Hello Sisir,
For SSLPassthrough mode, HAProxy is configured to use TCP protocol rather than HTTP and therefore looses the ability to use the X-Forwarded-* headers.
The solution to this problem is to make use of PROXY Protocol. You need to enable PROXY protocol by using send-proxy keyword in your HAProxy backend configuration.
server srv1 Y.Y.Y.Y:7654 send-proxy
You may refer to the following post for further details: HAProxy to retain client IP - #3 by Thoufiq
Thanks,
Shivharsh