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Linux/net/ipv4/icmp.c

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  1 /*
  2  *      NET3:   Implementation of the ICMP protocol layer.
  3  *
  4  *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
  5  *
  6  *      This program is free software; you can redistribute it and/or
  7  *      modify it under the terms of the GNU General Public License
  8  *      as published by the Free Software Foundation; either version
  9  *      2 of the License, or (at your option) any later version.
 10  *
 11  *      Some of the function names and the icmp unreach table for this
 12  *      module were derived from [icmp.c 1.0.11 06/02/93] by
 13  *      Ross Biro, Fred N. van Kempen, Mark Evans, Alan Cox, Gerhard Koerting.
 14  *      Other than that this module is a complete rewrite.
 15  *
 16  *      Fixes:
 17  *      Clemens Fruhwirth       :       introduce global icmp rate limiting
 18  *                                      with icmp type masking ability instead
 19  *                                      of broken per type icmp timeouts.
 20  *              Mike Shaver     :       RFC1122 checks.
 21  *              Alan Cox        :       Multicast ping reply as self.
 22  *              Alan Cox        :       Fix atomicity lockup in ip_build_xmit
 23  *                                      call.
 24  *              Alan Cox        :       Added 216,128 byte paths to the MTU
 25  *                                      code.
 26  *              Martin Mares    :       RFC1812 checks.
 27  *              Martin Mares    :       Can be configured to follow redirects
 28  *                                      if acting as a router _without_ a
 29  *                                      routing protocol (RFC 1812).
 30  *              Martin Mares    :       Echo requests may be configured to
 31  *                                      be ignored (RFC 1812).
 32  *              Martin Mares    :       Limitation of ICMP error message
 33  *                                      transmit rate (RFC 1812).
 34  *              Martin Mares    :       TOS and Precedence set correctly
 35  *                                      (RFC 1812).
 36  *              Martin Mares    :       Now copying as much data from the
 37  *                                      original packet as we can without
 38  *                                      exceeding 576 bytes (RFC 1812).
 39  *      Willy Konynenberg       :       Transparent proxying support.
 40  *              Keith Owens     :       RFC1191 correction for 4.2BSD based
 41  *                                      path MTU bug.
 42  *              Thomas Quinot   :       ICMP Dest Unreach codes up to 15 are
 43  *                                      valid (RFC 1812).
 44  *              Andi Kleen      :       Check all packet lengths properly
 45  *                                      and moved all kfree_skb() up to
 46  *                                      icmp_rcv.
 47  *              Andi Kleen      :       Move the rate limit bookkeeping
 48  *                                      into the dest entry and use a token
 49  *                                      bucket filter (thanks to ANK). Make
 50  *                                      the rates sysctl configurable.
 51  *              Yu Tianli       :       Fixed two ugly bugs in icmp_send
 52  *                                      - IP option length was accounted wrongly
 53  *                                      - ICMP header length was not accounted
 54  *                                        at all.
 55  *              Tristan Greaves :       Added sysctl option to ignore bogus
 56  *                                      broadcast responses from broken routers.
 57  *
 58  * To Fix:
 59  *
 60  *      - Should use skb_pull() instead of all the manual checking.
 61  *        This would also greatly simply some upper layer error handlers. --AK
 62  *
 63  */
 64 
 65 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 66 
 67 #include <linux/module.h>
 68 #include <linux/types.h>
 69 #include <linux/jiffies.h>
 70 #include <linux/kernel.h>
 71 #include <linux/fcntl.h>
 72 #include <linux/socket.h>
 73 #include <linux/in.h>
 74 #include <linux/inet.h>
 75 #include <linux/inetdevice.h>
 76 #include <linux/netdevice.h>
 77 #include <linux/string.h>
 78 #include <linux/netfilter_ipv4.h>
 79 #include <linux/slab.h>
 80 #include <net/snmp.h>
 81 #include <net/ip.h>
 82 #include <net/route.h>
 83 #include <net/protocol.h>
 84 #include <net/icmp.h>
 85 #include <net/tcp.h>
 86 #include <net/udp.h>
 87 #include <net/raw.h>
 88 #include <net/ping.h>
 89 #include <linux/skbuff.h>
 90 #include <net/sock.h>
 91 #include <linux/errno.h>
 92 #include <linux/timer.h>
 93 #include <linux/init.h>
 94 #include <asm/uaccess.h>
 95 #include <net/checksum.h>
 96 #include <net/xfrm.h>
 97 #include <net/inet_common.h>
 98 #include <net/ip_fib.h>
 99 
100 /*
101  *      Build xmit assembly blocks
102  */
103 
104 struct icmp_bxm {
105         struct sk_buff *skb;
106         int offset;
107         int data_len;
108 
109         struct {
110                 struct icmphdr icmph;
111                 __be32         times[3];
112         } data;
113         int head_len;
114         struct ip_options_data replyopts;
115 };
116 
117 /* An array of errno for error messages from dest unreach. */
118 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
119 
120 const struct icmp_err icmp_err_convert[] = {
121         {
122                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
123                 .fatal = 0,
124         },
125         {
126                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
127                 .fatal = 0,
128         },
129         {
130                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
131                 .fatal = 1,
132         },
133         {
134                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
135                 .fatal = 1,
136         },
137         {
138                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
139                 .fatal = 0,
140         },
141         {
142                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
143                 .fatal = 0,
144         },
145         {
146                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
147                 .fatal = 1,
148         },
149         {
150                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
151                 .fatal = 1,
152         },
153         {
154                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
155                 .fatal = 1,
156         },
157         {
158                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
159                 .fatal = 1,
160         },
161         {
162                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
163                 .fatal = 1,
164         },
165         {
166                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
167                 .fatal = 0,
168         },
169         {
170                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
171                 .fatal = 0,
172         },
173         {
174                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
175                 .fatal = 1,
176         },
177         {
178                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
179                 .fatal = 1,
180         },
181         {
182                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
183                 .fatal = 1,
184         },
185 };
186 EXPORT_SYMBOL(icmp_err_convert);
187 
188 /*
189  *      ICMP control array. This specifies what to do with each ICMP.
190  */
191 
192 struct icmp_control {
193         void (*handler)(struct sk_buff *skb);
194         short   error;          /* This ICMP is classed as an error message */
195 };
196 
197 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
198 
199 /*
200  *      The ICMP socket(s). This is the most convenient way to flow control
201  *      our ICMP output as well as maintain a clean interface throughout
202  *      all layers. All Socketless IP sends will soon be gone.
203  *
204  *      On SMP we have one ICMP socket per-cpu.
205  */
206 static struct sock *icmp_sk(struct net *net)
207 {
208         return net->ipv4.icmp_sk[smp_processor_id()];
209 }
210 
211 static inline struct sock *icmp_xmit_lock(struct net *net)
212 {
213         struct sock *sk;
214 
215         local_bh_disable();
216 
217         sk = icmp_sk(net);
218 
219         if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
220                 /* This can happen if the output path signals a
221                  * dst_link_failure() for an outgoing ICMP packet.
222                  */
223                 local_bh_enable();
224                 return NULL;
225         }
226         return sk;
227 }
228 
229 static inline void icmp_xmit_unlock(struct sock *sk)
230 {
231         spin_unlock_bh(&sk->sk_lock.slock);
232 }
233 
234 /*
235  *      Send an ICMP frame.
236  */
237 
238 static inline bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
239                                       struct flowi4 *fl4, int type, int code)
240 {
241         struct dst_entry *dst = &rt->dst;
242         bool rc = true;
243 
244         if (type > NR_ICMP_TYPES)
245                 goto out;
246 
247         /* Don't limit PMTU discovery. */
248         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
249                 goto out;
250 
251         /* No rate limit on loopback */
252         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
253                 goto out;
254 
255         /* Limit if icmp type is enabled in ratemask. */
256         if ((1 << type) & net->ipv4.sysctl_icmp_ratemask) {
257                 struct inet_peer *peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, 1);
258                 rc = inet_peer_xrlim_allow(peer,
259                                            net->ipv4.sysctl_icmp_ratelimit);
260                 if (peer)
261                         inet_putpeer(peer);
262         }
263 out:
264         return rc;
265 }
266 
267 /*
268  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
269  */
270 void icmp_out_count(struct net *net, unsigned char type)
271 {
272         ICMPMSGOUT_INC_STATS(net, type);
273         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
274 }
275 
276 /*
277  *      Checksum each fragment, and on the first include the headers and final
278  *      checksum.
279  */
280 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
281                           struct sk_buff *skb)
282 {
283         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
284         __wsum csum;
285 
286         csum = skb_copy_and_csum_bits(icmp_param->skb,
287                                       icmp_param->offset + offset,
288                                       to, len, 0);
289 
290         skb->csum = csum_block_add(skb->csum, csum, odd);
291         if (icmp_pointers[icmp_param->data.icmph.type].error)
292                 nf_ct_attach(skb, icmp_param->skb);
293         return 0;
294 }
295 
296 static void icmp_push_reply(struct icmp_bxm *icmp_param,
297                             struct flowi4 *fl4,
298                             struct ipcm_cookie *ipc, struct rtable **rt)
299 {
300         struct sock *sk;
301         struct sk_buff *skb;
302 
303         sk = icmp_sk(dev_net((*rt)->dst.dev));
304         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
305                            icmp_param->data_len+icmp_param->head_len,
306                            icmp_param->head_len,
307                            ipc, rt, MSG_DONTWAIT) < 0) {
308                 ICMP_INC_STATS_BH(sock_net(sk), ICMP_MIB_OUTERRORS);
309                 ip_flush_pending_frames(sk);
310         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
311                 struct icmphdr *icmph = icmp_hdr(skb);
312                 __wsum csum = 0;
313                 struct sk_buff *skb1;
314 
315                 skb_queue_walk(&sk->sk_write_queue, skb1) {
316                         csum = csum_add(csum, skb1->csum);
317                 }
318                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
319                                                  (char *)icmph,
320                                                  icmp_param->head_len, csum);
321                 icmph->checksum = csum_fold(csum);
322                 skb->ip_summed = CHECKSUM_NONE;
323                 ip_push_pending_frames(sk, fl4);
324         }
325 }
326 
327 /*
328  *      Driving logic for building and sending ICMP messages.
329  */
330 
331 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
332 {
333         struct ipcm_cookie ipc;
334         struct rtable *rt = skb_rtable(skb);
335         struct net *net = dev_net(rt->dst.dev);
336         struct flowi4 fl4;
337         struct sock *sk;
338         struct inet_sock *inet;
339         __be32 daddr, saddr;
340 
341         if (ip_options_echo(&icmp_param->replyopts.opt.opt, skb))
342                 return;
343 
344         sk = icmp_xmit_lock(net);
345         if (sk == NULL)
346                 return;
347         inet = inet_sk(sk);
348 
349         icmp_param->data.icmph.checksum = 0;
350 
351         inet->tos = ip_hdr(skb)->tos;
352         daddr = ipc.addr = ip_hdr(skb)->saddr;
353         saddr = fib_compute_spec_dst(skb);
354         ipc.opt = NULL;
355         ipc.tx_flags = 0;
356         if (icmp_param->replyopts.opt.opt.optlen) {
357                 ipc.opt = &icmp_param->replyopts.opt;
358                 if (ipc.opt->opt.srr)
359                         daddr = icmp_param->replyopts.opt.opt.faddr;
360         }
361         memset(&fl4, 0, sizeof(fl4));
362         fl4.daddr = daddr;
363         fl4.saddr = saddr;
364         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
365         fl4.flowi4_proto = IPPROTO_ICMP;
366         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
367         rt = ip_route_output_key(net, &fl4);
368         if (IS_ERR(rt))
369                 goto out_unlock;
370         if (icmpv4_xrlim_allow(net, rt, &fl4, icmp_param->data.icmph.type,
371                                icmp_param->data.icmph.code))
372                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
373         ip_rt_put(rt);
374 out_unlock:
375         icmp_xmit_unlock(sk);
376 }
377 
378 static struct rtable *icmp_route_lookup(struct net *net,
379                                         struct flowi4 *fl4,
380                                         struct sk_buff *skb_in,
381                                         const struct iphdr *iph,
382                                         __be32 saddr, u8 tos,
383                                         int type, int code,
384                                         struct icmp_bxm *param)
385 {
386         struct rtable *rt, *rt2;
387         struct flowi4 fl4_dec;
388         int err;
389 
390         memset(fl4, 0, sizeof(*fl4));
391         fl4->daddr = (param->replyopts.opt.opt.srr ?
392                       param->replyopts.opt.opt.faddr : iph->saddr);
393         fl4->saddr = saddr;
394         fl4->flowi4_tos = RT_TOS(tos);
395         fl4->flowi4_proto = IPPROTO_ICMP;
396         fl4->fl4_icmp_type = type;
397         fl4->fl4_icmp_code = code;
398         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
399         rt = __ip_route_output_key(net, fl4);
400         if (IS_ERR(rt))
401                 return rt;
402 
403         /* No need to clone since we're just using its address. */
404         rt2 = rt;
405 
406         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
407                                            flowi4_to_flowi(fl4), NULL, 0);
408         if (!IS_ERR(rt)) {
409                 if (rt != rt2)
410                         return rt;
411         } else if (PTR_ERR(rt) == -EPERM) {
412                 rt = NULL;
413         } else
414                 return rt;
415 
416         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
417         if (err)
418                 goto relookup_failed;
419 
420         if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) {
421                 rt2 = __ip_route_output_key(net, &fl4_dec);
422                 if (IS_ERR(rt2))
423                         err = PTR_ERR(rt2);
424         } else {
425                 struct flowi4 fl4_2 = {};
426                 unsigned long orefdst;
427 
428                 fl4_2.daddr = fl4_dec.saddr;
429                 rt2 = ip_route_output_key(net, &fl4_2);
430                 if (IS_ERR(rt2)) {
431                         err = PTR_ERR(rt2);
432                         goto relookup_failed;
433                 }
434                 /* Ugh! */
435                 orefdst = skb_in->_skb_refdst; /* save old refdst */
436                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
437                                      RT_TOS(tos), rt2->dst.dev);
438 
439                 dst_release(&rt2->dst);
440                 rt2 = skb_rtable(skb_in);
441                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
442         }
443 
444         if (err)
445                 goto relookup_failed;
446 
447         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
448                                             flowi4_to_flowi(&fl4_dec), NULL,
449                                             XFRM_LOOKUP_ICMP);
450         if (!IS_ERR(rt2)) {
451                 dst_release(&rt->dst);
452                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
453                 rt = rt2;
454         } else if (PTR_ERR(rt2) == -EPERM) {
455                 if (rt)
456                         dst_release(&rt->dst);
457                 return rt2;
458         } else {
459                 err = PTR_ERR(rt2);
460                 goto relookup_failed;
461         }
462         return rt;
463 
464 relookup_failed:
465         if (rt)
466                 return rt;
467         return ERR_PTR(err);
468 }
469 
470 /*
471  *      Send an ICMP message in response to a situation
472  *
473  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
474  *                MAY send more (we do).
475  *                      MUST NOT change this header information.
476  *                      MUST NOT reply to a multicast/broadcast IP address.
477  *                      MUST NOT reply to a multicast/broadcast MAC address.
478  *                      MUST reply to only the first fragment.
479  */
480 
481 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
482 {
483         struct iphdr *iph;
484         int room;
485         struct icmp_bxm icmp_param;
486         struct rtable *rt = skb_rtable(skb_in);
487         struct ipcm_cookie ipc;
488         struct flowi4 fl4;
489         __be32 saddr;
490         u8  tos;
491         struct net *net;
492         struct sock *sk;
493 
494         if (!rt)
495                 goto out;
496         net = dev_net(rt->dst.dev);
497 
498         /*
499          *      Find the original header. It is expected to be valid, of course.
500          *      Check this, icmp_send is called from the most obscure devices
501          *      sometimes.
502          */
503         iph = ip_hdr(skb_in);
504 
505         if ((u8 *)iph < skb_in->head ||
506             (skb_in->network_header + sizeof(*iph)) > skb_in->tail)
507                 goto out;
508 
509         /*
510          *      No replies to physical multicast/broadcast
511          */
512         if (skb_in->pkt_type != PACKET_HOST)
513                 goto out;
514 
515         /*
516          *      Now check at the protocol level
517          */
518         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
519                 goto out;
520 
521         /*
522          *      Only reply to fragment 0. We byte re-order the constant
523          *      mask for efficiency.
524          */
525         if (iph->frag_off & htons(IP_OFFSET))
526                 goto out;
527 
528         /*
529          *      If we send an ICMP error to an ICMP error a mess would result..
530          */
531         if (icmp_pointers[type].error) {
532                 /*
533                  *      We are an error, check if we are replying to an
534                  *      ICMP error
535                  */
536                 if (iph->protocol == IPPROTO_ICMP) {
537                         u8 _inner_type, *itp;
538 
539                         itp = skb_header_pointer(skb_in,
540                                                  skb_network_header(skb_in) +
541                                                  (iph->ihl << 2) +
542                                                  offsetof(struct icmphdr,
543                                                           type) -
544                                                  skb_in->data,
545                                                  sizeof(_inner_type),
546                                                  &_inner_type);
547                         if (itp == NULL)
548                                 goto out;
549 
550                         /*
551                          *      Assume any unknown ICMP type is an error. This
552                          *      isn't specified by the RFC, but think about it..
553                          */
554                         if (*itp > NR_ICMP_TYPES ||
555                             icmp_pointers[*itp].error)
556                                 goto out;
557                 }
558         }
559 
560         sk = icmp_xmit_lock(net);
561         if (sk == NULL)
562                 return;
563 
564         /*
565          *      Construct source address and options.
566          */
567 
568         saddr = iph->daddr;
569         if (!(rt->rt_flags & RTCF_LOCAL)) {
570                 struct net_device *dev = NULL;
571 
572                 rcu_read_lock();
573                 if (rt_is_input_route(rt) &&
574                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
575                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
576 
577                 if (dev)
578                         saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
579                 else
580                         saddr = 0;
581                 rcu_read_unlock();
582         }
583 
584         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
585                                            IPTOS_PREC_INTERNETCONTROL) :
586                                           iph->tos;
587 
588         if (ip_options_echo(&icmp_param.replyopts.opt.opt, skb_in))
589                 goto out_unlock;
590 
591 
592         /*
593          *      Prepare data for ICMP header.
594          */
595 
596         icmp_param.data.icmph.type       = type;
597         icmp_param.data.icmph.code       = code;
598         icmp_param.data.icmph.un.gateway = info;
599         icmp_param.data.icmph.checksum   = 0;
600         icmp_param.skb    = skb_in;
601         icmp_param.offset = skb_network_offset(skb_in);
602         inet_sk(sk)->tos = tos;
603         ipc.addr = iph->saddr;
604         ipc.opt = &icmp_param.replyopts.opt;
605         ipc.tx_flags = 0;
606 
607         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos,
608                                type, code, &icmp_param);
609         if (IS_ERR(rt))
610                 goto out_unlock;
611 
612         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
613                 goto ende;
614 
615         /* RFC says return as much as we can without exceeding 576 bytes. */
616 
617         room = dst_mtu(&rt->dst);
618         if (room > 576)
619                 room = 576;
620         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
621         room -= sizeof(struct icmphdr);
622 
623         icmp_param.data_len = skb_in->len - icmp_param.offset;
624         if (icmp_param.data_len > room)
625                 icmp_param.data_len = room;
626         icmp_param.head_len = sizeof(struct icmphdr);
627 
628         icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
629 ende:
630         ip_rt_put(rt);
631 out_unlock:
632         icmp_xmit_unlock(sk);
633 out:;
634 }
635 EXPORT_SYMBOL(icmp_send);
636 
637 
638 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
639 {
640         const struct iphdr *iph = (const struct iphdr *) skb->data;
641         const struct net_protocol *ipprot;
642         int protocol = iph->protocol;
643 
644         /* Checkin full IP header plus 8 bytes of protocol to
645          * avoid additional coding at protocol handlers.
646          */
647         if (!pskb_may_pull(skb, iph->ihl * 4 + 8))
648                 return;
649 
650         raw_icmp_error(skb, protocol, info);
651 
652         rcu_read_lock();
653         ipprot = rcu_dereference(inet_protos[protocol]);
654         if (ipprot && ipprot->err_handler)
655                 ipprot->err_handler(skb, info);
656         rcu_read_unlock();
657 }
658 
659 /*
660  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEED, and ICMP_QUENCH.
661  */
662 
663 static void icmp_unreach(struct sk_buff *skb)
664 {
665         const struct iphdr *iph;
666         struct icmphdr *icmph;
667         struct net *net;
668         u32 info = 0;
669 
670         net = dev_net(skb_dst(skb)->dev);
671 
672         /*
673          *      Incomplete header ?
674          *      Only checks for the IP header, there should be an
675          *      additional check for longer headers in upper levels.
676          */
677 
678         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
679                 goto out_err;
680 
681         icmph = icmp_hdr(skb);
682         iph   = (const struct iphdr *)skb->data;
683 
684         if (iph->ihl < 5) /* Mangled header, drop. */
685                 goto out_err;
686 
687         if (icmph->type == ICMP_DEST_UNREACH) {
688                 switch (icmph->code & 15) {
689                 case ICMP_NET_UNREACH:
690                 case ICMP_HOST_UNREACH:
691                 case ICMP_PROT_UNREACH:
692                 case ICMP_PORT_UNREACH:
693                         break;
694                 case ICMP_FRAG_NEEDED:
695                         if (ipv4_config.no_pmtu_disc) {
696                                 LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: fragmentation needed and DF set\n"),
697                                                &iph->daddr);
698                         } else {
699                                 info = ntohs(icmph->un.frag.mtu);
700                                 if (!info)
701                                         goto out;
702                         }
703                         break;
704                 case ICMP_SR_FAILED:
705                         LIMIT_NETDEBUG(KERN_INFO pr_fmt("%pI4: Source Route Failed\n"),
706                                        &iph->daddr);
707                         break;
708                 default:
709                         break;
710                 }
711                 if (icmph->code > NR_ICMP_UNREACH)
712                         goto out;
713         } else if (icmph->type == ICMP_PARAMETERPROB)
714                 info = ntohl(icmph->un.gateway) >> 24;
715 
716         /*
717          *      Throw it at our lower layers
718          *
719          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
720          *                header.
721          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
722          *                transport layer.
723          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
724          *                transport layer.
725          */
726 
727         /*
728          *      Check the other end isn't violating RFC 1122. Some routers send
729          *      bogus responses to broadcast frames. If you see this message
730          *      first check your netmask matches at both ends, if it does then
731          *      get the other vendor to fix their kit.
732          */
733 
734         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
735             inet_addr_type(net, iph->daddr) == RTN_BROADCAST) {
736                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
737                                      &ip_hdr(skb)->saddr,
738                                      icmph->type, icmph->code,
739                                      &iph->daddr, skb->dev->name);
740                 goto out;
741         }
742 
743         icmp_socket_deliver(skb, info);
744 
745 out:
746         return;
747 out_err:
748         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
749         goto out;
750 }
751 
752 
753 /*
754  *      Handle ICMP_REDIRECT.
755  */
756 
757 static void icmp_redirect(struct sk_buff *skb)
758 {
759         if (skb->len < sizeof(struct iphdr)) {
760                 ICMP_INC_STATS_BH(dev_net(skb->dev), ICMP_MIB_INERRORS);
761                 return;
762         }
763 
764         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
765                 return;
766 
767         icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway);
768 }
769 
770 /*
771  *      Handle ICMP_ECHO ("ping") requests.
772  *
773  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
774  *                requests.
775  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
776  *                included in the reply.
777  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
778  *                echo requests, MUST have default=NOT.
779  *      See also WRT handling of options once they are done and working.
780  */
781 
782 static void icmp_echo(struct sk_buff *skb)
783 {
784         struct net *net;
785 
786         net = dev_net(skb_dst(skb)->dev);
787         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
788                 struct icmp_bxm icmp_param;
789 
790                 icmp_param.data.icmph      = *icmp_hdr(skb);
791                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
792                 icmp_param.skb             = skb;
793                 icmp_param.offset          = 0;
794                 icmp_param.data_len        = skb->len;
795                 icmp_param.head_len        = sizeof(struct icmphdr);
796                 icmp_reply(&icmp_param, skb);
797         }
798 }
799 
800 /*
801  *      Handle ICMP Timestamp requests.
802  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
803  *                SHOULD be in the kernel for minimum random latency.
804  *                MUST be accurate to a few minutes.
805  *                MUST be updated at least at 15Hz.
806  */
807 static void icmp_timestamp(struct sk_buff *skb)
808 {
809         struct timespec tv;
810         struct icmp_bxm icmp_param;
811         /*
812          *      Too short.
813          */
814         if (skb->len < 4)
815                 goto out_err;
816 
817         /*
818          *      Fill in the current time as ms since midnight UT:
819          */
820         getnstimeofday(&tv);
821         icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
822                                          tv.tv_nsec / NSEC_PER_MSEC);
823         icmp_param.data.times[2] = icmp_param.data.times[1];
824         if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
825                 BUG();
826         icmp_param.data.icmph      = *icmp_hdr(skb);
827         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
828         icmp_param.data.icmph.code = 0;
829         icmp_param.skb             = skb;
830         icmp_param.offset          = 0;
831         icmp_param.data_len        = 0;
832         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
833         icmp_reply(&icmp_param, skb);
834 out:
835         return;
836 out_err:
837         ICMP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
838         goto out;
839 }
840 
841 static void icmp_discard(struct sk_buff *skb)
842 {
843 }
844 
845 /*
846  *      Deal with incoming ICMP packets.
847  */
848 int icmp_rcv(struct sk_buff *skb)
849 {
850         struct icmphdr *icmph;
851         struct rtable *rt = skb_rtable(skb);
852         struct net *net = dev_net(rt->dst.dev);
853 
854         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
855                 struct sec_path *sp = skb_sec_path(skb);
856                 int nh;
857 
858                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
859                                  XFRM_STATE_ICMP))
860                         goto drop;
861 
862                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
863                         goto drop;
864 
865                 nh = skb_network_offset(skb);
866                 skb_set_network_header(skb, sizeof(*icmph));
867 
868                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
869                         goto drop;
870 
871                 skb_set_network_header(skb, nh);
872         }
873 
874         ICMP_INC_STATS_BH(net, ICMP_MIB_INMSGS);
875 
876         switch (skb->ip_summed) {
877         case CHECKSUM_COMPLETE:
878                 if (!csum_fold(skb->csum))
879                         break;
880                 /* fall through */
881         case CHECKSUM_NONE:
882                 skb->csum = 0;
883                 if (__skb_checksum_complete(skb))
884                         goto error;
885         }
886 
887         if (!pskb_pull(skb, sizeof(*icmph)))
888                 goto error;
889 
890         icmph = icmp_hdr(skb);
891 
892         ICMPMSGIN_INC_STATS_BH(net, icmph->type);
893         /*
894          *      18 is the highest 'known' ICMP type. Anything else is a mystery
895          *
896          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
897          *                discarded.
898          */
899         if (icmph->type > NR_ICMP_TYPES)
900                 goto error;
901 
902 
903         /*
904          *      Parse the ICMP message
905          */
906 
907         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
908                 /*
909                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
910                  *        silently ignored (we let user decide with a sysctl).
911                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
912                  *        discarded if to broadcast/multicast.
913                  */
914                 if ((icmph->type == ICMP_ECHO ||
915                      icmph->type == ICMP_TIMESTAMP) &&
916                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
917                         goto error;
918                 }
919                 if (icmph->type != ICMP_ECHO &&
920                     icmph->type != ICMP_TIMESTAMP &&
921                     icmph->type != ICMP_ADDRESS &&
922                     icmph->type != ICMP_ADDRESSREPLY) {
923                         goto error;
924                 }
925         }
926 
927         icmp_pointers[icmph->type].handler(skb);
928 
929 drop:
930         kfree_skb(skb);
931         return 0;
932 error:
933         ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
934         goto drop;
935 }
936 
937 void icmp_err(struct sk_buff *skb, u32 info)
938 {
939         struct iphdr *iph = (struct iphdr *)skb->data;
940         struct icmphdr *icmph = (struct icmphdr *)(skb->data+(iph->ihl<<2));
941         int type = icmp_hdr(skb)->type;
942         int code = icmp_hdr(skb)->code;
943         struct net *net = dev_net(skb->dev);
944 
945         /*
946          * Use ping_err to handle all icmp errors except those
947          * triggered by ICMP_ECHOREPLY which sent from kernel.
948          */
949         if (icmph->type != ICMP_ECHOREPLY) {
950                 ping_err(skb, info);
951                 return;
952         }
953 
954         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
955                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0);
956         else if (type == ICMP_REDIRECT)
957                 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0);
958 }
959 
960 /*
961  *      This table is the definition of how we handle ICMP.
962  */
963 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
964         [ICMP_ECHOREPLY] = {
965                 .handler = ping_rcv,
966         },
967         [1] = {
968                 .handler = icmp_discard,
969                 .error = 1,
970         },
971         [2] = {
972                 .handler = icmp_discard,
973                 .error = 1,
974         },
975         [ICMP_DEST_UNREACH] = {
976                 .handler = icmp_unreach,
977                 .error = 1,
978         },
979         [ICMP_SOURCE_QUENCH] = {
980                 .handler = icmp_unreach,
981                 .error = 1,
982         },
983         [ICMP_REDIRECT] = {
984                 .handler = icmp_redirect,
985                 .error = 1,
986         },
987         [6] = {
988                 .handler = icmp_discard,
989                 .error = 1,
990         },
991         [7] = {
992                 .handler = icmp_discard,
993                 .error = 1,
994         },
995         [ICMP_ECHO] = {
996                 .handler = icmp_echo,
997         },
998         [9] = {
999                 .handler = icmp_discard,
1000                 .error = 1,
1001         },
1002         [10] = {
1003                 .handler = icmp_discard,
1004                 .error = 1,
1005         },
1006         [ICMP_TIME_EXCEEDED] = {
1007                 .handler = icmp_unreach,
1008                 .error = 1,
1009         },
1010         [ICMP_PARAMETERPROB] = {
1011                 .handler = icmp_unreach,
1012                 .error = 1,
1013         },
1014         [ICMP_TIMESTAMP] = {
1015                 .handler = icmp_timestamp,
1016         },
1017         [ICMP_TIMESTAMPREPLY] = {
1018                 .handler = icmp_discard,
1019         },
1020         [ICMP_INFO_REQUEST] = {
1021                 .handler = icmp_discard,
1022         },
1023         [ICMP_INFO_REPLY] = {
1024                 .handler = icmp_discard,
1025         },
1026         [ICMP_ADDRESS] = {
1027                 .handler = icmp_discard,
1028         },
1029         [ICMP_ADDRESSREPLY] = {
1030                 .handler = icmp_discard,
1031         },
1032 };
1033 
1034 static void __net_exit icmp_sk_exit(struct net *net)
1035 {
1036         int i;
1037 
1038         for_each_possible_cpu(i)
1039                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1040         kfree(net->ipv4.icmp_sk);
1041         net->ipv4.icmp_sk = NULL;
1042 }
1043 
1044 static int __net_init icmp_sk_init(struct net *net)
1045 {
1046         int i, err;
1047 
1048         net->ipv4.icmp_sk =
1049                 kzalloc(nr_cpu_ids * sizeof(struct sock *), GFP_KERNEL);
1050         if (net->ipv4.icmp_sk == NULL)
1051                 return -ENOMEM;
1052 
1053         for_each_possible_cpu(i) {
1054                 struct sock *sk;
1055 
1056                 err = inet_ctl_sock_create(&sk, PF_INET,
1057                                            SOCK_RAW, IPPROTO_ICMP, net);
1058                 if (err < 0)
1059                         goto fail;
1060 
1061                 net->ipv4.icmp_sk[i] = sk;
1062 
1063                 /* Enough space for 2 64K ICMP packets, including
1064                  * sk_buff/skb_shared_info struct overhead.
1065                  */
1066                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1067 
1068                 /*
1069                  * Speedup sock_wfree()
1070                  */
1071                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1072                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1073         }
1074 
1075         /* Control parameters for ECHO replies. */
1076         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1077         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1078 
1079         /* Control parameter - ignore bogus broadcast responses? */
1080         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1081 
1082         /*
1083          *      Configurable global rate limit.
1084          *
1085          *      ratelimit defines tokens/packet consumed for dst->rate_token
1086          *      bucket ratemask defines which icmp types are ratelimited by
1087          *      setting it's bit position.
1088          *
1089          *      default:
1090          *      dest unreachable (3), source quench (4),
1091          *      time exceeded (11), parameter problem (12)
1092          */
1093 
1094         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1095         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1096         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1097 
1098         return 0;
1099 
1100 fail:
1101         for_each_possible_cpu(i)
1102                 inet_ctl_sock_destroy(net->ipv4.icmp_sk[i]);
1103         kfree(net->ipv4.icmp_sk);
1104         return err;
1105 }
1106 
1107 static struct pernet_operations __net_initdata icmp_sk_ops = {
1108        .init = icmp_sk_init,
1109        .exit = icmp_sk_exit,
1110 };
1111 
1112 int __init icmp_init(void)
1113 {
1114         return register_pernet_subsys(&icmp_sk_ops);
1115 }
1116 

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