After overnight reboot I lost dhcp – no clients would get an IPv4 address. I did another reboot (unfortunately perhaps) but that didn’t fix it, then I generated some diagnostics. For immediate fix, setting clients to static addresses seemed to work.
Suspicious part, at a quick look:
4567 dnsmasq 2564 S /usr/sbin/dnsmasq -C /var/etc/dnsmasq.conf.cfg01411c -k -x /var/run/dnsmasq/dnsmasq.cfg01411c.pid
4575 root 2492 S /usr/sbin/dnsmasq -C /var/etc/dnsmasq.conf.cfg01411c -k -x /var/run/dnsmasq/dnsmasq.cfg01411c.pid
I found not a single log line from dnsmasq. I’m sending the diags to support.
EDIT: maybe it was caused by my experimental setup that switched WAN port with one of the LAN ones (but it’s been working fine for days). I rolled back before that config change, updated, rebooted and the issue didn’t re-appear.