[Bug 1646538] Re: pdns-recursor 4.0.0~alpha2-2 fails on FORMERR response to EDNS query

[Sebastien Bacher]

the update is in the SRU review queue so unsubscribing the sponsors from
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Title:
  pdns-recursor 4.0.0~alpha2-2 fails on FORMERR response to EDNS query

Status in pdns-recursor package in Ubuntu:
  Fix Released
Status in pdns-recursor source package in Xenial:
  In Progress

Bug description:
  [Impact]

  pdns-recursor in Xenial fails on FORMERR response to EDNS query.

  This can manifest itself through postfix not being able to send mail
  to Office 365 domains. When postfix tries to enable DNSSEC validation,
  the A record lookups start to fail, and this failure is cached for
  non-EDNS lookups as well.

  pdns-recursor in Xenial returns this:

      $ dig A umcg-nl.mail.protection.outlook.com. @127.0.0.1 +edns +dnssec
      ...
      ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 57895

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

      $ dig A umcg-nl.mail.protection.outlook.com. \
          @ns1-proddns.glbdns.o365filtering.com. +edns +dnssec
      ...
      ;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 1004
      ...
      ;; WARNING: EDNS query returned status FORMERR - retry with '+nodnssec +noedns'

  This has been fixed upstream, specifically here:

  https://github.com/PowerDNS/pdns/commit/9d534f2a12defc44d2a79291bf34b82e5ee28121

  [Test Case]

  Run dig with an NS that doesn't support EDNS: $ dig A [name]
  @127.0.0.1 +edns +dnssec

  For example: $ dig A umcg-nl.mail.protection.outlook.com. @127.0.0.1
  +edns +dnssec

  The correct A records should be returned similar to this:

      ...
      umcg-nl.mail.protection.outlook.com. 10 IN A 213.199.154.87
      umcg-nl.mail.protection.outlook.com. 10 IN A 213.199.154.23

  [Regression Potential]

  This is an upstream fix that has been out for a while.

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