[Users] Add NIC directly to VM (Dedicated)

[Shahar Havivi]

On 10.02.13 16:16, Matt . wrote:
> Hi Shahar,
> 
> Thanks, I need to work this out further to have it 100% visible.
> 
> I wonder why I was able in the past (3.1) to dedicate an NIC to a VM.
> 
> Do you also have an explanation why I cannot save a network configuration
> with a nic in DHCP mode ? It complains about a wrong IP and I have seen it
> should be a bug. Is this right ?
How did you that...
I.e can you tell me the steps that you made in the UI? (for both cases)
> 
> Cheers,
> 
> Matt
> 
> 
> 2013/2/10 Shahar Havivi <shaharh at redhat.com>
> 
> > On 10.02.13 14:13, Dan Kenigsberg wrote:
> > > On Sun, Feb 10, 2013 at 12:19:57PM +0100, Matt . wrote:
> > > > Hi,
> > > >
> > > > For setting up a firewall in a VM I would like to add 2 of my 4 nics
> > > > directly to a VM.
> > > >
> > > > In my previous setup I thought I have done that, but at the moment I
> > cannot
> > > > figure this out and cannot find the docs to accomplish this.
> > > >
> > > > I would like to dedicate those 2 nics to my firewall VM's to avoid
> > sharing
> > > > them using a network per accident to other VM's.
> > > >
> > > > How is this be done at the moment ?
> > >
> > > AFAIK it can be done only with a vdsm hook. You'd need to define your VM
> > > with no interface at all, but instead, mark it with a special custom
> > > property you define. Then, you should write a hook that adds the two
> > > host interfaces to the VM, by means of either
> > > http://libvirt.org/formatdomain.html#elementsNICSDirect or
> > > http://libvirt.org/formatdomain.html#elementsNICSHostdev
> > >
> > > Most probably, you would need to pin your firewall VM to a specific
> > > host.
> > >
> > > Writing a hook is not too complex, but it requires understanding of how
> > > vdsm and libvirt works. You can take
> > > http://gerrit.ovirt.org/gitweb?p=vdsm.git;a=tree;f=vdsm_hooks/vmfex as a
> > > reference, or ask for specific guidance here.
> > >
> > > Dan.
> > Dan is right,
> > Currently you can do it via hook,
> > We do have promisc mode but currently we have mirroring mode only (ie you
> > can
> > monitor each VM traffic but cannot intercept it).
> > The way to do it is via layer 2.
> >
> > its best to implement after_vm_start hook and use ebtables.
> > you can pass to the hook the network name.
> > when you have the network name you can prob for its mac address and in the
> > libvirt xml
> > you can view the interfaces that are part of that network and get the mac
> > addresses as well. (look at other hooks as Dan point out)
> >
> > when you have the network name the network mac and the target interface you
> > can use ebtables:
> > 1. set the bridge in promisc mode
> >    $ ifconfig <netwok name> promisc
> > 2. traffic to the monitoring machine
> >    $ ebtables -t nat -A PREROUTING -d 00:1a:4a:16:01:51 -i eth0 -j dnat
> > --to-destination 00:1a:4a:16:01:11
> > 3. traffic from the monitoring machine
> >    $ ebtables -t nat -A PREROUTING -s 00:1a:4a:16:01:51 -i vnet0 -j dnat
> > --to-destination 00:1a:4a:16:01:11
> >
> > 1. set the network interface in promiscous mode
> > 2. traffic that ment to the vm mac will go to the destination mac
> > 2. traffic that sent from the vm mac will go to the destination mac
> >
> > note that the -i <interface> is the interface name and I think it can be
> > omitted...
> >
> > Shahar Havivi.
> >