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 int __net_init arptable_filter_table_init(struct net *net);
21 
22 static const struct xt_table packet_filter = {
23 	.name		= "filter",
24 	.valid_hooks	= FILTER_VALID_HOOKS,
25 	.me		= THIS_MODULE,
26 	.af		= NFPROTO_ARP,
27 	.priority	= NF_IP_PRI_FILTER,
28 	.table_init	= arptable_filter_table_init,
29 };
30 
31 /* The work comes in here from netfilter.c */
32 static unsigned int
33 arptable_filter_hook(void *priv, struct sk_buff *skb,
34 		     const struct nf_hook_state *state)
35 {
36 	return arpt_do_table(skb, state, state->net->ipv4.arptable_filter);
37 }
38 
39 static struct nf_hook_ops *arpfilter_ops __read_mostly;
40 
41 static int __net_init arptable_filter_table_init(struct net *net)
42 {
43 	struct arpt_replace *repl;
44 	int err;
45 
46 	if (net->ipv4.arptable_filter)
47 		return 0;
48 
49 	repl = arpt_alloc_initial_table(&packet_filter);
50 	if (repl == NULL)
51 		return -ENOMEM;
52 	err = arpt_register_table(net, &packet_filter, repl, arpfilter_ops,
53 				  &net->ipv4.arptable_filter);
54 	kfree(repl);
55 	return err;
56 }
57 
58 static void __net_exit arptable_filter_net_exit(struct net *net)
59 {
60 	if (!net->ipv4.arptable_filter)
61 		return;
62 	arpt_unregister_table(net, net->ipv4.arptable_filter, arpfilter_ops);
63 	net->ipv4.arptable_filter = NULL;
64 }
65 
66 static struct pernet_operations arptable_filter_net_ops = {
67 	.exit = arptable_filter_net_exit,
68 };
69 
70 static int __init arptable_filter_init(void)
71 {
72 	int ret;
73 
74 	arpfilter_ops = xt_hook_ops_alloc(&packet_filter, arptable_filter_hook);
75 	if (IS_ERR(arpfilter_ops))
76 		return PTR_ERR(arpfilter_ops);
77 
78 	ret = register_pernet_subsys(&arptable_filter_net_ops);
79 	if (ret < 0) {
80 		kfree(arpfilter_ops);
81 		return ret;
82 	}
83 
84 	return ret;
85 }
86 
87 static void __exit arptable_filter_fini(void)
88 {
89 	unregister_pernet_subsys(&arptable_filter_net_ops);
90 	kfree(arpfilter_ops);
91 }
92 
93 module_init(arptable_filter_init);
94 module_exit(arptable_filter_fini);
95