NAME

       nbd_get_protocol - return the NBD protocol variant

SYNOPSIS

        #include <libnbd.h>

        const char * nbd_get_protocol (
                       struct nbd_handle *h
                     );

DESCRIPTION

       Return the NBD protocol variant in use on the connection.  At the moment this returns one of the strings
       "oldstyle", "newstyle" or "newstyle-fixed".  Other strings might be returned in the future.  Most modern
       NBD servers use "newstyle-fixed".

       This call does not block, because it returns data that is saved in the handle from the NBD protocol
       handshake.

RETURN VALUE

       This call returns a statically allocated string, valid for the lifetime of the process or until libnbd is
       unloaded by dlclose(3).  You must not try to free the string.

ERRORS

       On error "NULL" 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_get_protocol 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                │ ✅ allowed              │
        │ Handle dead                         │ ❌ error                │
        └─────────────────────────────────────┴─────────────────────────┘

VERSION

       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:

        #define LIBNBD_HAVE_NBD_GET_PROTOCOL 1

SEE ALSO

       nbd_create(3), nbd_get_block_size(3), nbd_get_handshake_flags(3),
       nbd_get_structured_replies_negotiated(3), nbd_get_tls_negotiated(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