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 const struct nf_conn *ct;
35 const struct nf_conntrack_tuple *t;
36 enum ip_conntrack_info ctinfo;
37 enum ip_conntrack_dir dir;
38 unsigned long statusbit;
40 ct = nf_ct_get(skb, &ctinfo);
43 dir = CTINFO2DIR(ctinfo);
44 t = &ct->tuplehash[dir].tuple;
46 if (dir == IP_CT_DIR_ORIGINAL)
47 statusbit = IPS_DST_NAT;
49 statusbit = IPS_SRC_NAT;
51 if (ct->status & statusbit) {
52 fl->fl4_dst = t->dst.u3.ip;
53 if (t->dst.protonum == IPPROTO_TCP ||
54 t->dst.protonum == IPPROTO_UDP ||
55 t->dst.protonum == IPPROTO_UDPLITE ||
56 t->dst.protonum == IPPROTO_DCCP ||
57 t->dst.protonum == IPPROTO_SCTP)
58 fl->fl_ip_dport = t->dst.u.tcp.port;
61 statusbit ^= IPS_NAT_MASK;
63 if (ct->status & statusbit) {
64 fl->fl4_src = t->src.u3.ip;
65 if (t->dst.protonum == IPPROTO_TCP ||
66 t->dst.protonum == IPPROTO_UDP ||
67 t->dst.protonum == IPPROTO_UDPLITE ||
68 t->dst.protonum == IPPROTO_DCCP ||
69 t->dst.protonum == IPPROTO_SCTP)
70 fl->fl_ip_sport = t->src.u.tcp.port;
76 nf_nat_fn(unsigned int hooknum,
78 const struct net_device *in,
79 const struct net_device *out,
80 int (*okfn)(struct sk_buff *))
83 enum ip_conntrack_info ctinfo;
84 struct nf_conn_nat *nat;
85 /* maniptype == SRC for postrouting. */
86 enum nf_nat_manip_type maniptype = HOOK2MANIP(hooknum);
88 /* We never see fragments: conntrack defrags on pre-routing
89 and local-out, and nf_nat_out protects post-routing. */
90 NF_CT_ASSERT(!(ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)));
92 ct = nf_ct_get(skb, &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
100 /* Don't try to NAT if this packet is not conntracked */
101 if (ct == &nf_conntrack_untracked)
106 /* NAT module was loaded late. */
107 if (nf_ct_is_confirmed(ct))
109 nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
111 pr_debug("failed to add NAT extension\n");
118 case IP_CT_RELATED+IP_CT_IS_REPLY:
119 if (ip_hdr(skb)->protocol == IPPROTO_ICMP) {
120 if (!nf_nat_icmp_reply_translation(ct, ctinfo,
126 /* Fall thru... (Only ICMPs can be IP_CT_IS_REPLY) */
129 /* Seen it before? This can happen for loopback, retrans,
130 or local packets.. */
131 if (!nf_nat_initialized(ct, maniptype)) {
134 if (hooknum == NF_INET_LOCAL_IN)
135 /* LOCAL_IN hook doesn't have a chain! */
136 ret = alloc_null_binding(ct, hooknum);
138 ret = nf_nat_rule_find(skb, hooknum, in, out,
141 if (ret != NF_ACCEPT) {
145 pr_debug("Already setup manip %s for ct %p\n",
146 maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
152 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
153 ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
156 return nf_nat_packet(ct, ctinfo, hooknum, skb);
160 nf_nat_in(unsigned int hooknum,
162 const struct net_device *in,
163 const struct net_device *out,
164 int (*okfn)(struct sk_buff *))
167 __be32 daddr = ip_hdr(skb)->daddr;
169 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
170 if (ret != NF_DROP && ret != NF_STOLEN &&
171 daddr != ip_hdr(skb)->daddr)
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))
248 /* We must be after connection tracking and before packet filtering. */
250 static struct nf_hook_ops nf_nat_ops[] __read_mostly = {
251 /* Before packet filtering, change destination */
254 .owner = THIS_MODULE,
256 .hooknum = NF_INET_PRE_ROUTING,
257 .priority = NF_IP_PRI_NAT_DST,
259 /* After packet filtering, change source */
262 .owner = THIS_MODULE,
264 .hooknum = NF_INET_POST_ROUTING,
265 .priority = NF_IP_PRI_NAT_SRC,
267 /* Before packet filtering, change destination */
269 .hook = nf_nat_local_fn,
270 .owner = THIS_MODULE,
272 .hooknum = NF_INET_LOCAL_OUT,
273 .priority = NF_IP_PRI_NAT_DST,
275 /* After packet filtering, change source */
278 .owner = THIS_MODULE,
280 .hooknum = NF_INET_LOCAL_IN,
281 .priority = NF_IP_PRI_NAT_SRC,
285 static int __init nf_nat_standalone_init(void)
289 need_ipv4_conntrack();
292 BUG_ON(ip_nat_decode_session != NULL);
293 rcu_assign_pointer(ip_nat_decode_session, nat_decode_session);
295 ret = nf_nat_rule_init();
297 printk("nf_nat_init: can't setup rules.\n");
298 goto cleanup_decode_session;
300 ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
302 printk("nf_nat_init: can't register hooks.\n");
303 goto cleanup_rule_init;
308 nf_nat_rule_cleanup();
309 cleanup_decode_session:
311 rcu_assign_pointer(ip_nat_decode_session, NULL);
317 static void __exit nf_nat_standalone_fini(void)
319 nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
320 nf_nat_rule_cleanup();
322 rcu_assign_pointer(ip_nat_decode_session, NULL);
325 /* Conntrack caches are unregistered in nf_conntrack_cleanup */
328 module_init(nf_nat_standalone_init);
329 module_exit(nf_nat_standalone_fini);
331 MODULE_LICENSE("GPL");
332 MODULE_ALIAS("ip_nat");