[CentOS-virt] xenbr0 isn't created anymore

Mon Mar 31 21:45:24 UTC 2008
Ross S. W. Walker <rwalker at medallion.com>

Kai Schaetzl wrote:
> 8EF9022A7066 at MFG-NYC-EXCH2.mfg.prv>
> Reply-To: centos-virt at centos.org
> X-Rcpt-To: <centos-virt at centos.org>
> Ross S. W. Walker wrote on Mon, 31 Mar 2008 15:09:37 -0400:
> > You can use the tcpdump logs in wireshark, or you can yum install
> > wireshark and use that interactively right on the bridge.
> tcpdump -i eth0 port 67 doesn't reveal much. The requests just look the same 
> like from other clients. But I don't catch all replies it seems. The problem 
> is that I catch replies for some clients and not for some other clients. But 
> they still get an IP number, except for the ones in xen vms. So, it looks 
> like the command doesn't catch all DHCP traffic. Do you have a better 
> suggestion what to catch?

It's not all port 67, the DHCP client sends DHCPREQ via UDP port 67 to
the broadcast address UDP port 68, the DHCP server responds with a
DHCPOFFER from it's IP address UDP port 68 to the clients broadcast
address UDP port 67.

> Apart from that the bridging looks like yours if I remember right. eth0 
> bridges to peth0 and vifx.0. No xenbr or virbr anymore. No tap devices, 
> though. Looking thru man xm I found a dhcp = "dhcp" directive for the config 
> file, but it didn't change anything. 

BTW I discovered that the tap devices are from qemu running in HVM
mode. In HVM qemu does the network emulation and uses the kernel
tun device for creating it's network interfaces.

> > Yes, the problem is actually in the Xen API for 3.2, they added an
> > option in the API, but didn't provide a default value if the client
> > doesn't provide one, so it bombs.
> > 
> > I have a fix for it.
> Thanks, I have looked at the patches, but they seem to be for something 
> different. I checked if I can create a new VM with virt-manager and this 
> fails in the network device step. But I think that's yet another bug, we 
> already discussed here, there's also a patch for that.

If you can create a VM with virt-manager, then you don't have Xen 3.2
installed or properly installed...

> No, my problem is different from both.
> I get an error when running "xm new <vmname>". Going by the short definition 
> in the xm help output (they forgot to add new to man xm) and what you told 
> about xenstore I deduced I would need to run this command to add an already 
> existing VM config to the store so I can manage it. (If there's a different 
> way ...). And this fails with a python trace that was already mentioned on 
> the Xen lists and seems to indicate a missing python module:
> ImportError: No module named xmlproc
> Here's why I think I need "python-xml" or something similar:
> http://www.google.de/search?num=30&hl=de&q=ImportError+xmlproc+xensource
> Also, this error seems to be quite old, so I would expect it being fixed in 
> 3.2 rpms, which also points to an external source.
> Didn't you get this for "xm new"?

I never encountered this error. If you upgraded to Xen 3.2 did you upgrade
both the xen-3.2 and xen-libs-3.2 packages? Did you edit your grub config
too to load xen-3.2 as well?

BTW xmlproc is handled completely in xend I believe, it all works
fine on my host and I have no python-xml installed!


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