nbd_set_keepalive - Man Page

 #include <libnbd.h>

 int nbd_set_keepalive (
       struct nbd_handle *h, bool enable
     );

Set the keepalive (SO_KEEPALIVE) flag on the socket after creating it.

On operating systems and protocols that support it, this means the OS sends periodic messages to the NBD server to detect if the socket is still connected.  If this feature is not supported then setting this does nothing.

If using TCP on Linux, keepalive can be tuned by calling nbd_set_tcp_option(3).

This only works if called on the handle before calls such as nbd_connect_tcp(3) where libnbd itself creates the socket. It does not apply to nbd_connect_socket(3) where a socket is created somewhere else and passed to libnbd.

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_keepalive 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 1.26.

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_KEEPALIVE 1

nbd_connect_socket(3), nbd_connect_tcp(3), nbd_create(3), nbd_get_keepalive(3), nbd_set_tcp_option(3), libnbd(3), setsockopt(2), socket(7).

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

libnbd(3), NBD(3), nbdfuse(1), nbd_get_keepalive(3), nbd_set_tcp_option(3), nbdublk(1).