.\"	$OpenBSD: strip.4,v 1.24 2008/01/06 18:40:24 jmc Exp $
.\"
.\" Copyright 1996 The Board of Trustees of The Leland Stanford
.\" Junior University. All Rights Reserved.
.\"
.\" Author: Jonathan Stone
.\"
.\" Permission to use, copy, modify, and distribute this
.\" software and its documentation for any purpose and without
.\" fee is hereby granted, provided that the above copyright
.\" notice and the above authorship notice appear in all copies.
.\" Stanford University makes no representations about the suitability
.\" of this software for any purpose.  It is provided "as is" without
.\" express or implied warranty.
.Dd $Mdocdate: January 6 2008 $
.Dt STRIP 4
.Os
.Sh NAME
.Nm strip
.Nd packet-mode network device driver for the Metricom Ricochet radio
.Sh SYNOPSIS
.Cd "pseudo-device strip" Op Ar count
.Sh DESCRIPTION
Configures
.Ar count
.Nm
interfaces, named
.Sy st Ns Ar 0 ,
.Sy st Ns Ar 1 ,
etc., into a kernel built from a config file containing the
given entry.
.Pp
Each
.Nm
interface is a pseudo-device driver for the Metricom Ricochet radio,
operating in peer-to-peer packet mode.
.Pp
The
.Nm
driver takes outbound network packets, encapsulates them using the
Metricom "starmode" framing, and sends the packets out an RS-232
interface to a Metricom
.Em Ricochet
radio.
Packets arriving from the radio via the serial link are decapsulated and then
passed up to the local host's networking stack.
.Pp
.Nm
is an acronym for
.Sy \&St Ns armode
.Sy R Ns adio
.Sy IP .
.Pp
In many ways,
the
.Nm
driver is very much like the
.Nm sl
SLIP pseudo-device driver.
A
.Nm
device is attached to a tty line with
.Xr ldattach 8 .
Once attached, the interface is configured via
.Xr ifconfig 8 .
The major difference between the
.Xr sl 4
SLIP pseudo-device driver and the
.Nm
driver is that SLIP works only between two hosts over
a dedicated point-to-point connection.
In contrast,
.Nm
sends
packets to a frequency-hopping radio, which can address packets to
any peer Metricom radio rather than just to a single host at the
other end of a point-to-point line.
Thus, one
.Nm
pseudo-device is usually sufficient for any kernel.
.Pp
In other respects, a
.Nm
interface is rather like an Ethernet interface.
Packets are individually addressed, and subsequent packets can
be sent independently to different MAC addresses.
However, the "Star-mode" framing and MAC addressing are not in any way
compatible with Ethernet.
Broadcast or multicast to more than one radio is not possible, due to the
independent frequency-hopping operation of the radios.
The interface flags
.Dv IFF_POINTOPOINT
and
.Dv IFF_BROADCAST
are not supported on
.Nm
interface.
.Pp
In other words,
.Nm
implements a multiple-access, non-broadcast device, accessed via
an RS-232 serial line, using a proprietary packet framing scheme.
.Pp
This version
.Nm
driver maps IP addresses to Metricom radio addresses using
statically configured entries in the normal routing table.
These entries map IP addresses of peer radios to the MAC-level addresses.
The exact syntax of this mapping and an example are discussed below.
The Internet Assigned Numbers Authority (IANA) has allocated an ARP
type code for use with STRIP.
A future version of this driver will support
.Xr arp 4
to obtain the IP address of reachable peer radios dynamically.
.Sh ADDRESS CONFIGURATION
This version of the
.Nm
driver requires static pre-configuration of
the mapping from IP addresses to radio MAC addresses.
The
.Xr route 8
command should be used to bind a peer STRIP host's radio IP address
to the peer's link-level radio address.
Radio addresses are encoded using the hex equivalent of the radio's
decimal ASCII address.
For example, the following route command will
configure a routing entry to a radio with a MAC address of 1234-5678,
and an IP address 10.11.12.13:
.Pp
.Dl "# route add -host 10.11.12.13 -link 1:2:3:4:5:6:7:8"
.Pp
Generalising from this example to other IP addresses and to other 8-digit MAC addresses
should be clear.
.Sh RADIO CONFIGURATION
The Metricom radios can auto-baud at speeds up to 38.4k baud.
At higher speeds \(em 57600 or 115200 \(em the radio cannot autobaud.
When running at high speeds, the radio's serial port should be
manually configured to permanently run at the desired speed.
Use a terminal emulator and the Hayes command
.Em ATS304=115200
to set the serial baudrate to the specified number (or 0 for autobaud).
The command
.Em AT&w
will then save the current radio state in non-volatile memory.
.Pp
Metricom radios can operate in either "modem-emulation" mode
or in packet mode (Starmode).
The
.Nm
driver automatically detects if the radio has fallen out of starmode,
and resets it back into starmode, if the baud rate was set correctly
by
.Xr ldattach 8 .
.\" .Sh DIAGNOSTICS
.Sh SEE ALSO
.Xr arp 4 ,
.Xr inet 4 ,
.Xr ldattach 8 ,
.Xr route 8 ,
.Xr slip 8
.Sh HISTORY
.Nm
was originally developed for the Linux kernel by Stuart
Cheshire of Stanford's Operating Systems and Networking group,
as part of Mary Baker's MosquitoNet
.Sy http://mosquitonet.stanford.edu/mosquitonet.html
project.
This
.Nm
driver was ported to BSD by Jonathan Stone at Stanford's Distributed
Systems Group and first distributed with
.Nx 1.2 .
.Sh BUGS
Currently is IP-only.
Encapsulations for AppleTalk and ARP have been defined,
but are not yet implemented in this driver.
.Pp
.Nm
has not been widely tested on a variety of lower-level tty drivers.
.P
The detection and resetting of radios that crash out of Starmode does
not always work in this version of the driver.
One workaround is to kill the
.Xr ldattach 8
process, ifconfig the
.Nm
interface down, and then start a new ldattach and rerun ifconfig.