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.

[Damien Miller]

Post by 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.

Support for establishing port forwardings over the multiplexing channel
was added in commit e1537f951f which was released in OpenSSH 5.4. There
maybe have been some bugs that we fixed later though.

-d