iptable_filter.c revision 2b21e051472fdb4680076278b2ccf63ebc1cc3bc 
1/*
2 * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
3 *
4 * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
5 * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 */
12
13#include <linux/module.h>
14#include <linux/moduleparam.h>
15#include <linux/netfilter_ipv4/ip_tables.h>
16#include <net/ip.h>
17
18MODULE_LICENSE("GPL");
19MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
20MODULE_DESCRIPTION("iptables filter table");
21
22#define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
23			    (1 << NF_INET_FORWARD) | \
24			    (1 << NF_INET_LOCAL_OUT))
25
26static struct
27{
28	struct ipt_replace repl;
29	struct ipt_standard entries[3];
30	struct ipt_error term;
31} initial_table __net_initdata = {
32	.repl = {
33		.name = "filter",
34		.valid_hooks = FILTER_VALID_HOOKS,
35		.num_entries = 4,
36		.size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
37		.hook_entry = {
38			[NF_INET_LOCAL_IN] = 0,
39			[NF_INET_FORWARD] = sizeof(struct ipt_standard),
40			[NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
41		},
42		.underflow = {
43			[NF_INET_LOCAL_IN] = 0,
44			[NF_INET_FORWARD] = sizeof(struct ipt_standard),
45			[NF_INET_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
46		},
47	},
48	.entries = {
49		IPT_STANDARD_INIT(NF_ACCEPT),	/* LOCAL_IN */
50		IPT_STANDARD_INIT(NF_ACCEPT),	/* FORWARD */
51		IPT_STANDARD_INIT(NF_ACCEPT),	/* LOCAL_OUT */
52	},
53	.term = IPT_ERROR_INIT,			/* ERROR */
54};
55
56static const struct xt_table packet_filter = {
57	.name		= "filter",
58	.valid_hooks	= FILTER_VALID_HOOKS,
59	.me		= THIS_MODULE,
60	.af		= NFPROTO_IPV4,
61};
62
63static unsigned int
64iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
65		    const struct net_device *in, const struct net_device *out,
66		    int (*okfn)(struct sk_buff *))
67{
68	const struct net *net;
69
70	if (hook == NF_INET_LOCAL_OUT &&
71	    (skb->len < sizeof(struct iphdr) ||
72	     ip_hdrlen(skb) < sizeof(struct iphdr)))
73		/* root is playing with raw sockets. */
74		return NF_ACCEPT;
75
76	net = dev_net((in != NULL) ? in : out);
77	return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
78}
79
80static struct nf_hook_ops ipt_ops[] __read_mostly = {
81	{
82		.hook		= iptable_filter_hook,
83		.owner		= THIS_MODULE,
84		.pf		= NFPROTO_IPV4,
85		.hooknum	= NF_INET_LOCAL_IN,
86		.priority	= NF_IP_PRI_FILTER,
87	},
88	{
89		.hook		= iptable_filter_hook,
90		.owner		= THIS_MODULE,
91		.pf		= NFPROTO_IPV4,
92		.hooknum	= NF_INET_FORWARD,
93		.priority	= NF_IP_PRI_FILTER,
94	},
95	{
96		.hook		= iptable_filter_hook,
97		.owner		= THIS_MODULE,
98		.pf		= NFPROTO_IPV4,
99		.hooknum	= NF_INET_LOCAL_OUT,
100		.priority	= NF_IP_PRI_FILTER,
101	},
102};
103
104/* Default to forward because I got too much mail already. */
105static int forward = NF_ACCEPT;
106module_param(forward, bool, 0000);
107
108static int __net_init iptable_filter_net_init(struct net *net)
109{
110	/* Register table */
111	net->ipv4.iptable_filter =
112		ipt_register_table(net, &packet_filter, &initial_table.repl);
113	if (IS_ERR(net->ipv4.iptable_filter))
114		return PTR_ERR(net->ipv4.iptable_filter);
115	return 0;
116}
117
118static void __net_exit iptable_filter_net_exit(struct net *net)
119{
120	ipt_unregister_table(net, net->ipv4.iptable_filter);
121}
122
123static struct pernet_operations iptable_filter_net_ops = {
124	.init = iptable_filter_net_init,
125	.exit = iptable_filter_net_exit,
126};
127
128static int __init iptable_filter_init(void)
129{
130	int ret;
131
132	if (forward < 0 || forward > NF_MAX_VERDICT) {
133		printk("iptables forward must be 0 or 1\n");
134		return -EINVAL;
135	}
136
137	/* Entry 1 is the FORWARD hook */
138	initial_table.entries[1].target.verdict = -forward - 1;
139
140	ret = register_pernet_subsys(&iptable_filter_net_ops);
141	if (ret < 0)
142		return ret;
143
144	/* Register hooks */
145	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
146	if (ret < 0)
147		goto cleanup_table;
148
149	return ret;
150
151 cleanup_table:
152	unregister_pernet_subsys(&iptable_filter_net_ops);
153	return ret;
154}
155
156static void __exit iptable_filter_fini(void)
157{
158	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
159	unregister_pernet_subsys(&iptable_filter_net_ops);
160}
161
162module_init(iptable_filter_init);
163module_exit(iptable_filter_fini);
164