add dante device discovery via mdns and ptp clock master detection

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

arp.go

@@ -126,3 +126,13 @@ func normalizeMACAddress(mac string) string {
 	}
 	return strings.Join(parts, ":")
 }
+
+func (t *Tendrils) requestARP(ip net.IP) {
+	if t.DisableARP {
+		return
+	}
+	conn, err := net.DialTimeout("udp4", ip.String()+":1", 100*time.Millisecond)
+	if err == nil {
+		conn.Close()
+	}
+}

cmd/tendrils/main.go

@@ -14,6 +14,7 @@ func main() {
 	noIGMP := flag.Bool("no-igmp", false, "disable IGMP querier")
 	noMDNS := flag.Bool("no-mdns", false, "disable mDNS discovery")
 	noArtNet := flag.Bool("no-artnet", false, "disable Art-Net discovery")
+	noDante := flag.Bool("no-dante", false, "disable Dante discovery")
 	logEvents := flag.Bool("log-events", false, "log node events")
 	logNodes := flag.Bool("log-nodes", false, "log full node details on changes")
 	debugARP := flag.Bool("debug-arp", false, "debug ARP discovery")
@@ -22,6 +23,7 @@ func main() {
 	debugIGMP := flag.Bool("debug-igmp", false, "debug IGMP querier")
 	debugMDNS := flag.Bool("debug-mdns", false, "debug mDNS discovery")
 	debugArtNet := flag.Bool("debug-artnet", false, "debug Art-Net discovery")
+	debugDante := flag.Bool("debug-dante", false, "debug Dante discovery")
 	flag.Parse()
 
 	t := tendrils.New()
@@ -32,6 +34,7 @@ func main() {
 	t.DisableIGMP = *noIGMP
 	t.DisableMDNS = *noMDNS
 	t.DisableArtNet = *noArtNet
+	t.DisableDante = *noDante
 	t.LogEvents = *logEvents
 	t.LogNodes = *logNodes
 	t.DebugARP = *debugARP
@@ -40,5 +43,6 @@ func main() {
 	t.DebugIGMP = *debugIGMP
 	t.DebugMDNS = *debugMDNS
 	t.DebugArtNet = *debugArtNet
+	t.DebugDante = *debugDante
 	t.Run()
 }

dante.go

@@ -0,0 +1,152 @@
+package tendrils
+
+import (
+	"context"
+	"log"
+	"net"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+func (t *Tendrils) listenDante(ctx context.Context, iface net.Interface) {
+	go t.queryDanteMDNS(ctx, iface)
+	go t.listenPTP(ctx, iface)
+}
+
+func (t *Tendrils) queryDanteMDNS(ctx context.Context, iface net.Interface) {
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return
+	}
+
+	var srcIP net.IP
+	for _, addr := range addrs {
+		if ipnet, ok := addr.(*net.IPNet); ok && ipnet.IP.To4() != nil {
+			srcIP = ipnet.IP.To4()
+			break
+		}
+	}
+	if srcIP == nil {
+		return
+	}
+
+	ticker := time.NewTicker(30 * time.Second)
+	defer ticker.Stop()
+
+	t.sendDanteMDNSQuery(iface.Name, srcIP)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			t.sendDanteMDNSQuery(iface.Name, srcIP)
+		}
+	}
+}
+
+func (t *Tendrils) sendDanteMDNSQuery(ifaceName string, srcIP net.IP) {
+	conn, err := net.DialUDP("udp4", &net.UDPAddr{IP: srcIP}, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 251), Port: 5353})
+	if err != nil {
+		return
+	}
+	defer conn.Close()
+
+	services := []string{
+		"_netaudio-arc._udp.local.",
+		"_netaudio-cmc._udp.local.",
+		"_netaudio-dbc._udp.local.",
+		"_netaudio-chan._udp.local.",
+		"_dantevideo._udp.local.",
+		"_dantevid-flow._udp.local.",
+	}
+
+	for _, service := range services {
+		msg := new(dns.Msg)
+		msg.SetQuestion(service, dns.TypePTR)
+		msg.RecursionDesired = false
+
+		data, err := msg.Pack()
+		if err != nil {
+			continue
+		}
+
+		conn.Write(data)
+	}
+
+	if t.DebugDante {
+		log.Printf("[dante] %s: sent mdns queries for netaudio services", ifaceName)
+	}
+}
+
+func (t *Tendrils) listenPTP(ctx context.Context, iface net.Interface) {
+	addr, err := net.ResolveUDPAddr("udp4", "224.0.1.129:319")
+	if err != nil {
+		return
+	}
+
+	conn, err := net.ListenMulticastUDP("udp4", &iface, addr)
+	if err != nil {
+		if t.DebugDante {
+			log.Printf("[dante] %s: failed to listen ptp: %v", iface.Name, err)
+		}
+		return
+	}
+	defer conn.Close()
+
+	buf := make([]byte, 1500)
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		conn.SetReadDeadline(time.Now().Add(1 * time.Second))
+		n, src, err := conn.ReadFromUDP(buf)
+		if err != nil {
+			if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+				continue
+			}
+			continue
+		}
+
+		t.handlePTPPacket(iface.Name, src.IP, buf[:n])
+	}
+}
+
+func (t *Tendrils) handlePTPPacket(ifaceName string, srcIP net.IP, data []byte) {
+	if len(data) < 34 {
+		return
+	}
+
+	messageType := data[0] & 0x0f
+
+	if messageType != 0x0b {
+		return
+	}
+
+	if len(data) < 64 {
+		return
+	}
+
+	clockClass := data[48]
+	clockAccuracy := data[49]
+	priority1 := data[47]
+	priority2 := data[51]
+
+	if t.DebugDante {
+		log.Printf("[dante] %s: ptp announce from %s class=%d accuracy=%d p1=%d p2=%d",
+			ifaceName, srcIP, clockClass, clockAccuracy, priority1, priority2)
+	}
+
+	t.nodes.SetDanteClockMaster(srcIP)
+}
+
+func (n *Nodes) UpdateDante(name string, ip net.IP) {
+	if n.t.DebugDante {
+		log.Printf("[dante] mdns response: %s -> %s", name, ip)
+	}
+	n.Update(nil, nil, []net.IP{ip}, "", name, "dante")
+}

mdns.go

@@ -14,6 +14,27 @@ const (
 	mdnsAddr = "224.0.0.251:5353"
 )
 
+func extractDanteName(s string) string {
+	var name string
+	for _, prefix := range []string{"._netaudio-", "._dante"} {
+		if idx := strings.Index(s, prefix); idx > 0 {
+			name = s[:idx]
+			break
+		}
+	}
+	if name == "" {
+		return ""
+	}
+	if at := strings.LastIndex(name, "@"); at >= 0 {
+		name = name[at+1:]
+	}
+	return name
+}
+
+func isDanteService(s string) bool {
+	return strings.Contains(s, "_netaudio-") || strings.Contains(s, "._dante")
+}
+
 func (t *Tendrils) listenMDNS(ctx context.Context, iface net.Interface) {
 	addr, err := net.ResolveUDPAddr("udp4", mdnsAddr)
 	if err != nil {
@@ -66,26 +87,67 @@ func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.
 	var hostname string
 
 	allRecords := append(msg.Answer, msg.Extra...)
+
+	if t.DebugMDNS {
+		for _, rr := range allRecords {
+			log.Printf("[mdns] %s: record %s", ifaceName, rr.String())
+		}
+	}
+
+	aRecords := map[string]net.IP{}
+	srvTargets := map[string]string{}
+	danteNames := map[string]bool{}
+
 	for _, rr := range allRecords {
 		switch r := rr.(type) {
 		case *dns.A:
-			name := strings.TrimSuffix(r.Hdr.Name, ".local.")
-			name = strings.TrimSuffix(name, ".")
-			if name != "" && r.A.Equal(srcIP) {
-				hostname = name
+			name := strings.TrimSuffix(r.Hdr.Name, ".")
+			aRecords[name] = r.A
+			localName := strings.TrimSuffix(name, ".local")
+			if localName != "" && r.A.Equal(srcIP) {
+				hostname = localName
 			}
 		case *dns.AAAA:
 			continue
 		case *dns.PTR:
+			if isDanteService(r.Hdr.Name) {
+				name := extractDanteName(r.Ptr)
+				if name != "" {
+					danteNames[name] = true
+				}
+			} else {
 				name := strings.TrimSuffix(r.Ptr, ".local.")
 				name = strings.TrimSuffix(name, ".")
 				if hostname == "" && name != "" && !strings.HasPrefix(name, "_") {
 					hostname = name
 				}
 			}
+		case *dns.SRV:
+			if isDanteService(r.Hdr.Name) {
+				name := extractDanteName(r.Hdr.Name)
+				target := strings.TrimSuffix(r.Target, ".")
+				if name != "" && target != "" {
+					srvTargets[name] = target
+				}
+			}
+		}
 	}
 
-	if hostname != "" {
+	for name := range danteNames {
+		var ip net.IP
+		if target, ok := srvTargets[name]; ok {
+			ip = aRecords[target]
+		}
+		if ip == nil {
+			ip = aRecords[name+".local"]
+		}
+		if ip == nil {
+			ip = srcIP
+		}
+		t.nodes.UpdateDante(name, ip)
+	}
+
+	if len(danteNames) == 0 && hostname != "" {
 		if t.DebugMDNS {
 			log.Printf("[mdns] %s: %s -> %s", ifaceName, srcIP, hostname)
 		}

nodes.go

@@ -106,6 +106,7 @@ type Node struct {
 	Interfaces        map[string]*Interface
 	MACTable          map[string]string // peer MAC -> local interface name
 	PoEBudget         *PoEBudget
+	IsDanteClockMaster bool
 	pollTrigger       chan struct{}
 }
 
@@ -148,9 +149,28 @@ func (g *MulticastGroup) Name() string {
 		return fmt.Sprintf("sacn:%d", universe)
 	}
 
+	if ip[0] == 239 && ip[1] >= 69 && ip[1] <= 71 {
+		flowID := (int(ip[1]-69) << 16) | (int(ip[2]) << 8) | int(ip[3])
+		return fmt.Sprintf("dante-mcast:%d", flowID)
+	}
+
 	return g.IP.String()
 }
 
+func (g *MulticastGroup) IsDante() bool {
+	ip := g.IP.To4()
+	if ip == nil {
+		return false
+	}
+	if ip[0] == 239 && ip[1] == 255 {
+		return false
+	}
+	if ip[0] == 239 && ip[1] >= 69 && ip[1] <= 71 {
+		return true
+	}
+	return false
+}
+
 type MulticastMembership struct {
 	Node     *Node
 	LastSeen time.Time
@@ -197,7 +217,7 @@ func (n *Nodes) Update(target *Node, mac net.HardwareAddr, ips []net.IP, ifaceNa
 	n.mu.Lock()
 	defer n.mu.Unlock()
 
-	if mac == nil && target == nil {
+	if mac == nil && target == nil && len(ips) == 0 {
 		return
 	}
 
@@ -228,6 +248,17 @@ func (n *Nodes) Update(target *Node, mac net.HardwareAddr, ips []net.IP, ifaceNa
 		}
 	}
 
+	if targetID == -1 {
+		for _, ip := range ips {
+			if id, exists := n.ipIndex[ip.String()]; exists {
+				if _, nodeExists := n.nodes[id]; nodeExists {
+					targetID = id
+					break
+				}
+			}
+		}
+	}
+
 	var node *Node
 	if targetID == -1 {
 		targetID = n.nextID
@@ -247,6 +278,15 @@ func (n *Nodes) Update(target *Node, mac net.HardwareAddr, ips []net.IP, ifaceNa
 	var added []string
 	if mac != nil {
 		added = n.updateNodeInterface(node, targetID, mac, ips, ifaceName)
+	} else {
+		for _, ip := range ips {
+			ipKey := ip.String()
+			if _, exists := n.ipIndex[ipKey]; !exists {
+				n.ipIndex[ipKey] = targetID
+				added = append(added, "ip="+ipKey)
+				go n.t.requestARP(ip)
+			}
+		}
 	}
 
 	if nodeName != "" && node.Name == "" {
@@ -463,6 +503,33 @@ func (n *Nodes) UpdateMACTable(node *Node, peerMAC net.HardwareAddr, ifaceName s
 	node.MACTable[peerMAC.String()] = ifaceName
 }
 
+func (n *Nodes) SetDanteClockMaster(ip net.IP) {
+	n.mu.RLock()
+	currentMaster := ""
+	for _, node := range n.nodes {
+		if node.IsDanteClockMaster {
+			currentMaster = ip.String()
+			break
+		}
+	}
+	n.mu.RUnlock()
+
+	if currentMaster != ip.String() {
+		n.Update(nil, nil, []net.IP{ip}, "", "", "ptp")
+	}
+
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	for _, node := range n.nodes {
+		node.IsDanteClockMaster = false
+	}
+
+	if id, exists := n.ipIndex[ip.String()]; exists {
+		n.nodes[id].IsDanteClockMaster = true
+	}
+}
+
 func (n *Nodes) UpdateMulticastMembership(sourceIP, groupIP net.IP) {
 	n.mu.Lock()
 	defer n.mu.Unlock()
@@ -514,8 +581,15 @@ func (n *Nodes) logNode(node *Node) {
 	if name == "" {
 		name = "??"
 	}
+	var tags []string
 	if node.PoEBudget != nil {
-		log.Printf("[node] %s [poe:%.0f/%.0fW]", name, node.PoEBudget.Power, node.PoEBudget.MaxPower)
+		tags = append(tags, fmt.Sprintf("poe:%.0f/%.0fW", node.PoEBudget.Power, node.PoEBudget.MaxPower))
+	}
+	if node.IsDanteClockMaster {
+		tags = append(tags, "dante-clock-master")
+	}
+	if len(tags) > 0 {
+		log.Printf("[node] %s [%s]", name, joinParts(tags))
 	} else {
 		log.Printf("[node] %s", name)
 	}

tendrils.go

@@ -22,6 +22,7 @@ type Tendrils struct {
 	DisableIGMP   bool
 	DisableMDNS   bool
 	DisableArtNet bool
+	DisableDante  bool
 	LogEvents     bool
 	LogNodes      bool
 	DebugARP      bool
@@ -30,6 +31,7 @@ type Tendrils struct {
 	DebugIGMP     bool
 	DebugMDNS     bool
 	DebugArtNet   bool
+	DebugDante    bool
 }
 
 func New() *Tendrils {
@@ -195,4 +197,7 @@ func (t *Tendrils) startInterface(ctx context.Context, iface net.Interface) {
 	if !t.DisableArtNet {
 		go t.listenArtNet(ctx, iface)
 	}
+	if !t.DisableDante {
+		go t.listenDante(ctx, iface)
+	}
 }