Three correctness bugs surfaced by post-fix re-audit, plus minor
cleanups.
- Bug A (validation hang): checkPathValidationTimeoutLocked was
only called from handlePtoFired. PATH_CHALLENGE is ack-eliciting
so the peer ACKs it; that ACK resets consecutivePtoCount, which
means the PTO timer that used to host the budget check stops
firing. Validation could hang indefinitely on a peer that ACKs
but doesn't reply with PATH_RESPONSE. Fix: drive the budget
check from drainOutbound (every send-loop wake).
- Bug B (stale retire): under abrupt-migration semantics the
prior CID is abandoned the moment we rotate. Queuing the retire
only inside applyPathResponse meant two consecutive failed
validations would leave the original seq=0 unretired forever.
Fix: queue priorSeq in tryStartValidation; advance
activeCidSequence at trigger time so it tracks the on-wire DCID.
- Bug C (spec MUST violation): RFC 9000 §5.1.2 requires server-
forced retirement of the active CID when the peer's
retire_prior_to advances past it. Previously the parser silently
accepted the offer and we kept stamping a now-retired CID.
Fix: new PathValidator.forceRotateToHigherSequence; called from
applyPeerNewConnectionIdLocked after a successful Stored result.
No PATH_CHALLENGE needed (same path, just different CID).
Closes connection with CONNECTION_ID_LIMIT_ERROR if the pool
is empty when forced rotation is needed.
Concurrency:
- Add @Volatile to consecutivePtoCount. The driver kdoc claimed
it already was; it wasn't. The send-loop reads it lockless for
backoff calculation while three writers mutate it (driver PTO
fire, parser ACK reset, applyPeerPathResponseLocked reset).
Cleanup:
- Drop redundant destinationConnectionId re-stamp in
applyPeerPathResponseLocked (already rotated at challenge time).
- Fix PathMigrationResult kdoc to acknowledge that NotConnected
is produced only by the connection-level wrapper.
- Update applyPeerNewConnectionIdLocked kdoc with the §5.1.2
forced-rotation contract.
Tests:
- PathValidatorTest:
+ triggerRetiresPriorSequenceImmediately (Bug B)
+ twoConsecutiveFailedValidationsRetireAllAbandonedSequences
(Bug B regression — would have caught the original miss)
+ forceRotateRunsWhenWatermarkPassesActiveCid (Bug C)
+ forceRotateNoOpWhenWatermarkBelowActive (Bug C edge)
+ forceRotateRotatesAgainWhenNewerOfferAdvancesWatermark (Bug C cascading)
- ClientPathMigrationTest:
+ newConnectionIdWithRetirePriorToPastActiveForcesRotationOnSamePath
(Bug C wire-level)
+ Updated fullMigrationRoundTrip to assert RETIRE rides in the
same packet as PATH_CHALLENGE under abrupt-migration semantics.
+ Updated pathResponseWithMismatchingPayloadKeepsValidatingAndDcid
to reflect activeCidSequence advances at trigger time.
All :quic:jvmTest (39 tests in path-validation suite) and
:nestsClient:jvmTest pass.
https://claude.ai/code/session_01PVVhSQXvw4K4oQ46FzpgaT
Claude
07ba23a71c