Server stops accepting connections after 10 client aborts — connection slot leak ("Connection limit reached (10)")

[serkud]

Summary

flm serve permanently rejects all new connections after roughly 10 client-side aborts, even though no TCP connections remain open. Only a process restart recovers the server.

Environment

• FastFlowLM 1.0.1
• Ubuntu 26.04, kernel 7.0.0-29, Ryzen AI MAX+ 395 (Strix Halo, XDNA2)
• Ryzen AI XRT 2.25.37, amdxdna DKMS 2.25.260102.56, NPU firmware 1.1.2.65
• Serving: flm serve gemma4-it:e2b --host 0.0.0.0 --port 52625 (systemd user service)

Steps to reproduce

1. Start flm serve <model>.
2. From an HTTP client, send a /v1/chat/completions request with a long generation, then abort the connection mid-stream (client timeout / connection close) — in our case the client is an LLM-harness advisor with a request timeout shorter than cold generation (~20 s).
3. Repeat ~10 times over the service lifetime.
4. All subsequent connections are rejected. ss shows zero established sockets on the port, yet the server logs Connection limit reached (10), rejecting new connection for every attempt.

Logs

[🔵 ]  NPU Lock Released!
[🔒 ]  TCP connection closed - Remote endpoint unavailable
[LOG]  Connection limit reached (10), rejecting new connection   ← repeats forever

Expected behavior

Aborted connections release their slot; the server keeps accepting new connections indefinitely.

Actual behavior

The internal connection counter is never decremented on client abort. After 10 aborts the server is deaf until restart.

Workaround

systemd watchdog probing /v1/models every 5 min, restarting the service on failure.