feat: negative-cache unreachable destinations and grow startup pre-warm#280
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#275: youtube_via_relay no longer routes video/image CDNs through Apps Script. The flag now correctly carves out only the API/HTML hosts where Restricted Mode is enforced; video chunks come direct from googlevideo.com (which was missing from the SNI rewrite list entirely — fixed). Long videos no longer hit Apps Script's 6-min execution cap, and single-chunk timeouts no longer abort playback. #280: TunnelMux now caches "destination unreachable" responses from the tunnel-node (Network is unreachable / No route to host) for 30 seconds, short-circuiting subsequent CONNECTs to that destination with 502 (HTTP) or 0x04 (SOCKS5). Saves ~5 batches/second on IPv6-only host probes. Startup pre-warm pool grew 12→24. 143/143 tests pass. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Two small perf fixes driven by an Android log review.
1. Negative-cache unreachable destinations
On a device without IPv6, OS/app probes to IPv6-only hostnames (e.g.
ds6.probe.whatismyipaddress.com) fail withNetwork is unreachable (os error 101). The probe gets retried every ~1.5s, and each retry was burning a fresh tunnel batch round-trip on a guaranteed failure — 5+ wasted sessions per probe in the logs.TunnelMuxnow keeps a 30s, 256-entry negative cache keyed by(host, port). When the tunnel-node returnsNetwork is unreachable/No route to host, the destination is remembered. The proxy front-end short-circuits subsequent CONNECTs:502 Bad Gateway0x04 Host unreachableCache write rules (after review feedback):
TunnelResponse.e— the tunnel-node's own connect result. Outer transport errors (relay → Apps Script never reached the tunnel-node) are never cached, so a momentary client-side WAN blip doesn't poison destinations.Example.COM.:443andexample.com:443share an entry.2. Bigger startup pre-warm pool
warm(3)was sized for one deployment. With multi-deployment configs, requests 4–10 of the opening burst paid a fresh TLS handshake each (~300ms). Now scales with deployment count:warm(num_scripts().clamp(6, 16)).Test plan
cargo test --lib(143 passed)