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/* 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 int
set_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 int
set_ect_tcp(struct sk_buff **pskb, const struct ipt_ECN_info *einfo, int inward)
{
struct tcphdr _tcph, *tcph;
u_int16_t diffs[2];
/* Not enought header? */
tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4,
sizeof(_tcph), &_tcph);
if (!tcph)
return 0;
if (!(einfo->operation & IPT_ECN_OP_SET_ECE
|| tcph->ece == einfo->proto.tcp.ece)
&& (!(einfo->operation & IPT_ECN_OP_SET_CWR
|| tcph->cwr == einfo->proto.tcp.cwr)))
return 1;
if (!skb_ip_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph)))
return 0;
tcph = (void *)(*pskb)->nh.iph + (*pskb)->nh.iph->ihl*4;
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];
diffs[0] = diffs[0] ^ 0xFFFF;
if ((*pskb)->ip_summed != CHECKSUM_HW)
tcph->check = csum_fold(csum_partial((char *)diffs,
sizeof(diffs),
tcph->check^0xFFFF));
else
if (skb_checksum_help(*pskb, inward))
return 0;
(*pskb)->nfcache |= NFC_ALTERED;
return 1;
}
static unsigned int
target(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 int
checkentry(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 || (e->ip.invflags & IPT_INV_PROTO))) {
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);
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