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=head1 NAME
nbd_shutdown - disconnect from the NBD server
=head1 SYNOPSIS
#include <libnbd.h>
int nbd_shutdown (
struct nbd_handle *h, uint32_t flags
);
=head1 DESCRIPTION
Issue the disconnect command to the NBD server. This is
a nice way to tell the server we are going away, but from the
client's point of view has no advantage over abruptly closing
the connection (see L<nbd_close(3)>).
This function works whether or not the handle is ready for
transmission of commands. If more fine-grained control is
needed, see L<nbd_aio_opt_abort(3)> and L<nbd_aio_disconnect(3)>.
The C<flags> argument is a bitmask, including zero or more of the
following shutdown flags:
=over 4
=item C<LIBNBD_SHUTDOWN_ABANDON_PENDING> = 0x10000
If there are any pending requests which have not yet been sent to
the server (see L<nbd_aio_in_flight(3)>), abandon them without
sending them to the server, rather than the usual practice of
issuing those commands before informing the server of the intent
to disconnect.
=back
For convenience, the constant C<LIBNBD_SHUTDOWN_MASK> is available
to describe all shutdown flags recognized by this build of libnbd.
A future version of the library may add new flags.
=head1 RETURN VALUE
If the call is successful the function returns C<0>.
=head1 ERRORS
On error C<-1> is returned.
Refer to L<libnbd(3)/ERROR HANDLING>
for how to get further details of the error.
The following parameters must not be NULL: C<h>.
For more information see L<libnbd(3)/Non-NULL parameters>.
=head1 HANDLE STATE
nbd_shutdown
can be called when the handle is in the following states:
┌─────────────────────────────────────┬─────────────────────────┐
│ Handle created, before connecting │ ❌ error │
│ Connecting │ ❌ error │
│ Connecting & handshaking (opt_mode) │ ✅ allowed │
│ Connected to the server │ ✅ allowed │
│ Connection shut down │ ❌ error │
│ Handle dead │ ❌ error │
└─────────────────────────────────────┴─────────────────────────┘
=head1 VERSION
This function first appeared in libnbd 1.0.
If you need to test if this function is available at compile time
check if the following macro is defined:
#define LIBNBD_HAVE_NBD_SHUTDOWN 1
=head1 EXAMPLE
This example is also available as F<examples/reads-and-writes.c>
in the libnbd source code.
/* This example shows how to do synchronous reads
* and writes randomly over the first megabyte of an
* NBD server. Note this will destroy any existing
* content on the NBD server.
*
* To test it with nbdkit and a RAM disk:
*
* nbdkit -U - memory 1M \
* --run './simple-reads-and-writes $unixsocket'
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <assert.h>
#include <time.h>
#include <libnbd.h>
int
main (int argc, char *argv[])
{
struct nbd_handle *nbd;
char buf[512];
size_t i;
int64_t exportsize;
uint64_t offset;
srand (time (NULL));
if (argc != 2) {
fprintf (stderr, "%s socket\n", argv[0]);
exit (EXIT_FAILURE);
}
/* Create the libnbd handle. */
nbd = nbd_create ();
if (nbd == NULL) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Connect to the NBD server over a
* Unix domain socket.
*/
if (nbd_connect_unix (nbd, argv[1]) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Get the size of the disk and check
* it's large enough.
*/
exportsize = nbd_get_size (nbd);
if (exportsize == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
assert (exportsize >= sizeof buf);
/* Check that the server is writable. */
if (nbd_is_read_only (nbd) == 1) {
fprintf (stderr, "%s: "
"error: this NBD export is read-only\n",
argv[0]);
exit (EXIT_FAILURE);
}
for (i = 0; i < sizeof buf; ++i)
buf[i] = rand ();
/* 1000 writes. */
for (i = 0; i < 1000; ++i) {
offset = rand () % (exportsize - sizeof buf);
if (nbd_pwrite (nbd, buf, sizeof buf,
offset, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
}
/* 1000 reads and writes. */
for (i = 0; i < 1000; ++i) {
offset = rand () % (exportsize - sizeof buf);
if (nbd_pread (nbd, buf, sizeof buf,
offset, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
offset = rand () % (exportsize - sizeof buf);
if (nbd_pwrite (nbd, buf, sizeof buf,
offset, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
}
/* Sends a graceful shutdown to the server. */
if (nbd_shutdown (nbd, 0) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
nbd_close (nbd);
exit (EXIT_SUCCESS);
}
=head1 SEE ALSO
L<nbd_aio_disconnect(3)>,
L<nbd_aio_in_flight(3)>,
L<nbd_aio_opt_abort(3)>,
L<nbd_close(3)>,
L<nbd_create(3)>,
L<libnbd(3)>.
=head1 AUTHORS
Eric Blake
Richard W.M. Jones
=head1 COPYRIGHT
Copyright Red Hat
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