[ipv6-wg] IPv4-mapped addresses in AAAA records (was: RIPE 88, presentations and a co chair change..)

On 25/03/2024 10:06, Thomas Schäfer wrote:
> I can't present, but I would suggest the topic:
>
> Lessons learned/ Lessons not learned - the mess with mapped IPv4 addresses -
> or just Layer 8 problems:
>
> Lessons learned:
> https://www.githubstatus.com/incidents/5y8b8lsqbbyq
>
> Lessons not learned:
> united by Postbank/Deutsche Bank, new relic, ns1, ibm, fastly and others
>
> https://forum.newrelic.com/s/hubtopic/aAX8W0000015BUvWAM/bamnrdatanet-resolves-with-wrong-aaaarecords
>
Hey Thomas,

I think this is a great topic and somebody should definitely cover it. I 
remember setting up a couple of test sites to prove wrong the claim: "We 
use IPv4-mapped AAAA records in order to save money on our authoritative 
DNS provider who charges us per query."

https://ipv4-mapped.0skar.cz/  - this has only IPv4-mapped AAAA record - 
should be unreachable
https://ipv4-mapped-pref.0skar.cz/ - this is "Postbank-style" dual stack 
with A and IPv4-mapped AAAA record - everybody should reach the A record 
website

However, my macOS 14.4 on IPv6-only network happily connect to both test 
sites from all browsers and even prefers IPv4-mapped AAAA over A 
records. So the aforementioned claim may not be completely wrong (though 
it is still stupid).

Any volunteer willing to try common OS behaviour while counting the 
number of DNS queries? :)

--
Best regards,

Ondřej Caletka
RIPE NCC
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