Implement -udp command-line flag.

galene.go

@@ -44,6 +44,8 @@ func main() {
 		"store mutex profile in `file`")
 	flag.StringVar(&udpRange, "udp-range", "",
 		"UDP port `range`")
+	flag.StringVar(&group.UDPAddr, "udp", "",
+		"UDP `address:port` (default dynamic)")
 	flag.BoolVar(&group.UseMDNS, "mdns", false, "gather mDNS addresses")
 	flag.BoolVar(&ice.ICERelayOnly, "relay-only", false,
 		"require use of TURN relays for all media traffic")

group/group.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"log"
+	"net"
 	"os"
 	"path"
 	"path/filepath"
@@ -20,6 +21,10 @@ var Directory string
 var UseMDNS bool
 var UDPMin, UDPMax uint16
 
+var UDPAddr string
+var udpListenerMu sync.Mutex
+var udpListener *net.UDPConn
+
 var ErrNotAuthorised = errors.New("not authorised")
 
 type UserError string
@@ -199,6 +204,27 @@ func payloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, error) {
 	}
 }
 
+func getUDPListener() (*net.UDPConn, error) {
+	if UDPAddr == "" {
+		return nil, nil
+	}
+	udpListenerMu.Lock()
+	defer udpListenerMu.Unlock()
+	if udpListener == nil {
+		addr, err := net.ResolveUDPAddr("udp", UDPAddr)
+		if err != nil {
+			return nil, err
+		}
+		udpListener, err = net.ListenUDP("udp", addr)
+		if err != nil {
+			udpListener = nil
+			return nil, err
+		}
+	}
+	return udpListener, nil
+
+}
+
 func APIFromCodecs(codecs []webrtc.RTPCodecCapability) (*webrtc.API, error) {
 	s := webrtc.SettingEngine{}
 	s.SetSRTPReplayProtectionWindow(512)
@@ -253,6 +279,14 @@ func APIFromCodecs(codecs []webrtc.RTPCodecCapability) (*webrtc.API, error) {
 		s.SetEphemeralUDPPortRange(UDPMin, UDPMax)
 	}
 
+	listener, err := getUDPListener()
+	if err != nil {
+		return nil, err
+	}
+	if listener != nil {
+		s.SetICEUDPMux(webrtc.NewICEUDPMux(nil, listener))
+	}
+
 	return webrtc.NewAPI(
 		webrtc.WithSettingEngine(s),
 		webrtc.WithMediaEngine(&m),