| 1 | /*
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| 2 | * Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/quic_statm.h"
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| 11 |
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| 12 | void ossl_statm_update_rtt(OSSL_STATM *statm,
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| 13 | OSSL_TIME ack_delay,
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| 14 | OSSL_TIME override_latest_rtt)
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| 15 | {
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| 16 | OSSL_TIME adjusted_rtt, latest_rtt = override_latest_rtt;
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| 17 |
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| 18 | /* Use provided RTT value, or else last RTT value. */
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| 19 | if (ossl_time_is_zero(latest_rtt))
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| 20 | latest_rtt = statm->latest_rtt;
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| 21 | else
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| 22 | statm->latest_rtt = latest_rtt;
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| 23 |
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| 24 | if (!statm->have_first_sample) {
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| 25 | statm->min_rtt = latest_rtt;
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| 26 | statm->smoothed_rtt = latest_rtt;
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| 27 | statm->rtt_variance = ossl_time_divide(latest_rtt, 2);
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| 28 | statm->have_first_sample = 1;
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| 29 | return;
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| 30 | }
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| 31 |
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| 32 | /* Update minimum RTT. */
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| 33 | if (ossl_time_compare(latest_rtt, statm->min_rtt) < 0)
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| 34 | statm->min_rtt = latest_rtt;
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| 35 |
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| 36 | /*
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| 37 | * Enforcement of max_ack_delay is the responsibility of
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| 38 | * the caller as it is context-dependent.
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| 39 | */
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| 40 |
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| 41 | adjusted_rtt = latest_rtt;
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| 42 | if (ossl_time_compare(latest_rtt, ossl_time_add(statm->min_rtt, ack_delay)) >= 0)
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| 43 | adjusted_rtt = ossl_time_subtract(latest_rtt, ack_delay);
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| 44 |
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| 45 | statm->rtt_variance = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->rtt_variance, 3),
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| 46 | ossl_time_abs_difference(statm->smoothed_rtt,
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| 47 | adjusted_rtt)), 4);
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| 48 | statm->smoothed_rtt = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->smoothed_rtt, 7),
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| 49 | adjusted_rtt), 8);
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| 50 | }
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| 51 |
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| 52 | /* RFC 9002 kInitialRtt value. RFC recommended value. */
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| 53 | #define K_INITIAL_RTT ossl_ms2time(333)
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| 54 |
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| 55 | int ossl_statm_init(OSSL_STATM *statm)
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| 56 | {
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| 57 | statm->smoothed_rtt = K_INITIAL_RTT;
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| 58 | statm->latest_rtt = ossl_time_zero();
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| 59 | statm->min_rtt = ossl_time_infinite();
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| 60 | statm->rtt_variance = ossl_time_divide(K_INITIAL_RTT, 2);
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| 61 | statm->have_first_sample = 0;
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| 62 | return 1;
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| 63 | }
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| 64 |
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| 65 | void ossl_statm_destroy(OSSL_STATM *statm)
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| 66 | {
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| 67 | /* No-op. */
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| 68 | }
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| 69 |
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| 70 | void ossl_statm_get_rtt_info(OSSL_STATM *statm, OSSL_RTT_INFO *rtt_info)
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| 71 | {
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| 72 | rtt_info->min_rtt = statm->min_rtt;
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| 73 | rtt_info->latest_rtt = statm->latest_rtt;
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| 74 | rtt_info->smoothed_rtt = statm->smoothed_rtt;
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| 75 | rtt_info->rtt_variance = statm->rtt_variance;
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| 76 | }
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