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5b1158e9 JK |
1 | /* (C) 1999-2001 Paul `Rusty' Russell |
2 | * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | #include <linux/types.h> | |
9 | #include <linux/icmp.h> | |
10 | #include <linux/ip.h> | |
11 | #include <linux/netfilter.h> | |
12 | #include <linux/netfilter_ipv4.h> | |
13 | #include <linux/module.h> | |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/proc_fs.h> | |
16 | #include <net/ip.h> | |
17 | #include <net/checksum.h> | |
18 | #include <linux/spinlock.h> | |
19 | ||
20 | #include <net/netfilter/nf_conntrack.h> | |
21 | #include <net/netfilter/nf_conntrack_core.h> | |
22 | #include <net/netfilter/nf_nat.h> | |
23 | #include <net/netfilter/nf_nat_rule.h> | |
24 | #include <net/netfilter/nf_nat_protocol.h> | |
25 | #include <net/netfilter/nf_nat_core.h> | |
26 | #include <net/netfilter/nf_nat_helper.h> | |
27 | #include <linux/netfilter_ipv4/ip_tables.h> | |
28 | ||
29 | #if 0 | |
30 | #define DEBUGP printk | |
31 | #else | |
32 | #define DEBUGP(format, args...) | |
33 | #endif | |
34 | ||
5b1158e9 JK |
35 | #ifdef CONFIG_XFRM |
36 | static void nat_decode_session(struct sk_buff *skb, struct flowi *fl) | |
37 | { | |
38 | struct nf_conn *ct; | |
39 | struct nf_conntrack_tuple *t; | |
40 | enum ip_conntrack_info ctinfo; | |
41 | enum ip_conntrack_dir dir; | |
42 | unsigned long statusbit; | |
43 | ||
44 | ct = nf_ct_get(skb, &ctinfo); | |
45 | if (ct == NULL) | |
46 | return; | |
47 | dir = CTINFO2DIR(ctinfo); | |
48 | t = &ct->tuplehash[dir].tuple; | |
49 | ||
50 | if (dir == IP_CT_DIR_ORIGINAL) | |
51 | statusbit = IPS_DST_NAT; | |
52 | else | |
53 | statusbit = IPS_SRC_NAT; | |
54 | ||
55 | if (ct->status & statusbit) { | |
56 | fl->fl4_dst = t->dst.u3.ip; | |
57 | if (t->dst.protonum == IPPROTO_TCP || | |
58 | t->dst.protonum == IPPROTO_UDP) | |
59 | fl->fl_ip_dport = t->dst.u.tcp.port; | |
60 | } | |
61 | ||
62 | statusbit ^= IPS_NAT_MASK; | |
63 | ||
64 | if (ct->status & statusbit) { | |
65 | fl->fl4_src = t->src.u3.ip; | |
66 | if (t->dst.protonum == IPPROTO_TCP || | |
67 | t->dst.protonum == IPPROTO_UDP) | |
68 | fl->fl_ip_sport = t->src.u.tcp.port; | |
69 | } | |
70 | } | |
71 | #endif | |
72 | ||
73 | static unsigned int | |
74 | nf_nat_fn(unsigned int hooknum, | |
75 | struct sk_buff **pskb, | |
76 | const struct net_device *in, | |
77 | const struct net_device *out, | |
78 | int (*okfn)(struct sk_buff *)) | |
79 | { | |
80 | struct nf_conn *ct; | |
81 | enum ip_conntrack_info ctinfo; | |
82 | struct nf_conn_nat *nat; | |
83 | struct nf_nat_info *info; | |
84 | /* maniptype == SRC for postrouting. */ | |
85 | enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum); | |
86 | ||
87 | /* We never see fragments: conntrack defrags on pre-routing | |
88 | and local-out, and nf_nat_out protects post-routing. */ | |
89 | NF_CT_ASSERT(!((*pskb)->nh.iph->frag_off | |
90 | & htons(IP_MF|IP_OFFSET))); | |
91 | ||
92 | ct = nf_ct_get(*pskb, &ctinfo); | |
93 | /* Can't track? It's not due to stress, or conntrack would | |
94 | have dropped it. Hence it's the user's responsibilty to | |
95 | packet filter it out, or implement conntrack/NAT for that | |
96 | protocol. 8) --RR */ | |
97 | if (!ct) { | |
98 | /* Exception: ICMP redirect to new connection (not in | |
99 | hash table yet). We must not let this through, in | |
100 | case we're doing NAT to the same network. */ | |
101 | if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) { | |
102 | struct icmphdr _hdr, *hp; | |
103 | ||
104 | hp = skb_header_pointer(*pskb, | |
105 | (*pskb)->nh.iph->ihl*4, | |
106 | sizeof(_hdr), &_hdr); | |
107 | if (hp != NULL && | |
108 | hp->type == ICMP_REDIRECT) | |
109 | return NF_DROP; | |
110 | } | |
111 | return NF_ACCEPT; | |
112 | } | |
113 | ||
114 | /* Don't try to NAT if this packet is not conntracked */ | |
115 | if (ct == &nf_conntrack_untracked) | |
116 | return NF_ACCEPT; | |
117 | ||
118 | nat = nfct_nat(ct); | |
119 | if (!nat) | |
ffed53d2 | 120 | return NF_ACCEPT; |
5b1158e9 JK |
121 | |
122 | switch (ctinfo) { | |
123 | case IP_CT_RELATED: | |
124 | case IP_CT_RELATED+IP_CT_IS_REPLY: | |
125 | if ((*pskb)->nh.iph->protocol == IPPROTO_ICMP) { | |
126 | if (!nf_nat_icmp_reply_translation(ct, ctinfo, | |
127 | hooknum, pskb)) | |
128 | return NF_DROP; | |
129 | else | |
130 | return NF_ACCEPT; | |
131 | } | |
132 | /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */ | |
133 | case IP_CT_NEW: | |
134 | info = &nat->info; | |
135 | ||
136 | /* Seen it before? This can happen for loopback, retrans, | |
137 | or local packets.. */ | |
138 | if (!nf_nat_initialized(ct, maniptype)) { | |
139 | unsigned int ret; | |
140 | ||
141 | if (unlikely(nf_ct_is_confirmed(ct))) | |
142 | /* NAT module was loaded late */ | |
143 | ret = alloc_null_binding_confirmed(ct, info, | |
144 | hooknum); | |
145 | else if (hooknum == NF_IP_LOCAL_IN) | |
146 | /* LOCAL_IN hook doesn't have a chain! */ | |
147 | ret = alloc_null_binding(ct, info, hooknum); | |
148 | else | |
149 | ret = nf_nat_rule_find(pskb, hooknum, in, out, | |
150 | ct, info); | |
151 | ||
152 | if (ret != NF_ACCEPT) { | |
153 | return ret; | |
154 | } | |
155 | } else | |
156 | DEBUGP("Already setup manip %s for ct %p\n", | |
157 | maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST", | |
158 | ct); | |
159 | break; | |
160 | ||
161 | default: | |
162 | /* ESTABLISHED */ | |
163 | NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED || | |
164 | ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY)); | |
165 | info = &nat->info; | |
166 | } | |
167 | ||
168 | NF_CT_ASSERT(info); | |
169 | return nf_nat_packet(ct, ctinfo, hooknum, pskb); | |
170 | } | |
171 | ||
172 | static unsigned int | |
173 | nf_nat_in(unsigned int hooknum, | |
174 | struct sk_buff **pskb, | |
175 | const struct net_device *in, | |
176 | const struct net_device *out, | |
177 | int (*okfn)(struct sk_buff *)) | |
178 | { | |
179 | unsigned int ret; | |
180 | __be32 daddr = (*pskb)->nh.iph->daddr; | |
181 | ||
182 | ret = nf_nat_fn(hooknum, pskb, in, out, okfn); | |
183 | if (ret != NF_DROP && ret != NF_STOLEN && | |
184 | daddr != (*pskb)->nh.iph->daddr) { | |
185 | dst_release((*pskb)->dst); | |
186 | (*pskb)->dst = NULL; | |
187 | } | |
188 | return ret; | |
189 | } | |
190 | ||
191 | static unsigned int | |
192 | nf_nat_out(unsigned int hooknum, | |
193 | struct sk_buff **pskb, | |
194 | const struct net_device *in, | |
195 | const struct net_device *out, | |
196 | int (*okfn)(struct sk_buff *)) | |
197 | { | |
198 | #ifdef CONFIG_XFRM | |
199 | struct nf_conn *ct; | |
200 | enum ip_conntrack_info ctinfo; | |
201 | #endif | |
202 | unsigned int ret; | |
203 | ||
204 | /* root is playing with raw sockets. */ | |
205 | if ((*pskb)->len < sizeof(struct iphdr) || | |
206 | (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) | |
207 | return NF_ACCEPT; | |
208 | ||
209 | ret = nf_nat_fn(hooknum, pskb, in, out, okfn); | |
210 | #ifdef CONFIG_XFRM | |
211 | if (ret != NF_DROP && ret != NF_STOLEN && | |
212 | (ct = nf_ct_get(*pskb, &ctinfo)) != NULL) { | |
213 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
214 | ||
215 | if (ct->tuplehash[dir].tuple.src.u3.ip != | |
216 | ct->tuplehash[!dir].tuple.dst.u3.ip | |
217 | || ct->tuplehash[dir].tuple.src.u.all != | |
218 | ct->tuplehash[!dir].tuple.dst.u.all | |
219 | ) | |
220 | return ip_xfrm_me_harder(pskb) == 0 ? ret : NF_DROP; | |
221 | } | |
222 | #endif | |
223 | return ret; | |
224 | } | |
225 | ||
226 | static unsigned int | |
227 | nf_nat_local_fn(unsigned int hooknum, | |
228 | struct sk_buff **pskb, | |
229 | const struct net_device *in, | |
230 | const struct net_device *out, | |
231 | int (*okfn)(struct sk_buff *)) | |
232 | { | |
233 | struct nf_conn *ct; | |
234 | enum ip_conntrack_info ctinfo; | |
235 | unsigned int ret; | |
236 | ||
237 | /* root is playing with raw sockets. */ | |
238 | if ((*pskb)->len < sizeof(struct iphdr) || | |
239 | (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) | |
240 | return NF_ACCEPT; | |
241 | ||
242 | ret = nf_nat_fn(hooknum, pskb, in, out, okfn); | |
243 | if (ret != NF_DROP && ret != NF_STOLEN && | |
244 | (ct = nf_ct_get(*pskb, &ctinfo)) != NULL) { | |
245 | enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo); | |
246 | ||
247 | if (ct->tuplehash[dir].tuple.dst.u3.ip != | |
248 | ct->tuplehash[!dir].tuple.src.u3.ip | |
249 | #ifdef CONFIG_XFRM | |
250 | || ct->tuplehash[dir].tuple.dst.u.all != | |
251 | ct->tuplehash[!dir].tuple.src.u.all | |
252 | #endif | |
253 | ) | |
254 | if (ip_route_me_harder(pskb, RTN_UNSPEC)) | |
255 | ret = NF_DROP; | |
256 | } | |
257 | return ret; | |
258 | } | |
259 | ||
260 | static unsigned int | |
261 | nf_nat_adjust(unsigned int hooknum, | |
262 | struct sk_buff **pskb, | |
263 | const struct net_device *in, | |
264 | const struct net_device *out, | |
265 | int (*okfn)(struct sk_buff *)) | |
266 | { | |
267 | struct nf_conn *ct; | |
268 | enum ip_conntrack_info ctinfo; | |
269 | ||
270 | ct = nf_ct_get(*pskb, &ctinfo); | |
271 | if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) { | |
272 | DEBUGP("nf_nat_standalone: adjusting sequence number\n"); | |
273 | if (!nf_nat_seq_adjust(pskb, ct, ctinfo)) | |
274 | return NF_DROP; | |
275 | } | |
276 | return NF_ACCEPT; | |
277 | } | |
278 | ||
279 | /* We must be after connection tracking and before packet filtering. */ | |
280 | ||
281 | static struct nf_hook_ops nf_nat_ops[] = { | |
282 | /* Before packet filtering, change destination */ | |
283 | { | |
284 | .hook = nf_nat_in, | |
285 | .owner = THIS_MODULE, | |
286 | .pf = PF_INET, | |
287 | .hooknum = NF_IP_PRE_ROUTING, | |
288 | .priority = NF_IP_PRI_NAT_DST, | |
289 | }, | |
290 | /* After packet filtering, change source */ | |
291 | { | |
292 | .hook = nf_nat_out, | |
293 | .owner = THIS_MODULE, | |
294 | .pf = PF_INET, | |
295 | .hooknum = NF_IP_POST_ROUTING, | |
296 | .priority = NF_IP_PRI_NAT_SRC, | |
297 | }, | |
298 | /* After conntrack, adjust sequence number */ | |
299 | { | |
300 | .hook = nf_nat_adjust, | |
301 | .owner = THIS_MODULE, | |
302 | .pf = PF_INET, | |
303 | .hooknum = NF_IP_POST_ROUTING, | |
304 | .priority = NF_IP_PRI_NAT_SEQ_ADJUST, | |
305 | }, | |
306 | /* Before packet filtering, change destination */ | |
307 | { | |
308 | .hook = nf_nat_local_fn, | |
309 | .owner = THIS_MODULE, | |
310 | .pf = PF_INET, | |
311 | .hooknum = NF_IP_LOCAL_OUT, | |
312 | .priority = NF_IP_PRI_NAT_DST, | |
313 | }, | |
314 | /* After packet filtering, change source */ | |
315 | { | |
316 | .hook = nf_nat_fn, | |
317 | .owner = THIS_MODULE, | |
318 | .pf = PF_INET, | |
319 | .hooknum = NF_IP_LOCAL_IN, | |
320 | .priority = NF_IP_PRI_NAT_SRC, | |
321 | }, | |
322 | /* After conntrack, adjust sequence number */ | |
323 | { | |
324 | .hook = nf_nat_adjust, | |
325 | .owner = THIS_MODULE, | |
326 | .pf = PF_INET, | |
327 | .hooknum = NF_IP_LOCAL_IN, | |
328 | .priority = NF_IP_PRI_NAT_SEQ_ADJUST, | |
329 | }, | |
330 | }; | |
331 | ||
332 | static int __init nf_nat_standalone_init(void) | |
333 | { | |
334 | int size, ret = 0; | |
335 | ||
336 | need_conntrack(); | |
337 | ||
338 | size = ALIGN(sizeof(struct nf_conn), __alignof__(struct nf_conn_nat)) + | |
339 | sizeof(struct nf_conn_nat); | |
340 | ret = nf_conntrack_register_cache(NF_CT_F_NAT, "nf_nat:base", size); | |
341 | if (ret < 0) { | |
342 | printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n"); | |
343 | return ret; | |
344 | } | |
345 | ||
346 | size = ALIGN(size, __alignof__(struct nf_conn_help)) + | |
347 | sizeof(struct nf_conn_help); | |
348 | ret = nf_conntrack_register_cache(NF_CT_F_NAT|NF_CT_F_HELP, | |
349 | "nf_nat:help", size); | |
350 | if (ret < 0) { | |
351 | printk(KERN_ERR "nf_nat_init: Unable to create slab cache\n"); | |
352 | goto cleanup_register_cache; | |
353 | } | |
354 | #ifdef CONFIG_XFRM | |
355 | BUG_ON(ip_nat_decode_session != NULL); | |
356 | ip_nat_decode_session = nat_decode_session; | |
357 | #endif | |
358 | ret = nf_nat_rule_init(); | |
359 | if (ret < 0) { | |
360 | printk("nf_nat_init: can't setup rules.\n"); | |
361 | goto cleanup_decode_session; | |
362 | } | |
363 | ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops)); | |
364 | if (ret < 0) { | |
365 | printk("nf_nat_init: can't register hooks.\n"); | |
366 | goto cleanup_rule_init; | |
367 | } | |
368 | nf_nat_module_is_loaded = 1; | |
369 | return ret; | |
370 | ||
371 | cleanup_rule_init: | |
372 | nf_nat_rule_cleanup(); | |
373 | cleanup_decode_session: | |
374 | #ifdef CONFIG_XFRM | |
375 | ip_nat_decode_session = NULL; | |
376 | synchronize_net(); | |
377 | #endif | |
378 | nf_conntrack_unregister_cache(NF_CT_F_NAT|NF_CT_F_HELP); | |
379 | cleanup_register_cache: | |
380 | nf_conntrack_unregister_cache(NF_CT_F_NAT); | |
381 | return ret; | |
382 | } | |
383 | ||
384 | static void __exit nf_nat_standalone_fini(void) | |
385 | { | |
386 | nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops)); | |
387 | nf_nat_rule_cleanup(); | |
388 | nf_nat_module_is_loaded = 0; | |
389 | #ifdef CONFIG_XFRM | |
390 | ip_nat_decode_session = NULL; | |
391 | synchronize_net(); | |
392 | #endif | |
393 | /* Conntrack caches are unregistered in nf_conntrack_cleanup */ | |
394 | } | |
395 | ||
396 | module_init(nf_nat_standalone_init); | |
397 | module_exit(nf_nat_standalone_fini); | |
398 | ||
399 | MODULE_LICENSE("GPL"); | |
400 | MODULE_ALIAS("ip_nat"); |