Allowing the common proxy headers' value to be appended in proxy chai…

…n scenarios.

lib/node-http-proxy/http-proxy.js

@@ -122,17 +122,36 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
 
   //
   // Add common proxy headers to the request so that they can
-  // be availible to the proxy target server:
+  // be availible to the proxy target server. If the proxy is 
+  // part of proxy chain it will append the address:
   //
   // * `x-forwarded-for`: IP Address of the original request
   // * `x-forwarded-proto`: Protocol of the original request
   // * `x-forwarded-port`: Port of the original request.
   //
-
   if (this.enable.xforward && req.connection && req.socket) {
-    req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.socket.remoteAddress;
-    req.headers['x-forwarded-port']  = req.connection.remotePort || req.socket.remotePort;
-    req.headers['x-forwarded-proto'] = req.connection.pair ? 'https' : 'http';
+
+    if (req.headers['x-forwarded-for']){
+        var addressToAppend = "," + req.connection.remoteAddress || req.socket.remoteAddress;
+        req.headers['x-forwarded-for']   += addressToAppend;
+    } else {
+        req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.socket.remoteAddress;
+    }
+
+    if (req.headers['x-forwarded-port']){
+        var portToAppend = "," + req.connection.remotePort || req.socket.remotePort;
+        req.headers['x-forwarded-port']   += portToAppend;
+    } else {
+        req.headers['x-forwarded-port']   = req.connection.remotePort || req.socket.remotePort;
+    }
+
+    if (req.headers['x-forwarded-proto']){
+        var protoToAppend = "," + req.connection.pair ? 'https' : 'http';
+        req.headers['x-forwarded-proto']   += protoToAppend;
+    } else {
+        req.headers['x-forwarded-proto']   = req.connection.pair ? 'https' : 'http';
+    }
+
   }
 
   //
@@ -299,6 +318,7 @@ HttpProxy.prototype.proxyRequest = function (req, res, buffer) {
   // `req` write it to the `reverseProxy` request.
   //
   req.on('data', function (chunk) {
+
     if (!errState) {
       var flushed = reverseProxy.write(chunk);
       if (!flushed) {
@@ -375,16 +395,36 @@ HttpProxy.prototype.proxyWebSocketRequest = function (req, socket, head, buffer)
 
   //
   // Add common proxy headers to the request so that they can
-  // be availible to the proxy target server:
+  // be availible to the proxy target server. If the proxy is 
+  // part of proxy chain it will append the address:
   //
   // * `x-forwarded-for`: IP Address of the original request
   // * `x-forwarded-proto`: Protocol of the original request
   // * `x-forwarded-port`: Port of the original request.
   //
   if (this.enable.xforward && req.connection && req.connection.socket) {
-    req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.connection.socket.remoteAddress;
-    req.headers['x-forwarded-port']  = req.connection.remotePort || req.connection.socket.remotePort;
-    req.headers['x-forwarded-proto'] = req.connection.pair ? 'https' : 'http';
+
+    if (req.headers['x-forwarded-for']){
+        var addressToAppend = "," + req.connection.remoteAddress || req.connection.socket.remoteAddress;
+        req.headers['x-forwarded-for']   += addressToAppend;
+    } else {
+        req.headers['x-forwarded-for']   = req.connection.remoteAddress || req.connection.socket.remoteAddress;
+    }
+
+    if (req.headers['x-forwarded-port']){
+        var portToAppend = "," + req.connection.remotePort || req.connection.socket.remotePort;
+        req.headers['x-forwarded-port']   += portToAppend;
+    } else {
+        req.headers['x-forwarded-port']   = req.connection.remotePort || req.connection.socket.remotePort;
+    }
+
+    if (req.headers['x-forwarded-proto']){
+        var protoToAppend = "," + req.connection.pair ? 'https' : 'http';
+        req.headers['x-forwarded-proto']   += protoToAppend;
+    } else {
+        req.headers['x-forwarded-proto']   = req.connection.pair ? 'https' : 'http';
+    }
+
   }
 
   //