dgram: generalized send queue to handle close

If the udp socket is not ready and we are accumulating
messages to send, it needs to delay closing the socket when
all messages are flushed.

Fixes: https://github.com/nodejs/node/issues/7061
PR-URL: https://github.com/nodejs/node/pull/7066
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/dgram.js

@@ -283,20 +283,25 @@ function fixBufferList(list) {
 function enqueue(self, toEnqueue) {
   // If the send queue hasn't been initialized yet, do it, and install an
   // event handler that flushes the send queue after binding is done.
-  if (!self._sendQueue) {
-    self._sendQueue = [];
-    self.once('listening', function() {
-      // Flush the send queue.
-      for (var i = 0; i < this._sendQueue.length; i++)
-        this.send.apply(self, this._sendQueue[i]);
-      this._sendQueue = undefined;
-    });
+  if (!self._queue) {
+    self._queue = [];
+    self.once('listening', clearQueue);
   }
-  self._sendQueue.push(toEnqueue);
+  self._queue.push(toEnqueue);
   return;
 }
 
 
+function clearQueue() {
+  const queue = this._queue;
+  this._queue = undefined;
+
+  // Flush the send queue.
+  for (var i = 0; i < queue.length; i++)
+    queue[i]();
+}
+
+
 // valid combinations
 // send(buffer, offset, length, port, address, callback)
 // send(buffer, offset, length, port, address)
@@ -353,7 +358,7 @@ Socket.prototype.send = function(buffer,
   // If the socket hasn't been bound yet, push the outbound packet onto the
   // send queue and send after binding is complete.
   if (self._bindState != BIND_STATE_BOUND) {
-    enqueue(self, [list, port, address, callback]);
+    enqueue(self, self.send.bind(self, list, port, address, callback));
     return;
   }
 
@@ -407,10 +412,15 @@ function afterSend(err, sent) {
   this.callback(err, sent);
 }
 
-
 Socket.prototype.close = function(callback) {
   if (typeof callback === 'function')
     this.on('close', callback);
+
+  if (this._queue) {
+    this._queue.push(this.close.bind(this));
+    return this;
+  }
+
   this._healthCheck();
   this._stopReceiving();
   this._handle.close();

test/parallel/test-dgram-close-in-listening.js

@@ -0,0 +1,18 @@
+'use strict';
+// Ensure that if a dgram socket is closed before the sendQueue is drained
+// will not crash
+
+const common = require('../common');
+const dgram = require('dgram');
+
+const buf = Buffer.alloc(1024, 42);
+
+const socket = dgram.createSocket('udp4');
+
+socket.on('listening', function() {
+  socket.close();
+});
+
+// adds a listener to 'listening' to send the data when
+// the socket is available
+socket.send(buf, 0, buf.length, common.PORT, 'localhost');