add multicast flow transmitter discovery via mdns _netaudio-chan service

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

mdns.go

@@ -31,6 +31,19 @@ func extractDanteName(s string) string {
 	return name
 }
 
+func extractDanteChanService(s string) (channel, device string) {
+	idx := strings.Index(s, "._netaudio-chan.")
+	if idx <= 0 {
+		return "", ""
+	}
+	name := s[:idx]
+	at := strings.Index(name, "@")
+	if at <= 0 {
+		return "", ""
+	}
+	return name[:at], name[at+1:]
+}
+
 func isDanteService(s string) bool {
 	return strings.Contains(s, "_netaudio-") || strings.Contains(s, "._dante")
 }
@@ -108,6 +121,7 @@ func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.
 	srvTargets := map[string]string{}
 	danteNames := map[string]bool{}
 	danteARCPorts := map[string]uint16{}
+	danteTxChannels := map[string]string{} // device name -> channel names
 	skaarhojNames := map[string]bool{}
 
 	for _, rr := range allRecords {
@@ -143,6 +157,16 @@ func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.
 						danteARCPorts[name] = r.Port
 					}
 				}
+				if strings.Contains(r.Hdr.Name, "_netaudio-chan.") {
+					channel, device := extractDanteChanService(r.Hdr.Name)
+					if channel != "" && device != "" {
+						if existing, ok := danteTxChannels[device]; ok {
+							danteTxChannels[device] = existing + "," + channel
+						} else {
+							danteTxChannels[device] = channel
+						}
+					}
+				}
 			}
 			if isSkaarhojService(r.Hdr.Name) {
 				name := extractSkaarhojName(r.Hdr.Name)
@@ -171,6 +195,23 @@ func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.
 		t.nodes.UpdateDante(name, ip, arcPort)
 	}
 
+	for device, channels := range danteTxChannels {
+		var ip net.IP
+		if target, ok := srvTargets[device]; ok {
+			ip = aRecords[target]
+		}
+		if ip == nil {
+			ip = aRecords[device+".local"]
+		}
+		if ip == nil {
+			ip = srcIP
+		}
+		if t.DebugMDNS {
+			log.Printf("[mdns] %s: dante tx channels %s@%s (%s)", ifaceName, channels, device, ip)
+		}
+		t.nodes.UpdateDanteTxChannels(device, ip, channels)
+	}
+
 	for name := range skaarhojNames {
 		var ip net.IP
 		if target, ok := srvTargets[name]; ok {