nbd_get_tls_negotiated(3)           LIBNBD           nbd_get_tls_negotiated(3)


NAME
       nbd_get_tls_negotiated - find out if TLS was negotiated on a connection

SYNOPSIS
        #include <libnbd.h>

        int nbd_get_tls_negotiated (
              struct nbd_handle *h
            );

DESCRIPTION
       After connecting you may call this to find out if the connection is
       using TLS.

       This is normally useful only if you set the TLS request mode to
       "LIBNBD_TLS_ALLOW" (see nbd_set_tls(3)), because in this mode we try to
       use TLS but fall back to unencrypted if it was not available.  This
       function will tell you if TLS was negotiated or not.

       In "LIBNBD_TLS_REQUIRE" mode (the most secure) the connection would
       have failed if TLS could not be negotiated.  With "LIBNBD_TLS_DISABLE"
       mode, TLS is not tried automatically; but if the NBD server uses the
       less-common "SELECTIVETLS" mode, this function reports whether a manual
       nbd_opt_starttls(3) enabled TLS or if the connection is still
       plaintext.

RETURN VALUE
       This call returns a boolean value.

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_get_tls_negotiated 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_TLS_NEGOTIATED 1

SEE ALSO
       nbd_create(3), nbd_get_tls(3), nbd_opt_starttls(3), nbd_set_tls(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_get_tls_negotiated(3)