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 struct xt_target *target,
28 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 ip6h->hop_limit = new_hl;
60 static int ip6t_hl_checkentry(const char *tablename,
62 const struct xt_target *target,
64 unsigned int hook_mask)
66 struct ip6t_HL_info *info = targinfo;
68 if (info->mode > IP6T_HL_MAXMODE) {
69 printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n",
73 if ((info->mode != IP6T_HL_SET) && (info->hop_limit == 0)) {
74 printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't "
75 "make sense with value 0\n");
81 static struct ip6t_target ip6t_HL = {
83 .target = ip6t_hl_target,
84 .targetsize = sizeof(struct ip6t_HL_info),
86 .checkentry = ip6t_hl_checkentry,
90 static int __init ip6t_hl_init(void)
92 return ip6t_register_target(&ip6t_HL);
95 static void __exit ip6t_hl_fini(void)
97 ip6t_unregister_target(&ip6t_HL);
100 module_init(ip6t_hl_init);
101 module_exit(ip6t_hl_fini);