--- Net2/sys/vsio.h	2018/04/24 18:03:58	1.1.1.1
+++ Net2/sys/vsio.h	2018/04/24 18:16:42	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)vsio.h	7.4 (Berkeley) 5/9/91
+ *	from: @(#)vsio.h	7.4 (Berkeley) 5/9/91
+ *	vsio.h,v 1.3 1993/05/20 16:23:55 cgd Exp
  */
 
+#ifndef _SYS_VSIO_H_
+#define _SYS_VSIO_H_
+
  /****************************************************************************
  *									    *
  *  Copyright (c) 1983, 1984 by						    *
@@ -151,3 +155,5 @@ typedef struct _vsIoAddr {
 	vsBox	 mbox;			/* atomic read/write */
 } vsIoAddr;
 typedef vsIoAddr *vsIoAddrAddr;
+
+#endif /* !_SYS_VSIO_H_ */