Explicit proxy being able to use XFF or Via header in Explicit Proxy ACLs as source IP?

[imverylame]

Is there any ability with FortiGate's explicit proxy to use an XFF or Via header provided by a client in ACL processing when evaluating the source iP?

Like squid's

  acl_uses_indirect_client on

  log_uses_indirect_client on

I have apps that use a load balancer VIP to target proxies so I can distribute traffic across various datacenters and Internet connections for availability, I clear then provide Via and XFF headers to the proxies which only allow connections from the translated IP of the load balancer...

This gives me access control to my apps and still lets me identify the source IP in the proxy logging...

We're looking at replacing the squid boxes with explicit proxy and web filter policies enabled on the egress firewalls in the variou datacenters, and I haven't found a way to do this with the FG's...

Thanks,

JJ