.\" Copyright (c) 1996-1999 Whistle Communications, Inc.
.\" All rights reserved.
.\"
.\" Subject to the following obligations and disclaimer of warranty, use and
.\" redistribution of this software, in source or object code forms, with or
.\" without modifications are expressly permitted by Whistle Communications;
.\" provided, however, that:
.\" 1. Any and all reproductions of the source or object code must include the
.\"    copyright notice above and the following disclaimer of warranties; and
.\" 2. No rights are granted, in any manner or form, to use Whistle
.\"    Communications, Inc. trademarks, including the mark "WHISTLE
.\"    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
.\"    such appears in the above copyright notice or in the software.
.\"
.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
.\" OF SUCH DAMAGE.
.\"
.\" Author: Archie Cobbs <archie@FreeBSD.org>
.\"
.\" $FreeBSD: head/share/man/man4/ng_tee.4 267938 2014-06-26 21:46:14Z bapt $
.\" $Whistle: ng_tee.8,v 1.4 1999/01/25 23:46:27 archie Exp $
.\"
.Dd May 28, 2004
.Dt NG_TEE 4
.Os
.Sh NAME
.Nm ng_tee
.Nd netgraph ``tee'' node type
.Sh SYNOPSIS
.In sys/types.h
.In netgraph/ng_tee.h
.Sh DESCRIPTION
The
.Nm tee
node type has a purpose similar to the
.Xr tee 1
command.
.Nm Tee
nodes are useful for debugging or
.Dq snooping
on a connection
between two netgraph nodes.
.Nm Tee
nodes have four hooks,
.Dv right ,
.Dv left ,
.Dv right2left ,
and
.Dv left2right .
All data received on
.Dv right
is sent unmodified to
.Em both
hooks
.Dv left
and
.Dv right2left .
Similarly, all data received on
.Dv left
is sent unmodified to both
.Dv right
and
.Dv left2right .
.Pp
Packets may also be received on
.Dv right2left
and
.Dv left2right ;
if so, they are forwarded unchanged out hooks
.Dv right
and
.Dv left ,
respectively.
.Sh HOOKS
This node type supports the following hooks:
.Bl -tag -width ".Va left2right"
.It Va right
The connection to the node on the right.
.It Va left
The connection to the node on the left.
.It Va right2left
Tap for right to left traffic.
.It Va left2right
Tap for left to right traffic.
.El
.Sh CONTROL MESSAGES
This node type supports the generic control messages, plus the following.
.Bl -tag -width foo
.It Dv NGM_TEE_GET_STATS Pq Ic getstats
Get statistics, returned as a
.Dv "struct ng_tee_stats" .
.It Dv NGM_TEE_CLR_STATS Pq Ic clrstats
Clear statistics.
.El
.Sh SHUTDOWN
This node shuts down upon receipt of an
.Dv NGM_SHUTDOWN
control message, or when all hooks have been disconnected.
If both
.Dv right
and
.Dv left
hooks are present, node removes itself from the chain gently,
connecting
.Dv right
and
.Dv left
together.
.Sh SEE ALSO
.Xr tee 1 ,
.Xr netgraph 4 ,
.Xr ngctl 8
.Sh HISTORY
The
.Nm
node type was implemented in
.Fx 4.0 .
.Sh AUTHORS
.An Julian Elischer Aq Mt julian@FreeBSD.org