[multiple] store ptrs to remote addr in request_st (#3192)

adds two pointers to (request_st *) (cost: 16 bytes in 64-bit builds)

prepares for upcoming changes to mod_extforward to manage remote add

[multiple] store ptrs to remote addr in request_st (#3192)

adds two pointers to (request_st *) (cost: 16 bytes in 64-bit builds)

prepares for upcoming changes to mod_extforward to manage remote addr
per request for HTTP/2 requests, rather than remote addr per connection.

Modern load balancers often provide options to reuse connections for
*different* clients, and therefore mod_extforward might change the
remote addr per request.

x-ref:
"RFE: mod_extforward and multiplexed requests via HTTP/2"
https://redmine.lighttpd.net/issues/3192
"Evaluation of remote_addr for mod_maxminddb for multiplexed connections"
https://redmine.lighttpd.net/issues/3191

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[multiple] quiet some coverity false positives

[multiple] employ ck_calloc, ck_malloc shared code

employ ck_calloc(), ck_malloc() shared code to slightly reduce code size
(centralize the ck_assert() to check that memory allocation succeeded)

[multiple] mark mod_*_plugin_init() funcs cold

[multiple] quiet coverity warnings using casts

[mod_status] display HTTP/2 control stream w/ reqs

display HTTP/2 control stream as pseudo-request in request list

HTTP/2 control stream has URI "*" from "PRI *" HTTP/2 connection preface

[multiple] use buffer_append_char()

[core] reusable code for r->state strings

convenience macros/functions for display purposes

(historical labels from mod_status are preserved for compatibility)

[mod_status] reusable code for r->state strings

[mod_status] fix counting of HTTP/2 bytes written

remove usused accounting
simplify to use (64-bit) off_t for counting, but preserve doubles for
pretty-printing numbers with decimal point and size

[mod_status] fix counting of HTTP/2 bytes written

remove usused accounting
simplify to use (64-bit) off_t for counting, but preserve doubles for
pretty-printing numbers with decimal point and size suffix

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[mod_status] con->h2 instead of r->http_version

check con->h2 instead of r->http_version

(additional safeguard for #3152)

x-ref:
"Random Segfaults with version 1.4.64 w/ mod_sockproxy and ALPN h

[mod_status] con->h2 instead of r->http_version

check con->h2 instead of r->http_version

(additional safeguard for #3152)

x-ref:
"Random Segfaults with version 1.4.64 w/ mod_sockproxy and ALPN h2"
https://redmine.lighttpd.net/issues/3152

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[core] pcre2 support (--with-pcre2)

x-ref:
"lighttpd: depends on obsolete pcre3 library"
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000063

[core] change srv->conns to doubly-linked-list

avoids separate memory allocation for list of pointers

[core] rename srv->max_conns -> srv->lim_conns

srv->lim_conns tracks remaining conns until limit is reached,
replacing (srv->max_conns - srv->conns.used)

srv->srvconf.max_conns is now updated at st

[core] rename srv->max_conns -> srv->lim_conns

srv->lim_conns tracks remaining conns until limit is reached,
replacing (srv->max_conns - srv->conns.used)

srv->srvconf.max_conns is now updated at startup, so
srv->srvconf.max_conns serves as srv->max_conns

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[multiple] Y2038 32-bit signed time_t mitigations

Most OS platforms have already provided solutions to
Y2038 32-bit signed time_t 5 - 10 years ago (or more!)
Notable exceptions are Linux i686 and Fr

[multiple] Y2038 32-bit signed time_t mitigations

Most OS platforms have already provided solutions to
Y2038 32-bit signed time_t 5 - 10 years ago (or more!)
Notable exceptions are Linux i686 and FreeBSD i386.

Since 32-bit systems tend to be embedded systems,
and since many distros take years to pick up new software,
this commit aims to provide Y2038 mitigations for lighttpd
running on 32-bit systems with Y2038-unsafe 32-bit signed time_t

* Y2038: lighttpd 1.4.60 and later report Y2038 safety
$ lighttpd -V
+ Y2038 support # Y2038-SAFE
$ lighttpd -V
- Y2038 support (unsafe 32-bit signed time_t) # Y2038-UNSAFE

* Y2038: general platform info
* Y2038-SAFE: lighttpd 64-bit builds on platforms using 64-bit time_t
- all major 64-bit platforms (known to this author) use 64-bit time_t
* Y2038-SAFE: lighttpd 32-bit builds on platforms using 64-bit time_t
- Linux x32 ABI (different from i686)
- FreeBSD all 32-bit and 64-bit architectures *except* 32-bit i386
- NetBSD 6.0 (released Oct 2012) all 32-bit and 64-bit architectures
- OpenBSD 5.5 (released May 2014) all 32-bit and 64-bit architectures
- Microsoft Windows XP and Visual Studio 2005 (? unsure ?)
Another reference suggests Visual Studio 2015 defaults to 64-bit time_t
- MacOS 10.15 Catalina (released 2019) drops support for 32-bit apps
* Y2038-SAFE: lighttpd 32-bit builds on platforms using 32-bit unsigned time_t
- e.g. OpenVMS (unknown if lighttpd builds on this platform)
* Y2038-UNSAFE: lighttpd 32-bit builds on platforms using 32-bit signed time_t
- Linux 32-bit (including i686)
- glibc 32-bit library support not yet available for 64-bit time_t
- https://sourceware.org/glibc/wiki/Y2038ProofnessDesign
- Linux kernel 5.6 on 32-bit platforms does support 64-bit time_t
https://itsubuntu.com/linux-kernel-5-6-to-fix-the-year-2038-issue-unix-y2k/
- https://www.gnu.org/software/libc/manual/html_node/64_002dbit-time-symbol-handling.html
"Note: at this point, 64-bit time support in dual-time
configurations is work-in-progress, so for these
configurations, the public API only makes the 32-bit time
support available. In a later change, the public API will
allow user code to choose the time size for a given
compilation unit."
- compiling with -D_TIME_BITS=64 currently has no effect
- glibc recent (Jul 2021) mailing list discussion
- https://public-inbox.org/bug-gnulib/[email protected]/T/
- FreeBSD i386
- DragonFlyBSD 32-bit

* Y2038 mitigations attempted on Y2038-UNSAFE platforms (32-bit signed time_t)
* lighttpd prefers system monotonic clock instead of realtime clock
in places where realtime clock is not required
* lighttpd treats negative time_t values as after 19 Jan 2038 03:14:07 GMT
* (lighttpd presumes that lighttpd will not encounter dates before 1970
during normal operation.)
* lighttpd casts struct stat st.st_mtime (and st.st_*time) through uint64_t
to convert negative timestamps for comparisions with 64-bit timestamps
(treating negative timestamp values as after 19 Jan 2038 03:14:07 GMT)
* lighttpd provides unix_time64_t (int64_t) and
* lighttpd provides struct unix_timespec64 (unix_timespec64_t)
(struct timespec equivalent using unix_time64_t tv_sec member)
* lighttpd provides gmtime64_r() and localtime64_r() wrappers
for platforms 32-bit platforms using 32-bit time_t and
lighttpd temporarily shifts the year in order to use
gmtime_r() and localtime_r() (or gmtime() and localtime())
from standard libraries, before readjusting year and passing
struct tm to formatting functions such as strftime()
* lighttpd provides TIME64_CAST() macro to cast signed 32-bit time_t to
unsigned 32-bit and then to unix_time64_t

* Note: while lighttpd tries handle times past 19 Jan 2038 03:14:07 GMT
on 32-bit platforms using 32-bit signed time_t, underlying libraries and
underlying filesystems might not behave properly after 32-bit signed time_t
overflows (19 Jan 2038 03:14:08 GMT). If a given 32-bit OS does not work
properly using negative time_t values, then lighttpd likely will not work
properly on that system.

* Other references and blogs
- https://en.wikipedia.org/wiki/Year_2038_problem
- https://en.wikipedia.org/wiki/Time_formatting_and_storage_bugs
- http://www.lieberbiber.de/2017/03/14/a-look-at-the-year-20362038-problems-and-time-proofness-in-various-systems/

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[multiple] inline struct in con->dst_addr_buf

(mod_extforward recently changed to use buffer_move() to save addr
instead of swapping pointers)

[multiple] reduce redundant NULL buffer checks

This commit is a large set of code changes and results in removal of
hundreds, perhaps thousands, of CPU instructions, a portion of which
are on hot co

[multiple] reduce redundant NULL buffer checks

This commit is a large set of code changes and results in removal of
hundreds, perhaps thousands, of CPU instructions, a portion of which
are on hot code paths.

Most (buffer *) used by lighttpd are not NULL, especially since buffers
were inlined into numerous larger structs such as request_st and chunk.

In the small number of instances where that is not the case, a NULL
check is often performed earlier in a function where that buffer is
later used with a buffer_* func. In the handful of cases that remained,
a NULL check was added, e.g. with r->http_host and r->conf.server_tag.

- check for empty strings at config time and set value to NULL if blank
string will be ignored at runtime; at runtime, simple pointer check
for NULL can be used to check for a value that has been set and is not
blank ("")
- use buffer_is_blank() instead of buffer_string_is_empty(),
and use buffer_is_unset() instead of buffer_is_empty(),
where buffer is known not to be NULL so that NULL check can be skipped
- use buffer_clen() instead of buffer_string_length() when buffer is
known not to be NULL (to avoid NULL check at runtime)
- use buffer_truncate() instead of buffer_string_set_length() to
truncate string, and use buffer_extend() to extend

Examples where buffer known not to be NULL:
- cpv->v.b from config_plugin_values_init is not NULL if T_CONFIG_BOOL
(though we might set it to NULL if buffer_is_blank(cpv->v.b))
- address of buffer is arg (&foo)
(compiler optimizer detects this in most, but not all, cases)
- buffer is checked for NULL earlier in func
- buffer is accessed in same scope without a NULL check (e.g. b->ptr)

internal behavior change:
callers must not pass a NULL buffer to some funcs.
- buffer_init_buffer() requires non-null args
- buffer_copy_buffer() requires non-null args
- buffer_append_string_buffer() requires non-null args
- buffer_string_space() requires non-null arg

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[multiple] use buffer_append_* aggregates

reduces the number of round-trips into some frequently-called routines

[mod_status] double-buffer large output to tmpfile

[multiple] strftime %F and %T

strftime %F for %Y-%m-%d, and %T for %H:%M:%S

[multiple] employ http_date.h, sys-time.h

- replace use of strptime() w/ implementation specialized for HTTP dates
- use thread-safe gmtime_r(), localtime_r() (replace localtime, gmtime)

[mod_status] add additional HTML-encoding

[multiple] inline chunkqueue where always alloc'd

inline struct chunkqueue where always allocated in other structs

(memory locality)

[core] reuse r->start_hp.tv_sec for r->start_ts

(remove duplicated field from (request_st *))

[mod_status] dedicated funcs for r->state labels

fork connection_get_state() for use by mod_status, which
might in the future choose to display different labels.
move and rename connection_get_short

[mod_status] dedicated funcs for r->state labels

fork connection_get_state() for use by mod_status, which
might in the future choose to display different labels.
move and rename connection_get_short_state() into mod_status,
as the func is used only by mod_status

(connection_get_state() is currently used elsewhere only for debugging
in connections.c)

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