Public bug reported:

The pdns-recursor in Xenial returns this:

    $ dig A @ +edns +dnssec
    ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 57895

While it should return this:

    ... 10     IN A 10     IN A

Because the relevant NS returns FORMERR (it doesn't support EDNS):

    $ dig A \ +edns +dnssec
    ;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 1004
    ;; WARNING: EDNS query returned status FORMERR - retry with '+nodnssec 

This has been fixed in later versions of pdns, specifically here:

After applying that patch onto 4.0.0~alpha2-2, pdns-recursor behaves as
expected and returns the correct A records.

This bug manifested itself in our case through Postfix not being able to
send mail to Office 365 domains. When postfix tried to enable optional
DNSSEC validation -- which it did because of a builtin default -- the A
record lookups would start to fail, and this failure would be cached for
non-EDNS lookups as well.

See original discussion here:
"EDNS / DANE trouble with Microsoft"

Attached, the patch that appears to fix the problem.

IMHO, Xenial (being an LTS) needs to get this fixed. Either by updating
from 4.0.0 to something more recent, or by applying this patch.

Walter Doekes

** Affects: pdns-recursor (Ubuntu)
     Importance: Undecided
         Status: New

** Tags: patch

** Patch added: "9d534f2a12defc44d2a79291bf34b82e5ee28121.patch"

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  pdns-recursor 4.0.0~alpha2-2 fails on FORMERR response to EDNS query

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