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/* Copyright (c) 2019-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file congestion_control_nola.c
* \brief Code that implements the TOR_NOLA congestion control algorithm
* from Proposal #324.
*/
#define TOR_CONGESTION_CONTROL_NOLA_PRIVATE
#include "core/or/or.h"
#include "core/or/crypt_path.h"
#include "core/or/or_circuit_st.h"
#include "core/or/sendme.h"
#include "core/or/congestion_control_st.h"
#include "core/or/congestion_control_common.h"
#include "core/or/congestion_control_nola.h"
#include "core/or/circuituse.h"
#include "core/or/circuitlist.h"
#include "core/or/origin_circuit_st.h"
#include "core/or/channel.h"
#include "feature/nodelist/networkstatus.h"
#define NOLA_BDP_OVERSHOOT 100
/**
* Cache NOLA consensus parameters.
*/
void
congestion_control_nola_set_params(congestion_control_t *cc)
{
tor_assert(cc->cc_alg == CC_ALG_NOLA);
cc->nola_params.bdp_overshoot =
networkstatus_get_param(NULL, "cc_nola_overshoot",
NOLA_BDP_OVERSHOOT,
0,
1000);
}
/**
* Process a SENDME and update the congestion window according to the
* rules specified in TOR_NOLA of Proposal #324.
*
* TOR_NOLA updates the congestion window to match the current
* BDP estimate, every sendme. Because this can result in downward
* drift, a fixed overhead is added to the BDP estimate. This will
* cause some queuing, but ensures that the algorithm always uses
* the full BDP.
*
* To handle the case where the local orconn blocks, TOR_NOLA uses
* the 'piecewise' BDP estimate, which uses more a conservative BDP
* estimate method when blocking occurrs, but a more aggressive BDP
* estimate when there is no local blocking. This minimizes local
* client queues.
*/
int
congestion_control_nola_process_sendme(congestion_control_t *cc,
const circuit_t *circ,
const crypt_path_t *layer_hint)
{
tor_assert(cc && cc->cc_alg == CC_ALG_NOLA);
tor_assert(circ);
if (cc->next_cc_event)
cc->next_cc_event--;
/* If we get a congestion event, the only thing NOLA
* does is note this as if we exited slow-start
* (which for NOLA just means we finished our ICW). */
if (cc->next_cc_event == 0)
cc->in_slow_start = 0;
/* If we did not successfully update BDP, we must return. Otherwise,
* NOLA can drift downwards */
if (!congestion_control_update_circuit_estimates(cc, circ, layer_hint)) {
cc->inflight = cc->inflight - cc->sendme_inc;
return 0;
}
/* We overshoot the BDP by the cwnd_inc param amount, because BDP
* may otherwise drift down. This helps us probe for more capacity.
* But there is no sense to do it if the local channel is blocked. */
if (cc->blocked_chan)
cc->cwnd = cc->bdp[cc->bdp_alg];
else
cc->cwnd = cc->bdp[cc->bdp_alg] + cc->nola_params.bdp_overshoot;
/* cwnd can never fall below 1 increment */
cc->cwnd = MAX(cc->cwnd, cc->cwnd_min);
if (CIRCUIT_IS_ORIGIN(circ)) {
log_info(LD_CIRC,
"CC TOR_NOLA: Circuit %d "
"CWND: %"PRIu64", "
"INFL: %"PRIu64", "
"NCCE: %"PRIu64", "
"SS: %d",
CONST_TO_ORIGIN_CIRCUIT(circ)->global_identifier,
cc->cwnd,
cc->inflight,
cc->next_cc_event,
cc->in_slow_start
);
} else {
log_info(LD_CIRC,
"CC TOR_NOLA: Circuit %"PRIu64":%d "
"CWND: %"PRIu64", "
"INFL: %"PRIu64", "
"NCCE: %"PRIu64", "
"SS: %d",
circ->n_chan->global_identifier, circ->n_circ_id,
cc->cwnd,
cc->inflight,
cc->next_cc_event,
cc->in_slow_start
);
}
/* Update inflight with ack */
cc->inflight = cc->inflight - cc->sendme_inc;
return 0;
}
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