---
name: "gnutls_ext_register"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_ext_register"
---

# gnutls\_ext\_register(3)

API function

## NAME

gnutls\_ext\_register - API function

## SYNOPSIS

**#include \<gnutls/gnutls.h\>**

**int gnutls\_ext\_register(const char \*** *name***, int** *id***, gnutls\_ext\_parse\_type\_t** *parse\_point***, gnutls\_ext\_recv\_func** *recv\_func***, gnutls\_ext\_send\_func** *send\_func***, gnutls\_ext\_deinit\_data\_func** *deinit\_func***, gnutls\_ext\_pack\_func** *pack\_func***, gnutls\_ext\_unpack\_func** *unpack\_func***);**

## ARGUMENTS

- const char \* name

  the name of the extension to register

- int id

  the numeric TLS id of the extension

- gnutls\_ext\_parse\_type\_t parse\_point

  the parse type of the extension (see gnutls\_ext\_parse\_type\_t)

- gnutls\_ext\_recv\_func recv\_func

  a function to receive the data

- gnutls\_ext\_send\_func send\_func

  a function to send the data

- gnutls\_ext\_deinit\_data\_func deinit\_func

  a function deinitialize any private data

- gnutls\_ext\_pack\_func pack\_func

  a function which serializes the extension's private data (used on session packing for resumption)

- gnutls\_ext\_unpack\_func unpack\_func

  a function which will deserialize the extension's private data

## DESCRIPTION

This function will register a new extension type. The extension will remain registered until **gnutls\_global\_deinit()** is called. If the extension type is already registered then **GNUTLS\_E\_ALREADY\_REGISTERED** will be returned.

Each registered extension can store temporary data into the gnutls\_session\_t structure using **gnutls\_ext\_set\_data()**, and they can be retrieved using **gnutls\_ext\_get\_data()**.

Any extensions registered with this function are valid for the client and TLS1.2 server hello (or encrypted extensions for TLS1.3).

This function is not thread safe.

## RETURNS

**GNUTLS\_E\_SUCCESS** on success, otherwise a negative error code.

## SINCE

3\.4.0

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/