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.\" ========================================================================
.\"
.IX Title "nbd_get_tls_negotiated 3"
.TH nbd_get_tls_negotiated 3 2024-05-31 libnbd-1.20.0 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
nbd_get_tls_negotiated \- find out if TLS was negotiated on a connection
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int nbd_get_tls_negotiated (
\&       struct nbd_handle *h
\&     );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
After connecting you may call this to find out if the
connection is using TLS.
.PP
This is normally useful only if you set the TLS request mode
to \f(CW\*(C`LIBNBD_TLS_ALLOW\*(C'\fR (see \fBnbd_set_tls\fR\|(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.
.PP
In \f(CW\*(C`LIBNBD_TLS_REQUIRE\*(C'\fR mode (the most secure) the connection
would have failed if TLS could not be negotiated.  With
\&\f(CW\*(C`LIBNBD_TLS_DISABLE\*(C'\fR mode, TLS is not tried automatically;
but if the NBD server uses the less-common \f(CW\*(C`SELECTIVETLS\*(C'\fR
mode, this function reports whether a manual \fBnbd_opt_starttls\fR\|(3)
enabled TLS or if the connection is still plaintext.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
This call returns a boolean value.
.SH ERRORS
.IX Header "ERRORS"
On error \f(CW\-1\fR is returned.
.PP
Refer to "ERROR HANDLING" in \fBlibnbd\fR\|(3)
for how to get further details of the error.
.PP
The following parameters must not be NULL: \f(CW\*(C`h\*(C'\fR.
For more information see "Non-NULL parameters" in \fBlibnbd\fR\|(3).
.SH "HANDLE STATE"
.IX Header "HANDLE STATE"
nbd_get_tls_negotiated
can be called when the handle is in the following states:
.PP
.Vb 8
\& ┌─────────────────────────────────────┬─────────────────────────┐
\& │ Handle created, before connecting   │ ❌ error                │
\& │ Connecting                          │ ❌ error                │
\& │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
\& │ Connected to the server             │ ✅ allowed              │
\& │ Connection shut down                │ ✅ allowed              │
\& │ Handle dead                         │ ❌ error                │
\& └─────────────────────────────────────┴─────────────────────────┘
.Ve
.SH VERSION
.IX Header "VERSION"
This function first appeared in libnbd 1.2.
.PP
If you need to test if this function is available at compile time
check if the following macro is defined:
.PP
.Vb 1
\& #define LIBNBD_HAVE_NBD_GET_TLS_NEGOTIATED 1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_create\fR\|(3),
\&\fBnbd_get_tls\fR\|(3),
\&\fBnbd_opt_starttls\fR\|(3),
\&\fBnbd_set_tls\fR\|(3),
\&\fBlibnbd\fR\|(3).
.SH AUTHORS
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "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.
.PP
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.
.PP
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