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/* IP tables module for matching the value of the IPv4 and TCP ECN bits
*
* ipt_ecn.c,v 1.3 2002/05/29 15:09:00 laforge Exp
*
* (C) 2002 by Harald Welte <laforge@gnumonks.org>
*
* This software is distributed under the terms GNU GPL v2
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_ecn.h>
MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
MODULE_DESCRIPTION("IP tables ECN matching module");
MODULE_LICENSE("GPL");
static inline int match_ip(const struct sk_buff *skb,
const struct iphdr *iph,
const struct ipt_ecn_info *einfo)
{
return ((iph->tos&IPT_ECN_IP_MASK) == einfo->ip_ect);
}
static inline int match_tcp(const struct sk_buff *skb,
const struct iphdr *iph,
const struct ipt_ecn_info *einfo)
{
struct tcphdr *tcph = (void *)iph + iph->ihl*4;
if (einfo->operation & IPT_ECN_OP_MATCH_ECE) {
if (einfo->invert & IPT_ECN_OP_MATCH_ECE) {
if (tcph->ece == 1)
return 0;
} else {
if (tcph->ece == 0)
return 0;
}
}
if (einfo->operation & IPT_ECN_OP_MATCH_CWR) {
if (einfo->invert & IPT_ECN_OP_MATCH_CWR) {
if (tcph->cwr == 1)
return 0;
} else {
if (tcph->cwr == 0)
return 0;
}
}
return 1;
}
static int match(const struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, const void *matchinfo,
int offset, const void *hdr, u_int16_t datalen,
int *hotdrop)
{
const struct ipt_ecn_info *info = matchinfo;
const struct iphdr *iph = skb->nh.iph;
if (info->operation & IPT_ECN_OP_MATCH_IP)
if (!match_ip(skb, iph, info))
return 0;
if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) {
if (iph->protocol != IPPROTO_TCP)
return 0;
if (!match_tcp(skb, iph, info))
return 0;
}
return 1;
}
static int checkentry(const char *tablename, const struct ipt_ip *ip,
void *matchinfo, unsigned int matchsize,
unsigned int hook_mask)
{
const struct ipt_ecn_info *info = matchinfo;
if (matchsize != IPT_ALIGN(sizeof(struct ipt_ecn_info)))
return 0;
if (info->operation & IPT_ECN_OP_MATCH_MASK)
return 0;
if (info->invert & IPT_ECN_OP_MATCH_MASK)
return 0;
if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)
&& ip->proto != IPPROTO_TCP) {
printk(KERN_WARNING "ipt_ecn: can't match TCP bits in rule for"
" non-tcp packets\n");
return 0;
}
return 1;
}
static struct ipt_match ecn_match = { { NULL, NULL }, "ecn", &match,
&checkentry, NULL, THIS_MODULE };
static int __init init(void)
{
return ipt_register_match(&ecn_match);
}
static void __exit fini(void)
{
ipt_unregister_match(&ecn_match);
}
module_init(init);
module_exit(fini);
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