diff --git a/Tethering/src/android/net/ip/IpServer.java b/Tethering/src/android/net/ip/IpServer.java
index 38f8609..5f5de9e 100644
--- a/Tethering/src/android/net/ip/IpServer.java
+++ b/Tethering/src/android/net/ip/IpServer.java
@@ -34,6 +34,7 @@
 import android.net.RouteInfo;
 import android.net.TetheredClient;
 import android.net.TetheringManager;
+import android.net.TetheringRequestParcel;
 import android.net.dhcp.DhcpLeaseParcelable;
 import android.net.dhcp.DhcpServerCallbacks;
 import android.net.dhcp.DhcpServingParamsParcel;
@@ -242,6 +243,10 @@
     private IDhcpServer mDhcpServer;
     private RaParams mLastRaParams;
     private LinkAddress mIpv4Address;
+
+    private LinkAddress mStaticIpv4ServerAddr;
+    private LinkAddress mStaticIpv4ClientAddr;
+
     @NonNull
     private List<TetheredClient> mDhcpLeases = Collections.emptyList();
 
@@ -544,6 +549,8 @@
         // into calls to InterfaceController, shared with startIPv4().
         mInterfaceCtrl.clearIPv4Address();
         mIpv4Address = null;
+        mStaticIpv4ServerAddr = null;
+        mStaticIpv4ClientAddr = null;
     }
 
     private boolean configureIPv4(boolean enabled) {
@@ -554,7 +561,10 @@
         final Inet4Address srvAddr;
         int prefixLen = 0;
         try {
-            if (mInterfaceType == TetheringManager.TETHERING_USB
+            if (mStaticIpv4ServerAddr != null) {
+                srvAddr = (Inet4Address) mStaticIpv4ServerAddr.getAddress();
+                prefixLen = mStaticIpv4ServerAddr.getPrefixLength();
+            } else if (mInterfaceType == TetheringManager.TETHERING_USB
                     || mInterfaceType == TetheringManager.TETHERING_NCM) {
                 srvAddr = (Inet4Address) parseNumericAddress(USB_NEAR_IFACE_ADDR);
                 prefixLen = USB_PREFIX_LENGTH;
@@ -599,10 +609,6 @@
             return false;
         }
 
-        if (!configureDhcp(enabled, srvAddr, prefixLen)) {
-            return false;
-        }
-
         // Directly-connected route.
         final IpPrefix ipv4Prefix = new IpPrefix(mIpv4Address.getAddress(),
                 mIpv4Address.getPrefixLength());
@@ -614,7 +620,8 @@
             mLinkProperties.removeLinkAddress(mIpv4Address);
             mLinkProperties.removeRoute(route);
         }
-        return true;
+
+        return configureDhcp(enabled, srvAddr, prefixLen);
     }
 
     private String getRandomWifiIPv4Address() {
@@ -934,6 +941,13 @@
         mLinkProperties.setInterfaceName(mIfaceName);
     }
 
+    private void maybeConfigureStaticIp(final TetheringRequestParcel request) {
+        if (request == null) return;
+
+        mStaticIpv4ServerAddr = request.localIPv4Address;
+        mStaticIpv4ClientAddr = request.staticClientAddress;
+    }
+
     class InitialState extends State {
         @Override
         public void enter() {
@@ -948,9 +962,11 @@
                     mLastError = TetheringManager.TETHER_ERROR_NO_ERROR;
                     switch (message.arg1) {
                         case STATE_LOCAL_ONLY:
+                            maybeConfigureStaticIp((TetheringRequestParcel) message.obj);
                             transitionTo(mLocalHotspotState);
                             break;
                         case STATE_TETHERED:
+                            maybeConfigureStaticIp((TetheringRequestParcel) message.obj);
                             transitionTo(mTetheredState);
                             break;
                         default:
diff --git a/Tethering/src/android/net/util/TetheringUtils.java b/Tethering/src/android/net/util/TetheringUtils.java
index 5a6d5c1..dd67ddd 100644
--- a/Tethering/src/android/net/util/TetheringUtils.java
+++ b/Tethering/src/android/net/util/TetheringUtils.java
@@ -15,8 +15,11 @@
  */
 package android.net.util;
 
+import android.net.TetheringRequestParcel;
+
 import java.io.FileDescriptor;
 import java.net.SocketException;
+import java.util.Objects;
 
 /**
  * Native methods for tethering utilization.
@@ -38,4 +41,17 @@
     public static int uint16(short s) {
         return s & 0xffff;
     }
+
+    /** Check whether two TetheringRequestParcels are the same. */
+    public static boolean isTetheringRequestEquals(final TetheringRequestParcel request,
+            final TetheringRequestParcel otherRequest) {
+        if (request == otherRequest) return true;
+
+        return request != null && otherRequest != null
+                && request.tetheringType == otherRequest.tetheringType
+                && Objects.equals(request.localIPv4Address, otherRequest.localIPv4Address)
+                && Objects.equals(request.staticClientAddress, otherRequest.staticClientAddress)
+                && request.exemptFromEntitlementCheck == otherRequest.exemptFromEntitlementCheck
+                && request.showProvisioningUi == otherRequest.showProvisioningUi;
+    }
 }
diff --git a/Tethering/src/com/android/server/connectivity/tethering/Tethering.java b/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
index 5539017..a9e9a75 100644
--- a/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
+++ b/Tethering/src/com/android/server/connectivity/tethering/Tethering.java
@@ -92,6 +92,7 @@
 import android.net.util.InterfaceSet;
 import android.net.util.PrefixUtils;
 import android.net.util.SharedLog;
+import android.net.util.TetheringUtils;
 import android.net.util.VersionedBroadcastListener;
 import android.net.wifi.WifiClient;
 import android.net.wifi.WifiManager;
@@ -196,6 +197,11 @@
     private final SharedLog mLog = new SharedLog(TAG);
     private final RemoteCallbackList<ITetheringEventCallback> mTetheringEventCallbacks =
             new RemoteCallbackList<>();
+    // Currently active tethering requests per tethering type. Only one of each type can be
+    // requested at a time. After a tethering type is requested, the map keeps tethering parameters
+    // to be used after the interface comes up asynchronously.
+    private final SparseArray<TetheringRequestParcel> mActiveTetheringRequests =
+            new SparseArray<>();
 
     // used to synchronize public access to members
     private final Object mPublicSync;
@@ -487,14 +493,31 @@
     }
 
     void startTethering(final TetheringRequestParcel request, final IIntResultListener listener) {
-        mEntitlementMgr.startProvisioningIfNeeded(request.tetheringType,
-                request.showProvisioningUi);
-        enableTetheringInternal(request.tetheringType, true /* enabled */, listener);
+        mHandler.post(() -> {
+            final TetheringRequestParcel unfinishedRequest = mActiveTetheringRequests.get(
+                    request.tetheringType);
+            // If tethering is already enabled with a different request,
+            // disable before re-enabling.
+            if (unfinishedRequest != null
+                    && !TetheringUtils.isTetheringRequestEquals(unfinishedRequest, request)) {
+                enableTetheringInternal(request.tetheringType, false /* disabled */, null);
+                mEntitlementMgr.stopProvisioningIfNeeded(request.tetheringType);
+            }
+            mActiveTetheringRequests.put(request.tetheringType, request);
+
+            mEntitlementMgr.startProvisioningIfNeeded(request.tetheringType,
+                    request.showProvisioningUi);
+            enableTetheringInternal(request.tetheringType, true /* enabled */, listener);
+        });
     }
 
     void stopTethering(int type) {
-        enableTetheringInternal(type, false /* disabled */, null);
-        mEntitlementMgr.stopProvisioningIfNeeded(type);
+        mHandler.post(() -> {
+            mActiveTetheringRequests.remove(type);
+
+            enableTetheringInternal(type, false /* disabled */, null);
+            mEntitlementMgr.stopProvisioningIfNeeded(type);
+        });
     }
 
     /**
@@ -503,39 +526,45 @@
      */
     private void enableTetheringInternal(int type, boolean enable,
             final IIntResultListener listener) {
-        int result;
+        int result = TETHER_ERROR_NO_ERROR;
         switch (type) {
             case TETHERING_WIFI:
                 result = setWifiTethering(enable);
-                sendTetherResult(listener, result);
                 break;
             case TETHERING_USB:
                 result = setUsbTethering(enable);
-                sendTetherResult(listener, result);
                 break;
             case TETHERING_BLUETOOTH:
                 setBluetoothTethering(enable, listener);
                 break;
             case TETHERING_NCM:
                 result = setNcmTethering(enable);
-                sendTetherResult(listener, result);
                 break;
             case TETHERING_ETHERNET:
                 result = setEthernetTethering(enable);
-                sendTetherResult(listener, result);
                 break;
             default:
                 Log.w(TAG, "Invalid tether type.");
-                sendTetherResult(listener, TETHER_ERROR_UNKNOWN_IFACE);
+                result = TETHER_ERROR_UNKNOWN_IFACE;
+        }
+
+        // The result of Bluetooth tethering will be sent by #setBluetoothTethering.
+        if (type != TETHERING_BLUETOOTH) {
+            sendTetherResult(listener, result, type);
         }
     }
 
-    private void sendTetherResult(final IIntResultListener listener, int result) {
+    private void sendTetherResult(final IIntResultListener listener, final int result,
+            final int type) {
         if (listener != null) {
             try {
                 listener.onResult(result);
             } catch (RemoteException e) { }
         }
+
+        // If changing tethering fail, remove corresponding request
+        // no matter who trigger the start/stop.
+        if (result != TETHER_ERROR_NO_ERROR) mActiveTetheringRequests.remove(type);
     }
 
     private int setWifiTethering(final boolean enable) {
@@ -565,7 +594,7 @@
         if (adapter == null || !adapter.isEnabled()) {
             Log.w(TAG, "Tried to enable bluetooth tethering with null or disabled adapter. null: "
                     + (adapter == null));
-            sendTetherResult(listener, TETHER_ERROR_SERVICE_UNAVAIL);
+            sendTetherResult(listener, TETHER_ERROR_SERVICE_UNAVAIL, TETHERING_BLUETOOTH);
             return;
         }
 
@@ -594,7 +623,7 @@
                 final int result = (((BluetoothPan) proxy).isTetheringOn() == enable)
                         ? TETHER_ERROR_NO_ERROR
                         : TETHER_ERROR_MASTER_ERROR;
-                sendTetherResult(listener, result);
+                sendTetherResult(listener, result, TETHERING_BLUETOOTH);
                 adapter.closeProfileProxy(BluetoothProfile.PAN, proxy);
             }
         }, BluetoothProfile.PAN);
@@ -672,12 +701,18 @@
                 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.
+            // 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.
             //
-            // TODO: reexamine the threading and messaging model.
-            tetherState.ipServer.sendMessage(IpServer.CMD_TETHER_REQUESTED, requestedState);
+            // 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;
         }
     }