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.\" $OpenBSD: clnp.4,v 1.8 2003/06/02 23:30:12 millert Exp $
.\" $NetBSD: clnp.4,v 1.4 1994/11/30 16:22:07 jtc Exp $
.\"
.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)clnp.4 8.2 (Berkeley) 4/2/94
.\"
.Dd April 2, 1994
.Dt CLNP 4
.Os
.Sh NAME
.Nm clnp
.Nd Connectionless-Mode Network Protocol
.Sh SYNOPSIS
.Fd #include <sys/socket.h>
.Fd #include <netiso/iso.h>
.Fd #include <netiso/clnp.h>
.Ft int
.Fn socket AF_ISO SOCK_RAW 0
.Sh DESCRIPTION
CLNP is the connectionless-mode network protocol used by the
connectionless-mode network service.
This protocol is specified in ISO 8473.
It may be accessed through a
.Dq raw socket
for debugging purposes only.
CLNP sockets are connectionless, and are normally used with the
.Xr sendto 2
and
.Xr recvfrom 2
calls, though the
.Xr connect 2
call may also be used to fix the destination for future
packets (in which case the
.Xr read 2
or
.Xr recv 2
and
.Xr write 2
or
.Xr send 2
system calls may be used).
.Pp
Outgoing packets automatically have a CLNP header prepended to them.
Incoming packets received by the user contain the full CLNP header.
The following
.Xr setsockopt 2
options apply to CLNP:
.Bl -tag -width CLNPOPT_FLAGS
.It Dv CLNPOPT_FLAGS
Sets the flags which are passed to clnp when sending a datagram.
Valid flags are:
.Pp
.Bl -tag -width "CLNP_NO_CKSUM" -offset indent -compact
.It Dv CLNP_NO_SEG
Do not allow segmentation.
.It Dv CLNP_NO_ER
Suppress ER pdus.
.It Dv CLNP_NO_CKSUM
Do not generate the CLNP checksum.
.El
.Pp
.It Dv CLNPOPT_OPTS
Sets CLNP options.
The options must be formatted exactly as specified by ISO 8473, section 7.5.
.Dq Options Part.
Once an option has been set, it will be sent on all packets until
a different option is set.
.El
.Sh CONGESTION EXPERIENCE BIT
Whenever a packet is transmitted, the globally unique quality of
service option is added to the packet.
The sequencing preferred bit and the low transit delay bit are set in
this option.
.Pp
If a packet is forwarded containing the globally unique quality of
service option, and the interface through which the packet will be
transmitted has a queue length greater than
.Em congest_threshold ,
then the congestion experienced bit is set in the quality of service option.
.Pp
The threshold value stored in
.Em congest_threshold
may be tuned.
.Pp
When a packet is received with the
globally unique quality of service option present, and the
congestion experienced bit is set, then the transport congestion
control function is called.
.Sh DIAGNOSTICS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width [EADDRNOTAVAIL]
.It Bq Er EISCONN
When trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected;
.It Bq Er ENOTCONN
When trying to send a datagram, but
no destination address is specified, and the socket hasn't been
connected;
.It Bq Er ENOBUFS
When the system runs out of memory for
an internal data structure;
.It Bq Er EADDRNOTAVAIL
When an attempt is made to create a
socket with a network address for which no network interface
exists;
.It Bq Er EHOSTUNREACH
When trying to send a datagram, but no route to the destination
address exists.
.It Bq Er EINVAL
When specifying unsupported options.
.El
.Sh SEE ALSO
.Xr recv 2 ,
.Xr send 2 ,
.Xr iso 4 ,
.Xr netintro 4
.Sh BUGS
Packets are sent with the type code of 0x1d (technically an invalid
packet type) for lack of a better way to identify raw CLNP packets.
.Pp
No more than
.Dv MLEN
bytes of options can be specified.
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