[AETHER-38] Extract pipeline-dependent code from current T3 implementation

- Exposes some ofdpa specific tables and types
- Introduces a new driver behavior PipelineTraceable
- OfdpaPipelineTraceable is the first implementation of the
  new driver behavior
- New abstractions are introduced to encapsulate the input/output
  of the traceables processing
- Implements some basic unit tests for Ofdpa implementation

Change-Id: I89d3fdeda445983ec7ebfa9ebb78afb1c6d3fd8f
diff --git a/core/api/src/main/java/org/onosproject/net/DataPlaneEntity.java b/core/api/src/main/java/org/onosproject/net/DataPlaneEntity.java
new file mode 100644
index 0000000..0c4628c
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/DataPlaneEntity.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net;
+
+import org.onosproject.net.flow.FlowEntry;
+import org.onosproject.net.group.Group;
+
+import java.util.Objects;
+
+/**
+ * Generic abstraction to hold dataplane entities.
+ */
+public class DataPlaneEntity {
+    private FlowEntry flowEntry;
+    private Group groupEntry;
+    private Type type;
+
+    /**
+     * Types of entity.
+     */
+    public enum Type {
+        /**
+         * Flow rule entity.
+         */
+        FLOWRULE,
+
+        /**
+         * Group entity.
+         */
+        GROUP
+    }
+
+    /**
+     * Creates a dataplane entity from a flow entry.
+     *
+     * @param flow the inner flow entry
+     */
+    public DataPlaneEntity(FlowEntry flow) {
+        flowEntry = flow;
+        type = Type.FLOWRULE;
+    }
+
+    /**
+     * Creates a dataplane entity from a group entry.
+     *
+     * @param group the inner group entry
+     */
+    public DataPlaneEntity(Group group) {
+        groupEntry = group;
+        type = Type.GROUP;
+    }
+
+    /**
+     * Returns the flow entry.
+     *
+     * @return the flow entry
+     */
+    public FlowEntry getFlowEntry() {
+        return flowEntry;
+    }
+
+    /**
+     * Returns the group entry.
+     *
+     * @return the group entry
+     */
+    public Group getGroupEntry() {
+        return groupEntry;
+    }
+
+    /**
+     * Returns the type of the entry.
+     *
+     * @return the type
+     */
+    public Type getType() {
+        return type;
+    }
+
+    @Override
+    public int hashCode() {
+        return type == Type.FLOWRULE ? flowEntry.hashCode() : groupEntry.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof DataPlaneEntity) {
+            DataPlaneEntity that = (DataPlaneEntity) obj;
+            if (this.type == that.type) {
+                return Objects.equals(flowEntry, that.flowEntry) &&
+                        Objects.equals(groupEntry, that.groupEntry);
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        Object entity = type == Type.FLOWRULE ? flowEntry : groupEntry;
+        return "DataPlaneEntity{" +
+                "entity=" + entity +
+                '}';
+    }
+}