[ONOS-7926] Implement IPAM service to allocate IP for Kubernetes POD

Change-Id: I32fd1fffb41ec728d0be092ac5a8f555179e7a9e
diff --git a/apps/k8s-networking/app/src/main/java/org/onosproject/k8snetworking/impl/K8sIpamHandler.java b/apps/k8s-networking/app/src/main/java/org/onosproject/k8snetworking/impl/K8sIpamHandler.java
new file mode 100644
index 0000000..5591d2e
--- /dev/null
+++ b/apps/k8s-networking/app/src/main/java/org/onosproject/k8snetworking/impl/K8sIpamHandler.java
@@ -0,0 +1,136 @@
+/*
+ * Copyright 2019-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.k8snetworking.impl;
+
+import org.onlab.packet.IpAddress;
+import org.onosproject.cluster.ClusterService;
+import org.onosproject.cluster.LeadershipService;
+import org.onosproject.cluster.NodeId;
+import org.onosproject.core.ApplicationId;
+import org.onosproject.core.CoreService;
+import org.onosproject.k8snetworking.api.K8sIpamAdminService;
+import org.onosproject.k8snetworking.api.K8sNetworkEvent;
+import org.onosproject.k8snetworking.api.K8sNetworkListener;
+import org.onosproject.k8snetworking.api.K8sNetworkService;
+import org.onosproject.mastership.MastershipService;
+import org.osgi.service.component.annotations.Activate;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.Deactivate;
+import org.osgi.service.component.annotations.Reference;
+import org.osgi.service.component.annotations.ReferenceCardinality;
+import org.slf4j.Logger;
+
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ExecutorService;
+
+import static java.util.concurrent.Executors.newSingleThreadExecutor;
+import static org.onlab.util.Tools.groupedThreads;
+import static org.onosproject.k8snetworking.api.Constants.K8S_NETWORKING_APP_ID;
+import static org.onosproject.k8snetworking.util.K8sNetworkingUtil.getSubnetIps;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Initializes and purges the kubernetes IPAM.
+ */
+@Component(immediate = true)
+public class K8sIpamHandler {
+
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected CoreService coreService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected MastershipService mastershipService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected ClusterService clusterService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected LeadershipService leadershipService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected K8sNetworkService k8sNetworkService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY)
+    protected K8sIpamAdminService k8sIpamAdminService;
+
+    private final ExecutorService eventExecutor = newSingleThreadExecutor(
+            groupedThreads(this.getClass().getSimpleName(), "event-handler"));
+    private final InternalK8sNetworkListener k8sNetworkListener =
+            new InternalK8sNetworkListener();
+
+    private ApplicationId appId;
+    private NodeId localNodeId;
+
+    @Activate
+    protected void activate() {
+        appId = coreService.registerApplication(K8S_NETWORKING_APP_ID);
+        localNodeId = clusterService.getLocalNode().id();
+        leadershipService.runForLeadership(appId.name());
+        k8sNetworkService.addListener(k8sNetworkListener);
+
+        log.info("Started");
+    }
+
+    @Deactivate
+    protected void deactivate() {
+        k8sNetworkService.removeListener(k8sNetworkListener);
+        leadershipService.withdraw(appId.name());
+        eventExecutor.shutdown();
+
+        log.info("Stopped");
+    }
+
+    private class InternalK8sNetworkListener implements K8sNetworkListener {
+
+        private boolean isRelevantHelper() {
+            return Objects.equals(localNodeId, leadershipService.getLeader(appId.name()));
+        }
+
+        @Override
+        public void event(K8sNetworkEvent event) {
+            switch (event.type()) {
+                case K8S_NETWORK_CREATED:
+                    eventExecutor.execute(() -> processNetworkAddition(event));
+                    break;
+                case K8S_NETWORK_REMOVED:
+                    eventExecutor.execute(() -> processNetworkRemoval(event));
+                    break;
+                default:
+                    break;
+            }
+        }
+
+        private void processNetworkAddition(K8sNetworkEvent event) {
+            if (!isRelevantHelper()) {
+                return;
+            }
+
+            Set<IpAddress> ips = getSubnetIps(event.subject().cidr());
+            k8sIpamAdminService.initializeIpPool(event.subject().networkId(), ips);
+        }
+
+        private void processNetworkRemoval(K8sNetworkEvent event) {
+            if (!isRelevantHelper()) {
+                return;
+            }
+
+            k8sIpamAdminService.purgeIpPool(event.subject().networkId());
+        }
+    }
+}