anchor.diff:  
   (deftype tcp-sequence-number ()
     '(unsigned-byte 32))
  +
  +(defun +u32 (x y)
  +  (ldb (byte 32 0) (+ x y)))
  +
  +(defun -u32 (x y)
  +  (ldb (byte 32 0) (- x y)))
   
   ;; FIXME: Inbount connections need to timeout if state :syn-received don't change.
   (defclass tcp-listener ()
  
positive.code:              (when (= seq (tcp-connection-r-next connection))
                 (cond ((logtest flags +tcp4-flag-fin+)
                        (setf (tcp-connection-r-next connection)
                              (logand (+ (tcp-connection-r-next connection) 1)
                                      #xFFFFFFFF))
                        (tcp4-send-packet connection
                                          (tcp-connection-s-next connection)
                                          (tcp-connection-r-next connection)
  
negative.code:                :do (setf (cdr (last (tcp-connection-rx-data connection)))
                           (list (list packet (+ start header-length) end)))
                 :do (setf (tcp-connection-r-next connection)
                           (+u32 (tcp-connection-r-next connection) data-length)))
           (setf (mezzano.supervisor:event-state
                  (tcp-connection-receive-event connection))
                 t))
  