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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 <linux/netfilter_ipv4.h> |
145 | #include <net/xfrm.h> |
146 | #include <linux/mroute.h> |
147 | #include <linux/netlink.h> |
148 | |
149 | /* |
150 | * Process Router Attention IP option (RFC 2113) |
151 | */ |
152 | bool ip_call_ra_chain(struct sk_buff *skb) |
153 | { |
154 | struct ip_ra_chain *ra; |
155 | u8 protocol = ip_hdr(skb)->protocol; |
156 | struct sock *last = NULL; |
157 | struct net_device *dev = skb->dev; |
158 | |
159 | for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) { |
160 | struct sock *sk = ra->sk; |
161 | |
162 | /* If socket is bound to an interface, only report |
163 | * the packet if it came from that interface. |
164 | */ |
165 | if (sk && inet_sk(sk)->inet_num == protocol && |
166 | (!sk->sk_bound_dev_if || |
167 | sk->sk_bound_dev_if == dev->ifindex) && |
168 | net_eq(sock_net(sk), dev_net(dev))) { |
169 | if (ip_is_fragment(ip_hdr(skb))) { |
170 | if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) |
171 | return true; |
172 | } |
173 | if (last) { |
174 | struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); |
175 | if (skb2) |
176 | raw_rcv(last, skb2); |
177 | } |
178 | last = sk; |
179 | } |
180 | } |
181 | |
182 | if (last) { |
183 | raw_rcv(last, skb); |
184 | return true; |
185 | } |
186 | return false; |
187 | } |
188 | |
189 | static int ip_local_deliver_finish(struct sk_buff *skb) |
190 | { |
191 | struct net *net = dev_net(skb->dev); |
192 | |
193 | __skb_pull(skb, ip_hdrlen(skb)); |
194 | |
195 | /* Point into the IP datagram, just past the header. */ |
196 | skb_reset_transport_header(skb); |
197 | |
198 | rcu_read_lock(); |
199 | { |
200 | int protocol = ip_hdr(skb)->protocol; |
201 | const struct net_protocol *ipprot; |
202 | int raw; |
203 | |
204 | resubmit: |
205 | raw = raw_local_deliver(skb, protocol); |
206 | |
207 | ipprot = rcu_dereference(inet_protos[protocol]); |
208 | if (ipprot != NULL) { |
209 | int ret; |
210 | |
211 | if (!ipprot->no_policy) { |
212 | if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { |
213 | kfree_skb(skb); |
214 | goto out; |
215 | } |
216 | nf_reset(skb); |
217 | } |
218 | ret = ipprot->handler(skb); |
219 | if (ret < 0) { |
220 | protocol = -ret; |
221 | goto resubmit; |
222 | } |
223 | IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); |
224 | } else { |
225 | if (!raw) { |
226 | if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { |
227 | IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); |
228 | icmp_send(skb, ICMP_DEST_UNREACH, |
229 | ICMP_PROT_UNREACH, 0); |
230 | } |
231 | kfree_skb(skb); |
232 | } else { |
233 | IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); |
234 | consume_skb(skb); |
235 | } |
236 | } |
237 | } |
238 | out: |
239 | rcu_read_unlock(); |
240 | |
241 | return 0; |
242 | } |
243 | |
244 | /* |
245 | * Deliver IP Packets to the higher protocol layers. |
246 | */ |
247 | int ip_local_deliver(struct sk_buff *skb) |
248 | { |
249 | /* |
250 | * Reassemble IP fragments. |
251 | */ |
252 | |
253 | if (ip_is_fragment(ip_hdr(skb))) { |
254 | if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) |
255 | return 0; |
256 | } |
257 | |
258 | return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, |
259 | ip_local_deliver_finish); |
260 | } |
261 | |
262 | static inline bool ip_rcv_options(struct sk_buff *skb) |
263 | { |
264 | struct ip_options *opt; |
265 | const struct iphdr *iph; |
266 | struct net_device *dev = skb->dev; |
267 | |
268 | /* It looks as overkill, because not all |
269 | IP options require packet mangling. |
270 | But it is the easiest for now, especially taking |
271 | into account that combination of IP options |
272 | and running sniffer is extremely rare condition. |
273 | --ANK (980813) |
274 | */ |
275 | if (skb_cow(skb, skb_headroom(skb))) { |
276 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); |
277 | goto drop; |
278 | } |
279 | |
280 | iph = ip_hdr(skb); |
281 | opt = &(IPCB(skb)->opt); |
282 | opt->optlen = iph->ihl*4 - sizeof(struct iphdr); |
283 | |
284 | if (ip_options_compile(dev_net(dev), opt, skb)) { |
285 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); |
286 | goto drop; |
287 | } |
288 | |
289 | if (unlikely(opt->srr)) { |
290 | struct in_device *in_dev = __in_dev_get_rcu(dev); |
291 | |
292 | if (in_dev) { |
293 | if (!IN_DEV_SOURCE_ROUTE(in_dev)) { |
294 | if (IN_DEV_LOG_MARTIANS(in_dev)) |
295 | net_info_ratelimited("source route option %pI4 -> %pI4\n", |
296 | &iph->saddr, |
297 | &iph->daddr); |
298 | goto drop; |
299 | } |
300 | } |
301 | |
302 | if (ip_options_rcv_srr(skb)) |
303 | goto drop; |
304 | } |
305 | |
306 | return false; |
307 | drop: |
308 | return true; |
309 | } |
310 | |
311 | int sysctl_ip_early_demux __read_mostly = 1; |
312 | EXPORT_SYMBOL(sysctl_ip_early_demux); |
313 | |
314 | static int ip_rcv_finish(struct sk_buff *skb) |
315 | { |
316 | const struct iphdr *iph = ip_hdr(skb); |
317 | struct rtable *rt; |
318 | |
319 | if (sysctl_ip_early_demux && !skb_dst(skb)) { |
320 | const struct net_protocol *ipprot; |
321 | int protocol = iph->protocol; |
322 | |
323 | ipprot = rcu_dereference(inet_protos[protocol]); |
324 | if (ipprot && ipprot->early_demux) { |
325 | ipprot->early_demux(skb); |
326 | /* must reload iph, skb->head might have changed */ |
327 | iph = ip_hdr(skb); |
328 | } |
329 | } |
330 | |
331 | /* |
332 | * Initialise the virtual path cache for the packet. It describes |
333 | * how the packet travels inside Linux networking. |
334 | */ |
335 | if (!skb_dst(skb)) { |
336 | int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, |
337 | iph->tos, skb->dev); |
338 | if (unlikely(err)) { |
339 | if (err == -EXDEV) |
340 | NET_INC_STATS_BH(dev_net(skb->dev), |
341 | LINUX_MIB_IPRPFILTER); |
342 | goto drop; |
343 | } |
344 | } |
345 | |
346 | #ifdef CONFIG_IP_ROUTE_CLASSID |
347 | if (unlikely(skb_dst(skb)->tclassid)) { |
348 | struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); |
349 | u32 idx = skb_dst(skb)->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(skb); |
361 | if (rt->rt_type == RTN_MULTICAST) { |
362 | IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST, |
363 | skb->len); |
364 | } else if (rt->rt_type == RTN_BROADCAST) |
365 | IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST, |
366 | skb->len); |
367 | |
368 | return dst_input(skb); |
369 | |
370 | drop: |
371 | kfree_skb(skb); |
372 | return NET_RX_DROP; |
373 | } |
374 | |
375 | /* |
376 | * Main IP Receive routine. |
377 | */ |
378 | int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) |
379 | { |
380 | const struct iphdr *iph; |
381 | u32 len; |
382 | |
383 | /* When the interface is in promisc. mode, drop all the crap |
384 | * that it receives, do not try to analyse it. |
385 | */ |
386 | if (skb->pkt_type == PACKET_OTHERHOST) |
387 | goto drop; |
388 | |
389 | |
390 | IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); |
391 | |
392 | if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { |
393 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); |
394 | goto out; |
395 | } |
396 | |
397 | if (!pskb_may_pull(skb, sizeof(struct iphdr))) |
398 | goto inhdr_error; |
399 | |
400 | iph = ip_hdr(skb); |
401 | |
402 | /* |
403 | * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. |
404 | * |
405 | * Is the datagram acceptable? |
406 | * |
407 | * 1. Length at least the size of an ip header |
408 | * 2. Version of 4 |
409 | * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] |
410 | * 4. Doesn't have a bogus length |
411 | */ |
412 | |
413 | if (iph->ihl < 5 || iph->version != 4) |
414 | goto inhdr_error; |
415 | |
416 | if (!pskb_may_pull(skb, iph->ihl*4)) |
417 | goto inhdr_error; |
418 | |
419 | iph = ip_hdr(skb); |
420 | |
421 | if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) |
422 | goto inhdr_error; |
423 | |
424 | len = ntohs(iph->tot_len); |
425 | if (skb->len < len) { |
426 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); |
427 | goto drop; |
428 | } else if (len < (iph->ihl*4)) |
429 | goto inhdr_error; |
430 | |
431 | /* Our transport medium may have padded the buffer out. Now we know it |
432 | * is IP we can trim to the true length of the frame. |
433 | * Note this now means skb->len holds ntohs(iph->tot_len). |
434 | */ |
435 | if (pskb_trim_rcsum(skb, len)) { |
436 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); |
437 | goto drop; |
438 | } |
439 | |
440 | /* Remove any debris in the socket control block */ |
441 | memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); |
442 | |
443 | /* Must drop socket now because of tproxy. */ |
444 | skb_orphan(skb); |
445 | |
446 | return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, |
447 | ip_rcv_finish); |
448 | |
449 | inhdr_error: |
450 | IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); |
451 | drop: |
452 | kfree_skb(skb); |
453 | out: |
454 | return NET_RX_DROP; |
455 | } |
456 |
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