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Claude
1df6441639
QuicLossDetection encapsulates the RFC 9002 §5–§6 algorithms:
- RTT estimation (§5): smoothedRtt, rttVar, latestRtt, minRtt
with first-sample bootstrap; ack-delay clamped against minRtt
so a peer reporting a large delay can't push the estimate
below its observed floor (§5.3 anti-exploit clamp).
- Loss-delay (§6.1.2): max(latestRtt, smoothedRtt) * 9/8,
clamped to GRANULARITY_MS (1 ms).
- detectAndRemoveLost (§6.1): walks the in-flight set,
removes entries that are either:
- more than PACKET_THRESHOLD (3) PNs below largestAckedPn,
OR
- sent more than lossDelay ago.
Returns the lost packets so step 6 can dispatch their tokens.
Wired into QuicConnectionParser's AckFrame handler:
1. Snapshot largest-acked send time BEFORE drain
2. Drain ACK'd packets (step 3)
3. If largestAckedPn advanced AND any drained packet was
ack-eliciting, update RTT (RFC 9002 §5.2 sample conditions)
4. detectAndRemoveLost on the surviving set; lost list dropped
for now — step 6 wires the dispatch
LevelState gains:
- largestAckedPn: Long? (high-water mark for packet-threshold)
- largestAckedSentTimeMs: Long? (RTT sample input)
QuicConnection gains:
- lossDetection: QuicLossDetection (single instance, RTT is
per-path; we model a single path)
Tests added (11, all pass):
- firstRttSample_setsAllRttFieldsAtomically
- secondRttSample_movesSmoothedRttTowardSample (math: 7/8 + 1/8)
- ackDelay_clampedAgainstMinRtt (anti-exploit clamp)
- negativeRttSample_isIgnored (clock skew defense)
- lossDelay_floor (initial 333*9/8 = 374)
- packetThresholdLost_removesPacketsBelowThreshold (PNs 0..6
when largestAcked=10, threshold=3 → 7..9 survive)
- timeThresholdLost_removesPacketsSentTooLongAgo (sentAt + delay
< now → lost; recent → kept)
- packetEqualToLargestAcked_notLost (edge case)
- emptyMap_returnsEmpty
- lostPackets_carryOriginalTokens (drain preserves token list)
- packetThresholdAndTimeThresholdMatch_singleRemoval (no
double-iteration)
Mirrors the subset of neqo's `recovery/mod.rs` tests in scope per
the plan: remove_acked, time_loss_detection_gap,
time_loss_detection_timeout, big_gap_loss,
duplicate_ack_does_not_update_largest_acked_sent_time. PTO tests
land in step 7.
Full :quic test suite passes.
https://claude.ai/code/session_01PYYez8a6sjiakyjAxsfCEQ