VNC-Clipboard: Cannot send text from noVNC client to QEMU VNC-Server

[MarkusF42]

Bug description
It is currently not possible to send text via clipboard to QEMU VMs.
However it is possible to send text from VM to VNC-Client.

According to the qemu developers the fix should be to flush the streams with Z_FINISH
https://lists.nongnu.org/archive/html/qemu-devel/2023-11/msg05722.html

To Reproduce
Steps to reproduce the behavior:

1. Start a VM with
   -chardev 'qemu-vdagent,id=vdagent,name=vdagent,clipboard=on' -device 'virtserialport,chardev=vdagent,name=com.redhat.spice.0'
2. Connect to VM with noVNC
3. Click on Clipboard button
4. Insert text in Clipboard field
5. VM will start to hang when trying to paste this text

Expected behavior
Send text via vnc clipboard to QEMU VMs.

Client:

• OS: Debian 12
• Browser: Firefox
• Browser version: 115.4.0esr

Server:

• noVNC version: 1.4.0
• VNC server: QEMU 8.1.2

[CendioOssman]

This extension has been deployed for some time now, so I think that ship has sailed. Compatible implementations will need to be able to deal with a lack of an end marker, as there are many noVNC and TigerVNC deployments out there already. :/

I also checked the original UltraVNC implementation, and it also omits an end marker. So I'm afraid this is simply how this protocol works and QEMU will need to adapt.

[foxmox]

Hi,
FYI, a change for QEMU 8.2 to revert to the previous behavior when there is no end marker has already been picked up: https://lists.nongnu.org/archive/html/qemu-devel/2023-12/msg00423.html

[CendioOssman]

Glad to hear it. That means the issue should be resolved for users in the next upgrade.

I'll go ahead and close this issue then.