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