iRule - create cookie and insert value of client FQDN

I am trying to create an iRule that will create a cookie on the client and insert the client FQDN and client IP address into the cookie. So far, the iRUle will insert the client IP address but I can't find how to insert the client FQDN. Any help would be appreciated. Thanks

 

when HTTP_RESPONSE {

 

Check if the cookie exists in request

if { not ( [HTTP::cookie exists "LBSRC"] ) } {

 

Change cookie's value

HTTP::cookie insert name "LBSRC" value [IP::client_addr] } }