From 6394b55191f1cf57c037b414e2bf5797787a6f23 Mon Sep 17 00:00:00 2001
From: Ian Gulliver <git@flamingcow.io>
Date: Fri, 23 Jan 2026 09:27:45 -0800
Subject: [PATCH] send mdns queries from listener socket for multicast
 responses

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 dante.go | 69 --------------------------------------------------------
 mdns.go  | 66 ++++++++++++++++++++++++-----------------------------
 2 files changed, 29 insertions(+), 106 deletions(-)

diff --git a/dante.go b/dante.go
index 2481499..19a4585 100644
--- a/dante.go
+++ b/dante.go
@@ -5,81 +5,12 @@ import (
 	"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.",
-		"_danteancil._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 {
diff --git a/mdns.go b/mdns.go
index f87f470..179275a 100644
--- a/mdns.go
+++ b/mdns.go
@@ -61,7 +61,7 @@ func (t *Tendrils) listenMDNS(ctx context.Context, iface net.Interface) {
 	}
 	defer conn.Close()
 
-	go t.runMDNSQuerier(ctx, iface)
+	go t.runMDNSQuerier(ctx, iface, conn)
 
 	buf := make([]byte, 65536)
 	for {
@@ -193,57 +193,49 @@ func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.
 	}
 }
 
-func (t *Tendrils) runMDNSQuerier(ctx context.Context, iface net.Interface) {
-	addrs, err := iface.Addrs()
-	if err != nil {
-		return
-	}
+var mdnsServices = []string{
+	"_services._dns-sd._udp.local.",
+	"_netaudio-arc._udp.local.",
+	"_netaudio-cmc._udp.local.",
+	"_netaudio-dbc._udp.local.",
+	"_netaudio-chan._udp.local.",
+	"_dantevideo._udp.local.",
+	"_danteancil._udp.local.",
+}
 
-	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(60 * time.Second)
+func (t *Tendrils) runMDNSQuerier(ctx context.Context, iface net.Interface, conn *net.UDPConn) {
+	ticker := time.NewTicker(30 * time.Second)
 	defer ticker.Stop()
 
-	t.sendMDNSQuery(iface.Name, srcIP)
+	t.sendMDNSQueries(iface.Name, conn)
 
 	for {
 		select {
 		case <-ctx.Done():
 			return
 		case <-ticker.C:
-			t.sendMDNSQuery(iface.Name, srcIP)
+			t.sendMDNSQueries(iface.Name, conn)
 		}
 	}
 }
 
-func (t *Tendrils) sendMDNSQuery(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
+func (t *Tendrils) sendMDNSQueries(ifaceName string, conn *net.UDPConn) {
+	dest := &net.UDPAddr{IP: net.IPv4(224, 0, 0, 251), Port: 5353}
+
+	for _, service := range mdnsServices {
+		msg := new(dns.Msg)
+		msg.SetQuestion(service, dns.TypePTR)
+		msg.RecursionDesired = false
+
+		data, err := msg.Pack()
+		if err != nil {
+			continue
+		}
+
+		conn.WriteToUDP(data, dest)
 	}
-	defer conn.Close()
-
-	msg := new(dns.Msg)
-	msg.SetQuestion("_services._dns-sd._udp.local.", dns.TypePTR)
-	msg.RecursionDesired = false
-
-	data, err := msg.Pack()
-	if err != nil {
-		return
-	}
-
-	conn.Write(data)
 
 	if t.DebugMDNS {
-		log.Printf("[mdns] %s: sent query", ifaceName)
+		log.Printf("[mdns] %s: sent queries for %d services", ifaceName, len(mdnsServices))
 	}
 }