Cap per-connection recv drain to prevent poll-loop starvation (fixes #76)

[cursor]

Security fix: server recv fairness cap

Fixes #76

Finding

Severity: Medium (availability / DoS)
Location: src/server/mod.rs

Problem

Server::process_connections() drained each peer's entire kernel recv buffer in an unbounded inner loop before servicing the next connection. A single high-volume sender could monopolize the single-threaded poll loop and starve every other session on the same Server.

Fix

Introduce MAX_RECV_BYTES_PER_CONN_PER_POLL (256 KiB) and stop recv-draining a connection once that budget is exhausted for the current poll pass. Remaining bytes are picked up on the next poll() call, giving other connections a turn.

Impact

Prevents connection-starvation DoS against co-located RTMP sessions without affecting normal throughput (256 KiB per poll is sufficient for steady-state media).

Tests

• server::tests::recv_budget_is_at_least_one_socket_read
• server::tests::recv_budget_is_small_enough_for_fairness_across_connections
• Full cargo test --no-default-features green

  

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