Enable IPv6 address discovery (#578)

Agents will use IPv6 when available for ICE negotiation

client/internal/peer/conn.go

@@ -29,7 +29,8 @@ type ConnConfig struct {
 
 	// InterfaceBlackList is a list of machine interfaces that should be filtered out by ICE Candidate gathering
 	// (e.g. if eth0 is in the list, host candidate of this interface won't be used)
-	InterfaceBlackList []string
+	InterfaceBlackList   []string
+	DisableIPv6Discovery bool
 
 	Timeout time.Duration
 
@@ -145,9 +146,9 @@ func (conn *Conn) reCreateAgent() error {
 
 	failedTimeout := 6 * time.Second
 	var err error
-	conn.agent, err = ice.NewAgent(&ice.AgentConfig{
+	agentConfig := &ice.AgentConfig{
 		MulticastDNSMode: ice.MulticastDNSModeDisabled,
-		NetworkTypes:     []ice.NetworkType{ice.NetworkTypeUDP4},
+		NetworkTypes:     []ice.NetworkType{ice.NetworkTypeUDP4, ice.NetworkTypeUDP6},
 		Urls:             conn.config.StunTurn,
 		CandidateTypes:   []ice.CandidateType{ice.CandidateTypeHost, ice.CandidateTypeServerReflexive, ice.CandidateTypeRelay},
 		FailedTimeout:    &failedTimeout,
@@ -155,7 +156,14 @@ func (conn *Conn) reCreateAgent() error {
 		UDPMux:           conn.config.UDPMux,
 		UDPMuxSrflx:      conn.config.UDPMuxSrflx,
 		NAT1To1IPs:       conn.config.NATExternalIPs,
-	})
+	}
+
+	if conn.config.DisableIPv6Discovery {
+		agentConfig.NetworkTypes = []ice.NetworkType{ice.NetworkTypeUDP4}
+	}
+
+	conn.agent, err = ice.NewAgent(agentConfig)
+
 	if err != nil {
 		return err
 	}