From: Dexuan Cui <decui@microsoft.com>
Date: Tue, 28 Jul 2015 05:35:11 -0700

With the 2 APIs supplied by the VMBus driver, the coming net/hvsock driver
can register 2 callbacks and can know when a new hvsock connection is
offered by the host, and when a hvsock connection is being closed by the
host.

Signed-off-by: Dexuan Cui <decui@microsoft.com>

This is an extremely terrible interface.

It's an opaque hook that allows on registry, and it's solve purpose
is to allow a backdoor call into a foreign driver in another module.

These are exactly the things we try to avoid.

Why not create a real abstraction where clients register an object,
that can be contained as a sub-member inside of their own driver
private, that provides the callback registry mechanism.

That way you can register multiple clients, do things like allow
AF_PACKET capturing of vmbus traffic, etc.