From e4076172c33810472d9d658554588b6e379a4fbe Mon Sep 17 00:00:00 2001
From: Arnaud Ebalard <arno@natisbad.org>
Date: Tue, 16 Jan 2007 14:19:20 +0000
Subject: Add ip6tables TCPMSS extension (Arnaud Ebalard <arno@natisbad.org>)

Kernel part will go in 2.6.21.
---
 extensions/libip6t_TCPMSS.c | 134 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 extensions/libip6t_TCPMSS.c

(limited to 'extensions/libip6t_TCPMSS.c')

diff --git a/extensions/libip6t_TCPMSS.c b/extensions/libip6t_TCPMSS.c
new file mode 100644
index 00000000..7fcccd5c
--- /dev/null
+++ b/extensions/libip6t_TCPMSS.c
@@ -0,0 +1,134 @@
+/* Shared library add-on to iptables to add TCPMSS target support.
+ *
+ * Copyright (c) 2000 Marc Boucher
+*/
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+#include <ip6tables.h>
+#include <linux/netfilter_ipv6/ip6_tables.h>
+#include <linux/netfilter_ipv6/ip6t_TCPMSS.h>
+
+struct mssinfo {
+	struct ip6t_entry_target t;
+	struct ip6t_tcpmss_info mss;
+};
+
+/* Function which prints out usage message. */
+static void
+help(void)
+{
+	printf(
+"TCPMSS target v%s mutually-exclusive options:\n"
+"  --set-mss value               explicitly set MSS option to specified value\n"
+"  --clamp-mss-to-pmtu           automatically clamp MSS value to (path_MTU - 60)\n",
+IPTABLES_VERSION);
+}
+
+static struct option opts[] = {
+	{ "set-mss", 1, 0, '1' },
+	{ "clamp-mss-to-pmtu", 0, 0, '2' },
+	{ 0 }
+};
+
+/* Initialize the target. */
+static void
+init(struct ip6t_entry_target *t, unsigned int *nfcache)
+{
+}
+
+/* Function which parses command options; returns true if it
+   ate an option */
+static int
+parse(int c, char **argv, int invert, unsigned int *flags,
+      const struct ip6t_entry *entry,
+      struct ip6t_entry_target **target)
+{
+	struct ip6t_tcpmss_info *mssinfo
+		= (struct ip6t_tcpmss_info *)(*target)->data;
+
+	switch (c) {
+		unsigned int mssval;
+
+	case '1':
+		if (*flags)
+			exit_error(PARAMETER_PROBLEM,
+			           "TCPMSS target: Only one option may be specified");
+		if (string_to_number(optarg, 0, 65535 - 60, &mssval) == -1)
+			exit_error(PARAMETER_PROBLEM, "Bad TCPMSS value `%s'", optarg);
+
+		mssinfo->mss = mssval;
+		*flags = 1;
+		break;
+
+	case '2':
+		if (*flags)
+			exit_error(PARAMETER_PROBLEM,
+			           "TCPMSS target: Only one option may be specified");
+		mssinfo->mss = IP6T_TCPMSS_CLAMP_PMTU;
+		*flags = 1;
+		break;
+
+	default:
+		return 0;
+	}
+
+	return 1;
+}
+
+static void
+final_check(unsigned int flags)
+{
+	if (!flags)
+		exit_error(PARAMETER_PROBLEM,
+		           "TCPMSS target: At least one parameter is required");
+}
+
+/* Prints out the targinfo. */
+static void
+print(const struct ip6t_ip6 *ip6,
+      const struct ip6t_entry_target *target,
+      int numeric)
+{
+	const struct ip6t_tcpmss_info *mssinfo =
+		(const struct ip6t_tcpmss_info *)target->data;
+	if(mssinfo->mss == IP6T_TCPMSS_CLAMP_PMTU)
+		printf("TCPMSS clamp to PMTU ");
+	else
+		printf("TCPMSS set %u ", mssinfo->mss);
+}
+
+/* Saves the union ip6t_targinfo in parsable form to stdout. */
+static void
+save(const struct ip6t_ip6 *ip, const struct ip6t_entry_target *target)
+{
+	const struct ip6t_tcpmss_info *mssinfo =
+		(const struct ip6t_tcpmss_info *)target->data;
+
+	if(mssinfo->mss == IP6T_TCPMSS_CLAMP_PMTU)
+		printf("--clamp-mss-to-pmtu ");
+	else
+		printf("--set-mss %u ", mssinfo->mss);
+}
+
+static struct ip6tables_target mss = {
+	.next		= NULL,
+	.name		= "TCPMSS",
+	.version	= IPTABLES_VERSION,
+	.size		= IP6T_ALIGN(sizeof(struct ip6t_tcpmss_info)),
+	.userspacesize	= IP6T_ALIGN(sizeof(struct ip6t_tcpmss_info)),
+	.help		= &help,
+	.init		= &init,
+	.parse		= &parse,
+	.final_check	= &final_check,
+	.print		= &print,
+	.save		= &save,
+	.extra_opts	= opts
+};
+
+void _init(void)
+{
+	register_target6(&mss);
+}
-- 
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