[sipcore] Push notifications with iOS 13 (RFC 8599)

[Yehoshua Gev <[e-mail]>]

Hi All,

I hope it is ok to post this here and not on sip-implementors...

We are trying to implement RFC 8599 for performing push notifications for
Apple devices.

Starting with iOS 13, there is a restriction on VoIP pushes [1]: "Apps
receiving VoIP push notifications *must report the call quickly to CallKit,
so it can alert the user* to the presence of the incoming call."

According to RFC 8599, pushes are used for (at least) two different goals:
  1) Initiating registration refreshes (section 5.5)
  2) Notifying of incoming calls (section 5.6.2)

Now, for a reasonable user experience, the registration refresh pushes must
not trigger the UI of incoming call.
However, when an INVITE is received, the UA must be awoken immediately,
which is the purpose of VoIP push.

Does it make sense to make a different push type for registration refresh
and for incoming calls?

I'm not sure this is possible with the current RFC (and it is also against
the spirit of the RFC), but I can't think of another way around it (besides
using regular pushes instead of VoIP pushes, which might introduce delays,
or having a registration with infinite expiration that will not require
refreshes, which might leave many zomby registrations).

See some discussion here: [2], [3].

Thanks,
Yehoshua

[1]
https://developer.apple.com/documentation/pushkit/pkpushtype/1614481-voip
[2] https://developer.apple.com/forums/thread/117939
[3] https://www.linphone.org/news/ios-13-important-changes-voipim-apps