if err != nil {
		return nil, err
	}

	cmd := testenv.Command(t, os.Args[0])
	cmd.Env = []string{
		"GO_NET_TEST_TRANSFER=1",
		"GO_NET_TEST_TRANSFER_OP=" + op,
		"GO_NET_TEST_TRANSFER_CHUNK_SIZE=" + strconv.Itoa(chunkSize),
		"GO_NET_TEST_TRANSFER_TOTAL_SIZE=" + strconv.Itoa(totalSize),
		"TMPDIR=" + os.Getenv("TMPDIR"),
	}
	cmd.ExtraFiles = append(cmd.ExtraFiles, f)
	cmd.Stdout = os.Stdout