DTLS_get_data_mtu¶

NAME¶

DTLS_get_data_mtu, DTLS_set_link_mtu, DTLS_get_link_min_mtu, SSL_set_mtu - DTLS MTU handling

SYNOPSIS¶

#include <openssl/ssl.h>

size_t DTLS_get_data_mtu(const SSL *ssl);
long DTLS_set_link_mtu(SSL *ssl, long mtu);
long DTLS_get_link_min_mtu(SSL *ssl);
long SSL_set_mtu(SSL *ssl, long mtu);

DESCRIPTION¶

DTLS_get_data_mtu() obtains the maximum data payload size for the established DTLS connection ssl, based on the DTLS record MTU and the overhead of the DTLS record header, encryption and authentication currently in use.

DTLS_set_link_mtu() sets the link layer MTU for the DTLS connection ssl to mtu. This is the maximum on-the-wire packet size including IP and UDP headers. OpenSSL subtracts the IP/UDP overhead internally to determine the maximum DTLS record size, and uses this to fragment handshake messages and limit the size of application data records.

DTLS_get_link_min_mtu() returns the minimum link MTU that OpenSSL will use for the DTLS connection ssl. This is the smallest MTU that still allows DTLS to function properly.

SSL_set_mtu() sets the DTLS record-level MTU for the connection ssl to mtu. Unlike DTLS_set_link_mtu(), this value should not include IP or UDP header overhead; it represents the maximum DTLS packet size directly.

RETURN VALUES¶

DTLS_get_data_mtu() returns the maximum data payload size on success, or 0 on failure.

DTLS_set_link_mtu() returns 1 on success or 0 on failure.

SSL_set_mtu() returns the MTU value on success or 0 on failure.

DTLS_get_link_min_mtu() returns the minimum link MTU value.

HISTORY¶

DTLS_get_data_mtu() was added in OpenSSL 1.1.1.

SSL_set_mtu() was added in OpenSSL 0.9.8.

DTLS_set_link_mtu() and DTLS_get_link_min_mtu() were added in OpenSSL 1.0.2.

COPYRIGHT¶

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.