Integration port collisions

[rday]

Problem:

xdist allows multiple workers to run integration tests. Each worker needs to have its own port range, or be sure that it is using a unique port at any given time. Otherwise we get errors when s2nd tries to bind to a port already in use.

Solution:

Assigning a unique port range, or grouping workers is the current approach- which breaks down when the number of workers exceeds 2. An alternatively, calling bind() with a port of zero will auto assign a random, available port should be an improvement, but will require a test framework refactor.

• Does this change what S2N sends over the wire? No
• Does this change any public APIs? No
• Which versions of TLS will this impact? None

Requirements / Acceptance Criteria:

Multiple workers don't use the same port at the same time.

Out of scope:

Is there anything the solution will intentionally NOT address?