root/net/netfilter/nf_conntrack_netbios_ns.c

DEFINITIONS

1. help
2. nf_conntrack_netbios_ns_init
3. nf_conntrack_netbios_ns_fini

/*
 *      NetBIOS name service broadcast connection tracking helper
 *
 *      (c) 2005 Patrick McHardy <kaber@trash.net>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */
/*
 *      This helper tracks locally originating NetBIOS name service
 *      requests by issuing permanent expectations (valid until
 *      timing out) matching all reply connections from the
 *      destination network. The only NetBIOS specific thing is
 *      actually the port number.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/if_addr.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <net/route.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>

#define NMBD_PORT       137

MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("NetBIOS name service broadcast connection tracking helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_conntrack_netbios_ns");

static unsigned int timeout __read_mostly = 3;
module_param(timeout, uint, 0400);
MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");

static int help(struct sk_buff *skb, unsigned int protoff,
                struct nf_conn *ct, enum ip_conntrack_info ctinfo)
{
        struct nf_conntrack_expect *exp;
        struct iphdr *iph = ip_hdr(skb);
        struct rtable *rt = skb->rtable;
        struct in_device *in_dev;
        __be32 mask = 0;

        /* we're only interested in locally generated packets */
        if (skb->sk == NULL)
                goto out;
        if (rt == NULL || !(rt->rt_flags & RTCF_BROADCAST))
                goto out;
        if (CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
                goto out;

        rcu_read_lock();
        in_dev = __in_dev_get_rcu(rt->u.dst.dev);
        if (in_dev != NULL) {
                for_primary_ifa(in_dev) {
                        if (ifa->ifa_broadcast == iph->daddr) {
                                mask = ifa->ifa_mask;
                                break;
                        }
                } endfor_ifa(in_dev);
        }
        rcu_read_unlock();

        if (mask == 0)
                goto out;

        exp = nf_ct_expect_alloc(ct);
        if (exp == NULL)
                goto out;

        exp->tuple                = ct->tuplehash[IP_CT_DIR_REPLY].tuple;
        exp->tuple.src.u.udp.port = htons(NMBD_PORT);

        exp->mask.src.u3.ip       = mask;
        exp->mask.src.u.udp.port  = htons(0xFFFF);

        exp->expectfn             = NULL;
        exp->flags                = NF_CT_EXPECT_PERMANENT;
        exp->class                = NF_CT_EXPECT_CLASS_DEFAULT;
        exp->helper               = NULL;

        nf_ct_expect_related(exp);
        nf_ct_expect_put(exp);

        nf_ct_refresh(ct, skb, timeout * HZ);
out:
        return NF_ACCEPT;
}

static struct nf_conntrack_expect_policy exp_policy = {
        .max_expected   = 1,
};

static struct nf_conntrack_helper helper __read_mostly = {
        .name                   = "netbios-ns",
        .tuple.src.l3num        = AF_INET,
        .tuple.src.u.udp.port   = __constant_htons(NMBD_PORT),
        .tuple.dst.protonum     = IPPROTO_UDP,
        .me                     = THIS_MODULE,
        .help                   = help,
        .expect_policy          = &exp_policy,
};

static int __init nf_conntrack_netbios_ns_init(void)
{
        exp_policy.timeout = timeout;
        return nf_conntrack_helper_register(&helper);
}

static void __exit nf_conntrack_netbios_ns_fini(void)
{
        nf_conntrack_helper_unregister(&helper);
}

module_init(nf_conntrack_netbios_ns_init);
module_exit(nf_conntrack_netbios_ns_fini);