wifi: Keep the WLAN network interface up whenever wifi is enabled.

We now only bring it down briefly and bring it back up again when
we want to reset the interface.

Signed-off-by: Mike Lockwood <lockwood@android.com>

core/java/android/net/NetworkUtils.java

@@ -25,6 +25,9 @@ import java.net.UnknownHostException;
  * {@hide}
  */
 public class NetworkUtils {
+    /** Bring the named network interface up. */
+    public native static int enableInterface(String interfaceName);
+
     /** Bring the named network interface down. */
     public native static int disableInterface(String interfaceName);
 

core/jni/android_net_NetUtils.cpp

@@ -23,6 +23,7 @@
 #include <arpa/inet.h>
 
 extern "C" {
+int ifc_enable(const char *ifname);
 int ifc_disable(const char *ifname);
 int ifc_add_host_route(const char *ifname, uint32_t addr);
 int ifc_remove_host_routes(const char *ifname);
@@ -66,6 +67,16 @@ static struct fieldIds {
     jfieldID leaseDuration;
 } dhcpInfoFieldIds;
 
+static jint android_net_utils_enableInterface(JNIEnv* env, jobject clazz, jstring ifname)
+{
+    int result;
+
+    const char *nameStr = env->GetStringUTFChars(ifname, NULL);
+    result = ::ifc_enable(nameStr);
+    env->ReleaseStringUTFChars(ifname, nameStr);
+    return (jint)result;
+}
+
 static jint android_net_utils_disableInterface(JNIEnv* env, jobject clazz, jstring ifname)
 {
     int result;
@@ -209,6 +220,7 @@ static jboolean android_net_utils_configureInterface(JNIEnv* env,
 static JNINativeMethod gNetworkUtilMethods[] = {
     /* name, signature, funcPtr */
 
+    { "enableInterface", "(Ljava/lang/String;)I",  (void *)android_net_utils_enableInterface },
     { "disableInterface", "(Ljava/lang/String;)I",  (void *)android_net_utils_disableInterface },
     { "addHostRoute", "(Ljava/lang/String;I)I",  (void *)android_net_utils_addHostRoute },
     { "removeHostRoutes", "(Ljava/lang/String;)I",  (void *)android_net_utils_removeHostRoutes },

services/java/com/android/server/WifiService.java

@@ -41,6 +41,7 @@ import android.net.wifi.WifiConfiguration;
 import android.net.wifi.SupplicantState;
 import android.net.NetworkStateTracker;
 import android.net.DhcpInfo;
+import android.net.NetworkUtils;
 import android.os.Binder;
 import android.os.Handler;
 import android.os.HandlerThread;
@@ -344,7 +345,7 @@ public class WifiService extends IWifiManager.Stub {
             }
 
             // We must reset the interface before we unload the driver
-            mWifiStateTracker.resetInterface();
+            mWifiStateTracker.resetInterface(false);
 
             if (!WifiNative.unloadDriver()) {
                 Log.e(TAG, "Failed to unload Wi-Fi driver.");
@@ -1045,7 +1046,13 @@ public class WifiService extends IWifiManager.Stub {
         enforceChangePermission();
 
         synchronized (mWifiStateTracker) {
-            return WifiNative.enableNetworkCommand(netId, disableOthers);
+            String ifname = mWifiStateTracker.getInterfaceName();
+            NetworkUtils.enableInterface(ifname);
+            boolean result = WifiNative.enableNetworkCommand(netId, disableOthers);
+            if (!result) {
+                NetworkUtils.disableInterface(ifname);
+            }
+            return result;
         }
     }
 

wifi/java/android/net/wifi/WifiStateTracker.java

@@ -377,6 +377,14 @@ public class WifiStateTracker extends NetworkStateTracker {
         return getNameServerList(sDnsPropNames);
     }
 
+    /**
+     * Return the name of our WLAN network interface.
+     * @return the name of our interface.
+     */
+    public String getInterfaceName() {
+        return mInterfaceName;
+    }
+
     /**
      * Return the system properties name associated with the tcp buffer sizes
      * for this network.
@@ -784,7 +792,7 @@ public class WifiStateTracker extends NetworkStateTracker {
                     WifiNative.closeSupplicantConnection();
                 }
                 if (died) {
-                    resetInterface();
+                    resetInterface(false);
                 }
                 // When supplicant dies, kill the DHCP thread
                 if (mDhcpTarget != null) {
@@ -1195,7 +1203,7 @@ public class WifiStateTracker extends NetworkStateTracker {
             cancelDisconnect();
         }
         mDisconnectExpected = false;
-        resetInterface();
+        resetInterface(true);
         setDetailedState(newState);
         sendNetworkStateChangeBroadcast(mLastBssid);
         mWifiInfo.setBSSID(null);
@@ -1208,7 +1216,7 @@ public class WifiStateTracker extends NetworkStateTracker {
      * Resets the Wi-Fi interface by clearing any state, resetting any sockets
      * using the interface, stopping DHCP, and disabling the interface.
      */
-    public void resetInterface() {
+    public void resetInterface(boolean reenable) {
         mHaveIpAddress = false;
         mObtainingIpAddress = false;
         mWifiInfo.setIpAddress(0);
@@ -1229,6 +1237,9 @@ public class WifiStateTracker extends NetworkStateTracker {
         }
         
         NetworkUtils.disableInterface(mInterfaceName);
+        if (reenable) {
+            NetworkUtils.enableInterface(mInterfaceName);
+        }
     }
 
     /**
@@ -1872,7 +1883,7 @@ public class WifiStateTracker extends NetworkStateTracker {
                         oDns2 != mDhcpInfo.dns2));
 
             if (changed) {
-                resetInterface();
+                resetInterface(true);
                 configureInterface();
                 if (mUseStaticIp) {
                     mTarget.sendEmptyMessage(EVENT_CONFIGURATION_CHANGED);