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/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/service/src/com/android/server/connectivity/NetworkRanker.java b/service/src/com/android/server/connectivity/NetworkRanker.java
index a4085cd..d7eb9c8 100644
--- a/service/src/com/android/server/connectivity/NetworkRanker.java
+++ b/service/src/com/android/server/connectivity/NetworkRanker.java
@@ -237,9 +237,9 @@
         partitionInto(candidates, nai -> nai.getScore().hasPolicy(POLICY_TRANSPORT_PRIMARY),
                 accepted, rejected);
         if (accepted.size() > 0) {
-            // Some networks are primary. For each transport, keep only the primary, but also
-            // keep all networks for which there isn't a primary (which are now in the |rejected|
-            // array).
+            // Some networks are primary for their transport. For each transport, keep only the
+            // primary, but also keep all networks for which there isn't a primary (which are now
+            // in the |rejected| array).
             // So for each primary network, remove from |rejected| all networks with the same
             // transports as one of the primary networks. The remaining networks should be accepted.
             for (final T defaultSubNai : accepted) {
@@ -247,6 +247,8 @@
                 rejected.removeIf(
                         nai -> Arrays.equals(transports, nai.getCapsNoCopy().getTransportTypes()));
             }
+            // Now the |rejected| list contains networks with transports for which there isn't
+            // a primary network. Add them back to the candidates.
             accepted.addAll(rejected);
             candidates = new ArrayList<>(accepted);
         }