[Bug 1950794] Re: DHCPv4 (IAID+DUID) networking broken in LXC containers

[Lukas Märdian]

Yes.. LXD's system containers and systemd/udev have a special kind of
relationship and we should strive to resolve that situation properly
long-term. I already talked to stgraber about that, but I guess we
should lay out a proper path forward as continuously patching more and
more components of systemd is not a sustainable approach.

I'll leave that new revert-patch in for now, tho, as we do not have
another short-term solution.

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https://bugs.launchpad.net/bugs/1950794

Title:
  DHCPv4 (IAID+DUID) networking broken in LXC containers

Status in lxd package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  Fix Committed

Bug description:
  DHCPv4 networking does not work in the default IAID+DUID
  (ClientIdentifier=duid) mode in LXC containers, using systemd-networkd
  v249.5-2ubuntu1. Static configuration and DHCPv6 work without problem.

  Reproducer:
  $ lxc launch ubuntu-daily:jammy jj
  $ lxc exec jj bash
  # add-apt-repository ppa:ci-train-ppa-service/4704
  # apt install systemd # install systemd 249.5-2ubuntu1
  # cat /etc/systemd/network/00-test.network
  [Match]
  Name=eth0

  [Network]
  DHCP=ipv4
  # systemctl restart systemd-networkd.service
  # networkctl 
  IDX LINK     TYPE     OPERATIONAL SETUP    
  [...]
  611 eth0     ether    carrier     failed  

  A workaround is to avoid IAID+DUID mode via:
  [DHCPv4]
  #ClientIdentifier=mac
  ClientIdentifier=duid-only

  Interesting logs:
  Nov 12 14:10:48 jj systemd-networkd[174]: eth0: Requested to activate link
  Nov 12 14:10:48 jj systemd-networkd[174]: eth0: DHCPv4 client: Failed to set IAID: Device or resource busy
  Nov 12 14:10:48 jj systemd-networkd[174]: eth0: DHCP4 CLIENT: Failed to set IAID+DUID: Device or resource busy
  Nov 12 14:10:48 jj systemd-networkd[174]: Failed to check link is initialized: Device or resource busy
  Nov 12 14:10:48 jj systemd-networkd[174]: eth0: Failed

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