Support openstack controller node status check feature

Change-Id: I285b977ae32dd6d140aca7f25b00962db77b1054
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/cli/OpenstackSyncStateCommand.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/cli/OpenstackSyncStateCommand.java
index 9f3f4a7..f21b79b 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/cli/OpenstackSyncStateCommand.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/cli/OpenstackSyncStateCommand.java
@@ -22,15 +22,10 @@
 import org.onosproject.openstacknetworking.api.OpenstackNetworkAdminService;
 import org.onosproject.openstacknetworking.api.OpenstackRouterAdminService;
 import org.onosproject.openstacknetworking.api.OpenstackSecurityGroupAdminService;
-import org.onosproject.openstacknode.api.OpenstackAuth;
+import org.onosproject.openstacknetworking.util.OpenstackNetworkingUtil;
 import org.onosproject.openstacknode.api.OpenstackNode;
 import org.onosproject.openstacknode.api.OpenstackNodeService;
 import org.openstack4j.api.OSClient;
-import org.openstack4j.api.client.IOSClientBuilder;
-import org.openstack4j.api.exceptions.AuthenticationException;
-import org.openstack4j.api.types.Facing;
-import org.openstack4j.core.transport.Config;
-import org.openstack4j.model.common.Identifier;
 import org.openstack4j.model.network.IP;
 import org.openstack4j.model.network.NetFloatingIP;
 import org.openstack4j.model.network.Network;
@@ -38,16 +33,9 @@
 import org.openstack4j.model.network.Router;
 import org.openstack4j.model.network.RouterInterface;
 import org.openstack4j.model.network.Subnet;
-import org.openstack4j.openstack.OSFactory;
 import org.openstack4j.openstack.networking.domain.NeutronRouterInterface;
 
-import javax.net.ssl.HostnameVerifier;
-import javax.net.ssl.HttpsURLConnection;
-import javax.net.ssl.SSLContext;
-import javax.net.ssl.TrustManager;
-import javax.net.ssl.X509TrustManager;
 import java.io.IOException;
-import java.security.cert.X509Certificate;
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
@@ -63,8 +51,6 @@
         description = "Synchronizes all OpenStack network states")
 public class OpenstackSyncStateCommand extends AbstractShellCommand {
 
-    private static final String DOMAIN_DEFUALT = "default";
-
     private static final String SECURITY_GROUP_FORMAT = "%-40s%-20s";
     private static final String NETWORK_FORMAT = "%-40s%-20s%-20s%-8s";
     private static final String SUBNET_FORMAT = "%-40s%-20s%-20s";
@@ -75,9 +61,6 @@
     private static final String DEVICE_OWNER_GW = "network:router_gateway";
     private static final String DEVICE_OWNER_IFACE = "network:router_interface";
 
-    private static final String KEYSTONE_V2 = "v2.0";
-    private static final String KEYSTONE_V3 = "v3";
-
     @Override
     protected void execute() {
         OpenstackSecurityGroupAdminService osSgAdminService = get(OpenstackSecurityGroupAdminService.class);
@@ -92,51 +75,9 @@
             return;
         }
 
-        OpenstackAuth auth = node.get().authentication();
-        String endpoint = buildEndpoint(node.get());
-        OpenstackAuth.Perspective perspective = auth.perspective();
+        OSClient osClient = OpenstackNetworkingUtil.getConnectedClient(node.get());
 
-        log.info("Access the ENDPOINT: {}, with AUTH_INFO username: {}, password: {}, project: {}",
-                endpoint, auth.username(), auth.password(), auth.project());
-
-        OSClient osClient;
-        Config config = getSslConfig();
-
-        try {
-            if (endpoint.contains(KEYSTONE_V2)) {
-                IOSClientBuilder.V2 builder = OSFactory.builderV2()
-                        .endpoint(endpoint)
-                        .tenantName(auth.project())
-                        .credentials(auth.username(), auth.password())
-                        .withConfig(config);
-
-                if (perspective != null) {
-                    builder.perspective(getFacing(perspective));
-                }
-
-                osClient = builder.authenticate();
-            } else if (endpoint.contains(KEYSTONE_V3)) {
-
-                Identifier project = Identifier.byName(auth.project());
-                Identifier domain = Identifier.byName(DOMAIN_DEFUALT);
-
-                IOSClientBuilder.V3 builder = OSFactory.builderV3()
-                        .endpoint(endpoint)
-                        .credentials(auth.username(), auth.password(), domain)
-                        .scopeToProject(project, domain)
-                        .withConfig(config);
-
-                if (perspective != null) {
-                    builder.perspective(getFacing(perspective));
-                }
-
-                osClient = builder.authenticate();
-            } else {
-                print("Unrecognized keystone version type");
-                return;
-            }
-        } catch (AuthenticationException e) {
-            print("Authentication failed");
+        if (osClient == null) {
             return;
         }
 
@@ -236,27 +177,6 @@
         });
     }
 
-    private String buildEndpoint(OpenstackNode node) {
-
-        OpenstackAuth auth = node.authentication();
-
-        StringBuilder endpointSb = new StringBuilder();
-        endpointSb.append(auth.protocol().name().toLowerCase());
-        endpointSb.append("://");
-        endpointSb.append(node.endPoint());
-        endpointSb.append(":");
-        endpointSb.append(auth.port());
-        endpointSb.append("/");
-
-        // in case the version is v3, we need to append identity path into endpoint
-        if (auth.version().equals("v3")) {
-            endpointSb.append("identity/");
-        }
-
-        endpointSb.append(auth.version());
-        return endpointSb.toString();
-    }
-
     private void printNetwork(Network osNet) {
         final String strNet = String.format(NETWORK_FORMAT,
                 osNet.getId(),
@@ -317,54 +237,4 @@
                         "" : floatingIp.getFixedIpAddress());
         print(strFloating);
     }
-
-    private Config getSslConfig() {
-        // we bypass the SSL certification verification for now
-        // TODO: verify server side SSL using a given certification
-        Config config = Config.newConfig().withSSLVerificationDisabled();
-
-        TrustManager[] trustAllCerts = new TrustManager[]{
-                new X509TrustManager() {
-                    public X509Certificate[] getAcceptedIssuers() {
-                        return null;
-                    }
-
-                    public void checkClientTrusted(X509Certificate[] certs, String authType) {
-                    }
-
-                    public void checkServerTrusted(X509Certificate[] certs, String authType) {
-                    }
-                }
-        };
-
-        HostnameVerifier allHostsValid = (hostname, session) -> true;
-
-        try {
-            SSLContext sc = SSLContext.getInstance("SSL");
-            sc.init(null, trustAllCerts, new java.security.SecureRandom());
-            HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
-            HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);
-
-            config.withSSLContext(sc);
-        } catch (Exception e) {
-            print("Failed to access OpenStack service");
-            return null;
-        }
-
-        return config;
-    }
-
-    private Facing getFacing(OpenstackAuth.Perspective perspective) {
-
-        switch (perspective) {
-            case PUBLIC:
-                return Facing.PUBLIC;
-            case ADMIN:
-                return Facing.ADMIN;
-            case INTERNAL:
-                return Facing.INTERNAL;
-            default:
-                return null;
-        }
-    }
 }
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingArpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingArpHandler.java
index 2919072..0319d40 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingArpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingArpHandler.java
@@ -701,7 +701,7 @@
         public boolean isRelevant(OpenstackNodeEvent event) {
             // do not allow to proceed without leadership
             NodeId leader = leadershipService.getLeader(appId.name());
-            return Objects.equals(localNodeId, leader);
+            return Objects.equals(localNodeId, leader) && event.subject().type() == GATEWAY;
         }
 
         @Override
@@ -709,17 +709,13 @@
             OpenstackNode osNode = event.subject();
             switch (event.type()) {
                 case OPENSTACK_NODE_COMPLETE:
-                    if (osNode.type().equals(GATEWAY)) {
-                        setDefaultArpRule(osNode, true);
-                        setFloatingIpArpRuleForGateway(osNode, true);
-                    }
+                    setDefaultArpRule(osNode, true);
+                    setFloatingIpArpRuleForGateway(osNode, true);
 
                     break;
                 case OPENSTACK_NODE_INCOMPLETE:
-                    if (osNode.type().equals(GATEWAY)) {
-                        setDefaultArpRule(osNode, false);
-                        setFloatingIpArpRuleForGateway(osNode, false);
-                    }
+                    setDefaultArpRule(osNode, false);
+                    setFloatingIpArpRuleForGateway(osNode, false);
                     break;
                 default:
                     break;
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingFloatingIpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingFloatingIpHandler.java
index ee8688d..dda949f 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingFloatingIpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingFloatingIpHandler.java
@@ -698,13 +698,6 @@
                     });
                     break;
                 case OPENSTACK_NODE_INCOMPLETE:
-
-                    // we only purge the routing related rules stored in each
-                    // compute node when gateway node becomes unavailable
-                    if (!event.subject().type().equals(GATEWAY))  {
-                        return;
-                    }
-
                     eventExecutor.execute(() -> {
                         for (NetFloatingIP fip : osRouterService.floatingIps()) {
                             if (Strings.isNullOrEmpty(fip.getPortId())) {
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingArpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingArpHandler.java
index 32c6785..f6b8e50 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingArpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingArpHandler.java
@@ -424,7 +424,7 @@
         public boolean isRelevant(OpenstackNodeEvent event) {
             // do not allow to proceed without leadership
             NodeId leader = leadershipService.getLeader(appId.name());
-            return Objects.equals(localNodeId, leader);
+            return Objects.equals(localNodeId, leader) && event.subject().type() == COMPUTE;
         }
 
         @Override
@@ -432,14 +432,10 @@
             OpenstackNode osNode = event.subject();
             switch (event.type()) {
                 case OPENSTACK_NODE_COMPLETE:
-                    if (osNode.type().equals(COMPUTE)) {
-                        setDefaultArpRule(osNode, true);
-                    }
+                    setDefaultArpRule(osNode, true);
                     break;
                 case OPENSTACK_NODE_INCOMPLETE:
-                    if (osNode.type().equals(COMPUTE)) {
-                        setDefaultArpRule(osNode, false);
-                    }
+                    setDefaultArpRule(osNode, false);
                     break;
                 default:
                     break;
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandler.java
index 65afbf8..2cc9671 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingDhcpHandler.java
@@ -82,7 +82,7 @@
 import static org.onosproject.openstacknetworking.api.Constants.DEFAULT_GATEWAY_MAC_STR;
 import static org.onosproject.openstacknetworking.api.Constants.DHCP_ARP_TABLE;
 import static org.onosproject.openstacknetworking.api.Constants.PRIORITY_DHCP_RULE;
-import static org.onosproject.openstacknode.api.OpenstackNode.NodeType.GATEWAY;
+import static org.onosproject.openstacknode.api.OpenstackNode.NodeType.COMPUTE;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -420,7 +420,7 @@
         public boolean isRelevant(OpenstackNodeEvent event) {
             // do not allow to proceed without leadership
             NodeId leader = leadershipService.getLeader(appId.name());
-            return Objects.equals(localNodeId, leader);
+            return Objects.equals(localNodeId, leader) && event.subject().type() == COMPUTE;
         }
 
         @Override
@@ -442,9 +442,6 @@
         }
 
         private void setDhcpRule(OpenstackNode openstackNode, boolean install) {
-            if (openstackNode.type().equals(GATEWAY)) {
-                return;
-            }
             TrafficSelector selector = DefaultTrafficSelector.builder()
                     .matchEthType(Ethernet.TYPE_IPV4)
                     .matchIPProtocol(IPv4.PROTOCOL_UDP)
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
index 538a5fd..e7492bf 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
@@ -68,6 +68,7 @@
 import static org.onosproject.openstacknetworking.impl.HostBasedInstancePort.ANNOTATION_CREATE_TIME;
 import static org.onosproject.openstacknetworking.impl.HostBasedInstancePort.ANNOTATION_NETWORK_ID;
 import static org.onosproject.openstacknetworking.impl.HostBasedInstancePort.ANNOTATION_PORT_ID;
+import static org.onosproject.openstacknode.api.OpenstackNode.NodeType.CONTROLLER;
 
 @Service
 @Component(immediate = true)
@@ -297,6 +298,10 @@
 
         @Override
         public boolean isRelevant(OpenstackNodeEvent event) {
+
+            if (event.subject().type() == CONTROLLER) {
+                return false;
+            }
             // do not allow to proceed without mastership
             Device device = deviceService.getDevice(event.subject().intgBridge());
             if (device == null) {
@@ -325,7 +330,6 @@
                     // not reacts to the events other than complete and incomplete states
                     break;
                 default:
-                    log.warn("Unsupported openstack node event type");
                     break;
             }
         }
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/OpenstackNetworkingUtil.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/OpenstackNetworkingUtil.java
index 7111820..58f3c33 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/OpenstackNetworkingUtil.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/OpenstackNetworkingUtil.java
@@ -19,14 +19,29 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import org.onosproject.net.DeviceId;
+import org.onosproject.openstacknode.api.OpenstackAuth;
+import org.onosproject.openstacknode.api.OpenstackAuth.Perspective;
 import org.onosproject.openstacknode.api.OpenstackNode;
+import org.openstack4j.api.OSClient;
+import org.openstack4j.api.client.IOSClientBuilder;
+import org.openstack4j.api.exceptions.AuthenticationException;
+import org.openstack4j.api.types.Facing;
+import org.openstack4j.core.transport.Config;
 import org.openstack4j.core.transport.ObjectMapperSingleton;
 import org.openstack4j.model.ModelEntity;
 import org.openstack4j.model.network.Port;
+import org.openstack4j.model.common.Identifier;
+import org.openstack4j.openstack.OSFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import javax.net.ssl.HostnameVerifier;
+import javax.net.ssl.HttpsURLConnection;
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.X509TrustManager;
 import java.io.InputStream;
+import java.security.cert.X509Certificate;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -46,10 +61,17 @@
     protected static final Logger log = LoggerFactory.getLogger(OpenstackNetworkingUtil.class);
 
     private static final int HEX_RADIX = 16;
-    private static final int ZERO_FUNCTION_NUMBER = 0;
+    private static final String ZERO_FUNCTION_NUMBER = "0";
     private static final String PREFIX_DEVICE_NUMBER = "s";
     private static final String PREFIX_FUNCTION_NUMBER = "f";
 
+    // keystone endpoint related variables
+    private static final String DOMAIN_DEFAULT = "default";
+    private static final String KEYSTONE_V2 = "v2.0";
+    private static final String KEYSTONE_V3 = "v3";
+    private static final String IDENTITY_PATH = "identity/";
+    private static final String SSL_TYPE = "SSL";
+
     /**
      * Prevents object instantiation from external.
      */
@@ -116,23 +138,56 @@
         return getGwByIndex(gws, gwIndex);
     }
 
-    private static OpenstackNode getGwByIndex(Set<OpenstackNode> gws, int index) {
-        Map<String, OpenstackNode> hashMap = new HashMap<>();
-        gws.forEach(gw -> hashMap.put(gw.hostname(), gw));
-        TreeMap<String, OpenstackNode> treeMap = new TreeMap<>(hashMap);
-        Iterator<String> iteratorKey = treeMap.keySet().iterator();
+    /**
+     * Obtains a connected openstack client.
+     *
+     * @param osNode openstack node
+     * @return a connected openstack client
+     */
+    public static OSClient getConnectedClient(OpenstackNode osNode) {
+        OpenstackAuth auth = osNode.authentication();
+        String endpoint = buildEndpoint(osNode);
+        Perspective perspective = auth.perspective();
 
-        int intIndex = 0;
-        OpenstackNode gw = null;
-        while (iteratorKey.hasNext()) {
-            String key = iteratorKey.next();
+        Config config = getSslConfig();
 
-            if (intIndex == index) {
-                gw = treeMap.get(key);
+        try {
+            if (endpoint.contains(KEYSTONE_V2)) {
+                IOSClientBuilder.V2 builder = OSFactory.builderV2()
+                        .endpoint(endpoint)
+                        .tenantName(auth.project())
+                        .credentials(auth.username(), auth.password())
+                        .withConfig(config);
+
+                if (perspective != null) {
+                    builder.perspective(getFacing(perspective));
+                }
+
+                return builder.authenticate();
+            } else if (endpoint.contains(KEYSTONE_V3)) {
+
+                Identifier project = Identifier.byName(auth.project());
+                Identifier domain = Identifier.byName(DOMAIN_DEFAULT);
+
+                IOSClientBuilder.V3 builder = OSFactory.builderV3()
+                        .endpoint(endpoint)
+                        .credentials(auth.username(), auth.password(), domain)
+                        .scopeToProject(project, domain)
+                        .withConfig(config);
+
+                if (perspective != null) {
+                    builder.perspective(getFacing(perspective));
+                }
+
+                return builder.authenticate();
+            } else {
+                log.warn("Unrecognized keystone version type");
+                return null;
             }
-            intIndex++;
+        } catch (AuthenticationException e) {
+            log.error("Authentication failed due to {}", e.toString());
+            return null;
         }
-        return gw;
     }
 
     /**
@@ -142,10 +197,17 @@
      * @return interface name
      */
     public static String getIntfNameFromPciAddress(Port port) {
+
+        if (port.getProfile() == null) {
+            log.error("Port profile is not found");
+            return null;
+        }
+
         if (port.getProfile() != null && port.getProfile().get(PCISLOT) == null) {
             log.error("Failed to retrieve the interface name because of no pci_slot information from the port");
             return null;
         }
+
         String busNumHex = port.getProfile().get(PCISLOT).toString().split(":")[1];
         String busNumDecimal = String.valueOf(Integer.parseInt(busNumHex, HEX_RADIX));
 
@@ -168,10 +230,7 @@
             return null;
         }
         String portNamePrefix = PORT_NAME_PREFIX_MAP.get(vendorInfoForPort);
-        if (vendorInfoForPort == null) {
-            log.error("Failed to retrieve the interface name because of no prefix information from the port");
-            return null;
-        }
+
         if (functionNumDecimal.equals(ZERO_FUNCTION_NUMBER)) {
             intfName = portNamePrefix + busNumDecimal + PREFIX_DEVICE_NUMBER + deviceNumDecimal;
         } else {
@@ -181,4 +240,121 @@
 
         return intfName;
     }
+
+    /**
+     * Builds up and a complete endpoint URL from gateway node.
+     *
+     * @param node gateway node
+     * @return a complete endpoint URL
+     */
+    private static String buildEndpoint(OpenstackNode node) {
+
+        OpenstackAuth auth = node.authentication();
+
+        StringBuilder endpointSb = new StringBuilder();
+        endpointSb.append(auth.protocol().name().toLowerCase());
+        endpointSb.append("://");
+        endpointSb.append(node.endPoint());
+        endpointSb.append(":");
+        endpointSb.append(auth.port());
+        endpointSb.append("/");
+
+        // in case the version is v3, we need to append identity path into endpoint
+        if (auth.version().equals(KEYSTONE_V3)) {
+            endpointSb.append(IDENTITY_PATH);
+        }
+
+        endpointSb.append(auth.version());
+        return endpointSb.toString();
+    }
+
+    /**
+     * Obtains the SSL config without verifying the certification.
+     *
+     * @return SSL config
+     */
+    private static Config getSslConfig() {
+        // we bypass the SSL certification verification for now
+        // TODO: verify server side SSL using a given certification
+        Config config = Config.newConfig().withSSLVerificationDisabled();
+
+        TrustManager[] trustAllCerts = new TrustManager[]{
+                new X509TrustManager() {
+                    public X509Certificate[] getAcceptedIssuers() {
+                        return null;
+                    }
+
+                    public void checkClientTrusted(X509Certificate[] certs,
+                                                   String authType) {
+                    }
+
+                    public void checkServerTrusted(X509Certificate[] certs,
+                                                   String authType) {
+                    }
+                }
+        };
+
+        HostnameVerifier allHostsValid = (hostname, session) -> true;
+
+        try {
+            SSLContext sc = SSLContext.getInstance(SSL_TYPE);
+            sc.init(null, trustAllCerts,
+                    new java.security.SecureRandom());
+            HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
+            HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);
+
+            config.withSSLContext(sc);
+        } catch (Exception e) {
+            log.error("Failed to access OpenStack service due to {}", e.toString());
+            return null;
+        }
+
+        return config;
+    }
+
+    /**
+     * Obtains the facing object with given openstack perspective.
+     *
+     * @param perspective keystone perspective
+     * @return facing object
+     */
+    private static Facing getFacing(Perspective perspective) {
+
+        switch (perspective) {
+            case PUBLIC:
+                return Facing.PUBLIC;
+            case ADMIN:
+                return Facing.ADMIN;
+            case INTERNAL:
+                return Facing.INTERNAL;
+            default:
+                return null;
+        }
+    }
+
+    /**
+     * Obtains gateway instance by giving index number.
+     *
+     * @param gws       a collection of gateway nodes
+     * @param index     index number
+     * @return gateway instance
+     */
+    private static OpenstackNode getGwByIndex(Set<OpenstackNode> gws, int index) {
+        Map<String, OpenstackNode> hashMap = new HashMap<>();
+        gws.forEach(gw -> hashMap.put(gw.hostname(), gw));
+        TreeMap<String, OpenstackNode> treeMap = new TreeMap<>(hashMap);
+        Iterator<String> iteratorKey = treeMap.keySet().iterator();
+
+        int intIndex = 0;
+        OpenstackNode gw = null;
+        while (iteratorKey.hasNext()) {
+            String key = iteratorKey.next();
+
+            if (intIndex == index) {
+                gw = treeMap.get(key);
+            }
+            intIndex++;
+        }
+        return gw;
+    }
 }
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/package-info.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/package-info.java
index 4b6cfb8..8d590eb 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/package-info.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/util/package-info.java
@@ -15,6 +15,6 @@
  */
 
 /**
- * Openstack utility package.
+ * Openstack networking utility package.
  */
 package org.onosproject.openstacknetworking.util;
\ No newline at end of file