Man page - nbd_get_extended_headers_negotiated(3)

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Manual

nbd_get_extended_headers_negotiated

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
HANDLE STATE
VERSION
SEE ALSO
AUTHORS
COPYRIGHT
LICENSE

NAME

nbd_get_extended_headers_negotiated - see if extended headers are in use

SYNOPSIS

#include <libnbd.h>
int nbd_get_extended_headers_negotiated (
struct nbd_handle *h
);

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 nbd_opt_extended_headers (3) returns false because the server detected a duplicate request.

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 nbd_get_block_size (3).

Note that when extended headers are negotiated, you should prefer the use of nbd_block_status_64 (3) instead of nbd_block_status (3) if any of the meta contexts you requested via nbd_add_meta_context (3) might return 64-bit status values; however, all of the well-known meta contexts covered by current "LIBNBD_CONTEXT_*" constants only return 32-bit status.

RETURN VALUE

This call returns a boolean value.

ERRORS

On error -1 is returned.

Refer to "ERROR HANDLING" in libnbd (3) for how to get further details of the error.

The following parameters must not be NULL: "h". For more information see "Non-NULL parameters" in libnbd (3).

HANDLE STATE

nbd_get_extended_headers_negotiated 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 │
└─────────────────────────────────────┴─────────────────────────┘

VERSION

This function first appeared in libnbd 1.18.

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

#define LIBNBD_HAVE_NBD_GET_EXTENDED_HEADERS_NEGOTIATED 1

SEE ALSO

nbd_add_meta_context (3), nbd_block_status (3), nbd_block_status_64 (3), nbd_cache (3), nbd_create (3), nbd_get_block_size (3), nbd_get_protocol (3), nbd_get_request_extended_headers (3), nbd_get_structured_replies_negotiated (3), nbd_opt_extended_headers (3), nbd_set_request_extended_headers (3), nbd_trim (3), nbd_zero (3), libnbd (3).

AUTHORS

Eric Blake

Richard W.M. Jones

COPYRIGHT

Copyright Red Hat

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.

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.

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