[Bug 1785108] Re: net-interface-handler operates on all adds and removes

[Francis Ginther]

I have tested the xenial package against the two partner reported issues
related to this and both now pass (while at the same time verifying that
an unpatched instance still reproduces the problem). In both tests, the
resolve.conf file was not modified for the patched instances.

** Tags removed: id-5b76d0fbc67b5470c265f714 verification-needed-xenial
** Tags added: verification-done-xenial

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Title:
  net-interface-handler operates on all adds and removes

Status in open-iscsi package in Ubuntu:
  Fix Released
Status in open-iscsi source package in Xenial:
  Fix Committed
Status in open-iscsi source package in Bionic:
  Fix Committed
Status in open-iscsi source package in Cosmic:
  Fix Released

Bug description:
  === Begin SRU Template ===
  [Impact]
  Incorrect handling of udev events by open-iscsi's net-interface-handler
  results in nameserver and dns search entries being removed from
  /etc/resolv.conf and thus potentially breaking dns on a system.

  This problem is limited to iscsi-root systems, but is easily tripped
  by common use of linux networking.  This was first discovered on
  Oracle Public Cloud, which utilizes iscsi-root for its systems.

  [Test Case]
  dep8 tests have been backported from cosmic with a functional reproducer.
  When run without the tests will fail.  So passing of dep8 actually indicates
  that the fix is working.

  As a manual test case:
  1. Start a system with iscsi root.  One such easily obtained environment is Oracle Public Cloud.
  2. Collect resolvconf and ifupdown state
     name="before"
     mkdir $name
     cp -r /run/resolvconf $name/run-resolvconf
     cp /etc/resolv.conf $name/etc-resolv.conf
     cp -r /run/network $name/run-network
  3. Create a tun/tap device
     sudo ip tuntap add mode tap user root mytap0
  4. Remove the tun/tap device.
     sudo ip tuntap del mode tap mytap0
  5. Collect resolvconf and ifupdown state and compare against '2'.  The creation and removal of a tuntap device should not have affected resolvconf or ifupdown state.  The 'diff' at the end should not show any differences.
     name="after"
     mkdir $name
     cp -r /run/resolvconf $name/run-resolvconf
     cp /etc/resolv.conf $name/etc-resolv.conf
     cp -r /run/network $name/run-network

     diff -Naur before/ after/

  [Regression Potential]
  The codepath executed was and is entirely limited to systems with iscsi-root.
  So regressions should also be limited as such.  The most likely regression
  would seem to be the failure to add or remove entries to resolvconf for the
  iscsi-root interface.  Before this was happening to often.  A bad fix could
  result in it happening not enough.

  [Other Info]
  net-interface-handler is currently executing 'resolvconf -a' on all
  new network interfaces and 'resolvconf -d' on removal of all network
  interfaces.

  The problem with that is that an add and remove of any new interface
  will have the result of effectively marking the iscsi-root interface down.
  That includes removing the resolvconf entries for that interface.

  This add/remove can happen for any number of reasons.  Two such examples:
   a.) docker container create/delete
       - sudo apt-get install -qy docker.io
       - sudo docker run --rm busybox date
   b.) add/remove of a tuntap device.
       - sudo ip tuntap add mode tap user root mytap0
       - sudo ip tuntap del mode tap mytap0
  === End SRU Template ===

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: open-iscsi 2.0.873+git0.3b4b4500-14ubuntu3.4 [modified: lib/open-iscsi/net-interface-handler]
  ProcVersionSignature: User Name 4.4.0-130.156-generic 4.4.134
  Uname: Linux 4.4.0-130-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.18
  Architecture: amd64
  Date: Thu Aug  2 17:18:06 2018
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: open-iscsi
  UpgradeStatus: No upgrade log present (probably fresh install)
  modified.conffile..etc.iscsi.iscsid.conf: [inaccessible: [Errno 13] Permission denied: '/etc/iscsi/iscsid.conf']

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