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

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Date:   Thu, 19 Nov 2020 14:03:59 +0000
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     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 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>

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