From 3afc2167f60a327a2c1e1e2600ef209a3c2b75b7 Mon Sep 17 00:00:00 2001 From: Emmanuel Grumbach Date: Tue, 4 Mar 2014 16:50:13 +0200 Subject: cfg80211/mac80211: ignore signal if the frame was heard on wrong channel On 2.4Ghz band, the channels overlap since the delta between different channels is 5Mhz while the width of the receiver is 20Mhz (at least). This means that we can hear beacons or probe responses from adjacent channels. These frames will have a significant lower RSSI which will feed all kinds of logic with inaccurate data. An obvious example is the roaming algorithm that will think our AP is getting weak and will try to move to another AP. In order to avoid this, update the signal only if the frame has been heard on the same channel as the one advertised by the AP in its DS / HT IEs. We refrain from updating the values only if the AP is already in the BSS list so that we will still have a valid (but inaccurate) value if the AP was heard on an adjacent channel only. To achieve this, stop taking the channel from DS / HT IEs in mac80211. The DS / HT IEs is taken into account to discard the frame if it was received on a disabled channel. This can happen due to the same phenomenon: the frame is sent on channel 12, but heard on channel 11 while channel 12 can be disabled on certain devices. Since this check is done in cfg80211, stop even checking this in mac80211. Signed-off-by: Emmanuel Grumbach [remove unused rx_freq variable] Signed-off-by: Johannes Berg --- net/mac80211/ibss.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) (limited to 'net/mac80211/ibss.c') diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c index e458ca0dffec..06d28787945b 100644 --- a/net/mac80211/ibss.c +++ b/net/mac80211/ibss.c @@ -991,7 +991,6 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata, struct ieee802_11_elems *elems) { struct ieee80211_local *local = sdata->local; - int freq; struct cfg80211_bss *cbss; struct ieee80211_bss *bss; struct sta_info *sta; @@ -1003,15 +1002,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata, struct ieee80211_supported_band *sband = local->hw.wiphy->bands[band]; bool rates_updated = false; - if (elems->ds_params) - freq = ieee80211_channel_to_frequency(elems->ds_params[0], - band); - else - freq = rx_status->freq; - - channel = ieee80211_get_channel(local->hw.wiphy, freq); - - if (!channel || channel->flags & IEEE80211_CHAN_DISABLED) + channel = ieee80211_get_channel(local->hw.wiphy, rx_status->freq); + if (!channel) return; if (sdata->vif.type == NL80211_IFTYPE_ADHOC && -- cgit v1.2.3