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This is a design page. It was used to design and discuss the initial implementation of the change. However, the state of this document does not necessarily correspond to the current state of the implementation since we do not keep this document up to date with further changes and bug fixes.

D-Bus Signal: Notify Property Changed

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This design document describes how to implement org.freedesktop.DBus.Properties.PropertiesChanged signal for SSSD objects exported in the IFP responder.

  • PropertiesChanged(s interface_name, {sv} changed_properties, as invalidated_properties)

    • interface_name: name of the interface on which the properties are defined

    • changed_properties: changed properties with new values

    • invalidated_properties: changed properties but the new values are not send with them

    • this signal is emitted for every property annotated with org.freedesktop.DBus.Property.EmitsChangedSignal, this annotation may be also used for the whole interface meaning that every property within this interface emits the signal

Changes in properties are detected in new LDB plugin inside a mod hook. The plugin writes list of changed properties in a TDB-based changelog which is periodically consumed by IFP responder. IFP then emits PropertiesChanged signal per each modified object.

  • TDB Name: ifp_changelog.tdb

  • Key: dn of modified object

  • Value: chained list of modified properties in the form total_num\0prop1\0prop2\0…\0

  1. TDB database is created on IFP start and deleted on IFP termination.

    • on IFP start:

      • if TDB file does not exist it is created

      • if TDB file exist (unexpected termination of IFP) it is flushed, we do not care about the data inside

    • on correct IFP termination

      • the TDB file is deleted

  2. A periodic task IFP: notify properties changed is created, it is responsible for emitting the PropertiesChanged signal

    • Periodic task flow:

      1. Lock TDB for read-only access

      2. Traverse the TDB and remember dn and properties for all modified objects

      3. Flush TDB

      4. Release the lock

      5. Create and emit D-Bus signal per each object that is exported on IFP bus and supports PropertiesChanged signal

  1. If TDB file does not exist just quit

  2. If modified object supports the signal store it in the TDB

In IFP section:

  • ifp_notification_interval: period of IFP: notify properties changed, disabled if 0, default 300 (5 minutes)

  1. Hook onto PropertiesChanged signal, e. g. with dbus-monitor’̈́’

  2. Trigger change of user/group

  3. Signal should be received

  1. Do we want to use changed_properties or invalidated_properties