--- Net2/sys/ktrace.h	2018/04/24 18:03:58	1.1.1.1
+++ Net2/sys/ktrace.h	2018/04/24 18:16:20	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)ktrace.h	7.4 (Berkeley) 5/7/91
+ *	from: @(#)ktrace.h	7.4 (Berkeley) 5/7/91
+ *	ktrace.h,v 1.3 1993/05/20 16:22:33 cgd Exp
  */
 
+#ifndef _SYS_KTRACE_H_
+#define _SYS_KTRACE_H_
+
 /*
  * operations to ktrace system call  (KTROP(op))
  */
@@ -142,3 +146,5 @@ int	ktrace __P((const char *, int, int,
 __END_DECLS
 
 #endif	/* !KERNEL */
+
+#endif /* !_SYS_KTRACE_H_ */