The Retry parser + integrity-tag verifier already existed in
RetryPacket.kt, but feedDatagram dropped Retry packets on the floor.
Hook them up:
- QuicConnectionParser.feedLongHeaderPacket detects RETRY type before
the standard parse-and-decrypt path, parses via RetryPacket, and
dispatches to QuicConnection.applyRetry.
- QuicConnection.start() now caches the ClientHello bytes (TLS only
emits ClientHello once; we need to re-queue the same bytes on the
fresh Initial keys after Retry). New applyRetry method:
verifies the integrity tag, swaps DCID to Retry's SCID, re-derives
Initial keys, resets the Initial PN space + sentPackets +
cryptoSend, re-enqueues the cached ClientHello, stores the Retry
token, and latches retryConsumed so a second Retry is dropped.
- LevelState.restoreFromRetry / PacketNumberSpaceState.resetForRetry
give applyRetry an in-place reset (the level reference is a `val`,
so we mirror discardKeys' field-reset pattern).
- QuicConnectionWriter.buildLongHeaderFromFrames threads
conn.retryToken through the Initial header's Token field on every
Initial we emit after Retry.
Per RFC 9001 §5.8, a Retry with a bad integrity tag is silently
dropped; per RFC 9000 §17.2.5.2, only one Retry is honored per
connection. Both invariants are tested.
New test: RetryHandlingTest covers the happy path (DCID swap, PN
reset, token threading, ClientHello replay, ≥1200-byte padding),
the bad-tag path, and the second-retry path.
Claude
d03e179816