iptable_filter.c revision 48dc7865aa3db9404aedc8677d9daf8f8f469ab0 
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 struct xt_table packet_filter = {
57	.name		= "filter",
58	.valid_hooks	= FILTER_VALID_HOOKS,
59	.lock		= __RW_LOCK_UNLOCKED(packet_filter.lock),
60	.me		= THIS_MODULE,
61	.af		= AF_INET,
62};
63
64/* The work comes in here from netfilter.c. */
65static unsigned int
66ipt_local_in_hook(unsigned int hook,
67		  struct sk_buff *skb,
68		  const struct net_device *in,
69		  const struct net_device *out,
70		  int (*okfn)(struct sk_buff *))
71{
72	return ipt_do_table(skb, hook, in, out,
73			    dev_net(in)->ipv4.iptable_filter);
74}
75
76static unsigned int
77ipt_hook(unsigned int hook,
78	 struct sk_buff *skb,
79	 const struct net_device *in,
80	 const struct net_device *out,
81	 int (*okfn)(struct sk_buff *))
82{
83	return ipt_do_table(skb, hook, in, out,
84			    dev_net(in)->ipv4.iptable_filter);
85}
86
87static unsigned int
88ipt_local_out_hook(unsigned int hook,
89		   struct sk_buff *skb,
90		   const struct net_device *in,
91		   const struct net_device *out,
92		   int (*okfn)(struct sk_buff *))
93{
94	/* root is playing with raw sockets. */
95	if (skb->len < sizeof(struct iphdr) ||
96	    ip_hdrlen(skb) < sizeof(struct iphdr)) {
97		if (net_ratelimit())
98			printk("iptable_filter: ignoring short SOCK_RAW "
99			       "packet.\n");
100		return NF_ACCEPT;
101	}
102
103	return ipt_do_table(skb, hook, in, out,
104			    dev_net(out)->ipv4.iptable_filter);
105}
106
107static struct nf_hook_ops ipt_ops[] __read_mostly = {
108	{
109		.hook		= ipt_local_in_hook,
110		.owner		= THIS_MODULE,
111		.pf		= PF_INET,
112		.hooknum	= NF_INET_LOCAL_IN,
113		.priority	= NF_IP_PRI_FILTER,
114	},
115	{
116		.hook		= ipt_hook,
117		.owner		= THIS_MODULE,
118		.pf		= PF_INET,
119		.hooknum	= NF_INET_FORWARD,
120		.priority	= NF_IP_PRI_FILTER,
121	},
122	{
123		.hook		= ipt_local_out_hook,
124		.owner		= THIS_MODULE,
125		.pf		= PF_INET,
126		.hooknum	= NF_INET_LOCAL_OUT,
127		.priority	= NF_IP_PRI_FILTER,
128	},
129};
130
131/* Default to forward because I got too much mail already. */
132static int forward = NF_ACCEPT;
133module_param(forward, bool, 0000);
134
135static int __net_init iptable_filter_net_init(struct net *net)
136{
137	/* Register table */
138	net->ipv4.iptable_filter =
139		ipt_register_table(net, &packet_filter, &initial_table.repl);
140	if (IS_ERR(net->ipv4.iptable_filter))
141		return PTR_ERR(net->ipv4.iptable_filter);
142	return 0;
143}
144
145static void __net_exit iptable_filter_net_exit(struct net *net)
146{
147	ipt_unregister_table(net->ipv4.iptable_filter);
148}
149
150static struct pernet_operations iptable_filter_net_ops = {
151	.init = iptable_filter_net_init,
152	.exit = iptable_filter_net_exit,
153};
154
155static int __init iptable_filter_init(void)
156{
157	int ret;
158
159	if (forward < 0 || forward > NF_MAX_VERDICT) {
160		printk("iptables forward must be 0 or 1\n");
161		return -EINVAL;
162	}
163
164	/* Entry 1 is the FORWARD hook */
165	initial_table.entries[1].target.verdict = -forward - 1;
166
167	ret = register_pernet_subsys(&iptable_filter_net_ops);
168	if (ret < 0)
169		return ret;
170
171	/* Register hooks */
172	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
173	if (ret < 0)
174		goto cleanup_table;
175
176	return ret;
177
178 cleanup_table:
179	unregister_pernet_subsys(&iptable_filter_net_ops);
180	return ret;
181}
182
183static void __exit iptable_filter_fini(void)
184{
185	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
186	unregister_pernet_subsys(&iptable_filter_net_ops);
187}
188
189module_init(iptable_filter_init);
190module_exit(iptable_filter_fini);
191