[libvirt] Adding support to limit client connections for vnc/spice display driver

[Patil, Tushar]

Hello,


Greeting!!!


We are using KVM hypervisor driver for running OpenStack IaaS. Couple of months back we have reported one security issue [1] in OS. Basically we want to limit on the number of vnc client connections that can be opened by users for a given VM. I know that there is share policy where you can specify "VNC_SHARE_MODE_EXCLUSIVE" share mode. But it only allows one client connection to the vnc console, it will disconnect all previously opened vnc client connections. Since vnc display driver already has the data of client connections, it would be possible to add the logic to limit on the number of client connections.

What we want is the ability to specify threshold how many vnc client connections should be allowed at any given point of time in the domain xml for graphics device (especially for vnc/spice)?

Example
<graphics type="vnc" autoport="yes" keymap="en-us" listen="127.0.0.1"/, share-policy="limit-connections", connections="5">

Add support to accept new share policy "limit-connections'.
So in the above example, when user tries to open vnc display for the 6th time, then the request should be rejected.

I need your expert opinion in deciding whether it's a good idea to add this support in the vnc/spice display driver or this kind of constraint should be imposed outside libvirt?

[1] : https://bugs.launchpad.net/nova/+bug/1227575

Tushar


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