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>
10 #include <linux/gfp.h>
12 #include <linux/netfilter.h>
13 #include <linux/netfilter_ipv4.h>
14 #include <linux/module.h>
15 #include <linux/skbuff.h>
16 #include <linux/proc_fs.h>
18 #include <net/checksum.h>
19 #include <linux/spinlock.h>
21 #include <net/netfilter/nf_conntrack.h>
22 #include <net/netfilter/nf_conntrack_core.h>
23 #include <net/netfilter/nf_conntrack_extend.h>
24 #include <net/netfilter/nf_nat.h>
25 #include <net/netfilter/nf_nat_rule.h>
26 #include <net/netfilter/nf_nat_protocol.h>
27 #include <net/netfilter/nf_nat_core.h>
28 #include <net/netfilter/nf_nat_helper.h>
29 #include <linux/netfilter_ipv4/ip_tables.h>
32 static void nat_decode_session(struct sk_buff *skb, struct flowi *fl)
34 struct flowi4 *fl4 = &fl->u.ip4;
35 const struct nf_conn *ct;
36 const struct nf_conntrack_tuple *t;
37 enum ip_conntrack_info ctinfo;
38 enum ip_conntrack_dir dir;
39 unsigned long statusbit;
41 ct = nf_ct_get(skb, &ctinfo);
44 dir = CTINFO2DIR(ctinfo);
45 t = &ct->tuplehash[dir].tuple;
47 if (dir == IP_CT_DIR_ORIGINAL)
48 statusbit = IPS_DST_NAT;
50 statusbit = IPS_SRC_NAT;
52 if (ct->status & statusbit) {
53 fl4->daddr = t->dst.u3.ip;
54 if (t->dst.protonum == IPPROTO_TCP ||
55 t->dst.protonum == IPPROTO_UDP ||
56 t->dst.protonum == IPPROTO_UDPLITE ||
57 t->dst.protonum == IPPROTO_DCCP ||
58 t->dst.protonum == IPPROTO_SCTP)
59 fl4->fl4_dport = t->dst.u.tcp.port;
62 statusbit ^= IPS_NAT_MASK;
64 if (ct->status & statusbit) {
65 fl4->saddr = t->src.u3.ip;
66 if (t->dst.protonum == IPPROTO_TCP ||
67 t->dst.protonum == IPPROTO_UDP ||
68 t->dst.protonum == IPPROTO_UDPLITE ||
69 t->dst.protonum == IPPROTO_DCCP ||
70 t->dst.protonum == IPPROTO_SCTP)
71 fl4->fl4_sport = t->src.u.tcp.port;
77 nf_nat_fn(unsigned int hooknum,
79 const struct net_device *in,
80 const struct net_device *out,
81 int (*okfn)(struct sk_buff *))
84 enum ip_conntrack_info ctinfo;
85 struct nf_conn_nat *nat;
86 /* maniptype == SRC for postrouting. */
87 enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
89 /* We never see fragments: conntrack defrags on pre-routing
90 and local-out, and nf_nat_out protects post-routing. */
91 NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb)));
93 ct = nf_ct_get(skb, &ctinfo);
94 /* Can't track? It's not due to stress, or conntrack would
95 have dropped it. Hence it's the user's responsibilty to
96 packet filter it out, or implement conntrack/NAT for that
101 /* Don't try to NAT if this packet is not conntracked */
102 if (nf_ct_is_untracked(ct))
107 /* NAT module was loaded late. */
108 if (nf_ct_is_confirmed(ct))
110 nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
112 pr_debug("failed to add NAT extension\n");
119 case IP_CT_RELATED_REPLY:
120 if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
121 if (!nf_nat_icmp_reply_translation(ct, ctinfo,
127 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
130 /* Seen it before? This can happen for loopback, retrans,
131 or local packets.. */
132 if (!nf_nat_initialized(ct, maniptype)) {
135 ret = nf_nat_rule_find(skb, hooknum, in, out, ct);
136 if (ret != NF_ACCEPT)
139 pr_debug("Already setup manip %s for ct %p\n",
140 maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
146 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
147 ctinfo == IP_CT_ESTABLISHED_REPLY);
150 return nf_nat_packet(ct, ctinfo, hooknum, skb);
154 nf_nat_in(unsigned int hooknum,
156 const struct net_device *in,
157 const struct net_device *out,
158 int (*okfn)(struct sk_buff *))
161 __be32 daddr = ip_hdr(skb)->daddr;
163 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
164 if (ret != NF_DROP && ret != NF_STOLEN &&
165 daddr != ip_hdr(skb)->daddr)
172 nf_nat_out(unsigned int hooknum,
174 const struct net_device *in,
175 const struct net_device *out,
176 int (*okfn)(struct sk_buff *))
179 const struct nf_conn *ct;
180 enum ip_conntrack_info ctinfo;
184 /* root is playing with raw sockets. */
185 if (skb->len < sizeof(struct iphdr) ||
186 ip_hdrlen(skb) < sizeof(struct iphdr))
189 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
191 if (ret != NF_DROP && ret != NF_STOLEN &&
192 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
193 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
195 if ((ct->tuplehash[dir].tuple.src.u3.ip !=
196 ct->tuplehash[!dir].tuple.dst.u3.ip) ||
197 (ct->tuplehash[dir].tuple.src.u.all !=
198 ct->tuplehash[!dir].tuple.dst.u.all)
200 return ip_xfrm_me_harder(skb) == 0 ? ret : NF_DROP;
207 nf_nat_local_fn(unsigned int hooknum,
209 const struct net_device *in,
210 const struct net_device *out,
211 int (*okfn)(struct sk_buff *))
213 const struct nf_conn *ct;
214 enum ip_conntrack_info ctinfo;
217 /* root is playing with raw sockets. */
218 if (skb->len < sizeof(struct iphdr) ||
219 ip_hdrlen(skb) < sizeof(struct iphdr))
222 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
223 if (ret != NF_DROP && ret != NF_STOLEN &&
224 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
225 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
227 if (ct->tuplehash[dir].tuple.dst.u3.ip !=
228 ct->tuplehash[!dir].tuple.src.u3.ip) {
229 if (ip_route_me_harder(skb, RTN_UNSPEC))
233 else if (ct->tuplehash[dir].tuple.dst.u.all !=
234 ct->tuplehash[!dir].tuple.src.u.all)
235 if (ip_xfrm_me_harder(skb))
242 /* We must be after connection tracking and before packet filtering. */
244 static struct nf_hook_ops nf_nat_ops[] __read_mostly = {
245 /* Before packet filtering, change destination */
248 .owner = THIS_MODULE,
250 .hooknum = NF_INET_PRE_ROUTING,
251 .priority = NF_IP_PRI_NAT_DST,
253 /* After packet filtering, change source */
256 .owner = THIS_MODULE,
258 .hooknum = NF_INET_POST_ROUTING,
259 .priority = NF_IP_PRI_NAT_SRC,
261 /* Before packet filtering, change destination */
263 .hook = nf_nat_local_fn,
264 .owner = THIS_MODULE,
266 .hooknum = NF_INET_LOCAL_OUT,
267 .priority = NF_IP_PRI_NAT_DST,
269 /* After packet filtering, change source */
272 .owner = THIS_MODULE,
274 .hooknum = NF_INET_LOCAL_IN,
275 .priority = NF_IP_PRI_NAT_SRC,
279 static int __init nf_nat_standalone_init(void)
283 need_ipv4_conntrack();
286 BUG_ON(ip_nat_decode_session != NULL);
287 RCU_INIT_POINTER(ip_nat_decode_session, nat_decode_session);
289 ret = nf_nat_rule_init();
291 pr_err("nf_nat_init: can't setup rules.\n");
292 goto cleanup_decode_session;
294 ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
296 pr_err("nf_nat_init: can't register hooks.\n");
297 goto cleanup_rule_init;
302 nf_nat_rule_cleanup();
303 cleanup_decode_session:
305 RCU_INIT_POINTER(ip_nat_decode_session, NULL);
311 static void __exit nf_nat_standalone_fini(void)
313 nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
314 nf_nat_rule_cleanup();
316 RCU_INIT_POINTER(ip_nat_decode_session, NULL);
319 /* Conntrack caches are unregistered in nf_conntrack_cleanup */
322 module_init(nf_nat_standalone_init);
323 module_exit(nf_nat_standalone_fini);
325 MODULE_LICENSE("GPL");
326 MODULE_ALIAS("ip_nat");