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dip (8)

>> dip (8) ( Linux man: Команды системного администрирования )

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 outgoing connections, using password security for incoming connections. 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 parameters to the shell program.

dip -k kills an existing dip process, closing the connection.

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 interactive 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 experiment a little to get the feel of it, and have a look at the sample script file, which also uses this command language (see EXAMPLES).

DIALOUT MODE

The second way of using dip is to initiate outgoing connections. 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 extension, 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 corresponding 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 username that must be used in this lookup, regardless the current 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 continues 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] {arguments...}

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. Otherwise, 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 present 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 generated 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 concatenated 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 substitution is performed before executing the command. 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, sunsite.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, <[email protected]>
# Modified:     Uri Blumenthal      <[email protected]>
#
# 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, <[email protected]>
#

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 <[email protected]>,


Uri Blumenthal <[email protected]>,


Paul Cadach <[email protected]>,


John Edwards <[email protected]>,


Olaf Kirch <[email protected]>,


Pauline Middelink <[email protected]>,


Paul Mossip <[email protected]>,


Bill Reynolds,


Jim Seagrave <[email protected]>,


Stephen Shortland <[email protected]>,


Daniel Suman,


Jeff Uphoff <[email protected]>