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

Anthony Liguori
2008-12-15T15:02:29Z

David Miller wrote:
> From: Gleb Natapov <gleb@redhat.com>
> Date: Sun, 14 Dec 2008 13:50:55 +0200
>
>
>> It is undesirable to use TCP/IP for this purpose since network
>> connectivity may not exist between host and guest and if it exists the
>> traffic can be not routable between host and guest for security reasons
>> or TCP/IP traffic can be firewalled (by mistake) by unsuspecting VM user.
>>
>
> I don't really accept this argument, sorry.
>

I couldn't agree more. That doesn't mean I don't think this isn't
valuable though.

Each of these sockets are going to be connected to a backend (to
implement guest<=>copy/paste for instance). We want to implement those
backends in userspace and preferably in QEMU.

Using some raw protocol over ethernet means you don't have reliability.
If you use a protocol to get reliability (like TCP), you now have to
implement a full TCP/IP stack in userspace or get the host kernel
involved. I'd rather not get the host kernel involved from a security
perspective.

An inherently reliable socket transport solves the above problem while
keeping things simple. Note, this is not a new concept. There is
already an AF_IUCV for s390. VMware is also developing an AF_VMCI
socket family.

Regards,

Anthony Liguori