nbd_opt_abort(3)                    LIBNBD                    nbd_opt_abort(3)


NAME
       nbd_opt_abort - end negotiation and close the connection

SYNOPSIS
        #include <libnbd.h>

        int nbd_opt_abort (
              struct nbd_handle *h
            );

DESCRIPTION
       Request that the server finish negotiation, gracefully if possible,
       then close the connection.  This can only be used if
       nbd_set_opt_mode(3) enabled option mode.

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.

       The following parameters must not be NULL: "h".  For more information
       see "Non-NULL parameters" in libnbd(3).

HANDLE STATE
       nbd_opt_abort can be called when the handle is in the following state:

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        | Handle created, before connecting   | <?> error                |
        | Connecting                          | <?> error                |
        | Connecting & handshaking (opt_mode) | <?> allowed              |
        | Connected to the server             | <?> error                |
        | Connection shut down                | <?> error                |
        | Handle dead                         | <?> error                |
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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_ABORT 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_abort(3), nbd_create(3), nbd_opt_go(3),
       nbd_set_opt_mode(3), libnbd(3).

AUTHORS
       Eric Blake

       Richard W.M. Jones

COPYRIGHT
       Copyright Red Hat

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

libnbd-1.20.0                     2024-05-31                  nbd_opt_abort(3)