[dnsdist] documentation for "showDOHFrontends()" output

[Remi Gacogne]

Hello!

On 6/9/19 9:54 PM, Christoph wrote:
>> most of the columns in the output of "showDOHFrontends()" are
>> self-explanatory, but it would be interesting to know the details behind
>>  "Bad" and "Errors".
>>
>> Are these columns documented somewhere?
>>
>> https://dnsdist.org/reference/config.html#showDOHFrontends
> 
> The "Errors" counter appears to match the amount of HTTP requests
> getting answered with:
> 
> 500 Internal Server Error
> 
> The "Bad" column is still unknown to me but it is not
> related to HTTP 400 or 408 response codes.

The "Bad" counter refers to queries that we could not interpret as a DoH
query, meaning that it was not a POST query and either there was no
'dns' parameter in the query or we couldn't not base64 decode the
content of the 'dns' parameter. We should return a 400 for these,
though, are you sure we don't?

The "Errors" counters refers to invalid or rejected DNS queries:
- smaller than a minimal DNS header or the QR bit is set, or QDCOUNT is
equal to zero (noncompliant-queries in the regular stats should increase
accordingly);
- blocked by the ACL (acl-drops should increase) ;
- query is dropped by a rule (the counter of the corresponding rule
should increase) ;
- we encountered an error when sending the query to the selected backend
(downstream-send-errors should increase, as well the 'sendErrors'
counter of the corresponding backend).

For that last one it looks like we don't display the value of the
'sendErrors' counters in the console, we do export it via carbon and the
API though.


Best regards,
-- 
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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