From 2cffe6526a3d6ef28530ddab10e902fef4ee98d9 Mon Sep 17 00:00:00 2001
From: braginini <bangvalo@gmail.com>
Date: Wed, 7 Sep 2022 19:02:17 +0200
Subject: [PATCH] Add more logging

---
 iface/bind.go    |  4 ++--
 iface/udp_mux.go | 10 +++++++---
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/iface/bind.go b/iface/bind.go
index 7ae68aa55..b11c0884d 100644
--- a/iface/bind.go
+++ b/iface/bind.go
@@ -96,7 +96,7 @@ func listenNet(network string, port int) (*net.UDPConn, int, error) {
 	return conn, uaddr.Port, nil
 }
 
-func parseStunMessage(raw []byte) (*stun.Message, error) {
+func parseSTUNMessage(raw []byte) (*stun.Message, error) {
 	msg := &stun.Message{
 		Raw: append([]byte{}, raw...),
 	}
@@ -126,7 +126,7 @@ func (b *ICEBind) makeReceiveIPv4(c net.PacketConn) conn.ReceiveFunc {
 			}), nil
 		}
 
-		msg, err := parseStunMessage(buff[:n])
+		msg, err := parseSTUNMessage(buff[:n])
 		if err != nil {
 			return 0, nil, err
 		}
diff --git a/iface/udp_mux.go b/iface/udp_mux.go
index 5fd512121..998c333f7 100644
--- a/iface/udp_mux.go
+++ b/iface/udp_mux.go
@@ -74,12 +74,15 @@ func (m *UDPMuxDefault) Type() string {
 
 func (m *UDPMuxDefault) HandleSTUNMessage(msg *stun.Message, addr net.Addr) error {
 
-	udpAddr, ok := addr.(*net.UDPAddr)
+	remoteAddr, ok := addr.(*net.UDPAddr)
 	if !ok {
 		return fmt.Errorf("underlying PacketConn did not return a UDPAddr")
 	}
 
 	// If we have already seen this address dispatch to the appropriate destination
+	// If you are using the same socket for the Host and SRFLX candidates, it might be that there are more than one
+	// muxed connection - one for the SRFLX candidate and the other one for the HOST one.
+	// We will then forward STUN packets to each of these connections.
 	m.addressMapMu.Lock()
 	var destinationConnList []*udpMuxedConn
 	if storedConns, ok := m.addressMap[addr.String()]; ok {
@@ -92,7 +95,6 @@ func (m *UDPMuxDefault) HandleSTUNMessage(msg *stun.Message, addr net.Addr) erro
 	// This block is needed to discover Peer Reflexive Candidates for which we don't know the Endpoint upfront.
 	// However, we can take a username attribute from the STUN message which contains ufrag.
 	// We can use ufrag to identify the destination conn to route packet to.
-
 	attr, stunAttrErr := msg.Get(stun.AttrUsername)
 	if stunAttrErr == nil {
 		ufrag := strings.Split(string(attr), ":")[0]
@@ -113,8 +115,10 @@ func (m *UDPMuxDefault) HandleSTUNMessage(msg *stun.Message, addr net.Addr) erro
 		m.mu.Unlock()
 	}
 
+	// Forward STUN packets to each destination connections even thought the STUN packet might not belong there.
+	// It will be discarded by the further ICE candidate logic if so.
 	for _, conn := range destinationConnList {
-		if err := conn.writePacket(msg.Raw, udpAddr); err != nil {
+		if err := conn.writePacket(msg.Raw, remoteAddr); err != nil {
 			log.Errorf("could not write packet: %v", err)
 		}
 	}