Hey Curtis,

Maybe im misunderstanding your request here but within nginx its very easy to attach the x-forwarded-for value and pass it to the next device/upstream.
All you have to do is set the following variable in your proxy configuration file (or per config if you choose to do it seperatly for different upstreams)

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

Regards,
Payam