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

Change-Id: I17d72338d4202117d08b3dca9463be35a87a0c1e
diff --git a/utils/misc/src/main/java/org/onlab/packet/ndp/RouterSolicitation.java b/utils/misc/src/main/java/org/onlab/packet/ndp/RouterSolicitation.java
index e279a40..20b6673 100644
--- a/utils/misc/src/main/java/org/onlab/packet/ndp/RouterSolicitation.java
+++ b/utils/misc/src/main/java/org/onlab/packet/ndp/RouterSolicitation.java
@@ -22,6 +22,7 @@
 import java.nio.ByteBuffer;
 import java.util.List;
 
+import static com.google.common.base.MoreObjects.toStringHelper;
 import static org.onlab.packet.PacketUtils.checkInput;
 
 /**
@@ -152,4 +153,11 @@
             return routerSolicitation;
         };
     }
+
+    @Override
+    public String toString() {
+        return toStringHelper(getClass())
+                .toString();
+        // TODO: need to handle options
+    }
 }