nghttpx: Preserve upgrade in Connection header field

src/shrpx_http_downstream_connection.cc

@@ -118,7 +118,7 @@ int HttpDownstreamConnection::push_request_headers()
   hdrs += downstream_->get_request_path();
   hdrs += " ";
   hdrs += "HTTP/1.1\r\n";
-  bool connection_upgrade = false;
+  std::string connection_upgrade;
   std::string via_value;
   std::string xff_value;
   const Headers& request_headers = downstream_->get_request_headers();
@@ -126,8 +126,9 @@ int HttpDownstreamConnection::push_request_headers()
       i != request_headers.end(); ++i) {
     if(util::strieq((*i).first.c_str(), "connection")) {
       if(util::strifind((*i).second.c_str(), "upgrade")) {
-        connection_upgrade = true;
+        connection_upgrade = (*i).second;
       }
+      continue;
     } else if(util::strieq((*i).first.c_str(), "x-forwarded-proto") ||
        util::strieq((*i).first.c_str(), "keep-alive") ||
        util::strieq((*i).first.c_str(), "proxy-connection")) {
@@ -153,8 +154,10 @@ int HttpDownstreamConnection::push_request_headers()
   }
   if(downstream_->get_request_connection_close()) {
     hdrs += "Connection: close\r\n";
-  } else if(connection_upgrade) {
-    hdrs += "Connection: upgrade\r\n";
+  } else if(!connection_upgrade.empty()) {
+    hdrs += "Connection: ";
+    hdrs += connection_upgrade;
+    hdrs += "\r\n";
   }
   if(get_config()->add_x_forwarded_for) {
     hdrs += "X-Forwarded-For: ";