[libvirt-users] Can I update the DNS configuration of an existing network?

[Kees van Reeuwijk]

Hello,

As part of a research project on cloud management, I am developing 
software to create on-demand networks between VMs on different hosts. 
The deployment of the VMs themselves is done by OpenNebula, but for the 
management of the networks I have to bypass OpenNebula, and I talk 
directly with libvirt.

One of the features of our network management is that we allow network 
connections to be created and destroyed at any moment in the life of a 
VM. This means that we use hotplugging. It also means that we want a VM 
to discover its network parameters for a particular NIC using DHCP and DNS.

I have something that mostly works now: I create an XML for each 
network, I can hot-plug new NICs in the VM using libvirt, and DHCP on 
the new interface works. However, DNS does not work properly. I have to 
create a mapping between the MAC, IP address, and the name of a VM at 
the moment I create the network XML. Setting the MAC <-> IP mapping at 
that time is fine, but fixing the mapping between IP address and name at 
that time is not reasonable. I do not know what name will be used before 
I add a new machine, and during the lifetime of the network there may 
even be different names associated with a particular IP address.

Is there a way I can change/update the DNS configuration of a network 
after it has been created? I could simply create a new network XML file 
and stop/start the network, but I suspect that is too disruptive. Is 
there a less intrusive way to do this?

Another thing I would very much like to do is to talk to libvirt 
directly from my management software (written in Java), rather than 
through the command line. I know there is a Java API for libvirt, but I 
have not been able  to find any up-to-date documentation on it. Is the 
functionality that I need accessible through the Java API? Is there 
enough documentation of the API for this, and where is it?

-- 
Dr. Ir. Kees van Reeuwijk, Vrije Universiteit Amsterdam