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, state->net->ipv4.arptable_filter);
  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         if (net->ipv4.arptable_filter)
  48                 return 0;
  49
  50         repl = arpt_alloc_initial_table(&packet_filter);
  51         if (repl == NULL)
  52                 return -ENOMEM;
  53         err = arpt_register_table(net, &packet_filter, repl, arpfilter_ops,
  54                                   &net->ipv4.arptable_filter);
  55         kfree(repl);
  56         return err;
  57 }
  58
  59 static void __net_exit arptable_filter_net_exit(struct net *net)
  60 {
  61         if (!net->ipv4.arptable_filter)
  62                 return;
  63         arpt_unregister_table(net, net->ipv4.arptable_filter, arpfilter_ops);
  64         net->ipv4.arptable_filter = NULL;
  65 }
  66
  67 static struct pernet_operations arptable_filter_net_ops = {
  68         .exit = arptable_filter_net_exit,
  69 };
  70
  71 static int __init arptable_filter_init(void)
  72 {
  73         int ret;
  74
  75         arpfilter_ops = xt_hook_ops_alloc(&packet_filter, arptable_filter_hook);
  76         if (IS_ERR(arpfilter_ops))
  77                 return PTR_ERR(arpfilter_ops);
  78
  79         ret = register_pernet_subsys(&arptable_filter_net_ops);
  80         if (ret < 0) {
  81                 kfree(arpfilter_ops);
  82                 return ret;
  83         }
  84
  85         ret = arptable_filter_table_init(&init_net);
  86         if (ret) {
  87                 unregister_pernet_subsys(&arptable_filter_net_ops);
  88                 kfree(arpfilter_ops);
  89         }
  90
  91         return ret;
  92 }
  93
  94 static void __exit arptable_filter_fini(void)
  95 {
  96         unregister_pernet_subsys(&arptable_filter_net_ops);
  97         kfree(arpfilter_ops);
  98 }
  99
 100 module_init(arptable_filter_init);
 101 module_exit(arptable_filter_fini);