Add listeners for CertificateTranspaency DeviceConfig flags

Flag: com.android.ct.flags.certificate_transparency_service
Bug: 319829948
Test: adb shell device_config put certificate_transparency log_list_data_url <url>
Change-Id: Ief074fbef21ca18e6882852d53e90e7ddbbd78fa
diff --git a/networksecurity/service/Android.bp b/networksecurity/service/Android.bp
index 66d201a..e33abd5 100644
--- a/networksecurity/service/Android.bp
+++ b/networksecurity/service/Android.bp
@@ -27,6 +27,7 @@
     ],
 
     libs: [
+        "framework-configinfrastructure",
         "framework-connectivity-pre-jarjar",
         "service-connectivity-pre-jarjar",
     ],
diff --git a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyFlagsListener.java b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyFlagsListener.java
new file mode 100644
index 0000000..8dd5951
--- /dev/null
+++ b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyFlagsListener.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.server.net.ct;
+
+import static android.provider.DeviceConfig.NAMESPACE_TETHERING;
+
+import android.content.Context;
+import android.provider.DeviceConfig;
+import android.provider.DeviceConfig.Properties;
+import android.text.TextUtils;
+import android.util.Log;
+
+import com.android.modules.utils.build.SdkLevel;
+
+import java.util.concurrent.Executors;
+
+/** Listener class for the Certificate Transparency Phenotype flags. */
+class CertificateTransparencyFlagsListener implements DeviceConfig.OnPropertiesChangedListener {
+
+    private static final String TAG = "CertificateTransparency";
+
+    private static final String VERSION = "version";
+    private static final String CONTENT_URL = "content_url";
+    private static final String METADATA_URL = "metadata_url";
+
+    CertificateTransparencyFlagsListener(Context context) {}
+
+    void initialize() {
+        DeviceConfig.addOnPropertiesChangedListener(
+                NAMESPACE_TETHERING, Executors.newSingleThreadExecutor(), this);
+        // TODO: handle property changes triggering on boot before registering this listener.
+    }
+
+    @Override
+    public void onPropertiesChanged(Properties properties) {
+        if (!SdkLevel.isAtLeastV() || !NAMESPACE_TETHERING.equals(properties.getNamespace())) {
+            return;
+        }
+
+        String newVersion = DeviceConfig.getString(NAMESPACE_TETHERING, VERSION, "");
+        String newContentUrl = DeviceConfig.getString(NAMESPACE_TETHERING, CONTENT_URL, "");
+        String newMetadataUrl = DeviceConfig.getString(NAMESPACE_TETHERING, METADATA_URL, "");
+        if (TextUtils.isEmpty(newVersion)
+                || TextUtils.isEmpty(newContentUrl)
+                || TextUtils.isEmpty(newMetadataUrl)) {
+            return;
+        }
+
+        Log.d(TAG, "newVersion=" + newVersion);
+        Log.d(TAG, "newContentUrl=" + newContentUrl);
+        Log.d(TAG, "newMetadataUrl=" + newMetadataUrl);
+        // TODO: start download of URLs.
+    }
+}
diff --git a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
index 8c53bf7..406a57f 100644
--- a/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
+++ b/networksecurity/service/src/com/android/server/net/ct/CertificateTransparencyService.java
@@ -23,6 +23,7 @@
 
 import com.android.net.ct.flags.Flags;
 import com.android.net.module.util.DeviceConfigUtils;
+import com.android.server.SystemService;
 
 /** Implementation of the Certificate Transparency service. */
 @RequiresApi(Build.VERSION_CODES.VANILLA_ICE_CREAM)
@@ -32,6 +33,8 @@
     private static final String CERTIFICATE_TRANSPARENCY_ENABLED =
             "certificate_transparency_service_enabled";
 
+    private final CertificateTransparencyFlagsListener mFlagsListener;
+
     /**
      * @return true if the CertificateTransparency service is enabled.
      */
@@ -43,7 +46,9 @@
     }
 
     /** Creates a new {@link CertificateTransparencyService} object. */
-    public CertificateTransparencyService(Context context) {}
+    public CertificateTransparencyService(Context context) {
+        mFlagsListener = new CertificateTransparencyFlagsListener(context);
+    }
 
     /**
      * Called by {@link com.android.server.ConnectivityServiceInitializer}.
@@ -51,6 +56,13 @@
      * @see com.android.server.SystemService#onBootPhase
      */
     public void onBootPhase(int phase) {
-        Log.d(TAG, "CertificateTransparencyService#onBootPhase " + phase);
+
+        switch (phase) {
+            case SystemService.PHASE_BOOT_COMPLETED:
+                Log.d(TAG, "setting up flags listeners");
+                mFlagsListener.initialize();
+                break;
+            default:
+        }
     }
 }