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

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Date:   Thu, 19 Nov 2020 15:41:13 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Alexander Graf <graf@...zon.com>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>, netdev@...r.kernel.org,
        Jorgen Hansen <jhansen@...are.com>,
        "David S. Miller" <davem@...emloft.net>,
        Dexuan Cui <decui@...rosoft.com>,
        Anthony Liguori <aliguori@...zon.com>,
        David Duncan <davdunc@...zon.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        Alexander Graf <graf@...zon.de>
Subject: Re: [PATCH net] vsock: forward all packets to the host when no H2G
 is registered

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@...are.com>
>>>Cc: Dexuan Cui <decui@...rosoft.com>
>>>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>>>Reported-by: Andra Paraschiv <andraprs@...zon.com>
>>>Tested-by: Andra Paraschiv <andraprs@...zon.com>
>>>Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>>>---
>>>  net/vmw_vsock/af_vsock.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>Acked-by: Stefan Hajnoczi <stefanha@...hat.com>
>
>
>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