when we can remove a prefix in SIOCDIFADDR_IN6, we should  be able to just call prelist_remove(). (I don't remember why I change the expire value and let the timer  to remove the structure when I first wrote the code...but the current  one should be correct.)
when we can remove a prefix in SIOCDIFADDR_IN6, we should  be able to
just call prelist_remove().
(I don't remember why I change the expire value and let the timer
 to remove the structure when I first wrote the code...but the current
 one should be correct.)

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame