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¶

The handle must be negotiating, or connected with the server, or shut down, otherwise this call will return an 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