Refactor into separate client and server classes

main.go

@@ -26,20 +26,21 @@ func makeDNSReply(r *dns.Msg, name string, addr net.IP) *dns.Msg {
 	return m
 }
 
-var mdnsClient *weavedns.MDNSClient
+var (
+	mdnsClient *weavedns.MDNSClient
+	mdnsServer *weavedns.MDNSServer
+)
 
 func handleMDNS(w dns.ResponseWriter, r *dns.Msg) {
-	// Here we have to handle both requests incoming, responses to queries
-	// we sent out, and responses to queries that other nodes sent
-	if len(r.Answer) > 0 {
-		mdnsClient.ResponseCallback(r)
-	} else if len(r.Question) > 0 {
+	// Ignore answers to other questions
+	if len(r.Answer) == 0 && len(r.Question) > 0 {
 		q := r.Question[0]
 		ip, err := zone.MatchLocal(q.Name)
 		if err == nil {
 			m := makeDNSReply(r, q.Name, ip)
-			mdnsClient.SendResponse(m)
+			mdnsServer.SendResponse(m)
 		} else if mdnsClient.IsInflightQuery(r) {
+			log.Println("Inflight Query", w.RemoteAddr(), w.LocalAddr())
 			// ignore this - it's our own query received via multicast
 		} else {
 			log.Printf("Failed MDNS lookup for %s", q.Name)
@@ -135,7 +136,14 @@ func main() {
 	} else {
 		log.Printf("Using mDNS on %s", ifaceName)
 	}
-	mdnsClient.Start()
+	err = mdnsClient.Start(iface)
+	if err != nil {
+		log.Fatal(err)
+	}
+	mdnsServer, err = weavedns.NewMDNSServer()
+	if err != nil {
+		log.Fatal(err)
+	}
 
 	go dns.ActivateAndServe(nil, conn, MDNSServeMux)
 

server/mdns_client.go

@@ -59,7 +59,6 @@ type mDNSQueryInfo struct {
 func NewMDNSClient() (*MDNSClient, error) {
 	conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero, Port: 0})
 	if err != nil {
-		log.Println(err)
 		return nil, err
 	}
 	retval := &MDNSClient{
@@ -69,10 +68,27 @@ func NewMDNSClient() (*MDNSClient, error) {
 	return retval, nil
 }
 
-func (c *MDNSClient) Start() {
+func (c *MDNSClient) Start(ifi *net.Interface) error {
+	multicast, err := LinkLocalMulticastListener(ifi)
+	if err != nil {
+		return err
+	}
+
+	handleMDNS := func(w dns.ResponseWriter, r *dns.Msg) {
+		//log.Println("client received:", r)
+		// Only handle responses here
+		if len(r.Answer) > 0 {
+			c.ResponseCallback(r)
+		}
+	}
+
+	go dns.ActivateAndServe(nil, multicast, dns.HandlerFunc(handleMDNS))
+
 	queryChan := make(chan *MDNSInteraction, 4)
 	c.queryChan = queryChan
 	go c.queryLoop(queryChan)
+
+	return nil
 }
 
 func LinkLocalMulticastListener(ifi *net.Interface) (net.PacketConn, error) {
@@ -80,15 +96,6 @@ func LinkLocalMulticastListener(ifi *net.Interface) (net.PacketConn, error) {
 	return conn, err
 }
 
-func (c *MDNSClient) SendResponse(m *dns.Msg) error {
-	buf, err := m.Pack()
-	if err != nil {
-		return err
-	}
-	_, err = c.conn.WriteTo(buf, c.addr)
-	return err
-}
-
 // ACTOR client API
 
 const (

server/mdns_client_test.go

@@ -10,11 +10,6 @@ import (
 
 var (
 	test_addr = net.ParseIP("9.8.7.6")
-	sendconn  *net.UDPConn
-	sendAddr  = &net.UDPAddr{
-		IP:   net.ParseIP(ipv4mdns),
-		Port: 0,
-	}
 )
 
 func minimalServer(w dns.ResponseWriter, req *dns.Msg) {
@@ -39,7 +34,13 @@ func minimalServer(w dns.ResponseWriter, req *dns.Msg) {
 		log.Fatal("Nil buffer")
 	}
 	//log.Println("minimalServer sending:", buf)
-	_, err = sendconn.WriteTo(buf, ipv4Addr)
+	// This is a bit of a kludge - per the RFC we should send responses from 5353, but that doesn't seem to work
+	sendconn, err := net.DialUDP("udp", nil, ipv4Addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	_, err = sendconn.Write(buf)
+	sendconn.Close()
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -62,24 +63,7 @@ func TestSimpleQuery(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	mdnsClient.Start()
-	mux := dns.NewServeMux()
-
-	handleMDNS := func(w dns.ResponseWriter, r *dns.Msg) {
-		//log.Println("test received:", r)
-		// Only handle responses here
-		if len(r.Answer) > 0 {
-			mdnsClient.ResponseCallback(r)
-		}
-	}
-
-	mux.HandleFunc("weave", handleMDNS)
-	multicast, err := net.ListenMulticastUDP("udp", nil, ipv4Addr)
-	if err != nil {
-		t.Fatal(err)
-	}
-	go dns.ActivateAndServe(nil, multicast, mux)
-	sendconn, err = net.ListenUDP("udp", sendAddr)
+	err = mdnsClient.Start(nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -98,9 +82,10 @@ func TestSimpleQuery(t *testing.T) {
 			received_addr = resp.Addr
 		}
 	}()
+
 	mdnsClient.SendQuery("test.weave.", dns.TypeA, channel)
 
-	time.Sleep(1 * time.Second)
+	time.Sleep(200 * time.Millisecond)
 
 	if !received_addr.Equal(test_addr) {
 		t.Log("Unexpected result for test.weave", received_addr)

server/mdns_server.go

@@ -0,0 +1,30 @@
+package weavedns
+
+import (
+	"github.com/miekg/dns"
+	"net"
+)
+
+type MDNSServer struct {
+	sendconn *net.UDPConn
+}
+
+func NewMDNSServer() (*MDNSServer, error) {
+	//log.Println("minimalServer sending:", buf)
+	// This is a bit of a kludge - per the RFC we should send responses from 5353, but that doesn't seem to work
+	sendconn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero, Port: 0})
+	if err != nil {
+		return nil, err
+	}
+	retval := &MDNSServer{sendconn: sendconn}
+	return retval, nil
+}
+
+func (s *MDNSServer) SendResponse(m *dns.Msg) error {
+	buf, err := m.Pack()
+	if err != nil {
+		return err
+	}
+	_, err = s.sendconn.WriteTo(buf, ipv4Addr)
+	return err
+}