summaryrefslogtreecommitdiff
path: root/lib/internal/child_process.js
blob: b07a38d6f6f5ac6112d6821395d1dd8242d650ed (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
'use strict';

const {
  ArrayIsArray,
  ObjectDefineProperty,
  ObjectSetPrototypeOf,
  Symbol,
} = primordials;

const {
  errnoException,
  codes: {
    ERR_INVALID_ARG_TYPE,
    ERR_INVALID_HANDLE_TYPE,
    ERR_INVALID_OPT_VALUE,
    ERR_INVALID_SYNC_FORK_INPUT,
    ERR_IPC_CHANNEL_CLOSED,
    ERR_IPC_DISCONNECTED,
    ERR_IPC_ONE_PIPE,
    ERR_IPC_SYNC_FORK,
    ERR_MISSING_ARGS
  }
} = require('internal/errors');
const { validateString } = require('internal/validators');
const EventEmitter = require('events');
const net = require('net');
const dgram = require('dgram');
const inspect = require('internal/util/inspect').inspect;
const assert = require('internal/assert');

const { Process } = internalBinding('process_wrap');
const {
  WriteWrap,
  kReadBytesOrError,
  kArrayBufferOffset,
  kLastWriteWasAsync,
  streamBaseState
} = internalBinding('stream_wrap');
const { Pipe, constants: PipeConstants } = internalBinding('pipe_wrap');
const { TCP } = internalBinding('tcp_wrap');
const { TTY } = internalBinding('tty_wrap');
const { UDP } = internalBinding('udp_wrap');
const SocketList = require('internal/socket_list');
const { owner_symbol } = require('internal/async_hooks').symbols;
const { convertToValidSignal, deprecate } = require('internal/util');
const { isArrayBufferView } = require('internal/util/types');
const spawn_sync = internalBinding('spawn_sync');
const { kStateSymbol } = require('internal/dgram');

const {
  UV_EACCES,
  UV_EAGAIN,
  UV_EINVAL,
  UV_EMFILE,
  UV_ENFILE,
  UV_ENOENT,
  UV_ENOSYS,
  UV_ESRCH
} = internalBinding('uv');

const { SocketListSend, SocketListReceive } = SocketList;

// Lazy loaded for startup performance and to allow monkey patching of
// internalBinding('http_parser').HTTPParser.
let freeParser;
let HTTPParser;

const MAX_HANDLE_RETRANSMISSIONS = 3;
const kIsUsedAsStdio = Symbol('kIsUsedAsStdio');

// This object contain function to convert TCP objects to native handle objects
// and back again.
const handleConversion = {
  'net.Native': {
    simultaneousAccepts: true,

    send(message, handle, options) {
      return handle;
    },

    got(message, handle, emit) {
      emit(handle);
    }
  },

  'net.Server': {
    simultaneousAccepts: true,

    send(message, server, options) {
      return server._handle;
    },

    got(message, handle, emit) {
      const server = new net.Server();
      server.listen(handle, () => {
        emit(server);
      });
    }
  },

  'net.Socket': {
    send(message, socket, options) {
      if (!socket._handle)
        return;

      // If the socket was created by net.Server
      if (socket.server) {
        // The worker should keep track of the socket
        message.key = socket.server._connectionKey;

        const firstTime = !this.channel.sockets.send[message.key];
        const socketList = getSocketList('send', this, message.key);

        // The server should no longer expose a .connection property
        // and when asked to close it should query the socket status from
        // the workers
        if (firstTime) socket.server._setupWorker(socketList);

        // Act like socket is detached
        if (!options.keepOpen)
          socket.server._connections--;
      }

      const handle = socket._handle;

      // Remove handle from socket object, it will be closed when the socket
      // will be sent
      if (!options.keepOpen) {
        handle.onread = nop;
        socket._handle = null;
        socket.setTimeout(0);

        if (freeParser === undefined)
          freeParser = require('_http_common').freeParser;
        if (HTTPParser === undefined)
          HTTPParser = require('_http_common').HTTPParser;

        // In case of an HTTP connection socket, release the associated
        // resources
        if (socket.parser && socket.parser instanceof HTTPParser) {
          freeParser(socket.parser, null, socket);
          if (socket._httpMessage)
            socket._httpMessage.detachSocket(socket);
        }
      }

      return handle;
    },

    postSend(message, handle, options, callback, target) {
      // Store the handle after successfully sending it, so it can be closed
      // when the NODE_HANDLE_ACK is received. If the handle could not be sent,
      // just close it.
      if (handle && !options.keepOpen) {
        if (target) {
          // There can only be one _pendingMessage as passing handles are
          // processed one at a time: handles are stored in _handleQueue while
          // waiting for the NODE_HANDLE_ACK of the current passing handle.
          assert(!target._pendingMessage);
          target._pendingMessage =
              { callback, message, handle, options, retransmissions: 0 };
        } else {
          handle.close();
        }
      }
    },

    got(message, handle, emit) {
      const socket = new net.Socket({
        handle: handle,
        readable: true,
        writable: true
      });

      // If the socket was created by net.Server we will track the socket
      if (message.key) {

        // Add socket to connections list
        const socketList = getSocketList('got', this, message.key);
        socketList.add({
          socket: socket
        });
      }

      emit(socket);
    }
  },

  'dgram.Native': {
    simultaneousAccepts: false,

    send(message, handle, options) {
      return handle;
    },

    got(message, handle, emit) {
      emit(handle);
    }
  },

  'dgram.Socket': {
    simultaneousAccepts: false,

    send(message, socket, options) {
      message.dgramType = socket.type;

      return socket[kStateSymbol].handle;
    },

    got(message, handle, emit) {
      const socket = new dgram.Socket(message.dgramType);

      socket.bind(handle, () => {
        emit(socket);
      });
    }
  }
};

function stdioStringToArray(stdio, channel) {
  const options = [];

  switch (stdio) {
    case 'ignore':
    case 'pipe': options.push(stdio, stdio, stdio); break;
    case 'inherit': options.push(0, 1, 2); break;
    default:
      throw new ERR_INVALID_OPT_VALUE('stdio', stdio);
  }

  if (channel) options.push(channel);

  return options;
}

function ChildProcess() {
  EventEmitter.call(this);

  this._closesNeeded = 1;
  this._closesGot = 0;
  this.connected = false;

  this.signalCode = null;
  this.exitCode = null;
  this.killed = false;
  this.spawnfile = null;

  this._handle = new Process();
  this._handle[owner_symbol] = this;

  this._handle.onexit = (exitCode, signalCode) => {
    if (signalCode) {
      this.signalCode = signalCode;
    } else {
      this.exitCode = exitCode;
    }

    if (this.stdin) {
      this.stdin.destroy();
    }

    this._handle.close();
    this._handle = null;

    if (exitCode < 0) {
      const syscall = this.spawnfile ? 'spawn ' + this.spawnfile : 'spawn';
      const err = errnoException(exitCode, syscall);

      if (this.spawnfile)
        err.path = this.spawnfile;

      err.spawnargs = this.spawnargs.slice(1);
      this.emit('error', err);
    } else {
      this.emit('exit', this.exitCode, this.signalCode);
    }

    // If any of the stdio streams have not been touched,
    // then pull all the data through so that it can get the
    // eof and emit a 'close' event.
    // Do it on nextTick so that the user has one last chance
    // to consume the output, if for example they only want to
    // start reading the data once the process exits.
    process.nextTick(flushStdio, this);

    maybeClose(this);
  };
}
ObjectSetPrototypeOf(ChildProcess.prototype, EventEmitter.prototype);
ObjectSetPrototypeOf(ChildProcess, EventEmitter);


function flushStdio(subprocess) {
  const stdio = subprocess.stdio;

  if (stdio == null) return;

  for (let i = 0; i < stdio.length; i++) {
    const stream = stdio[i];
    // TODO(addaleax): This doesn't necessarily account for all the ways in
    // which data can be read from a stream, e.g. being consumed on the
    // native layer directly as a StreamBase.
    if (!stream || !stream.readable ||
        stream._readableState.readableListening ||
        stream[kIsUsedAsStdio]) {
      continue;
    }
    stream.resume();
  }
}


function createSocket(pipe, readable) {
  return net.Socket({ handle: pipe, readable, writable: !readable });
}


function getHandleWrapType(stream) {
  if (stream instanceof Pipe) return 'pipe';
  if (stream instanceof TTY) return 'tty';
  if (stream instanceof TCP) return 'tcp';
  if (stream instanceof UDP) return 'udp';

  return false;
}

function closePendingHandle(target) {
  target._pendingMessage.handle.close();
  target._pendingMessage = null;
}


ChildProcess.prototype.spawn = function(options) {
  let i = 0;

  if (options === null || typeof options !== 'object') {
    throw new ERR_INVALID_ARG_TYPE('options', 'Object', options);
  }

  // If no `stdio` option was given - use default
  let stdio = options.stdio || 'pipe';

  stdio = getValidStdio(stdio, false);

  const ipc = stdio.ipc;
  const ipcFd = stdio.ipcFd;
  stdio = options.stdio = stdio.stdio;

  if (options.serialization !== undefined &&
      options.serialization !== 'json' &&
      options.serialization !== 'advanced') {
    throw new ERR_INVALID_OPT_VALUE('options.serialization',
                                    options.serialization);
  }

  const serialization = options.serialization || 'json';

  if (ipc !== undefined) {
    // Let child process know about opened IPC channel
    if (options.envPairs === undefined)
      options.envPairs = [];
    else if (!ArrayIsArray(options.envPairs)) {
      throw new ERR_INVALID_ARG_TYPE('options.envPairs',
                                     'Array',
                                     options.envPairs);
    }

    options.envPairs.push(`NODE_CHANNEL_FD=${ipcFd}`);
    options.envPairs.push(`NODE_CHANNEL_SERIALIZATION_MODE=${serialization}`);
  }

  validateString(options.file, 'options.file');
  this.spawnfile = options.file;

  if (ArrayIsArray(options.args))
    this.spawnargs = options.args;
  else if (options.args === undefined)
    this.spawnargs = [];
  else
    throw new ERR_INVALID_ARG_TYPE('options.args', 'Array', options.args);

  const err = this._handle.spawn(options);

  // Run-time errors should emit an error, not throw an exception.
  if (err === UV_EACCES ||
      err === UV_EAGAIN ||
      err === UV_EMFILE ||
      err === UV_ENFILE ||
      err === UV_ENOENT) {
    process.nextTick(onErrorNT, this, err);

    // There is no point in continuing when we've hit EMFILE or ENFILE
    // because we won't be able to set up the stdio file descriptors.
    if (err === UV_EMFILE || err === UV_ENFILE)
      return err;
  } else if (err) {
    // Close all opened fds on error
    for (i = 0; i < stdio.length; i++) {
      const stream = stdio[i];
      if (stream.type === 'pipe') {
        stream.handle.close();
      }
    }

    this._handle.close();
    this._handle = null;
    throw errnoException(err, 'spawn');
  }

  this.pid = this._handle.pid;

  for (i = 0; i < stdio.length; i++) {
    const stream = stdio[i];
    if (stream.type === 'ignore') continue;

    if (stream.ipc) {
      this._closesNeeded++;
      continue;
    }

    // The stream is already cloned and piped, thus stop its readable side,
    // otherwise we might attempt to read from the stream when at the same time
    // the child process does.
    if (stream.type === 'wrap') {
      stream.handle.reading = false;
      stream.handle.readStop();
      stream._stdio.pause();
      stream._stdio.readableFlowing = false;
      stream._stdio._readableState.reading = false;
      stream._stdio[kIsUsedAsStdio] = true;
      continue;
    }

    if (stream.handle) {
      // When i === 0 - we're dealing with stdin
      // (which is the only one writable pipe).
      stream.socket = createSocket(this.pid !== 0 ?
        stream.handle : null, i > 0);

      if (i > 0 && this.pid !== 0) {
        this._closesNeeded++;
        stream.socket.on('close', () => {
          maybeClose(this);
        });
      }
    }
  }

  this.stdin = stdio.length >= 1 && stdio[0].socket !== undefined ?
    stdio[0].socket : null;
  this.stdout = stdio.length >= 2 && stdio[1].socket !== undefined ?
    stdio[1].socket : null;
  this.stderr = stdio.length >= 3 && stdio[2].socket !== undefined ?
    stdio[2].socket : null;

  this.stdio = [];

  for (i = 0; i < stdio.length; i++)
    this.stdio.push(stdio[i].socket === undefined ? null : stdio[i].socket);

  // Add .send() method and start listening for IPC data
  if (ipc !== undefined) setupChannel(this, ipc, serialization);

  return err;
};


function onErrorNT(self, err) {
  self._handle.onexit(err);
}


ChildProcess.prototype.kill = function(sig) {

  const signal = sig === 0 ? sig :
    convertToValidSignal(sig === undefined ? 'SIGTERM' : sig);

  if (this._handle) {
    const err = this._handle.kill(signal);
    if (err === 0) {
      /* Success. */
      this.killed = true;
      return true;
    }
    if (err === UV_ESRCH) {
      /* Already dead. */
    } else if (err === UV_EINVAL || err === UV_ENOSYS) {
      /* The underlying platform doesn't support this signal. */
      throw errnoException(err, 'kill');
    } else {
      /* Other error, almost certainly EPERM. */
      this.emit('error', errnoException(err, 'kill'));
    }
  }

  /* Kill didn't succeed. */
  return false;
};


ChildProcess.prototype.ref = function() {
  if (this._handle) this._handle.ref();
};


ChildProcess.prototype.unref = function() {
  if (this._handle) this._handle.unref();
};

class Control extends EventEmitter {
  constructor(channel) {
    super();
    this.channel = channel;
    this.refs = 0;
  }
  ref() {
    if (++this.refs === 1) {
      this.channel.ref();
    }
  }
  unref() {
    if (--this.refs === 0) {
      this.channel.unref();
      this.emit('unref');
    }
  }
}

const channelDeprecationMsg = '_channel is deprecated. ' +
                              'Use ChildProcess.channel instead.';

let serialization;
function setupChannel(target, channel, serializationMode) {
  target.channel = channel;

  ObjectDefineProperty(target, '_channel', {
    get: deprecate(() => {
      return target.channel;
    }, channelDeprecationMsg, 'DEP0129'),
    set: deprecate((val) => {
      target.channel = val;
    }, channelDeprecationMsg, 'DEP0129'),
    configurable: true,
    enumerable: false
  });

  target._handleQueue = null;
  target._pendingMessage = null;

  const control = new Control(channel);

  if (serialization === undefined)
    serialization = require('internal/child_process/serialization');
  const {
    initMessageChannel,
    parseChannelMessages,
    writeChannelMessage
  } = serialization[serializationMode];

  let pendingHandle = null;
  initMessageChannel(channel);
  channel.pendingHandle = null;
  channel.onread = function(arrayBuffer) {
    const recvHandle = channel.pendingHandle;
    channel.pendingHandle = null;
    if (arrayBuffer) {
      const nread = streamBaseState[kReadBytesOrError];
      const offset = streamBaseState[kArrayBufferOffset];
      const pool = new Uint8Array(arrayBuffer, offset, nread);
      if (recvHandle)
        pendingHandle = recvHandle;

      for (const message of parseChannelMessages(channel, pool)) {
        // There will be at most one NODE_HANDLE message in every chunk we
        // read because SCM_RIGHTS messages don't get coalesced. Make sure
        // that we deliver the handle with the right message however.
        if (isInternal(message)) {
          if (message.cmd === 'NODE_HANDLE') {
            handleMessage(message, pendingHandle, true);
            pendingHandle = null;
          } else {
            handleMessage(message, undefined, true);
          }
        } else {
          handleMessage(message, undefined, false);
        }
      }
    } else {
      this.buffering = false;
      target.disconnect();
      channel.onread = nop;
      channel.close();
      target.channel = null;
      maybeClose(target);
    }
  };

  // Object where socket lists will live
  channel.sockets = { got: {}, send: {} };

  // Handlers will go through this
  target.on('internalMessage', function(message, handle) {
    // Once acknowledged - continue sending handles.
    if (message.cmd === 'NODE_HANDLE_ACK' ||
        message.cmd === 'NODE_HANDLE_NACK') {

      if (target._pendingMessage) {
        if (message.cmd === 'NODE_HANDLE_ACK') {
          closePendingHandle(target);
        } else if (target._pendingMessage.retransmissions++ ===
                   MAX_HANDLE_RETRANSMISSIONS) {
          closePendingHandle(target);
          process.emitWarning('Handle did not reach the receiving process ' +
                              'correctly', 'SentHandleNotReceivedWarning');
        }
      }

      assert(ArrayIsArray(target._handleQueue));
      const queue = target._handleQueue;
      target._handleQueue = null;

      if (target._pendingMessage) {
        target._send(target._pendingMessage.message,
                     target._pendingMessage.handle,
                     target._pendingMessage.options,
                     target._pendingMessage.callback);
      }

      for (let i = 0; i < queue.length; i++) {
        const args = queue[i];
        target._send(args.message, args.handle, args.options, args.callback);
      }

      // Process a pending disconnect (if any).
      if (!target.connected && target.channel && !target._handleQueue)
        target._disconnect();

      return;
    }

    if (message.cmd !== 'NODE_HANDLE') return;

    // It is possible that the handle is not received because of some error on
    // ancillary data reception such as MSG_CTRUNC. In this case, report the
    // sender about it by sending a NODE_HANDLE_NACK message.
    if (!handle)
      return target._send({ cmd: 'NODE_HANDLE_NACK' }, null, true);

    // Acknowledge handle receival. Don't emit error events (for example if
    // the other side has disconnected) because this call to send() is not
    // initiated by the user and it shouldn't be fatal to be unable to ACK
    // a message.
    target._send({ cmd: 'NODE_HANDLE_ACK' }, null, true);

    const obj = handleConversion[message.type];

    // Update simultaneous accepts on Windows
    if (process.platform === 'win32') {
      handle.setSimultaneousAccepts(false);
    }

    // Convert handle object
    obj.got.call(this, message, handle, (handle) => {
      handleMessage(message.msg, handle, isInternal(message.msg));
    });
  });

  target.send = function(message, handle, options, callback) {
    if (typeof handle === 'function') {
      callback = handle;
      handle = undefined;
      options = undefined;
    } else if (typeof options === 'function') {
      callback = options;
      options = undefined;
    } else if (options !== undefined &&
               (options === null || typeof options !== 'object')) {
      throw new ERR_INVALID_ARG_TYPE('options', 'Object', options);
    }

    options = { swallowErrors: false, ...options };

    if (this.connected) {
      return this._send(message, handle, options, callback);
    }
    const ex = new ERR_IPC_CHANNEL_CLOSED();
    if (typeof callback === 'function') {
      process.nextTick(callback, ex);
    } else {
      process.nextTick(() => this.emit('error', ex));
    }
    return false;
  };

  target._send = function(message, handle, options, callback) {
    assert(this.connected || this.channel);

    if (message === undefined)
      throw new ERR_MISSING_ARGS('message');

    // Non-serializable messages should not reach the remote
    // end point; as any failure in the stringification there
    // will result in error message that is weakly consumable.
    // So perform a sanity check on message prior to sending.
    if (typeof message !== 'string' &&
        typeof message !== 'object' &&
        typeof message !== 'number' &&
        typeof message !== 'boolean') {
      throw new ERR_INVALID_ARG_TYPE(
        'message', ['string', 'object', 'number', 'boolean'], message);
    }

    // Support legacy function signature
    if (typeof options === 'boolean') {
      options = { swallowErrors: options };
    }

    let obj;

    // Package messages with a handle object
    if (handle) {
      // This message will be handled by an internalMessage event handler
      message = {
        cmd: 'NODE_HANDLE',
        type: null,
        msg: message
      };

      if (handle instanceof net.Socket) {
        message.type = 'net.Socket';
      } else if (handle instanceof net.Server) {
        message.type = 'net.Server';
      } else if (handle instanceof TCP || handle instanceof Pipe) {
        message.type = 'net.Native';
      } else if (handle instanceof dgram.Socket) {
        message.type = 'dgram.Socket';
      } else if (handle instanceof UDP) {
        message.type = 'dgram.Native';
      } else {
        throw new ERR_INVALID_HANDLE_TYPE();
      }

      // Queue-up message and handle if we haven't received ACK yet.
      if (this._handleQueue) {
        this._handleQueue.push({
          callback: callback,
          handle: handle,
          options: options,
          message: message.msg,
        });
        return this._handleQueue.length === 1;
      }

      obj = handleConversion[message.type];

      // convert TCP object to native handle object
      handle = handleConversion[message.type].send.call(target,
                                                        message,
                                                        handle,
                                                        options);

      // If handle was sent twice, or it is impossible to get native handle
      // out of it - just send a text without the handle.
      if (!handle)
        message = message.msg;

      // Update simultaneous accepts on Windows
      if (obj.simultaneousAccepts && process.platform === 'win32') {
        handle.setSimultaneousAccepts(true);
      }
    } else if (this._handleQueue &&
               !(message && (message.cmd === 'NODE_HANDLE_ACK' ||
                             message.cmd === 'NODE_HANDLE_NACK'))) {
      // Queue request anyway to avoid out-of-order messages.
      this._handleQueue.push({
        callback: callback,
        handle: null,
        options: options,
        message: message,
      });
      return this._handleQueue.length === 1;
    }

    const req = new WriteWrap();

    const err = writeChannelMessage(channel, req, message, handle);
    const wasAsyncWrite = streamBaseState[kLastWriteWasAsync];

    if (err === 0) {
      if (handle) {
        if (!this._handleQueue)
          this._handleQueue = [];
        if (obj && obj.postSend)
          obj.postSend(message, handle, options, callback, target);
      }

      if (wasAsyncWrite) {
        req.oncomplete = () => {
          control.unref();
          if (typeof callback === 'function')
            callback(null);
        };
        control.ref();
      } else if (typeof callback === 'function') {
        process.nextTick(callback, null);
      }
    } else {
      // Cleanup handle on error
      if (obj && obj.postSend)
        obj.postSend(message, handle, options, callback);

      if (!options.swallowErrors) {
        const ex = errnoException(err, 'write');
        if (typeof callback === 'function') {
          process.nextTick(callback, ex);
        } else {
          process.nextTick(() => this.emit('error', ex));
        }
      }
    }

    /* If the master is > 2 read() calls behind, please stop sending. */
    return channel.writeQueueSize < (65536 * 2);
  };

  // Connected will be set to false immediately when a disconnect() is
  // requested, even though the channel might still be alive internally to
  // process queued messages. The three states are distinguished as follows:
  // - disconnect() never requested: channel is not null and connected
  //   is true
  // - disconnect() requested, messages in the queue: channel is not null
  //   and connected is false
  // - disconnect() requested, channel actually disconnected: channel is
  //   null and connected is false
  target.connected = true;

  target.disconnect = function() {
    if (!this.connected) {
      this.emit('error', new ERR_IPC_DISCONNECTED());
      return;
    }

    // Do not allow any new messages to be written.
    this.connected = false;

    // If there are no queued messages, disconnect immediately. Otherwise,
    // postpone the disconnect so that it happens internally after the
    // queue is flushed.
    if (!this._handleQueue)
      this._disconnect();
  };

  target._disconnect = function() {
    assert(this.channel);

    // This marks the fact that the channel is actually disconnected.
    this.channel = null;

    if (this._pendingMessage)
      closePendingHandle(this);

    let fired = false;
    function finish() {
      if (fired) return;
      fired = true;

      channel.close();
      target.emit('disconnect');
    }

    // If a message is being read, then wait for it to complete.
    if (channel.buffering) {
      this.once('message', finish);
      this.once('internalMessage', finish);

      return;
    }

    process.nextTick(finish);
  };

  function emit(event, message, handle) {
    target.emit(event, message, handle);
  }

  function handleMessage(message, handle, internal) {
    if (!target.channel)
      return;

    const eventName = (internal ? 'internalMessage' : 'message');

    process.nextTick(emit, eventName, message, handle);
  }

  channel.readStart();
  return control;
}

const INTERNAL_PREFIX = 'NODE_';
function isInternal(message) {
  return (message !== null &&
          typeof message === 'object' &&
          typeof message.cmd === 'string' &&
          message.cmd.length > INTERNAL_PREFIX.length &&
          message.cmd.slice(0, INTERNAL_PREFIX.length) === INTERNAL_PREFIX);
}

function nop() { }

function getValidStdio(stdio, sync) {
  let ipc;
  let ipcFd;

  // Replace shortcut with an array
  if (typeof stdio === 'string') {
    stdio = stdioStringToArray(stdio);
  } else if (!ArrayIsArray(stdio)) {
    throw new ERR_INVALID_OPT_VALUE('stdio', inspect(stdio));
  }

  // At least 3 stdio will be created
  // Don't concat() a new Array() because it would be sparse, and
  // stdio.reduce() would skip the sparse elements of stdio.
  // See http://stackoverflow.com/a/5501711/3561
  while (stdio.length < 3) stdio.push(undefined);

  // Translate stdio into C++-readable form
  // (i.e. PipeWraps or fds)
  stdio = stdio.reduce((acc, stdio, i) => {
    function cleanup() {
      for (let i = 0; i < acc.length; i++) {
        if ((acc[i].type === 'pipe' || acc[i].type === 'ipc') && acc[i].handle)
          acc[i].handle.close();
      }
    }

    // Defaults
    if (stdio == null) {
      stdio = i < 3 ? 'pipe' : 'ignore';
    }

    if (stdio === 'ignore') {
      acc.push({ type: 'ignore' });
    } else if (stdio === 'pipe' || (typeof stdio === 'number' && stdio < 0)) {
      const a = {
        type: 'pipe',
        readable: i === 0,
        writable: i !== 0
      };

      if (!sync)
        a.handle = new Pipe(PipeConstants.SOCKET);

      acc.push(a);
    } else if (stdio === 'ipc') {
      if (sync || ipc !== undefined) {
        // Cleanup previously created pipes
        cleanup();
        if (!sync)
          throw new ERR_IPC_ONE_PIPE();
        else
          throw new ERR_IPC_SYNC_FORK();
      }

      ipc = new Pipe(PipeConstants.IPC);
      ipcFd = i;

      acc.push({
        type: 'pipe',
        handle: ipc,
        ipc: true
      });
    } else if (stdio === 'inherit') {
      acc.push({
        type: 'inherit',
        fd: i
      });
    } else if (typeof stdio === 'number' || typeof stdio.fd === 'number') {
      acc.push({
        type: 'fd',
        fd: typeof stdio === 'number' ? stdio : stdio.fd
      });
    } else if (getHandleWrapType(stdio) || getHandleWrapType(stdio.handle) ||
               getHandleWrapType(stdio._handle)) {
      const handle = getHandleWrapType(stdio) ?
        stdio :
        getHandleWrapType(stdio.handle) ? stdio.handle : stdio._handle;

      acc.push({
        type: 'wrap',
        wrapType: getHandleWrapType(handle),
        handle: handle,
        _stdio: stdio
      });
    } else if (isArrayBufferView(stdio) || typeof stdio === 'string') {
      if (!sync) {
        cleanup();
        throw new ERR_INVALID_SYNC_FORK_INPUT(inspect(stdio));
      }
    } else {
      // Cleanup
      cleanup();
      throw new ERR_INVALID_OPT_VALUE('stdio', inspect(stdio));
    }

    return acc;
  }, []);

  return { stdio, ipc, ipcFd };
}


function getSocketList(type, worker, key) {
  const sockets = worker.channel.sockets[type];
  let socketList = sockets[key];
  if (!socketList) {
    const Construct = type === 'send' ? SocketListSend : SocketListReceive;
    socketList = sockets[key] = new Construct(worker, key);
  }
  return socketList;
}


function maybeClose(subprocess) {
  subprocess._closesGot++;

  if (subprocess._closesGot === subprocess._closesNeeded) {
    subprocess.emit('close', subprocess.exitCode, subprocess.signalCode);
  }
}

function spawnSync(options) {
  const result = spawn_sync.spawn(options);

  if (result.output && options.encoding && options.encoding !== 'buffer') {
    for (let i = 0; i < result.output.length; i++) {
      if (!result.output[i])
        continue;
      result.output[i] = result.output[i].toString(options.encoding);
    }
  }

  result.stdout = result.output && result.output[1];
  result.stderr = result.output && result.output[2];

  if (result.error) {
    result.error = errnoException(result.error, 'spawnSync ' + options.file);
    result.error.path = options.file;
    result.error.spawnargs = options.args.slice(1);
  }

  return result;
}

module.exports = {
  ChildProcess,
  setupChannel,
  getValidStdio,
  stdioStringToArray,
  spawnSync
};