[ONOS-2833] Define a DnatService interface providing the rules in DNAT

table.

Change-Id: I9133f4387fce0025797d9eea9744e8268ed851d4

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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.vtn.table;
+
+import org.onlab.packet.IpAddress;
+import org.onlab.packet.MacAddress;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.flowobjective.Objective;
+import org.onosproject.vtnrsc.SegmentationId;
+
+/**
+ * DnatService interface provides the rules in DNAT table which is Table(20) for ovs pipeline.
+ * DNAT means Destination Network Address Translation, it is acronym for network terminology.
+ * Handle the downward flows.
+ */
+public interface DnatService {
+
+    /**
+     * Assemble the DNAT table rules.
+     * Match: ipv4 type and destination ip.
+     * Action: set eth_src, set ip_dst, set vnid and goto L3Forward Table(30).
+     *
+     * @param deviceId Device Id
+     * @param dstIp floating ip
+     * @param ethSrc floating ip gateway mac
+     * @param ipDst destination vm ip
+     * @param actionVni the vni of L3 network
+     * @param type the operation type of the flow rules
+     */
+    void programRules(DeviceId deviceId, IpAddress dstIp,
+                          MacAddress ethSrc, IpAddress ipDst,
+                          SegmentationId actionVni, Objective.Operation type);
+}