Implement cluster-wide deterministic MAC generator

MACGeneratorClusterDeterministic generates the same MAC address for
a given app interface on every node in the cluster.
Additionally, the probability of MAC address conflict with other
devices outside the cluster is very low (same property
that MACGeneratorGloballyScoped provides).

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

pkg/pillar/cmd/zedrouter/appnetwork.go

@@ -418,7 +418,9 @@ func (z *zedrouter) selectMACGeneratorForApp(status *types.AppNetworkStatus) err
 	macGenerator, _, err := z.appMACGeneratorMap.Get(appKey)
 	if err != nil || macGenerator == types.MACGeneratorUnspecified {
 		// New app or an existing app but without MAC generator ID persisted.
-		if z.localLegacyMACAddr {
+		if z.withKubeNetworking {
+			macGenerator = types.MACGeneratorClusterDeterministic
+		} else if z.localLegacyMACAddr {
 			// Use older node-scoped MAC address generator.
 			macGenerator = types.MACGeneratorNodeScoped
 		} else {

pkg/pillar/cmd/zedrouter/ipam.go

@@ -49,7 +49,16 @@ func (z *zedrouter) generateAppMac(adapterNum int, appStatus *types.AppNetworkSt
 	h.Write(netInstStatus.UUIDandVersion.UUID[:])
 	nums := make([]byte, 2)
 	nums[0] = byte(adapterNum)
-	nums[1] = byte(appStatus.AppNum)
+	if appStatus.MACGenerator != types.MACGeneratorClusterDeterministic {
+		// Skipped for MACGeneratorClusterDeterministic.
+		// Appending AppNum into the hash calculation could result in cluster
+		// nodes generating different MAC address for the same app interface.
+		// This is because the order of application config processing can
+		// differ between nodes.
+		// This is undesirable. When application is rescheduled to another node,
+		// the aim is to preserve MAC addresses of its interfaces.
+		nums[1] = byte(appStatus.AppNum)
+	}
 	h.Write(nums)
 	hash := h.Sum(nil)
 	switch netInstStatus.Type {
@@ -63,7 +72,7 @@ func (z *zedrouter) generateAppMac(adapterNum int, appStatus *types.AppNetworkSt
 		case types.MACGeneratorNodeScoped:
 			return net.HardwareAddr{0x00, 0x16, 0x3e, 0x00,
 				byte(adapterNum), byte(appStatus.AppNum)}
-		case types.MACGeneratorGloballyScoped:
+		case types.MACGeneratorGloballyScoped, types.MACGeneratorClusterDeterministic:
 			mac := net.HardwareAddr{hash[0], hash[1], hash[2], hash[3], hash[4], hash[5]}
 			// Mark this MAC address as unicast by setting the I/G bit to zero.
 			mac[0] &= ^byte(1)

pkg/pillar/types/zedroutertypes.go

@@ -1360,4 +1360,10 @@ const (
 	// MACGeneratorGloballyScoped generates MAC addresses which are with high probability
 	// unique globally, i.e. across entire fleet of devices.
 	MACGeneratorGloballyScoped = 2
+	// MACGeneratorClusterDeterministic generates the same MAC address for a given
+	// app interface on every node in the cluster.
+	// Additionally, the probability of MAC address conflict with other devices outside
+	// the cluster is very low (same property that MACGeneratorGloballyScoped
+	// provides).
+	MACGeneratorClusterDeterministic = 3
 )