Systemd version 259 slows down DNS check during cloud-init local

[drzee99]

Bug report

cloud-init local (pre-networking) takes significant longer to complete after updating to Systemd version 259.

For <259 the cloud-init local DNS test, where lookups are made to 3 "fake" DNS names (does-not-exist.example.com, example.invalid and __cloud_init_expected_not_found__) took about <30s to complete. After upgrading to version 259 the lookup takes up to 2+ min and stalls the boot process. Eventually the boot continues after timeouts reached.

This seems to be related to a recent change in version 259: (from systemd whats new):

  systemd-resolved now allows local, privileged services to hook into
  local name resolution requests. For that a new directory
  /run/systemd/resolve.hook/ has been introduced. Any privileged local
  service can bind an AF_UNIX Varlink socket there, and implement the
  simple io.systemd.Resolve.Hook Varlink API on it. If so it will
  receive a method call on it for each name resolution request, which
  it can then reply to. It can reply positively, deny the request or
  let the regular request handling take place.

Steps to reproduce the problem

upgrade system to systemd version 259

Environment details

• Cloud-init version: 25.3
• Operating System Distribution: Arch Linux
• Cloud provider, platform or installer type: AWS/EC2

cloud-init logs

Journal logs of the relevant sections attached

• pre_259_journal.log before systemd update
• post_259_journal.log after systemd update

post_259_journal.log
pre_259_journal.log