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/* IP tables module for matching the value of the IPv4 and TCP ECN bits
*
* (C) 2002 by Harald Welte <laforge@gnumonks.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/in.h>
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/tcp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_ecn.h>
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match for IPv4");
MODULE_LICENSE("GPL");
static inline bool match_ip(const struct sk_buff *skb,
const struct ipt_ecn_info *einfo)
{
return (ip_hdr(skb)->tos & IPT_ECN_IP_MASK) == einfo->ip_ect;
}
static inline bool match_tcp(const struct sk_buff *skb,
const struct ipt_ecn_info *einfo,
bool *hotdrop)
{
struct tcphdr _tcph;
const struct tcphdr *th;
/* In practice, TCP match does this, so can't fail. But let's
* be good citizens.
*/
th = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_tcph), &_tcph);
if (th == NULL) {
*hotdrop = false;
return false;
}
if (einfo->operation & IPT_ECN_OP_MATCH_ECE) {
if (einfo->invert & IPT_ECN_OP_MATCH_ECE) {
if (th->ece == 1)
return false;
} else {
if (th->ece == 0)
return false;
}
}
if (einfo->operation & IPT_ECN_OP_MATCH_CWR) {
if (einfo->invert & IPT_ECN_OP_MATCH_CWR) {
if (th->cwr == 1)
return false;
} else {
if (th->cwr == 0)
return false;
}
}
return true;
}
static bool
ecn_mt(const struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, const struct xt_match *match,
const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
{
const struct ipt_ecn_info *info = matchinfo;
if (info->operation & IPT_ECN_OP_MATCH_IP)
if (!match_ip(skb, info))
return false;
if (info->operation & (IPT_ECN_OP_MATCH_ECE|IPT_ECN_OP_MATCH_CWR)) {
if (ip_hdr(skb)->protocol != IPPROTO_TCP)
return false;
if (!match_tcp(skb, info, hotdrop))
return false;
}
return true;
}
static bool
ecn_mt_check(const char *tablename, const void *ip_void,
const struct xt_match *match, void *matchinfo,
unsigned int hook_mask)
{
const struct ipt_ecn_info *info = matchinfo;
const struct ipt_ip *ip = ip_void;
if (info->operation & IPT_ECN_OP_MATCH_MASK)
return false;
if (info->invert & IPT_ECN_OP_MATCH_MASK)
return false;
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 false;
}
return true;
}
static struct xt_match ecn_mt_reg __read_mostly = {
.name = "ecn",
.family = AF_INET,
.match = ecn_mt,
.matchsize = sizeof(struct ipt_ecn_info),
.checkentry = ecn_mt_check,
.me = THIS_MODULE,
};
static int __init ecn_mt_init(void)
{
return xt_register_match(&ecn_mt_reg);
}
static void __exit ecn_mt_exit(void)
{
xt_unregister_match(&ecn_mt_reg);
}
module_init(ecn_mt_init);
module_exit(ecn_mt_exit);
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