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