1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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.
8 #include <linux/types.h>
9 #include <linux/icmp.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>
17 #include <net/checksum.h>
18 #include <linux/spinlock.h>
20 #include <net/netfilter/nf_conntrack.h>
21 #include <net/netfilter/nf_conntrack_core.h>
22 #include <net/netfilter/nf_conntrack_extend.h>
23 #include <net/netfilter/nf_nat.h>
24 #include <net/netfilter/nf_nat_rule.h>
25 #include <net/netfilter/nf_nat_protocol.h>
26 #include <net/netfilter/nf_nat_core.h>
27 #include <net/netfilter/nf_nat_helper.h>
28 #include <linux/netfilter_ipv4/ip_tables.h>
31 static void nat_decode_session(struct sk_buff *skb, struct flowi *fl)
33 const struct nf_conn *ct;
34 const struct nf_conntrack_tuple *t;
35 enum ip_conntrack_info ctinfo;
36 enum ip_conntrack_dir dir;
37 unsigned long statusbit;
39 ct = nf_ct_get(skb, &ctinfo);
42 dir = CTINFO2DIR(ctinfo);
43 t = &ct->tuplehash[dir].tuple;
45 if (dir == IP_CT_DIR_ORIGINAL)
46 statusbit = IPS_DST_NAT;
48 statusbit = IPS_SRC_NAT;
50 if (ct->status & statusbit) {
51 fl->fl4_dst = t->dst.u3.ip;
52 if (t->dst.protonum == IPPROTO_TCP ||
53 t->dst.protonum == IPPROTO_UDP ||
54 t->dst.protonum == IPPROTO_UDPLITE ||
55 t->dst.protonum == IPPROTO_DCCP ||
56 t->dst.protonum == IPPROTO_SCTP)
57 fl->fl_ip_dport = t->dst.u.tcp.port;
60 statusbit ^= IPS_NAT_MASK;
62 if (ct->status & statusbit) {
63 fl->fl4_src = t->src.u3.ip;
64 if (t->dst.protonum == IPPROTO_TCP ||
65 t->dst.protonum == IPPROTO_UDP ||
66 t->dst.protonum == IPPROTO_UDPLITE ||
67 t->dst.protonum == IPPROTO_DCCP ||
68 t->dst.protonum == IPPROTO_SCTP)
69 fl->fl_ip_sport = t->src.u.tcp.port;
75 nf_nat_fn(unsigned int hooknum,
77 const struct net_device *in,
78 const struct net_device *out,
79 int (*okfn)(struct sk_buff *))
82 enum ip_conntrack_info ctinfo;
83 struct nf_conn_nat *nat;
84 /* maniptype == SRC for postrouting. */
85 enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
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(!(ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)));
91 ct = nf_ct_get(skb, &ctinfo);
92 /* Can't track? It's not due to stress, or conntrack would
93 have dropped it. Hence it's the user's responsibilty to
94 packet filter it out, or implement conntrack/NAT for that
99 /* Don't try to NAT if this packet is not conntracked */
100 if (ct == &nf_conntrack_untracked)
105 /* NAT module was loaded late. */
106 if (nf_ct_is_confirmed(ct))
108 nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
110 pr_debug("failed to add NAT extension\n");
117 case IP_CT_RELATED+IP_CT_IS_REPLY:
118 if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
119 if (!nf_nat_icmp_reply_translation(ct, ctinfo,
125 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
128 /* Seen it before? This can happen for loopback, retrans,
129 or local packets.. */
130 if (!nf_nat_initialized(ct, maniptype)) {
133 if (hooknum == NF_INET_LOCAL_IN)
134 /* LOCAL_IN hook doesn't have a chain! */
135 ret = alloc_null_binding(ct, hooknum);
137 ret = nf_nat_rule_find(skb, hooknum, in, out,
140 if (ret != NF_ACCEPT) {
144 pr_debug("Already setup manip %s for ct %p\n",
145 maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
151 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
152 ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
155 return nf_nat_packet(ct, ctinfo, hooknum, skb);
159 nf_nat_in(unsigned int hooknum,
161 const struct net_device *in,
162 const struct net_device *out,
163 int (*okfn)(struct sk_buff *))
166 __be32 daddr = ip_hdr(skb)->daddr;
168 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
169 if (ret != NF_DROP && ret != NF_STOLEN &&
170 daddr != ip_hdr(skb)->daddr) {
171 dst_release(skb->dst);
178 nf_nat_out(unsigned int hooknum,
180 const struct net_device *in,
181 const struct net_device *out,
182 int (*okfn)(struct sk_buff *))
185 const struct nf_conn *ct;
186 enum ip_conntrack_info ctinfo;
190 /* root is playing with raw sockets. */
191 if (skb->len < sizeof(struct iphdr) ||
192 ip_hdrlen(skb) < sizeof(struct iphdr))
195 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
197 if (ret != NF_DROP && ret != NF_STOLEN &&
198 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
199 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
201 if (ct->tuplehash[dir].tuple.src.u3.ip !=
202 ct->tuplehash[!dir].tuple.dst.u3.ip
203 || ct->tuplehash[dir].tuple.src.u.all !=
204 ct->tuplehash[!dir].tuple.dst.u.all
206 return ip_xfrm_me_harder(skb) == 0 ? ret : NF_DROP;
213 nf_nat_local_fn(unsigned int hooknum,
215 const struct net_device *in,
216 const struct net_device *out,
217 int (*okfn)(struct sk_buff *))
219 const struct nf_conn *ct;
220 enum ip_conntrack_info ctinfo;
223 /* root is playing with raw sockets. */
224 if (skb->len < sizeof(struct iphdr) ||
225 ip_hdrlen(skb) < sizeof(struct iphdr))
228 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
229 if (ret != NF_DROP && ret != NF_STOLEN &&
230 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
231 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
233 if (ct->tuplehash[dir].tuple.dst.u3.ip !=
234 ct->tuplehash[!dir].tuple.src.u3.ip) {
235 if (ip_route_me_harder(skb, RTN_UNSPEC))
239 else if (ct->tuplehash[dir].tuple.dst.u.all !=
240 ct->tuplehash[!dir].tuple.src.u.all)
241 if (ip_xfrm_me_harder(skb))
249 nf_nat_adjust(unsigned int hooknum,
251 const struct net_device *in,
252 const struct net_device *out,
253 int (*okfn)(struct sk_buff *))
256 enum ip_conntrack_info ctinfo;
258 ct = nf_ct_get(skb, &ctinfo);
259 if (ct && test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
260 pr_debug("nf_nat_standalone: adjusting sequence number\n");
261 if (!nf_nat_seq_adjust(skb, ct, ctinfo))
267 /* We must be after connection tracking and before packet filtering. */
269 static struct nf_hook_ops nf_nat_ops[] __read_mostly = {
270 /* Before packet filtering, change destination */
273 .owner = THIS_MODULE,
275 .hooknum = NF_INET_PRE_ROUTING,
276 .priority = NF_IP_PRI_NAT_DST,
278 /* After packet filtering, change source */
281 .owner = THIS_MODULE,
283 .hooknum = NF_INET_POST_ROUTING,
284 .priority = NF_IP_PRI_NAT_SRC,
286 /* After conntrack, adjust sequence number */
288 .hook = nf_nat_adjust,
289 .owner = THIS_MODULE,
291 .hooknum = NF_INET_POST_ROUTING,
292 .priority = NF_IP_PRI_NAT_SEQ_ADJUST,
294 /* Before packet filtering, change destination */
296 .hook = nf_nat_local_fn,
297 .owner = THIS_MODULE,
299 .hooknum = NF_INET_LOCAL_OUT,
300 .priority = NF_IP_PRI_NAT_DST,
302 /* After packet filtering, change source */
305 .owner = THIS_MODULE,
307 .hooknum = NF_INET_LOCAL_IN,
308 .priority = NF_IP_PRI_NAT_SRC,
310 /* After conntrack, adjust sequence number */
312 .hook = nf_nat_adjust,
313 .owner = THIS_MODULE,
315 .hooknum = NF_INET_LOCAL_IN,
316 .priority = NF_IP_PRI_NAT_SEQ_ADJUST,
320 static int __init nf_nat_standalone_init(void)
324 need_ipv4_conntrack();
327 BUG_ON(ip_nat_decode_session != NULL);
328 rcu_assign_pointer(ip_nat_decode_session, nat_decode_session);
330 ret = nf_nat_rule_init();
332 printk("nf_nat_init: can't setup rules.\n");
333 goto cleanup_decode_session;
335 ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
337 printk("nf_nat_init: can't register hooks.\n");
338 goto cleanup_rule_init;
343 nf_nat_rule_cleanup();
344 cleanup_decode_session:
346 rcu_assign_pointer(ip_nat_decode_session, NULL);
352 static void __exit nf_nat_standalone_fini(void)
354 nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
355 nf_nat_rule_cleanup();
357 rcu_assign_pointer(ip_nat_decode_session, NULL);
360 /* Conntrack caches are unregistered in nf_conntrack_cleanup */
363 module_init(nf_nat_standalone_init);
364 module_exit(nf_nat_standalone_fini);
366 MODULE_LICENSE("GPL");
367 MODULE_ALIAS("ip_nat");