mod_h[ttp]2 v1.5.5

• Fix async write issue that sometimes led to selection of wrong timeout
  vs. keepalive timeout selection for idle sessions.
• Checking LimitRequestLine, LimitRequestFields and
  LimitRequestFieldSize configurated values for incoming streams. Returning
  HTTP status 431 for too long/many headers fields and 414 for a too long
  pseudo header.
• Tracking conn_rec->current_thread on slave connections, so
  that mod_lua finds the correct one. Fixes PR 59542.
• c->aborted also set for slave connections when main connection is closed by client

mod_h[ttp]2 v1.5.3

• slave connections have conn_rec->aborted flag set when a stream
  has been reset by the client.
• Small fixes in bucket beams when forwarding file buckets. Output handling
  on master connection uses less FLUSH and passes automatically when more
  than half of H2StreamMaxMemSize bytes have accumulated.
  Workaround for http: when forwarding partial file buckets to keep the
  output filter from closing these too early.
• elimination of fixed master connectin buffer for TLS connections. New
  scratch bucket handling optimized for TLS write sizes.
  File bucket data read directly into scratch buffers, avoiding one
  copy. Non-TLS connections continue to pass buckets unchanged to the core
  filters to allow sendfile() usage.
• h2_request.c is no longer shared between these modules. This simplifies
  building on platforms such as Windows, as module reference used in
  logging is now clear.

mod_h[ttp]2 v1.5.2

Recommended update for all 1.5.x users:

• fixed connection shutdown deadlock on linux when client closed early
• beam shutdown does now wait on endpoint to finish using buckets in flight,
  hopefully addressing crash issues completely
• Since 1.5.1 the internal HTTP/2 protocol is reported as "HTTP/2.0" for
  better compatibility and since CGI's SERVER_PROTOCOL seems to require this
  format

mod_h[ttp]2 v1.5.1

• fixed segmentation fault when connections where aborted by client in new
  bucket beam code
• eliminated one more memory pool per stream

mod_h[ttp]2 v1.5.0

• mod_proxy_http2 for backend HTTP/2 connections, currently cleartext only
• new "bucket beam" technology to transport buckets across threads without
  buffer copy.
• delaying response start until flush or enough body data has been accumulated.
• all fixed up to and including 1.4.7

mod_h[ttp]2 v1.4.7

• disabling file mmap handling as this leads to segmentation faults when files
  are truncates while being streamed out.
• Some additional trace1 logging when connections give unexpected errors, e.g.
  clients close connection without final GOAWAY frame.

mod_h[ttp]2, v1.4.6

This is the module exactly as released in Apache httpd 2.4.20. The list of changes to the last version here, 1.2.8, is:

• incrementing keepalives on each request started so that logging %k gives
  increasing numbers per master http2 connection. New documented variables
  in env, usable in custom log formats: H2_PUSH, H2_PUSHED, H2_PUSHED_ON,
  H2_STREAM_ID and H2_STREAM_TAG.
• more efficient passing of response bodies with less contention
  and file bucket forwarding.
• fix for missing score board updates on request count, fix for memory leak
  on slave connection reuse.
• disabling PUSH when client sends GOAWAY. Slave connections are reused for
  several requests, improved performance and better memory use.
• fixes problem with wrong lifetime of file buckets on main connection.
• fixes incorrect denial of requests without :authority header.
• give control to async mpm for keepalive timeouts only when no streams are
  open and even if only after 1 sec delay. Under load, event mpm discards
  connections otherwise too quickly.
• fixed possible read after free when streams were cancelled early by the
  client.
• fixed possible deadlock during connection shutdown. Thanks to @frankstolle
  for reporting and getting the necessary data.
• fixed apr_uint64_t formatting in a log statement to user proper APR def,
  thanks to @Sp1l.
• number of worker threads allowed to a connection is adjusting
  dynamically. Starting with 4, the number is doubled when streams can be
  served without block on http/2 connection flow. The number is halfed, when
  the server has to wait on client flow control grants.
  This can happen with a maximum frequency of 5 times per second.
  When a connection occupies too many workers, repeatable requests
  (GET/HEAD/OPTIONS) are cancelled and placed back in the queue. Should that
  not suffice and a stream is busy longer than the server timeout, the
  connection will be aborted with error code ENHANCE_YOUR_CALM.
  This does not limit the number of streams a client may open, rather the
  number of server threads a connection might use.
• allowing link header to specify multiple "rel" values, space-separated
  inside a quoted string. Prohibiting push when Link parameter "nopush" is
  present.
• reworked connection state handling. Idle connections accept a GOAWAY from
  the client without further reply. Otherwise the module makes a best effort
  to send one last GOAWAY to the client.
• the values from standard directives Timeout and KeepAliveTimeout properly
  are applied to http/2 connections.
• idle connections are returned to async mpms. new hook "pre_close_connection"
  used to send GOAWAY frame when not already done. Setting event mpm server
  config "by hand" for the main connection to the correct negotiated server.
• keep-alive blocking reads are done with 1 second timeouts to check for MPM
  stopping. Will announce early GOAWAY and finish processing open streams,
  then close.
• bytes read/written on slave connections are reported via the optional
  mod_logio functions. Fixes PR 58871.
• connections how keep a "push diary" where hashes of already pushed resources
  are kept. See directive H2PushDiarySize for managing this. Push diaries can
  be initialized by clients via the "Cache-Digest" request header.
  This carries a base64url encoded. compressed Golomb set as described
  in https://datatracker.ietf.org/doc/draft-kazuho-h2-cache-digest/
  Introduced a status handler for HTTP/2 connections, giving various counters
  and statistics about the current connection, plus its cache digest value
  in a JSON record. Not a replacement for more HTTP/2 in the server status.
  Configured as
  <Location "/http2-status">
  SetHandler http2-status
  
• Fixed flushing of last GOAWAY frame. Previously, that frame did not always
  reach the client, causing some to fail the next request.
  Fixed calculation of last stream id accepted as described in rfc7540.
  Reading in KEEPALIVE state now correctly shown in scoreboard.
  Fixed possible race in connection shutdown after review by Ylavic.
  Fixed segfault on connection shutdown, callback ran into a semi dismantled session.
• Added support for experimental accept-push-policy draft
  (https://tools.ietf.org/html/draft-ruellan-http-accept-push-policy-00). Clients
  may now influence server pushes by sending accept-push-policy headers.
• new r->subprocess_env variables HTTP2 and H2PUSH, set to "on"
  when available for request.
• mod_status/scoreboard: showing connection protocol in new column, new
  ap_update_child_status methods for updating server/description. mod_ssl
  sets vhost negotiated by servername directly.

mod_h[ttp]2 v1.2.8

• Requests without ':authority' header, using 'Host' instead, are no longer
  denied.

mod_h[ttp]2 v1.2.7

• Adding logio fix from apache trunk so that resource sizes are correcly
  reported in access logs. Thanks to Daan van Gorkum for reporting this.

mod_h[ttp]2 v1.2.6

• Adding accept-encoding to headers used in PUSHed resources - as sent by
  the initiating request.