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>
13 #include <linux/netfilter_ipv6/ip6_tables.h>
14 #include <linux/netfilter_ipv6/ip6t_HL.h>
16 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
17 MODULE_DESCRIPTION("IP tables Hop Limit modification module");
18 MODULE_LICENSE("GPL");
20 static unsigned int ip6t_hl_target(struct sk_buff
**pskb
,
21 const struct net_device
*in
,
22 const struct net_device
*out
,
24 const void *targinfo
, void *userinfo
)
27 const struct ip6t_HL_info
*info
= targinfo
;
31 if (!skb_make_writable(pskb
, (*pskb
)->len
))
34 ip6h
= (*pskb
)->nh
.ipv6h
;
38 new_hl
= info
->hop_limit
;
41 new_hl
= ip6h
->hop_limit
+ info
->hop_limit
;
46 new_hl
= ip6h
->hop_limit
- info
->hop_limit
;
51 new_hl
= ip6h
->hop_limit
;
55 if (new_hl
!= ip6h
->hop_limit
) {
56 diffs
[0] = htons(((unsigned)ip6h
->hop_limit
) << 8) ^ 0xFFFF;
57 ip6h
->hop_limit
= new_hl
;
58 diffs
[1] = htons(((unsigned)ip6h
->hop_limit
) << 8);
64 static int ip6t_hl_checkentry(const char *tablename
,
67 unsigned int targinfosize
,
68 unsigned int hook_mask
)
70 struct ip6t_HL_info
*info
= targinfo
;
72 if (targinfosize
!= IP6T_ALIGN(sizeof(struct ip6t_HL_info
))) {
73 printk(KERN_WARNING
"ip6t_HL: targinfosize %u != %Zu\n",
75 IP6T_ALIGN(sizeof(struct ip6t_HL_info
)));
79 if (strcmp(tablename
, "mangle")) {
80 printk(KERN_WARNING
"ip6t_HL: can only be called from "
81 "\"mangle\" table, not \"%s\"\n", tablename
);
85 if (info
->mode
> IP6T_HL_MAXMODE
) {
86 printk(KERN_WARNING
"ip6t_HL: invalid or unknown Mode %u\n",
91 if ((info
->mode
!= IP6T_HL_SET
) && (info
->hop_limit
== 0)) {
92 printk(KERN_WARNING
"ip6t_HL: increment/decrement doesn't "
93 "make sense with value 0\n");
100 static struct ip6t_target ip6t_HL
= {
102 .target
= ip6t_hl_target
,
103 .checkentry
= ip6t_hl_checkentry
,
107 static int __init
init(void)
109 return ip6t_register_target(&ip6t_HL
);
112 static void __exit
fini(void)
114 ip6t_unregister_target(&ip6t_HL
);