[ONOS-3222] Implement toString method for each Packet class

Change-Id: I17d72338d4202117d08b3dca9463be35a87a0c1e
diff --git a/utils/misc/src/main/java/org/onlab/packet/ndp/NeighborDiscoveryOptions.java b/utils/misc/src/main/java/org/onlab/packet/ndp/NeighborDiscoveryOptions.java
index 00a2606..18c0143 100644
--- a/utils/misc/src/main/java/org/onlab/packet/ndp/NeighborDiscoveryOptions.java
+++ b/utils/misc/src/main/java/org/onlab/packet/ndp/NeighborDiscoveryOptions.java
@@ -25,6 +25,7 @@
 import java.util.Arrays;
 import java.util.List;
 
+import static com.google.common.base.MoreObjects.toStringHelper;
 import static org.onlab.packet.PacketUtils.checkInput;
 
 /**
@@ -117,6 +118,18 @@
         private int optionWireLength() {
             return 8 * optionLengthField();
         }
+
+        @Override
+        public String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append("[");
+            sb.append("type= ");
+            sb.append(type);
+            sb.append("data= ");
+            sb.append(data);
+            sb.append("]");
+            return sb.toString();
+        }
     }
 
     /**
@@ -278,4 +291,11 @@
             return ndo;
         };
     }
+
+    @Override
+    public String toString() {
+        return toStringHelper(getClass())
+                .toString();
+        // TODO: need to handle options
+    }
 }