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 MODULE_ALIAS_NFCT_HELPER("netbios_ns");
  41
  42 static unsigned int timeout __read_mostly = 3;
  43 module_param(timeout, uint, 0400);
  44 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  45
  46 static int help(struct sk_buff *skb, unsigned int protoff,
  47                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  48 {
  49         struct nf_conntrack_expect *exp;
  50         struct iphdr *iph = ip_hdr(skb);
  51         struct rtable *rt = skb_rtable(skb);
  52         struct in_device *in_dev;
  53         __be32 mask = 0;
  54
  55         /* we're only interested in locally generated packets */
  56         if (skb->sk == NULL)
  57                 goto out;
  58         if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
  59                 goto out;
  60         if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
  61                 goto out;
  62
  63         rcu_read_lock();
  64         in_dev = __in_dev_get_rcu(rt->u.dst.dev);
  65         if (in_dev != NULL) {
  66                 for_primary_ifa(in_dev) {
  67                         if (ifa->ifa_broadcast == iph->daddr) {
  68                                 mask = ifa->ifa_mask;
  69                                 break;
  70                         }
  71                 } endfor_ifa(in_dev);
  72         }
  73         rcu_read_unlock();
  74
  75         if (mask == 0)
  76                 goto out;
  77
  78         exp = nf_ct_expect_alloc(ct);
  79         if (exp == NULL)
  80                 goto out;
  81
  82         exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
  83         exp->tuple.src.u.udp.port = htons(NMBD_PORT);
  84
  85         exp->mask.src.u3.ip       = mask;
  86         exp->mask.src.u.udp.port  = htons(0xFFFF);
  87
  88         exp->expectfn             = NULL;
  89         exp->flags                = NF_CT_EXPECT_PERMANENT;
  90         exp->class                = NF_CT_EXPECT_CLASS_DEFAULT;
  91         exp->helper               = NULL;
  92
  93         nf_ct_expect_related(exp);
  94         nf_ct_expect_put(exp);
  95
  96         nf_ct_refresh(ct, skb, timeout * HZ);
  97 out:
  98         return NF_ACCEPT;
  99 }
 100
 101 static struct nf_conntrack_expect_policy exp_policy = {
 102         .max_expected   = 1,
 103 };
 104
 105 static struct nf_conntrack_helper helper __read_mostly = {
 106         .name                   = "netbios-ns",
 107         .tuple.src.l3num        = AF_INET,
 108         .tuple.src.u.udp.port   = cpu_to_be16(NMBD_PORT),
 109         .tuple.dst.protonum     = IPPROTO_UDP,
 110         .me                     = THIS_MODULE,
 111         .help                   = help,
 112         .expect_policy          = &exp_policy,
 113 };
 114
 115 static int __init nf_conntrack_netbios_ns_init(void)
 116 {
 117         exp_policy.timeout = timeout;
 118         return nf_conntrack_helper_register(&helper);
 119 }
 120
 121 static void __exit nf_conntrack_netbios_ns_fini(void)
 122 {
 123         nf_conntrack_helper_unregister(&helper);
 124 }
 125
 126 module_init(nf_conntrack_netbios_ns_init);
 127 module_exit(nf_conntrack_netbios_ns_fini);