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/*
* Xtables module for matching the value of the IPv4/IPv6 and TCP ECN bits
*
* (C) 2002 by Harald Welte <laforge@gnumonks.org>
* (C) 2011 Patrick McHardy <kaber@trash.net>
*
* 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.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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/xt_ecn.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_DESCRIPTION("Xtables: Explicit Congestion Notification (ECN) flag match");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_ecn");
MODULE_ALIAS("ip6t_ecn");
static bool match_tcp(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_ecn_info *einfo = par->matchinfo;
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, par->thoff, sizeof(_tcph), &_tcph);
if (th == NULL)
return false;
if (einfo->operation & XT_ECN_OP_MATCH_ECE) {
if (einfo->invert & XT_ECN_OP_MATCH_ECE) {
if (th->ece == 1)
return false;
} else {
if (th->ece == 0)
return false;
}
}
if (einfo->operation & XT_ECN_OP_MATCH_CWR) {
if (einfo->invert & XT_ECN_OP_MATCH_CWR) {
if (th->cwr == 1)
return false;
} else {
if (th->cwr == 0)
return false;
}
}
return true;
}
static inline bool match_ip(const struct sk_buff *skb,
const struct xt_ecn_info *einfo)
{
return ((ip_hdr(skb)->tos & XT_ECN_IP_MASK) == einfo->ip_ect) ^
!!(einfo->invert & XT_ECN_OP_MATCH_IP);
}
static bool ecn_mt4(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_ecn_info *info = par->matchinfo;
if (info->operation & XT_ECN_OP_MATCH_IP && !match_ip(skb, info))
return false;
if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
!match_tcp(skb, par))
return false;
return true;
}
static int ecn_mt_check4(const struct xt_mtchk_param *par)
{
const struct xt_ecn_info *info = par->matchinfo;
const struct ipt_ip *ip = par->entryinfo;
if (info->operation & XT_ECN_OP_MATCH_MASK)
return -EINVAL;
if (info->invert & XT_ECN_OP_MATCH_MASK)
return -EINVAL;
if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
(ip->proto != IPPROTO_TCP || ip->invflags & IPT_INV_PROTO)) {
pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n");
return -EINVAL;
}
return 0;
}
static inline bool match_ipv6(const struct sk_buff *skb,
const struct xt_ecn_info *einfo)
{
return (((ipv6_hdr(skb)->flow_lbl[0] >> 4) & XT_ECN_IP_MASK) ==
einfo->ip_ect) ^
!!(einfo->invert & XT_ECN_OP_MATCH_IP);
}
static bool ecn_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_ecn_info *info = par->matchinfo;
if (info->operation & XT_ECN_OP_MATCH_IP && !match_ipv6(skb, info))
return false;
if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
!match_tcp(skb, par))
return false;
return true;
}
static int ecn_mt_check6(const struct xt_mtchk_param *par)
{
const struct xt_ecn_info *info = par->matchinfo;
const struct ip6t_ip6 *ip = par->entryinfo;
if (info->operation & XT_ECN_OP_MATCH_MASK)
return -EINVAL;
if (info->invert & XT_ECN_OP_MATCH_MASK)
return -EINVAL;
if (info->operation & (XT_ECN_OP_MATCH_ECE | XT_ECN_OP_MATCH_CWR) &&
(ip->proto != IPPROTO_TCP || ip->invflags & IP6T_INV_PROTO)) {
pr_info_ratelimited("cannot match TCP bits for non-tcp packets\n");
return -EINVAL;
}
return 0;
}
static struct xt_match ecn_mt_reg[] __read_mostly = {
{
.name = "ecn",
.family = NFPROTO_IPV4,
.match = ecn_mt4,
.matchsize = sizeof(struct xt_ecn_info),
.checkentry = ecn_mt_check4,
.me = THIS_MODULE,
},
{
.name = "ecn",
.family = NFPROTO_IPV6,
.match = ecn_mt6,
.matchsize = sizeof(struct xt_ecn_info),
.checkentry = ecn_mt_check6,
.me = THIS_MODULE,
},
};
static int __init ecn_mt_init(void)
{
return xt_register_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
}
static void __exit ecn_mt_exit(void)
{
xt_unregister_matches(ecn_mt_reg, ARRAY_SIZE(ecn_mt_reg));
}
module_init(ecn_mt_init);
module_exit(ecn_mt_exit);
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