allow remote debugging again

Dockerfile.template

@@ -38,6 +38,9 @@ RUN usermod -a -G audio,video,tty chromium
 RUN curl -skL https://raw.githubusercontent.com/balena-labs-projects/audio/master/scripts/alsa-bridge/debian-setup.sh| sh
 ENV PULSE_SERVER=tcp:audio:4317
 
+# install socat to forard chromiums debug port
+RUN install_packages socat
+
 COPY VERSION .
 
 # Start app

readme.md

@@ -92,7 +92,7 @@ The following environment variables allow configuration of the `browser` block:
 |`WINDOW_SIZE`|`x,y`|Detected screen resolution|Sets the browser window size, such as `800,600`. <br/> **Note:** Reverse the dimensions if you also rotate the display to `left` or `right` |
 |`WINDOW_POSITION`|`x,y`|`0,0`|Specifies the browser window position on the screen|
 |`API_PORT`|port number|5011|Specifies the port number the API runs on|
-|`REMOTE_DEBUG_PORT`|port number|35173|Specifies the port number the chrome remote debugger runs on|
+|`REMOTE_DEBUG_PORT`|port number|35173|Specifies the port number the chrome remote debugger runs on. The actual port a client (like chrome) might connect to it will be REMOTE_DEBUG_PORT + 1 due to a deprecation of [this chromium feature](https://issues.chromium.org/issues/41487252).|
 |`AUTO_REFRESH`|interval|0 (disabled)|Specifies the number of seconds before the page automatically refreshes|
 
 ---

src/start.sh

@@ -68,4 +68,13 @@ environment="${environment::-1}"
 
 # launch Chromium and whitelist the enVars so that they pass through to the su session
 su -w $environment -c "export DISPLAY=:$DISPLAY_NUM && startx /usr/src/app/startx.sh $CURSOR" - chromium
+
+# forward the chromium remote debugging port from 0.0.0.0 to localhost to deal with the dropped support to listen on all interfaces (https://issues.chromium.org/issues/41487252)
+REMOTE_DEBUG_PORT=${REMOTE_DEBUG_PORT:-35173}
+REMOTE_DEBUG_FORWARD_PORT=$(($REMOTE_DEBUG_PORT+1))
+echo "Forwarding remote debugging port 0.0.0.0:$REMOTE_DEBUG_FORWARD_PORT to (internal) localhost:$REMOTE_DEBUG_PORT"
+socat TCP-LISTEN:${REMOTE_DEBUG_FORWARD_PORT},fork,reuseaddr TCP:localhost:${REMOTE_DEBUG_PORT} &
+
+# TODO: We should use REMOTE_DEBUG_PORT as the main env var, and handle the forwarding internally instead of this workaround-convention. The main api to a user should remain REMOTE_DEBUG_PORT
+
 balena-idle