// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   *      NetBIOS name service broadcast connection tracking helper
   *
   *      (c) 2005 Patrick McHardy <kaber@trash.net>

   */
  /*
   *      This helper tracks locally originating NetBIOS name service
   *      requests by issuing permanent expectations (valid until
   *      timing out) matching all reply connections from the
   *      destination network. The only NetBIOS specific thing is
   *      actually the port number.
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>

  #include <linux/in.h>

  
  #include <net/netfilter/nf_conntrack.h>
  #include <net/netfilter/nf_conntrack_helper.h>
  #include <net/netfilter/nf_conntrack_expect.h>
  
  #define NMBD_PORT	137
  
  MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("ip_conntrack_netbios_ns");

  MODULE_ALIAS_NFCT_HELPER("netbios_ns");

  
  static unsigned int timeout __read_mostly = 3;

  module_param(timeout, uint, 0400);

  MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");

  static struct nf_conntrack_expect_policy exp_policy = {
  	.max_expected	= 1,
  };

  static int netbios_ns_help(struct sk_buff *skb, unsigned int protoff,

  			   struct nf_conn *ct,
  			   enum ip_conntrack_info ctinfo)

  {

  	return nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);

  }

  static struct nf_conntrack_helper helper __read_mostly = {
  	.name			= "netbios-ns",

  	.tuple.src.l3num	= NFPROTO_IPV4,

  	.tuple.src.u.udp.port	= cpu_to_be16(NMBD_PORT),

  	.tuple.dst.protonum	= IPPROTO_UDP,

  	.me			= THIS_MODULE,

  	.help			= netbios_ns_help,

  	.expect_policy		= &exp_policy,

  };
  
  static int __init nf_conntrack_netbios_ns_init(void)
  {

  	NF_CT_HELPER_BUILD_BUG_ON(0);

  	exp_policy.timeout = timeout;

  	return nf_conntrack_helper_register(&helper);
  }
  
  static void __exit nf_conntrack_netbios_ns_fini(void)
  {
  	nf_conntrack_helper_unregister(&helper);
  }
  
  module_init(nf_conntrack_netbios_ns_init);
  module_exit(nf_conntrack_netbios_ns_fini);