1 // SPDX-License-Identifier: GPL-2.0-only
2 /* (C) 1999-2001 Paul `Rusty' Russell
3  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
4  * (C) 2011 Patrick McHardy <kaber@trash.net>
5  */
6 
7 #include <linux/module.h>
8 #include <linux/netfilter.h>
9 #include <linux/netfilter_ipv4.h>
10 #include <linux/netfilter_ipv4/ip_tables.h>
11 #include <linux/ip.h>
12 #include <net/ip.h>
13 
14 #include <net/netfilter/nf_nat.h>
15 
16 struct iptable_nat_pernet {
17 	struct nf_hook_ops *nf_nat_ops;
18 };
19 
20 static unsigned int iptable_nat_net_id __read_mostly;
21 
22 static const struct xt_table nf_nat_ipv4_table = {
23 	.name		= "nat",
24 	.valid_hooks	= (1 << NF_INET_PRE_ROUTING) |
25 			  (1 << NF_INET_POST_ROUTING) |
26 			  (1 << NF_INET_LOCAL_OUT) |
27 			  (1 << NF_INET_LOCAL_IN),
28 	.me		= THIS_MODULE,
29 	.af		= NFPROTO_IPV4,
30 };
31 
32 static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
33 	{
34 		.hook		= ipt_do_table,
35 		.pf		= NFPROTO_IPV4,
36 		.hooknum	= NF_INET_PRE_ROUTING,
37 		.priority	= NF_IP_PRI_NAT_DST,
38 	},
39 	{
40 		.hook		= ipt_do_table,
41 		.pf		= NFPROTO_IPV4,
42 		.hooknum	= NF_INET_POST_ROUTING,
43 		.priority	= NF_IP_PRI_NAT_SRC,
44 	},
45 	{
46 		.hook		= ipt_do_table,
47 		.pf		= NFPROTO_IPV4,
48 		.hooknum	= NF_INET_LOCAL_OUT,
49 		.priority	= NF_IP_PRI_NAT_DST,
50 	},
51 	{
52 		.hook		= ipt_do_table,
53 		.pf		= NFPROTO_IPV4,
54 		.hooknum	= NF_INET_LOCAL_IN,
55 		.priority	= NF_IP_PRI_NAT_SRC,
56 	},
57 };
58 
ipt_nat_register_lookups(struct net * net)59 static int ipt_nat_register_lookups(struct net *net)
60 {
61 	struct iptable_nat_pernet *xt_nat_net;
62 	struct nf_hook_ops *ops;
63 	struct xt_table *table;
64 	int i, ret;
65 
66 	xt_nat_net = net_generic(net, iptable_nat_net_id);
67 	table = xt_find_table(net, NFPROTO_IPV4, "nat");
68 	if (WARN_ON_ONCE(!table))
69 		return -ENOENT;
70 
71 	ops = kmemdup(nf_nat_ipv4_ops, sizeof(nf_nat_ipv4_ops), GFP_KERNEL);
72 	if (!ops)
73 		return -ENOMEM;
74 
75 	for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++) {
76 		ops[i].priv = table;
77 		ret = nf_nat_ipv4_register_fn(net, &ops[i]);
78 		if (ret) {
79 			while (i)
80 				nf_nat_ipv4_unregister_fn(net, &ops[--i]);
81 
82 			kfree(ops);
83 			return ret;
84 		}
85 	}
86 
87 	xt_nat_net->nf_nat_ops = ops;
88 	return 0;
89 }
90 
ipt_nat_unregister_lookups(struct net * net)91 static void ipt_nat_unregister_lookups(struct net *net)
92 {
93 	struct iptable_nat_pernet *xt_nat_net = net_generic(net, iptable_nat_net_id);
94 	struct nf_hook_ops *ops = xt_nat_net->nf_nat_ops;
95 	int i;
96 
97 	if (!ops)
98 		return;
99 
100 	for (i = 0; i < ARRAY_SIZE(nf_nat_ipv4_ops); i++)
101 		nf_nat_ipv4_unregister_fn(net, &ops[i]);
102 
103 	kfree(ops);
104 }
105 
iptable_nat_table_init(struct net * net)106 static int iptable_nat_table_init(struct net *net)
107 {
108 	struct ipt_replace *repl;
109 	int ret;
110 
111 	repl = ipt_alloc_initial_table(&nf_nat_ipv4_table);
112 	if (repl == NULL)
113 		return -ENOMEM;
114 
115 	ret = ipt_register_table(net, &nf_nat_ipv4_table, repl, NULL);
116 	if (ret < 0) {
117 		kfree(repl);
118 		return ret;
119 	}
120 
121 	ret = ipt_nat_register_lookups(net);
122 	if (ret < 0)
123 		ipt_unregister_table_exit(net, "nat");
124 
125 	kfree(repl);
126 	return ret;
127 }
128 
iptable_nat_net_pre_exit(struct net * net)129 static void __net_exit iptable_nat_net_pre_exit(struct net *net)
130 {
131 	ipt_nat_unregister_lookups(net);
132 }
133 
iptable_nat_net_exit(struct net * net)134 static void __net_exit iptable_nat_net_exit(struct net *net)
135 {
136 	ipt_unregister_table_exit(net, "nat");
137 }
138 
139 static struct pernet_operations iptable_nat_net_ops = {
140 	.pre_exit = iptable_nat_net_pre_exit,
141 	.exit	= iptable_nat_net_exit,
142 	.id	= &iptable_nat_net_id,
143 	.size	= sizeof(struct iptable_nat_pernet),
144 };
145 
iptable_nat_init(void)146 static int __init iptable_nat_init(void)
147 {
148 	int ret = xt_register_template(&nf_nat_ipv4_table,
149 				       iptable_nat_table_init);
150 
151 	if (ret < 0)
152 		return ret;
153 
154 	ret = register_pernet_subsys(&iptable_nat_net_ops);
155 	if (ret < 0) {
156 		xt_unregister_template(&nf_nat_ipv4_table);
157 		return ret;
158 	}
159 
160 	return ret;
161 }
162 
iptable_nat_exit(void)163 static void __exit iptable_nat_exit(void)
164 {
165 	unregister_pernet_subsys(&iptable_nat_net_ops);
166 	xt_unregister_template(&nf_nat_ipv4_table);
167 }
168 
169 module_init(iptable_nat_init);
170 module_exit(iptable_nat_exit);
171 
172 MODULE_LICENSE("GPL");
173