mirror of
https://gitea.invidious.io/iv-org/litespeed-quic.git
synced 2024-08-15 00:53:43 +00:00
228 lines
7.8 KiB
Text
228 lines
7.8 KiB
Text
# Copyright (c) 2017 - 2019 LiteSpeed Technologies Inc. See LICENSE.
|
|
LSQUIC APIs
|
|
===========
|
|
|
|
LSQUIC exposes the following object types to the user:
|
|
|
|
- Engine Settings (struct lsquic_engine_settings)
|
|
- Stream Interface (struct lsquic_stream_if)
|
|
- Engine API (struct lsquic_engine_api)
|
|
- Engine
|
|
- Connection
|
|
- Stream
|
|
|
|
The first three -- engine settings, engine APIs, and stream interface --
|
|
are used to instantiate the engine. After engine is instantiated, the
|
|
user code need only concern itself with engine, connections, and streams.
|
|
|
|
|
|
Engine Settings
|
|
---------------
|
|
|
|
Engine settings is the struct lsquic_engine_settings. It contains various
|
|
QUIC settings and LSQUIC parameters. The usual way to use it is to initialize
|
|
it to default values using lsquic_engine_init_settings(), modify any values
|
|
if necessary, and pass it as parameter to lsquic_engine_new().
|
|
|
|
QUIC settings are specified by the following members:
|
|
|
|
lsquic_engine_settings QUIC
|
|
member parameter
|
|
---------------------- ---------
|
|
es_cfcw CFCW
|
|
es_sfcw SFCW
|
|
es_max_streams_in MIDS
|
|
es_ua UAID
|
|
es_versions VER
|
|
es_idle_conn_to ICSL
|
|
es_silent_close SCLS
|
|
es_support_srej COPT/SREJ
|
|
es_support_nstp COPT/NSTP
|
|
es_support_tcid0 TCID
|
|
|
|
The following parameters affect run-time behavior:
|
|
|
|
es_rw_once Important: affects event dispatch
|
|
es_handshake_to
|
|
es_support_push
|
|
es_pace_packets
|
|
|
|
Other noteworthy settings:
|
|
|
|
es_max_header_list_size
|
|
es_progress_check
|
|
|
|
To be sure your settings are good (in other words, passing this struct won't
|
|
trip up the engine constructor), use lsquic_engine_check_settings().
|
|
|
|
|
|
Stream Interface
|
|
----------------
|
|
|
|
The stream interface, lsquic_stream_if, specifies callbacks LSQUIC engine
|
|
will call for connections and streams.
|
|
|
|
The following callbacks should be specified for connection:
|
|
|
|
on_new_conn This is called when connection is created.
|
|
|
|
on_goaway_received This function is called when we receive GOAWAY
|
|
frame from peer. This callback is optional.
|
|
|
|
on_conn_closed Connection is closed: all streams have been
|
|
destroyed.
|
|
|
|
The streams have four callbacks:
|
|
|
|
on_new_stream Stream has been created.
|
|
|
|
on_read Stream can be read from (see Events).
|
|
|
|
on_write Stream can be written to (see Events).
|
|
|
|
on_close Stream has been closed.
|
|
|
|
For both connections and streams, the "on new" callback return value can
|
|
be use to specify user-supplied data. This data pointer is optional and
|
|
can be NULL. It can also refer to the same data for the connection and
|
|
its streams. "on close" callbacks should be used to free user-supplied
|
|
data.
|
|
|
|
|
|
Engine API
|
|
----------
|
|
|
|
The engine API, struct lsquic_engine_api, is a combination structure to
|
|
make calling lsquic_engine_new() manageable. It holds references to
|
|
struct lsquic_engine_settings and struct lsquic_stream_if, as well as:
|
|
|
|
- Interface for sending outgoing packets, ea_packets_out
|
|
- Interface for allocating memory for outgoing packet buffers
|
|
(optional).
|
|
|
|
ea_packets_out is a pointer to a function of type lsquic_packets_out_f.
|
|
The engine calls this function when it is appropriate to send out packets
|
|
for one or more connections, which it gives to the function in a batch.
|
|
This batch is an array of struct lsquic_out_spec.
|
|
|
|
|
|
Engine
|
|
------
|
|
|
|
The engine is instantiated using lsquic_engine_new(). The first parameter
|
|
is a list flags and the second parameter is the reference to the engine
|
|
api. The engine settings are specified, they are copied; changing
|
|
the setting after the engine has been created will not affect engine's
|
|
behavior. If the settings are not specified, the engine will use default
|
|
settings created by lsquic_engine_init_settings().
|
|
|
|
Once the engine is instantiated, there are four main ways to use it to
|
|
drive QUIC connections:
|
|
|
|
1. Create a connection using lsquic_engine_connect().
|
|
2. Feed it incoming packets using lsquic_engine_packet_in() function.
|
|
3. Process connections using one of the connection queue functions
|
|
(see Connection Queues).
|
|
4. Accept outgoing packets for sending (and send them!) using
|
|
ea_packets_out callback.
|
|
|
|
|
|
Connection Management
|
|
---------------------
|
|
|
|
A connections needs to be processed once in a while. It needs to be
|
|
processed when one of the following is true:
|
|
|
|
- There are incoming packets;
|
|
- A stream is both readable by the user code and the user code wants
|
|
to read from it;
|
|
- A stream is both writeable by the user code and the user code wants
|
|
to write to it;
|
|
- User has written to stream outside of on_write() callbacks (that is
|
|
allowed) and now there are packets ready to be sent;
|
|
- A timer (pacer, retransmission, idle, etc) has expired;
|
|
- A control frame needs to be sent out;
|
|
- A stream needs to be serviced or created.
|
|
|
|
Each of these use cases is handled by a single function:
|
|
|
|
lsquic_engine_process_conns()
|
|
|
|
The connections to which the conditions above apply are processed (or
|
|
"ticked") in the least recently ticked order. After calling this function,
|
|
you can see when is the next time a connection needs to be processed using
|
|
|
|
lsquic_engine_earliest_adv_tick()
|
|
|
|
Based on this value, next event can be scheduled (in the event loop of
|
|
your choice).
|
|
|
|
Connection
|
|
----------
|
|
|
|
A connection is created using lsquic_engine_connect(). When on_new_conn()
|
|
is called, the client code should call lsquic_conn_make_stream() one or
|
|
more times. One new stream will be created for each one of those calls.
|
|
|
|
Several auxiliary functions are available:
|
|
|
|
- lsquic_conn_id()
|
|
- lsquic_conn_going_away()
|
|
- lsquic_conn_get_peer_ctx()
|
|
- lsquic_conn_get_stream_by_id()
|
|
- lsquic_conn_get_ctx()
|
|
|
|
|
|
Stream
|
|
------
|
|
|
|
LSQUIC stream hides QUIC and HTTP/2 framing complexities from the user.
|
|
What it presents is a way to send HTTP headers and, optionally, body to
|
|
peer. On read side, the user gets what looks like HTTP/1.1 stream.
|
|
|
|
Expected usage for client is to express the desire to write to stream
|
|
using lsquic_stream_wantwrite() call. Once on_write() is called:
|
|
|
|
1. Write headers using lsquic_stream_send_headers()
|
|
2. Optionally write payload body using of of lsquic_stream_write(),
|
|
lsquic_stream_writev(), or lsquic_stream_writef().
|
|
|
|
That done, shutdown write side using lsquic_stream_shutdown(), unregister
|
|
for write events and register for read events using lsquic_stream_wantread().
|
|
|
|
Read and parse HTTP/1.1 stream from on_read() callback until end-of-stream
|
|
or an error is encountered.
|
|
|
|
Then unregister the read event and shutdown the read side. The stream will
|
|
be closed after that at some point and on_close() callback will be called,
|
|
at which point resources can be freed. (Internally, the stream object is
|
|
not destroyed until either all the packets carrying its data are ACKed or
|
|
the connection is destroyed).
|
|
|
|
on_read() and on_write() callbacks are dispatched differently based on the
|
|
value of es_rw_once:
|
|
|
|
If es_rw_once is false, then the callbacks are dispatched in a loop until
|
|
the user unregisters the event or the stream becomes unreadable (or
|
|
unwriteable).
|
|
|
|
If es_rw_once is true, on_read() and on_write() are called once "per tick".
|
|
It is the up to the user to read and write enough data.
|
|
|
|
|
|
Events
|
|
------
|
|
|
|
Stream events are persistent: once call lsquic_stream_wantwrite() or
|
|
lsquic_stream_wantread(), the event stays active until turned off.
|
|
|
|
Note that when an error is encountered (such as a stream reset), the
|
|
stream becomes readable and writeable: this allows user code to collect
|
|
the error.
|
|
|
|
|
|
Versions
|
|
--------
|
|
|
|
QUIC version are listed in enum lsquic_version. To specify a list of
|
|
versions, they are usually placed in a bitmask, e.g. es_versions.
|