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Re: [Xen-users] Xen Netloop module missing

On Thu, Jan 6, 2011 at 10:48 AM, Virajith Jalaparti
<virajith.j@xxxxxxxxx> wrote:
>> It means if you need xen netloop support, you need to have it compiled
>> either as module (CONFIG_XEN_NETDEV_LOOPBACK=y) or builtin
>> (CONFIG_XEN_NETDEV_LOOPBACK=y). If it's neither, then you can't use
>> it.
> Do both the cases (compiled as a module or builtin) have the same
> configuration? (CONFIG_XEN_NETDEV_LOOPBACK=y)

Typo on my part. When built as module, CONFIG_XEN_NETDEV_LOOPBACK=m

>>  You need to recompile the kernel.
> Is this as easy as just doing a "make world"?

Juding from your questions, the answer would be "no".

> Would that ensure that the
> kernel is re-compiled? The thing is when I do a "make world" the
> /boot/config-* file is re-created. How can I be sure that the new kernel is
> compiled with this flag enabled i.e. with the netloop module builtin?

Look at documentation (README, etc) found in xen source tarball. I
think something like

make linux-2.6-xen0-config CONFIGMODE=menuconfig

is necessary for 2.6.18 kernel.

Note that there are other kernels available for dom0:
and with newer (2.6.3x) kernels the process is similar with the usual
kernel compile process: make menuconfig, make, and so on. You just
need to enable xen-related options during menuconfig process.

>> Also, which Xen version are you using? Are you using the default
>> network-bridge or create your own bridges?
>> netloop is primarily needed for older versions of Xen where the
>> default bridged setup is :
>> - create virtual network device pairs for each dom0 interface (vif0.x
>> and vethx) using netloop module
>> - rename dom0 interfaces (eth0 ->  peth0, veth0 ->  eth0)
>> - create a bridge (xenbr0) with peth0 and vif0.0 as its members.
>> Newer bridge setup use "eth0" as bridge name, and doesn't need netloop
>> anymore.
>> It has nothing to do whatsoever with VM migration.
>> In short, if in your current setup your domU is able to access outside
>> network, most likely you don't need netloop support.
> I am using Xen-3.1.3 and I was creating my own bridges. In particular, I was
> using the following set of commands to set up the bridges in the original
> version of xen I had installed (from yum repos in CentOS).

If you use Centos, why would you need Xen 3.1.3, and why would you
need to compile your own kernel?
RHEL/Centos 5.5 comes with Xen 3.1.2+, and has a functional kernel-xen
by default.

> vconfig add peth2 513
> brctl addbr breth2.513
> brctl setfd breth2.513 0
> ip link set dev breth2.513 arp off multicast off up
> brctl addif breth2.513 peth2.513
> ip link set dev peth2.513 up
> ip link set dev vif0.4 arp off multicast off
> brctl addif breth2.513 vif0.4
> ip link set dev vif0.4 up
> ip link set dev veth4 name eth2.513 mtu 1400
> ip link set dev eth2.513 address `cat /sys/class/net/eth2/address`
> ifconfig eth2.513 $ip netmask up

You're mixing xen's default bridge script (which creates peth and
vif0.x, and need netloop support) with your own setup. Don't do that.

Just do everything using OS config files. For example, in my setup (I
use eth4 and vlan129. Adjust interface names, vlans, MAC, and IP with
your setup)

- comment-out network-script line on /etc/xen/xend-config.sxp
- some config files:
# cat /etc/sysconfig/network-scripts/ifcfg-eth4

# cat /etc/sysconfig/network-scripts/ifcfg-eth4.129

# cat /etc/sysconfig/network-scripts/ifcfg-br129

- assign domU to use br129 (or whatever bridge you use), with
something like this on your domU config file

vif = [ 'mac=00:16:3E:9A:89:3D, bridge=br129, vifname=myDomU-eth0' ]

Note that in this kind of setup you don't need netloop support.


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