Error detected while parsing switching rule


I’m trying to whitelist client hostnames. I’m getting an error(see below) when client hostname is not on our network and haproxy service is not starting. Is there a way to ignore/skip the hostnames when they are not in our network or is there an option available in haproxy configuration to handle this issue. I cannot whitelist using IP address because the IP addresses are dynamic and will not assign to the same client hostname. I’m a newbie to haproxy any help is appreciated.

frontend usertraffic
bind *:443
mode http
option httplog
maxconn 4096
use_backend appservers if { src -f /etc/haproxy/whitelist.lst }

Starting haproxy: [ALERT] 003/034045 (25299) : parsing [/etc/haproxy/haproxy.cfg:33] : error detected while parsing switching rule : 'Client Hostname ’ is not a valid IPv4 or IPv6 address at line 3 of file ‘/etc/haproxy/whitelist.lst’.
[ALERT] 003/034045 (25299) : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg
[ALERT] 003/034045 (25299) : Fatal errors found in configuration.

That’s not supported, we would need runtime dns resolution for this, which is not supported within ACL’s.