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   /*
    * Copyright 2014 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.channel.epoll;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelException;
  import io.netty.channel.ChannelOutboundBuffer;
  import io.netty.channel.socket.InternetProtocolFamily;
  import io.netty.channel.socket.ServerSocketChannel;
  import io.netty.channel.socket.SocketChannel;
  import io.netty.util.concurrent.GlobalEventExecutor;
  
  import java.io.IOException;
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Map;
  import java.util.concurrent.Executor;
  
  import static io.netty.channel.epoll.LinuxSocket.newSocketStream;
  import static io.netty.channel.epoll.Native.IS_SUPPORTING_TCP_FASTOPEN_CLIENT;
  
  /**
   * {@link SocketChannel} implementation that uses linux EPOLL Edge-Triggered Mode for
   * maximal performance.
   */
  public final class EpollSocketChannel extends AbstractEpollStreamChannel implements SocketChannel {
  
      private final EpollSocketChannelConfig config;
  
      private volatile Collection<InetAddress> tcpMd5SigAddresses = Collections.emptyList();
  
      public EpollSocketChannel() {
          super(newSocketStream(), false);
          config = new EpollSocketChannelConfig(this);
      }
  
      public EpollSocketChannel(InternetProtocolFamily protocol) {
          super(newSocketStream(protocol), false);
          config = new EpollSocketChannelConfig(this);
      }
  
      public EpollSocketChannel(int fd) {
          super(fd);
          config = new EpollSocketChannelConfig(this);
      }
  
      EpollSocketChannel(LinuxSocket fd, boolean active) {
          super(fd, active);
          config = new EpollSocketChannelConfig(this);
      }
  
      EpollSocketChannel(Channel parent, LinuxSocket fd, InetSocketAddress remoteAddress) {
          super(parent, fd, remoteAddress);
          config = new EpollSocketChannelConfig(this);
  
          if (parent instanceof EpollServerSocketChannel) {
              tcpMd5SigAddresses = ((EpollServerSocketChannel) parent).tcpMd5SigAddresses();
          }
      }
  
      /**
       * Returns the {@code TCP_INFO} for the current socket.
       * See <a href="https://linux.die.net//man/7/tcp">man 7 tcp</a>.
       */
      public EpollTcpInfo tcpInfo() {
          return tcpInfo(new EpollTcpInfo());
      }
  
      /**
       * Updates and returns the {@code TCP_INFO} for the current socket.
       * See <a href="https://linux.die.net//man/7/tcp">man 7 tcp</a>.
       */
      public EpollTcpInfo tcpInfo(EpollTcpInfo info) {
          try {
              socket.getTcpInfo(info);
              return info;
          } catch (IOException e) {
              throw new ChannelException(e);
          }
      }
  
      @Override
     public InetSocketAddress remoteAddress() {
         return (InetSocketAddress) super.remoteAddress();
     }
 
     @Override
     public InetSocketAddress localAddress() {
         return (InetSocketAddress) super.localAddress();
     }
 
     @Override
     public EpollSocketChannelConfig config() {
         return config;
     }
 
     @Override
     public ServerSocketChannel parent() {
         return (ServerSocketChannel) super.parent();
     }
 
     @Override
     protected AbstractEpollUnsafe newUnsafe() {
         return new EpollSocketChannelUnsafe();
     }
 
     @Override
     boolean doConnect0(SocketAddress remote) throws Exception {
         if (IS_SUPPORTING_TCP_FASTOPEN_CLIENT && config.isTcpFastOpenConnect()) {
             ChannelOutboundBuffer outbound = unsafe().outboundBuffer();
             outbound.addFlush();
             Object curr;
             if ((curr = outbound.current()) instanceof ByteBuf) {
                 ByteBuf initialData = (ByteBuf) curr;
                 // If no cookie is present, the write fails with EINPROGRESS and this call basically
                 // becomes a normal async connect. All writes will be sent normally afterwards.
                 long localFlushedAmount = doWriteOrSendBytes(
                         initialData, (InetSocketAddress) remote, true);
                 if (localFlushedAmount > 0) {
                     // We had a cookie and our fast-open proceeded. Remove written data
                     // then continue with normal TCP operation.
                     outbound.removeBytes(localFlushedAmount);
                     return true;
                 }
             }
         }
         return super.doConnect0(remote);
     }
 
     private final class EpollSocketChannelUnsafe extends EpollStreamUnsafe {
         @Override
         protected Executor prepareToClose() {
             try {
                 // Check isOpen() first as otherwise it will throw a RuntimeException
                 // when call getSoLinger() as the fd is not valid anymore.
                 if (isOpen() && config().getSoLinger() > 0) {
                     // We need to cancel this key of the channel so we may not end up in a eventloop spin
                     // because we try to read or write until the actual close happens which may be later due
                     // SO_LINGER handling.
                     // See https://github.com/netty/netty/issues/4449
                     ((EpollEventLoop) eventLoop()).remove(EpollSocketChannel.this);
                     return GlobalEventExecutor.INSTANCE;
                 }
             } catch (Throwable ignore) {
                 // Ignore the error as the underlying channel may be closed in the meantime and so
                 // getSoLinger() may produce an exception. In this case we just return null.
                 // See https://github.com/netty/netty/issues/4449
             }
             return null;
         }
     }
 
     void setTcpMd5Sig(Map<InetAddress, byte[]> keys) throws IOException {
         // Add synchronized as newTcpMp5Sigs might do multiple operations on the socket itself.
         synchronized (this) {
             tcpMd5SigAddresses = TcpMd5Util.newTcpMd5Sigs(this, tcpMd5SigAddresses, keys);
         }
     }
 }