PPP(8)

NAME
ppp - Point to Point Protocol (aka iijppp)

SYNOPSIS
ppp [-auto - -direct -dedicated]

DESCRIPTION
This is a user process PPP software package. Normally, PPP is implemented as a part of the kernel (e.g. as managed by pppd) and it's thus somewhat hard to debug and/or modify its behavior. However, in this implementation PPP is done as a user process with the help of the tunnel device driver (tun).

Major Features

Provides interactive user interface. Using its command mode, the user can easily enter commands to establish the connection with the remote end, check the status of connection and close the connection. All functions can also be optionally password protected for security.

Supports both manual and automatic dialing. Interactive mode has a “term” command which enables you to talk to your modem directly. When your modem is connected to the remote peer and it starts to talk PPP , the PPP software detects it and switches to packet mode automatically. Once you have determined the proper sequence for connecting with the remote host, you can write a chat script to define the necessary dialing and login procedure for later convenience.

Supports on-demand dialup capability. By using auto mode, ppp will act as a daemon and wait for a packet to be sent over the PPP link. When this happens, the daemon automatically dials and establishes the connection.

Supports server-side PPP connections. Can act as server which accepts incoming PPP connections.

Supports PAP and CHAP authentication.

Supports Proxy Arp. When PPP is set up as server, you can also configure it to do proxy arp for your connection.

Supports packet filtering. User can define four kinds of filters: ifilter for incoming packets, ofilter for outgoing packets, dfilter to define a dialing trigger packet and afilter for keeping a connection alive with the trigger packet.

Tunnel driver supports bpf. The user can use tcpdump(1) to check the packet flow over the PPP link.

Supports PPP over TCP capability.

Supports IETF draft Predictor-1 compression. ppp supports not only VJ-compression but also Predictor-1 compression. Normally, a modem has built-in compression (e.g. v42.bis) and the system may receive higher data rates from it as a result of such compression. While this is generally a good thing in most other situations, this higher speed data imposes a penalty on the system by increasing the number of serial interrupts the system has to process in talking to the modem and also increases latency. Unlike VJ-compression, Predictor-1 compression pre-compresses all data flowing through the link, thus reducing overhead to a minimum.

Runs under BSDI-1.1 and FreeBSD.
Patches for NeXTSTEP 3.2 are also available on the net.

GETTING STARTED
When you first run ppp you may need to deal with some initial configuration details. First, your kernel should include a tunnel device (the default in FreeBSD 2.0.5 and later). If it doesn't, you'll need to rebuild your kernel with the following line in your kernel configuration file:
    pseudo-device tun 1
You should set the numeric field to the maximum number of PPP connections you wish to support. Second, check your /dev directory for the tunnel device entry /dev/tun0. If it doesn't exist, you can create it by running "MAKEDEV tun0"

MANUAL DIALING
% ppp User Process PPP written by Toshiharu OHNO. * If you set your hostname and password in /etc/ppp/ppp.secret, you can't do anything except run the quit and help commands * ppp on "your hostname"> help passwd : Password for security quit : Quit the PPP program help : Display this message ppp on tama> pass <password> * "on" will change to "ON" if you specify the correct password. * ppp ON tama> * You can specify the device name and speed for your modem using the following commands: * ppp ON tama> set line /dev/cuaa0 ppp ON tama> set speed 38400 ppp ON tama> set parity even ppp ON tama> show modem * Modem related parameters are shown in here * ppp ON tama> * Use term command to talk with your modem * ppp ON tama> term at OK atdt123456 CONNECT login: ppp Password: * PPP started in remote side. When the peer start to talk PPP, the program will detect it automatically and return to command mode. * ppp ON tama> PPP ON tama> * NOW, you are connected! Note that ‘PPP’ in the prompt has changed to capital letters to indicate this. * PPP ON tama> show lcp * You'll see LCP status * PPP ON tama> show ipcp * You'll see IPCP status. At this point, your machine has a host route to the peer. If you want to add a default route entry, then enter the following command. * PPP ON tama> add 0 0 HISADDR * The string ‘HISADDR’ represents the IP address of connected peer. * PPP ON tama> * Use network applications (i.e. ping, telnet, ftp) in other windows * PPP ON tama> show log * Gives you some logging messages * PPP ON tama> close * The connection is closed and modem will be disconnected. * ppp ON tama> quit %

AUTOMATIC DIALING
To use automatic dialing, you must prepare some Dial and Login chat scripts. See the example definitions in /etc/ppp/ppp.conf.sample (the format of ppp.conf is pretty simple).
•   Each line contains one command, label or comment.
•   A line starting with a ‘#’ character is treated as a comment line.
•   A label name has to start in the first column and should be followed by a colon (:).
•   A command line must contain a space or tab in the first column.
Once ppp.conf is ready, specify the destination label name when you invoke ppp. Commands associated with the destination label are then executed. Note that the commands associated with the “default” label are ALWAYS executed. Once the connection is made, you'll find that the ppp portion of the prompt has changed to PPP. % ppp pm2 ... ppp ON tama> dial dial OK! login OK! PPP ON tama> If the /etc/ppp/ppp.linkup file is available, its contents are executed when the PPP connection is established. See the provided example which adds a default route. The string HISADDR represents the IP address of the remote peer.

DIAL ON DEMAND
To play with demand dialing, you must use the -auto option. You must also specify the destination label in /etc/ppp/ppp.conf to use. It should contain the “ifaddr” command to define the remote peer's IP address. (refer to /etc/ppp/ppp.conf.sample) % ppp -auto pm2demand ... % When -auto is specified, ppp runs as a daemon but you can still configure or examine its configuration by using the diagnostic port as follows: % telnet localhost 3000 Trying 127.0.0.1... Connected to localhost.spec.co.jp. Escape character is '^]'. User Process PPP. Written by Toshiharu OHNO. Working as auto mode. PPP on tama> show ipcp what ? PPP on tama> pass xxxx PPP ON tama> show ipcp IPCP [OPEND] his side: xxxx ....

Each ppp daemon has an associated port number which is computed as "3000 + tunnel_device_number". If 3000 is not good base number, edit defs.h in the ppp sources ( /usr/src/usr.sbin/ppp) and recompile it. When an outgoing packet is detected, ppp will perform the dialing action (chat script) and try to connect with the peer. If the connect fails, the default behavior is to wait 30 seconds and then attempt to connect when another outgoing packet is detected. This behavior can be changed with

    set redial seconds|random [dial_attempts]

Seconds is the number of seconds to wait before attempting to connect again. If the argument is ‘random’, the delay period is a random value between 0 and 30 seconds. ‘dial_attempts’ is the number of times to try to connect for each outgoing packet that is received. The previous value is unchanged if this parameter is omitted.

    set redial 10 4

will attempt to connect 4 times for each outgoing packet that is detected with a 10 second delay between each attempt. Modifying the dial delay is very useful when running ppp in demand dial mode on both ends of the link. If each end has the same timeout, both ends wind up calling each other at the same time if the link drops and both ends have packets queued. To terminate the program, type PPP ON tama> close ppp ON tama> quit all

A simple “quit” command will terminate the telnet connection but not the program itself. You must use “quit all” to terminate the program as well.

PACKET FILTERING
This implementation supports packet filtering. There are three kinds of filters: ifilter, ofilter and dfilter. Here are the basics:
•   A filter definition has the following syntax: set filter-name rule-no action [src_addr/src_width] [dst_addr/dst_width] [proto [src [lt|eq|gt] port ]] [dst [lt|eq|gt] port] [estab]

    1.  ‘filter-name’ should be one of ifilter, ofilter, or dfilter.

    2.  There are two actions: ‘permit’ and ‘deny’. If a given packet matches the rule, the associated action is taken immediately.

    3.  ‘src_width’ and ‘dst_width’ work like a netmask to represent an address range.

    4.  ‘proto’ must be one of icmp, udp or tcp.

    5.  ‘port number’ can be specified by number and service name from /etc/services.
•   Each filter can hold up to 20 rules, starting from rule 0. The entire rule set is not effective until rule 0 is defined.
•   If no rule is matched to a packet, that packet will be discarded (blocked).
•   Use “set filter-name -1” to flush all rules.
See /etc/ppp/ppp.conf.filter.example.

RECEIVING INCOMING PPP CONNECTIONS
To handle an incoming PPP connection request, follow these steps:

1.  Make sure the modem and (optionally) /etc/rc.serial is configured correctly.
    •   Use Hardware Handshake (CTS/RTS) for flow control.
    •   Modem should be set to NO echo back (ATE0) and NO results string (ATQ1).

2.  Edit /etc/ttys to enable a getty on the port where the modem is attached. For example:
        ttyd1 /usr/libexec/getty std.38400 dialup on secure
    Don't forget to send a HUP signal to the init process to start the getty.
        # kill -HUP 1

3.  Prepare an account for the incoming user.

        ppp:xxxx:66:66:PPP Login User:/home/ppp:/usr/local/bin/ppplogin

4.  Create a /usr/local/bin/ppplogin file with the following contents:

        #!/bin/sh -p
        exec /usr/sbin/ppp -direct

    (You can specify a label name for further control.)

Direct mode ( -direct) lets ppp work with stdin and stdout. You can also telnet to port 3000 to get command mode control in the same manner as client-side ppp.

SETTING IDLE, LINE QUALITY REQUEST, RETRY TIMER
To check/set idletimer, use the “show timeout” and “set timeout [lqrtimer [retrytimer]]” commands. Ex:
    ppp ON tama> set timeout 600
The timeout period is measured in seconds, the default values for which are timeout = 180 or 3 min, lqrtimer = 30sec and retrytimer = 3sec. To disable the idle timer function, use the command “set timeout 0”. In -auto mode, an idle timeout causes the PPP session to be closed, though the ppp program itself remains running. Another trigger packet will cause it to attempt to reestablish the link.

Predictor-1 compression
This version supports CCP and Predictor type 1 compression based on the current IETF-draft specs. As a default behavior, ppp will attempt to use (or be willing to accept) this capability when the peer agrees (or requests it). To disable CCP/predictor functionality completely, use the “disable pred1” and “deny pred1” commands.

Controlling IP address
ppp uses IPCP to negotiate IP addresses. Each side of the connection specifies the IP address that it's willing to use, and if the requested IP address is acceptable then ppp returns ACK to the requester. Otherwise, ppp returns NAK to suggest that the peer use a different IP address. When both sides of the connection agree to accept the received request (and send ACK), IPCP is set to the open state and a network level connection is established. To control this IPCP behavior, this implementation has the “set ifaddr” command for defining the local and remote IP address:
    ifaddr src_addr dst_addr
Where, ‘src_addr’ is the IP address that the local side is willing to use and ‘dst_addr’ is the IP address which the remote side should use. Ex:
    ifaddr 192.244.177.38 192.244.177.2
The above specification means:
•   I strongly want to use 192.244.177.38 as my IP address, and I'll disagree if the peer suggests that I use another address.
•   I strongly insist that peer use 192.244.177.2 as own side address and don't permit it to use any IP address but 192.244.177.2. When peer request another IP address, I always suggest that it use 192.244.177.2.
•   This is all fine when each side has a pre-determined IP address, however it is often the case that one side is acting as a server which controls all IP addresses and the other side should obey the direction from it.
In order to allow more flexible behavior, `ifaddr' command allows the user to specify IP address more loosely:
    ifaddr 192.244.177.38/24 192.244.177.2/20
A number followed by a slash (/) represent the number of bits significant in the IP address. The above example signifies that:
•   I'd like to use 192.244.177.38 as my address if it is possible, but I'll also accept any IP address between 192.244.177.0 and 192.244.177.255.
•   I'd like to make him use 192.244.177.2 as his own address, but I'll also permit him to use any IP address between 192.244.176.0 and 192.244.191.255.
•   As you may have already noticed, 192.244.177.2 is equivalent to saying 192.244.177.2/32.
•   As an exception, 0 is equivalent to 0.0.0.0/0, meaning that I have no preferred IP address and will obey the remote peer's selection.
•   192.244.177.2/0 means that I'll accept/permit any IP address but I'll try to insist that 192.244.177.2 be used first.

Connecting with your service provider

1.  Describe provider's phone number in DialScript: Use the “set dial” or “set phone” commands.

2.  Describe login procedure in LoginScript: Use the “set login” command.

3.  Use “set ifaddr” command to define the IP address.

    •   If you know what IP address provider uses, then use it as the remote address.

    •   If provider has assigned a particular IP address to you, then use it as your address.

    •   If provider assigns your address dynamically, use 0 as your address.

    •   If you have no idea which IP addresses to use, then try “set ifaddr 0 0”.

4.  If provider requests that you use PAP/CHAP authentication methods, add the next lines to your ppp.conf file:

        enable pap (or enable chap)
        disable chap (or disable pap)
        set authname MyName
        set authkey MyPassword

Please refer to /etc/ppp/ppp.conf.iij for some real examples.

Logging facility
ppp is able to generate the following log info into /var/log/ppp.log:
Phase Phase transition log output
Chat Generate Chat script trace log
LQM Generate LQR report
LCP Generate LCP/IPCP packet trace
TCP/IP Dump TCP/IP packet
HDLC Dump HDLC packet in hex
Async Dump async level packet in hex
The “set debug” command allows you to set logging output level, of which multiple levels can be specified. The default is equivalent to “set debug phase lcp”.

MORE DETAILS
•   Please read the Japanese doc for complete explanation. It may not be useful for non-japanese readers, but examples in the document may help you to guess.
•   Please read example configuration files.
•   Use “help”, “show”? and “set”? commands.
•   NetBSD and BSDI-1.0 were supported in previous releases but are no longer supported in this release. Please contact the author if you need old driver code.

FILES
ppp refers to three files: ppp.conf, ppp.linkup and ppp.secret. These files are placed in /etc/ppp, but the user can create his own files under his $HOME directory as ppp will always try to consult the user's personal setup first.

$HOME/ppp/.ppp.[conf|linkup|secret]
    User dependent configuration files.

/etc/ppp/ppp.conf
    System default configuration file.

/etc/ppp/ppp.secret
    An authorization file for each system.

/etc/ppp/ppp.linkup
    A file to check when ppp establishes a network level connection.

/var/log/ppp.log
    Logging and debugging information file.

/var/spool/lock/Lck..*
    tty port locking file.

/var/run/PPP.system
    Holds the pid for ppp -auto system.

/etc/services
    Get port number if port number is using service name.

HISTORY
This program was submitted in FreeBSD-2.0.5 Atsushi Murai (amurai@spec.co.jp).

AUTHORS
Toshiharu OHNO (tony-o@iij.ad.jp)