Can Openthread Leader become a commissioner?

[ksathara]

Hi,
I am trying a commissioner start and to join an ED. I have only one leader in the network. I can make him a commissioner and join an ED by using the cli, but when I try to do it via API, the commissioner gets stuck in petitioning.
Any ideas?
Cheers,
Kaushalya

[jwhui]

Yes, a Leader can serve as a Commissioner. Your successful results using the CLI demonstrates this.

Note that the CLI is simply built on top of the OT API and serves as an example of using OT API. I would suggest reviewing the CLI implementation to understand how best to call the OT APIs directly.

https://github.com/openthread/openthread/blob/main/src/cli/cli_commissioner.cpp

[ksathara]

Thanks Jonathan. My implementation was based on the cli.

Now if I implement commissioner start like this, it works. I am not creating a new dataset. but using the active dataset. The cli_cmsn () is a custom cli command that I have created to test.

otError cli_cmsn (void *aContext, uint8_t aArgsLength, char *aArgs[]) {
	otError error;
	
	otInstance *instance = openthread_get_default_instance();
	if (instance == NULL) {
		otCliOutputFormat ("get instantace  error");
		return OT_ERROR_FAILED;
	}

	otCommissionerStop (instance);

	error = otCommissionerStart (instance, aStateCallback, aJoinerCallback, NULL);
	if (error != OT_ERROR_NONE) {
		otCliOutputFormat ("commissioner start error %d\n\r", error);
		return (error);
	}

	return (OT_ERROR_NONE);
}

But I want to init the dataset and use the new dataset before starting the commissioner. So I did it like this.

otError cli_cmsn (void *aContext, uint8_t aArgsLength, char *aArgs[]) {
	otOperationalDataset aDataset;
	otError error;
	
	otInstance *instance = openthread_get_default_instance();

	error = otIp6SetEnabled(instance, false);	// ifconfig down

	error = otThreadSetEnabled (instance, false);	// thread stop

	error = otDatasetCreateNewNetwork(instance, &aDataset);	// create new dataset

	error = otDatasetSetActive(instance, &aDataset);	// active new dataset

	error = otIp6SetEnabled(instance, true);	// ifconfig up

	error = otThreadSetEnabled (instance, true); // thread start

	// spawn a thread to handle wait to connect to network
	k_tid_t my_tid = k_thread_create(&cmsn_thread_data, cmsn_stack_area,
                                 K_THREAD_STACK_SIZEOF(cmsn_stack_area),
                                 cmsn_handler,
                                 NULL, NULL, NULL,
                                 CMSN_THREAD_PRIORITY, 0, K_NO_WAIT);

         return (error);
	}

	return (OT_ERROR_NONE);
}

// thread handler
void cmsn_handler (void *, void *, void *) {
	otError error;
	
	while (ot_connected == true) {     //ot_connected is made true if thread role is either child, router or leader
		k_msleep (500);
	}
	while (ot_connected == false) {   //ot_connected is made false if thread role is either detached or disabled
		k_msleep (500);
	}
	
	otInstance *instance = openthread_get_default_instance();
	otCliOutputFormat ("\n\rdevice role %d", otThreadGetDeviceRole(instance));

	otCommissionerStop (instance);     // stop commissioner just in case 

	error = otCommissionerStart (instance, aStateCallback, aJoinerCallback, NULL);
	}
}

I can see the commissioner start happens when the thread role is leader. But it fails to get the petition.

Any clue why it behaves like this?

[jwhui]

OpenThread API is not thread safe. OpenThread APIs are designed to be called from a single execution context.

[ksathara]

Oh ok. I know this is not an OpenThread question, but what would you advise to do in this case? I have to do a busy wait till thread role changes to router or leader before continuing commissioner start.

[jwhui]

Register a callback with otSetStateChangedCallback() to receive events when states change. You can call OT APIs in the callback.

[ksathara]

Great !! it worked. Thanks heaps Jonathan.

[ksathara]

Sorry Jonathan, one more question. Is it ok to leave a router/leader permanently in a commissioner role?

[jwhui]

Thread only allows at most one active commissioner at any given time. You can leave the commissioner active, but it would not allow any other commissioner to become active.

[ksathara]

I can now get end to end commissioning under API control. I want to pass custom data to the commissioner state change cb. I see there is a second parameter as 'void *aContext'. I guess I can use this to pass my data to the cb. How can I implement it?