RE: How to reset DPS connection to Azure IoT hub?

Charlie — Wed, 21 Jun 2023 09:18:54 GMT

Hi,

[quote user=""]We found that there is a function called azure_iot_hub_dps_reset() to do this job.
We placed this function just before calling azure_iot_hub_dps_init().[/quote]

This is expected to not have the desired effect because the settings subsystem is initialized by azure_iot_hub_dps_init(). The APIs need to be called in the opposite order, always by initializing first.
Our library had a wrong assumption in the azure_iot_hub_dps_reset() code with regards to -ENOENT being returned by settings_delete() and hence returned success in this case. This is fixed (and explained in more detail) in https://github.com/nrfconnect/sdk-nrf/pull/11588. So in this case, azure_iot_hub_dps_reset() wrongly returned 0, while it should have returned an error because there was not even made an attempt to delete it from flash.

[quote user=""]Our understanding was, that our device should get a "new" device name from the IoT hub).[/quote]

This is true, but it is also a bit tricky as the device ID has to match the subject name in the device certificate which is used to make the connection to DPS in the first place. You can enable modem traces and take a look at the TLS connection in Wireshark using the nRF Connect for Desktop application Cellular Monitor and see what happens if you use a random device ID to connect to DPS. Then I would expect the TLS handshake to be successful but the server to close the connection after the device sends the MQTT connect message with an ID that does not match the common name in the device certificate.

Best regards,

Charlie

RE: How to reset DPS connection to Azure IoT hub?

Charlie — Tue, 20 Jun 2023 06:52:58 GMT

Hi Exelor,

I need some time to figure out this issue and will reply to you later.

Best regards,

Charlie