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/*
* Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/quic_statm.h"
void ossl_statm_update_rtt(OSSL_STATM *statm,
OSSL_TIME ack_delay,
OSSL_TIME override_latest_rtt)
{
OSSL_TIME adjusted_rtt, latest_rtt = override_latest_rtt;
/* Use provided RTT value, or else last RTT value. */
if (ossl_time_is_zero(latest_rtt))
latest_rtt = statm->latest_rtt;
else
statm->latest_rtt = latest_rtt;
if (!statm->have_first_sample) {
statm->min_rtt = latest_rtt;
statm->smoothed_rtt = latest_rtt;
statm->rtt_variance = ossl_time_divide(latest_rtt, 2);
statm->have_first_sample = 1;
return;
}
/* Update minimum RTT. */
if (ossl_time_compare(latest_rtt, statm->min_rtt) < 0)
statm->min_rtt = latest_rtt;
/*
* Enforcement of max_ack_delay is the responsibility of
* the caller as it is context-dependent.
*/
adjusted_rtt = latest_rtt;
if (ossl_time_compare(latest_rtt, ossl_time_add(statm->min_rtt, ack_delay)) >= 0)
adjusted_rtt = ossl_time_subtract(latest_rtt, ack_delay);
statm->rtt_variance = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->rtt_variance, 3),
ossl_time_abs_difference(statm->smoothed_rtt,
adjusted_rtt)), 4);
statm->smoothed_rtt = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->smoothed_rtt, 7),
adjusted_rtt), 8);
}
/* RFC 9002 kInitialRtt value. RFC recommended value. */
#define K_INITIAL_RTT ossl_ms2time(333)
int ossl_statm_init(OSSL_STATM *statm)
{
statm->smoothed_rtt = K_INITIAL_RTT;
statm->latest_rtt = ossl_time_zero();
statm->min_rtt = ossl_time_infinite();
statm->rtt_variance = ossl_time_divide(K_INITIAL_RTT, 2);
statm->have_first_sample = 0;
return 1;
}
void ossl_statm_destroy(OSSL_STATM *statm)
{
/* No-op. */
}
void ossl_statm_get_rtt_info(OSSL_STATM *statm, OSSL_RTT_INFO *rtt_info)
{
rtt_info->min_rtt = statm->min_rtt;
rtt_info->latest_rtt = statm->latest_rtt;
rtt_info->smoothed_rtt = statm->smoothed_rtt;
rtt_info->rtt_variance = statm->rtt_variance;
}
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