[Bug 1644330] [NEW] systemd-resolved assumes that /etc/hosts for one address family means it doesn't ask DNS for another

[Steve Langasek]

Public bug reported:

I have an ipv4 entry for a key host on my network listed in /etc/hosts,
for network recovery purposes.  This host also has ipv6 connectivity;
the ipv6 address is resolvable via DNS, but I do not have it in
/etc/hosts.  Resolution of hostname should be independent for each
address family.

Two days ago (I don't know what changed to trigger this), I stopped
being able to resolve the ipv6 address for this host.  I traced this
down to systemd-resolved, returning a lookup failure for the nss
request, because the ipv6 address is not listed in /etc/hosts.

Removing resolve from /etc/nsswitch.conf restores the correct behavior.

Removing the ipv4 entry for the host restores the correct behavior.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: systemd 231-9ubuntu1
ProcVersionSignature: Ubuntu 4.8.0-27.29-generic 4.8.1
Uname: Linux 4.8.0-27-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Nov 23 08:13:33 2016
InstallationDate: Installed on 2010-09-24 (2252 days ago)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
MachineType: LENOVO 2306CTO
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.8.0-27-generic.efi.signed root=/dev/mapper/hostname-root ro quiet splash vt.handoff=7
SourcePackage: systemd
UpgradeStatus: Upgraded to yakkety on 2016-10-28 (25 days ago)
dmi.bios.date: 10/25/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: G2ET97WW (2.57 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2306CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG2ET97WW(2.57):bd10/25/2013:svnLENOVO:pn2306CTO:pvrThinkPadX230:rvnLENOVO:rn2306CTO:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2306CTO
dmi.product.version: ThinkPad X230
dmi.sys.vendor: LENOVO

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug yakkety

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https://bugs.launchpad.net/bugs/1644330

Title:
  systemd-resolved assumes that /etc/hosts for one address family means
  it doesn't ask DNS for another

Status in systemd package in Ubuntu:
  New

Bug description:
  I have an ipv4 entry for a key host on my network listed in
  /etc/hosts, for network recovery purposes.  This host also has ipv6
  connectivity; the ipv6 address is resolvable via DNS, but I do not
  have it in /etc/hosts.  Resolution of hostname should be independent
  for each address family.

  Two days ago (I don't know what changed to trigger this), I stopped
  being able to resolve the ipv6 address for this host.  I traced this
  down to systemd-resolved, returning a lookup failure for the nss
  request, because the ipv6 address is not listed in /etc/hosts.

  Removing resolve from /etc/nsswitch.conf restores the correct
  behavior.

  Removing the ipv4 entry for the host restores the correct behavior.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: systemd 231-9ubuntu1
  ProcVersionSignature: Ubuntu 4.8.0-27.29-generic 4.8.1
  Uname: Linux 4.8.0-27-generic x86_64
  ApportVersion: 2.20.3-0ubuntu8
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Wed Nov 23 08:13:33 2016
  InstallationDate: Installed on 2010-09-24 (2252 days ago)
  InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
  MachineType: LENOVO 2306CTO
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.8.0-27-generic.efi.signed root=/dev/mapper/hostname-root ro quiet splash vt.handoff=7
  SourcePackage: systemd
  UpgradeStatus: Upgraded to yakkety on 2016-10-28 (25 days ago)
  dmi.bios.date: 10/25/2013
  dmi.bios.vendor: LENOVO
  dmi.bios.version: G2ET97WW (2.57 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 2306CTO
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Defined
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvrG2ET97WW(2.57):bd10/25/2013:svnLENOVO:pn2306CTO:pvrThinkPadX230:rvnLENOVO:rn2306CTO:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 2306CTO
  dmi.product.version: ThinkPad X230
  dmi.sys.vendor: LENOVO

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