Fix getWifiManager exception if phone is encrypted

[Issue Details]
NetworkPolicyManagerService may invoke
dispatchRestrictBackgroundChanged after reboot if settings changed, and
invokes untetherAll in turn, which triggers ServiceNotFoundException
indirectly if the device is under encryption. The cause is that
WifiService is not running if the device is still locked.

[Solution]
In order to avoid ServiceNotFoundException in setWifiTethering, we add
check on return value of getWifiManager. Moreover, check of UsbManager
is also added to prevent potential similar issues of USB tethering.

Bug: 123504004
Test: FrameworksNetTests
  adb shell am instrument -w com.android.frameworks.tests.net
Test: CTS - CtsNetTestCases
  ANDROID_BUILD_droid-cts/tools/cts-tradefed run cts -m CtsNetTestCases
Test: CTS - CtsNetTestCasesLegacyApi22
  ANDROID_BUILD_droid-cts/tools/cts-tradefed run cts -m
  CtsNetTestCasesLegacyApi22
Test: CTS - CtsNetTestCasesLegacyPermission22
  ANDROID_BUILD_droid-cts/tools/cts-tradefed run cts -m
  CtsNetTestCasesLegacyPermission22

Change-Id: I2643188b51900f97ba58c8614c66cb55ebfaa2f6

1 files changed, 13 insertions, 4 deletions

diff --git a/services/core/java/com/android/server/connectivity/Tethering.java b/services/core/java/com/android/server/connectivity/Tethering.java
index 35704d404ff3..6491cecdbed6 100644
--- a/services/core/java/com/android/server/connectivity/Tethering.java
+++ b/services/core/java/com/android/server/connectivity/Tethering.java
@@ -423,21 +423,25 @@ public class Tethering extends BaseNetworkObserver {
     }
 
     private int setWifiTethering(final boolean enable) {
-        int rval = TETHER_ERROR_MASTER_ERROR;
         final long ident = Binder.clearCallingIdentity();
         try {
             synchronized (mPublicSync) {
-                mWifiTetherRequested = enable;
                 final WifiManager mgr = getWifiManager();
+                if (mgr == null) {
+                    mLog.e("setWifiTethering: failed to get WifiManager!");
+                    return TETHER_ERROR_SERVICE_UNAVAIL;
+                }
                 if ((enable && mgr.startSoftAp(null /* use existing wifi config */)) ||
                     (!enable && mgr.stopSoftAp())) {
-                    rval = TETHER_ERROR_NO_ERROR;
+                    mWifiTetherRequested = enable;
+                    return TETHER_ERROR_NO_ERROR;
                 }
             }
         } finally {
             Binder.restoreCallingIdentity(ident);
         }
-        return rval;
+
+        return TETHER_ERROR_MASTER_ERROR;
     }
 
     private void setBluetoothTethering(final boolean enable, final ResultReceiver receiver) {
@@ -989,6 +993,11 @@ public class Tethering extends BaseNetworkObserver {
     public 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);