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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.channel.epoll;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.buffer.ByteBufAllocator;
20  import io.netty.buffer.ByteBufUtil;
21  import io.netty.buffer.Unpooled;
22  import io.netty.channel.AbstractChannel;
23  import io.netty.channel.Channel;
24  import io.netty.channel.ChannelConfig;
25  import io.netty.channel.ChannelException;
26  import io.netty.channel.ChannelFuture;
27  import io.netty.channel.ChannelFutureListener;
28  import io.netty.channel.ChannelMetadata;
29  import io.netty.channel.ChannelOutboundBuffer;
30  import io.netty.channel.ChannelPromise;
31  import io.netty.channel.ConnectTimeoutException;
32  import io.netty.channel.EventLoop;
33  import io.netty.channel.RecvByteBufAllocator;
34  import io.netty.channel.socket.ChannelInputShutdownEvent;
35  import io.netty.channel.socket.ChannelInputShutdownReadComplete;
36  import io.netty.channel.socket.SocketChannelConfig;
37  import io.netty.channel.unix.FileDescriptor;
38  import io.netty.channel.unix.IovArray;
39  import io.netty.channel.unix.Socket;
40  import io.netty.channel.unix.UnixChannel;
41  import io.netty.util.ReferenceCountUtil;
42  import io.netty.util.concurrent.Future;
43  
44  import java.io.IOException;
45  import java.net.InetSocketAddress;
46  import java.net.SocketAddress;
47  import java.nio.ByteBuffer;
48  import java.nio.channels.AlreadyConnectedException;
49  import java.nio.channels.ClosedChannelException;
50  import java.nio.channels.ConnectionPendingException;
51  import java.nio.channels.NotYetConnectedException;
52  import java.nio.channels.UnresolvedAddressException;
53  import java.util.concurrent.TimeUnit;
54  
55  import static io.netty.channel.internal.ChannelUtils.WRITE_STATUS_SNDBUF_FULL;
56  import static io.netty.channel.unix.UnixChannelUtil.computeRemoteAddr;
57  import static io.netty.util.internal.ObjectUtil.checkNotNull;
58  
59  abstract class AbstractEpollChannel extends AbstractChannel implements UnixChannel {
60      private static final ChannelMetadata METADATA = new ChannelMetadata(false);
61      final LinuxSocket socket;
62      /**
63       * The future of the current connection attempt.  If not null, subsequent
64       * connection attempts will fail.
65       */
66      private ChannelPromise connectPromise;
67      private Future<?> connectTimeoutFuture;
68      private SocketAddress requestedRemoteAddress;
69  
70      private volatile SocketAddress local;
71      private volatile SocketAddress remote;
72  
73      protected int flags = Native.EPOLLET;
74      boolean inputClosedSeenErrorOnRead;
75      boolean epollInReadyRunnablePending;
76  
77      protected volatile boolean active;
78  
79      AbstractEpollChannel(LinuxSocket fd) {
80          this(null, fd, false);
81      }
82  
83      AbstractEpollChannel(Channel parent, LinuxSocket fd, boolean active) {
84          super(parent);
85          this.socket = checkNotNull(fd, "fd");
86          this.active = active;
87          if (active) {
88              // Directly cache the remote and local addresses
89              // See https://github.com/netty/netty/issues/2359
90              this.local = fd.localAddress();
91              this.remote = fd.remoteAddress();
92          }
93      }
94  
95      AbstractEpollChannel(Channel parent, LinuxSocket fd, SocketAddress remote) {
96          super(parent);
97          this.socket = checkNotNull(fd, "fd");
98          this.active = true;
99          // Directly cache the remote and local addresses
100         // See https://github.com/netty/netty/issues/2359
101         this.remote = remote;
102         this.local = fd.localAddress();
103     }
104 
105     static boolean isSoErrorZero(Socket fd) {
106         try {
107             return fd.getSoError() == 0;
108         } catch (IOException e) {
109             throw new ChannelException(e);
110         }
111     }
112 
113     void setFlag(int flag) throws IOException {
114         if (!isFlagSet(flag)) {
115             flags |= flag;
116             modifyEvents();
117         }
118     }
119 
120     void clearFlag(int flag) throws IOException {
121         if (isFlagSet(flag)) {
122             flags &= ~flag;
123             modifyEvents();
124         }
125     }
126 
127     boolean isFlagSet(int flag) {
128         return (flags & flag) != 0;
129     }
130 
131     @Override
132     public final FileDescriptor fd() {
133         return socket;
134     }
135 
136     @Override
137     public abstract EpollChannelConfig config();
138 
139     @Override
140     public boolean isActive() {
141         return active;
142     }
143 
144     @Override
145     public ChannelMetadata metadata() {
146         return METADATA;
147     }
148 
149     @Override
150     protected void doClose() throws Exception {
151         active = false;
152         // Even if we allow half closed sockets we should give up on reading. Otherwise we may allow a read attempt on a
153         // socket which has not even been connected yet. This has been observed to block during unit tests.
154         inputClosedSeenErrorOnRead = true;
155         try {
156             ChannelPromise promise = connectPromise;
157             if (promise != null) {
158                 // Use tryFailure() instead of setFailure() to avoid the race against cancel().
159                 promise.tryFailure(new ClosedChannelException());
160                 connectPromise = null;
161             }
162 
163             Future<?> future = connectTimeoutFuture;
164             if (future != null) {
165                 future.cancel(false);
166                 connectTimeoutFuture = null;
167             }
168 
169             if (isRegistered()) {
170                 // Need to check if we are on the EventLoop as doClose() may be triggered by the GlobalEventExecutor
171                 // if SO_LINGER is used.
172                 //
173                 // See https://github.com/netty/netty/issues/7159
174                 EventLoop loop = eventLoop();
175                 if (loop.inEventLoop()) {
176                     doDeregister();
177                 } else {
178                     loop.execute(new Runnable() {
179                         @Override
180                         public void run() {
181                             try {
182                                 doDeregister();
183                             } catch (Throwable cause) {
184                                 pipeline().fireExceptionCaught(cause);
185                             }
186                         }
187                     });
188                 }
189             }
190         } finally {
191             socket.close();
192         }
193     }
194 
195     void resetCachedAddresses() {
196         local = socket.localAddress();
197         remote = socket.remoteAddress();
198     }
199 
200     @Override
201     protected void doDisconnect() throws Exception {
202         doClose();
203     }
204 
205     @Override
206     protected boolean isCompatible(EventLoop loop) {
207         return loop instanceof EpollEventLoop;
208     }
209 
210     @Override
211     public boolean isOpen() {
212         return socket.isOpen();
213     }
214 
215     @Override
216     protected void doDeregister() throws Exception {
217         ((EpollEventLoop) eventLoop()).remove(this);
218     }
219 
220     @Override
221     protected final void doBeginRead() throws Exception {
222         // Channel.read() or ChannelHandlerContext.read() was called
223         final AbstractEpollUnsafe unsafe = (AbstractEpollUnsafe) unsafe();
224         unsafe.readPending = true;
225 
226         // We must set the read flag here as it is possible the user didn't read in the last read loop, the
227         // executeEpollInReadyRunnable could read nothing, and if the user doesn't explicitly call read they will
228         // never get data after this.
229         setFlag(Native.EPOLLIN);
230 
231         // If EPOLL ET mode is enabled and auto read was toggled off on the last read loop then we may not be notified
232         // again if we didn't consume all the data. So we force a read operation here if there maybe more data.
233         if (unsafe.maybeMoreDataToRead) {
234             unsafe.executeEpollInReadyRunnable(config());
235         }
236     }
237 
238     final boolean shouldBreakEpollInReady(ChannelConfig config) {
239         return socket.isInputShutdown() && (inputClosedSeenErrorOnRead || !isAllowHalfClosure(config));
240     }
241 
242     private static boolean isAllowHalfClosure(ChannelConfig config) {
243         if (config instanceof EpollDomainSocketChannelConfig) {
244             return ((EpollDomainSocketChannelConfig) config).isAllowHalfClosure();
245         }
246         return config instanceof SocketChannelConfig &&
247                 ((SocketChannelConfig) config).isAllowHalfClosure();
248     }
249 
250     final void clearEpollIn() {
251         // Only clear if registered with an EventLoop as otherwise
252         if (isRegistered()) {
253             final EventLoop loop = eventLoop();
254             final AbstractEpollUnsafe unsafe = (AbstractEpollUnsafe) unsafe();
255             if (loop.inEventLoop()) {
256                 unsafe.clearEpollIn0();
257             } else {
258                 // schedule a task to clear the EPOLLIN as it is not safe to modify it directly
259                 loop.execute(new Runnable() {
260                     @Override
261                     public void run() {
262                         if (!unsafe.readPending && !config().isAutoRead()) {
263                             // Still no read triggered so clear it now
264                             unsafe.clearEpollIn0();
265                         }
266                     }
267                 });
268             }
269         } else  {
270             // The EventLoop is not registered atm so just update the flags so the correct value
271             // will be used once the channel is registered
272             flags &= ~Native.EPOLLIN;
273         }
274     }
275 
276     private void modifyEvents() throws IOException {
277         if (isOpen() && isRegistered()) {
278             ((EpollEventLoop) eventLoop()).modify(this);
279         }
280     }
281 
282     @Override
283     protected void doRegister() throws Exception {
284         // Just in case the previous EventLoop was shutdown abruptly, or an event is still pending on the old EventLoop
285         // make sure the epollInReadyRunnablePending variable is reset so we will be able to execute the Runnable on the
286         // new EventLoop.
287         epollInReadyRunnablePending = false;
288         ((EpollEventLoop) eventLoop()).add(this);
289     }
290 
291     @Override
292     protected abstract AbstractEpollUnsafe newUnsafe();
293 
294     /**
295      * Returns an off-heap copy of the specified {@link ByteBuf}, and releases the original one.
296      */
297     protected final ByteBuf newDirectBuffer(ByteBuf buf) {
298         return newDirectBuffer(buf, buf);
299     }
300 
301     /**
302      * Returns an off-heap copy of the specified {@link ByteBuf}, and releases the specified holder.
303      * The caller must ensure that the holder releases the original {@link ByteBuf} when the holder is released by
304      * this method.
305      */
306     protected final ByteBuf newDirectBuffer(Object holder, ByteBuf buf) {
307         final int readableBytes = buf.readableBytes();
308         if (readableBytes == 0) {
309             ReferenceCountUtil.release(holder);
310             return Unpooled.EMPTY_BUFFER;
311         }
312 
313         final ByteBufAllocator alloc = alloc();
314         if (alloc.isDirectBufferPooled()) {
315             return newDirectBuffer0(holder, buf, alloc, readableBytes);
316         }
317 
318         final ByteBuf directBuf = ByteBufUtil.threadLocalDirectBuffer();
319         if (directBuf == null) {
320             return newDirectBuffer0(holder, buf, alloc, readableBytes);
321         }
322 
323         directBuf.writeBytes(buf, buf.readerIndex(), readableBytes);
324         ReferenceCountUtil.safeRelease(holder);
325         return directBuf;
326     }
327 
328     private static ByteBuf newDirectBuffer0(Object holder, ByteBuf buf, ByteBufAllocator alloc, int capacity) {
329         final ByteBuf directBuf = alloc.directBuffer(capacity);
330         directBuf.writeBytes(buf, buf.readerIndex(), capacity);
331         ReferenceCountUtil.safeRelease(holder);
332         return directBuf;
333     }
334 
335     protected static void checkResolvable(InetSocketAddress addr) {
336         if (addr.isUnresolved()) {
337             throw new UnresolvedAddressException();
338         }
339     }
340 
341     /**
342      * Read bytes into the given {@link ByteBuf} and return the amount.
343      */
344     protected final int doReadBytes(ByteBuf byteBuf) throws Exception {
345         int writerIndex = byteBuf.writerIndex();
346         int localReadAmount;
347         unsafe().recvBufAllocHandle().attemptedBytesRead(byteBuf.writableBytes());
348         if (byteBuf.hasMemoryAddress()) {
349             localReadAmount = socket.readAddress(byteBuf.memoryAddress(), writerIndex, byteBuf.capacity());
350         } else {
351             ByteBuffer buf = byteBuf.internalNioBuffer(writerIndex, byteBuf.writableBytes());
352             localReadAmount = socket.read(buf, buf.position(), buf.limit());
353         }
354         if (localReadAmount > 0) {
355             byteBuf.writerIndex(writerIndex + localReadAmount);
356         }
357         return localReadAmount;
358     }
359 
360     protected final int doWriteBytes(ChannelOutboundBuffer in, ByteBuf buf) throws Exception {
361         if (buf.hasMemoryAddress()) {
362             int localFlushedAmount = socket.writeAddress(buf.memoryAddress(), buf.readerIndex(), buf.writerIndex());
363             if (localFlushedAmount > 0) {
364                 in.removeBytes(localFlushedAmount);
365                 return 1;
366             }
367         } else {
368             final ByteBuffer nioBuf = buf.nioBufferCount() == 1 ?
369                     buf.internalNioBuffer(buf.readerIndex(), buf.readableBytes()) : buf.nioBuffer();
370             int localFlushedAmount = socket.write(nioBuf, nioBuf.position(), nioBuf.limit());
371             if (localFlushedAmount > 0) {
372                 nioBuf.position(nioBuf.position() + localFlushedAmount);
373                 in.removeBytes(localFlushedAmount);
374                 return 1;
375             }
376         }
377         return WRITE_STATUS_SNDBUF_FULL;
378     }
379 
380     /**
381      * Write bytes to the socket, with or without a remote address.
382      * Used for datagram and TCP client fast open writes.
383      */
384     final long doWriteOrSendBytes(ByteBuf data, InetSocketAddress remoteAddress, boolean fastOpen)
385             throws IOException {
386         assert !(fastOpen && remoteAddress == null) : "fastOpen requires a remote address";
387         if (data.hasMemoryAddress()) {
388             long memoryAddress = data.memoryAddress();
389             if (remoteAddress == null) {
390                 return socket.writeAddress(memoryAddress, data.readerIndex(), data.writerIndex());
391             }
392             return socket.sendToAddress(memoryAddress, data.readerIndex(), data.writerIndex(),
393                     remoteAddress.getAddress(), remoteAddress.getPort(), fastOpen);
394         }
395 
396         if (data.nioBufferCount() > 1) {
397             IovArray array = ((EpollEventLoop) eventLoop()).cleanIovArray();
398             array.add(data, data.readerIndex(), data.readableBytes());
399             int cnt = array.count();
400             assert cnt != 0;
401 
402             if (remoteAddress == null) {
403                 return socket.writevAddresses(array.memoryAddress(0), cnt);
404             }
405             return socket.sendToAddresses(array.memoryAddress(0), cnt,
406                     remoteAddress.getAddress(), remoteAddress.getPort(), fastOpen);
407         }
408 
409         ByteBuffer nioData = data.internalNioBuffer(data.readerIndex(), data.readableBytes());
410         if (remoteAddress == null) {
411             return socket.write(nioData, nioData.position(), nioData.limit());
412         }
413         return socket.sendTo(nioData, nioData.position(), nioData.limit(),
414                 remoteAddress.getAddress(), remoteAddress.getPort(), fastOpen);
415     }
416 
417     protected abstract class AbstractEpollUnsafe extends AbstractUnsafe {
418         boolean readPending;
419         boolean maybeMoreDataToRead;
420         private EpollRecvByteAllocatorHandle allocHandle;
421         private final Runnable epollInReadyRunnable = new Runnable() {
422             @Override
423             public void run() {
424                 epollInReadyRunnablePending = false;
425                 epollInReady();
426             }
427         };
428 
429         /**
430          * Called once EPOLLIN event is ready to be processed
431          */
432         abstract void epollInReady();
433 
434         final void epollInBefore() {
435             maybeMoreDataToRead = false;
436         }
437 
438         final void epollInFinally(ChannelConfig config) {
439             maybeMoreDataToRead = allocHandle.maybeMoreDataToRead();
440 
441             if (allocHandle.isReceivedRdHup() || (readPending && maybeMoreDataToRead)) {
442                 // trigger a read again as there may be something left to read and because of epoll ET we
443                 // will not get notified again until we read everything from the socket
444                 //
445                 // It is possible the last fireChannelRead call could cause the user to call read() again, or if
446                 // autoRead is true the call to channelReadComplete would also call read, but maybeMoreDataToRead is set
447                 // to false before every read operation to prevent re-entry into epollInReady() we will not read from
448                 // the underlying OS again unless the user happens to call read again.
449                 executeEpollInReadyRunnable(config);
450             } else if (!readPending && !config.isAutoRead()) {
451                 // Check if there is a readPending which was not processed yet.
452                 // This could be for two reasons:
453                 // * The user called Channel.read() or ChannelHandlerContext.read() in channelRead(...) method
454                 // * The user called Channel.read() or ChannelHandlerContext.read() in channelReadComplete(...) method
455                 //
456                 // See https://github.com/netty/netty/issues/2254
457                 clearEpollIn();
458             }
459         }
460 
461         final void executeEpollInReadyRunnable(ChannelConfig config) {
462             if (epollInReadyRunnablePending || !isActive() || shouldBreakEpollInReady(config)) {
463                 return;
464             }
465             epollInReadyRunnablePending = true;
466             eventLoop().execute(epollInReadyRunnable);
467         }
468 
469         /**
470          * Called once EPOLLRDHUP event is ready to be processed
471          */
472         final void epollRdHupReady() {
473             // This must happen before we attempt to read. This will ensure reading continues until an error occurs.
474             recvBufAllocHandle().receivedRdHup();
475 
476             if (isActive()) {
477                 // If it is still active, we need to call epollInReady as otherwise we may miss to
478                 // read pending data from the underlying file descriptor.
479                 // See https://github.com/netty/netty/issues/3709
480                 epollInReady();
481             } else {
482                 // Just to be safe make sure the input marked as closed.
483                 shutdownInput(true);
484             }
485 
486             // Clear the EPOLLRDHUP flag to prevent continuously getting woken up on this event.
487             clearEpollRdHup();
488         }
489 
490         /**
491          * Clear the {@link Native#EPOLLRDHUP} flag from EPOLL, and close on failure.
492          */
493         private void clearEpollRdHup() {
494             try {
495                 clearFlag(Native.EPOLLRDHUP);
496             } catch (IOException e) {
497                 pipeline().fireExceptionCaught(e);
498                 close(voidPromise());
499             }
500         }
501 
502         /**
503          * Shutdown the input side of the channel.
504          */
505         void shutdownInput(boolean rdHup) {
506             if (!socket.isInputShutdown()) {
507                 if (isAllowHalfClosure(config())) {
508                     try {
509                         socket.shutdown(true, false);
510                     } catch (IOException ignored) {
511                         // We attempted to shutdown and failed, which means the input has already effectively been
512                         // shutdown.
513                         fireEventAndClose(ChannelInputShutdownEvent.INSTANCE);
514                         return;
515                     } catch (NotYetConnectedException ignore) {
516                         // We attempted to shutdown and failed, which means the input has already effectively been
517                         // shutdown.
518                     }
519                     clearEpollIn();
520                     pipeline().fireUserEventTriggered(ChannelInputShutdownEvent.INSTANCE);
521                 } else {
522                     close(voidPromise());
523                 }
524             } else if (!rdHup) {
525                 inputClosedSeenErrorOnRead = true;
526                 pipeline().fireUserEventTriggered(ChannelInputShutdownReadComplete.INSTANCE);
527             }
528         }
529 
530         private void fireEventAndClose(Object evt) {
531             pipeline().fireUserEventTriggered(evt);
532             close(voidPromise());
533         }
534 
535         @Override
536         public EpollRecvByteAllocatorHandle recvBufAllocHandle() {
537             if (allocHandle == null) {
538                 allocHandle = newEpollHandle((RecvByteBufAllocator.ExtendedHandle) super.recvBufAllocHandle());
539             }
540             return allocHandle;
541         }
542 
543         /**
544          * Create a new {@link EpollRecvByteAllocatorHandle} instance.
545          * @param handle The handle to wrap with EPOLL specific logic.
546          */
547         EpollRecvByteAllocatorHandle newEpollHandle(RecvByteBufAllocator.ExtendedHandle handle) {
548             return new EpollRecvByteAllocatorHandle(handle);
549         }
550 
551         @Override
552         protected final void flush0() {
553             // Flush immediately only when there's no pending flush.
554             // If there's a pending flush operation, event loop will call forceFlush() later,
555             // and thus there's no need to call it now.
556             if (!isFlagSet(Native.EPOLLOUT)) {
557                 super.flush0();
558             }
559         }
560 
561         /**
562          * Called once a EPOLLOUT event is ready to be processed
563          */
564         final void epollOutReady() {
565             if (connectPromise != null) {
566                 // pending connect which is now complete so handle it.
567                 finishConnect();
568             } else if (!socket.isOutputShutdown()) {
569                 // directly call super.flush0() to force a flush now
570                 super.flush0();
571             }
572         }
573 
574         protected final void clearEpollIn0() {
575             assert eventLoop().inEventLoop();
576             try {
577                 readPending = false;
578                 clearFlag(Native.EPOLLIN);
579             } catch (IOException e) {
580                 // When this happens there is something completely wrong with either the filedescriptor or epoll,
581                 // so fire the exception through the pipeline and close the Channel.
582                 pipeline().fireExceptionCaught(e);
583                 unsafe().close(unsafe().voidPromise());
584             }
585         }
586 
587         @Override
588         public void connect(
589                 final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {
590             if (!promise.setUncancellable() || !ensureOpen(promise)) {
591                 return;
592             }
593 
594             try {
595                 if (connectPromise != null) {
596                     throw new ConnectionPendingException();
597                 }
598 
599                 boolean wasActive = isActive();
600                 if (doConnect(remoteAddress, localAddress)) {
601                     fulfillConnectPromise(promise, wasActive);
602                 } else {
603                     connectPromise = promise;
604                     requestedRemoteAddress = remoteAddress;
605 
606                     // Schedule connect timeout.
607                     int connectTimeoutMillis = config().getConnectTimeoutMillis();
608                     if (connectTimeoutMillis > 0) {
609                         connectTimeoutFuture = eventLoop().schedule(new Runnable() {
610                             @Override
611                             public void run() {
612                                 ChannelPromise connectPromise = AbstractEpollChannel.this.connectPromise;
613                                 if (connectPromise != null && !connectPromise.isDone()
614                                         && connectPromise.tryFailure(new ConnectTimeoutException(
615                                         "connection timed out: " + remoteAddress))) {
616                                     close(voidPromise());
617                                 }
618                             }
619                         }, connectTimeoutMillis, TimeUnit.MILLISECONDS);
620                     }
621 
622                     promise.addListener(new ChannelFutureListener() {
623                         @Override
624                         public void operationComplete(ChannelFuture future) throws Exception {
625                             if (future.isCancelled()) {
626                                 if (connectTimeoutFuture != null) {
627                                     connectTimeoutFuture.cancel(false);
628                                 }
629                                 connectPromise = null;
630                                 close(voidPromise());
631                             }
632                         }
633                     });
634                 }
635             } catch (Throwable t) {
636                 closeIfClosed();
637                 promise.tryFailure(annotateConnectException(t, remoteAddress));
638             }
639         }
640 
641         private void fulfillConnectPromise(ChannelPromise promise, boolean wasActive) {
642             if (promise == null) {
643                 // Closed via cancellation and the promise has been notified already.
644                 return;
645             }
646             active = true;
647 
648             // Get the state as trySuccess() may trigger an ChannelFutureListener that will close the Channel.
649             // We still need to ensure we call fireChannelActive() in this case.
650             boolean active = isActive();
651 
652             // trySuccess() will return false if a user cancelled the connection attempt.
653             boolean promiseSet = promise.trySuccess();
654 
655             // Regardless if the connection attempt was cancelled, channelActive() event should be triggered,
656             // because what happened is what happened.
657             if (!wasActive && active) {
658                 pipeline().fireChannelActive();
659             }
660 
661             // If a user cancelled the connection attempt, close the channel, which is followed by channelInactive().
662             if (!promiseSet) {
663                 close(voidPromise());
664             }
665         }
666 
667         private void fulfillConnectPromise(ChannelPromise promise, Throwable cause) {
668             if (promise == null) {
669                 // Closed via cancellation and the promise has been notified already.
670                 return;
671             }
672 
673             // Use tryFailure() instead of setFailure() to avoid the race against cancel().
674             promise.tryFailure(cause);
675             closeIfClosed();
676         }
677 
678         private void finishConnect() {
679             // Note this method is invoked by the event loop only if the connection attempt was
680             // neither cancelled nor timed out.
681 
682             assert eventLoop().inEventLoop();
683 
684             boolean connectStillInProgress = false;
685             try {
686                 boolean wasActive = isActive();
687                 if (!doFinishConnect()) {
688                     connectStillInProgress = true;
689                     return;
690                 }
691                 fulfillConnectPromise(connectPromise, wasActive);
692             } catch (Throwable t) {
693                 fulfillConnectPromise(connectPromise, annotateConnectException(t, requestedRemoteAddress));
694             } finally {
695                 if (!connectStillInProgress) {
696                     // Check for null as the connectTimeoutFuture is only created if a connectTimeoutMillis > 0 is used
697                     // See https://github.com/netty/netty/issues/1770
698                     if (connectTimeoutFuture != null) {
699                         connectTimeoutFuture.cancel(false);
700                     }
701                     connectPromise = null;
702                 }
703             }
704         }
705 
706         /**
707          * Finish the connect
708          */
709         private boolean doFinishConnect() throws Exception {
710             if (socket.finishConnect()) {
711                 clearFlag(Native.EPOLLOUT);
712                 if (requestedRemoteAddress instanceof InetSocketAddress) {
713                     remote = computeRemoteAddr((InetSocketAddress) requestedRemoteAddress, socket.remoteAddress());
714                 }
715                 requestedRemoteAddress = null;
716 
717                 return true;
718             }
719             setFlag(Native.EPOLLOUT);
720             return false;
721         }
722     }
723 
724     @Override
725     protected void doBind(SocketAddress local) throws Exception {
726         if (local instanceof InetSocketAddress) {
727             checkResolvable((InetSocketAddress) local);
728         }
729         socket.bind(local);
730         this.local = socket.localAddress();
731     }
732 
733     /**
734      * Connect to the remote peer
735      */
736     protected boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
737         if (localAddress instanceof InetSocketAddress) {
738             checkResolvable((InetSocketAddress) localAddress);
739         }
740 
741         InetSocketAddress remoteSocketAddr = remoteAddress instanceof InetSocketAddress
742                 ? (InetSocketAddress) remoteAddress : null;
743         if (remoteSocketAddr != null) {
744             checkResolvable(remoteSocketAddr);
745         }
746 
747         if (remote != null) {
748             // Check if already connected before trying to connect. This is needed as connect(...) will not return -1
749             // and set errno to EISCONN if a previous connect(...) attempt was setting errno to EINPROGRESS and finished
750             // later.
751             throw new AlreadyConnectedException();
752         }
753 
754         if (localAddress != null) {
755             socket.bind(localAddress);
756         }
757 
758         boolean connected = doConnect0(remoteAddress);
759         if (connected) {
760             remote = remoteSocketAddr == null ?
761                     remoteAddress : computeRemoteAddr(remoteSocketAddr, socket.remoteAddress());
762         }
763         // We always need to set the localAddress even if not connected yet as the bind already took place.
764         //
765         // See https://github.com/netty/netty/issues/3463
766         local = socket.localAddress();
767         return connected;
768     }
769 
770     boolean doConnect0(SocketAddress remote) throws Exception {
771         boolean success = false;
772         try {
773             boolean connected = socket.connect(remote);
774             if (!connected) {
775                 setFlag(Native.EPOLLOUT);
776             }
777             success = true;
778             return connected;
779         } finally {
780             if (!success) {
781                 doClose();
782             }
783         }
784     }
785 
786     @Override
787     protected SocketAddress localAddress0() {
788         return local;
789     }
790 
791     @Override
792     protected SocketAddress remoteAddress0() {
793         return remote;
794     }
795 }