Dropped https client connection doesn't drop backend proxy_pass connection

[newnovice]

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!

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,237386,250224#msg-250224