2 * Hop Limit modification target for ip6tables
3 * Maciej Soltysiak <solt@dns.toxicfilms.tv>
4 * Based on HW's TTL module
6 * This software is distributed under the terms of GNU GPL
9 #include <linux/module.h>
10 #include <linux/skbuff.h>
12 #include <linux/ipv6.h>
14 #include <linux/netfilter/x_tables.h>
15 #include <linux/netfilter_ipv6/ip6t_HL.h>
17 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
18 MODULE_DESCRIPTION("Xtables: IPv6 Hop Limit field modification target");
19 MODULE_LICENSE("GPL");
22 hl_tg6(struct sk_buff
*skb
, const struct xt_target_param
*par
)
25 const struct ip6t_HL_info
*info
= par
->targinfo
;
28 if (!skb_make_writable(skb
, skb
->len
))
35 new_hl
= info
->hop_limit
;
38 new_hl
= ip6h
->hop_limit
+ info
->hop_limit
;
43 new_hl
= ip6h
->hop_limit
- info
->hop_limit
;
48 new_hl
= ip6h
->hop_limit
;
52 ip6h
->hop_limit
= new_hl
;
57 static bool hl_tg6_check(const struct xt_tgchk_param
*par
)
59 const struct ip6t_HL_info
*info
= par
->targinfo
;
61 if (info
->mode
> IP6T_HL_MAXMODE
) {
62 printk(KERN_WARNING
"ip6t_HL: invalid or unknown Mode %u\n",
66 if (info
->mode
!= IP6T_HL_SET
&& info
->hop_limit
== 0) {
67 printk(KERN_WARNING
"ip6t_HL: increment/decrement doesn't "
68 "make sense with value 0\n");
74 static struct xt_target hl_tg6_reg __read_mostly
= {
76 .family
= NFPROTO_IPV6
,
78 .targetsize
= sizeof(struct ip6t_HL_info
),
80 .checkentry
= hl_tg6_check
,
84 static int __init
hl_tg6_init(void)
86 return xt_register_target(&hl_tg6_reg
);
89 static void __exit
hl_tg6_exit(void)
91 xt_unregister_target(&hl_tg6_reg
);
94 module_init(hl_tg6_init
);
95 module_exit(hl_tg6_exit
);