Yeah, my question was specific about the new functions, so I understood that a separate PR should add that to the all the relevant functions.

I have a different problem now however: the test suite is failing in CI but not locally. It's giving me NameError about a function used by existing tests but for some reason, it's not defined in the scope of the new test functions?!?

The proactor version of sock_recvfrom_into() is giving me quite a bit of trouble, as it seems to require heavy handed changes in _overlapped.c. 

I'm also not very successful in testing cases where sendto() would fill the kernel buffer and raise BlockingIOError. With TCP this is easy but with UDP near impossible to do in a controlled fashion in the test suite.