/* This is a module which is used for setting the TOS field of a packet. *//* (C) 1999-2001 Paul `Rusty' Russell * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> * * 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/ip.h>#include <net/checksum.h>#include <linux/netfilter_ipv4/ip_tables.h>#include <linux/netfilter_ipv4/ipt_TOS.h>MODULE_LICENSE("GPL");MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");MODULE_DESCRIPTION("iptables TOS mangling module");static unsigned inttarget(struct sk_buff **pskb,       const struct net_device *in,       const struct net_device *out,       unsigned int hooknum,       const void *targinfo,       void *userinfo){	const struct ipt_tos_target_info *tosinfo = targinfo;	if (((*pskb)->nh.iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {		u_int16_t diffs[2];		if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))			return NF_DROP;		diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;		(*pskb)->nh.iph->tos			= ((*pskb)->nh.iph->tos & IPTOS_PREC_MASK)			| tosinfo->tos;		diffs[1] = htons((*pskb)->nh.iph->tos);		(*pskb)->nh.iph->check			= csum_fold(csum_partial((char *)diffs,						 sizeof(diffs),						 (*pskb)->nh.iph->check						 ^0xFFFF));		(*pskb)->nfcache |= NFC_ALTERED;	}	return IPT_CONTINUE;}static intcheckentry(const char *tablename,	   const struct ipt_entry *e,           void *targinfo,           unsigned int targinfosize,           unsigned int hook_mask){	const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;	if (targinfosize != IPT_ALIGN(sizeof(struct ipt_tos_target_info))) {		printk(KERN_WARNING "TOS: targinfosize %u != %Zu\n",		       targinfosize,		       IPT_ALIGN(sizeof(struct ipt_tos_target_info)));		return 0;	}	if (strcmp(tablename, "mangle") != 0) {		printk(KERN_WARNING "TOS: can only be called from \"mangle\" table, not \"%s\"\n", tablename);		return 0;	}	if (tos != IPTOS_LOWDELAY	    && tos != IPTOS_THROUGHPUT	    && tos != IPTOS_RELIABILITY	    && tos != IPTOS_MINCOST	    && tos != IPTOS_NORMALSVC) {		printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);		return 0;	}	return 1;}static struct ipt_target ipt_tos_reg = {	.name		= "TOS",	.target		= target,	.checkentry	= checkentry,	.me		= THIS_MODULE,};static int __init init(void){	return ipt_register_target(&ipt_tos_reg);}static void __exit fini(void){	ipt_unregister_target(&ipt_tos_reg);}module_init(init);module_exit(fini);