DDNS provider is not responding to error conditions correctly

[alexhorner]

Whilst investigating an issue with acme.sh which I have configured to use lexicon as the provider, I have found that lexicon is not correctly handling errors from DDNS updates.

According to RFC2136, an RCode of 9 means NOTAUTH - The server is not authoritative for the zone named in the Zone Section.

Attempting to update a zone which does not exist on the target server returns this NOTAUTH RCode and results in no change being made on the server, however lexicon still reports:

RESULT
------
True

I do not know if lexicon is failing to handle other RCodes in the RFC, I have not tested this.

This can be tested with the following setup:

• DNS server has a zone for domain.com
• The following command is used to try and update the zone _acme-challenge.domain.com with the name _acme-challenge.domain.com and the value abcdefg which will fail silently with RCode 9:

  lexicon ddns create _acme-challenge.domain.com TXT --ddns-server 1.2.3.4 --auth-token my_token --name _acme-challenge.domain.com --content abcdefg

• The following command is used to try and update the zone domain.com with the name _acme-challenge.domain.com and the value abcdefg which will succeed:

  lexicon ddns create domain.com TXT --ddns-server 1.2.3.4 --auth-token my_token --name _acme-challenge.domain.com --content abcdefg