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);