nbd_get_extended_headers_negotiated - see if extended headers are in use

       Eric Blake

       Richard W.M. Jones

       Copyright Red Hat

       After connecting you may call this to find out if the connection is using extended headers.  Note that
       this setting is sticky; this can return true even after a second nbd_opt_extended_headers(3) returns
       false because the server detected a duplicate request.

       When extended headers are not in use, commands are limited to a 32-bit length, 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, visible through nbd_get_block_size(3).

       Note that when extended headers are negotiated, you should prefer the use of 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, all of the well-known meta contexts covered by current
       "LIBNBD_CONTEXT_*" constants only return 32-bit status.

       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).

       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                │
        └─────────────────────────────────────┴─────────────────────────┘

       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

libnbd-1.22.2                                      2025-06-16             nbd_get_extended_headers_negotiated(3)

       nbd_get_extended_headers_negotiated - see if extended headers are in use

       This call returns a boolean value.

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).

        #include <libnbd.h>

        int nbd_get_extended_headers_negotiated (
              struct nbd_handle *h
            );

       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