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[Bug Watch Updater <1629972@xxxxxxxxxxxxxxxxxx>]

** Changed in: ifupdown (Debian)
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/1629972

Title:
  networking stop incorrectly disconnects from (network) root filesystem

Status in MAAS:
  Confirmed
Status in ifupdown package in Ubuntu:
  Fix Released
Status in ifupdown source package in Xenial:
  Fix Released
Status in ifupdown source package in Yakkety:
  Fix Released
Status in ifupdown package in Debian:
  Fix Released

Bug description:
  === Begin SRU Template ===
  [Impact]
  The systemd networking.service unit will bring down the loopback device (lo)
  when it is stopped.  This behavior differs from the behavior in other
  Ubuntu releases (upstart's networking.conf), where 'lo' is not taken down.

  The problem that was seen was that iscsi root over ipv6 would hang on
  shutdown.  

  [Test Case]
  Test is fairly simple and can be demonstrated in lxc container.
  The key is really that the lo device should not have its link set down
  after stopping networking.service.  So, below:
    out=$(ip address show dev lo up); [ -n "$out" ] && echo "$out" || echo empty

  should not show 'empty', but should have LOOPBACK,UP,LOWER in its
  output.

  $ release=yakkety; name=y1
  $ lxc launch ubuntu-daily:$release $name
  $ sleep 10
  $ lxc exec $name /bin/bash

  ## show only things that are up (note output has LOOPBACK,UP,LOWER_UP)
  % ip link show dev lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

  % ip address show dev lo up
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
         valid_lft forever preferred_lft forever
      inet6 ::1/128 scope host
         valid_lft forever preferred_lft forever

  ## Stop the service and show lo link is down (no 'UP' or 'LOWER_UP').
  % systemctl stop networking.service
  % ip link show dev lo
  1: lo: <LOOPBACK> mtu 65536 qdisc noqueue state DOWN mode DEFAULT group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  % out=$(ip address show dev lo up); [ -n "$out" ] && echo "$out" || echo empty
  empty

  ## Now enable proposed, install update, reboot and show.
  % rel=$(lsb_release -sc)
  % echo "deb http://archive.ubuntu.com/ubuntu $rel-proposed main" |
      sudo tee /etc/apt/sources.list.d/proposed.list
  % sudo apt update -qy && sudo apt install -qy ifupdown </dev/null
  % dpkg-query --show ifupdown
  ifupdown 0.8.13ubuntu3
  % sudo reboot

  ## in rebooted system
  % ip link show dev lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  % ip address show dev lo up
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
         valid_lft forever preferred_lft forever
      inet6 ::1/128 scope host
         valid_lft forever preferred_lft forever
  % systemctl stop networking.service
  % ip link show dev lo
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
  % out=$(ip address show dev lo up); [ -n "$out" ] && echo "$out" || echo empty
  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
      inet 127.0.0.1/8 scope host lo
         valid_lft forever preferred_lft forever
      inet6 ::1/128 scope host
         valid_lft forever preferred_lft forever

  
  [Regression Potential]
  Should be pretty low.  zesty and  yakkety-proposed have this.
  Taking down 'lo' is often cause of problems, and never the solution to
  problems as far as I'm aware.

  [Other Info]

  === End SRU Template ===

  With the switch to systemd, all support for iscsi root (and other)
  filesystems disappeared, since shutdown yanks the rug out from under
  us.

  Rather than just relying on /etc/iscsi/iscsi.initramfs (which d-i
  creates..), the DEV check should be expanded to include iscsi devices,
  and networking.service ExecStop should honor those checks.

  Related bugs:
    * bug 1229458: grub2 needed changes
    * bug 1621615: network not configured when ipv6 netbooted into cloud-init
    * bug 1621507: ipv6 network boot does not work

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