Cellular: disconnect does not deactivate context (for some cases) #13490
Description
Description of defect
I use a Quectel BG95 modem (similar to BG96) to connect and disconnect to the cellular network in my application. I noticed that during disconnection, the PDP context is not deactivated. I looked into the code and found some curious logic. There are two parts I believe are buggy or I do not understand.
In AT_CellularContext::do_disconnect(), the value of _is_context_activated is checked in order to deactivate the context.
However, this variable is not set in case an active context is found in AT_CellularContext::find_and_activate_context(). There, only _is_context_active is set.
This leads to the issue that the context is not deactivated if it is found active. Is this desired? I think disconnect should deactivate the context in both cases.
Also, what is the difference between _is_context_active and _is_context_activated? Are they redundant?
When I changed this, it went one step further but the context was still not getting deactivated. Looking further, I found that the only deactivate_context() call is inside this check:
mbed-os/connectivity/cellular/source/framework/AT/AT_CellularContext.cpp
Lines 758 to 761 in f83d100
which checks for something really unclear (3G and older RAT?) or active_contexts_count > 1, which I again do not understand. For my case, I am connected using NB-IoT and I have only 1 active context, so this check was failing and my context was not deactivated. Maybe only the _at.clear_error() should be in the if block and deactivate_context() should be after the block. When I changed it in that way, it finally worked for me.
I can open a PR with my changes if needed.
Target(s) affected by this defect ?
Not target specific.
Toolchain(s) (name and version) displaying this defect ?
Not relevant.
What version of Mbed-os are you using (tag or sha) ?
mbed-os-6.2.0
mbed-os-99.99.99
What version(s) of tools are you using. List all that apply (E.g. mbed-cli)
Not relevant.
How is this defect reproduced ?
Disconnect from cellular network using without activating (connect with a modem which has an active PDP context).
For the second issue, disconnect from a NB-IoT network with one active context.