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

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