net/netfilter/nf_conntrack_netbios_ns.c

   1 /*
   2  *      NetBIOS name service broadcast connection tracking helper
   3  *
   4  *      (c) 2005 Patrick McHardy <kaber@trash.net>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11 /*
  12  *      This helper tracks locally originating NetBIOS name service
  13  *      requests by issuing permanent expectations (valid until
  14  *      timing out) matching all reply connections from the
  15  *      destination network. The only NetBIOS specific thing is
  16  *      actually the port number.
  17  */
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/skbuff.h>
  22 #include <linux/netdevice.h>
  23 #include <linux/inetdevice.h>
  24 #include <linux/if_addr.h>
  25 #include <linux/in.h>
  26 #include <linux/ip.h>
  27 #include <linux/netfilter.h>
  28 #include <net/route.h>
  29
  30 #include <net/netfilter/nf_conntrack.h>
  31 #include <net/netfilter/nf_conntrack_helper.h>
  32 #include <net/netfilter/nf_conntrack_expect.h>
  33
  34 #define NMBD_PORT       137
  35
  36 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  37 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  38 MODULE_LICENSE("GPL");
  39 MODULE_ALIAS("ip_conntrack_netbios_ns");
  40
  41 static unsigned int timeout __read_mostly = 3;
  42 module_param(timeout, uint, 0400);
  43 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  44
  45 static int help(struct sk_buff **pskb, unsigned int protoff,
  46                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  47 {
  48         struct nf_conntrack_expect *exp;
  49         struct iphdr *iph = ip_hdr(*pskb);
  50         struct rtable *rt = (struct rtable *)(*pskb)->dst;
  51         struct in_device *in_dev;
  52         __be32 mask = 0;
  53
  54         /* we're only interested in locally generated packets */
  55         if ((*pskb)->sk == NULL)
  56                 goto out;
  57         if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  58                 goto out;
  59         if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  60                 goto out;
  61
  62         rcu_read_lock();
  63         in_dev = __in_dev_get_rcu(rt->u.dst.dev);
  64         if (in_dev != NULL) {
  65                 for_primary_ifa(in_dev) {
  66                         if (ifa->ifa_broadcast == iph->daddr) {
  67                                 mask = ifa->ifa_mask;
  68                                 break;
  69                         }
  70                 } endfor_ifa(in_dev);
  71         }
  72         rcu_read_unlock();
  73
  74         if (mask == 0)
  75                 goto out;
  76
  77         exp = nf_ct_expect_alloc(ct);
  78         if (exp == NULL)
  79                 goto out;
  80
  81         exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  82         exp->tuple.src.u.udp.port = htons(NMBD_PORT);
  83
  84         exp->mask.src.u3.ip       = mask;
  85         exp->mask.src.u.udp.port  = htons(0xFFFF);
  86
  87         exp->expectfn             = NULL;
  88         exp->flags                = NF_CT_EXPECT_PERMANENT;
  89         exp->helper               = NULL;
  90
  91         nf_ct_expect_related(exp);
  92         nf_ct_expect_put(exp);
  93
  94         nf_ct_refresh(ct, *pskb, timeout * HZ);
  95 out:
  96         return NF_ACCEPT;
  97 }
  98
  99 static struct nf_conntrack_helper helper __read_mostly = {
 100         .name                   = "netbios-ns",
 101         .tuple.src.l3num        = AF_INET,
 102         .tuple.src.u.udp.port   = __constant_htons(NMBD_PORT),
 103         .tuple.dst.protonum     = IPPROTO_UDP,
 104         .max_expected           = 1,
 105         .me                     = THIS_MODULE,
 106         .help                   = help,
 107 };
 108
 109 static int __init nf_conntrack_netbios_ns_init(void)
 110 {
 111         helper.timeout = timeout;
 112         return nf_conntrack_helper_register(&helper);
 113 }
 114
 115 static void __exit nf_conntrack_netbios_ns_fini(void)
 116 {
 117         nf_conntrack_helper_unregister(&helper);
 118 }
 119
 120 module_init(nf_conntrack_netbios_ns_init);
 121 module_exit(nf_conntrack_netbios_ns_fini);