Default route (IPv4) demolished by destroying clone (gif/gre) interface

[Yar Tikhiy]

On Wed, Aug 16, 2006 at 03:59:13PM -0500, Brooks Davis wrote:
> On Thu, Aug 17, 2006 at 08:49:27AM +1200, Andrew Thompson wrote:
> > On Wed, Aug 16, 2006 at 12:15:25PM -0500, Brooks Davis wrote:
> > > On Wed, Aug 16, 2006 at 07:58:44PM +0400, Yar Tikhiy wrote:
> > > > On Wed, Aug 16, 2006 at 09:54:19AM -0500, Brooks Davis wrote:
> > > > > On Wed, Aug 16, 2006 at 10:23:13AM +0200, Stefan Bethke wrote:
> > > > > > 
> > > > > > Ouch. Don't ppp(8), OpenVPN etc. destroy the tun interface they're  
> > > > > > using when they exit?  Flushing all routes then would be rather  
> > > > > > harmful.  I'm glad I haven't updated to a newer -stable yet then :-)
> > > > > 
> > > > > In general, no since tun interfaces can not be destroyed.
> > > > 
> > > > Did you mean "in particular"? :-)
> > > > 
> > > > The problem can be triggered by destroying any interface that can
> > > > be destroyed.  Just imagine getting rid of a defunct gif tunnel on
> > > > a remote router, or removing an unused vlan, and totally losing
> > > > connectivity to the router due to its default route having been
> > > > flushed.  The scenario still can be quite unpleasant.  I'd rather
> > > > change the default for $removable_route_flush to NO and let the
> > > > kernel choose which routes should be flushed upon the physical
> > > > ejection or software destruction of an interface.  Note that this
> > > > doesn't include static_routes_${ifn}, which are handled separately
> > > > by pccard_ether_stop().
> > > 
> > > Agreed.  That code shouldn't be on by default.  I've disabled in it HEAD
> > > and will MFC in a few days.  As another poster said, I'm not even sure
> > > it should exist as an option.
> > 
> > Thanks for fixing this up, it certainly was odd to be flushing routes in
> > userland. I have one more bug report from the ifnet/devd change to look
> > at where renamed interfaces give some sort of an error.
> 
> It is a rather weird bit of code.  It deletes all IPv4 routes on exit.
> I suspect it's a hack left over from before interface removal really
> worked.  I may just delete the code in HEAD after the MFC.  I think we
> could also remove the arp flush or move it into "netif stop" and narrow
> it with the -i option.

The -i option may not work in that case because the interface has
ceased to exist by the time devd(8) gets the notification and runs
/etc/pccard_ether.  It could be better just to remove the arp flush
completely.  The kernel should take care of the arp entries by itself.
Thanks!

-- 
Yar