I noticed that Firefox would always use Wi-Fi for screensharing, even if the reMarkables also connected over USB and advertised 10.11.99.1 as an ICE candidate.
In about:webrtc, Firefox initially only exposed my laptop's Wi-Fi address as a local candidate. The USB interface (10.11.99.5) was missing.
After granting the rmfakecloud site camera or microphone permission, Firefox also exposed the USB interface. ICE then selected:
10.11.99.5 <-> 10.11.99.1
and rmfakecloud reported:
[screenshare] peer: 10.11.99.1 (active)
Removing the media permission makes the USB candidate disappear again.
This seems to be intentional Firefox behavior. A Mozilla WebRTC developer explains that without capture permission, Firefox only uses the interface used to load the origin as a privacy measure, to avoid exposing additional local addresses: Bug 1970426, comment 4.
Since rmfakecloud only uses a WebRTC data channel and doesn't actually need camera/microphone access, this is quite unexpected.
Might be worth adding a short Firefox note to the screensharing docs. Another option could be to detect Firefox together with a reMarkable USB ICE candidate and show an explanation offering to request the required media permission before starting the connection.
I noticed that Firefox would always use Wi-Fi for screensharing, even if the reMarkables also connected over USB and advertised
10.11.99.1as an ICE candidate.In
about:webrtc, Firefox initially only exposed my laptop's Wi-Fi address as a local candidate. The USB interface (10.11.99.5) was missing.After granting the rmfakecloud site camera or microphone permission, Firefox also exposed the USB interface. ICE then selected:
and rmfakecloud reported:
Removing the media permission makes the USB candidate disappear again.
This seems to be intentional Firefox behavior. A Mozilla WebRTC developer explains that without capture permission, Firefox only uses the interface used to load the origin as a privacy measure, to avoid exposing additional local addresses: Bug 1970426, comment 4.
Since rmfakecloud only uses a WebRTC data channel and doesn't actually need camera/microphone access, this is quite unexpected.
Might be worth adding a short Firefox note to the screensharing docs. Another option could be to detect Firefox together with a reMarkable USB ICE candidate and show an explanation offering to request the required media permission before starting the connection.