[api] Update request event to be consistent by emitting both req …

…and `res`. Add `x-forwarded-for` header.

lib/node-http-proxy.js

@@ -104,7 +104,7 @@ exports.createServer = function () {
 
   proxy = new HttpProxy(options);
   server = http.createServer(function (req, res) {
-    proxy.emit('request', req, req.headers.host, req.url);
+    proxy.emit('request', req, res, req.headers.host, req.url);
 
     // If we were passed a callback to process the request
     // or response in some way, then call it.
@@ -276,6 +276,11 @@ HttpProxy.prototype.proxyRequest = function (req, res, port, host, buffer) {
     host = location.host;
   }
 
+  //
+  // Add `x-forwarded-for` header to availible client IP to apps behind proxy
+  //
+  req.headers['x-forwarded-for'] = req.connection.remoteAddress;
+
   //
   // Emit the `start` event indicating that we have begun the proxy operation.
   //