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linux-wlan-ng/FAQ

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********************** Linux-wlan-ng FAQ **************************
For additions, corrections, and clarifications, send mail to
solomon@linux-wlan.com with FAQ in the subject.
*******************************************************************
Q: What devices does the linux-wlan-ng driver support?
Currently, the linux-wlan-ng driver supports the Intersil
Prism2/2.5/3 chipsets. These chipsets are used in a wide
variety of PCMCIA, PCI, and USB products. If it has a Prism
chip in it, linux-wlan-ng should support it.
Q: Will linux-wlan-ng support some feature or funkiness in
the <pick one> Linux distribution?
Our development target always consists of stock kernels from
kernel.org and stock pcmcia_cs. If a given distribution
chooses to do something funky, we rely on users of that
distribution to contribute patches to deal with their
funkiness.
The quickest way to get some action on this kind of item is to
communicate with any users of the same distribution that you
can find on the linux-wlan-[devel|user] lists about working up
a patch. If it's reasonably sane and doesn't break things for
our development environment or for other distributions, we'll
be more than happy to roll that patch into the next release.
Q: What does "resultcode=implementation_failure" mean?
Complicated Answer:
Each command that can be issued with wlanctl-ng returns a status
called "resultcode". Resultcode is something that we picked up
from the 802.11 MLME definition. In the standard, resultcode
is an enumeration with a fixed set of values. To be able to
report failures that a driver detects that are outside the
context of the 802.11 standard set of resultcode values, we
invented the "implementation_failure" value.
Simple Answer:
Go look in your kernel log for more detailed error information.
Q: I'm trying to use the HostAP/orinoco/aironet/wvlan driver and it
won't work!
That has nothing to do with the linux-wlan-ng driver. Go ask
those responsible for those drivers.
Q: Can I get Debian packages of linux-wlan-ng?
A: Packages of linux-wlan-ng are available in the Debian unstable
and testing trees now, and will eventually be shipped with a stable
Debian release. The Debian packages include support for configuring
linux-wlan-ng interfaces via /etc/network/interfaces, amoung other
things. Complete details about the Debian-specific parts of these
packages, including instructions for building a linux-wlan-ng modules
package for your kernel can be found in the file
/usr/share/doc/linux-wlang-ng/README.Debian.gz
Q: Where do I find some RPMS for linux-wlan-ng? The ones on
the ftp are dreadfully out of date!
http://prism2.unixguru.raleigh.nc.us/
(Maintained by Tim Miller)
Q: I installed the RPMs/compiled the driver and installed it and it
won't work when I try to run 'ifup wlan0' or whatnot.
First, ensure you're running the most up-to-date version of
the driver. Many problems have been fixed in newer releases.
802.11 wireless networks are much more complex than wired
ethernet networks. They require much more configuration than
an ip address. If you are using pcmcia, edit the file
/etc/pcmcia/wlan-ng.opts to set the network parameters. For
PCI, PLX, or USB adapters, you need to edit /etc/wlan.conf.
You also need to make sure you have the correct settings in
/etc/modules.conf (alias wlan0 prism2_usb).
Might we suggest you read the README file?
Q: When I try to load the driver, I get a whole bunch of errors about
unresolved symbols.
The running kernel does not match the kernel the driver was
compiled for. If you downloaded a RPM, make sure you
downloaded the correct version for your kernel. This should not
happen if you compiled the driver from source -- if it does, the
kernel configuration you compiled against does not match the
running kernel. Probably a screwed-up distro kernel.
Q: I have a DWL-520 and it won't work!
The DWL-520 *requires* a PCI 2.2 compliant motherboard. Only
very new machines support this. Yes, the box lied. Check the
documentation for your system and/or motherboard to see if it is
PCI 2.2 compliant. If not, return the DWL-520 and buy a Linksys
WMP11 istead.
Q: All I see is "Tx attempt prior to association, frame dropped"
You are not associated with an access point. Double-check the
settings in /etc/wlan.conf (USB, PCI, PLX) or /etc/pcmcia/wlan-ng.opts
(for PCMCIA users). If all of these settings are correct (you
did check with your admin, right?) make sure the access point
doesn't have a MAC filter installed or has different WEP settings.
If all of this is verified correct, and are using a PCMCIA
card, try setting the "irq_mode=0" option. See the
documentaiton in the pcmcia-cs sources.
Q: I installed the modules, performed a 'wlanctl-ng wlan0 lnxreq_autojoin'
command, and it still won't work!
You did read the README, didn't you? You need to perform a
"wlanctl-ng wlan0 lnxreq_ifstate ifstate=enable" in order to
torn on the radio. The pcmcia scripts and the /etc/init.d/wlan
script do this for you.
Q: I have a XXX USB 802.11b device, will it work with this driver?
Most 802.11b USB devices use the ATMEL AT76C503A chipset, which
is not supported by the linux-wlan-ng project. However, there
are some prism2.5-based USB adapters, most notably the Linksys
WUSB v2.5. The other versions (1.0, 2.6, 3.0) are based on
ATMEL chipsets. Another supported USB device is the Actiontec
802UI3.
Q: The wlan-ng driver says my ATMEL AT76C503A device is unsupported!
That's because it's not a Prism-based device! Linux-wlan-ng
does not currently support ATMEL chipsets, mainly because ATMEL
has not been forthcoming with technical programming documentation.
However, ATMEL has an unspported binary-only Linux driver
that they make available to their vendors. So please
call/email your vendor (and/or ATMEL) for this driver.
If they get enough requests, they may eventually care about
supporting Linux users.
For more information on the ATMEL boards, see:
http://at76c503a.sourceforge.net/ (Open source driver)
http://www.fuw.edu.pl/~pliszka/hints/at76c503a.html (summary)
http://www.wireless.org.au/~jhecker/atmeldrv/atmeldrv.html (driver)
There is a mailing list for the ATMEL driver:
http://iprserv.jura.uni-leipzig.de/mailman/listinfo/atmel-wlan-usb
In the mean time, we suggest returning the ATMEL device and
buying one that the linux-wlan-ng driver supports. </plug>
Q: My prism2.5-based USB adapter won't work!
An excellent guide can be found at:
http://www.fuw.edu.pl/~pliszka/hints/prism2.html
Q: My prism2.5-based USB adapter won't come up if it's plugged in at boot!
Thanks to buggy firmware, it is often necessary to perform a
device reset on initialization. You can perform this by adding
"options prism2_usb prism2_doreset=1" in your /etc/modules.conf
Intersil has released Primary firmware 1.1.2, which seems to
have resolved this problem, at least on our test machines.
Contact your vendor for a firmware update.
To check the firmware version, run: "dmesg |grep ident"
Q: My PC crashes when the USB device is plugged in!
This is a result of the port reset necessitated by buggy firmware.
You are probably using the 'usb-uhci' driver with an intel
chipset. Unfortunately, the crashes happen deep within the USB
core, so there's nothing the linux-wlan-ng driver can do.
In the mean time, try using the 'uhci' host controller driver
instead ("alias usb-controller uhci" in /etc/modules.conf), or
plug the USB device into a hub.
Linux kernel 2.4.19 is known to improve the situation somewhat,
but the right way to fix it is to turn off the port reset
(options prism2_usb prism2_doreset=0). The current firmware
from Intersil alleviates the need to perform the reset.
Q: What's with these "Called from within soft interrupt context" messages?
This is the result of a workaround to avoid a kernel oops in
the USB driver code. You can ignore them.
As of 0.1.15-pre5, a different workaround is in place.
Q: Why doesn't promiscuous mode or monitor mode work under USB?
Promiscuous mode works just fine, as of 0.1.15-pre5.
Monitor mode also works, as of 0.1.14-pre6.
Both modes are likely to be quite unreliable, especially under
higher loads thanks to fundamental bandwidth limitations of the
USB interface.
Q: How come I can't transmit when in monitor mode?
You can't. It's a fundamental "feature" of the hardware.
Q: How come the /proc/net/wireless info isn't updated when in monitor mode?
The definition of "signal quality" refers to the quality of the
link to the associated access point. When you're in monitor
mode, you're not associated, so this information is by defintion
irrelevant.
And regardless, the hardware doesn't update the registers we poll to get
this information while in monitor mode.
Q: What do the various monitor mode options do?
enable=[true/false] Turn it on and off. required.
channel=[1-14] Sniff channel. required.
prismheader=[true/false] Optionally preppend a special
radio header on the packet.
Defaults to off.
keepwepflags=[true/false] If you had WEP configured correctly
the card will perform WEP decoding.
Defaults to off.
stripfcs=[true/false] When true, the 802.11 FCS is not
stripped from incoming packets.
Defaults off.
truncate=[number] Truncates the captured frame.
Q: How come iwconfig/iwspy/[random other wireless tool] doesn't work?
linux-wlan-ng only supports a subset of the wireless
extensions; generally read-only things. However, you won't
need any of those tools as wlan-ng comes with its own set of
tools that closely mirror the 802.11 spec. Have a look
through the documentation and supplied scripts.
That said, if full wireless extension support is really
important to you, you're more than welcome to implement it
and submit a patch.
Q: Where can I download updated firmware for my Prism2/2.5/3-based card?
Ask your vendor. Due to legal reasons, we cannot
provide updated frmware with the driver code.
Q: How can I update my firmware under Linux?
Use the 'prism2dl' utility. Note that it has been removed from
newer revisions of the driver sources due to liability reasons --
too many people fried their cards and blamed AVS for it.
Q: Can I use my 802.11b card as an AP under Linux?
Yes, and in the true free software fashion, there are several
ways:
a) linux-wlan-ng supports AP operation by using special tertiary
firmware on prism devices. This firmware is not generally
available, however. Contact Intersil for licensing terms.
b) The Prism2 HostAP driver uses the special HostAP mode of the
prism chipsets. http://people.ssh.com/jkm/Prism2/
c) The OpenAP project, which involves flashing Linux on access
points. http://opensource.instant802.com/
Q: After a few minutes of use, my card stops responding! I'm using WEP.
There seems to be card lockup problems with newer cards (new
DWL-650 cards, linksys WPC11v3) when WEP is turned on. Since
WEP is done in hardware, there is nothing the driver can do to
resolve this. We suggest you pester your vendor for a firmware
update.
Prism2.5 boards are also known to lock up under heavy use; this
is due to bugs in the WEP engine. Even if you perform a card
reset, the WEP engine remains stuck.
As an alternative, you can try out the host-based WEP present in
0.1.15-pre1 and newer. It is still considered experimental,
but the person typing this uses it on a daily basis.
Intersil claims to have fixed this in firmware 1.4.0:
"Fixed a hang condidion seen on certian hardware designs when
using firmware WEP"
Note there are other bugs in the firmware; as recently as 1.4.5
Intersil included a fix that would "Correct an error that could
cause the driver to no longer be able to communicate with the
firmware"
Contact your vendor and ask them to release updated firmware.
Q: When using host-based WEP I get these strange intermittent connection
lockups.
This should be fixed in 0.1.15-pre3. If you are sill having
problems, send a detailed message to the linux-wlan-devel
mailing list.
Q: When using the wlan-ng driver on a multiprocessor machine, I get
packet corruption or random crashes/lockups.
0.1.15-pre2 is the culmination of a major internal restructure
of driver internals. Please give it (or newer) a shot if you're
using a SMP system; we expect it to be much improved even on
uniprocessor systems as we lock out system interrupts for far
less time now.
Q: I have a PCI adapter, and upon resuming from a suspend, the device is not
responsive.
Much like you need to run some commands to bring the card to life
when the PC is first booted, you also need to perform similar
steps when the card comes out of suspend. Run '/etc/init.d/wlan start'
and all should be well.
You'll need to be running 0.1.15-pre3 or newer for this to work
properly.
The prism2.5/3 chipsets do not support PCI power management, so
this is the best we can realistically do.
Q: I have a Linksys WMP11, and under moderate to heavy traffic, I get
errors like "unknown port number" and "invalid frame type"
Make sure you're using the latest firmware avaliable from
Linksys's web site. According to the firmware release notes:
"Changes were made to prevent erroneous data from being
transferred over the PCI bus"
Note that this problem has also beeen confirmed on the D-Link
DWL-520. You will need firmware 1.3.5 or newer to resolve this.
Q: I have a D-Link DWL-650+/520+ card, why doesn't it work with this driver?
Notice the "plus" in the model number? The "plus" series of
cards from D-Link use the Texas Instruments ACX100 chipset. TI
has not been forthcoming with programming information.
Politely ask TI and D-Link for Linux drivers and/or docs.
We've been told that TI will be releaseing binary-only Linux
drivers sometime in December. In the mean time, return the
card and buy one that works with Linux.
Q: What other resources are there for Wireless LANs under Linux?
http://www.fuw.edu.pl/~pliszka/hints/wireless.html
http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Linux.Wireless.drivers.html