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 	if (state->hook == 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 	return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
48 }
49 
50 static struct nf_hook_ops *filter_ops __read_mostly;
51 
52 /* Default to forward because I got too much mail already. */
53 static bool forward __read_mostly = true;
54 module_param(forward, bool, 0000);
55 
56 static int __net_init iptable_filter_table_init(struct net *net)
57 {
58 	struct ipt_replace *repl;
59 	int err;
60 
61 	if (net->ipv4.iptable_filter)
62 		return 0;
63 
64 	repl = ipt_alloc_initial_table(&packet_filter);
65 	if (repl == NULL)
66 		return -ENOMEM;
67 	/* Entry 1 is the FORWARD hook */
68 	((struct ipt_standard *)repl->entries)[1].target.verdict =
69 		forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
70 
71 	err = ipt_register_table(net, &packet_filter, repl, filter_ops,
72 				 &net->ipv4.iptable_filter);
73 	kfree(repl);
74 	return err;
75 }
76 
77 static int __net_init iptable_filter_net_init(struct net *net)
78 {
79 	if (net == &init_net || !forward)
80 		return iptable_filter_table_init(net);
81 
82 	return 0;
83 }
84 
85 static void __net_exit iptable_filter_net_exit(struct net *net)
86 {
87 	if (!net->ipv4.iptable_filter)
88 		return;
89 	ipt_unregister_table(net, net->ipv4.iptable_filter, filter_ops);
90 	net->ipv4.iptable_filter = NULL;
91 }
92 
93 static struct pernet_operations iptable_filter_net_ops = {
94 	.init = iptable_filter_net_init,
95 	.exit = iptable_filter_net_exit,
96 };
97 
98 static int __init iptable_filter_init(void)
99 {
100 	int ret;
101 
102 	filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
103 	if (IS_ERR(filter_ops))
104 		return PTR_ERR(filter_ops);
105 
106 	ret = register_pernet_subsys(&iptable_filter_net_ops);
107 	if (ret < 0)
108 		kfree(filter_ops);
109 
110 	return ret;
111 }
112 
113 static void __exit iptable_filter_fini(void)
114 {
115 	unregister_pernet_subsys(&iptable_filter_net_ops);
116 	kfree(filter_ops);
117 }
118 
119 module_init(iptable_filter_init);
120 module_exit(iptable_filter_fini);
121