Looking into it in more details, there isn't an exported structure that we can use to fetch it, or a internal mechanism that exposes it, so we can't fetch it.
As this is literally the only place where it would be ever used - and that in a log - it hardly seems worth the effort of making convoluted workaround.
I'd simply like to drop that int from the log, and if we ever actually need it then figure something out.

The new logging framework I want to implement (based on callbacks) would have in-depth knowledge of which stream/socket you are using and should therefore be able to provide you with the exact info (including fd in case of socket) when needed anyway