Cleaner handling of our own multicast queries

dns/main.go

@@ -26,7 +26,6 @@ var mdnsClient *weavedns.MDNSClient
 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
-	// And we also get to see our own queries!
 	if len(r.Answer) > 0 {
 		mdnsClient.HandleResponse(r)
 	} else if len(r.Question) > 0 {
@@ -35,6 +34,10 @@ func handleMDNS(w dns.ResponseWriter, r *dns.Msg) {
 		if err == nil {
 			m := makeDNSReply(r, q.Name, net.ParseIP(ip))
 			mdnsClient.SendResponse(m)
+		} else if mdnsClient.IsInflightQuery(r) {
+			// ignore this - it's our own query received via multicast
+		} else {
+			log.Printf("Failed MDNS lookup for %s", q.Name)
 		}
 	}
 }

mdns_client.go

@@ -73,7 +73,7 @@ func (c *MDNSClient) SendQuery(name string, querytype uint16, responseCh chan<-
 	c.Lock()
 	query, found := c.inflight[name]
 	if !found {
-		query = &inflightQuery{name: name}
+		query = &inflightQuery{name: name, Id: m.Id}
 		c.inflight[name] = query
 	}
 	info := &responseInfo{ch: responseCh}
@@ -97,6 +97,22 @@ func (c *MDNSClient) SendResponse(m *dns.Msg) error {
 	return err
 }
 
+func (c *MDNSClient) IsInflightQuery(m *dns.Msg) bool {
+	if len(m.Question) == 1 {
+		q := m.Question[0]
+		if q.Qtype == dns.TypeA {
+			c.Lock()
+			defer c.Unlock()
+			if query, found := c.inflight[q.Name]; found {
+				if query.Id == m.Id {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}
+
 func (c *MDNSClient) HandleResponse(r *dns.Msg) {
 	for _, answer := range r.Answer {
 		switch rr := answer.(type) {