1*e7be843bSPierre Pronchery /*
2*e7be843bSPierre Pronchery * Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
3*e7be843bSPierre Pronchery *
4*e7be843bSPierre Pronchery * Licensed under the Apache License 2.0 (the "License"). You may not use
5*e7be843bSPierre Pronchery * this file except in compliance with the License. You can obtain a copy
6*e7be843bSPierre Pronchery * in the file LICENSE in the source distribution or at
7*e7be843bSPierre Pronchery * https://www.openssl.org/source/license.html
8*e7be843bSPierre Pronchery */
9*e7be843bSPierre Pronchery
10*e7be843bSPierre Pronchery #include "internal/quic_statm.h"
11*e7be843bSPierre Pronchery
ossl_statm_update_rtt(OSSL_STATM * statm,OSSL_TIME ack_delay,OSSL_TIME override_latest_rtt)12*e7be843bSPierre Pronchery void ossl_statm_update_rtt(OSSL_STATM *statm,
13*e7be843bSPierre Pronchery OSSL_TIME ack_delay,
14*e7be843bSPierre Pronchery OSSL_TIME override_latest_rtt)
15*e7be843bSPierre Pronchery {
16*e7be843bSPierre Pronchery OSSL_TIME adjusted_rtt, latest_rtt = override_latest_rtt;
17*e7be843bSPierre Pronchery
18*e7be843bSPierre Pronchery /* Use provided RTT value, or else last RTT value. */
19*e7be843bSPierre Pronchery if (ossl_time_is_zero(latest_rtt))
20*e7be843bSPierre Pronchery latest_rtt = statm->latest_rtt;
21*e7be843bSPierre Pronchery else
22*e7be843bSPierre Pronchery statm->latest_rtt = latest_rtt;
23*e7be843bSPierre Pronchery
24*e7be843bSPierre Pronchery if (!statm->have_first_sample) {
25*e7be843bSPierre Pronchery statm->min_rtt = latest_rtt;
26*e7be843bSPierre Pronchery statm->smoothed_rtt = latest_rtt;
27*e7be843bSPierre Pronchery statm->rtt_variance = ossl_time_divide(latest_rtt, 2);
28*e7be843bSPierre Pronchery statm->have_first_sample = 1;
29*e7be843bSPierre Pronchery return;
30*e7be843bSPierre Pronchery }
31*e7be843bSPierre Pronchery
32*e7be843bSPierre Pronchery /* Update minimum RTT. */
33*e7be843bSPierre Pronchery if (ossl_time_compare(latest_rtt, statm->min_rtt) < 0)
34*e7be843bSPierre Pronchery statm->min_rtt = latest_rtt;
35*e7be843bSPierre Pronchery
36*e7be843bSPierre Pronchery /*
37*e7be843bSPierre Pronchery * Enforcement of max_ack_delay is the responsibility of
38*e7be843bSPierre Pronchery * the caller as it is context-dependent.
39*e7be843bSPierre Pronchery */
40*e7be843bSPierre Pronchery
41*e7be843bSPierre Pronchery adjusted_rtt = latest_rtt;
42*e7be843bSPierre Pronchery if (ossl_time_compare(latest_rtt, ossl_time_add(statm->min_rtt, ack_delay)) >= 0)
43*e7be843bSPierre Pronchery adjusted_rtt = ossl_time_subtract(latest_rtt, ack_delay);
44*e7be843bSPierre Pronchery
45*e7be843bSPierre Pronchery statm->rtt_variance = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->rtt_variance, 3),
46*e7be843bSPierre Pronchery ossl_time_abs_difference(statm->smoothed_rtt,
47*e7be843bSPierre Pronchery adjusted_rtt)), 4);
48*e7be843bSPierre Pronchery statm->smoothed_rtt = ossl_time_divide(ossl_time_add(ossl_time_multiply(statm->smoothed_rtt, 7),
49*e7be843bSPierre Pronchery adjusted_rtt), 8);
50*e7be843bSPierre Pronchery }
51*e7be843bSPierre Pronchery
52*e7be843bSPierre Pronchery /* RFC 9002 kInitialRtt value. RFC recommended value. */
53*e7be843bSPierre Pronchery #define K_INITIAL_RTT ossl_ms2time(333)
54*e7be843bSPierre Pronchery
ossl_statm_init(OSSL_STATM * statm)55*e7be843bSPierre Pronchery int ossl_statm_init(OSSL_STATM *statm)
56*e7be843bSPierre Pronchery {
57*e7be843bSPierre Pronchery statm->smoothed_rtt = K_INITIAL_RTT;
58*e7be843bSPierre Pronchery statm->latest_rtt = ossl_time_zero();
59*e7be843bSPierre Pronchery statm->min_rtt = ossl_time_infinite();
60*e7be843bSPierre Pronchery statm->rtt_variance = ossl_time_divide(K_INITIAL_RTT, 2);
61*e7be843bSPierre Pronchery statm->have_first_sample = 0;
62*e7be843bSPierre Pronchery return 1;
63*e7be843bSPierre Pronchery }
64*e7be843bSPierre Pronchery
ossl_statm_destroy(OSSL_STATM * statm)65*e7be843bSPierre Pronchery void ossl_statm_destroy(OSSL_STATM *statm)
66*e7be843bSPierre Pronchery {
67*e7be843bSPierre Pronchery /* No-op. */
68*e7be843bSPierre Pronchery }
69*e7be843bSPierre Pronchery
ossl_statm_get_rtt_info(OSSL_STATM * statm,OSSL_RTT_INFO * rtt_info)70*e7be843bSPierre Pronchery void ossl_statm_get_rtt_info(OSSL_STATM *statm, OSSL_RTT_INFO *rtt_info)
71*e7be843bSPierre Pronchery {
72*e7be843bSPierre Pronchery rtt_info->min_rtt = statm->min_rtt;
73*e7be843bSPierre Pronchery rtt_info->latest_rtt = statm->latest_rtt;
74*e7be843bSPierre Pronchery rtt_info->smoothed_rtt = statm->smoothed_rtt;
75*e7be843bSPierre Pronchery rtt_info->rtt_variance = statm->rtt_variance;
76*e7be843bSPierre Pronchery }
77