Generally modernize the language.

Refer to TLS instead of SSL/TLS, and try to have more consistent
usage of commas and that/which.

Reword some descriptions to avoid implying that a list of potential
reasons for behavior is an exhaustive list.

Clarify how get_session_cb() is only called on servers (i.e., in general,
and that it's given the session ID proposed by the client).

Clarify the semantics of the get_cb()'s "copy" argument.
The behavior seems to have changed in commit
8876bc05, though the behavior prior
to that commit was not to leave the reference-count unchanged if
*copy was not written to -- instead, libssl seemed to assume that the
callback already had incremented the reference count.
Reviewed-by: NTomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10943)

(cherry picked from commit 06f876837a8ec76b28c42953731a156c0c3700e2)

The existing documentation for the new-session callback was unclear
about the requirements on the callback with respect to reference-handling
of the session object being created.  Be more explicit about the
(non-)requirements on the callback code for "success" (1) and "ignore"
(0) return values.
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10848)

(cherry picked from commit 188d4ec82a9b0085ac5841cce3eda95efb94f2b4)

Also fix some clumsy wording.

[skip_ci]
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6545)

Because the related PR/commits are merged in 2018...
Reviewed-by: NAndy Polyakov <appro@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4976)

All missing sections are added.
Reviewed-by: NAndy Polyakov <appro@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4976)

I tried hard to keep the lines at 80 characters or less, but in a few
cases I had to punt and just indented the subsequent lines by 4 spaces.

A few well-placed typedefs for callback functions would really help, but
these would be part of the API, so that's probably for later.

I also took the liberty of inserting empty lines in overlong blocks to
provide some visual space.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1956)

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3008)

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3008)

Add documentation for SSL_SESSION_is_resumable(). Also describe the interaction
of the various session functions and TLSv1.3 post-handshake sessions.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3008)

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1900)

Move manpages to manX directories
Add Windows/VMS install fix from Richard Levitte
Update README
Fix typo's
Remove some duplicates
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Fix some code examples, trailing whitespace
Fix TBA sections in verify, remove others.
Remove empty sections
Use Mixed Case not ALL CAPS in head2
Enhance doc-nits script.
Remove extra =cut line
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Add doc-nit-check to help find future issues.
Make podchecker be almost clean.
Remove trailing whitespace.
Tab expansion
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

PACKET contents should be read-only. To achieve this, also
- constify two user callbacks
- constify BUF_reverse.
Reviewed-by: NRich Salz <rsalz@openssl.org>

L<foo|foo> is sub-optimal  If the xref is the same as the title,
which is what we do, then you only need L<foo>.  This fixes all
1457 occurrences in 349 files.  Approximately.  (And pod used to
need both.)
Reviewed-by: NRichard Levitte <levitte@openssl.org>

sessions in the external session cache might be removed.
Submitted by: "Nadav Har'El" <nyh@math.technion.ac.il>

PR: 547

Submitted by: Richard.Koenning@fujitsu-siemens.com
Reviewed by:
PR: 129

  From: "Chris D. Peterson" <cpeterson@aventail.com>
  Subject: Implementation Issues with OpenSSL
  To: openssl-users@openssl.org
  Date: Wed, 22 Aug 2001 16:13:17 -0700
The patch included in the original post may improve the internal session
list handling (and is therefore worth a seperate investigation).
No change to the list handling will however solve the problems of incorrect
SSL_SESSION_free() calls. The session list is only one possible point of
failure, dangling pointers would also occur for SSL object currently
using the session. The correct solution is to only use SSL_SESSION_free()
when applicable!