Return-path: Received: from emh03.mail.saunalahti.fi ([62.142.5.109]:36566 "EHLO emh03.mail.saunalahti.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755388Ab3KEUzA (ORCPT ); Tue, 5 Nov 2013 15:55:00 -0500 From: Luciano Coelho To: linux-wireless@vger.kernel.org, sw@simonwunderlich.de Cc: johannes@sipsolutions.net Subject: [RFC v2 1/2] mac80211: don't transmit beacon with CSA count 0 Date: Tue, 5 Nov 2013 22:54:13 +0200 Message-Id: <1383684854-21663-1-git-send-email-luciano.coelho@intel.com> (sfid-20131105_215507_722544_3F836CA7) Sender: linux-wireless-owner@vger.kernel.org List-ID: A beacon should never have a Channel Switch Announcement information element with a count of 0, because a count of 1 means switch just before the next beacon. So, if a count of 0 was valid in a beacon, it would have been transmitted in the next channel already, which is useless. A CSA count equal to zero is only meaningful in action frames or probe_responses. Fix the ieee80211_csa_is_complete() and ieee80211_update_csa() functions accordingly. Cc: Simon Wunderlich Signed-off-by: Luciano Coelho --- In v2, updated the documentation to reflect the change. --- include/net/mac80211.h | 10 ++++++---- net/mac80211/tx.c | 10 +++++++--- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/include/net/mac80211.h b/include/net/mac80211.h index f386c48..2d0c6ab 100644 --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -2676,11 +2676,13 @@ enum ieee80211_roc_type { * @channel_switch_beacon: Starts a channel switch to a new channel. * Beacons are modified to include CSA or ECSA IEs before calling this * function. The corresponding count fields in these IEs must be - * decremented, and when they reach zero the driver must call + * decremented, and when they reach 1 the driver must call * ieee80211_csa_finish(). Drivers which use ieee80211_beacon_get() * get the csa counter decremented by mac80211, but must check if it is - * zero using ieee80211_csa_is_complete() after the beacon has been + * 1 using ieee80211_csa_is_complete() after the beacon has been * transmitted and then call ieee80211_csa_finish(). + * If the CSA count starts as zero or 1, this function will not be called, + * since there won't be any time to beacon before the switch anyway. * * @join_ibss: Join an IBSS (on an IBSS interface); this is called after all * information in bss_conf is set up and the beacon can be retrieved. A @@ -3379,13 +3381,13 @@ static inline struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw, * @vif: &struct ieee80211_vif pointer from the add_interface callback. * * After a channel switch announcement was scheduled and the counter in this - * announcement hit zero, this function must be called by the driver to + * announcement hits 1, this function must be called by the driver to * notify mac80211 that the channel can be changed. */ void ieee80211_csa_finish(struct ieee80211_vif *vif); /** - * ieee80211_csa_is_complete - find out if counters reached zero + * ieee80211_csa_is_complete - find out if counters reached 1 * @vif: &struct ieee80211_vif pointer from the add_interface callback. * * This function returns whether the channel switch counters reached zero. diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 9993fcb..1e0d40f 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -2376,8 +2376,12 @@ static void ieee80211_update_csa(struct ieee80211_sub_if_data *sdata, if (WARN_ON(counter_offset_beacon >= beacon_data_len)) return; - /* warn if the driver did not check for/react to csa completeness */ - if (WARN_ON(beacon_data[counter_offset_beacon] == 0)) + /* Warn if the driver did not check for/react to csa + * completeness. A beacon with CSA counter set to 0 should + * never occur, because a counter of 1 means switch just + * before the next beacon. + */ + if (WARN_ON(beacon_data[counter_offset_beacon] == 1)) return; beacon_data[counter_offset_beacon]--; @@ -2434,7 +2438,7 @@ bool ieee80211_csa_is_complete(struct ieee80211_vif *vif) if (WARN_ON(counter_beacon > beacon_data_len)) goto out; - if (beacon_data[counter_beacon] == 0) + if (beacon_data[counter_beacon] == 1) ret = true; out: rcu_read_unlock(); -- 1.8.4.rc3