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