[Dnsmasq-discuss] : Dns lookup failures if one of the upstream servers are down
Abhishek Patti
abhishek.patti at gmail.com
Thu Mar 26 14:39:21 GMT 2020
Hi Everyone
We are using dnsmasq version 2.80 and have multiple upstream servers
configured, with all-servers flag set. We noticed that if first upstream
server fails then we get dns lookup failures even though other upstream
servers are working fine.
Thank You
Abhishek Patti
On Thu, Mar 26, 2020, 5:28 AM <
dnsmasq-discuss-request at lists.thekelleys.org.uk> wrote:
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> Today's Topics:
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> 1. TFTP storage issue prevents other dnsmasq services (DHCP/DNS)
> to run (Ercolino De Spiacico)
> 2. Re: TFTP storage issue prevents other dnsmasq services
> (DHCP/DNS) to run (Geert Stappers)
> 3. Re: TFTP storage issue prevents other dnsmasq services
> (DHCP/DNS) to run (Simon Kelley)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 26 Mar 2020 09:15:09 +0000
> From: Ercolino De Spiacico <bellocarico at hotmail.com>
> To: "dnsmasq-discuss at lists.thekelleys.org.uk"
> <dnsmasq-discuss at lists.thekelleys.org.uk>
> Subject: [Dnsmasq-discuss] TFTP storage issue prevents other dnsmasq
> services (DHCP/DNS) to run
> Message-ID:
> <
> AM7P191MB08077EA4FA6296B4AA48D338B2CF0 at AM7P191MB0807.EURP191.PROD.OUTLOOK.COM
> >
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> It seems like enabling TFTP like:
>
> enable-tftp
> tftp-root=/mnt/usb/TFTP
> dhcp-boot=pxelinux.0,,192.168.0.1
>
> But experiencing an system storage issue (usb failure, unable to mount,
> etc) takes the full dnsmasq down e.g. prevent from running at all
>
> Can I suggest for dnmasq to take a softer approach when this happens and
> just skip the TFTP process execution rather than affect all the other
> internal services like DHCP and DNS?
>
> More than else it's that "external factor" that sucks in this situation.
>
> Thanks
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> ------------------------------
>
> Message: 2
> Date: Thu, 26 Mar 2020 12:14:33 +0100
> From: Geert Stappers <stappers at stappers.nl>
> To: dnsmasq-discuss at lists.thekelleys.org.uk
> Subject: Re: [Dnsmasq-discuss] TFTP storage issue prevents other
> dnsmasq services (DHCP/DNS) to run
> Message-ID: <20200326111433.i2gl53t73l3ixul3 at gpm.stappers.nl>
> Content-Type: text/plain; charset=utf-8
>
> On Thu, Mar 26, 2020 at 09:15:09AM +0000, Ercolino De Spiacico wrote:
> > It seems like enabling TFTP like:
> >
> > enable-tftp
> > tftp-root=/mnt/usb/TFTP
> tftp-no-fail
> > dhcp-boot=pxelinux.0,,192.168.0.1
> >
> > But experiencing an system storage issue (usb failure, unable to mount,
> > etc) takes the full dnsmasq down e.g. prevent from running at all
> >
> > Can I suggest for dnmasq to take a softer approach when this happens
> > and just skip the TFTP process execution rather than affect all the
> > other internal services like DHCP and DNS?
> >
> > More than else it's that "external factor" that sucks in this situation.
>
> Yes, hence the option `tftp-no-fail`
>
> Quoting the manual page
>
> --tftp-no-fail
> Do not abort startup if specified tftp root
> directories are in?accessible.
>
>
> > Thanks
>
> No problem. Feel welcome to also report that `tftp-no-fail` does what
> you expect from it.
>
>
> Regards
> Geert Stappers
> --
> Silence is hard to parse
>
>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 26 Mar 2020 11:53:54 +0000
> From: Simon Kelley <simon at thekelleys.org.uk>
> To: dnsmasq-discuss <Dnsmasq-discuss at lists.thekelleys.org.uk>
> Subject: Re: [Dnsmasq-discuss] TFTP storage issue prevents other
> dnsmasq services (DHCP/DNS) to run
> Message-ID: <42e7d990-df47-6ca4-45c1-fe8d4430563b at thekelleys.org.uk>
> Content-Type: text/plain; charset=windows-1252
>
> On 26/03/2020 09:15, Ercolino De Spiacico wrote:
> > It seems like enabling TFTP like:
> >
> > enable-tftp
> > tftp-root=/mnt/usb/TFTP
> > dhcp-boot=pxelinux.0,,192.168.0.1
> >
> > But experiencing an system storage issue (usb failure, unable to mount,
> > etc) takes the full dnsmasq down e.g. prevent from running at all
> >
> > Can I suggest for dnmasq to take a softer approach when this happens and
> > just skip the TFTP process execution rather than affect all the other
> > internal services like DHCP and DNS?
>
>
> This is much easier said than done, because file read/write can't be
> done in a non-blocking way in Unix/Linux. AFAIK all ordinary files are
> by definition non-blocking, and if they do block on the underlying
> device, that's just tough; there's no way to get your process scheduled
> again until the drive returns data.
>
> I think the lesson from this is: don't put any files dnsmasq accesses
> (tftp sources, DHCP lease file, log files, configuration files) on
> devices that may go away: copy the data to an internal drive.
>
> >
> > More than else it's that "external factor" that sucks in this situation.
>
>
> Agreed, and your message will lie in the list archive as a warning to
> anyone else tripping over the same gotcha. That's a good thing.
>
>
> Cheers,
>
>
> Simon.
>
> >
> > Thanks
> >
> > _______________________________________________
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> > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> >
>
>
>
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