NullLinkProvider to generate link events. This provider

currently chains null devices together in a linear topology.

The tunable parameters for this provider are:
  - flicker = [default false]  : flap the links by sending LinkEvents
  - eventRate = [default 3000] : time between LinkEvents, in msec

Reference: ONOS-446

Change-Id: I865c1c43c3216d9b64d67bda7c118bb041d5b1c9

@@ -31,4 +31,11 @@
 
     <description>ONOS Null link provider</description>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>org.osgi.compendium</artifactId>
+        </dependency>
+    </dependencies>
+
 </project>

+/*
+ * 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.provider.nil.link.impl;
+
+import static com.google.common.base.Strings.isNullOrEmpty;
+import static org.onlab.util.Tools.delay;
+import static org.onlab.util.Tools.namedThreads;
+import static org.slf4j.LoggerFactory.getLogger;
+
+import java.util.Dictionary;
+import java.util.List;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Property;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.onosproject.net.ConnectPoint;
+import org.onosproject.net.Device;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.Link;
+import org.onosproject.net.PortNumber;
+import org.onosproject.net.device.DeviceEvent;
+import org.onosproject.net.device.DeviceListener;
+import org.onosproject.net.device.DeviceService;
+import org.onosproject.net.link.DefaultLinkDescription;
+import org.onosproject.net.link.LinkDescription;
+import org.onosproject.net.link.LinkProvider;
+import org.onosproject.net.link.LinkProviderRegistry;
+import org.onosproject.net.link.LinkProviderService;
+import org.onosproject.net.provider.AbstractProvider;
+import org.onosproject.net.provider.ProviderId;
+import org.osgi.service.component.ComponentContext;
+import org.slf4j.Logger;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+
+/**
+ * Provider which advertises fake/nonexistent links to the core. To be used for
+ * benchmarking only.
+ */
+@Component(immediate = true)
+public class NullLinkProvider extends AbstractProvider implements LinkProvider {
+
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected DeviceService deviceService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected LinkProviderRegistry providerRegistry;
+
+    private LinkProviderService providerService;
+
+    private static final boolean FLICKER = false;
+    private static final int DEFAULT_RATE = 3000;
+    // For now, static switch port values
+    private static final PortNumber SRCPORT = PortNumber.portNumber(5);
+    private static final PortNumber DSTPORT = PortNumber.portNumber(6);
+
+    private final InternalLinkProvider linkProvider = new InternalLinkProvider();
+
+    // Link descriptions
+    private final ConcurrentMap<ConnectPoint, LinkDescription> descriptions = Maps
+            .newConcurrentMap();
+
+    // Device ID's that have been seen so far
+    private final List<DeviceId> devices = Lists.newArrayList();
+
+    private ExecutorService linkDriver = Executors.newFixedThreadPool(1,
+            namedThreads("null-link-driver"));
+
+    // If true, 'flickers' links by alternating link up/down events at eventRate
+    @Property(name = "flicker", boolValue = FLICKER,
+            label = "Setting to flap links")
+    private boolean flicker = FLICKER;
+
+    // For flicker = true, duration between events in msec.
+    @Property(name = "eventRate", intValue = DEFAULT_RATE,
+            label = "Duration between Link Event")
+    private int eventRate = 3000;
+
+    public NullLinkProvider() {
+        super(new ProviderId("null", "org.onosproject.provider.nil"));
+    }
+
+    @Activate
+    public void activate(ComponentContext context) {
+        providerService = providerRegistry.register(this);
+        deviceService.addListener(linkProvider);
+        modified(context);
+        if (flicker) {
+            linkDriver.submit(new LinkDriver());
+        }
+        log.info("started");
+    }
+
+    @Deactivate
+    public void deactivate(ComponentContext context) {
+        if (flicker) {
+            try {
+                linkDriver.awaitTermination(1000, TimeUnit.MILLISECONDS);
+            } catch (InterruptedException e) {
+                log.error("LinkBuilder did not terminate");
+            }
+            linkDriver.shutdownNow();
+        }
+        deviceService.removeListener(linkProvider);
+        providerRegistry.unregister(this);
+        deviceService = null;
+
+        log.info("stopped");
+    }
+
+    public void modified(ComponentContext context) {
+        if (context == null) {
+            log.info("No configs, using defaults: flicker={}, eventRate={}",
+                    FLICKER, DEFAULT_RATE);
+            return;
+        }
+        Dictionary<?, ?> properties = context.getProperties();
+
+        boolean flickSetting;
+        int newRate;
+        try {
+            String s = (String) properties.get("flicker");
+            flickSetting = isNullOrEmpty(s) ? flicker : Boolean.valueOf(s);
+            s = (String) properties.get("eventRate");
+            newRate = isNullOrEmpty(s) ? eventRate : Integer.valueOf(s);
+        } catch (Exception e) {
+            log.warn(e.getMessage());
+            flickSetting = flicker;
+            newRate = eventRate;
+        }
+
+        if (flicker != flickSetting) {
+            flicker = flickSetting;
+        }
+
+        if (flicker) {
+            if (eventRate != newRate) {
+                eventRate = newRate;
+            }
+            linkDriver.submit(new LinkDriver());
+        }
+        log.info("Using new settings: flicker={}, eventRate={}", flicker,
+                eventRate);
+    }
+
+    /**
+     * Adds links as devices are found, and generates LinkEvents.
+     */
+    private class InternalLinkProvider implements DeviceListener {
+
+        @Override
+        public void event(DeviceEvent event) {
+            switch (event.type()) {
+            case DEVICE_ADDED:
+                addLink(event.subject());
+                break;
+            case DEVICE_REMOVED:
+                removeLink(event.subject());
+                break;
+            default:
+                break;
+            }
+        }
+
+        private void addLink(Device current) {
+            devices.add(current.id());
+            // No link if only one device
+            if (devices.size() == 1) {
+                return;
+            }
+
+            // Attach new device to the last-seen device
+            DeviceId prev = devices.get(devices.size() - 2);
+            ConnectPoint src = new ConnectPoint(prev, SRCPORT);
+            ConnectPoint dst = new ConnectPoint(current.id(), DSTPORT);
+
+            LinkDescription fdesc = new DefaultLinkDescription(src, dst,
+                    Link.Type.DIRECT);
+            LinkDescription rdesc = new DefaultLinkDescription(dst, src,
+                    Link.Type.DIRECT);
+            descriptions.put(src, fdesc);
+            descriptions.put(dst, rdesc);
+
+            providerService.linkDetected(fdesc);
+            providerService.linkDetected(rdesc);
+        }
+
+        private void removeLink(Device device) {
+            providerService.linksVanished(device.id());
+            devices.remove(device.id());
+        }
+    }
+
+    /**
+     * Generates link events using fake links.
+     */
+    private class LinkDriver implements Runnable {
+
+        @Override
+        public void run() {
+            while (!linkDriver.isShutdown()) {
+                for (LinkDescription desc : descriptions.values()) {
+                    providerService.linkVanished(desc);
+                    delay(eventRate);
+                    providerService.linkDetected(desc);
+                    delay(eventRate);
+                }
+            }
+        }
+    }
+}

+# Sample configurations for the NullLinkProvider.
+
+#
+# If enabled, generates LinkDetected and LinkVanished events
+# to make the link appear to be flapping.
+#
+# flicker = true
+
+#
+# If enabled, sets the time between LinkEvent generation,
+# in milliseconds.
+#
+# eventRate = 2000