Tunneling NFS4 over SSH

Today we had the need to mount a filesystem from a system that was almost completely isolated and instead of having to transfer a huge amount of data over a tunneled SSH connection, I thought, why not pursue mounting NFS over an SSH tunnel.

Since NFS4 by default does TCP if both client and server can do that, this would be the perfect opportunity to test the new capability. In fact, it should not be hard at all.