nbd_opt_extended_headers - request the server to enable extended headers

       Eric Blake

       Richard W.M. Jones

       Copyright Red Hat

       Request that the server use extended headers, by sending "NBD_OPT_EXTENDED_HEADERS".  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_extended_headers(3) or nbd_set_request_structured_replies(3) prior to
       connecting.  This function is mainly useful for integration testing of corner cases in server handling.

       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 extended
       headers are supported (as visible by nbd_get_extended_headers_negotiated(3)) regardless if later calls to
       this function return false.  If this function returns true, the use of structured replies is implied.

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

       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_opt_extended_headers(3)

       nbd_opt_extended_headers - request the server to enable extended headers

       This call returns a boolean value.

nbd_aio_opt_extended_headers(3), nbd_create(3), nbd_get_extended_headers_negotiated(3), nbd_opt_go(3),
       nbd_set_opt_mode(3), nbd_set_request_extended_headers(3), nbd_set_request_structured_replies(3),
       libnbd(3).

        #include <libnbd.h>

        int nbd_opt_extended_headers (
              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_OPT_EXTENDED_HEADERS 1