/* iptables module for the IPv4 and TCP ECN bits, Version 1.5 * * (C) 2002 by Harald Welte <laforge@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. * * ipt_ECN.c,v 1.5 2002/08/18 19:36:51 laforge Exp*/#include <linux/module.h>#include <linux/skbuff.h>#include <linux/ip.h>#include <linux/tcp.h>#include <net/checksum.h>#include <linux/netfilter_ipv4/ip_tables.h>#include <linux/netfilter_ipv4/ipt_ECN.h>MODULE_LICENSE("GPL");MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");MODULE_DESCRIPTION("iptables ECN modification module");/* set ECT codepoint from IP header. * 	return 0 if there was an error. */static inline intset_ect_ip(struct sk_buff **pskb, const struct ipt_ECN_info *einfo){	if (((*pskb)->nh.iph->tos & IPT_ECN_IP_MASK)	    != (einfo->ip_ect & IPT_ECN_IP_MASK)) {		u_int16_t diffs[2];		if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))			return 0;		diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;		(*pskb)->nh.iph->tos &= ~IPT_ECN_IP_MASK;		(*pskb)->nh.iph->tos |= (einfo->ip_ect & IPT_ECN_IP_MASK);		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 1;}/* Return 0 if there was an error. */static inline intset_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward){	struct tcphdr tcph;	u_int16_t diffs[2];	/* Not enought header? */	if (skb_copy_bits(*pskb, (*pskb)->nh.iph->ihl*4, &tcph, sizeof(tcph))	    < 0)		return 0;	diffs[0] = ((u_int16_t *)&tcph)[6];	if (einfo->operation & IPT_ECN_OP_SET_ECE)		tcph.ece = einfo->proto.tcp.ece;	if (einfo->operation & IPT_ECN_OP_SET_CWR)		tcph.cwr = einfo->proto.tcp.cwr;	diffs[1] = ((u_int16_t *)&tcph)[6];	/* Only mangle if it's changed. */	if (diffs[0] != diffs[1]) {		diffs[0] = diffs[0] ^ 0xFFFF;		if (!skb_ip_make_writable(pskb,					  (*pskb)->nh.iph->ihl*4+sizeof(tcph)))			return 0;		if ((*pskb)->ip_summed != CHECKSUM_HW)			tcph.check = csum_fold(csum_partial((char *)diffs,					       sizeof(diffs),					       tcph.check^0xFFFF));		memcpy((*pskb)->data + (*pskb)->nh.iph->ihl*4,		       &tcph, sizeof(tcph));		if ((*pskb)->ip_summed == CHECKSUM_HW)			if (skb_checksum_help(pskb, inward))				return 0;		(*pskb)->nfcache |= NFC_ALTERED;	}	return 1;}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_ECN_info *einfo = targinfo;	if (einfo->operation & IPT_ECN_OP_SET_IP)		if (!set_ect_ip(pskb, einfo))			return NF_DROP;	if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)	    && (*pskb)->nh.iph->protocol == IPPROTO_TCP)		if (!set_ect_tcp(pskb, einfo, (out == NULL)))			return NF_DROP;	return IPT_CONTINUE;}static intcheckentry(const char *tablename,	   const struct ipt_entry *e,           void *targinfo,           unsigned int targinfosize,           unsigned int hook_mask){	const struct ipt_ECN_info *einfo = (struct ipt_ECN_info *)targinfo;	if (targinfosize != IPT_ALIGN(sizeof(struct ipt_ECN_info))) {		printk(KERN_WARNING "ECN: targinfosize %u != %Zu\n",		       targinfosize,		       IPT_ALIGN(sizeof(struct ipt_ECN_info)));		return 0;	}	if (strcmp(tablename, "mangle") != 0) {		printk(KERN_WARNING "ECN: can only be called from \"mangle\" table, not \"%s\"\n", tablename);		return 0;	}	if (einfo->operation & IPT_ECN_OP_MASK) {		printk(KERN_WARNING "ECN: unsupported ECN operation %x\n",			einfo->operation);		return 0;	}	if (einfo->ip_ect & ~IPT_ECN_IP_MASK) {		printk(KERN_WARNING "ECN: new ECT codepoint %x out of mask\n",			einfo->ip_ect);		return 0;	}	if ((einfo->operation & (IPT_ECN_OP_SET_ECE|IPT_ECN_OP_SET_CWR))	    && e->ip.proto != IPPROTO_TCP) {		printk(KERN_WARNING "ECN: cannot use TCP operations on a "		       "non-tcp rule\n");		return 0;	}	return 1;}static struct ipt_target ipt_ecn_reg = {	.name		= "ECN",	.target		= target,	.checkentry	= checkentry,	.me		= THIS_MODULE,};static int __init init(void){	return ipt_register_target(&ipt_ecn_reg);}static void __exit fini(void){	ipt_unregister_target(&ipt_ecn_reg);}module_init(init);module_exit(fini);