NAME

       nbd_set_request_block_size - control whether NBD_OPT_GO requests block size

SYNOPSIS

        #include <libnbd.h>

        int nbd_set_request_block_size (
              struct nbd_handle *h, bool request
            );

DESCRIPTION

       By default, when connecting to an export, libnbd requests that the server report any block
       size restrictions.  The NBD protocol states that a server may supply block sizes
       regardless of whether the client requests them, and libnbd will report those block sizes
       (see nbd_get_block_size(3)); conversely, if a client does not request block sizes, the
       server may reject the connection instead of dealing with a client sending unaligned
       requests.  This function makes it possible to test server behavior by emulating older
       clients.

       Note that even when block size is requested, the server is not obligated to provide any.
       Furthermore, if block sizes are provided (whether or not the client requested them),
       libnbd enforces alignment to those sizes unless nbd_set_strict_mode(3) is used to bypass
       client-side safety checks.

RETURN VALUE

       If the call is successful the function returns 0.

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_set_request_block_size can be called when the handle is in the following states:

        ┌─────────────────────────────────────┬─────────────────────────┐
        │ Handle created, before connecting   │ ✅ allowed              │
        │ Connecting                          │ ❌ error                │
        │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
        │ Connected to the server             │ ❌ error                │
        │ Connection shut down                │ ❌ error                │
        │ Handle dead                         │ ❌ error                │
        └─────────────────────────────────────┴─────────────────────────┘

VERSION

       This function first appeared in libnbd 1.12.

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

        #define LIBNBD_HAVE_NBD_SET_REQUEST_BLOCK_SIZE 1

SEE ALSO

       nbd_create(3), nbd_get_block_size(3), nbd_get_request_block_size(3), nbd_set_full_info(3),
       nbd_set_strict_mode(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