Retry with disable QNAME minimization when NOTIMPL or FORMERR is encountered in response

Resolving se01.se.prima-vod-prep-sec.service.cdn.cra.cz. is broken as service.cdn.cra.cz. returns NOTIMPL on QNAME minimization queries. This change drops QNAME minimization on first NOTIMPL/FORMERR in addition to dropping EDNS0 on (now second) NOTIMPL/FORMERR response.

fixes #132 (closed)

Currently, if we get NOTIMPL or FORMERR (for a legitimate query), we retry without fancy stuff such as EDNS – I suppose we can simply add minimization the this fancy list.

We could also somehow reflect this in that NS's reputation, to make us less likely to choose it next time, though often all of the authoritatives are broken (including this particular case).

That also sounds as a good plan.

The best course of action would be to:

• drop qname-min first
• drop EDNS if it still fails

And record both into reputation cache.

But as a quick fix any of the approaches is ok.

added 1 commit

• 82ad865c - When NOTIMPL or FORMERR is encountered, disable QNAME minimization

Compare with previous version

@vcunat There are two approaches:

1. drop QNAME minimization & EDNS0 in one step
2. drop QNAME minimization first and EDNS0 in second step (this adds one more roundtrip)

I chose the second approach as dropping EDNS0 also means dropping > 512 packets, so this is the safer path.

changed title from Treat NOTIMPL as SERVFAIL for sake of QNAME minimization brokeness in the wild to Retry with disable QNAME minimization when NOTIMPL or FORMERR is encountered in response

mentioned in commit 58f39afd

merged

(At first I thought this is is just an issue, i.e. without any code.)

mentioned in commit 75eca71f

mentioned in merge request !168 (merged)

mentioned in commit cae7846b

mentioned in issue #132 (closed)