unnecessary and frequency kernel routing update

[Slawa Olhovchenkov]

On Sun, Apr 28, 2013 at 09:17:54PM +0200, Ondrej Zajicek wrote:

> On Fri, Apr 26, 2013 at 05:12:47PM +0400, Slawa Olhovchenkov wrote:
> > bird router got from BGP peer update don't change routing table:
> ...
> > and send unneeded routing update to kernel (old route is same):
> ...
> > >From this BGP peer similar updates got very frequence (50 per second and higher).
> > How to prevent unneeded routing update to kernel?
> 
> Hello
> 
> If the received route update is exactly the same, then it should
> be ignored and not propagated further, but there is probably some
> minor change (like in BGP attributes) that forces the propagation.

How I can see in debug log whats chnged?

> BIRD currently does not support anything that could prevent propagation
> of frequent updates.

I thinks this is useful feature.

> For the kernel protocol it could be hacked by removing the code that
> handles route updates and depending just on periodic routing table scans
> for BIRD-kernel routing table synchronization.

This is bad point. For external BGP update this semi-reasonably, but
for OSPF/etc this is unacceptable.