blob: c703528e0bcd524751b8b4e43415e2b8e8ccadaf [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 * Version: $Id: ip_input.c,v 1.55 2002/01/12 07:39:45 davem Exp $
9 *
Jesper Juhl02c30a82005-05-05 16:16:16 -070010 * Authors: Ross Biro
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@super.org>
13 * Alan Cox, <Alan.Cox@linux.org>
14 * Richard Underwood
15 * Stefan Becker, <stefanb@yello.ping.de>
16 * Jorge Cwik, <jorge@laser.satlink.net>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 *
19 *
20 * Fixes:
21 * Alan Cox : Commented a couple of minor bits of surplus code
22 * Alan Cox : Undefining IP_FORWARD doesn't include the code
23 * (just stops a compiler warning).
24 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes
25 * are junked rather than corrupting things.
26 * Alan Cox : Frames to bad broadcast subnets are dumped
27 * We used to process them non broadcast and
28 * boy could that cause havoc.
29 * Alan Cox : ip_forward sets the free flag on the
30 * new frame it queues. Still crap because
31 * it copies the frame but at least it
32 * doesn't eat memory too.
33 * Alan Cox : Generic queue code and memory fixes.
34 * Fred Van Kempen : IP fragment support (borrowed from NET2E)
35 * Gerhard Koerting: Forward fragmented frames correctly.
36 * Gerhard Koerting: Fixes to my fix of the above 8-).
37 * Gerhard Koerting: IP interface addressing fix.
38 * Linus Torvalds : More robustness checks
39 * Alan Cox : Even more checks: Still not as robust as it ought to be
40 * Alan Cox : Save IP header pointer for later
41 * Alan Cox : ip option setting
42 * Alan Cox : Use ip_tos/ip_ttl settings
43 * Alan Cox : Fragmentation bogosity removed
44 * (Thanks to Mark.Bush@prg.ox.ac.uk)
45 * Dmitry Gorodchanin : Send of a raw packet crash fix.
46 * Alan Cox : Silly ip bug when an overlength
47 * fragment turns up. Now frees the
48 * queue.
49 * Linus Torvalds/ : Memory leakage on fragmentation
50 * Alan Cox : handling.
51 * Gerhard Koerting: Forwarding uses IP priority hints
52 * Teemu Rantanen : Fragment problems.
53 * Alan Cox : General cleanup, comments and reformat
54 * Alan Cox : SNMP statistics
55 * Alan Cox : BSD address rule semantics. Also see
56 * UDP as there is a nasty checksum issue
57 * if you do things the wrong way.
58 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file
59 * Alan Cox : IP options adjust sk->priority.
60 * Pedro Roque : Fix mtu/length error in ip_forward.
61 * Alan Cox : Avoid ip_chk_addr when possible.
62 * Richard Underwood : IP multicasting.
63 * Alan Cox : Cleaned up multicast handlers.
64 * Alan Cox : RAW sockets demultiplex in the BSD style.
65 * Gunther Mayer : Fix the SNMP reporting typo
66 * Alan Cox : Always in group 224.0.0.1
67 * Pauline Middelink : Fast ip_checksum update when forwarding
68 * Masquerading support.
69 * Alan Cox : Multicast loopback error for 224.0.0.1
70 * Alan Cox : IP_MULTICAST_LOOP option.
71 * Alan Cox : Use notifiers.
72 * Bjorn Ekwall : Removed ip_csum (from slhc.c too)
73 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!)
74 * Stefan Becker : Send out ICMP HOST REDIRECT
75 * Arnt Gulbrandsen : ip_build_xmit
76 * Alan Cox : Per socket routing cache
77 * Alan Cox : Fixed routing cache, added header cache.
78 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it.
79 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net.
80 * Alan Cox : Incoming IP option handling.
81 * Alan Cox : Set saddr on raw output frames as per BSD.
82 * Alan Cox : Stopped broadcast source route explosions.
83 * Alan Cox : Can disable source routing
84 * Takeshi Sone : Masquerading didn't work.
85 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible.
86 * Alan Cox : Memory leaks, tramples, misc debugging.
87 * Alan Cox : Fixed multicast (by popular demand 8))
88 * Alan Cox : Fixed forwarding (by even more popular demand 8))
89 * Alan Cox : Fixed SNMP statistics [I think]
90 * Gerhard Koerting : IP fragmentation forwarding fix
91 * Alan Cox : Device lock against page fault.
92 * Alan Cox : IP_HDRINCL facility.
93 * Werner Almesberger : Zero fragment bug
94 * Alan Cox : RAW IP frame length bug
95 * Alan Cox : Outgoing firewall on build_xmit
96 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel
97 * Alan Cox : Multicast routing hooks
98 * Jos Vos : Do accounting *before* call_in_firewall
99 * Willy Konynenberg : Transparent proxying support
100 *
101 *
102 *
103 * To Fix:
104 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
105 * and could be made very efficient with the addition of some virtual memory hacks to permit
106 * the allocation of a buffer that can then be 'grown' by twiddling page tables.
107 * Output fragmentation wants updating along with the buffer management to use a single
108 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
109 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
110 * fragmentation anyway.
111 *
112 * This program is free software; you can redistribute it and/or
113 * modify it under the terms of the GNU General Public License
114 * as published by the Free Software Foundation; either version
115 * 2 of the License, or (at your option) any later version.
116 */
117
118#include <asm/system.h>
119#include <linux/module.h>
120#include <linux/types.h>
121#include <linux/kernel.h>
122#include <linux/string.h>
123#include <linux/errno.h>
124#include <linux/config.h>
125
126#include <linux/net.h>
127#include <linux/socket.h>
128#include <linux/sockios.h>
129#include <linux/in.h>
130#include <linux/inet.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 <linux/netfilter_ipv4.h>
145#include <net/xfrm.h>
146#include <linux/mroute.h>
147#include <linux/netlink.h>
148
149/*
150 * SNMP management statistics
151 */
152
153DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics);
154
155/*
156 * Process Router Attention IP option
157 */
158int ip_call_ra_chain(struct sk_buff *skb)
159{
160 struct ip_ra_chain *ra;
161 u8 protocol = skb->nh.iph->protocol;
162 struct sock *last = NULL;
163
164 read_lock(&ip_ra_lock);
165 for (ra = ip_ra_chain; ra; ra = ra->next) {
166 struct sock *sk = ra->sk;
167
168 /* If socket is bound to an interface, only report
169 * the packet if it came from that interface.
170 */
171 if (sk && inet_sk(sk)->num == protocol &&
172 (!sk->sk_bound_dev_if ||
173 sk->sk_bound_dev_if == skb->dev->ifindex)) {
174 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
175 skb = ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN);
176 if (skb == NULL) {
177 read_unlock(&ip_ra_lock);
178 return 1;
179 }
180 }
181 if (last) {
182 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
183 if (skb2)
184 raw_rcv(last, skb2);
185 }
186 last = sk;
Patrick McHardy2715bcf2005-06-21 14:06:24 -0700187 nf_reset(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188 }
189 }
190
191 if (last) {
192 raw_rcv(last, skb);
193 read_unlock(&ip_ra_lock);
194 return 1;
195 }
196 read_unlock(&ip_ra_lock);
197 return 0;
198}
199
200static inline int ip_local_deliver_finish(struct sk_buff *skb)
201{
202 int ihl = skb->nh.iph->ihl*4;
203
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 __skb_pull(skb, ihl);
205
206 /* Free reference early: we don't need it any more, and it may
207 hold ip_conntrack module loaded indefinitely. */
208 nf_reset(skb);
209
210 /* Point into the IP datagram, just past the header. */
211 skb->h.raw = skb->data;
212
213 rcu_read_lock();
214 {
215 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
216 int protocol = skb->nh.iph->protocol;
217 int hash;
218 struct sock *raw_sk;
219 struct net_protocol *ipprot;
220
221 resubmit:
222 hash = protocol & (MAX_INET_PROTOS - 1);
223 raw_sk = sk_head(&raw_v4_htable[hash]);
224
225 /* If there maybe a raw socket we must check - if not we
226 * don't care less
227 */
228 if (raw_sk)
229 raw_v4_input(skb, skb->nh.iph, hash);
230
231 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) {
232 int ret;
233
234 if (!ipprot->no_policy &&
235 !xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
236 kfree_skb(skb);
237 goto out;
238 }
239 ret = ipprot->handler(skb);
240 if (ret < 0) {
241 protocol = -ret;
242 goto resubmit;
243 }
244 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
245 } else {
246 if (!raw_sk) {
247 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
248 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS);
249 icmp_send(skb, ICMP_DEST_UNREACH,
250 ICMP_PROT_UNREACH, 0);
251 }
252 } else
253 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS);
254 kfree_skb(skb);
255 }
256 }
257 out:
258 rcu_read_unlock();
259
260 return 0;
261}
262
263/*
264 * Deliver IP Packets to the higher protocol layers.
265 */
266int ip_local_deliver(struct sk_buff *skb)
267{
268 /*
269 * Reassemble IP fragments.
270 */
271
272 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
273 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER);
274 if (!skb)
275 return 0;
276 }
277
278 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL,
279 ip_local_deliver_finish);
280}
281
282static inline int ip_rcv_finish(struct sk_buff *skb)
283{
284 struct net_device *dev = skb->dev;
285 struct iphdr *iph = skb->nh.iph;
Dietmar Eggemann2c2910a2005-06-28 13:06:23 -0700286 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287
288 /*
289 * Initialise the virtual path cache for the packet. It describes
290 * how the packet travels inside Linux networking.
291 */
292 if (skb->dst == NULL) {
Dietmar Eggemann2c2910a2005-06-28 13:06:23 -0700293 if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
294 if (err == -EHOSTUNREACH)
295 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 goto drop;
Dietmar Eggemann2c2910a2005-06-28 13:06:23 -0700297 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 }
299
300#ifdef CONFIG_NET_CLS_ROUTE
301 if (skb->dst->tclassid) {
302 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id();
303 u32 idx = skb->dst->tclassid;
304 st[idx&0xFF].o_packets++;
305 st[idx&0xFF].o_bytes+=skb->len;
306 st[(idx>>16)&0xFF].i_packets++;
307 st[(idx>>16)&0xFF].i_bytes+=skb->len;
308 }
309#endif
310
311 if (iph->ihl > 5) {
312 struct ip_options *opt;
313
314 /* It looks as overkill, because not all
315 IP options require packet mangling.
316 But it is the easiest for now, especially taking
317 into account that combination of IP options
318 and running sniffer is extremely rare condition.
319 --ANK (980813)
320 */
321
322 if (skb_cow(skb, skb_headroom(skb))) {
323 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
324 goto drop;
325 }
326 iph = skb->nh.iph;
327
328 if (ip_options_compile(NULL, skb))
329 goto inhdr_error;
330
331 opt = &(IPCB(skb)->opt);
332 if (opt->srr) {
333 struct in_device *in_dev = in_dev_get(dev);
334 if (in_dev) {
335 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
336 if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit())
337 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n",
338 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
339 in_dev_put(in_dev);
340 goto drop;
341 }
342 in_dev_put(in_dev);
343 }
344 if (ip_options_rcv_srr(skb))
345 goto drop;
346 }
347 }
348
349 return dst_input(skb);
350
351inhdr_error:
352 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
353drop:
354 kfree_skb(skb);
355 return NET_RX_DROP;
356}
357
358/*
359 * Main IP Receive routine.
360 */
361int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
362{
363 struct iphdr *iph;
364
365 /* When the interface is in promisc. mode, drop all the crap
366 * that it receives, do not try to analyse it.
367 */
368 if (skb->pkt_type == PACKET_OTHERHOST)
369 goto drop;
370
371 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES);
372
373 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
374 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
375 goto out;
376 }
377
378 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
379 goto inhdr_error;
380
381 iph = skb->nh.iph;
382
383 /*
384 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
385 *
386 * Is the datagram acceptable?
387 *
388 * 1. Length at least the size of an ip header
389 * 2. Version of 4
390 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
391 * 4. Doesn't have a bogus length
392 */
393
394 if (iph->ihl < 5 || iph->version != 4)
395 goto inhdr_error;
396
397 if (!pskb_may_pull(skb, iph->ihl*4))
398 goto inhdr_error;
399
400 iph = skb->nh.iph;
401
402 if (ip_fast_csum((u8 *)iph, iph->ihl) != 0)
403 goto inhdr_error;
404
405 {
406 __u32 len = ntohs(iph->tot_len);
407 if (skb->len < len || len < (iph->ihl<<2))
408 goto inhdr_error;
409
410 /* Our transport medium may have padded the buffer out. Now we know it
411 * is IP we can trim to the true length of the frame.
412 * Note this now means skb->len holds ntohs(iph->tot_len).
413 */
414 if (pskb_trim_rcsum(skb, len)) {
415 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS);
416 goto drop;
417 }
418 }
419
420 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
421 ip_rcv_finish);
422
423inhdr_error:
424 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
425drop:
426 kfree_skb(skb);
427out:
428 return NET_RX_DROP;
429}
430
431EXPORT_SYMBOL(ip_rcv);
432EXPORT_SYMBOL(ip_statistics);