Using control path and port forwarding

[Tom Horsley]

I've been discovering that a slew of different older versions
of ssh clients on various linux distros cannot use the -L
option to forward a port and, at the same time, use the -S
option to point to an existing connection to avoid a password
prompt.

The actual login works, but the forwarded port is never
created.

Newer versions of ssh work fine with both -S and -L.

Weirdly, I've checked the ssh -V info from working and
non-working versions and there is overlap in the version
numbers.

So, my question is this: Is there a reliable way to guess
if this is going to work or not. Testing it is kind of
difficult without users getting password prompts and such.