net/ipv4/netfilter/ip_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/in.h>
  25 #include <linux/ip.h>
  26 #include <net/route.h>
  27
  28 #include <linux/netfilter.h>
  29 #include <linux/netfilter_ipv4.h>
  30 #include <linux/netfilter_ipv4/ip_conntrack.h>
  31 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  32
  33 #define NMBD_PORT       137
  34
  35 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  36 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  37 MODULE_LICENSE("GPL");
  38
  39 static unsigned int timeout = 3;
  40 module_param(timeout, uint, 0400);
  41 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  42
  43 static int help(struct sk_buff **pskb,
  44                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
  45 {
  46         struct ip_conntrack_expect *exp;
  47         struct iphdr *iph = (*pskb)->nh.iph;
  48         struct rtable *rt = (struct rtable *)(*pskb)->dst;
  49         struct in_device *in_dev;
  50         u_int32_t mask = 0;
  51
  52         /* we're only interested in locally generated packets */
  53         if ((*pskb)->sk == NULL)
  54                 goto out;
  55         if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  56                 goto out;
  57         if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  58                 goto out;
  59
  60         rcu_read_lock();
  61         in_dev = __in_dev_get_rcu(rt->u.dst.dev);
  62         if (in_dev != NULL) {
  63                 for_primary_ifa(in_dev) {
  64                         if (ifa->ifa_broadcast == iph->daddr) {
  65                                 mask = ifa->ifa_mask;
  66                                 break;
  67                         }
  68                 } endfor_ifa(in_dev);
  69         }
  70         rcu_read_unlock();
  71
  72         if (mask == 0)
  73                 goto out;
  74
  75         exp = ip_conntrack_expect_alloc(ct);
  76         if (exp == NULL)
  77                 goto out;
  78
  79         exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  80         exp->tuple.src.u.udp.port = ntohs(NMBD_PORT);
  81
  82         exp->mask.src.ip          = mask;
  83         exp->mask.src.u.udp.port  = 0xFFFF;
  84         exp->mask.dst.ip          = 0xFFFFFFFF;
  85         exp->mask.dst.u.udp.port  = 0xFFFF;
  86         exp->mask.dst.protonum    = 0xFF;
  87
  88         exp->expectfn             = NULL;
  89         exp->flags                = IP_CT_EXPECT_PERMANENT;
  90
  91         ip_conntrack_expect_related(exp);
  92         ip_conntrack_expect_put(exp);
  93
  94         ip_ct_refresh(ct, *pskb, timeout * HZ);
  95 out:
  96         return NF_ACCEPT;
  97 }
  98
  99 static struct ip_conntrack_helper helper = {
 100         .name                   = "netbios-ns",
 101         .tuple = {
 102                 .src = {
 103                         .u = {
 104                                 .udp = {
 105                                         .port   = __constant_htons(NMBD_PORT),
 106                                 }
 107                         }
 108                 },
 109                 .dst = {
 110                         .protonum       = IPPROTO_UDP,
 111                 },
 112         },
 113         .mask = {
 114                 .src = {
 115                         .u = {
 116                                 .udp = {
 117                                         .port   = 0xFFFF,
 118                                 }
 119                         }
 120                 },
 121                 .dst = {
 122                         .protonum       = 0xFF,
 123                 },
 124         },
 125         .max_expected           = 1,
 126         .me                     = THIS_MODULE,
 127         .help                   = help,
 128 };
 129
 130 static int __init init(void)
 131 {
 132         helper.timeout = timeout;
 133         return ip_conntrack_helper_register(&helper);
 134 }
 135
 136 static void __exit fini(void)
 137 {
 138         ip_conntrack_helper_unregister(&helper);
 139 }
 140
 141 module_init(init);
 142 module_exit(fini);