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