Re: Question about PRISM2 header rate field

[Andy Green <andy@warmcat.com>]

Andy Green wrote:

> On a capture of a broadcast which I believe was at 54Mbps, I see the 
> PRISM2 / ieee80211_frame_info field "datarate" is set to 0xf0, or 240 
> decimal.  I looked around at the various different ways of talking about 
> tx rate in the stack and drivers, but none that I found use 0xf0 for 
> 54Mbps.  Is it 48Mbps in units of 200kHz?  Or 54Mbps in units of 225kHz 
> (!!)  Or...?
> 
> I am trying to reissue this captured packet using the management 
> interface (which I can now conjure up) with a rate that I can control, 
> but I did not find any information on the coding for this field.

Well, I discover in fact you need to inject starting only from the 
IEEE802.11 header... and indeed that does work if you do it on the 
"Management Interface".  I found this from hostapd sources, since 
wpa_supplicant doesn't seem to inject packets from userspace, it seems 
to trigger the stack to do canned packets by a huge range of IOCTLs.  So 
I have unencrypted packets in both directions now without patching 
anything on the kernel side :-D  But, there is a but...

The packet seems to go out at a default rate, in my case 1Mbps.  Is 
there in fact a method for requesting the rate for injected packets, or 
is there at the moment a simple equivalence that all broadcasts will go 
out at 1Mbps?

-Andy