Arch Linux

Additional info:

wpa_supplicant 0.7.3-4

The wifi problem doesn't exist with Linux 3.0.7. I knew from kernel.org that there are some changes to ath9k but until now the wifi breakage still persist. In thread https://bugs.archlinux.org/task/26847, someone mention that ipv6 might cause wifi problem. I have tested on my laptop, the ipv6 module is fine, it is not the cause of wifi disconnection from router during rekey.

I played around with Fedora 16 today with linux-3.1.2-1 with NetworkManager 1:0.9.1.90-5-git20110927.fc16. The wifi has no disconnection problem. I just wonder is it that I am the only one using the following method to turn on wifi:

wpa_supplicant -Dwext -iwlan0 -c/etc/wpa_supplicant.conf
iwconfig wlan0 power off
dhcpd wlan0

I think it is because even kernel developers uses GNOME or KDE or XFCE (I used XFCE in Fedora 16), that is why no one met with the problem I encountered and so none can response to this tread.

Having my wpa_supplicant.conf under Arch Linux as follows:

ssid="LINUX-LINK"
proto=WPA2
key_mgmt=WPA-PSK
pairwise=TKIP
group=TKIP
wpa_ptk_rekey=600

will have wifi reconnection problem during wifi re-keying with TKIP protocol. For linux 3.1.5, the rekeying will just turn my AP and ath9k wifi card to suddenly speak different language and one constantly ask who is 192.168.1.1 and my AP will say 192.168.1.1 is at some MAC address and a link never establish! No such problem for the connection with linux 3.0.7 using the TKIP protocol.

However, Linux kernel wifi developer Jouni Malinen suggested that the encryption protocol be changed to CCMP:

ssid="LINUX-LINK"
proto=WPA2
key_mgmt=WPA-PSK
pairwise=CCMP
group=CCMP
wpa_ptk_rekey=600 # For testing purpose, will comment out later

and it works with my access point (AP) innacomm w3400v, a brand used by Telekom Malaysia, see http://www.innacomm.com.my/?page_id=225.

I still put the `wpa_ptk_rekey=600' just to test if rekeying will affect it. From Internet search results, if there is interference, the wifi connection between AP and laptop will break. For CCMP, during rekeying, there is a break of approximately 10 seconds which may be the time for random key generation and reconnection.

However, if I resume back to TKIP (the ISP set this as default. Well, Malaysia still lacks skilful technicians), after 10 minutes (wpa_ptk_rekey=600), the connection will break and NEVER RESUME (I called it `stall' previously). I believe during the code improvement from kernel 3.0 to 3.1, the changes in TKIP has created some bug in 3.1 (3.0 works and 3.1 fails, i.e. TKIP connection will resume in 3.0 but not 3.1). I perform a diff to see the changes but can't make much sense (I have extremely limited knowledge about linux kernel):

### diff -r linux-3.0/drivers/net/wireless/ath/ath9k/
linux-3.1/drivers/net/wireless/ath/ath9k/|grep -i tki
< #define is_mc_or_valid_tkip_keyix ((is_mc || \
< test_bit(rx_stats->rs_keyix, common->tkip_keymap))))
> bool is_mc, is_valid_tkip, strip_mic, mic_error;
> is_valid_tkip = rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID &&
> test_bit(rx_stats->rs_keyix, common->tkip_keymap);
> strip_mic = is_valid_tkip && !(rx_stats->rs_status &
> mic_error = is_valid_tkip && !ieee80211_is_ctl(fc) &&
< * decrypted using a valid TKIP key.
< is_mc_or_valid_tkip_keyix)
< #define AR_KEYTABLE_TYPE_TKIP 0x00000004

Since changing from TKIP to CCMP (using AES encryption) works, I will just ignore the problem with TKIP. However, I don't think the TKIP problem is resolved.

Just when I tought there is no problem with Linux 3.1.5's wifi (ath9k chip) connection with CCMP protocol with my router. The problem got even worst!!! Now I have `ath: Failed to stop TX DMA!' problem' (see the attachment). So I am moving back to linux 3.0.7.

Well, ath9k shown a similar error in linux 3.0.7 (as in 3.1.5, see the linux-3.1.5.dmesg). Apparently, there is some bug in linux 3.0 as well. I probably need to check if linux 2.26 has a similar problem.