[Txt Data] Try to read txtData description of a server service

[estelleOl]

Hello,

I have created a client service with a txtData description but I try to read TxtData serve on server side. I do not have the txtData filled.

In client part here my code :

/* Get buffer instance name */
serviceInst = otSrpClientBuffersGetServiceEntryInstanceNameString(entry, &size);

strcpy(serviceInst, "board2Instance");

/* Get buffer sub type labels array */
subTypeArray = otSrpClientBuffersGetSubTypeLabelsArray(entry, &size);


/* Set subType Label */
subTypeArray[0] = "subtypeBoard2\0";

/* Get service name buffer */
serviceName = otSrpClientBuffersGetServiceEntryServiceNameString(entry, &size);

strcpy(serviceName, "_subtypeBoard2._sub._testBoard2._udp");

/* Get buffer txt entry */
txtEntry = otSrpClientBuffersGetServiceEntryTxtBuffer(entry, &size);

/* Set txtEntry */
*txtEntry = 123;

/* Set weight port priority service*/
entry->mService.mPort = 111;
entry->mService.mPriority = 1;
entry->mService.mWeight = 1;

/* Add a service to be registered with server */
status = otSrpClientAddService(NULL, &entry->mService);

I can see that the TxtEntry is well set when I receive the srpClientCallback.

But when I try to use otSrpServerServiceGetTxtData on server side on this sqme service. I do have the txtEntry I have written.

Do I have misunderstood and the txtEntry is not the same as the txtData ?

[jwhui]

The length of the TXT entry value also needs to be set.

entry->mTxtEntry.mValueLength

The SRP Client CLI provides an example of configuring the TXT record:

openthread/src/cli/cli_srp_client.cpp

Lines 420 to 428 in 812c36f

	if (!aArgs[6].IsEmpty() && (aArgs[6] != "-"))
	{
	uint8_t *txtBuffer;
	txtBuffer = otSrpClientBuffersGetServiceEntryTxtBuffer(entry, &size);
	entry->mTxtEntry.mValueLength = size;
	SuccessOrExit(error = aArgs[6].ParseAsHexString(entry->mTxtEntry.mValueLength, txtBuffer));
	}

[estelleOl]

I have modify my txt entry and put the lenght value but I do not succeed to register my service. The srpClientCallback as soon I put a lenght value return 6.
My code :

strcpy(serviceInst, "board2Instance");

/* Get buffer sub type labels array */
subTypeArray = otSrpClientBuffersGetSubTypeLabelsArray(entry, &size);

/* Set subType Label */
subTypeArray[0] = "subtypeBoard2\0";

/* Get service name buffer */
serviceName = otSrpClientBuffersGetServiceEntryServiceNameString(entry, &size);

strcpy(serviceName, "_subtypeBoard2._sub._testBoard2._udp");

/* Get buffer txt entry */
txtEntry = otSrpClientBuffersGetServiceEntryTxtBuffer(entry, &size);

/* Set txtEntry */
  strcpy((char *)txtEntry, "testBoard2");
  entry->mTxtEntry.mValueLength = sizeof("testBoard2"); 

/* Set weight port priority service*/
entry->mService.mPort = 111;
entry->mService.mPriority = 1;
entry->mService.mWeight = 1;

/* Add a service to be registered with server */
status = otSrpClientAddService(NULL, &entry->mService);

If I do not put the length value I can register the service and the callback return no error but still the same problem srp server do not see the txt data with the method :

uint16_t aDataLenght;
const uint8_t * txtData = OtSrpServerServiceGetTxtData(pService, &aDataLenght);

dataLenght return 1 and txtData is empty.

Is txtEntry is the srp client input to set txtData in srp server side ?

[abtink]

The mTxtEntries that you include in the otSrpClientService must be an array of valid otDnsTxtEntry items.

Please check the documentation of otDnsTxtEntry (and/or RFC 6763):

/**
 * This structure represents a TXT record entry representing a key/value pair (RFC 6763 - section 6.3).
 *
 * The string buffers pointed to by `mKey` and `mValue` MUST persist and remain unchanged after an instance of such
 * structure is passed to OpenThread (as part of `otSrpClientService` instance).
 *
 * An array of `otDnsTxtEntry` entries are used in `otSrpClientService` to specify the full TXT record (a list of
 * entries).
 *
 */
typedef struct otDnsTxtEntry
{
    /**
     * The TXT record key string.
     *
     * If `mKey` is not NULL, then it MUST be a null-terminated C string. The entry is treated as key/value pair with
     * `mValue` buffer providing the value.
     *   - The entry is encoded as follows:
     *        - A single string length byte followed by "key=value" format (without the quotation marks).
              - In this case, the overall encoded length must be 255 bytes or less.
     *   - If `mValue` is NULL, then key is treated as a boolean attribute and encoded as "key" (with no `=`).
     *   - If `mValue` is not NULL but `mValueLength` is zero, then it is treated as empty value and encoded as "key=".
     *
     * If `mKey` is NULL, then `mValue` buffer is treated as an already encoded TXT-DATA and is appended as is in the
     * DNS message.
     *
     */
    const char *   mKey;
    const uint8_t *mValue;       ///< The TXT record value or already encoded TXT-DATA (depending on `mKey`).
    uint16_t       mValueLength; ///< Number of bytes in `mValue` buffer.
} otDnsTxtEntry;

You can provide a bunch of "key/value" pairs and then OT implementation will encode it and construct the TXT-Data.
Of if mKey is NULL, then caller must already provide the encoded TXT-DATA (which should follow format as in RFC 6763).

In your code, you seem to leave mKey as NULL, then copy "testBoard2" into the buffer which does not follow proper format.

[estelleOl]

Thank you , your response has resolved my issue