check_dns reports "OK" when nslookup fails with "connection refused"

[andrew bezella]

the behavior of `nslookup` appears to have changed between 9.16.1-Ubuntu and 9.18.1-1ubuntu1.2-Ubuntu. when a nameserver is down the 9.16.1-Ubuntu version reports:
;; connection timed out; no servers could be reached

while the 9.18.1-1ubuntu1.2-Ubuntu version reports:
;; communications error to 207.241.225.184#53: connection refused

however, the `check_dns` plugin was not updated for this new output. this results in an incorrect "OK" when the service being checked has in fact been stopped:

% nslookup -sil www.archive.org. 207.241.225.184
;; communications error to 207.241.225.184#53: connection refused
% /usr/lib/nagios/plugins/check_dns --server=207.241.225.184 --hostname=www.archive.org.
DNS OK: 0.031 seconds response time. www.archive.org. returns |time=0.030945s;;;0.000000

the attached patch (based on https://github.com/monitoring-plugins/monitoring-plugins/pull/1634) seems to resolve the issue.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: monitoring-plugins-standard 2.3.1-1ubuntu4
ProcVersionSignature: Ubuntu 5.15.0-48.54-generic 5.15.53
Uname: Linux 5.15.0-48-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Tue Oct 11 16:54:27 2022
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/zsh
SourcePackage: monitoring-plugins
UpgradeStatus: Upgraded to jammy on 2022-10-03 (8 days ago)

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "local-check_dns_nslookup_unreachable.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]