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authorEmmanuel Grumbach <emmanuel.grumbach@intel.com>2014-03-04 16:50:13 +0200
committerJohannes Berg <johannes.berg@intel.com>2014-03-19 21:29:56 +0100
commit3afc2167f60a327a2c1e1e2600ef209a3c2b75b7 (patch)
tree2588b9503edc6b574126f54eee64ccb00aceb863 /net/wireless/scan.c
parent2316d7b0544c4601cc852c801c93d1f451378740 (diff)
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 <emmanuel.grumbach@intel.com> [remove unused rx_freq variable] Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Diffstat (limited to 'net/wireless/scan.c')
-rw-r--r--net/wireless/scan.c28
1 files changed, 19 insertions, 9 deletions
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index d1ed4aebbbb7..7d9f5264a63c 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -680,7 +680,8 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *dev,
/* Returned bss is reference counted and must be cleaned up appropriately. */
static struct cfg80211_internal_bss *
cfg80211_bss_update(struct cfg80211_registered_device *dev,
- struct cfg80211_internal_bss *tmp)
+ struct cfg80211_internal_bss *tmp,
+ bool signal_valid)
{
struct cfg80211_internal_bss *found = NULL;
@@ -765,7 +766,12 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
}
found->pub.beacon_interval = tmp->pub.beacon_interval;
- found->pub.signal = tmp->pub.signal;
+ /*
+ * don't update the signal if beacon was heard on
+ * adjacent channel.
+ */
+ if (signal_valid)
+ found->pub.signal = tmp->pub.signal;
found->pub.capability = tmp->pub.capability;
found->ts = tmp->ts;
} else {
@@ -869,13 +875,14 @@ cfg80211_get_bss_channel(struct wiphy *wiphy, const u8 *ie, size_t ielen,
/* Returned bss is reference counted and must be cleaned up appropriately. */
struct cfg80211_bss*
cfg80211_inform_bss_width(struct wiphy *wiphy,
- struct ieee80211_channel *channel,
+ struct ieee80211_channel *rx_channel,
enum nl80211_bss_scan_width scan_width,
const u8 *bssid, u64 tsf, u16 capability,
u16 beacon_interval, const u8 *ie, size_t ielen,
s32 signal, gfp_t gfp)
{
struct cfg80211_bss_ies *ies;
+ struct ieee80211_channel *channel;
struct cfg80211_internal_bss tmp = {}, *res;
if (WARN_ON(!wiphy))
@@ -885,7 +892,7 @@ cfg80211_inform_bss_width(struct wiphy *wiphy,
(signal < 0 || signal > 100)))
return NULL;
- channel = cfg80211_get_bss_channel(wiphy, ie, ielen, channel);
+ channel = cfg80211_get_bss_channel(wiphy, ie, ielen, rx_channel);
if (!channel)
return NULL;
@@ -913,7 +920,8 @@ cfg80211_inform_bss_width(struct wiphy *wiphy,
rcu_assign_pointer(tmp.pub.beacon_ies, ies);
rcu_assign_pointer(tmp.pub.ies, ies);
- res = cfg80211_bss_update(wiphy_to_dev(wiphy), &tmp);
+ res = cfg80211_bss_update(wiphy_to_dev(wiphy), &tmp,
+ rx_channel == channel);
if (!res)
return NULL;
@@ -929,20 +937,21 @@ EXPORT_SYMBOL(cfg80211_inform_bss_width);
/* Returned bss is reference counted and must be cleaned up appropriately. */
struct cfg80211_bss *
cfg80211_inform_bss_width_frame(struct wiphy *wiphy,
- struct ieee80211_channel *channel,
+ struct ieee80211_channel *rx_channel,
enum nl80211_bss_scan_width scan_width,
struct ieee80211_mgmt *mgmt, size_t len,
s32 signal, gfp_t gfp)
{
struct cfg80211_internal_bss tmp = {}, *res;
struct cfg80211_bss_ies *ies;
+ struct ieee80211_channel *channel;
size_t ielen = len - offsetof(struct ieee80211_mgmt,
u.probe_resp.variable);
BUILD_BUG_ON(offsetof(struct ieee80211_mgmt, u.probe_resp.variable) !=
offsetof(struct ieee80211_mgmt, u.beacon.variable));
- trace_cfg80211_inform_bss_width_frame(wiphy, channel, scan_width, mgmt,
+ trace_cfg80211_inform_bss_width_frame(wiphy, rx_channel, scan_width, mgmt,
len, signal);
if (WARN_ON(!mgmt))
@@ -959,7 +968,7 @@ cfg80211_inform_bss_width_frame(struct wiphy *wiphy,
return NULL;
channel = cfg80211_get_bss_channel(wiphy, mgmt->u.beacon.variable,
- ielen, channel);
+ ielen, rx_channel);
if (!channel)
return NULL;
@@ -983,7 +992,8 @@ cfg80211_inform_bss_width_frame(struct wiphy *wiphy,
tmp.pub.beacon_interval = le16_to_cpu(mgmt->u.probe_resp.beacon_int);
tmp.pub.capability = le16_to_cpu(mgmt->u.probe_resp.capab_info);
- res = cfg80211_bss_update(wiphy_to_dev(wiphy), &tmp);
+ res = cfg80211_bss_update(wiphy_to_dev(wiphy), &tmp,
+ rx_channel == channel);
if (!res)
return NULL;