mcs/class/System/System.Net.NetworkInformation/Ping.cs

   1 //
   2 // System.Net.NetworkInformation.Ping
   3 //
   4 // Authors:
   5 //      Gonzalo Paniagua Javier (gonzalo@novell.com)
   6 //      Atsushi Enomoto (atsushi@ximian.com)
   7 //
   8 // Copyright (c) 2006-2007 Novell, Inc. (http://www.novell.com)
   9 // Copyright 2015 Xamarin Inc.
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining
  12 // a copy of this software and associated documentation files (the
  13 // "Software"), to deal in the Software without restriction, including
  14 // without limitation the rights to use, copy, modify, merge, publish,
  15 // distribute, sublicense, and/or sell copies of the Software, and to
  16 // permit persons to whom the Software is furnished to do so, subject to
  17 // the following conditions:
  18 //
  19 // The above copyright notice and this permission notice shall be
  20 // included in all copies or substantial portions of the Software.
  21 //
  22 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29 //
  30
  31 using System;
  32 using System.IO;
  33 using System.Text;
  34 using System.Diagnostics;
  35 using System.Globalization;
  36 using System.ComponentModel;
  37 using System.Net.Sockets;
  38 using System.Security.Principal;
  39 using System.Security.Cryptography;
  40 using System.Runtime.InteropServices;
  41 using System.Threading;
  42 using System.Threading.Tasks;
  43
  44 namespace System.Net.NetworkInformation {
  45         [MonoTODO ("IPv6 support is missing")]
  46         public class Ping : Component, IDisposable
  47         {
  48 #if !MONOTOUCH
  49                 [StructLayout(LayoutKind.Sequential)]
  50                 struct cap_user_header_t
  51                 {
  52                         public UInt32 version;
  53                         public Int32 pid;
  54                 };
  55
  56                 [StructLayout(LayoutKind.Sequential)]
  57                 struct cap_user_data_t
  58                 {
  59                         public UInt32 effective;
  60                         public UInt32 permitted;
  61                         public UInt32 inheritable;
  62                 }
  63
  64                 const int DefaultCount = 1;
  65                 static readonly string [] PingBinPaths = new string [] {
  66                         "/bin/ping",
  67                         "/sbin/ping",
  68                         "/usr/sbin/ping",
  69 #if MONODROID
  70                         "/system/bin/ping"
  71 #endif
  72                 };
  73                 static readonly string PingBinPath;
  74 #endif
  75                 const int default_timeout = 4000; // 4 sec.
  76                 ushort identifier;
  77
  78                 // This value is correct as of Linux kernel version 2.6.25.9
  79                 // See /usr/include/linux/capability.h
  80                 const UInt32 linux_cap_version = 0x20071026;
  81
  82                 static readonly byte [] default_buffer = new byte [0];
  83                 static bool canSendPrivileged;
  84
  85
  86                 BackgroundWorker worker;
  87                 object user_async_state;
  88                 CancellationTokenSource cts;
  89
  90                 public event PingCompletedEventHandler PingCompleted;
  91
  92 #if !MONOTOUCH
  93                 static Ping ()
  94                 {
  95                         if (Environment.OSVersion.Platform == PlatformID.Unix) {
  96                                 CheckLinuxCapabilities ();
  97                                 if (!canSendPrivileged && WindowsIdentity.GetCurrent ().Name == "root")
  98                                         canSendPrivileged = true;
  99
 100                                 // Since different Unix systems can have different path to bin, we try some
 101                                 // of the known ones.
 102                                 foreach (string ping_path in PingBinPaths)
 103                                         if (File.Exists (ping_path)) {
 104                                                 PingBinPath = ping_path;
 105                                                 break;
 106                                         }
 107                         }
 108                         else
 109                                 canSendPrivileged = true;
 110
 111                         if (PingBinPath == null)
 112                                 PingBinPath = "/bin/ping"; // default, fallback value
 113                 }
 114 #endif
 115
 116                 public Ping ()
 117                 {
 118                         // Generate a new random 16 bit identifier for every ping
 119                         RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider ();
 120                         byte [] randomIdentifier = new byte [2];
 121                         rng.GetBytes (randomIdentifier);
 122                         identifier = (ushort)(randomIdentifier [0] + (randomIdentifier [1] << 8));
 123                 }
 124
 125 #if !MONOTOUCH
 126                 [DllImport ("libc", EntryPoint="capget")]
 127                 static extern int capget (ref cap_user_header_t header, ref cap_user_data_t data);
 128
 129                 static void CheckLinuxCapabilities ()
 130                 {
 131                         try {
 132                                 cap_user_header_t header = new cap_user_header_t ();
 133                                 cap_user_data_t data = new cap_user_data_t ();
 134
 135                                 header.version = linux_cap_version;
 136
 137                                 int ret = -1;
 138
 139                                 try {
 140                                         ret = capget (ref header, ref data);
 141                                 } catch (Exception) {
 142                                 }
 143
 144                                 if (ret == -1)
 145                                         return;
 146
 147                                 canSendPrivileged = (data.effective & (1 << 13)) != 0;
 148                         } catch {
 149                                 canSendPrivileged = false;
 150                         }
 151                 }
 152 #endif
 153
 154                 void IDisposable.Dispose ()
 155                 {
 156                 }
 157
 158                 protected void OnPingCompleted (PingCompletedEventArgs e)
 159                 {
 160                         user_async_state = null;
 161                         worker = null;
 162
 163                         if (cts != null) {
 164                                 cts.Dispose();
 165                                 cts = null;
 166                         }
 167
 168                         if (PingCompleted != null)
 169                                 PingCompleted (this, e);
 170                 }
 171
 172                 // Sync
 173
 174                 public PingReply Send (IPAddress address)
 175                 {
 176                         return Send (address, default_timeout);
 177                 }
 178
 179                 public PingReply Send (IPAddress address, int timeout)
 180                 {
 181                         return Send (address, timeout, default_buffer);
 182                 }
 183
 184                 public PingReply Send (IPAddress address, int timeout, byte [] buffer)
 185                 {
 186                         return Send (address, timeout, buffer, new PingOptions ());
 187                 }
 188
 189                 public PingReply Send (string hostNameOrAddress)
 190                 {
 191                         return Send (hostNameOrAddress, default_timeout);
 192                 }
 193
 194                 public PingReply Send (string hostNameOrAddress, int timeout)
 195                 {
 196                         return Send (hostNameOrAddress, timeout, default_buffer);
 197                 }
 198
 199                 public PingReply Send (string hostNameOrAddress, int timeout, byte [] buffer)
 200                 {
 201                         return Send (hostNameOrAddress, timeout, buffer, new PingOptions ());
 202                 }
 203
 204                 public PingReply Send (string hostNameOrAddress, int timeout, byte [] buffer, PingOptions options)
 205                 {
 206                         IPAddress [] addresses = Dns.GetHostAddresses (hostNameOrAddress);
 207                         return Send (addresses [0], timeout, buffer, options);
 208                 }
 209
 210                 static IPAddress GetNonLoopbackIP ()
 211                 {
 212                         foreach (IPAddress addr in Dns.GetHostByName (Dns.GetHostName ()).AddressList)
 213                                 if (!IPAddress.IsLoopback (addr))
 214                                         return addr;
 215                         throw new InvalidOperationException ("Could not resolve non-loopback IP address for localhost");
 216                 }
 217
 218                 public PingReply Send (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 219                 {
 220                         if (address == null)
 221                                 throw new ArgumentNullException ("address");
 222                         if (timeout < 0)
 223                                 throw new ArgumentOutOfRangeException ("timeout", "timeout must be non-negative integer");
 224                         if (buffer == null)
 225                                 throw new ArgumentNullException ("buffer");
 226                         if (buffer.Length > 65500)
 227                                 throw new ArgumentException ("buffer");
 228                         // options can be null.
 229
 230 #if MONOTOUCH
 231                         throw new InvalidOperationException ();
 232 #else
 233                         if (canSendPrivileged)
 234                                 return SendPrivileged (address, timeout, buffer, options);
 235                         return SendUnprivileged (address, timeout, buffer, options);
 236 #endif
 237                 }
 238
 239 #if !MONOTOUCH
 240                 private PingReply SendPrivileged (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 241                 {
 242                         IPEndPoint target = new IPEndPoint (address, 0);
 243                         IPEndPoint client = new IPEndPoint (GetNonLoopbackIP (), 0);
 244
 245                         // FIXME: support IPv6
 246                         using (Socket s = new Socket (AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp)) {
 247                                 if (options != null) {
 248                                         s.DontFragment = options.DontFragment;
 249                                         s.Ttl = (short) options.Ttl;
 250                                 }
 251                                 s.SendTimeout = timeout;
 252                                 s.ReceiveTimeout = timeout;
 253                                 // not sure why Identifier = 0 is unacceptable ...
 254                                 IcmpMessage send = new IcmpMessage (8, 0, identifier, 0, buffer);
 255                                 byte [] bytes = send.GetBytes ();
 256                                 s.SendBufferSize = bytes.Length;
 257                                 s.SendTo (bytes, bytes.Length, SocketFlags.None, target);
 258
 259                                 DateTime sentTime = DateTime.Now;
 260
 261                                 // receive
 262                                 bytes = new byte [100];
 263                                 do {
 264                                         EndPoint endpoint = client;
 265                                         SocketError error = 0;
 266                                         int rc = s.ReceiveFrom (bytes, 0, 100, SocketFlags.None,
 267                                                         ref endpoint, out error);
 268
 269                                         if (error != SocketError.Success) {
 270                                                 if (error == SocketError.TimedOut) {
 271                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 272                                                 }
 273                                                 throw new NotSupportedException (String.Format ("Unexpected socket error during ping request: {0}", error));
 274                                         }
 275                                         long rtt = (long) (DateTime.Now - sentTime).TotalMilliseconds;
 276                                         int headerLength = (bytes [0] & 0xF) << 2;
 277                                         int bodyLength = rc - headerLength;
 278
 279                                         // Ping reply to different request. discard it.
 280                                         if (!((IPEndPoint) endpoint).Address.Equals (target.Address)) {
 281                                                 long t = timeout - rtt;
 282                                                 if (t <= 0)
 283                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 284                                                 s.ReceiveTimeout = (int) t;
 285                                                 continue;
 286                                         }
 287
 288                                         IcmpMessage recv = new IcmpMessage (bytes, headerLength, bodyLength);
 289
 290                                         /* discard ping reply to different request or echo requests if running on same host. */
 291                                         if (recv.Identifier != identifier || recv.Type == 8) {
 292                                                 long t = timeout - rtt;
 293                                                 if (t <= 0)
 294                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 295                                                 s.ReceiveTimeout = (int) t;
 296                                                 continue;
 297                                         }
 298
 299                                         return new PingReply (address, recv.Data, options, rtt, recv.IPStatus);
 300                                 } while (true);
 301                         }
 302                 }
 303
 304                 private PingReply SendUnprivileged (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 305                 {
 306 #if MONO_FEATURE_PROCESS_START
 307                         DateTime sentTime = DateTime.UtcNow;
 308
 309                         Process ping = new Process ();
 310                         string args = BuildPingArgs (address, timeout, options);
 311                         long trip_time = 0;
 312
 313                         ping.StartInfo.FileName = PingBinPath;
 314                         ping.StartInfo.Arguments = args;
 315
 316                         ping.StartInfo.CreateNoWindow = true;
 317                         ping.StartInfo.UseShellExecute = false;
 318
 319                         ping.StartInfo.RedirectStandardOutput = true;
 320                         ping.StartInfo.RedirectStandardError = true;
 321
 322                         IPStatus status = IPStatus.Unknown;
 323                         try {
 324                                 ping.Start ();
 325
 326 #pragma warning disable 219
 327                                 string stdout = ping.StandardOutput.ReadToEnd ();
 328                                 string stderr = ping.StandardError.ReadToEnd ();
 329 #pragma warning restore 219
 330
 331                                 trip_time = (long) (DateTime.UtcNow - sentTime).TotalMilliseconds;
 332                                 if (!ping.WaitForExit (timeout) || (ping.HasExited && ping.ExitCode == 2))
 333                                         status = IPStatus.TimedOut;
 334                                 else if (ping.ExitCode == 0)
 335                                         status = IPStatus.Success;
 336                                 else if (ping.ExitCode == 1)
 337                                         status = IPStatus.TtlExpired;
 338                         } catch {
 339                         } finally {
 340                                 if (!ping.HasExited)
 341                                         ping.Kill ();
 342                                 ping.Dispose ();
 343                         }
 344
 345                         return new PingReply (address, buffer, options, trip_time, status);
 346 #else
 347                         throw new PlatformNotSupportedException ("Ping is not supported on this platform.");
 348 #endif // MONO_FEATURE_PROCESS_START
 349                 }
 350 #endif // !MONOTOUCH
 351
 352                 // Async
 353
 354                 public void SendAsync (IPAddress address, int timeout, byte [] buffer, object userToken)
 355                 {
 356                         SendAsync (address, default_timeout, default_buffer, new PingOptions (), userToken);
 357                 }
 358
 359                 public void SendAsync (IPAddress address, int timeout, object userToken)
 360                 {
 361                         SendAsync (address, default_timeout, default_buffer, userToken);
 362                 }
 363
 364                 public void SendAsync (IPAddress address, object userToken)
 365                 {
 366                         SendAsync (address, default_timeout, userToken);
 367                 }
 368
 369                 public void SendAsync (string hostNameOrAddress, int timeout, byte [] buffer, object userToken)
 370                 {
 371                         SendAsync (hostNameOrAddress, timeout, buffer, new PingOptions (), userToken);
 372                 }
 373
 374                 public void SendAsync (string hostNameOrAddress, int timeout, byte [] buffer, PingOptions options, object userToken)
 375                 {
 376                         IPAddress address = Dns.GetHostEntry (hostNameOrAddress).AddressList [0];
 377                         SendAsync (address, timeout, buffer, options, userToken);
 378                 }
 379
 380                 public void SendAsync (string hostNameOrAddress, int timeout, object userToken)
 381                 {
 382                         SendAsync (hostNameOrAddress, timeout, default_buffer, userToken);
 383                 }
 384
 385                 public void SendAsync (string hostNameOrAddress, object userToken)
 386                 {
 387                         SendAsync (hostNameOrAddress, default_timeout, userToken);
 388                 }
 389
 390                 public void SendAsync (IPAddress address, int timeout, byte [] buffer, PingOptions options, object userToken)
 391                 {
 392                         if ((worker != null) || (cts != null))
 393                                 throw new InvalidOperationException ("Another SendAsync operation is in progress");
 394
 395                         worker = new BackgroundWorker ();
 396                         worker.DoWork += delegate (object o, DoWorkEventArgs ea) {
 397                                 try {
 398                                         user_async_state = ea.Argument;
 399                                         ea.Result = Send (address, timeout, buffer, options);
 400                                 } catch (Exception ex) {
 401                                         ea.Result = ex;
 402                                 }
 403                         };
 404                         worker.WorkerSupportsCancellation = true;
 405                         worker.RunWorkerCompleted += delegate (object o, RunWorkerCompletedEventArgs ea) {
 406                                 // Note that RunWorkerCompletedEventArgs.UserState cannot be used (LAMESPEC)
 407                                 OnPingCompleted (new PingCompletedEventArgs (ea.Error, ea.Cancelled, user_async_state, ea.Result as PingReply));
 408                         };
 409                         worker.RunWorkerAsync (userToken);
 410                 }
 411
 412                 // SendAsyncCancel
 413
 414                 public void SendAsyncCancel ()
 415                 {
 416                         if (cts != null) {
 417                                 cts.Cancel ();
 418                                 return;
 419                         }
 420
 421                         if (worker == null)
 422                                 throw new InvalidOperationException ("SendAsync operation is not in progress");
 423                         worker.CancelAsync ();
 424                 }
 425
 426 #if !MONOTOUCH
 427                 // ICMP message
 428
 429                 class IcmpMessage
 430                 {
 431                         byte [] bytes;
 432
 433                         // received
 434                         public IcmpMessage (byte [] bytes, int offset, int size)
 435                         {
 436                                 this.bytes = new byte [size];
 437                                 Buffer.BlockCopy (bytes, offset, this.bytes, 0, size);
 438                         }
 439
 440                         // to be sent
 441                         public IcmpMessage (byte type, byte code, ushort identifier, ushort sequence, byte [] data)
 442                         {
 443                                 bytes = new byte [data.Length + 8];
 444                                 bytes [0] = type;
 445                                 bytes [1] = code;
 446                                 bytes [4] = (byte) (identifier & 0xFF);
 447                                 bytes [5] = (byte) ((int) identifier >> 8);
 448                                 bytes [6] = (byte) (sequence & 0xFF);
 449                                 bytes [7] = (byte) ((int) sequence >> 8);
 450                                 Buffer.BlockCopy (data, 0, bytes, 8, data.Length);
 451
 452                                 ushort checksum = ComputeChecksum (bytes);
 453                                 bytes [2] = (byte) (checksum & 0xFF);
 454                                 bytes [3] = (byte) ((int) checksum >> 8);
 455                         }
 456
 457                         public byte Type {
 458                                 get { return bytes [0]; }
 459                         }
 460
 461                         public byte Code {
 462                                 get { return bytes [1]; }
 463                         }
 464
 465                         public ushort Identifier {
 466                                 get { return (ushort) (bytes [4] + (bytes [5] << 8)); }
 467                         }
 468
 469                         public ushort Sequence {
 470                                 get { return (ushort) (bytes [6] + (bytes [7] << 8)); }
 471                         }
 472
 473                         public byte [] Data {
 474                                 get {
 475                                         byte [] data = new byte [bytes.Length - 8];
 476                                         Buffer.BlockCopy (bytes, 8, data, 0, data.Length);
 477                                         return data;
 478                                 }
 479                         }
 480
 481                         public byte [] GetBytes ()
 482                         {
 483                                 return bytes;
 484                         }
 485
 486                         static ushort ComputeChecksum (byte [] data)
 487                         {
 488                                 uint ret = 0;
 489                                 for (int i = 0; i < data.Length; i += 2) {
 490                                         ushort us = i + 1 < data.Length ? data [i + 1] : (byte) 0;
 491                                         us <<= 8;
 492                                         us += data [i];
 493                                         ret += us;
 494                                 }
 495                                 ret = (ret >> 16) + (ret & 0xFFFF);
 496                                 return (ushort) ~ ret;
 497                         }
 498
 499                         public IPStatus IPStatus {
 500                                 get {
 501                                         switch (Type) {
 502                                         case 0:
 503                                                 return IPStatus.Success;
 504                                         case 3: // destination unreacheable
 505                                                 switch (Code) {
 506                                                 case 0:
 507                                                         return IPStatus.DestinationNetworkUnreachable;
 508                                                 case 1:
 509                                                         return IPStatus.DestinationHostUnreachable;
 510                                                 case 2:
 511                                                         return IPStatus.DestinationProtocolUnreachable;
 512                                                 case 3:
 513                                                         return IPStatus.DestinationPortUnreachable;
 514                                                 case 4:
 515                                                         return IPStatus.BadOption; // FIXME: likely wrong
 516                                                 case 5:
 517                                                         return IPStatus.BadRoute; // not sure if it is correct
 518                                                 }
 519                                                 break;
 520                                         case 11:
 521                                                 switch (Code) {
 522                                                 case 0:
 523                                                         return IPStatus.TimeExceeded;
 524                                                 case 1:
 525                                                         return IPStatus.TtlReassemblyTimeExceeded;
 526                                                 }
 527                                                 break;
 528                                         case 12:
 529                                                 return IPStatus.ParameterProblem;
 530                                         case 4:
 531                                                 return IPStatus.SourceQuench;
 532                                         case 8:
 533                                                 return IPStatus.Success;
 534                                         }
 535                                         return IPStatus.Unknown;
 536                                         //throw new NotSupportedException (String.Format ("Unexpected pair of ICMP message type and code: type is {0} and code is {1}", Type, Code));
 537                                 }
 538                         }
 539                 }
 540
 541                 private string BuildPingArgs (IPAddress address, int timeout, PingOptions options)
 542                 {
 543                         CultureInfo culture = CultureInfo.InvariantCulture;
 544                         StringBuilder args = new StringBuilder ();
 545                         uint t = Convert.ToUInt32 (Math.Floor ((timeout + 1000) / 1000.0));
 546                         bool is_mac = Platform.IsMacOS;
 547                         if (!is_mac)
 548                                 args.AppendFormat (culture, "-q -n -c {0} -w {1} -t {2} -M ", DefaultCount, t, options.Ttl);
 549                         else
 550                                 args.AppendFormat (culture, "-q -n -c {0} -t {1} -o -m {2} ", DefaultCount, t, options.Ttl);
 551                         if (!is_mac)
 552                                 args.Append (options.DontFragment ? "do " : "dont ");
 553                         else if (options.DontFragment)
 554                                 args.Append ("-D ");
 555
 556                         args.Append (address.ToString ());
 557
 558                         return args.ToString ();
 559                 }
 560 #endif // !MONOTOUCH
 561
 562                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout, byte [] buffer)
 563                 {
 564                         return SendPingAsync (address, default_timeout, default_buffer, new PingOptions ());
 565                 }
 566
 567                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout)
 568                 {
 569                         return SendPingAsync (address, default_timeout, default_buffer);
 570                 }
 571
 572                 public Task<PingReply> SendPingAsync (IPAddress address)
 573                 {
 574                         return SendPingAsync (address, default_timeout);
 575                 }
 576
 577                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout, byte [] buffer)
 578                 {
 579                         return SendPingAsync (hostNameOrAddress, timeout, buffer, new PingOptions ());
 580                 }
 581
 582                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout, byte [] buffer, PingOptions options)
 583                 {
 584                         IPAddress address = Dns.GetHostEntry (hostNameOrAddress).AddressList [0];
 585                         return SendPingAsync (address, timeout, buffer, options);
 586                 }
 587
 588                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout)
 589                 {
 590                         return SendPingAsync (hostNameOrAddress, timeout, default_buffer);
 591                 }
 592
 593                 public Task<PingReply> SendPingAsync (string hostNameOrAddress)
 594                 {
 595                         return SendPingAsync (hostNameOrAddress, default_timeout);
 596                 }
 597
 598                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 599                 {
 600                         if ((worker != null) || (cts != null))
 601                                 throw new InvalidOperationException ("Another SendAsync operation is in progress");
 602
 603                         cts = new CancellationTokenSource();
 604
 605                         var task = Task<PingReply>.Factory.StartNew (
 606                                 () => Send (address, timeout, buffer, options), cts.Token);
 607
 608                         task.ContinueWith ((t) => {
 609                                 if (t.IsCanceled)
 610                                         OnPingCompleted (new PingCompletedEventArgs (null, true, null, null));
 611                                 else if (t.IsFaulted)
 612                                         OnPingCompleted (new PingCompletedEventArgs (t.Exception, false, null, null));
 613                                 else
 614                                         OnPingCompleted (new PingCompletedEventArgs (null, false, null, t.Result));
 615                         });
 616
 617                         return task;
 618                 }
 619         }
 620 }