Re: WDS working (kind of)

From: Jouni Malinen (
Date: 2002-04-06 20:17:29 UTC

On Sat, Apr 06, 2002 at 08:06:34AM -0800, John D. Rowell wrote:

> Now comes the funky part. I can ping most IPs in either wireless or
> wired networks (some take a bit to show up, probably related to the
> bridging), using any ICMP packet size (I tried several up to 30Kb).
> OTOH, any UDP or TCP seems to get truncated. DNS does not work, and
> trying to fetch a page using HTTP only retrieves the first 4Kb. Needless
> to say, things like ssh do not work due to this...

Aaah.. My ping testing<TM> is apparently not enough anymore ;-). Actually, to be exact, my ping testing with even sized packets was not enough. Using odd sized packets duplicates the problem..

Fake-WDS header generation had bug in it.. I added the fourth address after the payload, but did not consider what would happen if the payload length was odd. Prism2 chipset does not support writes to odd offset, so this resulted in last byte of the payload being overwritten. Patch to fix this is attached and I'll have to apparently release new version of the driver, but that can wait till tomorrow.

> I'm getting lots of debug messages in the log files.

I was seing some dropped frames when using bridging code, but I haven't yet looked into them more closely since everything seemed to be working. Anyway, I didn't see any dropped frames with the latest driver and odd sized packets and TCP worked fine. However, I did not test bridging code this time. I'll take a closer look at it later.

> The MAC addresses after the "dropped received packet from" are always
> from one of the other two APs I'm WDSing with. A4 varies a lot (not only
> sequential octets). I've seen A4=68:65:3c:2f:54:54 and
> A4=70:3a:2f:2f:77:77, for instance.

Addr4 in those header dumps is from the Prism2 rx/tx frame header and it will contain some random information in more or less every case. If someone would happen to send standard-compiliant WDS frame, it might even be correct address.

> On a separate issue, doesn't the fact that WDS works on a single channel
> create inter-AP interference?

Yes and I would consider using two cards (on different channels) in each AP when WDS is used in an AP that has client stations. Making a wireless link between two wired networks on the other hand, would not suffer from this.

Jouni Malinen                                            PGP id EFC895FA

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