diff --git a/clatd.h b/clatd.h
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+/*
+ * Copyright 2011 Daniel Drown
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * clatd.h - main system definitions
+ */
+#ifndef __CLATD_H__
+#define __CLATD_H__
+
+#include <linux/if_tun.h>
+
+#define MAXMTU 1500
+#define PACKETLEN (MAXMTU+sizeof(struct tun_pi))
+
+// how frequently (in seconds) to poll for an address change while traffic is passing
+#define INTERFACE_POLL_FREQUENCY 30
+
+// how frequently (in seconds) to poll for an address change while there is no traffic
+#define NO_TRAFFIC_INTERFACE_POLL_FREQUENCY 90
+
+#endif /* __CLATD_H__ */