Commit 92703eee authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[NETFILTER]: nf_conntrack: add NetBIOS name service helper port



Add nf_conntrack port of the NetBIOS name service conntrack helper.
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 869f37d8
......@@ -194,6 +194,25 @@ config NF_CONNTRACK_IRC
To compile it as a module, choose M here. If unsure, say N.
config NF_CONNTRACK_NETBIOS_NS
tristate "NetBIOS name service protocol support (EXPERIMENTAL)"
depends on EXPERIMENTAL && NF_CONNTRACK
help
NetBIOS name service requests are sent as broadcast messages from an
unprivileged port and responded to with unicast messages to the
same port. This make them hard to firewall properly because connection
tracking doesn't deal with broadcasts. This helper tracks locally
originating NetBIOS name service requests and the corresponding
responses. It relies on correct IP address configuration, specifically
netmask and broadcast address. When properly configured, the output
of "ip address show" should look similar to this:
$ ip -4 address show eth0
4: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
inet 172.16.2.252/24 brd 172.16.2.255 scope global eth0
To compile it as a module, choose M here. If unsure, say N.
config NF_CT_NETLINK
tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK
......
......@@ -26,6 +26,7 @@ obj-$(CONFIG_NF_CONNTRACK_AMANDA) += nf_conntrack_amanda.o
obj-$(CONFIG_NF_CONNTRACK_FTP) += nf_conntrack_ftp.o
obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
# generic X tables
obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
......
/*
* 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 <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#define NMBD_PORT 137
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_conntrack_netbios_ns");
static unsigned int timeout __read_mostly = 3;
module_param(timeout, uint, 0400);
MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
static int help(struct sk_buff **pskb, unsigned int protoff,
struct nf_conn *ct, enum ip_conntrack_info ctinfo)
{
struct nf_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 = nf_conntrack_expect_alloc(ct);
if (exp == NULL)
goto out;
exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
exp->tuple.src.u.udp.port = htons(NMBD_PORT);
exp->mask.src.u3.ip = mask;
exp->mask.src.u.udp.port = htons(0xFFFF);
exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
exp->mask.dst.u.udp.port = htons(0xFFFF);
exp->mask.dst.protonum = 0xFF;
exp->expectfn = NULL;
exp->flags = NF_CT_EXPECT_PERMANENT;
nf_conntrack_expect_related(exp);
nf_conntrack_expect_put(exp);
nf_ct_refresh(ct, *pskb, timeout * HZ);
out:
return NF_ACCEPT;
}
static struct nf_conntrack_helper helper __read_mostly = {
.name = "netbios-ns",
.tuple.src.l3num = AF_INET,
.tuple.src.u.udp.port = __constant_htons(NMBD_PORT),
.tuple.dst.protonum = IPPROTO_UDP,
.mask.src.l3num = 0xFFFF,
.mask.src.u.udp.port = __constant_htons(0xFFFF),
.mask.dst.protonum = 0xFF,
.max_expected = 1,
.me = THIS_MODULE,
.help = help,
};
static int __init nf_conntrack_netbios_ns_init(void)
{
helper.timeout = timeout;
return nf_conntrack_helper_register(&helper);
}
static void __exit nf_conntrack_netbios_ns_fini(void)
{
nf_conntrack_helper_unregister(&helper);
}
module_init(nf_conntrack_netbios_ns_init);
module_exit(nf_conntrack_netbios_ns_fini);
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