diff --git a/Tethering/Android.bp b/Tethering/Android.bp
index 89f1505..b1ffbb1 100644
--- a/Tethering/Android.bp
+++ b/Tethering/Android.bp
@@ -30,6 +30,7 @@
         ":services-tethering-shared-srcs",
     ],
     static_libs: [
+        "NetworkStackApiStableShims",
         "androidx.annotation_annotation",
         "modules-utils-build",
         "netlink-client",
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index add4f37..2eed968 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -47,7 +47,6 @@
 import android.net.util.InterfaceParams;
 import android.net.util.SharedLog;
 import android.net.util.TetheringUtils.ForwardedStats;
-import android.os.ConditionVariable;
 import android.os.Handler;
 import android.system.ErrnoException;
 import android.text.TextUtils;
@@ -735,43 +734,35 @@
      * be allowed to be accessed on the handler thread.
      */
     public void dump(@NonNull IndentingPrintWriter pw) {
-        final ConditionVariable dumpDone = new ConditionVariable();
-        mHandler.post(() -> {
-            pw.println("mIsBpfEnabled: " + mIsBpfEnabled);
-            pw.println("Polling " + (mPollingStarted ? "started" : "not started"));
-            pw.println("Stats provider " + (mStatsProvider != null
-                    ? "registered" : "not registered"));
-            pw.println("Upstream quota: " + mInterfaceQuotas.toString());
-            pw.println("Polling interval: " + getPollingInterval() + " ms");
-            pw.println("Bpf shim: " + mBpfCoordinatorShim.toString());
+        pw.println("mIsBpfEnabled: " + mIsBpfEnabled);
+        pw.println("Polling " + (mPollingStarted ? "started" : "not started"));
+        pw.println("Stats provider " + (mStatsProvider != null
+                ? "registered" : "not registered"));
+        pw.println("Upstream quota: " + mInterfaceQuotas.toString());
+        pw.println("Polling interval: " + getPollingInterval() + " ms");
+        pw.println("Bpf shim: " + mBpfCoordinatorShim.toString());
 
-            pw.println("Forwarding stats:");
-            pw.increaseIndent();
-            if (mStats.size() == 0) {
-                pw.println("<empty>");
-            } else {
-                dumpStats(pw);
-            }
-            pw.decreaseIndent();
-
-            pw.println("Forwarding rules:");
-            pw.increaseIndent();
-            dumpIpv6UpstreamRules(pw);
-            dumpIpv6ForwardingRules(pw);
-            dumpIpv4ForwardingRules(pw);
-            pw.decreaseIndent();
-
-            pw.println();
-            pw.println("Forwarding counters:");
-            pw.increaseIndent();
-            dumpCounters(pw);
-            pw.decreaseIndent();
-
-            dumpDone.open();
-        });
-        if (!dumpDone.block(DUMP_TIMEOUT_MS)) {
-            pw.println("... dump timed-out after " + DUMP_TIMEOUT_MS + "ms");
+        pw.println("Forwarding stats:");
+        pw.increaseIndent();
+        if (mStats.size() == 0) {
+            pw.println("<empty>");
+        } else {
+            dumpStats(pw);
         }
+        pw.decreaseIndent();
+
+        pw.println("Forwarding rules:");
+        pw.increaseIndent();
+        dumpIpv6UpstreamRules(pw);
+        dumpIpv6ForwardingRules(pw);
+        dumpIpv4ForwardingRules(pw);
+        pw.decreaseIndent();
+
+        pw.println();
+        pw.println("Forwarding counters:");
+        pw.increaseIndent();
+        dumpCounters(pw);
+        pw.decreaseIndent();
     }
 
     private void dumpStats(@NonNull IndentingPrintWriter pw) {
diff --git a/Tethering/src/com/android/networkstack/tethering/EntitlementManager.java b/Tethering/src/com/android/networkstack/tethering/EntitlementManager.java
index b1e3cfe..60fcfd0 100644
--- a/Tethering/src/com/android/networkstack/tethering/EntitlementManager.java
+++ b/Tethering/src/com/android/networkstack/tethering/EntitlementManager.java
@@ -41,7 +41,6 @@
 import android.content.IntentFilter;
 import android.net.util.SharedLog;
 import android.os.Bundle;
-import android.os.ConditionVariable;
 import android.os.Handler;
 import android.os.Parcel;
 import android.os.PersistableBundle;
@@ -516,25 +515,18 @@
      * @param pw {@link PrintWriter} is used to print formatted
      */
     public void dump(PrintWriter pw) {
-        final ConditionVariable mWaiting = new ConditionVariable();
-        mHandler.post(() -> {
-            pw.print("isCellularUpstreamPermitted: ");
-            pw.println(isCellularUpstreamPermitted());
-            for (int type = mCurrentDownstreams.nextSetBit(0); type >= 0;
-                    type = mCurrentDownstreams.nextSetBit(type + 1)) {
-                pw.print("Type: ");
-                pw.print(typeString(type));
-                if (mCurrentEntitlementResults.indexOfKey(type) > -1) {
-                    pw.print(", Value: ");
-                    pw.println(errorString(mCurrentEntitlementResults.get(type)));
-                } else {
-                    pw.println(", Value: empty");
-                }
+        pw.print("isCellularUpstreamPermitted: ");
+        pw.println(isCellularUpstreamPermitted());
+        for (int type = mCurrentDownstreams.nextSetBit(0); type >= 0;
+                type = mCurrentDownstreams.nextSetBit(type + 1)) {
+            pw.print("Type: ");
+            pw.print(typeString(type));
+            if (mCurrentEntitlementResults.indexOfKey(type) > -1) {
+                pw.print(", Value: ");
+                pw.println(errorString(mCurrentEntitlementResults.get(type)));
+            } else {
+                pw.println(", Value: empty");
             }
-            mWaiting.open();
-        });
-        if (!mWaiting.block(DUMP_TIMEOUT)) {
-            pw.println("... dump timed out after " + DUMP_TIMEOUT + "ms");
         }
         pw.print("Exempted: [");
         for (int type = mExemptedDownstreams.nextSetBit(0); type >= 0;
diff --git a/Tethering/src/com/android/networkstack/tethering/OffloadController.java b/Tethering/src/com/android/networkstack/tethering/OffloadController.java
index 44e3916..beb1821 100644
--- a/Tethering/src/com/android/networkstack/tethering/OffloadController.java
+++ b/Tethering/src/com/android/networkstack/tethering/OffloadController.java
@@ -26,6 +26,8 @@
 import static android.net.netstats.provider.NetworkStatsProvider.QUOTA_UNLIMITED;
 import static android.provider.Settings.Global.TETHER_OFFLOAD_DISABLED;
 
+import static com.android.networkstack.tethering.OffloadHardwareInterface.OFFLOAD_HAL_VERSION_1_0;
+import static com.android.networkstack.tethering.OffloadHardwareInterface.OFFLOAD_HAL_VERSION_1_1;
 import static com.android.networkstack.tethering.OffloadHardwareInterface.OFFLOAD_HAL_VERSION_NONE;
 import static com.android.networkstack.tethering.TetheringConfiguration.DEFAULT_TETHER_OFFLOAD_POLL_INTERVAL_MS;
 
@@ -114,11 +116,42 @@
     private ConcurrentHashMap<String, ForwardedStats> mForwardedStats =
             new ConcurrentHashMap<>(16, 0.75F, 1);
 
+    private static class InterfaceQuota {
+        public final long warningBytes;
+        public final long limitBytes;
+
+        public static InterfaceQuota MAX_VALUE = new InterfaceQuota(Long.MAX_VALUE, Long.MAX_VALUE);
+
+        InterfaceQuota(long warningBytes, long limitBytes) {
+            this.warningBytes = warningBytes;
+            this.limitBytes = limitBytes;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o) return true;
+            if (!(o instanceof InterfaceQuota)) return false;
+            InterfaceQuota that = (InterfaceQuota) o;
+            return warningBytes == that.warningBytes
+                    && limitBytes == that.limitBytes;
+        }
+
+        @Override
+        public int hashCode() {
+            return (int) (warningBytes * 3 + limitBytes * 5);
+        }
+
+        @Override
+        public String toString() {
+            return "InterfaceQuota{" + "warning=" + warningBytes + ", limit=" + limitBytes + '}';
+        }
+    }
+
     // Maps upstream interface names to interface quotas.
     // Always contains the latest value received from the framework for each interface, regardless
     // of whether offload is currently running (or is even supported) on that interface. Only
     // includes upstream interfaces that have a quota set.
-    private HashMap<String, Long> mInterfaceQuotas = new HashMap<>();
+    private HashMap<String, InterfaceQuota> mInterfaceQuotas = new HashMap<>();
 
     // Tracking remaining alert quota. Unlike limit quota is subject to interface, the alert
     // quota is interface independent and global for tether offload. Note that this is only
@@ -250,6 +283,18 @@
                     }
 
                     @Override
+                    public void onWarningReached() {
+                        if (!started()) return;
+                        mLog.log("onWarningReached");
+
+                        updateStatsForCurrentUpstream();
+                        if (mStatsProvider != null) {
+                            mStatsProvider.pushTetherStats();
+                            mStatsProvider.notifyWarningReached();
+                        }
+                    }
+
+                    @Override
                     public void onNatTimeoutUpdate(int proto,
                                                    String srcAddr, int srcPort,
                                                    String dstAddr, int dstPort) {
@@ -263,7 +308,8 @@
             mLog.i("tethering offload control not supported");
             stop();
         } else {
-            mLog.log("tethering offload started");
+            mLog.log("tethering offload started, version: "
+                    + OffloadHardwareInterface.halVerToString(mControlHalVersion));
             mNatUpdateCallbacksReceived = 0;
             mNatUpdateNetlinkErrors = 0;
             maybeSchedulePollingStats();
@@ -322,24 +368,35 @@
 
         @Override
         public void onSetLimit(String iface, long quotaBytes) {
+            onSetWarningAndLimit(iface, QUOTA_UNLIMITED, quotaBytes);
+        }
+
+        @Override
+        public void onSetWarningAndLimit(@NonNull String iface,
+                long warningBytes, long limitBytes) {
             // Listen for all iface is necessary since upstream might be changed after limit
             // is set.
             mHandler.post(() -> {
-                final Long curIfaceQuota = mInterfaceQuotas.get(iface);
+                final InterfaceQuota curIfaceQuota = mInterfaceQuotas.get(iface);
+                final InterfaceQuota newIfaceQuota = new InterfaceQuota(
+                        warningBytes == QUOTA_UNLIMITED ? Long.MAX_VALUE : warningBytes,
+                        limitBytes == QUOTA_UNLIMITED ? Long.MAX_VALUE : limitBytes);
 
                 // If the quota is set to unlimited, the value set to HAL is Long.MAX_VALUE,
                 // which is ~8.4 x 10^6 TiB, no one can actually reach it. Thus, it is not
                 // useful to set it multiple times.
                 // Otherwise, the quota needs to be updated to tell HAL to re-count from now even
                 // if the quota is the same as the existing one.
-                if (null == curIfaceQuota && QUOTA_UNLIMITED == quotaBytes) return;
+                if (null == curIfaceQuota && InterfaceQuota.MAX_VALUE.equals(newIfaceQuota)) {
+                    return;
+                }
 
-                if (quotaBytes == QUOTA_UNLIMITED) {
+                if (InterfaceQuota.MAX_VALUE.equals(newIfaceQuota)) {
                     mInterfaceQuotas.remove(iface);
                 } else {
-                    mInterfaceQuotas.put(iface, quotaBytes);
+                    mInterfaceQuotas.put(iface, newIfaceQuota);
                 }
-                maybeUpdateDataLimit(iface);
+                maybeUpdateDataWarningAndLimit(iface);
             });
         }
 
@@ -374,7 +431,11 @@
 
         @Override
         public void onSetAlert(long quotaBytes) {
-            // TODO: Ask offload HAL to notify alert without stopping traffic.
+            // Ignore set alert calls from HAL V1.1 since the hardware supports set warning now.
+            // Thus, the software polling mechanism is not needed.
+            if (!useStatsPolling()) {
+                return;
+            }
             // Post it to handler thread since it access remaining quota bytes.
             mHandler.post(() -> {
                 updateAlertQuota(quotaBytes);
@@ -459,24 +520,32 @@
 
     private boolean isPollingStatsNeeded() {
         return started() && mRemainingAlertQuota > 0
+                && useStatsPolling()
                 && !TextUtils.isEmpty(currentUpstreamInterface())
                 && mDeps.getTetherConfig() != null
                 && mDeps.getTetherConfig().getOffloadPollInterval()
                 >= DEFAULT_TETHER_OFFLOAD_POLL_INTERVAL_MS;
     }
 
-    private boolean maybeUpdateDataLimit(String iface) {
-        // setDataLimit may only be called while offload is occurring on this upstream.
+    private boolean useStatsPolling() {
+        return mControlHalVersion == OFFLOAD_HAL_VERSION_1_0;
+    }
+
+    private boolean maybeUpdateDataWarningAndLimit(String iface) {
+        // setDataLimit or setDataWarningAndLimit may only be called while offload is occurring
+        // on this upstream.
         if (!started() || !TextUtils.equals(iface, currentUpstreamInterface())) {
             return true;
         }
 
-        Long limit = mInterfaceQuotas.get(iface);
-        if (limit == null) {
-            limit = Long.MAX_VALUE;
+        final InterfaceQuota quota = mInterfaceQuotas.getOrDefault(iface, InterfaceQuota.MAX_VALUE);
+        final boolean ret;
+        if (mControlHalVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            ret = mHwInterface.setDataWarningAndLimit(iface, quota.warningBytes, quota.limitBytes);
+        } else {
+            ret = mHwInterface.setDataLimit(iface, quota.limitBytes);
         }
-
-        return mHwInterface.setDataLimit(iface, limit);
+        return ret;
     }
 
     private void updateStatsForCurrentUpstream() {
@@ -630,7 +699,7 @@
         maybeUpdateStats(prevUpstream);
 
         // Data limits can only be set once offload is running on the upstream.
-        success = maybeUpdateDataLimit(iface);
+        success = maybeUpdateDataWarningAndLimit(iface);
         if (!success) {
             // If we failed to set a data limit, don't use this upstream, because we don't want to
             // blow through the data limit that we were told to apply.
diff --git a/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java b/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
index 7685847..e3ac660 100644
--- a/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
+++ b/Tethering/src/com/android/networkstack/tethering/OffloadHardwareInterface.java
@@ -24,10 +24,10 @@
 import android.annotation.NonNull;
 import android.hardware.tetheroffload.config.V1_0.IOffloadConfig;
 import android.hardware.tetheroffload.control.V1_0.IOffloadControl;
-import android.hardware.tetheroffload.control.V1_0.ITetheringOffloadCallback;
 import android.hardware.tetheroffload.control.V1_0.NatTimeoutUpdate;
 import android.hardware.tetheroffload.control.V1_0.NetworkProtocol;
 import android.hardware.tetheroffload.control.V1_0.OffloadCallbackEvent;
+import android.hardware.tetheroffload.control.V1_1.ITetheringOffloadCallback;
 import android.net.netlink.NetlinkSocket;
 import android.net.netlink.StructNfGenMsg;
 import android.net.netlink.StructNlMsgHdr;
@@ -39,6 +39,7 @@
 import android.system.ErrnoException;
 import android.system.Os;
 import android.system.OsConstants;
+import android.util.Log;
 import android.util.Pair;
 
 import com.android.internal.annotations.VisibleForTesting;
@@ -140,6 +141,8 @@
         public void onSupportAvailable() {}
         /** Offload stopped because of usage limit reached. */
         public void onStoppedLimitReached() {}
+        /** Indicate that data warning quota is reached. */
+        public void onWarningReached() {}
 
         /** Indicate to update NAT timeout. */
         public void onNatTimeoutUpdate(int proto,
@@ -381,7 +384,8 @@
                 (controlCb == null) ? "null"
                         : "0x" + Integer.toHexString(System.identityHashCode(controlCb)));
 
-        mTetheringOffloadCallback = new TetheringOffloadCallback(mHandler, mControlCallback, mLog);
+        mTetheringOffloadCallback = new TetheringOffloadCallback(
+                mHandler, mControlCallback, mLog, mOffloadControlVersion);
         final CbResults results = new CbResults();
         try {
             mOffloadControl.initOffload(
@@ -480,6 +484,33 @@
         return results.mSuccess;
     }
 
+    /** Set data warning and limit value to offload management process. */
+    public boolean setDataWarningAndLimit(String iface, long warning, long limit) {
+        if (mOffloadControlVersion < OFFLOAD_HAL_VERSION_1_1) {
+            throw new IllegalArgumentException(
+                    "setDataWarningAndLimit is not supported below HAL V1.1");
+        }
+        final String logmsg =
+                String.format("setDataWarningAndLimit(%s, %d, %d)", iface, warning, limit);
+
+        final CbResults results = new CbResults();
+        try {
+            ((android.hardware.tetheroffload.control.V1_1.IOffloadControl) mOffloadControl)
+                    .setDataWarningAndLimit(
+                            iface, warning, limit,
+                            (boolean success, String errMsg) -> {
+                                results.mSuccess = success;
+                                results.mErrMsg = errMsg;
+                            });
+        } catch (RemoteException e) {
+            record(logmsg, e);
+            return false;
+        }
+
+        record(logmsg, results);
+        return results.mSuccess;
+    }
+
     /** Set upstream parameters to offload management process. */
     public boolean setUpstreamParameters(
             String iface, String v4addr, String v4gateway, ArrayList<String> v6gws) {
@@ -565,35 +596,64 @@
         public final Handler handler;
         public final ControlCallback controlCb;
         public final SharedLog log;
+        private final int mOffloadControlVersion;
 
-        TetheringOffloadCallback(Handler h, ControlCallback cb, SharedLog sharedLog) {
+        TetheringOffloadCallback(
+                Handler h, ControlCallback cb, SharedLog sharedLog, int offloadControlVersion) {
             handler = h;
             controlCb = cb;
             log = sharedLog;
+            this.mOffloadControlVersion = offloadControlVersion;
+        }
+
+        private void handleOnEvent(int event) {
+            switch (event) {
+                case OffloadCallbackEvent.OFFLOAD_STARTED:
+                    controlCb.onStarted();
+                    break;
+                case OffloadCallbackEvent.OFFLOAD_STOPPED_ERROR:
+                    controlCb.onStoppedError();
+                    break;
+                case OffloadCallbackEvent.OFFLOAD_STOPPED_UNSUPPORTED:
+                    controlCb.onStoppedUnsupported();
+                    break;
+                case OffloadCallbackEvent.OFFLOAD_SUPPORT_AVAILABLE:
+                    controlCb.onSupportAvailable();
+                    break;
+                case OffloadCallbackEvent.OFFLOAD_STOPPED_LIMIT_REACHED:
+                    controlCb.onStoppedLimitReached();
+                    break;
+                case android.hardware.tetheroffload.control
+                        .V1_1.OffloadCallbackEvent.OFFLOAD_WARNING_REACHED:
+                    controlCb.onWarningReached();
+                    break;
+                default:
+                    log.e("Unsupported OffloadCallbackEvent: " + event);
+            }
         }
 
         @Override
         public void onEvent(int event) {
+            // The implementation should never call onEvent()) if the event is already reported
+            // through newer callback.
+            if (mOffloadControlVersion > OFFLOAD_HAL_VERSION_1_0) {
+                Log.wtf(TAG, "onEvent(" + event + ") fired on HAL "
+                        + halVerToString(mOffloadControlVersion));
+            }
             handler.post(() -> {
-                switch (event) {
-                    case OffloadCallbackEvent.OFFLOAD_STARTED:
-                        controlCb.onStarted();
-                        break;
-                    case OffloadCallbackEvent.OFFLOAD_STOPPED_ERROR:
-                        controlCb.onStoppedError();
-                        break;
-                    case OffloadCallbackEvent.OFFLOAD_STOPPED_UNSUPPORTED:
-                        controlCb.onStoppedUnsupported();
-                        break;
-                    case OffloadCallbackEvent.OFFLOAD_SUPPORT_AVAILABLE:
-                        controlCb.onSupportAvailable();
-                        break;
-                    case OffloadCallbackEvent.OFFLOAD_STOPPED_LIMIT_REACHED:
-                        controlCb.onStoppedLimitReached();
-                        break;
-                    default:
-                        log.e("Unsupported OffloadCallbackEvent: " + event);
-                }
+                handleOnEvent(event);
+            });
+        }
+
+        @Override
+        public void onEvent_1_1(int event) {
+            if (mOffloadControlVersion < OFFLOAD_HAL_VERSION_1_1) {
+                Log.wtf(TAG, "onEvent_1_1(" + event + ") fired on HAL "
+                        + halVerToString(mOffloadControlVersion));
+                return;
+            }
+            handler.post(() -> {
+                handleOnEvent(event);
             });
         }
 
diff --git a/Tethering/src/com/android/networkstack/tethering/Tethering.java b/Tethering/src/com/android/networkstack/tethering/Tethering.java
index 8db4cb9..0e8b2b5 100644
--- a/Tethering/src/com/android/networkstack/tethering/Tethering.java
+++ b/Tethering/src/com/android/networkstack/tethering/Tethering.java
@@ -128,7 +128,6 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
-import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.IndentingPrintWriter;
 import com.android.internal.util.MessageUtils;
@@ -147,8 +146,11 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
  *
@@ -166,6 +168,9 @@
     };
     private static final SparseArray<String> sMagicDecoderRing =
             MessageUtils.findMessageNames(sMessageClasses);
+
+    private static final int DUMP_TIMEOUT_MS = 10_000;
+
     // Keep in sync with NETID_UNSET in system/netd/include/netid_client.h
     private static final int NETID_UNSET = 0;
 
@@ -212,9 +217,6 @@
     private final SparseArray<TetheringRequestParcel> mActiveTetheringRequests =
             new SparseArray<>();
 
-    // used to synchronize public access to members
-    // TODO(b/153621704): remove mPublicSync to make Tethering lock free
-    private final Object mPublicSync;
     private final Context mContext;
     private final ArrayMap<String, TetherState> mTetherStates;
     private final BroadcastReceiver mStateReceiver;
@@ -240,8 +242,6 @@
     private final BpfCoordinator mBpfCoordinator;
     private final PrivateAddressCoordinator mPrivateAddressCoordinator;
     private int mActiveDataSubId = INVALID_SUBSCRIPTION_ID;
-    // All the usage of mTetheringEventCallback should run in the same thread.
-    private ITetheringEventCallback mTetheringEventCallback = null;
 
     private volatile TetheringConfiguration mConfig;
     private InterfaceSet mCurrentUpstreamIfaceSet;
@@ -255,11 +255,8 @@
     private String mWifiP2pTetherInterface = null;
     private int mOffloadStatus = TETHER_HARDWARE_OFFLOAD_STOPPED;
 
-    @GuardedBy("mPublicSync")
     private EthernetManager.TetheredInterfaceRequest mEthernetIfaceRequest;
-    @GuardedBy("mPublicSync")
     private String mConfiguredEthernetIface;
-    @GuardedBy("mPublicSync")
     private EthernetCallback mEthernetCallback;
 
     public Tethering(TetheringDependencies deps) {
@@ -270,8 +267,6 @@
         mLooper = mDeps.getTetheringLooper();
         mNotificationUpdater = mDeps.getNotificationUpdater(mContext, mLooper);
 
-        mPublicSync = new Object();
-
         mTetherStates = new ArrayMap<>();
         mConnectedClientsTracker = new ConnectedClientsTracker();
 
@@ -498,20 +493,18 @@
         // Never called directly: only called from interfaceLinkStateChanged.
         // See NetlinkHandler.cpp: notifyInterfaceChanged.
         if (VDBG) Log.d(TAG, "interfaceStatusChanged " + iface + ", " + up);
-        synchronized (mPublicSync) {
-            if (up) {
-                maybeTrackNewInterfaceLocked(iface);
+        if (up) {
+            maybeTrackNewInterfaceLocked(iface);
+        } else {
+            if (ifaceNameToType(iface) == TETHERING_BLUETOOTH
+                    || ifaceNameToType(iface) == TETHERING_WIGIG) {
+                stopTrackingInterfaceLocked(iface);
             } else {
-                if (ifaceNameToType(iface) == TETHERING_BLUETOOTH
-                        || ifaceNameToType(iface) == TETHERING_WIGIG) {
-                    stopTrackingInterfaceLocked(iface);
-                } else {
-                    // Ignore usb0 down after enabling RNDIS.
-                    // We will handle disconnect in interfaceRemoved.
-                    // Similarly, ignore interface down for WiFi.  We monitor WiFi AP status
-                    // through the WifiManager.WIFI_AP_STATE_CHANGED_ACTION intent.
-                    if (VDBG) Log.d(TAG, "ignore interface down for " + iface);
-                }
+                // Ignore usb0 down after enabling RNDIS.
+                // We will handle disconnect in interfaceRemoved.
+                // Similarly, ignore interface down for WiFi.  We monitor WiFi AP status
+                // through the WifiManager.WIFI_AP_STATE_CHANGED_ACTION intent.
+                if (VDBG) Log.d(TAG, "ignore interface down for " + iface);
             }
         }
     }
@@ -541,16 +534,12 @@
 
     void interfaceAdded(String iface) {
         if (VDBG) Log.d(TAG, "interfaceAdded " + iface);
-        synchronized (mPublicSync) {
-            maybeTrackNewInterfaceLocked(iface);
-        }
+        maybeTrackNewInterfaceLocked(iface);
     }
 
     void interfaceRemoved(String iface) {
         if (VDBG) Log.d(TAG, "interfaceRemoved " + iface);
-        synchronized (mPublicSync) {
-            stopTrackingInterfaceLocked(iface);
-        }
+        stopTrackingInterfaceLocked(iface);
     }
 
     void startTethering(final TetheringRequestParcel request, final IIntResultListener listener) {
@@ -635,17 +624,15 @@
     private int setWifiTethering(final boolean enable) {
         final long ident = Binder.clearCallingIdentity();
         try {
-            synchronized (mPublicSync) {
-                final WifiManager mgr = getWifiManager();
-                if (mgr == null) {
-                    mLog.e("setWifiTethering: failed to get WifiManager!");
-                    return TETHER_ERROR_SERVICE_UNAVAIL;
-                }
-                if ((enable && mgr.startTetheredHotspot(null /* use existing softap config */))
-                        || (!enable && mgr.stopSoftAp())) {
-                    mWifiTetherRequested = enable;
-                    return TETHER_ERROR_NO_ERROR;
-                }
+            final WifiManager mgr = getWifiManager();
+            if (mgr == null) {
+                mLog.e("setWifiTethering: failed to get WifiManager!");
+                return TETHER_ERROR_SERVICE_UNAVAIL;
+            }
+            if ((enable && mgr.startTetheredHotspot(null /* use existing softap config */))
+                    || (!enable && mgr.stopSoftAp())) {
+                mWifiTetherRequested = enable;
+                return TETHER_ERROR_NO_ERROR;
             }
         } finally {
             Binder.restoreCallingIdentity(ident);
@@ -697,18 +684,16 @@
     private int setEthernetTethering(final boolean enable) {
         final EthernetManager em = (EthernetManager) mContext.getSystemService(
                 Context.ETHERNET_SERVICE);
-        synchronized (mPublicSync) {
-            if (enable) {
-                if (mEthernetCallback != null) {
-                    Log.d(TAG, "Ethernet tethering already started");
-                    return TETHER_ERROR_NO_ERROR;
-                }
-
-                mEthernetCallback = new EthernetCallback();
-                mEthernetIfaceRequest = em.requestTetheredInterface(mExecutor, mEthernetCallback);
-            } else {
-                stopEthernetTetheringLocked();
+        if (enable) {
+            if (mEthernetCallback != null) {
+                Log.d(TAG, "Ethernet tethering already started");
+                return TETHER_ERROR_NO_ERROR;
             }
+
+            mEthernetCallback = new EthernetCallback();
+            mEthernetIfaceRequest = em.requestTetheredInterface(mExecutor, mEthernetCallback);
+        } else {
+            stopEthernetTetheringLocked();
         }
         return TETHER_ERROR_NO_ERROR;
     }
@@ -728,26 +713,22 @@
     private class EthernetCallback implements EthernetManager.TetheredInterfaceCallback {
         @Override
         public void onAvailable(String iface) {
-            synchronized (mPublicSync) {
-                if (this != mEthernetCallback) {
-                    // Ethernet callback arrived after Ethernet tethering stopped. Ignore.
-                    return;
-                }
-                maybeTrackNewInterfaceLocked(iface, TETHERING_ETHERNET);
-                changeInterfaceState(iface, getRequestedState(TETHERING_ETHERNET));
-                mConfiguredEthernetIface = iface;
+            if (this != mEthernetCallback) {
+                // Ethernet callback arrived after Ethernet tethering stopped. Ignore.
+                return;
             }
+            maybeTrackNewInterfaceLocked(iface, TETHERING_ETHERNET);
+            changeInterfaceState(iface, getRequestedState(TETHERING_ETHERNET));
+            mConfiguredEthernetIface = iface;
         }
 
         @Override
         public void onUnavailable() {
-            synchronized (mPublicSync) {
-                if (this != mEthernetCallback) {
-                    // onAvailable called after stopping Ethernet tethering.
-                    return;
-                }
-                stopEthernetTetheringLocked();
+            if (this != mEthernetCallback) {
+                // onAvailable called after stopping Ethernet tethering.
+                return;
             }
+            stopEthernetTetheringLocked();
         }
     }
 
@@ -761,57 +742,53 @@
 
     private int tether(String iface, int requestedState) {
         if (DBG) Log.d(TAG, "Tethering " + iface);
-        synchronized (mPublicSync) {
-            TetherState tetherState = mTetherStates.get(iface);
-            if (tetherState == null) {
-                Log.e(TAG, "Tried to Tether an unknown iface: " + iface + ", ignoring");
-                return TETHER_ERROR_UNKNOWN_IFACE;
-            }
-            // Ignore the error status of the interface.  If the interface is available,
-            // the errors are referring to past tethering attempts anyway.
-            if (tetherState.lastState != IpServer.STATE_AVAILABLE) {
-                Log.e(TAG, "Tried to Tether an unavailable iface: " + iface + ", ignoring");
-                return TETHER_ERROR_UNAVAIL_IFACE;
-            }
-            // NOTE: If a CMD_TETHER_REQUESTED message is already in the TISM's queue but not yet
-            // processed, this will be a no-op and it will not return an error.
-            //
-            // This code cannot race with untether() because they both synchronize on mPublicSync.
-            // TODO: reexamine the threading and messaging model to totally remove mPublicSync.
-            final int type = tetherState.ipServer.interfaceType();
-            final TetheringRequestParcel request = mActiveTetheringRequests.get(type, null);
-            if (request != null) {
-                mActiveTetheringRequests.delete(type);
-            }
-            tetherState.ipServer.sendMessage(IpServer.CMD_TETHER_REQUESTED, requestedState, 0,
-                    request);
-            return TETHER_ERROR_NO_ERROR;
+        TetherState tetherState = mTetherStates.get(iface);
+        if (tetherState == null) {
+            Log.e(TAG, "Tried to Tether an unknown iface: " + iface + ", ignoring");
+            return TETHER_ERROR_UNKNOWN_IFACE;
         }
+        // Ignore the error status of the interface.  If the interface is available,
+        // the errors are referring to past tethering attempts anyway.
+        if (tetherState.lastState != IpServer.STATE_AVAILABLE) {
+            Log.e(TAG, "Tried to Tether an unavailable iface: " + iface + ", ignoring");
+            return TETHER_ERROR_UNAVAIL_IFACE;
+        }
+        // NOTE: If a CMD_TETHER_REQUESTED message is already in the TISM's queue but not yet
+        // processed, this will be a no-op and it will not return an error.
+        //
+        // This code cannot race with untether() because they both run on the handler thread.
+        final int type = tetherState.ipServer.interfaceType();
+        final TetheringRequestParcel request = mActiveTetheringRequests.get(type, null);
+        if (request != null) {
+            mActiveTetheringRequests.delete(type);
+        }
+        tetherState.ipServer.sendMessage(IpServer.CMD_TETHER_REQUESTED, requestedState, 0,
+                request);
+        return TETHER_ERROR_NO_ERROR;
     }
 
     void untether(String iface, final IIntResultListener listener) {
         mHandler.post(() -> {
             try {
                 listener.onResult(untether(iface));
-            } catch (RemoteException e) { }
+            } catch (RemoteException e) {
+            }
         });
     }
 
     int untether(String iface) {
         if (DBG) Log.d(TAG, "Untethering " + iface);
-        synchronized (mPublicSync) {
-            TetherState tetherState = mTetherStates.get(iface);
-            if (tetherState == null) {
-                Log.e(TAG, "Tried to Untether an unknown iface :" + iface + ", ignoring");
-                return TETHER_ERROR_UNKNOWN_IFACE;
-            }
-            if (!tetherState.isCurrentlyServing()) {
-                Log.e(TAG, "Tried to untether an inactive iface :" + iface + ", ignoring");
-                return TETHER_ERROR_UNAVAIL_IFACE;
-            }
-            tetherState.ipServer.sendMessage(IpServer.CMD_TETHER_UNREQUESTED);
-            return TETHER_ERROR_NO_ERROR;
+        TetherState tetherState = mTetherStates.get(iface);
+        if (tetherState == null) {
+            Log.e(TAG, "Tried to Untether an unknown iface :" + iface + ", ignoring");
+            return TETHER_ERROR_UNKNOWN_IFACE;
         }
+        if (!tetherState.isCurrentlyServing()) {
+            Log.e(TAG, "Tried to untether an inactive iface :" + iface + ", ignoring");
+            return TETHER_ERROR_UNAVAIL_IFACE;
+        }
+        tetherState.ipServer.sendMessage(IpServer.CMD_TETHER_UNREQUESTED);
+        return TETHER_ERROR_NO_ERROR;
     }
 
     void untetherAll() {
@@ -822,16 +799,15 @@
         stopTethering(TETHERING_ETHERNET);
     }
 
-    int getLastTetherError(String iface) {
-        synchronized (mPublicSync) {
-            TetherState tetherState = mTetherStates.get(iface);
-            if (tetherState == null) {
-                Log.e(TAG, "Tried to getLastTetherError on an unknown iface :" + iface
-                        + ", ignoring");
-                return TETHER_ERROR_UNKNOWN_IFACE;
-            }
-            return tetherState.lastError;
+    @VisibleForTesting
+    int getLastErrorForTest(String iface) {
+        TetherState tetherState = mTetherStates.get(iface);
+        if (tetherState == null) {
+            Log.e(TAG, "Tried to getLastErrorForTest on an unknown iface :" + iface
+                    + ", ignoring");
+            return TETHER_ERROR_UNKNOWN_IFACE;
         }
+        return tetherState.lastError;
     }
 
     private boolean isProvisioningNeededButUnavailable() {
@@ -888,27 +864,25 @@
         mTetherStatesParcel = new TetherStatesParcel();
 
         int downstreamTypesMask = DOWNSTREAM_NONE;
-        synchronized (mPublicSync) {
-            for (int i = 0; i < mTetherStates.size(); i++) {
-                TetherState tetherState = mTetherStates.valueAt(i);
-                String iface = mTetherStates.keyAt(i);
-                if (tetherState.lastError != TETHER_ERROR_NO_ERROR) {
-                    erroredList.add(iface);
-                    lastErrorList.add(tetherState.lastError);
-                } else if (tetherState.lastState == IpServer.STATE_AVAILABLE) {
-                    availableList.add(iface);
-                } else if (tetherState.lastState == IpServer.STATE_LOCAL_ONLY) {
-                    localOnlyList.add(iface);
-                } else if (tetherState.lastState == IpServer.STATE_TETHERED) {
-                    if (cfg.isUsb(iface)) {
-                        downstreamTypesMask |= (1 << TETHERING_USB);
-                    } else if (cfg.isWifi(iface)) {
-                        downstreamTypesMask |= (1 << TETHERING_WIFI);
-                    } else if (cfg.isBluetooth(iface)) {
-                        downstreamTypesMask |= (1 << TETHERING_BLUETOOTH);
-                    }
-                    tetherList.add(iface);
+        for (int i = 0; i < mTetherStates.size(); i++) {
+            TetherState tetherState = mTetherStates.valueAt(i);
+            String iface = mTetherStates.keyAt(i);
+            if (tetherState.lastError != TETHER_ERROR_NO_ERROR) {
+                erroredList.add(iface);
+                lastErrorList.add(tetherState.lastError);
+            } else if (tetherState.lastState == IpServer.STATE_AVAILABLE) {
+                availableList.add(iface);
+            } else if (tetherState.lastState == IpServer.STATE_LOCAL_ONLY) {
+                localOnlyList.add(iface);
+            } else if (tetherState.lastState == IpServer.STATE_TETHERED) {
+                if (cfg.isUsb(iface)) {
+                    downstreamTypesMask |= (1 << TETHERING_USB);
+                } else if (cfg.isWifi(iface)) {
+                    downstreamTypesMask |= (1 << TETHERING_WIFI);
+                } else if (cfg.isBluetooth(iface)) {
+                    downstreamTypesMask |= (1 << TETHERING_BLUETOOTH);
                 }
+                tetherList.add(iface);
             }
         }
 
@@ -1006,21 +980,19 @@
             //       functions are ready to use.
             //
             // For more explanation, see b/62552150 .
-            synchronized (Tethering.this.mPublicSync) {
-                if (!usbConnected && mRndisEnabled) {
-                    // Turn off tethering if it was enabled and there is a disconnect.
-                    tetherMatchingInterfaces(IpServer.STATE_AVAILABLE, TETHERING_USB);
-                    mEntitlementMgr.stopProvisioningIfNeeded(TETHERING_USB);
-                } else if (usbConfigured && rndisEnabled) {
-                    // Tether if rndis is enabled and usb is configured.
-                    final int state = getRequestedState(TETHERING_USB);
-                    tetherMatchingInterfaces(state, TETHERING_USB);
-                } else if (usbConnected && ncmEnabled) {
-                    final int state = getRequestedState(TETHERING_NCM);
-                    tetherMatchingInterfaces(state, TETHERING_NCM);
-                }
-                mRndisEnabled = usbConfigured && rndisEnabled;
+            if (!usbConnected && mRndisEnabled) {
+                // Turn off tethering if it was enabled and there is a disconnect.
+                tetherMatchingInterfaces(IpServer.STATE_AVAILABLE, TETHERING_USB);
+                mEntitlementMgr.stopProvisioningIfNeeded(TETHERING_USB);
+            } else if (usbConfigured && rndisEnabled) {
+                // Tether if rndis is enabled and usb is configured.
+                final int state = getRequestedState(TETHERING_USB);
+                tetherMatchingInterfaces(state, TETHERING_USB);
+            } else if (usbConnected && ncmEnabled) {
+                final int state = getRequestedState(TETHERING_NCM);
+                tetherMatchingInterfaces(state, TETHERING_NCM);
             }
+            mRndisEnabled = usbConfigured && rndisEnabled;
         }
 
         private void handleWifiApAction(Intent intent) {
@@ -1028,23 +1000,21 @@
             final String ifname = intent.getStringExtra(EXTRA_WIFI_AP_INTERFACE_NAME);
             final int ipmode = intent.getIntExtra(EXTRA_WIFI_AP_MODE, IFACE_IP_MODE_UNSPECIFIED);
 
-            synchronized (Tethering.this.mPublicSync) {
-                switch (curState) {
-                    case WifiManager.WIFI_AP_STATE_ENABLING:
-                        // We can see this state on the way to both enabled and failure states.
-                        break;
-                    case WifiManager.WIFI_AP_STATE_ENABLED:
-                        enableWifiIpServingLocked(ifname, ipmode);
-                        break;
-                    case WifiManager.WIFI_AP_STATE_DISABLING:
-                        // We can see this state on the way to disabled.
-                        break;
-                    case WifiManager.WIFI_AP_STATE_DISABLED:
-                    case WifiManager.WIFI_AP_STATE_FAILED:
-                    default:
-                        disableWifiIpServingLocked(ifname, curState);
-                        break;
-                }
+            switch (curState) {
+                case WifiManager.WIFI_AP_STATE_ENABLING:
+                    // We can see this state on the way to both enabled and failure states.
+                    break;
+                case WifiManager.WIFI_AP_STATE_ENABLED:
+                    enableWifiIpServingLocked(ifname, ipmode);
+                    break;
+                case WifiManager.WIFI_AP_STATE_DISABLING:
+                    // We can see this state on the way to disabled.
+                    break;
+                case WifiManager.WIFI_AP_STATE_DISABLED:
+                case WifiManager.WIFI_AP_STATE_FAILED:
+                default:
+                    disableWifiIpServingLocked(ifname, curState);
+                    break;
             }
         }
 
@@ -1065,32 +1035,30 @@
                 Log.d(TAG, "WifiP2pAction: P2pInfo: " + p2pInfo + " Group: " + group);
             }
 
-            synchronized (Tethering.this.mPublicSync) {
-                // if no group is formed, bring it down if needed.
-                if (p2pInfo == null || !p2pInfo.groupFormed) {
-                    disableWifiP2pIpServingLockedIfNeeded(mWifiP2pTetherInterface);
-                    mWifiP2pTetherInterface = null;
-                    return;
-                }
-
-                // If there is a group but the device is not the owner, bail out.
-                if (!isGroupOwner(group)) return;
-
-                // If already serving from the correct interface, nothing to do.
-                if (group.getInterface().equals(mWifiP2pTetherInterface)) return;
-
-                // If already serving from another interface, turn it down first.
-                if (!TextUtils.isEmpty(mWifiP2pTetherInterface)) {
-                    mLog.w("P2P tethered interface " + mWifiP2pTetherInterface
-                            + "is different from current interface "
-                            + group.getInterface() + ", re-tether it");
-                    disableWifiP2pIpServingLockedIfNeeded(mWifiP2pTetherInterface);
-                }
-
-                // Finally bring up serving on the new interface
-                mWifiP2pTetherInterface = group.getInterface();
-                enableWifiIpServingLocked(mWifiP2pTetherInterface, IFACE_IP_MODE_LOCAL_ONLY);
+            // if no group is formed, bring it down if needed.
+            if (p2pInfo == null || !p2pInfo.groupFormed) {
+                disableWifiP2pIpServingLockedIfNeeded(mWifiP2pTetherInterface);
+                mWifiP2pTetherInterface = null;
+                return;
             }
+
+            // If there is a group but the device is not the owner, bail out.
+            if (!isGroupOwner(group)) return;
+
+            // If already serving from the correct interface, nothing to do.
+            if (group.getInterface().equals(mWifiP2pTetherInterface)) return;
+
+            // If already serving from another interface, turn it down first.
+            if (!TextUtils.isEmpty(mWifiP2pTetherInterface)) {
+                mLog.w("P2P tethered interface " + mWifiP2pTetherInterface
+                        + "is different from current interface "
+                        + group.getInterface() + ", re-tether it");
+                disableWifiP2pIpServingLockedIfNeeded(mWifiP2pTetherInterface);
+            }
+
+            // Finally bring up serving on the new interface
+            mWifiP2pTetherInterface = group.getInterface();
+            enableWifiIpServingLocked(mWifiP2pTetherInterface, IFACE_IP_MODE_LOCAL_ONLY);
         }
 
         private void handleUserRestrictionAction() {
@@ -1125,14 +1093,14 @@
     @VisibleForTesting
     protected static class UserRestrictionActionListener {
         private final UserManager mUserMgr;
-        private final Tethering mWrapper;
+        private final Tethering mTethering;
         private final TetheringNotificationUpdater mNotificationUpdater;
         public boolean mDisallowTethering;
 
-        public UserRestrictionActionListener(@NonNull UserManager um, @NonNull Tethering wrapper,
+        public UserRestrictionActionListener(@NonNull UserManager um, @NonNull Tethering tethering,
                 @NonNull TetheringNotificationUpdater updater) {
             mUserMgr = um;
-            mWrapper = wrapper;
+            mTethering = tethering;
             mNotificationUpdater = updater;
             mDisallowTethering = false;
         }
@@ -1159,13 +1127,13 @@
                 return;
             }
 
-            if (mWrapper.isTetheringActive()) {
+            if (mTethering.isTetheringActive()) {
                 // Restricted notification is shown when tethering function is disallowed on
                 // user's device.
                 mNotificationUpdater.notifyTetheringDisabledByRestriction();
 
                 // Untether from all downstreams since tethering is disallowed.
-                mWrapper.untetherAll();
+                mTethering.untetherAll();
             }
             // TODO(b/148139325): send tetheringSupported on restriction change
         }
@@ -1312,86 +1280,51 @@
         return hasDownstreamConfiguration && hasUpstreamConfiguration;
     }
 
-    // TODO - update callers to use getTetheringConfiguration(),
-    // which has only final members.
-    String[] getTetherableUsbRegexs() {
-        return copy(mConfig.tetherableUsbRegexs);
+    void setUsbTethering(boolean enable, IIntResultListener listener) {
+        mHandler.post(() -> {
+            try {
+                listener.onResult(setUsbTethering(enable));
+            } catch (RemoteException e) { }
+        });
     }
 
-    String[] getTetherableWifiRegexs() {
-        return copy(mConfig.tetherableWifiRegexs);
-    }
-
-    String[] getTetherableBluetoothRegexs() {
-        return copy(mConfig.tetherableBluetoothRegexs);
-    }
-
-    int setUsbTethering(boolean enable) {
+    private int setUsbTethering(boolean enable) {
         if (VDBG) Log.d(TAG, "setUsbTethering(" + enable + ")");
         UsbManager usbManager = (UsbManager) mContext.getSystemService(Context.USB_SERVICE);
         if (usbManager == null) {
             mLog.e("setUsbTethering: failed to get UsbManager!");
             return TETHER_ERROR_SERVICE_UNAVAIL;
         }
-
-        synchronized (mPublicSync) {
-            usbManager.setCurrentFunctions(enable ? UsbManager.FUNCTION_RNDIS
-                    : UsbManager.FUNCTION_NONE);
-        }
+        usbManager.setCurrentFunctions(enable ? UsbManager.FUNCTION_RNDIS
+                : UsbManager.FUNCTION_NONE);
         return TETHER_ERROR_NO_ERROR;
     }
 
     private int setNcmTethering(boolean enable) {
         if (VDBG) Log.d(TAG, "setNcmTethering(" + enable + ")");
         UsbManager usbManager = (UsbManager) mContext.getSystemService(Context.USB_SERVICE);
-        synchronized (mPublicSync) {
-            usbManager.setCurrentFunctions(enable ? UsbManager.FUNCTION_NCM
-                    : UsbManager.FUNCTION_NONE);
-        }
+        usbManager.setCurrentFunctions(enable ? UsbManager.FUNCTION_NCM : UsbManager.FUNCTION_NONE);
         return TETHER_ERROR_NO_ERROR;
     }
 
     // TODO review API - figure out how to delete these entirely.
     String[] getTetheredIfaces() {
         ArrayList<String> list = new ArrayList<String>();
-        synchronized (mPublicSync) {
-            for (int i = 0; i < mTetherStates.size(); i++) {
-                TetherState tetherState = mTetherStates.valueAt(i);
-                if (tetherState.lastState == IpServer.STATE_TETHERED) {
-                    list.add(mTetherStates.keyAt(i));
-                }
+        for (int i = 0; i < mTetherStates.size(); i++) {
+            TetherState tetherState = mTetherStates.valueAt(i);
+            if (tetherState.lastState == IpServer.STATE_TETHERED) {
+                list.add(mTetherStates.keyAt(i));
             }
         }
         return list.toArray(new String[list.size()]);
     }
 
-    String[] getTetherableIfaces() {
+    String[] getTetherableIfacesForTest() {
         ArrayList<String> list = new ArrayList<String>();
-        synchronized (mPublicSync) {
-            for (int i = 0; i < mTetherStates.size(); i++) {
-                TetherState tetherState = mTetherStates.valueAt(i);
-                if (tetherState.lastState == IpServer.STATE_AVAILABLE) {
-                    list.add(mTetherStates.keyAt(i));
-                }
-            }
-        }
-        return list.toArray(new String[list.size()]);
-    }
-
-    String[] getTetheredDhcpRanges() {
-        // TODO: this is only valid for the old DHCP server. Latest search suggests it is only used
-        // by WifiP2pServiceImpl to start dnsmasq: remove/deprecate after migrating callers.
-        return mConfig.legacyDhcpRanges;
-    }
-
-    String[] getErroredIfaces() {
-        ArrayList<String> list = new ArrayList<String>();
-        synchronized (mPublicSync) {
-            for (int i = 0; i < mTetherStates.size(); i++) {
-                TetherState tetherState = mTetherStates.valueAt(i);
-                if (tetherState.lastError != TETHER_ERROR_NO_ERROR) {
-                    list.add(mTetherStates.keyAt(i));
-                }
+        for (int i = 0; i < mTetherStates.size(); i++) {
+            TetherState tetherState = mTetherStates.valueAt(i);
+            if (tetherState.lastState == IpServer.STATE_AVAILABLE) {
+                list.add(mTetherStates.keyAt(i));
             }
         }
         return list.toArray(new String[list.size()]);
@@ -1403,10 +1336,7 @@
 
     private boolean upstreamWanted() {
         if (!mForwardedDownstreams.isEmpty()) return true;
-
-        synchronized (mPublicSync) {
-            return mWifiTetherRequested;
-        }
+        return mWifiTetherRequested;
     }
 
     // Needed because the canonical source of upstream truth is just the
@@ -2110,8 +2040,7 @@
     }
 
     private void startTrackDefaultNetwork() {
-        mUpstreamNetworkMonitor.startTrackDefaultNetwork(mDeps.getDefaultNetworkRequest(),
-                mEntitlementMgr);
+        mUpstreamNetworkMonitor.startTrackDefaultNetwork(mEntitlementMgr);
     }
 
     /** Get the latest value of the tethering entitlement check. */
@@ -2278,15 +2207,10 @@
         pw.decreaseIndent();
     }
 
-    void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer, @Nullable String[] args) {
+    void doDump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer, @Nullable String[] args) {
         // Binder.java closes the resource for us.
-        @SuppressWarnings("resource")
-        final IndentingPrintWriter pw = new IndentingPrintWriter(writer, "  ");
-        if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.DUMP)
-                != PERMISSION_GRANTED) {
-            pw.println("Permission Denial: can't dump.");
-            return;
-        }
+        @SuppressWarnings("resource") final IndentingPrintWriter pw = new IndentingPrintWriter(
+                writer, "  ");
 
         if (argsContain(args, "bpf")) {
             dumpBpf(pw);
@@ -2307,37 +2231,35 @@
         mEntitlementMgr.dump(pw);
         pw.decreaseIndent();
 
-        synchronized (mPublicSync) {
-            pw.println("Tether state:");
-            pw.increaseIndent();
-            for (int i = 0; i < mTetherStates.size(); i++) {
-                final String iface = mTetherStates.keyAt(i);
-                final TetherState tetherState = mTetherStates.valueAt(i);
-                pw.print(iface + " - ");
+        pw.println("Tether state:");
+        pw.increaseIndent();
+        for (int i = 0; i < mTetherStates.size(); i++) {
+            final String iface = mTetherStates.keyAt(i);
+            final TetherState tetherState = mTetherStates.valueAt(i);
+            pw.print(iface + " - ");
 
-                switch (tetherState.lastState) {
-                    case IpServer.STATE_UNAVAILABLE:
-                        pw.print("UnavailableState");
-                        break;
-                    case IpServer.STATE_AVAILABLE:
-                        pw.print("AvailableState");
-                        break;
-                    case IpServer.STATE_TETHERED:
-                        pw.print("TetheredState");
-                        break;
-                    case IpServer.STATE_LOCAL_ONLY:
-                        pw.print("LocalHotspotState");
-                        break;
-                    default:
-                        pw.print("UnknownState");
-                        break;
-                }
-                pw.println(" - lastError = " + tetherState.lastError);
+            switch (tetherState.lastState) {
+                case IpServer.STATE_UNAVAILABLE:
+                    pw.print("UnavailableState");
+                    break;
+                case IpServer.STATE_AVAILABLE:
+                    pw.print("AvailableState");
+                    break;
+                case IpServer.STATE_TETHERED:
+                    pw.print("TetheredState");
+                    break;
+                case IpServer.STATE_LOCAL_ONLY:
+                    pw.print("LocalHotspotState");
+                    break;
+                default:
+                    pw.print("UnknownState");
+                    break;
             }
-            pw.println("Upstream wanted: " + upstreamWanted());
-            pw.println("Current upstream interface(s): " + mCurrentUpstreamIfaceSet);
-            pw.decreaseIndent();
+            pw.println(" - lastError = " + tetherState.lastError);
         }
+        pw.println("Upstream wanted: " + upstreamWanted());
+        pw.println("Current upstream interface(s): " + mCurrentUpstreamIfaceSet);
+        pw.decreaseIndent();
 
         pw.println("Hardware offload:");
         pw.increaseIndent();
@@ -2363,6 +2285,40 @@
         pw.decreaseIndent();
     }
 
+    void dump(@NonNull FileDescriptor fd, @NonNull PrintWriter writer, @Nullable String[] args) {
+        if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.DUMP)
+                != PERMISSION_GRANTED) {
+            writer.println("Permission Denial: can't dump.");
+            return;
+        }
+
+        final CountDownLatch latch = new CountDownLatch(1);
+
+        // Don't crash the system if something in doDump throws an exception, but try to propagate
+        // the exception to the caller.
+        AtomicReference<RuntimeException> exceptionRef = new AtomicReference<>();
+        mHandler.post(() -> {
+            try {
+                doDump(fd, writer, args);
+            } catch (RuntimeException e) {
+                exceptionRef.set(e);
+            }
+            latch.countDown();
+        });
+
+        try {
+            if (!latch.await(DUMP_TIMEOUT_MS, TimeUnit.MILLISECONDS)) {
+                writer.println("Dump timeout after " + DUMP_TIMEOUT_MS + "ms");
+                return;
+            }
+        } catch (InterruptedException e) {
+            exceptionRef.compareAndSet(null, new IllegalStateException("Dump interrupted", e));
+        }
+
+        final RuntimeException e = exceptionRef.get();
+        if (e != null) throw e;
+    }
+
     private static boolean argsContain(String[] args, String target) {
         for (String arg : args) {
             if (target.equals(arg)) return true;
@@ -2404,14 +2360,12 @@
     // TODO: Move into TetherMainSM.
     private void notifyInterfaceStateChange(IpServer who, int state, int error) {
         final String iface = who.interfaceName();
-        synchronized (mPublicSync) {
-            final TetherState tetherState = mTetherStates.get(iface);
-            if (tetherState != null && tetherState.ipServer.equals(who)) {
-                tetherState.lastState = state;
-                tetherState.lastError = error;
-            } else {
-                if (DBG) Log.d(TAG, "got notification from stale iface " + iface);
-            }
+        final TetherState tetherState = mTetherStates.get(iface);
+        if (tetherState != null && tetherState.ipServer.equals(who)) {
+            tetherState.lastState = state;
+            tetherState.lastError = error;
+        } else {
+            if (DBG) Log.d(TAG, "got notification from stale iface " + iface);
         }
 
         mLog.log(String.format("OBSERVED iface=%s state=%s error=%s", iface, state, error));
@@ -2443,14 +2397,12 @@
     private void notifyLinkPropertiesChanged(IpServer who, LinkProperties newLp) {
         final String iface = who.interfaceName();
         final int state;
-        synchronized (mPublicSync) {
-            final TetherState tetherState = mTetherStates.get(iface);
-            if (tetherState != null && tetherState.ipServer.equals(who)) {
-                state = tetherState.lastState;
-            } else {
-                mLog.log("got notification from stale iface " + iface);
-                return;
-            }
+        final TetherState tetherState = mTetherStates.get(iface);
+        if (tetherState != null && tetherState.ipServer.equals(who)) {
+            state = tetherState.lastState;
+        } else {
+            mLog.log("got notification from stale iface " + iface);
+            return;
         }
 
         mLog.log(String.format(
diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringDependencies.java b/Tethering/src/com/android/networkstack/tethering/TetheringDependencies.java
index 45b9141..7df9475 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringDependencies.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringDependencies.java
@@ -20,7 +20,6 @@
 import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
 import android.net.INetd;
-import android.net.NetworkRequest;
 import android.net.ip.IpServer;
 import android.net.util.SharedLog;
 import android.os.Handler;
@@ -99,11 +98,6 @@
     }
 
     /**
-     * Get the NetworkRequest that should be fulfilled by the default network.
-     */
-    public abstract NetworkRequest getDefaultNetworkRequest();
-
-    /**
      * Get a reference to the EntitlementManager to be used by tethering.
      */
     public EntitlementManager getEntitlementManager(Context ctx, Handler h, SharedLog log,
diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringService.java b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
index 3438b9b..92dd921 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringService.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringService.java
@@ -35,8 +35,6 @@
 import android.net.INetworkStackConnector;
 import android.net.ITetheringConnector;
 import android.net.ITetheringEventCallback;
-import android.net.NetworkCapabilities;
-import android.net.NetworkRequest;
 import android.net.NetworkStack;
 import android.net.TetheringRequestParcel;
 import android.net.dhcp.DhcpServerCallbacks;
@@ -121,9 +119,7 @@
                 IIntResultListener listener) {
             if (checkAndNotifyCommonError(callerPkg, callingAttributionTag, listener)) return;
 
-            try {
-                listener.onResult(mTethering.setUsbTethering(enable));
-            } catch (RemoteException e) { }
+            mTethering.setUsbTethering(enable, listener);
         }
 
         @Override
@@ -309,19 +305,6 @@
     public TetheringDependencies makeTetheringDependencies() {
         return new TetheringDependencies() {
             @Override
-            public NetworkRequest getDefaultNetworkRequest() {
-                // TODO: b/147280869, add a proper system API to replace this.
-                final NetworkRequest trackDefaultRequest = new NetworkRequest.Builder()
-                        .clearCapabilities()
-                        .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED)
-                        .addCapability(NetworkCapabilities.NET_CAPABILITY_TRUSTED)
-                        .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)
-                        .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
-                        .build();
-                return trackDefaultRequest;
-            }
-
-            @Override
             public Looper getTetheringLooper() {
                 final HandlerThread tetherThread = new HandlerThread("android.tethering");
                 tetherThread.start();
diff --git a/Tethering/src/com/android/networkstack/tethering/UpstreamNetworkMonitor.java b/Tethering/src/com/android/networkstack/tethering/UpstreamNetworkMonitor.java
index 9de4c87..e615334 100644
--- a/Tethering/src/com/android/networkstack/tethering/UpstreamNetworkMonitor.java
+++ b/Tethering/src/com/android/networkstack/tethering/UpstreamNetworkMonitor.java
@@ -47,6 +47,9 @@
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.StateMachine;
+import com.android.networkstack.apishim.ConnectivityManagerShimImpl;
+import com.android.networkstack.apishim.common.ConnectivityManagerShim;
+import com.android.networkstack.apishim.common.UnsupportedApiLevelException;
 
 import java.util.HashMap;
 import java.util.HashSet;
@@ -142,33 +145,28 @@
         mWhat = what;
         mLocalPrefixes = new HashSet<>();
         mIsDefaultCellularUpstream = false;
-    }
-
-    @VisibleForTesting
-    public UpstreamNetworkMonitor(
-            ConnectivityManager cm, StateMachine tgt, SharedLog log, int what) {
-        this((Context) null, tgt, log, what);
-        mCM = cm;
+        mCM = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
     }
 
     /**
-     * Tracking the system default network. This method should be called when system is ready.
+     * Tracking the system default network. This method should be only called once when system is
+     * ready, and the callback is never unregistered.
      *
-     * @param defaultNetworkRequest should be the same as ConnectivityService default request
      * @param entitle a EntitlementManager object to communicate between EntitlementManager and
      * UpstreamNetworkMonitor
      */
-    public void startTrackDefaultNetwork(NetworkRequest defaultNetworkRequest,
-            EntitlementManager entitle) {
-
-        // defaultNetworkRequest is not really a "request", just a way of tracking the system
-        // default network. It's guaranteed not to actually bring up any networks because it's
-        // the should be the same request as the ConnectivityService default request, and thus
-        // shares fate with it. We can't use registerDefaultNetworkCallback because it will not
-        // track the system default network if there is a VPN that applies to our UID.
-        if (mDefaultNetworkCallback == null) {
-            mDefaultNetworkCallback = new UpstreamNetworkCallback(CALLBACK_DEFAULT_INTERNET);
-            cm().requestNetwork(defaultNetworkRequest, mDefaultNetworkCallback, mHandler);
+    public void startTrackDefaultNetwork(EntitlementManager entitle) {
+        if (mDefaultNetworkCallback != null) {
+            Log.wtf(TAG, "default network callback is already registered");
+            return;
+        }
+        ConnectivityManagerShim mCmShim = ConnectivityManagerShimImpl.newInstance(mContext);
+        mDefaultNetworkCallback = new UpstreamNetworkCallback(CALLBACK_DEFAULT_INTERNET);
+        try {
+            mCmShim.registerSystemDefaultNetworkCallback(mDefaultNetworkCallback, mHandler);
+        } catch (UnsupportedApiLevelException e) {
+            Log.wtf(TAG, "registerSystemDefaultNetworkCallback is not supported");
+            return;
         }
         if (mEntitlementMgr == null) {
             mEntitlementMgr = entitle;
diff --git a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
index fe4e696..de94cba 100644
--- a/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
+++ b/Tethering/tests/integration/src/android/net/EthernetTetheringTest.java
@@ -16,6 +16,7 @@
 
 package android.net;
 
+import static android.Manifest.permission.ACCESS_NETWORK_STATE;
 import static android.Manifest.permission.MANAGE_TEST_NETWORKS;
 import static android.Manifest.permission.NETWORK_SETTINGS;
 import static android.Manifest.permission.TETHER_PRIVILEGED;
@@ -121,7 +122,7 @@
         // Needed to create a TestNetworkInterface, to call requestTetheredInterface, and to receive
         // tethered client callbacks.
         mUiAutomation.adoptShellPermissionIdentity(
-                MANAGE_TEST_NETWORKS, NETWORK_SETTINGS, TETHER_PRIVILEGED);
+                MANAGE_TEST_NETWORKS, NETWORK_SETTINGS, TETHER_PRIVILEGED, ACCESS_NETWORK_STATE);
         mRunTests = mTm.isTetheringSupported() && mEm != null;
         assumeTrue(mRunTests);
 
diff --git a/Tethering/tests/jarjar-rules.txt b/Tethering/tests/jarjar-rules.txt
index c99ff7f..9cb143e 100644
--- a/Tethering/tests/jarjar-rules.txt
+++ b/Tethering/tests/jarjar-rules.txt
@@ -1,8 +1,8 @@
 # Don't jar-jar the entire package because this test use some
 # internal classes (like ArrayUtils in com.android.internal.util)
 rule com.android.internal.util.BitUtils* com.android.networkstack.tethering.util.BitUtils@1
-rule com.android.internal.util.IndentingPrintWriter.java* com.android.networkstack.tethering.util.IndentingPrintWriter.java@1
-rule com.android.internal.util.IState.java* com.android.networkstack.tethering.util.IState.java@1
+rule com.android.internal.util.IndentingPrintWriter* com.android.networkstack.tethering.util.IndentingPrintWriter@1
+rule com.android.internal.util.IState* com.android.networkstack.tethering.util.IState@1
 rule com.android.internal.util.MessageUtils* com.android.networkstack.tethering.util.MessageUtils@1
 rule com.android.internal.util.State* com.android.networkstack.tethering.util.State@1
 rule com.android.internal.util.StateMachine* com.android.networkstack.tethering.util.StateMachine@1
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadControllerTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadControllerTest.java
index 88f2054..d800816 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadControllerTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadControllerTest.java
@@ -58,7 +58,6 @@
 import android.app.usage.NetworkStatsManager;
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
-import android.net.ITetheringStatsProvider;
 import android.net.IpPrefix;
 import android.net.LinkAddress;
 import android.net.LinkProperties;
@@ -150,6 +149,7 @@
         when(mHardware.setUpstreamParameters(anyString(), any(), any(), any())).thenReturn(true);
         when(mHardware.getForwardedStats(any())).thenReturn(new ForwardedStats());
         when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(true);
+        when(mHardware.setDataWarningAndLimit(anyString(), anyLong(), anyLong())).thenReturn(true);
     }
 
     private void enableOffload() {
@@ -503,77 +503,167 @@
                 expectedUidStatsDiff);
     }
 
+    /**
+     * Test OffloadController with different combinations of HAL and framework versions can set
+     * data warning and/or limit correctly.
+     */
     @Test
-    public void testSetInterfaceQuota() throws Exception {
+    public void testSetDataWarningAndLimit() throws Exception {
+        // Verify the OffloadController is called by R framework, where the framework doesn't send
+        // warning.
+        checkSetDataWarningAndLimit(false, OFFLOAD_HAL_VERSION_1_0);
+        checkSetDataWarningAndLimit(false, OFFLOAD_HAL_VERSION_1_1);
+        // Verify the OffloadController is called by S+ framework, where the framework sends
+        // warning along with limit.
+        checkSetDataWarningAndLimit(true, OFFLOAD_HAL_VERSION_1_0);
+        checkSetDataWarningAndLimit(true, OFFLOAD_HAL_VERSION_1_1);
+    }
+
+    private void checkSetDataWarningAndLimit(boolean isProviderSetWarning, int controlVersion)
+            throws Exception {
         enableOffload();
         final OffloadController offload =
-                startOffloadController(OFFLOAD_HAL_VERSION_1_0, true /*expectStart*/);
+                startOffloadController(controlVersion, true /*expectStart*/);
 
         final String ethernetIface = "eth1";
         final String mobileIface = "rmnet_data0";
         final long ethernetLimit = 12345;
+        final long mobileWarning = 123456;
         final long mobileLimit = 12345678;
 
         final LinkProperties lp = new LinkProperties();
         lp.setInterfaceName(ethernetIface);
-        offload.setUpstreamLinkProperties(lp);
 
         final InOrder inOrder = inOrder(mHardware);
-        when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(true);
+        when(mHardware.setUpstreamParameters(
+                any(), any(), any(), any())).thenReturn(true);
         when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(true);
+        when(mHardware.setDataWarningAndLimit(anyString(), anyLong(), anyLong())).thenReturn(true);
+        offload.setUpstreamLinkProperties(lp);
+        // Applying an interface sends the initial quota to the hardware.
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            inOrder.verify(mHardware).setDataWarningAndLimit(ethernetIface, Long.MAX_VALUE,
+                    Long.MAX_VALUE);
+        } else {
+            inOrder.verify(mHardware).setDataLimit(ethernetIface, Long.MAX_VALUE);
+        }
+        inOrder.verifyNoMoreInteractions();
+
+        // Verify that set to unlimited again won't cause duplicated calls to the hardware.
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(ethernetIface,
+                    NetworkStatsProvider.QUOTA_UNLIMITED, NetworkStatsProvider.QUOTA_UNLIMITED);
+        } else {
+            mTetherStatsProvider.onSetLimit(ethernetIface, NetworkStatsProvider.QUOTA_UNLIMITED);
+        }
+        waitForIdle();
+        inOrder.verifyNoMoreInteractions();
 
         // Applying an interface quota to the current upstream immediately sends it to the hardware.
-        mTetherStatsProvider.onSetLimit(ethernetIface, ethernetLimit);
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(ethernetIface,
+                    NetworkStatsProvider.QUOTA_UNLIMITED, ethernetLimit);
+        } else {
+            mTetherStatsProvider.onSetLimit(ethernetIface, ethernetLimit);
+        }
         waitForIdle();
-        inOrder.verify(mHardware).setDataLimit(ethernetIface, ethernetLimit);
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            inOrder.verify(mHardware).setDataWarningAndLimit(ethernetIface, Long.MAX_VALUE,
+                    ethernetLimit);
+        } else {
+            inOrder.verify(mHardware).setDataLimit(ethernetIface, ethernetLimit);
+        }
         inOrder.verifyNoMoreInteractions();
 
         // Applying an interface quota to another upstream does not take any immediate action.
-        mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(mobileIface, mobileWarning, mobileLimit);
+        } else {
+            mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        }
         waitForIdle();
-        inOrder.verify(mHardware, never()).setDataLimit(anyString(), anyLong());
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            inOrder.verify(mHardware, never()).setDataWarningAndLimit(anyString(), anyLong(),
+                    anyLong());
+        } else {
+            inOrder.verify(mHardware, never()).setDataLimit(anyString(), anyLong());
+        }
 
         // Switching to that upstream causes the quota to be applied if the parameters were applied
         // correctly.
         lp.setInterfaceName(mobileIface);
         offload.setUpstreamLinkProperties(lp);
         waitForIdle();
-        inOrder.verify(mHardware).setDataLimit(mobileIface, mobileLimit);
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            inOrder.verify(mHardware).setDataWarningAndLimit(mobileIface,
+                    isProviderSetWarning ? mobileWarning : Long.MAX_VALUE,
+                    mobileLimit);
+        } else {
+            inOrder.verify(mHardware).setDataLimit(mobileIface, mobileLimit);
+        }
 
-        // Setting a limit of ITetheringStatsProvider.QUOTA_UNLIMITED causes the limit to be set
+        // Setting a limit of NetworkStatsProvider.QUOTA_UNLIMITED causes the limit to be set
         // to Long.MAX_VALUE.
-        mTetherStatsProvider.onSetLimit(mobileIface, ITetheringStatsProvider.QUOTA_UNLIMITED);
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(mobileIface,
+                    NetworkStatsProvider.QUOTA_UNLIMITED, NetworkStatsProvider.QUOTA_UNLIMITED);
+        } else {
+            mTetherStatsProvider.onSetLimit(mobileIface, NetworkStatsProvider.QUOTA_UNLIMITED);
+        }
         waitForIdle();
-        inOrder.verify(mHardware).setDataLimit(mobileIface, Long.MAX_VALUE);
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            inOrder.verify(mHardware).setDataWarningAndLimit(mobileIface, Long.MAX_VALUE,
+                    Long.MAX_VALUE);
+        } else {
+            inOrder.verify(mHardware).setDataLimit(mobileIface, Long.MAX_VALUE);
+        }
 
-        // If setting upstream parameters fails, then the data limit is not set.
+        // If setting upstream parameters fails, then the data warning and limit is not set.
         when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(false);
         lp.setInterfaceName(ethernetIface);
         offload.setUpstreamLinkProperties(lp);
-        mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(mobileIface, mobileWarning, mobileLimit);
+        } else {
+            mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        }
         waitForIdle();
         inOrder.verify(mHardware, never()).setDataLimit(anyString(), anyLong());
+        inOrder.verify(mHardware, never()).setDataWarningAndLimit(anyString(), anyLong(),
+                anyLong());
 
-        // If setting the data limit fails while changing upstreams, offload is stopped.
+        // If setting the data warning and/or limit fails while changing upstreams, offload is
+        // stopped.
         when(mHardware.setUpstreamParameters(any(), any(), any(), any())).thenReturn(true);
         when(mHardware.setDataLimit(anyString(), anyLong())).thenReturn(false);
+        when(mHardware.setDataWarningAndLimit(anyString(), anyLong(), anyLong())).thenReturn(false);
         lp.setInterfaceName(mobileIface);
         offload.setUpstreamLinkProperties(lp);
-        mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        if (isProviderSetWarning) {
+            mTetherStatsProvider.onSetWarningAndLimit(mobileIface, mobileWarning, mobileLimit);
+        } else {
+            mTetherStatsProvider.onSetLimit(mobileIface, mobileLimit);
+        }
         waitForIdle();
         inOrder.verify(mHardware).getForwardedStats(ethernetIface);
         inOrder.verify(mHardware).stopOffloadControl();
     }
 
     @Test
-    public void testDataLimitCallback() throws Exception {
+    public void testDataWarningAndLimitCallback() throws Exception {
         enableOffload();
-        final OffloadController offload =
-                startOffloadController(OFFLOAD_HAL_VERSION_1_0, true /*expectStart*/);
+        startOffloadController(OFFLOAD_HAL_VERSION_1_0, true /*expectStart*/);
 
         OffloadHardwareInterface.ControlCallback callback = mControlCallbackCaptor.getValue();
         callback.onStoppedLimitReached();
         mTetherStatsProviderCb.expectNotifyStatsUpdated();
+        mTetherStatsProviderCb.expectNotifyWarningOrLimitReached();
+
+        startOffloadController(OFFLOAD_HAL_VERSION_1_1, true /*expectStart*/);
+        callback = mControlCallbackCaptor.getValue();
+        callback.onWarningReached();
+        mTetherStatsProviderCb.expectNotifyStatsUpdated();
+        mTetherStatsProviderCb.expectNotifyWarningOrLimitReached();
     }
 
     @Test
@@ -761,9 +851,7 @@
         // Initialize with fake eth upstream.
         final String ethernetIface = "eth1";
         InOrder inOrder = inOrder(mHardware);
-        final LinkProperties lp = new LinkProperties();
-        lp.setInterfaceName(ethernetIface);
-        offload.setUpstreamLinkProperties(lp);
+        offload.setUpstreamLinkProperties(makeEthernetLinkProperties());
         // Previous upstream was null, so no stats are fetched.
         inOrder.verify(mHardware, never()).getForwardedStats(any());
 
@@ -796,4 +884,33 @@
         mTetherStatsProviderCb.assertNoCallback();
         verify(mHardware, never()).getForwardedStats(any());
     }
+
+    private static LinkProperties makeEthernetLinkProperties() {
+        final String ethernetIface = "eth1";
+        final LinkProperties lp = new LinkProperties();
+        lp.setInterfaceName(ethernetIface);
+        return lp;
+    }
+
+    private void checkSoftwarePollingUsed(int controlVersion) throws Exception {
+        enableOffload();
+        setOffloadPollInterval(DEFAULT_TETHER_OFFLOAD_POLL_INTERVAL_MS);
+        OffloadController offload =
+                startOffloadController(controlVersion, true /*expectStart*/);
+        offload.setUpstreamLinkProperties(makeEthernetLinkProperties());
+        mTetherStatsProvider.onSetAlert(0);
+        waitForIdle();
+        if (controlVersion >= OFFLOAD_HAL_VERSION_1_1) {
+            mTetherStatsProviderCb.assertNoCallback();
+        } else {
+            mTetherStatsProviderCb.expectNotifyAlertReached();
+        }
+        verify(mHardware, never()).getForwardedStats(any());
+    }
+
+    @Test
+    public void testSoftwarePollingUsed() throws Exception {
+        checkSoftwarePollingUsed(OFFLOAD_HAL_VERSION_1_0);
+        checkSoftwarePollingUsed(OFFLOAD_HAL_VERSION_1_1);
+    }
 }
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java
index f4194e5..a8b3b92 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/OffloadHardwareInterfaceTest.java
@@ -22,22 +22,27 @@
 import static android.system.OsConstants.SOCK_STREAM;
 
 import static com.android.networkstack.tethering.OffloadHardwareInterface.OFFLOAD_HAL_VERSION_1_0;
+import static com.android.networkstack.tethering.OffloadHardwareInterface.OFFLOAD_HAL_VERSION_1_1;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import android.hardware.tetheroffload.config.V1_0.IOffloadConfig;
 import android.hardware.tetheroffload.control.V1_0.IOffloadControl;
-import android.hardware.tetheroffload.control.V1_0.ITetheringOffloadCallback;
 import android.hardware.tetheroffload.control.V1_0.NatTimeoutUpdate;
 import android.hardware.tetheroffload.control.V1_0.NetworkProtocol;
-import android.hardware.tetheroffload.control.V1_0.OffloadCallbackEvent;
+import android.hardware.tetheroffload.control.V1_1.ITetheringOffloadCallback;
+import android.hardware.tetheroffload.control.V1_1.OffloadCallbackEvent;
 import android.net.netlink.StructNfGenMsg;
 import android.net.netlink.StructNlMsgHdr;
 import android.net.util.SharedLog;
@@ -56,6 +61,7 @@
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
+import org.mockito.InOrder;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -76,7 +82,7 @@
     private OffloadHardwareInterface.ControlCallback mControlCallback;
 
     @Mock private IOffloadConfig mIOffloadConfig;
-    @Mock private IOffloadControl mIOffloadControl;
+    private IOffloadControl mIOffloadControl;
     @Mock private NativeHandle mNativeHandle;
 
     // Random values to test Netlink message.
@@ -84,8 +90,10 @@
     private static final short TEST_FLAGS = 263;
 
     class MyDependencies extends OffloadHardwareInterface.Dependencies {
-        MyDependencies(SharedLog log) {
+        private final int mMockControlVersion;
+        MyDependencies(SharedLog log, final int mockControlVersion) {
             super(log);
+            mMockControlVersion = mockControlVersion;
         }
 
         @Override
@@ -95,7 +103,19 @@
 
         @Override
         public Pair<IOffloadControl, Integer> getOffloadControl() {
-            return new Pair<IOffloadControl, Integer>(mIOffloadControl, OFFLOAD_HAL_VERSION_1_0);
+            switch (mMockControlVersion) {
+                case OFFLOAD_HAL_VERSION_1_0:
+                    mIOffloadControl = mock(IOffloadControl.class);
+                    break;
+                case OFFLOAD_HAL_VERSION_1_1:
+                    mIOffloadControl =
+                            mock(android.hardware.tetheroffload.control.V1_1.IOffloadControl.class);
+                    break;
+                default:
+                    throw new IllegalArgumentException("Invalid offload control version "
+                            + mMockControlVersion);
+            }
+            return new Pair<IOffloadControl, Integer>(mIOffloadControl, mMockControlVersion);
         }
 
         @Override
@@ -107,14 +127,13 @@
     @Before
     public void setUp() {
         MockitoAnnotations.initMocks(this);
-        final SharedLog log = new SharedLog("test");
-        mOffloadHw = new OffloadHardwareInterface(new Handler(mTestLooper.getLooper()), log,
-                new MyDependencies(log));
         mControlCallback = spy(new OffloadHardwareInterface.ControlCallback());
     }
 
-    // TODO: Pass version to test version specific operations.
-    private void startOffloadHardwareInterface() throws Exception {
+    private void startOffloadHardwareInterface(int controlVersion) throws Exception {
+        final SharedLog log = new SharedLog("test");
+        mOffloadHw = new OffloadHardwareInterface(new Handler(mTestLooper.getLooper()), log,
+                new MyDependencies(log, controlVersion));
         mOffloadHw.initOffloadConfig();
         mOffloadHw.initOffloadControl(mControlCallback);
         final ArgumentCaptor<ITetheringOffloadCallback> mOffloadCallbackCaptor =
@@ -125,7 +144,7 @@
 
     @Test
     public void testGetForwardedStats() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         final OffloadHardwareInterface.ForwardedStats stats = mOffloadHw.getForwardedStats(RMNET0);
         verify(mIOffloadControl).getForwardedStats(eq(RMNET0), any());
         assertNotNull(stats);
@@ -133,7 +152,7 @@
 
     @Test
     public void testSetLocalPrefixes() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         final ArrayList<String> localPrefixes = new ArrayList<>();
         localPrefixes.add("127.0.0.0/8");
         localPrefixes.add("fe80::/64");
@@ -143,15 +162,32 @@
 
     @Test
     public void testSetDataLimit() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         final long limit = 12345;
         mOffloadHw.setDataLimit(RMNET0, limit);
         verify(mIOffloadControl).setDataLimit(eq(RMNET0), eq(limit), any());
     }
 
     @Test
+    public void testSetDataWarningAndLimit() throws Exception {
+        // Verify V1.0 control HAL would reject the function call with exception.
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
+        final long warning = 12345;
+        final long limit = 67890;
+        assertThrows(IllegalArgumentException.class,
+                () -> mOffloadHw.setDataWarningAndLimit(RMNET0, warning, limit));
+        reset(mIOffloadControl);
+
+        // Verify V1.1 control HAL could receive this function call.
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_1);
+        mOffloadHw.setDataWarningAndLimit(RMNET0, warning, limit);
+        verify((android.hardware.tetheroffload.control.V1_1.IOffloadControl) mIOffloadControl)
+                .setDataWarningAndLimit(eq(RMNET0), eq(warning), eq(limit), any());
+    }
+
+    @Test
     public void testSetUpstreamParameters() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         final String v4addr = "192.168.10.1";
         final String v4gateway = "192.168.10.255";
         final ArrayList<String> v6gws = new ArrayList<>(0);
@@ -170,7 +206,7 @@
 
     @Test
     public void testUpdateDownstreamPrefix() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         final String ifName = "wlan1";
         final String prefix = "192.168.43.0/24";
         mOffloadHw.addDownstreamPrefix(ifName, prefix);
@@ -182,7 +218,7 @@
 
     @Test
     public void testTetheringOffloadCallback() throws Exception {
-        startOffloadHardwareInterface();
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
 
         mTetheringOffloadCallback.onEvent(OffloadCallbackEvent.OFFLOAD_STARTED);
         mTestLooper.dispatchAll();
@@ -221,10 +257,26 @@
                 eq(uint16(udpParams.src.port)),
                 eq(udpParams.dst.addr),
                 eq(uint16(udpParams.dst.port)));
+        reset(mControlCallback);
+
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_1);
+
+        // Verify the interface will process the events that comes from V1.1 HAL.
+        mTetheringOffloadCallback.onEvent_1_1(OffloadCallbackEvent.OFFLOAD_STARTED);
+        mTestLooper.dispatchAll();
+        final InOrder inOrder = inOrder(mControlCallback);
+        inOrder.verify(mControlCallback).onStarted();
+        inOrder.verifyNoMoreInteractions();
+
+        mTetheringOffloadCallback.onEvent_1_1(OffloadCallbackEvent.OFFLOAD_WARNING_REACHED);
+        mTestLooper.dispatchAll();
+        inOrder.verify(mControlCallback).onWarningReached();
+        inOrder.verifyNoMoreInteractions();
     }
 
     @Test
     public void testSendIpv4NfGenMsg() throws Exception {
+        startOffloadHardwareInterface(OFFLOAD_HAL_VERSION_1_0);
         FileDescriptor writeSocket = new FileDescriptor();
         FileDescriptor readSocket = new FileDescriptor();
         try {
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TestConnectivityManager.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TestConnectivityManager.java
index df82d7c..6090213 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TestConnectivityManager.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TestConnectivityManager.java
@@ -16,6 +16,10 @@
 
 package com.android.networkstack.tethering;
 
+import static android.net.NetworkCapabilities.NET_CAPABILITY_DUN;
+import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
+import static android.net.NetworkCapabilities.TRANSPORT_CELLULAR;
+
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.fail;
 
@@ -64,12 +68,13 @@
     public static final boolean CALLBACKS_FIRST = true;
 
     final Map<NetworkCallback, NetworkRequestInfo> mAllCallbacks = new ArrayMap<>();
+    // This contains the callbacks tracking the system default network, whether it's registered
+    // with registerSystemDefaultNetworkCallback (S+) or with a custom request (R-).
     final Map<NetworkCallback, NetworkRequestInfo> mTrackingDefault = new ArrayMap<>();
     final Map<NetworkCallback, NetworkRequestInfo> mListening = new ArrayMap<>();
     final Map<NetworkCallback, NetworkRequestInfo> mRequested = new ArrayMap<>();
     final Map<NetworkCallback, Integer> mLegacyTypeMap = new ArrayMap<>();
 
-    private final NetworkRequest mDefaultRequest;
     private final Context mContext;
 
     private int mNetworkId = 100;
@@ -80,13 +85,10 @@
      * @param ctx the context to use. Must be a fake or a mock because otherwise the test will
      *            attempt to send real broadcasts and resulting in permission denials.
      * @param svc an IConnectivityManager. Should be a fake or a mock.
-     * @param defaultRequest the default NetworkRequest that will be used by Tethering.
      */
-    public TestConnectivityManager(Context ctx, IConnectivityManager svc,
-            NetworkRequest defaultRequest) {
+    public TestConnectivityManager(Context ctx, IConnectivityManager svc) {
         super(ctx, svc);
         mContext = ctx;
-        mDefaultRequest = defaultRequest;
     }
 
     class NetworkRequestInfo {
@@ -181,11 +183,19 @@
         makeDefaultNetwork(agent, BROADCAST_FIRST, null /* inBetween */);
     }
 
+    static boolean looksLikeDefaultRequest(NetworkRequest req) {
+        return req.hasCapability(NET_CAPABILITY_INTERNET)
+                && !req.hasCapability(NET_CAPABILITY_DUN)
+                && !req.hasTransport(TRANSPORT_CELLULAR);
+    }
+
     @Override
     public void requestNetwork(NetworkRequest req, NetworkCallback cb, Handler h) {
         assertFalse(mAllCallbacks.containsKey(cb));
         mAllCallbacks.put(cb, new NetworkRequestInfo(req, h));
-        if (mDefaultRequest.equals(req)) {
+        // For R- devices, Tethering will invoke this function in 2 cases, one is to request mobile
+        // network, the other is to track system default network.
+        if (looksLikeDefaultRequest(req)) {
             assertFalse(mTrackingDefault.containsKey(cb));
             mTrackingDefault.put(cb, new NetworkRequestInfo(req, h));
         } else {
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
index 7204ff6..941cd78 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringServiceTest.java
@@ -25,7 +25,10 @@
 import static android.net.TetheringManager.TETHER_ERROR_NO_ERROR;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -214,11 +217,15 @@
     }
 
     private void runSetUsbTethering(final TestTetheringResult result) throws Exception {
-        when(mTethering.setUsbTethering(true /* enable */)).thenReturn(TETHER_ERROR_NO_ERROR);
+        doAnswer((invocation) -> {
+            final IIntResultListener listener = invocation.getArgument(1);
+            listener.onResult(TETHER_ERROR_NO_ERROR);
+            return null;
+        }).when(mTethering).setUsbTethering(anyBoolean(), any(IIntResultListener.class));
         mTetheringConnector.setUsbTethering(true /* enable */, TEST_CALLER_PKG,
                 TEST_ATTRIBUTION_TAG, result);
         verify(mTethering).isTetheringSupported();
-        verify(mTethering).setUsbTethering(true /* enable */);
+        verify(mTethering).setUsbTethering(eq(true) /* enable */, any(IIntResultListener.class));
         result.assertResult(TETHER_ERROR_NO_ERROR);
     }
 
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
index 81ba450..69c1758 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
@@ -26,7 +26,6 @@
 import static android.net.ConnectivityManager.RESTRICT_BACKGROUND_STATUS_DISABLED;
 import static android.net.ConnectivityManager.RESTRICT_BACKGROUND_STATUS_ENABLED;
 import static android.net.ConnectivityManager.TYPE_MOBILE_DUN;
-import static android.net.ConnectivityManager.TYPE_NONE;
 import static android.net.ConnectivityManager.TYPE_WIFI;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_DUN;
 import static android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET;
@@ -75,7 +74,6 @@
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.argThat;
@@ -276,8 +274,6 @@
     private UpstreamNetworkMonitor mUpstreamNetworkMonitor;
 
     private TestConnectivityManager mCm;
-    private NetworkRequest mNetworkRequest;
-    private NetworkCallback mDefaultNetworkCallback;
 
     private class TestContext extends BroadcastInterceptingContext {
         TestContext(Context base) {
@@ -452,11 +448,6 @@
         }
 
         @Override
-        public NetworkRequest getDefaultNetworkRequest() {
-            return mNetworkRequest;
-        }
-
-        @Override
         public EntitlementManager getEntitlementManager(Context ctx, Handler h, SharedLog log,
                 Runnable callback) {
             mEntitleMgr = spy(super.getEntitlementManager(ctx, h, log, callback));
@@ -647,15 +638,7 @@
         mServiceContext.registerReceiver(mBroadcastReceiver,
                 new IntentFilter(ACTION_TETHER_STATE_CHANGED));
 
-        // TODO: add NOT_VCN_MANAGED here, but more importantly in the production code.
-        // TODO: even better, change TetheringDependencies.getDefaultNetworkRequest() to use
-        // registerSystemDefaultNetworkCallback() on S and above.
-        NetworkCapabilities defaultCaps = new NetworkCapabilities()
-                .addCapability(NET_CAPABILITY_INTERNET);
-        mNetworkRequest = new NetworkRequest(defaultCaps, TYPE_NONE, 1 /* requestId */,
-                NetworkRequest.Type.REQUEST);
-        mCm = spy(new TestConnectivityManager(mServiceContext, mock(IConnectivityManager.class),
-                mNetworkRequest));
+        mCm = spy(new TestConnectivityManager(mServiceContext, mock(IConnectivityManager.class)));
 
         mTethering = makeTethering();
         verify(mStatsManager, times(1)).registerNetworkStatsProvider(anyString(), any());
@@ -795,15 +778,13 @@
     }
 
     private void verifyDefaultNetworkRequestFiled() {
-        ArgumentCaptor<NetworkCallback> captor = ArgumentCaptor.forClass(NetworkCallback.class);
-        verify(mCm, times(1)).requestNetwork(eq(mNetworkRequest),
-                captor.capture(), any(Handler.class));
-        mDefaultNetworkCallback = captor.getValue();
-        assertNotNull(mDefaultNetworkCallback);
-
+        ArgumentCaptor<NetworkRequest> reqCaptor = ArgumentCaptor.forClass(NetworkRequest.class);
+        verify(mCm, times(1)).requestNetwork(reqCaptor.capture(),
+                any(NetworkCallback.class), any(Handler.class));
+        assertTrue(TestConnectivityManager.looksLikeDefaultRequest(reqCaptor.getValue()));
         // The default network request is only ever filed once.
         verifyNoMoreInteractions(mCm);
-        mUpstreamNetworkMonitor.startTrackDefaultNetwork(mNetworkRequest, mEntitleMgr);
+        mUpstreamNetworkMonitor.startTrackDefaultNetwork(mEntitleMgr);
         verifyNoMoreInteractions(mCm);
     }
 
@@ -943,7 +924,7 @@
         verifyNoMoreInteractions(mWifiManager);
         // Asking for the last error after the per-interface state machine
         // has been reaped yields an unknown interface error.
-        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastTetherError(TEST_WLAN_IFNAME));
+        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastErrorForTest(TEST_WLAN_IFNAME));
     }
 
     /**
@@ -1476,7 +1457,7 @@
         verifyNoMoreInteractions(mWifiManager);
         // Asking for the last error after the per-interface state machine
         // has been reaped yields an unknown interface error.
-        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastTetherError(TEST_WLAN_IFNAME));
+        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastErrorForTest(TEST_WLAN_IFNAME));
     }
 
     // TODO: Test with and without interfaceStatusChanged().
@@ -1945,7 +1926,7 @@
         // There are 2 IpServer state change events: STATE_AVAILABLE -> STATE_LOCAL_ONLY
         verify(mNotificationUpdater, times(2)).onDownstreamChanged(DOWNSTREAM_NONE);
 
-        assertEquals(TETHER_ERROR_NO_ERROR, mTethering.getLastTetherError(TEST_P2P_IFNAME));
+        assertEquals(TETHER_ERROR_NO_ERROR, mTethering.getLastErrorForTest(TEST_P2P_IFNAME));
 
         // Emulate externally-visible WifiP2pManager effects, when wifi p2p group
         // is being removed.
@@ -1964,7 +1945,7 @@
         verifyNoMoreInteractions(mNetd);
         // Asking for the last error after the per-interface state machine
         // has been reaped yields an unknown interface error.
-        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastTetherError(TEST_P2P_IFNAME));
+        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastErrorForTest(TEST_P2P_IFNAME));
     }
 
     private void workingWifiP2pGroupClient(
@@ -1994,7 +1975,7 @@
         verifyNoMoreInteractions(mNetd);
         // Asking for the last error after the per-interface state machine
         // has been reaped yields an unknown interface error.
-        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastTetherError(TEST_P2P_IFNAME));
+        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastErrorForTest(TEST_P2P_IFNAME));
     }
 
     @Test
@@ -2025,7 +2006,7 @@
         verify(mNetd, never()).networkAddInterface(INetd.LOCAL_NET_ID, TEST_P2P_IFNAME);
         verify(mNetd, never()).ipfwdEnableForwarding(TETHERING_NAME);
         verify(mNetd, never()).tetherStartWithConfiguration(any());
-        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastTetherError(TEST_P2P_IFNAME));
+        assertEquals(TETHER_ERROR_UNKNOWN_IFACE, mTethering.getLastErrorForTest(TEST_P2P_IFNAME));
     }
     @Test
     public void workingWifiP2pGroupOwnerLegacyModeWithIfaceChanged() throws Exception {
@@ -2390,10 +2371,10 @@
 
         mTethering.interfaceStatusChanged(TEST_USB_IFNAME, true);
         sendUsbBroadcast(true, true, true, TETHERING_USB);
-        assertContains(Arrays.asList(mTethering.getTetherableIfaces()), TEST_USB_IFNAME);
-        assertContains(Arrays.asList(mTethering.getTetherableIfaces()), TEST_ETH_IFNAME);
-        assertEquals(TETHER_ERROR_IFACE_CFG_ERROR, mTethering.getLastTetherError(TEST_USB_IFNAME));
-        assertEquals(TETHER_ERROR_IFACE_CFG_ERROR, mTethering.getLastTetherError(TEST_ETH_IFNAME));
+        assertContains(Arrays.asList(mTethering.getTetherableIfacesForTest()), TEST_USB_IFNAME);
+        assertContains(Arrays.asList(mTethering.getTetherableIfacesForTest()), TEST_ETH_IFNAME);
+        assertEquals(TETHER_ERROR_IFACE_CFG_ERROR, mTethering.getLastErrorForTest(TEST_USB_IFNAME));
+        assertEquals(TETHER_ERROR_IFACE_CFG_ERROR, mTethering.getLastErrorForTest(TEST_ETH_IFNAME));
     }
 
     @Test
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/UpstreamNetworkMonitorTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/UpstreamNetworkMonitorTest.java
index cee0365..ce4ba85 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/UpstreamNetworkMonitorTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/UpstreamNetworkMonitorTest.java
@@ -29,10 +29,10 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.any;
 import static org.mockito.Mockito.anyInt;
 import static org.mockito.Mockito.anyString;
-import static org.mockito.Mockito.eq;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
@@ -66,6 +66,7 @@
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.ArgumentCaptor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
@@ -83,10 +84,6 @@
     private static final boolean INCLUDES = true;
     private static final boolean EXCLUDES = false;
 
-    // Actual contents of the request don't matter for this test. The lack of
-    // any specific TRANSPORT_* is sufficient to identify this request.
-    private static final NetworkRequest sDefaultRequest = new NetworkRequest.Builder().build();
-
     private static final NetworkCapabilities CELL_CAPABILITIES = new NetworkCapabilities.Builder()
             .addTransportType(TRANSPORT_CELLULAR).addCapability(NET_CAPABILITY_INTERNET).build();
     private static final NetworkCapabilities DUN_CAPABILITIES = new NetworkCapabilities.Builder()
@@ -113,9 +110,10 @@
         when(mLog.forSubComponent(anyString())).thenReturn(mLog);
         when(mEntitleMgr.isCellularUpstreamPermitted()).thenReturn(true);
 
-        mCM = spy(new TestConnectivityManager(mContext, mCS, sDefaultRequest));
+        mCM = spy(new TestConnectivityManager(mContext, mCS));
+        when(mContext.getSystemService(eq(Context.CONNECTIVITY_SERVICE))).thenReturn(mCM);
         mSM = new TestStateMachine(mLooper.getLooper());
-        mUNM = new UpstreamNetworkMonitor(mCM, mSM, mLog, EVENT_UNM_UPDATE);
+        mUNM = new UpstreamNetworkMonitor(mContext, mSM, mLog, EVENT_UNM_UPDATE);
     }
 
     @After public void tearDown() throws Exception {
@@ -146,7 +144,7 @@
     @Test
     public void testDefaultNetworkIsTracked() throws Exception {
         assertTrue(mCM.hasNoCallbacks());
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
 
         mUNM.startObserveAllNetworks();
         assertEquals(1, mCM.mTrackingDefault.size());
@@ -159,7 +157,7 @@
     public void testListensForAllNetworks() throws Exception {
         assertTrue(mCM.mListening.isEmpty());
 
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
         mUNM.startObserveAllNetworks();
         assertFalse(mCM.mListening.isEmpty());
         assertTrue(mCM.isListeningForAll());
@@ -170,9 +168,17 @@
 
     @Test
     public void testCallbacksRegistered() {
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
+        // Verify the fired default request matches expectation.
+        final ArgumentCaptor<NetworkRequest> requestCaptor =
+                ArgumentCaptor.forClass(NetworkRequest.class);
         verify(mCM, times(1)).requestNetwork(
-                eq(sDefaultRequest), any(NetworkCallback.class), any(Handler.class));
+                requestCaptor.capture(), any(NetworkCallback.class), any(Handler.class));
+        // For R- devices, Tethering will invoke this function in 2 cases, one is to
+        // request mobile network, the other is to track system default network. Verify
+        // the request is the one tracks default network.
+        assertTrue(TestConnectivityManager.looksLikeDefaultRequest(requestCaptor.getValue()));
+
         mUNM.startObserveAllNetworks();
         verify(mCM, times(1)).registerNetworkCallback(
                 any(NetworkRequest.class), any(NetworkCallback.class), any(Handler.class));
@@ -293,7 +299,7 @@
         final Collection<Integer> preferredTypes = new ArrayList<>();
         preferredTypes.add(TYPE_WIFI);
 
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
         mUNM.startObserveAllNetworks();
         // There are no networks, so there is nothing to select.
         assertSatisfiesLegacyType(TYPE_NONE, mUNM.selectPreferredUpstreamType(preferredTypes));
@@ -366,7 +372,7 @@
 
     @Test
     public void testGetCurrentPreferredUpstream() throws Exception {
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
         mUNM.startObserveAllNetworks();
         mUNM.setUpstreamConfig(true /* autoUpstream */, false /* dunRequired */);
         mUNM.setTryCell(true);
@@ -438,7 +444,7 @@
 
     @Test
     public void testLocalPrefixes() throws Exception {
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
         mUNM.startObserveAllNetworks();
 
         // [0] Test minimum set of local prefixes.
@@ -549,7 +555,7 @@
         // Mobile has higher pirority than wifi.
         preferredTypes.add(TYPE_MOBILE_HIPRI);
         preferredTypes.add(TYPE_WIFI);
-        mUNM.startTrackDefaultNetwork(sDefaultRequest, mEntitleMgr);
+        mUNM.startTrackDefaultNetwork(mEntitleMgr);
         mUNM.startObserveAllNetworks();
         // Setup wifi and make wifi as default network.
         final TestNetworkAgent wifiAgent = new TestNetworkAgent(mCM, WIFI_CAPABILITIES);
diff --git a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
index f474e23..d9e3ccb 100644
--- a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
@@ -102,6 +102,7 @@
 import android.net.NetworkInfo.State;
 import android.net.NetworkRequest;
 import android.net.NetworkUtils;
+import android.net.ProxyInfo;
 import android.net.SocketKeepalive;
 import android.net.TestNetworkInterface;
 import android.net.TestNetworkManager;
@@ -1916,4 +1917,12 @@
         assertNull(NetworkInformationShimImpl.newInstance()
                 .getCapabilityCarrierName(ConstantsShim.NET_CAPABILITY_NOT_VCN_MANAGED));
     }
+
+    @Test
+    public void testSetGlobalProxy() {
+        assumeTrue(TestUtils.shouldTestSApis());
+        // Behavior is verified in gts. Verify exception thrown w/o permission.
+        assertThrows(SecurityException.class, () -> mCm.setGlobalProxy(
+                ProxyInfo.buildDirectProxy("example.com" /* host */, 8080 /* port */)));
+    }
 }
diff --git a/tests/cts/net/src/android/net/cts/IpSecManagerTest.java b/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
index 355b496..d08f6e9 100644
--- a/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/IpSecManagerTest.java
@@ -44,6 +44,11 @@
 import androidx.test.InstrumentationRegistry;
 import androidx.test.runner.AndroidJUnit4;
 
+import com.android.testutils.SkipPresubmit;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.net.DatagramPacket;
@@ -52,10 +57,6 @@
 import java.net.InetAddress;
 import java.util.Arrays;
 
-import org.junit.Before;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-
 @RunWith(AndroidJUnit4.class)
 @AppModeFull(reason = "Socket cannot bind in instant app mode")
 public class IpSecManagerTest extends IpSecBaseTest {
@@ -692,6 +693,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesCbcHmacMd5Tcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_MD5, getKey(128), 96);
@@ -724,6 +726,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesCbcHmacSha1Tcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_SHA1, getKey(160), 96);
@@ -756,6 +759,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesCbcHmacSha256Tcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_SHA256, getKey(256), 128);
@@ -788,6 +792,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesCbcHmacSha384Tcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_SHA384, getKey(384), 192);
@@ -820,6 +825,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesCbcHmacSha512Tcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_SHA512, getKey(512), 256);
@@ -852,6 +858,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesGcm64Tcp6() throws Exception {
         IpSecAlgorithm authCrypt =
                 new IpSecAlgorithm(IpSecAlgorithm.AUTH_CRYPT_AES_GCM, AEAD_KEY, 64);
@@ -884,6 +891,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesGcm96Tcp6() throws Exception {
         IpSecAlgorithm authCrypt =
                 new IpSecAlgorithm(IpSecAlgorithm.AUTH_CRYPT_AES_GCM, AEAD_KEY, 96);
@@ -916,6 +924,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAesGcm128Tcp6() throws Exception {
         IpSecAlgorithm authCrypt =
                 new IpSecAlgorithm(IpSecAlgorithm.AUTH_CRYPT_AES_GCM, AEAD_KEY, 128);
@@ -1110,6 +1119,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testCryptTcp6() throws Exception {
         IpSecAlgorithm crypt = new IpSecAlgorithm(IpSecAlgorithm.CRYPT_AES_CBC, CRYPT_KEY);
         checkTransform(IPPROTO_TCP, IPV6_LOOPBACK, crypt, null, null, false, 1, false);
@@ -1117,6 +1127,7 @@
     }
 
     @Test
+    @SkipPresubmit(reason = "b/186608065 - kernel 5.10 regression in TrafficStats with ipsec")
     public void testAuthTcp6() throws Exception {
         IpSecAlgorithm auth = new IpSecAlgorithm(IpSecAlgorithm.AUTH_HMAC_SHA256, getKey(256), 128);
         checkTransform(IPPROTO_TCP, IPV6_LOOPBACK, null, auth, null, false, 1, false);