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/878s2ozq70.fsf@oldenburg.str.redhat.com/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/
clear etag in stat_cache_get_entry_open() after opening file
(in case a different caller used stat_get_get_entry() and then file
changed before being opened)
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
Note: monotonic time does not change while VM is suspended
Continue to use real time where required by HTTP protocol, for logging
and for other user-visible instances, such as mod_status, as well as for
external databases and caches.
read() on inotify fd does not return partial records,
and the info from the kernel can be trusted. Still add a sanity check.
If initialization of inotify fails, server will subsequently exit,
so memory leak reported by coverity is insignificant.
more consistent use of shared code config_plugin_value_tobool()
(thx tow-conf)
x-ref:
"The on/off keywords in boolean configuration options is inconsistent, which might be misleading and error-prone."
https://redmine.lighttpd.net/issues/3036
This alternative approach attempts to work around error:
invalid application of 'sizeof' to incomplete type 'struct kevent'
seen in continuous integration (CI) autoconf build on FreeBSD VM
Note: there have always been limitations with lighttpd stat_cache.[ch]
using FAM/gamin on *BSD via kqueue() as lighttpd stat_cache.[ch] only
monitors directories. This kqueue() implementation also only monitors
directories and has limitations.
lighttpd stat_cache.[ch] is notified about additions and removals of
files within a monitored directory but might not be notified of changes
such as timestamps (touch), ownership, or even changes in contents
(e.g. if a file is edited through a hard link)
server.stat-cache-engine = "disable" should be used when files should
not be cached. Full stop. Similarly, "disable" is recommended if files
change frequently. If using server.stat-cache-engine with any engine,
there are caching effects and tradeoffs.
On *BSD and using kqueue() on directories, any change detected clears
the stat_cache of all entries in that directory, since monitoring only
the directory does not indicate which file was added or removed. This
is not efficient for directories containing frequently changed files.
simple interface to cache open file by extending struct stat_cache_entry
future: should probably create fd cache separate from stat_cache,
perhaps along w/ http-specific fields like etag and content_type
gamin should be used instead of fam; fam is no longer maintained
This patch makes it safe to build lighttpd with gamin, but run on
systems with the (deprecated) fam installed, which can happen due
to historical package dependency declarations on some platforms
(Debian, Ubuntu).
gamin and fam are not 100% binary compatible.
(Among other things, fam does not provide FAMNoExists())
x-ref:
"llibgamin vs libfam conflict solving"
https://salsa.debian.org/debian/lighttpd/-/merge_requests/18
"libgamin0: libfam shlib dependency wrongly set to libfam0"
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=510368
"undefined symbol: FAMNoExists"
https://bugs.launchpad.net/bugs/1453463
auth.cache = ("max-age" => "600")
vhostdb.cache = ("max-age" => "600")
If specified with an empty array, default max-age is 600 secs (10 mins)
auth.cache = ()
vhostdb.cache = ()
(Note: cache expiration occurs every 8 seconds, so maximum cache time
might be up to max-age + 8 seconds)
x-ref:
"mod_auth caching"
https://redmine.lighttpd.net/issues/2805
(expansion of buffer_string_lenth() inline function and CONST_BUF_LEN()
macro, which always check for NULL, appears to cause the analyzer to
believe that a pointer might be NULL in cases where it otherwise can
not be NULL)
x-ref:
http://clang-analyzer.llvm.org/faq.html
NB: r->tmp_buf == srv->tmp_buf (pointer is copied for quicker access)
NB: request read and write chunkqueues currently point to connection
chunkqueues; per-request and per-connection chunkqueues are
not distinct from one another
con->read_queue == r->read_queue
con->write_queue == r->write_queue
NB: in the future, a separate connection config may be needed for
connection-level module hooks. Similarly, might need to have
per-request chunkqueues separate from per-connection chunkqueues.
Should probably also have a request_reset() which is distinct from
connection_reset().
convert all log_error_write() to log_error() and pass (log_error_st *)
use con->errh in preference to srv->errh (even though currently same)
avoid passing (server *) when previously used only for logging (errh)
array_get_element_klen() is now intended for read-only access
array_get_data_unset() is used by config processing for r/w access
array_get_buf_ptr() is used for r/w access to ds->value (string buffer)
Glenn Strauss