Merge pull request #117 from cybozu-go/randomize-mac

Randomize MAC address for KVM

node.go

@@ -2,6 +2,7 @@ package placemat
 
 import (
 	"context"
+	"crypto/rand"
 	"crypto/sha1"
 	"errors"
 	"fmt"
@@ -267,7 +268,7 @@ func (n *Node) Start(ctx context.Context, r *Runtime, nodeCh chan<- bmcInfo) (*N
 		devParams := []string{
 			"virtio-net-pci",
 			fmt.Sprintf("netdev=%s", br.Name),
-			fmt.Sprintf("mac=%s", generateMACForKVM(n.Name)),
+			fmt.Sprintf("mac=%s", generateMACForKVM()),
 		}
 		if n.UEFI {
 			// disable iPXE boot
@@ -380,10 +381,14 @@ func (n *Node) Start(ctx context.Context, r *Runtime, nodeCh chan<- bmcInfo) (*N
 	return vm, err
 }
 
-func generateMACForKVM(name string) string {
+func generateMACForKVM() string {
 	vendorPrefix := "52:54:00" // QEMU's vendor prefix
-	bytes := sha1.Sum([]byte(name))
-	return fmt.Sprintf("%s:%02x:%02x:%02x", vendorPrefix, bytes[0], bytes[1], bytes[2])
+	buf := make([]byte, 3)
+	_, err := rand.Read(buf)
+	if err != nil {
+		panic(err)
+	}
+	return fmt.Sprintf("%s:%02x:%02x:%02x", vendorPrefix, buf[0], buf[1], buf[2])
 }
 
 func createNVRAM(ctx context.Context, p string) error {

node_test.go

@@ -6,11 +6,11 @@ import (
 )
 
 func TestGenerateRandomMacForKVM(t *testing.T) {
-	sut := generateMACForKVM("test")
+	sut := generateMACForKVM()
 	if len(sut) != 17 {
 		t.Fatal("length of MAC address string is not 17")
 	}
-	if sut == generateMACForKVM("hoge") {
+	if sut == generateMACForKVM() {
 		t.Fatal("it should generate unique address")
 	}
 	_, err := net.ParseMAC(sut)