=head1 NAME

nbd_clear_meta_contexts - reset the list of requested meta contexts

=head1 SYNOPSIS

 #include <libnbd.h>

 int nbd_clear_meta_contexts (
       struct nbd_handle *h
     );

=head1 DESCRIPTION

During connection libnbd can negotiate zero or more metadata
contexts with the server.  Metadata contexts are features (such
as C<"base:allocation">) which describe information returned
by the L<nbd_block_status_64(3)> command (for C<"base:allocation">
this is whether blocks of data are allocated, zero or sparse).

This command resets the list of meta contexts to request back to
an empty list, for re-population by further use of
L<nbd_add_meta_context(3)>.  It is primarily useful when option
negotiation mode is selected (see L<nbd_set_opt_mode(3)>), for
altering the list of attempted contexts between subsequent export
queries.

=head1 RETURN VALUE

If the call is successful the function returns C<0>.

=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>.
For more information see L<libnbd(3)/Non-NULL parameters>.

=head1 HANDLE STATE

nbd_clear_meta_contexts
can be called when the handle is in the following states:

 ┌─────────────────────────────────────┬─────────────────────────┐
 │ Handle created, before connecting   │ ✅ allowed              │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
 │ Connected to the server             │ ❌ error                │
 │ Connection shut down                │ ❌ error                │
 │ Handle dead                         │ ❌ error                │
 └─────────────────────────────────────┴─────────────────────────┘

=head1 VERSION

This function first appeared in libnbd 1.6.

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

 #define LIBNBD_HAVE_NBD_CLEAR_META_CONTEXTS 1

=head1 SEE ALSO

L<nbd_add_meta_context(3)>,
L<nbd_block_status_64(3)>,
L<nbd_can_meta_context(3)>,
L<nbd_create(3)>,
L<nbd_get_meta_context(3)>,
L<nbd_get_nr_meta_contexts(3)>,
L<nbd_set_opt_mode(3)>,
L<libnbd(3)>.

=head1 AUTHORS

Eric Blake

Richard W.M. Jones

=head1 COPYRIGHT

Copyright Red Hat
