Provided by: libnbd-dev_1.10.5-1_amd64 
NAME
nbd_opt_go - end negotiation and move on to using an export
SYNOPSIS
#include <libnbd.h>
int nbd_opt_go (struct nbd_handle *h);
DESCRIPTION
Request that the server finish negotiation and move on to serving the export previously specified by the
most recent nbd_set_export_name(3) or nbd_connect_uri(3). This can only be used if nbd_set_opt_mode(3)
enabled option mode.
If this fails, the server may still be in negotiation, where it is possible to attempt another option
such as a different export name; although older servers will instead have killed the connection.
RETURN VALUE
If the call is successful the function returns 0.
ERRORS
On error "-1" is returned.
Refer to "ERROR HANDLING" in libnbd(3) for how to get further details of the error.
HANDLE STATE
The handle must be negotiating, otherwise this call will return an error.
VERSION
This function first appeared in libnbd 1.4.
If you need to test if this function is available at compile time check if the following macro is
defined:
#define LIBNBD_HAVE_NBD_OPT_GO 1
EXAMPLE
This example is also available as examples/list-exports.c in the libnbd source code.
/* This example shows how to list NBD exports.
*
* To test this with qemu-nbd:
* $ qemu-nbd -x "hello" -t -k /tmp/sock disk.img
* $ ./run examples/list-exports /tmp/sock
* [0] hello
* Which export to connect to (-1 to quit)? 0
* Connecting to hello ...
* /tmp/sock: hello: size = 2048 bytes
*
* To test this with nbdkit (requires 1.22):
* $ nbdkit -U /tmp/sock sh - <<\EOF
* case $1 in
* list_exports) echo NAMES; echo foo; echo foobar ;;
* open) echo "$3" ;;
* get_size) echo "$2" | wc -c ;;
* pread) echo "$2" | dd bs=1 skip=$4 count=$3 ;;
* *) exit 2 ;;
* esac
* EOF
* $ ./run examples/list-exports /tmp/sock
* [0] foo
* [1] foobar
* Which export to connect to (-1 to quit)? 1
* Connecting to foobar ...
* /tmp/sock: foobar: size = 7 bytes
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <inttypes.h>
#include <errno.h>
#include <libnbd.h>
struct export_list {
int i;
char **names;
};
/* Callback function for nbd_opt_list */
static int
list_one (void *opaque, const char *name,
const char *description)
{
struct export_list *l = opaque;
char **names;
printf ("[%d] %s\n", l->i, name);
if (*description)
printf(" (%s)\n", description);
names = realloc (l->names,
(l->i + 1) * sizeof *names);
if (!names) {
perror ("realloc");
exit (EXIT_FAILURE);
}
names[l->i] = strdup (name);
if (!names[l->i]) {
perror ("strdup");
exit (EXIT_FAILURE);
}
l->names = names;
l->i++;
return 0;
}
int
main (int argc, char *argv[])
{
struct nbd_handle *nbd;
int i;
const char *name;
int64_t size;
struct export_list list = { 0 };
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);
}
/* Set opt mode. */
nbd_set_opt_mode (nbd, true);
/* Connect to the NBD server over a
* Unix domain socket. If we did not
* end up in option mode, then a
* listing is not possible.
*/
if (nbd_connect_unix (nbd, argv[1]) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
if (!nbd_aio_is_negotiating (nbd)) {
fprintf (stderr, "Server does not support "
"listing exports.\n");
exit (EXIT_FAILURE);
}
/* Print the export list. */
if (nbd_opt_list (nbd,
(nbd_list_callback) {
.callback = list_one,
.user_data = &list, }) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
/* Display the list of exports. */
printf ("Which export to connect to? ");
if (scanf ("%d", &i) != 1) exit (EXIT_FAILURE);
if (i == -1) {
if (nbd_opt_abort (nbd) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
nbd_close (nbd);
exit (EXIT_SUCCESS);
}
if (i < 0 || i >= list.i) {
fprintf (stderr, "index %d out of range", i);
exit (EXIT_FAILURE);
}
name = list.names[i];
printf ("Connecting to %s ...\n", name);
/* Resume connecting to the chosen export. */
if (nbd_set_export_name (nbd, name) == -1 ||
nbd_opt_go (nbd) == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
if (!nbd_aio_is_ready (nbd)) {
fprintf (stderr, "server closed early\n");
exit (EXIT_FAILURE);
}
/* Read the size in bytes and print it. */
size = nbd_get_size (nbd);
if (size == -1) {
fprintf (stderr, "%s\n", nbd_get_error ());
exit (EXIT_FAILURE);
}
printf ("%s: %s: size = %" PRIi64 " bytes\n",
argv[1], name, size);
/* Close the libnbd handle. */
nbd_close (nbd);
for (i = 0; i < list.i; i++)
free (list.names[i]);
free (list.names);
exit (EXIT_SUCCESS);
}
SEE ALSO
nbd_aio_opt_go(3), nbd_connect_uri(3), nbd_create(3), nbd_opt_abort(3), nbd_opt_info(3), nbd_set_export_name(3), nbd_set_opt_mode(3), libnbd(3).
AUTHORS
Eric Blake
Richard W.M. Jones
COPYRIGHT
Copyright (C) 2019-2021 Red Hat Inc.
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