musl - questions about musl DNS resolver

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Message-Id: <e1d7b3a2-334d-4bb7-9386-68e2c4013729@app.fastmail.com>
Date: Sat, 04 Nov 2023 12:12:58 +0530
From: "Ayush Agarwal" <ayush@...shnix.com>
To: musl@...ts.openwall.com
Subject: questions about musl DNS resolver

Hi,

I was reading about how DNS works in Linux distributions and I noticed
some differences in the way libc resolvers work in glibc and in musl.
I hope it's okay if I ask a few (potentially stupid) questions?

1. Why not offer a different man page on musl distributions for pages
like resolv.conf(5) and resolver(3) considering how their
implementation details and behavior are different from glibc? Is not
offering them intentional or does it require someone to step up and
write the documentation?

2. Which options in the resolv.conf(5) man page are supported by musl?
I know "search" and "nameserver" are supported but what about
"options" like "ndots", "edns0", "use-vc", "trust-ad"?

3. It seems that version 1.2.1 added support for DNSSEC queries but
how do I confirm if DNSSEC queries are sent and received with musl? Do
I need to use the "option edns0 trust-ad" directive in resolv.conf for
it work? The usual suspects like drill and kdig seem to use their own
resolver.

4. The musl version 1.2.4 added TCP fallback to DNS. Is this fallback
intended to work automatically when the size of a DNS query is large
or does it need any configuration?

Thanks,
Ayush

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