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 NMBD_PORT 137 24 25 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 26 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper"); 27 MODULE_LICENSE("GPL"); 28 MODULE_ALIAS("ip_conntrack_netbios_ns"); 29 MODULE_ALIAS_NFCT_HELPER("netbios_ns"); 30 31 static unsigned int timeout __read_mostly = 3; 32 module_param(timeout, uint, 0400); 33 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); 34 35 static struct nf_conntrack_expect_policy exp_policy = { 36 .max_expected = 1, 37 }; 38 39 static int netbios_ns_help(struct sk_buff *skb, unsigned int protoff, 40 struct nf_conn *ct, 41 enum ip_conntrack_info ctinfo) 42 { 43 return nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout); 44 } 45 46 static struct nf_conntrack_helper helper __read_mostly = { 47 .name = "netbios-ns", 48 .tuple.src.l3num = NFPROTO_IPV4, 49 .tuple.src.u.udp.port = cpu_to_be16(NMBD_PORT), 50 .tuple.dst.protonum = IPPROTO_UDP, 51 .me = THIS_MODULE, 52 .help = netbios_ns_help, 53 .expect_policy = &exp_policy, 54 }; 55 56 static int __init nf_conntrack_netbios_ns_init(void) 57 { 58 NF_CT_HELPER_BUILD_BUG_ON(0); 59 60 exp_policy.timeout = timeout; 61 return nf_conntrack_helper_register(&helper); 62 } 63 64 static void __exit nf_conntrack_netbios_ns_fini(void) 65 { 66 nf_conntrack_helper_unregister(&helper); 67 } 68 69 module_init(nf_conntrack_netbios_ns_init); 70 module_exit(nf_conntrack_netbios_ns_fini); 71