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
27 static 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
35 static unsigned int
iptable_filter_hook(void * priv,struct sk_buff * skb,const struct nf_hook_state * state)36 iptable_filter_hook(void *priv, struct sk_buff *skb,
37 const struct nf_hook_state *state)
38 {
39 if (state->hook == NF_INET_LOCAL_OUT &&
40 (skb->len < sizeof(struct iphdr) ||
41 ip_hdrlen(skb) < sizeof(struct iphdr)))
42 /* root is playing with raw sockets. */
43 return NF_ACCEPT;
44
45 return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
46 }
47
48 static struct nf_hook_ops *filter_ops __read_mostly;
49
50 /* Default to forward because I got too much mail already. */
51 static bool forward = true;
52 module_param(forward, bool, 0000);
53
iptable_filter_net_init(struct net * net)54 static int __net_init iptable_filter_net_init(struct net *net)
55 {
56 struct ipt_replace *repl;
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 net->ipv4.iptable_filter =
66 ipt_register_table(net, &packet_filter, repl);
67 kfree(repl);
68 return PTR_ERR_OR_ZERO(net->ipv4.iptable_filter);
69 }
70
iptable_filter_net_exit(struct net * net)71 static void __net_exit iptable_filter_net_exit(struct net *net)
72 {
73 ipt_unregister_table(net, net->ipv4.iptable_filter);
74 }
75
76 static struct pernet_operations iptable_filter_net_ops = {
77 .init = iptable_filter_net_init,
78 .exit = iptable_filter_net_exit,
79 };
80
iptable_filter_init(void)81 static int __init iptable_filter_init(void)
82 {
83 int ret;
84
85 ret = register_pernet_subsys(&iptable_filter_net_ops);
86 if (ret < 0)
87 return ret;
88
89 /* Register hooks */
90 filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
91 if (IS_ERR(filter_ops)) {
92 ret = PTR_ERR(filter_ops);
93 unregister_pernet_subsys(&iptable_filter_net_ops);
94 }
95
96 return ret;
97 }
98
iptable_filter_fini(void)99 static void __exit iptable_filter_fini(void)
100 {
101 xt_hook_unlink(&packet_filter, filter_ops);
102 unregister_pernet_subsys(&iptable_filter_net_ops);
103 }
104
105 module_init(iptable_filter_init);
106 module_exit(iptable_filter_fini);
107