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Message-ID: <20240614174004.GZ10433@brightrain.aerifal.cx>
Date: Fri, 14 Jun 2024 13:40:06 -0400
From: Rich Felker <dalias@...c.org>
To: AK47 <250200715@...com>
Cc: musl <musl@...ts.openwall.com>
Subject: Re: Question about res_msend_rc
On Fri, Jun 14, 2024 at 09:28:18PM +0800, AK47 wrote:
> Hi，
> In __res_msend_rc functions, if we send two A queries to two
> nameservers, One server first replied with ret code "no such
> name"(answer length is greater than 4), while the other server
> subsequently replied with the correct IP address（behind the first
> server). Will the current musl only capture the first "no such name"
> reply and totally miss the correct IP address reply? Is there a bug
> or any special reason?
This is the expected behavior. Support for multiple nameservers is for
redundancy, not unioning of inconsistent DNS namespaces, and in fact
these behaviors are mutually exclusive: If we were performing
unioning, every query for a nonexistent name would have to wait for
all N nameservers to reply before it could be serviced, and would
tempfail whenever any one of the N was down, while the whole point of
having N nameservers was to handle the case where one or more might be
down or responding slowly.
If you want unioning, you want to point resolv.conf at a unioning DNS
proxy running on localhost or somewhere on your network that takes the
two inconsistent upstream sources and applies whatever rules you want
for unioning them.
Rich
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