Return-path: Received: from senator.holtmann.net ([87.106.208.187]:35307 "EHLO mail.holtmann.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751757AbZGaJlE (ORCPT ); Fri, 31 Jul 2009 05:41:04 -0400 Subject: Re: [PATCH] mac80211: use beacons for connection monitoring From: Marcel Holtmann To: Maxim Levitsky Cc: Johannes Berg , Reinette Chatre , linville@tuxdriver.com, linux-wireless@vger.kernel.org In-Reply-To: <1249027460.2609.2.camel@maxim-laptop> References: <1248903159-17024-1-git-send-email-reinette.chatre@intel.com> <1249024097.7653.6.camel@maxim-laptop> <1249026181.29587.14.camel@johannes.local> <1249027087.29587.18.camel@johannes.local> <1249027460.2609.2.camel@maxim-laptop> Content-Type: text/plain Date: Fri, 31 Jul 2009 02:41:13 -0700 Message-Id: <1249033273.23662.7.camel@localhost.localdomain> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi Maxim, > > > Fix it then. Offer an implementation of your superior solution. > > > > I just don't think that this patch is a solution because it means that > > we'll be connected to the AP forever, without knowing anything is wrong, > > if the AP can reach us but we can't reach the AP (maybe because we have > > a good Intel card with great sensitivity). > > > > Sure -- it's possible to factor in transmit status reports (but remember > > that not all hardware gives those reliably) or do things on a different > > schedule etc. But as long as nobody wants to really improve things I > > don't see why we should take the regression and _remove_ the current > > behaviour. > > It is ok to send probes every minute or so, but not each second, and > probes must be retried. > > Because of these probes, wireless literally reconnects every 5 seconds, > here, and I am 10 meters from the AP. even with Reinette's patch, I am seeing this: [18594.423855] wlan0: cancelling probereq poll due to a received beacon [18629.544841] No probe response from AP 00:1c:f0:xx:xx:xx after 200ms, disconnecting. So that is with the patch, being 1m away from the AP, in the 18th floor of a building and with only another 10 APs around me. The Bluetooth world calls this link supervision timeout and the default value for that timeout is 30 seconds. I think it is the best to make this value configurable and increase it to at least 30 seconds by default. Within Bluetooth you can change it and runtime. Johannes, I don't care how good or bad some hardware is. How sensitive or not. This is a clear regression and you are overdoing it here with only waiting for 200ms. Regards Marcel