// 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 boollength_mt(const struct sk_buff *skb, struct xt_action_param *par){	const struct xt_length_info *info = par->matchinfo;	u32 pktlen = skb_ip_totlen(skb); 	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;} static boollength_mt6(const struct sk_buff *skb, struct xt_action_param *par){	const struct xt_length_info *info = par->matchinfo;	u32 pktlen = skb->len; 	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);