slattach(8)

NAME

slattach - attach serial lines as network interfaces

SYNOPSIS

slattach [-acfhLlnz] [-e exit-command]  [-K  keepalive]  [-O
outfill]
         [-r  redial-command]  [-S  unit]  [-s baudrate] [-u
unit-command]
         ttyname

DESCRIPTION

The slattach utility is used to assign a tty line to a net

work interface,
and to define the network source and destination addresses.

The following options are available:

-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.

-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.

-e exit-command

Specify a command to be invoked within a shell `sh

-c
exit-command' before slattach exits.

-f Disable the invocation of daemon() to run slattach

in the back

ground.

-h Turn on cts/rts style flow control on the slip port,

by default

no flow control is done.

-l Disable modem control (CLOCAL) and ignore carrier

detect on the

slip port. By default the redial-command is invoked

upon carrier
drop and slattach aborts if no redial-command is

specified.

-n Throw away ICMP packets. The slip interface will

ignore ICMP

packets to prevent slow lines being saturated by

ICMP responses.

-r redial-command

Specify a command to be invoked within a shell `sh

-c
redial-command' whenever carrier is lost on the mo

dem line.
Empty redial-command (i.e. -r "") cause connection

reestablishing
on leased line without any external command invoked.

-s baudrate

Specify the speed of the connection. If not speci

fied, the
default of 9600 is used.

-u unit-command

When the line is switched to slip discipline, run

``sh -c
unit-command old new'' where old and new are the

slip unit numbers when the line was last opened and the unit num

ber of the
current slip connection respectively. The unit num

ber can change
after redialing if you are using more than one slip

line. When
slattach is connected for the first time, ``sh -c

unit-command -1
new'' is run. When slattach is disconnected, ``sh

-c
unit-command old -1'' is run. The slattach utility

will abort if
the unit number changes and ``-u unit-command'' was

not specified.

-z Force redial redial-command upon startup irrespec

tive of carrier.

-L Use uucp-style device locking. You need it unless

you start

slattach from external program which already does

uucp locking.
Default case is no uucp locking to satisfy such pro

grams.

-K 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.

-O 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.

-S unit

Set the SLIP unit number directly. Use with cau

tion, because no
check is made for two interfaces with same number.

By default
sliplogin dynamically assigns the unit number.

ttyname

Specify the name of the tty device. Ttyname should

be a string
of the form `ttyXX' or `/dev/ttyXX'.

Only the super-user may attach a network interface.

To detach the interface, use ``ifconfig interface-name

down'' after
killing off the slattach process using `kill -INT'.

Interface-name is
the name that is shown by netstat(1).

To setup slattach to redial the phone when carrier is lost,

use the -r
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.

To reconfigure the network interface in case the slip unit

number
changes, use the -u unit-command option to specify a script

or executable
that will be invoked as `sh -c unit-command old new' where

old and new
are the slip unit numbers before and after reconnecting the

line. The
unit number can change if you have more than one line dis

connect at the
same time. The first to succeed in reconnecting will get

the lowest unit
number.

To kill slattach use `kill -INT' (SIGINT) which causes it to

close the
tty and exit.

To force a redial, use `kill -HUP' (SIGHUP) which causes

slattach to
think carrier was lost and thus invoke `sh -c

redial-command' to reconnect to the server.

If you use a hard-wired connection rather than a modem, in

voke slattach
with the -l option in order to ignore carrier on the slip

line.

FILES

/var/run/slattach.<tty>.pid with tty replaced by the

terminal path

name component of ttyname.

This file
contains the numerical pro

cess ID of the
slattach process and can be

examined by
scripts in order to send a

signal to
slattach

/usr/share/examples/slattach/*

EXAMPLES

slattach ttyd8
slattach -s 4800 /dev/ttyd1
slattach -c -s 38400 /dev/cuad1
slattach -r 'kermit -y dial.script >kermit.log 2>&1'

DIAGNOSTICS

Look for error messages in /var/log/messages (slattach 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 slattach

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.

SEE ALSO

netstat(1), startslip(1), netintro(4), ifconfig(8), rc(8),

sliplogin(8)

HISTORY

The slattach utility appeared in 4.3BSD.

BSD April 4, 1993

BSD