net/ipv4/netfilter/arptable_filter.c

   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);