Allow clients to query server about interface information in sDDF-Net protocol

[JE-Archer]

In the Net protocol, we have clients and servers in the sense that the virtualiser is a client of the driver, which is a server to the virtualiser, and end clients are clients of the virtualiser, which is a server to the clients. However, the only interaction between clients and servers allowed by the protocol is transmitting and receiving frames. It may be useful to allow the client to query the server about certain information or capabilities.

For example, a client could query the server about the server's MAC address (a virtualiser could query the driver, in which case the driver could report the hardware MAC address; clients could query the virtualiser about their MAC addresses, which would be virtual MAC addresses assigned by the virtualiser). Other information which might be useful would be hardware checksumming capabilities or link speed.