linux/net/netfilter/nf_conntrack_netbios_ns.c
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   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
  36MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
  37MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
  38MODULE_LICENSE("GPL");
  39MODULE_ALIAS("ip_conntrack_netbios_ns");
  40MODULE_ALIAS_NFCT_HELPER("netbios_ns");
  41
  42static unsigned int timeout __read_mostly = 3;
  43module_param(timeout, uint, 0400);
  44MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  45
  46static 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;
  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);
  97out:
  98        return NF_ACCEPT;
  99}
 100
 101static struct nf_conntrack_expect_policy exp_policy = {
 102        .max_expected   = 1,
 103};
 104
 105static 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
 115static int __init nf_conntrack_netbios_ns_init(void)
 116{
 117        exp_policy.timeout = timeout;
 118        return nf_conntrack_helper_register(&helper);
 119}
 120
 121static void __exit nf_conntrack_netbios_ns_fini(void)
 122{
 123        nf_conntrack_helper_unregister(&helper);
 124}
 125
 126module_init(nf_conntrack_netbios_ns_init);
 127module_exit(nf_conntrack_netbios_ns_fini);
 128