add dante device discovery via mdns and ptp clock master detection

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

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")
+}