nsd users - Feb 2025 - xfrd: failed reading tcp Operation now in progress

Hi

"xfrd: failed reading tcp Operation now in progress" has recently
started cropping up in my logs on an NSD secondary (pulling from a PowerDNS
primary). My other secondary runs Knot and has no issues.

What does the obscure message mean and (more importantly) how do I fix it ? A
reboot of the host did not help and there are no updates pending.

This is Debian Bookworm and NSD is from the distro.

NSD version 4.6.1
Configure line: --build=x86_64-linux-gnu --prefix=/usr
--includedir=${prefix}/include --mandir=${prefix}/share/man
--infodir=${prefix}/share/info --sysconfdir=/etc --localstatedir=/var
--disable-option-checking --disable-silent-rules
--libdir=${prefix}/lib/x86_64-linux-gnu --runstatedir=/run
--disable-maintainer-mode --disable-dependency-tracking
--with-configdir=/etc/nsd --with-nsd_conf_file=/etc/nsd/nsd.conf
--with-pidfile=/run/nsd/nsd.pid --with-dbfile=/var/lib/nsd/nsd.db
--with-zonesdir=/etc/nsd --with-xfrdfile=/var/lib/nsd/xfrd.state
--disable-largefile --disable-recvmmsg --enable-root-server --enable-mmap
--enable-ratelimit --enable-zone-stats --enable-systemd --enable-checking
--enable-dnstap
Event loop: libevent 2.1.12-stable (uses epoll)Linked with OpenSSL 3.0.15 3 Sep
2024
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