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cc: Add comments and clean up some syntax

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Signed-off-by: David Goulet <dgoulet@torproject.org>
This commit is contained in:
David Goulet 2021-10-04 10:32:59 -04:00
parent 322f213210
commit bfd69655af
2 changed files with 57 additions and 29 deletions
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43
src/core/or/congestion_control_common.c
View File

@ -26,30 +26,45 @@
#include "lib/time/compat_time.h"
#include "feature/nodelist/networkstatus.h"
/* Consensus parameter defaults */
/* Consensus parameter defaults.
*
* More details for each of the parameters can be found in proposal 324,
* section 6.5 including tuning notes. */
#define CIRCWINDOW_INIT (500)
#define CWND_INC_PCT_SS_DFLT (100)
#define SENDME_INC_DFLT (50)
#define CWND_MIN_DFLT (MAX(100, SENDME_INC_DFLT))
#define CWND_MAX_DFLT (INT32_MAX)
#define CWND_INC_DFLT (50)
#define CWND_INC_PCT_SS_DFLT (100)
#define CWND_INC_RATE_DFLT (1)
#define CWND_MAX_DFLT (INT32_MAX)
#define CWND_MIN_DFLT (MAX(100, SENDME_INC_DFLT))
#define BWE_SENDME_MIN_DFLT (5)
#define EWMA_CWND_COUNT_DFLT (2)
/* BDP algorithms for each congestion control algorithms use the piecewise
* estimattor. See section 3.1.4 of proposal 324. */
#define WESTWOOD_BDP_ALG BDP_ALG_PIECEWISE
#define VEGAS_BDP_MIX_ALG BDP_ALG_PIECEWISE
#define NOLA_BDP_ALG BDP_ALG_PIECEWISE
#define EWMA_CWND_COUNT_DFLT 2
#define BWE_SENDME_MIN_DFLT 5
/* Indicate OR connection buffer limitations used to stop or start accepting
* cells in its outbuf.
*
* These watermarks are historical to tor in a sense that they've been used
* almost from the genesis point. And were likely defined to fit the bounds of
* TLS records of 16KB which would be around 32 cells.
*
* These are defaults of the consensus parameter "orconn_high" and "orconn_low"
* values. */
#define OR_CONN_HIGHWATER_DFLT (32*1024)
#define OR_CONN_LOWWATER_DFLT (16*1024)
/* Low and high values of circuit cell queue sizes. They are used to tell when
* to start or stop reading on the streams attached on the circuit.
*
* These are defaults of the consensus parameters "cellq_high" and "cellq_low".
*/
#define CELL_QUEUE_LOW_DFLT (10)
#define CELL_QUEUE_HIGH_DFLT (256)
@ -60,12 +75,12 @@ static bool congestion_control_update_circuit_bdp(congestion_control_t *,
const crypt_path_t *,
uint64_t, uint64_t);
/* Consensus parameters cached. The non static ones are extern. */
static uint32_t cwnd_max = CWND_MAX_DFLT;
uint32_t or_conn_highwater = OR_CONN_HIGHWATER_DFLT;
uint32_t or_conn_lowwater = OR_CONN_LOWWATER_DFLT;
int32_t cell_queue_high = CELL_QUEUE_HIGH_DFLT;
int32_t cell_queue_low = CELL_QUEUE_LOW_DFLT;
uint32_t or_conn_highwater = OR_CONN_HIGHWATER_DFLT;
uint32_t or_conn_lowwater = OR_CONN_LOWWATER_DFLT;
/**
* Update global congestion control related consensus parameter values,

41
src/core/or/congestion_control_flow.c
View File

@ -32,28 +32,34 @@ static uint32_t xoff_client;
static uint32_t xoff_exit;
static uint32_t xon_change_pct;
static uint32_t xon_rate_bytes;
static uint32_t xon_ewma_cnt;
static uint32_t xon_rate_bytes;
/** In normal operation, we can get a burst of up to 32 cells before
* returning to libevent to flush the outbuf. This is a heuristic from
* hardcoded values and strange logic in connection_bucket_get_share(). */
/* In normal operation, we can get a burst of up to 32 cells before returning
* to libevent to flush the outbuf. This is a heuristic from hardcoded values
* and strange logic in connection_bucket_get_share(). */
#define MAX_EXPECTED_CELL_BURST 32
/**
* The following three are for dropmark rate limiting. They define when
* we scale down our XON, XOFF, and xmit byte counts. Early scaling
* is beneficial because it limits the ability of spurious XON/XOFF
* to be sent after large amounts of data without XON/XOFF. At these
* limits, after 10MB of data (or more), an adversary can only inject
* (log2(10MB)-log2(200*500))*100 ~= 1000 cells of fake XOFF/XON before
* the xmit byte * count will be halved enough to triggering a limit. */
/* The following three are for dropmark rate limiting. They define when we
* scale down our XON, XOFF, and xmit byte counts. Early scaling is beneficial
* because it limits the ability of spurious XON/XOFF to be sent after large
* amounts of data without XON/XOFF. At these limits, after 10MB of data (or
* more), an adversary can only inject (log2(10MB)-log2(200*500))*100 ~= 1000
* cells of fake XOFF/XON before the xmit byte count will be halved enough to
* triggering a limit. */
#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 TOTAL_XMIT_SCALE_AT (10 * ONE_MEGABYTE)
static const congestion_control_t *
/**
* Return the congestion control object of the given edge connection.
*
* Returns NULL if the edge connection doesn't have a cpath_layer or not
* attached to a circuit. But also if the cpath_layer or circuit doesn't have a
* congestion control object.
*/
static inline const congestion_control_t *
edge_get_ccontrol(const edge_connection_t *edge)
{
if (edge->cpath_layer)
@ -64,6 +70,13 @@ edge_get_ccontrol(const edge_connection_t *edge)
return NULL;
}
/**
* 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.
*/
void
flow_control_new_consensus_params(const networkstatus_t *ns)
{