1 /*
2  * Filtering ARP tables module.
3  *
4  * Copyright (C) 2002 David S. Miller (davem@redhat.com)
5  *
6  */
7 
8 #include <linux/module.h>
9 #include <linux/netfilter/x_tables.h>
10 #include <linux/netfilter_arp/arp_tables.h>
11 #include <linux/slab.h>
12 
13 MODULE_LICENSE("GPL");
14 MODULE_AUTHOR("David S. Miller <davem@redhat.com>");
15 MODULE_DESCRIPTION("arptables filter table");
16 
17 #define FILTER_VALID_HOOKS ((1 << NF_ARP_IN) | (1 << NF_ARP_OUT) | \
18 			   (1 << NF_ARP_FORWARD))
19 
20 static const struct xt_table packet_filter = {
21 	.name		= "filter",
22 	.valid_hooks	= FILTER_VALID_HOOKS,
23 	.me		= THIS_MODULE,
24 	.af		= NFPROTO_ARP,
25 	.priority	= NF_IP_PRI_FILTER,
26 };
27 
28 /* The work comes in here from netfilter.c */
29 static unsigned int
30 arptable_filter_hook(void *priv, struct sk_buff *skb,
31 		     const struct nf_hook_state *state)
32 {
33 	return arpt_do_table(skb, state, state->net->ipv4.arptable_filter);
34 }
35 
36 static struct nf_hook_ops *arpfilter_ops __read_mostly;
37 
38 static int __net_init arptable_filter_net_init(struct net *net)
39 {
40 	struct arpt_replace *repl;
41 
42 	repl = arpt_alloc_initial_table(&packet_filter);
43 	if (repl == NULL)
44 		return -ENOMEM;
45 	net->ipv4.arptable_filter =
46 		arpt_register_table(net, &packet_filter, repl);
47 	kfree(repl);
48 	return PTR_ERR_OR_ZERO(net->ipv4.arptable_filter);
49 }
50 
51 static void __net_exit arptable_filter_net_exit(struct net *net)
52 {
53 	arpt_unregister_table(net->ipv4.arptable_filter);
54 }
55 
56 static struct pernet_operations arptable_filter_net_ops = {
57 	.init = arptable_filter_net_init,
58 	.exit = arptable_filter_net_exit,
59 };
60 
61 static int __init arptable_filter_init(void)
62 {
63 	int ret;
64 
65 	ret = register_pernet_subsys(&arptable_filter_net_ops);
66 	if (ret < 0)
67 		return ret;
68 
69 	arpfilter_ops = xt_hook_link(&packet_filter, arptable_filter_hook);
70 	if (IS_ERR(arpfilter_ops)) {
71 		ret = PTR_ERR(arpfilter_ops);
72 		goto cleanup_table;
73 	}
74 	return ret;
75 
76 cleanup_table:
77 	unregister_pernet_subsys(&arptable_filter_net_ops);
78 	return ret;
79 }
80 
81 static void __exit arptable_filter_fini(void)
82 {
83 	xt_hook_unlink(&packet_filter, arpfilter_ops);
84 	unregister_pernet_subsys(&arptable_filter_net_ops);
85 }
86 
87 module_init(arptable_filter_init);
88 module_exit(arptable_filter_fini);
89