2004.10_Ndiswrapper-Using Windows Wireless Drivers in Linux.pdf

COVER STORY

NdisWrapper

All Wrapped Up

The idea of Linux users scouring the

Web for Windows drivers may sound

like an April Fool’s Day prank, or

something from “Candid Camera”,

but ever since the NdisWrapper Pro-

ject was launched, this scenario is not

as absurd as it might seem.

BY ANDREA MÜLLER

gles of wires below their desks, and

are thinking of setting up a wireless

network to fight the bird’s nest, are not

exactly spoiled for choice. NICs with

native Linux support are few and far

between. To be on the safe side, most

people opt for an adapter with an

Orinoco chipset, like the Lancom Air

Lancer MC-11 (see Figure 1). Unfortu-

nately, the only place you can buy these

somewhat ancient NICs is at on online

auction site like Ebay.

If you would prefer something quicker,

like a card that supports the 802.11g

standard, models that use the Prism

Duette ISL3890 chipset are a good

choice, for example, the ALL0271 by All-

net (PCI), or the Netgear WG511GR

(PCMCIA). Kernel version 2.6.5 or newer

will have a driver by default, but you can

convince older Linux versions to cooper-

ate with these adapters if you are

prepared to work a little [1].

In many cases the WLAN adapter pre-

dates Linux, or it arrives with another

piece of hardware. Laptops with the Cen-

trino chip are just one example of this.

To be able to sport the Centrino badge, a

laptop needs to have the Intel Pro/Wire-

less 2100 chip. Some cards that do not

have native support can benefit from

NdisWrapper [2], and you may be able

to get them to talk on Linux.

cols can use to communicate with the

network adapter, with the network card

driver residing on the other side. The

NdisWrapper module emulates this

interface, allowing the Windows drivers

provided with state of the art WLAN

adapters to work under Linux. There is a

list of supported chipsets at [5].

While I was researching this article, I

found out that an entry in the compati-

bility list does not guarantee that a NIC

will work. For example, no matter how

hard I tried, I was unable to get a Belkin

PCI card with a Broadcom chipset,

labeled F5D6001 (printed on top of the

bar code) running. I had slightly more

luck with a Belkin 802.11g PCMCIA card

(product ID F5D7010), which also had a

Broadcom and worked perfectly with

NdisWrapper 0.8-rc2.

In contrast, I was positively surprised

by the Intel-Pro/Wireless-2100 chipsets,

and the Netgear MA521, which has a

Realtek chipset (see Figure 2). These

cards proved to be perfectly stable over a

period of several hours using multiple

kernel (2.4.22, 2.4.23, 2.4.26, 2.6.3,

2.6.5) and NdisWrapper versions (0.4.0,

The Roundabout Way

The NdisWrapper Project is a fairly

recent invention, but thanks to the rapid

pace of development, it has already

reached version 0.9. NdisWrapper is a

kernel module that does not support any

hardware itself. Instead it emulates an

NDIS environment on Linux, making

Windows drivers feel at home. NDIS is

the abbreviation for Network Driver

Interface Specification [3], a specifica-

tion that was jointly developed by

Microsoft and 3COM, which is used by

more or less any network interface dri-

vers on Windows.

NDIS is the interface that sits between

the second and third layers of the OSI

Reference Model [4] as specified by the

International Standards Organization

(ISO). On one side, it defines a software

interface that individual transport proto-

October 2004

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Using Windows drivers with NdisWrapper

L inux users who are tired of the tan-

NdisWrapper

COVER STORY

is quite stable on this 0.4 version.

The jump from version 0.4

to 0.5 was accompanied by

a simplified configuration. The

source code includes a script that

installs, lists, and removes

Windows drivers, and stores

the module configuration in

/etc/modules.conf . Before an

update, Mandrake Linux users

will need to remove the older

NdisWrapper module first:

tributions that use kernel 2.4.20 or

newer. Although you can build older

NdisWrapper versions with kernel

2.4.22, the modules will not load when

you have completed them.

Troubleshooting ACPI

The Advanced Configuration and Power

Interface will typically be the toughest

nut to crack, especially for laptop users.

If you stipulate acpi=off or acpi=ht for

the kernel when booting, that is, if you

disable ACPI, loading the NdisWrapper

module will make the system unstable,

and may even cause kernel panic.

acpi=ht does not completely disable

ACPI, but instead loads just enough ACPI

code to support hyperthreading on Pen-

tium IV computers, for example.

Some distributions (Mandrake Linux is

one of them) automatically set the boot

option acpi=ht for a default laptop

installation. This is just to be cautious,

as some modern devices will not run at

all if ACPI is disabled. This said, Man-

drake does not check whether the laptop

is one of the models affected by this

issue. It won’t hurt to specify acpi=force

at the boot prompt, and test whether

your machine is stable with power man-

agement enabled.

If the test is successful, you need to

change the option in the boot manager

configuration file. This is /boot/grub/

menu.lst for grub; if you have lilo, you

need to edit /etc/lilo.conf instead, and

then call /sbin/lilo to enable the

changes. You simply need to remove the

entry for acpi=off , or acpi=ht , in the

configuration file. acpi=force at the boot

prompt is only needed to overrule any

options that disable ACPI. Linux will

Figure 1: The Lancom Air Lancer MC-11 has a Lucent Orinoco

chipset. The antenna bulge on the left is characteristic for

the card, and includes a connector for external antennas.

rm `find /lib/modules/$ U

(uname -r) -name U

ndiswrapper.ko`

0.5.0, 0.6.0, 0.7.0, 0.8, 0.9), achieving

transfer rates of between 650 and 830

KBytes per second.

I can recommend Centrino notebooks

with the Intel Pro/Wireless 2100 to Linux

users; at least you know exactly what

chipset you are buying. Also, Intel has

transferred a driver to a Sourceforge

project [6], thus providing another alter-

native to using the cards on Linux.

If you are planning on purchasing a

WLAN card, because someone you know

has the same model running with the

NdisWrapper, make sure that the seller

will let you return the card and refund

the purchasing price if the card doesn’t

work the way you planned. In the worst

case, the manufacturer may have

changed the chipset, but kept the name,

leaving you with a card that NdisWrap-

per does not support.

After fulfilling all the system require-

ments, it is quite easy to add a new

NdisWrapper version to the system.

System Requirements

Whether or not a WLAN card will work

with NdisWrapper depends on a number

of factors:

• the chipset,

• the kernel version – 2.4.20 or newer,

•ACPI.

The easiest way to identify a chipset is to

type lspci -n > before.txt (before insert-

ing the card) and lspci -n > after.txt

(after inserting the card). lspci -n shows

the manufacturer and device ID for a

machine’s hardware. You can then diff

before.txt after.txt to view the IDs for

your WLAN card. Another approach

would be to check the fourth column of

the lspci output for a combination of IDs

that occurs in the PCI-Ids (lspci -n) in the

list of supported chipsets [5].

After fulfilling these conditions, you

need to look to the kernel version and

ACPI (Advanced Configuration

and Power Interface) [7]. Any

more or less recent distribution

will have the kernel 2.4.20 or

later, removing the need to

re-compile, as was the case

with earlier distributions. Ndis-

Wrapper versions prior to and

including 0.6 need at least a ker-

nel 2.4.23. This is a requirement

that only Suse Linux 9.1, Man-

drake Linux 10 or Fedora Core 2

fulfill at present. But users have

put pressure on the NdisWrapper

developers to modify version 0.7

allowing it to run with older dis-

Selecting a Version

Users wanting to run a wireless card

with Windows drivers should opt for the

latest version of NdisWrapper. Most dis-

tributions will supply an older version by

default, so check out for people offering

packages for your distro. For example,

the NdisWrapper homepage has links to

RPM packages for Red Hat Linux. Occa-

sionally, you see postings in newsgroups

such as alt.linux.suse from users, who

have created NdisWrapper packages.

Users of Suse Linux 9.1 do not have to

go to this trouble, as this version of Suse

includes NdisWrapper 0.6 by default.

Mandrake Linux 10 also has NdisWrap-

per, although this is the older version 0.4

which does not support a large number

of chipsets. The Intel Pro/Wireless 2100

Figure 2: The Netgear MA521 has a selling price of about 30

Euro at present, and supports Linux via NdisWrapper.

www.linux-magazine.com

October 2004

COVER STORY

NdisWrapper

Figure 3: In the second to last line of this output, NdisWrapper indicates that the Broadcom driver has

initialized successfully.

Call the script by typing ndiswrapper -i

driver.inf . The script parses the inf file to

locate the driver and configuration infor-

mation, and copies both to a directory

below /etc/ndiswrapper . The folder is

named after the driver file, for example,

Broadcom-Driver in /etc/ndiswrapper/

bcmwl5 . After inserting the card, you can

type ndiswrapper -l to check if you have

the right driver.

The output:

automatically use ACPI if no options are

specified.

If your machine does not support

ACPI, you can still try a workaround

with a recent kernel (2.6 if possible), or

build a kernel without ACPI support. To

do so, you need to disable the ACPI Sup-

port below General Setup in the

configuration interface, and rebuild the

kernel. To use your distributor’s configu-

ration, which will have a name such as

config-kernelversion , copy it from the

/boot directory to .config in the directory

with the kernel sources. You need to

make this one change after calling make

menuconfig or make xconfig . You can

then quit the configuration program, and

rebuild the kernel [8].

For some laptops that do not support

ACPI on account of an invalid DSTD

(Differentiated System Description Table,

[9]) – the X10 and X05 models by Sam-

sung, to name just two –, you could

possibly try a modified ACPI table [10],

which the kernel would load from an ini-

tial RAM disk. To allow this to happen

you need to build a kernel with the

DSTD-from-Initrd patch [11]. Users of

Suse Linux 9.0 or newer can save them-

selves the effort; the Suse kernel has this

feature by default. All you need to do is

add the path to the alternative ACPI table

in YaST ( System | Editor for /etc/syscon-

fig files | System | Kernel | ACPI_DSTD ).

ing an appropriate module configuration

in /etc/modules.conf or in /etc/mod-

probe.conf , if you have a 2.6 kernel

running on your system.

Looking for Drivers

The chipset compatibility list provided

by the NdisWrapper Project at [3] will

point you to the right driver. The Win-

dows Driver(s) column has links to

downloads, helping you avoid time-con-

suming searches across manufacturer

pages. Most drivers are zipped archives

and can be unpacked by entering unzip

driver.zip in your current working direc-

tory. Drivers with a .exe extension are

often self-extracting zip archives and can

be unpacked by typing unzip driver.exe .

If you are unable to unpack a required

driver archive under Linux, the only

workaround available is to launch the

installation routine on a Windows sys-

tem. After accepting the license

conditions, store the files in a temporary

directory. You can use the Windows

search tool to find the driver files, setting

the last change date to today as a search

condition. This said, an external tool

such as filemon [12], which provides

details on any files you have open, and

also has extensive filtering functionality,

may provide more reliable results.

After locating the right directory, you

need to copy the driver to a different

location, as the setup routine will delete

the folder if you cancel the install. After

moving the driver to a different location,

you can can- cel

the install. This

gives you the files

without complet-

ing the setup, and

without modifying

the Windows sys-

tem. NdisWrapper

needs the .inf and

.sys files. A helper

script called ndis-

wrapper handles

the install.

bcmwl5 present

net8180

includes a list of installed drivers. The

driver for the current card is marked as

present and is initialized by NdisWrapper

when the kernel module is loaded.

If ndiswrapper -l does not say present

although you have a driver, you may

have picked the wrong one, or the manu-

facturer may have created an update that

does not work with NdisWrapper. You

can try the driver supplied with the man-

ufacturer’s CD in this case, removing the

need to unpack the driver. All the cards

we tested had uncompressed drivers on

the CD supplied by the manufacturer.

First Contact

To get your wireless card talking to other

WLAN devices, you need to enable the

kernel module by typing modprobe

ndiswrapper . This loads the correct Win-

dows driver. A line like the one shown in

Figure 3 should appear in the system log-

file. The new network interface then

appears in the output from iwconfig (see

Figure 4).

You can configure the card just like

any other WLAN device. iwconfig will

tell you the name of the interface, typi-

cally wlan0 . Working as root, you can

type:

Setting up NdisWrapper

After setting up your system for Ndis-

Wrapper, you can quickly compile the

kernel module. Assuming that you have

installed the kernel sources, typing make

in the NdisWrapper directory, will build

both the kernel module and the load-

ndisdriver , which is later required to

load the Windows driver. make install

copies the ndiswrapper module to the

misc subdirectory below your module

directory, and loadndisdriver to /sbin .

Additionally, the ndiswrapper Perl script

is copied to /usr /sbin . The script installs

and deinstalls the Windows driver, creat-

Figure 4: After loading the NdisWrapper module, the output from iwconfig

should show your WLAN card.

October 2004

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COVER STORY

NdisWrapper

iwconfig wlan0 mode U

Ad-Hoc

risking instability by using a

Windows driver to access a

hardware device. The willing-

ness of some manufacturers

to write free drivers, or at

least publish the specifica-

tions for their devices,

although laudable, will not

do much to help a project like

NdisWrapper.

On a more positive note,

there are innumerable end

users who would be unable

to use their hardware on

Linux without NdisWrapper.

Our test demonstrated that

NdisWrapper support does

not impact the stability or

speed, at least for the cards

we looked at. Let’s not forget

the positive factor of an active developer

community, which does not merely

focus its activities on bug-hunting, but is

genuinely interested in responding to its

users’ demands for better usability and

more chipset support.

to set up the interface and

specify ad-hoc mode. This is

the right choice for a direct

connection to another

machine. Windows refers to

this ad-hoc mode as a Peer-to-

Peer Connection . If you use

an Access Point to manage

your network, and assign IP

addresses to your devices,

you should select Managed

mode. Master mode, the

mode in which you can use a

WLAN card as an Access

Point on your network, is not

supported, as Windows dri-

vers do not support this

functionality.

To enable an encrypted connection,

and this makes sense for security rea-

sons, you need to assign a WEP key to

the card. For example, typing

Figure 5: Suse Linux uses YaST to configure wireless network devices. To allow

the tool to load the right driver, you need to specify ndiswrapper as the mod-

ule name.

below Network devices | Network card .

You need to select Wireless as the Device

type and enter ndiswrapper in the Mod-

ule name text box (see Figure 5).

Use the Wireless settings to define the

options such as the mode, the ESSID,

and the WEP key. In the case of mobile

devices, it makes sense to select Manual

in Advanced | Detailed settings | Device

Activation and use the ifup wlan0 com-

mand to enable the wireless interface

only when needed. This prevents delays

on booting if the device is missing. Inter-

nal components typically have a switch

to disable the WLAN component, which

could help conserve battery power. If

you will be using the card permanently,

leave the default setting as it is. This tells

YaST to enable the WLAN card along

with any other network interfaces.

You should not set too much store by

the Link Quality: display in the output

from iwconfig . Windows drivers do not

have a function for measuring signal

quality. The Intel-Pro/Wireless 2100

cards in our test always had a zero in

this field, although the card was busy

transferring data. The Belkin PCMCIA

card with the Broadcom chipset showed

values of 97 and 98 , and the Netgear

card with the Realtek chipset had a full

100 . You can check out the statistical val-

ues available via the NDIS interface in

/proc/net/ndiswrapper /wlan0/stats .

In contrast to cards with native Linux

support, cards with NdisWrapper are not

capable of providing a full WLAN solu-

tion. Add to that the scary feeling of

■

iwconfig wlan0 key U

9f65129e50c93c389ebd531da8

INFO

assigns a hexadecimal WEP key of

9f65129e50c93c389ebd531da8 without

the separators. Finally,

[1] Setting up WLAN cards with the Prism 54

chipset: http://prism54.org/

[2] NdisWrapper Project:

http://ndiswrapper.sourceforge.net/

[3] NDIS specification:

http://www.microsoft.com/whdc/device/

network/ndis/default.mspx

[4] OSI Reference Model explained: http://

www.freesoft.org/CIE/Topics/15.htm

[5] List of chipsets supported by NdisWrap-

per: http://ndiswrapper.sourceforge.net/

supported_chipsets.html

[6] Intel drivers for Centrino WLAN compo-

nents: http://ipw2100.sourceforge.net/

[7] ACPI: http://www.acpi.info/

[8] Kernel Rebuild Guide:

http://www.digitalhermit.com/linux/

Kernel-Build-HOWTO.html

[9] Timo Hönig, ACPI Implementation: Linux

Magazine, Issue 40, March 2004,

http://www.linux-magazine.com/issue/

40/ACPI.pdf

[10] Overview of Linux ACPI and DSTD:

http://acpi.sourceforge.net/

[11] DSTD-Initrd patch:

http://gaugusch.at/kernel.shtml

[12] Filemon for Windows:

http://www.sysinternals.com/ntw2k/

source/filemon.shtml

[13] FAQ for NdisWrapper: http://ndiswrapper.

sourceforge.net/faq.html

iwconfig wlan0 essid homenet

sets the ESSID. You can use iwconfig to

ensure that the card really is using all the

options you specified, before entering

ifconfig wlan0 192.168.1.6 up to enable

the network interface. You will typically

need to supply an IP address for ad-hoc

mode, but not for managed mode, as

most Access Points also have DHCP

server functionality to automatically

assign an IP to each wireless device. If

you want to use an AP, but can not asso-

ciate with the AP, the NdisWrapper FAQ

[13] suggests that you activate ESSID

broadcast at the Access Point, then retry.

Suse Linux has an alternative YaST-

based approach to setting up the card.

Avoid configuring the wired Ethernet

card that the Suse configuration tool mis-

takenly identifies. In this case, you will

not be able to access the wireless

options, and your card will not work.

The right approach is to launch YaST

manually, and select Other (not detected)

October 2004

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