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.IX Title "nbd_set_tcp_option 3"
.TH nbd_set_tcp_option 3 2026-10-11 libnbd-1.25.7 LIBNBD
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH NAME
nbd_set_tcp_option \- set TCP options on the socket
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <libnbd.h>
\&
\& int nbd_set_tcp_option (
\&       struct nbd_handle *h, int option, int v
\&     );
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
If making a TCP connection then you can call
this function to set a subset of TCP options on the socket.
.PP
Currently the \f(CW\*(C`option\*(C'\fR parameter may be one of:
.IP \(bu 4
TCP_KEEPCNT
.IP \(bu 4
TCP_KEEPIDLE
.IP \(bu 4
TCP_KEEPINTVL
.PP
These options may not work on non\-Linux systems.
.PP
For the \f(CW\*(C`TCP_KEEP*\*(C'\fR options, keepalive must also be enabled
by calling \fBnbd_set_keepalive\fR\|(3)).
.SH "RETURN VALUE"
.IX Header "RETURN VALUE"
If the call is successful the function returns \f(CW0\fR.
.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_set_tcp_option
can be called when the handle is in the following state:
.PP
.Vb 8
\& ┌─────────────────────────────────────┬─────────────────────────┐
\& │ Handle created, before connecting   │ ✅ allowed              │
\& │ Connecting                          │ ❌ error                │
\& │ Connecting & handshaking (opt_mode) │ ❌ error                │
\& │ Connected to the server             │ ❌ error                │
\& │ Connection shut down                │ ❌ error                │
\& │ Handle dead                         │ ❌ error                │
\& └─────────────────────────────────────┴─────────────────────────┘
.Ve
.SH VERSION
.IX Header "VERSION"
This function first appeared in libnbd 1.26.
.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_SET_TCP_OPTION 1
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbd_create\fR\|(3),
\&\fBnbd_set_keepalive\fR\|(3),
\&\fBlibnbd\fR\|(3),
\&\fBsetsockopt\fR\|(2),
\&\fBtcp\fR\|(7).
.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