1. Where can i get a full list of these disabled headers:
"By default, nginx does not pass the header fields “Date”, “Server”, “X-Pad”, and “X-Accel-...” from the response of a proxied server to a client. The proxy_hide_header directive sets additional fields that will not be passed. If, on the contrary, the passing of fields needs to be permitted, the proxy_pass_header directive can be used."

2. Can you suggest how I can accomplish preserving and passing on Connection and Keep-Alive headers from upstream server to client. I am not sure I follow: "using combination of add_header and $upstream_http_* variables"

Thanks a lot!