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/*
* NetBIOS name service broadcast connection tracking helper
*
* (c) 2005 Patrick McHardy <kaber@trash.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
/*
* This helper tracks locally originating NetBIOS name service
* requests by issuing permanent expectations (valid until
* timing out) matching all reply connections from the
* destination network. The only NetBIOS specific thing is
* actually the port number.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/if_addr.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <net/route.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_conntrack.h>
#include <linux/netfilter_ipv4/ip_conntrack_helper.h>
#define NMBD_PORT 137
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
MODULE_LICENSE("GPL");
static unsigned int timeout = 3;
module_param(timeout, uint, 0400);
MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
static int help(struct sk_buff **pskb,
struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
{
struct ip_conntrack_expect *exp;
struct iphdr *iph = (*pskb)->nh.iph;
struct rtable *rt = (struct rtable *)(*pskb)->dst;
struct in_device *in_dev;
__be32 mask = 0;
/* we're only interested in locally generated packets */
if ((*pskb)->sk == NULL)
goto out;
if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
goto out;
if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
goto out;
rcu_read_lock();
in_dev = __in_dev_get_rcu(rt->u.dst.dev);
if (in_dev != NULL) {
for_primary_ifa(in_dev) {
if (ifa->ifa_broadcast == iph->daddr) {
mask = ifa->ifa_mask;
break;
}
} endfor_ifa(in_dev);
}
rcu_read_unlock();
if (mask == 0)
goto out;
exp = ip_conntrack_expect_alloc(ct);
if (exp == NULL)
goto out;
exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
exp->tuple.src.u.udp.port = ntohs(NMBD_PORT);
exp->mask.src.ip = mask;
exp->mask.src.u.udp.port = 0xFFFF;
exp->mask.dst.ip = 0xFFFFFFFF;
exp->mask.dst.u.udp.port = 0xFFFF;
exp->mask.dst.protonum = 0xFF;
exp->expectfn = NULL;
exp->flags = IP_CT_EXPECT_PERMANENT;
ip_conntrack_expect_related(exp);
ip_conntrack_expect_put(exp);
ip_ct_refresh(ct, *pskb, timeout * HZ);
out:
return NF_ACCEPT;
}
static struct ip_conntrack_helper helper = {
.name = "netbios-ns",
.tuple = {
.src = {
.u = {
.udp = {
.port = __constant_htons(NMBD_PORT),
}
}
},
.dst = {
.protonum = IPPROTO_UDP,
},
},
.mask = {
.src = {
.u = {
.udp = {
.port = 0xFFFF,
}
}
},
.dst = {
.protonum = 0xFF,
},
},
.max_expected = 1,
.me = THIS_MODULE,
.help = help,
};
static int __init ip_conntrack_netbios_ns_init(void)
{
helper.timeout = timeout;
return ip_conntrack_helper_register(&helper);
}
static void __exit ip_conntrack_netbios_ns_fini(void)
{
ip_conntrack_helper_unregister(&helper);
}
module_init(ip_conntrack_netbios_ns_init);
module_exit(ip_conntrack_netbios_ns_fini);
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