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/* iptables module for the IPv4 and TCP ECN bits, Version 1.2
*
* (C) 2002 by Harald Welte <laforge@gnumonks.org>
*
* This software is distributed under GNU GPL v2, 1991
*
* ipt_ECN.c,v 1.4 2002/08/05 19:36:51 laforge Exp
*/
#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_ECN.h>
MODULE_LICENSE("GPL");
/* set ECT codepoint from IP header.
* return 0 in case there was no ECT codepoint
* return 1 in case ECT codepoint has been overwritten
* return < 0 in case there was error */
static int inline
set_ect_ip(struct sk_buff **pskb, struct iphdr *iph,
const struct ipt_ECN_info *einfo)
{
if ((iph->tos & IPT_ECN_IP_MASK)
!= (einfo->ip_ect & IPT_ECN_IP_MASK)) {
u_int16_t diffs[2];
/* raw socket (tcpdump) may have clone of incoming
* skb: don't disturb it --RR */
if (skb_cloned(*pskb) && !(*pskb)->sk) {
struct sk_buff *nskb = skb_copy(*pskb, GFP_ATOMIC);
if (!nskb)
return NF_DROP;
kfree_skb(*pskb);
*pskb = nskb;
iph = (*pskb)->nh.iph;
}
diffs[0] = htons(iph->tos) ^ 0xFFFF;
iph->tos = iph->tos & ~IPT_ECN_IP_MASK;
iph->tos = iph->tos | (einfo->ip_ect & IPT_ECN_IP_MASK);
diffs[1] = htons(iph->tos);
iph->check = csum_fold(csum_partial((char *)diffs,
sizeof(diffs),
iph->check^0xFFFF));
(*pskb)->nfcache |= NFC_ALTERED;
return 1;
}
return 0;
}
static int inline
set_ect_tcp(struct sk_buff **pskb, struct iphdr *iph,
const struct ipt_ECN_info *einfo)
{
struct tcphdr *tcph = (void *) iph + iph->ihl * 4;
u_int16_t *tcpflags = (u_int16_t *)tcph + 6;
u_int16_t diffs[2];
/* raw socket (tcpdump) may have clone of incoming
* skb: don't disturb it --RR */
if (skb_cloned(*pskb) && !(*pskb)->sk) {
struct sk_buff *nskb = skb_copy(*pskb, GFP_ATOMIC);
if (!nskb)
return NF_DROP;
kfree_skb(*pskb);
*pskb = nskb;
iph = (*pskb)->nh.iph;
}
diffs[0] = *tcpflags;
if (einfo->operation & IPT_ECN_OP_SET_ECE
&& tcph->ece != einfo->proto.tcp.ece) {
tcph->ece = einfo->proto.tcp.ece;
}
if (einfo->operation & IPT_ECN_OP_SET_CWR
&& tcph->cwr != einfo->proto.tcp.cwr) {
tcph->cwr = einfo->proto.tcp.cwr;
}
if (diffs[0] != *tcpflags) {
diffs[0] = diffs[0] ^ 0xFFFF;
diffs[1] = *tcpflags;
tcph->check = csum_fold(csum_partial((char *)diffs,
sizeof(diffs),
tcph->check^0xFFFF));
(*pskb)->nfcache |= NFC_ALTERED;
return 1;
}
return 0;
}
static unsigned int
target(struct sk_buff **pskb,
unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
const void *targinfo,
void *userinfo)
{
struct iphdr *iph = (*pskb)->nh.iph;
const struct ipt_ECN_info *einfo = targinfo;
if (einfo->operation & IPT_ECN_OP_SET_IP)
set_ect_ip(pskb, iph, einfo);
if (einfo->operation & (IPT_ECN_OP_SET_ECE | IPT_ECN_OP_SET_CWR)
&& iph->protocol == IPPROTO_TCP)
set_ect_tcp(pskb, iph, einfo);
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) {
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
= { { NULL, NULL }, "ECN", target, checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
if (ipt_register_target(&ipt_ecn_reg))
return -EINVAL;
return 0;
}
static void __exit fini(void)
{
ipt_unregister_target(&ipt_ecn_reg);
}
module_init(init);
module_exit(fini);
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