NAME

       nbd_get_extended_headers_negotiated - see if extended headers are in use

SYNOPSIS

        #include <libnbd.h>

        int nbd_get_extended_headers_negotiated (
              struct nbd_handle *h
            );

DESCRIPTION

       After connecting you may call this to find out if the connection is using extended
       headers.  Note that this setting is sticky; this can return true even after a second
       nbd_opt_extended_headers(3) returns false because the server detected a duplicate request.

       When extended headers are not in use, commands are limited to a 32-bit length, even when
       the libnbd API uses a 64-bit parameter to express the length.  But even when extended
       headers are supported, the server may enforce other limits, visible through
       nbd_get_block_size(3).

       Note that when extended headers are negotiated, you should prefer the use of
       nbd_block_status_64(3) instead of nbd_block_status(3) if any of the meta contexts you
       requested via nbd_add_meta_context(3) might return 64-bit status values; however, all of
       the well-known meta contexts covered by current "LIBNBD_CONTEXT_*" constants only return
       32-bit status.

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_extended_headers_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 1.18.

       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_EXTENDED_HEADERS_NEGOTIATED 1

SEE ALSO

       nbd_add_meta_context(3), nbd_block_status(3), nbd_block_status_64(3), nbd_cache(3),
       nbd_create(3), nbd_get_block_size(3), nbd_get_protocol(3),
       nbd_get_request_extended_headers(3), nbd_get_structured_replies_negotiated(3),
       nbd_opt_extended_headers(3), nbd_set_request_extended_headers(3), nbd_trim(3),
       nbd_zero(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