[libvirt] invoking interface.script - missing interface name of domain

[Daniel P. Berrange]

On Tue, Jan 20, 2009 at 04:44:22PM +0100, Daniel Schwager wrote:
> Hi Daniel,
> 
> thx for the fast answer. 
> 
> > QEMU is responsible for passing arguments to the interface scripts,
> > so its out of libvirt's control. QEMU passes a single paramter to
> > the script, which is the name of the TAP device interface being
> > added.  If you don't give a <target dev='tap3'> libvirt generates
> > a TAP device name vnetXXXX.
> 
> If I do not specify the <target>-element inside of <interface>,
> your docu told me 
> 
> 	"The guest will have a tun device created with a name of vnetN,
> which can also be overridden with the <target> element."
> 	(http://www.libvirt.org/formatdomain.html#elementsNICS)
> 
> I understood this in the following way: I can remove the target-element
> and 
> I will get automatically a target name "vnet<N>" - if I do this, I will
> get an
> interfacename "(null") :
> 
> 5459 ?        Sl     0:01 /usr/bin/kvm -S -M pc -m 500 -smp 1 -name
> solidcam -uuid 60a8db24-86a5-f9fc-16ee-b60b32411dd8 -monitor pty -boot c
> -drive file=/srv/winxp127-xxx.dsk,if=ide,index=0,boot=on -net
> nic,macaddr=52:54:00:46:58:41,vlan=0 -net
> tap,ifname=(null),script=/etc/kvm/qemu-ifup,vlan=0 -serial pty -parallel
> none -usb -usbdevice tablet -vnc 0.0.0.0:0

That is a bug I'm afraid - it *should* pass the real auto-generated
interface name but for some reason it isn't. I see this is one of the 
XML configs we don't have tested in our xml -> ARGV conversion test.

> So, this means libvirt is NOT responsible for the naming auf the target.
> Maybe you have to clarify this in the docu.

> For my case, I have to write a domain-xml dynamically and specify the
> interface name (target-element) to the domain-xml
> like 
> 
>      <interface type='ethernet'>
>        <script path='/etc/kvm/qemu-ifup'/>
>        <target dev='my-new-name001122'/>
>      </interface>

Yes, explicitly giving a interface name is a reasonable workaround until
i fix the bug.

Daniel
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