=head1 NAME

nbd_set_request_meta_context - control whether connect automatically
requests meta contexts

=head1 SYNOPSIS

 #include <libnbd.h>

 int nbd_set_request_meta_context (
       struct nbd_handle *h, bool request
     );

=head1 DESCRIPTION

This function controls whether the act of
connecting to an export
(all C<nbd_connect_*> calls when L<nbd_set_opt_mode(3)> is false,
or L<nbd_opt_go(3)> and L<nbd_opt_info(3)> when option mode is
enabled) will also try to issue NBD_OPT_SET_META_CONTEXT when
the server supports structured replies or extended headers and
any contexts were registered by L<nbd_add_meta_context(3)>.  The
default setting is true; however the extra step of negotiating
meta contexts is not always desirable: performing both info and
go on the same export works without needing to re-negotiate
contexts on the second call; integration testing of other servers
may benefit from manual invocation of L<nbd_opt_set_meta_context(3)>
at other times in the negotiation sequence; and even when using
just L<nbd_opt_info(3)>, it can be faster to collect the server's
results by relying on the callback function passed to
L<nbd_opt_list_meta_context(3)> than a series of post-process
calls to L<nbd_can_meta_context(3)>.

Note that this control has no effect if the server does not
negotiate structured replies or extended headers, or if the
client did not request any contexts via L<nbd_add_meta_context(3)>.
Setting this control to false may cause L<nbd_block_status(3)>
to fail.

=head1 RETURN VALUE

If the call is successful the function returns C<0>.

=head1 ERRORS

On error C<-1> is returned.

Refer to L<libnbd(3)/ERROR HANDLING>
for how to get further details of the error.

The following parameters must not be NULL: C<h>.
For more information see L<libnbd(3)/Non-NULL parameters>.

=head1 HANDLE STATE

nbd_set_request_meta_context
can be called when the handle is in the following states:

 ┌─────────────────────────────────────┬─────────────────────────┐
 │ Handle created, before connecting   │ ✅ allowed              │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
 │ Connected to the server             │ ❌ error                │
 │ Connection shut down                │ ❌ error                │
 │ Handle dead                         │ ❌ error                │
 └─────────────────────────────────────┴─────────────────────────┘

=head1 VERSION

This function first appeared in libnbd 1.16.

If you need to test if this function is available at compile time
check if the following macro is defined:

 #define LIBNBD_HAVE_NBD_SET_REQUEST_META_CONTEXT 1

=head1 SEE ALSO

L<nbd_add_meta_context(3)>,
L<nbd_block_status(3)>,
L<nbd_can_meta_context(3)>,
L<nbd_create(3)>,
L<nbd_get_request_meta_context(3)>,
L<nbd_get_structured_replies_negotiated(3)>,
L<nbd_opt_go(3)>,
L<nbd_opt_info(3)>,
L<nbd_opt_list_meta_context(3)>,
L<nbd_opt_set_meta_context(3)>,
L<nbd_set_opt_mode(3)>,
L<libnbd(3)>.

=head1 AUTHORS

Eric Blake

Richard W.M. Jones

=head1 COPYRIGHT

Copyright Red Hat
