Update from "Wireless Communication from the sources"

Dr. Edgar Alwers edgaralwers at gmx.de
Sun Mar 26 01:33:47 PST 2006


Please find an upgrade attached. It includes considerations to DHCP and some 
improvements.
Edgar
-- 
---------------------
Dr.-Ing. Edgar Alwers
Weinheim
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AUTHOR:				Dr. Edgar Alwers <edgaralwers at gmx.de>

DATE:					2006-03-26

LICENSE:				GNU Free Documentation License Version 1.2

SYNOPSIS:				Wireless Communication from the sources

PREREQUISITES:	

BLFS 6.x with  kernel 2.6.15...Older kernels shoud work accordingly, with the correspondent firmware.

DESCRIPTION:

This is a Hint explaining how to prepare a PC for wireless communication with the Internet and how to put it into operation. I solved this problem with the help of hints and advices given by many persons, and working through lots of papers, many of them not beeing actual anymore at this time. 
The object I had to deal with is an 'Acer' TravelMate 291LCi with Intel Centrino Mobile Technology, equiped with an Intel PRO/Wireless 2200BG(IEEE 802.11b/g) chip. The Laptop communicates with an 54 Mbps Wireless Netgear ADSL Firewall Router DG834G as access point However, there are good chances, that this hint may also be applied to other PC's with other drivers. If you cannot obtain a native Linux driver for your wireless NIC, you may want to try 'ndiswrapper', a package that will allow to load a Windows driver under Linux.

The kernel compiled is version 2.6.15. This kernel includes already the driver ipw2200-1.0.8 and the iee802 subsystem and you may ask, why to build this two items additionally. I experienced serious difficulties not compiling them and decided to become independent from the kernel.

This second issue of the hint deals with additional instructions, how to operate a PC in a wireless field under a DHCP Server ( Dynamic Host Configuration Protocol ) providing  IP's to the clients. This is the probably situation which will be found in most public locations, like airports, hotels etc. 

HINT:

KERNEL:

Download:
	Kernel v. 2.6.15
	http://www.kernel.org

Configuring the kernel:

	enable Networking->
			Networking support->
				Networking options->
					Packet socket
					TCP/IP networking
	device drivers->
			Generic driver options->
				Hotplug firmware loading support
	device drivers->
			Network device support->
				Wireless LAN (non-harmradio)->
					Wireless LAN drivers & Wireless Extensions
	cryptographic API->
			ARC4 cipher algorithm (Modul)

compile and install the kernel according to the instructions of the book 'Linux From Scratch'

HOTPLUG-2004_09_23:

Scripts that react upon hotplug events generated by the kernel
Download:
	hotplug-2004_09_23.tar.bz2
	Http://www.kernel.org/pub/linux/utils/kernel/hotplug

Install hotplug according to the instructions given e.g. In the LFS-Book SVN-20060125, Chapter 6.49

UDEV-071.TAR.BZ2:

Programs for dynamic creation of device nodes

Download
	udev-071.tar.bz2
	ftp://ftp.kernel.org/pub/linux/utils/kernel/hotplug

make DESTDIR=/ EXTRAS="extras=firmware extras/run_directory" 
make DESTDIR=/ EXTRAS="extras=firmware extras/run_directory" install  
install -m644 -D -v docs/writing_udev_rules/index.html /usr/share/doc/udev/071/index.html
/sbin/udevstart

Check that 'firmware_helper', 'udev_run_devd' and 'udev_run_hotplugd' are installed in the /sbin directory.

Download the new udev-rules developed by Jim Gifford's cross lfs team
	udev-cross-lfs.tar.bz2 
	http://ftp.jg555.com/udev
Untar the file, change to the 'udev-cross-lfs' directory and enter 'make install'. This  installs the new udev-rules in /etc/udev/rules.d

IEE80211-1.1.12:

Kernel subsystem dealing with communications security

Download
	ieee80211-1.1.12.tgz
	http://ieee80211.sourceforge.net
Untar the file, change to the ieee80211-1.1.12 directory and enter make, make install. 
Includes headerfiles in /lib/modules/2.6.15/net

INTEL'S FIRMWARE:

Download the Firmware
	ipw2200-fw-2.4
	http://ipw2200.sourceforge.net
Untar the file in the directory /lib/firmware. Seven files ipw-2.4-xxx.fw will be found there after untaring

INTEL PRO/WIRELESS DRIVER :

Driver that works on the Intel hardware adapter PRO/Wireless 2200BG Network Connection
Download the driver
	ipw2200-1.0.10.tgz	
	http://ipw2200.sourceforge.net
Untar the file, change to the ipw2200-1.0.10 directory and enter make, make install. ( as su )
I experienced serious problems compiling the new driver versions 1.0.12 and 1.0.13, so I would advice to stick to the above one for the time beeing.
The driver requires the firmware image as well as the ieee80211 module installed.sysfs should be already mounted.

See also the INSTALL file for more instructions

THE WIRELESS TOOLS:

Set of tools that allows to manipulate Wireless Extensions
Download the wireless tools:
	wireless_tools.27.tar.gz
	http://pcmcia-cs.sourceforge.net/ftp/contrib/
Untar the file, change to the wireless_tools.27 directory and enter make, make install
Seven tools will be installed in /usr/local/sbin: iwconfig, iwlist, ifrename,iwevent,iwgetid, iwpriv and iwspy
Make a link from KDE_Prefix/bin to /usr/local/sbin: 
	ln -s /usr/local/sbin/iwconfig KDE_Prefix/bin/iwconfig

THE DHCPCD CLIENT SOFTWARE:

Software to connect a computer to a network which uses DHCP to assign network addresses.There are two alternatives: dhcp, which includes also the server software, and dhcpcd, an implementation of the DHCP client specified in RFC2131. I prefered  dhcpcd, wich seems to be more simple.
Download 
	dhcpcd-2.0.1.tar.bz2
	http://developer.berlios.de/projects/dhcpcd/
Untar, change to the dhcpcd-2.0.1 directory and enter
	./configure --prefix="" --sysconfdir=/var/lib
	and, as superuser, make.
The reason for the prefix "" in the configuration command is explained in the blfs-book, version 6.1, chapter 14. Install the network service script /etc/sysconfig/network-devices/services/dhcpcd as indicated in the same place
	
BOOTING THE PC:

If everything went right, the PC boots and loads firmware and wireless-driver. The corresponding booting  messages will look like
	........
	ieee80211_crypt: registered algorithm 'NULL'
	ieee80211: 802.11 data/management/control stack, 1.1.6
	ieee80211: Copyright (C) 2004-2005 Intel Corporation <jketreno at linux.intel.com>
	ipw2200: Intel(R) PRO/Wireless 2200/2915 Network Driver, 1.0.8
	ipw2200: Copyright(c) 2003-2005 Intel Corporation
	ACPI: PCI Interrupt Link [LNKG] enabled at IRQ 10
	ACPI: PCI Interrupt 0000:01:02.0[A] -> Link [LNKG] -> GSI 10 (level, low) -> IRQ 10
	ipw2200: Detected Intel PRO/Wireless 2200BG Network Connection
	.........

MONITORING PROGRAMS:

There are many prrograms that allows the monitoring of wireless communications. I installed two of them: 'kismet' and 'KWiFiManager'.

'kismet' is a small wireless network detector, sniffer and intrusion detection system. 
Download 'kismet-2005-08-R1.tar.gz' from http://www.kismetwireless.net/download.shtml
untar the file, enter make and make suidinstall. Run kismet the first time as root. Kismet runs on a  shell console.

'kwifimanager' is a KDE frontend program used to configure and monitor wireless LAN cards. 'kwifimanager' is part of 'kdenetwork'. Download kdenetwork_3.4.1.tar.bz2 and follow the instructions given e.g. In BLFS - Version 6.1, chapter 29. Wireless tools should be installed before building this packet.

CONFIGURING THE ROUTER -  SAFETY CONSIDERATIONS:

during the installation of the wireless system, the safety options of the router are deactivated. Now, it is time to activate them. Access the settings menu of the router through a browser, entering something like http://192.168.0.1. I activated WEP ( Wired Equivalent Privacy ) with  64 bit encryption. You may consider a 125 bit encryption

Enter a password in the encryption field, and the router will generate four keys, each one consisting of 10 characters, combining numbers 1 to 9 and letters A-F, like:EC670531BE. The first of this four keys is the one beeing normally used.

Furthermore, the MAC-addresses ( Media Access Control ) of the laptop's and PC's wich are allowed to access the router shoud be entered in the access list 'trusted wireless stations'. You may get the MAC addresses  from the list of connected devices in the settings menu of the router or with the help of a network exploration tool like 'nmap' ( Network Mapper ), in  the last case e.g. entering 'nmap -sP 192.168.0.1/22'

However, even a 125 bit encryption does not give a real security today. According to a note contributed by Bryan Kadzban,  real security can only be obtained with WPA or WPA2 encryption. You may want to consider this, if you have confidential data to transmit.

CONFIGURING THE PC FOR WIRELESS COMMUNICATIONS:

immediately after the safety options of the router are activated, the PC will not more be able to see the access point: the PC also needs to be configured. 

Entering the command 'iwconfig eth1 key xxxxxxxxxx'  enables the communication, but not permanently. For a permanent configuration, write a shell-script e.g.'connect' in /etc/rc.d/init.d:
	$!/bin/sh
	/usr/local/sbin/iwconfig eth1 key xxxxxxxxxx
and make this script executable: chmod ug+x connect. Make a symbolic link in /etc/rc.d/rc3.d that points to this script: ln -s /etc/rc.d/init.d/connect S19connect. The link should start with something like S19, as the script should be run before the S20network script is executed. For an unencrypted system, likely to be found on public places, the command in the script should not contain a key:
	/usr/local/sbin/iwconfig eth1

Create a directory 'ifconfig.eth1' in '/etc/sysconfig/network-devices', and cd to this directory. 
For operation withouth DHCP create a ipv4 file:
	ONBOOT=yes
	SERVICE=ipv4-static
	IP=192.168.1.3			// the address of your box
	GATEWAY=192.168.1.9	// the address of your router
	PREFIX=24
	BROADCAST=192.168.1.255
	NETMASK=255.255.255.0
and change GATEWAY_IF in /etc/sysconfig/network to eth1.

For operation with DHCP create instead ipv4 a file dhcpcd:
	ONBOOT="no"
	SERVICE="dhcpcd"
	DHCP_START="eth1 -t 20"
	DHCP_STOP="-k "

	# Set PRINTIP="yes" to have the script print
	# the DHCP assigned IP address
	PRINTIP="yes"

	# Set PRINTALL="yes" to print the DHCP assigned values for
	# IP, SM, DG, and 1st NS. This requires PRINTIP="yes".
	PRINTALL="no"

USING THE WIRELESS CONNECTION :

After booting, lsmod shows
	Module				Size			Used by
	ipw2200			176576	0
	ieee80211		  42664	1  		ipw2200 
	ieee80211_crypt	    4804	1  		ieee80211 

The command 'iwconfig eth1' entered in a console delivers
		eth1      IEEE 802.11g  ESSID:"Mannheim"  
          	Mode:Managed  Frequency:2.462 GHz  Access Point: 00:0A:B5:CF:64:28   
          	Bit Rate=48 Mb/s   Tx-Power=20 dBm   
          	Retry limit:7   RTS thr:off   Fragment thr:off
          	Encryption key:57E4-DB3A-B1   Security mode:open
          	Power Management:off
          	Link Quality=95/100  Signal level=-29 dBm  Noise level=-86 dBm
          	Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          	Tx excessive retries:0  Invalid misc:0   Missed beacon:0
As the ONBOOT parameter was set to 'yes', the connection to the access point is already activ.

The internet browser should be configured with direct access to the internet. Opening the browser should establish immediately a connection.

USING THE WIRELESS CONNECTION UNDER A DHCP SERVER:

I experienced some problems starting the dhcpcd daemon during the boot process. So I decided to set the ONBOOT parameter in the file /etc/sysconfig/network-devices/ifconfig.eth1/dhcpcd to 'no', as indicated above, and to start as 'su' a little script 'eth1_connect' :
	#!/bin/bash
	/sbin/dhcpcd eth1
	# end
After starting the daemon dhcpcd, the connection to the access point is activ.

AKNOWLEDGEMENTS:

I have tryed to compile articles, informations, hints and answers to questions I put in the BLFS-mailing list to this hint. Many thanks to all those who contributed: Gabe Yoder, Andrew Benton, Alexander E. Patrakov, Jim Gifford, David Fix, Rainer Peter Feller, Chris Staub, Randy McMurchy,
Jeremy Monnet, Stefan Krah, Bryan Kadzban.


LINKS AND LITERATURE:

Intel PRO/Wireless driver
http://ipw2200.sourceforge.net						

Linux Wireless Networking 	
http://www.linuxhomenetworking.com/linux-hn/wmp11-linux.html

Wireless LAN Resources for Linux
http://www.hpl.hp.com/personal/jean_Tourrilhes/Linux/Tools.html
Kismet
http://www.kismetwireless.net/documentation.shtml

The devices, the drivers... Jean Tourrilhes
http://www.hpl.hp.com/personal/jean_Tourrilhes/Linux/Linux.Wireless.drivers.802.1.11ag.html#CentrinoAG

Sane network interface management with Hotplug. Jean Tourrilhes
http://www.hpl.hp.com/personal/jean_Tourrilhes/Linux/HOTPLUG.txt

ndiswraper
http://ndiswrapper.sourceforge.net/mediawiki/index.php/Installation


CHANGELOG:

[2006-03-26]

 Remarks concerning safety considerations
 Additional notes concerning DHCP-Server operation
 Chapter "The DHCPCD Client Software" 
 Configuring the PC for operation under DHCP 
 Subsystem IEE80211-1.1.6 changed to IEE80211-1.1.12
 Intel PRO/WIRELESS driver ipw2200-1.0.8 changed to ipw2200-1.0.10
 Using the wireless connection under a DHCP server
	


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