// SPDX-License-Identifier: GPL-2.0-only

  /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>

   */
  
  #include <linux/module.h>

  #include <linux/udp.h>

  #include <net/netfilter/nf_conntrack_helper.h>
  #include <net/netfilter/nf_conntrack_expect.h>

  #include <net/netfilter/nf_nat_helper.h>

  #include <linux/netfilter/nf_conntrack_tftp.h>

  #define NAT_HELPER_NAME "tftp"

  MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  MODULE_DESCRIPTION("TFTP NAT helper");
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_NF_NAT_HELPER(NAT_HELPER_NAME);
  
  static struct nf_conntrack_nat_helper nat_helper_tftp =
  	NF_CT_NAT_HELPER_INIT(NAT_HELPER_NAME);

  static unsigned int help(struct sk_buff *skb,

  			 enum ip_conntrack_info ctinfo,
  			 struct nf_conntrack_expect *exp)
  {

  	const struct nf_conn *ct = exp->master;

  
  	exp->saved_proto.udp.port
  		= ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
  	exp->dir = IP_CT_DIR_REPLY;
  	exp->expectfn = nf_nat_follow_master;

  	if (nf_ct_expect_related(exp, 0) != 0) {

  		nf_ct_helper_log(skb, exp->master, "cannot add expectation");

  		return NF_DROP;

  	}

  	return NF_ACCEPT;
  }
  
  static void __exit nf_nat_tftp_fini(void)
  {

  	nf_nat_helper_unregister(&nat_helper_tftp);

  	RCU_INIT_POINTER(nf_nat_tftp_hook, NULL);

  	synchronize_rcu();
  }
  
  static int __init nf_nat_tftp_init(void)
  {

  	BUG_ON(nf_nat_tftp_hook != NULL);

  	nf_nat_helper_register(&nat_helper_tftp);

  	RCU_INIT_POINTER(nf_nat_tftp_hook, help);

  	return 0;
  }
  
  module_init(nf_nat_tftp_init);
  module_exit(nf_nat_tftp_fini);