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