[libvirt-users] Bridging Wireless Cards for KVM

[Joshua McKee]

Thanks! Unfortunately, I am running into the following issue when
attempting to use the generic ethernet configuration:

$ virsh -c qemu:///system create /tmp/generic.xml
error: Failed to create domain from /tmp/generic.xml
error: internal error process exited while connecting to monitor: kvm:
-netdev tap,id=hostnet0: could not configure /dev/net/tun: Operation not
permitted
kvm: -netdev tap,id=hostnet0: Device 'tap' could not be initialized

This is the network part of my xml file:

<devices>
   <interface type="ethernet"/>


 ...
  <devices>
    <interface type='ethernet'/>
    ...
    <interface type='ethernet'>
      <target dev='vnet7'/>
      <script path='/etc/qemu-ifup-mynet'/>
    </interface>
  </devices>
  ...



In my /etc/libvirt/qemu.conf file I have the following set:

user = "root"
group ="root"
dynamic ownership = 0
clear_emulator_capabilities = 0
cgroup_device_acl = [
    "/dev/null", "/dev/full", "/dev/zero",
    "/dev/random", "/dev/urandom",
    "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
    "/dev/rtc", "/dev/hpet",
    "/dev/net/tun",
]

I am running Ubuntu 12, which does not use SELinux.


On Fri, Aug 9, 2013 at 8:01 AM, Daniel P. Berrange <berrange at redhat.com>wrote:

> On Thu, Aug 08, 2013 at 08:55:27PM -0600, Joshua McKee wrote:
> > Hi,
> >
> > I hope this is the right place to ask this question. I was wondering if
> > there is a way to set up a KVM VM using an XML document as input into
> Virsh
> > that uses bridged networking over a wireless card.
> >
> > I understand that wireless cards to not natively support, but I was able
> to
> > find a working solution here:
> > http://blog.ericwhite.ca/articles/2011/04/creating-a-wireless-bridge/.
>
> Ok, that's slightly different. The traditional integration with Linux
> bridge devices is doing ethernet layer bridging - so all protocols
> like IPv4, IPv6, etc, etc will "just work".
>
> What that blog describes is protocol layer bridging, which with those
> instructions only works for IPv4.
>
> Libvirt doesn't have any explicit support for the latter. Though we have
> thought about implementing it in the virtual network APIs, we've never
> got around to it.
>
> > The issue is, I can use this bridge by calling KVM directly. However, I
> > cannot figure out how to get this same configuration on an XML file that
> I
> > input into Virsh for the creation of a VM.
> >
> > My understanding is that libvirt calls KVM/QEMU at some point, but I may
> be
> > mistaken.
>
> You might be able to get it working using the generic ethernet config
>
>    http://libvirt.org/formatdomain.html#elementsNICSEthernet
>
> That setup you specify a pre-created TAP device for the VM to use.
> Of course it is upto you todo the manal config steps described in
> that blog, so is more tedious from an admin pov.
>
>
> Daniel
> --
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