[Babel-users] Babel MAC auth fails due to packet reordering

[Daniel Gröber]

Hi Juliusz,

On Tue, May 03, 2022 at 08:18:07PM +0200, Juliusz Chroboczek wrote:
> So the multicast packet overtook the unicast one.  That's probably due to
> neighbour discovery delaying the unicast packet.  Could you please provide
> the timestamps?

I don't think it is ND. I started noticing this when I enabled fq_codel on
my Debian systems so I have a hunch it's because of the more fancy per-flow
queueing which it does. Was the MAC stuff ever tested on any openwrt
systems? Those have had fq_codel by default for a while now. Debian only
recently switched to it in unstable.

I'm attaching a filtered down pcap from the receiving side showing the
problem. Wireshark filter: (babel && ipv6.src == fe80::1) || icmpv6. The
sending side is running babeld the receiving side bird2 if that matters.

> Daniel, how often does it happen? 

Very frequently. AFAICT the neighbour never gets assigned anything better
than the infintiy metric so it's unusable.

Thanks,
--Daniel
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