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 <linux/udp.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 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  35 MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  36 MODULE_LICENSE("GPL");
  37
  38 static unsigned int timeout = 3;
  39 module_param(timeout, int, 0600);
  40 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  41
  42 static int help(struct sk_buff **pskb,
  43                 struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
  44 {
  45         struct ip_conntrack_expect *exp;
  46         struct iphdr *iph = (*pskb)->nh.iph;
  47         struct udphdr _uh, *uh;
  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(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         uh = skb_header_pointer(*pskb, iph->ihl * 4, sizeof(_uh), &_uh);
  76         BUG_ON(uh == NULL);
  77
  78         exp = ip_conntrack_expect_alloc(ct);
  79         if (exp == NULL)
  80                 goto out;
  81         memset(&exp->tuple, 0, sizeof(exp->tuple));
  82         exp->tuple.src.ip         = iph->daddr & mask;
  83         exp->tuple.dst.ip         = iph->saddr;
  84         exp->tuple.dst.u.udp.port = uh->source;
  85         exp->tuple.dst.protonum   = IPPROTO_UDP;
  86
  87         memset(&exp->mask, 0, sizeof(exp->mask));
  88         exp->mask.src.ip          = mask;
  89         exp->mask.dst.ip          = 0xFFFFFFFF;
  90         exp->mask.dst.u.udp.port  = 0xFFFF;
  91         exp->mask.dst.protonum    = 0xFF;
  92
  93         exp->expectfn             = NULL;
  94         exp->flags                = IP_CT_EXPECT_PERMANENT;
  95
  96         ip_conntrack_expect_related(exp);
  97         ip_conntrack_expect_put(exp);
  98
  99         ip_ct_refresh_acct(ct, ctinfo, NULL, timeout * HZ);
 100 out:
 101         return NF_ACCEPT;
 102 }
 103
 104 static struct ip_conntrack_helper helper = {
 105         .name                   = "netbios-ns",
 106         .tuple = {
 107                 .src = {
 108                         .u = {
 109                                 .udp = {
 110                                         .port   = __constant_htons(137),
 111                                 }
 112                         }
 113                 },
 114                 .dst = {
 115                         .protonum       = IPPROTO_UDP,
 116                 },
 117         },
 118         .mask = {
 119                 .src = {
 120                         .u = {
 121                                 .udp = {
 122                                         .port   = 0xFFFF,
 123                                 }
 124                         }
 125                 },
 126                 .dst = {
 127                         .protonum       = 0xFF,
 128                 },
 129         },
 130         .max_expected           = 1,
 131         .me                     = THIS_MODULE,
 132         .help                   = help,
 133 };
 134
 135 static int __init init(void)
 136 {
 137         helper.timeout = timeout;
 138         return ip_conntrack_helper_register(&helper);
 139 }
 140
 141 static void __exit fini(void)
 142 {
 143         ip_conntrack_helper_unregister(&helper);
 144 }
 145
 146 module_init(init);
 147 module_exit(fini);