| /* |
| * 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; |
| |
| import static android.net.NetworkUtils.resNetworkCancel; |
| import static android.net.NetworkUtils.resNetworkQuery; |
| import static android.net.NetworkUtils.resNetworkResult; |
| import static android.net.NetworkUtils.resNetworkSend; |
| import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_ERROR; |
| import static android.os.MessageQueue.OnFileDescriptorEventListener.EVENT_INPUT; |
| |
| import android.annotation.CallbackExecutor; |
| import android.annotation.IntDef; |
| import android.annotation.NonNull; |
| import android.annotation.Nullable; |
| import android.os.CancellationSignal; |
| import android.os.Looper; |
| import android.system.ErrnoException; |
| import android.util.Log; |
| |
| import java.io.FileDescriptor; |
| import java.lang.annotation.Retention; |
| import java.lang.annotation.RetentionPolicy; |
| import java.net.InetAddress; |
| import java.net.UnknownHostException; |
| import java.util.ArrayList; |
| import java.util.List; |
| import java.util.concurrent.Executor; |
| |
| /** |
| * Dns resolver class for asynchronous dns querying |
| * |
| * Note that if a client sends a query with more than 1 record in the question section but |
| * the remote dns server does not support this, it may not respond at all, leading to a timeout. |
| * |
| */ |
| public final class DnsResolver { |
| private static final String TAG = "DnsResolver"; |
| private static final int FD_EVENTS = EVENT_INPUT | EVENT_ERROR; |
| private static final int MAXPACKET = 8 * 1024; |
| |
| @IntDef(prefix = { "CLASS_" }, value = { |
| CLASS_IN |
| }) |
| @Retention(RetentionPolicy.SOURCE) |
| @interface QueryClass {} |
| public static final int CLASS_IN = 1; |
| |
| @IntDef(prefix = { "TYPE_" }, value = { |
| TYPE_A, |
| TYPE_AAAA |
| }) |
| @Retention(RetentionPolicy.SOURCE) |
| @interface QueryType {} |
| public static final int TYPE_A = 1; |
| public static final int TYPE_AAAA = 28; |
| |
| @IntDef(prefix = { "FLAG_" }, value = { |
| FLAG_EMPTY, |
| FLAG_NO_RETRY, |
| FLAG_NO_CACHE_STORE, |
| FLAG_NO_CACHE_LOOKUP |
| }) |
| @Retention(RetentionPolicy.SOURCE) |
| @interface QueryFlag {} |
| public static final int FLAG_EMPTY = 0; |
| public static final int FLAG_NO_RETRY = 1 << 0; |
| public static final int FLAG_NO_CACHE_STORE = 1 << 1; |
| public static final int FLAG_NO_CACHE_LOOKUP = 1 << 2; |
| |
| private static final int NETID_UNSET = 0; |
| |
| private static final DnsResolver sInstance = new DnsResolver(); |
| |
| /** |
| * Get instance for DnsResolver |
| */ |
| public static @NonNull DnsResolver getInstance() { |
| return sInstance; |
| } |
| |
| private DnsResolver() {} |
| |
| /** |
| * Answer parser for parsing raw answers |
| * |
| * @param <T> The type of the parsed answer |
| */ |
| public interface AnswerParser<T> { |
| /** |
| * Creates a <T> answer by parsing the given raw answer. |
| * |
| * @param rawAnswer the raw answer to be parsed |
| * @return a parsed <T> answer |
| * @throws ParseException if parsing failed |
| */ |
| @NonNull T parse(@NonNull byte[] rawAnswer) throws ParseException; |
| } |
| |
| /** |
| * Base class for answer callbacks |
| * |
| * @param <T> The type of the parsed answer |
| */ |
| public abstract static class AnswerCallback<T> { |
| /** @hide */ |
| public final AnswerParser<T> parser; |
| |
| public AnswerCallback(@NonNull AnswerParser<T> parser) { |
| this.parser = parser; |
| }; |
| |
| /** |
| * Success response to |
| * {@link android.net.DnsResolver#query query()}. |
| * |
| * Invoked when the answer to a query was successfully parsed. |
| * |
| * @param answer parsed answer to the query. |
| * |
| * {@see android.net.DnsResolver#query query()} |
| */ |
| public abstract void onAnswer(@NonNull T answer); |
| |
| /** |
| * Error response to |
| * {@link android.net.DnsResolver#query query()}. |
| * |
| * Invoked when there is no valid answer to |
| * {@link android.net.DnsResolver#query query()} |
| * |
| * @param exception a {@link ParseException} object with additional |
| * detail regarding the failure |
| */ |
| public abstract void onParseException(@NonNull ParseException exception); |
| |
| /** |
| * Error response to |
| * {@link android.net.DnsResolver#query query()}. |
| * |
| * Invoked if an error happens when |
| * issuing the DNS query or receiving the result. |
| * {@link android.net.DnsResolver#query query()} |
| * |
| * @param exception an {@link ErrnoException} object with additional detail |
| * regarding the failure |
| */ |
| public abstract void onQueryException(@NonNull ErrnoException exception); |
| } |
| |
| /** |
| * Callback for receiving raw answers |
| */ |
| public abstract static class RawAnswerCallback extends AnswerCallback<byte[]> { |
| public RawAnswerCallback() { |
| super(rawAnswer -> rawAnswer); |
| } |
| } |
| |
| /** |
| * Callback for receiving parsed {@link InetAddress} answers |
| * |
| * Note that if the answer does not contain any IP addresses, |
| * onAnswer will be called with an empty list. |
| */ |
| public abstract static class InetAddressAnswerCallback |
| extends AnswerCallback<List<InetAddress>> { |
| public InetAddressAnswerCallback() { |
| super(rawAnswer -> new DnsAddressAnswer(rawAnswer).getAddresses()); |
| } |
| } |
| |
| /** |
| * Send a raw DNS query. |
| * The answer will be provided asynchronously through the provided {@link AnswerCallback}. |
| * |
| * @param network {@link Network} specifying which network for querying. |
| * {@code null} for query on default network. |
| * @param query blob message |
| * @param flags flags as a combination of the FLAGS_* constants |
| * @param executor The {@link Executor} that the callback should be executed on. |
| * @param cancellationSignal used by the caller to signal if the query should be |
| * cancelled. May be {@code null}. |
| * @param callback an {@link AnswerCallback} which will be called to notify the caller |
| * of the result of dns query. |
| */ |
| public <T> void query(@Nullable Network network, @NonNull byte[] query, @QueryFlag int flags, |
| @NonNull @CallbackExecutor Executor executor, |
| @Nullable CancellationSignal cancellationSignal, |
| @NonNull AnswerCallback<T> callback) { |
| if (cancellationSignal != null && cancellationSignal.isCanceled()) { |
| return; |
| } |
| final FileDescriptor queryfd; |
| try { |
| queryfd = resNetworkSend((network != null |
| ? network.netId : NETID_UNSET), query, query.length, flags); |
| } catch (ErrnoException e) { |
| callback.onQueryException(e); |
| return; |
| } |
| |
| maybeAddCancellationSignal(cancellationSignal, queryfd); |
| registerFDListener(executor, queryfd, callback); |
| } |
| |
| /** |
| * Send a DNS query with the specified name, class and query type. |
| * The answer will be provided asynchronously through the provided {@link AnswerCallback}. |
| * |
| * @param network {@link Network} specifying which network for querying. |
| * {@code null} for query on default network. |
| * @param domain domain name for querying |
| * @param nsClass dns class as one of the CLASS_* constants |
| * @param nsType dns resource record (RR) type as one of the TYPE_* constants |
| * @param flags flags as a combination of the FLAGS_* constants |
| * @param executor The {@link Executor} that the callback should be executed on. |
| * @param cancellationSignal used by the caller to signal if the query should be |
| * cancelled. May be {@code null}. |
| * @param callback an {@link AnswerCallback} which will be called to notify the caller |
| * of the result of dns query. |
| */ |
| public <T> void query(@Nullable Network network, @NonNull String domain, |
| @QueryClass int nsClass, @QueryType int nsType, @QueryFlag int flags, |
| @NonNull @CallbackExecutor Executor executor, |
| @Nullable CancellationSignal cancellationSignal, |
| @NonNull AnswerCallback<T> callback) { |
| if (cancellationSignal != null && cancellationSignal.isCanceled()) { |
| return; |
| } |
| final FileDescriptor queryfd; |
| try { |
| queryfd = resNetworkQuery((network != null |
| ? network.netId : NETID_UNSET), domain, nsClass, nsType, flags); |
| } catch (ErrnoException e) { |
| callback.onQueryException(e); |
| return; |
| } |
| |
| maybeAddCancellationSignal(cancellationSignal, queryfd); |
| registerFDListener(executor, queryfd, callback); |
| } |
| |
| private <T> void registerFDListener(@NonNull Executor executor, |
| @NonNull FileDescriptor queryfd, @NonNull AnswerCallback<T> answerCallback) { |
| Looper.getMainLooper().getQueue().addOnFileDescriptorEventListener( |
| queryfd, |
| FD_EVENTS, |
| (fd, events) -> { |
| executor.execute(() -> { |
| byte[] answerbuf = null; |
| try { |
| answerbuf = resNetworkResult(fd); |
| } catch (ErrnoException e) { |
| Log.e(TAG, "resNetworkResult:" + e.toString()); |
| answerCallback.onQueryException(e); |
| return; |
| } |
| |
| try { |
| answerCallback.onAnswer( |
| answerCallback.parser.parse(answerbuf)); |
| } catch (ParseException e) { |
| answerCallback.onParseException(e); |
| } |
| }); |
| // Unregister this fd listener |
| return 0; |
| }); |
| } |
| |
| private void maybeAddCancellationSignal(@Nullable CancellationSignal cancellationSignal, |
| @NonNull FileDescriptor queryfd) { |
| if (cancellationSignal == null) return; |
| cancellationSignal.setOnCancelListener( |
| () -> { |
| Looper.getMainLooper().getQueue() |
| .removeOnFileDescriptorEventListener(queryfd); |
| resNetworkCancel(queryfd); |
| }); |
| } |
| |
| private static class DnsAddressAnswer extends DnsPacket { |
| private static final String TAG = "DnsResolver.DnsAddressAnswer"; |
| private static final boolean DBG = false; |
| |
| private final int mQueryType; |
| |
| DnsAddressAnswer(@NonNull byte[] data) throws ParseException { |
| super(data); |
| if ((mHeader.flags & (1 << 15)) == 0) { |
| throw new ParseException("Not an answer packet"); |
| } |
| if (mHeader.getRecordCount(QDSECTION) == 0) { |
| throw new ParseException("No question found"); |
| } |
| // Expect only one question in question section. |
| mQueryType = mRecords[QDSECTION].get(0).nsType; |
| } |
| |
| public @NonNull List<InetAddress> getAddresses() { |
| final List<InetAddress> results = new ArrayList<InetAddress>(); |
| if (mHeader.getRecordCount(ANSECTION) == 0) return results; |
| |
| for (final DnsRecord ansSec : mRecords[ANSECTION]) { |
| // Only support A and AAAA, also ignore answers if query type != answer type. |
| int nsType = ansSec.nsType; |
| if (nsType != mQueryType || (nsType != TYPE_A && nsType != TYPE_AAAA)) { |
| continue; |
| } |
| try { |
| results.add(InetAddress.getByAddress(ansSec.getRR())); |
| } catch (UnknownHostException e) { |
| if (DBG) { |
| Log.w(TAG, "rr to address fail"); |
| } |
| } |
| } |
| return results; |
| } |
| } |
| |
| } |