net/netfilter/nf_conntrack_netbios_ns.c

   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);