An old NSD daemon, stuck with old data?

[Stephane Bortzmeyer]

We experienced a funny problem with a nsd name server. Serial numbers
seem to oscillate between an old value and the current one:

% check_soa ma
ns2.nic.fr has serial number 2005112202
% check_soa ma
ns2.nic.fr has serial number 2005111902

nsd logs show nothing and the zone did not change between the two tests.

I notice old daemons on the machines:

[bortzmeyer at ns2 ~]$ ps auxww|grep nsd
nsd      24699  0.0 21.9 459176 455580 ?     S    Nov21   0:43 /usr/local/nsd/sbin/nsd -a 192.93.0.4 -a 2001:660:3005:1::1:2 -n 15
nsd      24720  4.3 21.9 459752 455964 ?     S    Nov21  71:25 /usr/local/nsd/sbin/nsd -a 192.93.0.4 -a 2001:660:3005:1::1:2 -n 15
nsd      31290  0.0  0.0     0    0 ?        Z    Nov21   0:43 [nsd] <defunct>
nsd      18064  1.9 21.9 459844 456164 ?     S    10:25   0:44 /usr/local/nsd/sbin/nsd -a 192.93.0.4 -a 2001:660:3005:1::1:2 -n 15
nsd      18074  5.2 21.9 460304 456408 ?     S    10:25   1:55 /usr/local/nsd/sbin/nsd -a 192.93.0.4 -a 2001:660:3005:1::1:2 -n 15

Killing them all (they require a -KILL) apparently solved the
problem. Is it possible that the "old" daemons were still receiving
some of the UDP requests (I did not test with TCP, unfortunately) and
replied with old data?

NSD 2.3.0
CentOS release 4.2 (Final)
Linux 2.6.9-22.0.1.ELsmp