There is currently no way to get the abstract namespace of a UDS.

Mio's SocketAddr knows internally through AddressKind::Abstract(&'a [u8]) whether a UDS is abstract but that is not exposed to the user.

There is a tracking issue for improving abstract UDS support in libstd and the accompanying pull request seems close to landing. It includes an as_abstract_namespace() method.

General observation: I don't know if it's a design consideration but the proposed API is quite different from mio's current UDS API.