--- Net2/sys/protosw.h	2018/04/24 18:03:58	1.1
+++ Net2/sys/protosw.h	2018/04/24 18:16:08	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)protosw.h	7.8 (Berkeley) 4/28/91
+ *	from: @(#)protosw.h	7.8 (Berkeley) 4/28/91
+ *	protosw.h,v 1.3 1993/05/20 16:22:52 cgd Exp
  */
 
+#ifndef _SYS_PROTOSW_H_
+#define _SYS_PROTOSW_H_
+
 /*
  * Protocol switch table.
  *
@@ -207,3 +211,5 @@ char	*prcorequests[] = {
 #ifdef KERNEL
 extern	struct protosw *pffindproto(), *pffindtype();
 #endif
+
+#endif /* !_SYS_PROTOSW_H_ */