ot-br-posix losing network configuration sporadically

[dakhnod]

I have ot-br-posix running under linux, and it allows to join a network using ot-ctl.
This all works fine, until the RCP refuses to connect all of a sudden.
ot-ctl dataset active yields Not found.
Only re-joining the network helps.

By now I found out that the host system stores the configuration under /var/lib/thread.
So far, I cannot tell if the configuration in the folder also disappears.

In any case, whould could cause the border router to simply lose its dataset?

[jwhui]

On posix systems, OpenThread stores the settings in a file. You can find the implementation here:
https://github.com/openthread/openthread/blob/main/src/posix/platform/settings.cpp

The settings will only be list if:

1. the settings are explicitly deleted (e.g. by a call to otPlatSettingsDelete())
2. the settings file is deleted
3. the settings file becomes corrupt