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/skbuff.h>
22#include <linux/netdevice.h>
23#include <linux/inetdevice.h>
24#include <linux/if_addr.h>
25#include <linux/in.h>
26#include <linux/ip.h>
27#include <linux/netfilter.h>
28#include <net/route.h>
29
30#include <net/netfilter/nf_conntrack.h>
31#include <net/netfilter/nf_conntrack_helper.h>
32#include <net/netfilter/nf_conntrack_expect.h>
33
34#define NMBD_PORT	137
35
36MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
37MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
38MODULE_LICENSE("GPL");
39MODULE_ALIAS("ip_conntrack_netbios_ns");
40
41static unsigned int timeout __read_mostly = 3;
42module_param(timeout, uint, 0400);
43MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
44
45static int help(struct sk_buff **pskb, unsigned int protoff,
46		struct nf_conn *ct, enum ip_conntrack_info ctinfo)
47{
48	struct nf_conntrack_expect *exp;
49	struct iphdr *iph = ip_hdr(*pskb);
50	struct rtable *rt = (struct rtable *)(*pskb)->dst;
51	struct in_device *in_dev;
52	__be32 mask = 0;
53
54	/* we're only interested in locally generated packets */
55	if ((*pskb)->sk == NULL)
56		goto out;
57	if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
58		goto out;
59	if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
60		goto out;
61
62	rcu_read_lock();
63	in_dev = __in_dev_get_rcu(rt->u.dst.dev);
64	if (in_dev != NULL) {
65		for_primary_ifa(in_dev) {
66			if (ifa->ifa_broadcast == iph->daddr) {
67				mask = ifa->ifa_mask;
68				break;
69			}
70		} endfor_ifa(in_dev);
71	}
72	rcu_read_unlock();
73
74	if (mask == 0)
75		goto out;
76
77	exp = nf_conntrack_expect_alloc(ct);
78	if (exp == NULL)
79		goto out;
80
81	exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
82	exp->tuple.src.u.udp.port = htons(NMBD_PORT);
83
84	exp->mask.src.u3.ip       = mask;
85	exp->mask.src.u.udp.port  = htons(0xFFFF);
86	exp->mask.dst.u3.ip       = htonl(0xFFFFFFFF);
87	exp->mask.dst.u.udp.port  = htons(0xFFFF);
88	exp->mask.dst.protonum    = 0xFF;
89
90	exp->expectfn             = NULL;
91	exp->flags                = NF_CT_EXPECT_PERMANENT;
92	exp->helper               = NULL;
93
94	nf_conntrack_expect_related(exp);
95	nf_conntrack_expect_put(exp);
96
97	nf_ct_refresh(ct, *pskb, timeout * HZ);
98out:
99	return NF_ACCEPT;
100}
101
102static struct nf_conntrack_helper helper __read_mostly = {
103	.name			= "netbios-ns",
104	.tuple.src.l3num	= AF_INET,
105	.tuple.src.u.udp.port	= __constant_htons(NMBD_PORT),
106	.tuple.dst.protonum	= IPPROTO_UDP,
107	.mask.src.l3num		= 0xFFFF,
108	.mask.src.u.udp.port	= __constant_htons(0xFFFF),
109	.mask.dst.protonum	= 0xFF,
110	.max_expected		= 1,
111	.me			= THIS_MODULE,
112	.help			= help,
113};
114
115static int __init nf_conntrack_netbios_ns_init(void)
116{
117	helper.timeout = timeout;
118	return nf_conntrack_helper_register(&helper);
119}
120
121static void __exit nf_conntrack_netbios_ns_fini(void)
122{
123	nf_conntrack_helper_unregister(&helper);
124}
125
126module_init(nf_conntrack_netbios_ns_init);
127module_exit(nf_conntrack_netbios_ns_fini);
128