.\" $OpenBSD: tpmr.4,v 1.10 2021/07/28 19:19:38 benno Exp $
.\"
.\" Copyright (c) 2019 David Gwynne <dlg@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 28 2021 $
.Dt TPMR 4
.Os
.Sh NAME
.Nm tpmr
.Nd IEEE 802.1Q Two-Port MAC Relay interface
.Sh SYNOPSIS
.Cd "pseudo-device tpmr"
.Sh DESCRIPTION
The
.Nm
driver implements an 802.1Q (originally 802.1aj) Two-Port MAC Relay
(TPMR).
A TPMR is a simplified Ethernet bridge with exactly two member ports,
and it unconditionally relays Ethernet packets between those ports.
.Pp
.Nm
interfaces can be created at runtime using the
.Ic ifconfig tpmr Ns Ar N Ic create
command or by setting up a
.Xr hostname.if 5
configuration file for
.Xr netstart 8 .
.Pp
Other forms of Ethernet bridging are available using the
.Xr bridge 4
Ethernet bridge driver and the
.Xr veb 4
Virtual Ethernet Bridge device.
Link aggregation of Ethernet interfaces can be achieved
using the
.Xr aggr 4
and
.Xr trunk 4
drivers.
.Sh IOCTLS
The following
.Xr ioctl 2
calls and their structures are commonly use by
.Nm
and
.Xr bridge 4 :
.Pp
.Bl -bullet -offset indent -compact
.It
.Dv SIOCBRDGADD
.It
.Dv SIOCBRDGDEL
.El
.Sh EXAMPLES
.Nm
can be used to cross-connect Ethernet devices that support different
physical media.
For example, a device that supports a 100baseTX half-duplex connection
can be connected to a switch with 1000baseSX optical ports by using
.Nm
with a pair of physical network interfaces, each of which supports
the required media types.
If
.Xr fxp 4
is used to connect to the 100baseTX device, and
.Xr em 4
is used to connect to the 1000baseSX switch, the following configuration
can be used:
.Bd -literal -offset indent
# ifconfig tpmr0 create
# ifconfig tpmr0 add fxp0 add em0
# ifconfig fxp0 up
# ifconfig em0 up
# ifconfig tpmr0 up
.Ed
.Pp
Multiple TPMRs can be chained to transport Ethernet traffic for a
pair of devices over another network.
Given two physically separate Ethernet switches, TPMRs can be used
as follows to provide a point-to-point Ethernet link between them.
.Nm
with the
.Cm link0
flag set allows the use of the Link Aggregation Control Protocol (LACP)
or Spanning Tree Protocol (STP) by the switches to detect communication
failures or connectivity loops respectively, which is not possible
using
.Xr bridge 4
as it filters those protocols.
.Pp
If Host A connected to Router B has the external IP address 192.0.2.10
on em0, Host D connected to Router C has the external IP address
198.51.100.14 on em0, and both hosts have em1 connected to the
switches, the following configuration can be used to connect the
switches together.
.Xr etherip 4
is used to transport the Ethernet packets over the IP network.
.Bd -literal
Switch X ---- Host A ---------- tunnel ----------- Host D ---- Switch E
               \e                                    /
                \e                                  /
                 +---- Router B ---- Router C ----+
.Ed
.Pp
Create the
.Nm
and
.Xr etherip 4
interfaces:
.Bd -literal -offset indent
# ifconfig etherip0 create
# ifconfig tpmr0 create link0
.Ed
.Pp
Configure the etherip interface:
.Bd -literal -offset indent
(on Host A) # ifconfig etherip0 tunnel 192.0.2.10 198.51.100.14 up
(on Host D) # ifconfig etherip0 tunnel 198.51.100.14 192.0.2.10 up
.Ed
.Pp
Add the etherip interface and physical interface to the TPMR:
.Bd -literal -offset indent
# ifconfig tpmr0 add em1 add etherip0 up
.Ed
.Pp
An equivalent setup using MPLS pseudowires instead of IP as the
transport can be built using
.Xr mpw 4
interfaces.
.Sh SEE ALSO
.Xr aggr 4 ,
.Xr bridge 4 ,
.Xr pf 4 ,
.Xr trunk 4 ,
.Xr veb 4 ,
.Xr hostname.if 5 ,
.Xr ifconfig 8 ,
.Xr netstart 8
.\" .Sh STANDARDS
.\" .Rs
.\" .%T IEEE 802.1Q
.\" .Re
.\" .Rs
.\" .%T IEEE 802.1aj
.\" .Re
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 6.6 .