[Babel-users] Babel in Bird 1.6.0

[Toke Høiland-Jørgensen]

Juliusz Chroboczek <jch at pps.univ-paris-diderot.fr> writes:

>> I remember running into this. What happens here is that babeld sends an
>> update without a preceding router_id TLV, with a wildcard address, but
>> flag 0x40 set (meaning "infer the router ID from the address").
>> While I'm not sure what the purpose of this is (a null update with a
>> null router ID with infinity metric and interval?) it *is* technically
>> in spec.
>
> No, it isn't.
>
> Earlier versions of babeld allowed a retraction (update with infinite
> metric) without a router-id.  This is not allowed by RFC 6126.  Current
> versions of babeld no longer send such retractions, but still honour them
> when received.

But those updates seem to set flag 0x40, so that's not "without a router
ID" is it?

> The plan is to explicitly allow such retractions in RFC 6126-bis, but
> they are clearly not allowed by RFC 6126.

Hmm, the RFC says this (which I seem to have previously missed):

  If the metric field is FFFF hexadecimal, this TLV specifies a
  retraction.  In that case, the current router-id and the Seqno are
  not used.  AE MAY then be 0, in which case this Update retracts all
  of the routes previously advertised on this interface.

Doesn't that make them in spec?

-Toke