Linux** – Installing of a pptp-Client (for xDSL-connection with an USB modem)

This document describes the installation of a pptp-Client for a xDSL-connection using an USB-modem.

With the separation of Telecom-Access-Provider (having a monopoly over the cables in a certain area) and Internet-Service-Provider (ISP, offering connection to the internet, providing mailboxes and webspace), the Telecom-Access-Provider needs an instrument to identify to which ISP the TCP/IP-packets should be forwarded and to wrap the throughpassing packets in a way that they retain their information.
To achieve these goals, the TCP/IP-packets are transported using the pptp (Point to Point Tunneling Protocol).

Alternatively to xDSL-Ethernet-modems, Telecom-Access-Providers offer USB-modems. Those are often included in 'self-install' packages and are delivered with a much lower subscription fee than Ethernet-modems - or even for free.

The setup is specific for ADSL of Telekom Austria - but might work with other Telekoms using pptp.
It was tested with an Alcatel-SpeedTouch-USB modem of the first generation - the 'green flounder'.
I did not test the successing models (now sold by Thomson) – but there is a Web-site dealing with numerous models of the modem. The reference to this Web-site is further down when this document deals with the installation of the USB-modem..

Credits:

The anonymous authors of The Linux Kernel Speedtouch Driver for Fedora Core 3 and related topics.
Additional hints I derived from Heimo Schöns HOWTO (http://howto.htlw16.ac.at/at-highspeed-howto.html - in german) particularly the hint of Martin Großhauser how to start / restart the connection using crontab.

Preface:

To find guidance in the internet was a pretty painful task. There were a lot of descriptions from early adoptors (starting with early Linux 2.4.2 kernels) - and all of them had broken links to requiered drivers.

After hours of effortless trials, I decided to upgrade the router to a Linux with Fedora Core 3.
By the way, this kernel runs pretty well on a machine with a 200 MHz Pentium I and 64 MB RAM.
It has already built-in-support for USB-hardware and 'USB-hotplug'.
'USB-hotplug' detects the connection or disconnection of an USB-device and tries to load the fitting driver (called 'firmware').
The operating-system has also built-in support for 'ppp over ATM' (point-to-point-protocol over Asynchronous-Transfer-Mode connections - temini technici a telecom-engineer can explain in a little bit less than a month).

So Linux Fedora Core 3 takes a lot of work away from you and and leave over the installation of the correct firmware and the editing of the configuration-file specific to your Telecom- and ISP-providers.

Prerequisites:

• Operating-system installed ;-).
  The operating-system must be a Linux Fedora Core 3

• Firewall including IP-forwarding and Native-Address-Translation installed (see Linux** - Firewall and Masquerading).
  This is a prerequisite only if installing the pptp-Client on a router.

• Logged on as user root.

Intermediate test:

To check, if the modem is recognized by the 'USB hotplug', unplug it from the USB-connector and replug it.

At least the USB-light should be green and on the terminal you should see - amongst others - a message similar like this:
usb 1-2: no stage 1 firmware found

If GNOME is already started, you will see the messages in the log-file; it can be displayed by entering dmesg | tail on the command line of a Terminal-window.

Installation-instruction:

Installing the firmware:

Guidelines for downloading and extracting the firmware can be found on The Linux Kernel Speedtouch Driver for Fedora Core 3 .

For my early revision SpeedTouch modem, I found a misleading description (Juli 2006) on the above site;
the correct procedure was described on Extracting the Firmware.

There is an excellent description how to identify your modem, download the necessary files and install it.
My description would not be better for this complex topic.

After extracting the firmware for my 'green flounder', I got the following confirmation output on the console:
** Boot block from mgmt.o:
   CRC: 0xd80bf9f7
   Length: 991
** Firmware block from mgmt.o:
   CRC: 0x94a45435
   Length: 526187

Next, move the two extracted files to the directory where Fedora keeps the firmware for attached devices:
mv speedtch-1.bin /lib/firmware
mv speedtch-2.bin /lib/firmware

Intermediate test:

To check, if the modem is loading the firmware, unplug the modem from the USB-connector and replug it.

After about 10 seconds, the ADSL-light should start blinking green with spurious red flashes and on the terminal you should see - amongst others - the message:
ADSL line is synchronising

If GNOME is already started, you will see the messages in the log-file; it can be displayed by entering dmesg | tail on the command line of a Terminal-window.

Store the user-id and password for the connection to the ISP:

The Internet-Service-Provider usually provides an user-id and a password to identify individual clients.
During the dial-in-procedure the ISP performs an identification and requests user-id and password.

There are 2 different authentification-protocols (PAP and CHAP); if you are not sure what protocol the ISP uses it is recommended to store user-id and password for both protocols.

For the PAP-authentification edit the file /etc/ppp/pap-secrets and add the bold printed line.
Instead of the values printed in italics, enter user-id and password provided by the ISP:

# Secrets for authentication using PAP
# client server secret IP adresses
user-id * password

For the CHAP-authentification edit the file /etc/ppp/chap-secrets and add the bold printed line.
Instead of the values printed in italics, enter user-id and password provided by the ISP:

# Secrets for authentication using PAP
# client server secret IP adresses
user-id * password

To protect the files, change the access-rights:

chmod 400 /etc/ppp/pap-secrets
chmod 400 /etc/ppp/chap-secrets

Edit the configuration file for the pppd (Point-to-Point-Protocol-daemon):

The pppd-daemon can is configureded by a parameter-file. As an improvement over the description for the ppp-dialer (where the configuration-file is /etc/ppp/options), the newer versions can be controlled by any file. In our case the configuration-file is /etc/ppp/peers/speedtch :

#
# Debug-option; recommended for the trial-phase.
# Can be commented out if the connection is proven as stable
debug
#
# The computer at the Internet-Service-Provider (ISP) must provide a temporary TCP/IP-address
noipdefault
#
# This connection is the default-router from the internal network to the ISP.
defaultroute
#
# The computer at the Internet-Service-Provider (ISP) does not have to identify itself
# against the computer dialing-in
noauth
#
# User, for whom the password is read out of the file 'pap-secrets' or 'chap-secrets'
user 'user-id'
#
# Some parameters with special function for a ppp over ATM connection
lcp-echo-interval 30
lcp-echo-failure 3
noaccomp
nopcomp
noccp
novj
holdoff 4
persist
maxfail 25
updetach
usepeerdns
plugin pppoatm.so
# VPI and VCI numbers. These are unique to the ISP (Internet-Service-Providers)
# This pair must be in the line under 'plugin pppoatm.so'
8.48
#
# End of file

Intermediate test:

To check if a connection to the Internet-Service-Provider can be established, the following command is issued (in a Terminal-window):
pppd call speedtch

This should result in an output on the console which looks similar to this:
Plugin pppoatm.so loaded
PPPoATM plugin_init
PPPoATM setdevname_PPPoatm – SUCCESS:8:48
Using interface ppp0
Connect: ppp0 <--> 8.48
CHAP authentication succeeded
local IP address 88.117.84.212
remote IP address 88.117.84.1
primary DNS address 195.3.96.67
secondary DNS address 195.3.96.68

Additionally, you can check if the interface 'ppp0' is established by issuing the command:
ifconfig

If the interface 'ppp0' is established the contact to the internet can be tested _ e.g by pinging a DNS-server:
ping 195.3.96.67

If you do not get a response, the 'Default Gateway' may be set to a machine within the local network.
Do verify and correct this, open >Application >System Settings >Network , go to the Tab Device and click the [Edit] button.
Verify, that the field 'Default gateway address' is empty.

Additional hint: if the connection breaks or you want to restart it for some other reasons, you have to 'kill' it before reestablishing the connection:
killall pppd

Start / stop / restart script for the pptp-Client

To start or to restart the pppd-daemon, I modified a suitable script in Heimo Schöns HOWTO. The command are stored in the file /etc/rc.d/adsl :

#!/bin/bash
#
# /etc/rc.d/adsl
#
# Script to start / stop /restart the ADSL-connection for an USB-ADSL-modem
#
# Tested with Linux Fedora Core 3.
# April 2005
# Kurt Gstoettner
#
# This script is based on examples published by
# Sebasian C.B. Sauer <scbATenemyDOTorg>
# Nicolas Croiset <ncroisetATvdldiffussionDOTcom>
# Philippe Jouguet <pjouguetATvdldiffusionDOTcom>
#
# Permission to copy is granted provided that credit is given to all
# documentation you used to understand these procedures
#
# No warranty is implied. Use at your own risk !!
#
start() {
# start the adsl-Client on the USB-ADSL-modem
/usr/sbin/pppd call speedtch
# touch the process to lock them
touch /var/lock/subsys/pppd
echo -n "adsl:procedure start()."
# Wait 15 seconds to allow the pppd-client to get the TCP/IP-address
# from the Internet-Service-Provider.
# Start the firewall thereafter.
sleep 15s

# Start the firewall and the ip-forwarding if this script runs on the router.
# Otherwise comment out the next line.
firewall
return 1
}
#
stop() {
echo -n "Shutting down PPTP tunnel. "
# Kill the processes for the ppp-protocol (Point-to-Point-Protocol)
# and the Point-to-Point-Tunneling-Protocol
# to free the devices for a new start.
killall /usr/sbin/pppd
echo -n "adsl:procedure stop()."
return 1
}
#
firewall()
{
# Run the script to configure the firewall
/etc/rc.d/rc.firewall-iptables
return 1
}
#
#
case "$1" in
start)
echo -n "Starting PPTP/PPP tunnel. "
start
;;
#
stop)
stop
;;
#
restart)
# stop, wait 15 seconds to make sure all asynchronus tasks are completet, start
stop
sleep 15s
start
;;
#
*)
echo -n "Usage: adsl {start|stop|restart}"
exit 1
;;
esac
exit $?

Setting the access-rights for an automated startup

As a prerequisite for automated startup or restart the access-rights of the script must be set as follows:
chmod 4711 /etc/rc.d/adsl

Automatic start / restart of the ADSL-connection using crontab

As mentioned in the credits, Martin Großhauser developed a pretty smart method to start or restart the pptp-client.
Every 5 minutes a ping is issued to a known TCP/IP-address on the internet. If this ping is without an answer, the Start /stop / restart script is run with the parameter 'restart'.
All this is achieved by simply adding one line to the file /etc/crontab .
As my connection is with the Telekom Austria, I ping their primary nameserver.

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/
#
# run-parts
01 * * * * root run-parts /etc/cron.hourly
02 4 * * * root run-parts /etc/cron.daily
22 4 * * 0 root run-parts /etc/cron.weekly
42 4 1 * * root run-parts /etc/cron.monthly
# Check periodically if connection to Internet-Service-Provider is still alive;
# Restart the pptp-Client if no response.
0,5,10,15,20,25,30,35,40,45,50,55 * * * * root ping -c 1 195.3.96.67 || /etc/rc.d/adsl restart

Additional hints:

The file can only be edited with access-rights as 'root'.

Test:

When the connection is established, the ADSL-light on the modem stays solid green.

On a workstation, set the 'gateway' to the machine that serves as 'Router' and ping a known address; e.g. the Domain-Name-Server of the Internet-Service-Provider:
ping 195.3.96.67

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