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.\"
.IX Title "nbd_get_extended_headers_negotiated 3"
.TH nbd_get_extended_headers_negotiated 3 2024-05-31 libnbd-1.20.0 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
nbd_get_extended_headers_negotiated \- see if extended headers are in
use
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int nbd_get_extended_headers_negotiated (
\&       struct nbd_handle *h
\&     );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
After connecting you may call this to find out if the connection is
using extended headers.  Note that this setting is sticky; this
can return true even after a second \fBnbd_opt_extended_headers\fR\|(3)
returns false because the server detected a duplicate request.
.PP
When extended headers are not in use, commands are limited to a
32\-bit length, even when the libnbd API uses a 64\-bit parameter
to express the length.  But even when extended headers are
supported, the server may enforce other limits, visible through
\&\fBnbd_get_block_size\fR\|(3).
.PP
Note that when extended headers are negotiated, you should
prefer the use of \fBnbd_block_status_64\fR\|(3) instead of
\&\fBnbd_block_status\fR\|(3) if any of the meta contexts you requested
via \fBnbd_add_meta_context\fR\|(3) might return 64\-bit status
values; however, all of the well-known meta contexts covered
by current \f(CW\*(C`LIBNBD_CONTEXT_*\*(C'\fR constants only return 32\-bit
status.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
This call returns a boolean value.
.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_get_extended_headers_negotiated
can be called when the handle is in the following states:
.PP
.Vb 8
\& ┌─────────────────────────────────────┬─────────────────────────┐
\& │ Handle created, before connecting   │ ❌ error                │
\& │ Connecting                          │ ❌ error                │
\& │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
\& │ Connected to the server             │ ✅ allowed              │
\& │ Connection shut down                │ ✅ allowed              │
\& │ Handle dead                         │ ❌ error                │
\& └─────────────────────────────────────┴─────────────────────────┘
.Ve
.SH VERSION
.IX Header "VERSION"
This function first appeared in libnbd 1.18.
.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_GET_EXTENDED_HEADERS_NEGOTIATED 1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_add_meta_context\fR\|(3),
\&\fBnbd_block_status\fR\|(3),
\&\fBnbd_block_status_64\fR\|(3),
\&\fBnbd_cache\fR\|(3),
\&\fBnbd_create\fR\|(3),
\&\fBnbd_get_block_size\fR\|(3),
\&\fBnbd_get_protocol\fR\|(3),
\&\fBnbd_get_request_extended_headers\fR\|(3),
\&\fBnbd_get_structured_replies_negotiated\fR\|(3),
\&\fBnbd_opt_extended_headers\fR\|(3),
\&\fBnbd_set_request_extended_headers\fR\|(3),
\&\fBnbd_trim\fR\|(3),
\&\fBnbd_zero\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