=head1 NAME

nbd_aio_opt_info - request the server for information about an export

=head1 SYNOPSIS

 #include <libnbd.h>

 typedef struct {
   int (*callback) (void *user_data, int *error);
   void *user_data;
   void (*free) (void *user_data);
 } nbd_completion_callback;

 int nbd_aio_opt_info (
       struct nbd_handle *h,
       nbd_completion_callback completion_callback
     );

=head1 DESCRIPTION

Request that the server supply information about
the export name
previously specified by the most recent L<nbd_set_export_name(3)>
or L<nbd_connect_uri(3)>.  This can only be used if
L<nbd_set_opt_mode(3)> enabled option mode.

To determine when the request completes, wait for
L<nbd_aio_is_connecting(3)> to return false.  Or supply the optional
C<completion_callback> which will be invoked as described in
L<libnbd(3)/Completion callbacks>, except that it is automatically
retired regardless of return value.  Note that detecting whether the
server returns an error (as is done by the return value of the
synchronous counterpart) is only possible with a completion
callback.

=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_aio_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                │
 └─────────────────────────────────────┴─────────────────────────┘

=head1 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_AIO_OPT_INFO 1

=head1 SEE ALSO

L<nbd_aio_is_connecting(3)>,
L<nbd_connect_uri(3)>,
L<nbd_create(3)>,
L<nbd_is_read_only(3)>,
L<nbd_opt_info(3)>,
L<nbd_set_export_name(3)>,
L<nbd_set_opt_mode(3)>,
L<libnbd(3)>.

=head1 AUTHORS

Eric Blake

Richard W.M. Jones

=head1 COPYRIGHT

Copyright Red Hat
