Neither link each other at the moment. the manager holds a list of references to the connections, which are removed when a connection destructs.
So the connection could hold a link to the manager without involving a circular reference I think and probably a wise change, but as you say not for 4.2.6.

I'd can still mark the manager and connection as closed still when closeSDS() is called, suppressing e.g. any commits etc. after that point. I'll open a separate issue targeting 5.2.