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
netbios_ns_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)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
nf_conntrack_netbios_ns_init(void)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
nf_conntrack_netbios_ns_fini(void)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