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 (nf_ct_is_untracked(ct))
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 ret = nf_nat_rule_find(skb, hooknum, in, out, ct);
135 if (ret != NF_ACCEPT)
138 pr_debug("Already setup manip %s for ct %p\n",
139 maniptype == IP_NAT_MANIP_SRC ? "SRC" : "DST",
145 NF_CT_ASSERT(ctinfo == IP_CT_ESTABLISHED ||
146 ctinfo == (IP_CT_ESTABLISHED+IP_CT_IS_REPLY));
149 return nf_nat_packet(ct, ctinfo, hooknum, skb);
153 nf_nat_in(unsigned int hooknum,
155 const struct net_device *in,
156 const struct net_device *out,
157 int (*okfn)(struct sk_buff *))
160 __be32 daddr = ip_hdr(skb)->daddr;
162 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
163 if (ret != NF_DROP && ret != NF_STOLEN &&
164 daddr != ip_hdr(skb)->daddr)
171 nf_nat_out(unsigned int hooknum,
173 const struct net_device *in,
174 const struct net_device *out,
175 int (*okfn)(struct sk_buff *))
178 const struct nf_conn *ct;
179 enum ip_conntrack_info ctinfo;
183 /* root is playing with raw sockets. */
184 if (skb->len < sizeof(struct iphdr) ||
185 ip_hdrlen(skb) < sizeof(struct iphdr))
188 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
190 if (ret != NF_DROP && ret != NF_STOLEN &&
191 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
192 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
194 if ((ct->tuplehash[dir].tuple.src.u3.ip !=
195 ct->tuplehash[!dir].tuple.dst.u3.ip) ||
196 (ct->tuplehash[dir].tuple.src.u.all !=
197 ct->tuplehash[!dir].tuple.dst.u.all)
199 return ip_xfrm_me_harder(skb) == 0 ? ret : NF_DROP;
206 nf_nat_local_fn(unsigned int hooknum,
208 const struct net_device *in,
209 const struct net_device *out,
210 int (*okfn)(struct sk_buff *))
212 const struct nf_conn *ct;
213 enum ip_conntrack_info ctinfo;
216 /* root is playing with raw sockets. */
217 if (skb->len < sizeof(struct iphdr) ||
218 ip_hdrlen(skb) < sizeof(struct iphdr))
221 ret = nf_nat_fn(hooknum, skb, in, out, okfn);
222 if (ret != NF_DROP && ret != NF_STOLEN &&
223 (ct = nf_ct_get(skb, &ctinfo)) != NULL) {
224 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
226 if (ct->tuplehash[dir].tuple.dst.u3.ip !=
227 ct->tuplehash[!dir].tuple.src.u3.ip) {
228 if (ip_route_me_harder(skb, RTN_UNSPEC))
232 else if (ct->tuplehash[dir].tuple.dst.u.all !=
233 ct->tuplehash[!dir].tuple.src.u.all)
234 if (ip_xfrm_me_harder(skb))
241 /* We must be after connection tracking and before packet filtering. */
243 static struct nf_hook_ops nf_nat_ops[] __read_mostly = {
244 /* Before packet filtering, change destination */
247 .owner = THIS_MODULE,
249 .hooknum = NF_INET_PRE_ROUTING,
250 .priority = NF_IP_PRI_NAT_DST,
252 /* After packet filtering, change source */
255 .owner = THIS_MODULE,
257 .hooknum = NF_INET_POST_ROUTING,
258 .priority = NF_IP_PRI_NAT_SRC,
260 /* Before packet filtering, change destination */
262 .hook = nf_nat_local_fn,
263 .owner = THIS_MODULE,
265 .hooknum = NF_INET_LOCAL_OUT,
266 .priority = NF_IP_PRI_NAT_DST,
268 /* After packet filtering, change source */
271 .owner = THIS_MODULE,
273 .hooknum = NF_INET_LOCAL_IN,
274 .priority = NF_IP_PRI_NAT_SRC,
278 static int __init nf_nat_standalone_init(void)
282 need_ipv4_conntrack();
285 BUG_ON(ip_nat_decode_session != NULL);
286 rcu_assign_pointer(ip_nat_decode_session, nat_decode_session);
288 ret = nf_nat_rule_init();
290 pr_err("nf_nat_init: can't setup rules.\n");
291 goto cleanup_decode_session;
293 ret = nf_register_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
295 pr_err("nf_nat_init: can't register hooks.\n");
296 goto cleanup_rule_init;
301 nf_nat_rule_cleanup();
302 cleanup_decode_session:
304 rcu_assign_pointer(ip_nat_decode_session, NULL);
310 static void __exit nf_nat_standalone_fini(void)
312 nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
313 nf_nat_rule_cleanup();
315 rcu_assign_pointer(ip_nat_decode_session, NULL);
318 /* Conntrack caches are unregistered in nf_conntrack_cleanup */
321 module_init(nf_nat_standalone_init);
322 module_exit(nf_nat_standalone_fini);
324 MODULE_LICENSE("GPL");
325 MODULE_ALIAS("ip_nat");