On 11/14/2012 05:42 PM, Mark Wu wrote:
On 11/14/2012 07:53 PM, Gary Kotton wrote:
On 11/14/2012 11:53 AM, Livnat Peer wrote:
On 14/11/12 00:28, Adam Litke wrote:
On Sun, Nov 11, 2012 at 09:46:43AM -0500, Alon Bar-Lev wrote:

----- Original Message -----
From: "Dan Kenigsberg"<dan...@redhat.com>
To: vdsm-de...@fedorahosted.org
Sent: Sunday, November 11, 2012 4:07:30 PM
Subject: [vdsm] Future of Vdsm network configuration


Nowadays, when vdsm receives the setupNetowrk verb, it mangles
/etc/sysconfig/network-scripts/ifcfg-* files and restarts the network
service, so they are read by the responsible SysV service.

This is very much Fedora-oriented, and not up with the new themes
in Linux network configuration. Since we want oVirt and Vdsm to be
distribution agnostic, and support new features, we have to change.

setupNetwork is responsible for two different things:
(1) configure the host networking interfaces, and
(2) create virtual networks for guests and connect the to the world
over (1).

Functionality (2) is provided by building Linux software bridges, and
vlan devices. I'd like to explore moving it to Open vSwitch, which
enable a host of functionalities that we currently lack (e.g.
tunneling). One thing that worries me is the need to reimplement our
config snapshot/recovery on ovs's database.

As far as I know, ovs is unable to maintain host level parameters of
interfaces (e.g. eth0's IPv4 address), so we need another
tool for functionality (1): either speak to NetworkManager directly,
to use NetCF, via its libvirt virInterface* wrapper.

I have minor worries about NetCF's breadth of testing and usage; I
it is intended to be cross-platform, but unlike ovs, I am not aware
of a
wide Debian usage thereof. On the other hand, its API is ready for
usage for quite a while.

NetworkManager has become ubiquitous, and we'd better integrate with
better than our current setting of NM_CONTROLLED=no. But as DPB tells
we'd better offload integration with NM to libvirt.

We would like to take Network configuration in VDSM to the next level
and make it distribution agnostic in addition for setting the
infrastructure for more advanced features to be used going forward.
The path we think of taking is to integrate with OVS and for feature
completeness use NetCF, via its libvirt virInterface* wrapper. Any
comments or feedback on this proposal is welcomed.

Thanks to the oVirt net team members who's input has helped writing

As far as I see this, network manager is a monster that is a huge dependency to have just to create bridges or configure network interfaces... It is true that on a host where network manager lives it would be not polite to define network resources not via its interface, however I don't like we force network

libvirt is long not used as virtualization library but system management agent, I am not sure this is the best system agent I would have chosen.

I think that all the terms and building blocks got lost in time... and the
result integration became more and more complex.

Stabilizing such multi-layered component environment is much harder than
monolithic environment.

I would really want to see vdsm as monolithic component with full control over its resources, I believe this is the only way vdsm can be stable enough to be
production grade.

Hypervisor should be a total slave of manager (or cluster), so I have no problem in bypassing/disabling any distribution specific tool in favour of
atoms (brctl, iproute), in non persistence mode.

I know this derive some more work, but I don't think it is that complex to
implement and maintain.

Just my 2 cents...
I couldn't disagree more. What you are suggesting requires that we reimplement every single networking feature in oVirt by ourselves. If we want to support the (absolutely critical) goal of being distro agnostic, then we need to implement the same functionality across multiple distros too. This is more work than we will ever be able to keep up with. If you think it's hard to stabilize the integration of an external networking library, imagine how hard it will be to stabilize our own rewritten and buggy version. This is not how open source is supposed to work. We should be assembling distinct, modular, pre-existing components together when they are available. If NetworkManager has integration problems, let's work upstream to fix them. If it's dependencies are too great, let's modularize it so we don't need to ship the parts that we don't need.

I agree with Adam on this one, reimplementing the networking management
layer by ourselves using only atoms seems like duplication of work that
was already done and available for our use both by NM and by libvirt.

Yes, it is not perfect (far from it actually) but I think we better
focus our efforts around adding new functionalities to VDSM and
improving the current robustness of the code (we have issues regardless
of any external component we're using).

For the sake of being distribution agnostic I support the original plan
proposed by danken, using OVS combined with libvirt virInterface* wrapper.

The addition of OVS is nice and refreshing (it is the new black). The issue with OVS is that a controller is required, there are a number of proprietary once and there are open source solutions. Something/someone needs to configure and manage the OVS. Just adding the libvirt support is not enough - in a nut shell this is just a matter of setting the network type for the vnic and passing a few additional parameters. Managing and assigning physical NICs to OVS is interesting and challenging. Do you guys have any thoughts about how you want to go about this?

Can we just start with running ovs in standalone mode at first?

Yes, most certainly.
It could have the basic forward function based on MAC-learning and bond/vlans/tunnel function by specifying related options when adding a new port. We could connect each physical nic for vm network with an ovs bridge, and then the VM can get external network access. I agree with that without adding a controller, we can't get a unified control panel. But I think the standalone mode could fit current oVirt network model well.
Gary, please correct me if I am wrong or any suggestions from you?

You are correct. This is certainly one way of achieving a first step for integrating with the OVS. My concerns are as follows (maybe some of them do not exist :)):
1. Boot process with binding to physical NICS to the OVS
2. The OVS maintains a database. This may need to be cleaned of tap devices when the appliance reboots - lets take an edge case into account - say the appliance has a number of VMs running - there will be tap devices for these VMs registered with the OVS. If there is a exception or power failure the appliance will reset. These devices will still be registered when the appliance reboots. Who cleans them and when? 3. What about the traditional bridged network - will these be migrated to OVS. The idea of moving to OVS is great. I just think that all of the flows should be mapped out listed on a wiki. This will give a nice picture of how the integration can achieved.



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