Default version of core object is not handled correctly

[sbernard31]

When client send supported object to the server, it can omit the version of this object.

In Leshan we consider that a missing version always means 1.0.
But this is is not what is described in LWM2M specification concerning core object.

See :

• LWM2M-v1.1.1@core§7.2.3. Object Definition and Object Version Usage
• LWM2M-v1.2.1@core§7.2.3. Object Definition and Object Version Usage.

We currently target 1.1.x. (for Leshan v2.x)
I'm not so sure to understand correctly the v1.1.x but I feel both try to describe the same idea... version 1.2.x is much clearer :

If a Core Object version does not correspond to version contained in the LwM2M Enabler release supported by the LwM2M Client, the Object Version MUST be provided by the LwM2M Client to the LwM2M Server.

Here is OMA question relative to this issue : OpenMobileAlliance/OMA_LwM2M_for_Developers#561

[JaroslawLegierski]

Based on information about the Object 4 (Connectivity Monitoring)
In OMA Registry there is all these following versions of this Object 4:

if the device says it support globally lwm2m version 1.1, we can see among the 4 above versions, that the Minimum Object Version compatible with LwM2M Version 1.1 is Object Version 1.2
Therefore this is not necessary to explicitly mention ver="1.2" in registration

[JaroslawLegierski]

I also added comment in this discussion.
Together with @Warmek we preparred PoC demonstrated how this issue can be addressed in Leshan. In first commit we are using most recent object version, in second one we getting minimum value (for a given version of the lwm2m) from objects registry.
It would be great for us if "new default object versioning" could be available in the next release of Leshan.

[sbernard31]

I looked at the PoC and I do not like so much the idea about giving the "responsibility" to choose the default version in LwM2mModelProvider. I feel maybe we should rather have a new dedicated class. (:warning: I didn't take to much time on this so I can change my mind)

But before to search another way, I have one question : Do we want this behavior customizable or is it OK to have hardcoded behavior which strictly follow LWM2M specification ?

It would be great for us if "new default object versioning" could be available in the next release of Leshan.

Yep, let's try to do it.

[sbernard31]

About :

But before to search another way, I have one question : Do we want this behavior customizable or is it OK to have hardcoded behavior which strictly follow LWM2M specification ?

As we have doubt about how specification should be understood maybe safer to have a customizable way. 🤔
I will try to think more about this 🤔

[JaroslawLegierski]

As we have doubt about how specification should be understood maybe safer to have a customizable way. 🤔
I will try to think more about this 🤔

We don't have response from OMA yet. We do not know when we will receive an answer and what will be the this answer. Therefore I think that customization is the best idea.

[sbernard31]

I created a PR about that see #1452, you can review / test if you want.
Any feedback is welcomed.

[JaroslawLegierski]

I created a PR about that see #1452, you can review / test if you want.
Any feedback is welcomed.

Thank You very much ! Today I did some tests. They focused on the situation when we will need CustomLwM2mCoreObjectVersionRegistry instance (if, for example, the minimal version of the core object is needed 😉)
For InMemoryRegistrationStore I used:
builder.setRegistrationDataExtractor(new CustomDefaultRegistrationDataExtractor());
and everything works fine.

I plan to test on Monday this scenario for RedisRegistrationStore (tomorrow we have bank holiday in PL).

[sbernard31]

If you need to have different default version, it is also possible to override DefaultRegistrationDataExtractor.getDefaultVersion(LwM2mVersion lwM2mVersion, int objectId)

[JaroslawLegierski]

I finished today tests of CustomLwM2mCoreObjectVersionRegistry with RedisRegistrationStore. This feature is working correctly I'm able to define own, custom version for core objects. Thank you!

[sbernard31]

Does it mean you think I should consider to integrate #1452 in master ?

[JaroslawLegierski]

I think, it's a very good idea.

[sbernard31]

This now be integrated in master.
About ambiguity in the LWM2M specification reported at OpenMobileAlliance/OMA_LwM2M_for_Developers#561, we decide to use last version of object waiting we get clarification from OMA.

See : https://github.com/eclipse/leshan/blob/cd2239184aba4d9df4d55fc8fb43f3b8f62a660a/leshan-core/src/main/java/org/eclipse/leshan/core/model/LwM2mCoreObjectVersionRegistry.java#L60-L75

@JaroslawLegierski thx for your help 🙏

[sbernard31]

Just for documentation purpose, I explain more precisely our choice at : OpenMobileAlliance/OMA_LwM2M_for_Developers#561 (comment)