Delayed ACKs; limit receive history

• [FEATURE] Improve Delayed ACKs extension and turn it on by default.
• Limit receive history to a finite amount of memory.

Bug fixes: CC, CIDs, memory leak

• [BUGFIX] Check whether ECN counts are set in ACK struct before using them.
• [BUGFIX] Calculate TLP timer correctly when only one packet is in flight.
• [BUGFIX] Min RTO delay is 200 milliseconds, not 1 second.
• [BUGFIX] Memory leak in QPACK decoder handler: discard hset when necessary.
• Allow retired and drained CIDs to be reused after a timeout.

Bug fixes

• [BUGFIX] min RTO delay is 200 ms , not 1 second.
• [BUGFIX] calculate TLP timer correctly when only one packet is in flight.
• [BUGFIX] discard CRYPTO frames from lower levels after connection promotion.
• [BUGFIX] cancel path response if path could not be initialized.
• [BUGFIX] if push promise fails, do not invoke hset destructor.

Bug fixes: client BBR, memory leak

• [BUGFIX] Get rough RTT estimate on receipt of Handshake packet. This prevents BBR on the client from miscalculating pacing rate, slowing down sending of ACK packets.
• [BUGFIX] Packets sent during handshake are app-limited.
• [BUGFIX] Bandwidth sampler starts in app-limited mode.
• [BUGFIX] Memory leak: free QPACK handler context in stream dtor.
• Logging improvements.

Migration and coalescing bug fixes

• [BUGFIX] Allow peer to migrate when its SCID is zero-length.
• [BUGFIX] PADDING size calculation: only one Short packet can be coalesced. (This should have been part of the fix in 2.24.1).
• Abort connect if received NEW_CONNECTION_ID but current DCID is zero-length.
• Improve log messages

SSL_CTX for client; bug fixes

• [API] Allow use of ea_get_ssl_ctx() on the client (optional). PR #186.
• [BUGFIX] Expand datagram with ack-eliciting Initial to 1200 bytes after connection promotion.
• [BUGFIX] Discard CRYPTO frames from lower encryption levels after connection promotion.
• [BUGFIX] Cancel path response if path could not be initialized.

ID-32 support; a couple of bug fixes

• [FEATURE] QUIC and HTTP/3 Internet Draft 31 support. Drop ID-30 and ID-31 support.
• [BUGFIX] Divide-by-zero in newly enabled conn stats code when no packets were sent.
• [BUGFIX] Memory leak in gQUIC client when server hello cannot be parsed.
• [BUGFIX] Server Initial packet size calculation.
• Log user-agent and CONN_CLOSE reason when peer reports error.
• Example programs: Specify ALPN for echo and md5 clients and servers (issue #184).
• Example programs: Don't add "QUIC_" prefix to lines in keylog file (issue #185).
• http_server: Fix fd leak in preadv mode; fix preadv() usage when reading from disk.

Revert 2.12.11

Release 2.12.12

Undo change in 2.12.11

Fix packetization threshold

• [BUGFIX] Update packetization threshold when writing to stream after packet size is reduced following an RTO.

QPACK experiments, log connection stats

• Add QPACK stats collection and experimentation mode, see the new es_qpack_experiment setting.
• Log busy connection stats every second using the new "conn-stats" log module.
• Log about skipping only once.
• Update HTTP/3 greased frame type formula.
• Use ls-qpack v2.2.1.