make TorService fit into the Android lifecycle as a "Bound Service"
One key reason why
TorService was created was to embed Tor daemon in a native Android
Service. That works now, so now this opens up a lot of possibilities for making Tor work in a way that Android wants background systems to operate. First, I'm regularly seeing sub 5 second
TorService starts, which means from zero Tor running to viewing https://check.torproject.org within 5 second. With all the sleep/restore work in Core Tor, I think we remove the "always running" model that we've used for the past 10 years, and instead think of
TorService as something that runs on demand, then stops when not needed.
While reading about the background service restrictions:
I noticed that these restrictions do not apply to "bound services", where there is a
Binder IPC connection between
TorService and an Android app. So for the Tor Browser or Briar model, where they ship with embedded
TorService, they can use the
bindService() interface to prevent
TorService from being killed without needing a permanent
Notification in the toolbar.
That app binding to
TorService need not be the app that ships with it. So we could also make NetCipher connect the client apps to
TorService to keep it alive, in cases where the embedded
TorService is expected to be used by other apps, e.g. Orbot and a Feed Reader app.
Something like using the ControlPort via stdin/stdout or direct method call would make rapid (re)starts work more reliably, e.g. https://trac.torproject.org/projects/tor/ticket/32476#comment:5
Also tracking this in Tor: https://trac.torproject.org/projects/tor/ticket/32780