[Thread] add an integration test case for resolving a host via DNS recursive resolver

This CL adds new test cases for verifying the Thread Border Router's
DNS Recursive Resolver feature: The DNS clients resolves google.com
successfully when the feature is enabled.

Bug: 354868095
Test: atest ThreadNetworkIntegrationTests:android.net.thread.InternetAccessTest

Change-Id: I1b021151c6843b30c3f47559ab20dec405af5dea
diff --git a/thread/tests/integration/src/android/net/thread/InternetAccessTest.kt b/thread/tests/integration/src/android/net/thread/InternetAccessTest.kt
new file mode 100644
index 0000000..9b787f5
--- /dev/null
+++ b/thread/tests/integration/src/android/net/thread/InternetAccessTest.kt
@@ -0,0 +1,173 @@
+/*
+ * 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 android.net.thread
+
+import android.content.Context
+import android.net.DnsResolver.CLASS_IN
+import android.net.DnsResolver.TYPE_A
+import android.net.DnsResolver.TYPE_AAAA
+import android.net.InetAddresses.parseNumericAddress
+import android.net.thread.utils.FullThreadDevice
+import android.net.thread.utils.InfraNetworkDevice
+import android.net.thread.utils.IntegrationTestUtils.DEFAULT_DATASET
+import android.net.thread.utils.IntegrationTestUtils.joinNetworkAndWaitForOmr
+import android.net.thread.utils.IntegrationTestUtils.newPacketReader
+import android.net.thread.utils.IntegrationTestUtils.setUpInfraNetwork
+import android.net.thread.utils.IntegrationTestUtils.startInfraDeviceAndWaitForOnLinkAddr
+import android.net.thread.utils.IntegrationTestUtils.tearDownInfraNetwork
+import android.net.thread.utils.IntegrationTestUtils.waitFor
+import android.net.thread.utils.OtDaemonController
+import android.net.thread.utils.TestDnsServer
+import android.net.thread.utils.ThreadFeatureCheckerRule
+import android.net.thread.utils.ThreadFeatureCheckerRule.RequiresSimulationThreadDevice
+import android.net.thread.utils.ThreadFeatureCheckerRule.RequiresThreadFeature
+import android.net.thread.utils.ThreadNetworkControllerWrapper
+import android.os.Handler
+import android.os.HandlerThread
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.filters.LargeTest
+import com.android.net.module.util.DnsPacket
+import com.android.net.module.util.DnsPacket.ANSECTION
+import com.android.testutils.PollPacketReader
+import com.android.testutils.TestNetworkTracker
+import com.google.common.truth.Truth.assertThat
+import java.net.Inet4Address
+import java.net.InetAddress
+import java.time.Duration
+import org.junit.After
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/** Integration test cases for Thread Internet Access features. */
+@RunWith(AndroidJUnit4::class)
+@RequiresThreadFeature
+@RequiresSimulationThreadDevice
+@LargeTest
+class InternetAccessTest {
+    private val TAG = BorderRoutingTest::class.java.simpleName
+    private val NUM_FTD = 1
+    private val DNS_SERVER_ADDR = parseNumericAddress("8.8.8.8") as Inet4Address
+    private val ANSWER_RECORDS =
+        listOf(
+            DnsPacket.DnsRecord.makeAOrAAAARecord(
+                ANSECTION,
+                "google.com",
+                CLASS_IN,
+                30 /* ttl */,
+                parseNumericAddress("1.2.3.4"),
+            ),
+            DnsPacket.DnsRecord.makeAOrAAAARecord(
+                ANSECTION,
+                "google.com",
+                CLASS_IN,
+                30 /* ttl */,
+                parseNumericAddress("2001::234"),
+            ),
+        )
+
+    @get:Rule val threadRule = ThreadFeatureCheckerRule()
+
+    private val context: Context = ApplicationProvider.getApplicationContext()
+    private val controller = requireNotNull(ThreadNetworkControllerWrapper.newInstance(context))
+    private lateinit var otCtl: OtDaemonController
+    private lateinit var handlerThread: HandlerThread
+    private lateinit var handler: Handler
+    private lateinit var infraNetworkTracker: TestNetworkTracker
+    private lateinit var ftds: ArrayList<FullThreadDevice>
+    private lateinit var infraNetworkReader: PollPacketReader
+    private lateinit var infraDevice: InfraNetworkDevice
+    private lateinit var dnsServer: TestDnsServer
+
+    @Before
+    @Throws(Exception::class)
+    fun setUp() {
+        // TODO: b/323301831 - This is a workaround to avoid unnecessary delay to re-form a network
+        otCtl = OtDaemonController()
+        otCtl.factoryReset()
+
+        handlerThread = HandlerThread(javaClass.simpleName)
+        handlerThread.start()
+        handler = Handler(handlerThread.looper)
+        ftds = ArrayList()
+
+        infraNetworkTracker = setUpInfraNetwork(context, controller)
+        controller.setEnabledAndWait(true)
+        controller.joinAndWait(DEFAULT_DATASET)
+
+        // Creates a infra network device.
+        infraNetworkReader = newPacketReader(infraNetworkTracker.testIface, handler)
+        infraDevice = startInfraDeviceAndWaitForOnLinkAddr(infraNetworkReader)
+
+        // Create a DNS server
+        dnsServer = TestDnsServer(infraNetworkReader, DNS_SERVER_ADDR, ANSWER_RECORDS)
+
+        // Create Ftds
+        for (i in 0 until NUM_FTD) {
+            ftds.add(FullThreadDevice(15 + i /* node ID */))
+        }
+    }
+
+    @After
+    @Throws(Exception::class)
+    fun tearDown() {
+        controller.setTestNetworkAsUpstreamAndWait(null)
+        controller.leaveAndWait()
+        tearDownInfraNetwork(infraNetworkTracker)
+
+        dnsServer.stop()
+
+        handlerThread.quitSafely()
+        handlerThread.join()
+
+        ftds.forEach { it.destroy() }
+        ftds.clear()
+    }
+
+    @Test
+    fun nat64Enabled_threadDeviceResolvesHost_hostIsResolved() {
+        controller.setNat64EnabledAndWait(true)
+        waitFor({ otCtl.hasNat64PrefixInNetdata() }, Duration.ofSeconds(10))
+        val ftd = ftds[0]
+        joinNetworkAndWaitForOmr(ftd, DEFAULT_DATASET)
+        dnsServer.start()
+
+        val ipv4Addresses =
+            ftd.resolveHost("google.com", TYPE_A).map { extractIpv4AddressFromMappedAddress(it) }
+        assertThat(ipv4Addresses).isEqualTo(listOf(parseNumericAddress("1.2.3.4")))
+        val ipv6Addresses = ftd.resolveHost("google.com", TYPE_AAAA)
+        assertThat(ipv6Addresses).isEqualTo(listOf(parseNumericAddress("2001::234")))
+    }
+
+    @Test
+    fun nat64Disabled_threadDeviceResolvesHost_hostIsNotResolved() {
+        controller.setNat64EnabledAndWait(false)
+        val ftd = ftds[0]
+        joinNetworkAndWaitForOmr(ftd, DEFAULT_DATASET)
+        dnsServer.start()
+
+        assertThat(ftd.resolveHost("google.com", TYPE_A)).isEmpty()
+        assertThat(ftd.resolveHost("google.com", TYPE_AAAA)).isEmpty()
+    }
+
+    private fun extractIpv4AddressFromMappedAddress(address: InetAddress): Inet4Address {
+        return InetAddress.getByAddress(address.address.slice(12 until 16).toByteArray())
+            as Inet4Address
+    }
+}
diff --git a/thread/tests/integration/src/android/net/thread/utils/FullThreadDevice.java b/thread/tests/integration/src/android/net/thread/utils/FullThreadDevice.java
index 083a841..5b532c7 100644
--- a/thread/tests/integration/src/android/net/thread/utils/FullThreadDevice.java
+++ b/thread/tests/integration/src/android/net/thread/utils/FullThreadDevice.java
@@ -15,6 +15,8 @@
  */
 package android.net.thread.utils;
 
+import static android.net.DnsResolver.TYPE_A;
+import static android.net.DnsResolver.TYPE_AAAA;
 import static android.net.thread.utils.IntegrationTestUtils.SERVICE_DISCOVERY_TIMEOUT;
 import static android.net.thread.utils.IntegrationTestUtils.waitFor;
 
@@ -354,6 +356,31 @@
         executeCommand("dns config " + address);
     }
 
+    /** Resolves the {@code queryType} record of the {@code hostname} via DNS. */
+    public List<InetAddress> resolveHost(String hostname, int queryType) {
+        // CLI output:
+        // DNS response for hostname.com. - fd12::abc1 TTL:50 fd12::abc2 TTL:50 fd12::abc3 TTL:50
+
+        String command;
+        switch (queryType) {
+            case TYPE_A -> command = "resolve4";
+            case TYPE_AAAA -> command = "resolve";
+            default -> throw new IllegalArgumentException("Invalid query type: " + queryType);
+        }
+        final List<InetAddress> addresses = new ArrayList<>();
+        String line;
+        try {
+            line = executeCommand("dns " + command + " " + hostname).get(0);
+        } catch (IllegalStateException e) {
+            return addresses;
+        }
+        final String[] addressTtlPairs = line.split("-")[1].strip().split(" ");
+        for (int i = 0; i < addressTtlPairs.length; i += 2) {
+            addresses.add(InetAddresses.parseNumericAddress(addressTtlPairs[i]));
+        }
+        return addresses;
+    }
+
     /** Returns the first browsed service instance of {@code serviceType}. */
     public NsdServiceInfo browseService(String serviceType) {
         // CLI output:
diff --git a/thread/tests/integration/src/android/net/thread/utils/TestDnsServer.kt b/thread/tests/integration/src/android/net/thread/utils/TestDnsServer.kt
new file mode 100644
index 0000000..c52fc49
--- /dev/null
+++ b/thread/tests/integration/src/android/net/thread/utils/TestDnsServer.kt
@@ -0,0 +1,170 @@
+/*
+ * 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 android.net.thread.utils
+
+import android.net.thread.utils.IntegrationTestUtils.pollForPacket
+import android.system.OsConstants.IPPROTO_IP
+import android.system.OsConstants.IPPROTO_UDP
+import com.android.net.module.util.DnsPacket
+import com.android.net.module.util.PacketBuilder
+import com.android.net.module.util.Struct
+import com.android.net.module.util.structs.Ipv4Header
+import com.android.net.module.util.structs.UdpHeader
+import com.android.testutils.PollPacketReader
+import java.net.InetAddress
+import java.nio.ByteBuffer
+import kotlin.concurrent.thread
+
+/**
+ * A class that simulates a DNS server.
+ *
+ * <p>The server responds to DNS requests with the given {@code answerRecords}.
+ *
+ * @param packetReader the packet reader to poll DNS requests from
+ * @param serverAddress the address of the DNS server
+ * @param answerRecords the records to respond to the DNS requests
+ */
+class TestDnsServer(
+    private val packetReader: PollPacketReader,
+    private val serverAddress: InetAddress,
+    private val answerRecords: List<DnsPacket.DnsRecord>,
+) {
+    private val TAG = TestDnsServer::class.java.simpleName
+    private val DNS_UDP_PORT = 53
+    private var workerThread: Thread? = null
+
+    private class TestDnsPacket : DnsPacket {
+
+        constructor(buf: ByteArray) : super(buf)
+
+        constructor(
+            header: DnsHeader,
+            qd: List<DnsRecord>,
+            an: List<DnsRecord>,
+        ) : super(header, qd, an) {}
+
+        val header = super.mHeader
+        val records = super.mRecords
+    }
+
+    /**
+     * Starts the DNS server to respond to DNS requests.
+     *
+     * <p> The server polls the DNS requests from the {@code packetReader} and responds with the
+     * {@code answerRecords}. The server will automatically stop when it fails to poll a DNS request
+     * within the timeout (3000 ms, as defined in IntegrationTestUtils).
+     */
+    fun start() {
+        workerThread = thread {
+            var requestPacket: ByteArray
+            while (true) {
+                requestPacket = pollForDnsPacket() ?: break
+                val buf = ByteBuffer.wrap(requestPacket)
+                packetReader.sendResponse(buildDnsResponse(buf, answerRecords))
+            }
+        }
+    }
+
+    /** Stops the DNS server. */
+    fun stop() {
+        workerThread?.join()
+    }
+
+    private fun pollForDnsPacket(): ByteArray? {
+        val filter =
+            fun(packet: ByteArray): Boolean {
+                val buf = ByteBuffer.wrap(packet)
+                val ipv4Header = Struct.parse(Ipv4Header::class.java, buf) ?: return false
+                val udpHeader = Struct.parse(UdpHeader::class.java, buf) ?: return false
+                return ipv4Header.dstIp == serverAddress && udpHeader.dstPort == DNS_UDP_PORT
+            }
+        return pollForPacket(packetReader, filter)
+    }
+
+    private fun buildDnsResponse(
+        requestPacket: ByteBuffer,
+        serverAnswers: List<DnsPacket.DnsRecord>,
+    ): ByteBuffer? {
+        val requestIpv4Header = Struct.parse(Ipv4Header::class.java, requestPacket) ?: return null
+        val requestUdpHeader = Struct.parse(UdpHeader::class.java, requestPacket) ?: return null
+        val remainingRequestPacket = ByteArray(requestPacket.remaining())
+        requestPacket.get(remainingRequestPacket)
+        val requestDnsPacket = TestDnsPacket(remainingRequestPacket)
+        val requestDnsHeader = requestDnsPacket.header
+
+        val answerRecords =
+            buildDnsAnswerRecords(requestDnsPacket.records[DnsPacket.QDSECTION], serverAnswers)
+        // TODO: return NXDOMAIN if no answer is found.
+        val responseFlags = 1 shl 15 // QR bit
+        val responseDnsHeader =
+            DnsPacket.DnsHeader(
+                requestDnsHeader.id,
+                responseFlags,
+                requestDnsPacket.records[DnsPacket.QDSECTION].size,
+                answerRecords.size,
+            )
+        val responseDnsPacket =
+            TestDnsPacket(
+                responseDnsHeader,
+                requestDnsPacket.records[DnsPacket.QDSECTION],
+                answerRecords,
+            )
+
+        val buf =
+            PacketBuilder.allocate(
+                false /* hasEther */,
+                IPPROTO_IP,
+                IPPROTO_UDP,
+                responseDnsPacket.bytes.size,
+            )
+
+        val packetBuilder = PacketBuilder(buf)
+        packetBuilder.writeIpv4Header(
+            requestIpv4Header.tos,
+            requestIpv4Header.id,
+            requestIpv4Header.flagsAndFragmentOffset,
+            0x40 /* ttl */,
+            IPPROTO_UDP.toByte(),
+            requestIpv4Header.dstIp, /* srcIp */
+            requestIpv4Header.srcIp, /* dstIp */
+        )
+        packetBuilder.writeUdpHeader(
+            requestUdpHeader.dstPort.toShort() /* srcPort */,
+            requestUdpHeader.srcPort.toShort(), /* dstPort */
+        )
+        buf.put(responseDnsPacket.bytes)
+
+        return packetBuilder.finalizePacket()
+    }
+
+    private fun buildDnsAnswerRecords(
+        questions: List<DnsPacket.DnsRecord>,
+        serverAnswers: List<DnsPacket.DnsRecord>,
+    ): List<DnsPacket.DnsRecord> {
+        val answers = ArrayList<DnsPacket.DnsRecord>()
+        for (answer in serverAnswers) {
+            if (
+                questions.any {
+                    answer.dName.equals(it.dName, ignoreCase = true) && answer.nsType == it.nsType
+                }
+            ) {
+                answers.add(answer)
+            }
+        }
+        return answers
+    }
+}