ngx_http_v2_huff_decode.c and ngx_http_v2_huff_encode.c are renamed
to ngx_http_huff_decode.c and ngx_http_huff_encode.c.

The variable contains a negotiated curve used for the handshake key
exchange process.  Known curves are listed by their names, unknown
ones are shown in hex.

Note that for resumed sessions in TLSv1.2 and older protocols,
$ssl_curve contains the curve used during the initial handshake,
while in TLSv1.3 it contains the curve used during the session
resumption (see the SSL_get_negotiated_group manual page for
details).

The variable is only meaningful when using OpenSSL 3.0 and above.
With older versions the variable is empty.

The directive enables including all frames from start time to the most recent
key frame in the result.  Those frames are removed from presentation timeline
using mp4 edit lists.

Edit lists are currently supported by popular players and browsers such as
Chrome, Safari, QuickTime and ffmpeg.  Among those not supporting them properly
is Firefox[1].

Based on a patch by Tracey Jaquith, Internet Archive.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1735300

The function updates the duration field of mdhd atom.  Previously it was
updated in ngx_http_mp4_read_mdhd_atom().  The change makes it possible to
alter track duration as a result of processing track frames.

This is a recommended behavior by RFC 7301 and is useful
for mitigation of protocol confusion attacks [1].

To avoid possible negative effects, list of supported protocols
was extended to include all possible HTTP protocol ALPN IDs
registered by IANA [2], i.e. "http/1.0" and "http/0.9".

[1] https://alpaca-attack.com/
[2] https://www.iana.org/assignments/tls-extensiontype-values/

The variable contains protocol selected by ALPN during handshake and
is empty otherwise.

NPN was replaced with ALPN, published as RFC 7301 in July 2014.
It used to negotiate SPDY (and, in transition, HTTP/2).

NPN supported appeared in OpenSSL 1.0.1. It does not work with TLSv1.3 [1].
ALPN is supported since OpenSSL 1.0.2.

The NPN support was dropped in Firefox 53 [2] and Chrome 51 [3].

[1] https://github.com/openssl/openssl/issues/3665.
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1248198
[3] https://www.chromestatus.com/feature/5767920709795840

In b87b7092cedb (nginx 1.21.1), logging level of "upstream sent invalid
header" errors was accidentally changed to "info".  This change restores
the "error" level, which is a proper logging level for upstream-side
errors.

The u->keepalive flag is initialized early if the response has no body
(or an empty body), and needs to be reset if there are any extra data,
similarly to how it is done in ngx_http_proxy_copy_filter().  Missed
in 83c4622053b0.

To load old/weak server or client certificates it might be needed to adjust
the security level, as introduced in OpenSSL 1.1.0.  This change ensures that
ciphers are set before loading the certificates, so security level changes
via the cipher string apply to certificate loading.