fix(connection): do not leak a connection if initial handshak fails

Fixes NODE-1909

Author: daprahamian

lib/connection/connect.js

@@ -100,7 +100,14 @@ function checkSupportedServer(ismaster, options) {
  return new MongoError(message);
 }
 
-function performInitialHandshake(conn, options, callback) {
+function performInitialHandshake(conn, options, _callback) {
+ const callback = function(err, ret) {
+ if (err && conn) {
+ conn.destroy();
+ }
+ _callback(err, ret);
+ };
+
  let compressors = [];
  if (options.compression && options.compression.compressors) {
  compressors = options.compression.compressors;
@@ -229,7 +236,7 @@ function parseSslOptions(family, options) {
  return result;
 }
 
-function makeConnection(family, options, callback) {
+function makeConnection(family, options, _callback) {
  const useSsl = typeof options.ssl === 'boolean' ? options.ssl : false;
  const keepAlive = typeof options.keepAlive === 'boolean' ? options.keepAlive : true;
  let keepAliveInitialDelay =
@@ -246,6 +253,13 @@ function makeConnection(family, options, callback) {
  }
 
  let socket;
+ const callback = function(err, ret) {
+ if (err && socket) {
+ socket.destroy();
+ }
+ _callback(err, ret);
+ };
+
  try {
  if (useSsl) {
  socket = tls.connect(parseSslOptions(family, options));