Strange wifi behavior using raspberry pi zero as portable AP

Question

I have a raspberry pi Zero with a 4 port USB hub attached to it (via pins on the back). The WiFi dongles that I'm using are twin Edimax EW-7811UN models. What I'm trying to use it for is Internet Connection Sharing. Where I connect to an AP with one dongle and route the traffic to the second dongle which acts as an AP. This set-up mostly works though there is one nagging problem. After a short period of time internet connectivity stops. For instance, when my phone is associated with the AP it displays "Connected. No Internet". The strange part is when I disconnect from the AP and then reconnect the internet connection works again for a short period of time then stops working. This can be done consistently.

I have tried the power saving fix which can sometimes plague these modules by creating a custom .config file as described here I've tried running hostapd in -dd mode but there are no significant log entries to note when the connection drops out. The log looks the same as it did when internet connection is present and when it somehow disconnects. I've even increased the logging output in the hostadp.conf file to see if that would give me something to work with to no avail. I initially thought this was somehow related to iptables so i installed iptables-persistent but this did not help. I also tried to use a completely different WiFi module from a different manufacturer. This did not help and the problem was still there with identical properties.

I'd really like to figure out why the internet connection goes down after a few minutes but then magically reconnects if I cycle my association to the AP. I'd love to be able to troubleshoot this myself but I have no idea which tools/command line options to use to do so. An out and out answer from someone on how to fix this would , of course, be great too!

Answer 1

Frankly speaking, I'd just go back to wheezy if that was working for you. If your RPi sits in a local network and is not exposed to the Internet via NAT or similar, there's no reason to upgrade at any cost. Security-wise it's no worse than using a router you have bought a few years back.

Having said that, there are several paths you might want to explore. First, I would try to download old wheezy firmware for your WiFi adapters and try to use that. It's possible that new Jessie drivers will work with old Wheezy firmware.

Second, since you have already tried playing with driver parameters, you might as well dig to the bottom here. Run modinfo rt8192cu | grep parm (or whatever your WiFi driver is) and note which parameters it has. Try setting these to sensible/safe values, reboot and retry.

Finally, you might want to run sudo iwevent in a terminal while running the AP. Hopefully something will appear in the log when the disconnect happens, getting you one step closer to the solution.

Answer 2

So as it turns out, recompiling hostapd to work with the edimax dongles or using the hostapd provided by edimax, as described in many other tutorials and posts all over the internet, only works when the dongle that is providing an internet connection is connected to an open access point or the internet connection is supplied by an ethernet link. The only dongles that work without issue in this type of configuration can be found here: pirate box wifi dongle compatibility. After securing Ralink RT5370 based USB-devices there were no further issues. Thanks to everyone for their assistance.