Now there's no need to annotate every frame in ACK-eliciting packet.
Sending ACK was moved to the first place, so that queueing ACK frame
no longer postponed up to the next packet after pushing STREAM frames.
+ added "quic" prefix to all error messages
+ rephrased some messages
+ removed excessive error logging from frame parser
+ added ngx_quic_check_peer() function to check proper source/destination
match and do it one place
- the ngx_quic_hexdump0() macro is renamed to ngx_quic_hexdump();
the original ngx_quic_hexdump() macro with variable argument is
removed, extra information is logged normally, with ngx_log_debug()
- all labels in hex dumps are prefixed with "quic"
- the hexdump format is simplified, length is moved forward to avoid
situations when the dump is truncated, and length is not shown
- ngx_quic_flush_flight() function contents is debug-only, placed under
NGX_DEBUG macro to avoid "unused variable" warnings from compiler
- frame names in labels are capitalized, similar to other places
+ all dumps are moved under one of the following macros (undefined by default):
NGX_QUIC_DEBUG_PACKETS
NGX_QUIC_DEBUG_FRAMES
NGX_QUIC_DEBUG_FRAMES_ALLOC
NGX_QUIC_DEBUG_CRYPTO
+ all QUIC debug messages got "quic " prefix
+ all input frames are reported as "quic frame in FOO_FRAME bar:1 baz:2"
+ all outgoing frames re reported as "quic frame out foo bar baz"
+ all stream operations are prefixed with id, like: "quic stream id 0x33 recv"
+ all transport parameters are prefixed with "quic tp"
(hex dump is moved to caller, to avoid using ngx_cycle->log)
+ packet flags and some other debug messages are updated to
include packet type
As per https://tools.ietf.org/html/rfc7540#section-8.1,
: A server can send a complete response prior to the client
: sending an entire request if the response does not depend on
: any portion of the request that has not been sent and
: received. When this is true, a server MAY request that the
: client abort transmission of a request without error by
: sending a RST_STREAM with an error code of NO_ERROR after
: sending a complete response (i.e., a frame with the
: END_STREAM flag). Clients MUST NOT discard responses as a
: result of receiving such a RST_STREAM, though clients can
: always discard responses at their discretion for other
: reasons.
Previously, RST_STREAM(NO_ERROR) received from upstream after
a frame with the END_STREAM flag was incorrectly treated as an
error. Now, a single RST_STREAM(NO_ERROR) is properly handled.
This fixes problems observed with modern grpc-c [1], as well
as with the Go gRPC module.
[1] https://github.com/grpc/grpc/pull/1661
We always generate stream frames that have length. The 'len' member is used
during parsing incoming frames and can be safely ignored when generating
output.
There are following flags in quic connection:
closing - true, when a connection close is initiated, for whatever reason
draining - true, when a CC frame is received from peer
The following state machine is used for closing:
+------------------+
| I/HS/AD |
+------------------+
| | |
| | V
| | immediate close initiated:
| | reasons: close by top-level protocol, fatal error
| | + sends CC (probably with app-level message)
| | + starts close_timer: 3 * PTO (current probe timeout)
| | |
| | V
| | +---------+ - Reply to input with CC (rate-limited)
| | | CLOSING | - Close/Reset all streams
| | +---------+
| | | |
| V V |
| receives CC |
| | |
idle | |
timer | |
| V |
| +----------+ | - MUST NOT send anything (MAY send a single CC)
| | DRAINING | | - if not already started, starts close_timer: 3 * PTO
| +----------+ | - if not already done, close all streams
| | |
| | |
| close_timer fires
| |
V V
+------------------------+
| CLOSED | - clean up all the resources, drop connection
+------------------------+ state completely
The ngx_quic_close_connection() function gets an "rc" argument, that signals
reason of connection closing:
NGX_OK - initiated by application (i.e. http/3), follow state machine
NGX_DONE - timedout (while idle or draining)
NGX_ERROR - fatal error, destroy connection immediately
The PTO calculations are not yet implemented, hardcoded value of 5s is used.
The function is split into three:
ngx_quic_close_connection() itself cleans up all core nginx things
ngx_quic_close_quic() deals with everything inside c->quic
ngx_quic_close_streams() deals with streams cleanup
The quic and streams cleanup functions may return NGX_AGAIN, thus signalling
that cleanup is not ready yet, and the close cannot continue to next step.
The header size macros for long and short packets were fixed to provide
correct values in bytes.
Currently the sending code limits frames so they don't exceed max_packet_size.
But it does not account the case when a single frame can exceed the limit.
As a result of this patch, big payload (CRYPTO and STREAM) will be split
into a number of smaller frames that fit into advertised max_packet_size
(which specifies final packet size, after encryption).
chrome-unstable 83.0.4103.7 starts with Initial packet number 1.
I couldn't find a proper explanation besides this text in quic-transport:
An endpoint MAY skip packet numbers when sending
packets to detect this (Optimistic ACK Attack) behavior.
+ MAX_STREAM_DATA frame is sent when recv() is performed on stream
The new value is a sum of total bytes received by stream + free
space in a buffer;
The sending of MAX_STREM_DATA frame in response to STREAM_DATA_BLOCKED
frame is adjusted to follow the same logic as above.
+ MAX_DATA frame is sent when total amount of received data is 2x
of current limit. The limit is doubled.
+ Default values of transport parameters are adjusted to more meaningful
values:
initial stream limits are set to quic buffer size instead of
unrealistically small 255.
initial max data is decreased to 16 buffer sizes, in an assumption that
this is enough for a relatively short connection, instead of randomly
chosen big number.
All this allows to initiate a stable flow of streams that does not block
on stream/connection limits (tested with FF 77.0a1 and 100K requests)
Before the patch, full STREAM frame handling was delayed until the frame with
zero offset is received. Only node in the streams tree was created.
This lead to problems when such stream was deleted, in particular, it had no
handlers set for read events.
This patch creates new stream immediately, but delays data delivery until
the proper offset will arrive. This is somewhat similar to how accept()
operation works.
The ngx_quic_add_stream() function is no longer needed and merged into stream
handler. The ngx_quic_stream_input() now only handles frames for existing
streams and does not deal with stream creation.
Frames can still float in the following queues:
- crypto frames reordering queues (one per encryption level)
- moved crypto frames cleanup to the moment where all streams are closed
- stream frames reordering queues (one per packet number namespace)
- frames retransmit queues (one per packet number namespace)
Each stream node now includes incoming frames queue and sent/received counters
for tracking offset. The sent counter is not used, c->sent is used, not like
in crypto buffers, which have no connections.
If offset in CRYPTO frame doesn't match expected, following actions are taken:
a) Duplicate frames or frames within [0...current offset] are ignored
b) New data from intersecting ranges (starts before current_offset, ends
after) is consumed
c) "Future" frames are stored in a sorted queue (min offset .. max offset)
Once a frame is consumed, current offset is updated and the queue is inspected:
we iterate the queue until the gap is found and act as described
above for each frame.
The amount of data in buffered frames is limited by corresponding macro.
The CRYPTO and STREAM frame structures are now compatible: they share
the same set of initial fields. This allows to have code that deals with
both of this frames.
The ordering layer now processes the frame with offset and invokes the
handler when it can organise an ordered stream of data.
Quote: Conceptually, a packet number space is the context in which a packet
can be processed and acknowledged.
ngx_quic_namespace_t => ngx_quic_send_ctx_t
qc->ns => qc->send_ctx
ns->largest => send_ctx->largest_ack
The ngx_quic_ns(level) macro now returns pointer, not just index:
ngx_quic_get_send_ctx(c->quic, level)
ngx_quic_retransmit_ns() => ngx_quic_retransmit()
ngx_quic_output_ns() => ngx_quic_output_frames()
The request processing is delayed by a timer. Since nginx updates
internal time once at the start of each event loop iteration, this
normally ensures constant time delay, adding a mitigation from
time-based attacks.
A notable exception to this is the case when there are no additional
events before the timer expires. To ensure constant-time processing
in this case as well, we trigger an additional event loop iteration
by posting a dummy event for the next event loop iteration.
