anchor.diff:  	 (tha-start (+ spa-start plen))
   	 (tpa-start (+ tha-start hlen))
   	 (packet-end (+ tpa-start plen))
  -	 (merge-flag nil))
  +	 (merge-flag nil)
  +         (address (ipv4-interface-address interface nil)))
       ;; Ethernet hardware type and IPv4.
       (when (and (eql htype +arp-hrd-ethernet+) (eql hlen 6)
   	       (eql ptype +ethertype-ipv4+) (eql plen 4))
  
positive.code: 	    (setf (third e) (subseq packet sha-start spa-start)
  		  merge-flag t)
  	    (return)))
  	(when (eql tpa (ipv4-interface-address interface))
  	  (unless merge-flag
  	    (push (list ptype spa (subseq packet sha-start spa-start) 0) *arp-table*))
  	  (when (eql oper +arp-op-request+)
  
negative.code: 	      (dotimes (i 6)
  		(setf (aref packet (+ 6 i)) (aref mac i)
  		      (aref packet (+ sha-start i)) (aref mac i))))
  	    (setf (ub32ref/be packet spa-start) address
  		  (ub16ref/be packet 20) +arp-op-reply+)
  	    (transmit-packet interface (list packet))))))))
  
  