nbd_set_request_extended_headers - control use of extended headers


 #include <libnbd.h>

 int nbd_set_request_extended_headers (
       struct nbd_handle *h, bool request


By default, libnbd tries to negotiate extended headers with the server, as this protocol extension permits the use of 64-bit zero, trim, and block status actions. However, for integration testing, it can be useful to clear this flag rather than find a way to alter the server to fail the negotiation request.

For backwards compatibility, the setting of this knob is ignored if nbd_set_request_structured_replies(3) is also set to false, since the use of extended headers implies structured replies.


If the call is successful the function returns 0.


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_set_request_extended_headers can be called when the handle is in the following state:

 │ Handle created, before connecting   │ ✅ allowed              │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ❌ error                │
 │ Connected to the server             │ ❌ error                │
 │ Connection shut down                │ ❌ error                │
 │ 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:



nbd_block_status_64(3), nbd_cache(3), nbd_create(3), nbd_get_extended_headers_negotiated(3), nbd_get_request_extended_headers(3), nbd_opt_extended_headers(3), nbd_set_handshake_flags(3), nbd_set_request_structured_replies(3), nbd_set_strict_mode(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