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
14 MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
15 MODULE_DESCRIPTION("Xtables: Packet length (Layer3,4,5) match");
16 MODULE_LICENSE("GPL");
17 MODULE_ALIAS("ipt_length");
18 MODULE_ALIAS("ip6t_length");
19
20 static bool
length_mt(const struct sk_buff * skb,struct xt_action_param * par)21 length_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
29 static bool
length_mt6(const struct sk_buff * skb,struct xt_action_param * par)30 length_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
38 static 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
length_mt_init(void)55 static int __init length_mt_init(void)
56 {
57 return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
58 }
59
length_mt_exit(void)60 static void __exit length_mt_exit(void)
61 {
62 xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
63 }
64
65 module_init(length_mt_init);
66 module_exit(length_mt_exit);
67