DESK-MX9-L-TN-0003: Weston-rdp screen share

Info Box Applies to AURA Technical Notes

This application note has been validated using the kit version in the History table.

History
Issue Date	Notes
2024/09/26	DESK-MX9-L 5.x.x

Introduction

Weston-RDP is an RDP backend allowing to run a Weston environment without needing specific graphic hardware, or input devices. Users can interact with weston only by connecting using the RDP protocol.

A useful FOSDEM presentation illustrates the main topics about the RDP protocol integration and Yocto guidelines for enabling weston to remotely share the screen

Yocto recipes

To enable the RDP protocol on Weston, a simple way is to add a bbappend to the the Weston recipe, i.e. meta-desk-mx/recipes-graphics/wayland/weston_%.bbappend:

EXTRA_OEMESON:append = " -Dbackend-rdp=true"

DEPENDS:append = " freerdp"

PACKAGECONFIG:append = "rdp"

and add the freerdp package to the dave-image-devel target image:

diff --git a/recipes-core/images/dave-image-devel.bbappend b/recipes-core/images/dave-image-devel.bbappend
index 03b74b6..9e87565 100644
--- a/recipes-core/images/dave-image-devel.bbappend
+++ b/recipes-core/images/dave-image-devel.bbappend
@@ -16,6 +16,12 @@ IMAGE_FEATURES += " \
        hwcodecs \
 "
 
+# add freerdp
+
+IMAGE_INSTALL += " \
+       freerdp \
+"
+
 # add meta-desk packages
 
 IMAGE_INSTALL += " \

Weston in the target

Weston has to be aware of the screen share enabling during the service activation: both systems service file and the configuration file have to be properly modified using the following description.

weston.service

The systems weston service (i.e. /lib/systemd/system/weston.service) should be modified adding the screen-share.so module loading at the service activation:

[Service]
# Requires systemd-notify.so Weston plugin.
Type=notify
EnvironmentFile=/etc/default/weston
ExecStart=/usr/bin/weston --log=${XDG_RUNTIME_DIR}/weston.log --modules=systemd-notify.so,screen-share.so

weston.ini

In the same way, the configuration file (i.e. /etc/xdg/weston/weston.ini) should be modified for enabling the rdp-backend.so backend module with the proper TLS certificate and key:

[screen-share]
command=/usr/bin/weston --backend=rdp-backend.so --rdp-tls-cert=/etc/freerdp/keys/desk-mx93-rev1.crt --rdp-tls-key=/etc/freerdp/keys/desk-mx93-rev1.key --shell=fullscreen-shell.so --no-clients-resize --socket=wayland-1 --width=800 --height=480

The --width=800 --height=480 lets the client to properly configure the receiving window.

In the same [screen-share] section, adding the following line:

start-on-startup=true

will enable the backend to be started properly at the weston activation.

Before start the RDP protocol, the keys have to be created in the configured directory:

root@desk-mx93-rev1:~# mkdir -p /etc/freerdp/keys
root@desk-mx93-rev1:~# winpr-makecert -rdp -path /etc/freerdp/keys/

Usage example

On a Windows PC it is possible to start the Remote Desktop connections application: it is enough to set the AURA Evaluation Kit IP address to start the remote screen share:

Windows 11 Remote Desktop connection