--- Net2/netccitt/hdlc.h	2018/04/24 18:04:01	1.1
+++ Net2/netccitt/hdlc.h	2018/04/24 18:21:28	1.1.1.2
@@ -35,9 +35,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)hdlc.h	7.4 (Berkeley) 5/6/91
+ *	from: @(#)hdlc.h	7.4 (Berkeley) 5/6/91
+ *	hdlc.h,v 1.3 1993/05/20 04:12:11 cgd Exp
  */
 
+#ifndef _NETCCITT_HDLC_H_
+#define _NETCCITT_HDLC_H_
+
 #ifndef ORDER4
 #define FALSE   0
 #define TRUE    1
@@ -154,3 +158,5 @@ struct	Hdlc_frame {
 bool	range_check ();
 bool	valid_nr ();
 struct	mbuf *hd_remove ();
+
+#endif /* !_NETCCITT_HDLC_H_ */