net/ipv4/netfilter/ip_nat_tftp.c

   1 /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu>
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License version 2 as
   5  * published by the Free Software Foundation.
   6  *
   7  * Version: 0.0.7
   8  *
   9  * Thu 21 Mar 2002 Harald Welte <laforge@gnumonks.org>
  10  *      - Port to newnat API
  11  *
  12  * This module currently supports DNAT:
  13  * iptables -t nat -A PREROUTING -d x.x.x.x -j DNAT --to-dest x.x.x.y
  14  *
  15  * and SNAT:
  16  * iptables -t nat -A POSTROUTING { -j MASQUERADE , -j SNAT --to-source x.x.x.x }
  17  *
  18  * It has not been tested with
  19  * -j SNAT --to-source x.x.x.x-x.x.x.y since I only have one external ip
  20  * If you do test this please let me know if it works or not.
  21  *
  22  */
  23
  24 #include <linux/module.h>
  25 #include <linux/netfilter_ipv4.h>
  26 #include <linux/ip.h>
  27 #include <linux/udp.h>
  28
  29 #include <linux/netfilter.h>
  30 #include <linux/netfilter_ipv4/ip_tables.h>
  31 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  32 #include <linux/netfilter_ipv4/ip_conntrack_tftp.h>
  33 #include <linux/netfilter_ipv4/ip_nat_helper.h>
  34 #include <linux/netfilter_ipv4/ip_nat_rule.h>
  35 #include <linux/moduleparam.h>
  36
  37 MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>");
  38 MODULE_DESCRIPTION("tftp NAT helper");
  39 MODULE_LICENSE("GPL");
  40
  41 static unsigned int help(struct sk_buff **pskb,
  42                          enum ip_conntrack_info ctinfo,
  43                          struct ip_conntrack_expect *exp)
  44 {
  45         struct ip_conntrack *ct = exp->master;
  46
  47         exp->saved_proto.udp.port
  48                 = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u.udp.port;
  49         exp->dir = IP_CT_DIR_REPLY;
  50         exp->expectfn = ip_nat_follow_master;
  51         if (ip_conntrack_expect_related(exp) != 0)
  52                 return NF_DROP;
  53         return NF_ACCEPT;
  54 }
  55
  56 static void __exit fini(void)
  57 {
  58         ip_nat_tftp_hook = NULL;
  59         /* Make sure noone calls it, meanwhile. */
  60         synchronize_net();
  61 }
  62
  63 static int __init init(void)
  64 {
  65         BUG_ON(ip_nat_tftp_hook);
  66         ip_nat_tftp_hook = help;
  67         return 0;
  68 }
  69
  70 module_init(init);
  71 module_exit(fini);