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

[Kirill Peskov]

Hi All,

Since couple of months I'm playing with hostapd on Raspberry Pi 3,
prototyping sort of smart access point with multiple SSIDs (each SSID
has its own set of routing, security and QoS rules).

As soon as only small subset of USB WLAN cards has an AP mode and even
smaller subset is able to serve more than one SSID, currently I stick
with 2 chipsets:

* Atheros-based cards (up to 2 SSIDs), driver ath9k_htc

* Ralink-based cards (up to 8 SSIDs), driver rt2800usb/rt2x00usb


Additional tools used:

* Stock hostapd from Raspbian (ARM) or Debian Jessie (x86_64), version 2.3

* dnsmasq as DHCP server

* iptables (for packet mangling and masquerading)

* tor daemon (one of SSIDs is to provide Tor routed internet access)

* openvpn for tunneled virtual uplinks


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.

Watching -dd output of hostapd shows nothing unusual.

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.


Thanx a lot in advance,

Kirill