anchor.diff:                                                                            (if syn-p +tcp4-flag-syn+ 0)
                                                                             (if rst-p +tcp4-flag-rst+ 0)
                                                                             (if psh-p +tcp4-flag-psh+ 0)
  -                                                                          (if ack-p +tcp4-flag-ack+ 0))
  +                                                                          (if ack-p +tcp4-flag-ack+ 0)
  +                                                                          (if urg-p +tcp4-flag-urg+ 0)
  +                                                                          (if ece-p +tcp4-flag-ece+ 0)
  +                                                                          (if cwr-p +tcp4-flag-cwr+ 0))
             ;; Window.
             (ub16ref/be header +tcp4-header-window-size+) window
             ;; Checksum.
  
positive.code:                                        seq ack
                                         (tcp-connection-window-size connection)
                                         data
                                         :ack-p ack-p
                                         :psh-p psh-p
                                         :rst-p rst-p
  
negative.code:            (setf (tcp-connection-state connection) :closed))))
      (mezzano.supervisor:condition-notify (tcp-connection-cvar connection) t)))
  
  (defun tcp4-send-packet (connection seq ack data &key cwr-p ece-p urg-p (ack-p t) psh-p rst-p syn-p fin-p)
    (let* ((source (tcp-connection-local-ip connection))
           (source-port (tcp-connection-local-port connection))
           (packet (assemble-tcp4-packet source source-port
  