.NET 设置Socket 对象的“TFO”快速打开连接选项（跨平台兼容的）

调用示例：

Socket socket = new Socket(AF_INET, SOCK_STREAM, 0);
1: socket.SetFastOpen(); 
2: SetFastOpen(socket);

函数实现

#if NETCOREAPP
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
#endif
        public static bool SetFastOpen(this Socket socket, bool fastOpen = true)
        {
            if (SocketExtension.CleanedUp(socket) || socket.ProtocolType != ProtocolType.Tcp)
            {
                return false; // https://github.com/dotnet/runtime/issues/1476#issue-547173361
            }
            PlatformID platform = Environments.Platform;
            if (platform == PlatformID.Win32NT)
            {
                // #define TCP_FASTOPEN 15 
                try
                {
                    socket.SetSocketOption(SocketOptionLevel.Tcp, (SocketOptionName)15, fastOpen);
                    return true;
                }
                catch
                {
                    return false;
                }
            }
            else if (platform == PlatformID.Unix)
            {
                // #define TCP_FASTOPEN 23 /* Enable FastOpen on listeners */
                // #define SOL_TCP      6  /* TCP level */
                int v = fastOpen ? 1 : 0;
                int r = NativeMethods.linux_setsockopt(socket.Handle.ToInt32(), 6, 23,
                               (IntPtr)(&v), sizeof(int));
                return r == 0;
            }
            else
            {
                return false;
            }
        }

外部函数：

            [DllImport("libc", EntryPoint = "setsockopt", CallingConvention = CallingConvention.Cdecl)]
            public static extern int linux_setsockopt(int socket, int level, int option_name, IntPtr option_value, int option_len);