1/* IP tables module for matching the value of the TTL
2 *
3 * ipt_ttl.c,v 1.5 2000/11/13 11:16:08 laforge Exp
4 *
5 * (C) 2000,2001 by Harald Welte <laforge@gnumonks.org>
6 *
7 * This software is distributed under the terms  GNU GPL
8 */
9
10#include <linux/module.h>
11#include <linux/skbuff.h>
12
13#include <linux/netfilter_ipv4/ipt_ttl.h>
14#include <linux/netfilter_ipv4/ip_tables.h>
15
16MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
17MODULE_DESCRIPTION("IP tables TTL matching module");
18MODULE_LICENSE("GPL");
19
20static int match(const struct sk_buff *skb, const struct net_device *in,
21		 const struct net_device *out, const void *matchinfo,
22		 int offset, const void *hdr, u_int16_t datalen,
23		 int *hotdrop)
24{
25	const struct ipt_ttl_info *info = matchinfo;
26	const struct iphdr *iph = skb->nh.iph;
27
28	switch (info->mode) {
29		case IPT_TTL_EQ:
30			return (iph->ttl == info->ttl);
31			break;
32		case IPT_TTL_NE:
33			return (!(iph->ttl == info->ttl));
34			break;
35		case IPT_TTL_LT:
36			return (iph->ttl < info->ttl);
37			break;
38		case IPT_TTL_GT:
39			return (iph->ttl > info->ttl);
40			break;
41		default:
42			printk(KERN_WARNING "ipt_ttl: unknown mode %d\n",
43				info->mode);
44			return 0;
45	}
46
47	return 0;
48}
49
50static int checkentry(const char *tablename, const struct ipt_ip *ip,
51		      void *matchinfo, unsigned int matchsize,
52		      unsigned int hook_mask)
53{
54	if (matchsize != IPT_ALIGN(sizeof(struct ipt_ttl_info)))
55		return 0;
56
57	return 1;
58}
59
60static struct ipt_match ttl_match = { { NULL, NULL }, "ttl", &match,
61		&checkentry, NULL, THIS_MODULE };
62
63static int __init init(void)
64{
65	return ipt_register_match(&ttl_match);
66}
67
68static void __exit fini(void)
69{
70	ipt_unregister_match(&ttl_match);
71
72}
73
74module_init(init);
75module_exit(fini);
76