Return-path: Received: from mail-vx0-f174.google.com ([209.85.220.174]:37944 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752180Ab2BTLDg (ORCPT ); Mon, 20 Feb 2012 06:03:36 -0500 Received: by vcge1 with SMTP id e1so3522713vcg.19 for ; Mon, 20 Feb 2012 03:03:35 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <201202201048.01883.chunkeey@googlemail.com> References: <201202201048.01883.chunkeey@googlemail.com> Date: Mon, 20 Feb 2012 16:33:35 +0530 Message-ID: (sfid-20120220_120339_900810_70F86FBC) Subject: Re: AP send null-data packet? From: Mohammed Shafi To: Christian Lamparter Cc: Yingang Fu , linux-wireless@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: > Don't know much about other AP software. But hostapd sends them > to check if a station is still in range and active. > > quote from hostapd.conf: > > # Station inactivity limit > # > # If a station does not send anything in ap_max_inactivity seconds, an > # empty data frame is sent to it in order to verify whether it is > # still in range. If this frame is not ACKed, the station will be > # disassociated and then deauthenticated. This feature is used to > # clear station table of old entries when the STAs move out of the > # range. i think also in this path in mac80211 sta_notify (driver call back) for AP mode ieee80211_sta_block_awake sta_unblock -> ieee80211_sta_ps_deliver_poll_response -> ieee80211_sta_ps_deliver_response -> ieee80211_send_null_response also in UAPSD path. i don't know much about the technical details -- thanks, shafi