fix: lock adding to tailnet waitgroup to avoid race (and fix flake) #14195
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deansheather
approved these changes
Aug 7, 2024
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Fixes #14143.
Fixes a race condition that can occur when a
tailnetconnection is closed just before a network telemetry event is about to be sent off. Specifically, wherewaitgroup.Add(n)is called on a waitgroup wherewaitgroup.Wait()is currently blocking another goroutine.This works as we only call
Wait()on thetelemetryWgwaitgroup when theConnmutex is held, and only after the closed channel has been closed. We then require that the goroutine sending the telemetry event acquire said mutex, and that the channel is not closed, before adding to the waitgroup and sending the event.