Makes captive portal server calculation in one place.

This also creates a hidden api for the captive portal server calculation
so that the Setup Wizard can use this as well.

bug:13246857
Change-Id: I4dfd0916df97cfce13252c7cc15f7bd05ed95f77

core/java/android/net/ConnectivityManager.java

@@ -19,6 +19,7 @@ import static com.android.internal.util.Preconditions.checkNotNull;
 
 import android.annotation.SdkConstant;
 import android.annotation.SdkConstant.SdkConstantType;
+import android.annotation.SystemApi;
 import android.app.PendingIntent;
 import android.content.Context;
 import android.content.Intent;
@@ -897,6 +898,24 @@ public class ConnectivityManager {
         }
     }
 
+    /**
+     * Gets the URL that should be used for resolving whether a captive portal is present.
+     * 1. This URL should respond with a 204 response to a GET request to indicate no captive
+     *    portal is present.
+     * 2. This URL must be HTTP as redirect responses are used to find captive portal
+     *    sign-in pages. Captive portals cannot respond to HTTPS requests with redirects.
+     *
+     * @hide
+     */
+    @SystemApi
+    public String getCaptivePortalServerUrl() {
+        try {
+            return mService.getCaptivePortalServerUrl();
+        } catch (RemoteException e) {
+            return null;
+        }
+    }
+
     /**
      * Tells the underlying networking system that the caller wants to
      * begin using the named feature. The interpretation of {@code feature}

core/java/android/net/IConnectivityManager.aidl

@@ -165,4 +165,6 @@ interface IConnectivityManager
             in IBinder binder, String srcAddr, int srcPort, String dstAddr);
 
     void stopKeepalive(in Network network, int slot);
+
+    String getCaptivePortalServerUrl();
 }

services/core/java/com/android/server/ConnectivityService.java

@@ -4847,6 +4847,11 @@ public class ConnectivityService extends IConnectivityManager.Stub
         return success;
     }
 
+    @Override
+    public String getCaptivePortalServerUrl() {
+        return NetworkMonitor.getCaptivePortalServerUrl(mContext);
+    }
+
     @Override
     public void startNattKeepalive(Network network, int intervalSeconds, Messenger messenger,
             IBinder binder, String srcAddr, int srcPort, String dstAddr) {

services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java

@@ -59,6 +59,7 @@ import android.os.MessageQueue;
 import android.os.MessageQueue.IdleHandler;
 import android.test.AndroidTestCase;
 import android.test.suitebuilder.annotation.LargeTest;
+import android.test.suitebuilder.annotation.SmallTest;
 import android.util.Log;
 import android.util.LogPrinter;
 
@@ -1504,4 +1505,10 @@ public class ConnectivityServiceTest extends AndroidTestCase {
         ka3.stop();
         callback3.expectStopped();
     }
+
+    @SmallTest
+    public void testGetCaptivePortalServerUrl() throws Exception {
+        String url = mCm.getCaptivePortalServerUrl();
+        assertEquals("http://connectivitycheck.gstatic.com/generate_204", url);
+    }
 }