Eubulides,
I actually didn't give the most pertinent answer to your question.
In the "freedom is mastery of necessity" Hegelian trope, the knowledge of necessity (that is at the heart the realm of freedom that the world wide web of workers bursts its fetters and enters) the knowledge is due to understanding the laws of motion that Marx discovered, the laws of motion of capitalism, and the class struggle. These laws are of the second type that Engels mentions. ."... those which govern the bodily and mental existence of men themselves" * With capitalism there is enormous ( though of course not total) mastery of physical necessity. But there is not mastery of the mastery of physical necessity; there is not mastery of the political economy, the general laws of capitalist accumulation, etc. , so the actual masters have to be "mastered" in the revolution. With the socialist revolution the necessity of capitalism imposed by the masters is mastered, and by that the economy can be planned and appropriation socialized, the realm of freedom broached. Marxism is the knowledge of necessity of capitalism that makes possible planning the economy, freeing all from the limitations of poverty, i.e. not having all of many people's necessities met.
If and when the workers establish appropriation as equally social as production, that will be the capitalist private property integument burst asunder. The necessities of each individual will be satisfied, rendering them free to play music in the morning and fish at night most days; how to produce the necessities of life for all society will be met through full understanding of social economy that allows thorough and efficient planning, freeing society from mass misery, poverty, unemployment, business cycles. Necessity will be mastered/understood at two levels , perhaps.
However, we can be sure that new , different contradictions will arise in communism, new necessities will have to be mastered.
Prometheus
* "This holds good in relation both to the laws of external nature and to those which govern the bodily and mental existence of men themselves - two classes of laws which we can separate from each other at most only in thought but not in reality. Freedom of the will therefore means nothing but the capacity to make decisions with knowledge of the subject."