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 HELPER_NAME "netbios-ns" 24 #define NMBD_PORT 137 25 26 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 27 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper"); 28 MODULE_LICENSE("GPL"); 29 MODULE_ALIAS("ip_conntrack_netbios_ns"); 30 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); 31 32 static unsigned int timeout __read_mostly = 3; 33 module_param(timeout, uint, 0400); 34 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds"); 35 36 static struct nf_conntrack_expect_policy exp_policy = { 37 .max_expected = 1, 38 }; 39 40 static int netbios_ns_help(struct sk_buff *skb, unsigned int protoff, 41 struct nf_conn *ct, 42 enum ip_conntrack_info ctinfo) 43 { 44 return nf_conntrack_broadcast_help(skb, ct, ctinfo, timeout); 45 } 46 47 static struct nf_conntrack_helper helper __read_mostly = { 48 .name = HELPER_NAME, 49 .tuple.src.l3num = NFPROTO_IPV4, 50 .tuple.src.u.udp.port = cpu_to_be16(NMBD_PORT), 51 .tuple.dst.protonum = IPPROTO_UDP, 52 .me = THIS_MODULE, 53 .help = netbios_ns_help, 54 .expect_policy = &exp_policy, 55 }; 56 57 static int __init nf_conntrack_netbios_ns_init(void) 58 { 59 NF_CT_HELPER_BUILD_BUG_ON(0); 60 61 exp_policy.timeout = timeout; 62 return nf_conntrack_helper_register(&helper); 63 } 64 65 static void __exit nf_conntrack_netbios_ns_fini(void) 66 { 67 nf_conntrack_helper_unregister(&helper); 68 } 69 70 module_init(nf_conntrack_netbios_ns_init); 71 module_exit(nf_conntrack_netbios_ns_fini); 72