TCP Connection details

[nginxsantos]

I am using the Nginx as a reverse proxy and I want to find out the TCP
connection information on both east and west bound connections.
With the following params on the access log, I am able to get the info about
the client TCP connection. Now, I want to find the RTT between Nginx and the
backend webserver.  Any idea how can I get this ?

$tcpinfo_rtt, $tcpinfo_rttvar, $tcpinfo_snd_cwnd, $tcpinfo_rcv_space
information about the client TCP connection; available on systems that
support the TCP_INFO socket option

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,258958,258958#msg-258958