[Dnsmasq-discuss] editing resolv.conf blocks dnsmasq, but not right away

Geert Stappers stappers at stappers.nl
Thu Mar 31 11:31:03 UTC 2022


On Wed, Mar 30, 2022 at 10:57:38PM +0000, Edward McGuire wrote:
> Dnsmasq 2.86
> Slackware Linux 15.0
> 
> This dnsmasq server provides DNS and DHCP service to a local network
> of about 150 devices. My problem emerges when I uncomment the first
> line of /etc/resolv.conf:
> 
> #nameserver 127.0.0.1
> nameserver [ISP ip redacted]
> nameserver [ISP ip redacted]
> 
> For 10 or 20 minutes after the edit,
> dnsmasq continues to operate perfectly.

Most likely due cache content considered valid.


> Then all client queries begin to time out.

Dnsmasq cache content expired.


> If I comment out the line again, the problem immediately disappears.
> 
> The problem is reliably reproducible. if I uncomment the line again,
> dnsmasq again operates perfectly for some time, then all client queries
> begin to time out again.
> 
> In /etc/dnsmasq.conf I have option "no-resolv" set. So it mystifies
> me that dnsmasq behavior would be affected by changes to resolv.conf.
> 
> Not seeing any error messages logged. What I do see is the rate of all
> activities logged slows to a crawl. I get about two messages per minute
> where the normal rate is hundreds per minute. Here's an example with
> "log-dhcp" turned on:
> 
> Mar 30 17:33:40 slack dnsmasq-dhcp[946]: 940533162 next server: [ip redacted]
> Mar 30 17:34:05 slack dnsmasq-dhcp[946]: 940533162 sent size:  1 option: 53 message-type  5
> Mar 30 17:34:40 slack dnsmasq-dhcp[946]: 940533162 sent size:  4 option: 54 server-identifier  [ip redacted]
> Mar 30 17:35:16 slack dnsmasq-dhcp[946]: 940533162 sent size:  4 option: 28 broadcast  [ip redacted]
> Mar 30 17:35:52 slack dnsmasq-dhcp[946]: 940533162 sent size:  4 option:  3 router  [ip redacted]
> Mar 30 17:36:22 slack dnsmasq-dhcp[946]: 940533162 sent size:  4 option:  1 netmask  [ip redacted]
> Mar 30 17:36:52 slack dnsmasq-dhcp[946]: 940533162 sent size: 12 option:  6 dns-server  [local ip redacted], [ISP ip redacted], [ISP ip redacted]
> 
> These log entries show a single DHCP response taking the daemon several
> MINUTES to complete! So something is blocking dnsmasq pretty badly.

s/something is blocking dnsmasq/something is blocking name resolving/

 
> This is my first attempt at a dnsmasq installation. So my fear is
> I've made a clueless error and just don't know enough to recognize
> it. Any ideas?

dig @[ISP ip redacted]  dnsmasq.org

 
> Cheers
> Edward


Groeten
Geert Stappers
-- 
Silence is hard to parse



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