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, const struct net_device *in,
  25          const struct net_device *out, const struct xt_match *match,
  26          const void *matchinfo, int offset, unsigned int protoff,
  27          bool *hotdrop)
  28 {
  29         const struct xt_state_info *sinfo = matchinfo;
  30         enum ip_conntrack_info ctinfo;
  31         unsigned int statebit;
  32
  33         if (nf_ct_is_untracked(skb))
  34                 statebit = XT_STATE_UNTRACKED;
  35         else if (!nf_ct_get(skb, &ctinfo))
  36                 statebit = XT_STATE_INVALID;
  37         else
  38                 statebit = XT_STATE_BIT(ctinfo);
  39
  40         return (sinfo->statemask & statebit);
  41 }
  42
  43 static bool
  44 state_mt_check(const char *tablename, const void *inf,
  45                const struct xt_match *match, void *matchinfo,
  46                unsigned int hook_mask)
  47 {
  48         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
  49                 printk(KERN_WARNING "can't load conntrack support for "
  50                                     "proto=%u\n", match->family);
  51                 return false;
  52         }
  53         return true;
  54 }
  55
  56 static void state_mt_destroy(const struct xt_match *match, void *matchinfo)
  57 {
  58         nf_ct_l3proto_module_put(match->family);
  59 }
  60
  61 static struct xt_match state_mt_reg[] __read_mostly = {
  62         {
  63                 .name           = "state",
  64                 .family         = AF_INET,
  65                 .checkentry     = state_mt_check,
  66                 .match          = state_mt,
  67                 .destroy        = state_mt_destroy,
  68                 .matchsize      = sizeof(struct xt_state_info),
  69                 .me             = THIS_MODULE,
  70         },
  71         {
  72                 .name           = "state",
  73                 .family         = AF_INET6,
  74                 .checkentry     = state_mt_check,
  75                 .match          = state_mt,
  76                 .destroy        = state_mt_destroy,
  77                 .matchsize      = sizeof(struct xt_state_info),
  78                 .me             = THIS_MODULE,
  79         },
  80 };
  81
  82 static int __init state_mt_init(void)
  83 {
  84         return xt_register_matches(state_mt_reg, ARRAY_SIZE(state_mt_reg));
  85 }
  86
  87 static void __exit state_mt_exit(void)
  88 {
  89         xt_unregister_matches(state_mt_reg, ARRAY_SIZE(state_mt_reg));
  90 }
  91
  92 module_init(state_mt_init);
  93 module_exit(state_mt_exit);