Infer VPN packet traffic class

agents/rap-node-agent/internal/mesh/server.go

@@ -833,7 +833,7 @@ func (s Server) handleVPNPacketHTTP(w http.ResponseWriter, r *http.Request, clus
 			http.Error(w, ErrRouteNotFound.Error(), vpnIngressStatusCode(ErrRouteNotFound))
 			return true
 		}
-		trafficClass := r.Header.Get("X-RAP-Traffic-Class")
+		trafficClass := inferVPNPacketTrafficClass(r.Header.Get("X-RAP-Traffic-Class"), packets)
 		var sendErr error
 		if classIngress, ok := s.VPNPacketIngress.(VPNPacketIngressTrafficClass); ok {
 			sendErr = classIngress.SendClientPacketBatchWithTrafficClass(r.Context(), clusterID, vpnConnectionID, trafficClass, packets)
@@ -951,7 +951,7 @@ func (s Server) readVPNPacketWebSocket(ctx context.Context, conn *websocket.Conn
 			}
 			continue
 		}
-		sendErr := s.sendVPNPacketWebSocketBatch(ctx, clusterID, vpnConnectionID, trafficClass, packets, !backendFallbackAllowed)
+		sendErr := s.sendVPNPacketWebSocketBatch(ctx, clusterID, vpnConnectionID, inferVPNPacketTrafficClass(trafficClass, packets), packets, !backendFallbackAllowed)
 		if sendErr != nil {
 			if !backendFallbackAllowed {
 				s.logFabricServiceChannelViolation(nil, clusterID, channelID, vpnConnectionID, backendRelayPolicy, "fabric_route_send_failed_backend_fallback_blocked", sendErr.Error())

agents/rap-node-agent/internal/mesh/server_test.go

@@ -4523,6 +4523,55 @@ func TestFabricServiceChannelVPNPacketWebSocketPreservesTrafficClass(t *testing.
 	}
 }
 
+func TestFabricServiceChannelVPNPacketWebSocketInfersInteractiveTrafficClass(t *testing.T) {
+	ingress := &recordingVPNPacketIngress{
+		receive: [][]byte{[]byte("reply")},
+	}
+	server := httptest.NewServer(Server{
+		Local:            PeerIdentity{ClusterID: "cluster-1", NodeID: "entry-1"},
+		VPNPacketIngress: ingress,
+	}.Handler())
+	defer server.Close()
+
+	wsURL := "ws" + strings.TrimPrefix(server.URL, "http") + "/api/v1/clusters/cluster-1/fabric/service-channels/channel-1/vpn-connections/vpn-1/packets/ws"
+	headers := http.Header{}
+	headers.Set("Authorization", "Bearer rap_fsc_testtoken")
+	headers.Set("X-RAP-Service-Class", FabricServiceClassVPNPackets)
+	headers.Set("X-RAP-Channel-Class", ProductionChannelVPNPacket)
+	headers.Set("X-RAP-Fabric-Channel-ID", "channel-1")
+	conn, _, err := websocket.DefaultDialer.Dial(wsURL, headers)
+	if err != nil {
+		t.Fatalf("dial websocket: %v", err)
+	}
+	defer conn.Close()
+
+	packet := testVPNIPv4TCPPacket([4]byte{10, 77, 0, 2}, [4]byte{192, 168, 200, 95}, 51000, 3389, 0x02)
+	if err := conn.WriteMessage(websocket.BinaryMessage, encodeVPNIngressPacketBatch([][]byte{packet})); err != nil {
+		t.Fatalf("write packet batch: %v", err)
+	}
+	if err := conn.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
+		t.Fatalf("set read deadline: %v", err)
+	}
+	if _, _, err := conn.ReadMessage(); err != nil {
+		t.Fatalf("read packet batch: %v", err)
+	}
+
+	deadline := time.Now().Add(2 * time.Second)
+	for {
+		ingress.mu.Lock()
+		trafficClass := ingress.trafficClass
+		sent := append([][]byte(nil), ingress.sent...)
+		ingress.mu.Unlock()
+		if trafficClass == "interactive" && len(sent) == 1 {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("traffic class = %q sent packets = %#v, want inferred interactive packet", trafficClass, sent)
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+}
+
 func TestVPNPacketIngressWebSocketFallsBackToBackendRelay(t *testing.T) {
 	var backendBody []byte
 	postSeen := make(chan struct{}, 1)
@@ -4707,6 +4756,24 @@ func (i *recordingVPNPacketIngress) ReceiveClientPacketBatch(_ context.Context,
 	return packets, nil
 }
 
+func testVPNIPv4TCPPacket(src [4]byte, dst [4]byte, srcPort uint16, dstPort uint16, flags byte) []byte {
+	packet := make([]byte, 40)
+	packet[0] = 0x45
+	packet[2] = 0
+	packet[3] = 40
+	packet[8] = 64
+	packet[9] = 6
+	copy(packet[12:16], src[:])
+	copy(packet[16:20], dst[:])
+	packet[20] = byte(srcPort >> 8)
+	packet[21] = byte(srcPort)
+	packet[22] = byte(dstPort >> 8)
+	packet[23] = byte(dstPort)
+	packet[32] = 0x50
+	packet[33] = flags
+	return packet
+}
+
 func hasProductionForwardEvent(events []ProductionForwardLogEntry, event string) bool {
 	for _, item := range events {
 		if item.Event == event {

agents/rap-node-agent/internal/mesh/vpn_packet.go

@@ -5,6 +5,7 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"strings"
 	"time"
 )
 
@@ -119,3 +120,28 @@ func cleanProductionVPNPacketBatch(packets [][]byte) [][]byte {
 	}
 	return cleaned
 }
+
+func inferVPNPacketTrafficClass(explicit string, packets [][]byte) string {
+	explicit = strings.TrimSpace(strings.ToLower(explicit))
+	if explicit != "" && explicit != "bulk" {
+		return explicit
+	}
+	for _, packet := range packets {
+		if isVPNPacketTCPControl(packet) {
+			return "interactive"
+		}
+	}
+	return explicit
+}
+
+func isVPNPacketTCPControl(packet []byte) bool {
+	if len(packet) < 20 || packet[0]>>4 != 4 {
+		return false
+	}
+	ihl := int(packet[0]&0x0f) * 4
+	if ihl < 20 || len(packet) < ihl+20 || packet[9] != 6 {
+		return false
+	}
+	flags := packet[ihl+13]
+	return flags&0x17 != 0
+}