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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 | |
17 | MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>"); |
18 | MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match"); |
19 | MODULE_LICENSE("GPL"); |
20 | MODULE_ALIAS("ipt_length"); |
21 | MODULE_ALIAS("ip6t_length"); |
22 | |
23 | static bool |
24 | length_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 | |
32 | static bool |
33 | length_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 | |
42 | static 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 | |
59 | static int __init length_mt_init(void) |
60 | { |
61 | return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
62 | } |
63 | |
64 | static void __exit length_mt_exit(void) |
65 | { |
66 | xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg)); |
67 | } |
68 | |
69 | module_init(length_mt_init); |
70 | module_exit(length_mt_exit); |
71 |
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