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The logic implementing the network timezone loading was holding a strong reference to the modem (inside the GTask) while waiting to be registered. This was triggering some possible memory leaks as the modem object could have been left around even after the modem was disconnected. E.g. if the modem booted without antennas plugged in, it was never getting registered, and if we unplugged it right away in that state, the network timezone logic would have left a modem reference around without disposing it. This issue, combined with e.g. other interfaces relying on disposing its own logic with the last object reference (e.g. Signal interface sets up its logic in a context bound to the lifetime of the object) would mean that a lot of different logic blocks were kept running even after the modem device was unplugged from the system. We avoid this issue by making sure that no new additional reference is taken by the logic in charge of updating the network timezone. We just make the timezone update context be bound to the lifetime of the object, as other interfaces do. While doing this, we also remove the logic in charge of "cancelling" the context, as it isn't needed. If the logic needs to be cancelled, we would just remove any configured timeout, which is enough. As part of the changes, the logic has also been improved so that the network timezone isn't only updated the first time the modem gets registered. If the modem gets unregistered and re-registered, we would reload the network timezone information.
ModemManager. ModemManager provides a unified high level API for communicating with mobile broadband modems, regardless of the protocol used to communicate with the actual device (Generic AT, vendor-specific AT, QCDM, QMI, MBIM...). Using. ModemManager is a system daemon and is not meant to be used directly from the command line. However, since it provides a DBus API, it is possible to use 'dbus-send' commands or the new 'mmcli' command line interface to control it from the terminal. The devices are queried from udev and automatically updated based on hardware events, although a manual re-scan can also be requested to look for RS232 modems. Implementation. ModemManager is a DBus system bus activated service (meaning it's started automatically when a request arrives). It is written in C, using glib and gio. Several GInterfaces specify different features that the modems support, including the generic MMIfaceModem3gpp and MMIfaceModemCdma which provice basic operations for 3GPP (GSM, UMTS, LTE) or CDMA (CDMA1x, EV-DO) modems. If a given feature is not available in the modem, the specific interface will not be exported in DBus. Plugins. Plugins are loaded on startup, and must implement the MMPlugin interface. It consists of a couple of methods which tell the daemon whether the plugin supports a port and to create custom MMBroadbandModem implementations. It most likely makes sense to derive custom modem implementations from one of the generic classes and just add (or override) operations which are not standard. There are multiple fully working plugins in the plugins/ directory that can be used as an example for writing new plugins. Writing new plugins is highly encouraged! The plugin API is open for changes, so if you're writing a plugin and need to add or change some public method, feel free to suggest it! License. The ModemManager and mmcli binaries are both GPLv2+. The libmm-glib library is LGPLv2+.