[Dnsmasq-discuss] Question about --all-servers in man page

Masanari Iida standby24x7 at gmail.com
Mon Sep 6 13:49:25 UTC 2021


On Sun, Sep 5, 2021 at 4:02 AM Dominik DL6ER <dl6er at dl6er.de> wrote:

> Hey Masanari,
>
> On Fri, 2021-09-03 at 19:26 +0900, Masanari Iida wrote:
> > dnsmasq-2.85 (Fedora 33, x86_64)
> > multiple upstream DNS servers in config file.
> > No --strict-order, No --all-server setting .
> >
> > Symptom
> > Explanation about --all-servers in dnsmasq(8) man page could
> > be different from actual dnsmasq behavior.
> >
> > In man page, it is written that
> > "By default, when dnsmasq has more than one upstream server
> > available, it will send queries  to  just one server"
> >
> > But actual behavior is, it sends queries to _ALL_ upstream DNS
> > servers in config at once.
> > And if I set --strict-order in dnsmasq.conf, then it send a query to
> > one
> > server at a time.
>
> This is expected behavior, the man page explains this somewhat hidden
> in the option --strict-order:
>
> > By default, dnsmasq will send queries to any of the upstream servers
> it knows about and tries to favour servers that are known to be up.
>
> This probing of the fastest happens every now and then, to be precise
> every 50 queries or every 20 seconds, see
>
> https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=blob;f=src/config.h;h=30e23d8e8fb6a0b78d479f77ea021fe126e0670c;hb=HEAD#l27
> and the line below. The default probing could likely be made less
> often, but else than that, I don't think there is an inconsistency
> here.
>
> Best,
> Dominik
>
> Hello Dominik,
Thanks for the hint.
I have confirmed that what I was seeing is  sending queries to upstream DNS
servers every 20 seconds,
in case I did not specify strict-order and all-server.
Regards,
Masanari Iida
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