Add support for user-defined network interface order to domainmgr/kvm

Currently, when application has both virtual network interfaces
configured and some network devices directly assigned, EVE will first
attach virtual interfaces in the order that follows ACL IDs (a historical
workaround for missing interface order field), followed by directly assigned
network adapters, in the order of the AppInstanceConfig.adapters list.

To allow the user to specify the order between all application
network interfaces (across both virtual and passthrough devices), we
introduced a new boolean flag EnforceNetworkInterfaceOrder inside
the application instance config and allow the controller to pass the order
requirements for all the application network adapters.

For the KVM hypervisor, and depending on the application’s operating system,
we can influence the interface order through the PCI topology. A network
device that should appear earlier in the interface list is assigned a lower
PCI address. This ensures the desired network interface order, at least for
Linux-based operating systems with systemd (see [1]). However, there are
limitations when assigning multifunction PCI devices to applications.
Specifically, the functions of a multifunction device cannot be interleaved
with other virtual or passthrough devices. If the user configures a network
interface order that violates this constraint, EVE will report an error for
the application, and it will not be started.

[1] https://www.freedesktop.org/software/systemd/man/latest/systemd.net-naming-scheme.html

Signed-off-by: Milan Lenco <milan@zededa.com>

pkg/pillar/hypervisor/kubevirt.go

@@ -191,6 +191,12 @@ func (ctx kubevirtContext) Setup(status types.DomainStatus, config types.DomainC
 
 	logrus.Debugf("Setup called for Domain: %s, vmmode %v", domainName, config.VirtualizationMode)
 
+	if config.EnforceNetworkInterfaceOrder {
+		logrus.Errorf("Enforcing user-defined network interface order is not supported "+
+			"with the KubeVirt hypervisor. Ignoring EnforceNetworkInterfaceOrder flag "+
+			"for app %s", config.DisplayName)
+	}
+
 	if config.VirtualizationMode == types.NOHYPER {
 		if err := ctx.CreatePodConfig(domainName, config, status, diskStatusList, aa, file); err != nil {
 			return logError("failed to build kube pod config: %v", err)