TCP proxy session idle timeout

[shaneutt]

TCP proxy connections need configurable idle timeouts at the session level. A bidirectional TCP proxy connection that is idle for longer than the configured duration should be closed gracefully.

Goal

Prevent stale TCP proxy connections from consuming resources indefinitely.

Requirements

• Per-listener configurable idle timeout for TCP proxy sessions
• Bidirectional idle detection (no data in either direction)
• Graceful close (FIN, not RST) on timeout
• Distinct from socket-level TCP tuning (TCP Tuning Configuration #149) this is application-layer session management
• Reasonable default (e.g., 1 hour)