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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 <linux/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 #include <net/l3mdev.h>
100 
101 /*
102  *      Build xmit assembly blocks
103  */
104 
105 struct icmp_bxm {
106         struct sk_buff *skb;
107         int offset;
108         int data_len;
109 
110         struct {
111                 struct icmphdr icmph;
112                 __be32         times[3];
113         } data;
114         int head_len;
115         struct ip_options_data replyopts;
116 };
117 
118 /* An array of errno for error messages from dest unreach. */
119 /* RFC 1122: 3.2.2.1 States that NET_UNREACH, HOST_UNREACH and SR_FAILED MUST be considered 'transient errs'. */
120 
121 const struct icmp_err icmp_err_convert[] = {
122         {
123                 .errno = ENETUNREACH,   /* ICMP_NET_UNREACH */
124                 .fatal = 0,
125         },
126         {
127                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNREACH */
128                 .fatal = 0,
129         },
130         {
131                 .errno = ENOPROTOOPT    /* ICMP_PROT_UNREACH */,
132                 .fatal = 1,
133         },
134         {
135                 .errno = ECONNREFUSED,  /* ICMP_PORT_UNREACH */
136                 .fatal = 1,
137         },
138         {
139                 .errno = EMSGSIZE,      /* ICMP_FRAG_NEEDED */
140                 .fatal = 0,
141         },
142         {
143                 .errno = EOPNOTSUPP,    /* ICMP_SR_FAILED */
144                 .fatal = 0,
145         },
146         {
147                 .errno = ENETUNREACH,   /* ICMP_NET_UNKNOWN */
148                 .fatal = 1,
149         },
150         {
151                 .errno = EHOSTDOWN,     /* ICMP_HOST_UNKNOWN */
152                 .fatal = 1,
153         },
154         {
155                 .errno = ENONET,        /* ICMP_HOST_ISOLATED */
156                 .fatal = 1,
157         },
158         {
159                 .errno = ENETUNREACH,   /* ICMP_NET_ANO */
160                 .fatal = 1,
161         },
162         {
163                 .errno = EHOSTUNREACH,  /* ICMP_HOST_ANO */
164                 .fatal = 1,
165         },
166         {
167                 .errno = ENETUNREACH,   /* ICMP_NET_UNR_TOS */
168                 .fatal = 0,
169         },
170         {
171                 .errno = EHOSTUNREACH,  /* ICMP_HOST_UNR_TOS */
172                 .fatal = 0,
173         },
174         {
175                 .errno = EHOSTUNREACH,  /* ICMP_PKT_FILTERED */
176                 .fatal = 1,
177         },
178         {
179                 .errno = EHOSTUNREACH,  /* ICMP_PREC_VIOLATION */
180                 .fatal = 1,
181         },
182         {
183                 .errno = EHOSTUNREACH,  /* ICMP_PREC_CUTOFF */
184                 .fatal = 1,
185         },
186 };
187 EXPORT_SYMBOL(icmp_err_convert);
188 
189 /*
190  *      ICMP control array. This specifies what to do with each ICMP.
191  */
192 
193 struct icmp_control {
194         bool (*handler)(struct sk_buff *skb);
195         short   error;          /* This ICMP is classed as an error message */
196 };
197 
198 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
199 
200 /*
201  *      The ICMP socket(s). This is the most convenient way to flow control
202  *      our ICMP output as well as maintain a clean interface throughout
203  *      all layers. All Socketless IP sends will soon be gone.
204  *
205  *      On SMP we have one ICMP socket per-cpu.
206  */
207 static struct sock *icmp_sk(struct net *net)
208 {
209         return *this_cpu_ptr(net->ipv4.icmp_sk);
210 }
211 
212 /* Called with BH disabled */
213 static inline struct sock *icmp_xmit_lock(struct net *net)
214 {
215         struct sock *sk;
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                 return NULL;
224         }
225         return sk;
226 }
227 
228 static inline void icmp_xmit_unlock(struct sock *sk)
229 {
230         spin_unlock(&sk->sk_lock.slock);
231 }
232 
233 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
234 int sysctl_icmp_msgs_burst __read_mostly = 50;
235 
236 static struct {
237         spinlock_t      lock;
238         u32             credit;
239         u32             stamp;
240 } icmp_global = {
241         .lock           = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
242 };
243 
244 /**
245  * icmp_global_allow - Are we allowed to send one more ICMP message ?
246  *
247  * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec.
248  * Returns false if we reached the limit and can not send another packet.
249  * Note: called with BH disabled
250  */
251 bool icmp_global_allow(void)
252 {
253         u32 credit, delta, incr = 0, now = (u32)jiffies;
254         bool rc = false;
255 
256         /* Check if token bucket is empty and cannot be refilled
257          * without taking the spinlock.
258          */
259         if (!icmp_global.credit) {
260                 delta = min_t(u32, now - icmp_global.stamp, HZ);
261                 if (delta < HZ / 50)
262                         return false;
263         }
264 
265         spin_lock(&icmp_global.lock);
266         delta = min_t(u32, now - icmp_global.stamp, HZ);
267         if (delta >= HZ / 50) {
268                 incr = sysctl_icmp_msgs_per_sec * delta / HZ ;
269                 if (incr)
270                         icmp_global.stamp = now;
271         }
272         credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst);
273         if (credit) {
274                 credit--;
275                 rc = true;
276         }
277         icmp_global.credit = credit;
278         spin_unlock(&icmp_global.lock);
279         return rc;
280 }
281 EXPORT_SYMBOL(icmp_global_allow);
282 
283 static bool icmpv4_mask_allow(struct net *net, int type, int code)
284 {
285         if (type > NR_ICMP_TYPES)
286                 return true;
287 
288         /* Don't limit PMTU discovery. */
289         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
290                 return true;
291 
292         /* Limit if icmp type is enabled in ratemask. */
293         if (!((1 << type) & net->ipv4.sysctl_icmp_ratemask))
294                 return true;
295 
296         return false;
297 }
298 
299 static bool icmpv4_global_allow(struct net *net, int type, int code)
300 {
301         if (icmpv4_mask_allow(net, type, code))
302                 return true;
303 
304         if (icmp_global_allow())
305                 return true;
306 
307         return false;
308 }
309 
310 /*
311  *      Send an ICMP frame.
312  */
313 
314 static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
315                                struct flowi4 *fl4, int type, int code)
316 {
317         struct dst_entry *dst = &rt->dst;
318         struct inet_peer *peer;
319         bool rc = true;
320         int vif;
321 
322         if (icmpv4_mask_allow(net, type, code))
323                 goto out;
324 
325         /* No rate limit on loopback */
326         if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
327                 goto out;
328 
329         vif = l3mdev_master_ifindex(dst->dev);
330         peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr, vif, 1);
331         rc = inet_peer_xrlim_allow(peer, net->ipv4.sysctl_icmp_ratelimit);
332         if (peer)
333                 inet_putpeer(peer);
334 out:
335         return rc;
336 }
337 
338 /*
339  *      Maintain the counters used in the SNMP statistics for outgoing ICMP
340  */
341 void icmp_out_count(struct net *net, unsigned char type)
342 {
343         ICMPMSGOUT_INC_STATS(net, type);
344         ICMP_INC_STATS(net, ICMP_MIB_OUTMSGS);
345 }
346 
347 /*
348  *      Checksum each fragment, and on the first include the headers and final
349  *      checksum.
350  */
351 static int icmp_glue_bits(void *from, char *to, int offset, int len, int odd,
352                           struct sk_buff *skb)
353 {
354         struct icmp_bxm *icmp_param = (struct icmp_bxm *)from;
355         __wsum csum;
356 
357         csum = skb_copy_and_csum_bits(icmp_param->skb,
358                                       icmp_param->offset + offset,
359                                       to, len, 0);
360 
361         skb->csum = csum_block_add(skb->csum, csum, odd);
362         if (icmp_pointers[icmp_param->data.icmph.type].error)
363                 nf_ct_attach(skb, icmp_param->skb);
364         return 0;
365 }
366 
367 static void icmp_push_reply(struct icmp_bxm *icmp_param,
368                             struct flowi4 *fl4,
369                             struct ipcm_cookie *ipc, struct rtable **rt)
370 {
371         struct sock *sk;
372         struct sk_buff *skb;
373 
374         sk = icmp_sk(dev_net((*rt)->dst.dev));
375         if (ip_append_data(sk, fl4, icmp_glue_bits, icmp_param,
376                            icmp_param->data_len+icmp_param->head_len,
377                            icmp_param->head_len,
378                            ipc, rt, MSG_DONTWAIT) < 0) {
379                 __ICMP_INC_STATS(sock_net(sk), ICMP_MIB_OUTERRORS);
380                 ip_flush_pending_frames(sk);
381         } else if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
382                 struct icmphdr *icmph = icmp_hdr(skb);
383                 __wsum csum = 0;
384                 struct sk_buff *skb1;
385 
386                 skb_queue_walk(&sk->sk_write_queue, skb1) {
387                         csum = csum_add(csum, skb1->csum);
388                 }
389                 csum = csum_partial_copy_nocheck((void *)&icmp_param->data,
390                                                  (char *)icmph,
391                                                  icmp_param->head_len, csum);
392                 icmph->checksum = csum_fold(csum);
393                 skb->ip_summed = CHECKSUM_NONE;
394                 ip_push_pending_frames(sk, fl4);
395         }
396 }
397 
398 /*
399  *      Driving logic for building and sending ICMP messages.
400  */
401 
402 static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
403 {
404         struct ipcm_cookie ipc;
405         struct rtable *rt = skb_rtable(skb);
406         struct net *net = dev_net(rt->dst.dev);
407         struct flowi4 fl4;
408         struct sock *sk;
409         struct inet_sock *inet;
410         __be32 daddr, saddr;
411         u32 mark = IP4_REPLY_MARK(net, skb->mark);
412         int type = icmp_param->data.icmph.type;
413         int code = icmp_param->data.icmph.code;
414 
415         if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
416                 return;
417 
418         /* Needed by both icmp_global_allow and icmp_xmit_lock */
419         local_bh_disable();
420 
421         /* global icmp_msgs_per_sec */
422         if (!icmpv4_global_allow(net, type, code))
423                 goto out_bh_enable;
424 
425         sk = icmp_xmit_lock(net);
426         if (!sk)
427                 goto out_bh_enable;
428         inet = inet_sk(sk);
429 
430         icmp_param->data.icmph.checksum = 0;
431 
432         inet->tos = ip_hdr(skb)->tos;
433         sk->sk_mark = mark;
434         daddr = ipc.addr = ip_hdr(skb)->saddr;
435         saddr = fib_compute_spec_dst(skb);
436         ipc.opt = NULL;
437         ipc.tx_flags = 0;
438         ipc.ttl = 0;
439         ipc.tos = -1;
440 
441         if (icmp_param->replyopts.opt.opt.optlen) {
442                 ipc.opt = &icmp_param->replyopts.opt;
443                 if (ipc.opt->opt.srr)
444                         daddr = icmp_param->replyopts.opt.opt.faddr;
445         }
446         memset(&fl4, 0, sizeof(fl4));
447         fl4.daddr = daddr;
448         fl4.saddr = saddr;
449         fl4.flowi4_mark = mark;
450         fl4.flowi4_uid = sock_net_uid(net, NULL);
451         fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
452         fl4.flowi4_proto = IPPROTO_ICMP;
453         fl4.flowi4_oif = l3mdev_master_ifindex(skb->dev);
454         security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
455         rt = ip_route_output_key(net, &fl4);
456         if (IS_ERR(rt))
457                 goto out_unlock;
458         if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
459                 icmp_push_reply(icmp_param, &fl4, &ipc, &rt);
460         ip_rt_put(rt);
461 out_unlock:
462         icmp_xmit_unlock(sk);
463 out_bh_enable:
464         local_bh_enable();
465 }
466 
467 static struct rtable *icmp_route_lookup(struct net *net,
468                                         struct flowi4 *fl4,
469                                         struct sk_buff *skb_in,
470                                         const struct iphdr *iph,
471                                         __be32 saddr, u8 tos, u32 mark,
472                                         int type, int code,
473                                         struct icmp_bxm *param)
474 {
475         struct rtable *rt, *rt2;
476         struct flowi4 fl4_dec;
477         int err;
478 
479         memset(fl4, 0, sizeof(*fl4));
480         fl4->daddr = (param->replyopts.opt.opt.srr ?
481                       param->replyopts.opt.opt.faddr : iph->saddr);
482         fl4->saddr = saddr;
483         fl4->flowi4_mark = mark;
484         fl4->flowi4_uid = sock_net_uid(net, NULL);
485         fl4->flowi4_tos = RT_TOS(tos);
486         fl4->flowi4_proto = IPPROTO_ICMP;
487         fl4->fl4_icmp_type = type;
488         fl4->fl4_icmp_code = code;
489         fl4->flowi4_oif = l3mdev_master_ifindex(skb_dst(skb_in)->dev);
490 
491         security_skb_classify_flow(skb_in, flowi4_to_flowi(fl4));
492         rt = ip_route_output_key_hash(net, fl4, skb_in);
493         if (IS_ERR(rt))
494                 return rt;
495 
496         /* No need to clone since we're just using its address. */
497         rt2 = rt;
498 
499         rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
500                                            flowi4_to_flowi(fl4), NULL, 0);
501         if (!IS_ERR(rt)) {
502                 if (rt != rt2)
503                         return rt;
504         } else if (PTR_ERR(rt) == -EPERM) {
505                 rt = NULL;
506         } else
507                 return rt;
508 
509         err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
510         if (err)
511                 goto relookup_failed;
512 
513         if (inet_addr_type_dev_table(net, skb_dst(skb_in)->dev,
514                                      fl4_dec.saddr) == RTN_LOCAL) {
515                 rt2 = __ip_route_output_key(net, &fl4_dec);
516                 if (IS_ERR(rt2))
517                         err = PTR_ERR(rt2);
518         } else {
519                 struct flowi4 fl4_2 = {};
520                 unsigned long orefdst;
521 
522                 fl4_2.daddr = fl4_dec.saddr;
523                 rt2 = ip_route_output_key(net, &fl4_2);
524                 if (IS_ERR(rt2)) {
525                         err = PTR_ERR(rt2);
526                         goto relookup_failed;
527                 }
528                 /* Ugh! */
529                 orefdst = skb_in->_skb_refdst; /* save old refdst */
530                 skb_dst_set(skb_in, NULL);
531                 err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
532                                      RT_TOS(tos), rt2->dst.dev);
533 
534                 dst_release(&rt2->dst);
535                 rt2 = skb_rtable(skb_in);
536                 skb_in->_skb_refdst = orefdst; /* restore old refdst */
537         }
538 
539         if (err)
540                 goto relookup_failed;
541 
542         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
543                                             flowi4_to_flowi(&fl4_dec), NULL,
544                                             XFRM_LOOKUP_ICMP);
545         if (!IS_ERR(rt2)) {
546                 dst_release(&rt->dst);
547                 memcpy(fl4, &fl4_dec, sizeof(*fl4));
548                 rt = rt2;
549         } else if (PTR_ERR(rt2) == -EPERM) {
550                 if (rt)
551                         dst_release(&rt->dst);
552                 return rt2;
553         } else {
554                 err = PTR_ERR(rt2);
555                 goto relookup_failed;
556         }
557         return rt;
558 
559 relookup_failed:
560         if (rt)
561                 return rt;
562         return ERR_PTR(err);
563 }
564 
565 /*
566  *      Send an ICMP message in response to a situation
567  *
568  *      RFC 1122: 3.2.2 MUST send at least the IP header and 8 bytes of header.
569  *                MAY send more (we do).
570  *                      MUST NOT change this header information.
571  *                      MUST NOT reply to a multicast/broadcast IP address.
572  *                      MUST NOT reply to a multicast/broadcast MAC address.
573  *                      MUST reply to only the first fragment.
574  */
575 
576 void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
577 {
578         struct iphdr *iph;
579         int room;
580         struct icmp_bxm icmp_param;
581         struct rtable *rt = skb_rtable(skb_in);
582         struct ipcm_cookie ipc;
583         struct flowi4 fl4;
584         __be32 saddr;
585         u8  tos;
586         u32 mark;
587         struct net *net;
588         struct sock *sk;
589 
590         if (!rt)
591                 goto out;
592         net = dev_net(rt->dst.dev);
593 
594         /*
595          *      Find the original header. It is expected to be valid, of course.
596          *      Check this, icmp_send is called from the most obscure devices
597          *      sometimes.
598          */
599         iph = ip_hdr(skb_in);
600 
601         if ((u8 *)iph < skb_in->head ||
602             (skb_network_header(skb_in) + sizeof(*iph)) >
603             skb_tail_pointer(skb_in))
604                 goto out;
605 
606         /*
607          *      No replies to physical multicast/broadcast
608          */
609         if (skb_in->pkt_type != PACKET_HOST)
610                 goto out;
611 
612         /*
613          *      Now check at the protocol level
614          */
615         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
616                 goto out;
617 
618         /*
619          *      Only reply to fragment 0. We byte re-order the constant
620          *      mask for efficiency.
621          */
622         if (iph->frag_off & htons(IP_OFFSET))
623                 goto out;
624 
625         /*
626          *      If we send an ICMP error to an ICMP error a mess would result..
627          */
628         if (icmp_pointers[type].error) {
629                 /*
630                  *      We are an error, check if we are replying to an
631                  *      ICMP error
632                  */
633                 if (iph->protocol == IPPROTO_ICMP) {
634                         u8 _inner_type, *itp;
635 
636                         itp = skb_header_pointer(skb_in,
637                                                  skb_network_header(skb_in) +
638                                                  (iph->ihl << 2) +
639                                                  offsetof(struct icmphdr,
640                                                           type) -
641                                                  skb_in->data,
642                                                  sizeof(_inner_type),
643                                                  &_inner_type);
644                         if (!itp)
645                                 goto out;
646 
647                         /*
648                          *      Assume any unknown ICMP type is an error. This
649                          *      isn't specified by the RFC, but think about it..
650                          */
651                         if (*itp > NR_ICMP_TYPES ||
652                             icmp_pointers[*itp].error)
653                                 goto out;
654                 }
655         }
656 
657         /* Needed by both icmp_global_allow and icmp_xmit_lock */
658         local_bh_disable();
659 
660         /* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
661          * incoming dev is loopback.  If outgoing dev change to not be
662          * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
663          */
664         if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
665               !icmpv4_global_allow(net, type, code))
666                 goto out_bh_enable;
667 
668         sk = icmp_xmit_lock(net);
669         if (!sk)
670                 goto out_bh_enable;
671 
672         /*
673          *      Construct source address and options.
674          */
675 
676         saddr = iph->daddr;
677         if (!(rt->rt_flags & RTCF_LOCAL)) {
678                 struct net_device *dev = NULL;
679 
680                 rcu_read_lock();
681                 if (rt_is_input_route(rt) &&
682                     net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr)
683                         dev = dev_get_by_index_rcu(net, inet_iif(skb_in));
684 
685                 if (dev)
686                         saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
687                 else
688                         saddr = 0;
689                 rcu_read_unlock();
690         }
691 
692         tos = icmp_pointers[type].error ? ((iph->tos & IPTOS_TOS_MASK) |
693                                            IPTOS_PREC_INTERNETCONTROL) :
694                                           iph->tos;
695         mark = IP4_REPLY_MARK(net, skb_in->mark);
696 
697         if (ip_options_echo(net, &icmp_param.replyopts.opt.opt, skb_in))
698                 goto out_unlock;
699 
700 
701         /*
702          *      Prepare data for ICMP header.
703          */
704 
705         icmp_param.data.icmph.type       = type;
706         icmp_param.data.icmph.code       = code;
707         icmp_param.data.icmph.un.gateway = info;
708         icmp_param.data.icmph.checksum   = 0;
709         icmp_param.skb    = skb_in;
710         icmp_param.offset = skb_network_offset(skb_in);
711         inet_sk(sk)->tos = tos;
712         sk->sk_mark = mark;
713         ipc.addr = iph->saddr;
714         ipc.opt = &icmp_param.replyopts.opt;
715         ipc.tx_flags = 0;
716         ipc.ttl = 0;
717         ipc.tos = -1;
718 
719         rt = icmp_route_lookup(net, &fl4, skb_in, iph, saddr, tos, mark,
720                                type, code, &icmp_param);
721         if (IS_ERR(rt))
722                 goto out_unlock;
723 
724         /* peer icmp_ratelimit */
725         if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
726                 goto ende;
727 
728         /* RFC says return as much as we can without exceeding 576 bytes. */
729 
730         room = dst_mtu(&rt->dst);
731         if (room > 576)
732                 room = 576;
733         room -= sizeof(struct iphdr) + icmp_param.replyopts.opt.opt.optlen;
734         room -= sizeof(struct icmphdr);
735 
736         icmp_param.data_len = skb_in->len - icmp_param.offset;
737         if (icmp_param.data_len > room)
738                 icmp_param.data_len = room;
739         icmp_param.head_len = sizeof(struct icmphdr);
740 
741         icmp_push_reply(&icmp_param, &fl4, &ipc, &rt);
742 ende:
743         ip_rt_put(rt);
744 out_unlock:
745         icmp_xmit_unlock(sk);
746 out_bh_enable:
747         local_bh_enable();
748 out:;
749 }
750 EXPORT_SYMBOL(icmp_send);
751 
752 
753 static void icmp_socket_deliver(struct sk_buff *skb, u32 info)
754 {
755         const struct iphdr *iph = (const struct iphdr *) skb->data;
756         const struct net_protocol *ipprot;
757         int protocol = iph->protocol;
758 
759         /* Checkin full IP header plus 8 bytes of protocol to
760          * avoid additional coding at protocol handlers.
761          */
762         if (!pskb_may_pull(skb, iph->ihl * 4 + 8)) {
763                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
764                 return;
765         }
766 
767         raw_icmp_error(skb, protocol, info);
768 
769         ipprot = rcu_dereference(inet_protos[protocol]);
770         if (ipprot && ipprot->err_handler)
771                 ipprot->err_handler(skb, info);
772 }
773 
774 static bool icmp_tag_validation(int proto)
775 {
776         bool ok;
777 
778         rcu_read_lock();
779         ok = rcu_dereference(inet_protos[proto])->icmp_strict_tag_validation;
780         rcu_read_unlock();
781         return ok;
782 }
783 
784 /*
785  *      Handle ICMP_DEST_UNREACH, ICMP_TIME_EXCEEDED, ICMP_QUENCH, and
786  *      ICMP_PARAMETERPROB.
787  */
788 
789 static bool icmp_unreach(struct sk_buff *skb)
790 {
791         const struct iphdr *iph;
792         struct icmphdr *icmph;
793         struct net *net;
794         u32 info = 0;
795 
796         net = dev_net(skb_dst(skb)->dev);
797 
798         /*
799          *      Incomplete header ?
800          *      Only checks for the IP header, there should be an
801          *      additional check for longer headers in upper levels.
802          */
803 
804         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
805                 goto out_err;
806 
807         icmph = icmp_hdr(skb);
808         iph   = (const struct iphdr *)skb->data;
809 
810         if (iph->ihl < 5) /* Mangled header, drop. */
811                 goto out_err;
812 
813         switch (icmph->type) {
814         case ICMP_DEST_UNREACH:
815                 switch (icmph->code & 15) {
816                 case ICMP_NET_UNREACH:
817                 case ICMP_HOST_UNREACH:
818                 case ICMP_PROT_UNREACH:
819                 case ICMP_PORT_UNREACH:
820                         break;
821                 case ICMP_FRAG_NEEDED:
822                         /* for documentation of the ip_no_pmtu_disc
823                          * values please see
824                          * Documentation/networking/ip-sysctl.txt
825                          */
826                         switch (net->ipv4.sysctl_ip_no_pmtu_disc) {
827                         default:
828                                 net_dbg_ratelimited("%pI4: fragmentation needed and DF set\n",
829                                                     &iph->daddr);
830                                 break;
831                         case 2:
832                                 goto out;
833                         case 3:
834                                 if (!icmp_tag_validation(iph->protocol))
835                                         goto out;
836                                 /* fall through */
837                         case 0:
838                                 info = ntohs(icmph->un.frag.mtu);
839                         }
840                         break;
841                 case ICMP_SR_FAILED:
842                         net_dbg_ratelimited("%pI4: Source Route Failed\n",
843                                             &iph->daddr);
844                         break;
845                 default:
846                         break;
847                 }
848                 if (icmph->code > NR_ICMP_UNREACH)
849                         goto out;
850                 break;
851         case ICMP_PARAMETERPROB:
852                 info = ntohl(icmph->un.gateway) >> 24;
853                 break;
854         case ICMP_TIME_EXCEEDED:
855                 __ICMP_INC_STATS(net, ICMP_MIB_INTIMEEXCDS);
856                 if (icmph->code == ICMP_EXC_FRAGTIME)
857                         goto out;
858                 break;
859         }
860 
861         /*
862          *      Throw it at our lower layers
863          *
864          *      RFC 1122: 3.2.2 MUST extract the protocol ID from the passed
865          *                header.
866          *      RFC 1122: 3.2.2.1 MUST pass ICMP unreach messages to the
867          *                transport layer.
868          *      RFC 1122: 3.2.2.2 MUST pass ICMP time expired messages to
869          *                transport layer.
870          */
871 
872         /*
873          *      Check the other end isn't violating RFC 1122. Some routers send
874          *      bogus responses to broadcast frames. If you see this message
875          *      first check your netmask matches at both ends, if it does then
876          *      get the other vendor to fix their kit.
877          */
878 
879         if (!net->ipv4.sysctl_icmp_ignore_bogus_error_responses &&
880             inet_addr_type_dev_table(net, skb->dev, iph->daddr) == RTN_BROADCAST) {
881                 net_warn_ratelimited("%pI4 sent an invalid ICMP type %u, code %u error to a broadcast: %pI4 on %s\n",
882                                      &ip_hdr(skb)->saddr,
883                                      icmph->type, icmph->code,
884                                      &iph->daddr, skb->dev->name);
885                 goto out;
886         }
887 
888         icmp_socket_deliver(skb, info);
889 
890 out:
891         return true;
892 out_err:
893         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
894         return false;
895 }
896 
897 
898 /*
899  *      Handle ICMP_REDIRECT.
900  */
901 
902 static bool icmp_redirect(struct sk_buff *skb)
903 {
904         if (skb->len < sizeof(struct iphdr)) {
905                 __ICMP_INC_STATS(dev_net(skb->dev), ICMP_MIB_INERRORS);
906                 return false;
907         }
908 
909         if (!pskb_may_pull(skb, sizeof(struct iphdr))) {
910                 /* there aught to be a stat */
911                 return false;
912         }
913 
914         icmp_socket_deliver(skb, icmp_hdr(skb)->un.gateway);
915         return true;
916 }
917 
918 /*
919  *      Handle ICMP_ECHO ("ping") requests.
920  *
921  *      RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
922  *                requests.
923  *      RFC 1122: 3.2.2.6 Data received in the ICMP_ECHO request MUST be
924  *                included in the reply.
925  *      RFC 1812: 4.3.3.6 SHOULD have a config option for silently ignoring
926  *                echo requests, MUST have default=NOT.
927  *      See also WRT handling of options once they are done and working.
928  */
929 
930 static bool icmp_echo(struct sk_buff *skb)
931 {
932         struct net *net;
933 
934         net = dev_net(skb_dst(skb)->dev);
935         if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
936                 struct icmp_bxm icmp_param;
937 
938                 icmp_param.data.icmph      = *icmp_hdr(skb);
939                 icmp_param.data.icmph.type = ICMP_ECHOREPLY;
940                 icmp_param.skb             = skb;
941                 icmp_param.offset          = 0;
942                 icmp_param.data_len        = skb->len;
943                 icmp_param.head_len        = sizeof(struct icmphdr);
944                 icmp_reply(&icmp_param, skb);
945         }
946         /* should there be an ICMP stat for ignored echos? */
947         return true;
948 }
949 
950 /*
951  *      Handle ICMP Timestamp requests.
952  *      RFC 1122: 3.2.2.8 MAY implement ICMP timestamp requests.
953  *                SHOULD be in the kernel for minimum random latency.
954  *                MUST be accurate to a few minutes.
955  *                MUST be updated at least at 15Hz.
956  */
957 static bool icmp_timestamp(struct sk_buff *skb)
958 {
959         struct icmp_bxm icmp_param;
960         /*
961          *      Too short.
962          */
963         if (skb->len < 4)
964                 goto out_err;
965 
966         /*
967          *      Fill in the current time as ms since midnight UT:
968          */
969         icmp_param.data.times[1] = inet_current_timestamp();
970         icmp_param.data.times[2] = icmp_param.data.times[1];
971 
972         BUG_ON(skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4));
973 
974         icmp_param.data.icmph      = *icmp_hdr(skb);
975         icmp_param.data.icmph.type = ICMP_TIMESTAMPREPLY;
976         icmp_param.data.icmph.code = 0;
977         icmp_param.skb             = skb;
978         icmp_param.offset          = 0;
979         icmp_param.data_len        = 0;
980         icmp_param.head_len        = sizeof(struct icmphdr) + 12;
981         icmp_reply(&icmp_param, skb);
982         return true;
983 
984 out_err:
985         __ICMP_INC_STATS(dev_net(skb_dst(skb)->dev), ICMP_MIB_INERRORS);
986         return false;
987 }
988 
989 static bool icmp_discard(struct sk_buff *skb)
990 {
991         /* pretend it was a success */
992         return true;
993 }
994 
995 /*
996  *      Deal with incoming ICMP packets.
997  */
998 int icmp_rcv(struct sk_buff *skb)
999 {
1000         struct icmphdr *icmph;
1001         struct rtable *rt = skb_rtable(skb);
1002         struct net *net = dev_net(rt->dst.dev);
1003         bool success;
1004 
1005         if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
1006                 struct sec_path *sp = skb_sec_path(skb);
1007                 int nh;
1008 
1009                 if (!(sp && sp->xvec[sp->len - 1]->props.flags &
1010                                  XFRM_STATE_ICMP))
1011                         goto drop;
1012 
1013                 if (!pskb_may_pull(skb, sizeof(*icmph) + sizeof(struct iphdr)))
1014                         goto drop;
1015 
1016                 nh = skb_network_offset(skb);
1017                 skb_set_network_header(skb, sizeof(*icmph));
1018 
1019                 if (!xfrm4_policy_check_reverse(NULL, XFRM_POLICY_IN, skb))
1020                         goto drop;
1021 
1022                 skb_set_network_header(skb, nh);
1023         }
1024 
1025         __ICMP_INC_STATS(net, ICMP_MIB_INMSGS);
1026 
1027         if (skb_checksum_simple_validate(skb))
1028                 goto csum_error;
1029 
1030         if (!pskb_pull(skb, sizeof(*icmph)))
1031                 goto error;
1032 
1033         icmph = icmp_hdr(skb);
1034 
1035         ICMPMSGIN_INC_STATS(net, icmph->type);
1036         /*
1037          *      18 is the highest 'known' ICMP type. Anything else is a mystery
1038          *
1039          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
1040          *                discarded.
1041          */
1042         if (icmph->type > NR_ICMP_TYPES)
1043                 goto error;
1044 
1045 
1046         /*
1047          *      Parse the ICMP message
1048          */
1049 
1050         if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
1051                 /*
1052                  *      RFC 1122: 3.2.2.6 An ICMP_ECHO to broadcast MAY be
1053                  *        silently ignored (we let user decide with a sysctl).
1054                  *      RFC 1122: 3.2.2.8 An ICMP_TIMESTAMP MAY be silently
1055                  *        discarded if to broadcast/multicast.
1056                  */
1057                 if ((icmph->type == ICMP_ECHO ||
1058                      icmph->type == ICMP_TIMESTAMP) &&
1059                     net->ipv4.sysctl_icmp_echo_ignore_broadcasts) {
1060                         goto error;
1061                 }
1062                 if (icmph->type != ICMP_ECHO &&
1063                     icmph->type != ICMP_TIMESTAMP &&
1064                     icmph->type != ICMP_ADDRESS &&
1065                     icmph->type != ICMP_ADDRESSREPLY) {
1066                         goto error;
1067                 }
1068         }
1069 
1070         success = icmp_pointers[icmph->type].handler(skb);
1071 
1072         if (success)  {
1073                 consume_skb(skb);
1074                 return NET_RX_SUCCESS;
1075         }
1076 
1077 drop:
1078         kfree_skb(skb);
1079         return NET_RX_DROP;
1080 csum_error:
1081         __ICMP_INC_STATS(net, ICMP_MIB_CSUMERRORS);
1082 error:
1083         __ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
1084         goto drop;
1085 }
1086 
1087 void icmp_err(struct sk_buff *skb, u32 info)
1088 {
1089         struct iphdr *iph = (struct iphdr *)skb->data;
1090         int offset = iph->ihl<<2;
1091         struct icmphdr *icmph = (struct icmphdr *)(skb->data + offset);
1092         int type = icmp_hdr(skb)->type;
1093         int code = icmp_hdr(skb)->code;
1094         struct net *net = dev_net(skb->dev);
1095 
1096         /*
1097          * Use ping_err to handle all icmp errors except those
1098          * triggered by ICMP_ECHOREPLY which sent from kernel.
1099          */
1100         if (icmph->type != ICMP_ECHOREPLY) {
1101                 ping_err(skb, offset, info);
1102                 return;
1103         }
1104 
1105         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1106                 ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ICMP, 0);
1107         else if (type == ICMP_REDIRECT)
1108                 ipv4_redirect(skb, net, 0, 0, IPPROTO_ICMP, 0);
1109 }
1110 
1111 /*
1112  *      This table is the definition of how we handle ICMP.
1113  */
1114 static const struct icmp_control icmp_pointers[NR_ICMP_TYPES + 1] = {
1115         [ICMP_ECHOREPLY] = {
1116                 .handler = ping_rcv,
1117         },
1118         [1] = {
1119                 .handler = icmp_discard,
1120                 .error = 1,
1121         },
1122         [2] = {
1123                 .handler = icmp_discard,
1124                 .error = 1,
1125         },
1126         [ICMP_DEST_UNREACH] = {
1127                 .handler = icmp_unreach,
1128                 .error = 1,
1129         },
1130         [ICMP_SOURCE_QUENCH] = {
1131                 .handler = icmp_unreach,
1132                 .error = 1,
1133         },
1134         [ICMP_REDIRECT] = {
1135                 .handler = icmp_redirect,
1136                 .error = 1,
1137         },
1138         [6] = {
1139                 .handler = icmp_discard,
1140                 .error = 1,
1141         },
1142         [7] = {
1143                 .handler = icmp_discard,
1144                 .error = 1,
1145         },
1146         [ICMP_ECHO] = {
1147                 .handler = icmp_echo,
1148         },
1149         [9] = {
1150                 .handler = icmp_discard,
1151                 .error = 1,
1152         },
1153         [10] = {
1154                 .handler = icmp_discard,
1155                 .error = 1,
1156         },
1157         [ICMP_TIME_EXCEEDED] = {
1158                 .handler = icmp_unreach,
1159                 .error = 1,
1160         },
1161         [ICMP_PARAMETERPROB] = {
1162                 .handler = icmp_unreach,
1163                 .error = 1,
1164         },
1165         [ICMP_TIMESTAMP] = {
1166                 .handler = icmp_timestamp,
1167         },
1168         [ICMP_TIMESTAMPREPLY] = {
1169                 .handler = icmp_discard,
1170         },
1171         [ICMP_INFO_REQUEST] = {
1172                 .handler = icmp_discard,
1173         },
1174         [ICMP_INFO_REPLY] = {
1175                 .handler = icmp_discard,
1176         },
1177         [ICMP_ADDRESS] = {
1178                 .handler = icmp_discard,
1179         },
1180         [ICMP_ADDRESSREPLY] = {
1181                 .handler = icmp_discard,
1182         },
1183 };
1184 
1185 static void __net_exit icmp_sk_exit(struct net *net)
1186 {
1187         int i;
1188 
1189         for_each_possible_cpu(i)
1190                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
1191         free_percpu(net->ipv4.icmp_sk);
1192         net->ipv4.icmp_sk = NULL;
1193 }
1194 
1195 static int __net_init icmp_sk_init(struct net *net)
1196 {
1197         int i, err;
1198 
1199         net->ipv4.icmp_sk = alloc_percpu(struct sock *);
1200         if (!net->ipv4.icmp_sk)
1201                 return -ENOMEM;
1202 
1203         for_each_possible_cpu(i) {
1204                 struct sock *sk;
1205 
1206                 err = inet_ctl_sock_create(&sk, PF_INET,
1207                                            SOCK_RAW, IPPROTO_ICMP, net);
1208                 if (err < 0)
1209                         goto fail;
1210 
1211                 *per_cpu_ptr(net->ipv4.icmp_sk, i) = sk;
1212 
1213                 /* Enough space for 2 64K ICMP packets, including
1214                  * sk_buff/skb_shared_info struct overhead.
1215                  */
1216                 sk->sk_sndbuf = 2 * SKB_TRUESIZE(64 * 1024);
1217 
1218                 /*
1219                  * Speedup sock_wfree()
1220                  */
1221                 sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
1222                 inet_sk(sk)->pmtudisc = IP_PMTUDISC_DONT;
1223         }
1224 
1225         /* Control parameters for ECHO replies. */
1226         net->ipv4.sysctl_icmp_echo_ignore_all = 0;
1227         net->ipv4.sysctl_icmp_echo_ignore_broadcasts = 1;
1228 
1229         /* Control parameter - ignore bogus broadcast responses? */
1230         net->ipv4.sysctl_icmp_ignore_bogus_error_responses = 1;
1231 
1232         /*
1233          *      Configurable global rate limit.
1234          *
1235          *      ratelimit defines tokens/packet consumed for dst->rate_token
1236          *      bucket ratemask defines which icmp types are ratelimited by
1237          *      setting it's bit position.
1238          *
1239          *      default:
1240          *      dest unreachable (3), source quench (4),
1241          *      time exceeded (11), parameter problem (12)
1242          */
1243 
1244         net->ipv4.sysctl_icmp_ratelimit = 1 * HZ;
1245         net->ipv4.sysctl_icmp_ratemask = 0x1818;
1246         net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0;
1247 
1248         return 0;
1249 
1250 fail:
1251         for_each_possible_cpu(i)
1252                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.icmp_sk, i));
1253         free_percpu(net->ipv4.icmp_sk);
1254         return err;
1255 }
1256 
1257 static struct pernet_operations __net_initdata icmp_sk_ops = {
1258        .init = icmp_sk_init,
1259        .exit = icmp_sk_exit,
1260 };
1261 
1262 int __init icmp_init(void)
1263 {
1264         return register_pernet_subsys(&icmp_sk_ops);
1265 }
1266 

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