CrossDevice implementation

[tim-gromeyer]

I think we should create a list of every feature we want for the crossdevice stuff and create documentation for like a api/interface/what packages will be send

Talking about the linux version, there are several code pieces for cross device stuff, but I also saw, that some are not working (like the "media startet playing, sending disconnect request to android and taking over audio" thing)

[kavishdevar]

I am actually not planning to work on "Continuity"/"cross device" features until I work on the BLE advertisements. Because if we have that, we will not have to work on anything except relaying the raw packets. If we do not have BLE advertisements to our help, we will have to implement a whole another protocol for communicating with the app- when we can switch, if the AirPods are nearby, etc..

[tim-gromeyer]

Is there any way I can help with the ble stuff? I don't have a mac, just my airpods (pro 2) and a linux laptop

[kavishdevar]

Yeah! We probably need to just figure out how to use the IRK and/or the encryption key we have from AirPods to identify a BLE broadcast as ours. Probably the bytes not used by the the BLE app, last ~10 bytes, would be the data that is encrypted with the key, but @\steam3d said that if they changed that encrypted part Apple devices would still be able to recognize the AirPods' broadcast. Maybe Apple is using their own non-standard resolution method.

[kavishdevar]

Ok, so it is the IRK that we need. Probably, the references I had for the hashing functions were wrong. I used bumble's ble-rpa-tool, and it works. The IRK is indeed the MagicAccIRK. We should be able to implement a better version of this now.

But, we still have a lot of work to do for "TiPi" and "SmartRouting". Apparently, AirPods can be told that a MAC address is to be included in its easy switching network.

[Jacobtims]

I would love to see this!

[kavishdevar]

Currently, if your android is rooted, it can automatically connect to AirPods based on your preferences. If you are not rooted, you can still try out the existing implementation of relaying data between android and Linux.

[kavishdevar]

Deprecating the existing cross-device impl in favour of the native BT multipoint that AirPods support when manufacturer id in SDP is set to that of Apple.