quic-transport
5.2:
Packets that are matched to an existing connection are discarded if
the packets are inconsistent with the state of that connection.
5.2.2:
Servers MUST drop incoming packets under all other circumstances.
The removal of QUIC packet protection depends on the largest packet number
received. When a garbage packet was received, the decoder still updated the
largest packet number from that packet. This could affect removing protection
from subsequent QUIC packets.
As per HTTP/3 draft 29, section 4.1:
When the server does not need to receive the remainder of the request,
it MAY abort reading the request stream, send a complete response, and
cleanly close the sending part of the stream.
On QUIC connections, SSL_shutdown() is used to call the send_alert callback
to send a CONNECTION_CLOSE frame. The reverse side is handled by other means.
At least BoringSSL doesn't differentiate whether this is a QUIC SSL method,
so waiting for the peer's close_notify alert should be explicitly disabled.
The logical quic connection state is tested by handler functions that
process corresponding types of packets (initial/handshake/application).
The packet is declined if state is incorrect.
No timeout is required for the input queue.
If a client attemtps to start a new connection with unsupported version,
a version negotiation packet is sent that contains a list of supported
versions (currently this is a single version, selected at compile time).
The function ngx_http_upstream_check_broken_connection() terminates the HTTP/1
request if client sends eof. For QUIC (including HTTP/3) the c->write->error
flag is now checked instead. This flag is set when the entire QUIC connection
is closed or STOP_SENDING was received from client.
Previously the request body DATA frame header was read by one byte because
filters were called only when the requested number of bytes were read. Now,
after 08ff2e10ae92 (1.19.2), filters are called after each read. More bytes
can be read at once, which simplifies and optimizes the code.
This also reduces diff with the default branch.
Previously, such packets weren't handled as the resulting zero remaining time
prevented setting the loss detection timer, which, instead, could be disarmed.
For implementation details, see quic-recovery draft 29, appendix A.10.
The PTO handler is split into separate PTO and loss detection handlers
that operate interchangeably depending on which timer should be set.
The present ngx_quic_lost_handler is now only used for packet loss detection.
It replaces ngx_quic_pto_handler if there are packets preceeding largest_ack.
Once there is no more such packets, ngx_quic_pto_handler is installed again.
Probes carry unacknowledged data previously sent in the oldest packet number,
one per each packet number space. That is, it could be up to two probes.
PTO backoff is now increased before scheduling next probes.
In particular, this prevents declaring packet number 0 as lost if
there aren't yet any acknowledgements in this packet number space.
For example, only Initial packets were acknowledged in handshake.
Previously a single STREAM frame was created for each buffer in stream output
chain which is wasteful with respect to memory. The following changes were
made in the stream send code:
- ngx_quic_stream_send_chain() no longer calls ngx_quic_stream_send() and got
a separate implementation that coalesces neighbouring buffers into a single
frame
- the new ngx_quic_stream_send_chain() respects the limit argument, which fixes
sendfile_max_chunk and limit_rate
- ngx_quic_stream_send() is reimplemented to call ngx_quic_stream_send_chain()
- stream frame size limit is moved out to a separate function
ngx_quic_max_stream_frame()
- flow control is moved out to a separate function ngx_quic_max_stream_flow()
- ngx_quic_stream_send_chain() is relocated next to ngx_quic_stream_send()
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).
