net/ipv4/netfilter/iptable_filter.c

   1 /*
   2  * This is the 1999 rewrite of IP Firewalling, aiming for kernel 2.3.x.
   3  *
   4  * Copyright (C) 1999 Paul `Rusty' Russell & Michael J. Neuling
   5  * Copyright (C) 2000-2004 Netfilter Core Team <coreteam@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/netfilter_ipv4/ip_tables.h>
  16 #include <linux/slab.h>
  17 #include <net/ip.h>
  18
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  21 MODULE_DESCRIPTION("iptables filter table");
  22
  23 #define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
  24                             (1 << NF_INET_FORWARD) | \
  25                             (1 << NF_INET_LOCAL_OUT))
  26 static int __net_init iptable_filter_table_init(struct net *net);
  27
  28 static const struct xt_table packet_filter = {
  29         .name           = "filter",
  30         .valid_hooks    = FILTER_VALID_HOOKS,
  31         .me             = THIS_MODULE,
  32         .af             = NFPROTO_IPV4,
  33         .priority       = NF_IP_PRI_FILTER,
  34         .table_init     = iptable_filter_table_init,
  35 };
  36
  37 static unsigned int
  38 iptable_filter_hook(void *priv, struct sk_buff *skb,
  39                     const struct nf_hook_state *state)
  40 {
  41         return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
  42 }
  43
  44 static struct nf_hook_ops *filter_ops __read_mostly;
  45
  46 /* Default to forward because I got too much mail already. */
  47 static bool forward __read_mostly = true;
  48 module_param(forward, bool, 0000);
  49
  50 static int __net_init iptable_filter_table_init(struct net *net)
  51 {
  52         struct ipt_replace *repl;
  53         int err;
  54
  55         if (net->ipv4.iptable_filter)
  56                 return 0;
  57
  58         repl = ipt_alloc_initial_table(&packet_filter);
  59         if (repl == NULL)
  60                 return -ENOMEM;
  61         /* Entry 1 is the FORWARD hook */
  62         ((struct ipt_standard *)repl->entries)[1].target.verdict =
  63                 forward ? -NF_ACCEPT - 1 : -NF_DROP - 1;
  64
  65         err = ipt_register_table(net, &packet_filter, repl, filter_ops,
  66                                  &net->ipv4.iptable_filter);
  67         kfree(repl);
  68         return err;
  69 }
  70
  71 static int __net_init iptable_filter_net_init(struct net *net)
  72 {
  73         if (net == &init_net || !forward)
  74                 return iptable_filter_table_init(net);
  75
  76         return 0;
  77 }
  78
  79 static void __net_exit iptable_filter_net_exit(struct net *net)
  80 {
  81         if (!net->ipv4.iptable_filter)
  82                 return;
  83         ipt_unregister_table(net, net->ipv4.iptable_filter, filter_ops);
  84         net->ipv4.iptable_filter = NULL;
  85 }
  86
  87 static struct pernet_operations iptable_filter_net_ops = {
  88         .init = iptable_filter_net_init,
  89         .exit = iptable_filter_net_exit,
  90 };
  91
  92 static int __init iptable_filter_init(void)
  93 {
  94         int ret;
  95
  96         filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
  97         if (IS_ERR(filter_ops))
  98                 return PTR_ERR(filter_ops);
  99
 100         ret = register_pernet_subsys(&iptable_filter_net_ops);
 101         if (ret < 0)
 102                 kfree(filter_ops);
 103
 104         return ret;
 105 }
 106
 107 static void __exit iptable_filter_fini(void)
 108 {
 109         unregister_pernet_subsys(&iptable_filter_net_ops);
 110         kfree(filter_ops);
 111 }
 112
 113 module_init(iptable_filter_init);
 114 module_exit(iptable_filter_fini);