2 files changed, 93 insertions, 0 deletions

diff --git a/src/android/net/util/DataStallUtils.java b/src/android/net/util/DataStallUtils.java
new file mode 100644
index 0000000..b6dbeb1
--- /dev/null
+++ b/src/android/net/util/DataStallUtils.java
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2019 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 android.net.util;
+
+/**
+ * Collection of utilities for data stall.
+ */
+public class DataStallUtils {
+    /**
+     * Detect data stall via using dns timeout counts.
+     */
+    public static final int DATA_STALL_EVALUATION_TYPE_DNS = 1;
+    // Default configuration values for data stall detection.
+    public static final int DEFAULT_CONSECUTIVE_DNS_TIMEOUT_THRESHOLD = 5;
+    public static final int DEFAULT_DATA_STALL_MIN_EVALUATE_TIME_MS = 60 * 1000;
+    public static final int DEFAULT_DATA_STALL_VALID_DNS_TIME_THRESHOLD_MS = 30 * 60 * 1000;
+    /**
+     * The threshold value for the number of consecutive dns timeout events received to be a
+     * signal of data stall. The number of consecutive timeouts needs to be {@code >=} this
+     * threshold to be considered a data stall. Set the value to {@code <= 0} to disable. Note
+     * that the value should be {@code > 0} if the DNS data stall detection is enabled.
+     *
+     */
+    public static final String CONFIG_DATA_STALL_CONSECUTIVE_DNS_TIMEOUT_THRESHOLD =
+            "data_stall_consecutive_dns_timeout_threshold";
+
+    /**
+     * The minimal time interval in milliseconds for data stall reevaluation.
+     *
+     */
+    public static final String CONFIG_DATA_STALL_MIN_EVALUATE_INTERVAL =
+            "data_stall_min_evaluate_interval";
+
+    /**
+     * DNS timeouts older than this timeout (in milliseconds) are not considered for detecting
+     * a data stall.
+     *
+     */
+    public static final String CONFIG_DATA_STALL_VALID_DNS_TIME_THRESHOLD =
+            "data_stall_valid_dns_time_threshold";
+
+    /**
+     * Which data stall detection signal to use. This is a bitmask constructed by bitwise-or-ing
+     * (i.e. {@code |}) the DATA_STALL_EVALUATION_TYPE_* values.
+     *
+     * Type: int
+     * Valid values:
+     *   {@link #DATA_STALL_EVALUATION_TYPE_DNS} : Use dns as a signal.
+     */
+    public static final String CONFIG_DATA_STALL_EVALUATION_TYPE = "data_stall_evaluation_type";
+    public static final int DEFAULT_DATA_STALL_EVALUATION_TYPES = DATA_STALL_EVALUATION_TYPE_DNS;
+    // The default number of DNS events kept of the log kept for dns signal evaluation. Each event
+    // is represented by a {@link com.android.server.connectivity.NetworkMonitor#DnsResult} objects.
+    // It's also the size of array of {@link com.android.server.connectivity.nano.DnsEvent} kept in
+    // metrics. Note that increasing the size may cause statsd log buffer bust. Need to check the
+    // design in statsd when you try to increase the size.
+    public static final int DEFAULT_DNS_LOG_SIZE = 20;
+}
diff --git a/src/android/net/util/NetworkStackUtils.java b/src/android/net/util/NetworkStackUtils.java
index ee83a85..fa8f65e 100644
--- a/src/android/net/util/NetworkStackUtils.java
+++ b/src/android/net/util/NetworkStackUtils.java
@@ -31,6 +31,9 @@ import java.util.function.Predicate;
  * Collection of utilities for the network stack.
  */
 public class NetworkStackUtils {
+    // TODO: Refer to DeviceConfig definition.
+    public static final String NAMESPACE_CONNECTIVITY = "connectivity";
+
     static {
         System.loadLibrary("networkstackutilsjni");
     }
@@ -103,6 +106,24 @@ public class NetworkStackUtils {
     }
 
     /**
+     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.
+     * @param namespace The namespace containing the property to look up.
+     * @param name The name of the property to look up.
+     * @param defaultValue The value to return if the property does not exist or has no non-null
+     *                     value.
+     * @return the corresponding value, or defaultValue if none exists.
+     */
+    public static int getDeviceConfigPropertyInt(@NonNull String namespace, @NonNull String name,
+            int defaultValue) {
+        String value = getDeviceConfigProperty(namespace, name, null /* defaultValue */);
+        try {
+            return (value != null) ? Integer.parseInt(value) : defaultValue;
+        } catch (NumberFormatException e) {
+            return defaultValue;
+        }
+    }
+
+    /**
      * Attaches a socket filter that accepts DHCP packets to the given socket.
      */
     public static native void attachDhcpFilter(FileDescriptor fd) throws SocketException;