vm: let libvirt choose the MAC address for us

There appear to be some weird conflicts within libvirt when creating a
VM with a MAC address that already has a DHCP lease. To work around
this, make sure to always get a fresh MAC address by letting libvirt
choose one for us.

Also adapt the tests; the fake libvirt implementation should "allocate"
a MAC address for us on DomainDefineXML. We also don't want to assert
the correctness of the returned MAC address anymore, because we don't
deal with that value anymore.

internal/virter/dhcp.go

@@ -75,13 +75,6 @@ func ipToID(ipnet net.IPNet, ip net.IP) (uint, error) {
 	return v - sv, nil
 }
 
-func qemuMAC(id uint) string {
-	id0 := byte((id >> 16) & 0xFF)
-	id1 := byte((id >> 8) & 0xFF)
-	id2 := byte(id & 0xFF)
-	return fmt.Sprintf("52:54:00:%02x:%02x:%02x", id0, id1, id2)
-}
-
 func (v *Virter) getIPNet(network libvirt.Network) (net.IPNet, error) {
 	ipNet := net.IPNet{}
 

internal/virter/libvirt_test.go

@@ -264,6 +264,11 @@ func (l *FakeLibvirtConnection) DomainDefineXML(XML string) (rDom libvirt.Domain
 	if err := description.Unmarshal(XML); err != nil {
 		return libvirt.Domain{}, fmt.Errorf("invalid domain XML: %w", err)
 	}
+	if description.Devices.Interfaces[0].MAC == nil {
+		description.Devices.Interfaces[0].MAC = &libvirtxml.DomainInterfaceMAC{
+			Address: "00:11:22:33:44:55",
+		}
+	}
 	l.domains[description.Name] = &FakeLibvirtDomain{
 		description: description,
 		persistent:  true,

internal/virter/libvirtxml.go

@@ -89,7 +89,7 @@ func vmDisksToLibvirtDisks(vmDisks []VMDisk) ([]lx.DomainDisk, error) {
 	return result, nil
 }
 
-func (v *Virter) vmXML(poolName string, vm VMConfig, mac string) (string, error) {
+func (v *Virter) vmXML(poolName string, vm VMConfig) (string, error) {
 	vmDisks := []VMDisk{
 		VMDisk{device: VMDiskDeviceDisk, poolName: poolName, volumeName: vm.Name, bus: "virtio", format: "qcow2"},
 		VMDisk{device: VMDiskDeviceCDROM, poolName: poolName, volumeName: ciDataVolumeName(vm.Name), bus: "ide", format: "raw"},
@@ -158,9 +158,6 @@ func (v *Virter) vmXML(poolName string, vm VMConfig, mac string) (string, error)
 			},
 			Interfaces: []lx.DomainInterface{
 				lx.DomainInterface{
-					MAC: &lx.DomainInterfaceMAC{
-						Address: mac,
-					},
 					Source: &lx.DomainInterfaceSource{
 						Network: &lx.DomainInterfaceSourceNetwork{
 							Network: v.networkName,

internal/virter/vm.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/LINBIT/virter/pkg/netcopy"
+	libvirtxml "github.com/libvirt/libvirt-go-xml"
 	"github.com/rck/unit"
 
 	log "github.com/sirupsen/logrus"
@@ -187,8 +188,7 @@ func diskVolumeName(vmName string, diskName string) string {
 }
 
 func (v *Virter) createVM(sp libvirt.StoragePool, vmConfig VMConfig) (net.IP, error) {
-	mac := qemuMAC(vmConfig.ID)
-	xml, err := v.vmXML(sp.Name, vmConfig, mac)
+	xml, err := v.vmXML(sp.Name, vmConfig)
 	if err != nil {
 		return nil, err
 	}
@@ -201,6 +201,19 @@ func (v *Virter) createVM(sp libvirt.StoragePool, vmConfig VMConfig) (net.IP, er
 		return nil, fmt.Errorf("could not define domain: %w", err)
 	}
 
+	domainXML, err := v.libvirt.DomainGetXMLDesc(d, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	domcfg := &libvirtxml.Domain{}
+	err = domcfg.Unmarshal(domainXML)
+	if err != nil {
+		return nil, err
+	}
+
+	mac := domcfg.Devices.Interfaces[0].MAC.Address
+
 	// Add DHCP entry after defining the VM to ensure that it can be
 	// removed when removing the VM, but before starting it to ensure that
 	// it gets the correct IP address

internal/virter/vm_test.go

@@ -71,7 +71,6 @@ func TestVMRun(t *testing.T) {
 	assert.Empty(t, l.vols[vmName].content)
 
 	host := l.network.description.IPs[0].DHCP.Hosts[0]
-	assert.Equal(t, "52:54:00:00:00:2a", host.MAC)
 	assert.Equal(t, "192.168.122.42", host.IP)
 
 	domain := l.domains[vmName]