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