add mdns hostname discovery and artnet universe tracking

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-01-22 23:59:32 -08:00
parent 7bced7b350
commit 536c2d3dc9
7 changed files with 570 additions and 16 deletions
--- a/artnet.go
+++ b/artnet.go
@@ -0,0 +1,366 @@
+package tendrils
+
+import (
+	"context"
+	"encoding/binary"
+	"fmt"
+	"log"
+	"net"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/fvbommel/sortorder"
+)
+
+const (
+	artNetPort     = 6454
+	artNetID       = "Art-Net\x00"
+	opPoll         = 0x2000
+	opPollReply    = 0x2100
+	protocolVersion = 14
+)
+
+type ArtNetNode struct {
+	IP        net.IP
+	MAC       net.HardwareAddr
+	ShortName string
+	LongName  string
+	Inputs    []int
+	Outputs   []int
+	LastSeen  time.Time
+}
+
+func (t *Tendrils) listenArtNet(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
+	}
+
+	conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: srcIP, Port: artNetPort})
+	if err != nil {
+		log.Printf("[ERROR] failed to listen artnet on %s: %v", iface.Name, err)
+		return
+	}
+	defer conn.Close()
+
+	go t.runArtNetPoller(ctx, iface, conn)
+
+	buf := make([]byte, 65536)
+	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.handleArtNetPacket(iface.Name, src.IP, buf[:n])
+	}
+}
+
+func (t *Tendrils) handleArtNetPacket(ifaceName string, srcIP net.IP, data []byte) {
+	if len(data) < 12 {
+		return
+	}
+
+	if string(data[:8]) != artNetID {
+		return
+	}
+
+	opcode := binary.LittleEndian.Uint16(data[8:10])
+
+	switch opcode {
+	case opPollReply:
+		t.handleArtPollReply(ifaceName, srcIP, data)
+	}
+}
+
+func (t *Tendrils) handleArtPollReply(ifaceName string, srcIP net.IP, data []byte) {
+	if len(data) < 207 {
+		return
+	}
+
+	ip := net.IPv4(data[10], data[11], data[12], data[13])
+
+	var mac net.HardwareAddr
+	if len(data) >= 207 {
+		mac = net.HardwareAddr(data[201:207])
+	}
+
+	shortName := strings.TrimRight(string(data[26:44]), "\x00")
+	longName := strings.TrimRight(string(data[44:108]), "\x00")
+
+	netSwitch := int(data[18])
+	subSwitch := int(data[19])
+
+	numPorts := int(data[173])
+	if numPorts > 4 {
+		numPorts = 4
+	}
+
+	var inputs, outputs []int
+	for i := 0; i < numPorts; i++ {
+		portType := data[174+i]
+		swIn := int(data[186+i])
+		swOut := int(data[190+i])
+
+		universe := netSwitch<<8 | subSwitch<<4
+
+		if portType&0x40 != 0 {
+			inputs = append(inputs, universe|swIn)
+		}
+		if portType&0x80 != 0 {
+			outputs = append(outputs, universe|swOut)
+		}
+	}
+
+	if t.DebugArtNet {
+		log.Printf("[artnet] %s: %s %s short=%q long=%q numPorts=%d portTypes=%v in=%v out=%v", ifaceName, ip, mac, shortName, longName, numPorts, data[174:178], inputs, outputs)
+	}
+
+	node := &ArtNetNode{
+		IP:        ip,
+		MAC:       mac,
+		ShortName: shortName,
+		LongName:  longName,
+		Inputs:    inputs,
+		Outputs:   outputs,
+		LastSeen:  time.Now(),
+	}
+
+	t.nodes.UpdateArtNet(node)
+
+	name := longName
+	if name == "" {
+		name = shortName
+	}
+	if name != "" {
+		t.nodes.Update(nil, mac, []net.IP{ip}, "", name, "artnet")
+	}
+}
+
+func (t *Tendrils) runArtNetPoller(ctx context.Context, iface net.Interface, conn *net.UDPConn) {
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return
+	}
+
+	var broadcast net.IP
+	for _, addr := range addrs {
+		if ipnet, ok := addr.(*net.IPNet); ok && ipnet.IP.To4() != nil {
+			ip := ipnet.IP.To4()
+			mask := ipnet.Mask
+			broadcast = make(net.IP, 4)
+			for i := 0; i < 4; i++ {
+				broadcast[i] = ip[i] | ^mask[i]
+			}
+			break
+		}
+	}
+	if broadcast == nil {
+		return
+	}
+
+	ticker := time.NewTicker(10 * time.Second)
+	defer ticker.Stop()
+
+	t.sendArtPoll(conn, broadcast, iface.Name)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			t.sendArtPoll(conn, broadcast, iface.Name)
+		}
+	}
+}
+
+func (t *Tendrils) sendArtPoll(conn *net.UDPConn, broadcast net.IP, ifaceName string) {
+	packet := make([]byte, 14)
+	copy(packet[0:8], artNetID)
+	binary.LittleEndian.PutUint16(packet[8:10], opPoll)
+	binary.LittleEndian.PutUint16(packet[10:12], protocolVersion)
+	packet[12] = 0x00
+	packet[13] = 0x00
+
+	_, err := conn.WriteToUDP(packet, &net.UDPAddr{IP: broadcast, Port: artNetPort})
+	if err != nil {
+		if t.DebugArtNet {
+			log.Printf("[artnet] %s: failed to send poll: %v", ifaceName, err)
+		}
+		return
+	}
+
+	if t.DebugArtNet {
+		log.Printf("[artnet] %s: sent poll to %s", ifaceName, broadcast)
+	}
+}
+
+type ArtNetNodes struct {
+	mu    sync.RWMutex
+	nodes map[string]*ArtNetNode
+}
+
+func NewArtNetNodes() *ArtNetNodes {
+	return &ArtNetNodes{
+		nodes: map[string]*ArtNetNode{},
+	}
+}
+
+func (a *ArtNetNodes) Update(node *ArtNetNode) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	key := node.IP.String()
+
+	existing, exists := a.nodes[key]
+	if exists {
+		for _, u := range node.Inputs {
+			if !containsInt(existing.Inputs, u) {
+				existing.Inputs = append(existing.Inputs, u)
+			}
+		}
+		for _, u := range node.Outputs {
+			if !containsInt(existing.Outputs, u) {
+				existing.Outputs = append(existing.Outputs, u)
+			}
+		}
+		existing.LastSeen = node.LastSeen
+		if node.ShortName != "" {
+			existing.ShortName = node.ShortName
+		}
+		if node.LongName != "" {
+			existing.LongName = node.LongName
+		}
+	} else {
+		a.nodes[key] = node
+	}
+}
+
+func containsInt(slice []int, val int) bool {
+	for _, v := range slice {
+		if v == val {
+			return true
+		}
+	}
+	return false
+}
+
+func (a *ArtNetNodes) Expire() {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	expireTime := time.Now().Add(-60 * time.Second)
+	for key, node := range a.nodes {
+		if node.LastSeen.Before(expireTime) {
+			delete(a.nodes, key)
+		}
+	}
+}
+
+func (a *ArtNetNodes) GetAll() []*ArtNetNode {
+	a.mu.RLock()
+	defer a.mu.RUnlock()
+	result := make([]*ArtNetNode, 0, len(a.nodes))
+	for _, node := range a.nodes {
+		result = append(result, node)
+	}
+	return result
+}
+
+func (a *ArtNetNodes) LogAll() {
+	a.Expire()
+
+	a.mu.RLock()
+	defer a.mu.RUnlock()
+
+	if len(a.nodes) == 0 {
+		return
+	}
+
+	var nodes []*ArtNetNode
+	for _, node := range a.nodes {
+		nodes = append(nodes, node)
+	}
+	sort.Slice(nodes, func(i, j int) bool {
+		return sortorder.NaturalLess(nodes[i].LongName, nodes[j].LongName)
+	})
+
+	inputUniverses := map[int][]string{}
+	outputUniverses := map[int][]string{}
+
+	for _, node := range nodes {
+		name := node.LongName
+		if name == "" {
+			name = node.ShortName
+		}
+		if name == "" {
+			name = node.IP.String()
+		}
+		for _, u := range node.Inputs {
+			inputUniverses[u] = append(inputUniverses[u], name)
+		}
+		for _, u := range node.Outputs {
+			outputUniverses[u] = append(outputUniverses[u], name)
+		}
+	}
+
+	var allUniverses []int
+	seen := map[int]bool{}
+	for u := range inputUniverses {
+		if !seen[u] {
+			allUniverses = append(allUniverses, u)
+			seen[u] = true
+		}
+	}
+	for u := range outputUniverses {
+		if !seen[u] {
+			allUniverses = append(allUniverses, u)
+			seen[u] = true
+		}
+	}
+	sort.Ints(allUniverses)
+
+	log.Printf("[sigusr1] ================ %d artnet universes ================", len(allUniverses))
+	for _, u := range allUniverses {
+		ins := inputUniverses[u]
+		outs := outputUniverses[u]
+		var parts []string
+		if len(ins) > 0 {
+			sort.Slice(ins, func(i, j int) bool { return sortorder.NaturalLess(ins[i], ins[j]) })
+			parts = append(parts, fmt.Sprintf("in:%v", ins))
+		}
+		if len(outs) > 0 {
+			sort.Slice(outs, func(i, j int) bool { return sortorder.NaturalLess(outs[i], outs[j]) })
+			parts = append(parts, fmt.Sprintf("out:%v", outs))
+		}
+		net := (u >> 8) & 0x7f
+		subnet := (u >> 4) & 0x0f
+		universe := u & 0x0f
+		log.Printf("[sigusr1]   artnet:%d (%d/%d/%d) %s", u, net, subnet, universe, strings.Join(parts, " "))
+	}
+}
+
+func (n *Nodes) UpdateArtNet(artNode *ArtNetNode) {
+	n.t.artnet.Update(artNode)
+}
--- a/cmd/tendrils/main.go
+++ b/cmd/tendrils/main.go
@@ -12,12 +12,16 @@ func main() {
 	noLLDP := flag.Bool("no-lldp", false, "disable LLDP discovery")
 	noSNMP := flag.Bool("no-snmp", false, "disable SNMP discovery")
 	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")
 	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")
 	debugLLDP := flag.Bool("debug-lldp", false, "debug LLDP discovery")
 	debugSNMP := flag.Bool("debug-snmp", false, "debug SNMP discovery")
 	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")
 	flag.Parse()

 	t := tendrils.New()
@@ -26,11 +30,15 @@ func main() {
 	t.DisableLLDP = *noLLDP
 	t.DisableSNMP = *noSNMP
 	t.DisableIGMP = *noIGMP
+	t.DisableMDNS = *noMDNS
+	t.DisableArtNet = *noArtNet
 	t.LogEvents = *logEvents
 	t.LogNodes = *logNodes
 	t.DebugARP = *debugARP
 	t.DebugLLDP = *debugLLDP
 	t.DebugSNMP = *debugSNMP
 	t.DebugIGMP = *debugIGMP
+	t.DebugMDNS = *debugMDNS
+	t.DebugArtNet = *debugArtNet
 	t.Run()
 }
--- a/go.mod
+++ b/go.mod
@@ -6,6 +6,13 @@ require (
 	github.com/fvbommel/sortorder v1.1.0
 	github.com/google/gopacket v1.1.19
 	github.com/gosnmp/gosnmp v1.42.1
+	github.com/miekg/dns v1.1.72
 )

-require golang.org/x/sys v0.13.0 // indirect
+require (
+	golang.org/x/mod v0.31.0 // indirect
+	golang.org/x/net v0.48.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/tools v0.40.0 // indirect
+)
--- a/go.sum
+++ b/go.sum
@@ -2,10 +2,14 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fvbommel/sortorder v1.1.0 h1:fUmoe+HLsBTctBDoaBwpQo5N+nrCp8g/BjKb/6ZQmYw=
 github.com/fvbommel/sortorder v1.1.0/go.mod h1:uk88iVf1ovNn1iLfgUVU2F9o5eO30ui720w+kxuqRs0=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/google/gopacket v1.1.19 h1:ves8RnFZPGiFnTS0uPQStjwru6uO6h+nlr9j6fL7kF8=
 github.com/google/gopacket v1.1.19/go.mod h1:iJ8V8n6KS+z2U1A8pUwu8bW5SyEMkXJB8Yo/Vo+TKTo=
 github.com/gosnmp/gosnmp v1.42.1 h1:MEJxhpC5v1coL3tFRix08PYmky9nyb1TLRRgJAmXm8A=
 github.com/gosnmp/gosnmp v1.42.1/go.mod h1:CxVS6bXqmWZlafUj9pZUnQX5e4fAltqPcijxWpCitDo=
+github.com/miekg/dns v1.1.72 h1:vhmr+TF2A3tuoGNkLDFK9zi36F2LS+hKTRW0Uf8kbzI=
+github.com/miekg/dns v1.1.72/go.mod h1:+EuEPhdHOsfk6Wk5TT2CzssZdqkmFhf8r+aVyDEToIs=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
@@ -14,17 +18,23 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
 golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
+golang.org/x/mod v0.31.0 h1:HaW9xtz0+kOcWKwli0ZXy79Ix+UW/vOfmWI5QVd2tgI=
+golang.org/x/mod v0.31.0/go.mod h1:43JraMp9cGx1Rx3AqioxrbrhNsLl2l/iNAvuBkrezpg=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.15.0 h1:ugBLEUaxABaB5AJqW9enI0ACdci2RUd4eP51NTBvuJ8=
-golang.org/x/net v0.15.0/go.mod h1:idbUs1IY1+zTqbi8yxTbhexhEEk5ur9LInksu6HrEpk=
+golang.org/x/net v0.48.0 h1:zyQRTTrjc33Lhh0fBgT/H3oZq9WuvRR5gPC70xpDiQU=
+golang.org/x/net v0.48.0/go.mod h1:+ndRgGjkh8FGtu1w1FGbEC31if4VrNVMuKTgcAAnQRY=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
+golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
-golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
+golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=
+golang.org/x/tools v0.40.0/go.mod h1:Ik/tzLRlbscWpqqMRjyWYDisX8bG13FrdXp3o4Sr9lc=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
--- a/mdns.go
+++ b/mdns.go
@@ -0,0 +1,149 @@
+package tendrils
+
+import (
+	"context"
+	"log"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/miekg/dns"
+)
+
+const (
+	mdnsAddr = "224.0.0.251:5353"
+)
+
+func (t *Tendrils) listenMDNS(ctx context.Context, iface net.Interface) {
+	addr, err := net.ResolveUDPAddr("udp4", mdnsAddr)
+	if err != nil {
+		log.Printf("[ERROR] failed to resolve mdns address: %v", err)
+		return
+	}
+
+	conn, err := net.ListenMulticastUDP("udp4", &iface, addr)
+	if err != nil {
+		log.Printf("[ERROR] failed to listen mdns on %s: %v", iface.Name, err)
+		return
+	}
+	defer conn.Close()
+
+	go t.runMDNSQuerier(ctx, iface)
+
+	buf := make([]byte, 65536)
+	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.handleMDNSPacket(iface.Name, src.IP, buf[:n])
+	}
+}
+
+func (t *Tendrils) handleMDNSPacket(ifaceName string, srcIP net.IP, data []byte) {
+	msg := new(dns.Msg)
+	if err := msg.Unpack(data); err != nil {
+		return
+	}
+
+	if msg.Response {
+		t.processMDNSResponse(ifaceName, srcIP, msg)
+	}
+}
+
+func (t *Tendrils) processMDNSResponse(ifaceName string, srcIP net.IP, msg *dns.Msg) {
+	var hostname string
+
+	allRecords := append(msg.Answer, msg.Extra...)
+	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
+			}
+		case *dns.AAAA:
+			continue
+		case *dns.PTR:
+			name := strings.TrimSuffix(r.Ptr, ".local.")
+			name = strings.TrimSuffix(name, ".")
+			if hostname == "" && name != "" && !strings.HasPrefix(name, "_") {
+				hostname = name
+			}
+		}
+	}
+
+	if hostname != "" {
+		if t.DebugMDNS {
+			log.Printf("[mdns] %s: %s -> %s", ifaceName, srcIP, hostname)
+		}
+		t.nodes.Update(nil, nil, []net.IP{srcIP}, "", hostname, "mdns")
+	}
+}
+
+func (t *Tendrils) runMDNSQuerier(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(60 * time.Second)
+	defer ticker.Stop()
+
+	t.sendMDNSQuery(iface.Name, srcIP)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			t.sendMDNSQuery(iface.Name, srcIP)
+		}
+	}
+}
+
+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
+	}
+	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)
+	}
+}
--- a/nodes.go
+++ b/nodes.go
@@ -617,6 +617,8 @@ func (n *Nodes) LogAll() {
 			log.Printf("[sigusr1]   %s: %v", gm.Group.Name(), memberNames)
 		}
 	}
+
+	n.t.artnet.LogAll()
 }

 func (n *Nodes) expireMulticastMemberships() {
--- a/tendrils.go
+++ b/tendrils.go
@@ -13,23 +13,29 @@ import (
 type Tendrils struct {
 	activeInterfaces map[string]context.CancelFunc
 	nodes            *Nodes
+	artnet           *ArtNetNodes

 	Interface     string
 	DisableARP    bool
 	DisableLLDP   bool
 	DisableSNMP   bool
 	DisableIGMP   bool
+	DisableMDNS   bool
+	DisableArtNet bool
 	LogEvents     bool
 	LogNodes      bool
 	DebugARP      bool
 	DebugLLDP     bool
 	DebugSNMP     bool
 	DebugIGMP     bool
+	DebugMDNS     bool
+	DebugArtNet   bool
 }

 func New() *Tendrils {
 	t := &Tendrils{
 		activeInterfaces: map[string]context.CancelFunc{},
+		artnet:           NewArtNetNodes(),
 	}
 	t.nodes = NewNodes(t)
 	return t
@@ -183,4 +189,10 @@ func (t *Tendrils) startInterface(ctx context.Context, iface net.Interface) {
 	if !t.DisableIGMP {
 		go t.listenIGMP(ctx, iface)
 	}
+	if !t.DisableMDNS {
+		go t.listenMDNS(ctx, iface)
+	}
+	if !t.DisableArtNet {
+		go t.listenArtNet(ctx, iface)
+	}
 }