Re: [PATCH net-next v2 2/4] vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag

[Stefano Garzarella]

On Fri, Dec 04, 2020 at 07:02:33PM +0200, Andra Paraschiv wrote:
> Add VMADDR_FLAG_TO_HOST vsock flag that is used to setup a vsock
> connection where all the packets are forwarded to the host.
>
> Then, using this type of vsock channel, vsock communication between
> sibling VMs can be built on top of it.
>
> Changelog
>
> v1 -> v2
>
> * New patch in v2, it was split from the first patch in the series.
> * Remove the default value for the vsock flags field.
> * Update the naming for the vsock flag to "VMADDR_FLAG_TO_HOST".
>
> Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> ---
> include/uapi/linux/vm_sockets.h | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/include/uapi/linux/vm_sockets.h b/include/uapi/linux/vm_sockets.h
> index 46735376a57a8..72e1a3d05682d 100644
> --- a/include/uapi/linux/vm_sockets.h
> +++ b/include/uapi/linux/vm_sockets.h
> @@ -114,6 +114,21 @@
>
> #define VMADDR_CID_HOST 2
>
> +/* The current default use case for the vsock channel is the following:
> + * local vsock communication between guest and host and nested VMs setup.
> + * In addition to this, implicitly, the vsock packets are forwarded to the host
> + * if no host->guest vsock transport is set.
> + *
> + * Set this flag value in the sockaddr_vm corresponding field if the vsock
> + * packets need to be always forwarded to the host. Using this behavior,
> + * vsock communication between sibling VMs can be setup.

Maybe we can add a sentence saying that this flag is set on the remote 
peer address for an incoming connection when it is routed from the host 
(local CID and remote CID > VMADDR_CID_HOST).

> + *
> + * This way can explicitly distinguish between vsock channels created for
> + * different use cases, such as nested VMs (or local communication between
> + * guest and host) and sibling VMs.
> + */
> +#define VMADDR_FLAG_TO_HOST 0x0001
> +
> /* Invalid vSockets version. */
>
> #define VM_SOCKETS_INVALID_VERSION -1U
> --
> 2.20.1 (Apple Git-117)
>
>
>
>
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