[Bug 1728181] [NEW] systemd-networkd-wait-online waits when devices are unmanaged

[Mathieu Trudel-Lapierre]

Public bug reported:

I started a system with cloud-init disabled, etc. and a single real
network interface (ens3) that could be configured.

That VM has no configuration whatsoever for systemd-networkd, as that
would have to have been written by netplan, and cloud-init did not
generate netplan config (because it was disabled).

So:

root at ubuntu:/etc/systemd/system/network-online.target.wants# ip route
d-networkd-wait-online --ignore=lo
ignoring: lo
Event loop failed: Connection timed out
root at ubuntu:/etc/systemd/system/network-online.target.wants# ip route
root at ubuntu:/etc/systemd/system/network-online.target.wants# networkctl
IDX LINK             TYPE               OPERATIONAL SETUP     
  1 lo               loopback           carrier     unmanaged 
  2 ens3             ether              off         unmanaged 
  3 sit0             sit                off         unmanaged 

3 links listed.
root at ubuntu:/etc/systemd/system/network-online.target.wants# 


The system took 120 seconds to complete boot, because wait-online had to finish; and running wait-online from the system afterwards also waits 120 seconds (its default timeout). If there is no configuration for an interface, it's unmanaged (as shown by networkctl), so wait-online should not wait, and simply report that all interfaces are unmanaged, possibly returning an error so we don't reach network-online.

FWIW, having wait-online look up configuration might later be useful
also to figure out if an interface was configured, but marked as
optional (such that it is explicitly not required to be up at boot), or
if we want to configure network devices but specify that networkd should
*not* bring them online (like "administratively disabled" interfaces in
Cisco world using the "shutdown" command).

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

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https://bugs.launchpad.net/bugs/1728181

Title:
  systemd-networkd-wait-online waits when devices are unmanaged

Status in systemd package in Ubuntu:
  New

Bug description:
  I started a system with cloud-init disabled, etc. and a single real
  network interface (ens3) that could be configured.

  That VM has no configuration whatsoever for systemd-networkd, as that
  would have to have been written by netplan, and cloud-init did not
  generate netplan config (because it was disabled).

  So:

  root at ubuntu:/etc/systemd/system/network-online.target.wants# ip route
  d-networkd-wait-online --ignore=lo
  ignoring: lo
  Event loop failed: Connection timed out
  root at ubuntu:/etc/systemd/system/network-online.target.wants# ip route
  root at ubuntu:/etc/systemd/system/network-online.target.wants# networkctl
  IDX LINK             TYPE               OPERATIONAL SETUP     
    1 lo               loopback           carrier     unmanaged 
    2 ens3             ether              off         unmanaged 
    3 sit0             sit                off         unmanaged 

  3 links listed.
  root at ubuntu:/etc/systemd/system/network-online.target.wants# 

  
  The system took 120 seconds to complete boot, because wait-online had to finish; and running wait-online from the system afterwards also waits 120 seconds (its default timeout). If there is no configuration for an interface, it's unmanaged (as shown by networkctl), so wait-online should not wait, and simply report that all interfaces are unmanaged, possibly returning an error so we don't reach network-online.

  FWIW, having wait-online look up configuration might later be useful
  also to figure out if an interface was configured, but marked as
  optional (such that it is explicitly not required to be up at boot),
  or if we want to configure network devices but specify that networkd
  should *not* bring them online (like "administratively disabled"
  interfaces in Cisco world using the "shutdown" command).

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