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/* 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
* (C) 2006-2012 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.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/udp.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_nat_helper.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 protoff,
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++) {
int res;
exp->tuple.dst.u.tcp.port = htons(port);
res = nf_ct_expect_related(exp);
if (res == 0)
break;
else if (res != -EBUSY) {
port = 0;
break;
}
}
if (port == 0) {
nf_ct_helper_log(skb, exp->master, "all ports in use");
return NF_DROP;
}
sprintf(buffer, "%u", port);
ret = nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
protoff, matchoff, matchlen,
buffer, strlen(buffer));
if (ret != NF_ACCEPT) {
nf_ct_helper_log(skb, exp->master, "cannot mangle packet");
nf_ct_unexpect_related(exp);
}
return ret;
}
static void __exit nf_nat_amanda_fini(void)
{
RCU_INIT_POINTER(nf_nat_amanda_hook, NULL);
synchronize_rcu();
}
static int __init nf_nat_amanda_init(void)
{
BUG_ON(nf_nat_amanda_hook != NULL);
RCU_INIT_POINTER(nf_nat_amanda_hook, help);
return 0;
}
module_init(nf_nat_amanda_init);
module_exit(nf_nat_amanda_fini);
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