From c18ea8ec6dfdb942801b575b9fa202b49a1deecc Mon Sep 17 00:00:00 2001 From: Remi NGUYEN VAN Date: Tue, 18 Jan 2022 19:44:57 +0900 Subject: [PATCH] Support discovering services with a NetworkRequest A common mistake when using service discovery is to mismanage networks, expecting to find or be able to access services on networks that may not be available yet, or may be stale/lost. This new API allows clients to start service discovery with just a NetworkRequest, letting NsdManager track networks and notify when services are found/lost for each network. Bug: 190249673 Test: atest NsdManagerTest Change-Id: I12e799aa48fce2d1a35f708c5617386b1cc70f21 --- .../src/android/net/nsd/NsdManager.java | 249 +++++++++++++++++- 1 file changed, 248 insertions(+), 1 deletion(-) diff --git a/packages/ConnectivityT/framework-t/src/android/net/nsd/NsdManager.java b/packages/ConnectivityT/framework-t/src/android/net/nsd/NsdManager.java index ea69e092c4f3..512fbcee9330 100644 --- a/packages/ConnectivityT/framework-t/src/android/net/nsd/NsdManager.java +++ b/packages/ConnectivityT/framework-t/src/android/net/nsd/NsdManager.java @@ -18,6 +18,7 @@ package android.net.nsd; import android.annotation.NonNull; import android.annotation.Nullable; +import android.annotation.RequiresPermission; import android.annotation.SdkConstant; import android.annotation.SdkConstant.SdkConstantType; import android.annotation.SystemService; @@ -25,16 +26,22 @@ import android.app.compat.CompatChanges; import android.compat.annotation.ChangeId; import android.compat.annotation.EnabledSince; import android.content.Context; +import android.net.ConnectivityManager; +import android.net.ConnectivityManager.NetworkCallback; import android.net.Network; +import android.net.NetworkRequest; import android.os.Handler; import android.os.HandlerThread; import android.os.Looper; import android.os.Message; import android.os.RemoteException; import android.text.TextUtils; +import android.util.ArrayMap; +import android.util.ArraySet; import android.util.Log; import android.util.SparseArray; +import com.android.internal.annotations.GuardedBy; import com.android.internal.annotations.VisibleForTesting; import java.util.Objects; @@ -281,9 +288,180 @@ public final class NsdManager { private final SparseArray mListenerMap = new SparseArray(); private final SparseArray mServiceMap = new SparseArray<>(); private final Object mMapLock = new Object(); + // Map of listener key sent by client -> per-network discovery tracker + @GuardedBy("mPerNetworkDiscoveryMap") + private final ArrayMap + mPerNetworkDiscoveryMap = new ArrayMap<>(); private final ServiceHandler mHandler; + private class PerNetworkDiscoveryTracker { + final String mServiceType; + final int mProtocolType; + final DiscoveryListener mBaseListener; + final ArrayMap mPerNetworkListeners = + new ArrayMap<>(); + + final NetworkCallback mNetworkCb = new NetworkCallback() { + @Override + public void onAvailable(@NonNull Network network) { + final DelegatingDiscoveryListener wrappedListener = new DelegatingDiscoveryListener( + network, mBaseListener); + mPerNetworkListeners.put(network, wrappedListener); + discoverServices(mServiceType, mProtocolType, network, wrappedListener); + } + + @Override + public void onLost(@NonNull Network network) { + final DelegatingDiscoveryListener listener = mPerNetworkListeners.get(network); + if (listener == null) return; + listener.notifyAllServicesLost(); + // Listener will be removed from map in discovery stopped callback + stopServiceDiscovery(listener); + } + }; + + // Accessed from mHandler + private boolean mStopRequested; + + public void start(@NonNull NetworkRequest request) { + final ConnectivityManager cm = mContext.getSystemService(ConnectivityManager.class); + cm.registerNetworkCallback(request, mNetworkCb, mHandler); + mHandler.post(() -> mBaseListener.onDiscoveryStarted(mServiceType)); + } + + /** + * Stop discovery on all networks tracked by this class. + * + * This will request all underlying listeners to stop, and the last one to stop will call + * onDiscoveryStopped or onStopDiscoveryFailed. + * + * Must be called on the handler thread. + */ + public void requestStop() { + mHandler.post(() -> { + mStopRequested = true; + final ConnectivityManager cm = mContext.getSystemService(ConnectivityManager.class); + cm.unregisterNetworkCallback(mNetworkCb); + if (mPerNetworkListeners.size() == 0) { + mBaseListener.onDiscoveryStopped(mServiceType); + return; + } + for (int i = 0; i < mPerNetworkListeners.size(); i++) { + final DelegatingDiscoveryListener listener = mPerNetworkListeners.valueAt(i); + stopServiceDiscovery(listener); + } + }); + } + + private PerNetworkDiscoveryTracker(String serviceType, int protocolType, + DiscoveryListener baseListener) { + mServiceType = serviceType; + mProtocolType = protocolType; + mBaseListener = baseListener; + } + + /** + * Subset of NsdServiceInfo that is tracked to generate service lost notifications when a + * network is lost. + * + * Service lost notifications only contain service name, type and network, so only track + * that information (Network is known from the listener). This also implements + * equals/hashCode for usage in maps. + */ + private class TrackedNsdInfo { + private final String mServiceName; + private final String mServiceType; + TrackedNsdInfo(NsdServiceInfo info) { + mServiceName = info.getServiceName(); + mServiceType = info.getServiceType(); + } + + @Override + public int hashCode() { + return Objects.hash(mServiceName, mServiceType); + } + + @Override + public boolean equals(Object obj) { + if (!(obj instanceof TrackedNsdInfo)) return false; + final TrackedNsdInfo other = (TrackedNsdInfo) obj; + return Objects.equals(mServiceName, other.mServiceName) + && Objects.equals(mServiceType, other.mServiceType); + } + } + + private class DelegatingDiscoveryListener implements DiscoveryListener { + private final Network mNetwork; + private final DiscoveryListener mWrapped; + private final ArraySet mFoundInfo = new ArraySet<>(); + + private DelegatingDiscoveryListener(Network network, DiscoveryListener listener) { + mNetwork = network; + mWrapped = listener; + } + + void notifyAllServicesLost() { + for (int i = 0; i < mFoundInfo.size(); i++) { + final TrackedNsdInfo trackedInfo = mFoundInfo.valueAt(i); + final NsdServiceInfo serviceInfo = new NsdServiceInfo( + trackedInfo.mServiceName, trackedInfo.mServiceType); + serviceInfo.setNetwork(mNetwork); + mWrapped.onServiceLost(serviceInfo); + } + } + + @Override + public void onStartDiscoveryFailed(String serviceType, int errorCode) { + // The delegated listener is used when NsdManager takes care of starting/stopping + // discovery on multiple networks. Failure to start on one network is not a global + // failure to be reported up, as other networks may succeed: just log. + Log.e(TAG, "Failed to start discovery for " + serviceType + " on " + mNetwork + + " with code " + errorCode); + mPerNetworkListeners.remove(mNetwork); + } + + @Override + public void onDiscoveryStarted(String serviceType) { + // Wrapped listener was called upon registration, it is not called for discovery + // on each network + } + + @Override + public void onStopDiscoveryFailed(String serviceType, int errorCode) { + Log.e(TAG, "Failed to stop discovery for " + serviceType + " on " + mNetwork + + " with code " + errorCode); + mPerNetworkListeners.remove(mNetwork); + if (mStopRequested && mPerNetworkListeners.size() == 0) { + // Do not report onStopDiscoveryFailed when some underlying listeners failed: + // this does not mean that all listeners did, and onStopDiscoveryFailed is not + // actionable anyway. Just report that discovery stopped. + mWrapped.onDiscoveryStopped(serviceType); + } + } + + @Override + public void onDiscoveryStopped(String serviceType) { + mPerNetworkListeners.remove(mNetwork); + if (mStopRequested && mPerNetworkListeners.size() == 0) { + mWrapped.onDiscoveryStopped(serviceType); + } + } + + @Override + public void onServiceFound(NsdServiceInfo serviceInfo) { + mFoundInfo.add(new TrackedNsdInfo(serviceInfo)); + mWrapped.onServiceFound(serviceInfo); + } + + @Override + public void onServiceLost(NsdServiceInfo serviceInfo) { + mFoundInfo.remove(new TrackedNsdInfo(serviceInfo)); + mWrapped.onServiceLost(serviceInfo); + } + } + } + /** * Create a new Nsd instance. Applications use * {@link android.content.Context#getSystemService Context.getSystemService()} to retrieve @@ -641,7 +819,7 @@ public final class NsdManager { * {@link Network}. */ public void discoverServices(String serviceType, int protocolType, DiscoveryListener listener) { - discoverServices(serviceType, protocolType, null, listener); + discoverServices(serviceType, protocolType, (Network) null, listener); } /** @@ -692,6 +870,67 @@ public final class NsdManager { } } + /** + * Initiate service discovery to browse for instances of a service type. Service discovery + * consumes network bandwidth and will continue until the application calls + * {@link #stopServiceDiscovery}. + * + *

The function call immediately returns after sending a request to start service + * discovery to the framework. The application is notified of a success to initiate + * discovery through the callback {@link DiscoveryListener#onDiscoveryStarted} or a failure + * through {@link DiscoveryListener#onStartDiscoveryFailed}. + * + *

Upon successful start, application is notified when a service is found with + * {@link DiscoveryListener#onServiceFound} or when a service is lost with + * {@link DiscoveryListener#onServiceLost}. + * + *

Upon failure to start, service discovery is not active and application does + * not need to invoke {@link #stopServiceDiscovery} + * + *

The application should call {@link #stopServiceDiscovery} when discovery of this + * service type is no longer required, and/or whenever the application is paused or + * stopped. + * + *

During discovery, new networks may connect or existing networks may disconnect - for + * example if wifi is reconnected. When a service was found on a network that disconnects, + * {@link DiscoveryListener#onServiceLost} will be called. If a new network connects that + * matches the {@link NetworkRequest}, {@link DiscoveryListener#onServiceFound} will be called + * for services found on that network. Applications that do not want to track networks + * themselves are encouraged to use this method instead of other overloads of + * {@code discoverServices}, as they will receive proper notifications when a service becomes + * available or unavailable due to network changes. + * + * @param serviceType The service type being discovered. Examples include "_http._tcp" for + * http services or "_ipp._tcp" for printers + * @param protocolType The service discovery protocol + * @param networkRequest Request specifying networks that should be considered when discovering + * @param listener The listener notifies of a successful discovery and is used + * to stop discovery on this serviceType through a call on {@link #stopServiceDiscovery}. + * Cannot be null. Cannot be in use for an active service discovery. + */ + @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE) + public void discoverServices(@NonNull String serviceType, int protocolType, + @NonNull NetworkRequest networkRequest, @NonNull DiscoveryListener listener) { + if (TextUtils.isEmpty(serviceType)) { + throw new IllegalArgumentException("Service type cannot be empty"); + } + Objects.requireNonNull(networkRequest, "NetworkRequest cannot be null"); + checkProtocol(protocolType); + + NsdServiceInfo s = new NsdServiceInfo(); + s.setServiceType(serviceType); + + final int baseListenerKey = putListener(listener, s); + + final PerNetworkDiscoveryTracker discoveryInfo = new PerNetworkDiscoveryTracker( + serviceType, protocolType, listener); + + synchronized (mPerNetworkDiscoveryMap) { + mPerNetworkDiscoveryMap.put(baseListenerKey, discoveryInfo); + discoveryInfo.start(networkRequest); + } + } + /** * Stop service discovery initiated with {@link #discoverServices}. An active service * discovery is notified to the application with {@link DiscoveryListener#onDiscoveryStarted} @@ -710,6 +949,14 @@ public final class NsdManager { */ public void stopServiceDiscovery(DiscoveryListener listener) { int id = getListenerKey(listener); + // If this is a PerNetworkDiscovery request, handle it as such + synchronized (mPerNetworkDiscoveryMap) { + final PerNetworkDiscoveryTracker info = mPerNetworkDiscoveryMap.get(id); + if (info != null) { + info.requestStop(); + return; + } + } try { mService.stopDiscovery(id); } catch (RemoteException e) {