[multicast] fix the issue multicast does not work if antreaPolicy is …

…disabled

Currently, packetIn reason only supports 0 and 1. There is no more available packetIn reasons
as traceflow and antreaPolicy use both. Multicast reuses packetIn reason with antreaPolicy, and
uses a different register bit to indicate the real reason. There is no queue for packetIn reason
'PacketInReasonNP' if antreaPloicy is disabled. And multicast will not work then.

This patch fixes #3808

Signed-off-by: Bin Liu <biliu@vmware.com>

cmd/antrea-agent/agent.go

@@ -633,17 +633,8 @@ func run(o *Options) error {
 	}
 	go apiServer.Run(stopCh)
 
-	// Start PacketIn for features and specify their own reason.
-	var packetInReasons []uint8
-	if features.DefaultFeatureGate.Enabled(features.Traceflow) {
-		packetInReasons = append(packetInReasons, uint8(openflow.PacketInReasonTF))
-	}
-	if features.DefaultFeatureGate.Enabled(features.AntreaPolicy) {
-		packetInReasons = append(packetInReasons, uint8(openflow.PacketInReasonNP))
-	}
-	if len(packetInReasons) > 0 {
-		go ofClient.StartPacketInHandler(packetInReasons, stopCh)
-	}
+	// Start PacketIn
+	go ofClient.StartPacketInHandler(stopCh)
 
 	// Start the goroutine to periodically export IPFIX flow records.
 	if features.DefaultFeatureGate.Enabled(features.FlowExporter) {

pkg/agent/openflow/client.go

@@ -215,7 +215,7 @@ type Client interface {
 	// packets through registered handlers.
 	RegisterPacketInHandler(packetHandlerReason uint8, packetHandlerName string, packetInHandler interface{})
 
-	StartPacketInHandler(packetInStartedReason []uint8, stopCh <-chan struct{})
+	StartPacketInHandler(stopCh <-chan struct{})
 	// Get traffic metrics of each NetworkPolicy rule.
 	NetworkPolicyMetrics() map[uint32]*types.RuleMetric
 	// SendTCPPacketOut sends TCP packet as a packet-out to OVS.

pkg/agent/openflow/packetin.go

@@ -84,13 +84,13 @@ func newfeatureStartPacketIn(reason uint8, stopCh <-chan struct{}) *featureStart
 }
 
 // StartPacketInHandler is the starting point for processing feature packetin requests.
-func (c *client) StartPacketInHandler(packetInStartedReason []uint8, stopCh <-chan struct{}) {
-	if len(c.packetInHandlers) == 0 || len(packetInStartedReason) == 0 {
+func (c *client) StartPacketInHandler(stopCh <-chan struct{}) {
+	if len(c.packetInHandlers) == 0 {
 		return
 	}
 
 	// Iterate through each feature that starts packetin. Subscribe with their specified reason.
-	for _, reason := range packetInStartedReason {
+	for reason := range c.packetInHandlers {
 		featurePacketIn := newfeatureStartPacketIn(reason, stopCh)
 		err := c.subscribeFeaturePacketIn(featurePacketIn)
 		if err != nil {