Remove NETWORK_STACK_SERVICE constant

Instead, have a dedicated method in android.net.NetworkStack allowing to
fetch the stable AIDL token for the service.

This avoids returning IBinder from getSystemService, as getSystemService
should generally return manager classes.

Test: atest FrameworksNetTests NetworkStackTests
Fixes: 151243982
Merged-In: I58a6e1f27aff052050197d1901f43a98d7aa1167
(clean cherry-pick from internal branch)

Change-Id: I75aba269595f3e315dd5e0693c878b2026e8e299

api/system-current.txt

@@ -1612,7 +1612,6 @@ package android.content {
     field public static final String NETD_SERVICE = "netd";
     field public static final String NETWORK_POLICY_SERVICE = "netpolicy";
     field public static final String NETWORK_SCORE_SERVICE = "network_score";
-    field public static final String NETWORK_STACK_SERVICE = "network_stack";
     field public static final String OEM_LOCK_SERVICE = "oem_lock";
     field public static final String PERMISSION_SERVICE = "permission";
     field public static final String PERSISTENT_DATA_BLOCK_SERVICE = "persistent_data_block";
@@ -4740,6 +4739,7 @@ package android.net {
   }
 
   public class NetworkStack {
+    method @Nullable public static android.os.IBinder getService();
     field public static final String PERMISSION_MAINLINE_NETWORK_STACK = "android.permission.MAINLINE_NETWORK_STACK";
   }
 

api/test-current.txt

@@ -658,7 +658,6 @@ package android.content {
     field public static final String BUGREPORT_SERVICE = "bugreport";
     field public static final String CONTENT_CAPTURE_MANAGER_SERVICE = "content_capture";
     field public static final String ETHERNET_SERVICE = "ethernet";
-    field public static final String NETWORK_STACK_SERVICE = "network_stack";
     field public static final String PERMISSION_SERVICE = "permission";
     field public static final String ROLLBACK_SERVICE = "rollback";
     field public static final String STATUS_BAR_SERVICE = "statusbar";
@@ -1518,6 +1517,7 @@ package android.net {
   }
 
   public class NetworkStack {
+    method @Nullable public static android.os.IBinder getService();
     field public static final String PERMISSION_MAINLINE_NETWORK_STACK = "android.permission.MAINLINE_NETWORK_STACK";
   }
 

core/java/android/app/SystemServiceRegistry.java

@@ -347,14 +347,6 @@ final class SystemServiceRegistry {
             }
         });
 
-        registerService(Context.NETWORK_STACK_SERVICE, IBinder.class,
-                new StaticServiceFetcher<IBinder>() {
-                    @Override
-                    public IBinder createService() {
-                        return ServiceManager.getService(Context.NETWORK_STACK_SERVICE);
-                    }
-                });
-
         registerService(Context.TETHERING_SERVICE, TetheringManager.class,
                 new CachedServiceFetcher<TetheringManager>() {
             @Override

core/java/android/content/Context.java

@@ -3864,8 +3864,6 @@ public abstract class Context {
      * @hide
      * @see NetworkStackClient
      */
-    @SystemApi
-    @TestApi
     public static final String NETWORK_STACK_SERVICE = "network_stack";
 
     /**

core/java/android/net/NetworkStack.java

@@ -19,15 +19,17 @@ import static android.Manifest.permission.NETWORK_STACK;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.content.Context;
+import android.os.IBinder;
+import android.os.ServiceManager;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 /**
- *
+ * Constants and utilities for client code communicating with the network stack service.
- * Constants for client code communicating with the network stack service.
  * @hide
  */
 @SystemApi
@@ -43,6 +45,17 @@ public class NetworkStack {
     public static final String PERMISSION_MAINLINE_NETWORK_STACK =
             "android.permission.MAINLINE_NETWORK_STACK";
 
+    /**
+     * Get an {@link IBinder} representing the NetworkStack stable AIDL Interface, if registered.
+     * @hide
+     */
+    @Nullable
+    @SystemApi
+    @TestApi
+    public static IBinder getService() {
+        return ServiceManager.getService(Context.NETWORK_STACK_SERVICE);
+    }
+
     private NetworkStack() {}
 
     /**