iptable_nat.c

  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
 16struct iptable_nat_pernet {
 17	struct nf_hook_ops *nf_nat_ops;
 18};
 19
 20static unsigned int iptable_nat_net_id __read_mostly;
 21
 22static 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
 32static 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
 59static 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
 91static 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
106static 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
129static void __net_exit iptable_nat_net_pre_exit(struct net *net)
130{
131	ipt_nat_unregister_lookups(net);
132}
133
134static void __net_exit iptable_nat_net_exit(struct net *net)
135{
136	ipt_unregister_table_exit(net, "nat");
137}
138
139static 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
146static int __init iptable_nat_init(void)
147{
148	int ret;
149
150	/* net->gen->ptr[iptable_nat_net_id] must be allocated
151	 * before calling iptable_nat_table_init().
152	 */
153	ret = register_pernet_subsys(&iptable_nat_net_ops);
154	if (ret < 0)
155		return ret;
156
157	ret = xt_register_template(&nf_nat_ipv4_table,
158				   iptable_nat_table_init);
159	if (ret < 0)
160		unregister_pernet_subsys(&iptable_nat_net_ops);
161
162	return ret;
163}
164
165static void __exit iptable_nat_exit(void)
166{
167	xt_unregister_template(&nf_nat_ipv4_table);
168	unregister_pernet_subsys(&iptable_nat_net_ops);
169}
170
171module_init(iptable_nat_init);
172module_exit(iptable_nat_exit);
173
174MODULE_LICENSE("GPL");
175MODULE_DESCRIPTION("iptables legacy nat table");