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.\" ========================================================================
.\"
.IX Title "nbd_aio_opt_info 3"
.TH nbd_aio_opt_info 3 2024-05-08 libnbd-1.20.1 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
nbd_aio_opt_info \- request the server for information about an export
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #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
\&     );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Request that the server supply information about the export name
previously specified by the most recent \fBnbd_set_export_name\fR\|(3)
or \fBnbd_connect_uri\fR\|(3).  This can only be used if
\&\fBnbd_set_opt_mode\fR\|(3) enabled option mode.
.PP
To determine when the request completes, wait for
\&\fBnbd_aio_is_connecting\fR\|(3) to return false.  Or supply the optional
\&\f(CW\*(C`completion_callback\*(C'\fR which will be invoked as described in
"Completion callbacks" in \fBlibnbd\fR\|(3), 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.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
If the call is successful the function returns \f(CW0\fR.
.SH ERRORS
.IX Header "ERRORS"
On error \f(CW\-1\fR is returned.
.PP
Refer to "ERROR HANDLING" in \fBlibnbd\fR\|(3)
for how to get further details of the error.
.PP
The following parameters must not be NULL: \f(CW\*(C`h\*(C'\fR.
For more information see "Non-NULL parameters" in \fBlibnbd\fR\|(3).
.SH "HANDLE STATE"
.IX Header "HANDLE STATE"
nbd_aio_opt_info
can be called when the handle is in the following state:
.PP
.Vb 8
\& ┌─────────────────────────────────────┬─────────────────────────┐
\& │ Handle created, before connecting   │ ❌ error                │
\& │ Connecting                          │ ❌ error                │
\& │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
\& │ Connected to the server             │ ❌ error                │
\& │ Connection shut down                │ ❌ error                │
\& │ Handle dead                         │ ❌ error                │
\& └─────────────────────────────────────┴─────────────────────────┘
.Ve
.SH VERSION
.IX Header "VERSION"
This function first appeared in libnbd 1.4.
.PP
If you need to test if this function is available at compile time
check if the following macro is defined:
.PP
.Vb 1
\& #define LIBNBD_HAVE_NBD_AIO_OPT_INFO 1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_aio_is_connecting\fR\|(3),
\&\fBnbd_connect_uri\fR\|(3),
\&\fBnbd_create\fR\|(3),
\&\fBnbd_is_read_only\fR\|(3),
\&\fBnbd_opt_info\fR\|(3),
\&\fBnbd_set_export_name\fR\|(3),
\&\fBnbd_set_opt_mode\fR\|(3),
\&\fBlibnbd\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "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.
.PP
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.
.PP
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