nbd_opt_info(3)                     LIBNBD                     nbd_opt_info(3)


NAME
       nbd_opt_info - request the server for information about an export

SYNOPSIS
        #include <libnbd.h>

        int nbd_opt_info (
              struct nbd_handle *h
            );

DESCRIPTION
       Request that the server supply information about the export name
       previously specified by the most recent nbd_set_export_name(3) or
       nbd_connect_uri(3).  This can only be used if nbd_set_opt_mode(3)
       enabled option mode.

       If successful, functions like nbd_is_read_only(3) and nbd_get_size(3)
       will report details about that export.  If
       nbd_set_request_meta_context(3) is set (the default) and structured
       replies or extended headers were negotiated, it is also valid to use
       nbd_can_meta_context(3) after this call.  However, it may be more
       efficient to clear that setting and manually utilize
       nbd_opt_list_meta_context(3) with its callback approach, for learning
       which contexts an export supports.  In general, if nbd_opt_go(3) is
       called next, that call will likely succeed with the details remaining
       the same, although this is not guaranteed by all servers.

       Not all servers understand this request, and even when it is
       understood, the server might fail the request even when a corresponding
       nbd_opt_go(3) would succeed.

RETURN VALUE
       If the call is successful the function returns 0.

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_info 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 1.4.

       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_INFO 1

SEE ALSO
       nbd_aio_opt_info(3), nbd_can_meta_context(3), nbd_connect_uri(3),
       nbd_create(3), nbd_get_size(3), nbd_is_read_only(3), nbd_opt_go(3),
       nbd_opt_list_meta_context(3), nbd_set_export_name(3),
       nbd_set_opt_mode(3), nbd_set_request_meta_context(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_opt_info(3)