[Babel-users] Babel: Clarifications on seqno request handling in bird

[Daniel Gröber]

Hi Maria,

On Sun, Feb 26, 2023 at 07:34:06PM +0100, Maria Matejka wrote:
> > I don't think RFC8966 is really framed in bird's "multi protocol" mindset
> > so it's unclear to me whether this is something we have to fix or
> > not. Section 3.8.2.1. says:
> > 
> > > A node that has lost all feasible routes to a given destination but still
> > > has unexpired unfeasible routes to that destination MUST send a seqno
> > > request;
> > 
> > I could for example read this as the above mentioned static route
> > constituting a feasible route received from a bird "internal" babel
> > neighbour which would make the behaviour described above perfectly fine,
> > no?
> 
> From my point of view, this is perfectly fine.

I did just do another reivew on the knock on effects of interpreting it
like that and I do tend to agree it all looks fine. The (!best) thing I
mentioned actually works in our favor here since getting rt_notifi'ed of
another protocols route will then still trigger the 3.8.2.2, as it should,
if we receive an unfeasible update.

> > @Bird folks: can anyone think of a way to be notified of any and all
> > changes in rt_notify? I assume it's not possible from some light reading of
> > the nest code but figured I might as well ask.
> 
> You may set channel ra_mode to RA_ANY, getting called rt_notify() for all
> route updates.
> 
> Or in BIRD 3, you can override the channel logic at all and if you don't
> mind calling your filters yourself, you can just request "on any change,
> give me all the routes for one prefix at once" and do whatever you want with
> the routes. Yet these changes most probably won't get backported to BIRD 2.

Hmm RA_ANY might actually be just fine if it comes to that, I'd still
prefer not having to do it tho :)

Thanks,
--Daniel