CHANGELOG revision 2f2f4363
12020-09-08
2    - 2.19.9
3    - [FEATURE] Add lsquic_stream_pwritev().  This function allows one to
4      reduce the number of system calls required to read a file from disk
5      by using lsquic_stream_pwritev() together with preadv(2).
6    - [BUGFIX] When stream is reset, it is writeable -- let user collect
7      the error.
8    - [BUGFIX] Calculate correct conn flow control if reading ends early.
9    - [BUGFIX] Remove stream from read and write queues on internal
10      shutdown.  This is a regression introduced in 2.19.7.
11    - [BUGFIX] Swapped arguments in IETF RESET_FRAME generation.
12    - Turn off mini conn history when compiling with Visual Studio; this
13      allows the project to compile on Windows again.
14    - http_client: Add -3 flag to stop reading from streams early; code
15      cleanup.
16    - Don't use -Werror.
17
182020-09-02
19    - 2.19.8
20    - [FEATURE] Update the timestamp extension to latest version.
21    - [FEATURE] Cope with appearance of ECN blackholes.
22    - [OPTIMIZATION] return packno offset and size when header is generated.
23    - [BUGFIX] ignore old ACK frames in mini conns.
24    - [BUGFIX] Mark initial server path as initialized.
25    - [BUGFIX] Do not merge ACK if ECN counts do not match.
26    - Turn incoming packet number history in mini conn back on.
27    - Record mini conn event history again when compiled in debug mode.
28    - IETF mini conn: log when ACK is queued.
29    - Clean up and refactor code in several places.
30
312020-08-26
32    - 2.19.7
33    - Handle ECT-CE event: issue a loss event.
34    - Log the fact that we ignore SETTINGS_MAX_HEADER_LIST_SIZE.
35    - Use Max Push ID in GOAWAY frame to cancel promises.
36    - Add support for HTTP/3 CANCEL_PUSH frame.
37    - lsquic_stream_is_pushed: streams without headers are never pushed.
38    - [BUGFIX] Regression in lsquic_stream_shutdown_internal: now it shuts down.
39    - Improve logic whether to generate CONNECTION_CLOSE.
40
412020-08-20
42    - 2.19.6
43    - Don't process incoming ECN marks if ECN is not enabled.
44    - Schedule ACK when incoming packet is marked with CE.
45
462020-08-11
47    - 2.19.5
48    - [BUGFIX] Generate frame record when moving an ACK from one buffered
49      packet to another.
50
512020-08-06
52    - 2.19.4
53    - [BUGFIX] Do not return an oversize MTU probe to connection twice.
54    - [FEATURE] Delayed Acks updated to latest draft.  Still experimental.
55    - Minor code cleanup in IETF full connection.
56
572020-08-04
58    - 2.19.3
59    - [BUGFIX] Regression in 2.19.1 that breaks Q050
60
612020-07-30
62    - 2.19.2
63    - [BUGFIX] Do not reduce PLPMTU size by network overhead.
64    - [BUGFIX] Windows build.
65
662020-07-29
67    - 2.19.1
68    - [FEATURE] DPLPMTUD support.  IETF connections now search for the
69      maximum packet size, improving throughput.
70    - [DEBUG] Record event in stream history when on_close() is called
71      in dtor.
72
732020-07-22
74    - 2.18.2
75    - [BUGFIX] Send prediction: lone path challenges do not get squeezed out
76    - Fix crash in http_client: now -K and -B can be used simultaneously
77
782020-07-14
79    - 2.18.1
80    - [FEATURE] Implement the "QUIC bit grease" extension.
81    - [BUGFIX] Selecting CID used for logging on client.
82    - [BUGFIX] Header protection assertion.
83    - [BUGFIX] Server: enable SSL key logging when cert lookup callback
84      is not set.
85    - Remove some dead code.
86
872020-07-06
88    - 2.18.0
89    - [API] Rename "0-RTT" to "session resumption." In IETF QUIC, "0-RTT"
90      always refers to early data, meaning a request that the server can
91      reply to in the very first return flight.  A more appropriate name
92      for what we support on the client site is "session resumption," which
93      is standard TLS terminology.  Later, when we add support for 0-RTT
94      (early data), we can use the 0-RTT terminology again, this time in
95      proper context.
96    - [BUGFIX] Do not set certificate callback if ea_lookup_cert is NULL.
97    - [BUGFIX] Make connection tickable when it's marked as closed.
98    - [BUGFIX] Fail certificate lookup if SNI is not present in HTTP mode.
99    - Several documentation fixes and improvements.
100    - Minor code cleanup.
101
1022020-06-24
103    - 2.17.2
104    - [BUGFIX] Infinite loop in stream: advance read offset when discarding
105      data.
106    - [OPTIMIZATION] Header protection: only initialize cipher once.
107    - [OPTIMIZATION] Batch header protection application.
108
1092020-06-18
110    - 2.17.1
111    - [FEATURE] QUIC and HTTP/3 Internet Draft 29 support.
112    - [BUGFIX] Check that scheduled packets are also sendable when
113      calculating a connection's "tickable" property.
114    - [BUGFIX] Don't count scheduled packets as in-flight when pacer is
115      checked on tick.
116    - gQUIC: delay calling on_new for pushed stream until headers are
117      available.
118    - Allow nested calls to lsquic_engine_connect().
119
1202020-06-15
121    - 2.16.3
122    - [OPTIMIZATION] Stash up to two reordered packets in IETF mini conn
123      instead of dropping them.
124    - [BUGFIX] Crash: check decrypt context before using it.  This regression
125      was introduced in 2.16.2.
126
1272020-06-12
128    - 2.16.2
129    - [BUGFIX] ID-28: do not use TLS middlebox compatibility mode in
130      ClientHello.  This change requires using a newer version of BoringSSL.
131    - [BUGFIX] Free connections in Advisory Tick Time Queue in engine dtor.
132    - [BUGFIX] IETF QUIC client: narrow migration check to a single path.
133    - [BUGFIX] NULL dereference: set function pointers for alarm for path
134      challenges 2 and 3.
135    - [BUGFIX] HTTP/3 headers may be followed immediately by trailers.
136    - [BUGFIX] Log messages when SCID changes.
137
1382020-06-09
139    - 2.16.1
140    - [FEATURE] Use "no-progress timeout" after which connection is closed.
141    - [BUGFIX] Select new SCID when current SCID is retired.
142    - [BUGFIX] Don't warn about dropped Initial packet sequence gaps during
143      mini/full handoff.
144    - [BUGFIX] Send correct conn error when HTTP/3 frame is truncated.
145    - [BUGFIX] Mini conn: consider amplification when deciding to return
146      TICK_SEND.
147    - [BUGFIX] Don't double-count tag length in amplification logic.
148    - [BUGFIX] Don't squeeze out lone path challenges.
149    - [BUGFIX] Log messages dealing with scheduled packet queue squeezing.
150    - [BUGFIX] don't wipe current path if no path challenge responses
151      come back.
152    - [BUGFIX] When path is reset, don't lose path_id which is used for
153      logging.
154    - Downgrade flow control violations to info log level from warnings.
155    - Fix connection cap extra check, avoid checks in nested calls.
156    - Fix some unit tests when extra checks are enabled.
157    - Use ls-hpack 2.2.1.
158    - Turn off unconditional extra checks for IETF clients.
159    - Extra checks: don't verify sent size of hello packets.  Client
160      changes DCID length and this check will fail.
161
1622020-06-03
163    - 2.16.0
164    - [API] Use lsxpack_header v206.
165    - [FEATURE] Windows supported.
166    - [BUGFIX] Fix uninitialized variable use in client (regression in
167      2.15.0).
168    - Use ls-hpack 2.2.0.
169    - Use ls-qpack 2.2.0.
170    - Sample programs: fix the way maximum number of packets is
171      calculated.
172    - Remove some dead code.
173
1742020-05-27
175    - 2.15.0
176    - [FEATURE] QUIC and HTTP/3 Internet Draft 28 support.
177    - [BUGFIX] Ignore Retry packets after other packets are decrypted
178      successfully.
179    - [BUGFIX] Transport parameter decoding: CID no longer has 4-byte
180      length minimum.
181    - http_client: fix and optimize lsxpack_header allocator.
182    - Drop support for Internet Draft 25.
183
1842020-05-19
185    - 2.14.8
186    - Support Android.
187    - Rerrange tree: move command-line examples into bin/ and unit
188      tests into tests/ from test/unittests/.
189
1902020-05-12
191    - 2.14.7
192    - [BUGFIX] ALPN-to-version mapping: do not skip h3-Q050.
193    - [BUGFIX] Frame reader: skip headers if target stream is closed.
194
1952020-05-06
196    - 2.14.6
197    - [BUGFIX] Fix amplification mitigation in 0-RTT case.
198    - [BUGFIX] IETF mini connection should not tickable if cannot send
199      a packet due to amplification.
200    - [BUGFIX] Fail if active_connection_id_limit TP is smaller than 2.
201    - [BUGFIX] Qlog server certificates for IETF QUIC connections.
202    - [BUGFIX] Uninitialized struct padding usage in tokgen (benign).
203    - [BUGFIX] Incorrect argument to shi_lookup() (benign).
204
2052020-04-29
206    - 2.14.5
207    - [BUGFIX] In coalesced datagram, ignore packets whose CID does not match.
208    - [BUGFIX] Frame reader: skip headers if target stream is not found.
209    - [BUGFIX] Log message in QPACK decoder handler.
210
2112020-04-24
212    - 2.14.4
213    - [BUGFIX] Heed es_rw_once for pushed HTTP/3 streams.
214    - [BUGFIX] IETF client: set correct flags on bidirectional streams.
215    - [BUGFIX] Generate Cancel Stream QPACK instructions for abandoned
216      streams.
217    - [BUGFIX] Do not call header callbacks after stream is closed.
218    - Use ls-qpack 2.1.1
219
2202020-04-15
221    - 2.14.3
222    - [BUGFIX] gQUIC: pass correct stream to hsi_create_header_set() callback.
223    - [BUGFIX] Use ls-hpack 2.1.1
224    - Improve stream code readability.
225    - Use ls-qpack 2.0.5
226
2272020-04-08
228    - 2.14.2
229    - [BUGFIX] Use ls-qpack 2.0.4
230    - [BUGFIX] Honor max packet size on the client and when path changes.
231    - http_server: fix prepare_decode() function.
232
2332020-04-07
234    - 2.14.1
235    - [BUGFIX] Place connections on tickable queue when sending is reenabled.
236    - [BUGFIX] A connection is tickable if it has unsent packets.
237    - [BUGFIX] Heed peer's max_packet_size transport parameter.
238
2392020-03-30
240    - 2.14.0
241    - [API] Use lsxpack_header structure to send HTTP headers.
242    - [OPTIMIZATION] nocopy's readable_bytes() function.
243    - http_server: fix typo in error message
244    - Use ls-hpack 2.1.0.
245    - Use ls-qpack 2.0.0.
246
2472020-03-23
248    - 2.13.3
249    - [BUGFIX] ACK ping-pong: TIMESTAMP frame is not to be acked.
250
2512020-03-13
252    - 2.13.2
253    - [BUGFIX] Use of new lsxpack_header API's hsi_prepare_decode().
254
2552020-03-12
256    - 2.13.1
257    - [API] Use lsxpack_header structure to process incoming headers.
258    - [BUGFIX] Fix assertion when zero-padding Initial packet.
259    - [BUGFIX] Use idle timeout before we learn of peer's value.
260    - Use ls-hpack 2.0.1 -- has lsxpack_header changes.
261    - Use ls-qpack 0.14.0 -- new, common with ls-hpack, XXH seed (not
262      used yet).
263    - Code cleanup: prefix exported functions with "lsquic_".
264
2652020-03-02
266    - 2.12.0
267    - [FEATURE] QUIC timestamps extension.
268    - [API] New: ea_alpn that is used when not in HTTP mode.
269    - [BUGFIX] SNI is mandatory only for HTTP/3 and gQUIC.
270    - [BUGFIX] Benign double-free -- issue #110.
271    - [BUGFIX] Printing of transport parameters.
272
2732020-02-24
274    - 2.11.1
275    - [FEATURE] QUIC and HTTP/3 Internet Draft 27 support.
276    - [FEATURE] Add experimental delayed ACKs extension.
277    - Drop support for Internet Draft 24.
278    - Code cleanup.
279
2802020-02-14
281    - 2.10.6
282    - [BUGFIX] HTTP/3 framing: don't misinterpret rare occurence as error.
283    - [BUGFIX] Send gap warning due to missing poisoned packet.
284    - Stream unit test for scenario in issue #106.
285
2862020-02-13
287    - 2.10.5
288    - [BUGFIX] BBR: call cci_sent() with correct arguments and at correct
289      time.
290    - Refactor transport parameters module.
291    - Minor code cleanup.
292
2932020-02-11
294    - 2.10.4
295    - [BUGFIX] Send HANDSHAKE_DONE only after Finished is received.
296    - [BUGFIX] Don't treat garbage UDP padding as library error; ignore
297      it instead.
298    - [BUGFIX] Fix compilation on FreeBSD (missing header).
299    - Code cleanup: remove unnecessary #includes.
300
3012020-01-31
302    - 2.10.3
303    - [BUGFIX] Cancel path responses and challenges on old path when
304      switching to new path
305    - Logging network path information.
306
3072020-01-30
308    - 2.10.2
309    - [BUGFIX] Do not delay ACKs for Initial and Handshake packets.
310    - [BUGFIX] Send PATH_CHALLENGE if path changed before mini conn
311      promotion.
312    - Logging improvements.
313    - http_client: discard data faster.
314
3152020-01-29
316    - 2.10.1
317    - [BUGFIX] Coalesced packets could get longer than normal packet
318      size.
319    - Add spin bit configuration option es_spin (-o spin=[01]).
320    - Disable spin bit in 1/16 of connections.
321    - Improve logging a bit.
322
3232020-01-28
324    - 2.10.0
325    - [FEATURE] QUIC and HTTP/3 Internet Draft 25 support.
326    - [API] Drop support for ID-23.
327    - [BUGFIX] Set key phase bit on outgoing packets correctly.
328    - Code cleanup.
329
3302020-01-20
331    - 2.9.0
332    - [API] Drop support for Q039.
333    - Improve ACK-queuing logic.  Send an ACK once in a while if
334      peer keeps on sending non-ack-eliciting packets.
335    - Improve Alt-Svc string: Q050 and later are not included in
336      the old-style "quic" string.
337    - Send stateless resets if connection could not be promoted.
338    - Schedule MAX_DATA if needed when DATA_BLOCKED is received.
339    - Use ls-qpack 0.11.2 -- needed for server push optimization.
340    - Code cleanup: handle some error cases, improve logging.
341
3422020-01-16
343    - 2.8.9
344    - [BUGFIX] Use ls-qpack 0.11.1
345    - [OPTIMIZATION] Generate random bytes in batches.
346    - Change loss_bits transport parameter ID to 0x1057 following
347      latest draft.
348    - Randomize period with which PINGs are sent to elicit ACKs.
349    - Some refactoring and code cleanup.
350
3512020-01-14
352    - 2.8.8
353    - [BUGFIX] Invalid read when parsing IETF transport parameters
354      (this was benign).
355    - [OPTIMIZATION] Frame bundling when using buffered packets in
356      IETF QUIC: a) flush QPACK decoder stream and b) include ACKs
357      in opportunistic fashion.
358    - Fix HTTP/3 framing unit test.
359    - Code cleanup.
360
3612020-01-09
362    - 2.8.7
363    - [BUGFIX] Initial packet size check for IETF mini conn applies to
364      UDP payload, not QUIC packet.
365    - Support old and new school loss_bits transport parameter.
366    - Use Q run length of 64 as suggested in the loss bits Draft.
367    - Undo square wave count when packet is delayed.
368    - Code cleanup; minor fixes.
369
3702020-01-06
371    - 2.8.5
372    - [HTTP3] Verify number of bytes in incoming DATA frames against
373      content-length.
374    - [HTTP3] Stop issuing streams credits if peer stops opening QPACK
375      decoder window.  This addresses a potential attack whereby client
376      can cause the server to keep allocating memory.  See Security
377      Considerations in the QPACK draft.
378    - [BUGFIX] Mini conn: don't shorten max packet size for Q050 and later.
379    - [BUGFIX] Init IETF connection flow controller using correct setting.
380    - [BUGFIX] Fix unintended sign extension when removing header protection.
381    - Code cleanup and minor fixes.
382
3832019-12-30
384    - 2.8.1
385    - [FEATURE] Use occasional packet number gaps to detect optimistic
386      ACK attacks.
387    - [BUGFIX] Q050 client: all packet numbers are in the App PNS.
388    - [OPTIMIZATION] Merge multi-range ACK frames, not just single-range
389      ACK frames.
390    - IETF QUIC: use RTT estimate in ack timeout calculation.
391    - IETF handshake: abort conn when unexpected errors occur.
392    - Use PING rather than MAX_DATA frames to elicit ACKs from peer.
393    - Server: enforce 1200 byte Initial minimum packet size.
394    - [CLEANUP] Remove code to disable gQUIC crypto.
395    - [CLEANUP] Remove n_timestamps from ACK info struct.
396    - Optimize driver: reuse previous ancillary message when possible.
397
3982019-12-23
399    - 2.8.0
400    - [FEATURE] Add support for Q050.
401    - [OPTIMIZATION] Reduce mallocs in gQUIC handshake.
402    - [BUGFIX] Disable redo of failed STREAM frame insertion with debug
403      logging.
404
4052019-12-18
406    - 2.7.3
407    - [DEBUG] Further dedup next advisory tick messages when reason is
408      the same.
409    - [BUGFIX] Update size of `a` array in TP struct.  Fixes (benign)
410      GitHub bug #94.
411    - Use Cubic by default again instead of BBR, as it delivers more
412      consistent performance.
413
4142019-12-11
415    - 2.7.2
416    - [BUGFIX] Send controller: update scheduled bytes when DCID length
417      changes (IETF client).
418    - [BUGFIX] Drop alarm check from sanity test.  It no longer works now
419      that we use loss chains.
420    - [PORTABILITY] Fix build on Alpine Linux.
421    - [PORTABILITY] Fix build using XCode.
422    - Client initial DCID length: use RAND_bytes() instead of rand(3).
423    - Add unit tests for connection min heap.
424    - [DEBUG] Log CID in gQUIC handshake module
425    - [DEBUG] Turn on extra checks for IETF client send controller.
426    - [DEBUG] Dedup next advisory tick messages when reason is IDLE timer.
427    - [DEBUG] QPACK decoder handler: log header error code.
428
4292019-12-05
430    - 2.7.1
431    - [BUGFIX] client: don't call ignore_init() in middle of batch send.
432      ignore_init() makes an assumption that the send controller has access
433      to all outgoing packets.  This change wraps a few IETF full connection
434      methods to delay calling ignore_init() until the engine returns all
435      outgoing packets that were batched.
436    - [BUGFIX] set errno to EAGAIN if sendmmsg() can't send all of them.
437      This needs to be done because the value of errno may be lost on
438      some platforms.
439    - [BUGFIX] Typo that set all bits in sm_qflags lead to crashes.
440    - [BUGFIX] Do not cancel header block processing after failure, as
441      QPACK releases the reference in that case.
442    - [CLEANUP] IETF encrypt: replace assert(0) with a warning.
443    - Several small improvements to the test server.
444
4452019-11-27
446    - 2.7.0
447    - [API, FEATURE] Close connection immediately when ea_packets_out()
448      fails with errno != EAGAIN.  The API change is that errno is now
449      examined.  Make sure to set it if using something other than
450      sendmsg() to send packets.
451    - [CLEANUP] Immediate close logic in IETF full conn.
452    - [CLEANUP] Fix bogus warning about uninitialized `pair' variable.
453
4542019-11-22
455    - 2.6.7
456    - [FEATURE] Implement the QL extension (offered by default).
457    - [BUGFIX] Abort when encountering unexpected HTTP/3 frames.
458    - [BUGFIX] Acknowledge (QPACK) HTTP/3 trailers correctly.
459    - [DEBUG] Turn on debug message for next advisory tick.
460
4612019-11-20
462    - 2.6.6
463    - [BUGFIX] Using HTTP/3 to HTTP/1.x converter.
464    - [BUGFIX] Truncate log messages instead of throwing them away.
465
4662019-11-15
467    - 2.6.5
468    - [BUGFIX] High priority buffered packet queue length.
469    - [BUGFIX] Rain time calculation: max_ack_delay is in milliseconds.
470
4712019-11-12
472    - 2.6.3
473    - [BUGFIX] Close DATA frames with empty payload correctly.
474
4752019-11-11
476    - 2.6.2
477    - [BUGFIX] SCID!=ODCID rule applies to Retry packets, not regular
478      packets.
479    - [BUGFIX] Zero-RTT: BoringSSL no longer flips read/write secrets.
480    - [BUGFIX] Truncate ACK frame rather instead of aborting IETF
481      connection.
482    - [BUGFIX] Client: don't send duplicate reset tokens.
483    - [BUGFIX] Remove invalid assertion in H3 framing code.
484    - Silence a warning in send ctl by restructuring switch() statement.
485
4862019-11-08
487    - 2.6.1
488    - [BUGFIX] set retry token on all resubmitted packets.
489    - Event log: log sent packet flags.  In particular, this allows one
490      to see whether token was sent.
491    - Don't migrate client if es_allow_migration is false.
492
4932019-11-07
494    - 2.6.0
495    - [FEATURE] QUIC and HTTP/3 Internet Draft 24 support
496
4972019-11-07
498    - 2.5.2
499    - [BUGFIX] argument order to gQUIC client constructor.  Regression
500      introduced in 2.5.0.
501    - [BUGFIX] split buffered packet error recovery: destroy the correct
502      packet.
503
5042019-11-04
505    - 2.5.1
506    - [BUGFIX] Fix double-free when emptying a packet number space.
507    - [BUGFIX] http_server: fix md5sum handler: handle EOF correctly.
508    - [BUGFIX] Use random values in bits 4 and 5 of the first byte of
509      verneg packets (regression introduced in 2.5.0).
510    - [OPTIMIZATION] Don't compile in expensive attq checks by default.
511    - [OPTIMIZATION] http_server: compile regexes only once.
512
5132019-10-31
514    - 2.5.0
515    - [API] lsquic_engine_connect() can now be passed QUIC version to use.
516    - [OPTIMIZATION] Queue opportunistic ACKs if there is data to be sent.
517    - [BUGFIX] Don't evict streams from priority iterator if there is
518      only one queue.
519    - [OPTIMIZATION, BUGFIX] Several other optimizations and bug fixes.
520    - Use ls-qpack v0.10.7.
521
5222019-10-24
523    - 2.4.10
524    - [BUGFIX] IETF QUIC server: fix uninitialized variable use.
525    - [BUGFIX] make sure TLSv1.3 is not disabled in SSL object.
526    - [BUGFIX] Use issuer name and serial number to cache certs (SKID
527      values are not unique).
528    - [BUGFIX] Always set the idle alarm in IETF connection so that it
529      can time out.
530    - Use ls-qpack v0.10.6, as it silences some warnings.
531
5322019-10-21
533    - 2.4.8
534    - [OPTIMIZATION, BUGFIX] Use ls-qpack v0.10.5.
535
5362019-10-15
537    - 2.4.7
538    - Add echo client and server to the distibution.
539    - Add MD5 client and server to the distibution.
540    - Fix http_client: check command-line arguments better, prevent crash.
541    - Fix IETF conn: can_write_ack() should only care about APP PNS.
542    - Client: delay stream creation until handshake succeds.
543    - Reset HTTP stream whose write end is closed prematurely.
544    - Fix tickable(): mirror behavior of tick() wrt buffered packets.
545    - Log reason why engine is tickable.
546
5472019-10-11
548    - 2.4.6
549    - Minor code cleanup and logging improvements.
550    - Server and client programs: include library version (e.g. 2.4.6)
551      into `server' and `user-agent' headers.
552
5532019-10-08
554    - 2.4.5
555    - [OPTIMIZATION]: flush encoder stream only when necessary.
556    - [BUGFIX] Use ls-qpack v0.10.2 for new API -- and for a bug fix.
557    - [BUGFIX] Typo in IETF conn SETTINGS writer.
558    - Use latest BoringSSL.
559
5602019-10-08
561    - 2.4.4
562    - [API] Add lsquic_alpn2ver() to aid parsing Alt-Svc header.
563    - [BUGFIX] NULL dereference when H3 frame header would be split.
564    - [BUGFIX] Do not close fixed-size H3 frame prematurely.
565    - [BUGFIX] Allow PING frames in IETF mini conn.
566    - [BUGFIX] Mini conns: don't send any packets after receiving
567      CONNECTION_CLOSE.
568    - [BUGFIX] Client migration: reserve slot for DCID from transport params.
569    - [BUGFIX] Allow max_early_data_size=0 -- early_data might not be there.
570    - [BUGFIX] Use an invalid stream number to reset BPT cache (zero is now a
571      valid stream number).
572    - [SPEC] Use FINAL_SIZE_ERROR when FIN mismatch is detected.
573    - [OPTIMIZATION] Closed connection only gets one chance to send packets.
574    - [OPTIMIZATION] Flush headers stream before packetizing stream data.
575    - [OPTIMIZATION] process QPACK encoder STREAM frames immediately.
576    - Update ls-qpack to v0.10.1.
577
5782019-09-30
579    - 2.4.3
580    - Add GQUIC versions to the list of h3 ALPNs for Alt-Svc header.
581      For example, h3-Q043.  Chrome will switch to using this format at
582      some point in the future.
583    - [BUGFIX] Send correct value in max_streams_uni transport param
584    - [SPEC] Abort IETF QUIC connection if max_early_data_size is not set
585      to 0xFFFFFFFF
586
5872019-09-23
588    - 2.4.2
589    - [BUGFIX] H3 framing: fix zero-byte write when space is available
590    - [BUGFIX] Don't send STREAM frame when incoming unidirectgional stream
591      is closed
592    - [BUGFIX] Cancel all pending writes by stream reset by a GOAWAY
593    - [BUGFIX] Fix use-after-free in IETF full conn
594    - [OPTIMIZATION] Wait for session tickets for two seconds and then drop
595      SSL object and crypto streams.
596
5972019-09-18
598    - 2.4.0
599    - [FEATURE] QUIC and HTTP/3 Internet Draft 23 support
600
6012019-09-13
602    - 2.3.1
603    - [BUGFIX] Fix memory leaks
604    - [BUGFIX] Fix unit tests
605
6062019-09-12
607    - 2.3.0
608    - [FEATURE] BBR congestion control is on by default
609    - [BUGFIX] BBR app-limited logic
610    - [BUGFIX] Fix uninitialized warnings in IETF
611    - [BUGFIX] Update ls-qpack to v0.9.14
612    - [CLEANUP] Code cleanup
613
6142019-09-11
615    - 2.2.0
616    - [FEATURE] Server code is included in the library
617    - [FEATURE] IETF QUIC and HTTP/3 Support (ID-22)
618
6192019-05-13
620    - 1.21.2
621    - [OPTIMIZATION] HPACK: use history to improve compression performance
622
6232019-05-06
624    - 1.21.1
625    - [BUGFIX] If FIN or RST not received, don't delay stream destruction.
626    - [OPTIMIZATION] Speed up HPACK encoder by using same hash value to
627      search static and dynamic tables.
628
6292019-04-12
630    - 1.21.0
631    - [FEATURE] Add qlog log module.
632
6332019-04-01
634    - 1.20.0
635    - [FEATURE] Add support for Q046.
636
6372019-03-19
638    - 1.19.6
639    - [BUGFIX] Ensure that Largest Observed does not decrease in ACKs we
640      send.  ACK frames placed in packets in buffered queues (optimization
641      introduced in 1.17.15) can be preceded by an ACK frame generated later.
642      In this case, the older ACK frame should not be sent out, as Chromium-
643      based servers flags decrease in the ACK frame's Largest Observed value
644      as an error.
645
6462019-03-05
647    - 1.19.5
648    - [BUGFIX] Use correct public key from PUBS based on KEXS index.
649    - [BUGFIX] Check flags before dispatching writes, avoiding assert.
650    - [BUGFIX] Set :scheme to "https" (instead of "HTTP").
651
6522019-02-25
653    - 1.19.4
654    - [BUGFIX] Check buffer bounds when looking up version in 0-RTT blob.
655    - [BUGFIX] http_client: don't fetch 0-rtt info if handshake failed.
656    - Log number of pacer calls at DEBUG, rather than NOTICE, level.
657
6582019-02-18
659    - 1.19.3
660    - [BUGFIX] Q044: don't encode packet number in 6 bytes.  Six-byte
661      packet number encoding does not exist in Q044.  This fixes a
662      regression introduced in '[BUGFIX] Buffered packets can contain
663      ACK frames' -- we need to keep QUIC version in mind when selecting
664      the longest possible packet number encoding used for the buffered
665      packet that carries the ACK.
666    - [BUGFIX] Do not increase CWND when timeout occurs.
667    - http_client: support setting handshake timeout on command line.
668      Use -o handshake_to=timeout.
669    - http_client: use -k to connect UDP socket to pick up ICMP errors.
670    - http_client: allow pathless mode, when only handshake is performed
671      without issuing any requests.  This can be done by simply not
672      specifying a -p flag on the command line.
673
6742019-02-11
675    - 1.19.2
676    - [BUGFIX] Begin negotiation with version provided in 0-RTT info.
677    - [BUGFIX] Version checking in zero_rtt deserialize function.
678
6792019-02-04
680    - 1.19.1
681    - [BUGFIX] Fix Windows build.
682
6832019-02-04
684    - 1.19.0
685    - [FEATURE, API Change] 0-RTT support.  Add function to export 0-RTT
686      information; it can be supplied to a subsequent connect() call.
687    - [FEATURE] Add -0 flag to http_client to exercise 0-RTT support.
688    - [BUGFIX] Resuscitate the Windows build.
689    - [BUGFIX] Send HTTP settings (max header list size) if necessary.
690    - [BUGFIX] Buffered packets can contain ACK frames.
691    - [BUGFIX] Make packet writeable once all STREAM frames are elided.
692    - [BUGFIX] Fix potential null dereference when realloc fails.
693    - cmake: simplify build configuration.
694
6952019-01-28
696    - 1.18.0
697    - [API Change] Can specify clock granularity in engine settings.
698    - [BUGFIX] Pacer uses fixed clock granularity.  Since the change on
699      2018-04-09, it is not necessary to try to approximate the next tick
700      time in the pacer: it can use fix clock granularity specified by
701      the user.
702    - [BUGFIX] Do not tick constantly before handshake is done.
703    - [BUGFIX] Do not exit tick prematurely: reuse packet with ACK.  Even
704      if we cannot allocate *more* packets, we could still be able to write
705      to one already allocated.
706    - [BUGFIX] Do not schedule pacer if there are no lost packets.
707
7082019-01-17
709    - 1.17.15
710    - [BUGFIX] http_client: make sure only one read per on_read() callback
711      is performed in the header conversion bypass (-B) mode.
712    - http_client: with -E, assign random priority when stream is created.
713    - [OPTIMIZATION] On immediate write, place an ACK frame into the first
714      buffered packet if an ACK is queued.  This reduces the number of
715      standalone ACK packets.
716    - [OPTIMIZATION] Allow placing more than one STREAM frame from the same
717      stream into an outgoing packet.  This change minimizes the number of
718      buffered packets required to store several small HTTP messages by
719      virtue of allowing more than one STREAM frame from HEADERS stream in
720      the same packet.
721    - [OPTIMIZATION] Flush headers when writing to buffered packets.  This
722      causes the headers to be written to the same buffered packet queue,
723      thereby improving packet utilization, especially for small HTTP
724      messages.
725
7262019-01-16
727    - 1.17.14
728    - [FEATURE] http_client can now collect stats: time to connect, TTFB,
729      time to download, requests per seconds, and bandwidth.  See -t flag.
730    - [BUGFIX] http_client: -B, -K, and -r can be used at the same time.
731    - [BUGFIX] http_client: do not display cert chain before each request.
732      Now this is only done once per connection, if the handshake is
733      successful and -a option is given.
734    - [BUGFIX] Do not wait to dispatch on_close() after reading.  If a
735      stream is scheduled to be closed after on_read() callback returns,
736      close it immediately instead of waiting until the end of the tick.
737      If client creates new request from on_close() event, they will be
738      processed in the same tick instead of waiting for the next one.
739    - [BUGFIX] HEADERS stream is critical: always treat it with highest
740      priority.
741
7422019-01-10
743    - 1.17.12
744    - [FEATURE] http_client can now issue parallel requests in the context
745      of a single connection.  See -w option.
746
7472019-01-03
748    - 1.17.11
749    - Fix strict aliasing warning in optimized compilation.
750
7512018-12-27
752    - 1.17.10
753    - Fix the example program to be able to use parallel connections
754      again.  (See the -n argument.)
755
7562018-12-18
757    - 1.17.9
758    - [BUGFIX] Engine: reduce minimum batch size from 256 to 4
759
7602018-12-10
761    - 1.17.8
762    - [BUGFIX] Fix compilation on FreeBSD and 32-bit Linux
763
7642018-12-03
765    - 1.17.7
766    - [BUGFIX] Do not unset PING alarm before ringing expired alarms.
767      This prevented PING from ever being sent.
768
7692018-11-29
770    - 1.17.6
771    - Add failsafe: resume sending packets after some time
772
773      The change puts a 1-second limit on the amount of time the engine
774      will not send packets after some packets are delayed.  This makes
775      the library robust in case the user does not unblock the engine
776      explicitly using lsquic_engine_send_unsent_packets() call.
777
778    - [BUGFIX] Handle corner cases in send controller when packets are
779      a) delayed or b) dropped during repackaging.
780    - [BUGFIX] Memory leak: destroy buffered packets during controller
781      cleanup.
782
7832018-11-16
784    - 1.17.3
785    - [BUGFIX] Do not send STOP_WAITING frames when using Q044
786
7872018-10-19
788    - 1.17.2
789    - [BUGFIX] Memory leak in test_frame_rw unit test.
790    - [BUGFIX] Parsing packets with short IETF header: do not overwrite
791      flags.  (Only a problem in unit tests -- benign otherwise.)
792
7932018-10-16
794    - 1.17.0
795    - [API Change] Packet out Memory Interface (PMI) update:
796      - Split PMI pool return into pmi_release and pmi_return
797      - PMI callbacks take peer_ctx and is_ipv6 arguments
798    - [BUGFIX] Fix use-after-free when certificate is updated
799    - Silence gcc warning in optimized mode by performing useless
800      initialization
801    - cmake: use the standard variable CMAKE_BUILD_TYPE instead of
802      DEVEL_MODE
803
8042018-10-03
805    - 1.16.0
806    - [API Change] Add lsquic_conn_n_avail_streams()
807    - [BUGFIX] only dispatch crypto stream read events if WANT_READ is on
808
8092018-09-27
810    - 1.15.0
811    - [API Change] Add LSCONN_ST_PEER_GOING_AWAY to the list of conn statuses
812    - [BUGFIX] free uncompressed headers correctly when error occurs
813
8142018-09-12
815    - 1.14.3
816    - [BUGFIX] Do not abort conn on STREAM frame for a reset stream
817    - [BUGFIX] Drop packets that would become empty due to repackaging.
818      Packets on the scheduled queue may be marked for repackaging.
819      Frames such as ACK frame that are never resent are removed from
820      repackaged packets.  We must check that the newly repackaged packet
821      would not be empty.  If it would be, it is destroyed instead and
822      the next packet on the scheduled queue is used.  Note that this
823      change only affects the logic to return the next packet to be sent.
824      Lost packets that are being rescheduled are already processed in
825      this fashion.
826    - Byteswap CID before logging it - this makes it match Chrome CIDs.
827      (Except Q035, which is the last little-endian GQUIC version we
828      support.)
829
8302018-09-06
831    - 1.14.0
832    - [API Change] Disable packet sending if full batch cannot be sent
833      If lsquic_packets_out_f() cannot send the whole batch, disable
834      packet sending until lsquic_engine_send_unsent_packets() is called.
835    - [BUGFIX] Handle case when STREAM frame does not fit.
836    - [BUGFIX] Always allow incoming STREAM frames to overlap.  Peers
837      may send overlapping STREAM frames even if using versions older
838      than Q043.
839    - Custom header set fixes:
840      - set "FIN reached" flag when custom header with FIN flag is
841        claimed;
842      - do not return custom header set for a reset stream.
843
8442018-08-27
845
846    - 1.13.0
847    - [FEATURE, API Change] Add ability to create custom header set
848      objects via callbacks.  This avoids reading and re-parsing
849      headers from the stream.
850
8512018-08-27
852
853    - 1.12.4
854    - Fix memory leak when engine is destroyed
855    - Fix memory leak in http_client
856    - Fix gcc warning in unit tests
857
8582018-08-22
859
860    - 1.12.3
861    - [BUGFIX] Fix duplicate STREAM frame detection
862
8632018-08-20
864
865    - 1.12.2
866    - [BUGFIX] Update count of scheduled bytes when adjusting size of
867      an already-scheduled packet.
868    - Emit info instead of warning messages when stream is used in
869      unexpected ways.
870
8712018-08-17
872
873    - 1.12.0
874    - [FEATURE, API Change] Add support for certificate verification
875
8762018-08-16
877
878    - 1.11.1
879    - [BUGFIX] Fix STOP_WAITING frame processing in the new Q044 code
880
8812018-08-15
882
883    - 1.11.0
884    - [FEATURE] Add support for Q044.
885
8862018-08-09
887
888    - 1.10.2
889    - [BUGFIX] Don't go over limit when creating delayed streams
890
8912018-07-10
892
893    - 1.10.1
894    - [BUGFIX]  process connections after each batch of packets is read
895      This avoids a problem of accumulating a very large list of packets
896      (possible when speeds are high and socket's receive buffer is large)
897      and processing it all at once.
898    - If glibc is older than 2.17, link with rt.  This is necessary for
899      clock_getres(2).
900    - Add version macros to lsquic.h; remove unnecessary includes.
901
9022018-06-13
903
904    - [BUGFIX] allow multiple parallel connections by default
905
906      Use the original method of tracking connections by CIDs by default.
907      If zero-sized CID support is turned on, connections are tracked by
908      the address.  A new connection is not created if another connection
909      is using the same network address
910
9112018-05-30
912
913    - [FEATURE, API CHANGE] Support zero-sized CIDs in received packets
914
9152018-05-24
916
917    - Close connection properly when packet encryption fails
918
9192018-05-23
920
921    - [BUGFIX] Do not produce packet sequence gaps due to delayed packets
922
9232018-05-21
924
925    - [API Change] Add optional callback to call when handshake is done
926    - [API Change, BUGFIX] After send failure, wait until transport available
927
9282018-05-18
929
930    - [API] Expose useful lsquic_ver2str[] in lsquic.h
931    - [BUGFIX] Do not produce packet sequence gaps due to STREAM frame elision
932    - Improve checks of number of incoming streams limit and associated
933      error reporting.
934    - [BUGFIX] Command-line option `-6` now works correctly.
935
9362018-05-16
937
938    - [FEATURE] DNS resolution
939    - [BUGFIX] Frame insertion mis-ID as overlap instead of dup
940    - http_client: fix priority range generated by -E flag
941
9422018-05-09
943
944    - [FEATURE] Add support for Q043.
945    - Support for versions Q037, Q038, Q041, and Q042 has been removed.
946    - Fix typo in debug message.
947    - Fix code indentation.
948    - Add /* fallthru */ comment to stop newer gcc from complaining.
949    - Logger: fix compilation of optimized Windows build.
950
9512018-05-04
952
953    - [FEATURE] Add support for Q042.
954    - Remove comment: MSPC is obsolete (no code changes)
955    - Prog: use lsquic_str2ver() when processing -o version flag
956    - Remove unused CTIM and SRBF transport parameters
957    - Disable QUIC versions Q037 and Q038 by default
958    - Fix Windows compilation by including compat header file in
959      lshpack.c
960    - Address warnings produced by newer versions of gcc
961    - Future-proof: turn off -Werror
962
9632018-05-02
964
965    - [BUGFIX] Make lsquic_conn_quic_version() available
966    - Switch to using ls-hpack 1.1
967    - [BUGFIX] Do not ignore stream resets after receiving FIN
968
9692018-04-27
970
971    - HPACK: do not allow header block to end with table size update.
972
9732018-04-25
974
975    - [BUGFIX] Do not create gap in sent packnos when squeezing delayed
976      packets.
977    - [BUGFIX] sendctl checks for all unacked bytes, not just retx bytes.
978    - [BUGFIX] connections with blocked scheduled packets are not tickable
979      for sending.
980    - [BUGFIX] Conn is tickable if it wants to send a connection-level
981      frame.
982
9832018-04-23
984
985    - Fix busy loop: tickable must make progress.  When connection is
986      self-reporting as tickable, it must make progress when ticked.  There
987      are two issues:
988        1. If there are buffered packets, the connection is only tickable if
989           they can be sent out.
990        2. A connection is tickable if there are streams on the servicing
991           queue.  When the tick occurs, we must service the stream
992           independent of whether any packets are sent.
993    - Fix assertion in pacer which can be incorrect under some
994      conditions.
995    - cmake: do not turn on address sanitizer if in Travis.
996
9972018-04-20
998
999    - [BUGFIX] Fix bug in lsquic_engine_connect() exposed by yesterday's
1000      changes.
1001
10022018-04-19
1003
1004    - [BUGFIX] Add connection to Tickable Queue on stream write
1005    - cmake: use MSVC variable instead of trying to detect
1006    - engine: improve connection incref/decref logging
1007    - stream: don't ignore errors that may occur on triggered flush
1008    - connection: remove obsolete method
1009    - engine: indicate connection as tickable if previous call went
1010      over threshold
1011
10122018-04-09
1013
1014    [API Change, OPTIMIZATION] Only process conns that need to be processed
1015
1016    The API is simplified: do not expose the user code to several
1017    queues.  A "connection queue" is now an internal concept.
1018    The user processes connections using the single function
1019    lsquic_engine_process_conns().  When this function is called,
1020    only those connections are processed that need to be processed.
1021    A connection needs to be processed when:
1022
1023        1. New incoming packets have been fed to the connection.
1024        2. User wants to read from a stream that is readable.
1025        3. User wants to write to a stream that is writeable.
1026        4. There are buffered packets that can be sent out.  (This
1027           means that the user wrote to a stream outside of the
1028           lsquic library callback.)
1029        5. A control frame (such as BLOCKED) needs to be sent out.
1030        6. A stream needs to be serviced or delayed stream needs to
1031           be created.
1032        7. An alarm rings.
1033        8. Pacer timer expires.
1034
1035    To achieve this, the library places the connections into two
1036    priority queues (min heaps):
1037
1038        1. Tickable Queue; and
1039        2. Advisory Tick Time queue (ATTQ).
1040
1041    Each time lsquic_engine_process_conns() is called, the Tickable
1042    Queue is emptied.  After the connections have been ticked, they are
1043    queried again: if a connection is not being closed, it is placed
1044    either in the Tickable Queue if it is ready to be ticked again or
1045    it is placed in the Advisory Tick Time Queue.  It is assumed that
1046    a connection always has at least one timer set (the idle alarm).
1047
1048    The connections in the Tickable Queue are arranged in the least
1049    recently ticked order.  This lets connections that have been quiet
1050    longer to get their packets scheduled first.
1051
1052    This change means that the library no longer needs to be ticked
1053    periodically.  The user code can query the library when is the
1054    next tick event and schedule it exactly.  When connections are
1055    processed, only the tickable connections are processed, not *all*
1056    the connections.  When there are no tick events, it means that no
1057    timer event is necessary -- only the file descriptor READ event
1058    is active.
1059
1060    The following are improvements and simplifications that have
1061    been triggered:
1062
1063        - Queue of connections with incoming packets is gone.
1064        - "Pending Read/Write Events" Queue is gone (along with its
1065          history and progress checks).  This queue has become the
1066          Tickable Queue.
1067        - The connection hash no longer needs to track the connection
1068          insertion order.
1069
10702018-04-02
1071
1072    - [FEATURE] Windows support
1073
1074    - Reduce stack use -- outgoing packet batch is now allocated on the heap.
1075
10762018-03-09
1077
1078    - [OPTIMIZATION] Merge series of ACKs if possible
1079
1080      Parsed single-range ACK frames (that is the majority of frames) are
1081      saved in the connection and their processing is deferred until the
1082      connection is ticked.  If several ACKs come in a series between
1083      adjacent ticks, we check whether the latest ACK is a strict superset
1084      of the saved ACK.  If it is, the older ACK is not processed.
1085
1086      If ACK frames can be merged, they are merged and only one of them is
1087      either processed or saved.
1088
1089    - [OPTIMIZATION] Speed up ACK verification by simplifying send history.
1090
1091      Never generate a gap in the sent packet number sequence.  This reduces
1092      the send history to a single number instead of potentially a series of
1093      packet ranges and thereby speeds up ACK verification.
1094
1095      By default, detecting a gap in the send history is not fatal: only a
1096      single warning is generated per connection.  The connection can continue
1097      to operate even if the ACK verification code is not able to detect some
1098      inconsistencies.
1099
1100    - [OPTIMIZATION] Rearrange the lsquic_send_ctl struct
1101
1102      The first part of struct lsquic_send_ctl now consists of members that
1103      are used in lsquic_send_ctl_got_ack() (in the absense of packet loss,
1104      which is the normal case).  To speed up reads and writes, we no longer
1105      try to save space by using 8- and 16-bit integers.  Use regular integer
1106      width for everything.
1107
1108    - [OPTIMIZATION] Cache size of sent packet.
1109
1110    - [OPTIMIZATION] Keep track of the largest ACKed in packet_out
1111
1112      Instead of parsing our own ACK frames when packet has been acked,
1113      use the value saved in the packet_out structure when the ACK frame
1114      was generated.
1115
1116    - [OPTIMIZATION] Take RTT sampling conditional out of ACK loop
1117
1118    - [OPTIMIZATION] ACK processing: only call clock_gettime() if needed
1119
1120    - [OPTIMIZATION] Several code-level optimizations to ACK processing.
1121
1122    - Fix: http_client: fix -I flag; switch assert() to abort()
1123
11242018-02-26
1125    - [API Change] lsquic_engine_connect() returns pointer to the connection
1126      object.
1127    - [API Change] Add lsquic_conn_get_engine() to get engine object from
1128      connection object.
1129    - [API Change] Add lsquic_conn_status() to query connection status.
1130    - [API Change] Add add lsquic_conn_set_ctx().
1131    - [API Change] Add new timestamp format, e.g. 2017-03-21 13:43:46.671345
1132    - [OPTIMIZATION] Process handshake STREAM frames as soon as packet
1133      arrives.
1134    - [OPTIMIZATION] Do not compile expensive send controller sanity check
1135      by default.
1136    - [OPTIMIZATION] Add fast path to gquic_be_gen_reg_pkt_header.
1137    - [OPTIMIZATION] Only make squeeze function call if necessary.
1138    - [OPTIMIZATION] Speed up Q039 ACK frame parsing.
1139    - [OPTIMIZATION] Fit most used elements of packet_out into first 64 bytes.
1140    - [OPTIMIZATION] Keep track of scheduled bytes instead of calculating.
1141    - [OPTIMIZATION] Prefetch next unacked packet when processing ACK.
1142    - [OPTIMIZATION] Leverage fact that ACK ranges and unacked list are.
1143      ordered.
1144    - [OPTIMIZATION] Reduce function pointer use for STREAM frame generation
1145    - Fix: reset incoming streams that arrive after we send GOAWAY.
1146    - Fix: delay client on_new_conn() call until connection is fully set up.
1147    - Fixes to buffered packets logic: splitting, STREAM frame elision.
1148    - Fix: do not dispatch on_write callback if no packets are available.
1149    - Fix WINDOW_UPDATE send and resend logic.
1150    - Fix STREAM frame extension code.
1151    - Fix: Drop unflushed data when stream is reset.
1152    - Switch to tracking CWND using bytes rather than packets.
1153    - Fix TCP friendly adjustment in cubic.
1154    - Fix: do not generate invalid STOP_WAITING frames during high packet
1155      loss.
1156    - Pacer fixes.
1157
11582017-12-18
1159
1160    - Fix: better follow cubic curve after idle period
1161    - Fix: add missing parts to outgoing packet splitting code
1162    - Fix: compilation using gcc 4.8.4
1163
11642017-10-31
1165
1166    - Add APIs.txt -- describes LSQUIC APIs
1167
11682017-10-31
1169
1170    - [API Change] Sendfile-like functionality is gone.  The stream no
1171      longer opens files and deals with file descriptors.  (Among other
1172      things, this makes the code more portable.)  Three writing functions
1173      are provided:
1174
1175        lsquic_stream_write
1176        lsquic_stream_writev
1177        lsquic_stream_writef    (NEW)
1178
1179      lsquic_stream_writef() is given an abstract reader that has function
1180      pointers for size() and read() functions which the user can implement.
1181      This is the most flexible way.  lsquic_stream_write() and
1182      lsquic_stream_writev() are now both implemented as wrappers around
1183      lsquic_stream_writef().
1184
1185    - [OPTIMIZATION] When writing to stream, be it within or without the
1186      on_write() callback, place data directly into packet buffer,
1187      bypassing auxiliary data structures.  This reduces amount of memory
1188      required, for the amount of data that can be written is limited
1189      by the congestion window.
1190
1191      To support writes outside the on_write() callback, we keep N
1192      outgoing packet buffers per connection which can be written to
1193      by any stream.  One half of these are reserved for the highest
1194      priority stream(s), the other half for all other streams.  This way,
1195      low-priority streams cannot write instead of high-priority streams
1196      and, on the other hand, low-priority streams get a chance to send
1197      their packets out.
1198
1199      The algorithm is as follows:
1200
1201      - When user writes to stream outside of the callback:
1202        - If this is the highest priority stream, place it onto the
1203          reserved N/2 queue or fail.
1204            (The actual size of this queue is dynamic -- MAX(N/2, CWND) --
1205             rather than N/2, allowing high-priority streams to write as
1206             much as can be sent.)
1207        - If the stream is not the highest priority, try to place the
1208          data onto the reserved N/2 queue or fail.
1209      - When tick occurs *and* more packets can be scheduled:
1210        - Transfer packets from the high N/2 queue to the scheduled
1211          queue.
1212        - If more scheduling is allowed:
1213          - Call on_write callbacks for highest-priority streams,
1214            placing resulting packets directly onto the scheduled queue.
1215        - If more scheduling is allowed:
1216          - Transfer packets from the low N/2 queue to the scheduled
1217            queue.
1218        - If more scheduling is allowed:
1219          - Call on_write callbacks for non-highest-priority streams,
1220            placing resulting packets directly onto the scheduled queue
1221
1222      The number N is currently 20, but it could be varied based on
1223      resource usage.
1224
1225    - If stream is created due to incoming headers, make headers readable
1226      from on_new.
1227
1228    - Outgoing packets are no longer marked non-writeable to prevent placing
1229      more than one STREAM frame from the same stream into a single packet.
1230      This property is maintained via code flow and an explicit check.
1231      Packets for stream data are allocated using a special function.
1232
1233    - STREAM frame elision is cheaper, as we only perform it if a reset
1234      stream has outgoing packets referencing it.
1235
1236    - lsquic_packet_out_t is smaller, as stream_rec elements are now
1237      inside a union.
1238
12392017-10-12
1240
1241    - Do not send RST_STREAM when stream is closed for reading
1242    - Raise maximum header size from 4K to 64K
1243    - Check header name and value lengths against maximum imposed by HPACK
1244    - Fix NULL dereference in stream flow controller
1245
12462017-10-09
1247
1248    - Hide handshake implementation behind a set of function pointers
1249    - Use monotonically increasing clock
1250    - Make sure that retx delay is not larger than the max of 60 seconds
1251
12522017-09-29
1253
1254    - A few fixes to code and README
1255
12562017-09-28
1257
1258    - Add support for Q041; drop support for Q040
1259
12602017-09-27
1261
1262    - Fix CMakeLists.txt: BoringSSL include and lib was mixed up
1263
12642017-09-26
1265
1266    - Add support for Mac OS
1267    - Add support for Raspberry Pi
1268    - Fix BoringSSL compilation: include <openssl/hmac.h> explicitly
1269
12702017-09-22
1271
1272    - Initial release
1273