iptable_filter.c revision 8c6ffba0eddc8c110dbf444f51354ce42069abfc 
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 <linux/slab.h>
17#include <net/ip.h>
18
19MODULE_LICENSE("GPL");
20MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
21MODULE_DESCRIPTION("iptables filter table");
22
23#define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
24			    (1 << NF_INET_FORWARD) | \
25			    (1 << NF_INET_LOCAL_OUT))
26
27static const struct xt_table packet_filter = {
28	.name		= "filter",
29	.valid_hooks	= FILTER_VALID_HOOKS,
30	.me		= THIS_MODULE,
31	.af		= NFPROTO_IPV4,
32	.priority	= NF_IP_PRI_FILTER,
33};
34
35static unsigned int
36iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
37		    const struct net_device *in, const struct net_device *out,
38		    int (*okfn)(struct sk_buff *))
39{
40	const struct net *net;
41
42	if (hook == NF_INET_LOCAL_OUT &&
43	    (skb->len < sizeof(struct iphdr) ||
44	     ip_hdrlen(skb) < sizeof(struct iphdr)))
45		/* root is playing with raw sockets. */
46		return NF_ACCEPT;
47
48	net = dev_net((in != NULL) ? in : out);
49	return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
50}
51
52static struct nf_hook_ops *filter_ops __read_mostly;
53
54/* Default to forward because I got too much mail already. */
55static bool forward = true;
56module_param(forward, bool, 0000);
57
58static int __net_init iptable_filter_net_init(struct net *net)
59{
60	struct ipt_replace *repl;
61
62	repl = ipt_alloc_initial_table(&packet_filter);
63	if (repl == NULL)
64		return -ENOMEM;
65	/* Entry 1 is the FORWARD hook */
66	((struct ipt_standard *)repl->entries)[1].target.verdict =
67		forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
68
69	net->ipv4.iptable_filter =
70		ipt_register_table(net, &packet_filter, repl);
71	kfree(repl);
72	return PTR_ERR_OR_ZERO(net->ipv4.iptable_filter);
73}
74
75static void __net_exit iptable_filter_net_exit(struct net *net)
76{
77	ipt_unregister_table(net, net->ipv4.iptable_filter);
78}
79
80static struct pernet_operations iptable_filter_net_ops = {
81	.init = iptable_filter_net_init,
82	.exit = iptable_filter_net_exit,
83};
84
85static int __init iptable_filter_init(void)
86{
87	int ret;
88
89	ret = register_pernet_subsys(&iptable_filter_net_ops);
90	if (ret < 0)
91		return ret;
92
93	/* Register hooks */
94	filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
95	if (IS_ERR(filter_ops)) {
96		ret = PTR_ERR(filter_ops);
97		unregister_pernet_subsys(&iptable_filter_net_ops);
98	}
99
100	return ret;
101}
102
103static void __exit iptable_filter_fini(void)
104{
105	xt_hook_unlink(&packet_filter, filter_ops);
106	unregister_pernet_subsys(&iptable_filter_net_ops);
107}
108
109module_init(iptable_filter_init);
110module_exit(iptable_filter_fini);
111