On Mon, Feb 17, 2020 at 06:31:21PM +0100, Stefano Garzarella wrote:
> Linux 5.6 added the new well-known VMADDR_CID_LOCAL for
> local communication.
> 
> This patch explains how to use it and remove the legacy
> VMADDR_CID_RESERVED no longer available.
> 
> Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> v3:
>     * rephrased "Previous versions" part [Jorgen]
> v2:
>     * rephrased "Local communication" description [Stefan]
>     * added a mention of previous versions that supported
>       loopback only in the guest [Stefan]
> ---
>  man7/vsock.7 | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/man7/vsock.7 b/man7/vsock.7
> index c5ffcf07d..219e3505f 100644
> --- a/man7/vsock.7
> +++ b/man7/vsock.7
> @@ -127,8 +127,8 @@ There are several special addresses:
>  means any address for binding;
>  .B VMADDR_CID_HYPERVISOR
>  (0) is reserved for services built into the hypervisor;
> -.B VMADDR_CID_RESERVED
> -(1) must not be used;
> +.B VMADDR_CID_LOCAL
> +(1) is the well-known address for local communication (loopback);
>  .B VMADDR_CID_HOST
>  (2)
>  is the well-known address of the host.
> @@ -164,6 +164,16 @@ Consider using
>  .B VMADDR_CID_ANY
>  when binding instead of getting the local CID with
>  .BR IOCTL_VM_SOCKETS_GET_LOCAL_CID .
> +.SS Local communication
> +The
> +.B VMADDR_CID_LOCAL
> +(1) directs packets to the same host that generated them. This is useful

Please see my comment on v2.  "The VMADDR_CID_LOCAL (1) directs packets
..." sounds unnatural.  Please drop "The".