plucky (3) nbd_get_extended_headers_negotiated.3.gz

Provided by: libnbd-dev_1.22.0-1_amd64 bug

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 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