#include <cwist/net/quic_flow_control.h>

Include dependency graph for quic_flow_control.c:

Macros
#define	QUIC_MAX_VARINT ((1ULL << 62) - 1)

#define	QUIC_FRAME_MAX_DATA 0x10

#define	QUIC_FRAME_MAX_STREAM_DATA 0x11

Functions
void	quic_flow_control_init (quic_conn_fc_t *fc, uint64_t initial_conn_window, uint64_t initial_stream_window, uint64_t max_conn_window, uint64_t max_stream_window)
	Initialize the connection-level flow control state.

void	quic_stream_fc_init (quic_stream_fc_t *sfc, uint64_t stream_id, uint64_t initial_stream_window)
	Initialize the flow control state for a single stream.

void	quic_flow_control_update_rtt (quic_conn_fc_t *fc, uint64_t rtt_sample_us)
	Feed an RTT sample into the smoothed RTT estimator and re-evaluate quality.

quic_net_quality_t	quic_flow_control_evaluate_quality (quic_conn_fc_t *fc)
	Recompute the network quality class from the smoothed RTT.

void	quic_flow_control_adjust_windows (quic_conn_fc_t fc, quic_stream_fc_t sfc)
	Grow flow control windows when the network quality is degraded.

void	quic_flow_control_consume_conn (quic_conn_fc_t *fc, uint64_t bytes)
	Account for connection-level flow control bytes consumed by the peer.

void	quic_flow_control_consume_stream (quic_conn_fc_t fc, quic_stream_fc_t sfc, uint64_t bytes)
	Account for stream-level flow control bytes consumed by the peer.

int	quic_flow_control_maybe_send_max_data (quic_conn_fc_t fc, uint8_t buf, size_t buf_len, size_t *written, bool force)
	Write a MAX_DATA frame if the connection limit should be raised.

int	quic_flow_control_maybe_send_max_stream_data (quic_conn_fc_t fc, quic_stream_fc_t sfc, uint8_t buf, size_t buf_len, size_t written, bool force)
	Write a MAX_STREAM_DATA frame if the stream limit should be raised.

Macro Definition Documentation

◆ QUIC_FRAME_MAX_DATA

#define QUIC_FRAME_MAX_DATA 0x10

Definition at line 4 of file quic_flow_control.c.

◆ QUIC_FRAME_MAX_STREAM_DATA

#define QUIC_FRAME_MAX_STREAM_DATA 0x11

Definition at line 5 of file quic_flow_control.c.

◆ QUIC_MAX_VARINT

#define QUIC_MAX_VARINT ((1ULL << 62) - 1)

Definition at line 3 of file quic_flow_control.c.

Function Documentation

◆ quic_flow_control_adjust_windows()

void quic_flow_control_adjust_windows	(	quic_conn_fc_t *	fc,
		quic_stream_fc_t *	sfc
	)

Grow flow control windows when the network quality is degraded.

Only acts when the connection quality is at least QUIC_NET_QUALITY_HIGH_RTT. Each window that is below its configured maximum is doubled, capped at that maximum. No-op if fc is NULL or quality is better than QUIC_NET_QUALITY_HIGH_RTT; sfc may be NULL, in which case only the connection window is adjusted.

Parameters

fc	Connection flow control state.
sfc	Stream flow control state to adjust, or NULL.

Definition at line 206 of file quic_flow_control.c.

References cap, quic_conn_fc::conn_max_window, quic_conn_fc::conn_window_size, quic_conn_fc::quality, QUIC_NET_QUALITY_HIGH_RTT, and quic_conn_fc::stream_max_window.

◆ quic_flow_control_consume_conn()

void quic_flow_control_consume_conn	(	quic_conn_fc_t *	fc,
		uint64_t	bytes
	)

Account for connection-level flow control bytes consumed by the peer.

The consumed counter saturates at the QUIC varint maximum instead of wrapping. No-op if fc is NULL.

Parameters

fc	Connection flow control state.
bytes	Number of bytes consumed.

Definition at line 230 of file quic_flow_control.c.

References quic_conn_fc::conn_consumed.

◆ quic_flow_control_consume_stream()

void quic_flow_control_consume_stream	(	quic_conn_fc_t *	fc,
		quic_stream_fc_t *	sfc,
		uint64_t	bytes
	)

Account for stream-level flow control bytes consumed by the peer.

The consumed counter saturates at the QUIC varint maximum instead of wrapping. The connection state fc is not touched; sfc may be NULL, in which case the call is a no-op.

Parameters

fc	Connection flow control state (currently unused).
sfc	Stream flow control state.
bytes	Number of bytes consumed.

Definition at line 245 of file quic_flow_control.c.

References cap.

◆ quic_flow_control_evaluate_quality()

quic_net_quality_t quic_flow_control_evaluate_quality ( quic_conn_fc_t * fc )

Recompute the network quality class from the smoothed RTT.

Classifies by srtt thresholds: <= 50 ms excellent, <= 150 ms normal, <= 500 ms high RTT, above that poor. The result is stored in fc->quality and returned. Returns QUIC_NET_QUALITY_NORMAL if fc is NULL or no RTT sample has been recorded yet.

Parameters

fc	Connection flow control state.

Returns: The (updated) quality classification.

Definition at line 179 of file quic_flow_control.c.

References quic_conn_fc::quality, QUIC_NET_QUALITY_EXCELLENT, QUIC_NET_QUALITY_HIGH_RTT, QUIC_NET_QUALITY_NORMAL, QUIC_NET_QUALITY_POOR, quic_conn_fc::rtt_initialized, and quic_conn_fc::srtt_us.

Referenced by quic_flow_control_update_rtt().

◆ quic_flow_control_init()

void quic_flow_control_init	(	quic_conn_fc_t *	fc,
		uint64_t	initial_conn_window,
		uint64_t	initial_stream_window,
		uint64_t	max_conn_window,
		uint64_t	max_stream_window
	)

Initialize the connection-level flow control state.

Initial and maximum windows are clamped to QUIC_FLOW_CONTROL_MIN_INITIAL_WINDOW, and each maximum is raised to at least the corresponding initial value. No-op if fc is NULL.

Parameters

fc	Flow control state to initialize.
initial_conn_window	Initial connection-level window in bytes.
initial_stream_window	Initial per-stream window in bytes.
max_conn_window	Upper bound for the connection window in bytes.
max_stream_window	Upper bound for the per-stream window in bytes.

Definition at line 90 of file quic_flow_control.c.

References cap, quic_conn_fc::quality, and QUIC_NET_QUALITY_NORMAL.

◆ quic_flow_control_maybe_send_max_data()

int quic_flow_control_maybe_send_max_data	(	quic_conn_fc_t *	fc,
		uint8_t *	buf,
		size_t	buf_len,
		size_t *	written,
		bool	force
	)

Write a MAX_DATA frame if the connection limit should be raised.

Unless force is set, a frame is produced only when at least half of the connection window has been consumed (see should_update()). The new maximum is consumed + window, never lower than the current maximum, and is stored back in fc->max_data on success. On entry *written is cleared to 0 when written is non-NULL.

Parameters

fc	Connection flow control state.
buf	Output buffer for the encoded frame.
buf_len	Capacity of `buf` in bytes.
written	Receives the encoded frame length in bytes.
force	Emit the frame even if the update threshold is not met.

Return values

1	Frame written; *written holds its length.
0	No update needed; nothing written.
-1	Invalid argument or `buf` too small; nothing written.

Definition at line 268 of file quic_flow_control.c.

References cap, quic_conn_fc::conn_consumed, quic_conn_fc::conn_window_size, quic_conn_fc::max_data, and QUIC_FRAME_MAX_DATA.

◆ quic_flow_control_maybe_send_max_stream_data()

int quic_flow_control_maybe_send_max_stream_data	(	quic_conn_fc_t *	fc,
		quic_stream_fc_t *	sfc,
		uint8_t *	buf,
		size_t	buf_len,
		size_t *	written,
		bool	force
	)

Write a MAX_STREAM_DATA frame if the stream limit should be raised.

Unless force is set, a frame is produced only when at least half of the stream window has been consumed (see should_update()). The new maximum is consumed + window, never lower than the current maximum, and is stored back in sfc->max_stream_data on success. On entry *written is cleared to 0 when written is non-NULL.

Parameters

fc	Connection flow control state.
sfc	Stream flow control state.
buf	Output buffer for the encoded frame.
buf_len	Capacity of `buf` in bytes.
written	Receives the encoded frame length in bytes.
force	Emit the frame even if the update threshold is not met.

Return values

1	Frame written; *written holds its length.
0	No update needed; nothing written.
-1	Invalid argument or `buf` too small; nothing written.

Definition at line 308 of file quic_flow_control.c.

References cap, and QUIC_FRAME_MAX_STREAM_DATA.

◆ quic_flow_control_update_rtt()

void quic_flow_control_update_rtt	(	quic_conn_fc_t *	fc,
		uint64_t	rtt_sample_us
	)

Feed an RTT sample into the smoothed RTT estimator and re-evaluate quality.

Uses RFC 6298-style smoothing: rttvar is updated with weight 1/4 and srtt with weight 1/8; the first sample initializes both. Tracked state is confined to fc and is not thread-safe across concurrent calls on the same connection. No-op if fc is NULL or rtt_sample_us is zero.

Parameters

fc	Connection flow control state.
rtt_sample_us	Latest RTT sample in microseconds.

Definition at line 147 of file quic_flow_control.c.

References cap, quic_conn_fc::min_rtt_us, quic_flow_control_evaluate_quality(), quic_conn_fc::rtt_initialized, quic_conn_fc::rttvar_us, and quic_conn_fc::srtt_us.

◆ quic_stream_fc_init()

void quic_stream_fc_init	(	quic_stream_fc_t *	sfc,
		uint64_t	stream_id,
		uint64_t	initial_stream_window
	)

Initialize the flow control state for a single stream.

The initial window is clamped to QUIC_FLOW_CONTROL_MIN_INITIAL_WINDOW. No-op if sfc is NULL.

Parameters

sfc	Stream flow control state to initialize.
stream_id	ID of the stream this state belongs to.
initial_stream_window	Initial per-stream window in bytes.

Definition at line 124 of file quic_flow_control.c.

References cap.

Macros

Functions

Macro Definition Documentation

◆ QUIC_FRAME_MAX_DATA

◆ QUIC_FRAME_MAX_STREAM_DATA

◆ QUIC_MAX_VARINT

Function Documentation

◆ quic_flow_control_adjust_windows()

◆ quic_flow_control_consume_conn()

◆ quic_flow_control_consume_stream()

◆ quic_flow_control_evaluate_quality()

◆ quic_flow_control_init()

◆ quic_flow_control_maybe_send_max_data()

◆ quic_flow_control_maybe_send_max_stream_data()

◆ quic_flow_control_update_rtt()

◆ quic_stream_fc_init()