kernel/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
  27 static const struct xt_table packet_filter = {
  28         .name           = "filter",
  29         .valid_hooks    = FILTER_VALID_HOOKS,
  30         .me             = THIS_MODULE,
  31         .af             = NFPROTO_IPV4,
  32         .priority       = NF_IP_PRI_FILTER,
  33 };
  34
  35 static unsigned int
  36 iptable_filter_hook(void *priv, struct sk_buff *skb,
  37                     const struct nf_hook_state *state)
  38 {
  39         if (state->hook == NF_INET_LOCAL_OUT &&
  40             (skb->len < sizeof(struct iphdr) ||
  41              ip_hdrlen(skb) < sizeof(struct iphdr)))
  42                 /* root is playing with raw sockets. */
  43                 return NF_ACCEPT;
  44
  45         return ipt_do_table(skb, state, state->net->ipv4.iptable_filter);
  46 }
  47
  48 static struct nf_hook_ops *filter_ops __read_mostly;
  49
  50 /* Default to forward because I got too much mail already. */
  51 static bool forward = true;
  52 module_param(forward, bool, 0000);
  53
  54 static int __net_init iptable_filter_net_init(struct net *net)
  55 {
  56         struct ipt_replace *repl;
  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         net->ipv4.iptable_filter =
  66                 ipt_register_table(net, &packet_filter, repl);
  67         kfree(repl);
  68         return PTR_ERR_OR_ZERO(net->ipv4.iptable_filter);
  69 }
  70
  71 static void __net_exit iptable_filter_net_exit(struct net *net)
  72 {
  73         ipt_unregister_table(net, net->ipv4.iptable_filter);
  74 }
  75
  76 static struct pernet_operations iptable_filter_net_ops = {
  77         .init = iptable_filter_net_init,
  78         .exit = iptable_filter_net_exit,
  79 };
  80
  81 static int __init iptable_filter_init(void)
  82 {
  83         int ret;
  84
  85         ret = register_pernet_subsys(&iptable_filter_net_ops);
  86         if (ret < 0)
  87                 return ret;
  88
  89         /* Register hooks */
  90         filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
  91         if (IS_ERR(filter_ops)) {
  92                 ret = PTR_ERR(filter_ops);
  93                 unregister_pernet_subsys(&iptable_filter_net_ops);
  94         }
  95
  96         return ret;
  97 }
  98
  99 static void __exit iptable_filter_fini(void)
 100 {
 101         xt_hook_unlink(&packet_filter, filter_ops);
 102         unregister_pernet_subsys(&iptable_filter_net_ops);
 103 }
 104
 105 module_init(iptable_filter_init);
 106 module_exit(iptable_filter_fini);