From b80e515eb04a8326336524ea80ecf711a3013293 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Thu, 29 Apr 2021 20:51:44 +0200
Subject: [PATCH] Implement -udp command-line flag.

---
 galene.go      |  2 ++
 group/group.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/galene.go b/galene.go
index b384d52..66ff2be 100644
--- a/galene.go
+++ b/galene.go
@@ -45,6 +45,8 @@ 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")
diff --git a/group/group.go b/group/group.go
index c900f23..c2f3c64 100644
--- a/group/group.go
+++ b/group/group.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"errors"
 	"log"
+	"net"
 	"os"
 	"path"
 	"path/filepath"
@@ -21,6 +22,10 @@ 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
@@ -333,6 +338,14 @@ func APIFromCodecs(codecs []webrtc.RTPCodecParameters) (*webrtc.API, error) {
 		webrtc.RTPHeaderExtensionCapability{sdp.SDESRTPStreamIDURI},
 		webrtc.RTPCodecTypeVideo)
 
+	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),
@@ -356,6 +369,26 @@ func APIFromNames(names []string) (*webrtc.API, error) {
 	return APIFromCodecs(codecs)
 }
 
+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 Add(name string, desc *Description) (*Group, error) {
 	g, notify, err := add(name, desc)
 	for _, c := range notify {