tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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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("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(skb->nh.iph->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 u_int16_t pktlen = ntohs(skb->nh.ipv6h->payload_len) + sizeof(struct ipv6hdr);
51
52 return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
53}
54
55static struct xt_match length_match = {
56 .name = "length",
57 .match = match,
58 .matchsize = sizeof(struct xt_length_info),
59 .family = AF_INET,
60 .me = THIS_MODULE,
61};
62
63static struct xt_match length6_match = {
64 .name = "length",
65 .match = match6,
66 .matchsize = sizeof(struct xt_length_info),
67 .family = AF_INET6,
68 .me = THIS_MODULE,
69};
70
71static int __init xt_length_init(void)
72{
73 int ret;
74 ret = xt_register_match(&length_match);
75 if (ret)
76 return ret;
77 ret = xt_register_match(&length6_match);
78 if (ret)
79 xt_unregister_match(&length_match);
80
81 return ret;
82}
83
84static void __exit xt_length_fini(void)
85{
86 xt_unregister_match(&length_match);
87 xt_unregister_match(&length6_match);
88}
89
90module_init(xt_length_init);
91module_exit(xt_length_fini);