On 13/12/2023 15:25, Chris Green wrote:
I run dnsmasq version 2.89 on my laptop which is running [x]ubuntu
23.04.
I have systemd.resolvd disabled.
I'm occasionally seeing the following error when getting a host's IP:-
chris$ host homepi
;; communications error to 127.0.0.1#53: timed out
homepi has address 192.168.1.113
chris$ ps -ef | grep dnsmasq
dnsmasq 933 1 0 Dec06 ? 00:00:22 /usr/sbin/dnsmasq -x
/run/dnsmasq/dnsmasq.pid -u dnsmasq -7
/etc/dnsmasq.d,.dpkg-dist,.dpkg-old,.dpkg-new --local-service
--trust-anchor=.,20326,8,2,e06d44b80b8f1d39a95c0b0d7c65d08458e880409bbc683457104237c7f8ec8d
chris 86541 3774 0 15:05 pts/1 00:00:00 grep --color=auto
dnsmasq
chris$
As can be seen dnsmasq is running and subsequent queries work without any
error (or delay). The above timeout is a few seconds, maybe five or a bit
less.
There's no dnsmasq related error message in syslog (nothing for today at
all). The system homepi is a Raspberry Pi on the same LAN as the laptop
running dnsmasq, The error isn't only for one particular host, I've seen
it for other systems on my LAN.
Can anyone suggest what might be causing the error and/or how to diagnose
what's wrong?
It looks like the first query (or its reply) was dropped, host retried,
and it worked second time around.
Since DNS transport is normally across UDP, which is defined as
unreliable, this is completely normal. Except that the UDP packets are
not actually traversing a network, they're going via the lo interface
within one machine. I'm sure there are circumstances where UDP packets
can get dropped in the kernel when going via the lo interface, but it
shouldn't happen very often. Is the machine under heavy load or memory
pressure? Maybe a network reconfiguration event could drop packets?
Simon.
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