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

[Edward McGuire]

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. Then all client queries begin to time out. 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.

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?

Cheers
Edward
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