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(const struct nf_hook_ops *ops, struct sk_buff *skb,
37		    const struct nf_hook_state *state)
38{
39	const struct net *net;
40
41	if (ops->hooknum == NF_INET_LOCAL_OUT &&
42	    (skb->len < sizeof(struct iphdr) ||
43	     ip_hdrlen(skb) < sizeof(struct iphdr)))
44		/* root is playing with raw sockets. */
45		return NF_ACCEPT;
46
47	net = dev_net(state->in ? state->in : state->out);
48	return ipt_do_table(skb, ops->hooknum, state, net->ipv4.iptable_filter);
49}
50
51static struct nf_hook_ops *filter_ops __read_mostly;
52
53/* Default to forward because I got too much mail already. */
54static bool forward = true;
55module_param(forward, bool, 0000);
56
57static int __net_init iptable_filter_net_init(struct net *net)
58{
59	struct ipt_replace *repl;
60
61	repl = ipt_alloc_initial_table(&packet_filter);
62	if (repl == NULL)
63		return -ENOMEM;
64	/* Entry 1 is the FORWARD hook */
65	((struct ipt_standard *)repl->entries)[1].target.verdict =
66		forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
67
68	net->ipv4.iptable_filter =
69		ipt_register_table(net, &packet_filter, repl);
70	kfree(repl);
71	return PTR_ERR_OR_ZERO(net->ipv4.iptable_filter);
72}
73
74static void __net_exit iptable_filter_net_exit(struct net *net)
75{
76	ipt_unregister_table(net, net->ipv4.iptable_filter);
77}
78
79static struct pernet_operations iptable_filter_net_ops = {
80	.init = iptable_filter_net_init,
81	.exit = iptable_filter_net_exit,
82};
83
84static int __init iptable_filter_init(void)
85{
86	int ret;
87
88	ret = register_pernet_subsys(&iptable_filter_net_ops);
89	if (ret < 0)
90		return ret;
91
92	/* Register hooks */
93	filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
94	if (IS_ERR(filter_ops)) {
95		ret = PTR_ERR(filter_ops);
96		unregister_pernet_subsys(&iptable_filter_net_ops);
97	}
98
99	return ret;
100}
101
102static void __exit iptable_filter_fini(void)
103{
104	xt_hook_unlink(&packet_filter, filter_ops);
105	unregister_pernet_subsys(&iptable_filter_net_ops);
106}
107
108module_init(iptable_filter_init);
109module_exit(iptable_filter_fini);
110