2022-05-06 16:49:46 +00:00
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/* Copyright (c) 2017 - 2022 LiteSpeed Technologies Inc. See LICENSE. */
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2017-09-22 21:00:03 +00:00
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/*
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* lsquic_conn_flow.h -- Connection flow control-related functions
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*/
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#ifndef LSQUIC_CONN_FLOW_H
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#define LSQUIC_CONN_FLOW_H 1
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struct lsquic_conn_public;
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typedef struct lsquic_cfcw {
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struct lsquic_conn_public
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*cf_conn_pub;
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uint64_t cf_max_recv_off; /* Largest offset observed (cumulative) */
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uint64_t cf_recv_off; /* Flow control receive offset */
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uint64_t cf_read_off; /* Number of bytes consumed (cumulative) */
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lsquic_time_t cf_last_updated;
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unsigned cf_max_recv_win; /* Maximum receive window */
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} lsquic_cfcw_t;
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struct lsquic_conn_cap {
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uint64_t cc_sent; /* Number of bytes sent on connection */
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uint64_t cc_max; /* Maximum cumulative number of bytes allowed
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* to be sent on this connection.
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*/
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uint64_t cc_blocked; /* Last blocked offset used */
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};
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#define lsquic_conn_cap_init(cc, max) do { \
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(cc)->cc_sent = 0; \
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(cc)->cc_max = max; \
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} while (0)
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#define lsquic_conn_cap_avail(cap) ( \
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Latest changes
- [API Change] Sendfile-like functionality is gone. The stream no
longer opens files and deals with file descriptors. (Among other
things, this makes the code more portable.) Three writing functions
are provided:
lsquic_stream_write
lsquic_stream_writev
lsquic_stream_writef (NEW)
lsquic_stream_writef() is given an abstract reader that has function
pointers for size() and read() functions which the user can implement.
This is the most flexible way. lsquic_stream_write() and
lsquic_stream_writev() are now both implemented as wrappers around
lsquic_stream_writef().
- [OPTIMIZATION] When writing to stream, be it within or without the
on_write() callback, place data directly into packet buffer,
bypassing auxiliary data structures. This reduces amount of memory
required, for the amount of data that can be written is limited
by the congestion window.
To support writes outside the on_write() callback, we keep N
outgoing packet buffers per connection which can be written to
by any stream. One half of these are reserved for the highest
priority stream(s), the other half for all other streams. This way,
low-priority streams cannot write instead of high-priority streams
and, on the other hand, low-priority streams get a chance to send
their packets out.
The algorithm is as follows:
- When user writes to stream outside of the callback:
- If this is the highest priority stream, place it onto the
reserved N/2 queue or fail.
(The actual size of this queue is dynamic -- MAX(N/2, CWND) --
rather than N/2, allowing high-priority streams to write as
much as can be sent.)
- If the stream is not the highest priority, try to place the
data onto the reserved N/2 queue or fail.
- When tick occurs *and* more packets can be scheduled:
- Transfer packets from the high N/2 queue to the scheduled
queue.
- If more scheduling is allowed:
- Call on_write callbacks for highest-priority streams,
placing resulting packets directly onto the scheduled queue.
- If more scheduling is allowed:
- Transfer packets from the low N/2 queue to the scheduled
queue.
- If more scheduling is allowed:
- Call on_write callbacks for non-highest-priority streams,
placing resulting packets directly onto the scheduled queue
The number N is currently 20, but it could be varied based on
resource usage.
- If stream is created due to incoming headers, make headers readable
from on_new.
- Outgoing packets are no longer marked non-writeable to prevent placing
more than one STREAM frame from the same stream into a single packet.
This property is maintained via code flow and an explicit check.
Packets for stream data are allocated using a special function.
- STREAM frame elision is cheaper, as we only perform it if a reset
stream has outgoing packets referencing it.
- lsquic_packet_out_t is smaller, as stream_rec elements are now
inside a union.
2017-10-31 13:35:58 +00:00
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(assert((cap)->cc_max >= (cap)->cc_sent)), \
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(cap)->cc_max - (cap)->cc_sent)
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2017-09-22 21:00:03 +00:00
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void
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lsquic_cfcw_init (lsquic_cfcw_t *, struct lsquic_conn_public *,
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unsigned initial_max_recv_window);
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/* If update is to be sent, updates max_recv_off and returns true. Note
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* that if you call this function twice, the second call will return false.
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*/
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int
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lsquic_cfcw_fc_offsets_changed (lsquic_cfcw_t *);
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#define lsquic_cfcw_get_fc_recv_off(fc) (+(fc)->cf_recv_off)
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#define lsquic_cfcw_get_max_recv_off(fc) (+(fc)->cf_max_recv_off)
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#define lsquic_cfcw_get_max_recv_window(fc) (+(fc)->cf_max_recv_win)
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/* Returns false if flow control violation is encountered */
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int
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lsquic_cfcw_incr_max_recv_off (lsquic_cfcw_t *, uint64_t);
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/* Void because we do not expect the caller to make a mistake.
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*/
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void
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lsquic_cfcw_incr_read_off (lsquic_cfcw_t *, uint64_t);
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#endif
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