export filter that checks for existance of another route?

[Job Snijders]

On Tue, Sep 02, 2014 at 01:44:59PM +0200, Ondrej Zajicek wrote:
> On Sat, Aug 30, 2014 at 12:13:30AM +1000, Paul J R wrote:
> > Hi All,
> > 
> > First time post, i've been playing with bird for some time, but there is one
> > thing i cant figure out how to do and that is use the existence of a
> > specific route as part of a filter.
> > 
> > for example, if the filter is processing a route to 4.3.2.0/24, check if a
> > route to 1.2.3.4/32 (exact) exists, if so then accept, otherwise reject. Is
> > this something that is possible? or do route filters only have the ability
> > to check against the information thats sent to the filter itself?
> 
> It is not possible, for several reasons filters could only check each
> route independently.

I think it would be a terrific feature that would have lots of
interesting properties in the traffic engineering space or other area's
such as routing security/RPKI.

A small write up on one example is detailed in this thread:

    http://mailman.nanog.org/pipermail/nanog/2014-August/069506.html

The short version is that some operators feel that today's RPKI
deployment options in terms of local policy are too black/white. It
would be nice if I can reject invalid prefixes as long as there is a
covering valid announcement, if the valid announcement disappears I'd
want to accept invalid announcements if they are from the registered
origin. 

Kind regards,

Job