Clipboard sharing protocol

This protocol allows an in-guest agent to share clipboard data with dom0, so that it could be integrated with an emulated frame buffer, such as that exposed by qemu over VNC.

Status

Status: version 0.1 (early draft)

Overview

The protocol is intended to be used over a 'channel' with name: org.xenproject.guest.clipboard.0.1

The protocol is a subset of the VNC RFB protocol (http://www.realvnc.com/docs/rfbproto.pdf). Since the main expected use is to integrate with a qemu VNC frame buffer, RFB primitives should be readily available in the implementation.

We use only the following messages:

• ProtocolVersion
• SecurityVersion
• ClientInit
• ServerInit
• ClientCutText
• ServerCutText

Protocol

The backend acts as the RFB server, the guest acts as the RFB client.

• The server sends 'ProtocolVersion' with RFB protocol version 3.8
• The client sends 'ProtocolVersion' with RFB protocol version 3.8
• The server sends a single security type: None
• The server sends a 'SecurityResult' indicating success
• The client sends a 'ClientInit' message with shared = 1
• The server sends a 'ServerInit' message with the frame buffer size set to (0, 0) and any valid pixel format

We now consider the connection established. The following messages are now possible:

• The server sends a 'ServerCutText' when it wants to push data into the guest's cut buffer
• The client sends a 'ClientCutText' when it wants to push data into the server's cut buffer