/*
    * Copyright 2020 The Netty Project
    *
    * The Netty Project licenses this file to you 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:
    *
    *   https://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 io.netty.handler.codec.quic;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.buffer.Unpooled;
  import io.netty.channel.AbstractChannel;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelMetadata;
  import io.netty.channel.ChannelOption;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.ConnectTimeoutException;
  import io.netty.channel.DefaultChannelPipeline;
  import io.netty.channel.EventLoop;
  import io.netty.channel.RecvByteBufAllocator;
  import io.netty.channel.socket.DatagramPacket;
  import io.netty.handler.ssl.SniCompletionEvent;
  import io.netty.handler.ssl.SslHandshakeCompletionEvent;
  import io.netty.util.AttributeKey;
  import io.netty.util.collection.LongObjectHashMap;
  import io.netty.util.collection.LongObjectMap;
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.ImmediateEventExecutor;
  import io.netty.util.concurrent.ImmediateExecutor;
  import io.netty.util.concurrent.Promise;
  import io.netty.util.internal.StringUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  import org.jetbrains.annotations.Nullable;
  
  import javax.net.ssl.SSLEngine;
  import javax.net.ssl.SSLHandshakeException;
  import java.io.File;
  import java.net.ConnectException;
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.nio.BufferUnderflowException;
  import java.nio.ByteBuffer;
  import java.nio.channels.AlreadyConnectedException;
  import java.nio.channels.ClosedChannelException;
  import java.nio.channels.ConnectionPendingException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.Executor;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicLongFieldUpdater;
  import java.util.function.Consumer;
  import java.util.function.Function;
  
  /**
   * {@link QuicChannel} implementation that uses <a href="https://github.com/cloudflare/quiche">quiche</a>.
   */
  final class QuicheQuicChannel extends AbstractChannel implements QuicChannel {
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(QuicheQuicChannel.class);
      private static final String QLOG_FILE_EXTENSION = ".qlog";
  
      enum StreamRecvResult {
          /**
           * Nothing more to read from the stream.
           */
          DONE,
          /**
           * FIN flag received.
           */
          FIN,
          /**
           * Normal read without FIN flag.
           */
          OK
      }
  
      private enum ChannelState {
          OPEN,
          ACTIVE,
          CLOSED
     }
 
     private enum SendResult {
         SOME,
         NONE,
         CLOSE
     }
 
     private static final class CloseData implements ChannelFutureListener {
         final boolean applicationClose;
         final int err;
         final ByteBuf reason;
 
         CloseData(boolean applicationClose, int err, ByteBuf reason) {
             this.applicationClose = applicationClose;
             this.err = err;
             this.reason = reason;
         }
 
         @Override
         public void operationComplete(ChannelFuture future) {
             reason.release();
         }
     }
 
     private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
     private long[] readableStreams = new long[4];
     private long[] writableStreams = new long[4];
     private final LongObjectMap<QuicheQuicStreamChannel> streams = new LongObjectHashMap<>();
     private final QuicheQuicChannelConfig config;
     private final boolean server;
     private final QuicStreamIdGenerator idGenerator;
     private final ChannelHandler streamHandler;
     private final Map.Entry<ChannelOption<?>, Object>[] streamOptionsArray;
     private final Map.Entry<AttributeKey<?>, Object>[] streamAttrsArray;
     private final TimeoutHandler timeoutHandler;
     private final QuicConnectionIdGenerator connectionIdAddressGenerator;
     private final QuicResetTokenGenerator resetTokenGenerator;
     private final Set<ByteBuffer> sourceConnectionIds = new HashSet<>();
 
     private Consumer<QuicheQuicChannel> freeTask;
     private Executor sslTaskExecutor;
     private boolean inFireChannelReadCompleteQueue;
     private boolean fireChannelReadCompletePending;
     private ByteBuf finBuffer;
     private ByteBuf outErrorCodeBuffer;
     private ChannelPromise connectPromise;
     private ScheduledFuture<?> connectTimeoutFuture;
     private QuicConnectionAddress connectLocalAddress;
     private QuicConnectionAddress connectRemoteAddress;
     private CloseData closeData;
     private QuicConnectionCloseEvent connectionCloseEvent;
     private QuicConnectionStats statsAtClose;
     private boolean supportsDatagram;
     private boolean recvDatagramPending;
     private boolean datagramReadable;
     private boolean recvStreamPending;
     private boolean streamReadable;
     private boolean handshakeCompletionNotified;
     private boolean earlyDataReadyNotified;
     private int reantranceGuard;
     private static final int IN_RECV = 1 << 1;
     private static final int IN_CONNECTION_SEND = 1 << 2;
     private static final int IN_HANDLE_WRITABLE_STREAMS = 1 << 3;
     private volatile ChannelState state = ChannelState.OPEN;
     private volatile boolean timedOut;
     private volatile String traceId;
     private volatile QuicheQuicConnection connection;
     private volatile InetSocketAddress local;
     private volatile InetSocketAddress remote;
 
     private final ChannelFutureListener continueSendingListener = f -> {
         if (connectionSend(connection) != SendResult.NONE) {
             flushParent();
         }
     };
 
     private static final AtomicLongFieldUpdater<QuicheQuicChannel> UNI_STREAMS_LEFT_UPDATER =
             AtomicLongFieldUpdater.newUpdater(QuicheQuicChannel.class, "uniStreamsLeft");
     private volatile long uniStreamsLeft;
 
     private static final AtomicLongFieldUpdater<QuicheQuicChannel> BIDI_STREAMS_LEFT_UPDATER =
             AtomicLongFieldUpdater.newUpdater(QuicheQuicChannel.class, "bidiStreamsLeft");
     private volatile long bidiStreamsLeft;
 
     private QuicheQuicChannel(Channel parent, boolean server, @Nullable ByteBuffer key, InetSocketAddress local,
                               InetSocketAddress remote, boolean supportsDatagram, ChannelHandler streamHandler,
                               Map.Entry<ChannelOption<?>, Object>[] streamOptionsArray,
                               Map.Entry<AttributeKey<?>, Object>[] streamAttrsArray,
                               @Nullable Consumer<QuicheQuicChannel> freeTask,
                               @Nullable Executor sslTaskExecutor,
                               @Nullable QuicConnectionIdGenerator connectionIdAddressGenerator,
                               @Nullable QuicResetTokenGenerator resetTokenGenerator) {
         super(parent);
         config = new QuicheQuicChannelConfig(this);
         this.freeTask = freeTask;
         this.server = server;
         this.idGenerator = new QuicStreamIdGenerator(server);
         this.connectionIdAddressGenerator = connectionIdAddressGenerator;
         this.resetTokenGenerator = resetTokenGenerator;
         if (key != null) {
             this.sourceConnectionIds.add(key);
         }
 
         this.supportsDatagram = supportsDatagram;
         this.local = local;
         this.remote = remote;
 
         this.streamHandler = streamHandler;
         this.streamOptionsArray = streamOptionsArray;
         this.streamAttrsArray = streamAttrsArray;
         timeoutHandler = new TimeoutHandler();
         this.sslTaskExecutor = sslTaskExecutor == null ? ImmediateExecutor.INSTANCE : sslTaskExecutor;
     }
 
     static QuicheQuicChannel forClient(Channel parent, InetSocketAddress local, InetSocketAddress remote,
                                        ChannelHandler streamHandler,
                                        Map.Entry<ChannelOption<?>, Object>[] streamOptionsArray,
                                        Map.Entry<AttributeKey<?>, Object>[] streamAttrsArray) {
         return new QuicheQuicChannel(parent, false, null, local, remote, false, streamHandler,
                 streamOptionsArray, streamAttrsArray, null, null, null, null);
     }
 
     static QuicheQuicChannel forServer(Channel parent, ByteBuffer key, InetSocketAddress local,
                                        InetSocketAddress remote,
                                        boolean supportsDatagram, ChannelHandler streamHandler,
                                        Map.Entry<ChannelOption<?>, Object>[] streamOptionsArray,
                                        Map.Entry<AttributeKey<?>, Object>[] streamAttrsArray,
                                        Consumer<QuicheQuicChannel> freeTask, Executor sslTaskExecutor,
                                        QuicConnectionIdGenerator connectionIdAddressGenerator,
                                        QuicResetTokenGenerator resetTokenGenerator) {
         return new QuicheQuicChannel(parent, true, key, local, remote, supportsDatagram,
                 streamHandler, streamOptionsArray, streamAttrsArray, freeTask,
                 sslTaskExecutor, connectionIdAddressGenerator, resetTokenGenerator);
     }
 
     private static final int MAX_ARRAY_LEN = 128;
 
     private static long[] growIfNeeded(long[] array, int maxLength) {
         if (maxLength > array.length) {
             if (array.length == MAX_ARRAY_LEN) {
                 return array;
             }
             // Increase by 4 until we reach MAX_ARRAY_LEN
             return new long[Math.min(MAX_ARRAY_LEN, array.length + 4)];
         }
         return array;
     }
 
     @Override
     public boolean isTimedOut() {
         return timedOut;
     }
 
     @Override
     public SSLEngine sslEngine() {
         QuicheQuicConnection connection = this.connection;
         return connection == null ? null : connection.engine();
     }
 
     private void notifyAboutHandshakeCompletionIfNeeded(QuicheQuicConnection conn,
                                                         @Nullable SSLHandshakeException cause) {
         if (handshakeCompletionNotified) {
             return;
         }
         if (cause != null) {
             pipeline().fireUserEventTriggered(new SslHandshakeCompletionEvent(cause));
             return;
         }
         if (conn.isFreed()) {
             return;
         }
         switch (connection.engine().getHandshakeStatus()) {
             case NOT_HANDSHAKING:
             case FINISHED:
                 handshakeCompletionNotified = true;
                 pipeline().fireUserEventTriggered(SslHandshakeCompletionEvent.SUCCESS);
                 break;
             default:
                 break;
         }
     }
 
     @Override
     public long peerAllowedStreams(QuicStreamType type) {
         switch (type) {
             case BIDIRECTIONAL:
                 return bidiStreamsLeft;
             case UNIDIRECTIONAL:
                 return uniStreamsLeft;
             default:
                 return 0;
         }
     }
 
     void attachQuicheConnection(QuicheQuicConnection connection) {
         this.connection = connection;
 
         byte[] traceId = Quiche.quiche_conn_trace_id(connection.address());
         if (traceId != null) {
             this.traceId = new String(traceId);
         }
 
         connection.init(local, remote,
                 sniHostname -> pipeline().fireUserEventTriggered(new SniCompletionEvent(sniHostname)));
 
         // Setup QLOG if needed.
         QLogConfiguration configuration = config.getQLogConfiguration();
         if (configuration != null) {
             final String fileName;
             File file = new File(configuration.path());
             if (file.isDirectory()) {
                 // Create directory if needed.
                 file.mkdir();
                 if (this.traceId != null) {
                     fileName = configuration.path() + File.separatorChar + this.traceId + "-" +
                             id().asShortText() + QLOG_FILE_EXTENSION;
                 } else {
                     fileName = configuration.path() + File.separatorChar + id().asShortText() + QLOG_FILE_EXTENSION;
                 }
             } else {
                 fileName = configuration.path();
             }
 
             if (!Quiche.quiche_conn_set_qlog_path(connection.address(), fileName,
                     configuration.logTitle(), configuration.logDescription())) {
                 logger.info("Unable to create qlog file: {} ", fileName);
             }
         }
     }
 
     void connectNow(Function<QuicChannel, ? extends QuicSslEngine> engineProvider, Executor sslTaskExecutor,
                     Consumer<QuicheQuicChannel> freeTask, long configAddr, int localConnIdLength,
                     boolean supportsDatagram, ByteBuffer fromSockaddrMemory, ByteBuffer toSockaddrMemory)
             throws Exception {
         assert this.connection == null;
         assert this.traceId == null;
         assert this.sourceConnectionIds.isEmpty();
 
         this.sslTaskExecutor = sslTaskExecutor;
         this.freeTask = freeTask;
 
         QuicConnectionAddress connectLocalAddress = this.connectLocalAddress;
 
         if (connectLocalAddress == QuicConnectionAddress.EPHEMERAL) {
             connectLocalAddress = QuicConnectionAddress.random(localConnIdLength);
         }
         ByteBuffer localConnectId = connectLocalAddress.id();
         if (localConnectId.remaining() != localConnIdLength) {
             failConnectPromiseAndThrow(new IllegalArgumentException("connectionAddress has length "
                     + localConnectId.remaining()
                     + " instead of " + localConnIdLength));
         }
         QuicConnectionAddress connectRemoteAddress = this.connectRemoteAddress;
 
         QuicSslEngine engine = engineProvider.apply(this);
         if (!(engine instanceof QuicheQuicSslEngine)) {
             failConnectPromiseAndThrow(new IllegalArgumentException("QuicSslEngine is not of type "
                     + QuicheQuicSslEngine.class.getSimpleName()));
             return;
         }
         if (!engine.getUseClientMode()) {
             failConnectPromiseAndThrow(new IllegalArgumentException("QuicSslEngine is not create in client mode"));
         }
         QuicheQuicSslEngine quicheEngine = (QuicheQuicSslEngine) engine;
         ByteBuf localIdBuffer = alloc().directBuffer(localConnectId.remaining()).writeBytes(localConnectId.duplicate());
         ByteBuf remoteIdBuffer;
         if (connectRemoteAddress != QuicConnectionAddress.EPHEMERAL) {
             ByteBuffer remoteId = connectRemoteAddress.id();
             remoteIdBuffer = alloc().directBuffer(remoteId.remaining()).writeBytes(remoteId.duplicate());
         } else {
             remoteIdBuffer = null;
         }
         try {
             int fromSockaddrLen = SockaddrIn.setAddress(fromSockaddrMemory, local);
             int toSockaddrLen = SockaddrIn.setAddress(toSockaddrMemory, remote);
             QuicheQuicConnection connection = quicheEngine.createConnection(ssl -> {
                 long localIdMemoryAddress = Quiche.readerMemoryAddress(localIdBuffer);
                 int localIdLength = localIdBuffer.readableBytes();
 
                 final long remoteIdMemoryAddress;
                 final int remoteIdLength;
                 if (remoteIdBuffer == null) {
                     return Quiche.quiche_conn_new_with_tls(localIdMemoryAddress, localIdLength,
                             -1, -1,
                             Quiche.memoryAddressWithPosition(fromSockaddrMemory), fromSockaddrLen,
                             Quiche.memoryAddressWithPosition(toSockaddrMemory), toSockaddrLen,
                             configAddr, ssl, false);
                 } else {
                     return Quiche.quiche_conn_new_with_tls_and_client_dcid(localIdMemoryAddress, localIdLength,
                             Quiche.readerMemoryAddress(remoteIdBuffer), remoteIdBuffer.readableBytes(),
                             Quiche.memoryAddressWithPosition(fromSockaddrMemory), fromSockaddrLen,
                             Quiche.memoryAddressWithPosition(toSockaddrMemory), toSockaddrLen,
                             configAddr, ssl);
                 }
             });
             if (connection == null) {
                 failConnectPromiseAndThrow(new ConnectException());
                 return;
             }
             attachQuicheConnection(connection);
             QuicClientSessionCache sessionCache = quicheEngine.ctx.getSessionCache();
             if (sessionCache != null) {
                 byte[] sessionBytes = sessionCache
                         .getSession(quicheEngine.getSession().getPeerHost(), quicheEngine.getSession().getPeerPort());
                 if (sessionBytes != null) {
                     Quiche.quiche_conn_set_session(connection.address(), sessionBytes);
                 }
             }
             this.supportsDatagram = supportsDatagram;
             sourceConnectionIds.add(localConnectId);
         } finally {
             localIdBuffer.release();
             if (remoteIdBuffer != null) {
                 remoteIdBuffer.release();
             }
         }
     }
 
     private void failConnectPromiseAndThrow(Exception e) throws Exception {
         tryFailConnectPromise(e);
         throw e;
     }
 
     private boolean tryFailConnectPromise(Exception e) {
         ChannelPromise promise = connectPromise;
         if (promise != null) {
             connectPromise = null;
             promise.tryFailure(e);
             return true;
         }
         return false;
     }
 
     Set<ByteBuffer> sourceConnectionIds() {
         return sourceConnectionIds;
     }
 
     boolean markInFireChannelReadCompleteQueue() {
         if (inFireChannelReadCompleteQueue) {
             return false;
         }
         inFireChannelReadCompleteQueue = true;
         return true;
     }
 
     private void failPendingConnectPromise() {
         ChannelPromise promise = QuicheQuicChannel.this.connectPromise;
         if (promise != null) {
             QuicheQuicChannel.this.connectPromise = null;
             promise.tryFailure(new QuicClosedChannelException(this.connectionCloseEvent));
         }
     }
 
     void forceClose() {
         unsafe().close(voidPromise());
     }
 
     @Override
     protected DefaultChannelPipeline newChannelPipeline() {
         return new DefaultChannelPipeline(this) {
             @Override
             protected void onUnhandledInboundMessage(ChannelHandlerContext ctx, Object msg) {
                 if (msg instanceof QuicStreamChannel) {
                     QuicStreamChannel channel = (QuicStreamChannel) msg;
                     Quic.setupChannel(channel, streamOptionsArray, streamAttrsArray, streamHandler, logger);
                     ctx.channel().eventLoop().register(channel);
                 } else {
                     super.onUnhandledInboundMessage(ctx, msg);
                 }
             }
         };
     }
 
     @Override
     public QuicChannel flush() {
         super.flush();
         return this;
     }
 
     @Override
     public QuicChannel read() {
         super.read();
         return this;
     }
 
     @Override
     public Future<QuicStreamChannel> createStream(QuicStreamType type, @Nullable ChannelHandler handler,
                                                   Promise<QuicStreamChannel> promise) {
         if (eventLoop().inEventLoop()) {
             ((QuicChannelUnsafe) unsafe()).connectStream(type, handler, promise);
         } else {
             eventLoop().execute(() -> ((QuicChannelUnsafe) unsafe()).connectStream(type, handler, promise));
         }
         return promise;
     }
 
     @Override
     public ChannelFuture close(boolean applicationClose, int error, ByteBuf reason, ChannelPromise promise) {
         if (eventLoop().inEventLoop()) {
             close0(applicationClose, error, reason, promise);
         } else {
             eventLoop().execute(() -> close0(applicationClose, error, reason, promise));
         }
         return promise;
     }
 
     private void close0(boolean applicationClose, int error, ByteBuf reason, ChannelPromise promise) {
         if (closeData == null) {
             if (!reason.hasMemoryAddress()) {
                 // Copy to direct buffer as that's what we need.
                 ByteBuf copy = alloc().directBuffer(reason.readableBytes()).writeBytes(reason);
                 reason.release();
                 reason = copy;
             }
             closeData = new CloseData(applicationClose, error, reason);
             promise.addListener(closeData);
         } else {
             // We already have a close scheduled that uses a close data. Lets release the buffer early.
             reason.release();
         }
         close(promise);
     }
 
     @Override
     public String toString() {
         String traceId = this.traceId;
         if (traceId == null) {
             return "()" + super.toString();
         } else {
             return '(' + traceId + ')' + super.toString();
         }
     }
 
     @Override
     protected AbstractUnsafe newUnsafe() {
         return new QuicChannelUnsafe();
     }
 
     @Override
     protected boolean isCompatible(EventLoop eventLoop) {
         return parent().eventLoop() == eventLoop;
     }
 
     @Override
     @Nullable
     protected QuicConnectionAddress localAddress0() {
         QuicheQuicConnection connection = this.connection;
         return connection == null ? null : connection.sourceId();
     }
 
     @Override
     @Nullable
     protected QuicConnectionAddress remoteAddress0() {
         QuicheQuicConnection connection = this.connection;
         return connection == null ? null : connection.destinationId();
     }
 
     @Override
     @Nullable
     public QuicConnectionAddress localAddress() {
         // Override so we never cache as the sourceId() can change over life-time.
         return localAddress0();
     }
 
     @Override
     @Nullable
     public QuicConnectionAddress remoteAddress() {
         // Override so we never cache as the destinationId() can change over life-time.
         return remoteAddress0();
     }
 
     @Override
     @Nullable
     public SocketAddress localSocketAddress() {
         return local;
     }
 
     @Override
     @Nullable
     public SocketAddress remoteSocketAddress() {
         return remote;
     }
 
     @Override
     protected void doBind(SocketAddress socketAddress) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     protected void doDisconnect() throws Exception {
         doClose();
     }
 
     @Override
     protected void doClose() throws Exception {
         if (state == ChannelState.CLOSED) {
             return;
         }
         state = ChannelState.CLOSED;
 
         QuicheQuicConnection conn = this.connection;
         if (conn == null || conn.isFreed()) {
             if (closeData != null) {
                 closeData.reason.release();
                 closeData = null;
             }
             failPendingConnectPromise();
             return;
         }
 
         // Call connectionSend() so we ensure we send all that is queued before we close the channel
         SendResult sendResult = connectionSend(conn);
 
         final boolean app;
         final int err;
         final ByteBuf reason;
         if (closeData == null) {
             app = false;
             err = 0;
             reason = Unpooled.EMPTY_BUFFER;
         } else {
             app = closeData.applicationClose;
             err = closeData.err;
             reason = closeData.reason;
             closeData = null;
         }
 
         failPendingConnectPromise();
         try {
             int res = Quiche.quiche_conn_close(conn.address(), app, err,
                     Quiche.readerMemoryAddress(reason), reason.readableBytes());
             if (res < 0 && res != Quiche.QUICHE_ERR_DONE) {
                 throw Quiche.convertToException(res);
             }
             // As we called quiche_conn_close(...) we need to ensure we will call quiche_conn_send(...) either
             // now or we will do so once we see the channelReadComplete event.
             //
             // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.close
             if (connectionSend(conn) == SendResult.SOME) {
                 sendResult = SendResult.SOME;
             }
         } finally {
 
             // making sure that connection statistics is available
             // even after channel is closed
             statsAtClose = collectStats0(conn, eventLoop().newPromise());
             try {
                 timedOut = Quiche.quiche_conn_is_timed_out(conn.address());
 
                 closeStreams();
                 if (finBuffer != null) {
                     finBuffer.release();
                     finBuffer = null;
                 }
                 if (outErrorCodeBuffer != null) {
                     outErrorCodeBuffer.release();
                     outErrorCodeBuffer = null;
                 }
             } finally {
                 if (sendResult == SendResult.SOME) {
                     // As this is the close let us flush it asap.
                     forceFlushParent();
                 } else {
                     flushParent();
                 }
                 conn.free();
                 if (freeTask != null) {
                     freeTask.accept(this);
                 }
                 timeoutHandler.cancel();
 
                 local = null;
                 remote = null;
             }
         }
     }
 
     @Override
     protected void doBeginRead() {
         recvDatagramPending = true;
         recvStreamPending = true;
         if (datagramReadable || streamReadable) {
             ((QuicChannelUnsafe) unsafe()).recv();
         }
     }
 
     @Override
     protected Object filterOutboundMessage(Object msg) {
         if (msg instanceof ByteBuf) {
             return msg;
         }
         throw new UnsupportedOperationException("Unsupported message type: " + StringUtil.simpleClassName(msg));
     }
 
     @Override
     protected void doWrite(ChannelOutboundBuffer channelOutboundBuffer) throws Exception {
         if (!supportsDatagram) {
             throw new UnsupportedOperationException("Datagram extension is not supported");
         }
         boolean sendSomething = false;
         boolean retry = false;
         QuicheQuicConnection conn = connection;
         try {
             for (;;) {
                 ByteBuf buffer = (ByteBuf) channelOutboundBuffer.current();
                 if (buffer == null) {
                     break;
                 }
 
                 int readable = buffer.readableBytes();
                 if (readable == 0) {
                     // Skip empty buffers.
                     channelOutboundBuffer.remove();
                     continue;
                 }
 
                 final int res;
                 if (!buffer.isDirect() || buffer.nioBufferCount() > 1) {
                     ByteBuf tmpBuffer = alloc().directBuffer(readable);
                     try {
                         tmpBuffer.writeBytes(buffer, buffer.readerIndex(), readable);
                         res = sendDatagram(conn, tmpBuffer);
                     } finally {
                         tmpBuffer.release();
                     }
                 } else {
                     res = sendDatagram(conn, buffer);
                 }
                 if (res >= 0) {
                     channelOutboundBuffer.remove();
                     sendSomething = true;
                     retry = false;
                 } else {
                     if (res == Quiche.QUICHE_ERR_BUFFER_TOO_SHORT) {
                         retry = false;
                         channelOutboundBuffer.remove(new BufferUnderflowException());
                     } else if (res == Quiche.QUICHE_ERR_INVALID_STATE) {
                         throw new UnsupportedOperationException("Remote peer does not support Datagram extension");
                     } else if (res == Quiche.QUICHE_ERR_DONE) {
                         if (retry) {
                             // We already retried and it didn't work. Let's drop the datagrams on the floor.
                             for (;;) {
                                 if (!channelOutboundBuffer.remove()) {
                                     // The buffer is empty now.
                                     return;
                                 }
                             }
                         }
                         // Set sendSomething to false a we will call connectionSend() now.
                         sendSomething = false;
                         // If this returned DONE we couldn't write anymore. This happens if the internal queue
                         // is full. In this case we should call quiche_conn_send(...) and so make space again.
                         if (connectionSend(conn) != SendResult.NONE) {
                             forceFlushParent();
                         }
                         // Let's try again to write the message.
                         retry = true;
                     } else {
                         throw Quiche.convertToException(res);
                     }
                 }
             }
         } finally {
             if (sendSomething && connectionSend(conn) != SendResult.NONE) {
                 flushParent();
             }
         }
     }
 
     private static int sendDatagram(QuicheQuicConnection conn, ByteBuf buf) throws ClosedChannelException {
         return Quiche.quiche_conn_dgram_send(connectionAddressChecked(conn),
                 Quiche.readerMemoryAddress(buf), buf.readableBytes());
     }
 
     @Override
     public QuicChannelConfig config() {
         return config;
     }
 
     @Override
     public boolean isOpen() {
         return state != ChannelState.CLOSED;
     }
 
     @Override
     public boolean isActive() {
         return state == ChannelState.ACTIVE;
     }
 
     @Override
     public ChannelMetadata metadata() {
         return METADATA;
     }
 
     /**
      * This may call {@link #flush()} on the parent channel if needed. The flush may be delayed until the read loop
      * is over.
      */
     private void flushParent() {
         if (!inFireChannelReadCompleteQueue) {
             forceFlushParent();
         }
     }
 
     /**
      * Call {@link #flush()} on the parent channel.
      */
     private void forceFlushParent() {
         parent().flush();
     }
 
     private static long connectionAddressChecked(@Nullable QuicheQuicConnection conn) throws ClosedChannelException {
         if (conn == null || conn.isFreed()) {
             throw new ClosedChannelException();
         }
         return conn.address();
     }
 
     boolean freeIfClosed() {
         QuicheQuicConnection conn = connection;
         if (conn == null || conn.isFreed()) {
             return true;
         }
         if (conn.isClosed()) {
             unsafe().close(newPromise());
             return true;
         }
         return false;
     }
 
     private void closeStreams() {
         if (streams.isEmpty()) {
             return;
         }
         final ClosedChannelException closedChannelException;
         if (isTimedOut()) {
             // Close the streams because of a timeout.
             closedChannelException = new QuicTimeoutClosedChannelException();
         } else {
             closedChannelException = new ClosedChannelException();
         }
         // Make a copy to ensure we not run into a situation when we change the underlying iterator from
         // another method and so run in an assert error.
         for (QuicheQuicStreamChannel stream: streams.values().toArray(new QuicheQuicStreamChannel[0])) {
             stream.unsafe().close(closedChannelException, voidPromise());
         }
         streams.clear();
     }
 
     void streamPriority(long streamId, byte priority, boolean incremental) throws Exception {
        int res = Quiche.quiche_conn_stream_priority(connectionAddressChecked(connection), streamId,
                priority, incremental);
        if (res < 0 && res != Quiche.QUICHE_ERR_DONE) {
            throw Quiche.convertToException(res);
        }
     }
 
     void streamClosed(long streamId) {
         streams.remove(streamId);
     }
 
     boolean isStreamLocalCreated(long streamId) {
         return (streamId & 0x1) == (server ? 1 : 0);
     }
 
     QuicStreamType streamType(long streamId) {
         return (streamId & 0x2) == 0 ? QuicStreamType.BIDIRECTIONAL : QuicStreamType.UNIDIRECTIONAL;
     }
 
     void streamShutdown(long streamId, boolean read, boolean write, int err, ChannelPromise promise) {
         QuicheQuicConnection conn = this.connection;
         final long connectionAddress;
         try {
             connectionAddress = connectionAddressChecked(conn);
         } catch (ClosedChannelException e) {
             promise.setFailure(e);
             return;
         }
         int res = 0;
         if (read) {
             res |= Quiche.quiche_conn_stream_shutdown(connectionAddress, streamId, Quiche.QUICHE_SHUTDOWN_READ, err);
         }
         if (write) {
             res |= Quiche.quiche_conn_stream_shutdown(connectionAddress, streamId, Quiche.QUICHE_SHUTDOWN_WRITE, err);
         }
 
         // As we called quiche_conn_stream_shutdown(...) we need to ensure we will call quiche_conn_send(...) either
         // now or we will do so once we see the channelReadComplete event.
         //
         // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.send
         if (connectionSend(conn) != SendResult.NONE) {
             // Force the flush so the shutdown can be seen asap.
             forceFlushParent();
         }
         if (res < 0 && res != Quiche.QUICHE_ERR_DONE) {
             promise.setFailure(Quiche.convertToException(res));
         } else {
             promise.setSuccess();
         }
     }
 
     void streamSendFin(long streamId) throws Exception {
         QuicheQuicConnection conn = connection;
         try {
             // Just write an empty buffer and set fin to true.
             int res = streamSend0(conn, streamId, Unpooled.EMPTY_BUFFER, true);
             if (res < 0 && res != Quiche.QUICHE_ERR_DONE) {
                 throw Quiche.convertToException(res);
             }
         } finally {
             // As we called quiche_conn_stream_send(...) we need to ensure we will call quiche_conn_send(...) either
             // now or we will do so once we see the channelReadComplete event.
             //
             // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.send
             if (connectionSend(conn) != SendResult.NONE) {
                 flushParent();
             }
         }
     }
 
     int streamSend(long streamId, ByteBuf buffer, boolean fin) throws ClosedChannelException {
         QuicheQuicConnection conn = connection;
         if (buffer.nioBufferCount() == 1) {
             return streamSend0(conn, streamId, buffer, fin);
         }
         ByteBuffer[] nioBuffers  = buffer.nioBuffers();
         int lastIdx = nioBuffers.length - 1;
         int res = 0;
         for (int i = 0; i < lastIdx; i++) {
             ByteBuffer nioBuffer = nioBuffers[i];
             while (nioBuffer.hasRemaining()) {
                 int localRes = streamSend(conn, streamId, nioBuffer, false);
                 if (localRes <= 0) {
                     return res;
                 }
                 res += localRes;
 
                 nioBuffer.position(nioBuffer.position() + localRes);
             }
         }
         int localRes = streamSend(conn, streamId, nioBuffers[lastIdx], fin);
         if (localRes > 0) {
             res += localRes;
         }
         return res;
     }
 
     void connectionSendAndFlush() {
         if (inFireChannelReadCompleteQueue || (reantranceGuard & IN_HANDLE_WRITABLE_STREAMS) != 0) {
             return;
         }
         if (connectionSend(connection) != SendResult.NONE) {
             flushParent();
         }
     }
 
     private int streamSend0(QuicheQuicConnection conn, long streamId, ByteBuf buffer, boolean fin)
             throws ClosedChannelException {
         return Quiche.quiche_conn_stream_send(connectionAddressChecked(conn), streamId,
                 Quiche.readerMemoryAddress(buffer), buffer.readableBytes(), fin);
     }
 
     private int streamSend(QuicheQuicConnection conn, long streamId, ByteBuffer buffer, boolean fin)
             throws ClosedChannelException {
         return Quiche.quiche_conn_stream_send(connectionAddressChecked(conn), streamId,
                 Quiche.memoryAddressWithPosition(buffer), buffer.remaining(), fin);
     }
 
     StreamRecvResult streamRecv(long streamId, ByteBuf buffer) throws Exception {
         QuicheQuicConnection conn = connection;
         long connAddr = connectionAddressChecked(conn);
         if (finBuffer == null) {
             finBuffer = alloc().directBuffer(1);
         }
         if (outErrorCodeBuffer == null) {
             outErrorCodeBuffer = alloc().directBuffer(8);
         }
         outErrorCodeBuffer.setLongLE(0, -1L);
         int writerIndex = buffer.writerIndex();
         int recvLen = Quiche.quiche_conn_stream_recv(connAddr, streamId,
                 Quiche.writerMemoryAddress(buffer), buffer.writableBytes(), Quiche.writerMemoryAddress(finBuffer),
                 Quiche.writerMemoryAddress(outErrorCodeBuffer));
         long errorCode = outErrorCodeBuffer.getLongLE(0);
         if (recvLen == Quiche.QUICHE_ERR_DONE) {
             return StreamRecvResult.DONE;
         } else if (recvLen < 0) {
             throw Quiche.convertToException(recvLen, errorCode);
         }
         buffer.writerIndex(writerIndex + recvLen);
         return finBuffer.getBoolean(0) ? StreamRecvResult.FIN : StreamRecvResult.OK;
     }
 
     /**
      * Receive some data on a QUIC connection.
      */
     void recv(InetSocketAddress sender, InetSocketAddress recipient, ByteBuf buffer) {
         ((QuicChannelUnsafe) unsafe()).connectionRecv(sender, recipient, buffer);
     }
 
     /**
      * Return all source connection ids that are retired and so should be removed to map to the channel.
      *
      * @return retired ids.
      */
     List<ByteBuffer> retiredSourceConnectionId() {
         QuicheQuicConnection connection = this.connection;
         if (connection == null || connection.isFreed()) {
             return Collections.emptyList();
         }
         long connAddr = connection.address();
         assert connAddr != -1;
         List<ByteBuffer> retiredSourceIds = null;
         for (;;) {
             byte[] retired = Quiche.quiche_conn_retired_scid_next(connAddr);
             if (retired == null) {
                 break;
             }
             if (retiredSourceIds == null) {
                 retiredSourceIds = new ArrayList<>();
             }
             ByteBuffer retiredId = ByteBuffer.wrap(retired);
             retiredSourceIds.add(retiredId);
             sourceConnectionIds.remove(retiredId);
         }
         if (retiredSourceIds == null) {
             return Collections.emptyList();
         }
         return retiredSourceIds;
     }
 
     List<ByteBuffer> newSourceConnectionIds() {
         if (connectionIdAddressGenerator != null && resetTokenGenerator != null) {
             QuicheQuicConnection connection = this.connection;
             if (connection == null || connection.isFreed()) {
                 return Collections.emptyList();
             }
             long connAddr = connection.address();
             // Generate all extra source ids that we can provide. This will cause frames that need to be sent. Which
             // is the reason why we might need to call connectionSendAndFlush().
             int left = Quiche.quiche_conn_scids_left(connAddr);
             if (left > 0) {
                 QuicConnectionAddress sourceAddr = connection.sourceId();
                 if (sourceAddr == null) {
                     return Collections.emptyList();
                 }
                 List<ByteBuffer> generatedIds = new ArrayList<>(left);
                 boolean sendAndFlush = false;
                 ByteBuffer key = sourceAddr.id();
                 ByteBuf connIdBuffer = alloc().directBuffer(key.remaining());
 
                 byte[] resetTokenArray = new byte[Quic.RESET_TOKEN_LEN];
                 try {
                     do {
                         ByteBuffer srcId = connectionIdAddressGenerator.newId(key.duplicate(), key.remaining())
                                 .asReadOnlyBuffer();
                         connIdBuffer.clear();
                         connIdBuffer.writeBytes(srcId.duplicate());
                         ByteBuffer resetToken = resetTokenGenerator.newResetToken(srcId.duplicate());
                         resetToken.get(resetTokenArray);
                         long result = Quiche.quiche_conn_new_scid(
                                 connAddr, Quiche.memoryAddress(connIdBuffer, 0, connIdBuffer.readableBytes()),
                                 connIdBuffer.readableBytes(), resetTokenArray, false, -1);
                         if (result < 0) {
                             break;
                         }
                         sendAndFlush = true;
                         generatedIds.add(srcId.duplicate());
                         sourceConnectionIds.add(srcId);
                     } while (--left > 0);
                 } finally {
                     connIdBuffer.release();
                 }
 
                 if (sendAndFlush) {
                     connectionSendAndFlush();
                 }
                 return generatedIds;
             }
         }
         return Collections.emptyList();
     }
 
     void writable() {
         QuicheQuicConnection conn = connection;
         SendResult result = connectionSend(conn);
         handleWritableStreams(conn);
         if (connectionSend(conn) == SendResult.SOME) {
             result = SendResult.SOME;
         }
         if (result == SendResult.SOME) {
             // The writability changed so lets flush as fast as possible.
             forceFlushParent();
         }
         freeIfClosed();
     }
 
     long streamCapacity(long streamId) {
         QuicheQuicConnection conn = connection;
         if (conn.isClosed()) {
             return 0;
         }
         return Quiche.quiche_conn_stream_capacity(conn.address(), streamId);
     }
 
     private boolean handleWritableStreams(QuicheQuicConnection conn) {
         if (conn.isFreed()) {
             return false;
         }
         reantranceGuard |= IN_HANDLE_WRITABLE_STREAMS;
         try {
             long connAddr = conn.address();
             boolean mayNeedWrite = false;
 
             if (Quiche.quiche_conn_is_established(connAddr) ||
                     Quiche.quiche_conn_is_in_early_data(connAddr)) {
                 long writableIterator = Quiche.quiche_conn_writable(connAddr);
 
                 int totalWritable = 0;
                 try {
                     // For streams we always process all streams when at least on read was requested.
                     for (;;) {
                         int writable = Quiche.quiche_stream_iter_next(
                                 writableIterator, writableStreams);
                         for (int i = 0; i < writable; i++) {
                             long streamId = writableStreams[i];
                             QuicheQuicStreamChannel streamChannel = streams.get(streamId);
                             if (streamChannel != null) {
                                 long capacity = Quiche.quiche_conn_stream_capacity(connAddr, streamId);
                                 if (streamChannel.writable(capacity)) {
                                     mayNeedWrite = true;
                                 }
                             }
                         }
                         if (writable > 0) {
                             totalWritable += writable;
                         }
                         if (writable < writableStreams.length) {
                             // We did handle all writable streams.
                             break;
                         }
                     }
                 } finally {
                     Quiche.quiche_stream_iter_free(writableIterator);
                 }
                 writableStreams = growIfNeeded(writableStreams, totalWritable);
             }
             return mayNeedWrite;
         } finally {
             reantranceGuard &= ~IN_HANDLE_WRITABLE_STREAMS;
         }
     }
 
     /**
      * Called once we receive a channelReadComplete event. This method will take care of calling
      * {@link ChannelPipeline#fireChannelReadComplete()} if needed and also to handle pending flushes of
      * writable {@link QuicheQuicStreamChannel}s.
      */
     void recvComplete() {
         try {
             QuicheQuicConnection conn = connection;
             if (conn.isFreed()) {
                 // Ensure we flush all pending writes.
                 forceFlushParent();
                 return;
             }
             fireChannelReadCompleteIfNeeded();
 
             // If we had called recv we need to ensure we call send as well.
             // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.send
             connectionSend(conn);
 
             // We are done with the read loop, flush all pending writes now.
             forceFlushParent();
             freeIfClosed();
         } finally {
             inFireChannelReadCompleteQueue = false;
         }
     }
 
     private void fireChannelReadCompleteIfNeeded() {
         if (fireChannelReadCompletePending) {
             fireChannelReadCompletePending = false;
             pipeline().fireChannelReadComplete();
         }
     }
 
     private void fireExceptionEvents(QuicheQuicConnection conn, Throwable cause) {
         if (cause instanceof SSLHandshakeException) {
             notifyAboutHandshakeCompletionIfNeeded(conn, (SSLHandshakeException) cause);
         }
         pipeline().fireExceptionCaught(cause);
     }
 
     private boolean runTasksDirectly() {
         return sslTaskExecutor == null || sslTaskExecutor == ImmediateExecutor.INSTANCE ||
                 sslTaskExecutor == ImmediateEventExecutor.INSTANCE;
     }
 
     private void runAllTaskSend(QuicheQuicConnection conn, Runnable task) {
         sslTaskExecutor.execute(decorateTaskSend(conn, task));
     }
 
     private void runAll(QuicheQuicConnection conn, Runnable task) {
         do {
             task.run();
         } while ((task = conn.sslTask()) != null);
     }
 
     private Runnable decorateTaskSend(QuicheQuicConnection conn, Runnable task) {
         return () -> {
             try {
                 runAll(conn, task);
             } finally {
                 // Move back to the EventLoop.
                 eventLoop().execute(() -> {
                     // Call connection send to continue handshake if needed.
                     if (connectionSend(conn) != SendResult.NONE) {
                         forceFlushParent();
                     }
                     freeIfClosed();
                 });
             }
         };
     }
 
     private SendResult connectionSendSegments(QuicheQuicConnection conn,
                                               SegmentedDatagramPacketAllocator segmentedDatagramPacketAllocator) {
         if (conn.isClosed()) {
             return SendResult.NONE;
         }
         List<ByteBuf> bufferList = new ArrayList<>(segmentedDatagramPacketAllocator.maxNumSegments());
         long connAddr = conn.address();
         int maxDatagramSize = Quiche.quiche_conn_max_send_udp_payload_size(connAddr);
         SendResult sendResult = SendResult.NONE;
         boolean close = false;
         try {
             for (;;) {
                 int len = calculateSendBufferLength(connAddr, maxDatagramSize);
                 ByteBuf out = alloc().directBuffer(len);
 
                 ByteBuffer sendInfo = conn.nextSendInfo();
                 InetSocketAddress sendToAddress = this.remote;
 
                 int writerIndex = out.writerIndex();
                 int written = Quiche.quiche_conn_send(
                         connAddr, Quiche.writerMemoryAddress(out), out.writableBytes(),
                         Quiche.memoryAddressWithPosition(sendInfo));
                 if (written == 0) {
                     out.release();
                     // No need to create a new datagram packet. Just try again.
                     continue;
                 }
                 final boolean done;
                 if (written < 0) {
                     done = true;
                     if (written != Quiche.QUICHE_ERR_DONE) {
                         close = Quiche.shouldClose(written);
                         Exception e = Quiche.convertToException(written);
                         if (!tryFailConnectPromise(e)) {
                             // Only fire through the pipeline if this does not fail the connect promise.
                             fireExceptionEvents(conn, e);
                         }
                     }
                 } else {
                     done = false;
                 }
                 int size = bufferList.size();
                 if (done) {
                     // We are done, release the buffer and send what we did build up so far.
                     out.release();
 
                     switch (size) {
                         case 0:
                             // Nothing more to write.
                             break;
                         case 1:
                             // We can write a normal datagram packet.
                             parent().write(new DatagramPacket(bufferList.get(0), sendToAddress));
                             sendResult = SendResult.SOME;
                             break;
                         default:
                             int segmentSize = segmentSize(bufferList);
                             ByteBuf compositeBuffer = Unpooled.wrappedBuffer(bufferList.toArray(new ByteBuf[0]));
                             // We had more than one buffer, create a segmented packet.
                             parent().write(segmentedDatagramPacketAllocator.newPacket(
                                     compositeBuffer, segmentSize, sendToAddress));
                             sendResult = SendResult.SOME;
                             break;
                     }
                     bufferList.clear();
                     if (close) {
                         sendResult = SendResult.CLOSE;
                     }
                     return sendResult;
                 }
                 out.writerIndex(writerIndex + written);
 
                 int segmentSize = -1;
                 if (conn.isSendInfoChanged()) {
                     // Change the cached address and let the user know there was a connection migration.
                     remote = QuicheSendInfo.getToAddress(sendInfo);
                     local = QuicheSendInfo.getFromAddress(sendInfo);
 
                     if (size > 0) {
                         // We have something in the out list already, we need to send this now and so we set the
                         // segmentSize.
                         segmentSize = segmentSize(bufferList);
                     }
                 } else if (size > 0) {
                     int lastReadable = segmentSize(bufferList);
                     // Check if we either need to send now because the last buffer we added has a smaller size then this
                     // one or if we reached the maximum number of segments that we can send.
                     if (lastReadable != out.readableBytes() ||
                             size == segmentedDatagramPacketAllocator.maxNumSegments()) {
                         segmentSize = lastReadable;
                     }
                 }
 
                 // If the segmentSize is not -1 we know we need to send now what was in the out list.
                 if (segmentSize != -1) {
                     final boolean stop;
                     if (size == 1) {
                         // Only one buffer in the out list, there is no need to use segments.
                         stop = writePacket(new DatagramPacket(
                                 bufferList.get(0), sendToAddress), maxDatagramSize, len);
                     } else {
                         // Create a packet with segments in.
                         ByteBuf compositeBuffer = Unpooled.wrappedBuffer(bufferList.toArray(new ByteBuf[0]));
                         stop = writePacket(segmentedDatagramPacketAllocator.newPacket(
                                 compositeBuffer, segmentSize, sendToAddress), maxDatagramSize, len);
                     }
                     bufferList.clear();
                     sendResult = SendResult.SOME;
 
                     if (stop) {
                         // Nothing left in the window, continue later. That said we still need to also
                         // write the previous filled out buffer as otherwise we would either leak or need
                         // to drop it and so produce some loss.
                         if (out.isReadable()) {
                             parent().write(new DatagramPacket(out, sendToAddress));
                         } else {
                             out.release();
                         }
                         if (close) {
                             sendResult = SendResult.CLOSE;
                         }
                         return sendResult;
                     }
                 }
                 // Let's add a touch with the bufferList as a hint. This will help us to debug leaks if there
                 // are any.
                 out.touch(bufferList);
                 // store for later, so we can make use of segments.
                 bufferList.add(out);
             }
         } finally {
             // NOOP
         }
     }
 
     private static int segmentSize(List<ByteBuf> bufferList) {
         assert !bufferList.isEmpty();
         int size = bufferList.size();
         return bufferList.get(size - 1).readableBytes();
     }
 
     private SendResult connectionSendSimple(QuicheQuicConnection conn) {
         if (conn.isClosed()) {
             return SendResult.NONE;
         }
         long connAddr = conn.address();
         SendResult sendResult = SendResult.NONE;
         boolean close = false;
         int maxDatagramSize = Quiche.quiche_conn_max_send_udp_payload_size(connAddr);
         for (;;) {
             ByteBuffer sendInfo = conn.nextSendInfo();
 
             int len = calculateSendBufferLength(connAddr, maxDatagramSize);
             ByteBuf out = alloc().directBuffer(len);
             int writerIndex = out.writerIndex();
 
             int written = Quiche.quiche_conn_send(
                     connAddr, Quiche.writerMemoryAddress(out), out.writableBytes(),
                     Quiche.memoryAddressWithPosition(sendInfo));
 
             if (written == 0) {
                 // No need to create a new datagram packet. Just release and try again.
                 out.release();
                 continue;
             }
             if (written < 0) {
                 out.release();
                 if (written != Quiche.QUICHE_ERR_DONE) {
                     close = Quiche.shouldClose(written);
 
                     Exception e = Quiche.convertToException(written);
                     if (!tryFailConnectPromise(e)) {
                         fireExceptionEvents(conn, e);
                     }
                 }
                 break;
             }
             if (conn.isSendInfoChanged()) {
                 // Change the cached address
                 remote = QuicheSendInfo.getToAddress(sendInfo);
                 local = QuicheSendInfo.getFromAddress(sendInfo);
             }
             out.writerIndex(writerIndex + written);
             boolean stop = writePacket(new DatagramPacket(out, remote), maxDatagramSize, len);
             sendResult = SendResult.SOME;
             if (stop) {
                 // Nothing left in the window, continue later
                 break;
             }
         }
         if (close) {
             sendResult = SendResult.CLOSE;
         }
         return sendResult;
     }
 
     private boolean writePacket(DatagramPacket packet, int maxDatagramSize, int len) {
         ChannelFuture future = parent().write(packet);
         if (isSendWindowUsed(maxDatagramSize, len)) {
             // Nothing left in the window, continue later
             future.addListener(continueSendingListener);
             return true;
         }
         return false;
     }
 
     private static boolean isSendWindowUsed(int maxDatagramSize, int len) {
         return len < maxDatagramSize;
     }
 
     private static int calculateSendBufferLength(long connAddr, int maxDatagramSize) {
         int len = Math.min(maxDatagramSize, Quiche.quiche_conn_send_quantum(connAddr));
         if (len <= 0) {
             // If there is no room left we just return some small number to reduce the risk of packet drop
             // while still be able to attach the listener to the write future.
             // We use the value of 8 because such an allocation will be cheap to serve from the
             // PooledByteBufAllocator while still serve our need.
             return 8;
         }
         return len;
     }
 
     /**
      * Write datagrams if needed and return {@code true} if something was written and we need to call
      * {@link Channel#flush()} at some point.
      */
     private SendResult connectionSend(QuicheQuicConnection conn) {
         if (conn.isFreed()) {
             return SendResult.NONE;
         }
         if ((reantranceGuard & IN_CONNECTION_SEND) != 0) {
             // Let's notify about early data if needed.
             notifyEarlyDataReadyIfNeeded(conn);
             return SendResult.NONE;
         }
 
         reantranceGuard |= IN_CONNECTION_SEND;
         try {
             SendResult sendResult;
             SegmentedDatagramPacketAllocator segmentedDatagramPacketAllocator =
                     config.getSegmentedDatagramPacketAllocator();
             if (segmentedDatagramPacketAllocator.maxNumSegments() > 0) {
                 sendResult = connectionSendSegments(conn, segmentedDatagramPacketAllocator);
             } else {
                 sendResult = connectionSendSimple(conn);
             }
 
             // Process / schedule all tasks that were created.
 
             Runnable task = conn.sslTask();
             if (task != null) {
                 if (runTasksDirectly()) {
                     // Consume all tasks
                     do {
                         task.run();
                         // Notify about early data ready if needed.
                         notifyEarlyDataReadyIfNeeded(conn);
                     } while ((task = conn.sslTask()) != null);
 
                     // Let's try again sending after we did process all tasks.
                     // We schedule this on the EventLoop as otherwise we will get into trouble with re-entrance.
                     eventLoop().execute(new Runnable() {
                         @Override
                         public void run() {
                             // Call connection send to continue handshake if needed.
                             if (connectionSend(conn) != SendResult.NONE) {
                                 forceFlushParent();
                             }
                             freeIfClosed();
                         }
                     });
                 } else {
                     runAllTaskSend(conn, task);
                 }
             } else {
                 // Notify about early data ready if needed.
                 notifyEarlyDataReadyIfNeeded(conn);
             }
 
             // Whenever we called connection_send we should also schedule the timer if needed.
             timeoutHandler.scheduleTimeout();
             return sendResult;
         } finally {
             reantranceGuard &= ~IN_CONNECTION_SEND;
         }
     }
 
     private final class QuicChannelUnsafe extends AbstractChannel.AbstractUnsafe {
 
         void connectStream(QuicStreamType type, @Nullable ChannelHandler handler,
                            Promise<QuicStreamChannel> promise) {
             if (!promise.setUncancellable()) {
                 return;
             }
             long streamId = idGenerator.nextStreamId(type == QuicStreamType.BIDIRECTIONAL);
 
             try {
                 int res = streamSend0(connection, streamId, Unpooled.EMPTY_BUFFER, false);
                 if (res < 0 && res != Quiche.QUICHE_ERR_DONE) {
                     throw Quiche.convertToException(res);
                 }
             } catch (Exception e) {
                 promise.setFailure(e);
                 return;
             }
             if (type == QuicStreamType.UNIDIRECTIONAL) {
                 UNI_STREAMS_LEFT_UPDATER.decrementAndGet(QuicheQuicChannel.this);
             } else {
                 BIDI_STREAMS_LEFT_UPDATER.decrementAndGet(QuicheQuicChannel.this);
             }
             QuicheQuicStreamChannel streamChannel = addNewStreamChannel(streamId);
             if (handler != null) {
                 streamChannel.pipeline().addLast(handler);
             }
             eventLoop().register(streamChannel).addListener((ChannelFuture f) -> {
                 if (f.isSuccess()) {
                     promise.setSuccess(streamChannel);
                 } else {
                     promise.setFailure(f.cause());
                     streams.remove(streamId);
                 }
             });
         }
 
         @Override
         public void connect(SocketAddress remote, SocketAddress local, ChannelPromise channelPromise) {
             assert eventLoop().inEventLoop();
             if (!channelPromise.setUncancellable()) {
                 return;
             }
             if (server) {
                 channelPromise.setFailure(new UnsupportedOperationException());
                 return;
             }
 
             if (connectPromise != null) {
                 channelPromise.setFailure(new ConnectionPendingException());
                 return;
             }
 
             if (remote instanceof QuicConnectionAddress) {
                 if (!sourceConnectionIds.isEmpty()) {
                     // If a key is assigned we know this channel was already connected.
                     channelPromise.setFailure(new AlreadyConnectedException());
                     return;
                 }
 
                 connectLocalAddress = (QuicConnectionAddress) local;
                 connectRemoteAddress = (QuicConnectionAddress) remote;
                 connectPromise = channelPromise;
 
                 // Schedule connect timeout.
                 int connectTimeoutMillis = config().getConnectTimeoutMillis();
                 if (connectTimeoutMillis > 0) {
                     connectTimeoutFuture = eventLoop().schedule(() -> {
                         ChannelPromise connectPromise = QuicheQuicChannel.this.connectPromise;
                         if (connectPromise != null && !connectPromise.isDone()
                                 && connectPromise.tryFailure(new ConnectTimeoutException(
                                 "connection timed out: " + local + " -> " +  remote))) {
                             close(voidPromise());
                         }
                     }, connectTimeoutMillis, TimeUnit.MILLISECONDS);
                 }
 
                 connectPromise.addListener((ChannelFuture future) -> {
                     if (future.isCancelled()) {
                         if (connectTimeoutFuture != null) {
                             connectTimeoutFuture.cancel(false);
                         }
                         connectPromise = null;
                         close(voidPromise());
                     }
                 });
 
                 parent().connect(new QuicheQuicChannelAddress(QuicheQuicChannel.this))
                         .addListener(f -> {
                             ChannelPromise connectPromise = QuicheQuicChannel.this.connectPromise;
                             if (connectPromise != null && !f.isSuccess()) {
                                 connectPromise.tryFailure(f.cause());
                                 // close everything after notify about failure.
                                 unsafe().closeForcibly();
                             }
                         });
                 return;
             }
 
             channelPromise.setFailure(new UnsupportedOperationException());
         }
 
         private void fireConnectCloseEventIfNeeded(QuicheQuicConnection conn) {
             if (connectionCloseEvent == null && !conn.isFreed()) {
                 connectionCloseEvent = Quiche.quiche_conn_peer_error(conn.address());
                 if (connectionCloseEvent != null) {
                     pipeline().fireUserEventTriggered(connectionCloseEvent);
                 }
             }
         }
 
         void connectionRecv(InetSocketAddress sender, InetSocketAddress recipient, ByteBuf buffer) {
             QuicheQuicConnection conn = QuicheQuicChannel.this.connection;
             if (conn.isFreed()) {
                 return;
             }
             int bufferReadable = buffer.readableBytes();
             if (bufferReadable == 0) {
                 // Nothing to do here. Just return...
                 // See also https://github.com/cloudflare/quiche/issues/817
                 return;
             }
 
             reantranceGuard |= IN_RECV;
             boolean close = false;
             try {
                 ByteBuf tmpBuffer = null;
                 // We need to make a copy if the buffer is read only as recv(...) may modify the input buffer as well.
                 // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.recv
                 if (buffer.isReadOnly()) {
                     tmpBuffer = alloc().directBuffer(buffer.readableBytes());
                     tmpBuffer.writeBytes(buffer);
                     buffer = tmpBuffer;
                 }
                 long memoryAddress = Quiche.readerMemoryAddress(buffer);
 
                 ByteBuffer recvInfo = conn.nextRecvInfo();
                 QuicheRecvInfo.setRecvInfo(recvInfo, sender, recipient);
 
                 remote = sender;
                 local = recipient;
 
                 try {
                     do  {
                         // Call quiche_conn_recv(...) until we consumed all bytes or we did receive some error.
                         int res = Quiche.quiche_conn_recv(conn.address(), memoryAddress, bufferReadable,
                                 Quiche.memoryAddressWithPosition(recvInfo));
                         final boolean done;
                         if (res < 0) {
                             done = true;
                             if (res != Quiche.QUICHE_ERR_DONE) {
                                 close = Quiche.shouldClose(res);
                                 Exception e = Quiche.convertToException(res);
                                 if (tryFailConnectPromise(e)) {
                                     break;
                                 }
                                 fireExceptionEvents(conn, e);
                             }
                         } else {
                             done = false;
                         }
                         // Process / schedule all tasks that were created.
                         Runnable task = conn.sslTask();
                         if (task != null) {
                             if (runTasksDirectly()) {
                                 // Consume all tasks
                                 do {
                                     task.run();
                                 } while ((task = conn.sslTask()) != null);
                                 processReceived(conn);
                             } else {
                                 runAllTaskRecv(conn, task);
                             }
                         } else {
                             processReceived(conn);
                         }
 
                         if (done) {
                             break;
                         }
                         memoryAddress += res;
                         bufferReadable -= res;
                     } while (bufferReadable > 0 && !conn.isFreed());
                 } finally {
                     buffer.skipBytes((int) (memoryAddress - Quiche.readerMemoryAddress(buffer)));
                     if (tmpBuffer != null) {
                         tmpBuffer.release();
                     }
                 }
                 if (close) {
                     // Let's close now as there is no way to recover
                     unsafe().close(newPromise());
                 }
             } finally {
                 reantranceGuard &= ~IN_RECV;
             }
         }
 
         private void processReceived(QuicheQuicConnection conn) {
             // Handle pending channelActive if needed.
             if (handlePendingChannelActive(conn)) {
                 // Connection was closed right away.
                 return;
             }
 
             notifyAboutHandshakeCompletionIfNeeded(conn, null);
             fireConnectCloseEventIfNeeded(conn);
 
             if (conn.isFreed()) {
                 return;
             }
 
             long connAddr = conn.address();
             if (Quiche.quiche_conn_is_established(connAddr) ||
                     Quiche.quiche_conn_is_in_early_data(connAddr)) {
                 long uniLeftOld = uniStreamsLeft;
                 long bidiLeftOld = bidiStreamsLeft;
                 // Only fetch new stream info when we used all our credits
                 if (uniLeftOld == 0 || bidiLeftOld == 0) {
                     long uniLeft = Quiche.quiche_conn_peer_streams_left_uni(connAddr);
                     long bidiLeft = Quiche.quiche_conn_peer_streams_left_bidi(connAddr);
                     uniStreamsLeft = uniLeft;
                     bidiStreamsLeft = bidiLeft;
                     if (uniLeftOld != uniLeft || bidiLeftOld != bidiLeft) {
                         pipeline().fireUserEventTriggered(QuicStreamLimitChangedEvent.INSTANCE);
                     }
                 }
 
                 handlePathEvents(conn);
 
                 if (handleWritableStreams(conn)) {
                     // Some data was produced, let's flush.
                     flushParent();
                 }
 
                 datagramReadable = true;
                 streamReadable = true;
 
                 recvDatagram(conn);
                 recvStream(conn);
             }
         }
 
         private void handlePathEvents(QuicheQuicConnection conn) {
             long event;
             while (!conn.isFreed() && (event = Quiche.quiche_conn_path_event_next(conn.address())) > 0) {
                 try {
                     int type = Quiche.quiche_path_event_type(event);
 
                     if (type == Quiche.QUICHE_PATH_EVENT_NEW) {
                         Object[] ret = Quiche.quiche_path_event_new(event);
                         InetSocketAddress local = (InetSocketAddress) ret[0];
                         InetSocketAddress peer = (InetSocketAddress) ret[1];
                         pipeline().fireUserEventTriggered(new QuicPathEvent.New(local, peer));
                     } else if (type == Quiche.QUICHE_PATH_EVENT_VALIDATED) {
                         Object[] ret = Quiche.quiche_path_event_validated(event);
                         InetSocketAddress local = (InetSocketAddress) ret[0];
                         InetSocketAddress peer = (InetSocketAddress) ret[1];
                         pipeline().fireUserEventTriggered(new QuicPathEvent.Validated(local, peer));
                     } else if (type == Quiche.QUICHE_PATH_EVENT_FAILED_VALIDATION) {
                         Object[] ret = Quiche.quiche_path_event_failed_validation(event);
                         InetSocketAddress local = (InetSocketAddress) ret[0];
                         InetSocketAddress peer = (InetSocketAddress) ret[1];
                         pipeline().fireUserEventTriggered(new QuicPathEvent.FailedValidation(local, peer));
                     } else if (type == Quiche.QUICHE_PATH_EVENT_CLOSED) {
                         Object[] ret = Quiche.quiche_path_event_closed(event);
                         InetSocketAddress local = (InetSocketAddress) ret[0];
                         InetSocketAddress peer = (InetSocketAddress) ret[1];
                         pipeline().fireUserEventTriggered(new QuicPathEvent.Closed(local, peer));
                     } else if (type == Quiche.QUICHE_PATH_EVENT_REUSED_SOURCE_CONNECTION_ID) {
                         Object[] ret = Quiche.quiche_path_event_reused_source_connection_id(event);
                         Long seq = (Long) ret[0];
                         InetSocketAddress localOld = (InetSocketAddress) ret[1];
                         InetSocketAddress peerOld = (InetSocketAddress) ret[2];
                         InetSocketAddress local = (InetSocketAddress) ret[3];
                         InetSocketAddress peer = (InetSocketAddress) ret[4];
                         pipeline().fireUserEventTriggered(
                                 new QuicPathEvent.ReusedSourceConnectionId(seq, localOld, peerOld, local, peer));
                     } else if (type == Quiche.QUICHE_PATH_EVENT_PEER_MIGRATED) {
                         Object[] ret = Quiche.quiche_path_event_peer_migrated(event);
                         InetSocketAddress local = (InetSocketAddress) ret[0];
                         InetSocketAddress peer = (InetSocketAddress) ret[1];
                         pipeline().fireUserEventTriggered(new QuicPathEvent.PeerMigrated(local, peer));
                     }
                 } finally {
                     Quiche.quiche_path_event_free(event);
                 }
             }
         }
 
         private void runAllTaskRecv(QuicheQuicConnection conn, Runnable task) {
             sslTaskExecutor.execute(decorateTaskRecv(conn, task));
         }
 
         private Runnable decorateTaskRecv(QuicheQuicConnection conn, Runnable task) {
             return () -> {
                 try {
                     runAll(conn, task);
                 } finally {
                     // Move back to the EventLoop.
                     eventLoop().execute(() -> {
                         if (!conn.isFreed()) {
                             processReceived(conn);
 
                             // Call connection send to continue handshake if needed.
                             if (connectionSend(conn) != SendResult.NONE) {
                                 forceFlushParent();
                             }
 
                             freeIfClosed();
                         }
                     });
                 }
             };
         }
         void recv() {
             QuicheQuicConnection conn = connection;
             if ((reantranceGuard & IN_RECV) != 0 || conn.isFreed()) {
                 return;
             }
 
             long connAddr = conn.address();
             // Check if we can read anything yet.
             if (!Quiche.quiche_conn_is_established(connAddr) &&
                     !Quiche.quiche_conn_is_in_early_data(connAddr)) {
                 return;
             }
 
             reantranceGuard |= IN_RECV;
             try {
                 recvDatagram(conn);
                 recvStream(conn);
             } finally {
                 fireChannelReadCompleteIfNeeded();
                 reantranceGuard &= ~IN_RECV;
             }
         }
 
         private void recvStream(QuicheQuicConnection conn) {
             if (conn.isFreed()) {
                 return;
             }
             long connAddr = conn.address();
             long readableIterator = Quiche.quiche_conn_readable(connAddr);
             int totalReadable = 0;
             if (readableIterator != -1) {
                 try {
                     // For streams we always process all streams when at least on read was requested.
                     if (recvStreamPending && streamReadable) {
                         for (;;) {
                             int readable = Quiche.quiche_stream_iter_next(
                                     readableIterator, readableStreams);
                             for (int i = 0; i < readable; i++) {
                                 long streamId = readableStreams[i];
                                 QuicheQuicStreamChannel streamChannel = streams.get(streamId);
                                 if (streamChannel == null) {
                                     recvStreamPending = false;
                                     fireChannelReadCompletePending = true;
                                     streamChannel = addNewStreamChannel(streamId);
                                     streamChannel.readable();
                                     pipeline().fireChannelRead(streamChannel);
                                 } else {
                                     streamChannel.readable();
                                 }
                             }
                             if (readable < readableStreams.length) {
                                 // We did consume all readable streams.
                                 streamReadable = false;
                                 break;
                             }
                             if (readable > 0) {
                                 totalReadable += readable;
                             }
                         }
                     }
                 } finally {
                     Quiche.quiche_stream_iter_free(readableIterator);
                 }
                 readableStreams = growIfNeeded(readableStreams, totalReadable);
             }
         }
 
         private void recvDatagram(QuicheQuicConnection conn) {
             if (!supportsDatagram) {
                 return;
             }
             while (recvDatagramPending && datagramReadable && !conn.isFreed()) {
                 @SuppressWarnings("deprecation")
                 RecvByteBufAllocator.Handle recvHandle = recvBufAllocHandle();
                 recvHandle.reset(config());
 
                 int numMessagesRead = 0;
                 do {
                     long connAddr = conn.address();
                     int len = Quiche.quiche_conn_dgram_recv_front_len(connAddr);
                     if (len == Quiche.QUICHE_ERR_DONE) {
                         datagramReadable = false;
                         return;
                     }
 
                     ByteBuf datagramBuffer = alloc().directBuffer(len);
                     recvHandle.attemptedBytesRead(datagramBuffer.writableBytes());
                     int writerIndex = datagramBuffer.writerIndex();
                     long memoryAddress = Quiche.writerMemoryAddress(datagramBuffer);
 
                     int written = Quiche.quiche_conn_dgram_recv(connAddr,
                             memoryAddress, datagramBuffer.writableBytes());
                     if (written < 0) {
                         datagramBuffer.release();
                         if (written == Quiche.QUICHE_ERR_DONE) {
                             // We did consume all datagram packets.
                             datagramReadable = false;
                             break;
                         }
                         pipeline().fireExceptionCaught(Quiche.convertToException(written));
                     }
                     recvHandle.lastBytesRead(written);
                     recvHandle.incMessagesRead(1);
                     numMessagesRead++;
                     datagramBuffer.writerIndex(writerIndex + written);
                     recvDatagramPending = false;
                     fireChannelReadCompletePending = true;
 
                     pipeline().fireChannelRead(datagramBuffer);
                 } while (recvHandle.continueReading() && !conn.isFreed());
                 recvHandle.readComplete();
 
                 // Check if we produced any messages.
                 if (numMessagesRead > 0) {
                     fireChannelReadCompleteIfNeeded();
                 }
             }
         }
 
         private boolean handlePendingChannelActive(QuicheQuicConnection conn) {
             if (conn.isFreed() || state == ChannelState.CLOSED) {
                 return true;
             }
             if (server) {
                 if (state == ChannelState.OPEN && Quiche.quiche_conn_is_established(conn.address())) {
                     // We didn't notify before about channelActive... Update state and fire the event.
                     state = ChannelState.ACTIVE;
 
                     fireDatagramExtensionEvent(conn);
                     pipeline().fireChannelActive();
                     notifyAboutHandshakeCompletionIfNeeded(conn, null);
                 }
             } else if (connectPromise != null && Quiche.quiche_conn_is_established(conn.address())) {
                 ChannelPromise promise = connectPromise;
                 connectPromise = null;
                 state = ChannelState.ACTIVE;
 
                 boolean promiseSet = promise.trySuccess();
                 fireDatagramExtensionEvent(conn);
                 pipeline().fireChannelActive();
                 notifyAboutHandshakeCompletionIfNeeded(conn, null);
                 if (!promiseSet) {
                     fireConnectCloseEventIfNeeded(conn);
                     this.close(this.voidPromise());
                     return true;
                 }
             }
             return false;
         }
 
         private void fireDatagramExtensionEvent(QuicheQuicConnection conn) {
             if (conn.isClosed()) {
                 return;
             }
             long connAddr = conn.address();
             int len = Quiche.quiche_conn_dgram_max_writable_len(connAddr);
             // QUICHE_ERR_DONE means the remote peer does not support the extension.
             if (len != Quiche.QUICHE_ERR_DONE) {
                 pipeline().fireUserEventTriggered(new QuicDatagramExtensionEvent(len));
             }
         }
 
         private QuicheQuicStreamChannel addNewStreamChannel(long streamId) {
             QuicheQuicStreamChannel streamChannel = new QuicheQuicStreamChannel(
                     QuicheQuicChannel.this, streamId);
             QuicheQuicStreamChannel old = streams.put(streamId, streamChannel);
             assert old == null;
             streamChannel.writable(streamCapacity(streamId));
             return streamChannel;
         }
     }
 
     /**
      * Finish the connect operation of a client channel.
      */
     void finishConnect() {
         assert !server;
         assert connection != null;
         if (connectionSend(connection) != SendResult.NONE) {
             flushParent();
         }
     }
 
     private void notifyEarlyDataReadyIfNeeded(QuicheQuicConnection conn) {
         if (!server && !earlyDataReadyNotified &&
                 !conn.isFreed() && Quiche.quiche_conn_is_in_early_data(conn.address())) {
             earlyDataReadyNotified = true;
             pipeline().fireUserEventTriggered(SslEarlyDataReadyEvent.INSTANCE);
         }
     }
 
     private final class TimeoutHandler implements Runnable {
         private ScheduledFuture<?> timeoutFuture;
 
         @Override
         public void run() {
             QuicheQuicConnection conn = connection;
             if (conn.isFreed()) {
                 return;
             }
             if (!freeIfClosed()) {
                 long connAddr = conn.address();
                 timeoutFuture = null;
                 // Notify quiche there was a timeout.
                 Quiche.quiche_conn_on_timeout(connAddr);
                 if (!freeIfClosed()) {
                     // We need to call connectionSend when a timeout was triggered.
                     // See https://docs.rs/quiche/0.6.0/quiche/struct.Connection.html#method.send.
                     if (connectionSend(conn) != SendResult.NONE) {
                         flushParent();
                     }
                     boolean closed = freeIfClosed();
                     if (!closed) {
                         // The connection is alive, reschedule.
                         scheduleTimeout();
                     }
                 }
             }
         }
 
         // Schedule timeout.
         // See https://docs.rs/quiche/0.6.0/quiche/#generating-outgoing-packets
         void scheduleTimeout() {
             QuicheQuicConnection conn = connection;
             if (conn.isFreed()) {
                 cancel();
                 return;
             }
             if (conn.isClosed()) {
                 cancel();
                 unsafe().close(newPromise());
                 return;
             }
             long nanos = Quiche.quiche_conn_timeout_as_nanos(conn.address());
             if (nanos < 0 || nanos == Long.MAX_VALUE) {
                 // No timeout needed.
                 cancel();
                 return;
             }
             if (timeoutFuture == null) {
                 timeoutFuture = eventLoop().schedule(this,
                         nanos, TimeUnit.NANOSECONDS);
             } else {
                 long remaining = timeoutFuture.getDelay(TimeUnit.NANOSECONDS);
                 if (remaining <= 0) {
                     // This means the timer already elapsed. In this case just cancel the future and call run()
                     // directly. This will ensure we correctly call quiche_conn_on_timeout() etc.
                     cancel();
                     run();
                 } else if (remaining > nanos) {
                     // The new timeout is smaller then what was scheduled before. Let's cancel the old timeout
                     // and schedule a new one.
                     cancel();
                     timeoutFuture = eventLoop().schedule(this, nanos, TimeUnit.NANOSECONDS);
                 }
             }
         }
 
         void cancel() {
             if (timeoutFuture != null) {
                 timeoutFuture.cancel(false);
                 timeoutFuture = null;
             }
         }
     }
 
     @Override
     public Future<QuicConnectionStats> collectStats(Promise<QuicConnectionStats> promise) {
         if (eventLoop().inEventLoop()) {
             collectStats0(promise);
         } else {
             eventLoop().execute(() -> collectStats0(promise));
         }
         return promise;
     }
 
     private void collectStats0(Promise<QuicConnectionStats> promise) {
         QuicheQuicConnection conn = connection;
         if (conn.isFreed()) {
             promise.setSuccess(statsAtClose);
             return;
         }
 
         collectStats0(connection, promise);
     }
 
     @Nullable
     private QuicConnectionStats collectStats0(QuicheQuicConnection connection, Promise<QuicConnectionStats> promise) {
         final long[] stats = Quiche.quiche_conn_stats(connection.address());
         if (stats == null) {
             promise.setFailure(new IllegalStateException("native quiche_conn_stats(...) failed"));
             return null;
         }
 
         final QuicheQuicConnectionStats connStats =
             new QuicheQuicConnectionStats(stats);
         promise.setSuccess(connStats);
         return connStats;
     }
 
     @Override
     public Future<QuicConnectionPathStats> collectPathStats(int pathIdx, Promise<QuicConnectionPathStats> promise) {
         if (eventLoop().inEventLoop()) {
             collectPathStats0(pathIdx, promise);
         } else {
             eventLoop().execute(() -> collectPathStats0(pathIdx, promise));
         }
         return promise;
     }
 
     private void collectPathStats0(int pathIdx, Promise<QuicConnectionPathStats> promise) {
         QuicheQuicConnection conn = connection;
         if (conn.isFreed()) {
             promise.setFailure(new IllegalStateException("Connection is closed"));
             return;
         }
 
         final Object[] stats = Quiche.quiche_conn_path_stats(connection.address(), pathIdx);
         if (stats == null) {
             promise.setFailure(new IllegalStateException("native quiche_conn_path_stats(...) failed"));
             return;
         }
         promise.setSuccess(new QuicheQuicConnectionPathStats(stats));
     }
 
     @Override
     public QuicTransportParameters peerTransportParameters() {
         return connection.peerParameters();
     }
 }