Commit 338e8a79 authored by Sven Schnelle's avatar Sven Schnelle Committed by David S. Miller

[NETFILTER]: x_tables: add TCPOPTSTRIP target

Signed-off-by: default avatarSven Schnelle <svens@bitebene.org>
Signed-off-by: default avatarJan Engelhardt <jengelh@gmx.de>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0eeb8ffc
#ifndef _XT_TCPOPTSTRIP_H
#define _XT_TCPOPTSTRIP_H
#define tcpoptstrip_set_bit(bmap, idx) \
(bmap[(idx) >> 5] |= 1U << (idx & 31))
#define tcpoptstrip_test_bit(bmap, idx) \
(((1U << (idx & 31)) & bmap[(idx) >> 5]) != 0)
struct xt_tcpoptstrip_target_info {
u_int32_t strip_bmap[8];
};
#endif /* _XT_TCPOPTSTRIP_H */
......@@ -411,6 +411,14 @@ config NETFILTER_XT_TARGET_TCPMSS
To compile it as a module, choose M here. If unsure, say N.
config NETFILTER_XT_TARGET_TCPOPTSTRIP
tristate '"TCPOPTSTRIP" target support (EXPERIMENTAL)'
depends on EXPERIMENTAL && NETFILTER_XTABLES
depends on IP_NF_MANGLE || IP6_NF_MANGLE
help
This option adds a "TCPOPTSTRIP" target, which allows you to strip
TCP options from TCP packets.
config NETFILTER_XT_MATCH_COMMENT
tristate '"comment" match support'
depends on NETFILTER_XTABLES
......
......@@ -48,6 +48,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o
obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TCPOPTSTRIP) += xt_TCPOPTSTRIP.o
obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o
# matches
......
/*
* A module for stripping a specific TCP option from TCP packets.
*
* Copyright (C) 2007 Sven Schnelle <svens@bitebene.org>
* Copyright © CC Computer Consultants GmbH, 2007
* Contact: Jan Engelhardt <jengelh@computergmbh.de>
*
* 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/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_TCPOPTSTRIP.h>
static inline unsigned int optlen(const u_int8_t *opt, unsigned int offset)
{
/* Beware zero-length options: make finite progress */
if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0)
return 1;
else
return opt[offset+1];
}
static unsigned int
tcpoptstrip_mangle_packet(struct sk_buff *skb,
const struct xt_tcpoptstrip_target_info *info,
unsigned int tcphoff, unsigned int minlen)
{
unsigned int optl, i, j;
struct tcphdr *tcph;
u_int16_t n, o;
u_int8_t *opt;
if (!skb_make_writable(skb, skb->len))
return NF_DROP;
tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
opt = (u_int8_t *)tcph;
/*
* Walk through all TCP options - if we find some option to remove,
* set all octets to %TCPOPT_NOP and adjust checksum.
*/
for (i = sizeof(struct tcphdr); i < tcp_hdrlen(skb); i += optl) {
optl = optlen(opt, i);
if (i + optl > tcp_hdrlen(skb))
break;
if (!tcpoptstrip_test_bit(info->strip_bmap, opt[i]))
continue;
for (j = 0; j < optl; ++j) {
o = opt[i+j];
n = TCPOPT_NOP;
if ((i + j) % 2 == 0) {
o <<= 8;
n <<= 8;
}
inet_proto_csum_replace2(&tcph->check, skb, htons(o),
htons(n), 0);
}
memset(opt + i, TCPOPT_NOP, optl);
}
return XT_CONTINUE;
}
static unsigned int
tcpoptstrip_tg4(struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, unsigned int hooknum,
const struct xt_target *target, const void *targinfo)
{
return tcpoptstrip_mangle_packet(skb, targinfo, ip_hdrlen(skb),
sizeof(struct iphdr) + sizeof(struct tcphdr));
}
#if defined(CONFIG_IP6_NF_MANGLE) || defined(CONFIG_IP6_NF_MANGLE_MODULE)
static unsigned int
tcpoptstrip_tg6(struct sk_buff *skb, const struct net_device *in,
const struct net_device *out, unsigned int hooknum,
const struct xt_target *target, const void *targinfo)
{
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
unsigned int tcphoff;
u_int8_t nexthdr;
nexthdr = ipv6h->nexthdr;
tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
if (tcphoff < 0)
return NF_DROP;
return tcpoptstrip_mangle_packet(skb, targinfo, tcphoff,
sizeof(*ipv6h) + sizeof(struct tcphdr));
}
#endif
static struct xt_target tcpoptstrip_tg_reg[] __read_mostly = {
{
.name = "TCPOPTSTRIP",
.family = AF_INET,
.table = "mangle",
.proto = IPPROTO_TCP,
.target = tcpoptstrip_tg4,
.targetsize = sizeof(struct xt_tcpoptstrip_target_info),
.me = THIS_MODULE,
},
#if defined(CONFIG_IP6_NF_MANGLE) || defined(CONFIG_IP6_NF_MANGLE_MODULE)
{
.name = "TCPOPTSTRIP",
.family = AF_INET6,
.table = "mangle",
.proto = IPPROTO_TCP,
.target = tcpoptstrip_tg6,
.targetsize = sizeof(struct xt_tcpoptstrip_target_info),
.me = THIS_MODULE,
},
#endif
};
static int __init tcpoptstrip_tg_init(void)
{
return xt_register_targets(tcpoptstrip_tg_reg,
ARRAY_SIZE(tcpoptstrip_tg_reg));
}
static void __exit tcpoptstrip_tg_exit(void)
{
xt_unregister_targets(tcpoptstrip_tg_reg,
ARRAY_SIZE(tcpoptstrip_tg_reg));
}
module_init(tcpoptstrip_tg_init);
module_exit(tcpoptstrip_tg_exit);
MODULE_AUTHOR("Sven Schnelle <svens@bitebene.org>, Jan Engelhardt <jengelh@computergmbh.de>");
MODULE_DESCRIPTION("netfilter \"TCPOPTSTRIP\" target module");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_TCPOPTSTRIP");
MODULE_ALIAS("ip6t_TCPOPTSTRIP");
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