1/* Kernel module to match packet length. */
2/* (C) 1999-2001 James Morris <jmorros@intercode.com.au>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 */
8
9#include <linux/module.h>
10#include <linux/skbuff.h>
11#include <linux/ipv6.h>
12#include <net/ip.h>
13
14#include <linux/netfilter/xt_length.h>
15#include <linux/netfilter/x_tables.h>
16
17MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
18MODULE_DESCRIPTION("IP tables packet length matching module");
19MODULE_LICENSE("GPL");
20MODULE_ALIAS("ipt_length");
21MODULE_ALIAS("ip6t_length");
22
23static int
24match(const struct sk_buff *skb,
25      const struct net_device *in,
26      const struct net_device *out,
27      const struct xt_match *match,
28      const void *matchinfo,
29      int offset,
30      unsigned int protoff,
31      int *hotdrop)
32{
33	const struct xt_length_info *info = matchinfo;
34	u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len);
35
36	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
37}
38
39static int
40match6(const struct sk_buff *skb,
41       const struct net_device *in,
42       const struct net_device *out,
43       const struct xt_match *match,
44       const void *matchinfo,
45       int offset,
46       unsigned int protoff,
47       int *hotdrop)
48{
49	const struct xt_length_info *info = matchinfo;
50	const u_int16_t pktlen = (ntohs(ipv6_hdr(skb)->payload_len) +
51				  sizeof(struct ipv6hdr));
52
53	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
54}
55
56static struct xt_match xt_length_match[] = {
57	{
58		.name		= "length",
59		.family		= AF_INET,
60		.match		= match,
61		.matchsize	= sizeof(struct xt_length_info),
62		.me		= THIS_MODULE,
63	},
64	{
65		.name		= "length",
66		.family		= AF_INET6,
67		.match		= match6,
68		.matchsize	= sizeof(struct xt_length_info),
69		.me		= THIS_MODULE,
70	},
71};
72
73static int __init xt_length_init(void)
74{
75	return xt_register_matches(xt_length_match,
76				   ARRAY_SIZE(xt_length_match));
77}
78
79static void __exit xt_length_fini(void)
80{
81	xt_unregister_matches(xt_length_match, ARRAY_SIZE(xt_length_match));
82}
83
84module_init(xt_length_init);
85module_exit(xt_length_fini);
86