--- Net2/netinet/udp.h	2018/04/24 18:03:54	1.1
+++ Net2/netinet/udp.h	2018/04/24 18:13:37	1.1.1.2
@@ -30,9 +30,13 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)udp.h	7.4 (Berkeley) 6/28/90
+ *	from: @(#)udp.h	7.4 (Berkeley) 6/28/90
+ *	udp.h,v 1.3 1993/05/20 03:50:46 cgd Exp
  */
 
+#ifndef _NETINET_UDP_H_
+#define _NETINET_UDP_H_
+
 /*
  * Udp protocol header.
  * Per RFC 768, September, 1981.
@@ -43,3 +47,5 @@ struct udphdr {
 	short	uh_ulen;		/* udp length */
 	u_short	uh_sum;			/* udp checksum */
 };
+
+#endif /* !_NETINET_UDP_H_ */