Identify empty community list?

[Ondrej Zajicek]

On Tue, Dec 21, 2010 at 12:15:45PM +0100, Lars-Johan Liman wrote:
> Hi!
> 
> I'm trying to get a grip on BIRD, and I'm slowly getting there.
> 
> One thing that puzzles me, though, is how to catch a BGP route entry
> that has no community list at all. What is the appropriate syntax?
> I'm runnig out of character combinations to try ... ;-)

There is probably no natural way to do this. Community lists
currently support just variants of membership testing.

But your last idea should work:

> I suppose one could also turn it all around and try to say:
> 
> 		if bgp_community ~ [(*,*)] then
> 			reject;
> 		accept;
> 
> doesn't work either. You can't say set A is member of set B. I
> understand that.

Expression  clist ~ pair_set should work like 'exists C from clist
such that C ~ pair_set'. In your example the problem is that we currently 
support '*' in pair_set only in the second part of the pair, like (123,*),
but you can write something like [(0,0)..(65535,65535)].

Therefore expression  bgp_community ~ [(0,0)..(65535,65535)] should do
what you want (if you have version 1.2.5, there is a bug in older ones
in pair sets).

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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