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 <net/ip.h>
  17
  18 MODULE_LICENSE("GPL");
  19 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  20 MODULE_DESCRIPTION("iptables filter table");
  21
  22 #define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
  23                             (1 << NF_INET_FORWARD) | \
  24                             (1 << NF_INET_LOCAL_OUT))
  25
  26 static const struct xt_table packet_filter = {
  27         .name           = "filter",
  28         .valid_hooks    = FILTER_VALID_HOOKS,
  29         .me             = THIS_MODULE,
  30         .af             = NFPROTO_IPV4,
  31         .priority       = NF_IP_PRI_FILTER,
  32 };
  33
  34 static unsigned int
  35 iptable_filter_hook(unsigned int hook, struct sk_buff *skb,
  36                     const struct net_device *in, const struct net_device *out,
  37                     int (*okfn)(struct sk_buff *))
  38 {
  39         const struct net *net;
  40
  41         if (hook == NF_INET_LOCAL_OUT &&
  42             (skb->len < sizeof(struct iphdr) ||
  43              ip_hdrlen(skb) < sizeof(struct iphdr)))
  44                 /* root is playing with raw sockets. */
  45                 return NF_ACCEPT;
  46
  47         net = dev_net((in != NULL) ? in : out);
  48         return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_filter);
  49 }
  50
  51 static struct nf_hook_ops *filter_ops __read_mostly;
  52
  53 /* Default to forward because I got too much mail already. */
  54 static int forward = NF_ACCEPT;
  55 module_param(forward, bool, 0000);
  56
  57 static int __net_init iptable_filter_net_init(struct net *net)
  58 {
  59         struct ipt_replace *repl;
  60
  61         repl = ipt_alloc_initial_table(&packet_filter);
  62         if (repl == NULL)
  63                 return -ENOMEM;
  64         /* Entry 1 is the FORWARD hook */
  65         ((struct ipt_standard *)repl->entries)[1].target.verdict =
  66                 -forward - 1;
  67
  68         net->ipv4.iptable_filter =
  69                 ipt_register_table(net, &packet_filter, repl);
  70         kfree(repl);
  71         if (IS_ERR(net->ipv4.iptable_filter))
  72                 return PTR_ERR(net->ipv4.iptable_filter);
  73         return 0;
  74 }
  75
  76 static void __net_exit iptable_filter_net_exit(struct net *net)
  77 {
  78         ipt_unregister_table(net, net->ipv4.iptable_filter);
  79 }
  80
  81 static struct pernet_operations iptable_filter_net_ops = {
  82         .init = iptable_filter_net_init,
  83         .exit = iptable_filter_net_exit,
  84 };
  85
  86 static int __init iptable_filter_init(void)
  87 {
  88         int ret;
  89
  90         if (forward < 0 || forward > NF_MAX_VERDICT) {
  91                 printk("iptables forward must be 0 or 1\n");
  92                 return -EINVAL;
  93         }
  94
  95         ret = register_pernet_subsys(&iptable_filter_net_ops);
  96         if (ret < 0)
  97                 return ret;
  98
  99         /* Register hooks */
 100         filter_ops = xt_hook_link(&packet_filter, iptable_filter_hook);
 101         if (IS_ERR(filter_ops)) {
 102                 ret = PTR_ERR(filter_ops);
 103                 goto cleanup_table;
 104         }
 105
 106         return ret;
 107
 108  cleanup_table:
 109         unregister_pernet_subsys(&iptable_filter_net_ops);
 110         return ret;
 111 }
 112
 113 static void __exit iptable_filter_fini(void)
 114 {
 115         xt_hook_unlink(&packet_filter, filter_ops);
 116         unregister_pernet_subsys(&iptable_filter_net_ops);
 117 }
 118
 119 module_init(iptable_filter_init);
 120 module_exit(iptable_filter_fini);