[bird-users] Optional attribute error peering BGP with FRR

[Ondrej Zajicek]

On Thu, Jul 11, 2019 at 04:01:19PM +0200, Hansen, Christoffer wrote:
> Derrick,
> 
> Donald is right. Ignore earlier comment. (rfc4760[0], p. 5)
> 
> > From the pcap this looks like FRR is sending an empty NLRI and
> > according to RFC 2858:
> > 
> >    An UPDATE message that carries no NLRI, other than the one encoded in
> >    the MP_REACH_NLRI attribute, should not carry the NEXT_HOP attribute.
> >    If such a message contains the NEXT_HOP attribute, the BGP speaker
> >    that receives the message should ignore this attribute.
> > 
> > So the enclosed pcap looks correct too me as that we are sending a
> > default route to our peer to be pointed back at us.
> 
> [0]: https://tools.ietf.org/html/rfc4760
> 
> Ondrej: Possible bird is checking for an NEXT_HOP field to be present in the
> mentioned BGP Update Message?

Hi

BIRD is generally doing revised error handling per RFC 7606, so most
attribute errors are treated by handled by treat-as-withdraw policy
instead of optional attribute error.

By quick view i found only a few case that could generate optional
attribute error: MP_REACH_NLRI / MP_UNREACH_NLRI of invalid (too small)
length and NEXT_HOP (or next-hop part of MP_REACH_NLRI) of unrecognized
length.

Is any of this in the pcap file? Could you send me a pcap file?

-- 
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."