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1da177e4 LT |
1 | /* This file contains all the functions required for the standalone |
2 | ip_nat module. | |
3 | ||
4 | These are not required by the compatibility layer. | |
5 | */ | |
6 | ||
7 | /* (C) 1999-2001 Paul `Rusty' Russell | |
8 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> | |
9 | * | |
10 | * This program is free software; you can redistribute it and/or modify | |
11 | * it under the terms of the GNU General Public License version 2 as | |
12 | * published by the Free Software Foundation. | |
13 | */ | |
14 | ||
15 | /* | |
16 | * 23 Apr 2001: Harald Welte <laforge@gnumonks.org> | |
17 | * - new API and handling of conntrack/nat helpers | |
18 | * - now capable of multiple expectations for one master | |
19 | * */ | |
20 | ||
21 | #include <linux/config.h> | |
22 | #include <linux/types.h> | |
23 | #include <linux/icmp.h> | |
24 | #include <linux/ip.h> | |
25 | #include <linux/netfilter.h> | |
26 | #include <linux/netfilter_ipv4.h> | |
27 | #include <linux/module.h> | |
28 | #include <linux/skbuff.h> | |
29 | #include <linux/proc_fs.h> | |
30 | #include <net/ip.h> | |
31 | #include <net/checksum.h> | |
32 | #include <linux/spinlock.h> | |
33 | ||
e45b1be8 PM |
34 | #define ASSERT_READ_LOCK(x) |
35 | #define ASSERT_WRITE_LOCK(x) | |
1da177e4 LT |
36 | |
37 | #include <linux/netfilter_ipv4/ip_nat.h> | |
38 | #include <linux/netfilter_ipv4/ip_nat_rule.h> | |
39 | #include <linux/netfilter_ipv4/ip_nat_protocol.h> | |
40 | #include <linux/netfilter_ipv4/ip_nat_core.h> | |
41 | #include <linux/netfilter_ipv4/ip_nat_helper.h> | |
42 | #include <linux/netfilter_ipv4/ip_tables.h> | |
43 | #include <linux/netfilter_ipv4/ip_conntrack_core.h> | |
44 | #include <linux/netfilter_ipv4/listhelp.h> | |
45 | ||
46 | #if 0 | |
47 | #define DEBUGP printk | |
48 | #else | |
49 | #define DEBUGP(format, args...) | |
50 | #endif | |
51 | ||
52 | #define HOOKNAME(hooknum) ((hooknum) == NF_IP_POST_ROUTING ? "POST_ROUTING" \ | |
53 | : ((hooknum) == NF_IP_PRE_ROUTING ? "PRE_ROUTING" \ | |
54 | : ((hooknum) == NF_IP_LOCAL_OUT ? "LOCAL_OUT" \ | |
55 | : ((hooknum) == NF_IP_LOCAL_IN ? "LOCAL_IN" \ | |
56 | : "*ERROR*"))) | |
57 | ||
eb9c7ebe PM |
58 | #ifdef CONFIG_XFRM |
59 | static void nat_decode_session(struct sk_buff *skb, struct flowi *fl) | |
60 | { | |
61 | struct ip_conntrack *ct; | |
62 | struct ip_conntrack_tuple *t; | |
63 | enum ip_conntrack_info ctinfo; | |
64 | enum ip_conntrack_dir dir; | |
65 | unsigned long statusbit; | |
66 | ||
67 | ct = ip_conntrack_get(skb, &ctinfo); | |
68 | if (ct == NULL) | |
69 | return; | |
70 | dir = CTINFO2DIR(ctinfo); | |
71 | t = &ct->tuplehash[dir].tuple; | |
72 | ||
73 | if (dir == IP_CT_DIR_ORIGINAL) | |
74 | statusbit = IPS_DST_NAT; | |
75 | else | |
76 | statusbit = IPS_SRC_NAT; | |
77 | ||
78 | if (ct->status & statusbit) { | |
79 | fl->fl4_dst = t->dst.ip; | |
80 | if (t->dst.protonum == IPPROTO_TCP || | |
81 | t->dst.protonum == IPPROTO_UDP) | |
82 | fl->fl_ip_dport = t->dst.u.tcp.port; | |
83 | } | |
84 | ||
85 | statusbit ^= IPS_NAT_MASK; | |
86 | ||
87 | if (ct->status & statusbit) { | |
88 | fl->fl4_src = t->src.ip; | |
89 | if (t->dst.protonum == IPPROTO_TCP || | |
90 | t->dst.protonum == IPPROTO_UDP) | |
91 | fl->fl_ip_sport = t->src.u.tcp.port; | |
92 | } | |
93 | } | |
94 | #endif | |
95 | ||
1da177e4 LT |
96 | static unsigned int |
97 | ip_nat_fn(unsigned int hooknum, | |
98 | struct sk_buff **pskb, | |
99 | const struct net_device *in, | |
100 | const struct net_device *out, | |
101 | int (*okfn)(struct sk_buff *)) | |
102 | { | |
103 | struct ip_conntrack *ct; | |
104 | enum ip_conntrack_info ctinfo; | |
105 | struct ip_nat_info *info; | |
106 | /* maniptype == SRC for postrouting. */ | |
107 | enum ip_nat_manip_type maniptype = HOOK2MANIP(hooknum); | |
108 | ||
109 | /* We never see fragments: conntrack defrags on pre-routing | |
110 | and local-out, and ip_nat_out protects post-routing. */ | |
111 | IP_NF_ASSERT(!((*pskb)->nh.iph->frag_off | |
112 | & htons(IP_MF|IP_OFFSET))); | |
113 | ||
1da177e4 LT |
114 | /* If we had a hardware checksum before, it's now invalid */ |
115 | if ((*pskb)->ip_summed == CHECKSUM_HW) | |
116 | if (skb_checksum_help(*pskb, (out == NULL))) | |
117 | return NF_DROP; | |
118 | ||
119 | ct = ip_conntrack_get(*pskb, &ctinfo); | |
120 | /* Can't track? It's not due to stress, or conntrack would | |
121 | have dropped it. Hence it's the user's responsibilty to | |
122 | packet filter it out, or implement conntrack/NAT for that | |
123 | protocol. 8) --RR */ | |
124 | if (!ct) { | |
125 | /* Exception: ICMP redirect to new connection (not in | |
126 | hash table yet). We must not let this through, in | |
127 | case we're doing NAT to the same network. */ | |
128 | if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) { | |
129 | struct icmphdr _hdr, *hp; | |
130 | ||
131 | hp = skb_header_pointer(*pskb, | |
132 | (*pskb)->nh.iph->ihl*4, | |
133 | sizeof(_hdr), &_hdr); | |
134 | if (hp != NULL && | |
135 | hp->type == ICMP_REDIRECT) | |
136 | return NF_DROP; | |
137 | } | |
138 | return NF_ACCEPT; | |
139 | } | |
140 | ||
8b83bc77 HW |
141 | /* Don't try to NAT if this packet is not conntracked */ |
142 | if (ct == &ip_conntrack_untracked) | |
143 | return NF_ACCEPT; | |
144 | ||
1da177e4 LT |
145 | switch (ctinfo) { |
146 | case IP_CT_RELATED: | |
147 | case IP_CT_RELATED+IP_CT_IS_REPLY: | |
148 | if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) { | |
188bab3a HW |
149 | if (!ip_nat_icmp_reply_translation(pskb, ct, maniptype, |
150 | CTINFO2DIR(ctinfo))) | |
1da177e4 LT |
151 | return NF_DROP; |
152 | else | |
153 | return NF_ACCEPT; | |
154 | } | |
155 | /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */ | |
156 | case IP_CT_NEW: | |
157 | info = &ct->nat.info; | |
158 | ||
159 | /* Seen it before? This can happen for loopback, retrans, | |
160 | or local packets.. */ | |
161 | if (!ip_nat_initialized(ct, maniptype)) { | |
162 | unsigned int ret; | |
163 | ||
03486a4f PM |
164 | if (unlikely(is_confirmed(ct))) |
165 | /* NAT module was loaded late */ | |
166 | ret = alloc_null_binding_confirmed(ct, info, | |
167 | hooknum); | |
168 | else if (hooknum == NF_IP_LOCAL_IN) | |
169 | /* LOCAL_IN hook doesn't have a chain! */ | |
1da177e4 LT |
170 | ret = alloc_null_binding(ct, info, hooknum); |
171 | else | |
172 | ret = ip_nat_rule_find(pskb, hooknum, | |
173 | in, out, ct, | |
174 | info); | |
175 | ||
176 | if (ret != NF_ACCEPT) { | |
177 | return ret; | |
178 | } | |
179 | } else | |
180 | DEBUGP("Already setup manip %s for ct %p\n", | |
181 | maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST", | |
182 | ct); | |
183 | break; | |
184 | ||
185 | default: | |
186 | /* ESTABLISHED */ | |
187 | IP_NF_ASSERT(ctinfo == IP_CT_ESTABLISHED | |
188 | || ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY)); | |
189 | info = &ct->nat.info; | |
190 | } | |
191 | ||
192 | IP_NF_ASSERT(info); | |
188bab3a | 193 | return ip_nat_packet(ct, ctinfo, hooknum, pskb); |
1da177e4 LT |
194 | } |
195 | ||
196 | static unsigned int | |
197 | ip_nat_in(unsigned int hooknum, | |
198 | struct sk_buff **pskb, | |
199 | const struct net_device *in, | |
200 | const struct net_device *out, | |
201 | int (*okfn)(struct sk_buff *)) | |
202 | { | |
1da177e4 | 203 | unsigned int ret; |
8e249f08 | 204 | u_int32_t daddr = (*pskb)->nh.iph->daddr; |
1da177e4 | 205 | |
1da177e4 LT |
206 | ret = ip_nat_fn(hooknum, pskb, in, out, okfn); |
207 | if (ret != NF_DROP && ret != NF_STOLEN | |
8e249f08 PM |
208 | && daddr != (*pskb)->nh.iph->daddr) { |
209 | dst_release((*pskb)->dst); | |
210 | (*pskb)->dst = NULL; | |
1da177e4 LT |
211 | } |
212 | return ret; | |
213 | } | |
214 | ||
215 | static unsigned int | |
216 | ip_nat_out(unsigned int hooknum, | |
217 | struct sk_buff **pskb, | |
218 | const struct net_device *in, | |
219 | const struct net_device *out, | |
220 | int (*okfn)(struct sk_buff *)) | |
221 | { | |
5c901daa PM |
222 | struct ip_conntrack *ct; |
223 | enum ip_conntrack_info ctinfo; | |
224 | unsigned int ret; | |
225 | ||
1da177e4 LT |
226 | /* root is playing with raw sockets. */ |
227 | if ((*pskb)->len < sizeof(struct iphdr) | |
228 | || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) | |
229 | return NF_ACCEPT; | |
230 | ||
5c901daa | 231 | ret = ip_nat_fn(hooknum, pskb, in, out, okfn); |
ee68cea2 | 232 | #ifdef CONFIG_XFRM |
5c901daa PM |
233 | if (ret != NF_DROP && ret != NF_STOLEN |
234 | && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) { | |
235 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
236 | ||
237 | if (ct->tuplehash[dir].tuple.src.ip != | |
238 | ct->tuplehash[!dir].tuple.dst.ip | |
5c901daa PM |
239 | || ct->tuplehash[dir].tuple.src.u.all != |
240 | ct->tuplehash[!dir].tuple.dst.u.all | |
5c901daa | 241 | ) |
ee68cea2 | 242 | return ip_xfrm_me_harder(pskb) == 0 ? ret : NF_DROP; |
5c901daa | 243 | } |
ee68cea2 | 244 | #endif |
5c901daa | 245 | return ret; |
1da177e4 LT |
246 | } |
247 | ||
248 | static unsigned int | |
249 | ip_nat_local_fn(unsigned int hooknum, | |
250 | struct sk_buff **pskb, | |
251 | const struct net_device *in, | |
252 | const struct net_device *out, | |
253 | int (*okfn)(struct sk_buff *)) | |
254 | { | |
4e8e9de7 PM |
255 | struct ip_conntrack *ct; |
256 | enum ip_conntrack_info ctinfo; | |
1da177e4 LT |
257 | unsigned int ret; |
258 | ||
259 | /* root is playing with raw sockets. */ | |
260 | if ((*pskb)->len < sizeof(struct iphdr) | |
261 | || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) | |
262 | return NF_ACCEPT; | |
263 | ||
1da177e4 LT |
264 | ret = ip_nat_fn(hooknum, pskb, in, out, okfn); |
265 | if (ret != NF_DROP && ret != NF_STOLEN | |
4e8e9de7 PM |
266 | && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) { |
267 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
268 | ||
269 | if (ct->tuplehash[dir].tuple.dst.ip != | |
5c901daa PM |
270 | ct->tuplehash[!dir].tuple.src.ip |
271 | #ifdef CONFIG_XFRM | |
272 | || ct->tuplehash[dir].tuple.dst.u.all != | |
8e249f08 | 273 | ct->tuplehash[!dir].tuple.src.u.all |
5c901daa PM |
274 | #endif |
275 | ) | |
4e8e9de7 PM |
276 | return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP; |
277 | } | |
1da177e4 LT |
278 | return ret; |
279 | } | |
280 | ||
e281e3ac PM |
281 | static unsigned int |
282 | ip_nat_adjust(unsigned int hooknum, | |
283 | struct sk_buff **pskb, | |
284 | const struct net_device *in, | |
285 | const struct net_device *out, | |
286 | int (*okfn)(struct sk_buff *)) | |
287 | { | |
288 | struct ip_conntrack *ct; | |
289 | enum ip_conntrack_info ctinfo; | |
290 | ||
291 | ct = ip_conntrack_get(*pskb, &ctinfo); | |
292 | if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) { | |
293 | DEBUGP("ip_nat_standalone: adjusting sequence number\n"); | |
294 | if (!ip_nat_seq_adjust(pskb, ct, ctinfo)) | |
295 | return NF_DROP; | |
296 | } | |
297 | return NF_ACCEPT; | |
298 | } | |
299 | ||
1da177e4 LT |
300 | /* We must be after connection tracking and before packet filtering. */ |
301 | ||
964ddaa1 PM |
302 | static struct nf_hook_ops ip_nat_ops[] = { |
303 | /* Before packet filtering, change destination */ | |
304 | { | |
305 | .hook = ip_nat_in, | |
306 | .owner = THIS_MODULE, | |
307 | .pf = PF_INET, | |
308 | .hooknum = NF_IP_PRE_ROUTING, | |
309 | .priority = NF_IP_PRI_NAT_DST, | |
310 | }, | |
311 | /* After packet filtering, change source */ | |
312 | { | |
313 | .hook = ip_nat_out, | |
314 | .owner = THIS_MODULE, | |
315 | .pf = PF_INET, | |
316 | .hooknum = NF_IP_POST_ROUTING, | |
317 | .priority = NF_IP_PRI_NAT_SRC, | |
318 | }, | |
319 | /* After conntrack, adjust sequence number */ | |
320 | { | |
321 | .hook = ip_nat_adjust, | |
322 | .owner = THIS_MODULE, | |
323 | .pf = PF_INET, | |
324 | .hooknum = NF_IP_POST_ROUTING, | |
325 | .priority = NF_IP_PRI_NAT_SEQ_ADJUST, | |
326 | }, | |
327 | /* Before packet filtering, change destination */ | |
328 | { | |
329 | .hook = ip_nat_local_fn, | |
330 | .owner = THIS_MODULE, | |
331 | .pf = PF_INET, | |
332 | .hooknum = NF_IP_LOCAL_OUT, | |
333 | .priority = NF_IP_PRI_NAT_DST, | |
334 | }, | |
335 | /* After packet filtering, change source */ | |
336 | { | |
337 | .hook = ip_nat_fn, | |
338 | .owner = THIS_MODULE, | |
339 | .pf = PF_INET, | |
340 | .hooknum = NF_IP_LOCAL_IN, | |
341 | .priority = NF_IP_PRI_NAT_SRC, | |
342 | }, | |
343 | /* After conntrack, adjust sequence number */ | |
344 | { | |
345 | .hook = ip_nat_adjust, | |
346 | .owner = THIS_MODULE, | |
347 | .pf = PF_INET, | |
348 | .hooknum = NF_IP_LOCAL_IN, | |
349 | .priority = NF_IP_PRI_NAT_SEQ_ADJUST, | |
350 | }, | |
1da177e4 LT |
351 | }; |
352 | ||
32292a7f | 353 | static int __init ip_nat_standalone_init(void) |
1da177e4 LT |
354 | { |
355 | int ret = 0; | |
356 | ||
2e4e6a17 | 357 | need_conntrack(); |
1da177e4 | 358 | |
eb9c7ebe PM |
359 | #ifdef CONFIG_XFRM |
360 | BUG_ON(ip_nat_decode_session != NULL); | |
361 | ip_nat_decode_session = nat_decode_session; | |
362 | #endif | |
1da177e4 LT |
363 | ret = ip_nat_rule_init(); |
364 | if (ret < 0) { | |
365 | printk("ip_nat_init: can't setup rules.\n"); | |
eb9c7ebe | 366 | goto cleanup_decode_session; |
1da177e4 | 367 | } |
964ddaa1 | 368 | ret = nf_register_hooks(ip_nat_ops, ARRAY_SIZE(ip_nat_ops)); |
1da177e4 | 369 | if (ret < 0) { |
964ddaa1 | 370 | printk("ip_nat_init: can't register hooks.\n"); |
188bab3a | 371 | goto cleanup_rule_init; |
1da177e4 | 372 | } |
1da177e4 LT |
373 | return ret; |
374 | ||
1da177e4 LT |
375 | cleanup_rule_init: |
376 | ip_nat_rule_cleanup(); | |
eb9c7ebe PM |
377 | cleanup_decode_session: |
378 | #ifdef CONFIG_XFRM | |
379 | ip_nat_decode_session = NULL; | |
380 | synchronize_net(); | |
381 | #endif | |
1da177e4 LT |
382 | return ret; |
383 | } | |
384 | ||
65b4b4e8 | 385 | static void __exit ip_nat_standalone_fini(void) |
1da177e4 | 386 | { |
32292a7f PM |
387 | nf_unregister_hooks(ip_nat_ops, ARRAY_SIZE(ip_nat_ops)); |
388 | ip_nat_rule_cleanup(); | |
389 | #ifdef CONFIG_XFRM | |
390 | ip_nat_decode_session = NULL; | |
391 | synchronize_net(); | |
392 | #endif | |
1da177e4 LT |
393 | } |
394 | ||
65b4b4e8 AM |
395 | module_init(ip_nat_standalone_init); |
396 | module_exit(ip_nat_standalone_fini); | |
1da177e4 | 397 | |
1da177e4 | 398 | MODULE_LICENSE("GPL"); |