nbd_get_extended_headers_negotiated(3)                                  LIBNBD


NAME
       nbd_get_extended_headers_negotiated - see if extended headers are in
       use

SYNOPSIS
        #include <libnbd.h>

        int nbd_get_extended_headers_negotiated (
              struct nbd_handle *h
            );

DESCRIPTION
       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.

RETURN VALUE
       This call returns a boolean value.

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_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                |
        <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?><?>

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

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).

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

libnbd-1.20.0                     2024-05-31
                                        nbd_get_extended_headers_negotiated(3)