SSL_ALLOC_BUFFERS(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

💅 SSL_ALLOC_BUFFERS(3ossl) — bestie's guide to SSL buffer management ✨

okay so this is a page from the OpenSSL manual, section 3ossl, and it's literally about two little functions that let you be the main character of your own memory management. no cap.

🌸 NAME 🌸

SSL_free_buffers, SSL_alloc_buffers — manage SSL structure buffers 🎀

✨ SYNOPSIS ✨

like, the vibes in code form:

#include <openssl/ssl.h>

int SSL_free_buffers(SSL *ssl);
int SSL_alloc_buffers(SSL *ssl);

that's it. that's the whole API. two ints, two SSL *s, zero drama. 🫶

💖 DESCRIPTION 💖

So SSL_free_buffers() frees the read and write buffers of the given ssl. And SSL_alloc_buffers() allocates the read and write buffers of the given ssl. That's the whole thing. They're fr fr complementary besties. 💅

Now — the SSL_MODE_RELEASE_BUFFERS mode will release read or write buffers whenever the buffers have been drained. Iconic behaviour, honestly, very "clean up after yourself" of it. But sometimes you wanna be the one calling the shots, yk? So these two functions exist so applications can manually control when buffers are freed and allocated. you get to be the manager. 🔥

Here's the part where you go "oh word": after freeing the buffers, the buffers are automatically reallocated upon a new read or write. So calling SSL_alloc_buffers() is not required — nobody's making you. But you can use it to make sure the buffers are preallocated ahead of time. That's useful for:

  • avoiding allocation during data processing (no mid-conversation malloc jumpscares 💀), or
  • pairing with CRYPTO_set_mem_functions() to control where and how buffers are allocated. very custom, very you. ✨
⚠️ and now the plot twist: these functions are no-ops when used with QUIC SSL objects. For QUIC, SSL_free_buffers() always fails, and SSL_alloc_buffers() always succeeds. that's just how it is, bestie. 🙈

🦋 RETURN VALUES 🦋

two possible outcomes, both honestly kind of valid:

  • 0 (Failure) — SSL_free_buffers() returns 0 when there is pending data to be read or written. (like, there's unfinished business, can't free anything yet 😭) SSL_alloc_buffers() returns 0 when there is an allocation failure.
  • 1 (Success) — SSL_free_buffers() returns 1 if the buffers have been freed. This value is also returned if the buffers had been freed before calling SSL_free_buffers(). SSL_alloc_buffers() returns 1 if the buffers have been allocated. This value is also returned if the buffers had been allocated before calling SSL_alloc_buffers(). so like, double-success, no problem, we love an idempotent queen 👑💖

🌈 SEE ALSO 🌈

go read these next, bestie, they're all in the friend group:

Copyright 2017-2023 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>.

🧚 sign-off szn: this lil page is from OpenSSL 3.5.0, dated 2026-09-25, and it lives in section 3ossl of the manual. slay. 💅✨🌸
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