ssh check local and remote forwarding

[Luca Di Gregorio]

Currently ssh -O check doesn't show active forwardings.
Do you think it's possible to add this feature?
To check if a local or remote forwarding is active?

Something like this:
ssh -O check -L 127.0.0.1:2000:127.0.0.1:9999 -S /tmp/to_remote remote