[linux-wireless added to cc list] Igor Perminov wrote: > I have an issue related to handling power-saving stations by hostapd > and/or mac80211 stack. A station can't reconnect after it wakes up. > > The problems looks similar to another one having been reported to this > list earlier (STA can connect, but fails to reconnect within > ap_max_inactivity): > http://lists.shmoo.com/pipermail/hostap/2009-February/019192.html > > AP: Linux box with D-Link DWA-110 USB Wi-Fi stick (rt73usb kernel > driver), kernel 2.6.30 with some patches, hostapd 0.6.9. > Station: Toshiba G900 PDA under Windows Mobile 6.0. > > The environment is described in details here: > http://rt2x00.serialmonkey.com/phpBB/viewtopic.php?f=5&t=5486&start=10 > > Consider the following step-by-step: > 1. A station authenticates and associates with the AP and exchanges > traffic. > 2. The station indicates to the AP that it is going to sleep. > 3. The station device goes to the stand-by mode (not only its wi-fi > card, but the device itself). > 4. The station device wakes up and begins authentication with an > Authentication management frame. > > This is the behavior of my PDA. > > The problem is the mac80211 stack at the point 4 "remembers" that the > station has gone to sleep. So, the response frames from hostapd are > buffered by mac80211. > The station indicates in the Authentication frame that it isn't sleeping > anymore. But the mac80211 stack analyzes sleep/wake transitions in > _data_ frames only, but not in management ones. See > ieee80211_rx_h_sta_process in net/mac80211/rx.c. A comment there notes: > "Ignore doze->wake transitions that are indicated by non-data frames, > the standard is unclear here". > As the result, the station never receives the authentication response > from the AP. > > One solution against this problem could be implemented in hostapd: to > force the mac80211 stack to "forget" the station just after receiving an > authentication frame (the patch is below). After this change the station > can reconnect successfully. i just did a quick test and your hostapd patch does indeed fix my problem too (p54+hostapd with a winmobile device that couldn't reconnect after turning the wifi module off and on). > Another solution (in theory) would be to improve the mac80211 > implementation: to analyze not only data frames, but also > management ones (or may be just some kinds of them) in > ieee80211_rx_h_sta_process. would seem to make sense, but having not read the spec i have no idea if that's the right answer; hence the linux-wireless cc... > I've asked this question to the linux-wireless mailing list few days > ago, but nobody has answered still: > http://marc.info/?l=linux-wireless&m=124879549212741&w=2 > > And what is your opinion, what is a better way: should this problem be > fixed in hostapd or in mac80211? > > === Begin diff === > --- a/hostapd/ieee802_11.c 2009-06-29 14:21:59.000000000 +0400 > +++ b/hostapd/ieee802_11.c 2009-07-21 16:28:17.000000000 +0400 > @@ -583,6 +583,13 @@ > goto fail; > } > > + res = hostapd_sta_remove(hapd, mgmt->sa); > + if (res) { > + wpa_printf(MSG_DEBUG, "authentication: STA=" MACSTR > + ", hostapd_sta_remove returned %d\n", > + MAC2STR(mgmt->sa), res); > + } > + > if (vlan_id > 0) { > if (hostapd_get_vlan_id_ifname(hapd->conf->vlan, > sta->vlan_id) == NULL) { > === End diff === Thanks for the cc, added this to my local hostapd patch set, until the issue gets resolved one way or another. artur -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
