iRule Request - strip sub domains

Hi Brett,

I tried a regex, but it was about 10x less efficient than a couple of string and list operations:

Simple perf test:

% time {set host_list [split $host "."]; lindex $host_list [expr {[llength $host_list] -3}]} 1000

13 microseconds per iteration

% time {regexp -inline -nocase {(?:[^.]+\.){0,}([^.]+)\.mydomain\.com} test.mydomain.com} 1000

133 microseconds per iteration

when HTTP_REQUEST {
   log local0. "[IP::client_addr]:[TCP::client_port]: [HTTP::method] request to [HTTP::host][HTTP::uri]"
    Split the host header value on periods into a list
   set host_list [split [HTTP::host] "."]
   log local0. "[IP::client_addr]:[TCP::client_port]: Parsed host list $host_list"
    Check if there were more than three fields
   if {[llength $host_list] > 3}{
       Send a redirect with the third to last field from the requested host prepended to .mydomain.com
      HTTP::respond 301 Location "https://[lindex $host_list [expr {[llength $host_list] -3}]].mydomain.com"
      log local0. "[IP::client_addr]:[TCP::client_port]: Redirecting to\
         https://[lindex $host_list [expr {[llength $host_list] -3}]].mydomain.com"
   }
}

Aaron