[Bug 2077779] Re: PTP device symlink missing after running udevadm trigger command

[Chengen Du]

Both -proposed versions in Jammy and Noble have been tested and
confirmed to work without any issues.

[Jammy]
root at jammy-ptp:~# apt policy udev
udev:
  Installed: 249.11-0ubuntu3.13
  Candidate: 249.11-0ubuntu3.13
  Version table:
 *** 249.11-0ubuntu3.13 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     249.11-0ubuntu3.12 500
        500 http://tw.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
     249.11-0ubuntu3.7 500
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
     249.11-0ubuntu3 500
        500 http://tw.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
root at jammy-ptp:~# ll /dev/ptp*
crw------- 1 root root 246, 0 Nov 18 03:50 /dev/ptp0
lrwxrwxrwx 1 root root      4 Nov 18 03:50 /dev/ptp_kvm -> ptp0
root at jammy-ptp:~# udevadm trigger
root at jammy-ptp:~# ll /dev/ptp*
crw------- 1 root root 246, 0 Nov 18 03:51 /dev/ptp0
lrwxrwxrwx 1 root root      4 Nov 18 03:51 /dev/ptp_kvm -> ptp0

[Noble]
root at noble-ptp:~# apt policy udev
udev:
  Installed: 255.4-1ubuntu8.5
  Candidate: 255.4-1ubuntu8.5
  Version table:
 *** 255.4-1ubuntu8.5 100
        100 http://tw.archive.ubuntu.com/ubuntu noble-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     255.4-1ubuntu8.4 500
        500 http://tw.archive.ubuntu.com/ubuntu noble-updates/main amd64 Packages
     255.4-1ubuntu8 500
        500 http://tw.archive.ubuntu.com/ubuntu noble/main amd64 Packages
root at noble-ptp:~# ll /dev/ptp*
crw------- 1 root root 246, 0 Nov 18 05:09 /dev/ptp0
lrwxrwxrwx 1 root root      4 Nov 18 05:09 /dev/ptp_kvm -> ptp0
root at noble-ptp:~# udevadm trigger
root at noble-ptp:~# ll /dev/ptp*
crw------- 1 root root 246, 0 Nov 18 05:09 /dev/ptp0
lrwxrwxrwx 1 root root      4 Nov 18 05:09 /dev/ptp_kvm -> ptp0

** Tags removed: verification-needed verification-needed-jammy verification-needed-noble
** Tags added: verification-done verification-done-jammy verification-done-noble

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https://bugs.launchpad.net/bugs/2077779

Title:
  PTP device symlink missing after running udevadm trigger command

Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Focal:
  Triaged
Status in systemd source package in Jammy:
  Fix Committed
Status in systemd source package in Noble:
  Fix Committed
Status in systemd source package in Oracular:
  Fix Released

Bug description:
  [Impact]
  PTP device symlink creation rules are executed only when the udev action is 'add'.
  If the rules are reloaded and the udevadm trigger command is run to reapply changes, the symlink may be deleted.
  This can prevent the chronyd service from restarting properly.

  [Fix]
  Upstream has a patch to fix this issue.

  commit 6bd12be3fa7761f190e17efdbdbff4440da7528b
  Author:     Chengen Du <chengen.du at canonical.com>
  CommitDate: Thu Aug 15 15:38:46 2024 +0900

      udev: Handle PTP device symlink properly on udev action 'change'

      PTP device symlink creation rules are currently executed only when the
      udev action is 'add'. If a user reloads the rules and runs the udevadm
      trigger command to reapply changes, the symlink may be deleted, which
      can prevent the chronyd service from restarting properly.

      Signed-off-by: Chengen Du <chengen.du at canonical.com>

  [Test Plan]
  1. Create a VM with a PTP device.
  2. Verify that the PTP device symlink is present:
  > ll /dev/ptp*
  crw------- 1 root root 246, 0 Oct 14 02:26 /dev/ptp0
  lrwxrwxrwx 1 root root      4 Oct 14 02:26 /dev/ptp_hyperv -> ptp0
  2. Run the `udevadm trigger` command.
  3. Verify again that the PTP device symlink is still present.

  [Where problems could occur]
  The patch allows PTP device symlink creation rules to be executed when the udev action is 'change'.
  This update primarily affects services that rely on the PTP device symlink, such as chronyd.

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