Re: [PATCH] AF_VMCHANNEL address family for guest<->host communication.

Dor Laor
2008-12-16T00:01:52Z

Evgeniy Polyakov wrote:
> On Mon, Dec 15, 2008 at 05:08:29PM -0600, Anthony Liguori (anthony@codemonkey.ws) wrote:
>
>> The KVM model is that a guest is a process. Any IO operations original
>> from the process (QEMU). The advantage to this is that you get very
>> good security because you can use things like SELinux and simply treat
>> the QEMU process as you would the guest. In fact, in general, I think
>> we want to assume that QEMU is guest code from a security perspective.
>>
>> By passing up the network traffic to the host kernel, we now face a
>> problem when we try to get the data back. We could setup a tun device
>> to send traffic to the kernel but then the rest of the system can see
>> that traffic too. If that traffic is sensitive, it's potentially unsafe.
>>
>
> You can even use unix sockets in this case, and each socket will be
> named as virtio channels names. IIRC tun/tap devices can be virtualizen
> with recent kernels, which also solves all problems of shared access.
>
> There are plenty of ways to implement this kind of functionality instead
> of developing some new protocol, which is effectively a duplication of
> what already exists in the kernel.
>
>

Well, it is kinda pv-unix-domain-socket.
I did not understand how a standard unix domain in the guest can reach
the host according
to your solution.

The initial implementation was some sort of pv-serial. Serial itself is
low performing and
there is no naming services what so every. Gleb did offer the netlink
option as a beginning
but we though a new address family would be more robust (you say too
robust).
So by suggestion new address family what can think of it as a
pv-unix-domain-socket.
Networking IS used since we think it is a good 'wheel'.
Indeed, David is right that instead of adding a new chunk of code we can
re-use the
existing one. But we do have some 'new' (afraid to tell virtualization)
problems that
might prevent us of using a standard virtual nic:
- Even if we can teach iptables to ignore this interface, other
3rd firewall might not obey: What if the VM is a Checkpoint firewall?
What if the VM is windows? + using a non MS firewall?
- Who will assign IPs for the vnic? How can I assure there is no ip
clash?
The standard dhcp for the other standard vnics might not be in
our control.

So I do understand the idea of using a standard network interface. It's
just not that simple.
So ideas to handle the above are welcomed.
Otherwise we might need to go back to serial/pv-serial approach.

btw: here are the usages/next usages of vmchannel:
VMchannel is a host-guest interface and in the future guest-guest interface.
Currently/soon it is used for
- guest statistics
- guest info
- guest single sign own
- guest log-in log-out
- mouse channel for multiple monitors
- cut&paste (guest-host, sometimes client-host-guest, company
firewall blocks client-guest).
- fencing (potentially)

tw2: without virtualization we wouldn't have new passionate issues to
discuss about!
Cheers,
Dor