/*
 * 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;
}