root/net/ipv4/netfilter/nf_nat_amanda.c

DEFINITIONS

1. help
2. nf_nat_amanda_fini
3. nf_nat_amanda_init

/* Amanda extension for TCP NAT alteration.
 * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
 * based on a copy of HW's ip_nat_irc.c as well as other modules
 *
 * 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.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/udp.h>

#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_nat_rule.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <linux/netfilter/nf_conntrack_amanda.h>

MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
MODULE_DESCRIPTION("Amanda NAT helper");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ip_nat_amanda");

static unsigned int help(struct sk_buff *skb,
                         enum ip_conntrack_info ctinfo,
                         unsigned int matchoff,
                         unsigned int matchlen,
                         struct nf_conntrack_expect *exp)
{
        char buffer[sizeof("65535")];
        u_int16_t port;
        unsigned int ret;

        /* Connection comes from client. */
        exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
        exp->dir = IP_CT_DIR_ORIGINAL;

        /* When you see the packet, we need to NAT it the same as the
         * this one (ie. same IP: it will be TCP and master is UDP). */
        exp->expectfn = nf_nat_follow_master;

        /* Try to get same port: if not, try to change it. */
        for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
                exp->tuple.dst.u.tcp.port = htons(port);
                if (nf_ct_expect_related(exp) == 0)
                        break;
        }

        if (port == 0)
                return NF_DROP;

        sprintf(buffer, "%u", port);
        ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
                                       matchoff, matchlen,
                                       buffer, strlen(buffer));
        if (ret != NF_ACCEPT)
                nf_ct_unexpect_related(exp);
        return ret;
}

static void __exit nf_nat_amanda_fini(void)
{
        rcu_assign_pointer(nf_nat_amanda_hook, NULL);
        synchronize_rcu();
}

static int __init nf_nat_amanda_init(void)
{
        BUG_ON(nf_nat_amanda_hook != NULL);
        rcu_assign_pointer(nf_nat_amanda_hook, help);
        return 0;
}

module_init(nf_nat_amanda_init);
module_exit(nf_nat_amanda_fini);