ospf6d: fix interface_down() stopping hellos

interface_down() - which also handles some nonobvious cases like the
last linklocal address disappearing - was previously not cancelling the
hello timer.  This had the effect of multiple such threads ending up
scheduled after a quick down-up cycle.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
1 file changed