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 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       bool *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(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 bool check(const char *tablename,
  48                   const void *inf,
  49                   const struct xt_match *match,
  50                   void *matchinfo,
  51                   unsigned int hook_mask)
  52 {
  53         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
  54                 printk(KERN_WARNING "can't load conntrack support for "
  55                                     "proto=%d\n", match->family);
  56                 return false;
  57         }
  58         return true;
  59 }
  60
  61 static void
  62 destroy(const struct xt_match *match, void *matchinfo)
  63 {
  64         nf_ct_l3proto_module_put(match->family);
  65 }
  66
  67 static struct xt_match xt_state_match[] __read_mostly = {
  68         {
  69                 .name           = "state",
  70                 .family         = AF_INET,
  71                 .checkentry     = check,
  72                 .match          = match,
  73                 .destroy        = destroy,
  74                 .matchsize      = sizeof(struct xt_state_info),
  75                 .me             = THIS_MODULE,
  76         },
  77         {
  78                 .name           = "state",
  79                 .family         = AF_INET6,
  80                 .checkentry     = check,
  81                 .match          = match,
  82                 .destroy        = destroy,
  83                 .matchsize      = sizeof(struct xt_state_info),
  84                 .me             = THIS_MODULE,
  85         },
  86 };
  87
  88 static int __init xt_state_init(void)
  89 {
  90         return xt_register_matches(xt_state_match, ARRAY_SIZE(xt_state_match));
  91 }
  92
  93 static void __exit xt_state_fini(void)
  94 {
  95         xt_unregister_matches(xt_state_match, ARRAY_SIZE(xt_state_match));
  96 }
  97
  98 module_init(xt_state_init);
  99 module_exit(xt_state_fini);