nbd_get_extended_headers_negotiated - see if extended headers are in use
#include <libnbd.h>
int nbd_get_extended_headers_negotiated (
struct nbd_handle *h
);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.
This call returns a boolean value.
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).
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 │
└─────────────────────────────────────┴─────────────────────────┘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 1nbd_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).
Eric Blake
Richard W.M. Jones
Copyright Red Hat
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