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 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, priv);
  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         repl = arpt_alloc_initial_table(&packet_filter);
  48         if (repl == NULL)
  49                 return -ENOMEM;
  50         err = arpt_register_table(net, &packet_filter, repl, arpfilter_ops);
  51         kfree(repl);
  52         return err;
  53 }
  54
  55 static void __net_exit arptable_filter_net_pre_exit(struct net *net)
  56 {
  57         arpt_unregister_table_pre_exit(net, "filter");
  58 }
  59
  60 static void __net_exit arptable_filter_net_exit(struct net *net)
  61 {
  62         arpt_unregister_table(net, "filter");
  63 }
  64
  65 static struct pernet_operations arptable_filter_net_ops = {
  66         .exit = arptable_filter_net_exit,
  67         .pre_exit = arptable_filter_net_pre_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         ret = arptable_filter_table_init(&init_net);
  85         if (ret) {
  86                 unregister_pernet_subsys(&arptable_filter_net_ops);
  87                 kfree(arpfilter_ops);
  88         }
  89
  90         return ret;
  91 }
  92
  93 static void __exit arptable_filter_fini(void)
  94 {
  95         unregister_pernet_subsys(&arptable_filter_net_ops);
  96         kfree(arpfilter_ops);
  97 }
  98
  99 module_init(arptable_filter_init);
 100 module_exit(arptable_filter_fini);