udp: Fold buffer handoff into ListenOut

udp/udp_tester.go

@@ -182,22 +182,14 @@ func (u *TesterConn) WriteBatch(bufs [][]byte, addrs []netip.AddrPort) (int, err
 	return written, nil
 }
 
-func (u *TesterConn) ListenOut(r EncReader, flush func()) error {
-	// The batcher borrows plaintext decrypted in place inside p.Data
-	// until Flush, so the packet must stay alive across flush()
-	return u.ListenOutHandoff(r, func(bufs [][]byte) [][]byte {
-		flush()
-		return bufs
-	})
-}
-
 // HandoffShape is one buffer per handoff; the pool resizes the replacements it gets back as it needs.
 func (u *TesterConn) HandoffShape() (n, size int) { return 1, MTU }
 
-// ListenOutHandoff hands each packet's buffer over as a batch of one, the buffer it gets back goes to the pool. Like
-// StdConn it carries on with the slice handoff returns, since a reader that keeps the packets keeps the one it was
-// given.
-func (u *TesterConn) ListenOutHandoff(r EncReader, handoff func(bufs [][]byte) [][]byte) error {
+// ListenOut hands each packet's buffer over as a batch of one, the buffer it gets back goes to the pool. Like StdConn
+// it carries on with the slice handoff returns, since a reader that keeps the packets keeps the one it was given.
+// The batcher borrows plaintext decrypted in place inside p.Data until it flushes, inside handoff, so the packet
+// must stay alive until handoff returns.
+func (u *TesterConn) ListenOut(r EncReader, handoff func(bufs [][]byte) [][]byte) error {
 	bufs := make([][]byte, 1)
 	for {
 		select {