Package: nrpe-ng
Version: 0.2.0-1
Severity: normal
Dear Maintainer,
I have a setup in which nrpe-ng is used to remotely check DNS
connectivity using check_dns. That is:
Host A (monitoring):
- Installed: nagios4, nrpe-ng
- IP address: 192.0.2.1
Host B (monitored):
- Installed: nrpe-ng, monitoring-plugins-standard, bind9-dnsutils
- IP address: 192.0.2.2
Host C (monitored through host B):
- Installed: bind9
- IP address: 192.0.2.3
- Configured to answer authoritatively for example.com on port 53.
nrpe
over HTTPS DNS
Host A ------------------> Host B -------------> Host C
When nrpe-ng is running on host B, and host A runs the following, this
is the result:
$ /usr/lib/nagios/plugins/check_nrpe_ng -H 192.0.2.2 -c check_dns -a
example.com 192.0.2.3 0.1 1.0
DNS CRITICAL - '/usr/bin/nslookup -sil' msg parsing exited with no address
With some help over at the bind-users mailing list [1], I discovered
that nrpe-ng closes stdin when launching the command [2], and the new
version of nslookup (invoked by check_dns) has issues when stdin is
closed [3].
Redirecting stdin to /dev/null fixes the issue:
$ diff -u /usr/lib/python3/dist-packages/nrpe_ng/commands.py{.old,}
--- /usr/lib/python3/dist-packages/nrpe_ng/commands.py.old 2017-08-08
13:05:02.000000000 -0600
+++ /usr/lib/python3/dist-packages/nrpe_ng/commands.py 2022-09-13
17:00:36.767239885 -0600
@@ -85,6 +85,7 @@
proc = tornado.process.Subprocess(
run_args,
+ stdin=subprocess.DEVNULL,
stdout=tornado.process.Subprocess.STREAM,
close_fds=True,
env=env)
Thanks,
Casey
[1] https://lists.isc.org/pipermail/bind-users/2022-September/106666.html
[2] https://github.com/bootc/nrpe-ng/blob/master/nrpe_ng/commands.py#L86
[3] https://github.com/libuv/libuv/blob/v1.x/src/unix/core.c#L602
-- System Information:
Debian Release: 11.5
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 5.10.0-8-amd64 (SMP w/8 CPU threads)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages nrpe-ng depends on:
ii adduser 3.118
ii init-system-helpers 1.60
ii lsb-base 11.1.0
ii python3 3.9.2-3
ii python3-daemon 2.2.4-1.1
ii python3-pkg-resources 52.0.0-4
ii python3-requests 2.25.1+dfsg-2
ii python3-tornado 6.1.0-1+b1
ii ssl-cert 1.1.0+nmu1
nrpe-ng recommends no packages.
nrpe-ng suggests no packages.
-- Configuration Files:
/etc/nagios/nrpe-ng.cfg changed [not included]
-- no debconf information
