diff --git a/ggsn/tun.h b/ggsn/tun.h
new file mode 100644
index 0000000..03dc7df
--- /dev/null
+++ b/ggsn/tun.h
@@ -0,0 +1,48 @@
+/* 
+ *  OpenGGSN - Gateway GPRS Support Node
+ *  Copyright (C) 2002 Mondru AB.
+ * 
+ *  The contents of this file may be used under the terms of the GNU
+ *  General Public License Version 2, provided that the above copyright
+ *  notice and this permission notice is included in all copies or
+ *  substantial portions of the software.
+ * 
+ *  The initial developer of the original code is
+ *  Jens Jakobsen <jj@openggsn.org>
+ * 
+ *  Contributor(s):
+ * 
+ */
+
+#ifndef _TUN_H
+#define _TUN_H
+
+#define hton8(x)  (x)
+#define ntoh8(x)  (x)
+#define hton16(x) htons(x)
+#define ntoh16(x) ntohs(x)
+#define hton32(x) htonl(x)
+#define ntoh32(x) ntohl(x)
+
+#define PACKET_MAX      8196 /* TODO */
+
+/* ***********************************************************
+ * Information storage for each tun instance
+ *************************************************************/
+
+struct tun_t {
+  int fd;                /* File descriptor to network interface */
+  struct in_addr addr;   /* IP address of tun interface */
+  char devname[IFNAMSIZ];/* Name of the tun device */
+};
+
+
+extern int tun_newtun(struct tun_t **tun);
+extern int tun_freetun(struct tun_t *tun);
+extern int tun_decaps(struct tun_t *tun, 
+     int (*cb) (void *cl, struct tun_t*, void *pack, unsigned len),
+		      void *cl);
+extern int tun_encaps(struct tun_t *tun, void *pack, unsigned len);
+
+
+#endif	/* !_TUN_H */