Re: [Libguestfs] [PATCH FOR DISCUSSION ONLY 0/2] v2v: Copy static IP address information over for Windows guests (RHBZ#1626503).

On Wed, Dec 5, 2018 at 12:01 PM Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > On Wed, Dec 05, 2018 at 09:01:16AM +0000, Roman Kagan wrote: > > On Tue, Dec 04, 2018 at 05:29:31PM +0000, Richard W.M. Jones wrote: > > > This patch is just for discussion. There are still a couple of issues > > > that I'm trying to fix. > > > > Sorry if I missed the original discussion on that, but why is copying > > the static IP configuraition even considered to be a good thing? > > > > For one, it's unlikely that the IP address will remain valid in the > > target environment. > > For our v2v conversions (generally from VMware to oVirt or OpenStack) > we're trying to maintain a near-identical network configuration on > both sides. So for example a guest will have the same MAC addresses > before and after and, if using DHCP, will pick up the exact same IP > address (probably served by the same DHCP server) and be able to > access the same set of services etc. > > Also we're doing like 1000s of VMs in one go, so manual > reconfiguration of anything is a non-starter. > > However let me describe the problem we're seeing, as it is a bit more > general and might even apply in some cloud scenarios. If you have a > Windows guest which starts out with a static IP address (no DHCP) it > might be configured like this on VMware: > > 00:50:56:01:02:03 192.168.128.10 vmxnet3 "Ethernet0" EnableDHCP=0 > > After conversion we preserve the MAC address and add virtio drivers, > but the new netkvm.sys driver just adds a new network interface so > it'll end up like this: > > (no hardware) 192.168.128.10 vmxnet3 "Ethernet0" EnableDHCP=0 > 00:50:56:01:02:03 (no address) netkvm "Ethernet1" EnableDHCP=1 > > It has no address in the second case because this is a non-DHCP > network. (The DHCP situation is better because the second network > will be assigned the right IP address because of the preserved MAC > address, although it still has the unnecessary network adapter.) > > Note that Windows < 10 doesn't have a concept of persistent network > names like we do in Linux which mostly solves this problem. (Windows > 10 on the other hand does save the MAC address in the Registry, but I > haven't fully investigated yet what it's doing.) > > Anyway if you have another suggestion how to solve this, I'm all ears ... > For other areas we'd fix things up using an Ansible post-copy script, > but in this case we can't do that since Ansible cannot reconfigure a > guest that has no working network. > As you mention, using Ansible means that the IP address of the VM is correctly set. In another discussion, you mentioned using transient DHCP, but would mean that we reconfigure one of the NICs before conversion to use DHCP. That would alter the original VM.

And in the case of multiple NICs, how do we know which one to reconfigure.

That would be quite specific to each customer, meaning customized playbook / role.

And IIRC, there's a good chance that it breaks WinRM configuration with regards to certificates, meaning reconfiguring WinRM after DHCP and after conversion.

But maybe I'm too pessimistic ;) > > For two, in a typical cloud setup static IP addresses are configured by > > some sort of a cloud-specific management agent, and bypassing it is > > likely to cause conflicts. > In the case of OpenStack, we keep the MAC address by creating the network ports with it and the IP address pre-allocated. This allows neutron to have working security groups. As Richard says, we're looking at the case of a massive migration where adapting the VM is out of scope. It's a mainly a 1:1 relationship. Anyway, we're still looking at more complex scenarios with tenant networks and floating IPs. It promises to be fun :) > > For three, network configuration is a notoriously complex thing. I > > think I can recall a dozen of network configuration systems in Linux > > that claimed to provide the ultimate solution to all problems and none > > that delivered to the promise. I guess in Windows the situation is > > hardly much simpler. Creating yet another universal solution doesn't > > appear to be in scope for v2v (if realistic at all); and I'm not sure > > that having a very limited solution for a very basic use case only is > > better than explicitly telling the user not to rely on v2v for network > > configuration. > > Rich.