[musl] EDNS0 support?

[musl] EDNS0 support?

[Bartłomiej Palmowski]

Hi,
we run alpine based docker images in AWS (inside our VPCs). Which
means that we're using dns servers provided by the AWS[1]. The problem
arises when we want to resolve a dns record that yields a large
response, for example:

$ nslookup eu.data.logs.insight.rapid7.com
Server:        10.11.12.13
Address:    10.11.12.13:53

Non-authoritative answer:
*** Can't find eu.data.logs.insight.rapid7.com: No answer

Non-authoritative answer:
*** Can't find eu.data.logs.insight.rapid7.com: No answer

According to what I managed to find out the reasons are as follows:
* edns0 is not advertise by the resolver
* there is no retry with TCP

Please advise on how we could reconfigure our images so that we're
able to resolve records with lots of RRs with a musl resolver.

1 - https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/DNSBehavior.html

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Re: [musl] EDNS0 support?

[Florian Weimer]

* Bartłomiej Palmowski:

> we run alpine based docker images in AWS (inside our VPCs). Which
> means that we're using dns servers provided by the AWS[1]. The problem
> arises when we want to resolve a dns record that yields a large
> response, for example:

There has been a previous thread on this topic, around this message:

  <https://www.openwall.com/lists/musl/2020/04/18/7>

Not sure if anything has changed in the code since then.

Thanks,
Florian
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Re: [musl] EDNS0 support?

[Bartłomiej Palmowski]

I'm not an expert on this so it's possible that I'm mixing things up,
but from my tests it seems like enabling edns0 extension would help a
great deal with this type of issue. With glibc it is an option in
resolv.conf, I don't see if musl supports this.

On Tue, 3 Nov 2020 at 18:07, Florian Weimer <fweimer@redhat.com> wrote:
>
> * Bartłomiej Palmowski:
>
> > we run alpine based docker images in AWS (inside our VPCs). Which
> > means that we're using dns servers provided by the AWS[1]. The problem
> > arises when we want to resolve a dns record that yields a large
> > response, for example:
>
> There has been a previous thread on this topic, around this message:
>
>   <https://www.openwall.com/lists/musl/2020/04/18/7>
>
> Not sure if anything has changed in the code since then.
>
> Thanks,
> Florian
> --
> Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
> Commercial register: Amtsgericht Muenchen, HRB 153243,
> Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill
>

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