anchor.diff:      (handler-case
           (%if-indextoname index buffer)
         (isys:enxio ()
  -        (signal-unknown-interface-error index))
  +        (signal-unknown-interface-error "if_indextoname" index))
         (:no-error (name)
           (make-interface name index)))))
   
  
positive.code:   (handler-case
        (%if-nametoindex name)
      (isys:enxio ()
        (signal-unknown-interface-error name))
      (:no-error (index)
        (make-interface (copy-seq name) index))))
  
  
negative.code: (setf (documentation 'unknown-interface-datum 'function)
        "Return the datum that caused the signalling of an UNKNOWN-INTERFACE condition.")
  
  (defun signal-unknown-interface-error (syscall datum)
    (error 'unknown-interface :syscall syscall :datum datum))
  
  (defun list-network-interfaces ()
    "Returns a list of network interfaces currently available."
  