[Dnsmasq-discuss] Possible to reuse Cache over restats?

[Petr Menšík]

I am maintainer of Fedora dnsmasq package.  I don't know about any issue 
with latest dnsmasq on f36. It should work reliably.

I agree with Geert, log-queries option should reveal the most details 
for troubleshooting. Default logging to journal should be enough. Use 
"journalctl -xeu dnsmasq" command to see the most recent output of dnsmasq.

You should see whether incoming query were received by the dnsmasq. And 
where did it forwarded it. It should log also what forwarder replied. If 
reply after forward is not logged but wireshark can record such packets, 
it would mean some error in socket handling code. But I think all known 
errors in Fedora 36 were fixed.

It is possible to send SIGHUP to dnsmasq to clear just cache. Just use 
kill -SIGHUP $(pidof dnsmasq). But that should not be necessary, 
especially not periodic way. Because systemd-resolved is enabled by 
default on Fedora, are you sure you have disabled it correctly? Are you 
connected by multiple interfaces at the same time? Would it work with 
just one interface connected?

Lets find somehow a reason for your broken resolution instead of dumping 
the cache periodically. While it should work even with that, it 
definitely should not be required.

Cheers,
Petr

On 30. 06. 22 14:32, Tobias Hochgürtel wrote:
>
> On Wed, Jun 29, 2022 at 08:25:18PM +0000, Dominik Derigs wrote:
>
>   * Tell us which version of dnsmasq is being used
>
>   * Reread the manual page and in particular --log-queries option
>
> [root at router-fedora ~]# *hostnamectl*
>
> Static hostname: router-fedora
>
>        Icon name: computer-desktop
>
>          Chassis: desktop 🖥
>
>       Machine ID: c9c0e33265b848bfbce224fd8615fb30
>
>          Boot ID: 0824361c352745c0a35a75167a2f81a0
>
> Operating System: *Fedora Linux 36 (Server Edition)*
>
>      CPE OS Name: cpe:/o:fedoraproject:fedora:36
>
>           Kernel: *Linux 5.18.6-200.fc36.x86_64*
>
>     Architecture: x86-64
>
> Hardware Vendor: BIOSTAR Group
>
>   Hardware Model: N3150NH
>
> [root at router-fedora ~]# *dnsmasq --version*
>
> *Dnsmasq version 2.86*Copyright (c) 2000-2021 Simon Kelley
>
> Compile time options: *IPv6 GNU-getopt DBus no-UBus no-i18n IDN2 DHCP 
> DHCPv6 no-Lua TFTP conntrack ipset auth cryptohash DNSSEC loop-detect 
> inotify dumpfile*
>
> This software comes with ABSOLUTELY NO WARRANTY.
>
> Dnsmasq is free software, and you are welcome to redistribute it
>
> under the terms of the GNU General Public License, version 2 or 3.
>
> From: Dnsmasq-discuss 
> <dnsmasq-discuss-bounces at lists.thekelleys.org.uk> on behalf of Donald 
> Muller <donmuller22 at outlook.com>
>
> Date: Thursday, 30. June 2022 at 02:48
>
> To: Geert Stappers <stappers at stappers.nl>, 
> "dnsmasq-discuss at lists.thekelleys.org.uk" 
> <dnsmasq-discuss at lists.thekelleys.org.uk>
>
> Subject: Re: [Dnsmasq-discuss] Possible to reuse Cache over restats?
>
> Also, what you are running it on?
>
> From: Dnsmasq-discuss 
> <dnsmasq-discuss-bounces at lists.thekelleys.org.uk> on behalf of Geert 
> Stappers via Dnsmasq-discuss <dnsmasq-discuss at lists.thekelleys.org.uk>
>
> Sent: Wednesday, June 29, 2022 6:14:30 PM
>
> To: dnsmasq-discuss at lists.thekelleys.org.uk 
> <dnsmasq-discuss at lists.thekelleys.org.uk>
>
> Subject: Re: [Dnsmasq-discuss] Possible to reuse Cache over restats?
>
> On Wed, Jun 29, 2022 at 08:25:18PM +0000, Dominik Derigs wrote:
>
> > On Wed, 2022-06-29 at 18:37 +0000, Tobias Hochgürtel wrote:
>
> > > There isn't a feature to reuse the dns-cache?
>
> > > or a plan to add this feature?
>
> > > 
>
> > 
>
> > There is no such feature and there is also nothing planned at the moment
>
> Oh, it was not a joke.
>
> > However, restarting dnsmasq once per hour surely is the least optimal
>
> > solution to circumvent what you are observing.
>
> So true.
>
> > On Wed, 2022-06-29 at 18:37 +0000, Tobias Hochgürtel wrote:
>
> > > I also don't know how I can analyse that behavior.
>
> > 
>
> > You could use some widely known and used tools like Wireshark where various
>
> > tutorial are available to see whether the issue is dnsmasq not responding
>
> > or the queries not making their way to dnsmasq or if something happens to
>
> > the queries sent upstream to the forward destionation, or whatever else may
>
> > be happening. We can surely give some assistance here, if you want.
>
> Here already some assistance:
>
> * Tell us which version of dnsmasq is being used
>
> * Reread the manual page and in particular --log-queries option
>
> Groeten
>
> Geert Stappers
>
> -- 
>
> Silence is hard to parse
>
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>
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>
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>
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-- 
Petr Menšík
Software Engineer, RHEL
Red Hat,http://www.redhat.com/
PGP: DFCF908DB7C87E8E529925BC4931CA5B6C9FC5CB
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