1 files changed, 154 insertions, 0 deletions
diff --git a/extensions/libxt_TCPMSS.c b/extensions/libxt_TCPMSS.c
new file mode 100644
index 0000000..ac9e2d0
--- /dev/null
+++ b/extensions/libxt_TCPMSS.c
@@ -0,0 +1,154 @@
+/* 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 <xtables.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_TCPMSS.h>
+
+struct mssinfo {
+	struct xt_entry_target t;
+	struct xt_tcpmss_info mss;
+};
+
+static void __TCPMSS_help(int hdrsize)
+{
+	printf(
+"TCPMSS target 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 - %d)\n",
+hdrsize);
+}
+
+static void TCPMSS_help(void)
+{
+	__TCPMSS_help(40);
+}
+
+static void TCPMSS_help6(void)
+{
+	__TCPMSS_help(60);
+}
+
+static const struct option TCPMSS_opts[] = {
+	{ "set-mss", 1, NULL, '1' },
+	{ "clamp-mss-to-pmtu", 0, NULL, '2' },
+	{ .name = NULL }
+};
+
+static int __TCPMSS_parse(int c, char **argv, int invert, unsigned int *flags,
+                          const void *entry, struct xt_entry_target **target,
+                          int hdrsize)
+{
+	struct xt_tcpmss_info *mssinfo
+		= (struct xt_tcpmss_info *)(*target)->data;
+
+	switch (c) {
+		unsigned int mssval;
+
+	case '1':
+		if (*flags)
+			xtables_error(PARAMETER_PROBLEM,
+			           "TCPMSS target: Only one option may be specified");
+		if (!xtables_strtoui(optarg, NULL, &mssval,
+		    0, UINT16_MAX - hdrsize))
+			xtables_error(PARAMETER_PROBLEM, "Bad TCPMSS value \"%s\"", optarg);
+		
+		mssinfo->mss = mssval;
+		*flags = 1;
+		break;
+
+	case '2':
+		if (*flags)
+			xtables_error(PARAMETER_PROBLEM,
+			           "TCPMSS target: Only one option may be specified");
+		mssinfo->mss = XT_TCPMSS_CLAMP_PMTU;
+		*flags = 1;
+		break;
+
+	default:
+		return 0;
+	}
+
+	return 1;
+}
+
+static int TCPMSS_parse(int c, char **argv, int invert, unsigned int *flags,
+                        const void *entry, struct xt_entry_target **target)
+{
+	return __TCPMSS_parse(c, argv, invert, flags, entry, target, 40);
+}
+
+static int TCPMSS_parse6(int c, char **argv, int invert, unsigned int *flags,
+                         const void *entry, struct xt_entry_target **target)
+{
+	return __TCPMSS_parse(c, argv, invert, flags, entry, target, 60);
+}
+
+static void TCPMSS_check(unsigned int flags)
+{
+	if (!flags)
+		xtables_error(PARAMETER_PROBLEM,
+		           "TCPMSS target: At least one parameter is required");
+}
+
+static void TCPMSS_print(const void *ip, const struct xt_entry_target *target,
+                         int numeric)
+{
+	const struct xt_tcpmss_info *mssinfo =
+		(const struct xt_tcpmss_info *)target->data;
+	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
+		printf("TCPMSS clamp to PMTU ");
+	else
+		printf("TCPMSS set %u ", mssinfo->mss);
+}
+
+static void TCPMSS_save(const void *ip, const struct xt_entry_target *target)
+{
+	const struct xt_tcpmss_info *mssinfo =
+		(const struct xt_tcpmss_info *)target->data;
+
+	if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
+		printf("--clamp-mss-to-pmtu ");
+	else
+		printf("--set-mss %u ", mssinfo->mss);
+}
+
+static struct xtables_target tcpmss_target = {
+	.family		= NFPROTO_IPV4,
+	.name		= "TCPMSS",
+	.version	= XTABLES_VERSION,
+	.size		= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
+	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
+	.help		= TCPMSS_help,
+	.parse		= TCPMSS_parse,
+	.final_check	= TCPMSS_check,
+	.print		= TCPMSS_print,
+	.save		= TCPMSS_save,
+	.extra_opts	= TCPMSS_opts,
+};
+
+static struct xtables_target tcpmss_target6 = {
+	.family		= NFPROTO_IPV6,
+	.name		= "TCPMSS",
+	.version	= XTABLES_VERSION,
+	.size		= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
+	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcpmss_info)),
+	.help		= TCPMSS_help6,
+	.parse		= TCPMSS_parse6,
+	.final_check	= TCPMSS_check,
+	.print		= TCPMSS_print,
+	.save		= TCPMSS_save,
+	.extra_opts	= TCPMSS_opts,
+};
+
+void _init(void)
+{
+	xtables_register_target(&tcpmss_target);
+	xtables_register_target(&tcpmss_target6);
+}