Respect IncludeLoopback in UDPMuxDefault with unspecified IP

gather.go

@@ -266,6 +266,11 @@ func (a *Agent) gatherCandidatesLocalUDPMux(ctx context.Context) error { //nolin
 			return errInvalidAddress
 		}
 		candidateIP := udpAddr.IP
+		if _, ok := a.udpMux.(*UDPMuxDefault); ok && !a.includeLoopback && candidateIP.IsLoopback() {
+			// Unlike MultiUDPMux Default, UDPMuxDefault doesn't have
+			// a separate param to include loopback, so we respect agent config
+			continue
+		}
 		if a.extIPMapper != nil && a.extIPMapper.candidateType == CandidateTypeHost {
 			mappedIP, err := a.extIPMapper.findExternalIP(candidateIP.String())
 			if err != nil {

gather_test.go

@@ -133,6 +133,16 @@ func TestLoopbackCandidate(t *testing.T) {
 	assert.NoError(t, err)
 	muxWithLo, errlo := NewMultiUDPMuxFromPort(12501, UDPMuxFromPortWithLoopback())
 	assert.NoError(t, errlo)
+
+	unspecConn, errconn := net.ListenPacket("udp", ":0")
+	assert.NoError(t, errconn)
+	defer func() {
+		_ = unspecConn.Close()
+	}()
+	muxUnspecDefault := NewUDPMuxDefault(UDPMuxParams{
+		UDPConn: unspecConn,
+	})
+
 	testCases := []testCase{
 		{
 			name: "mux should not have loopback candidate",
@@ -150,6 +160,23 @@ func TestLoopbackCandidate(t *testing.T) {
 			},
 			loExpected: true,
 		},
+		{
+			name: "UDPMuxDefault with unspecified IP should not have loopback candidate",
+			agentConfig: &AgentConfig{
+				NetworkTypes: []NetworkType{NetworkTypeUDP4, NetworkTypeUDP6},
+				UDPMux:       muxUnspecDefault,
+			},
+			loExpected: false,
+		},
+		{
+			name: "UDPMuxDefault with unspecified IP should respect agent includeloopback",
+			agentConfig: &AgentConfig{
+				NetworkTypes:    []NetworkType{NetworkTypeUDP4, NetworkTypeUDP6},
+				UDPMux:          muxUnspecDefault,
+				IncludeLoopback: true,
+			},
+			loExpected: true,
+		},
 		{
 			name: "includeloopback enabled",
 			agentConfig: &AgentConfig{
@@ -198,6 +225,7 @@ func TestLoopbackCandidate(t *testing.T) {
 
 	assert.NoError(t, mux.Close())
 	assert.NoError(t, muxWithLo.Close())
+	assert.NoError(t, muxUnspecDefault.Close())
 }
 
 // Assert that STUN gathering is done concurrently

udp_mux.go

@@ -93,7 +93,7 @@ func NewUDPMuxDefault(params UDPMuxParams) *UDPMuxDefault {
 				}
 			}
 
-			ips, err := localInterfaces(params.Net, nil, nil, networks, false)
+			ips, err := localInterfaces(params.Net, nil, nil, networks, true)
 			if err == nil {
 				for _, ip := range ips {
 					localAddrsForUnspecified = append(localAddrsForUnspecified, &net.UDPAddr{IP: ip, Port: addr.Port})