--- Net2/sys/unpcb.h	2018/04/24 18:03:57	1.1
+++ Net2/sys/unpcb.h	2018/04/24 18:16:03	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)unpcb.h	7.6 (Berkeley) 6/28/90
+ *	from: @(#)unpcb.h	7.6 (Berkeley) 6/28/90
+ *	unpcb.h,v 1.3 1993/05/20 16:23:43 cgd Exp
  */
 
+#ifndef _SYS_UNPCB_H_
+#define _SYS_UNPCB_H_
+
 /*
  * Protocol control block for an active
  * instance of a UNIX internal protocol.
@@ -71,3 +75,5 @@ struct	unpcb {
 };
 
 #define	sotounpcb(so)	((struct unpcb *)((so)->so_pcb))
+
+#endif /* !_SYS_UNPCB_H_ */