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 * Version: $Id: ip_input.c,v 1.51 2000/12/08 17:15:53 davem Exp $
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
11 * 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/types.h>
120 #include <linux/kernel.h>
121 #include <linux/string.h>
122 #include <linux/errno.h>
123 #include <linux/config.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/netdevice.h>
131 #include <linux/etherdevice.h>
132
133 #include <net/snmp.h>
134 #include <net/ip.h>
135 #include <net/protocol.h>
136 #include <net/route.h>
137 #include <linux/skbuff.h>
138 #include <net/sock.h>
139 #include <net/arp.h>
140 #include <net/icmp.h>
141 #include <net/raw.h>
142 #include <net/checksum.h>
143 #include <linux/netfilter_ipv4.h>
144 #include <linux/mroute.h>
145 #include <linux/netlink.h>
146
147 /*
148 * SNMP management statistics
149 */
150
151 struct ip_mib ip_statistics[NR_CPUS*2];
152
153 /*
154 * Process Router Attention IP option
155 */
156 int ip_call_ra_chain(struct sk_buff *skb)
157 {
158 struct ip_ra_chain *ra;
159 u8 protocol = skb->nh.iph->protocol;
160 struct sock *last = NULL;
161
162 read_lock(&ip_ra_lock);
163 for (ra = ip_ra_chain; ra; ra = ra->next) {
164 struct sock *sk = ra->sk;
165
166 /* If socket is bound to an interface, only report
167 * the packet if it came from that interface.
168 */
169 if (sk && sk->num == protocol
170 && ((sk->bound_dev_if == 0)
171 || (sk->bound_dev_if == skb->dev->ifindex))) {
172 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
173 skb = ip_defrag(skb);
174 if (skb == NULL) {
175 read_unlock(&ip_ra_lock);
176 return 1;
177 }
178 }
179 if (last) {
180 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
181 if (skb2)
182 raw_rcv(last, skb2);
183 }
184 last = sk;
185 }
186 }
187
188 if (last) {
189 raw_rcv(last, skb);
190 read_unlock(&ip_ra_lock);
191 return 1;
192 }
193 read_unlock(&ip_ra_lock);
194 return 0;
195 }
196
197 /* Handle this out of line, it is rare. */
198 static int ip_run_ipprot(struct sk_buff *skb, struct iphdr *iph,
199 struct inet_protocol *ipprot, int force_copy)
200 {
201 int ret = 0;
202
203 do {
204 if (ipprot->protocol == iph->protocol) {
205 struct sk_buff *skb2 = skb;
206 if (ipprot->copy || force_copy)
207 skb2 = skb_clone(skb, GFP_ATOMIC);
208 if(skb2 != NULL) {
209 ret = 1;
210 ipprot->handler(skb2,
211 ntohs(iph->tot_len) - (iph->ihl * 4));
212 }
213 }
214 ipprot = (struct inet_protocol *) ipprot->next;
215 } while(ipprot != NULL);
216
217 return ret;
218 }
219
220 static inline int ip_local_deliver_finish(struct sk_buff *skb)
221 {
222 struct iphdr *iph = skb->nh.iph;
223
224 #ifdef CONFIG_NETFILTER_DEBUG
225 nf_debug_ip_local_deliver(skb);
226 #endif /*CONFIG_NETFILTER_DEBUG*/
227
228 /* Point into the IP datagram, just past the header. */
229 skb->h.raw = skb->nh.raw + iph->ihl*4;
230
231 {
232 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
233 int hash = iph->protocol & (MAX_INET_PROTOS - 1);
234 struct sock *raw_sk = raw_v4_htable[hash];
235 struct inet_protocol *ipprot;
236 int flag;
237
238 /* If there maybe a raw socket we must check - if not we
239 * don't care less
240 */
241 if(raw_sk != NULL)
242 raw_sk = raw_v4_input(skb, iph, hash);
243
244 ipprot = (struct inet_protocol *) inet_protos[hash];
245 flag = 0;
246 if(ipprot != NULL) {
247 if(raw_sk == NULL &&
248 ipprot->next == NULL &&
249 ipprot->protocol == iph->protocol) {
250 int ret;
251
252 /* Fast path... */
253 ret = ipprot->handler(skb, (ntohs(iph->tot_len) -
254 (iph->ihl * 4)));
255
256 return ret;
257 } else {
258 flag = ip_run_ipprot(skb, iph, ipprot, (raw_sk != NULL));
259 }
260 }
261
262 /* All protocols checked.
263 * If this packet was a broadcast, we may *not* reply to it, since that
264 * causes (proven, grin) ARP storms and a leakage of memory (i.e. all
265 * ICMP reply messages get queued up for transmission...)
266 */
267 if(raw_sk != NULL) { /* Shift to last raw user */
268 raw_rcv(raw_sk, skb);
269 sock_put(raw_sk);
270 } else if (!flag) { /* Free and report errors */
271 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);
272 kfree_skb(skb);
273 }
274 }
275
276 return 0;
277 }
278
279 /*
280 * Deliver IP Packets to the higher protocol layers.
281 */
282 int ip_local_deliver(struct sk_buff *skb)
283 {
284 struct iphdr *iph = skb->nh.iph;
285
286 /*
287 * Reassemble IP fragments.
288 */
289
290 if (iph->frag_off & htons(IP_MF|IP_OFFSET)) {
291 skb = ip_defrag(skb);
292 if (!skb)
293 return 0;
294 }
295
296 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL,
297 ip_local_deliver_finish);
298 }
299
300 static inline int ip_rcv_finish(struct sk_buff *skb)
301 {
302 struct net_device *dev = skb->dev;
303 struct iphdr *iph = skb->nh.iph;
304
305 /*
306 * Initialise the virtual path cache for the packet. It describes
307 * how the packet travels inside Linux networking.
308 */
309 if (skb->dst == NULL) {
310 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))
311 goto drop;
312 }
313
314 #ifdef CONFIG_NET_CLS_ROUTE
315 if (skb->dst->tclassid) {
316 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id();
317 u32 idx = skb->dst->tclassid;
318 st[idx&0xFF].o_packets++;
319 st[idx&0xFF].o_bytes+=skb->len;
320 st[(idx>>16)&0xFF].i_packets++;
321 st[(idx>>16)&0xFF].i_bytes+=skb->len;
322 }
323 #endif
324
325 if (iph->ihl > 5) {
326 struct ip_options *opt;
327
328 /* It looks as overkill, because not all
329 IP options require packet mangling.
330 But it is the easiest for now, especially taking
331 into account that combination of IP options
332 and running sniffer is extremely rare condition.
333 --ANK (980813)
334 */
335
336 skb = skb_cow(skb, skb_headroom(skb));
337 if (skb == NULL)
338 return NET_RX_DROP;
339 iph = skb->nh.iph;
340
341 skb->ip_summed = 0;
342 if (ip_options_compile(NULL, skb))
343 goto inhdr_error;
344
345 opt = &(IPCB(skb)->opt);
346 if (opt->srr) {
347 struct in_device *in_dev = in_dev_get(dev);
348 if (in_dev) {
349 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
350 if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit())
351 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n",
352 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
353 in_dev_put(in_dev);
354 goto drop;
355 }
356 in_dev_put(in_dev);
357 }
358 if (ip_options_rcv_srr(skb))
359 goto drop;
360 }
361 }
362
363 return skb->dst->input(skb);
364
365 inhdr_error:
366 IP_INC_STATS_BH(IpInHdrErrors);
367 drop:
368 kfree_skb(skb);
369 return NET_RX_DROP;
370 }
371
372 /*
373 * Main IP Receive routine.
374 */
375 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
376 {
377 struct iphdr *iph = skb->nh.iph;
378
379 /* When the interface is in promisc. mode, drop all the crap
380 * that it receives, do not try to analyse it.
381 */
382 if (skb->pkt_type == PACKET_OTHERHOST)
383 goto drop;
384
385 IP_INC_STATS_BH(IpInReceives);
386
387 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
388 goto out;
389
390 /*
391 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
392 *
393 * Is the datagram acceptable?
394 *
395 * 1. Length at least the size of an ip header
396 * 2. Version of 4
397 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
398 * 4. Doesn't have a bogus length
399 */
400
401 if (skb->len < sizeof(struct iphdr) || skb->len < (iph->ihl<<2))
402 goto inhdr_error;
403 if (iph->ihl < 5 || iph->version != 4 || ip_fast_csum((u8 *)iph, iph->ihl) != 0)
404 goto inhdr_error;
405
406 {
407 __u32 len = ntohs(iph->tot_len);
408 if (skb->len < len || len < (iph->ihl<<2))
409 goto inhdr_error;
410
411 /* Our transport medium may have padded the buffer out. Now we know it
412 * is IP we can trim to the true length of the frame.
413 * Note this now means skb->len holds ntohs(iph->tot_len).
414 */
415 __skb_trim(skb, len);
416 }
417
418 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
419 ip_rcv_finish);
420
421 inhdr_error:
422 IP_INC_STATS_BH(IpInHdrErrors);
423 drop:
424 kfree_skb(skb);
425 out:
426 return NET_RX_DROP;
427 }
428
429
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