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("Xtables: Packet length (Layer3,4,5) match");
19MODULE_LICENSE("GPL");
20MODULE_ALIAS("ipt_length");
21MODULE_ALIAS("ip6t_length");
22
23static bool
24length_mt(const struct sk_buff *skb, struct xt_action_param *par)
25{
26	const struct xt_length_info *info = par->matchinfo;
27	u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len);
28
29	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
30}
31
32static bool
33length_mt6(const struct sk_buff *skb, struct xt_action_param *par)
34{
35	const struct xt_length_info *info = par->matchinfo;
36	const u_int16_t pktlen = ntohs(ipv6_hdr(skb)->payload_len) +
37				 sizeof(struct ipv6hdr);
38
39	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
40}
41
42static struct xt_match length_mt_reg[] __read_mostly = {
43	{
44		.name		= "length",
45		.family		= NFPROTO_IPV4,
46		.match		= length_mt,
47		.matchsize	= sizeof(struct xt_length_info),
48		.me		= THIS_MODULE,
49	},
50	{
51		.name		= "length",
52		.family		= NFPROTO_IPV6,
53		.match		= length_mt6,
54		.matchsize	= sizeof(struct xt_length_info),
55		.me		= THIS_MODULE,
56	},
57};
58
59static int __init length_mt_init(void)
60{
61	return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
62}
63
64static void __exit length_mt_exit(void)
65{
66	xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
67}
68
69module_init(length_mt_init);
70module_exit(length_mt_exit);

 1// SPDX-License-Identifier: GPL-2.0-only
 2/* Kernel module to match packet length. */
 3/* (C) 1999-2001 James Morris <jmorros@intercode.com.au>
 
 
 
 
 4 */
 5
 6#include <linux/module.h>
 7#include <linux/skbuff.h>
 8#include <linux/ipv6.h>
 9#include <net/ip.h>
10
11#include <linux/netfilter/xt_length.h>
12#include <linux/netfilter/x_tables.h>
13
14MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
15MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match");
16MODULE_LICENSE("GPL");
17MODULE_ALIAS("ipt_length");
18MODULE_ALIAS("ip6t_length");
19
20static bool
21length_mt(const struct sk_buff *skb, struct xt_action_param *par)
22{
23	const struct xt_length_info *info = par->matchinfo;
24	u32 pktlen = skb_ip_totlen(skb);
25
26	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
27}
28
29static bool
30length_mt6(const struct sk_buff *skb, struct xt_action_param *par)
31{
32	const struct xt_length_info *info = par->matchinfo;
33	u32 pktlen = skb->len;
 
34
35	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
36}
37
38static struct xt_match length_mt_reg[] __read_mostly = {
39	{
40		.name		= "length",
41		.family		= NFPROTO_IPV4,
42		.match		= length_mt,
43		.matchsize	= sizeof(struct xt_length_info),
44		.me		= THIS_MODULE,
45	},
46	{
47		.name		= "length",
48		.family		= NFPROTO_IPV6,
49		.match		= length_mt6,
50		.matchsize	= sizeof(struct xt_length_info),
51		.me		= THIS_MODULE,
52	},
53};
54
55static int __init length_mt_init(void)
56{
57	return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
58}
59
60static void __exit length_mt_exit(void)
61{
62	xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
63}
64
65module_init(length_mt_init);
66module_exit(length_mt_exit);