The effective state was computed under serverStateLock but published after
releasing it, so two transitions could reorder between compute and notify
and leave the listener on a state the notifier had already superseded,
e.g. NoNetwork surviving after the network came back.
Hold a publish lock across compute and notify on every publishing path.
On mobile the client kept dialing management, signal, relay and peer
connections while the device had no usable network at all (airplane
mode), burning battery for attempts that cannot succeed. Stopping the
engine is not an option: tearing it down destroys the TUN device, and
traffic can leak outside the tunnel until it is rebuilt.
Add client/netstate, a small gate the platform feeds from its own
connectivity callbacks. Every reconnection loop waits on it instead of
retrying blindly, and resets its backoff when the network returns so
recovery is immediate. The state is injected through functional options
and consumers hold a *State that may be nil, so every platform that does
not report availability behaves exactly as before.
The relay quick-reconnect rechecks availability after its 1.5s wait: the
disconnect that triggers it is usually the first symptom of the network
going away, so the flag typically arrives while it sleeps.
Report the suspension to the UI as well. peer.Listener grows
OnStateChanged with a typed ClientState, re-exported across the gomobile
boundary as integer constants, and the notifier maps Connecting to a new
NoNetwork state while the OS reports no network, so mobile clients can
show "no network available" instead of a misleading "connecting".
Finally, exit the client retry loop cleanly when its context is
cancelled. backoff.WithContext surfaces the bare context error, which
callers could not distinguish from a real failure — on Android that
turned an engine restart into an unrecoverable error.
In case of 'always-on' feature has switched on, after the reboot the service do not start properly in all cases.
If the device is in offline state (no internet connection) the auth login steps will fail and the service will stop.
For the auth steps make no sense in this case because if the OS start the service we do not have option for
the user interaction.
Refactored updateServerStates and calculateState
added some checks to ensure we are not sending connecting on context canceled
removed some state updates from the RunClient function
