Fix DHCP handling at disconnect/reconnect

Wifi can have a quick disconnection followed by a reconnection. We used to
create a new DHCP state machine thread for every new connection and
never really waited until it quit after disconnect. This may have lead to
situations where repeated disconnect/reconnects resulted in multiple dhcp
start calls.

We now keep the statemachine after a disconnect and only shut it at supplicant
stop.

Bug: 6417686
Change-Id: Icf66efdc654be886e3eb46c81f09f8cce536f2f6

core/java/android/net/DhcpStateMachine.java

@@ -92,10 +92,12 @@ public class DhcpStateMachine extends StateMachine {
     /* Notification from DHCP state machine post DHCP discovery/renewal. Indicates
      * success/failure */
     public static final int CMD_POST_DHCP_ACTION            = BASE + 5;
+    /* Notification from DHCP state machine before quitting */
+    public static final int CMD_ON_QUIT                     = BASE + 6;
 
     /* Command from controller to indicate DHCP discovery/renewal can continue
      * after pre DHCP action is complete */
-    public static final int CMD_PRE_DHCP_ACTION_COMPLETE    = BASE + 6;
+    public static final int CMD_PRE_DHCP_ACTION_COMPLETE    = BASE + 7;
 
     /* Message.arg1 arguments to CMD_POST_DHCP notification */
     public static final int DHCP_SUCCESS = 1;
@@ -172,6 +174,10 @@ public class DhcpStateMachine extends StateMachine {
         quit();
     }
 
+    protected void onQuitting() {
+        mController.sendMessage(CMD_ON_QUIT);
+    }
+
     class DefaultState extends State {
         @Override
         public void exit() {

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

@@ -240,7 +240,7 @@ public class WifiService extends IWifiManager.Stub {
             switch (msg.what) {
                 case AsyncChannel.CMD_CHANNEL_HALF_CONNECTED: {
                     if (msg.arg1 == AsyncChannel.STATUS_SUCCESSFUL) {
-                        Slog.d(TAG, "New client listening to asynchronous messages");
+                        if (DBG) Slog.d(TAG, "New client listening to asynchronous messages");
                         mClients.add((AsyncChannel) msg.obj);
                     } else {
                         Slog.e(TAG, "Client connection failure, error=" + msg.arg1);
@@ -249,9 +249,9 @@ public class WifiService extends IWifiManager.Stub {
                 }
                 case AsyncChannel.CMD_CHANNEL_DISCONNECTED: {
                     if (msg.arg1 == AsyncChannel.STATUS_SEND_UNSUCCESSFUL) {
-                        Slog.d(TAG, "Send failed, client connection lost");
+                        if (DBG) Slog.d(TAG, "Send failed, client connection lost");
                     } else {
-                        Slog.d(TAG, "Client connection lost with reason: " + msg.arg1);
+                        if (DBG) Slog.d(TAG, "Client connection lost with reason: " + msg.arg1);
                     }
                     mClients.remove((AsyncChannel) msg.obj);
                     break;

wifi/java/android/net/wifi/WifiStateMachine.java

@@ -1672,10 +1672,7 @@ public class WifiStateMachine extends StateMachine {
             /* In case we were in middle of DHCP operation
                restore back powermode */
             handlePostDhcpSetup();
-
             mDhcpStateMachine.sendMessage(DhcpStateMachine.CMD_STOP_DHCP);
-            mDhcpStateMachine.doQuit();
-            mDhcpStateMachine = null;
         }
 
         try {
@@ -1928,6 +1925,9 @@ public class WifiStateMachine extends StateMachine {
                 case CMD_CLEAR_SUSPEND_OPTIMIZATIONS:
                 case CMD_NO_NETWORKS_PERIODIC_SCAN:
                     break;
+                case DhcpStateMachine.CMD_ON_QUIT:
+                    mDhcpStateMachine = null;
+                    break;
                 case CMD_SET_SUSPEND_OPTIMIZATIONS:
                     mSuspendWakeLock.release();
                     break;
@@ -2498,6 +2498,9 @@ public class WifiStateMachine extends StateMachine {
 
             /* Send any reset commands to supplicant before shutting it down */
             handleNetworkDisconnect();
+            if (mDhcpStateMachine != null) {
+                mDhcpStateMachine.doQuit();
+            }
 
             if (DBG) log("stopping supplicant");
             if (!mWifiNative.stopSupplicant()) {
@@ -3197,8 +3200,11 @@ public class WifiStateMachine extends StateMachine {
 
             if (!mWifiConfigStore.isUsingStaticIp(mLastNetworkId)) {
                 //start DHCP
-                mDhcpStateMachine = DhcpStateMachine.makeDhcpStateMachine(
-                        mContext, WifiStateMachine.this, mInterfaceName);
+                if (mDhcpStateMachine == null) {
+                    mDhcpStateMachine = DhcpStateMachine.makeDhcpStateMachine(
+                            mContext, WifiStateMachine.this, mInterfaceName);
+
+                }
                 mDhcpStateMachine.registerForPreDhcpNotification();
                 mDhcpStateMachine.sendMessage(DhcpStateMachine.CMD_START_DHCP);
             } else {