mirror of https://github.com/openssl/openssl
58 lines
2.0 KiB
Plaintext
58 lines
2.0 KiB
Plaintext
=pod
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=head1 NAME
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SSL_get_handshake_rtt
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- get round trip time for SSL Handshake
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_get_handshake_rtt(const SSL *s, uint64_t *rtt);
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=head1 DESCRIPTION
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SSL_get_handshake_rtt() retrieves the round-trip time (RTT) for I<ssl>.
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This metric is represented in microseconds (us) as a uint64_t data type.
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=head1 NOTES
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This metric is created by taking two timestamps during the handshake and
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providing the difference between these two times.
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When acting as the server, one timestamp is taken when the server is finished
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writing to the client. This is during the ServerFinished in TLS 1.3 and
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ServerHelloDone in TLS 1.2. The other timestamp is taken when the server is
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done reading the client's response. This is after the client has responded
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with ClientFinished.
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When acting as the client, one timestamp is taken when the client is finished
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writing the ClientHello and early data (if any). The other is taken when
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client is done reading the server's response. This is after ServerFinished in
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TLS 1.3 and after ServerHelloDone in TLS 1.2.
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In addition to network propagation delay and network stack overhead, this
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metric includes processing time on both endpoints, as this is based on TLS
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protocol-level messages and the TLS protocol is not designed to measure
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network timings. In some cases the processing time can be significant,
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especially when the processing includes asymmetric cryptographic operations.
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=head1 RETURN VALUES
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Returns 1 if the TLS handshake RTT is successfully retrieved.
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Returns 0 if the TLS handshake RTT cannot be determined yet.
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Returns -1 if, while retrieving the TLS handshake RTT, an error occurs.
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=head1 COPYRIGHT
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Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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