Re: [Xen-devel] Attaching pre created tap interfaces to a VM in Xen for Routed Networking

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Hi

This list is mainly about Xen development.

You might have better luck asking this kind of questions on
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Wei.

On Fri, May 24, 2013 at 09:11:04PM -0700, Raghu Nallamothu wrote:
> Hi All.,
>          I am not sure if this is possible in xen via Libvirt, but what I
> am trying to do is, I want libvirt to launch a VM and attach a pre-created
> tap interface to that VM ( I do not want XEN to create one, as I am running
> a lot of custom scripts on my tap interface). I also dont want xen to
> attach this tap interface to a bridge.
> 
> For example, lets say I have created a tap interface with name "tap123456"
> when libvirt launches my VM in xen, I want the VM to read its networking
> info from this tap interface.
> 
> But I wasn't so successful in doing this when ever I am trying to do this,
> I am seeing the following error message "VmError: Device 0 (vif) could not
> be connected. Hotplug scripts not working." and "error: POST operation
> failed: xend_post: error from xen daemon: (xend.err 'Device 0 (vif) could
> not be connected. Cannot rename interface vif4.0. An interface with name
> tap12345 already exists.')". But I dont want xen to create  another
> interface and rename it, rather want xen to use the existing one
> 
> === output of lsmod ===
> 
> bash-4.1# lsmod | grep xen
> xen_acpi_processor      4465  0
> xen_netback            25455  0 [permanent]
> xen_gntdev              9504  2
> xen_evtchn              4899  3
> xenfs                   2943  1
> xen_privcmd             4972  19 xenfs
> 
> ==== end of output ====
> 
> My Configuration : Centos 6.2 with Xen 4.2.5 along with Libvirt
> 
> 
> Libvirt Configuration file,
> 
> <domain type='xen'>
> 
> <name>raghu_12345</name>
> <uuid>12113325-d948-4a1b-b673-888a16b90726</uuid>
> <memory>1048576</memory>
> <vcpu>1</vcpu>
> 
> 
> <os>
> <type>hvm</type>
> <loader>/usr/lib/xen/boot/hvmloader</loader>
> <boot dev='hd'/>
> </os>
> 
> <on_poweroff>destroy</on_poweroff>
> <on_reboot>restart</on_reboot>
> <on_crash>restart</on_crash>
> 
> <features>
> <pae/>
> <acpi/>
> <apic/>
> </features>
> 
> 
> <devices>
> <emulator>/usr/lib/xen/bin/qemu-dm</emulator>
> <interface type="ethernet">
> <mac address='00:25:90:3f:25:91'/>  <!-- I want this mac to be mac address
> of a vm -->
> <target dev='tap123456'/>
> </interface>
> <disk type='file' device='disk'>
> <source file='~/tmp/lucid.img'/>
> <target dev='hda'/>
> </disk>
> <console type='pty'>
> <target port='0'/>
> </console>
> <graphics port='-1' type='vnc' autoport='yes' listen='0.0.0.0'/>
> </devices>
> 
> </domain>
> 
> 
> I have a pre-created  tap interface with name 'tap123456'  with all the
> networking setup with dhcp and dns running.
> 
> Thanks for your time and help.
> 
> Regards
> Raghu

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