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

Alfred Kenny alfred.kenny at mail.mcgill.ca
Thu May 28 11:27:32 EDT 2015


Thanks for your response, Jouni.

> hostapd does not receive or process an ACK frame; the WLAN hardware,
> firmware, and/or driver are the places where this is done and the result
> (TX status) is reported to hostapd.

I think I understand this point. Does this mean that ACKs should be forwarded to the wlanX interface associated with mon.wlanX rather than mon.wlanX itself?

> The actual ACK frame has nothing to do with that, i.e., this is based on internal knowledge of
> which radio(s) are awake on the channel on which a frame is transmitted.
> This has little to do with how IEEE 802.11 works over real hardware and
> as such, you cannot really do what you are describing here with
> mac80211_hwsim.

I'm not sure I understand this, though. Would it be possible for you to describe a simple test setup for proper routing of ACK frames in the context of a system running mac80211_hwsim? Currently, we require hwsim0 to see the all management frames generated by hostapd, as mon.wlan0 appears to show everything but beacon frames, and obviously beacon frames are essential.

Our current setup isn't using wlan interfaces to directly communicate with stations, but rather looks something like this:

LAN<-->eth0<-->bridge<-->wlan0<-->ovs<-->eth1<-->AP<-->air
                         hostapd-->hwism0-->libtins-->|
                                ^---mon.wlan0<--libtins<--'

i.e. the wlan interface is used for frames whose source or destination is the LAN (e.g. data). Management frames (and ACKs at the moment) from STAs are forwarded by a libtins agent to mon.wlan0 and the management frames generated by hostapd are forwarded from hwsim0 to eth1 by another libtins agent. In essence, wlan0 is just an interface that we use for traffic-shaping purposes. Everything but ACKs seem to work fine with this setup, so what might you suggest in terms of routing/interfacing modifications such that the reception of ACK frames are recognized by hostapd?

My apologies if this reply doesn't show up properly. This is my first time using a mailing list.

Thanks,
Al


More information about the HostAP mailing list