Add NACK processing
diff --git a/model/ccnx-interest-header.h b/model/ccnx-interest-header.h
index d7be5fe..d93b42a 100644
--- a/model/ccnx-interest-header.h
+++ b/model/ccnx-interest-header.h
@@ -207,6 +207,7 @@
       NORMAL_INTEREST = 0,
       NACK_LOOP = 1,
       NACK_CONGESTION,
+      NACK_GIVEUP_PIT,
     };
 
   void