Version:  2.0.40 2.2.26 2.4.37 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17

Linux/net/ipv4/ip_input.c

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The Internet Protocol (IP) module.
  7  *
  8  * Authors:     Ross Biro
  9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 10  *              Donald Becker, <becker@super.org>
 11  *              Alan Cox, <alan@lxorguk.ukuu.org.uk>
 12  *              Richard Underwood
 13  *              Stefan Becker, <stefanb@yello.ping.de>
 14  *              Jorge Cwik, <jorge@laser.satlink.net>
 15  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 16  *
 17  *
 18  * Fixes:
 19  *              Alan Cox        :       Commented a couple of minor bits of surplus code
 20  *              Alan Cox        :       Undefining IP_FORWARD doesn't include the code
 21  *                                      (just stops a compiler warning).
 22  *              Alan Cox        :       Frames with >=MAX_ROUTE record routes, strict routes or loose routes
 23  *                                      are junked rather than corrupting things.
 24  *              Alan Cox        :       Frames to bad broadcast subnets are dumped
 25  *                                      We used to process them non broadcast and
 26  *                                      boy could that cause havoc.
 27  *              Alan Cox        :       ip_forward sets the free flag on the
 28  *                                      new frame it queues. Still crap because
 29  *                                      it copies the frame but at least it
 30  *                                      doesn't eat memory too.
 31  *              Alan Cox        :       Generic queue code and memory fixes.
 32  *              Fred Van Kempen :       IP fragment support (borrowed from NET2E)
 33  *              Gerhard Koerting:       Forward fragmented frames correctly.
 34  *              Gerhard Koerting:       Fixes to my fix of the above 8-).
 35  *              Gerhard Koerting:       IP interface addressing fix.
 36  *              Linus Torvalds  :       More robustness checks
 37  *              Alan Cox        :       Even more checks: Still not as robust as it ought to be
 38  *              Alan Cox        :       Save IP header pointer for later
 39  *              Alan Cox        :       ip option setting
 40  *              Alan Cox        :       Use ip_tos/ip_ttl settings
 41  *              Alan Cox        :       Fragmentation bogosity removed
 42  *                                      (Thanks to Mark.Bush@prg.ox.ac.uk)
 43  *              Dmitry Gorodchanin :    Send of a raw packet crash fix.
 44  *              Alan Cox        :       Silly ip bug when an overlength
 45  *                                      fragment turns up. Now frees the
 46  *                                      queue.
 47  *              Linus Torvalds/ :       Memory leakage on fragmentation
 48  *              Alan Cox        :       handling.
 49  *              Gerhard Koerting:       Forwarding uses IP priority hints
 50  *              Teemu Rantanen  :       Fragment problems.
 51  *              Alan Cox        :       General cleanup, comments and reformat
 52  *              Alan Cox        :       SNMP statistics
 53  *              Alan Cox        :       BSD address rule semantics. Also see
 54  *                                      UDP as there is a nasty checksum issue
 55  *                                      if you do things the wrong way.
 56  *              Alan Cox        :       Always defrag, moved IP_FORWARD to the config.in file
 57  *              Alan Cox        :       IP options adjust sk->priority.
 58  *              Pedro Roque     :       Fix mtu/length error in ip_forward.
 59  *              Alan Cox        :       Avoid ip_chk_addr when possible.
 60  *      Richard Underwood       :       IP multicasting.
 61  *              Alan Cox        :       Cleaned up multicast handlers.
 62  *              Alan Cox        :       RAW sockets demultiplex in the BSD style.
 63  *              Gunther Mayer   :       Fix the SNMP reporting typo
 64  *              Alan Cox        :       Always in group 224.0.0.1
 65  *      Pauline Middelink       :       Fast ip_checksum update when forwarding
 66  *                                      Masquerading support.
 67  *              Alan Cox        :       Multicast loopback error for 224.0.0.1
 68  *              Alan Cox        :       IP_MULTICAST_LOOP option.
 69  *              Alan Cox        :       Use notifiers.
 70  *              Bjorn Ekwall    :       Removed ip_csum (from slhc.c too)
 71  *              Bjorn Ekwall    :       Moved ip_fast_csum to ip.h (inline!)
 72  *              Stefan Becker   :       Send out ICMP HOST REDIRECT
 73  *      Arnt Gulbrandsen        :       ip_build_xmit
 74  *              Alan Cox        :       Per socket routing cache
 75  *              Alan Cox        :       Fixed routing cache, added header cache.
 76  *              Alan Cox        :       Loopback didn't work right in original ip_build_xmit - fixed it.
 77  *              Alan Cox        :       Only send ICMP_REDIRECT if src/dest are the same net.
 78  *              Alan Cox        :       Incoming IP option handling.
 79  *              Alan Cox        :       Set saddr on raw output frames as per BSD.
 80  *              Alan Cox        :       Stopped broadcast source route explosions.
 81  *              Alan Cox        :       Can disable source routing
 82  *              Takeshi Sone    :       Masquerading didn't work.
 83  *      Dave Bonn,Alan Cox      :       Faster IP forwarding whenever possible.
 84  *              Alan Cox        :       Memory leaks, tramples, misc debugging.
 85  *              Alan Cox        :       Fixed multicast (by popular demand 8))
 86  *              Alan Cox        :       Fixed forwarding (by even more popular demand 8))
 87  *              Alan Cox        :       Fixed SNMP statistics [I think]
 88  *      Gerhard Koerting        :       IP fragmentation forwarding fix
 89  *              Alan Cox        :       Device lock against page fault.
 90  *              Alan Cox        :       IP_HDRINCL facility.
 91  *      Werner Almesberger      :       Zero fragment bug
 92  *              Alan Cox        :       RAW IP frame length bug
 93  *              Alan Cox        :       Outgoing firewall on build_xmit
 94  *              A.N.Kuznetsov   :       IP_OPTIONS support throughout the kernel
 95  *              Alan Cox        :       Multicast routing hooks
 96  *              Jos Vos         :       Do accounting *before* call_in_firewall
 97  *      Willy Konynenberg       :       Transparent proxying support
 98  *
 99  *
100  *
101  * To Fix:
102  *              IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
103  *              and could be made very efficient with the addition of some virtual memory hacks to permit
104  *              the allocation of a buffer that can then be 'grown' by twiddling page tables.
105  *              Output fragmentation wants updating along with the buffer management to use a single
106  *              interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
107  *              output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
108  *              fragmentation anyway.
109  *
110  *              This program is free software; you can redistribute it and/or
111  *              modify it under the terms of the GNU General Public License
112  *              as published by the Free Software Foundation; either version
113  *              2 of the License, or (at your option) any later version.
114  */
115 
116 #define pr_fmt(fmt) "IPv4: " fmt
117 
118 #include <linux/module.h>
119 #include <linux/types.h>
120 #include <linux/kernel.h>
121 #include <linux/string.h>
122 #include <linux/errno.h>
123 #include <linux/slab.h>
124 
125 #include <linux/net.h>
126 #include <linux/socket.h>
127 #include <linux/sockios.h>
128 #include <linux/in.h>
129 #include <linux/inet.h>
130 #include <linux/inetdevice.h>
131 #include <linux/netdevice.h>
132 #include <linux/etherdevice.h>
133 
134 #include <net/snmp.h>
135 #include <net/ip.h>
136 #include <net/protocol.h>
137 #include <net/route.h>
138 #include <linux/skbuff.h>
139 #include <net/sock.h>
140 #include <net/arp.h>
141 #include <net/icmp.h>
142 #include <net/raw.h>
143 #include <net/checksum.h>
144 #include <net/inet_ecn.h>
145 #include <linux/netfilter_ipv4.h>
146 #include <net/xfrm.h>
147 #include <linux/mroute.h>
148 #include <linux/netlink.h>
149 
150 /*
151  *      Process Router Attention IP option (RFC 2113)
152  */
153 bool ip_call_ra_chain(struct sk_buff *skb)
154 {
155         struct ip_ra_chain *ra;
156         u8 protocol = ip_hdr(skb)->protocol;
157         struct sock *last = NULL;
158         struct net_device *dev = skb->dev;
159 
160         for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) {
161                 struct sock *sk = ra->sk;
162 
163                 /* If socket is bound to an interface, only report
164                  * the packet if it came  from that interface.
165                  */
166                 if (sk && inet_sk(sk)->inet_num == protocol &&
167                     (!sk->sk_bound_dev_if ||
168                      sk->sk_bound_dev_if == dev->ifindex) &&
169                     net_eq(sock_net(sk), dev_net(dev))) {
170                         if (ip_is_fragment(ip_hdr(skb))) {
171                                 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN))
172                                         return true;
173                         }
174                         if (last) {
175                                 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
176                                 if (skb2)
177                                         raw_rcv(last, skb2);
178                         }
179                         last = sk;
180                 }
181         }
182 
183         if (last) {
184                 raw_rcv(last, skb);
185                 return true;
186         }
187         return false;
188 }
189 
190 static int ip_local_deliver_finish(struct sk_buff *skb)
191 {
192         struct net *net = dev_net(skb->dev);
193 
194         __skb_pull(skb, skb_network_header_len(skb));
195 
196         rcu_read_lock();
197         {
198                 int protocol = ip_hdr(skb)->protocol;
199                 const struct net_protocol *ipprot;
200                 int raw;
201 
202         resubmit:
203                 raw = raw_local_deliver(skb, protocol);
204 
205                 ipprot = rcu_dereference(inet_protos[protocol]);
206                 if (ipprot != NULL) {
207                         int ret;
208 
209                         if (!ipprot->no_policy) {
210                                 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
211                                         kfree_skb(skb);
212                                         goto out;
213                                 }
214                                 nf_reset(skb);
215                         }
216                         ret = ipprot->handler(skb);
217                         if (ret < 0) {
218                                 protocol = -ret;
219                                 goto resubmit;
220                         }
221                         IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
222                 } else {
223                         if (!raw) {
224                                 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
225                                         IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS);
226                                         icmp_send(skb, ICMP_DEST_UNREACH,
227                                                   ICMP_PROT_UNREACH, 0);
228                                 }
229                                 kfree_skb(skb);
230                         } else {
231                                 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
232                                 consume_skb(skb);
233                         }
234                 }
235         }
236  out:
237         rcu_read_unlock();
238 
239         return 0;
240 }
241 
242 /*
243  *      Deliver IP Packets to the higher protocol layers.
244  */
245 int ip_local_deliver(struct sk_buff *skb)
246 {
247         /*
248          *      Reassemble IP fragments.
249          */
250 
251         if (ip_is_fragment(ip_hdr(skb))) {
252                 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER))
253                         return 0;
254         }
255 
256         return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL,
257                        ip_local_deliver_finish);
258 }
259 
260 static inline bool ip_rcv_options(struct sk_buff *skb)
261 {
262         struct ip_options *opt;
263         const struct iphdr *iph;
264         struct net_device *dev = skb->dev;
265 
266         /* It looks as overkill, because not all
267            IP options require packet mangling.
268            But it is the easiest for now, especially taking
269            into account that combination of IP options
270            and running sniffer is extremely rare condition.
271                                               --ANK (980813)
272         */
273         if (skb_cow(skb, skb_headroom(skb))) {
274                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
275                 goto drop;
276         }
277 
278         iph = ip_hdr(skb);
279         opt = &(IPCB(skb)->opt);
280         opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
281 
282         if (ip_options_compile(dev_net(dev), opt, skb)) {
283                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
284                 goto drop;
285         }
286 
287         if (unlikely(opt->srr)) {
288                 struct in_device *in_dev = __in_dev_get_rcu(dev);
289 
290                 if (in_dev) {
291                         if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
292                                 if (IN_DEV_LOG_MARTIANS(in_dev))
293                                         net_info_ratelimited("source route option %pI4 -> %pI4\n",
294                                                              &iph->saddr,
295                                                              &iph->daddr);
296                                 goto drop;
297                         }
298                 }
299 
300                 if (ip_options_rcv_srr(skb))
301                         goto drop;
302         }
303 
304         return false;
305 drop:
306         return true;
307 }
308 
309 int sysctl_ip_early_demux __read_mostly = 1;
310 EXPORT_SYMBOL(sysctl_ip_early_demux);
311 
312 static int ip_rcv_finish(struct sk_buff *skb)
313 {
314         const struct iphdr *iph = ip_hdr(skb);
315         struct rtable *rt;
316 
317         if (sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
318                 const struct net_protocol *ipprot;
319                 int protocol = iph->protocol;
320 
321                 ipprot = rcu_dereference(inet_protos[protocol]);
322                 if (ipprot && ipprot->early_demux) {
323                         ipprot->early_demux(skb);
324                         /* must reload iph, skb->head might have changed */
325                         iph = ip_hdr(skb);
326                 }
327         }
328 
329         /*
330          *      Initialise the virtual path cache for the packet. It describes
331          *      how the packet travels inside Linux networking.
332          */
333         if (!skb_dst(skb)) {
334                 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
335                                                iph->tos, skb->dev);
336                 if (unlikely(err)) {
337                         if (err == -EXDEV)
338                                 NET_INC_STATS_BH(dev_net(skb->dev),
339                                                  LINUX_MIB_IPRPFILTER);
340                         goto drop;
341                 }
342         }
343 
344 #ifdef CONFIG_IP_ROUTE_CLASSID
345         if (unlikely(skb_dst(skb)->tclassid)) {
346                 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
347                 u32 idx = skb_dst(skb)->tclassid;
348                 st[idx&0xFF].o_packets++;
349                 st[idx&0xFF].o_bytes += skb->len;
350                 st[(idx>>16)&0xFF].i_packets++;
351                 st[(idx>>16)&0xFF].i_bytes += skb->len;
352         }
353 #endif
354 
355         if (iph->ihl > 5 && ip_rcv_options(skb))
356                 goto drop;
357 
358         rt = skb_rtable(skb);
359         if (rt->rt_type == RTN_MULTICAST) {
360                 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST,
361                                 skb->len);
362         } else if (rt->rt_type == RTN_BROADCAST)
363                 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST,
364                                 skb->len);
365 
366         return dst_input(skb);
367 
368 drop:
369         kfree_skb(skb);
370         return NET_RX_DROP;
371 }
372 
373 /*
374  *      Main IP Receive routine.
375  */
376 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
377 {
378         const struct iphdr *iph;
379         u32 len;
380 
381         /* When the interface is in promisc. mode, drop all the crap
382          * that it receives, do not try to analyse it.
383          */
384         if (skb->pkt_type == PACKET_OTHERHOST)
385                 goto drop;
386 
387 
388         IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len);
389 
390         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
391                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
392                 goto out;
393         }
394 
395         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
396                 goto inhdr_error;
397 
398         iph = ip_hdr(skb);
399 
400         /*
401          *      RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
402          *
403          *      Is the datagram acceptable?
404          *
405          *      1.      Length at least the size of an ip header
406          *      2.      Version of 4
407          *      3.      Checksums correctly. [Speed optimisation for later, skip loopback checksums]
408          *      4.      Doesn't have a bogus length
409          */
410 
411         if (iph->ihl < 5 || iph->version != 4)
412                 goto inhdr_error;
413 
414         BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1);
415         BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0);
416         BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE);
417         IP_ADD_STATS_BH(dev_net(dev),
418                         IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK),
419                         max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
420 
421         if (!pskb_may_pull(skb, iph->ihl*4))
422                 goto inhdr_error;
423 
424         iph = ip_hdr(skb);
425 
426         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
427                 goto csum_error;
428 
429         len = ntohs(iph->tot_len);
430         if (skb->len < len) {
431                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
432                 goto drop;
433         } else if (len < (iph->ihl*4))
434                 goto inhdr_error;
435 
436         /* Our transport medium may have padded the buffer out. Now we know it
437          * is IP we can trim to the true length of the frame.
438          * Note this now means skb->len holds ntohs(iph->tot_len).
439          */
440         if (pskb_trim_rcsum(skb, len)) {
441                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
442                 goto drop;
443         }
444 
445         skb->transport_header = skb->network_header + iph->ihl*4;
446 
447         /* Remove any debris in the socket control block */
448         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
449 
450         /* Must drop socket now because of tproxy. */
451         skb_orphan(skb);
452 
453         return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL,
454                        ip_rcv_finish);
455 
456 csum_error:
457         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_CSUMERRORS);
458 inhdr_error:
459         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
460 drop:
461         kfree_skb(skb);
462 out:
463         return NET_RX_DROP;
464 }
465 

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