Merge pull request #1393 from sanimej/2782

Relax SRV name validation and fix external SRV query handling

Author: mrjana

libnetwork_internal_test.go

@@ -411,10 +411,10 @@ func TestSRVServiceQuery(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	// Try resolving a service name with invalid protocol, should fail..
-	_, _, err = ep.Info().Sandbox().ResolveService("_http._icmp.web.swarm")
-	if err == nil {
-		t.Fatal(err)
+	// Service name with invalid protocol name. Should fail without error
+	_, ip, err = ep.Info().Sandbox().ResolveService("_http._icmp.web.swarm")
+	if len(ip) != 0 {
+		t.Fatal("Valid response for invalid service name")
 	}
 }
 

resolver.go

@@ -255,6 +255,9 @@ func (r *resolver) handleSRVQuery(svc string, query *dns.Msg) (*dns.Msg, error)
 	if err != nil {
 		return nil, err
 	}
+	if len(srv) == 0 {
+		return nil, nil
+	}
 	if len(srv) != len(ip) {
 		return nil, fmt.Errorf("invalid reply for SRV query %s", svc)
 	}

sandbox.go

@@ -444,16 +444,16 @@ func (sb *sandbox) ResolveService(name string) ([]*net.SRV, []net.IP, error) {
 
 	log.Debugf("Service name To resolve: %v", name)
 
+	// There are DNS implementaions that allow SRV queries for names not in
+	// the format defined by RFC 2782. Hence specific validations checks are
+	// not done
 	parts := strings.Split(name, ".")
 	if len(parts) < 3 {
-		return nil, nil, fmt.Errorf("invalid service name, %s", name)
+		return nil, nil, nil
 	}
 
 	portName := parts[0]
 	proto := parts[1]
-	if proto != "_tcp" && proto != "_udp" {
-		return nil, nil, fmt.Errorf("invalid protocol in service, %s", name)
-	}
 	svcName := strings.Join(parts[2:], ".")
 
 	for _, ep := range sb.getConnectedEndpoints() {