DTLS_SET_TIMER_CB(3ossl)

💖 DTLS_SET_TIMER_CB 💖

okay bestie, so this is the OpenSSL manual page for DTLS_timer_cb and DTLS_set_timer_cb — aka the little duo that lets you take the wheel on how long DTLS waits between retries. timer drama? we're controlling it now. 🎀

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✨ NAME ✨

DTLS_timer_cb, DTLS_set_timer_cb — set the callback that controls DTLS timer duration, periodt.

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🌸 SYNOPSIS 🌸

#include <openssl/ssl.h>

typedef unsigned int (*DTLS_timer_cb)(SSL *s, unsigned int timer_us);

void DTLS_set_timer_cb(SSL *s, DTLS_timer_cb cb);

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🦋 DESCRIPTION 🦋

So here's the vibe: this function sets an optional callback function that controls the timeout interval on the DTLS protocol. DTLS will call your callback for every single new DTLS packet that gets sent. every one. no skipping. 💅

Your callback should return the timeout interval — and heads up, it's measured in micro seconds. yes, microseconds. tiny little units. ⏱️

The timer_us parameter of the callback is the last set timeout interval that was returned. And on the very first invocation of the callback? that value is gonna be 0. fresh start energy. 🌱

At the beginning of the connection, if you haven't set a timeout callback via DTLS_set_timer_cb(), the default timeout value is 1 second. Then for all subsequent timeouts, the default behavior is to double the duration, up to a maximum of 1 minute. it just keeps doubling like it's in its growth era. 📈

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👑 RETURN VALUES 👑

Returns void. nothing. nada. it gives you no return value, bestie — it's not that kind of function. 🫶

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🌈 HISTORY 🌈

The DTLS_set_timer_cb() function was added in OpenSSL 1.1.1. so it's been iconic for a while now. ⭐

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💜 COPYRIGHT 💜

Copyright 2017-2025 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 in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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k bye bestie!! this page was brought to you by OpenSSL version 3.5.9, dated 2026-09-29, and filed under DTLS_SET_TIMER_CB(3ossl). go forth and time those packets, you absolute main character. 💅✨🦋🌸