1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Filtering ARP tables module.
4  *
5  * Copyright (C) 2002 David S. Miller (davem@redhat.com)
6  *
7  */
8 
9 #include <linux/module.h>
10 #include <linux/netfilter/x_tables.h>
11 #include <linux/netfilter_arp/arp_tables.h>
12 #include <linux/slab.h>
13 
14 MODULE_LICENSE("GPL");
15 MODULE_AUTHOR("David S. Miller <davem@redhat.com>");
16 MODULE_DESCRIPTION("arptables filter table");
17 
18 #define FILTER_VALID_HOOKS ((1 << NF_ARP_IN) | (1 << NF_ARP_OUT) | \
19 			   (1 << NF_ARP_FORWARD))
20 
21 static int __net_init arptable_filter_table_init(struct net *net);
22 
23 static const struct xt_table packet_filter = {
24 	.name		= "filter",
25 	.valid_hooks	= FILTER_VALID_HOOKS,
26 	.me		= THIS_MODULE,
27 	.af		= NFPROTO_ARP,
28 	.priority	= NF_IP_PRI_FILTER,
29 	.table_init	= arptable_filter_table_init,
30 };
31 
32 /* The work comes in here from netfilter.c */
33 static unsigned int
34 arptable_filter_hook(void *priv, struct sk_buff *skb,
35 		     const struct nf_hook_state *state)
36 {
37 	return arpt_do_table(skb, state, state->net->ipv4.arptable_filter);
38 }
39 
40 static struct nf_hook_ops *arpfilter_ops __read_mostly;
41 
42 static int __net_init arptable_filter_table_init(struct net *net)
43 {
44 	struct arpt_replace *repl;
45 	int err;
46 
47 	if (net->ipv4.arptable_filter)
48 		return 0;
49 
50 	repl = arpt_alloc_initial_table(&packet_filter);
51 	if (repl == NULL)
52 		return -ENOMEM;
53 	err = arpt_register_table(net, &packet_filter, repl, arpfilter_ops,
54 				  &net->ipv4.arptable_filter);
55 	kfree(repl);
56 	return err;
57 }
58 
59 static void __net_exit arptable_filter_net_exit(struct net *net)
60 {
61 	if (!net->ipv4.arptable_filter)
62 		return;
63 	arpt_unregister_table(net, net->ipv4.arptable_filter, arpfilter_ops);
64 	net->ipv4.arptable_filter = NULL;
65 }
66 
67 static struct pernet_operations arptable_filter_net_ops = {
68 	.exit = arptable_filter_net_exit,
69 };
70 
71 static int __init arptable_filter_init(void)
72 {
73 	int ret;
74 
75 	arpfilter_ops = xt_hook_ops_alloc(&packet_filter, arptable_filter_hook);
76 	if (IS_ERR(arpfilter_ops))
77 		return PTR_ERR(arpfilter_ops);
78 
79 	ret = register_pernet_subsys(&arptable_filter_net_ops);
80 	if (ret < 0) {
81 		kfree(arpfilter_ops);
82 		return ret;
83 	}
84 
85 	ret = arptable_filter_table_init(&init_net);
86 	if (ret) {
87 		unregister_pernet_subsys(&arptable_filter_net_ops);
88 		kfree(arpfilter_ops);
89 	}
90 
91 	return ret;
92 }
93 
94 static void __exit arptable_filter_fini(void)
95 {
96 	unregister_pernet_subsys(&arptable_filter_net_ops);
97 	kfree(arpfilter_ops);
98 }
99 
100 module_init(arptable_filter_init);
101 module_exit(arptable_filter_fini);
102