nbd_connect_vsock - Man Page

connect to NBD server over AF_VSOCK protocol


 #include <libnbd.h>

 int nbd_connect_vsock (
       struct nbd_handle *h, uint32_t cid, uint32_t port


Connect (synchronously) over the AF_VSOCK protocol from a virtual machine to an NBD server, usually running on the host.  The cid and port parameters specify the server address.  Usually cid should be 2 (to connect to the host), and port might be 10809 or another port number assigned to you by the host administrator.

Not all systems support AF_VSOCK; to determine if libnbd was built on a system with vsock support, see nbd_supports_vsock(3).

This call returns when the connection has been made.  By default, this proceeds all the way to transmission phase, but nbd_set_opt_mode(3) can be used for manual control over option negotiation performed before transmission phase.

Return Value

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).

Handle State

The handle must be newly created, otherwise this call will return an error.


This function first appeared in libnbd 1.2.

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


See Also

nbd_aio_connect_vsock(3), nbd_create(3), nbd_set_opt_mode(3), nbd_supports_vsock(3), libnbd(3).


Eric Blake

Richard W.M. Jones


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

Referenced By

libnbd(3), libnbd-release-notes-1.2(1), NBD(3), nbd_aio_connect_vsock(3), nbd_connect_uri(3), nbdfuse(1), nbd_supports_vsock(3), nbdublk(1).

2023-08-30 libnbd-1.17.4