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);
72