[PATCH] Babel: add RFC9229 (v4 via v6) support

[Ondrej Zajicek]

On Sun, Dec 18, 2022 at 06:57:48PM +0100, andreas--- via Bird-users wrote:
> From: Andreas Rammhold <andreas at rammhold.de>
> 
> This implements [RFC9229] an IPv4 via IPv6 extension
> to the Babel routing protocol that allows annoncing routes to an IPv4
> prefix with an IPv6 next-hop, which makes it possible for IPv4 traffic
> to flow through interfaces that have not been assigned an IPv4 address.
> 
> I'd like to drive this to the finish goal soon. I've been using it
> ever since and know of other users as well.

Hi

Thanks for the patch, will check that during this week.

Just few random notes:

The RFC says "ordinary IPv4 announcements are preferred to v4-via-v6
announcements when the outgoing interface has an assigned IPv4 address",
but there is also the third option - using an IPv4 address from another
interface as a next hop.

What happens if route is announced with IPv6 next hop and the interface later?

What do you think about changing the option name to 'extended next hop',
like the equivalent BGP option? On the one hand, it improves consistency
within BIRD, on the other hand, 'v4-via-v6' is used by the RFC.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."