tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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, const struct net_device *in,
25 const struct net_device *out, const struct xt_match *match,
26 const void *matchinfo, int offset, unsigned int protoff,
27 bool *hotdrop)
28{
29 const struct xt_length_info *info = matchinfo;
30 u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len);
31
32 return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
33}
34
35static bool
36length_mt6(const struct sk_buff *skb, const struct net_device *in,
37 const struct net_device *out, const struct xt_match *match,
38 const void *matchinfo, int offset, unsigned int protoff,
39 bool *hotdrop)
40{
41 const struct xt_length_info *info = matchinfo;
42 const u_int16_t pktlen = ntohs(ipv6_hdr(skb)->payload_len) +
43 sizeof(struct ipv6hdr);
44
45 return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
46}
47
48static struct xt_match length_mt_reg[] __read_mostly = {
49 {
50 .name = "length",
51 .family = AF_INET,
52 .match = length_mt,
53 .matchsize = sizeof(struct xt_length_info),
54 .me = THIS_MODULE,
55 },
56 {
57 .name = "length",
58 .family = AF_INET6,
59 .match = length_mt6,
60 .matchsize = sizeof(struct xt_length_info),
61 .me = THIS_MODULE,
62 },
63};
64
65static int __init length_mt_init(void)
66{
67 return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
68}
69
70static void __exit length_mt_exit(void)
71{
72 xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
73}
74
75module_init(length_mt_init);
76module_exit(length_mt_exit);