Which timeouts are used by BIND when resolving recursive queries?

[Warren Kumari]

On Fri, Oct 5, 2018 at 11:12 AM Alberto Colosi <alcol at hotmail.com> wrote:

> RFC say all
>
> read RFC
>
>
> BIND is a DNS system not an alien so follow RFC
>

No, BIND is an **implementation** of DNS software.

There is much in the RFCs that is subject to interpretation, or not
necessarily well defined. Things like preferred timeouts fall into this
category.

This answer is almost as helpful as Alberto's, but as far as I know, these
timeouts are not well defined, other than in the BIND source.

Here is some of what you are looking for:
http://users.isc.org/~each/doxygen/bind9/resolver_8c-source.html#l00143
and
http://users.isc.org/~each/doxygen/bind9/resolver_8c-source.html#l00178
and
http://users.isc.org/~each/doxygen/bind9/resolver_8c-source.html#l02083


and some of the defaults:
https://github.com/isc-projects/bind9/blob/fa03f941027cdcccc060613f773e63701b5baa77/bin/named/config.c




The ARM ("https://www.isc.org/downloads/bind/doc/bind-9-10/" ) has some
useful info too -- https://www.isc.org/downloads/bind/doc/bind-9-10/


>
> Go and read RFC
>

Great. Please point at the RFC which specifies the base timeout and EDNS0
backoff.

W




>
>
>
> ------------------------------
> *From:* bind-users <bind-users-bounces at lists.isc.org> on behalf of ip
> admin via bind-users <bind-users at lists.isc.org>
> *Sent:* Friday, October 5, 2018 4:13 PM
> *To:* bind-users at lists.isc.org
> *Subject:* Which timeouts are used by BIND when resolving recursive
> queries?
>
> Hi,
>
>  I understand that I can configure a global timeout for resolving
> recursive queries (resolver-query-timeout) but find that I cannot configure
> the timeout for an individual query used during DNS resolution.
>
>  For testing I configured one unreachable forwarder (and enabled forward
> only) and saw (tcpdump) that BIND (9.10.6-P1) is first trying two queries
> with EDNS which each seems to have a timeout of 1.2s. Afterwards queries
> without ENDS are sent which seem to have a timeout of 1.6s, then 3.2s, then
> 6.4s, then 9s, finally the maximum (=total) resolver-query-timeout of 30s
> is reached.
>
>  Is the timeout behaviour documented anywhere (similar to a stub resolver
> or dig, i.e. how long are timeouts, how many tries per server etc).
>
>  If someone did find a logging setting that shows which servers are used
> when recursing (forwarding or delegations) to find a response (and when the
> individual queries time out) that would be helpful as well.
>
> Regards
>  Tom
>
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-- 
I don't think the execution is relevant when it was obviously a bad idea in
the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair of
pants.
   ---maf
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