net/netfilter/xt_state.c

   1 /* Kernel module to match connection tracking information. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2005 Netfilter Core Team <coreteam@netfilter.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <net/netfilter/nf_conntrack_compat.h>
  14 #include <linux/netfilter/x_tables.h>
  15 #include <linux/netfilter/xt_state.h>
  16
  17 MODULE_LICENSE("GPL");
  18 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  19 MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
  20 MODULE_ALIAS("ipt_state");
  21 MODULE_ALIAS("ip6t_state");
  22
  23 static int
  24 match(const struct sk_buff *skb,
  25       const struct net_device *in,
  26       const struct net_device *out,
  27       const void *matchinfo,
  28       int offset,
  29       unsigned int protoff,
  30       int *hotdrop)
  31 {
  32         const struct xt_state_info *sinfo = matchinfo;
  33         enum ip_conntrack_info ctinfo;
  34         unsigned int statebit;
  35
  36         if (nf_ct_is_untracked(skb))
  37                 statebit = XT_STATE_UNTRACKED;
  38         else if (!nf_ct_get_ctinfo(skb, &ctinfo))
  39                 statebit = XT_STATE_INVALID;
  40         else
  41                 statebit = XT_STATE_BIT(ctinfo);
  42
  43         return (sinfo->statemask & statebit);
  44 }
  45
  46 static int check(const char *tablename,
  47                  const void *ip,
  48                  void *matchinfo,
  49                  unsigned int matchsize,
  50                  unsigned int hook_mask)
  51 {
  52         if (matchsize != XT_ALIGN(sizeof(struct xt_state_info)))
  53                 return 0;
  54
  55         return 1;
  56 }
  57
  58 static struct xt_match state_match = {
  59         .name           = "state",
  60         .match          = &match,
  61         .checkentry     = &check,
  62         .me             = THIS_MODULE,
  63 };
  64
  65 static struct xt_match state6_match = {
  66         .name           = "state",
  67         .match          = &match,
  68         .checkentry     = &check,
  69         .me             = THIS_MODULE,
  70 };
  71
  72 static int __init init(void)
  73 {
  74         int ret;
  75
  76         need_conntrack();
  77
  78         ret = xt_register_match(AF_INET, &state_match);
  79         if (ret < 0)
  80                 return ret;
  81
  82         ret = xt_register_match(AF_INET6, &state6_match);
  83         if (ret < 0)
  84                 xt_unregister_match(AF_INET,&state_match);
  85
  86         return ret;
  87 }
  88
  89 static void __exit fini(void)
  90 {
  91         xt_unregister_match(AF_INET, &state_match);
  92         xt_unregister_match(AF_INET6, &state6_match);
  93 }
  94
  95 module_init(init);
  96 module_exit(fini);