--- Net2/net/if_llc.h	2018/04/24 18:04:02	1.1.1.1
+++ Net2/net/if_llc.h	2018/04/24 18:21:48	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *      @(#)if_llc.h	7.2 (Berkeley) 6/28/90
+ *      from: @(#)if_llc.h	7.2 (Berkeley) 6/28/90
+ *	if_llc.h,v 1.3 1993/05/20 03:06:00 cgd Exp
  */
 
+#ifndef _NET_IF_LLC_H_
+#define _NET_IF_LLC_H_
+
 /*
  * IEEE 802.2 Link Level Control headers, for use in conjunction with
  * 802.{3,4,5} media access control methods.
@@ -80,3 +84,5 @@ struct llc {
 
 #define LLC_ISO_LSAP	0xfe
 #define LLC_SNAP_LSAP	0xaa
+
+#endif /* !_NET_IF_LLC_H_ */