Referencing an External File from within an iRule

Using the BIG-IP^® Configuration utility or tmsh, you can import a file or URL from another system to the BIG-IP system, with content that you want an iRule to return to a client, based on some iRule event. Possible uses for this feature are:

• To send a web page other than the page that the client requested. For example, you might want the system to send a maintenance page instead of the requested page.
• To send an image.
• To use a file as a template and modify the file in the iRule before sending the file.
• To download policy information from an external server and merge that data with a locally-stored policy.

The file that an iRule accesses is known as an iFile, and can be any type of file, such as a binary file or a text file. These files are read-only files.

This example shows an iRule that references an iFile named ifileURL, in partition Common:

  ltm rule ifile_rule {
     when HTTP_RESPONSE {
     # return a list of iFiles in all partitions 
     set listifiles [ifile listall]                                        
     log local0. "list of ifiles: $listifiles" 
  
     # return the attributes of an iFile specified
     array set array_attributes [ifile attributes "/Common/ifileURL"]     
     foreach {array attr} [array get array_attributes ] {
     log local0. "$array : $attr"
     }
  
     # serve an iFile when http status is 404.
     set file [ifile get "/Common/ifileURL"]
     log local0. "file: $file"
     if { [HTTP::status] equals "404" } {
       HTTP::respond 200 ifile "/Common/ifileURL"
  
    }
  }
  }

You can import an existing file to the BIG-IP^® system, create an iFile that is based on the imported file, and then write an iRule that returns the content of that file to a client system, based on an iRule event.

You now have an iRule that accesses a file on the BIG-IP^®system, based on a particular iRule event.