Server displaying incorrect for multiple object links information is sent from the client.

[venpu]

Hello there,

I am testing the object link feature and found this issue.

When the client sends multiple object links of 0x00640001 (100:1) and 0x0065002(100:2) to the Leshan server, for some reason it only displays in the following format in the GUI. I don't see multiple object links in the server.

Resource 22 /3/0/22 Observe Read Write 0=0,0,6,5,0,0,0,2

Here is the sample hexdump of the COAP + LWM2M packet being sent to the server.

65 45 5d cf c1 99 af a5 d7 c2 2d 16 ff 88
16 0c 44 00 00 64 00 01 44 00 00 65 00 02

Can you please let me know if the scenario is supported or is there any issue from the server side.

Hope that helps.

Thank you.

[sbernard31]

I write a quick junit tests and I decode your payload with Leshan I get :

public static void main(String[] args) throws TlvException {
        byte[] rawMessage = Hex.decodeHex("65455dcfc199afa5d7c22d16ff88160c440000640001440000650002".toCharArray());
        Message coapMessage = new UdpDataParser().parseMessage(rawMessage);
        System.out.println(coapMessage);

        byte[] payload = coapMessage.getPayload();
        Tlv[] tlv = TlvDecoder.decode(ByteBuffer.wrap(payload));
        System.out.println(Arrays.toString(tlv));

        LwM2mResource lwNode = LwM2mNodeTlvDecoder.decode(payload, new LwM2mPath("3/0/22"),
                new LwM2mModel(ObjectLoader.loadDefault()), LwM2mResource.class);
        System.out.println(lwNode);
}

Coap :

ACK-2.05   MID=24015, Token=c199afa5d7, 
OptionSet={"Content-Format":"application/vnd.oma.lwm2m+tlv"}, 
88 16 0c 44 00 00 64 00 01 44 00 00 65 00 02 

TLV :

[Tlv [type=MULTIPLE_RESOURCE, children=
     [Tlv [type=RESOURCE_INSTANCE, children=null, value=[0, 100, 0, 1], identifier=0],
      Tlv [type=RESOURCE_INSTANCE, children=null, value=[0, 101, 0, 2], identifier=0]],
 value=null, identifier=22]]

LM2MNode :

LwM2mMultipleResource [id=22, values={0=/101/2}, type=OBJLNK]

As you can see the both resource instances as the same identifier, this looks like a bug in the payload ?

[sbernard31]

@venpu could you confirm this is a payload error from your client ?

[sbernard31]

I add create a PR to send a CodecException if this happened instead of accept it silently.
I add a test case too.
see #426

[venpu]

Hi Bernard,

Correct. The TLV payload had the same identifier for the resource instance. Fixed that TLV encoder at the LWM2M client. Thanks for adding an additional test case to test the scenario and also raise an error.

Thanks!