Public bug reported: [ Impact ]
This bug affects Unicast PTP setups where the ptp4l service fails to properly recover and resume tracking the master clock following a network interruption or fault. When a master recovers from a FAULTY state back to MASTER, it correctly grants the unicast lease renewal from existing clients but fails to actually send the requested Announce messages. The client, on the other hand, fails to promptly renegotiate its subscriptions if its existing foreign master record becomes unqualified during the outage, waiting instead for the original grant's renewal deadline (which could be up to 45 minutes for a 3600-second grant). This results in a total loss of synchronization after a link flap. This update backports two complementary fixes: The upstream server fix clears the stale unicast state on the master during fault recovery, ensuring that when the client requests a renewal with the exact same parameters, the master properly processes it and resumes sending the Announce stream. https://github.com/nwtime/linuxptp/commit/dbc9e7792793600bb94003aa2ae9dba84a37a7bd The client fix (pending upstream, adapted from StarlingX) forces the client to immediately renew its Announce subscription if the cached foreign master record falls below the qualification threshold, rather than silently waiting in the UC_WAIT state until the long-term lease expires. https://lists.nwtime.org/sympa/arc/linuxptp-devel/2026-10/msg00048.html Patch: https://lists.nwtime.org/sympa/arc/linuxptp-devel/2026-10/msg00048/binpkiVvQBmTe.bin [ Reproducer ] Since a full manual PTP configuration is complex to set up, a script will be provided to reproduce the issue by simulating the raw ptp packets. [ Additional Info ] This was verified to affect resolute and noble, and might after other versions as well. The server fix (commit dbc9e7792793600bb94003aa2ae9dba84a37a7bd) is already merged into the upstream linuxptp repository. The client fix (https://lists.nwtime.org/sympa/arc/linuxptp- devel/2026-10/msg00048/binpkiVvQBmTe.bin) was proposed on the linuxptp- devel mailing list and is based on a patch from the StarlingX project, but has not yet been accepted upstream. Both patches apply cleanly to the Resolute package. ** Affects: linuxptp (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2173661 Title: Fix delayed client recovery and missing Announce after master fault To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linuxptp/+bug/2173661/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
