[ath9k-devel] Ath9k packets dropping issue

[Wang Jian <lark@linux.net.cn>]

Hi there,

I am using openwrt on TL-WR941ND, using dev snapshot build ( http://downloads.openwrt.org/people/agb/ar71xx-ath9k-snapshots/ ).

  root at OpenWrt:~# uname -a
  Linux OpenWrt 2.6.28.7 #2 Sat Feb 28 23:35:50 PST 2009 mips unknown

TL-WR941ND is an consumer router based on AP81, using AR9132/AR9103 chips (per RoundSparrow).

I notice strange packets dropping, for example, I can (telnet) connect from wireless client to the other side of (wired) network to port 22, but got stuck when connection established. After random but
long freezing time, I get ssh banner. But ping from wireless client to the other side of (wired) network is very smooth.

The scenario:

A(XP box) .......(wireless)...... B (WR941N as pure AP) ------------(wired)------------ C(Linux box)
 192.168.0.121                          192.168.1.1                                     192.168.0.254

1. A ping C: very smooth
2. C ping A: most ping lost, with one or two responses out of 40+ pings


I silent A by closing most packet sending program, run sniffers (wireshark or tcpdump) on A,B,C, and watch tx/rx counters of B's wlan0 interface. Then I run ping from A to C, and C to A.

1. For every ping packets A sends to C, B's rx and tx counter increase.
2. For nearly every ping packets C sends to A, B's tx counter increases, A doesn't receive this ping, B's rx counter stays unchanged.
3. Every a few seconds, arp requests occurs, and C may get one and only one ping response.
4. All ping request shows itself in B's tcpdump output.

So, things get clear here: B seems only succeed to do tx after rx on wireless interface.

This looks like queue related problem or interrupt handler problem.