[Bug 1732342] [NEW] DNS info removed when any interface removed, not just iSCSI interface

[Daniel Axtens]

Public bug reported:

If a system only has DNS server info via open-iscsi (putting aside
whether or not that's a good idea), and then starts a Docker container
or LXD container, name resolution breaks.

The open-iscsi udev rules invokes net-interface-handler when a network
device is added or removed. This helper deals with dns resolution. On
boot, this sets up dns resolution based on the information gathered
during early boot.

However:

1) The udev rule and script run the full script for all network
interfaces, whether or not they are the iscsi interface - they do not
bail out early if there is a mismatch. So, the removal of any device
triggers 'net-interface-handler stop', which removes the
/run/resolvconf/interface/ethX.iscsi-target file, breaking resolution.
This occurs even if the interface being removed is *not* ethX.

2) For some reason, both starting a docker container and starting an LXD
container involve adding 2 interfaces and then removing one. The
additions do nothing, as the resolution rule has already been installed.
The removal, however, causes the resolution rule to be removed, breaking
DNS.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: open-iscsi 2.0.873+git0.3b4b4500-14ubuntu3.4
ProcVersionSignature: Ubuntu 4.4.0-98.121-generic 4.4.90
Uname: Linux 4.4.0-98-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
Date: Wed Nov 15 05:19:12 2017
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: open-iscsi
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.iscsi.iscsid.conf: 2017-10-20T20:38:27.028134

** Affects: open-iscsi (Ubuntu)
     Importance: Undecided
         Status: Confirmed


** Tags: apport-bug uec-images

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https://bugs.launchpad.net/bugs/1732342

Title:
  DNS info removed when any interface removed, not just iSCSI interface

Status in open-iscsi package in Ubuntu:
  Confirmed

Bug description:
  If a system only has DNS server info via open-iscsi (putting aside
  whether or not that's a good idea), and then starts a Docker container
  or LXD container, name resolution breaks.

  The open-iscsi udev rules invokes net-interface-handler when a network
  device is added or removed. This helper deals with dns resolution. On
  boot, this sets up dns resolution based on the information gathered
  during early boot.

  However:

  1) The udev rule and script run the full script for all network
  interfaces, whether or not they are the iscsi interface - they do not
  bail out early if there is a mismatch. So, the removal of any device
  triggers 'net-interface-handler stop', which removes the
  /run/resolvconf/interface/ethX.iscsi-target file, breaking resolution.
  This occurs even if the interface being removed is *not* ethX.

  2) For some reason, both starting a docker container and starting an
  LXD container involve adding 2 interfaces and then removing one. The
  additions do nothing, as the resolution rule has already been
  installed. The removal, however, causes the resolution rule to be
  removed, breaking DNS.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: open-iscsi 2.0.873+git0.3b4b4500-14ubuntu3.4
  ProcVersionSignature: Ubuntu 4.4.0-98.121-generic 4.4.90
  Uname: Linux 4.4.0-98-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.10
  Architecture: amd64
  Date: Wed Nov 15 05:19:12 2017
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: open-iscsi
  UpgradeStatus: No upgrade log present (probably fresh install)
  mtime.conffile..etc.iscsi.iscsid.conf: 2017-10-20T20:38:27.028134

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