congestion_control_flow.c File Reference

Code that implements flow control for congestion controlled circuits. More...

#include "core/or/or.h"
#include "core/or/relay.h"
#include "core/mainloop/connection.h"
#include "core/or/connection_edge.h"
#include "core/mainloop/mainloop.h"
#include "core/or/congestion_control_common.h"
#include "core/or/congestion_control_flow.h"
#include "core/or/congestion_control_st.h"
#include "core/or/circuitlist.h"
#include "core/or/trace_probes_cc.h"
#include "feature/nodelist/networkstatus.h"
#include "trunnel/flow_control_cells.h"
#include "feature/control/control_events.h"
#include "lib/math/stats.h"
#include "core/or/connection_st.h"
#include "core/or/cell_st.h"
#include "app/config/config.h"
#include "core/or/conflux_util.h"

Go to the source code of this file.

Macros
#define	TOR_CONGESTION_CONTROL_FLOW_PRIVATE
#define	MAX_EXPECTED_CELL_BURST   32
#define	XOFF_GRACE_PERIOD_USEC   (5000)
#define	XON_COUNT_SCALE_AT   200
#define	XOFF_COUNT_SCALE_AT   200
#define	ONE_MEGABYTE   (UINT64_C(1) << 20)
#define	TOTAL_XMIT_SCALE_AT   (10 * ONE_MEGABYTE)
#define	CC_XOFF_CLIENT_DFLT   500
#define	CC_XOFF_CLIENT_MIN   1
#define	CC_XOFF_CLIENT_MAX   10000
#define	CC_XOFF_EXIT_DFLT   500
#define	CC_XOFF_EXIT_MIN   1
#define	CC_XOFF_EXIT_MAX   10000
#define	CC_XON_CHANGE_PCT_DFLT   25
#define	CC_XON_CHANGE_PCT_MIN   1
#define	CC_XON_CHANGE_PCT_MAX   99
#define	CC_XON_RATE_BYTES_DFLT   (500)
#define	CC_XON_RATE_BYTES_MIN   (1)
#define	CC_XON_RATE_BYTES_MAX   (5000)
#define	CC_XON_EWMA_CNT_DFLT   (2)
#define	CC_XON_EWMA_CNT_MIN   (2)
#define	CC_XON_EWMA_CNT_MAX   (100)

Functions
void	flow_control_new_consensus_params (const networkstatus_t *ns)
static void	circuit_send_stream_xoff (edge_connection_t *stream)
static uint32_t	compute_drain_rate (const edge_connection_t *stream)
static void	circuit_send_stream_xon (edge_connection_t *stream)
bool	circuit_process_stream_xoff (edge_connection_t *conn, const crypt_path_t *layer_hint)
bool	circuit_process_stream_xon (edge_connection_t *conn, const crypt_path_t *layer_hint, const relay_msg_t *msg)
int	flow_control_decide_xoff (edge_connection_t *stream)
static bool	stream_drain_rate_changed (const edge_connection_t *stream)
void	flow_control_decide_xon (edge_connection_t *stream, size_t n_written)
void	flow_control_note_sent_data (edge_connection_t *stream, size_t len)
bool	edge_uses_flow_control (const edge_connection_t *stream)
bool	conn_uses_flow_control (connection_t *conn)

Variables
static uint32_t	xoff_client
static uint32_t	xoff_exit
static uint32_t	xon_change_pct
static uint32_t	xon_ewma_cnt
static uint32_t	xon_rate_bytes
uint64_t	cc_stats_flow_num_xoff_sent
uint64_t	cc_stats_flow_num_xon_sent
double	cc_stats_flow_xoff_outbuf_ma = 0
double	cc_stats_flow_xon_outbuf_ma = 0

Detailed Description

Code that implements flow control for congestion controlled circuits.

Definition in file congestion_control_flow.c.

Macro Definition Documentation

MAX_EXPECTED_CELL_BURST

#define MAX_EXPECTED_CELL_BURST   32

Definition at line 50 of file congestion_control_flow.c.

ONE_MEGABYTE

#define ONE_MEGABYTE   (UINT64_C(1) << 20)

Definition at line 88 of file congestion_control_flow.c.

TOR_CONGESTION_CONTROL_FLOW_PRIVATE

#define TOR_CONGESTION_CONTROL_FLOW_PRIVATE

Definition at line 10 of file congestion_control_flow.c.

TOTAL_XMIT_SCALE_AT

#define TOTAL_XMIT_SCALE_AT   (10 * ONE_MEGABYTE)

Definition at line 89 of file congestion_control_flow.c.

XOFF_COUNT_SCALE_AT

#define XOFF_COUNT_SCALE_AT   200

Definition at line 87 of file congestion_control_flow.c.

XOFF_GRACE_PERIOD_USEC

#define XOFF_GRACE_PERIOD_USEC   (5000)

Definition at line 77 of file congestion_control_flow.c.

XON_COUNT_SCALE_AT

#define XON_COUNT_SCALE_AT   200

Definition at line 86 of file congestion_control_flow.c.

Function Documentation

circuit_process_stream_xoff()

bool circuit_process_stream_xoff	(	edge_connection_t *	conn,
		const crypt_path_t *	layer_hint )

Process a stream XOFF, parsing it, and then stopping reading on the edge connection.

Record that we have received an xoff, so we know not to resume reading on this edge conn until we get an XON.

Returns false if the XOFF did not validate; true if it does.

Definition at line 261 of file congestion_control_flow.c.

Referenced by handle_relay_msg().

circuit_process_stream_xon()

bool circuit_process_stream_xon	(	edge_connection_t *	conn,
		const crypt_path_t *	layer_hint,
		const relay_msg_t *	msg )

Process a stream XON, and if it validates, clear the xoff flag and resume reading on this edge connection.

Also, use provided rate information to rate limit reading on this edge (or packagaing from it onto the circuit), to avoid XON/XOFF chatter.

Returns true if the XON validates, false otherwise.

Definition at line 353 of file congestion_control_flow.c.

Referenced by handle_relay_msg().

circuit_send_stream_xoff()

static void circuit_send_stream_xoff ( edge_connection_t * stream )

static

Send an XOFF for this stream, and note that we sent one

Definition at line 146 of file congestion_control_flow.c.

Referenced by flow_control_decide_xoff().

circuit_send_stream_xon()

static void circuit_send_stream_xon ( edge_connection_t * stream )

static

Send an XON for this stream, with appropriate advisory rate information.

Reverts the xoff sent status, and stores the rate information we sent, in case it changes.

Definition at line 214 of file congestion_control_flow.c.

Referenced by flow_control_decide_xon().

compute_drain_rate()

static uint32_t compute_drain_rate ( const edge_connection_t * stream )

inlinestatic

Compute the recent drain rate (write rate) for this edge connection and return it, in KB/sec (1000 bytes/sec).

Returns 0 if the monotime clock is busted.

Definition at line 183 of file congestion_control_flow.c.

Referenced by flow_control_decide_xon().

conn_uses_flow_control()

bool conn_uses_flow_control

(

connection_t *

conn

)

Returns true if a connection is an edge conn that uses flow control

Definition at line 753 of file congestion_control_flow.c.

Referenced by connection_handle_write_impl().

edge_uses_flow_control()

bool edge_uses_flow_control

(

const edge_connection_t *

stream

)

Returns true if an edge connection uses flow control

Definition at line 742 of file congestion_control_flow.c.

Referenced by circuit_process_stream_xoff(), circuit_process_stream_xon(), conn_uses_flow_control(), connection_half_edge_add(), flow_control_decide_xoff(), and sendme_connection_edge_consider_sending().

flow_control_decide_xoff()

int flow_control_decide_xoff

(

edge_connection_t *

stream

)

Called from sendme_stream_data_received(), when data arrives from a circuit to our edge's outbuf, to decide if we need to send an XOFF.

Returns the amount of cells remaining until the buffer is full, at which point it sends an XOFF, and returns 0.

Returns less than 0 if we have queued more than a congestion window worth of data and need to close the circuit.

Definition at line 466 of file congestion_control_flow.c.

flow_control_decide_xon()

void flow_control_decide_xon	(	edge_connection_t *	stream,
		size_t	n_written )

Called whenever we drain an edge connection outbuf by writing on its socket, to decide if it is time to send an xon.

The n_written parameter tells us how many bytes we have written this time, which is used to compute the advisory drain rate fields.

Definition at line 581 of file congestion_control_flow.c.

Referenced by connection_handle_write_impl(), and flow_control_decide_xoff().

flow_control_new_consensus_params()

void flow_control_new_consensus_params

(

const networkstatus_t *

ns

)

Update global congestion control related consensus parameter values, every consensus update.

More details for each of the parameters can be found in proposal 324, section 6.5 including tuning notes.

Definition at line 99 of file congestion_control_flow.c.

Referenced by tor_init().

flow_control_note_sent_data()

void flow_control_note_sent_data	(	edge_connection_t *	stream,
		size_t	len )

Note that we packaged some data on this stream. Used to enforce client-side dropmark limits

Definition at line 723 of file congestion_control_flow.c.

stream_drain_rate_changed()

static bool stream_drain_rate_changed ( const edge_connection_t * stream )

static

Returns true if the stream's drain rate has changed significantly.

Returns false if the monotime clock is stalled, or if we have no previous drain rate information.

Definition at line 550 of file congestion_control_flow.c.

Referenced by flow_control_decide_xon().

Variable Documentation

cc_stats_flow_num_xoff_sent

uint64_t cc_stats_flow_num_xoff_sent

Metricsport stats

Definition at line 42 of file congestion_control_flow.c.

Referenced by circuit_send_stream_xoff(), and fill_cc_counters_values().

cc_stats_flow_num_xon_sent

uint64_t cc_stats_flow_num_xon_sent

Definition at line 43 of file congestion_control_flow.c.

cc_stats_flow_xoff_outbuf_ma

double cc_stats_flow_xoff_outbuf_ma = 0

Definition at line 44 of file congestion_control_flow.c.

cc_stats_flow_xon_outbuf_ma

double cc_stats_flow_xon_outbuf_ma = 0

Definition at line 45 of file congestion_control_flow.c.

xoff_client

uint32_t xoff_client

static

Cache consensus parameters

Definition at line 34 of file congestion_control_flow.c.

Referenced by circuit_process_stream_xoff(), circuit_process_stream_xon(), flow_control_decide_xoff(), and flow_control_new_consensus_params().

xoff_exit

uint32_t xoff_exit

static

Definition at line 35 of file congestion_control_flow.c.

xon_change_pct

uint32_t xon_change_pct

static

Definition at line 37 of file congestion_control_flow.c.

xon_ewma_cnt

uint32_t xon_ewma_cnt

static

Definition at line 38 of file congestion_control_flow.c.

xon_rate_bytes

uint32_t xon_rate_bytes

static

Definition at line 39 of file congestion_control_flow.c.