net/netfilter/nf_conntrack_netbios_ns.c

   1 /*
   2  *      NetBIOS name service broadcast connection tracking helper
   3  *
   4  *      (c) 2005 Patrick McHardy <kaber@trash.net>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11 /*
  12  *      This helper tracks locally originating NetBIOS name service
  13  *      requests by issuing permanent expectations (valid until
  14  *      timing out) matching all reply connections from the
  15  *      destination network. The only NetBIOS specific thing is
  16  *      actually the port number.
  17  */
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/in.h>
  22
  23 #include <net/netfilter/nf_conntrack.h>
  24 #include <net/netfilter/nf_conntrack_helper.h>
  25 #include <net/netfilter/nf_conntrack_expect.h>
  26
  27 #define NMBD_PORT       137
  28
  29 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  30 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  31 MODULE_LICENSE("GPL");
  32 MODULE_ALIAS("ip_conntrack_netbios_ns");
  33 MODULE_ALIAS_NFCT_HELPER("netbios_ns");
  34
  35 static unsigned int timeout __read_mostly = 3;
  36 module_param(timeout, uint, S_IRUSR);
  37 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  38
  39 static struct nf_conntrack_expect_policy exp_policy = {
  40         .max_expected   = 1,
  41 };
  42
  43 static int netbios_ns_help(struct sk_buff *skb, unsigned int protoff,
  44                    struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  45 {
  46         return nf_conntrack_broadcast_help(skb, protoff, ct, ctinfo, timeout);
  47 }
  48
  49 static struct nf_conntrack_helper helper __read_mostly = {
  50         .name                   = "netbios-ns",
  51         .tuple.src.l3num        = NFPROTO_IPV4,
  52         .tuple.src.u.udp.port   = cpu_to_be16(NMBD_PORT),
  53         .tuple.dst.protonum     = IPPROTO_UDP,
  54         .me                     = THIS_MODULE,
  55         .help                   = netbios_ns_help,
  56         .expect_policy          = &exp_policy,
  57 };
  58
  59 static int __init nf_conntrack_netbios_ns_init(void)
  60 {
  61         exp_policy.timeout = timeout;
  62         return nf_conntrack_helper_register(&helper);
  63 }
  64
  65 static void __exit nf_conntrack_netbios_ns_fini(void)
  66 {
  67         nf_conntrack_helper_unregister(&helper);
  68 }
  69
  70 module_init(nf_conntrack_netbios_ns_init);
  71 module_exit(nf_conntrack_netbios_ns_fini);