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