6 - get round trip time for SSL Handshake
10 #include <openssl/ssl.h>
12 int SSL_get_handshake_rtt(const SSL *s, uint64_t *rtt);
16 SSL_get_handshake_rtt() retrieves the round-trip time (RTT) for I<ssl>.
18 This metric is represented in microseconds (us) as a uint64_t data type.
22 This metric is created by taking two timestamps during the handshake and
23 providing the difference between these two times.
25 When acting as the server, one timestamp is taken when the server is finished
26 writing to the client. This is during the ServerFinished in TLS 1.3 and
27 ServerHelloDone in TLS 1.2. The other timestamp is taken when the server is
28 done reading the client's response. This is after the client has responded
31 When acting as the client, one timestamp is taken when the client is finished
32 writing the ClientHello and early data (if any). The other is taken when
33 client is done reading the server's response. This is after ServerFinished in
34 TLS 1.3 and after ServerHelloDone in TLS 1.2.
36 In addition to network propagation delay and network stack overhead, this
37 metric includes processing time on both endpoints, as this is based on TLS
38 protocol-level messages and the TLS protocol is not designed to measure
39 network timings. In some cases the processing time can be significant,
40 especially when the processing includes asymmetric cryptographic operations.
44 Returns 1 if the TLS handshake RTT is successfully retrieved.
45 Returns 0 if the TLS handshake RTT cannot be determined yet.
46 Returns -1 if, while retrieving the TLS handshake RTT, an error occurs.
50 Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
52 Licensed under the Apache License 2.0 (the "License"). You may not use
53 this file except in compliance with the License. You can obtain a copy
54 in the file LICENSE in the source distribution or at
55 L<https://www.openssl.org/source/license.html>.