Hostapd recognizing ACKs from wpa_supplicant, but not external stations nor a packet crafter immediately adjacent to hostapd's interfaces

Ben Greear greearb
Thu May 28 10:46:35 PDT 2015

Are you effectively trying to use this WARP thing as the transport for
the hwsim driver?

Maybe you could back up a bit and explain the high level goals
that you are trying to accomplish?


On 05/28/2015 10:26 AM, Alfred Kenny wrote:
> I appreciate the replies thus far, but -- before this goes any further -- I should mention that I 
> am really quite the amateur when it comes to working with hardware, firmware and drivers. 
> I've been looking for documentation that spells things out in detail for hostapd, mac80211_hwsim,
> associated drivers and their interaction, but it seems like I need to have a bachelors in computer/software 
> engineering (rather than my lowly electrical degree) to fully understand what's going on. 
> So, I apologize if it'll be frustrating, but I'd be grateful if you could imagine that I'm a 15 year 
> old who is interested in working with the open-source software and hardware components 
> involved in 802.11 wireless communications. 
> This is the setup for our system, with each component shown existing on a linux machine: 
> That is to say, at no point does a wireless card come into play. All wireless transmissions are 
> handled by a WARP board which is listening for ethernet packets that have been placed on the 
> PC's eth1 and forwarding all relevant packets from the air back to the eth1.
> There, now that that huge preamble is complete, let's get to the points you've made.
>> You will need to sniff with a second radio that is only acting as sniffer
>> if you want to see all frames on the air (from other radios).
> Do you mean that I need to use a wireless card for the sole purpose of recognizing 
> ACKs directed toward this network? We're attempting to operate several networks 
> simultaneously with our setup, with each using a dedicated wlan interface. How would
> this work in such a configuration?
>> And some drivers/firmware, such as ath10k, still has issues sniffing certain packets.
>> ath9k (a/b/g/n) is a very good sniffer, and definitely shows beacons and such.
> Can these drivers somehow be operated independently of our system without 
> additional hardware? Remember that our system functions without the use of a wireless
> card. In fact, you could strip every networking device from the linux machine except for
> the ethernet card (eth1) and motherboard (eth0) and everything would function exactly
> as it does now.
>> As far as I know, no ACK frames are actually handed up the stack for any real driver.  The firmware and/or
>> hardware consumes them.  The tx-status often indicates whether ACK happened or not, however.
> Where would we be able to see this tx-status on the linux machine? Or is this only produced when 
> a wireless card is in place for receiving frames from air? When we run our system exactly as is with
> hostapd and mac80211_hwsim and then use wpa_supplicant as a test station, its ACKs are only seen
> at hwsim0 and apparently hostapd has been notified that they were received. This seems incongruous
> with the above point.
> Thanks again for all the replies. This is still mostly greek to me at this point. If anyone has any
> comprehensive documentation with test examples for the components that have been mentioned 
> thus far, I'd be more than happy to pore over them rather than bothering all of you.
> Cheers,
> Al

Ben Greear <greearb at>
Candela Technologies Inc

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