2012-10-16 06:40:00

by Antonio Quartulli

Subject: [PATCHv3] nl/cfg80211: force scan using an AP vif if requested

If the user wants to scan using a vif configured as AP, cfg80211 must give him a
chance to do it, even if this will disrupt the stations performance due to
off-channel scanning. To do so, this patch adds a 'force' flag to the
SCAN_TRIGGER command which tells cfg80211 to perform the scanning operation even
if the vif is an AP and the beaconing has already started.

Signed-off-by: Antonio Quartulli <[email protected]>
---

v2:
- Rebased on latest mac80211-next/master
v3:
- Introduced nl80211_feature flag to advertise this feature to the userspace
and to allow drivers to do not support it


include/linux/nl80211.h | 8 ++++++++
net/mac80211/cfg.c | 11 ++++++++++-
net/mac80211/main.c | 4 +++-
3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index 0e6277a..617d0fb 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -3050,6 +3050,7 @@ enum nl80211_ap_sme_features {
* mode
* @NL80211_FEATURE_LOW_PRIORITY_SCAN: This driver supports low priority scan
* @NL80211_FEATURE_SCAN_FLUSH: Scan flush is supported
+ * @NL80211_FEATURE_AP_SCAN: Support scanning using an AP vif
*/
enum nl80211_feature_flags {
NL80211_FEATURE_SK_TX_STATUS = 1 << 0,
@@ -3060,6 +3061,7 @@ enum nl80211_feature_flags {
NL80211_FEATURE_SAE = 1 << 5,
NL80211_FEATURE_LOW_PRIORITY_SCAN = 1 << 6,
NL80211_FEATURE_SCAN_FLUSH = 1 << 7,
+ NL80211_FEATURE_AP_SCAN = 1 << 8,
};

/**
@@ -3103,10 +3105,16 @@ enum nl80211_connect_failed_reason {
*
* @NL80211_SCAN_FLAG_LOW_PRIORITY: scan request has low priority
* @NL80211_SCAN_FLAG_FLUSH: flush cache before scanning
+ * @NL80211_SCAN_FLAG_AP: force a scan even if the interface is configured
+ * as AP and the beaconing has already been configured. This attribute is
+ * dangerous because will destroy stations performance as a lot of frames
+ * will be lost while scanning off-channel, therefore it must be used only
+ * when really needed
*/
enum nl80211_scan_flags {
NL80211_SCAN_FLAG_LOW_PRIORITY = 1<<0,
NL80211_SCAN_FLAG_FLUSH = 1<<1,
+ NL80211_SCAN_FLAG_AP = 1<<2,
};

#endif /* __LINUX_NL80211_H */
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index ed27988..c45c62e 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1855,7 +1855,16 @@ static int ieee80211_scan(struct wiphy *wiphy,
* beaconing hasn't been configured yet
*/
case NL80211_IFTYPE_AP:
- if (sdata->u.ap.beacon)
+ /*
+ * If the scan has been forced (and the driver supports
+ * forcing), don't care about being beaconing already.
+ * This will create problems to the attached stations (e.g. all
+ * the frames sent while scanning on other channel will be
+ * lost)
+ */
+ if (sdata->u.ap.beacon &&
+ (!(wiphy->features & NL80211_FEATURE_AP_SCAN) ||
+ !(req->flags & NL80211_SCAN_FLAG_AP)))
return -EOPNOTSUPP;
break;
default:
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index ba5a232..c42094b 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -603,7 +603,9 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
NL80211_FEATURE_HT_IBSS;

if (!ops->hw_scan)
- wiphy->features |= NL80211_FEATURE_LOW_PRIORITY_SCAN;
+ wiphy->features |= NL80211_FEATURE_LOW_PRIORITY_SCAN |
+ NL80211_FEATURE_AP_SCAN;
+

if (!ops->set_key)
wiphy->flags |= WIPHY_FLAG_IBSS_RSN;
--
1.7.12.3

2012-10-18 15:21:23

by Johannes Berg

Subject: Re: [PATCHv3] nl/cfg80211: force scan using an AP vif if requested

On Tue, 2012-10-16 at 08:39 +0200, Antonio Quartulli wrote:
> If the user wants to scan using a vif configured as AP, cfg80211 must give him a
> chance to do it, even if this will disrupt the stations performance due to
> off-channel scanning. To do so, this patch adds a 'force' flag to the
> SCAN_TRIGGER command which tells cfg80211 to perform the scanning operation even
> if the vif is an AP and the beaconing has already started.

Applied, but please break commit logs to < 72 characters in the future
yourself.

johannes