[net-dns-users] Problems with strange NXDOMAIN errors coming from Net::DNS code

[Alex Monk]

Hi,

At Wikimedia, ferm is used as a firewall. It allows you to specify a
host by writing something like:
@resolve((deployment-prometheus01.deployment-prep.eqiad.wmflabs), AAAA)
The problem is, this hostname has no AAAA record, just A (the hostname
is filled in automatically by a template that assumes everything will
have one). But that should be fine, except Net::DNS gives us a
NXDOMAIN error (where the DNS server does not), causing errors that
prevent ferm from starting:

root at deployment-deploy01:/etc/ferm/conf.d# perl -e "require Net::DNS; my
\$resolver = new Net::DNS::Resolver;
\$resolver->search('deployment-prometheus01.deployment-prep.eqiad.wmflabs',
'AAAA'); print \$resolver->errorstring"
NXDOMAIN

Please see https://phabricator.wikimedia.org/T153468 for more information

Many thanks
Alex
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