New API to listen service update

Currently, the resolution is a one shot query, it only notifies
the first finding service information. There is no way to listen
the service update. Thus, add a new API that can register a
callback to listen to the service updates continuously.

Bug: 245369943
Test: atest FrameworksNetTests CtsNetTestCases
Change-Id: I0e9d92b9028375feb3e344ab6c4acb515c5b2be9

framework-t/api/current.txt

@@ -192,14 +192,17 @@ package android.net.nsd {
     method @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE) public void discoverServices(@NonNull String, int, @NonNull android.net.NetworkRequest, @NonNull java.util.concurrent.Executor, @NonNull android.net.nsd.NsdManager.DiscoveryListener);
     method public void registerService(android.net.nsd.NsdServiceInfo, int, android.net.nsd.NsdManager.RegistrationListener);
     method public void registerService(@NonNull android.net.nsd.NsdServiceInfo, int, @NonNull java.util.concurrent.Executor, @NonNull android.net.nsd.NsdManager.RegistrationListener);
-    method public void resolveService(android.net.nsd.NsdServiceInfo, android.net.nsd.NsdManager.ResolveListener);
+    method public void registerServiceInfoCallback(@NonNull android.net.nsd.NsdServiceInfo, @NonNull java.util.concurrent.Executor, @NonNull android.net.nsd.NsdManager.ServiceInfoCallback);
-    method public void resolveService(@NonNull android.net.nsd.NsdServiceInfo, @NonNull java.util.concurrent.Executor, @NonNull android.net.nsd.NsdManager.ResolveListener);
+    method @Deprecated public void resolveService(android.net.nsd.NsdServiceInfo, android.net.nsd.NsdManager.ResolveListener);
+    method @Deprecated public void resolveService(@NonNull android.net.nsd.NsdServiceInfo, @NonNull java.util.concurrent.Executor, @NonNull android.net.nsd.NsdManager.ResolveListener);
     method public void stopServiceDiscovery(android.net.nsd.NsdManager.DiscoveryListener);
     method public void stopServiceResolution(@NonNull android.net.nsd.NsdManager.ResolveListener);
     method public void unregisterService(android.net.nsd.NsdManager.RegistrationListener);
+    method public void unregisterServiceInfoCallback(@NonNull android.net.nsd.NsdManager.ServiceInfoCallback);
     field public static final String ACTION_NSD_STATE_CHANGED = "android.net.nsd.STATE_CHANGED";
     field public static final String EXTRA_NSD_STATE = "nsd_state";
     field public static final int FAILURE_ALREADY_ACTIVE = 3; // 0x3
+    field public static final int FAILURE_BAD_PARAMETERS = 6; // 0x6
     field public static final int FAILURE_INTERNAL_ERROR = 0; // 0x0
     field public static final int FAILURE_MAX_LIMIT = 4; // 0x4
     field public static final int FAILURE_OPERATION_NOT_RUNNING = 5; // 0x5
@@ -231,18 +234,27 @@ package android.net.nsd {
     method public default void onStopResolutionFailed(@NonNull android.net.nsd.NsdServiceInfo, int);
   }
 
+  public static interface NsdManager.ServiceInfoCallback {
+    method public void onServiceInfoCallbackRegistrationFailed(int);
+    method public void onServiceInfoCallbackUnregistered();
+    method public void onServiceLost();
+    method public void onServiceUpdated(@NonNull android.net.nsd.NsdServiceInfo);
+  }
+
   public final class NsdServiceInfo implements android.os.Parcelable {
     ctor public NsdServiceInfo();
     method public int describeContents();
     method public java.util.Map<java.lang.String,byte[]> getAttributes();
-    method public java.net.InetAddress getHost();
+    method @Deprecated public java.net.InetAddress getHost();
+    method @NonNull public java.util.List<java.net.InetAddress> getHostAddresses();
     method @Nullable public android.net.Network getNetwork();
     method public int getPort();
     method public String getServiceName();
     method public String getServiceType();
     method public void removeAttribute(String);
     method public void setAttribute(String, String);
-    method public void setHost(java.net.InetAddress);
+    method @Deprecated public void setHost(java.net.InetAddress);
+    method public void setHostAddresses(@NonNull java.util.List<java.net.InetAddress>);
     method public void setNetwork(@Nullable android.net.Network);
     method public void setPort(int);
     method public void setServiceName(String);

framework-t/src/android/net/nsd/INsdManagerCallback.aidl

@@ -38,4 +38,8 @@ oneway interface INsdManagerCallback {
     void onResolveServiceSucceeded(int listenerKey, in NsdServiceInfo info);
     void onStopResolutionFailed(int listenerKey, int error);
     void onStopResolutionSucceeded(int listenerKey);
+    void onServiceInfoCallbackRegistrationFailed(int listenerKey, int error);
+    void onServiceUpdated(int listenerKey, in NsdServiceInfo info);
+    void onServiceUpdatedLost(int listenerKey);
+    void onServiceInfoCallbackUnregistered(int listenerKey);
 }

framework-t/src/android/net/nsd/INsdServiceConnector.aidl

@@ -33,4 +33,6 @@ interface INsdServiceConnector {
     void resolveService(int listenerKey, in NsdServiceInfo serviceInfo);
     void startDaemon();
     void stopResolution(int listenerKey);
+    void registerServiceInfoCallback(int listenerKey, in NsdServiceInfo serviceInfo);
+    void unregisterServiceInfoCallback(int listenerKey);
 }

framework-t/src/android/net/nsd/NsdManager.java

@@ -254,6 +254,20 @@ public final class NsdManager {
     /** @hide */
     public static final int STOP_RESOLUTION_SUCCEEDED               = 26;
 
+    /** @hide */
+    public static final int REGISTER_SERVICE_CALLBACK               = 27;
+    /** @hide */
+    public static final int REGISTER_SERVICE_CALLBACK_FAILED        = 28;
+    /** @hide */
+    public static final int SERVICE_UPDATED                         = 29;
+    /** @hide */
+    public static final int SERVICE_UPDATED_LOST                    = 30;
+
+    /** @hide */
+    public static final int UNREGISTER_SERVICE_CALLBACK             = 31;
+    /** @hide */
+    public static final int UNREGISTER_SERVICE_CALLBACK_SUCCEEDED   = 32;
+
     /** Dns based service discovery protocol */
     public static final int PROTOCOL_DNS_SD = 0x0001;
 
@@ -282,6 +296,12 @@ public final class NsdManager {
         EVENT_NAMES.put(STOP_RESOLUTION, "STOP_RESOLUTION");
         EVENT_NAMES.put(STOP_RESOLUTION_FAILED, "STOP_RESOLUTION_FAILED");
         EVENT_NAMES.put(STOP_RESOLUTION_SUCCEEDED, "STOP_RESOLUTION_SUCCEEDED");
+        EVENT_NAMES.put(REGISTER_SERVICE_CALLBACK, "REGISTER_SERVICE_CALLBACK");
+        EVENT_NAMES.put(REGISTER_SERVICE_CALLBACK_FAILED, "REGISTER_SERVICE_CALLBACK_FAILED");
+        EVENT_NAMES.put(SERVICE_UPDATED, "SERVICE_UPDATED");
+        EVENT_NAMES.put(UNREGISTER_SERVICE_CALLBACK, "UNREGISTER_SERVICE_CALLBACK");
+        EVENT_NAMES.put(UNREGISTER_SERVICE_CALLBACK_SUCCEEDED,
+                "UNREGISTER_SERVICE_CALLBACK_SUCCEEDED");
     }
 
     /** @hide */
@@ -617,6 +637,26 @@ public final class NsdManager {
         public void onStopResolutionSucceeded(int listenerKey) {
             sendNoArg(STOP_RESOLUTION_SUCCEEDED, listenerKey);
         }
+
+        @Override
+        public void onServiceInfoCallbackRegistrationFailed(int listenerKey, int error) {
+            sendError(REGISTER_SERVICE_CALLBACK_FAILED, listenerKey, error);
+        }
+
+        @Override
+        public void onServiceUpdated(int listenerKey, NsdServiceInfo info) {
+            sendInfo(SERVICE_UPDATED, listenerKey, info);
+        }
+
+        @Override
+        public void onServiceUpdatedLost(int listenerKey) {
+            sendNoArg(SERVICE_UPDATED_LOST, listenerKey);
+        }
+
+        @Override
+        public void onServiceInfoCallbackUnregistered(int listenerKey) {
+            sendNoArg(UNREGISTER_SERVICE_CALLBACK_SUCCEEDED, listenerKey);
+        }
     }
 
     /**
@@ -646,6 +686,14 @@ public final class NsdManager {
      */
     public static final int FAILURE_OPERATION_NOT_RUNNING       = 5;
 
+    /**
+     * Indicates that the service has failed to resolve because of bad parameters.
+     *
+     * This failure is passed with
+     * {@link ServiceInfoCallback#onServiceInfoCallbackRegistrationFailed}.
+     */
+    public static final int FAILURE_BAD_PARAMETERS              = 6;
+
     /** @hide */
     @Retention(RetentionPolicy.SOURCE)
     @IntDef(value = {
@@ -654,6 +702,15 @@ public final class NsdManager {
     public @interface StopOperationFailureCode {
     }
 
+    /** @hide */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef(value = {
+            FAILURE_ALREADY_ACTIVE,
+            FAILURE_BAD_PARAMETERS,
+    })
+    public @interface ResolutionFailureCode {
+    }
+
     /** Interface for callback invocation for service discovery */
     public interface DiscoveryListener {
 
@@ -727,6 +784,54 @@ public final class NsdManager {
                 @StopOperationFailureCode int errorCode) { }
     }
 
+    /**
+     * Callback to listen to service info updates.
+     *
+     * For use with {@link NsdManager#registerServiceInfoCallback} to register, and with
+     * {@link NsdManager#unregisterServiceInfoCallback} to stop listening.
+     */
+    public interface ServiceInfoCallback {
+
+        /**
+         * Reports that registering the callback failed with an error.
+         *
+         * Called on the executor passed to {@link NsdManager#registerServiceInfoCallback}.
+         *
+         * onServiceInfoCallbackRegistrationFailed will be called exactly once when the callback
+         * could not be registered. No other callback will be sent in that case.
+         */
+        void onServiceInfoCallbackRegistrationFailed(@ResolutionFailureCode int errorCode);
+
+        /**
+         * Reports updated service info.
+         *
+         * Called on the executor passed to {@link NsdManager#registerServiceInfoCallback}. Any
+         * service updates will be notified via this callback until
+         * {@link NsdManager#unregisterServiceInfoCallback} is called. This will only be called once
+         * the service is found, so may never be called if the service is never present.
+         */
+        void onServiceUpdated(@NonNull NsdServiceInfo serviceInfo);
+
+        /**
+         * Reports when the service that this callback listens to becomes unavailable.
+         *
+         * Called on the executor passed to {@link NsdManager#registerServiceInfoCallback}. The
+         * service may become available again, in which case {@link #onServiceUpdated} will be
+         * called.
+         */
+        void onServiceLost();
+
+        /**
+         * Reports that service info updates have stopped.
+         *
+         * Called on the executor passed to {@link NsdManager#registerServiceInfoCallback}.
+         *
+         * A callback unregistration operation will call onServiceInfoCallbackUnregistered
+         * once. After this, the callback may be reused.
+         */
+        void onServiceInfoCallbackUnregistered();
+    }
+
     @VisibleForTesting
     class ServiceHandler extends Handler {
         ServiceHandler(Looper looper) {
@@ -827,6 +932,23 @@ public final class NsdManager {
                     executor.execute(() -> ((ResolveListener) listener).onResolveStopped(
                             ns));
                     break;
+                case REGISTER_SERVICE_CALLBACK_FAILED:
+                    removeListener(key);
+                    executor.execute(() -> ((ServiceInfoCallback) listener)
+                            .onServiceInfoCallbackRegistrationFailed(errorCode));
+                    break;
+                case SERVICE_UPDATED:
+                    executor.execute(() -> ((ServiceInfoCallback) listener)
+                            .onServiceUpdated((NsdServiceInfo) obj));
+                    break;
+                case SERVICE_UPDATED_LOST:
+                    executor.execute(() -> ((ServiceInfoCallback) listener).onServiceLost());
+                    break;
+                case UNREGISTER_SERVICE_CALLBACK_SUCCEEDED:
+                    removeListener(key);
+                    executor.execute(() -> ((ServiceInfoCallback) listener)
+                            .onServiceInfoCallbackUnregistered());
+                    break;
                 default:
                     Log.d(TAG, "Ignored " + message);
                     break;
@@ -1138,7 +1260,14 @@ public final class NsdManager {
      * @param serviceInfo service to be resolved
      * @param listener to receive callback upon success or failure. Cannot be null.
      * Cannot be in use for an active service resolution.
+     *
+     * @deprecated the returned ServiceInfo may get stale at any time after resolution, including
+     * immediately after the callback is called, and may not contain some service information that
+     * could be delivered later, like additional host addresses. Prefer using
+     * {@link #registerServiceInfoCallback}, which will keep the application up-to-date with the
+     * state of the service.
      */
+    @Deprecated
     public void resolveService(NsdServiceInfo serviceInfo, ResolveListener listener) {
         resolveService(serviceInfo, Runnable::run, listener);
     }
@@ -1150,7 +1279,14 @@ public final class NsdManager {
      * @param serviceInfo service to be resolved
      * @param executor Executor to run listener callbacks with
      * @param listener to receive callback upon success or failure.
+     *
+     * @deprecated the returned ServiceInfo may get stale at any time after resolution, including
+     * immediately after the callback is called, and may not contain some service information that
+     * could be delivered later, like additional host addresses. Prefer using
+     * {@link #registerServiceInfoCallback}, which will keep the application up-to-date with the
+     * state of the service.
      */
+    @Deprecated
     public void resolveService(@NonNull NsdServiceInfo serviceInfo,
             @NonNull Executor executor, @NonNull ResolveListener listener) {
         checkServiceInfo(serviceInfo);
@@ -1185,6 +1321,62 @@ public final class NsdManager {
         }
     }
 
+    /**
+     * Register a callback to listen for updates to a service.
+     *
+     * An application can listen to a service to continuously monitor availability of given service.
+     * The callback methods will be called on the passed executor. And service updates are sent with
+     * continuous calls to {@link ServiceInfoCallback#onServiceUpdated}.
+     *
+     * This is different from {@link #resolveService} which provides one shot service information.
+     *
+     * <p> An application can listen to a service once a time. It needs to cancel the registration
+     * before registering other callbacks. Upon failure to register a callback for example if
+     * it's a duplicated registration, the application is notified through
+     * {@link ServiceInfoCallback#onServiceInfoCallbackRegistrationFailed} with
+     * {@link #FAILURE_BAD_PARAMETERS} or {@link #FAILURE_ALREADY_ACTIVE}.
+     *
+     * @param serviceInfo the service to receive updates for
+     * @param executor Executor to run callbacks with
+     * @param listener to receive callback upon service update
+     */
+    public void registerServiceInfoCallback(@NonNull NsdServiceInfo serviceInfo,
+            @NonNull Executor executor, @NonNull ServiceInfoCallback listener) {
+        checkServiceInfo(serviceInfo);
+        int key = putListener(listener, executor, serviceInfo);
+        try {
+            mService.registerServiceInfoCallback(key, serviceInfo);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
+    /**
+     * Unregister a callback registered with {@link #registerServiceInfoCallback}.
+     *
+     * A successful unregistration is notified with a call to
+     * {@link ServiceInfoCallback#onServiceInfoCallbackUnregistered}. The same callback can only be
+     * reused after this is called.
+     *
+     * <p>If the callback is not already registered, this will throw with
+     * {@link IllegalArgumentException}.
+     *
+     * @param listener This should be a listener object that was passed to
+     *                 {@link #registerServiceInfoCallback}. It identifies the registration that
+     *                 should be unregistered and notifies of a successful or unsuccessful stop.
+     *                 Throws {@code IllegalArgumentException} if the listener was not passed to
+     *                 {@link #registerServiceInfoCallback} before.
+     */
+    public void unregisterServiceInfoCallback(@NonNull ServiceInfoCallback listener) {
+        // Will throw IllegalArgumentException if the listener is not known
+        int id = getListenerKey(listener);
+        try {
+            mService.unregisterServiceInfoCallback(id);
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+        }
+    }
+
     private static void checkListener(Object listener) {
         Objects.requireNonNull(listener, "listener cannot be null");
     }

framework-t/src/android/net/nsd/NsdServiceInfo.java

@@ -26,10 +26,14 @@ import android.text.TextUtils;
 import android.util.ArrayMap;
 import android.util.Log;
 
+import com.android.net.module.util.InetAddressUtils;
+
 import java.io.UnsupportedEncodingException;
 import java.net.InetAddress;
 import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -46,7 +50,7 @@ public final class NsdServiceInfo implements Parcelable {
 
     private final ArrayMap<String, byte[]> mTxtRecord = new ArrayMap<>();
 
-    private InetAddress mHost;
+    private final List<InetAddress> mHostAddresses = new ArrayList<>();
 
     private int mPort;
 
@@ -84,17 +88,32 @@ public final class NsdServiceInfo implements Parcelable {
         mServiceType = s;
     }
 
-    /** Get the host address. The host address is valid for a resolved service. */
+    /**
+     * Get the host address. The host address is valid for a resolved service.
+     *
+     * @deprecated Use {@link #getHostAddresses()} to get the entire list of addresses for the host.
+     */
+    @Deprecated
     public InetAddress getHost() {
-        return mHost;
+        return mHostAddresses.size() == 0 ? null : mHostAddresses.get(0);
     }
 
-    /** Set the host address */
+    /**
+     * Set the host address
+     *
+     * @deprecated Use {@link #setHostAddresses(List)} to set multiple addresses for the host.
+     */
+    @Deprecated
     public void setHost(InetAddress s) {
-        mHost = s;
+        setHostAddresses(Collections.singletonList(s));
     }
 
-    /** Get port number. The port number is valid for a resolved service. */
+    /**
+     * Get port number. The port number is valid for a resolved service.
+     *
+     * The port is valid for all addresses.
+     * @see #getHostAddresses()
+     */
     public int getPort() {
         return mPort;
     }
@@ -104,6 +123,24 @@ public final class NsdServiceInfo implements Parcelable {
         mPort = p;
     }
 
+    /**
+     * Get the host addresses.
+     *
+     * All host addresses are valid for the resolved service.
+     * All addresses share the same port
+     * @see #getPort()
+     */
+    @NonNull
+    public List<InetAddress> getHostAddresses() {
+        return new ArrayList<>(mHostAddresses);
+    }
+
+    /** Set the host addresses */
+    public void setHostAddresses(@NonNull List<InetAddress> addresses) {
+        mHostAddresses.clear();
+        mHostAddresses.addAll(addresses);
+    }
+
     /**
      * Unpack txt information from a base-64 encoded byte array.
      *
@@ -359,7 +396,7 @@ public final class NsdServiceInfo implements Parcelable {
         StringBuilder sb = new StringBuilder();
         sb.append("name: ").append(mServiceName)
                 .append(", type: ").append(mServiceType)
-                .append(", host: ").append(mHost)
+                .append(", hostAddresses: ").append(TextUtils.join(", ", mHostAddresses))
                 .append(", port: ").append(mPort)
                 .append(", network: ").append(mNetwork);
 
@@ -377,12 +414,6 @@ public final class NsdServiceInfo implements Parcelable {
     public void writeToParcel(Parcel dest, int flags) {
         dest.writeString(mServiceName);
         dest.writeString(mServiceType);
-        if (mHost != null) {
-            dest.writeInt(1);
-            dest.writeByteArray(mHost.getAddress());
-        } else {
-            dest.writeInt(0);
-        }
         dest.writeInt(mPort);
 
         // TXT record key/value pairs.
@@ -401,6 +432,10 @@ public final class NsdServiceInfo implements Parcelable {
 
         dest.writeParcelable(mNetwork, 0);
         dest.writeInt(mInterfaceIndex);
+        dest.writeInt(mHostAddresses.size());
+        for (InetAddress address : mHostAddresses) {
+            InetAddressUtils.parcelInetAddress(dest, address, flags);
+        }
     }
 
     /** Implement the Parcelable interface */
@@ -410,13 +445,6 @@ public final class NsdServiceInfo implements Parcelable {
                 NsdServiceInfo info = new NsdServiceInfo();
                 info.mServiceName = in.readString();
                 info.mServiceType = in.readString();
-
-                if (in.readInt() == 1) {
-                    try {
-                        info.mHost = InetAddress.getByAddress(in.createByteArray());
-                    } catch (java.net.UnknownHostException e) {}
-                }
-
                 info.mPort = in.readInt();
 
                 // TXT record key/value pairs.
@@ -432,6 +460,10 @@ public final class NsdServiceInfo implements Parcelable {
                 }
                 info.mNetwork = in.readParcelable(null, Network.class);
                 info.mInterfaceIndex = in.readInt();
+                int size = in.readInt();
+                for (int i = 0; i < size; i++) {
+                    info.mHostAddresses.add(InetAddressUtils.unparcelInetAddress(in));
+                }
                 return info;
             }
 

service-t/src/com/android/server/NsdService.java

@@ -83,6 +83,7 @@ import java.nio.charset.StandardCharsets;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -412,6 +413,13 @@ public class NsdService extends INsdManager.Stub {
                                     clientId, NsdManager.FAILURE_OPERATION_NOT_RUNNING);
                         }
                         break;
+                    case NsdManager.REGISTER_SERVICE_CALLBACK:
+                        cInfo = getClientInfoForReply(msg);
+                        if (cInfo != null) {
+                            cInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                        }
+                        break;
                     case NsdManager.DAEMON_CLEANUP:
                         maybeStopDaemon();
                         break;
@@ -490,6 +498,11 @@ public class NsdService extends INsdManager.Stub {
                 maybeStopMonitoringSocketsIfNoActiveRequest();
             }
 
+            private void clearRegisteredServiceInfo(ClientInfo clientInfo) {
+                clientInfo.mRegisteredService = null;
+                clientInfo.mClientIdForServiceUpdates = 0;
+            }
+
             /**
              * Check the given service type is valid and construct it to a service type
              * which can use for discovery / resolution service.
@@ -793,6 +806,56 @@ public class NsdService extends INsdManager.Stub {
                         clientInfo.mResolvedService = null;
                         // TODO: Implement the stop resolution with MdnsDiscoveryManager.
                         break;
+                    case NsdManager.REGISTER_SERVICE_CALLBACK:
+                        if (DBG) Log.d(TAG, "Register a service callback");
+                        args = (ListenerArgs) msg.obj;
+                        clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in callback registration");
+                            break;
+                        }
+
+                        if (clientInfo.mRegisteredService != null) {
+                            clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_ALREADY_ACTIVE);
+                            break;
+                        }
+
+                        maybeStartDaemon();
+                        id = getUniqueId();
+                        if (resolveService(id, args.serviceInfo)) {
+                            clientInfo.mRegisteredService = new NsdServiceInfo();
+                            clientInfo.mClientIdForServiceUpdates = clientId;
+                            storeRequestMap(clientId, id, clientInfo, msg.what);
+                        } else {
+                            clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                    clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                        }
+                        break;
+                    case NsdManager.UNREGISTER_SERVICE_CALLBACK:
+                        if (DBG) Log.d(TAG, "Unregister a service callback");
+                        args = (ListenerArgs) msg.obj;
+                        clientInfo = mClients.get(args.connector);
+                        // If the binder death notification for a INsdManagerCallback was received
+                        // before any calls are received by NsdService, the clientInfo would be
+                        // cleared and cause NPE. Add a null check here to prevent this corner case.
+                        if (clientInfo == null) {
+                            Log.e(TAG, "Unknown connector in callback unregistration");
+                            break;
+                        }
+
+                        id = clientInfo.mClientIds.get(clientId);
+                        removeRequestMap(clientId, id, clientInfo);
+                        if (stopResolveService(id)) {
+                            clientInfo.onServiceInfoCallbackUnregistered(clientId);
+                        } else {
+                            Log.e(TAG, "Failed to unregister service info callback");
+                        }
+                        clearRegisteredServiceInfo(clientInfo);
+                        break;
                     case MDNS_SERVICE_EVENT:
                         if (!handleMDnsServiceEvent(msg.arg1, msg.arg2, msg.obj)) {
                             return NOT_HANDLED;
@@ -809,6 +872,19 @@ public class NsdService extends INsdManager.Stub {
                 return HANDLED;
             }
 
+            private void notifyResolveFailedResult(boolean isListenedToUpdates, int clientId,
+                    ClientInfo clientInfo, int error) {
+                if (isListenedToUpdates) {
+                    clientInfo.onServiceInfoCallbackRegistrationFailed(clientId, error);
+                    clearRegisteredServiceInfo(clientInfo);
+                } else {
+                    // The resolve API always returned FAILURE_INTERNAL_ERROR on error; keep it
+                    // for backwards compatibility.
+                    clientInfo.onResolveServiceFailed(clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                    clientInfo.mResolvedService = null;
+                }
+            }
+
             private boolean handleMDnsServiceEvent(int code, int id, Object obj) {
                 NsdServiceInfo servInfo;
                 ClientInfo clientInfo = mIdToClientInfoMap.get(id);
@@ -859,6 +935,8 @@ public class NsdService extends INsdManager.Stub {
                         // found services on the same interface index and their network at the time
                         setServiceNetworkForCallback(servInfo, lostNetId, info.interfaceIdx);
                         clientInfo.onServiceLost(clientId, servInfo);
+                        // TODO: also support registered service lost when not discovering
+                        clientInfo.maybeNotifyRegisteredServiceLost(servInfo);
                         break;
                     }
                     case IMDnsEventListener.SERVICE_DISCOVERY_FAILED:
@@ -895,10 +973,15 @@ public class NsdService extends INsdManager.Stub {
                         String rest = fullName.substring(index);
                         String type = rest.replace(".local.", "");
 
-                        clientInfo.mResolvedService.setServiceName(name);
+                        final boolean isListenedToUpdates =
-                        clientInfo.mResolvedService.setServiceType(type);
+                                clientId == clientInfo.mClientIdForServiceUpdates;
-                        clientInfo.mResolvedService.setPort(info.port);
+                        final NsdServiceInfo serviceInfo = isListenedToUpdates
-                        clientInfo.mResolvedService.setTxtRecords(info.txtRecord);
+                                ? clientInfo.mRegisteredService : clientInfo.mResolvedService;
+
+                        serviceInfo.setServiceName(name);
+                        serviceInfo.setServiceType(type);
+                        serviceInfo.setPort(info.port);
+                        serviceInfo.setTxtRecords(info.txtRecord);
                         // Network will be added after SERVICE_GET_ADDR_SUCCESS
 
                         stopResolveService(id);
@@ -908,9 +991,8 @@ public class NsdService extends INsdManager.Stub {
                         if (getAddrInfo(id2, info.hostname, info.interfaceIdx)) {
                             storeRequestMap(clientId, id2, clientInfo, NsdManager.RESOLVE_SERVICE);
                         } else {
-                            clientInfo.onResolveServiceFailed(
+                            notifyResolveFailedResult(isListenedToUpdates, clientId, clientInfo,
-                                    clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                                    NsdManager.FAILURE_BAD_PARAMETERS);
-                            clientInfo.mResolvedService = null;
                         }
                         break;
                     }
@@ -918,17 +1000,17 @@ public class NsdService extends INsdManager.Stub {
                         /* NNN resolveId errorCode */
                         stopResolveService(id);
                         removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
+                        notifyResolveFailedResult(
-                        clientInfo.onResolveServiceFailed(
+                                clientId == clientInfo.mClientIdForServiceUpdates,
-                                clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                                clientId, clientInfo, NsdManager.FAILURE_BAD_PARAMETERS);
                         break;
                     case IMDnsEventListener.SERVICE_GET_ADDR_FAILED:
                         /* NNN resolveId errorCode */
                         stopGetAddrInfo(id);
                         removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
+                        notifyResolveFailedResult(
-                        clientInfo.onResolveServiceFailed(
+                                clientId == clientInfo.mClientIdForServiceUpdates,
-                                clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                                clientId, clientInfo, NsdManager.FAILURE_BAD_PARAMETERS);
                         break;
                     case IMDnsEventListener.SERVICE_GET_ADDR_SUCCESS: {
                         /* NNN resolveId hostname ttl addr interfaceIdx netId */
@@ -945,19 +1027,38 @@ public class NsdService extends INsdManager.Stub {
                         // If the resolved service is on an interface without a network, consider it
                         // as a failure: it would not be usable by apps as they would need
                         // privileged permissions.
-                        if (netId != NETID_UNSET && serviceHost != null) {
+                        if (clientId == clientInfo.mClientIdForServiceUpdates) {
-                            clientInfo.mResolvedService.setHost(serviceHost);
+                            if (netId != NETID_UNSET && serviceHost != null) {
-                            setServiceNetworkForCallback(clientInfo.mResolvedService,
+                                setServiceNetworkForCallback(clientInfo.mRegisteredService,
-                                    netId, info.interfaceIdx);
+                                        netId, info.interfaceIdx);
-                            clientInfo.onResolveServiceSucceeded(
+                                final List<InetAddress> addresses =
-                                    clientId, clientInfo.mResolvedService);
+                                        clientInfo.mRegisteredService.getHostAddresses();
+                                addresses.add(serviceHost);
+                                clientInfo.mRegisteredService.setHostAddresses(addresses);
+                                clientInfo.onServiceUpdated(
+                                        clientId, clientInfo.mRegisteredService);
+                            } else {
+                                stopGetAddrInfo(id);
+                                removeRequestMap(clientId, id, clientInfo);
+                                clearRegisteredServiceInfo(clientInfo);
+                                clientInfo.onServiceInfoCallbackRegistrationFailed(
+                                        clientId, NsdManager.FAILURE_BAD_PARAMETERS);
+                            }
                         } else {
-                            clientInfo.onResolveServiceFailed(
+                            if (netId != NETID_UNSET && serviceHost != null) {
-                                    clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                                clientInfo.mResolvedService.setHost(serviceHost);
+                                setServiceNetworkForCallback(clientInfo.mResolvedService,
+                                        netId, info.interfaceIdx);
+                                clientInfo.onResolveServiceSucceeded(
+                                        clientId, clientInfo.mResolvedService);
+                            } else {
+                                clientInfo.onResolveServiceFailed(
+                                        clientId, NsdManager.FAILURE_INTERNAL_ERROR);
+                            }
+                            stopGetAddrInfo(id);
+                            removeRequestMap(clientId, id, clientInfo);
+                            clientInfo.mResolvedService = null;
                         }
-                        stopGetAddrInfo(id);
-                        removeRequestMap(clientId, id, clientInfo);
-                        clientInfo.mResolvedService = null;
                         break;
                     }
                     default:
@@ -1342,6 +1443,20 @@ public class NsdService extends INsdManager.Stub {
                     NsdManager.STOP_RESOLUTION, 0, listenerKey, new ListenerArgs(this, null)));
         }
 
+        @Override
+        public void registerServiceInfoCallback(int listenerKey, NsdServiceInfo serviceInfo) {
+            mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
+                    NsdManager.REGISTER_SERVICE_CALLBACK, 0, listenerKey,
+                    new ListenerArgs(this, serviceInfo)));
+        }
+
+        @Override
+        public void unregisterServiceInfoCallback(int listenerKey) {
+            mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
+                    NsdManager.UNREGISTER_SERVICE_CALLBACK, 0, listenerKey,
+                    new ListenerArgs(this, null)));
+        }
+
         @Override
         public void startDaemon() {
             mNsdStateMachine.sendMessage(mNsdStateMachine.obtainMessage(
@@ -1503,6 +1618,11 @@ public class NsdService extends INsdManager.Stub {
         // The target SDK of this client < Build.VERSION_CODES.S
         private boolean mIsLegacy = false;
 
+        /*** The service that is registered to listen to its updates */
+        private NsdServiceInfo mRegisteredService;
+        /*** The client id that listen to updates */
+        private int mClientIdForServiceUpdates;
+
         private ClientInfo(INsdManagerCallback cb) {
             mCb = cb;
             if (DBG) Log.d(TAG, "New client");
@@ -1584,6 +1704,18 @@ public class NsdService extends INsdManager.Stub {
             return mClientIds.keyAt(idx);
         }
 
+        private void maybeNotifyRegisteredServiceLost(@NonNull NsdServiceInfo info) {
+            if (mRegisteredService == null) return;
+            if (!Objects.equals(mRegisteredService.getServiceName(), info.getServiceName())) return;
+            // Resolved services have a leading dot appended at the beginning of their type, but in
+            // discovered info it's at the end
+            if (!Objects.equals(
+                    mRegisteredService.getServiceType() + ".", "." + info.getServiceType())) {
+                return;
+            }
+            onServiceUpdatedLost(mClientIdForServiceUpdates);
+        }
+
         void onDiscoverServicesStarted(int listenerKey, NsdServiceInfo info) {
             try {
                 mCb.onDiscoverServicesStarted(listenerKey, info);
@@ -1695,5 +1827,37 @@ public class NsdService extends INsdManager.Stub {
                 Log.e(TAG, "Error calling onStopResolutionSucceeded", e);
             }
         }
+
+        void onServiceInfoCallbackRegistrationFailed(int listenerKey, int error) {
+            try {
+                mCb.onServiceInfoCallbackRegistrationFailed(listenerKey, error);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceInfoCallbackRegistrationFailed", e);
+            }
+        }
+
+        void onServiceUpdated(int listenerKey, NsdServiceInfo info) {
+            try {
+                mCb.onServiceUpdated(listenerKey, info);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceUpdated", e);
+            }
+        }
+
+        void onServiceUpdatedLost(int listenerKey) {
+            try {
+                mCb.onServiceUpdatedLost(listenerKey);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceUpdatedLost", e);
+            }
+        }
+
+        void onServiceInfoCallbackUnregistered(int listenerKey) {
+            try {
+                mCb.onServiceInfoCallbackUnregistered(listenerKey);
+            } catch (RemoteException e) {
+                Log.e(TAG, "Error calling onServiceInfoCallbackUnregistered", e);
+            }
+        }
     }
 }

tests/unit/java/android/net/nsd/NsdServiceInfoTest.java

@@ -21,6 +21,7 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+import android.net.InetAddresses;
 import android.net.Network;
 import android.os.Build;
 import android.os.Bundle;
@@ -38,6 +39,7 @@ import org.junit.runner.RunWith;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.util.Arrays;
+import java.util.List;
 import java.util.Map;
 
 @RunWith(DevSdkIgnoreRunner.class)
@@ -45,6 +47,8 @@ import java.util.Map;
 @DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.S_V2)
 public class NsdServiceInfoTest {
 
+    private static final InetAddress IPV4_ADDRESS = InetAddresses.parseNumericAddress("192.0.2.1");
+    private static final InetAddress IPV6_ADDRESS = InetAddresses.parseNumericAddress("2001:db8::");
     public final static InetAddress LOCALHOST;
     static {
         // Because test.
@@ -124,6 +128,7 @@ public class NsdServiceInfoTest {
         fullInfo.setServiceType("_kitten._tcp");
         fullInfo.setPort(4242);
         fullInfo.setHost(LOCALHOST);
+        fullInfo.setHostAddresses(List.of(IPV4_ADDRESS));
         fullInfo.setNetwork(new Network(123));
         fullInfo.setInterfaceIndex(456);
         checkParcelable(fullInfo);
@@ -139,6 +144,7 @@ public class NsdServiceInfoTest {
         attributedInfo.setServiceType("_kitten._tcp");
         attributedInfo.setPort(4242);
         attributedInfo.setHost(LOCALHOST);
+        fullInfo.setHostAddresses(List.of(IPV6_ADDRESS, IPV4_ADDRESS));
         attributedInfo.setAttribute("color", "pink");
         attributedInfo.setAttribute("sound", (new String("にゃあ")).getBytes("UTF-8"));
         attributedInfo.setAttribute("adorable", (String) null);

tests/unit/java/com/android/server/NsdServiceTest.java

@@ -17,6 +17,7 @@
 package com.android.server;
 
 import static android.net.InetAddresses.parseNumericAddress;
+import static android.net.nsd.NsdManager.FAILURE_BAD_PARAMETERS;
 import static android.net.nsd.NsdManager.FAILURE_INTERNAL_ERROR;
 import static android.net.nsd.NsdManager.FAILURE_OPERATION_NOT_RUNNING;
 
@@ -29,6 +30,7 @@ import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyString;
@@ -666,6 +668,133 @@ public class NsdServiceTest {
                         && request.getServiceType().equals(ns.getServiceType())));
     }
 
+    private void verifyUpdatedServiceInfo(NsdServiceInfo info, String serviceName,
+            String serviceType, String address, int port, int interfaceIndex, Network network) {
+        assertEquals(serviceName, info.getServiceName());
+        assertEquals(serviceType, info.getServiceType());
+        assertTrue(info.getHostAddresses().contains(parseNumericAddress(address)));
+        assertEquals(port, info.getPort());
+        assertEquals(network, info.getNetwork());
+        assertEquals(interfaceIndex, info.getInterfaceIndex());
+    }
+
+    @Test
+    public void testRegisterAndUnregisterServiceInfoCallback() throws RemoteException {
+        final NsdManager client = connectClient(mService);
+        final NsdServiceInfo request = new NsdServiceInfo(SERVICE_NAME, SERVICE_TYPE);
+        final NsdManager.ServiceInfoCallback serviceInfoCallback = mock(
+                NsdManager.ServiceInfoCallback.class);
+        client.registerServiceInfoCallback(request, Runnable::run, serviceInfoCallback);
+        waitForIdle();
+
+        final IMDnsEventListener eventListener = getEventListener();
+        final ArgumentCaptor<Integer> resolvIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).resolve(resolvIdCaptor.capture(), eq(SERVICE_NAME), eq(SERVICE_TYPE),
+                eq("local.") /* domain */, eq(IFACE_IDX_ANY));
+
+        // Resolve service successfully.
+        final ResolutionInfo resolutionInfo = new ResolutionInfo(
+                resolvIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_RESOLVED,
+                null /* serviceName */,
+                null /* serviceType */,
+                null /* domain */,
+                SERVICE_FULL_NAME,
+                DOMAIN_NAME,
+                PORT,
+                new byte[0] /* txtRecord */,
+                IFACE_IDX_ANY);
+        doReturn(true).when(mMockMDnsM).getServiceAddress(anyInt(), any(), anyInt());
+        eventListener.onServiceResolutionStatus(resolutionInfo);
+        waitForIdle();
+
+        final ArgumentCaptor<Integer> getAddrIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).getServiceAddress(getAddrIdCaptor.capture(), eq(DOMAIN_NAME),
+                eq(IFACE_IDX_ANY));
+
+        // First address info
+        final String v4Address = "192.0.2.1";
+        final String v6Address = "2001:db8::";
+        final GetAddressInfo addressInfo1 = new GetAddressInfo(
+                getAddrIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_GET_ADDR_SUCCESS,
+                SERVICE_FULL_NAME,
+                v4Address,
+                IFACE_IDX_ANY,
+                999 /* netId */);
+        eventListener.onGettingServiceAddressStatus(addressInfo1);
+        waitForIdle();
+
+        final ArgumentCaptor<NsdServiceInfo> updateInfoCaptor =
+                ArgumentCaptor.forClass(NsdServiceInfo.class);
+        verify(serviceInfoCallback, timeout(TIMEOUT_MS).times(1))
+                .onServiceUpdated(updateInfoCaptor.capture());
+        verifyUpdatedServiceInfo(updateInfoCaptor.getAllValues().get(0) /* info */, SERVICE_NAME,
+                "." + SERVICE_TYPE, v4Address, PORT, IFACE_IDX_ANY, new Network(999));
+
+        // Second address info
+        final GetAddressInfo addressInfo2 = new GetAddressInfo(
+                getAddrIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_GET_ADDR_SUCCESS,
+                SERVICE_FULL_NAME,
+                v6Address,
+                IFACE_IDX_ANY,
+                999 /* netId */);
+        eventListener.onGettingServiceAddressStatus(addressInfo2);
+        waitForIdle();
+
+        verify(serviceInfoCallback, timeout(TIMEOUT_MS).times(2))
+                .onServiceUpdated(updateInfoCaptor.capture());
+        verifyUpdatedServiceInfo(updateInfoCaptor.getAllValues().get(1) /* info */, SERVICE_NAME,
+                "." + SERVICE_TYPE, v6Address, PORT, IFACE_IDX_ANY, new Network(999));
+
+        client.unregisterServiceInfoCallback(serviceInfoCallback);
+        waitForIdle();
+
+        verify(serviceInfoCallback, timeout(TIMEOUT_MS)).onServiceInfoCallbackUnregistered();
+    }
+
+    @Test
+    public void testRegisterServiceCallbackFailed() throws Exception {
+        final NsdManager client = connectClient(mService);
+        final NsdServiceInfo request = new NsdServiceInfo(SERVICE_NAME, SERVICE_TYPE);
+        final NsdManager.ServiceInfoCallback subscribeListener = mock(
+                NsdManager.ServiceInfoCallback.class);
+        client.registerServiceInfoCallback(request, Runnable::run, subscribeListener);
+        waitForIdle();
+
+        final IMDnsEventListener eventListener = getEventListener();
+        final ArgumentCaptor<Integer> resolvIdCaptor = ArgumentCaptor.forClass(Integer.class);
+        verify(mMockMDnsM).resolve(resolvIdCaptor.capture(), eq(SERVICE_NAME), eq(SERVICE_TYPE),
+                eq("local.") /* domain */, eq(IFACE_IDX_ANY));
+
+        // Fail to resolve service.
+        final ResolutionInfo resolutionFailedInfo = new ResolutionInfo(
+                resolvIdCaptor.getValue(),
+                IMDnsEventListener.SERVICE_RESOLUTION_FAILED,
+                null /* serviceName */,
+                null /* serviceType */,
+                null /* domain */,
+                null /* serviceFullName */,
+                null /* domainName */,
+                0 /* port */,
+                new byte[0] /* txtRecord */,
+                IFACE_IDX_ANY);
+        eventListener.onServiceResolutionStatus(resolutionFailedInfo);
+        verify(subscribeListener, timeout(TIMEOUT_MS))
+                .onServiceInfoCallbackRegistrationFailed(eq(FAILURE_BAD_PARAMETERS));
+    }
+
+    @Test
+    public void testUnregisterNotRegisteredCallback() {
+        final NsdManager client = connectClient(mService);
+        final NsdManager.ServiceInfoCallback serviceInfoCallback = mock(
+                NsdManager.ServiceInfoCallback.class);
+
+        assertThrows(IllegalArgumentException.class, () ->
+                client.unregisterServiceInfoCallback(serviceInfoCallback));
+    }
+
     private void makeServiceWithMdnsDiscoveryManagerEnabled() {
         doReturn(true).when(mDeps).isMdnsDiscoveryManagerEnabled(any(Context.class));
         doReturn(mDiscoveryManager).when(mDeps).makeMdnsDiscoveryManager(any(), any());