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                 static bool canSendPrivileged;
  75 #endif
  76                 const int default_timeout = 4000; // 4 sec.
  77                 ushort identifier;
  78
  79                 // This value is correct as of Linux kernel version 2.6.25.9
  80                 // See /usr/include/linux/capability.h
  81                 const UInt32 linux_cap_version = 0x20071026;
  82
  83                 static readonly byte [] default_buffer = new byte [0];
  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 #pragma warning disable 618
 213                         foreach (IPAddress addr in Dns.GetHostByName (Dns.GetHostName ()).AddressList)
 214                                 if (!IPAddress.IsLoopback (addr))
 215                                         return addr;
 216 #pragma warning restore 618
 217
 218                         throw new InvalidOperationException ("Could not resolve non-loopback IP address for localhost");
 219                 }
 220
 221                 public PingReply Send (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 222                 {
 223                         if (address == null)
 224                                 throw new ArgumentNullException ("address");
 225                         if (timeout < 0)
 226                                 throw new ArgumentOutOfRangeException ("timeout", "timeout must be non-negative integer");
 227                         if (buffer == null)
 228                                 throw new ArgumentNullException ("buffer");
 229                         if (buffer.Length > 65500)
 230                                 throw new ArgumentException ("buffer");
 231                         // options can be null.
 232
 233 #if MONOTOUCH
 234                         throw new InvalidOperationException ();
 235 #else
 236                         if (canSendPrivileged)
 237                                 return SendPrivileged (address, timeout, buffer, options);
 238                         return SendUnprivileged (address, timeout, buffer, options);
 239 #endif
 240                 }
 241
 242 #if !MONOTOUCH
 243                 private PingReply SendPrivileged (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 244                 {
 245                         IPEndPoint target = new IPEndPoint (address, 0);
 246                         IPEndPoint client = new IPEndPoint (GetNonLoopbackIP (), 0);
 247
 248                         // FIXME: support IPv6
 249                         using (Socket s = new Socket (AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp)) {
 250                                 if (options != null) {
 251                                         s.DontFragment = options.DontFragment;
 252                                         s.Ttl = (short) options.Ttl;
 253                                 }
 254                                 s.SendTimeout = timeout;
 255                                 s.ReceiveTimeout = timeout;
 256                                 // not sure why Identifier = 0 is unacceptable ...
 257                                 IcmpMessage send = new IcmpMessage (8, 0, identifier, 0, buffer);
 258                                 byte [] bytes = send.GetBytes ();
 259                                 s.SendBufferSize = bytes.Length;
 260                                 s.SendTo (bytes, bytes.Length, SocketFlags.None, target);
 261
 262                                 DateTime sentTime = DateTime.Now;
 263
 264                                 // receive
 265                                 bytes = new byte [100];
 266                                 do {
 267                                         EndPoint endpoint = client;
 268                                         SocketError error = 0;
 269                                         int rc = s.ReceiveFrom (bytes, 0, 100, SocketFlags.None,
 270                                                         ref endpoint, out error);
 271
 272                                         if (error != SocketError.Success) {
 273                                                 if (error == SocketError.TimedOut) {
 274                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 275                                                 }
 276                                                 throw new NotSupportedException (String.Format ("Unexpected socket error during ping request: {0}", error));
 277                                         }
 278                                         long rtt = (long) (DateTime.Now - sentTime).TotalMilliseconds;
 279                                         int headerLength = (bytes [0] & 0xF) << 2;
 280                                         int bodyLength = rc - headerLength;
 281
 282                                         // Ping reply to different request. discard it.
 283                                         if (!((IPEndPoint) endpoint).Address.Equals (target.Address)) {
 284                                                 long t = timeout - rtt;
 285                                                 if (t <= 0)
 286                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 287                                                 s.ReceiveTimeout = (int) t;
 288                                                 continue;
 289                                         }
 290
 291                                         IcmpMessage recv = new IcmpMessage (bytes, headerLength, bodyLength);
 292
 293                                         /* discard ping reply to different request or echo requests if running on same host. */
 294                                         if (recv.Identifier != identifier || recv.Type == 8) {
 295                                                 long t = timeout - rtt;
 296                                                 if (t <= 0)
 297                                                         return new PingReply (null, new byte [0], options, 0, IPStatus.TimedOut);
 298                                                 s.ReceiveTimeout = (int) t;
 299                                                 continue;
 300                                         }
 301
 302                                         return new PingReply (address, recv.Data, options, rtt, recv.IPStatus);
 303                                 } while (true);
 304                         }
 305                 }
 306
 307                 private PingReply SendUnprivileged (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 308                 {
 309 #if MONO_FEATURE_PROCESS_START
 310                         DateTime sentTime = DateTime.UtcNow;
 311
 312                         Process ping = new Process ();
 313                         string args = BuildPingArgs (address, timeout, options);
 314                         long trip_time = 0;
 315
 316                         ping.StartInfo.FileName = PingBinPath;
 317                         ping.StartInfo.Arguments = args;
 318
 319                         ping.StartInfo.CreateNoWindow = true;
 320                         ping.StartInfo.UseShellExecute = false;
 321
 322                         ping.StartInfo.RedirectStandardOutput = true;
 323                         ping.StartInfo.RedirectStandardError = true;
 324
 325                         IPStatus status = IPStatus.Unknown;
 326                         try {
 327                                 ping.Start ();
 328
 329 #pragma warning disable 219
 330                                 string stdout = ping.StandardOutput.ReadToEnd ();
 331                                 string stderr = ping.StandardError.ReadToEnd ();
 332 #pragma warning restore 219
 333
 334                                 trip_time = (long) (DateTime.UtcNow - sentTime).TotalMilliseconds;
 335                                 if (!ping.WaitForExit (timeout) || (ping.HasExited && ping.ExitCode == 2))
 336                                         status = IPStatus.TimedOut;
 337                                 else if (ping.ExitCode == 0)
 338                                         status = IPStatus.Success;
 339                                 else if (ping.ExitCode == 1)
 340                                         status = IPStatus.TtlExpired;
 341                         } catch {
 342                         } finally {
 343                                 if (!ping.HasExited)
 344                                         ping.Kill ();
 345                                 ping.Dispose ();
 346                         }
 347
 348                         return new PingReply (address, buffer, options, trip_time, status);
 349 #else
 350                         throw new PlatformNotSupportedException ("Ping is not supported on this platform.");
 351 #endif // MONO_FEATURE_PROCESS_START
 352                 }
 353 #endif // !MONOTOUCH
 354
 355                 // Async
 356
 357                 public void SendAsync (IPAddress address, int timeout, byte [] buffer, object userToken)
 358                 {
 359                         SendAsync (address, default_timeout, default_buffer, new PingOptions (), userToken);
 360                 }
 361
 362                 public void SendAsync (IPAddress address, int timeout, object userToken)
 363                 {
 364                         SendAsync (address, default_timeout, default_buffer, userToken);
 365                 }
 366
 367                 public void SendAsync (IPAddress address, object userToken)
 368                 {
 369                         SendAsync (address, default_timeout, userToken);
 370                 }
 371
 372                 public void SendAsync (string hostNameOrAddress, int timeout, byte [] buffer, object userToken)
 373                 {
 374                         SendAsync (hostNameOrAddress, timeout, buffer, new PingOptions (), userToken);
 375                 }
 376
 377                 public void SendAsync (string hostNameOrAddress, int timeout, byte [] buffer, PingOptions options, object userToken)
 378                 {
 379                         IPAddress address = Dns.GetHostEntry (hostNameOrAddress).AddressList [0];
 380                         SendAsync (address, timeout, buffer, options, userToken);
 381                 }
 382
 383                 public void SendAsync (string hostNameOrAddress, int timeout, object userToken)
 384                 {
 385                         SendAsync (hostNameOrAddress, timeout, default_buffer, userToken);
 386                 }
 387
 388                 public void SendAsync (string hostNameOrAddress, object userToken)
 389                 {
 390                         SendAsync (hostNameOrAddress, default_timeout, userToken);
 391                 }
 392
 393                 public void SendAsync (IPAddress address, int timeout, byte [] buffer, PingOptions options, object userToken)
 394                 {
 395                         if ((worker != null) || (cts != null))
 396                                 throw new InvalidOperationException ("Another SendAsync operation is in progress");
 397
 398                         worker = new BackgroundWorker ();
 399                         worker.DoWork += delegate (object o, DoWorkEventArgs ea) {
 400                                 try {
 401                                         user_async_state = ea.Argument;
 402                                         ea.Result = Send (address, timeout, buffer, options);
 403                                 } catch (Exception ex) {
 404                                         ea.Result = ex;
 405                                 }
 406                         };
 407                         worker.WorkerSupportsCancellation = true;
 408                         worker.RunWorkerCompleted += delegate (object o, RunWorkerCompletedEventArgs ea) {
 409                                 // Note that RunWorkerCompletedEventArgs.UserState cannot be used (LAMESPEC)
 410                                 OnPingCompleted (new PingCompletedEventArgs (ea.Error, ea.Cancelled, user_async_state, ea.Result as PingReply));
 411                         };
 412                         worker.RunWorkerAsync (userToken);
 413                 }
 414
 415                 // SendAsyncCancel
 416
 417                 public void SendAsyncCancel ()
 418                 {
 419                         if (cts != null) {
 420                                 cts.Cancel ();
 421                                 return;
 422                         }
 423
 424                         if (worker == null)
 425                                 throw new InvalidOperationException ("SendAsync operation is not in progress");
 426                         worker.CancelAsync ();
 427                 }
 428
 429 #if !MONOTOUCH
 430                 // ICMP message
 431
 432                 class IcmpMessage
 433                 {
 434                         byte [] bytes;
 435
 436                         // received
 437                         public IcmpMessage (byte [] bytes, int offset, int size)
 438                         {
 439                                 this.bytes = new byte [size];
 440                                 Buffer.BlockCopy (bytes, offset, this.bytes, 0, size);
 441                         }
 442
 443                         // to be sent
 444                         public IcmpMessage (byte type, byte code, ushort identifier, ushort sequence, byte [] data)
 445                         {
 446                                 bytes = new byte [data.Length + 8];
 447                                 bytes [0] = type;
 448                                 bytes [1] = code;
 449                                 bytes [4] = (byte) (identifier & 0xFF);
 450                                 bytes [5] = (byte) ((int) identifier >> 8);
 451                                 bytes [6] = (byte) (sequence & 0xFF);
 452                                 bytes [7] = (byte) ((int) sequence >> 8);
 453                                 Buffer.BlockCopy (data, 0, bytes, 8, data.Length);
 454
 455                                 ushort checksum = ComputeChecksum (bytes);
 456                                 bytes [2] = (byte) (checksum & 0xFF);
 457                                 bytes [3] = (byte) ((int) checksum >> 8);
 458                         }
 459
 460                         public byte Type {
 461                                 get { return bytes [0]; }
 462                         }
 463
 464                         public byte Code {
 465                                 get { return bytes [1]; }
 466                         }
 467
 468                         public ushort Identifier {
 469                                 get { return (ushort) (bytes [4] + (bytes [5] << 8)); }
 470                         }
 471
 472                         public ushort Sequence {
 473                                 get { return (ushort) (bytes [6] + (bytes [7] << 8)); }
 474                         }
 475
 476                         public byte [] Data {
 477                                 get {
 478                                         byte [] data = new byte [bytes.Length - 8];
 479                                         Buffer.BlockCopy (bytes, 8, data, 0, data.Length);
 480                                         return data;
 481                                 }
 482                         }
 483
 484                         public byte [] GetBytes ()
 485                         {
 486                                 return bytes;
 487                         }
 488
 489                         static ushort ComputeChecksum (byte [] data)
 490                         {
 491                                 uint ret = 0;
 492                                 for (int i = 0; i < data.Length; i += 2) {
 493                                         ushort us = i + 1 < data.Length ? data [i + 1] : (byte) 0;
 494                                         us <<= 8;
 495                                         us += data [i];
 496                                         ret += us;
 497                                 }
 498                                 ret = (ret >> 16) + (ret & 0xFFFF);
 499                                 return (ushort) ~ ret;
 500                         }
 501
 502                         public IPStatus IPStatus {
 503                                 get {
 504                                         switch (Type) {
 505                                         case 0:
 506                                                 return IPStatus.Success;
 507                                         case 3: // destination unreacheable
 508                                                 switch (Code) {
 509                                                 case 0:
 510                                                         return IPStatus.DestinationNetworkUnreachable;
 511                                                 case 1:
 512                                                         return IPStatus.DestinationHostUnreachable;
 513                                                 case 2:
 514                                                         return IPStatus.DestinationProtocolUnreachable;
 515                                                 case 3:
 516                                                         return IPStatus.DestinationPortUnreachable;
 517                                                 case 4:
 518                                                         return IPStatus.BadOption; // FIXME: likely wrong
 519                                                 case 5:
 520                                                         return IPStatus.BadRoute; // not sure if it is correct
 521                                                 }
 522                                                 break;
 523                                         case 11:
 524                                                 switch (Code) {
 525                                                 case 0:
 526                                                         return IPStatus.TimeExceeded;
 527                                                 case 1:
 528                                                         return IPStatus.TtlReassemblyTimeExceeded;
 529                                                 }
 530                                                 break;
 531                                         case 12:
 532                                                 return IPStatus.ParameterProblem;
 533                                         case 4:
 534                                                 return IPStatus.SourceQuench;
 535                                         case 8:
 536                                                 return IPStatus.Success;
 537                                         }
 538                                         return IPStatus.Unknown;
 539                                         //throw new NotSupportedException (String.Format ("Unexpected pair of ICMP message type and code: type is {0} and code is {1}", Type, Code));
 540                                 }
 541                         }
 542                 }
 543
 544                 private string BuildPingArgs (IPAddress address, int timeout, PingOptions options)
 545                 {
 546                         CultureInfo culture = CultureInfo.InvariantCulture;
 547                         StringBuilder args = new StringBuilder ();
 548                         uint t = Convert.ToUInt32 (Math.Floor ((timeout + 1000) / 1000.0));
 549                         bool is_mac = Platform.IsMacOS;
 550                         if (!is_mac)
 551                                 args.AppendFormat (culture, "-q -n -c {0} -w {1} -t {2} -M ", DefaultCount, t, options.Ttl);
 552                         else
 553                                 args.AppendFormat (culture, "-q -n -c {0} -t {1} -o -m {2} ", DefaultCount, t, options.Ttl);
 554                         if (!is_mac)
 555                                 args.Append (options.DontFragment ? "do " : "dont ");
 556                         else if (options.DontFragment)
 557                                 args.Append ("-D ");
 558
 559                         args.Append (address.ToString ());
 560
 561                         return args.ToString ();
 562                 }
 563 #endif // !MONOTOUCH
 564
 565                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout, byte [] buffer)
 566                 {
 567                         return SendPingAsync (address, default_timeout, default_buffer, new PingOptions ());
 568                 }
 569
 570                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout)
 571                 {
 572                         return SendPingAsync (address, default_timeout, default_buffer);
 573                 }
 574
 575                 public Task<PingReply> SendPingAsync (IPAddress address)
 576                 {
 577                         return SendPingAsync (address, default_timeout);
 578                 }
 579
 580                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout, byte [] buffer)
 581                 {
 582                         return SendPingAsync (hostNameOrAddress, timeout, buffer, new PingOptions ());
 583                 }
 584
 585                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout, byte [] buffer, PingOptions options)
 586                 {
 587                         IPAddress address = Dns.GetHostEntry (hostNameOrAddress).AddressList [0];
 588                         return SendPingAsync (address, timeout, buffer, options);
 589                 }
 590
 591                 public Task<PingReply> SendPingAsync (string hostNameOrAddress, int timeout)
 592                 {
 593                         return SendPingAsync (hostNameOrAddress, timeout, default_buffer);
 594                 }
 595
 596                 public Task<PingReply> SendPingAsync (string hostNameOrAddress)
 597                 {
 598                         return SendPingAsync (hostNameOrAddress, default_timeout);
 599                 }
 600
 601                 public Task<PingReply> SendPingAsync (IPAddress address, int timeout, byte [] buffer, PingOptions options)
 602                 {
 603                         if ((worker != null) || (cts != null))
 604                                 throw new InvalidOperationException ("Another SendAsync operation is in progress");
 605
 606                         cts = new CancellationTokenSource();
 607
 608                         var task = Task<PingReply>.Factory.StartNew (
 609                                 () => Send (address, timeout, buffer, options), cts.Token);
 610
 611                         task.ContinueWith ((t) => {
 612                                 if (t.IsCanceled)
 613                                         OnPingCompleted (new PingCompletedEventArgs (null, true, null, null));
 614                                 else if (t.IsFaulted)
 615                                         OnPingCompleted (new PingCompletedEventArgs (t.Exception, false, null, null));
 616                                 else
 617                                         OnPingCompleted (new PingCompletedEventArgs (null, false, null, t.Result));
 618                         });
 619
 620                         return task;
 621                 }
 622         }
 623 }