net/netfilter/xt_state.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Kernel module to match connection tracking information. */
   3
   4 /* (C) 1999-2001 Paul `Rusty' Russell
   5  * (C) 2002-2005 Netfilter Core Team <coreteam@netfilter.org>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/skbuff.h>
  10 #include <net/netfilter/nf_conntrack.h>
  11 #include <linux/netfilter/x_tables.h>
  12 #include <linux/netfilter/xt_state.h>
  13
  14 MODULE_LICENSE("GPL");
  15 MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");
  16 MODULE_DESCRIPTION("ip[6]_tables connection tracking state match module");
  17 MODULE_ALIAS("ipt_state");
  18 MODULE_ALIAS("ip6t_state");
  19
  20 static bool
  21 state_mt(const struct sk_buff *skb, struct xt_action_param *par)
  22 {
  23         const struct xt_state_info *sinfo = par->matchinfo;
  24         enum ip_conntrack_info ctinfo;
  25         unsigned int statebit;
  26         struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  27
  28         if (ct)
  29                 statebit = XT_STATE_BIT(ctinfo);
  30         else if (ctinfo == IP_CT_UNTRACKED)
  31                 statebit = XT_STATE_UNTRACKED;
  32         else
  33                 statebit = XT_STATE_INVALID;
  34
  35         return (sinfo->statemask & statebit);
  36 }
  37
  38 static int state_mt_check(const struct xt_mtchk_param *par)
  39 {
  40         int ret;
  41
  42         ret = nf_ct_netns_get(par->net, par->family);
  43         if (ret < 0)
  44                 pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
  45                                     par->family);
  46         return ret;
  47 }
  48
  49 static void state_mt_destroy(const struct xt_mtdtor_param *par)
  50 {
  51         nf_ct_netns_put(par->net, par->family);
  52 }
  53
  54 static struct xt_match state_mt_reg __read_mostly = {
  55         .name       = "state",
  56         .family     = NFPROTO_UNSPEC,
  57         .checkentry = state_mt_check,
  58         .match      = state_mt,
  59         .destroy    = state_mt_destroy,
  60         .matchsize  = sizeof(struct xt_state_info),
  61         .me         = THIS_MODULE,
  62 };
  63
  64 static int __init state_mt_init(void)
  65 {
  66         return xt_register_match(&state_mt_reg);
  67 }
  68
  69 static void __exit state_mt_exit(void)
  70 {
  71         xt_unregister_match(&state_mt_reg);
  72 }
  73
  74 module_init(state_mt_init);
  75 module_exit(state_mt_exit);