Please suggest the best way to debug hostapd on Debian (Access Point stability problem)

Jouni Malinen j at
Tue Sep 6 09:03:45 PDT 2016

On Tue, Sep 06, 2016 at 10:54:39AM +0200, Kirill Peskov wrote:
> So the symptoms are:
> Once initialized (with combination of 2, 3 or 4 SSIDs), AP works fine.
> But depending on traffic (I've tested it with normal 'gadget-level'
> internet usage, e.g. listening Internet Radio, watching YouTube,
> chatting via WhatsApp, etc.) it takes several hours and AP occasionally
> stops working. It still able to authenticate clients, but no real
> traffic comes through. The problem appears not simultaneously on all
> active SSIDs, but one-by-one (the hostapd daemon is not crashing). To
> restore the functionality hostapd restart is enough, in other words I do
> not need to fiddle with iptables/routing/tunnels/tor again, just need to
> restart hostapd and it starts to work again. So I assume (maybe I'm
> wrong), that the problem is either with hostapd and/or its nl80211 or
> with the card driver itself.

That sounds like a driver issue or something in the kernel 802.11
implementation rather than something in hostapd.

> Watching -dd output of hostapd shows nothing unusual.

hostapd should not be involved during normal data traffic, so this is
not surprising. Restarting hostapd will reset state in the driver and
hardware/firmware and that seems to be sufficient to recover from
whatever state the device reached.

> What would be the best approach to debug/pinpoint the problem? I can
> download hostapd sources and use (for example) CodeLite as IDE for
> debugging or any other suggested debugger.

I'd look at the driver behavior rather than hostapd..

Jouni Malinen                                            PGP id EFC895FA

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