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=head1 NAME
nbd_can_meta_context - does the server support a specific meta context?
=head1 SYNOPSIS
#include <libnbd.h>
int nbd_can_meta_context (
struct nbd_handle *h, const char *metacontext
);
=head1 DESCRIPTION
Returns true if the server supports the given meta context
(see L<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
L<nbd_can_block_status_payload(3)>, this function must return
true for any filter name passed to L<nbd_block_status_filter(3)>.
The single parameter is the name of the metadata context,
for example C<LIBNBD_CONTEXT_BASE_ALLOCATION>.
B<E<lt>libnbd.hE<gt>> includes defined constants for well-known
namespace contexts beginning with C<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.
=head1 RETURN VALUE
This call returns a boolean value.
=head1 ERRORS
On error C<-1> is returned.
Refer to L<libnbd(3)/ERROR HANDLING>
for how to get further details of the error.
The following parameters must not be NULL: C<h>, C<metacontext>.
For more information see L<libnbd(3)/Non-NULL parameters>.
=head1 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 │
└─────────────────────────────────────┴─────────────────────────┘
=head1 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
=head1 SEE ALSO
L<nbd_add_meta_context(3)>,
L<nbd_aio_block_status_64(3)>,
L<nbd_block_status_64(3)>,
L<nbd_block_status_filter(3)>,
L<nbd_can_block_status_payload(3)>,
L<nbd_create(3)>,
L<nbd_opt_info(3)>,
L<nbd_opt_set_meta_context(3)>,
L<nbd_set_request_meta_context(3)>,
L<libnbd(3)/Flag calls>,
L<libnbd(3)>.
=head1 AUTHORS
Eric Blake
Richard W.M. Jones
=head1 COPYRIGHT
Copyright Red Hat
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