Rewrite host with an iRule?

You aren't stuck. You can do something like the following:

when HTTP_REQUEST {
   Don't allow data to be chunked so we can correctly
   replace payload below
  if { [HTTP::version] eq "1.1" } {
      if { [HTTP::header is_keepalive] } {
         HTTP::header replace "Connection" "Keep-Alive"
      }
      HTTP::version "1.0"
  }
   change host header
  if { [HTTP::host] eq "apple.fruit.com" } {
    HTTP::header replace "Host" "peanut.bean.com"
  }
}
when HTTP_RESPONSE {
    collect response data
   if { [HTTP::header exists "Content-Length"] } {
      set content_length [HTTP::header "Content-Length"]
   } else {
      set content_length 4294967295
   }
   if { $content_length > 0 } {
      HTTP::collect $content_length
   }
}
when HTTP_RESPONSE_DATA {
  set find "peanut.bean.com"
  set replace "apple.fruit.com"
  set offset 0
  set diff [expr [string length $replace] - [string length $find]]
   Get indices of all instances of find string in the payload
  set indices [regexp -all -inline -indices $find [HTTP::payload]]  
  foreach idx $indices {
    set start [expr [lindex $idx 0] + $offset]
    set end [expr [lindex $idx 1] + $offset]
    set len [expr {$end - $start + 1}]
     replace the instance of find with the contents of replace
    HTTP::payload replace $start $len $replace
     modify offset if the replace string is larger or smaller
     than find.
    incr offset $diff
  }
}

In the HTTP_REQUEST event, I've used the HTTP::header replace command to replace the host header. and in the HTTP_RESPONSE_DATA event, I've used a regexp call to return all start,end pairs of the peanut.bean.com string and replaced it with apple.fruit.com.

Good luck!

-Joe

I would like to add a note that Joe's example is a good complete example that shows how to abstract the find and replace strings into variables. In reality, you could save some performance in the iRule by replacing the diff variable with the actual literal difference value. For example, "peanut.bean.com" is 15 characters and "apple.fruit.com" is also 15 characters, so instead of calculating: [string length $replace] - [string length $find], simply remove the line for setting the diff variable and also replace the $diff with 0. This optimization logic could also be applied to the find and replace variables as well. Simply using the strings "peanut.bean.com" and "apple.fruit.com" instead of the variables will improve the performance of the iRule. Basically, the more literals you can use vs. evaluating commands, the better the performance will be.

 

Oh, I also forgot to mention, that you may want to set a variable in the HTTP_REQUEST event when the host matches peanut.bean.com. This variable can then be used in the HTTP_RESPONSE event to trigger the actual collection of the response for the search and replace. This prevents the unnecessary buffering and searching of the response when the original host was not peanut.bean.com.

 

Thanks everyone for the info. I haven't had time to put everything into the LB yet but should be a piece of cake to do what we need. Thanks again.