Commit e3673581f9 for openssl.org

commit e3673581f935756f1c5267c338af3bb814c3a8a3
Author: Kit Dallege <xaum.io@gmail.com>
Date:   Fri May 15 05:17:10 2026 +0200

    doc: Add documentation for DTLS MTU functions

    Reviewed-by: Eugene Syromiatnikov <esyr@openssl.org>
    Reviewed-by: Frederik Wedel-Heinen <fwh.openssl@gmail.com>
    MergeDate: Mon May 18 07:33:03 2026
    (Merged from https://github.com/openssl/openssl/pull/29901)

diff --git a/doc/man3/DTLS_get_data_mtu.pod b/doc/man3/DTLS_get_data_mtu.pod
index ee74fa1704..f68fe85d5c 100644
--- a/doc/man3/DTLS_get_data_mtu.pod
+++ b/doc/man3/DTLS_get_data_mtu.pod
@@ -2,31 +2,60 @@

 =head1 NAME

-DTLS_get_data_mtu - Get maximum data payload size
+DTLS_get_data_mtu, DTLS_set_link_mtu, DTLS_get_link_min_mtu, SSL_set_mtu
+- DTLS MTU handling

 =head1 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);

 =head1 DESCRIPTION

-This function obtains the maximum data payload size for the established
-DTLS connection B<ssl>, based on the DTLS record MTU and the overhead
+DTLS_get_data_mtu() obtains the maximum data payload size for the established
+DTLS connection I<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 I<ssl>
+to I<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 I<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 I<ssl> to
+I<mtu>. Unlike DTLS_set_link_mtu(), this value should not include IP or UDP
+header overhead; it represents the maximum DTLS packet size directly.
+
 =head1 RETURN VALUES

-Returns the maximum data payload size on success, or 0 on failure.
+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.

 =head1 HISTORY

-The DTLS_get_data_mtu() function was added in OpenSSL 1.1.1.
+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.

 =head1 COPYRIGHT

-Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2016-2026 The OpenSSL Project Authors. All Rights Reserved.

 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