anchor.diff:    (handler-case
         (%if-nametoindex name)
       (isys:enxio ()
  -      (signal-unknown-interface-error name))
  +      (signal-unknown-interface-error "if_nametoindex" name))
       (:no-error (index)
         (make-interface (copy-seq name) index))))
   
  
positive.code:     (handler-case
          (%if-indextoname index buffer)
        (isys:enxio ()
          (signal-unknown-interface-error index))
        (:no-error (name)
          (make-interface 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."
  