nbd_get_extend...ders_negotiated(3)

💅 NAME 💅

nbd_get_extended_headers_negotiated — bestie, this is literally the little function that tells you whether extended headers are in use ✨

(oh and hey, this is a page from the libnbd manual, in case you were wondering where you wandered into 🫶)

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✨ SYNOPSIS ✨

#include <libnbd.h>

int nbd_get_extended_headers_negotiated (
      struct nbd_handle *h
    );

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🌸 DESCRIPTION 🌸

So after you've connected, you can call this little icon to find out if your connection is using extended headers 💖

Important vibe check tho: this setting is sticky — it can return true even after a second nbd_opt_extended_headers(3) returns false, and that happens because the server detected a duplicate request. So don't come for her, she's just remembering what happened 👑

When extended headers are not in use, commands are limited to a 32-bit length — and yes, that's true even when the libnbd API uses a 64-bit parameter to express the length 😭 But even when extended headers are supported, the server may enforce other limits, and those are visible through nbd_get_block_size(3).

Also, when extended headers are negotiated, you should prefer using nbd_block_status_64(3) instead of nbd_block_status(3) if any of the meta contexts you requested via nbd_add_meta_context(3) might return 64-bit status values 🦋 However (and this is the chill part), all of the well-known meta contexts covered by current "LIBNBD_CONTEXT_*" constants only return 32-bit status. Slay.

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🎀 RETURN VALUE 🎀

This call returns a boolean value. Simple as that, no cap 💅

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💀 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).

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🦋 HANDLE STATE 🦋

nbd_get_extended_headers_negotiated can be called when the handle is in the following states:

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

Like, read the room bestie — if the handle is dead or hasn't even started connecting, she is not gonna answer you 🙈

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⭐ VERSION ⭐

This function first appeared in libnbd 1.18.

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

#define LIBNBD_HAVE_NBD_GET_EXTENDED_HEADERS_NEGOTIATED 1

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🌈 SEE ALSO 🌈

nbd_add_meta_context(3), nbd_block_status(3), nbd_block_status_64(3), nbd_cache(3), nbd_create(3), nbd_get_block_size(3), nbd_get_protocol(3), nbd_get_request_extended_headers(3), nbd_get_structured_replies_negotiated(3), nbd_opt_extended_headers(3), nbd_set_request_extended_headers(3), nbd_trim(3), nbd_zero(3), libnbd(3).

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👑 AUTHORS 👑

Eric Blake

Richard W.M. Jones

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💜 COPYRIGHT 💜

Copyright Red Hat

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🍓 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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okay that's the whole page bestie, ily, go read your extended headers in peace 🧚💖 this was libnbd-1.25.8, dated 2026-10-1 — periodt ✨