Port forwarding silently fails when source ports are privileged

[meta]

I just spent a really unproductive hour or so trying to work out why I was getting "Connection refused" from a test LDAP server in a VM.

Then I resorted to trying to forward the port using SSH. The SSH client reminded me that privileged ports cannot be forwarded unless you're root. (Oh yeah, Unix. Privileged ports. I remember now.)

So my suggestion is:

• The VirtualBox GUI should warn the user about this.

• There should be an error displayed if port forwarding fails because the port is privileged.

The documentation at https://www.virtualbox.org/manual/ch06.html mentions the limitation, but it states that the VM will refuse to start in such a situation. That doesn't appear to be true -- I tried restarting the VM and didn't get a useful error message.