linux/net/netfilter/xt_state.c
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   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
  17MODULE_LICENSE("GPL");
  18MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  19MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
  20MODULE_ALIAS("ipt_state");
  21MODULE_ALIAS("ip6t_state");
  22
  23static bool
  24state_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
  42static 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
  53static void state_mt_destroy(const struct xt_mtdtor_param *par)
  54{
  55        nf_ct_l3proto_module_put(par->family);
  56}
  57
  58static 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
  68static int __init state_mt_init(void)
  69{
  70        return xt_register_match(&state_mt_reg);
  71}
  72
  73static void __exit state_mt_exit(void)
  74{
  75        xt_unregister_match(&state_mt_reg);
  76}
  77
  78module_init(state_mt_init);
  79module_exit(state_mt_exit);
  80
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