unable to connect via rpcbind behind NAT / docker port forwarding

[lmm-git]

This is expected behavior but it remains the port forwarding usage of rpcbind useless.

Background: With newer versions of rpcbind clients will use a newer protocol version. These versions will use the GETADDR call which returns the IP from the server on application level. As with a typical docker port forwarding we are doing a source NAT, the IP in response of GETADDR will not be equal to the external one and even worse, it is typically an unreachable address. So basically listing the exports is not possible with newer clients (depending on the version of rpcbind).

I do not have any idea how to fix that properly. But a note in the docs would be nice.

This image is pretty useful in some use cases but e.g. with newer versions of Proxmox it just doesn't work for non obvious reasons.