Re-join by UDP gives MAC Payload decrypt error

[scartill]

When trying to join an already joined device via UDP, "downlink error : MACPayload must be of type*MACPayload" happens

[Gillani0]

Hi @scartill

As we discussed earlier, there was this same issue with the join and rejoin request. After some debugging I've found the culprit.

To decrypt the Join Accept payload, you're using Nwkey, however, you need to use the AppKey. So on this line in lds.go, you need to change d.NwkKey --> d.AppKey. This will properly decode it and will solve the problem. Cheers

Syed

[scartill]

HI @Gillani0

The problem is that the code you point to already assumes that a downlink is a frame, whereas on rejoin it is in fact a join response, hence the wrong key is chosen. So the real problem resides upstream the call chain here.

Boris

[4br3mm0rd]

Hi everyone,

I read in LoRa's Specification that sending a Re-Join Request requires to change the headers of the PHYPayload. Is this automatically done when clicking the Join button once we already have the Session Keys? Or does LDS send a regular Join Request?

When I press Join after receiving the Session Keys, the request is sent, but my app server throws an error: "object already exists".

I guess in terms of implementations, it would be easier to have a Re-Join button, this could also solve this issue by waiting for the Join-Accept after sending it? Or maybe before decrypting, LDS should check the MType?

(I am quite bad at Go, so I'm trying to help this way, I hope I'm not offending or wasting your time)

[scartill]

Hi @4br3mm0rd ! May thanks for pointing out, separate "re-join" seem more reasonable since we target a flexible simulator, not a regular device. I've been overwhelmed a bit in recent weeks, but will take a look a.s.a.p, and proceeed with new GUI as well.