delete streams from the streams map when closing

[marten-seemann]

This should fix the incorrect memory accounting that users have been reporting (for example filecoin-project/lotus#8632).

There are two actions (at least) that release memory:

• closing / resetting a stream
• closing the connection, which releases the memory for all streams

These can happen concurrently, which is not a problem, as we're holding the streamLock. We're also only releasing memory with the resource manager when the stream is still in our streams map.
The condition that made us release too much memory was the following: First, we'd close the session, which would release the memory of all streams. At the same time, the user reset one of the streams. This call would execute once the session is closed and all memory is released. However, since we didn't delete the stream from the map, we'd effectively release the memory allocated for that stream twice.

[vyzo]

good catch!

[BigLep]

@marten-seemann : do we not have a unit test because this isn't easy-enough to unit test?

[marten-seemann]

@marten-seemann : do we not have a unit test because this isn't easy-enough to unit test?

Correct. You'd have to trigger the race condition where you close the yamux session at exactly the same time you hit Reset on the stream.