sk_init(struct net *net)
1230 {
1231         int i, err;
1232 
1233         net->ipv4.icmp_sk = alloc_percpu(struct sock *);
1234         if (!net->ipv4.icmp_sk)
1235                 return -ENOMEM;
1236 
1237         for_each_possible_cpu(i) {
1238                 struct sock *sk;
1239 
1240                 err = inet_ctl_sock_create(&sk, PF_INET,
1241                                            SOCK_RAW, IPPROTO_ICMP, net);
1242                 if (err < 0)
1243                         goto fail;
1244 
1245                 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk;
1246 
1247                 /* Enough space for 2 64K ICMP packets, including
1248                  * sk_buff/skb_shared_info struct overhead.
1249                  */
1250                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1251 
1252                 /*
1253                  * Speedup sock_wfree()
1254                  */
1255                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1256                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1257         }
1258 
1259         /* Control parameters for ECHO replies. */
1260         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1261         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1262 
1263         /* Control parameter - ignore bogus broadcast responses? */
1264         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1265 
1266         /*
1267          *      Configurable global rate limit.
1268          *
1269          *      ratelimit defines tokens/packet consumed for dst->rate_token
1270          *      bucket ratemask defines which icmp types are ratelimited by
1271          *      setting it's bit position.
1272          *
1273          *      default:
1274          *      dest unreachable (3), source quench (4),
1275          *      time exceeded (11), parameter problem (12)
1276          */
1277 
1278         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1279         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1280         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1281 
1282         return 0;
1283 
1284 fail:
1285         icmp_sk_exit(net);
1286         return err;
1287 }
1288 
1289 static struct pernet_operations __net_initdata icmp_sk_ops = {
1290        .init = icmp_sk_init,
1291        .exit = icmp_sk_exit,
1292 };
1293 
1294 int __init icmp_init(void)
1295 {
1296         return register_pernet_subsys(&icmp_sk_ops);
1297 }
1298 

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