[BR07.1] Expose setDataSaverEnabled from ConnectivityManager

Currently, data saver switch is controlled in NPMS, which
calls into NetworkManagementService and netd when switching
status. In netd, BandwidthController manipulates the
bw_data_saver chain to control the overall behavior.

However, this code are all platform implementation, which
are not updatable. In order to migrate data saver switch
from iptables to bpf, this API is needed for Connectivity to
change the implementation to directly write bpf in later
patches.

Test: atest CtsHostsideNetworkTests:com.android.cts.net.HostsideRestrictBackgroundNetworkTests
Test: atest FrameworksServicesTests:NetworkManagementServiceTest
Bug: 297836825
Change-Id: I71fa41ca739fef8e191fba91b02758ad5f732d5c

common/flags.aconfig

@@ -20,3 +20,10 @@ flag {
   description: "Remove expired services from MdnsServiceCache"
   bug: "304649384"
 }
+
+flag {
+  name: "set_data_saver_via_cm"
+  namespace: "android_core_networking"
+  description: "Set data saver through ConnectivityManager API"
+  bug: "297836825"
+}

framework/api/module-lib-current.txt

@@ -24,6 +24,7 @@ package android.net {
     method @RequiresPermission(anyOf={android.Manifest.permission.NETWORK_SETTINGS, android.Manifest.permission.NETWORK_SETUP_WIZARD, android.Manifest.permission.NETWORK_STACK, android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK}) public void setAcceptPartialConnectivity(@NonNull android.net.Network, boolean, boolean);
     method @RequiresPermission(anyOf={android.Manifest.permission.NETWORK_SETTINGS, android.Manifest.permission.NETWORK_SETUP_WIZARD, android.Manifest.permission.NETWORK_STACK, android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK}) public void setAcceptUnvalidated(@NonNull android.net.Network, boolean, boolean);
     method @RequiresPermission(anyOf={android.Manifest.permission.NETWORK_SETTINGS, android.Manifest.permission.NETWORK_SETUP_WIZARD, android.Manifest.permission.NETWORK_STACK, android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK}) public void setAvoidUnvalidated(@NonNull android.net.Network);
+    method @FlaggedApi("com.android.net.flags.set_data_saver_via_cm") @RequiresPermission(anyOf={android.Manifest.permission.NETWORK_SETTINGS, android.Manifest.permission.NETWORK_STACK, android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK}) public void setDataSaverEnabled(boolean);
     method @RequiresPermission(anyOf={android.Manifest.permission.NETWORK_SETTINGS, android.Manifest.permission.NETWORK_STACK, android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK}) public void setFirewallChainEnabled(int, boolean);
     method @RequiresPermission(android.Manifest.permission.NETWORK_STACK) public void setGlobalProxy(@Nullable android.net.ProxyInfo);
     method @RequiresPermission(anyOf={android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK, android.Manifest.permission.NETWORK_STACK, android.Manifest.permission.NETWORK_SETTINGS}) public void setLegacyLockdownVpnEnabled(boolean);

framework/src/android/net/ConnectivityManager.java

@@ -26,6 +26,7 @@ import static android.net.NetworkRequest.Type.TRACK_SYSTEM_DEFAULT;
 import static android.net.QosCallback.QosCallbackRegistrationException;
 
 import android.annotation.CallbackExecutor;
+import android.annotation.FlaggedApi;
 import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -115,6 +116,14 @@ public class ConnectivityManager {
     private static final String TAG = "ConnectivityManager";
     private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
 
+    // TODO : remove this class when udc-mainline-prod is abandoned and android.net.flags.Flags is
+    // available here
+    /** @hide */
+    public static class Flags {
+        static final String SET_DATA_SAVER_VIA_CM =
+                "com.android.net.flags.set_data_saver_via_cm";
+    }
+
     /**
      * A change in network connectivity has occurred. A default connection has either
      * been established or lost. The NetworkInfo for the affected network is
@@ -5940,6 +5949,28 @@ public class ConnectivityManager {
         return new Range(TUN_INTF_NETID_START, TUN_INTF_NETID_START + TUN_INTF_NETID_RANGE - 1);
     }
 
+    /**
+     * Sets data saver switch.
+     *
+     * @param enable True if enable.
+     * @throws IllegalStateException if failed.
+     * @hide
+     */
+    @FlaggedApi(Flags.SET_DATA_SAVER_VIA_CM)
+    @SystemApi(client = MODULE_LIBRARIES)
+    @RequiresPermission(anyOf = {
+            android.Manifest.permission.NETWORK_SETTINGS,
+            android.Manifest.permission.NETWORK_STACK,
+            NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK
+    })
+    public void setDataSaverEnabled(final boolean enable) {
+        try {
+            mService.setDataSaverEnabled(enable);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Adds the specified UID to the list of UIds that are allowed to use data on metered networks
      * even when background data is restricted. The deny list takes precedence over the allow list.

framework/src/android/net/IConnectivityManager.aidl

@@ -238,6 +238,8 @@ interface IConnectivityManager
 
     void setTestAllowBadWifiUntil(long timeMs);
 
+    void setDataSaverEnabled(boolean enable);
+
     void updateMeteredNetworkAllowList(int uid, boolean add);
 
     void updateMeteredNetworkDenyList(int uid, boolean add);

service/src/com/android/server/ConnectivityService.java

@@ -12544,6 +12544,20 @@ public class ConnectivityService extends IConnectivityManager.Stub
         }
     }
 
+    @Override
+    public void setDataSaverEnabled(final boolean enable) {
+        enforceNetworkStackOrSettingsPermission();
+        try {
+            final boolean ret = mNetd.bandwidthEnableDataSaver(enable);
+            if (!ret) {
+                throw new IllegalStateException("Error when changing iptables: " + enable);
+            }
+        } catch (RemoteException e) {
+            // Lack of permission or binder errors.
+            throw new IllegalStateException(e);
+        }
+    }
+
     @Override
     public void updateMeteredNetworkAllowList(final int uid, final boolean add) {
         enforceNetworkStackOrSettingsPermission();