nbd_opt_structured_reply(3)

🎀 NAME 🎀

nbd_opt_structured_reply — request the server to enable structured replies, and yes bestie this is the nbd_opt_structured_reply(3) page from the LIBNBD manual 💅✨

🌸 SYNOPSIS 🌸

Include the header and call it like this, fr fr:

#include <libnbd.h>

int nbd_opt_structured_reply (
      struct nbd_handle *h
    );

🦋 DESCRIPTION 🦋

Okay so the whole vibe is: you're requesting that the server use structured replies by sending "NBD_OPT_STRUCTURED_REPLY" 🫶. This can only be used if nbd_set_opt_mode(3) enabled option mode; furthermore, libnbd defaults to automatically requesting this unless you use nbd_set_request_structured_replies(3) prior to connecting. This function is mainly useful for integration testing of corner cases in server handling — no cap, it's giving "tiny gremlin test button" energy 🔥.

This function returns true if the server replies with success, false if the server replies with an error, and fails only if the server does not reply (such as for a loss of connection). Note that some servers fail a second request as redundant; libnbd assumes that once one request has succeeded, then structured replies are supported (as visible by nbd_get_structured_replies_negotiated(3)) regardless if later calls to this function return false. Similarly, a server may fail this request if extended headers are already negotiated, since extended headers take priority. That's the tea ☕.

💖 RETURN VALUE 💖

This call returns a boolean value. Literally true/false, bestie ✨.

😭 ERRORS 😭

On error -1 is returned.

Refer to "ERROR HANDLING" in libnbd(3) for how to get further details of the error.

The following parameters must not be NULL: "h". For more information see "Non-NULL parameters" in libnbd(3).

👑 HANDLE STATE 👑

nbd_opt_structured_reply can be called when the handle is in the following state:

• Handle created, before connecting — ❌ error
• Connecting — ❌ error
• Connecting & handshaking (opt_mode) — ✅ allowed
• Connected to the server — ❌ error
• Connection shut down — ❌ error
• Handle dead — ❌ error

⭐ VERSION ⭐

This function first appeared in libnbd 1.16.

If you need to test if this function is available at compile time check if the following macro is defined:

#define LIBNBD_HAVE_NBD_OPT_STRUCTURED_REPLY 1

🌈 SEE ALSO 🌈

nbd_aio_opt_structured_reply(3), nbd_create(3), nbd_get_structured_replies_negotiated(3), nbd_opt_go(3), nbd_set_opt_mode(3), nbd_set_request_structured_replies(3), libnbd(3).

🧚 AUTHORS 🧚

• Eric Blake
• Richard W.M. Jones

🍓 COPYRIGHT 🍓

Copyright Red Hat

💜 LICENSE 💜

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

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k bye bestie — this page is from libnbd-1.25.8, dated 2026-10-13, and it's nbd_opt_structured_reply(3) signing off 💅✨