Add TestNetworkTracker to test utils.

/*

 * Copyright (C) 2020 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.testutils

import android.content.Context

import android.net.ConnectivityManager

import android.net.ConnectivityManager.NetworkCallback

import android.net.LinkAddress

import android.net.Network

import android.net.NetworkCapabilities

import android.net.NetworkRequest

import android.net.StringNetworkSpecifier

import android.net.TestNetworkInterface

import android.net.TestNetworkManager

import android.os.Binder

import java.util.concurrent.CompletableFuture

import java.util.concurrent.TimeUnit

/**

 * Create a test network based on a TUN interface.

 *

 * This method will block until the test network is available. Requires

 * [android.Manifest.permission.CHANGE_NETWORK_STATE] and

 * [android.Manifest.permission.MANAGE_TEST_NETWORKS].

 */

fun initTestNetwork(context: Context, interfaceAddr: LinkAddress, setupTimeoutMs: Long = 10_000L):

        TestNetworkTracker {

    val tnm = context.getSystemService(TestNetworkManager::class.java)

    val iface = tnm.createTunInterface(arrayOf(interfaceAddr))

    return TestNetworkTracker(context, iface, tnm, setupTimeoutMs)

}

/**

 * Utility class to create and track test networks.

 *

 * This class is not thread-safe.

 */

class TestNetworkTracker internal constructor(

    val context: Context,

    val iface: TestNetworkInterface,

    tnm: TestNetworkManager,

    setupTimeoutMs: Long

) {

    private val cm = context.getSystemService(ConnectivityManager::class.java)

    private val binder = Binder()

    private val networkCallback: NetworkCallback

    val network: Network

    init {

        val networkFuture = CompletableFuture<Network>()

        val networkRequest = NetworkRequest.Builder()

                .addTransportType(NetworkCapabilities.TRANSPORT_TEST)

                // Test networks do not have NOT_VPN or TRUSTED capabilities by default

                .removeCapability(NetworkCapabilities.NET_CAPABILITY_NOT_VPN)

                .removeCapability(NetworkCapabilities.NET_CAPABILITY_TRUSTED)

                .setNetworkSpecifier(StringNetworkSpecifier(iface.interfaceName))

                .build()

        networkCallback = object : NetworkCallback() {

            override fun onAvailable(network: Network) {

                networkFuture.complete(network)

            }

        }

        cm.requestNetwork(networkRequest, networkCallback)

        try {

            tnm.setupTestNetwork(iface.interfaceName, binder)

            network = networkFuture.get(setupTimeoutMs, TimeUnit.MILLISECONDS)

        } catch (e: Throwable) {

            teardown()

            throw e

        }

    }

    fun teardown() {

        cm.unregisterNetworkCallback(networkCallback)

    }

}

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