/* Kernel module to match packet length. *//* (C) 1999-2001 James Morris <jmorros@intercode.com.au> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */#include <linux/module.h>#include <linux/skbuff.h>#include <linux/netfilter_ipv4/ipt_length.h>#include <linux/netfilter_ipv4/ip_tables.h>MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");MODULE_DESCRIPTION("IP tables packet length matching module");MODULE_LICENSE("GPL");static intmatch(const struct sk_buff *skb,      const struct net_device *in,      const struct net_device *out,      const void *matchinfo,      int offset,      int *hotdrop){	const struct ipt_length_info *info = matchinfo;	u_int16_t pktlen = ntohs(skb->nh.iph->tot_len);		return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;}static intcheckentry(const char *tablename,           const struct ipt_ip *ip,           void *matchinfo,           unsigned int matchsize,           unsigned int hook_mask){	if (matchsize != IPT_ALIGN(sizeof(struct ipt_length_info)))		return 0;	return 1;}static struct ipt_match length_match = {	.name		= "length",	.match		= &match,	.checkentry	= &checkentry,	.me		= THIS_MODULE,};static int __init init(void){	return ipt_register_match(&length_match);}static void __exit fini(void){	ipt_unregister_match(&length_match);}module_init(init);module_exit(fini);