[SRP Client] How to create an SRP service subtype using OT methods

[estelleOl]

I try to create an SRP service subtype without using cli commands.
In CLI command it would be : "srp client service add ins1 _test._udp,_sub1 111 1 1"

So in my code I have created a service to add and tried to had it, but I do not succeed to have the right service name with sub type.

My code to add a basic type service :
static otSrpClientService services[2] = {0};

services[0].mInstanceName = "ins1";
services[0].mName = "_test._udp";
services[0].mPort = 111;
services[0].mPriority = 1;
services[0].mWeight = 1;

otSrpClientAddService(NULL, &services[0]);

I have tried to modify the service name to declared a sub type but it did not work :
static otSrpClientService services[2] = {0};

services[0].mInstanceName = "ins1";
services[0].mName = "_test._udp_sub1._sub";
services[0].mPort = 111;
services[0].mPriority = 1;
services[0].mWeight = 1;

otSrpClientAddService(NULL, &services[0]);

Can someone explain me what I did not understood in the service subtype creation ?

Thanks

[jwhui]

You need to add the sub-type labels separately via the mSubTypeLabels array in the otSrpClientService struct.

You can also see how the CLI implementation processes sub-types:

openthread/src/cli/cli_srp_client.cpp

Lines 386 to 406 in 0756d1e

	if (label != nullptr)
	{
	uint16_t arrayLength;
	const char **subTypeLabels = otSrpClientBuffersGetSubTypeLabelsArray(entry, &arrayLength);
	// Leave the last array element as `nullptr` to indicate end of array.
	for (uint16_t index = 0; index + 1 < arrayLength; index++)
	{
	*label++ = '\0';
	subTypeLabels[index] = label;
	label = strchr(label, ',');
	if (label == nullptr)
	{
	break;
	}
	}
	VerifyOrExit(label == nullptr, error = OT_ERROR_NO_BUFS);
	}

[estelleOl]

Thank you for your reponse, I cannot activate OPENTHREAD_CONFIG_SRP_CLIENT_BUFFERS_ENABLE so I cannot use the otSrpClientBuffersGetSubTypeLabelsArray ... .

Can I directly modify the mSubTypeLabels ?

Something like that ?
services[0].mSubTypeLabels[0]="test";

[jwhui]

No, the caller needs to provide the buffer for the char* array itself.

[estelleOl]

Thank you for your help !

[abtink]

Let me also highlight couple of notes (which I hope helps):

• The mSubTypeLabels array (of strings or char *) MUST end with NULL (which indicate end of the array).
• The entries in otSrpClientService must persist and stay same after an instance of this struct is passed to OpenThread.

openthread/include/openthread/srp_client.h

Lines 84 to 102 in 2cab708

	/**
	* This structure represents an SRP client service.
	*
	* The values in this structure, including the string buffers for the names and the TXT record entries, MUST persist
	* and stay constant after an instance of this structure is passed to OpenThread from `otSrpClientAddService()` or
	* `otSrpClientRemoveService()`.
	*
	*/
	typedef struct otSrpClientService
	{
	const char * mName; ///< The service name labels (e.g., "_chip._udp", not the full domain name).
	const char * mInstanceName; ///< The service instance name label (not the full name).
	const char *const * mSubTypeLabels; ///< Array of service sub-type labels (must end with `NULL` or can be `NULL`).
	const otDnsTxtEntry *mTxtEntries; ///< Array of TXT entries (number of entries is given by `mNumTxtEntries`).
	uint16_t mPort; ///< The service port number.
	uint16_t mPriority; ///< The service priority.
	uint16_t mWeight; ///< The service weight.
	uint8_t mNumTxtEntries; ///< Number of entries in the `mTxtEntries` array.