Add asynchronous DNS query API in Java
DnsResolver for asynchronous DNS querying
DnsPacket for parsing answer
Test: built, flashed, booted
atest DnsResolverTest
atest DnsPacketTest
Change-Id: Id014bc7387dd940cfaa270f68e7d4d85fab320a0
This commit is contained in:
Luke Huang
289
core/java/android/net/DnsResolver.java
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289
core/java/android/net/DnsResolver.java
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/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.net;
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import static android.net.NetworkUtils.resNetworkQuery;
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import static android.net.NetworkUtils.resNetworkResult;
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import static android.net.NetworkUtils.resNetworkSend;
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import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_ERROR;
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import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_INPUT;
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import android.annotation.IntDef;
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import android.annotation.NonNull;
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import android.annotation.Nullable;
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import android.os.Handler;
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import android.os.MessageQueue;
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import android.system.ErrnoException;
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import android.util.Log;
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import java.io.FileDescriptor;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.net.InetAddress;
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import java.net.UnknownHostException;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.function.Consumer;
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/**
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* Dns resolver class for asynchronous dns querying
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*
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*/
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public final class DnsResolver {
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private static final String TAG = "DnsResolver";
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private static final int FD_EVENTS = EVENT_INPUT | EVENT_ERROR;
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private static final int MAXPACKET = 8 * 1024;
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@IntDef(prefix = { "CLASS_" }, value = {
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CLASS_IN
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})
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@Retention(RetentionPolicy.SOURCE)
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@interface QueryClass {}
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public static final int CLASS_IN = 1;
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@IntDef(prefix = { "TYPE_" }, value = {
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TYPE_A,
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TYPE_AAAA
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})
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@Retention(RetentionPolicy.SOURCE)
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@interface QueryType {}
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public static final int TYPE_A = 1;
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public static final int TYPE_AAAA = 28;
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@IntDef(prefix = { "FLAG_" }, value = {
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FLAG_EMPTY,
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FLAG_NO_RETRY,
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FLAG_NO_CACHE_STORE,
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FLAG_NO_CACHE_LOOKUP
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})
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@Retention(RetentionPolicy.SOURCE)
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@interface QueryFlag {}
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public static final int FLAG_EMPTY = 0;
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public static final int FLAG_NO_RETRY = 1 << 0;
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public static final int FLAG_NO_CACHE_STORE = 1 << 1;
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public static final int FLAG_NO_CACHE_LOOKUP = 1 << 2;
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private static final int DNS_RAW_RESPONSE = 1;
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private static final int NETID_UNSET = 0;
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private static final DnsResolver sInstance = new DnsResolver();
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/**
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* listener for receiving raw answers
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*/
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public interface RawAnswerListener {
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/**
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* {@code byte[]} is {@code null} if query timed out
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*/
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void onAnswer(@Nullable byte[] answer);
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}
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/**
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* listener for receiving parsed answers
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*/
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public interface InetAddressAnswerListener {
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/**
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* Will be called exactly once with all the answers to the query.
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* size of addresses will be zero if no available answer could be parsed.
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*/
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void onAnswer(@NonNull List<InetAddress> addresses);
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}
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/**
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* Get instance for DnsResolver
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*/
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public static DnsResolver getInstance() {
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return sInstance;
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}
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private DnsResolver() {}
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/**
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* Pass in a blob and corresponding setting,
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* get a blob back asynchronously with the entire raw answer.
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*
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* @param network {@link Network} specifying which network for querying.
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* {@code null} for query on default network.
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* @param query blob message
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* @param flags flags as a combination of the FLAGS_* constants
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* @param handler {@link Handler} to specify the thread
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* upon which the {@link RawAnswerListener} will be invoked.
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* @param listener a {@link RawAnswerListener} which will be called to notify the caller
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* of the result of dns query.
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*/
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public void query(@Nullable Network network, @NonNull byte[] query, @QueryFlag int flags,
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@NonNull Handler handler, @NonNull RawAnswerListener listener) throws ErrnoException {
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final FileDescriptor queryfd = resNetworkSend((network != null
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? network.netId : NETID_UNSET), query, query.length, flags);
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registerFDListener(handler.getLooper().getQueue(), queryfd,
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answerbuf -> listener.onAnswer(answerbuf));
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}
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/**
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* Pass in a domain name and corresponding setting,
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* get a blob back asynchronously with the entire raw answer.
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*
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* @param network {@link Network} specifying which network for querying.
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* {@code null} for query on default network.
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* @param domain domain name for querying
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* @param nsClass dns class as one of the CLASS_* constants
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* @param nsType dns resource record (RR) type as one of the TYPE_* constants
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* @param flags flags as a combination of the FLAGS_* constants
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* @param handler {@link Handler} to specify the thread
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* upon which the {@link RawAnswerListener} will be invoked.
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* @param listener a {@link RawAnswerListener} which will be called to notify the caller
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* of the result of dns query.
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*/
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public void query(@Nullable Network network, @NonNull String domain, @QueryClass int nsClass,
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@QueryType int nsType, @QueryFlag int flags,
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@NonNull Handler handler, @NonNull RawAnswerListener listener) throws ErrnoException {
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final FileDescriptor queryfd = resNetworkQuery((network != null
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? network.netId : NETID_UNSET), domain, nsClass, nsType, flags);
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registerFDListener(handler.getLooper().getQueue(), queryfd,
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answerbuf -> listener.onAnswer(answerbuf));
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}
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/**
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* Pass in a domain name and corresponding setting,
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* get back a set of InetAddresses asynchronously.
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*
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* @param network {@link Network} specifying which network for querying.
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* {@code null} for query on default network.
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* @param domain domain name for querying
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* @param flags flags as a combination of the FLAGS_* constants
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* @param handler {@link Handler} to specify the thread
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* upon which the {@link InetAddressAnswerListener} will be invoked.
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* @param listener an {@link InetAddressAnswerListener} which will be called to
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* notify the caller of the result of dns query.
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*
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*/
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public void query(@Nullable Network network, @NonNull String domain, @QueryFlag int flags,
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@NonNull Handler handler, @NonNull InetAddressAnswerListener listener)
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throws ErrnoException {
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final FileDescriptor v4fd = resNetworkQuery((network != null
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? network.netId : NETID_UNSET), domain, CLASS_IN, TYPE_A, flags);
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final FileDescriptor v6fd = resNetworkQuery((network != null
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? network.netId : NETID_UNSET), domain, CLASS_IN, TYPE_AAAA, flags);
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final InetAddressAnswerAccumulator accmulator =
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new InetAddressAnswerAccumulator(2, listener);
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final Consumer<byte[]> consumer = answerbuf ->
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accmulator.accumulate(parseAnswers(answerbuf));
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registerFDListener(handler.getLooper().getQueue(), v4fd, consumer);
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registerFDListener(handler.getLooper().getQueue(), v6fd, consumer);
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}
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private void registerFDListener(@NonNull MessageQueue queue,
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@NonNull FileDescriptor queryfd, @NonNull Consumer<byte[]> answerConsumer) {
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queue.addOnFileDescriptorEventListener(
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queryfd,
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FD_EVENTS,
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(fd, events) -> {
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byte[] answerbuf = null;
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try {
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// TODO: Implement result function in Java side instead of using JNI
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// Because JNI method close fd prior than unregistering fd on
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// event listener.
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answerbuf = resNetworkResult(fd);
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} catch (ErrnoException e) {
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Log.e(TAG, "resNetworkResult:" + e.toString());
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}
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answerConsumer.accept(answerbuf);
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// Unregister this fd listener
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return 0;
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});
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}
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private class DnsAddressAnswer extends DnsPacket {
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private static final String TAG = "DnsResolver.DnsAddressAnswer";
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private static final boolean DBG = false;
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private final int mQueryType;
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DnsAddressAnswer(@NonNull byte[] data) throws ParseException {
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super(data);
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if ((mHeader.flags & (1 << 15)) == 0) {
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throw new ParseException("Not an answer packet");
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}
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if (mHeader.rcode != 0) {
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throw new ParseException("Response error, rcode:" + mHeader.rcode);
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}
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if (mHeader.getSectionCount(ANSECTION) == 0) {
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throw new ParseException("No available answer");
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}
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if (mHeader.getSectionCount(QDSECTION) == 0) {
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throw new ParseException("No question found");
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}
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// Assume only one question per answer packet. (RFC1035)
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mQueryType = mSections[QDSECTION].get(0).nsType;
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}
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public @NonNull List<InetAddress> getAddresses() {
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final List<InetAddress> results = new ArrayList<InetAddress>();
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for (final DnsSection ansSec : mSections[ANSECTION]) {
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// Only support A and AAAA, also ignore answers if query type != answer type.
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int nsType = ansSec.nsType;
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if (nsType != mQueryType || (nsType != TYPE_A && nsType != TYPE_AAAA)) {
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continue;
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}
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try {
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results.add(InetAddress.getByAddress(ansSec.getRR()));
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} catch (UnknownHostException e) {
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if (DBG) {
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Log.w(TAG, "rr to address fail");
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}
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}
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}
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return results;
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}
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}
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private @Nullable List<InetAddress> parseAnswers(@Nullable byte[] data) {
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try {
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return (data == null) ? null : new DnsAddressAnswer(data).getAddresses();
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} catch (DnsPacket.ParseException e) {
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Log.e(TAG, "Parse answer fail " + e.getMessage());
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return null;
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}
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}
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private class InetAddressAnswerAccumulator {
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private final List<InetAddress> mAllAnswers;
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private final InetAddressAnswerListener mAnswerListener;
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private final int mTargetAnswerCount;
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private int mReceivedAnswerCount = 0;
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InetAddressAnswerAccumulator(int size, @NonNull InetAddressAnswerListener listener) {
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mTargetAnswerCount = size;
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mAllAnswers = new ArrayList<>();
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mAnswerListener = listener;
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}
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public void accumulate(@Nullable List<InetAddress> answer) {
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if (null != answer) {
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mAllAnswers.addAll(answer);
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}
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if (++mReceivedAnswerCount == mTargetAnswerCount) {
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mAnswerListener.onAnswer(mAllAnswers);
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}
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}
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}
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}
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