net/ipv4/netfilter/arptable_filter.c

   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 const struct xt_table packet_filter = {
  22         .name           = "filter",
  23         .valid_hooks    = FILTER_VALID_HOOKS,
  24         .me             = THIS_MODULE,
  25         .af             = NFPROTO_ARP,
  26         .priority       = NF_IP_PRI_FILTER,
  27 };
  28
  29 /* The work comes in here from netfilter.c */
  30 static unsigned int
  31 arptable_filter_hook(void *priv, struct sk_buff *skb,
  32                      const struct nf_hook_state *state)
  33 {
  34         return arpt_do_table(skb, state, priv);
  35 }
  36
  37 static struct nf_hook_ops *arpfilter_ops __read_mostly;
  38
  39 static int arptable_filter_table_init(struct net *net)
  40 {
  41         struct arpt_replace *repl;
  42         int err;
  43
  44         repl = arpt_alloc_initial_table(&packet_filter);
  45         if (repl == NULL)
  46                 return -ENOMEM;
  47         err = arpt_register_table(net, &packet_filter, repl, arpfilter_ops);
  48         kfree(repl);
  49         return err;
  50 }
  51
  52 static void __net_exit arptable_filter_net_pre_exit(struct net *net)
  53 {
  54         arpt_unregister_table_pre_exit(net, "filter");
  55 }
  56
  57 static void __net_exit arptable_filter_net_exit(struct net *net)
  58 {
  59         arpt_unregister_table(net, "filter");
  60 }
  61
  62 static struct pernet_operations arptable_filter_net_ops = {
  63         .exit = arptable_filter_net_exit,
  64         .pre_exit = arptable_filter_net_pre_exit,
  65 };
  66
  67 static int __init arptable_filter_init(void)
  68 {
  69         int ret = xt_register_template(&packet_filter,
  70                                        arptable_filter_table_init);
  71
  72         if (ret < 0)
  73                 return ret;
  74
  75         arpfilter_ops = xt_hook_ops_alloc(&packet_filter, arptable_filter_hook);
  76         if (IS_ERR(arpfilter_ops)) {
  77                 xt_unregister_template(&packet_filter);
  78                 return PTR_ERR(arpfilter_ops);
  79         }
  80
  81         ret = register_pernet_subsys(&arptable_filter_net_ops);
  82         if (ret < 0) {
  83                 xt_unregister_template(&packet_filter);
  84                 kfree(arpfilter_ops);
  85                 return ret;
  86         }
  87
  88         return ret;
  89 }
  90
  91 static void __exit arptable_filter_fini(void)
  92 {
  93         unregister_pernet_subsys(&arptable_filter_net_ops);
  94         xt_unregister_template(&packet_filter);
  95         kfree(arpfilter_ops);
  96 }
  97
  98 module_init(arptable_filter_init);
  99 module_exit(arptable_filter_fini);