Promiscuous strangeness with Prism II card + orinoco-0.11 driver

[David Gibson]

On Fri, Apr 26, 2002 at 09:04:30AM +0200, Miklos Szeredi wrote:
> 
> I'm using the orinoco-0.11 driver with an SMC-2632W card in managed
> mode.  I've tested it with a Lucent AP as well as a with another
> SMC-2632W card driven by the PrismII host-AP driver.
> 
> When the card is put into promiscuous mode (e.g. by starting tcpdump)
> the receiving throughput drops from 4.5Mb/s to about 300kb/s.
> 
> Using a wireless sniffer I've managed to uncover the cause of this:
> the card in not sending ACK's in reply to data frames, even though it
> does receive them.  This will cause the AP to retransmit the data
> frames many times, thus decreasing the throughput.

Well that is interesting.  I'd suspected the slow througput problems
that some people have been seing on Intersil firmware were due to
missing ACKs, but it's very useful to have confirmation.

> Has anyone experienced similar problems?

I haven't been able to reproduce it myself yet, but I've had lots of
bug reports of slow throughput.  It would have been even worse in the
0.09 versions since these versions put the card into promiscuous mode
if there were any multicast addresses set (if the Intersil cards are
even capable of multicast reception I don't know how to set it up).

> The same behavior can be observed with the wvlan_cs driver.  Only the
> orinoco and the wvlan_cs driver seem to actually implement promiscuous
> mode, so I cannot test this with other drivers (wlan-ng, PrismII).
> Lucent cards using the same driver work normally in promiscuous mode.
> 
> The f/w version of the SMC card is reported as 0.08 by the orinoco
> driver, and 0.8.3 by the PrismII driver.
> 
> Is it possible that this is a firmware bug?  Where do I report such a bug?

Quite possibly.  Or it could just be that we don't understand how the
firmware operates and we need to poke it differently somehow to make
it generate acks.  The fact that they are generated if the card isn't
in promiscuous mode does suggest a bug, though.

I've not idea where you would report such a bug.  I suspect that
Intersil won't actually care if they have a workaround in the Windows
driver.

-- 
David Gibson			| For every complex problem there is a
david at gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.  -- H.L. Mencken
http://www.ozlabs.org/people/dgibson