net: lwm2m: Stop the LwM2M engine in case of fatal network error #92041
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SeppoTakalo
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Jun 24, 2025
jukkar
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Jun 24, 2025
In case of fatal network error (i.e. when the LwM2M client runs out of retries), call lwm2m_engine_stop() to cleanup any allocated resources for the client. The engine is dead at that point anyway so the application needs to recover. If this isn't done, it is theoretically possible to restart the LwM2M client (with lwm2m_rd_client_start() which does not report an error in such case), which in turn could lead to resource leaks (like for example the observer list is reinitialized) if the application didn't call lwm2m_rd_client_stop() first. Calling lwm2m_engine_stop() ensures that all resources are freed even if the application doesn't call stop before restarting. Stopping the engine is also needed when the network error occurs when de-registering - in such case the engine goes straight into the IDLE state, where it's possible to restart the client and thus reinitialize the observer lists. Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
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I've updated the PR as I've identified one more problematic place where we could leak observers - if the network error happens while deregistering (which isn't that difficult, quite easy to reproduce with net/lwm2m shell, just put the network interface down and stop the client) we could leak observers too. |
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SeppoTakalo
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Jul 24, 2025
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In case of fatal network error (i.e. when the LwM2M client runs out of retries), call lwm2m_engine_stop() to cleanup any allocated resources for the client. The engine is dead at that point anyway so the application needs to recover.
If this isn't done, it is theoretically possible to restart the LwM2M client (with lwm2m_rd_client_start() which does not report an error in such case), which in turn could lead to resource leaks (like for example the observer list is reinitialized) if the application didn't call lwm2m_rd_client_stop() first. Calling lwm2m_engine_stop() ensures that all resources are freed even if the application doesn't call stop before restarting.
Potentially fixes #91383