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

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