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// SPDX-License-Identifier: GPL-2.0-only
/* Kernel module to match packet length. */
/* (C) 1999-2001 James Morris <jmorros@intercode.com.au>
*/
#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("Xtables: Packet length (Layer3,4,5) match");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_length");
MODULE_ALIAS("ip6t_length");
static bool
length_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_length_info *info = par->matchinfo;
u_int16_t pktlen = ntohs(ip_hdr(skb)->tot_len);
return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
}
static bool
length_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_length_info *info = par->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 length_mt_reg[] __read_mostly = {
{
.name = "length",
.family = NFPROTO_IPV4,
.match = length_mt,
.matchsize = sizeof(struct xt_length_info),
.me = THIS_MODULE,
},
{
.name = "length",
.family = NFPROTO_IPV6,
.match = length_mt6,
.matchsize = sizeof(struct xt_length_info),
.me = THIS_MODULE,
},
};
static int __init length_mt_init(void)
{
return xt_register_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
}
static void __exit length_mt_exit(void)
{
xt_unregister_matches(length_mt_reg, ARRAY_SIZE(length_mt_reg));
}
module_init(length_mt_init);
module_exit(length_mt_exit);
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