[FrankWuwuwu]

Summary

• Admit HTTP Host and TLS SNI classification only after resolving the source sandbox and acquiring a 64-slot per-sandbox classification budget. This limits connections waiting before the existing route handler and its connection limiter.
• Set a five-second read deadline for classification. Expired connections are closed at the route boundary, including the TLS CIDR fallback, instead of being forwarded.
• Release the temporary classification slot at route entry, then preserve the existing per-sandbox connection limiter for the rest of the connection. Non-HTTP/TLS traffic retains its current path.

Why

Issue #3681 documented that incomplete HTTP headers can occupy orchestrator file descriptors and goroutines before HandleConn reaches the existing per-sandbox connection limiter. The same ordering applies to TLS SNI parsing. This change bounds that pre-route stage without changing egress policy decisions or normal proxying.

Validation

• go test ./pkg/tcpfirewall -run '^(TestClassificationAdmission|TestSlowHTTPClassification|TestIsTransientAcceptError)' -count=1
• go test -race ./pkg/tcpfirewall -run '^(TestClassificationAdmission|TestSlowHTTPClassification)' -count=1
• go vet ./pkg/tcpfirewall

The tests cover per-sandbox budget isolation, one-time slot release, timeout rejection through tcpproxy routing, and a complete HTTP request that proceeds after the slow connection. The change does not claim to establish a production DoS threshold or solve accounting for other shared host services discussed in #3681.

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[FrankWuwuwu]

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