nbd_can_meta_context(3)             LIBNBD             nbd_can_meta_context(3)


NAME
       nbd_can_meta_context - does the server support a specific meta context?

SYNOPSIS
        #include <libnbd.h>

        int nbd_can_meta_context (
              struct nbd_handle *h, const char *metacontext
            );

DESCRIPTION
       Returns true if the server supports the given meta context (see
       nbd_add_meta_context(3)).  Returns false if the server does not.  It is
       possible for this command to fail if meta contexts were requested but
       there is a missing or failed attempt at NBD_OPT_SET_META_CONTEXT during
       option negotiation.

       If the server supports block status filtering (see
       nbd_can_block_status_payload(3), this function must return true for any
       filter name passed to nbd_block_status_filter(3).

       The single parameter is the name of the metadata context, for example
       "LIBNBD_CONTEXT_BASE_ALLOCATION".  <libnbd.h> includes defined
       constants for well-known namespace contexts beginning with
       "LIBNBD_CONTEXT_", but you are free to pass in other contexts.

       This call does not block, because it returns data that is saved in the
       handle from the NBD protocol handshake.

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", "metacontext".  For
       more information see "Non-NULL parameters" in libnbd(3).

HANDLE STATE
       nbd_can_meta_context 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 1.0.

       If you need to test if this function is available at compile time check
       if the following macro is defined:

        #define LIBNBD_HAVE_NBD_CAN_META_CONTEXT 1

SEE ALSO
       nbd_add_meta_context(3), nbd_aio_block_status_64(3),
       nbd_block_status_64(3), nbd_block_status_filter(3),
       nbd_can_block_status_payload(3), nbd_create(3), nbd_opt_info(3),
       nbd_opt_set_meta_context(3), nbd_set_request_meta_context(3), "Flag
       calls" in libnbd(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_can_meta_context(3)