[ONOS-2835] Define a SnatService interface providing the rules in SNAT

table.

Change-Id: Ib7be8684ce2dfdc7b22526163c1e4b2f2b8aceba

+/*
+ * 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;
+
+/**
+ * SnatService interface provides the rules in SNAT table which is Table(40) for ovs pipeline.
+ * SNAT means Source Network Address Translation, it is acronym for network terminology.
+ * Handle the upward flows.
+ */
+public interface SnatService {
+
+    /**
+     * Assemble the SNAT table rules.
+     * Match: ipv4 type, vnid and source ip.
+     * Action: set eth_src, set eth_dst, set ip_src, set vnid and goto L2Forward Table(50).
+     *
+     * @param deviceId Device Id
+     * @param matchVni the vni of L3 network
+     * @param srcIP source ip
+     * @param ethDst external gateway mac
+     * @param ethSrc external port mac
+     * @param ipSrc floating ip
+     * @param actionVni external network VNI
+     * @param type the operation type of the flow rules
+     */
+    void programRules(DeviceId deviceId, SegmentationId matchVni,
+                          IpAddress srcIP, MacAddress ethDst,
+                          MacAddress ethSrc, IpAddress ipSrc,
+                          SegmentationId actionVni, Objective.Operation type);
+}