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_ipv4/ip_tables.h>
16 #include <linux/netfilter_ipv4/ipt_TTL.h>
18 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
19 MODULE_DESCRIPTION("IP tables TTL modification module");
20 MODULE_LICENSE("GPL");
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
,
29 const struct ipt_TTL_info
*info
= targinfo
;
32 if (!skb_make_writable(pskb
, (*pskb
)->len
))
35 iph
= (*pskb
)->nh
.iph
;
42 new_ttl
= iph
->ttl
+ info
->ttl
;
47 new_ttl
= iph
->ttl
- info
->ttl
;
56 if (new_ttl
!= iph
->ttl
) {
57 iph
->check
= nf_csum_update((iph
->ttl
<< 8) ^ 0xFFFF,
66 static int ipt_ttl_checkentry(const char *tablename
,
68 const struct xt_target
*target
,
70 unsigned int hook_mask
)
72 struct ipt_TTL_info
*info
= targinfo
;
74 if (info
->mode
> IPT_TTL_MAXMODE
) {
75 printk(KERN_WARNING
"ipt_TTL: invalid or unknown Mode %u\n",
79 if ((info
->mode
!= IPT_TTL_SET
) && (info
->ttl
== 0))
84 static struct ipt_target ipt_TTL
= {
86 .target
= ipt_ttl_target
,
87 .targetsize
= sizeof(struct ipt_TTL_info
),
89 .checkentry
= ipt_ttl_checkentry
,
93 static int __init
ipt_ttl_init(void)
95 return ipt_register_target(&ipt_TTL
);
98 static void __exit
ipt_ttl_fini(void)
100 ipt_unregister_target(&ipt_TTL
);
103 module_init(ipt_ttl_init
);
104 module_exit(ipt_ttl_fini
);
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