[NETFILTER]: x_tables: add TCPOPTSTRIP target
Signed-off-by: Sven Schnelle <svens@xxxxxxxxxxxx>
Signed-off-by: Jan Engelhardt <jengelh@xxxxxx>
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
---
commit b3e4042d568acf92a0e4b5334c8a9ca499bb3a4a
tree bbcd2fdf9fc37af122af3bb8f63caed8bf83b68c
parent f2d0e339181e7973299401191dd22031494114ae
author Sven Schnelle <svens@xxxxxxxxxxxx> Tue, 04 Dec 2007 10:46:50 +0100
committer Patrick McHardy <kaber@xxxxxxxxx> Tue, 04 Dec 2007 10:46:50 +0100
include/linux/netfilter/xt_TCPOPTSTRIP.h | 13 +++
net/netfilter/Kconfig | 8 ++
net/netfilter/Makefile | 1
net/netfilter/xt_TCPOPTSTRIP.c | 147 ++++++++++++++++++++++++++++++
4 files changed, 169 insertions(+), 0 deletions(-)
diff --git a/include/linux/netfilter/xt_TCPOPTSTRIP.h b/include/linux/netfilter/xt_TCPOPTSTRIP.h
new file mode 100644
index 0000000..2db5432
--- /dev/null
+++ b/include/linux/netfilter/xt_TCPOPTSTRIP.h
@@ -0,0 +1,13 @@
+#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 */
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 21a9fcc..693f861 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -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
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index ad0e36e..7763dea 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -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
diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c
new file mode 100644
index 0000000..43d6ac2
--- /dev/null
+++ b/net/netfilter/xt_TCPOPTSTRIP.c
@@ -0,0 +1,147 @@
+/*
+ * A module for stripping a specific TCP option from TCP packets.
+ *
+ * Copyright (C) 2007 Sven Schnelle <svens@xxxxxxxxxxxx>
+ * Copyright © CC Computer Consultants GmbH, 2007
+ * Contact: Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>
+ *
+ * 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@xxxxxxxxxxxx>, Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("netfilter \"TCPOPTSTRIP\" target module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_TCPOPTSTRIP");
+MODULE_ALIAS("ip6t_TCPOPTSTRIP");
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