Add tethering client callbacks

The callbacks are fired when the list of connected clients or their IP
addresses / hostname change.

Test: flashed, connected 2 devices, verified callbacks
Test: atest TetheringTests
Bug: 135411507
Change-Id: I96291038cf7b39a67547a5f74fcd7cbedc1ca002

Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl

@@ -1,16 +1,16 @@
-/**
- * Copyright (c) 2019, The Android Open Source Project
+/*
+ * Copyright (C) 2020 The Android Open Source Project
  *
  * 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
+ *      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 perNmissions and
+ * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package android.net;

Tethering/common/TetheringLib/src/android/net/ITetheringEventCallback.aidl

@@ -17,6 +17,7 @@
 package android.net;
 
 import android.net.Network;
+import android.net.TetheredClient;
 import android.net.TetheringConfigurationParcel;
 import android.net.TetheringCallbackStartedParcel;
 import android.net.TetherStatesParcel;
@@ -33,4 +34,5 @@ oneway interface ITetheringEventCallback
     void onUpstreamChanged(in Network network);
     void onConfigurationChanged(in TetheringConfigurationParcel config);
     void onTetherStatesChanged(in TetherStatesParcel states);
+    void onTetherClientsChanged(in List<TetheredClient> clients);
 }

Tethering/common/TetheringLib/src/android/net/TetheredClient.java

@@ -191,6 +191,15 @@ public final class TetheredClient implements Parcelable {
                 return new AddressInfo[size];
             }
         };
+
+        @NonNull
+        @Override
+        public String toString() {
+            return "AddressInfo {"
+                    + mAddress
+                    + (mHostname != null ? ", hostname " + mHostname : "")
+                    + "}";
+        }
     }
 
     @Override
@@ -212,4 +221,13 @@ public final class TetheredClient implements Parcelable {
             return new TetheredClient[size];
         }
     };
+
+    @NonNull
+    @Override
+    public String toString() {
+        return "TetheredClient {hwAddr " + mMacAddress
+                + ", addresses " + mAddresses
+                + ", tetheringType " + mTetheringType
+                + "}";
+    }
 }

Tethering/common/TetheringLib/src/android/net/TetheringCallbackStartedParcel.aidl

@@ -17,6 +17,7 @@
 package android.net;
 
 import android.net.Network;
+import android.net.TetheredClient;
 import android.net.TetheringConfigurationParcel;
 import android.net.TetherStatesParcel;
 
@@ -29,4 +30,5 @@ parcelable TetheringCallbackStartedParcel {
     Network upstreamNetwork;
     TetheringConfigurationParcel config;
     TetherStatesParcel states;
+    List<TetheredClient> tetheredClients;
 }

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -375,6 +375,9 @@ public class TetheringManager {
             mTetherStatesParcel = states;
         }
 
+        @Override
+        public void onTetherClientsChanged(List<TetheredClient> clients) { }
+
         public void waitForStarted() {
             mWaitForCallback.block(DEFAULT_TIMEOUT_MS);
             throwIfPermissionFailure(mError);
@@ -921,6 +924,7 @@ public class TetheringManager {
                         sendRegexpsChanged(parcel.config);
                         maybeSendTetherableIfacesChangedCallback(parcel.states);
                         maybeSendTetheredIfacesChangedCallback(parcel.states);
+                        callback.onClientsChanged(parcel.tetheredClients);
                     });
                 }
 
@@ -951,6 +955,11 @@ public class TetheringManager {
                         maybeSendTetheredIfacesChangedCallback(states);
                     });
                 }
+
+                @Override
+                public void onTetherClientsChanged(final List<TetheredClient> clients) {
+                    executor.execute(() -> callback.onClientsChanged(clients));
+                }
             };
             getConnector(c -> c.registerTetheringEventCallback(remoteCallback, callerPkg));
             mTetheringEventCallbacks.put(callback, remoteCallback);