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 #include <asm/system.h>
117 #include <linux/module.h>
118 #include <linux/types.h>
119 #include <linux/kernel.h>
120 #include <linux/string.h>
121 #include <linux/errno.h>
122
123 #include <linux/net.h>
124 #include <linux/socket.h>
125 #include <linux/sockios.h>
126 #include <linux/in.h>
127 #include <linux/inet.h>
128 #include <linux/inetdevice.h>
129 #include <linux/netdevice.h>
130 #include <linux/etherdevice.h>
131
132 #include <net/snmp.h>
133 #include <net/ip.h>
134 #include <net/protocol.h>
135 #include <net/route.h>
136 #include <linux/skbuff.h>
137 #include <net/sock.h>
138 #include <net/arp.h>
139 #include <net/icmp.h>
140 #include <net/raw.h>
141 #include <net/checksum.h>
142 #include <linux/netfilter_ipv4.h>
143 #include <net/xfrm.h>
144 #include <linux/mroute.h>
145 #include <linux/netlink.h>
146
147 /*
148 * Process Router Attention IP option
149 */
ip_call_ra_chain(struct sk_buff * skb)150 int ip_call_ra_chain(struct sk_buff *skb)
151 {
152 struct ip_ra_chain *ra;
153 u8 protocol = ip_hdr(skb)->protocol;
154 struct sock *last = NULL;
155 struct net_device *dev = skb->dev;
156
157 read_lock(&ip_ra_lock);
158 for (ra = ip_ra_chain; ra; ra = ra->next) {
159 struct sock *sk = ra->sk;
160
161 /* If socket is bound to an interface, only report
162 * the packet if it came from that interface.
163 */
164 if (sk && inet_sk(sk)->num == protocol &&
165 (!sk->sk_bound_dev_if ||
166 sk->sk_bound_dev_if == dev->ifindex) &&
167 sock_net(sk) == dev_net(dev)) {
168 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
169 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) {
170 read_unlock(&ip_ra_lock);
171 return 1;
172 }
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 read_unlock(&ip_ra_lock);
186 return 1;
187 }
188 read_unlock(&ip_ra_lock);
189 return 0;
190 }
191
ip_local_deliver_finish(struct sk_buff * skb)192 static int ip_local_deliver_finish(struct sk_buff *skb)
193 {
194 struct net *net = dev_net(skb->dev);
195
196 __skb_pull(skb, ip_hdrlen(skb));
197
198 /* Point into the IP datagram, just past the header. */
199 skb_reset_transport_header(skb);
200
201 rcu_read_lock();
202 {
203 int protocol = ip_hdr(skb)->protocol;
204 int hash, raw;
205 struct net_protocol *ipprot;
206
207 resubmit:
208 raw = raw_local_deliver(skb, protocol);
209
210 hash = protocol & (MAX_INET_PROTOS - 1);
211 ipprot = rcu_dereference(inet_protos[hash]);
212 if (ipprot != NULL) {
213 int ret;
214
215 if (!net_eq(net, &init_net) && !ipprot->netns_ok) {
216 if (net_ratelimit())
217 printk("%s: proto %d isn't netns-ready\n",
218 __func__, protocol);
219 kfree_skb(skb);
220 goto out;
221 }
222
223 if (!ipprot->no_policy) {
224 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
225 kfree_skb(skb);
226 goto out;
227 }
228 nf_reset(skb);
229 }
230 ret = ipprot->handler(skb);
231 if (ret < 0) {
232 protocol = -ret;
233 goto resubmit;
234 }
235 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
236 } else {
237 if (!raw) {
238 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
239 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS);
240 icmp_send(skb, ICMP_DEST_UNREACH,
241 ICMP_PROT_UNREACH, 0);
242 }
243 } else
244 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
245 kfree_skb(skb);
246 }
247 }
248 out:
249 rcu_read_unlock();
250
251 return 0;
252 }
253
254 /*
255 * Deliver IP Packets to the higher protocol layers.
256 */
ip_local_deliver(struct sk_buff * skb)257 int ip_local_deliver(struct sk_buff *skb)
258 {
259 /*
260 * Reassemble IP fragments.
261 */
262
263 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
264 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER))
265 return 0;
266 }
267
268 return NF_HOOK(PF_INET, NF_INET_LOCAL_IN, skb, skb->dev, NULL,
269 ip_local_deliver_finish);
270 }
271
ip_rcv_options(struct sk_buff * skb)272 static inline int ip_rcv_options(struct sk_buff *skb)
273 {
274 struct ip_options *opt;
275 struct iphdr *iph;
276 struct net_device *dev = skb->dev;
277
278 /* It looks as overkill, because not all
279 IP options require packet mangling.
280 But it is the easiest for now, especially taking
281 into account that combination of IP options
282 and running sniffer is extremely rare condition.
283 --ANK (980813)
284 */
285 if (skb_cow(skb, skb_headroom(skb))) {
286 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
287 goto drop;
288 }
289
290 iph = ip_hdr(skb);
291 opt = &(IPCB(skb)->opt);
292 opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
293
294 if (ip_options_compile(dev_net(dev), opt, skb)) {
295 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
296 goto drop;
297 }
298
299 if (unlikely(opt->srr)) {
300 struct in_device *in_dev = in_dev_get(dev);
301 if (in_dev) {
302 if (!IN_DEV_SOURCE_ROUTE(in_dev)) {
303 if (IN_DEV_LOG_MARTIANS(in_dev) &&
304 net_ratelimit())
305 printk(KERN_INFO "source route option %pI4 -> %pI4\n",
306 &iph->saddr, &iph->daddr);
307 in_dev_put(in_dev);
308 goto drop;
309 }
310
311 in_dev_put(in_dev);
312 }
313
314 if (ip_options_rcv_srr(skb))
315 goto drop;
316 }
317
318 return 0;
319 drop:
320 return -1;
321 }
322
ip_rcv_finish(struct sk_buff * skb)323 static int ip_rcv_finish(struct sk_buff *skb)
324 {
325 const struct iphdr *iph = ip_hdr(skb);
326 struct rtable *rt;
327
328 /*
329 * Initialise the virtual path cache for the packet. It describes
330 * how the packet travels inside Linux networking.
331 */
332 if (skb->dst == NULL) {
333 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos,
334 skb->dev);
335 if (unlikely(err)) {
336 if (err == -EHOSTUNREACH)
337 IP_INC_STATS_BH(dev_net(skb->dev),
338 IPSTATS_MIB_INADDRERRORS);
339 else if (err == -ENETUNREACH)
340 IP_INC_STATS_BH(dev_net(skb->dev),
341 IPSTATS_MIB_INNOROUTES);
342 goto drop;
343 }
344 }
345
346 #ifdef CONFIG_NET_CLS_ROUTE
347 if (unlikely(skb->dst->tclassid)) {
348 struct ip_rt_acct *st = per_cpu_ptr(ip_rt_acct, smp_processor_id());
349 u32 idx = skb->dst->tclassid;
350 st[idx&0xFF].o_packets++;
351 st[idx&0xFF].o_bytes += skb->len;
352 st[(idx>>16)&0xFF].i_packets++;
353 st[(idx>>16)&0xFF].i_bytes += skb->len;
354 }
355 #endif
356
357 if (iph->ihl > 5 && ip_rcv_options(skb))
358 goto drop;
359
360 rt = skb->rtable;
361 if (rt->rt_type == RTN_MULTICAST)
362 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INMCASTPKTS);
363 else if (rt->rt_type == RTN_BROADCAST)
364 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INBCASTPKTS);
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 */
ip_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt,struct net_device * orig_dev)376 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
377 {
378 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 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INRECEIVES);
388
389 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) {
390 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
391 goto out;
392 }
393
394 if (!pskb_may_pull(skb, sizeof(struct iphdr)))
395 goto inhdr_error;
396
397 iph = ip_hdr(skb);
398
399 /*
400 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum.
401 *
402 * Is the datagram acceptable?
403 *
404 * 1. Length at least the size of an ip header
405 * 2. Version of 4
406 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums]
407 * 4. Doesn't have a bogus length
408 */
409
410 if (iph->ihl < 5 || iph->version != 4)
411 goto inhdr_error;
412
413 if (!pskb_may_pull(skb, iph->ihl*4))
414 goto inhdr_error;
415
416 iph = ip_hdr(skb);
417
418 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
419 goto inhdr_error;
420
421 len = ntohs(iph->tot_len);
422 if (skb->len < len) {
423 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
424 goto drop;
425 } else if (len < (iph->ihl*4))
426 goto inhdr_error;
427
428 /* Our transport medium may have padded the buffer out. Now we know it
429 * is IP we can trim to the true length of the frame.
430 * Note this now means skb->len holds ntohs(iph->tot_len).
431 */
432 if (pskb_trim_rcsum(skb, len)) {
433 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
434 goto drop;
435 }
436
437 /* Remove any debris in the socket control block */
438 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
439
440 return NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, dev, NULL,
441 ip_rcv_finish);
442
443 inhdr_error:
444 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
445 drop:
446 kfree_skb(skb);
447 out:
448 return NET_RX_DROP;
449 }
450