[mirror_ubuntu-artful-kernel.git] / net / netfilter / nf_nat_amanda.c

/* 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;

	/* 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);
	if (!nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
				      protoff, matchoff, matchlen,
				      buffer, strlen(buffer))) {
		nf_ct_helper_log(skb, exp->master, "cannot mangle packet");
		nf_ct_unexpect_related(exp);
		return NF_DROP;
	}
	return NF_ACCEPT;
}

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);
Commit	Line	Data
16958900 PM	1	/* Amanda extension for TCP NAT alteration.
	2	* (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
	3	* based on a copy of HW's ip_nat_irc.c as well as other modules
f229f6ce	4	* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
16958900 PM	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	#include <linux/kernel.h>
	13	#include <linux/module.h>
	14	#include <linux/skbuff.h>
	15	#include <linux/udp.h>
	16
16958900 PM	17	#include <net/netfilter/nf_conntrack_helper.h>
16958900 PM	18	#include <net/netfilter/nf_conntrack_expect.h>
1afc5679	19	#include <net/netfilter/nf_nat_helper.h>
16958900 PM	20	#include <linux/netfilter/nf_conntrack_amanda.h>
	21
	22	MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
	23	MODULE_DESCRIPTION("Amanda NAT helper");
	24	MODULE_LICENSE("GPL");
	25	MODULE_ALIAS("ip_nat_amanda");
	26
3db05fea	27	static unsigned int help(struct sk_buff *skb,
16958900	28	enum ip_conntrack_info ctinfo,
051966c0	29	unsigned int protoff,
16958900 PM	30	unsigned int matchoff,
	31	unsigned int matchlen,
	32	struct nf_conntrack_expect *exp)
	33	{
	34	char buffer[sizeof("65535")];
	35	u_int16_t port;
16958900 PM	36
	37	/* Connection comes from client. */
	38	exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
	39	exp->dir = IP_CT_DIR_ORIGINAL;
	40
	41	/* When you see the packet, we need to NAT it the same as the
	42	* this one (ie. same IP: it will be TCP and master is UDP). */
	43	exp->expectfn = nf_nat_follow_master;
	44
	45	/* Try to get same port: if not, try to change it. */
	46	for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) {
ab0cba25	47	int res;
5b92b61f	48
16958900	49	exp->tuple.dst.u.tcp.port = htons(port);
ab0cba25 ED	50	res = nf_ct_expect_related(exp);
ab0cba25 ED	51	if (res == 0)
5b92b61f	52	break;
ab0cba25	53	else if (res != -EBUSY) {
5b92b61f	54	port = 0;
16958900	55	break;
5b92b61f	56	}
16958900 PM	57	}
16958900 PM	58
b20ab9cc PNA	59	if (port == 0) {
b20ab9cc PNA	60	nf_ct_helper_log(skb, exp->master, "all ports in use");
16958900	61	return NF_DROP;
b20ab9cc	62	}
16958900 PM	63
16958900 PM	64	sprintf(buffer, "%u", port);
cba81cc4 GF	65	if (!nf_nat_mangle_udp_packet(skb, exp->master, ctinfo,
	66	protoff, matchoff, matchlen,
	67	buffer, strlen(buffer))) {
b20ab9cc	68	nf_ct_helper_log(skb, exp->master, "cannot mangle packet");
6823645d	69	nf_ct_unexpect_related(exp);
cba81cc4	70	return NF_DROP;
b20ab9cc	71	}
cba81cc4	72	return NF_ACCEPT;
16958900 PM	73	}
	74
	75	static void __exit nf_nat_amanda_fini(void)
	76	{
a9b3cd7f	77	RCU_INIT_POINTER(nf_nat_amanda_hook, NULL);
16958900 PM	78	synchronize_rcu();
	79	}
	80
	81	static int __init nf_nat_amanda_init(void)
	82	{
d1332e0a	83	BUG_ON(nf_nat_amanda_hook != NULL);
a9b3cd7f	84	RCU_INIT_POINTER(nf_nat_amanda_hook, help);
16958900 PM	85	return 0;
	86	}
	87
	88	module_init(nf_nat_amanda_init);
	89	module_exit(nf_nat_amanda_fini);