diff --git a/core/java/android/app/usage/NetworkStatsManager.java b/core/java/android/app/usage/NetworkStatsManager.java
index 1d5dc1d..098d8b6 100644
--- a/core/java/android/app/usage/NetworkStatsManager.java
+++ b/core/java/android/app/usage/NetworkStatsManager.java
@@ -16,6 +16,8 @@
 
 package android.app.usage;
 
+import static android.annotation.SystemApi.Client.MODULE_LIBRARIES;
+
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
@@ -28,8 +30,11 @@
 import android.net.ConnectivityManager;
 import android.net.DataUsageRequest;
 import android.net.INetworkStatsService;
+import android.net.Network;
 import android.net.NetworkStack;
+import android.net.NetworkStateSnapshot;
 import android.net.NetworkTemplate;
+import android.net.UnderlyingNetworkInfo;
 import android.net.netstats.provider.INetworkStatsProviderCallback;
 import android.net.netstats.provider.NetworkStatsProvider;
 import android.os.Binder;
@@ -48,6 +53,7 @@
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.net.module.util.NetworkIdentityUtils;
 
+import java.util.List;
 import java.util.Objects;
 
 /**
@@ -633,6 +639,50 @@
         return template;
     }
 
+    /**
+     *  Notify {@code NetworkStatsService} about network status changed.
+     *
+     *  Notifies NetworkStatsService of network state changes for data usage accounting purposes.
+     *
+     *  To avoid races that attribute data usage to wrong network, such as new network with
+     *  the same interface after SIM hot-swap, this function will not return until
+     *  {@code NetworkStatsService} finishes its work of retrieving traffic statistics from
+     *  all data sources.
+     *
+     * @param defaultNetworks the list of all networks that could be used by network traffic that
+     *                        does not explicitly select a network.
+     * @param networkStateSnapshots a list of {@link NetworkStateSnapshot}s, one for
+     *                              each network that is currently connected.
+     * @param activeIface the active (i.e., connected) default network interface for the calling
+     *                    uid. Used to determine on which network future calls to
+     *                    {@link android.net.TrafficStats#incrementOperationCount} applies to.
+     * @param underlyingNetworkInfos the list of underlying network information for all
+     *                               currently-connected VPNs.
+     *
+     * @hide
+     */
+    @SystemApi(client = MODULE_LIBRARIES)
+    @RequiresPermission(anyOf = {
+            NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK,
+            android.Manifest.permission.NETWORK_STACK})
+    public void notifyNetworkStatus(
+            @NonNull List<Network> defaultNetworks,
+            @NonNull List<NetworkStateSnapshot> networkStateSnapshots,
+            @Nullable String activeIface,
+            @NonNull List<UnderlyingNetworkInfo> underlyingNetworkInfos) {
+        try {
+            Objects.requireNonNull(defaultNetworks);
+            Objects.requireNonNull(networkStateSnapshots);
+            Objects.requireNonNull(underlyingNetworkInfos);
+            // TODO: Change internal namings after the name is decided.
+            mService.forceUpdateIfaces(defaultNetworks.toArray(new Network[0]),
+                    networkStateSnapshots.toArray(new NetworkStateSnapshot[0]), activeIface,
+                    underlyingNetworkInfos.toArray(new UnderlyingNetworkInfo[0]));
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     private static class CallbackHandler extends Handler {
         private final int mNetworkType;
         private final String mSubscriberId;
diff --git a/services/core/java/com/android/server/net/NetworkStatsService.java b/services/core/java/com/android/server/net/NetworkStatsService.java
index 3a5e10e..ebf1fe9 100644
--- a/services/core/java/com/android/server/net/NetworkStatsService.java
+++ b/services/core/java/com/android/server/net/NetworkStatsService.java
@@ -379,6 +379,7 @@
                 case MSG_UPDATE_IFACES: {
                     // If no cached states, ignore.
                     if (mLastNetworkStateSnapshots == null) break;
+                    // TODO (b/181642673): Protect mDefaultNetworks from concurrent accessing.
                     updateIfaces(mDefaultNetworks, mLastNetworkStateSnapshots, mActiveIface);
                     break;
                 }
@@ -1266,7 +1267,7 @@
      * they are combined under a single {@link NetworkIdentitySet}.
      */
     @GuardedBy("mStatsLock")
-    private void updateIfacesLocked(@Nullable Network[] defaultNetworks,
+    private void updateIfacesLocked(@NonNull Network[] defaultNetworks,
             @NonNull NetworkStateSnapshot[] snapshots) {
         if (!mSystemReady) return;
         if (LOGV) Slog.v(TAG, "updateIfacesLocked()");
@@ -1282,10 +1283,8 @@
         // Rebuild active interfaces based on connected networks
         mActiveIfaces.clear();
         mActiveUidIfaces.clear();
-        if (defaultNetworks != null) {
-            // Caller is ConnectivityService. Update the list of default networks.
-            mDefaultNetworks = defaultNetworks;
-        }
+        // Update the list of default networks.
+        mDefaultNetworks = defaultNetworks;
 
         mLastNetworkStateSnapshots = snapshots;