[mirror_ubuntu-hirsute-kernel.git] / net / ipv4 / netfilter / ipt_TTL.c

/* TTL modification target for IP tables
 * (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/checksum.h>

#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_TTL.h>

MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("IP tables TTL modification module");
MODULE_LICENSE("GPL");

static unsigned int 
ipt_ttl_target(struct sk_buff **pskb,
	       const struct net_device *in, const struct net_device *out,
	       unsigned int hooknum, const struct xt_target *target,
	       const void *targinfo, void *userinfo)
{
	struct iphdr *iph;
	const struct ipt_TTL_info *info = targinfo;
	u_int16_t diffs[2];
	int new_ttl;

	if (!skb_make_writable(pskb, (*pskb)->len))
		return NF_DROP;

	iph = (*pskb)->nh.iph;

	switch (info->mode) {
		case IPT_TTL_SET:
			new_ttl = info->ttl;
			break;
		case IPT_TTL_INC:
			new_ttl = iph->ttl + info->ttl;
			if (new_ttl > 255)
				new_ttl = 255;
			break;
		case IPT_TTL_DEC:
			new_ttl = iph->ttl - info->ttl;
			if (new_ttl < 0)
				new_ttl = 0;
			break;
		default:
			new_ttl = iph->ttl;
			break;
	}

	if (new_ttl != iph->ttl) {
		diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
		iph->ttl = new_ttl;
		diffs[1] = htons(((unsigned)iph->ttl) << 8);
		iph->check = csum_fold(csum_partial((char *)diffs,
						    sizeof(diffs),
						    iph->check^0xFFFF));
	}

	return IPT_CONTINUE;
}

static int ipt_ttl_checkentry(const char *tablename,
		const void *e,
		const struct xt_target *target,
		void *targinfo,
		unsigned int targinfosize,
		unsigned int hook_mask)
{
	struct ipt_TTL_info *info = targinfo;

	if (info->mode > IPT_TTL_MAXMODE) {
		printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n", 
			info->mode);
		return 0;
	}
	if ((info->mode != IPT_TTL_SET) && (info->ttl == 0))
		return 0;
	return 1;
}

static struct ipt_target ipt_TTL = { 
	.name 		= "TTL",
	.target 	= ipt_ttl_target, 
	.targetsize	= sizeof(struct ipt_TTL_info),
	.table		= "mangle",
	.checkentry 	= ipt_ttl_checkentry, 
	.me 		= THIS_MODULE,
};

static int __init ipt_ttl_init(void)
{
	return ipt_register_target(&ipt_TTL);
}

static void __exit ipt_ttl_fini(void)
{
	ipt_unregister_target(&ipt_TTL);
}

module_init(ipt_ttl_init);
module_exit(ipt_ttl_fini);
Commit	Line	Data
5f2c3b91 HW	1	/* TTL modification target for IP tables
	2	* (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License version 2 as
	6	* published by the Free Software Foundation.
	7	*
	8	*/
	9
	10	#include <linux/module.h>
	11	#include <linux/skbuff.h>
	12	#include <linux/ip.h>
	13	#include <net/checksum.h>
	14
	15	#include <linux/netfilter_ipv4/ip_tables.h>
	16	#include <linux/netfilter_ipv4/ipt_TTL.h>
	17
	18	MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
	19	MODULE_DESCRIPTION("IP tables TTL modification module");
	20	MODULE_LICENSE("GPL");
	21
	22	static unsigned int
c4986734 PM	23	ipt_ttl_target(struct sk_buff **pskb,
	24	const struct net_device in, const struct net_device out,
	25	unsigned int hooknum, const struct xt_target *target,
	26	const void targinfo, void userinfo)
5f2c3b91 HW	27	{
	28	struct iphdr *iph;
	29	const struct ipt_TTL_info *info = targinfo;
	30	u_int16_t diffs[2];
	31	int new_ttl;
	32
	33	if (!skb_make_writable(pskb, (*pskb)->len))
	34	return NF_DROP;
	35
	36	iph = (*pskb)->nh.iph;
	37
	38	switch (info->mode) {
	39	case IPT_TTL_SET:
	40	new_ttl = info->ttl;
	41	break;
	42	case IPT_TTL_INC:
	43	new_ttl = iph->ttl + info->ttl;
	44	if (new_ttl > 255)
	45	new_ttl = 255;
	46	break;
	47	case IPT_TTL_DEC:
	48	new_ttl = iph->ttl - info->ttl;
	49	if (new_ttl < 0)
	50	new_ttl = 0;
	51	break;
	52	default:
	53	new_ttl = iph->ttl;
	54	break;
	55	}
	56
	57	if (new_ttl != iph->ttl) {
	58	diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
	59	iph->ttl = new_ttl;
	60	diffs[1] = htons(((unsigned)iph->ttl) << 8);
	61	iph->check = csum_fold(csum_partial((char *)diffs,
	62	sizeof(diffs),
	63	iph->check^0xFFFF));
	64	}
	65
	66	return IPT_CONTINUE;
	67	}
	68
	69	static int ipt_ttl_checkentry(const char *tablename,
2e4e6a17	70	const void *e,
c4986734	71	const struct xt_target *target,
5f2c3b91 HW	72	void *targinfo,
	73	unsigned int targinfosize,
	74	unsigned int hook_mask)
	75	{
	76	struct ipt_TTL_info *info = targinfo;
	77
5f2c3b91 HW	78	if (info->mode > IPT_TTL_MAXMODE) {
	79	printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n",
	80	info->mode);
	81	return 0;
	82	}
5f2c3b91 HW	83	if ((info->mode != IPT_TTL_SET) && (info->ttl == 0))
5f2c3b91 HW	84	return 0;
5f2c3b91 HW	85	return 1;
	86	}
	87
	88	static struct ipt_target ipt_TTL = {
	89	.name = "TTL",
	90	.target = ipt_ttl_target,
1d5cd909 PM	91	.targetsize = sizeof(struct ipt_TTL_info),
1d5cd909 PM	92	.table = "mangle",
5f2c3b91 HW	93	.checkentry = ipt_ttl_checkentry,
	94	.me = THIS_MODULE,
	95	};
	96
65b4b4e8	97	static int __init ipt_ttl_init(void)
5f2c3b91 HW	98	{
	99	return ipt_register_target(&ipt_TTL);
	100	}
	101
65b4b4e8	102	static void __exit ipt_ttl_fini(void)
5f2c3b91 HW	103	{
	104	ipt_unregister_target(&ipt_TTL);
	105	}
	106
65b4b4e8 AM	107	module_init(ipt_ttl_init);
65b4b4e8 AM	108	module_exit(ipt_ttl_fini);