refuse excess h2 streams up to stream id 199 within 1-2 seconds of
establishing connection. This attempts to more gracefully handle
excessively agressive browsers sending too many new requests *before*
processing the initial SETTINGS frame sent by the server.
lighttpd HTTP/2 support limits SETTINGS_MAX_CONCURRENT_STREAMS to 8
and communicates this in the initial SETTINGS sent by the server.
x-ref:
"Chrome 92, HTTP/2, fcgi, mutiple puts no response"
https://redmine.lighttpd.net/issues/3093
"POST request DATA part for non-existing URI closes HTTP/2 connection prematurely"
https://redmine.lighttpd.net/issues/3078
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/
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
improve HTTP/2 behavior when server.max-request-size reached
accept slightly more data than max-request-size if END_STREAM flag recvd
reduce rwin so that client may exceed server.max-request-size, but not
by much. (client might ignore and might send a firehose of data anyway)
accept up to 64k more data to potentially sink data that was in-flight
beyond the rwin, in order to allow server to send 413 Payload Too Large
before resetting the stream.
(thx oldium)
improve handling of HTTP/2 DATA frames received
a short time after sending response
x-ref:
"POST request DATA part for non-existing URI closes HTTP/2 connection prematurely"
https://redmine.lighttpd.net/issues/3078
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.
cast high uint8_t byte to uint32_t before bit shifting << 24 to avoid
(pedantic) undefined behavior of uint8_t byte with high bit set when
it is promoted to int and then bit-shifted left 24 bytes. The high bit
gets shifted into the sign-bit, which is technically undefined behavior
in C, but is defined behavior in C++.
x-ref:
"pedantic warning from -fsanitize=undefined"
https://redmine.lighttpd.net/issues/3067
(thx flynn)
fix decoding chunked from backend
truncate response and error out if backend sends excess data
after chunked encoding
x-ref:
"Too much content with HTTP/2.0"
https://redmine.lighttpd.net/issues/3049
relay 1xx from backend over HTTP/2, e.g. 103 Early Hints
(if client is connected using HTTP/2)
enabled by default unless disabled in lighttpd.conf with:
server.feature-flags += ( "server.h2-discard-backend-1xx" = "enable" )
Warning: backends which send 103 Early Hints should check User-Agent
before doing so since naive clients might not handle unexpected 1xx.
Some clients may take the 1xx response as the final response, expecting
only one response. Some clients might not properly handle 100 Continue
if the client did not send Expect: 100-continue with the request.
https://tools.ietf.org/html/rfc8297#section-3 Security Considerations
x-ref:
An HTTP Status Code for Indicating Hints (103 Early Hints)
https://tools.ietf.org/html/rfc8297
allow h2.c layer to modify r->state in addition to r->h2state
Do not retire/release r on error if trailers (as opposed to headers)
(stream r was just allocated in the same scope for headers,
so ok to release)
http_request_parse_header() specialized for HTTP/2 request headers
to be parsed as each field-name and value is HPACK-decoded; send headers
directly from HPACK decoder, rather than double-buffering in chunkqueue
http_request_headers_process_h2() for post-processing
(subsequently incrementally updated using git rebase)
huge props and many thank yous to writers of testing tools used while
developing HTTP/2 support in lighttpd:
h2spec - conformance testing tool for HTTP/2 implementation
https://github.com/summerwind/h2spec
h2load - HTTP/2 benchmarking tool
https://nghttp2.org/documentation/h2load-howto.html
curl - command line tool and library for transferring data with URLs
https://curl.haxx.se/
