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