The disco key subscriber could deadlock in a scenario where a self node
update came through the control path into the mapSession after the disco
key subscriber had taken the lock, but before it had pushed the netmap
change, as both the subscriber and onSelfNodeChanged needs the
controlclient lock.
The subscriber can safely take the mapsession as the changequeue has its
own lock for inserting records, and also checks if the queue has been
closed before inserting.
Updates #12639
Signed-off-by: Claus Lensbøl <claus@tailscale.com>
Claus Lensbøl
4334dfa7d5