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 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(unsigned int hook, struct sk_buff *skb,
  31                      const struct net_device *in, const struct net_device *out,
  32                      int (*okfn)(struct sk_buff *))
  33 {
  34         const struct net *net = dev_net((in != NULL) ? in : out);
  35
  36         return arpt_do_table(skb, hook, in, out, net->ipv4.arptable_filter);
  37 }
  38
  39 static struct nf_hook_ops *arpfilter_ops __read_mostly;
  40
  41 static int __net_init arptable_filter_net_init(struct net *net)
  42 {
  43         struct arpt_replace *repl;
  44
  45         repl = arpt_alloc_initial_table(&packet_filter);
  46         if (repl == NULL)
  47                 return -ENOMEM;
  48         net->ipv4.arptable_filter =
  49                 arpt_register_table(net, &packet_filter, repl);
  50         kfree(repl);
  51         if (IS_ERR(net->ipv4.arptable_filter))
  52                 return PTR_ERR(net->ipv4.arptable_filter);
  53         return 0;
  54 }
  55
  56 static void __net_exit arptable_filter_net_exit(struct net *net)
  57 {
  58         arpt_unregister_table(net->ipv4.arptable_filter);
  59 }
  60
  61 static struct pernet_operations arptable_filter_net_ops = {
  62         .init = arptable_filter_net_init,
  63         .exit = arptable_filter_net_exit,
  64 };
  65
  66 static int __init arptable_filter_init(void)
  67 {
  68         int ret;
  69
  70         ret = register_pernet_subsys(&arptable_filter_net_ops);
  71         if (ret < 0)
  72                 return ret;
  73
  74         arpfilter_ops = xt_hook_link(&packet_filter, arptable_filter_hook);
  75         if (IS_ERR(arpfilter_ops)) {
  76                 ret = PTR_ERR(arpfilter_ops);
  77                 goto cleanup_table;
  78         }
  79         return ret;
  80
  81 cleanup_table:
  82         unregister_pernet_subsys(&arptable_filter_net_ops);
  83         return ret;
  84 }
  85
  86 static void __exit arptable_filter_fini(void)
  87 {
  88         xt_hook_unlink(&packet_filter, arpfilter_ops);
  89         unregister_pernet_subsys(&arptable_filter_net_ops);
  90 }
  91
  92 module_init(arptable_filter_init);
  93 module_exit(arptable_filter_fini);