[NETFILTER]: Fix check whether dst_entry needs to be released after NAT
[linux-2.6.git] / net / ipv4 / netfilter / ip_nat_standalone.c
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
34 #define ASSERT_READ_LOCK(x)
35 #define ASSERT_WRITE_LOCK(x)
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
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                 
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
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
141         /* Don't try to NAT if this packet is not conntracked */
142         if (ct == &ip_conntrack_untracked)
143                 return NF_ACCEPT;
144
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) {
149                         if (!ip_nat_icmp_reply_translation(pskb, ct, maniptype,
150                                                            CTINFO2DIR(ctinfo)))
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
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!  */
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);
193         return ip_nat_packet(ct, ctinfo, hooknum, pskb);
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 {
203         struct ip_conntrack *ct;
204         enum ip_conntrack_info ctinfo;
205         unsigned int ret;
206
207         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
208         if (ret != NF_DROP && ret != NF_STOLEN
209             && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) {
210                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
211
212                 if (ct->tuplehash[dir].tuple.dst.ip !=
213                     ct->tuplehash[!dir].tuple.src.ip) {
214                         dst_release((*pskb)->dst);
215                         (*pskb)->dst = NULL;
216                 }
217         }
218         return ret;
219 }
220
221 static unsigned int
222 ip_nat_out(unsigned int hooknum,
223            struct sk_buff **pskb,
224            const struct net_device *in,
225            const struct net_device *out,
226            int (*okfn)(struct sk_buff *))
227 {
228         struct ip_conntrack *ct;
229         enum ip_conntrack_info ctinfo;
230         unsigned int ret;
231
232         /* root is playing with raw sockets. */
233         if ((*pskb)->len < sizeof(struct iphdr)
234             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
235                 return NF_ACCEPT;
236
237         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
238         if (ret != NF_DROP && ret != NF_STOLEN
239             && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) {
240                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
241
242                 if (ct->tuplehash[dir].tuple.src.ip !=
243                     ct->tuplehash[!dir].tuple.dst.ip
244 #ifdef CONFIG_XFRM
245                     || ct->tuplehash[dir].tuple.src.u.all !=
246                        ct->tuplehash[!dir].tuple.dst.u.all
247 #endif
248                     )
249                         return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
250         }
251         return ret;
252 }
253
254 static unsigned int
255 ip_nat_local_fn(unsigned int hooknum,
256                 struct sk_buff **pskb,
257                 const struct net_device *in,
258                 const struct net_device *out,
259                 int (*okfn)(struct sk_buff *))
260 {
261         struct ip_conntrack *ct;
262         enum ip_conntrack_info ctinfo;
263         unsigned int ret;
264
265         /* root is playing with raw sockets. */
266         if ((*pskb)->len < sizeof(struct iphdr)
267             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
268                 return NF_ACCEPT;
269
270         ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
271         if (ret != NF_DROP && ret != NF_STOLEN
272             && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) {
273                 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
274
275                 if (ct->tuplehash[dir].tuple.dst.ip !=
276                     ct->tuplehash[!dir].tuple.src.ip
277 #ifdef CONFIG_XFRM
278                     || ct->tuplehash[dir].tuple.dst.u.all !=
279                        ct->tuplehash[dir].tuple.src.u.all
280 #endif
281                     )
282                         return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
283         }
284         return ret;
285 }
286
287 static unsigned int
288 ip_nat_adjust(unsigned int hooknum,
289               struct sk_buff **pskb,
290               const struct net_device *in,
291               const struct net_device *out,
292               int (*okfn)(struct sk_buff *))
293 {
294         struct ip_conntrack *ct;
295         enum ip_conntrack_info ctinfo;
296
297         ct = ip_conntrack_get(*pskb, &ctinfo);
298         if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
299                 DEBUGP("ip_nat_standalone: adjusting sequence number\n");
300                 if (!ip_nat_seq_adjust(pskb, ct, ctinfo))
301                         return NF_DROP;
302         }
303         return NF_ACCEPT;
304 }
305
306 /* We must be after connection tracking and before packet filtering. */
307
308 /* Before packet filtering, change destination */
309 static struct nf_hook_ops ip_nat_in_ops = {
310         .hook           = ip_nat_in,
311         .owner          = THIS_MODULE,
312         .pf             = PF_INET,
313         .hooknum        = NF_IP_PRE_ROUTING,
314         .priority       = NF_IP_PRI_NAT_DST,
315 };
316
317 /* After packet filtering, change source */
318 static struct nf_hook_ops ip_nat_out_ops = {
319         .hook           = ip_nat_out,
320         .owner          = THIS_MODULE,
321         .pf             = PF_INET,
322         .hooknum        = NF_IP_POST_ROUTING,
323         .priority       = NF_IP_PRI_NAT_SRC,
324 };
325
326 /* After conntrack, adjust sequence number */
327 static struct nf_hook_ops ip_nat_adjust_out_ops = {
328         .hook           = ip_nat_adjust,
329         .owner          = THIS_MODULE,
330         .pf             = PF_INET,
331         .hooknum        = NF_IP_POST_ROUTING,
332         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
333 };
334
335 /* Before packet filtering, change destination */
336 static struct nf_hook_ops ip_nat_local_out_ops = {
337         .hook           = ip_nat_local_fn,
338         .owner          = THIS_MODULE,
339         .pf             = PF_INET,
340         .hooknum        = NF_IP_LOCAL_OUT,
341         .priority       = NF_IP_PRI_NAT_DST,
342 };
343
344 /* After packet filtering, change source for reply packets of LOCAL_OUT DNAT */
345 static struct nf_hook_ops ip_nat_local_in_ops = {
346         .hook           = ip_nat_fn,
347         .owner          = THIS_MODULE,
348         .pf             = PF_INET,
349         .hooknum        = NF_IP_LOCAL_IN,
350         .priority       = NF_IP_PRI_NAT_SRC,
351 };
352
353 /* After conntrack, adjust sequence number */
354 static struct nf_hook_ops ip_nat_adjust_in_ops = {
355         .hook           = ip_nat_adjust,
356         .owner          = THIS_MODULE,
357         .pf             = PF_INET,
358         .hooknum        = NF_IP_LOCAL_IN,
359         .priority       = NF_IP_PRI_NAT_SEQ_ADJUST,
360 };
361
362
363 static int init_or_cleanup(int init)
364 {
365         int ret = 0;
366
367         need_conntrack();
368
369         if (!init) goto cleanup;
370
371 #ifdef CONFIG_XFRM
372         BUG_ON(ip_nat_decode_session != NULL);
373         ip_nat_decode_session = nat_decode_session;
374 #endif
375         ret = ip_nat_rule_init();
376         if (ret < 0) {
377                 printk("ip_nat_init: can't setup rules.\n");
378                 goto cleanup_decode_session;
379         }
380         ret = nf_register_hook(&ip_nat_in_ops);
381         if (ret < 0) {
382                 printk("ip_nat_init: can't register in hook.\n");
383                 goto cleanup_rule_init;
384         }
385         ret = nf_register_hook(&ip_nat_out_ops);
386         if (ret < 0) {
387                 printk("ip_nat_init: can't register out hook.\n");
388                 goto cleanup_inops;
389         }
390         ret = nf_register_hook(&ip_nat_adjust_in_ops);
391         if (ret < 0) {
392                 printk("ip_nat_init: can't register adjust in hook.\n");
393                 goto cleanup_outops;
394         }
395         ret = nf_register_hook(&ip_nat_adjust_out_ops);
396         if (ret < 0) {
397                 printk("ip_nat_init: can't register adjust out hook.\n");
398                 goto cleanup_adjustin_ops;
399         }
400         ret = nf_register_hook(&ip_nat_local_out_ops);
401         if (ret < 0) {
402                 printk("ip_nat_init: can't register local out hook.\n");
403                 goto cleanup_adjustout_ops;;
404         }
405         ret = nf_register_hook(&ip_nat_local_in_ops);
406         if (ret < 0) {
407                 printk("ip_nat_init: can't register local in hook.\n");
408                 goto cleanup_localoutops;
409         }
410         return ret;
411
412  cleanup:
413         nf_unregister_hook(&ip_nat_local_in_ops);
414  cleanup_localoutops:
415         nf_unregister_hook(&ip_nat_local_out_ops);
416  cleanup_adjustout_ops:
417         nf_unregister_hook(&ip_nat_adjust_out_ops);
418  cleanup_adjustin_ops:
419         nf_unregister_hook(&ip_nat_adjust_in_ops);
420  cleanup_outops:
421         nf_unregister_hook(&ip_nat_out_ops);
422  cleanup_inops:
423         nf_unregister_hook(&ip_nat_in_ops);
424  cleanup_rule_init:
425         ip_nat_rule_cleanup();
426  cleanup_decode_session:
427 #ifdef CONFIG_XFRM
428         ip_nat_decode_session = NULL;
429         synchronize_net();
430 #endif
431         return ret;
432 }
433
434 static int __init init(void)
435 {
436         return init_or_cleanup(1);
437 }
438
439 static void __exit fini(void)
440 {
441         init_or_cleanup(0);
442 }
443
444 module_init(init);
445 module_exit(fini);
446
447 MODULE_LICENSE("GPL");