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 struct xt_match *match,
  28       const void *matchinfo,
  29       int offset,
  30       unsigned int protoff,
  31       int *hotdrop)
  32 {
  33         const struct xt_state_info *sinfo = matchinfo;
  34         enum ip_conntrack_info ctinfo;
  35         unsigned int statebit;
  36
  37         if (nf_ct_is_untracked(skb))
  38                 statebit = XT_STATE_UNTRACKED;
  39         else if (!nf_ct_get_ctinfo(skb, &ctinfo))
  40                 statebit = XT_STATE_INVALID;
  41         else
  42                 statebit = XT_STATE_BIT(ctinfo);
  43
  44         return (sinfo->statemask & statebit);
  45 }
  46
  47 static int check(const char *tablename,
  48                  const void *inf,
  49                  const struct xt_match *match,
  50                  void *matchinfo,
  51                  unsigned int matchsize,
  52                  unsigned int hook_mask)
  53 {
  54 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  55         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
  56                 printk(KERN_WARNING "can't load nf_conntrack support for "
  57                                     "proto=%d\n", match->family);
  58                 return 0;
  59         }
  60 #endif
  61         return 1;
  62 }
  63
  64 static void
  65 destroy(const struct xt_match *match, void *matchinfo, unsigned int matchsize)
  66 {
  67 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  68         nf_ct_l3proto_module_put(match->family);
  69 #endif
  70 }
  71
  72 static struct xt_match state_match = {
  73         .name           = "state",
  74         .match          = match,
  75         .checkentry     = check,
  76         .destroy        = destroy,
  77         .matchsize      = sizeof(struct xt_state_info),
  78         .family         = AF_INET,
  79         .me             = THIS_MODULE,
  80 };
  81
  82 static struct xt_match state6_match = {
  83         .name           = "state",
  84         .match          = match,
  85         .checkentry     = check,
  86         .destroy        = destroy,
  87         .matchsize      = sizeof(struct xt_state_info),
  88         .family         = AF_INET6,
  89         .me             = THIS_MODULE,
  90 };
  91
  92 static int __init xt_state_init(void)
  93 {
  94         int ret;
  95
  96         need_conntrack();
  97
  98         ret = xt_register_match(&state_match);
  99         if (ret < 0)
 100                 return ret;
 101
 102         ret = xt_register_match(&state6_match);
 103         if (ret < 0)
 104                 xt_unregister_match(&state_match);
 105
 106         return ret;
 107 }
 108
 109 static void __exit xt_state_fini(void)
 110 {
 111         xt_unregister_match(&state_match);
 112         xt_unregister_match(&state6_match);
 113 }
 114
 115 module_init(xt_state_init);
 116 module_exit(xt_state_fini);