[RFCv2] Babel: add v4viav6 support

[Andreas Rammhold]

Toke Høiland-Jørgensen <toke at toke.dk> writes:

> Andreas Rammhold <andreas at rammhold.de> writes:
>
>> This implements [draft-ietf-babel-v4viav6] 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.
>>
>> The implementation is compatible with the current Babeld version (the
>> relevant changes can be seen in the [babeld PR]). I've verified this
>> with a few VMs in the following setup:
>>
>> Bird <- v4 only -> Bird <- v6 only -> Babeld <- v4 only -> Babeld
>>
>> Each routing daemon was running on their own VM and had L2 connectivity
>> to only its direct neighbors. At the nodes at the edges v4 networks have
>> been announced and full end-to-end communication was possible over the
>> mixed AF network. The v6 only link between Babel and Bird (at the
>> "center" of the above setup) did transport the v4 packets via the v6
>> link-local next hop addresses just as expected.
>>
>> Thanks to Toke Høiland-Jørgensen for early review on this work.
>>
>> [draft-ietf-babel-v4viav6]: https://datatracker.ietf.org/doc/draft-ietf-babel-v4viav6/
>> [babeld PR]: https://github.com/jech/babeld/pull/56
>
> Thank you for the respin! Code LGTM; only comment is that it would be
> nice if the documentation was changed to refer to the proper RFC number
> instead of draft-ieft-babel-v4viav6; but that can be fixed up when
> applying (after the number gets assigned hopefully soonish).

Agreed.

>
> Also, one small nit regarding the comment you left in:
>
>> +  /*
>> +   * When receiving requests, AEs 1 (IPv4) and 4 (v4-via-v6) MUST be
>> +   * treated in the same manner: the receiver processes the request as
>> +   * described in Section 3.8 of [RFC6126bis].  If an Update is sent, then
>> +   * it MAY be sent with AE 1 or 4, as described in Section 2.1 above,
>> +   * irrespective of which AE was used in the request.
>> +   */
>
> This is a bit long, especially when repeated in two places; also the ref
> to RFC6126bis is outdated. But maybe just shorten it to:
>
> /* RFCXXXX section 2.3: When receiving requests, AEs 1 (IPv4) and 4
>  * (v4-via-v6) MUST be treated in the same manner.
>  */

Agreed. 


@Maintainers: let me know if you want me to do these minor modifications
(once we have the required information) or if you are fine applying
those.



Regards,

Andi