--- name: "dip" section: "8" platform: "linux" package: "dip" version: "3.3.7p-2" release: "Debian 2.1 (Slink)" platforms: ["linux"] url: "https://new.carta.tech/dip" --- # dip(8) handle dialup IP connections ## 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)](/login/1.md) 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, SLIP6, CLSIP6, 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)](/login/1.md) 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)](/getuid/2.md) 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.\ **AUTO** to autodetect whether the client uses SLIP or CSLIP\ **SLIP6** to indicate we must use the SLIP6 protocol.\ **CSLIP6** to indicate Compressed SLIP6 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* \[*timeout*\] Sends the string in the **init** variable to initialize the modem and then 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 securid securidfixed 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 with the **dial** command) to the indicated string (default is ATE0 Q0 V1 X4). *Please* use it! - **mode SLIP**\|**CSLIP**\|**SLIP6**\|**CSLIP6**\|**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** ....... Execute a command upon dip's exit. This works exactly like the shell command, but it is only executed when dip finishes (as it's name indicates ... ;). The onexit command which is executed is the one you entered last, thus, previous onexit commands are deleted by the new ones (confused? me too :). - **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".) Does not work properly on several modems, so beware! I do not use it. - **securidfixed** *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)](/setserial/8.md). 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, # Modified: Uri Blumenthal # # 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, # 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. get $init ATQ0V1E1X4 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 , Uri Blumenthal , Paul Cadach , Colten Edwards , Olaf Kirch , Pauline Middelink , Paul Mossip , Bill Reynolds, Jim Seagrave , Stephen Shortland , Daniel Suman, Jeff Uphoff ``` ## SEE ALSO [**login**(1)](/login/1.md), [**skey**(1)](/skey/1.md), [**getuid**(2)](/getuid/2.md), **dial**(3), [**ifconfig**(8)](/ifconfig/8.md), [**netstat**(8)](/netstat/8.md), [**route**(8)](/route/8.md), [**setserial**(8)](/setserial/8.md)