Re: [PATCH net] vsock: forward all packets to the host when no H2G is registered

[Stefano Garzarella]

On Thu, Nov 19, 2020 at 03:25:42PM +0100, Alexander Graf wrote:
> On 19.11.20 15:03, Stefan Hajnoczi wrote:
> > On Thu, Nov 12, 2020 at 02:38:37PM +0100, Stefano Garzarella wrote:
> > > Before commit c0cfa2d8a788 ("vsock: add multi-transports support"),
> > > if a G2H transport was loaded (e.g. virtio transport), every packets
> > > was forwarded to the host, regardless of the destination CID.
> > > The H2G transports implemented until then (vhost-vsock, VMCI) always
> > > responded with an error, if the destination CID was not
> > > VMADDR_CID_HOST.
> > >
> > > From that commit, we are using the remote CID to decide which
> > > transport to use, so packets with remote CID > VMADDR_CID_HOST(2)
> > > are sent only through H2G transport. If no H2G is available, packets
> > > are discarded directly in the guest.
> > >
> > > Some use cases (e.g. Nitro Enclaves [1]) rely on the old behaviour
> > > to implement sibling VMs communication, so we restore the old
> > > behavior when no H2G is registered.
> > > It will be up to the host to discard packets if the destination is
> > > not the right one. As it was already implemented before adding
> > > multi-transport support.
> > >
> > > Tested with nested QEMU/KVM by me and Nitro Enclaves by Andra.
> > >
> > > [1] Documentation/virt/ne_overview.rst
> > >
> > > Cc: Jorgen Hansen <jhansen@xxxxxxxxxx>
> > > Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
> > > Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
> > > Reported-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> > > Tested-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> > > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> > > ---
> > >  net/vmw_vsock/af_vsock.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > Acked-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
>
>
> Is there anything we have to do to also get this into the affected 
> stable trees? :)

The patch is already queued by Jakub in the netdev stable queue:
https://patchwork.kernel.org/bundle/netdev/stable/?series=382773&state=*

Stefano