test(transport/cc): don't reenter recovery #2409
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> A NewReno sender enters a recovery period when it detects the loss of > a packet or when the ECN-CE count reported by its peer increases. A > sender that is already in a recovery period stays in it and does not > reenter it. https://www.rfc-editor.org/rfc/rfc9002.html#section-7.3.2 When in a transient state (i.e. `State::RecoveryStart` and `State::PersistentCongestion`) we return early, i.e. don't reenter recovery: https://github.com/mozilla/neqo/blob/6cdbc0c33197aaf3cfc6240bed9cb6681afcafc7/neqo-transport/src/cc/classic_cc.rs#L546-L553 But when in `State::Recovery`, as far as I can tell, we do reenter `Recovery`, i.e. call `self.cc_algorithm.reduce_cwnd`: https://github.com/mozilla/neqo/blob/e3657305dcba2842f505d941e94d5a805a1f50aa/neqo-transport/src/cc/classic_cc.rs#L577 Thus in the following scenario we might reduce the cwnd twice in the same loss episode: 1. Send packet A. 2. Declare packet A as lost, reduce cwnd and transitioning into `RecoveryStart`. 3. Send packet B and transitioning into `Recovery`. 4. Declare packet B as lost, thus reduce cwnd a second time in the same loss epoch.
Failed Interop TestsQUIC Interop Runner, client vs. server, differences relative to 108fb8d. neqo-latest as client
neqo-latest as server
All resultsSucceeded Interop TestsQUIC Interop Runner, client vs. server neqo-latest as client
neqo-latest as server
Unsupported Interop TestsQUIC Interop Runner, client vs. server neqo-latest as client
neqo-latest as server
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Closing here, see #2408 (comment). |
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https://www.rfc-editor.org/rfc/rfc9002.html#section-7.3.2
When in a transient state (i.e.
State::RecoveryStartandState::PersistentCongestion) we return early, i.e. don't reenter recovery:neqo/neqo-transport/src/cc/classic_cc.rs
Lines 546 to 553 in 6cdbc0c
But when in
State::Recovery, we do reenterRecovery, i.e. callself.cc_algorithm.reduce_cwnd:neqo/neqo-transport/src/cc/classic_cc.rs
Line 577 in e365730
Thus in the following scenario we might reduce the cwnd twice in the same loss episode:
RecoveryStart.Recovery.Test for #2408.