Added unknown source frame handler

serverhandler.go

@@ -164,3 +164,16 @@ type ServerHandlerOnFrameCtx struct {
 type ServerHandlerOnFrame interface {
 	OnFrame(*ServerHandlerOnFrameCtx)
 }
+
+// ServerHandlerOnUnknownClientCtx is the context of an UDP frame coming from an unknown source.
+type ServerHandlerOnUnknownClientCtx struct {
+	StreamType StreamType
+	Payload    []byte
+	Clients    map[clientAddr]*clientData
+	ClientAddr clientAddr
+}
+
+// ServerHandlerOnUnknownClient can be implemented by a ServerHandler.
+type ServerHandlerOnUnknownClient interface {
+	OnUnknownClient(*ServerHandlerOnUnknownClientCtx) error
+}

serverudpl.go

@@ -118,7 +118,22 @@ func (u *serverUDPListener) run() {
 				clientAddr.fill(addr.IP, addr.Port)
 				clientData, ok := u.clients[clientAddr]
 				if !ok {
-					return
+					//Call handler to allow user to handle frame from unknown source (NAT hole punch)
+					if h, ok := u.s.Handler.(ServerHandlerOnUnknownClient); ok {
+						err = h.OnUnknownClient(&ServerHandlerOnUnknownClientCtx{
+							StreamType: u.streamType,
+							Payload:    buf[:n],
+							Clients:    u.clients,
+							ClientAddr: clientAddr,
+						})
+						//Check if clientData exists in possibly modified clients list
+						clientData, ok = u.clients[clientAddr]
+						if  err != nil || !ok {
+							return
+						}
+					} else {
+            return
+          }
 				}
 
 				if clientData.isPublishing {