child_process: workaround fd passing issue on OS X

lib/internal/child_process.js

@@ -94,10 +94,21 @@ const handleConversion = {
       return handle;
     },
 
-    postSend: function(handle, options) {
-      // Close the Socket handle after sending it
-      if (handle && !options.keepOpen)
-        handle.close();
+    postSend: function(handle, options, 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 _pendingHandle 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._pendingHandle);
+          target._pendingHandle = handle;
+        } else {
+          handle.close();
+        }
+      }
     },
 
     got: function(message, handle, emit) {
@@ -400,6 +411,7 @@ ChildProcess.prototype.unref = function() {
 function setupChannel(target, channel) {
   target._channel = channel;
   target._handleQueue = null;
+  target._pendingHandle = null;
 
   const control = new class extends EventEmitter {
     constructor() {
@@ -465,6 +477,11 @@ function setupChannel(target, channel) {
   target.on('internalMessage', function(message, handle) {
     // Once acknowledged - continue sending handles.
     if (message.cmd === 'NODE_HANDLE_ACK') {
+      if (target._pendingHandle) {
+        target._pendingHandle.close();
+        target._pendingHandle = null;
+      }
+
       assert(Array.isArray(target._handleQueue));
       var queue = target._handleQueue;
       target._handleQueue = null;
@@ -610,13 +627,16 @@ function setupChannel(target, channel) {
     var err = channel.writeUtf8String(req, string, handle);
 
     if (err === 0) {
-      if (handle && !this._handleQueue)
-        this._handleQueue = [];
+      if (handle) {
+        if (!this._handleQueue)
+          this._handleQueue = [];
+        if (obj && obj.postSend)
+          obj.postSend(handle, options, target);
+      }
+
       req.oncomplete = function() {
         if (this.async === true)
           control.unref();
-        if (obj && obj.postSend)
-          obj.postSend(handle, options);
         if (typeof callback === 'function')
           callback(null);
       };
@@ -677,6 +697,11 @@ function setupChannel(target, channel) {
     // This marks the fact that the channel is actually disconnected.
     this._channel = null;
 
+    if (this._pendingHandle) {
+      this._pendingHandle.close();
+      this._pendingHandle = null;
+    }
+
     var fired = false;
     function finish() {
       if (fired) return;

test/sequential/test-child-process-pass-fd.js

@@ -0,0 +1,53 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const fork = require('child_process').fork;
+const net = require('net');
+
+if ((process.config.variables.arm_version === '6') ||
+    (process.config.variables.arm_version === '7')) {
+  common.skip('Too slow for armv6 and armv7 bots');
+  return;
+}
+
+const N = 80;
+
+if (process.argv[2] !== 'child') {
+  for (let i = 0; i < N; ++i) {
+    const worker = fork(__filename, ['child', common.PORT + i]);
+    worker.once('message', common.mustCall((msg, handle) => {
+      assert.strictEqual(msg, 'handle');
+      assert.ok(handle);
+      worker.send('got');
+
+      let recvData = '';
+      handle.on('data', common.mustCall((data) => {
+        recvData += data;
+      }));
+
+      handle.on('end', () => {
+        assert.strictEqual(recvData, 'hello');
+        worker.kill();
+      });
+    }));
+  }
+} else {
+  let socket;
+  const port = process.argv[3];
+  let cbcalls = 0;
+  function socketConnected() {
+    if (++cbcalls === 2)
+      process.send('handle', socket);
+  }
+
+  const server = net.createServer((c) => {
+    process.once('message', function(msg) {
+      assert.strictEqual(msg, 'got');
+      c.end('hello');
+    });
+    socketConnected();
+  });
+  server.listen(port, common.localhostIPv4, () => {
+    socket = net.connect(port, common.localhostIPv4, socketConnected);
+  });
+}