[Babel-users] battling with babel and route changes

[Julien Cristau]

On Wed, Jun 22, 2011 at 08:35:53 -0600, Dave Taht wrote:

> In order to disrupt a flow less, babel could
> 
> A) install a new route with a higher metric (priority)
> B) remove the old route
> C) install the new route again with the right metric (priority)
> D) Remove the new route with the higher metric
> 
> instead, right now, when metrics are equal (which they usually are) it
> removes the route entirely, leaving a window where packets drop
> (particularly under load), then adds it again going to the right place.
> 
> It SHOULD be easier than this, and perhaps babeld is working around an
> old bug in the kernel here, but I don't think so. The above is kind of
> crufty, and I hope it's just possible to combine C and D into one
> operation.
> 
I believe this is indeed working around an old kernel bug.  We needed to
make this work with some old 2.4.x kernel.  A quick test on 2.6.32
suggests that adding a two routes with the same metric and different
gateways works just fine now.

Cheers,
Julien