Two live gates were lost to a second variable I had been asked to eliminate.
The Rust redirector was pointed at the repo's fifa17-recon/tools/redir_cert.pem
(fingerprint F9:16:1A...), while the running container serves a different cert
baked into its image (E7:F9:46...) which the Python redirector, roster and the
rest of the stack all share. So the A/B compared TLS implementation AND
certificate identity at once.
FIFA 17's ProtoSSL caches the server certificate for a backend. The redirector
is the first TLS connection of a session, so its cert becomes the one the client
expects; the next service presenting a different cert fails its handshake. That
is why the redirect itself always succeeded and the failure surfaced later, on
the roster fetch -- "An error occurred downloading the FUT Squad Update".
It stayed invisible because Python's socketserver swallows it: a handshake
failure at accept() raises ssl.SSLError, which subclasses OSError and is
discarded by _handle_request_noblock. No request log, no stderr. Every server
looked healthy while the client could not talk to any of them.
Confirmed on the wire: tls-observe in front of the roster server captured four
ClientHellos from the client, correct SNI and the same 8 static-RSA suites it
offers the redirector, none of which produced a request.
The check is mutation-tested against the real bug: with a redirector started on
the stale repo cert it exits 1 and names the mismatch.
funman300