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_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | (1 << NF_IP_LOCAL_OUT))
23
24static struct
25{
26	struct ipt_replace repl;
27	struct ipt_standard entries[3];
28	struct ipt_error term;
29} initial_table __initdata = {
30	.repl = {
31		.name = "filter",
32		.valid_hooks = FILTER_VALID_HOOKS,
33		.num_entries = 4,
34		.size = sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),
35		.hook_entry = {
36			[NF_IP_LOCAL_IN] = 0,
37			[NF_IP_FORWARD] = sizeof(struct ipt_standard),
38			[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
39		},
40		.underflow = {
41			[NF_IP_LOCAL_IN] = 0,
42			[NF_IP_FORWARD] = sizeof(struct ipt_standard),
43			[NF_IP_LOCAL_OUT] = sizeof(struct ipt_standard) * 2,
44		},
45	},
46	.entries = {
47		IPT_STANDARD_INIT(NF_ACCEPT),	/* LOCAL_IN */
48		IPT_STANDARD_INIT(NF_ACCEPT),	/* FORWARD */
49		IPT_STANDARD_INIT(NF_ACCEPT),	/* LOCAL_OUT */
50	},
51	.term = IPT_ERROR_INIT,			/* ERROR */
52};
53
54static struct xt_table packet_filter = {
55	.name		= "filter",
56	.valid_hooks	= FILTER_VALID_HOOKS,
57	.lock		= RW_LOCK_UNLOCKED,
58	.me		= THIS_MODULE,
59	.af		= AF_INET,
60};
61
62/* The work comes in here from netfilter.c. */
63static unsigned int
64ipt_hook(unsigned int hook,
65	 struct sk_buff **pskb,
66	 const struct net_device *in,
67	 const struct net_device *out,
68	 int (*okfn)(struct sk_buff *))
69{
70	return ipt_do_table(pskb, hook, in, out, &packet_filter);
71}
72
73static unsigned int
74ipt_local_out_hook(unsigned int hook,
75		   struct sk_buff **pskb,
76		   const struct net_device *in,
77		   const struct net_device *out,
78		   int (*okfn)(struct sk_buff *))
79{
80	/* root is playing with raw sockets. */
81	if ((*pskb)->len < sizeof(struct iphdr)
82	    || ip_hdrlen(*pskb) < sizeof(struct iphdr)) {
83		if (net_ratelimit())
84			printk("iptable_filter: ignoring short SOCK_RAW "
85			       "packet.\n");
86		return NF_ACCEPT;
87	}
88
89	return ipt_do_table(pskb, hook, in, out, &packet_filter);
90}
91
92static struct nf_hook_ops ipt_ops[] = {
93	{
94		.hook		= ipt_hook,
95		.owner		= THIS_MODULE,
96		.pf		= PF_INET,
97		.hooknum	= NF_IP_LOCAL_IN,
98		.priority	= NF_IP_PRI_FILTER,
99	},
100	{
101		.hook		= ipt_hook,
102		.owner		= THIS_MODULE,
103		.pf		= PF_INET,
104		.hooknum	= NF_IP_FORWARD,
105		.priority	= NF_IP_PRI_FILTER,
106	},
107	{
108		.hook		= ipt_local_out_hook,
109		.owner		= THIS_MODULE,
110		.pf		= PF_INET,
111		.hooknum	= NF_IP_LOCAL_OUT,
112		.priority	= NF_IP_PRI_FILTER,
113	},
114};
115
116/* Default to forward because I got too much mail already. */
117static int forward = NF_ACCEPT;
118module_param(forward, bool, 0000);
119
120static int __init iptable_filter_init(void)
121{
122	int ret;
123
124	if (forward < 0 || forward > NF_MAX_VERDICT) {
125		printk("iptables forward must be 0 or 1\n");
126		return -EINVAL;
127	}
128
129	/* Entry 1 is the FORWARD hook */
130	initial_table.entries[1].target.verdict = -forward - 1;
131
132	/* Register table */
133	ret = ipt_register_table(&packet_filter, &initial_table.repl);
134	if (ret < 0)
135		return ret;
136
137	/* Register hooks */
138	ret = nf_register_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
139	if (ret < 0)
140		goto cleanup_table;
141
142	return ret;
143
144 cleanup_table:
145	ipt_unregister_table(&packet_filter);
146	return ret;
147}
148
149static void __exit iptable_filter_fini(void)
150{
151	nf_unregister_hooks(ipt_ops, ARRAY_SIZE(ipt_ops));
152	ipt_unregister_table(&packet_filter);
153}
154
155module_init(iptable_filter_init);
156module_exit(iptable_filter_fini);
157