Verify that a DNS-SD service registered via the D-Bus RegisterService()
call is bound to the lifetime of the client's bus connection: since
busctl disconnects right after the call returns, the service must be
unregistered again shortly after. Wait for resolved's vanish handler
log message as proof that the client tracking triggered the
unregistration, check that a subsequent UnregisterService() fails
specifically because the service is not known anymore, and verify that
the identifier can be registered again — previously it stayed taken by
the vanished client's service forever, failing with
DNSSD_SERVICE_EXISTS.
A dummy link with mDNS enabled makes sure the per-scope goodbye/zone
teardown path actually runs, and since resolved would be restarted
automatically if it crashed in it, letting the D-Bus level checks pass
vacuously, verify the InvocationID stayed the same throughout.
Stefan Agner
908c38f300