=head1 NAME

nbd_set_tcp_option - set TCP options on the socket

=head1 SYNOPSIS

 #include <libnbd.h>

 int nbd_set_tcp_option (
       struct nbd_handle *h, int option, int v
     );

=head1 DESCRIPTION

If making a TCP connection then you can call
this function to set a subset of TCP options on the socket.

Currently the C<option> parameter may be one of:

=over 4

=item *

TCP_KEEPCNT

=item *

TCP_KEEPIDLE

=item *

TCP_KEEPINTVL

=back

These options may not work on non-Linux systems.

For the C<TCP_KEEP*> options, keepalive must also be enabled
by calling L<nbd_set_keepalive(3)>).

=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_tcp_option
can be called when the handle is in the following state:

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

=head1 VERSION

This function first appeared in libnbd 1.26.

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_TCP_OPTION 1

=head1 SEE ALSO

L<nbd_create(3)>,
L<nbd_set_keepalive(3)>,
L<libnbd(3)>,
L<setsockopt(2)>,
L<tcp(7)>.

=head1 AUTHORS

Eric Blake

Richard W.M. Jones

=head1 COPYRIGHT

Copyright Red Hat
