Computer Science
DIP(8) Reference DIP(8)
NAME
dip - handle dialup IP connections
SYNOPSIS
dip [-v] [-m mtu] [-p proto] scriptfile
dip -t [-v]
dip -i [-a] [-v]
diplogin [username]
diplogini
dip [-v] -k [-l tty_line]
DESCRIPTION
dip handles the connections needed for dialup IP links,
like SLIP or PPP. It can handle both incoming and outgo-
ing connections, using password security for incoming con-
nections. The outgoing connections use the system's
dial(3) library if available.
The first form interprets scriptfile to dial out and open
an IP connection (see DIALOUT MODE below).
The -t option runs dip interactively (see COMMAND MODE
below). This is most useful while gathering data to set
up a chat script.
dip -i handles incoming connections (see DIALIN MODE
below). diplogin is equivalent to dip -i, and diplogini
is equivalent to dip -i -a. These are mainly for use with
versions of login(1) that do not pass command line parame-
ters to the shell program.
dip -k kills an existing dip process, closing the connec-
tion.
OPTIONS
-a Prompt for user name and password.
-i Act as a dialin server (see DIALIN MODE below).
-k Kill the dip process that runs (has locked) the
specified tty device (see -l option), or else the
most recent invocation of dip. Note that dip takes
care not to kill a process started by somebody else
(unless it's root who demands the operation :-).
-l tty_line
Indicate the line to be killed. (Requires -k
option.)
-m mtu Set the Maximum Transfer Unit (MTU) (default 296).
-p proto
Set the line protocol. proto must be one of: SLIP,
CSLIP, PPP, or TERM.
-t Run in test mode (see COMMAND MODE below).
-v Set verbose mode. This enables various debug
printouts, including an echo of each line of the
chat script.
COMMAND MODE
The first possible use of dip is as an interactive program
to set up an outgoing IP connection. This can be done by
invoking dip with the -t option, which means enter TEST
mode and, more precisely, dumps you in the COMMAND-MODE of
the dip program. You are reminded of this by the DIP>
prompt, or, if you also specified the -v debugging flag,
the DIP [NNNN]> prompt. The latter prompt also displays
the current value of the global $errlvl variable, which is
used mostly when dip runs in script mode. For the inter-
active mode, it can be used to determine if the result of
the previous command was OK or not.
The following is a sample taken from a live session:
$dip -t
DIP: Dialup IP Protocol Driver version 3.3.7n-uri (7 Mar 95)
Written by Fred N. van Kempen, MicroWalt Corporation.
DIP> _
The possible commands are listed below (see COMMANDS).
Note particularly the help command. Each command displays
a usage message if it is invoked incorrectly. Just exper-
iment a little to get the feel of it, and have a look at
the sample script file, which also uses this command lan-
guage (see EXAMPLES).
DIALOUT MODE
The second way of using dip is to initiate outgoing con-
nections. To make life easier for the people who have to
manage links of this type, dip uses a chat script to set
up a link to a remote system. This gives the user an
enormous amount of flexibility when making the connection,
which otherwise could require many command-line options.
The path name of the script to be run is then given as the
single argument to dip. If scriptfile has no file exten-
sion, dip will automatically add the extension ".dip".
This is just a way to group scripts together in a single
directory.
DIALIN MODE
The third possible way of using dip is as a login shell
for incoming IP connections, as in dialup SLIP and PPP
connections. To make integration into the existing UNIX
system as easy as possible, dip can be installed by simply
naming it as the login shell in /etc/passwd. A sample
entry looks like:
suunet:ij/SMxiTlGVCo:1004:10:UUNET:/tmp:/usr/sbin/diplogin
When user suunet logs in, the login(1) program sets the
home directory to /tmp and executes the diplogin program.
diplogin should be a symbolic link to dip, which means
that dip must run in input mode. dip then tries to locate
the name of the logged in user (i.e. the name correspond-
ing to its current user id, as returned by the getuid(2)
system call) in its database file. An optional single
argument to the dip program in this mode can be the user-
name that must be used in this lookup, regardless the cur-
rent user id.
dip now scans /etc/diphosts for an entry for the given
user name. This file contains lines of text (much like
the standard password file). Any line starting with # is
a comment. Otherwise, each line has seven colon-separated
items, in the format
user : password : remote host : local host : netmask :
comments : protocol,MTU
The first field of a line is the user name, which we must
match.
The second field can contain an encrypted password. If
this field is non-null, dip displays the prompt "External
security password:", and the reply must match the password
in this field. If this field is "s/key" (check the value
of SKEY_TOKEN in dip.h) and dip was compiled with S/Key
enabled, then S/Key authentication will take place (see
README.SKEY in the dip source directory).
The third field contains the name (or raw IP address) of
the remote host. If a host name is given, the usual
address resolving process is started, using either a name
server or a local hosts file.
The fourth field contains the name (or raw IP address) of
the local host. If a host name is given, it's resolved,
just like the remote host name in the third field.
The fifth field contains the netmask in decimal dotted
notation (like 255.255.255.0). If empty, 255.255.255.0 is
used by default.
The sixth field may contain any text; it is not used by
dip.
Finally, the seventh field of a line contains a mixture of
comma-separated flags. Possible flags are:
SLIP to indicate we must use the SLIP protocol.
CSLIP to indicate Compressed SLIP protocol.
PPP to indicate we must use the PPP protocol.
number which gives the MTU parameter of this connection.
Please note: my experience shows smaller blocks (i.e.
smaller MTU) work better. You *can* define MTU 1500, but
it won't vouch for your sanity.
After finding the correct line, dip puts the terminal line
into RAW mode, and asks the system networking layer to
allocate a channel of the desired protocol. Finally, if
the channel is activated, it adds an entry to the system's
routing table to make the connection work.
dip now goes into an endless loop of sleeping, which con-
tinues until the connection is physically aborted (i.e.
the line is dropped). At that time, dip removes the entry
it made in the system's routing table, and releases the
protocol channel for re-use. It then exits, making room
for another session.
COMMANDS
The following may appear in a chat script. Most can also
be used in command mode:
label: Define a label.
beep [times]
Beep on user's terminal [this many times].
bootp [howmany [howlong]]
Use BOOTP protocol to fetch local and remote IP
addresses.
break Send a BREAK.
chatkey keyword [code]
Add to dip's collection of modem response words.
For example,
chatkey CONNECT 1
would duplicate one of the existing entries.
config [interface|routing] [pre|up|down|post] {argu-
ments...}
Store interface configuration parameters. (This
may be disabled by the administrator.)
databits 7|8
Set the number of data bits.
dec $variable [decrement-value|$variable]
Decrement a variable. The default decrement-value
is 1.
default
Tells DIP to set up the default route to the remote
host it made a connection to. If this command
isn't present in the command file, the default
route won't be set/changed.
dial phonenumber [timeout]
Dials the indicated number. The default timeout is
60 sec. dip parses the string returned by the
modem, and sets $errlvl accordingly. The standard
codes are as follows:
0 OK
1 CONNECT
2 ERROR
3 BUSY
4 NO CARRIER
5 NO DIALTONE
You can change or add to these with the chatkey
command.
echo on|off
Enables or disables the display of modem commands.
exit [exit-status]
Exit script leaving established [C]SLIP connection
intact and dip running.
flush Flush input on the terminal.
get $variable [value | ask | remote [timeout_value |
$variable]]
Get or ask for the value of a variable. If the
second parameter is ask, a prompt is printed and
the value is read from standard input. If it is
remote, it is read from the remote machine. Other-
wise, the second parameter is a constant or another
variable which supplies the value.
goto label
Transfer control to the indicated label in the chat
script.
help Print list of commands, similar to this:
DIP> help
DIP knows about the following commands:
beep bootp break chatkey config databits
dec default dial echo flush get
goto help if inc init mode
modem netmask onexit parity password proxyarp
print port quit reset securidf securid
send shell sleep speed stopbits term
timeout wait
DIP> _
if expr goto label
Test some result code. The expr must have the form
$variable op constant
where op is one of: == != < > <= >=.
inc $variable [increment-value|$variable]
Increment a variable. The default increment-value
is 1.
init init-string
Set the initialization string (sent to the modem
before dialing) to the indicated string (default
ATE0 Q0 V1 X1). Please use it!
mode SLIP|CSLIP|PPP|TERM
Set the line protocol (default SLIP).
modem modem-name
Set the type of modem. (The default, and at pre-
sent the only legal value, is HAYES).
netmask xxx.xxx.xxx.xxx
Indicate the netmask we will want to use.
onexit .......
Description is missing - look through the source in
command.c. Or ask <inaky@@peloncho.fis.ucm.es> -
he wrote it (:-).
parity E|O|N
Set the type of parity.
password
Prompt for a password and send it.
proxyarp
Request Proxy ARP to be set.
print $variable
Print the contents of some variable.
psend command [arguments]
Send the output of command to the serial driver,
optionally passing arguments to command. The UID is
reset to the real UID before running command.
port tty_name
Set the name of the terminal port to use. (The
path /dev/ is assumed.)
quit Exit with nonzero exit status.
reset Reset the modem. (Sends "+++" then "ATZ".)
securidf fixedpart
Store the fixed part of the SecureID password.
securid
Prompt for the variable part of the password gener-
ated by the ACE System SecureID card. The fixed
part of the password must already have been stored
using a secureidf command. The two parts are con-
catenated and sent to the remote terminal server.
send text-string
Send a string to the serial driver.
shell command [parameters]
Executes command through the default shell
(obtained from the SHELL variable) with parameters
as the command-line arguments. Dip variable sub-
stitution is performed before executing the com-
mand. If you don't want a parameter beginning with
a $ to be interpreted as a dip variable, precede it
with a \.
skey [timeout | $variable]
This tells dip to look for an S/Key challenge from
the remote terminal server. dip then prompts the
user for the secret password, generates the
response, and sends it to the remote host. The
optional parameter timeout sets how long dip is to
wait to see the challenge. $errlvl is set to 1 if
the skey command times out. If skey successfully
sends a response, $errlvl is set to 0. Requires
S/Key support to be compiled in.
sleep time-in-secs
Wait some time.
speed bits-per-sec
Set port speed (default 38400). Note that the
actual speed associated with "38400" can be changed
using setserial(8). Also, you should tell port's
real speed here, as dip takes care of the set_hi
and such bits by itself. Also, don't be afraid, if
you told the speed "57600" and it reports back
"38400" - everything's OK, the proper flags were
applied and the real port speed will be what you
told it to be, i.e. "57600".
stopbits 1|2
Set the number of stop bits.
term Enter a terminal mode.
timeout time-in-sec
Set timeout. This defines the period of inactivity
on the line, after which DIP will force the line
down and break the connection (and exit).
wait text [timeout_value | $variable]
Wait for some string to arrive.
SPECIAL VARIABLES
$errlvl
Holds the result of the previous command.
$locip IP number of local host in dotted quad notation
(for example, 128.96.41.50).
$local Fully qualified local host name (for example, sun-
site.unc.edu).
$rmtip IP number of remote host in dotted quad notation.
$remote
Fully qualified remote host name.
$mtu Maximum Transfer Unit (maximum number of bytes
transferred at once).
$modem Modem type (at present the only valid value is
HAYES).
$port The name of the terminal port to use. (The path
/dev/ is assumed.)
$speed Transfer rate between the local host and the modem,
in bits/sec.
EXAMPLES
Here is a sample /etc/diphosts:
#
# diphosts This file describes a number of name-to-address
# mappings for the DIP program. It is used to determine
# which host IP address to use for an incoming call of
# some user.
#
# Version: @(#)diphosts 1.20 05/31/94
#
# Author: Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
# Modified: Uri Blumenthal <uri@watson.ibm.com>
#
# name : pwd : hostname : local server: netmask: comments : protocol,mtu
#==================================================
sbonjovi::bonjovi:server1:netmask:MicroWalt "bonjovi" SLIP:SLIP,296
sroxette::roxette:server2:netmask:MicroWalt "roxette" SLIP:CSLIP,296
stephen:s/key:tuin:server3:netmask:S/Key Authenticated login:CSLIP,296
# End of diphosts.
A chat script should look something like this:
#
# sample.dip Dialup IP connection support program.
#
# Version: @(#)sample.dip 1.40 07/20/93
#
# Author: Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
#
main:
# First of all, set up our name for this connection.
# I am called "uwalt.hacktic.nl" (== 193.78.33.238)
get $local uwalt.hacktic.nl
# Next, set up the other side's name and address.
# My dialin machine is called 'xs4all.hacktic.nl' (== 193.78.33.42)
get $remote xs4all.hacktic.nl
# Set netmask on sl0 to 255.255.255.0
netmask 255.255.255.0
# Set the desired serial port and speed.
port cua02
speed 38400
# Reset the modem and terminal line.
# This seems to cause trouble for some people!
reset
# Note! "Standard" pre-defined "errlvl" values:
# 0 - OK
# 1 - CONNECT
# 2 - ERROR
# 3 - BUSY
# 4 - NO CARRIER
# 5 - NO DIALTONE
#
# You can change these with the chatkey command
# Prepare for dialing.
send ATQ0V1E1X4\r
wait OK 2
if $errlvl != 0 goto modem_trouble
dial 555-1234567
if $errlvl != 1 goto modem_trouble
# We are connected. Login to the system.
login:
sleep 2
wait ogin: 20
if $errlvl != 0 goto login_error
send MYLOGIN\n
wait ord: 20
if $errlvl != 0 goto password_error
send MYPASSWD\n
loggedin:
# We are now logged in.
wait SOMETEXT 15
if $errlvl != 0 goto prompt_error
# Set up the SLIP operating parameters.
get $mtu 296
# Ensure "route add -net default xs4all.hacktic.nl" will be done
default
# Say hello and fire up!
done:
print CONNECTED $locip ---> $rmtip
mode CSLIP
goto exit
prompt_error:
print TIME-OUT waiting for SLIPlogin to fire up...
goto error
login_trouble:
print Trouble waiting for the Login: prompt...
goto error
password_error:
print Trouble waiting for the Password: prompt...
goto error
modem_trouble:
print Trouble occurred with the modem...
error:
print CONNECT FAILED to $remote
quit 1
exit:
exit
This script causes dip to dial up a host, log in, and get
a SLIP interface channel going (in the same manner as with
incoming connections). When all is set up, it simply goes
into the background and waits for a hangup (or just a
lethal signal), at which it hangs up and exits.
FILES
/etc/passwd
/etc/diphosts
/etc/rc.dip (for example)
BUGS
Virtually none - what you see are features (:-).
AUTHORS
Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>,
Uri Blumenthal <uri@watson.ibm.com>,
Paul Cadach <paul@paul.east.alma-ata.su>,
John Edwards <pje120@cs.usask.ca>,
Olaf Kirch <okir@monad.sub.de>,
Pauline Middelink <middelin@calvin.iaf.nl>,
Paul Mossip <mossip@vizlab.rutgers.edu>,
Bill Reynolds,
Jim Seagrave <jes@grendel.demon.co.uk>,
Stephen Shortland <stephen@cork.cig.mot.com>,
Daniel Suman,
Jeff Uphoff <juphoff@aoc.nrao.edu>
SEE ALSO
login(1), skey(1), getuid(2), dial(3), ifconfig(8), net-
stat(8), route(8), setserial(8)
Version 3.3.7o 3/7/95 1
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