[Bug 2036358] Re: systemd wait-online now times out after jammy and lunar upgrade

[Nick Rosbrook]

** Description changed:

+ [Impact]
+ 
+ When all interfaces "not required for online", e.g. when they are marked
+ "optional: true" in netplan, systemd-networkd-wait-online will timeout.
+ Or, in other words, systemd-networkd-wait-online will timeout even
+ though all interfaces are ignored, hence none of them will ever be
+ marked as "ready." Depending on what units depend on network-
+ online.target, this can delay boot by 120 seconds (the default timeout
+ for systemd-networkd-wait-online).
+ 
+ [Test Plan]
+ 
+ 1. Create a new LXD container. These instructions assume jammy is the
+ release, but the same can be done for lunar.
+ 
+ $ lxc launch ubuntu-daily:jammy jammy
+ $ lxc exec jammy bash
+ 
+ 2. Once in the container, modify the default /etc/netplan/10-lxc.yaml so
+ that eth0 is configured with "optional: true":
+ 
+ $ vi /etc/netplan/10-lxc.yaml # Use whatever editor you like
+ $ cat /etc/netplan/10-lxc.yaml
+ network:
+   version: 2
+   ethernets:
+     eth0:
+       dhcp4: true
+       dhcp-identifier: mac
+       optional: true
+ 
+ 3. Re-generate and apply the netplan configuration.
+ 
+ $ netplan generate
+ $ netplan apply
+ 
+ 4. Manually run systemd-networkd-wait-online, and observe that all links
+ are ignored, and the command times out:
+ 
+ $ SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd-wait-online --timeout=10
+ Found link lo(1)
+ Found link eth0(19)
+ lo: link is ignored
+ eth0: link is ignored
+ Timeout occurred while waiting for network connectivity.
+ 
+ [Where problems could occur]
+ 
+ This patch partially re-instates a patch remove in bug 1982218. However,
+ instead of exiting if all links are unmanaged, we exit if all links are
+ ignored in manager_configured(). If the patch was wrong, we may re-
+ introduce bug 1982218, so as part of this SRU verification, that bug
+ should be tested too. Any other regressions would also be related to
+ systemd-networkd-wait-online behavior.
+ 
+ [Original Description]
+ 
  On Ubuntu 22.04 desktop system using network-manager and upgrading to
  systemd 249.11-0ubuntu3.10, wait-online now times out which prevents
  logins (GDM, ssh, console) until it does time out. This seems to be
  introduced by the change for
  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1982218.
  
  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1982218/comments/21
  also mentioned the problem on Lunar.

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https://bugs.launchpad.net/bugs/2036358

Title:
  systemd wait-online now times out after jammy and lunar upgrade

Status in systemd package in Ubuntu:
  Triaged
Status in systemd source package in Jammy:
  Triaged
Status in systemd source package in Lunar:
  Triaged

Bug description:
  [Impact]

  When all interfaces "not required for online", e.g. when they are
  marked "optional: true" in netplan, systemd-networkd-wait-online will
  timeout. Or, in other words, systemd-networkd-wait-online will timeout
  even though all interfaces are ignored, hence none of them will ever
  be marked as "ready." Depending on what units depend on network-
  online.target, this can delay boot by 120 seconds (the default timeout
  for systemd-networkd-wait-online).

  [Test Plan]

  1. Create a new LXD container. These instructions assume jammy is the
  release, but the same can be done for lunar.

  $ lxc launch ubuntu-daily:jammy jammy
  $ lxc exec jammy bash

  2. Once in the container, modify the default /etc/netplan/10-lxc.yaml
  so that eth0 is configured with "optional: true":

  $ vi /etc/netplan/10-lxc.yaml # Use whatever editor you like
  $ cat /etc/netplan/10-lxc.yaml
  network:
    version: 2
    ethernets:
      eth0:
        dhcp4: true
        dhcp-identifier: mac
        optional: true

  3. Re-generate and apply the netplan configuration.

  $ netplan generate
  $ netplan apply

  4. Manually run systemd-networkd-wait-online, and observe that all
  links are ignored, and the command times out:

  $ SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-networkd-wait-online --timeout=10
  Found link lo(1)
  Found link eth0(19)
  lo: link is ignored
  eth0: link is ignored
  Timeout occurred while waiting for network connectivity.

  [Where problems could occur]

  This patch partially re-instates a patch remove in bug 1982218.
  However, instead of exiting if all links are unmanaged, we exit if all
  links are ignored in manager_configured(). If the patch was wrong, we
  may re-introduce bug 1982218, so as part of this SRU verification,
  that bug should be tested too. Any other regressions would also be
  related to systemd-networkd-wait-online behavior.

  [Original Description]

  On Ubuntu 22.04 desktop system using network-manager and upgrading to
  systemd 249.11-0ubuntu3.10, wait-online now times out which prevents
  logins (GDM, ssh, console) until it does time out. This seems to be
  introduced by the change for
  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1982218.

  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1982218/comments/21
  also mentioned the problem on Lunar.

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