[Babel-users] Babel in Bird 1.6.0

[Juliusz Chroboczek]

> Okay, actually trying to put this into code: Is the intention here that
> a null-router ID update is acceptable only on *wildcard* retractions or
> on *all* retractions?

In RFC 6126, there's nothing special about a null router-ID: it's just
a router ID.

However, for AEs 0 and 1, the address is too short to carry a router-ID
(it's 0 and 4 octets respectively, while a router-ID is 8 octets).  The
intention was that a shorter address should be stored in the right side of
a router-ID, and padded with zeroes; e.g. the IPv4 address (AE 1) 1.2.3.4
maps to the router-ID 0:0:0:0:1:2:3:4, and the zero-length address (AE 0)
maps to 0:0:0:0:0:0:0:0.  However, I don't think this is spelled out in
RFC 6126.

So my current thinking is:

  - if a Babel speaker receives an update with AE 0 or 1 and bit 0x40 set,
    it MUST set the router-ID to the address in the update, right justified
    and padded with zeroes;
  - a Babel speaker SHOULD NOT set bit 0x40 in updates with AE 0 or 1,
    lest the author meet the wrath of Markus.

-- Juliusz