iRule for IE8

A global variable will be accessible and changeable across all TCP connections. You'd want to use a local variable so that it's only accessible across a single TCP connection.

With that said, I don't think there is any reason to check whether to insert the response header or not. Just insert it in every response and non-IE8 browsers will ignore it.

If you do want to check the User-Agent header before setting the custom X-UA-Compatible header in the response, you could do something like this. Note, as Joe always says, you should use string operations instead of regexes whenever possible to save CPU cycles/memory.

 
 when HTTP_REQUEST { 
  
     Check if User-Agent header is IE 8 
    if { [HTTP::header User-Agent] contains "MSIE 8" } { 
       set IE8Resp 1 
    } else  { 
       set IE8Resp 0 
    } 
 } 
 when HTTP_RESPONSE { 
  
    if { $IE8Resp } { 
  
       log "[IP::client_addr]:[TCP::client_port] inserting header" 
       HTTP::header insert "X-UA-Compatible" "IE=EmulateIE7" 
    } 
 } 
 

Aaron