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,
25 const void *targinfo, void *userinfo)
28 const struct ip6t_HL_info *info = targinfo;
32 if (!skb_make_writable(pskb, (*pskb)->len))
35 ip6h = (*pskb)->nh.ipv6h;
39 new_hl = info->hop_limit;
42 new_hl = ip6h->hop_limit + info->hop_limit;
47 new_hl = ip6h->hop_limit - info->hop_limit;
52 new_hl = ip6h->hop_limit;
56 if (new_hl != ip6h->hop_limit) {
57 diffs[0] = htons(((unsigned)ip6h->hop_limit) << 8) ^ 0xFFFF;
58 ip6h->hop_limit = new_hl;
59 diffs[1] = htons(((unsigned)ip6h->hop_limit) << 8);
65 static int ip6t_hl_checkentry(const char *tablename,
67 const struct xt_target *target,
69 unsigned int targinfosize,
70 unsigned int hook_mask)
72 struct ip6t_HL_info *info = targinfo;
74 if (info->mode > IP6T_HL_MAXMODE) {
75 printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n",
79 if ((info->mode != IP6T_HL_SET) && (info->hop_limit == 0)) {
80 printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't "
81 "make sense with value 0\n");
87 static struct ip6t_target ip6t_HL = {
89 .target = ip6t_hl_target,
90 .targetsize = sizeof(struct ip6t_HL_info),
92 .checkentry = ip6t_hl_checkentry,
96 static int __init ip6t_hl_init(void)
98 return ip6t_register_target(&ip6t_HL);
101 static void __exit ip6t_hl_fini(void)
103 ip6t_unregister_target(&ip6t_HL);
106 module_init(ip6t_hl_init);
107 module_exit(ip6t_hl_fini);