Re: [PATCH qemu-kvm] Add raw(af_packet) network backend to qemu

Sridhar Samudrala
2010-01-26T23:19:22Z

On Tue, 2010-01-26 at 14:50 -0600, Anthony Liguori wrote:
> On 01/26/2010 02:47 PM, Anthony Liguori wrote:
> > On 01/26/2010 02:40 PM, Sridhar Samudrala wrote:
> >> This patch adds raw socket backend to qemu and is based on Or Gerlitz's
> >> patch re-factored and ported to the latest qemu-kvm git tree.
> >> It also includes support for vnet_hdr option that enables gso/checksum
> >> offload with raw backend. You can find the linux kernel patch to support
> >> this feature here.
> >> http://thread.gmane.org/gmane.linux.network/150308
> >>
> >> Signed-off-by: Sridhar Samudrala<sri@us.ibm.com>
> >
> > See the previous discussion about the raw backend from Or's original
> > patch. There's no obvious reason why we should have this in addition
> > to a tun/tap backend.
> >
> > The only use-case I know of is macvlan but macvtap addresses this
> > functionality while not introduce the rather nasty security problems
> > associated with a raw backend.
>
> Not to mention that from a user perspective, raw makes almost no sense
> as it's an obscure socket protocol family.
Not clear what you mean here. AF_PACKET socket is just a transport
mechanism for the host kernel to put the packets from the guest directly
to an attached interface and vice-versa.

> A user wants to do useful things like bridged networking or direct VF
> assignment. We should have -net backends that reflect things that make
> sense to a user.

Binding to a SR-IOV VF is one of the use-case that is supported by raw
backend.

Thanks
Sridhar