My haproxy.cfg has a frontend which then redirects to a bunch of backends,
here is a sample backend (note that connections into this have already been through stunnel to rip out SSL:
backend thenameofit reqadd X-Forwarded-Proto:\ https reqadd FRONT_END_HTTPS:\ on server myserver1 serverhostnamex:80 weight 1 maxconn 5000 check server myserver2 serverhostnamey:80 weight 1 maxconn 5000 check appsession ASP.NET_SessionId len 100 timeout 3h
I'm sure I'm simply missing a setting somewhere, but I must be missing it when reading the config documentation.
I'm using HAProxy 1.4.13.