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[NETFILTER]: nf_conntrack: add NetBIOS name service helper port
Add nf_conntrack port of the NetBIOS name service conntrack helper. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -194,6 +194,25 @@ config NF_CONNTRACK_IRC
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To compile it as a module, choose M here. If unsure, say N.
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config NF_CONNTRACK_NETBIOS_NS
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tristate "NetBIOS name service protocol support (EXPERIMENTAL)"
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depends on EXPERIMENTAL && NF_CONNTRACK
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help
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NetBIOS name service requests are sent as broadcast messages from an
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unprivileged port and responded to with unicast messages to the
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same port. This make them hard to firewall properly because connection
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tracking doesn't deal with broadcasts. This helper tracks locally
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originating NetBIOS name service requests and the corresponding
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responses. It relies on correct IP address configuration, specifically
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netmask and broadcast address. When properly configured, the output
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of "ip address show" should look similar to this:
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$ ip -4 address show eth0
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4: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
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inet 172.16.2.252/24 brd 172.16.2.255 scope global eth0
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To compile it as a module, choose M here. If unsure, say N.
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config NF_CT_NETLINK
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tristate 'Connection tracking netlink interface (EXPERIMENTAL)'
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depends on EXPERIMENTAL && NF_CONNTRACK && NETFILTER_NETLINK
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@ -26,6 +26,7 @@ obj-$(CONFIG_NF_CONNTRACK_AMANDA) += nf_conntrack_amanda.o
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obj-$(CONFIG_NF_CONNTRACK_FTP) += nf_conntrack_ftp.o
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obj-$(CONFIG_NF_CONNTRACK_H323) += nf_conntrack_h323.o
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obj-$(CONFIG_NF_CONNTRACK_IRC) += nf_conntrack_irc.o
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obj-$(CONFIG_NF_CONNTRACK_NETBIOS_NS) += nf_conntrack_netbios_ns.o
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# generic X tables
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obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o
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125
net/netfilter/nf_conntrack_netbios_ns.c
Normal file
125
net/netfilter/nf_conntrack_netbios_ns.c
Normal file
@ -0,0 +1,125 @@
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/*
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* NetBIOS name service broadcast connection tracking helper
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*
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* (c) 2005 Patrick McHardy <kaber@trash.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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/*
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* This helper tracks locally originating NetBIOS name service
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* requests by issuing permanent expectations (valid until
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* timing out) matching all reply connections from the
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* destination network. The only NetBIOS specific thing is
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* actually the port number.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/skbuff.h>
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#include <linux/netdevice.h>
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#include <linux/inetdevice.h>
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#include <linux/if_addr.h>
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <net/route.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#define NMBD_PORT 137
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MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
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MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ip_conntrack_netbios_ns");
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static unsigned int timeout __read_mostly = 3;
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module_param(timeout, uint, 0400);
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MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
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static int help(struct sk_buff **pskb, unsigned int protoff,
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struct nf_conn *ct, enum ip_conntrack_info ctinfo)
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{
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struct nf_conntrack_expect *exp;
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struct iphdr *iph = (*pskb)->nh.iph;
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struct rtable *rt = (struct rtable *)(*pskb)->dst;
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struct in_device *in_dev;
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__be32 mask = 0;
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/* we're only interested in locally generated packets */
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if ((*pskb)->sk == NULL)
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goto out;
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if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
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goto out;
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if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
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goto out;
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rcu_read_lock();
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in_dev = __in_dev_get_rcu(rt->u.dst.dev);
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if (in_dev != NULL) {
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for_primary_ifa(in_dev) {
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if (ifa->ifa_broadcast == iph->daddr) {
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mask = ifa->ifa_mask;
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break;
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}
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} endfor_ifa(in_dev);
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}
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rcu_read_unlock();
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if (mask == 0)
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goto out;
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exp = nf_conntrack_expect_alloc(ct);
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if (exp == NULL)
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goto out;
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exp->tuple = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
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exp->tuple.src.u.udp.port = htons(NMBD_PORT);
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exp->mask.src.u3.ip = mask;
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exp->mask.src.u.udp.port = htons(0xFFFF);
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exp->mask.dst.u3.ip = htonl(0xFFFFFFFF);
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exp->mask.dst.u.udp.port = htons(0xFFFF);
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exp->mask.dst.protonum = 0xFF;
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exp->expectfn = NULL;
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exp->flags = NF_CT_EXPECT_PERMANENT;
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nf_conntrack_expect_related(exp);
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nf_conntrack_expect_put(exp);
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nf_ct_refresh(ct, *pskb, timeout * HZ);
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out:
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return NF_ACCEPT;
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}
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static struct nf_conntrack_helper helper __read_mostly = {
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.name = "netbios-ns",
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.tuple.src.l3num = AF_INET,
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.tuple.src.u.udp.port = __constant_htons(NMBD_PORT),
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.tuple.dst.protonum = IPPROTO_UDP,
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.mask.src.l3num = 0xFFFF,
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.mask.src.u.udp.port = __constant_htons(0xFFFF),
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.mask.dst.protonum = 0xFF,
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.max_expected = 1,
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.me = THIS_MODULE,
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.help = help,
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};
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static int __init nf_conntrack_netbios_ns_init(void)
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{
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helper.timeout = timeout;
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return nf_conntrack_helper_register(&helper);
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}
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static void __exit nf_conntrack_netbios_ns_fini(void)
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{
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nf_conntrack_helper_unregister(&helper);
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}
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module_init(nf_conntrack_netbios_ns_init);
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module_exit(nf_conntrack_netbios_ns_fini);
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