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 
19 MODULE_LICENSE("GPL");
20 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
21 MODULE_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 static int __net_init iptable_filter_table_init(struct net *net);
27 
28 static const struct xt_table packet_filter = {
29 	.name		= "filter",
30 	.valid_hooks	= FILTER_VALID_HOOKS,
31 	.me		= THIS_MODULE,
32 	.af		= NFPROTO_IPV4,
33 	.priority	= NF_IP_PRI_FILTER,
34 	.table_init	= iptable_filter_table_init,
35 };
36 
37 static unsigned int
38 iptable_filter_hook(void *priv, struct sk_buff *skb,
39 		    const struct nf_hook_state *state)
40 {
41 	return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
42 }
43 
44 static struct nf_hook_ops *filter_ops __read_mostly;
45 
46 /* Default to forward because I got too much mail already. */
47 static bool forward __read_mostly = true;
48 module_param(forward, bool, 0000);
49 
50 static int __net_init iptable_filter_table_init(struct net *net)
51 {
52 	struct ipt_replace *repl;
53 	int err;
54 
55 	if (net->ipv4.iptable_filter)
56 		return 0;
57 
58 	repl = ipt_alloc_initial_table(&packet_filter);
59 	if (repl == NULL)
60 		return -ENOMEM;
61 	/* Entry 1 is the FORWARD hook */
62 	((struct ipt_standard *)repl->entries)[1].target.verdict =
63 		forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
64 
65 	err = ipt_register_table(net, &packet_filter, repl, filter_ops,
66 				 &net->ipv4.iptable_filter);
67 	kfree(repl);
68 	return err;
69 }
70 
71 static int __net_init iptable_filter_net_init(struct net *net)
72 {
73 	if (net == &init_net || !forward)
74 		return iptable_filter_table_init(net);
75 
76 	return 0;
77 }
78 
79 static void __net_exit iptable_filter_net_exit(struct net *net)
80 {
81 	if (!net->ipv4.iptable_filter)
82 		return;
83 	ipt_unregister_table(net, net->ipv4.iptable_filter, filter_ops);
84 	net->ipv4.iptable_filter = NULL;
85 }
86 
87 static struct pernet_operations iptable_filter_net_ops = {
88 	.init = iptable_filter_net_init,
89 	.exit = iptable_filter_net_exit,
90 };
91 
92 static int __init iptable_filter_init(void)
93 {
94 	int ret;
95 
96 	filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
97 	if (IS_ERR(filter_ops))
98 		return PTR_ERR(filter_ops);
99 
100 	ret = register_pernet_subsys(&iptable_filter_net_ops);
101 	if (ret < 0)
102 		kfree(filter_ops);
103 
104 	return ret;
105 }
106 
107 static void __exit iptable_filter_fini(void)
108 {
109 	unregister_pernet_subsys(&iptable_filter_net_ops);
110 	kfree(filter_ops);
111 }
112 
113 module_init(iptable_filter_init);
114 module_exit(iptable_filter_fini);
115