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.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 bool
  24 state_mt(const struct sk_buff *skb, struct xt_action_param *par)
  25 {
  26         const struct xt_state_info *sinfo = par->matchinfo;
  27         enum ip_conntrack_info ctinfo;
  28         unsigned int statebit;
  29
  30         if (nf_ct_is_untracked(skb))
  31                 statebit = XT_STATE_UNTRACKED;
  32         else if (!nf_ct_get(skb, &ctinfo))
  33                 statebit = XT_STATE_INVALID;
  34         else
  35                 statebit = XT_STATE_BIT(ctinfo);
  36
  37         return (sinfo->statemask & statebit);
  38 }
  39
  40 static int state_mt_check(const struct xt_mtchk_param *par)
  41 {
  42         int ret;
  43
  44         ret = nf_ct_l3proto_try_module_get(par->family);
  45         if (ret < 0)
  46                 pr_info("cannot load conntrack support for proto=%u\n",
  47                         par->family);
  48         return ret;
  49 }
  50
  51 static void state_mt_destroy(const struct xt_mtdtor_param *par)
  52 {
  53         nf_ct_l3proto_module_put(par->family);
  54 }
  55
  56 static struct xt_match state_mt_reg __read_mostly = {
  57         .name       = "state",
  58         .family     = NFPROTO_UNSPEC,
  59         .checkentry = state_mt_check,
  60         .match      = state_mt,
  61         .destroy    = state_mt_destroy,
  62         .matchsize  = sizeof(struct xt_state_info),
  63         .me         = THIS_MODULE,
  64 };
  65
  66 static int __init state_mt_init(void)
  67 {
  68         return xt_register_match(&state_mt_reg);
  69 }
  70
  71 static void __exit state_mt_exit(void)
  72 {
  73         xt_unregister_match(&state_mt_reg);
  74 }
  75
  76 module_init(state_mt_init);
  77 module_exit(state_mt_exit);