netdev - Re: [PATCH net-next v2 2/4] vm_sockets: Add VMADDR_FLAG_TO

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Date:   Mon, 7 Dec 2020 10:59:35 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Andra Paraschiv <andraprs@...zon.com>
Cc:     netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        David Duncan <davdunc@...zon.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Alexander Graf <graf@...zon.de>,
        Jorgen Hansen <jhansen@...are.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH net-next v2 2/4] vm_sockets: Add VMADDR_FLAG_TO_HOST
 vsock flag

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@...zon.com>
>---
> 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)
>
>
>
>
>Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.
>