6348a793936e9e0d8df6f98232c7cc7930860b44
[linux-2.6.git] / net / ipv4 / netfilter / nf_nat_rule.c
1 /* (C) 1999-2001 Paul `Rusty' Russell
2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
3  *
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.
7  */
8
9 /* Everything about the rules for NAT. */
10 #include <linux/types.h>
11 #include <linux/ip.h>
12 #include <linux/netfilter.h>
13 #include <linux/netfilter_ipv4.h>
14 #include <linux/module.h>
15 #include <linux/kmod.h>
16 #include <linux/skbuff.h>
17 #include <linux/proc_fs.h>
18 #include <net/checksum.h>
19 #include <net/route.h>
20 #include <linux/bitops.h>
21
22 #include <linux/netfilter_ipv4/ip_tables.h>
23 #include <net/netfilter/nf_nat.h>
24 #include <net/netfilter/nf_nat_core.h>
25 #include <net/netfilter/nf_nat_rule.h>
26
27 #define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
28                          (1 << NF_INET_POST_ROUTING) | \
29                          (1 << NF_INET_LOCAL_OUT))
30
31 static struct
32 {
33         struct ipt_replace repl;
34         struct ipt_standard entries[3];
35         struct ipt_error term;
36 } nat_initial_table __net_initdata = {
37         .repl = {
38                 .name = "nat",
39                 .valid_hooks = NAT_VALID_HOOKS,
40                 .num_entries = 4,
41                 .size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
42                 .hook_entry = {
43                         [NF_INET_PRE_ROUTING] = 0,
44                         [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
45                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
46                 },
47                 .underflow = {
48                         [NF_INET_PRE_ROUTING] = 0,
49                         [NF_INET_POST_ROUTING] = sizeof(struct ipt_standard),
50                         [NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2
51                 },
52         },
53         .entries = {
54                 IPT_STANDARD_INIT(NF_ACCEPT),   /* PRE_ROUTING */
55                 IPT_STANDARD_INIT(NF_ACCEPT),   /* POST_ROUTING */
56                 IPT_STANDARD_INIT(NF_ACCEPT),   /* LOCAL_OUT */
57         },
58         .term = IPT_ERROR_INIT,                 /* ERROR */
59 };
60
61 static struct xt_table nat_table = {
62         .name           = "nat",
63         .valid_hooks    = NAT_VALID_HOOKS,
64         .me             = THIS_MODULE,
65         .af             = AF_INET,
66 };
67
68 /* Source NAT */
69 static unsigned int
70 ipt_snat_target(struct sk_buff *skb, const struct xt_target_param *par)
71 {
72         struct nf_conn *ct;
73         enum ip_conntrack_info ctinfo;
74         const struct nf_nat_multi_range_compat *mr = par->targinfo;
75
76         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
77
78         ct = nf_ct_get(skb, &ctinfo);
79
80         /* Connection must be valid and new. */
81         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
82                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
83         NF_CT_ASSERT(par->out != NULL);
84
85         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
86 }
87
88 static unsigned int
89 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
90 {
91         struct nf_conn *ct;
92         enum ip_conntrack_info ctinfo;
93         const struct nf_nat_multi_range_compat *mr = par->targinfo;
94
95         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
96                      par->hooknum == NF_INET_LOCAL_OUT);
97
98         ct = nf_ct_get(skb, &ctinfo);
99
100         /* Connection must be valid and new. */
101         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
102
103         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
104 }
105
106 static bool ipt_snat_checkentry(const struct xt_tgchk_param *par)
107 {
108         const struct nf_nat_multi_range_compat *mr = par->targinfo;
109
110         /* Must be a valid range */
111         if (mr->rangesize != 1) {
112                 printk("SNAT: multiple ranges no longer supported\n");
113                 return false;
114         }
115         return true;
116 }
117
118 static bool ipt_dnat_checkentry(const struct xt_tgchk_param *par)
119 {
120         const struct nf_nat_multi_range_compat *mr = par->targinfo;
121
122         /* Must be a valid range */
123         if (mr->rangesize != 1) {
124                 printk("DNAT: multiple ranges no longer supported\n");
125                 return false;
126         }
127         return true;
128 }
129
130 unsigned int
131 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
132 {
133         /* Force range to this IP; let proto decide mapping for
134            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
135            Use reply in case it's already been mangled (eg local packet).
136         */
137         __be32 ip
138                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
139                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
140                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
141         struct nf_nat_range range
142                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
143
144         pr_debug("Allocating NULL binding for %p (%pI4)\n", ct, &ip);
145         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
146 }
147
148 int nf_nat_rule_find(struct sk_buff *skb,
149                      unsigned int hooknum,
150                      const struct net_device *in,
151                      const struct net_device *out,
152                      struct nf_conn *ct)
153 {
154         struct net *net = nf_ct_net(ct);
155         int ret;
156
157         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
158
159         if (ret == NF_ACCEPT) {
160                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
161                         /* NUL mapping */
162                         ret = alloc_null_binding(ct, hooknum);
163         }
164         return ret;
165 }
166
167 static struct xt_target ipt_snat_reg __read_mostly = {
168         .name           = "SNAT",
169         .target         = ipt_snat_target,
170         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
171         .table          = "nat",
172         .hooks          = 1 << NF_INET_POST_ROUTING,
173         .checkentry     = ipt_snat_checkentry,
174         .family         = AF_INET,
175 };
176
177 static struct xt_target ipt_dnat_reg __read_mostly = {
178         .name           = "DNAT",
179         .target         = ipt_dnat_target,
180         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
181         .table          = "nat",
182         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
183         .checkentry     = ipt_dnat_checkentry,
184         .family         = AF_INET,
185 };
186
187 static int __net_init nf_nat_rule_net_init(struct net *net)
188 {
189         net->ipv4.nat_table = ipt_register_table(net, &nat_table,
190                                                  &nat_initial_table.repl);
191         if (IS_ERR(net->ipv4.nat_table))
192                 return PTR_ERR(net->ipv4.nat_table);
193         return 0;
194 }
195
196 static void __net_exit nf_nat_rule_net_exit(struct net *net)
197 {
198         ipt_unregister_table(net->ipv4.nat_table);
199 }
200
201 static struct pernet_operations nf_nat_rule_net_ops = {
202         .init = nf_nat_rule_net_init,
203         .exit = nf_nat_rule_net_exit,
204 };
205
206 int __init nf_nat_rule_init(void)
207 {
208         int ret;
209
210         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
211         if (ret != 0)
212                 goto out;
213         ret = xt_register_target(&ipt_snat_reg);
214         if (ret != 0)
215                 goto unregister_table;
216
217         ret = xt_register_target(&ipt_dnat_reg);
218         if (ret != 0)
219                 goto unregister_snat;
220
221         return ret;
222
223  unregister_snat:
224         xt_unregister_target(&ipt_snat_reg);
225  unregister_table:
226         unregister_pernet_subsys(&nf_nat_rule_net_ops);
227  out:
228         return ret;
229 }
230
231 void nf_nat_rule_cleanup(void)
232 {
233         xt_unregister_target(&ipt_dnat_reg);
234         xt_unregister_target(&ipt_snat_reg);
235         unregister_pernet_subsys(&nf_nat_rule_net_ops);
236 }