1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *      NetBIOS name service broadcast connection tracking helper
4 *
5 *      (c) 2005 Patrick McHardy <kaber@trash.net>
6 */
7/*
8 *      This helper tracks locally originating NetBIOS name service
9 *      requests by issuing permanent expectations (valid until
10 *      timing out) matching all reply connections from the
11 *      destination network. The only NetBIOS specific thing is
12 *      actually the port number.
13 */
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/init.h>
17#include <linux/in.h>
18
19#include <net/netfilter/nf_conntrack.h>
20#include <net/netfilter/nf_conntrack_helper.h>
21#include <net/netfilter/nf_conntrack_expect.h>
22
23#define HELPER_NAME	"netbios-ns"
24#define NMBD_PORT	137
25
26MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
27MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
28MODULE_LICENSE("GPL");
29MODULE_ALIAS("ip_conntrack_netbios_ns");
30MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
31
32static unsigned int timeout __read_mostly = 3;
33module_param(timeout, uint, 0400);
34MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
35
36static struct nf_conntrack_expect_policy exp_policy = {
37	.max_expected	= 1,
38};
39
40static int netbios_ns_help(struct sk_buff *skb, unsigned int protoff,
41			   struct nf_conn *ct,
42			   enum ip_conntrack_info ctinfo)
43{
44	return nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout);
45}
46
47static struct nf_conntrack_helper helper __read_mostly = {
48	.name			= HELPER_NAME,
49	.tuple.src.l3num	= NFPROTO_IPV4,
50	.tuple.src.u.udp.port	= cpu_to_be16(NMBD_PORT),
51	.tuple.dst.protonum	= IPPROTO_UDP,
52	.me			= THIS_MODULE,
53	.help			= netbios_ns_help,
54	.expect_policy		= &exp_policy,
55};
56
57static int __init nf_conntrack_netbios_ns_init(void)
58{
59	NF_CT_HELPER_BUILD_BUG_ON(0);
60
61	exp_policy.timeout = timeout;
62	return nf_conntrack_helper_register(&helper);
63}
64
65static void __exit nf_conntrack_netbios_ns_fini(void)
66{
67	nf_conntrack_helper_unregister(&helper);
68}
69
70module_init(nf_conntrack_netbios_ns_init);
71module_exit(nf_conntrack_netbios_ns_fini);
72