Reworked connections reuse, so closing connections is attempted in
advance, as long as number of free connections is less than 1/16 of
worker connections configured. This ensures that new connections can
be handled even if closing a reusable connection requires some time,
for example, for a lingering close (ticket #2017).
The 1/16 ratio is selected to be smaller than 1/8 used for disabling
accept when working with accept mutex, so nginx will try to balance
new connections to different workers first, and will start reusing
connections only if this won't help.
Previously, reusing connections happened silently and was only
visible in monitoring systems. This was shown to be not very user-friendly,
and administrators often didn't realize there were too few connections
available to withstand the load, and configured timeouts (keepalive_timeout
and http2_idle_timeout) were effectively reduced to keep things running.
To provide at least some information about this, a warning is now logged
(at most once per second, to avoid flooding the logs).
Sending shutdown when ngx_http_test_reading() detects the connection is
closed can result in "SSL_shutdown() failed (SSL: ... bad write retry)"
critical log messages if there are blocked writes.
Fix is to avoid sending shutdown via the c->ssl->no_send_shutdown flag,
similarly to how it is done in ngx_http_keepalive_handler() for kqueue
when pending EOF is detected.
Reported by Jan Prachař
(http://mailman.nginx.org/pipermail/nginx-devel/2018-December/011702.html).
Without the flag, SSL shutdown is attempted on such connections,
resulting in useless work and/or bogus "SSL_shutdown() failed
(SSL: ... bad write retry)" critical log messages if there are
blocked writes.
Previously, bidirectional shutdown never worked, due to two issues
in the code:
1. The code only tested SSL_ERROR_WANT_READ and SSL_ERROR_WANT_WRITE
when there was an error in the error queue, which cannot happen.
The bug was introduced in an attempt to fix unexpected error logging
as reported with OpenSSL 0.9.8g
(http://mailman.nginx.org/pipermail/nginx/2008-January/003084.html).
2. The code never called SSL_shutdown() for the second time to wait for
the peer's close_notify alert.
This change fixes both issues.
Note that after this change bidirectional shutdown is expected to work for
the first time, so c->ssl->no_wait_shutdown now makes a difference. This
is not a problem for HTTP code which always uses c->ssl->no_wait_shutdown,
but might be a problem for stream and mail code, as well as 3rd party
modules.
To minimize the effect of the change, the timeout, which was used to be 30
seconds and not configurable, though never actually used, is now set to
3 seconds. It is also expanded to apply to both SSL_ERROR_WANT_READ and
SSL_ERROR_WANT_WRITE, so timeout is properly set if writing to the socket
buffer is not possible.
If some additional data from a pipelined request happens to be
read into the body buffer, we copy it to r->header_in or allocate
an additional large client header buffer for it.
This ensures that copying won't write more than the buffer size
even if the buffer comes from hc->free and it is smaller than the large
client header buffer size in the virtual host configuration. This might
happen if size of large client header buffers is different in name-based
virtual hosts, similarly to the problem with number of buffers fixed
in 6926:e662cbf1b932.
Creating client-initiated streams is moved from ngx_quic_handle_stream_frame()
to a separate function ngx_quic_create_client_stream(). This function is
responsible for creating streams with lower ids as well.
Also, simplified and fixed initial data buffering in
ngx_quic_handle_stream_frame(). It is now done before calling the initial
handler as the handler can destroy the stream.
Previously this function generated an error trying to figure out if client shut
down the write end of the connection. The reason for this error was that a
QUIC stream has no socket descriptor. However checking for eof is not the
right thing to do for an HTTP/3 QUIC stream since HTTP/3 clients are expected
to shut down the write end of the stream after sending the request.
Now the function handles QUIC streams separately. It checks if c->read->error
is set. The error flags for c->read and c->write are now set for all streams
when closing the QUIC connection instead of setting the pending_eof flag.
According to quic-transport draft 29, section 19.3.1:
The value of the Gap field establishes the largest packet number
value for the subsequent ACK Range using the following formula:
largest = previous_smallest - gap - 2
Thus, given a largest packet number for the range, the smallest value
is determined by the formula:
smallest = largest - ack_range
While here, changed min/max to uint64_t for consistency.
A QUIC stream could be destroyed by handler while in ngx_quic_stream_input().
To detect this, ngx_quic_find_stream() is used to check that it still exists.
Previously, a stream id was passed to this routine off the frame structure.
In case of stream cleanup, it is freed along with other frames belonging to
the stream on cleanup. Then, a cleanup handler reuses last frames to update
MAX_STREAMS and serve other purpose. Thus, ngx_quic_find_stream() is passed
a reused frame with zeroed out part pointed by stream_id. If a stream with
id 0x0 still exists, this leads to use-after-free.
After 05e42236e95b (1.19.1) responses with extra data might result in
zero size buffers being generated and "zero size buf" alerts in writer
(if f->rest happened to be 0 when processing additional stdout data).
The limits on active bidi and uni client streams are maintained at their
initial values initial_max_streams_bidi and initial_max_streams_uni by sending
a MAX_STREAMS frame upon each client stream closure.
Also, the following is changed for data arriving to non-existing streams:
- if a stream was already closed, such data is ignored
- when creating a new stream, all streams of the same type with lower ids are
created too
Previously, the document generated by the xslt filter was always fully sent
to client even if a range was requested and response status was 206 with
appropriate Content-Range.
The xslt module is unable to serve a range because of suspending the header
filter chain. By the moment full response xml is buffered by the xslt filter,
range header filter is not called yet, but the range body filter has already
been called and did nothing.
The fix is to disable ranges by resetting the r->allow_ranges flag much like
the image filter that employs a similar technique.
The ngx_http_perl_module module doesn't have a notion of including additional
search paths through --with-cc-opt, which results in compile error incomplete
type 'enum ssl_encryption_level_t' when building nginx without QUIC support.
The enum is visible from quic event headers and eventually pollutes ngx_core.h.
The fix is to limit including headers to compile units that are real consumers.
According to quic-transport draft 29, section 21.12.1.1:
Prior to validation, endpoints are limited in what they are able to
send. During the handshake, a server cannot send more than three
times the data it receives; clients that initiate new connections or
migrate to a new network path are limited.
The ngx_quic_queue_frame() functions puts a frame into send queue and
schedules a push timer to actually send data.
The patch adds tracking for data amount in the queue and sends data
immediately if amount of data exceeds limit.
Instead of timer-based retransmissions with constant packet lifetime,
this patch implements ack-based loss detection and probe timeout
for the cases, when no ack is received, according to the quic-recovery
draft 29.
The c->quic->retransmit timer is now called "pto".
The ngx_quic_retransmit() function is renamed to "ngx_quic_detect_lost()".
This is a preparation for the following patches.
