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[tor-commits] [tor/main] TOR_NOLA: Implement a pure BDP tracking CC alg
commit ed1e91ffc29a707443d89e0f06732d8bab656c33
Author: Mike Perry <mikeperry-git@xxxxxxxxxxxxxx>
Date: Fri Jun 11 23:50:37 2021 +0000
TOR_NOLA: Implement a pure BDP tracking CC alg
How come no one ever named a congestion control algorithm after New Orleans?
---
src/core/or/congestion_control_nola.c | 126 ++++++++++++++++++++++++++++++++++
src/core/or/congestion_control_nola.h | 33 +++++++++
2 files changed, 159 insertions(+)
diff --git a/src/core/or/congestion_control_nola.c b/src/core/or/congestion_control_nola.c
new file mode 100644
index 0000000000..09f88d4699
--- /dev/null
+++ b/src/core/or/congestion_control_nola.c
@@ -0,0 +1,126 @@
+/* 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;
+}
diff --git a/src/core/or/congestion_control_nola.h b/src/core/or/congestion_control_nola.h
new file mode 100644
index 0000000000..9c7d6e0635
--- /dev/null
+++ b/src/core/or/congestion_control_nola.h
@@ -0,0 +1,33 @@
+/* Copyright (c) 2019-2021, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file congestion_control_nola.h
+ * \brief Private-ish APIs for the TOR_NOLA congestion control algorithm
+ **/
+
+#ifndef TOR_CONGESTION_CONTROL_NOLA_H
+#define TOR_CONGESTION_CONTROL_NOLA_H
+
+#include "core/or/crypt_path_st.h"
+#include "core/or/circuit_st.h"
+
+/* Processing SENDME cell. */
+int congestion_control_nola_process_sendme(struct congestion_control_t *cc,
+ const circuit_t *circ,
+ const crypt_path_t *layer_hint);
+void congestion_control_nola_set_params(struct congestion_control_t *cc);
+
+/* Private section starts. */
+#ifdef TOR_CONGESTION_CONTROL_NOLA_PRIVATE
+
+/*
+ * Unit tests declaractions.
+ */
+#ifdef TOR_UNIT_TESTS
+
+#endif /* defined(TOR_UNIT_TESTS) */
+
+#endif /* defined(TOR_CONGESTION_CONTROL_NOLA_PRIVATE) */
+
+#endif /* !defined(TOR_CONGESTION_CONTROL_NOLA_H) */
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