1 /* TTL modification target for IP tables
2 * (C) 2000,2005 by Harald Welte <laforge@netfilter.org>
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.
10 #include <linux/module.h>
11 #include <linux/skbuff.h>
13 #include <net/checksum.h>
15 #include <linux/netfilter/x_tables.h>
16 #include <linux/netfilter_ipv4/ipt_TTL.h>
18 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
19 MODULE_DESCRIPTION("Xtables: IPv4 TTL field modification target");
20 MODULE_LICENSE("GPL");
23 ttl_tg(struct sk_buff
*skb
, const struct xt_target_param
*par
)
26 const struct ipt_TTL_info
*info
= par
->targinfo
;
29 if (!skb_make_writable(skb
, skb
->len
))
39 new_ttl
= iph
->ttl
+ info
->ttl
;
44 new_ttl
= iph
->ttl
- info
->ttl
;
53 if (new_ttl
!= iph
->ttl
) {
54 csum_replace2(&iph
->check
, htons(iph
->ttl
<< 8),
62 static bool ttl_tg_check(const struct xt_tgchk_param
*par
)
64 const struct ipt_TTL_info
*info
= par
->targinfo
;
66 if (info
->mode
> IPT_TTL_MAXMODE
) {
67 printk(KERN_WARNING
"ipt_TTL: invalid or unknown Mode %u\n",
71 if (info
->mode
!= IPT_TTL_SET
&& info
->ttl
== 0)
76 static struct xt_target ttl_tg_reg __read_mostly
= {
78 .family
= NFPROTO_IPV4
,
80 .targetsize
= sizeof(struct ipt_TTL_info
),
82 .checkentry
= ttl_tg_check
,
86 static int __init
ttl_tg_init(void)
88 return xt_register_target(&ttl_tg_reg
);
91 static void __exit
ttl_tg_exit(void)
93 xt_unregister_target(&ttl_tg_reg
);
96 module_init(ttl_tg_init
);
97 module_exit(ttl_tg_exit
);