Ensure socket 'connect' listener is always removed

Fixes: #2438

request.js

@@ -767,7 +767,8 @@ Request.prototype.start = function () {
   })
   self.req.on('socket', function(socket) {
     if (timeout !== undefined) {
-      socket.once('connect', function() {
+      var onReqSockConnect = function() {
+        socket.removeListener('connect', onReqSockConnect)
         clearTimeout(self.timeoutTimer)
         self.timeoutTimer = null
         // Set an additional timeout on the socket, via the `setsockopt` syscall.
@@ -785,13 +786,15 @@ Request.prototype.start = function () {
             self.emit('error', e)
           }
         })
-      })
+      }
+      socket.on('connect', onReqSockConnect)
 
       // Set a timeout in memory - this block will throw if the server takes more
       // than `timeout` to write the HTTP status and headers (corresponding to
       // the on('response') event on the client). NB: this measures wall-clock
       // time, not the time between bytes sent by the server.
       self.timeoutTimer = setTimeout(function () {
+        socket.removeListener('connect', onReqSockConnect)
         self.abort()
         var e = new Error('ETIMEDOUT')
         e.code = 'ETIMEDOUT'

tests/test-timeout.js

@@ -75,10 +75,22 @@ tape('should not timeout', function(t) {
     timeout: 1200
   }
 
+  var socket
   request(shouldntTimeout, function(err, res, body) {
     t.equal(err, null)
     t.equal(body, 'waited')
+
+    var connectListeners = socket.listeners('connect')
+    for (var i = 0; i < connectListeners.length; ++i) {
+      var fn = connectListeners[i]
+      if (typeof fn === 'function' && fn.name === 'onReqSockConnect') {
+        t.ok(false, 'Connect listener should not exist')
+      }
+    }
+
     t.end()
+  }).on('socket', function(socket_) {
+    socket = socket_
   })
 })
 
@@ -131,10 +143,22 @@ tape('connect timeout', function(t) {
     url: tarpitHost + '/timeout',
     timeout: 100
   }
+  var socket
   request(shouldConnectTimeout, function(err) {
     checkErrCode(t, err)
     t.ok(err.connect === true, 'Connect Timeout Error should set \'connect\' property to true')
+
+    var connectListeners = socket.listeners('connect')
+    for (var i = 0; i < connectListeners.length; ++i) {
+      var fn = connectListeners[i]
+      if (typeof fn === 'function' && fn.name === 'onReqSockConnect') {
+        t.ok(false, 'Connect listener should not exist')
+      }
+    }
+
     t.end()
+  }).on('socket', function(socket_) {
+    socket = socket_
   })
 })