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.\"     @(#)slattach.8	6.4 (Berkeley) 3/16/91
.\"
.\" $FreeBSD: src/sbin/slattach/slattach.8,v 1.16.2.6 2003/02/23 21:17:43 trhodes Exp $
.\" $DragonFly: src/sbin/slattach/slattach.8,v 1.4 2008/05/09 20:31:04 swildner Exp $
.\"
.Dd April 4, 1993
.Dt SLATTACH 8
.Os
.Sh NAME
.Nm slattach
.Nd attach serial lines as network interfaces
.Sh SYNOPSIS
.Nm
.Op Fl a
.Op Fl c
.Op Fl e Ar exit-command
.Op Fl f
.Op Fl h
.Op Fl l
.Op Fl n
.Op Fl z
.Op Fl L
.Op Fl r Ar redial-command
.Op Fl s Ar baudrate
.Op Fl u Ar unit-command
.Op Fl K Ar keepalive
.Op Fl O Ar outfill
.Op Fl S Ar unit
.Ar ttyname
.Sh DESCRIPTION
The
.Nm
utility is used to assign a tty line to a network interface,
and to define the network source and destination addresses.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl a
Autoenable the VJ header compression option, if the other end of the link
is capable of VJ header compression then it will be used otherwise normal
headers will be used.
.It Fl c
Enable the VJ header compression option.  Note that both ends of the link
must be able to use VJ header compression for this to work.
.It Fl e Ar exit-command
Specify a command to be invoked within a shell
.Ql sh \-c Ar exit-command
before
.Nm
exits.
.It Fl f
Disable the invocation of daemon() to run
.Nm
in the background.
.It Fl h
Turn on cts/rts style flow control on the slip port, by default no flow
control is done.
.It Fl l
Disable modem control (CLOCAL) and ignore carrier detect on the slip
port.  By default the
.Ar redial-command
is invoked upon carrier drop and
.Nm
aborts if no
.Ar redial-command
is specified.
.It Fl n
Throw away ICMP packets.  The slip interface will ignore ICMP packets
to prevent slow lines being saturated by ICMP responses.
.It Fl r Ar redial-command
Specify a command to be invoked within a shell
.Ql sh \-c Ar redial-command
whenever carrier is lost on the modem line.
Empty
.Ar redial-command
(i.e.\&
.Fl r Qq "" )
cause connection reestablishing on leased line
without any external command invoked.
.It Fl s Ar baudrate
Specify the speed of the connection.
If not specified, the
default of 9600 is used.
.It Fl u Ar unit-command
When the line is switched to slip discipline, run
.Dq Nm "sh -c" Ar unit-command old new
where
.Ar old
and
.Ar new
are the slip unit numbers when the line was
last opened and the unit number of the current slip connection
respectively.  The unit number can change after redialing if you are
using more than one slip line.
When
.Nm
is connected for the first time,
.Dq Nm "sh -c" Ar unit-command \-1 new
is run.
When
.Nm
is disconnected,
.Dq Nm "sh -c" Ar unit-command old \-1
is run.
The
.Nm
utility will abort if the unit number
changes and
.Dq Fl u Ar \%unit-command
was not specified.
.It Fl z
Force redial
.Ar redial-command
upon startup irrespective of carrier.
.It Fl L
Use uucp-style device locking.
You need it unless you start
.Nm
from external program which already does uucp locking.
Default case is no uucp locking to satisfy such programs.
.It Fl K Ar keepalive
Set SLIP "keep alive" timeout in seconds.
If FRAME_END is not received in
this amount of time, re-connect occurs.
The default value is no timeout.
.It Fl O Ar outfill
Set SLIP "out fill" timeout in seconds.  It forces at least one FRAME_END
to be sent during this time period, which is necessary for the "keep alive"
timeout on the remote side.
The default value is no timeout.
.It Fl S Ar unit
Set the SLIP unit number directly.
Use with caution, because no check is made
for two interfaces with same number.
By default sliplogin dynamically assigns the unit number.
.It Ar ttyname
Specify the name of the tty device.
.Ar Ttyname
should be a string of the form
.Ql ttyXX
or
.Ql /dev/ttyXX .
.El
.Pp
Only the super-user may attach a network interface.
.Pp
To detach the interface, use
.Dq Li ifconfig interface-name down
after killing off the
.Nm
process using
.Ql kill -INT .
.Ar Interface-name
is the name that is shown by
.Xr netstat 1 .
.Pp
To setup
.Nm
to redial the phone when carrier is lost, use the
.Fl r Ar redial-command
option to specify a script or executable that will reconnect the
serial line to the slip server.  For example, the script could redial
the server and log in, etc.
.Pp
To reconfigure the network interface in case the slip unit number
changes, use the
.Fl u Ar unit-command
option to specify a script or executable that will be invoked as
.Ql sh \-c Ar unit-command old new
where
.Ar old
and
.Ar new
are the slip unit numbers before and after
reconnecting the line.  The unit number can change if you have more
than one line disconnect at the same time.  The first to succeed in
reconnecting will get the lowest unit number.
.Pp
To kill
.Nm
use
.Ql kill -INT
.Dv ( SIGINT )
which causes it to close the tty and exit.
.Pp
To force a redial, use
.Ql kill -HUP
.Dv ( SIGHUP )
which causes
.Nm
to think carrier was lost and thus invoke
.Ql sh \-c Ar redial-command
to reconnect to the server.
.Pp
If you use a hard-wired connection rather than a modem, invoke
.Nm
with the
.Fl l
option in order to ignore carrier on the slip line.
.Sh FILES
.Bl -tag -width /usr/share/examples/slattach/* -compact
.It Pa /var/run/slattach.<tty>.pid
with
.Ar tty
replaced by the terminal path name component of
.Ar ttyname .
This file contains the numerical process ID of the
.Nm
process and can be examined by scripts in order to send a signal to
.Nm
.It Pa /usr/share/examples/slattach/*
.El
.Sh EXAMPLES
.Bd -literal -offset indent -compact
slattach ttyd8
slattach \-s 4800 /dev/ttyd1
slattach \-c \-s 38400 /dev/cuaa1
slattach \-r 'kermit -y dial.script >kermit.log 2>&1'
.Ed
.Sh DIAGNOSTICS
Look for error messages in
.Pa /var/log/messages
.No ( Nm
is a daemon).
Messages indicating the specified interface does not exit, the
requested address is unknown, the user is not privileged and tried to
alter an interface's configuration are logged there.
The
.Nm
utility
also logs failure to set the controlling terminal or failure to install
signal handlers.  Upon connection and redial the ttyname and baud rate
are logged and on shutdown the ttyname is logged.
.Sh SEE ALSO
.Xr netstat 1 ,
.Xr startslip 1 ,
.Xr uustat 1 ,
.Xr netintro 4 ,
.Xr ifconfig 8 ,
.Xr rc 8 ,
.Xr sliplogin 8
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.3 .