return FEC segments to xmitBuf when session closes

fec.go

@@ -209,6 +209,13 @@ func (dec *fecDecoder) freeRange(first, n int, q []fecElement) []fecElement {
 	return q[:len(q)-n]
 }
 
+// release all segments back to xmitBuf
+func (dec *fecDecoder) release() {
+	if n := len(dec.rx); n > 0 {
+		dec.rx = dec.freeRange(0, n, dec.rx)
+	}
+}
+
 type (
 	// fecEncoder for encoding outgoing packets
 	fecEncoder struct {

sess.go

@@ -360,6 +360,9 @@ func (s *UDPSession) Close() error {
 		s.uncork()
 		// release pending segments
 		s.kcp.ReleaseTX()
+		if s.fecDecoder != nil {
+			s.fecDecoder.release()
+		}
 		s.mu.Unlock()
 
 		if s.l != nil { // belongs to listener