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.\" ========================================================================
.\"
.IX Title "nbd_get_protocol 3"
.TH nbd_get_protocol 3 "2023-01-04" "libnbd-1.14.2" "LIBNBD"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
nbd_get_protocol \- return the NBD protocol variant
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& const char * nbd_get_protocol (struct nbd_handle *h);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Return the \s-1NBD\s0 protocol variant in use on the connection.  At
the moment this returns one of the strings \f(CW"oldstyle"\fR,
\&\f(CW"newstyle"\fR or \f(CW"newstyle\-fixed"\fR.  Other strings might
be returned in the future.
Most modern \s-1NBD\s0 servers use \f(CW"newstyle\-fixed"\fR.
.PP
This call does not block, because it returns data that is saved in
the handle from the \s-1NBD\s0 protocol handshake.
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
This call returns a statically allocated string, valid for the
lifetime of the process or until libnbd is unloaded by
\&\fBdlclose\fR\|(3).  You \fBmust not\fR try to free the string.
.SH "ERRORS"
.IX Header "ERRORS"
On error \f(CW\*(C`NULL\*(C'\fR is returned.
.PP
Refer to \*(L"\s-1ERROR HANDLING\*(R"\s0 in \fBlibnbd\fR\|(3)
for how to get further details of the error.
.PP
The following parameters must not be \s-1NULL:\s0 \f(CW\*(C`h\*(C'\fR.
For more information see \*(L"Non-NULL parameters\*(R" in \fBlibnbd\fR\|(3).
.SH "HANDLE STATE"
.IX Header "HANDLE STATE"
The handle must be
negotiating, or
connected with the server, or
shut down,
otherwise this call will return an error.
.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_PROTOCOL 1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_create\fR\|(3),
\&\fBnbd_get_block_size\fR\|(3),
\&\fBnbd_get_handshake_flags\fR\|(3),
\&\fBnbd_get_structured_replies_negotiated\fR\|(3),
\&\fBnbd_get_tls_negotiated\fR\|(3),
\&\fBlibnbd\fR\|(3).
.SH "AUTHORS"
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2019\-2021 Red Hat Inc.
.SH "LICENSE"
.IX Header "LICENSE"
This library is free software; you can redistribute it and/or
modify it under the terms of the \s-1GNU\s0 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 \s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of
\&\s-1MERCHANTABILITY\s0 or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the \s-1GNU\s0
Lesser General Public License for more details.
.PP
You should have received a copy of the \s-1GNU\s0 Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, \s-1MA 02110\-1301 USA\s0