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 }
237
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