[Bug 1785383] Re: missing EDNS0 record confuses systemd-resolved

[Robie Basak]

Hello Steve, or anyone else affected,

Accepted dnsmasq into bionic-proposed. The package will build now and be
available at
https://launchpad.net/ubuntu/+source/dnsmasq/2.79-1ubuntu0.5 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
bionic to verification-done-bionic. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-bionic. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: dnsmasq (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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https://bugs.launchpad.net/bugs/1785383

Title:
  missing EDNS0 record confuses systemd-resolved

Status in systemd:
  Fix Released
Status in dnsmasq package in Ubuntu:
  Fix Released
Status in systemd package in Ubuntu:
  Fix Released
Status in dnsmasq source package in Bionic:
  Fix Committed
Status in systemd source package in Bionic:
  Fix Released
Status in dnsmasq source package in Focal:
  Fix Released
Status in systemd source package in Focal:
  Fix Released
Status in dnsmasq source package in Groovy:
  Fix Released
Status in systemd source package in Groovy:
  Fix Released
Status in dnsmasq source package in Hirsute:
  Fix Released
Status in systemd source package in Hirsute:
  Fix Released
Status in dnsmasq source package in Impish:
  Fix Released
Status in systemd source package in Impish:
  Fix Released

Bug description:
  [Impact]

  dnsmasq 2.79 and below omits EDNS0 OPT records [1] when returning an
  empty answer for a domain it is authoritative for. systemd-resolved
  seems to get confused by this in certain circumstances; when using the
  stub resolver and requesting an address for which there are no AAAA
  records, there can sometimes be a five second hang in resolution.

  [1] https://en.wikipedia.org/wiki/Extension_Mechanisms_for_DNS

  [Test Plan]

  Test case for bionic:

  -----------------------------------------
  IFACE=dummy0
  SUBNET=10.0.0

  ip link add $IFACE type dummy
  ifconfig $IFACE ${SUBNET}.1/24
  dnsmasq -h -R -d -C /dev/null -2 $IFACE -z -i $IFACE -I lo --host-record=test.test,${SUBNET}.1 --server=/test/ &

  dig -t a test.test @10.0.0.1 | grep EDNS
  # returns "; EDNS ..."
  dig -t aaaa test.test @10.0.0.1 | grep EDNS
  # again, should return "; EDNS ..." but doesn't.
  # does so with the -proposed package.
  -----------------------------------------

  [Where problems could occur]

  Problems may occur in case a client queries dnsmasq and relies on
  EDNS0 not being available for behaving correctly. This covers cases
  where the software querying dnsmasq is buggy or misconfigured.

  [Development Fix]

  Fixed upstream in dnsmasq >= 2.80.

  [Stable Fix]

  Partial cherry-pick of upstream commit
  http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=1682d15a744880b0398af75eadf68fe66128af78

  The cherry-pick is partial because half if it is already in the
  package .diff we have in Bionic.

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