83170ff131f984d3ec8f4e436654922e8efe6da9
[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         .lock           = __RW_LOCK_UNLOCKED(__nat_table.lock),
65         .me             = THIS_MODULE,
66         .af             = AF_INET,
67 };
68
69 /* Source NAT */
70 static unsigned int
71 ipt_snat_target(struct sk_buff *skb, const struct xt_target_param *par)
72 {
73         struct nf_conn *ct;
74         enum ip_conntrack_info ctinfo;
75         const struct nf_nat_multi_range_compat *mr = par->targinfo;
76
77         NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
78
79         ct = nf_ct_get(skb, &ctinfo);
80
81         /* Connection must be valid and new. */
82         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
83                             ctinfo == IP_CT_RELATED + IP_CT_IS_REPLY));
84         NF_CT_ASSERT(par->out != NULL);
85
86         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_SRC);
87 }
88
89 /* Before 2.6.11 we did implicit source NAT if required. Warn about change. */
90 static void warn_if_extra_mangle(struct net *net, __be32 dstip, __be32 srcip)
91 {
92         static int warned = 0;
93         struct flowi fl = { .nl_u = { .ip4_u = { .daddr = dstip } } };
94         struct rtable *rt;
95
96         if (ip_route_output_key(net, &rt, &fl) != 0)
97                 return;
98
99         if (rt->rt_src != srcip && !warned) {
100                 printk("NAT: no longer support implicit source local NAT\n");
101                 printk("NAT: packet src %u.%u.%u.%u -> dst %u.%u.%u.%u\n",
102                        NIPQUAD(srcip), NIPQUAD(dstip));
103                 warned = 1;
104         }
105         ip_rt_put(rt);
106 }
107
108 static unsigned int
109 ipt_dnat_target(struct sk_buff *skb, const struct xt_target_param *par)
110 {
111         struct nf_conn *ct;
112         enum ip_conntrack_info ctinfo;
113         const struct nf_nat_multi_range_compat *mr = par->targinfo;
114
115         NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
116                      par->hooknum == NF_INET_LOCAL_OUT);
117
118         ct = nf_ct_get(skb, &ctinfo);
119
120         /* Connection must be valid and new. */
121         NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
122
123         if (par->hooknum == NF_INET_LOCAL_OUT &&
124             mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)
125                 warn_if_extra_mangle(dev_net(par->out), ip_hdr(skb)->daddr,
126                                      mr->range[0].min_ip);
127
128         return nf_nat_setup_info(ct, &mr->range[0], IP_NAT_MANIP_DST);
129 }
130
131 static bool ipt_snat_checkentry(const char *tablename,
132                                 const void *entry,
133                                 const struct xt_target *target,
134                                 void *targinfo,
135                                 unsigned int hook_mask)
136 {
137         const struct nf_nat_multi_range_compat *mr = targinfo;
138
139         /* Must be a valid range */
140         if (mr->rangesize != 1) {
141                 printk("SNAT: multiple ranges no longer supported\n");
142                 return false;
143         }
144         return true;
145 }
146
147 static bool ipt_dnat_checkentry(const char *tablename,
148                                 const void *entry,
149                                 const struct xt_target *target,
150                                 void *targinfo,
151                                 unsigned int hook_mask)
152 {
153         const struct nf_nat_multi_range_compat *mr = targinfo;
154
155         /* Must be a valid range */
156         if (mr->rangesize != 1) {
157                 printk("DNAT: multiple ranges no longer supported\n");
158                 return false;
159         }
160         return true;
161 }
162
163 unsigned int
164 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
165 {
166         /* Force range to this IP; let proto decide mapping for
167            per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).
168            Use reply in case it's already been mangled (eg local packet).
169         */
170         __be32 ip
171                 = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
172                    ? ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip
173                    : ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
174         struct nf_nat_range range
175                 = { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } };
176
177         pr_debug("Allocating NULL binding for %p (%u.%u.%u.%u)\n",
178                  ct, NIPQUAD(ip));
179         return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
180 }
181
182 int nf_nat_rule_find(struct sk_buff *skb,
183                      unsigned int hooknum,
184                      const struct net_device *in,
185                      const struct net_device *out,
186                      struct nf_conn *ct)
187 {
188         struct net *net = nf_ct_net(ct);
189         int ret;
190
191         ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
192
193         if (ret == NF_ACCEPT) {
194                 if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
195                         /* NUL mapping */
196                         ret = alloc_null_binding(ct, hooknum);
197         }
198         return ret;
199 }
200
201 static struct xt_target ipt_snat_reg __read_mostly = {
202         .name           = "SNAT",
203         .target         = ipt_snat_target,
204         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
205         .table          = "nat",
206         .hooks          = 1 << NF_INET_POST_ROUTING,
207         .checkentry     = ipt_snat_checkentry,
208         .family         = AF_INET,
209 };
210
211 static struct xt_target ipt_dnat_reg __read_mostly = {
212         .name           = "DNAT",
213         .target         = ipt_dnat_target,
214         .targetsize     = sizeof(struct nf_nat_multi_range_compat),
215         .table          = "nat",
216         .hooks          = (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
217         .checkentry     = ipt_dnat_checkentry,
218         .family         = AF_INET,
219 };
220
221 static int __net_init nf_nat_rule_net_init(struct net *net)
222 {
223         net->ipv4.nat_table = ipt_register_table(net, &nat_table,
224                                                  &nat_initial_table.repl);
225         if (IS_ERR(net->ipv4.nat_table))
226                 return PTR_ERR(net->ipv4.nat_table);
227         return 0;
228 }
229
230 static void __net_exit nf_nat_rule_net_exit(struct net *net)
231 {
232         ipt_unregister_table(net->ipv4.nat_table);
233 }
234
235 static struct pernet_operations nf_nat_rule_net_ops = {
236         .init = nf_nat_rule_net_init,
237         .exit = nf_nat_rule_net_exit,
238 };
239
240 int __init nf_nat_rule_init(void)
241 {
242         int ret;
243
244         ret = register_pernet_subsys(&nf_nat_rule_net_ops);
245         if (ret != 0)
246                 goto out;
247         ret = xt_register_target(&ipt_snat_reg);
248         if (ret != 0)
249                 goto unregister_table;
250
251         ret = xt_register_target(&ipt_dnat_reg);
252         if (ret != 0)
253                 goto unregister_snat;
254
255         return ret;
256
257  unregister_snat:
258         xt_unregister_target(&ipt_snat_reg);
259  unregister_table:
260         unregister_pernet_subsys(&nf_nat_rule_net_ops);
261  out:
262         return ret;
263 }
264
265 void nf_nat_rule_cleanup(void)
266 {
267         xt_unregister_target(&ipt_dnat_reg);
268         xt_unregister_target(&ipt_snat_reg);
269         unregister_pernet_subsys(&nf_nat_rule_net_ops);
270 }