[RFC] mac80211: notify the user space about low signal quality

[Helmut Schaa <hschaa@suse.de>]

This patch adds a new wext event that notifies the user space about a low
signal quality. The currently used indicator is as follows: If three
successive beacons are received with a signal quality lower then 40%
user space gets informed.

Any ideas about which indicators should be used? Comments?

Signed-off-by: Helmut Schaa <hschaa@suse.de>
---
diff --git a/include/linux/wireless.h b/include/linux/wireless.h
index d7958f9..6229aa2 100644
--- a/include/linux/wireless.h
+++ b/include/linux/wireless.h
@@ -294,6 +294,7 @@
 #define SIOCSIWPOWER	0x8B2C		/* set Power Management settings */
 #define SIOCGIWPOWER	0x8B2D		/* get Power Management settings */
 
+
 /* WPA : Generic IEEE 802.11 informatiom element (e.g., for WPA/RSN/WMM).
  * This ioctl uses struct iw_point and data buffer that includes IE id and len
  * fields. More than one IE may be included in the request. Setting the generic
@@ -389,6 +390,8 @@
 					 * pre-authentication
 					 * (struct iw_pmkid_cand) */
 
+#define IWEVROAM	0x8C0A		/* roaming threshold exceeded */
+
 #define IWEVFIRST	0x8C00
 #define IW_EVENT_IDX(cmd)	((cmd) - IWEVFIRST)
 
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 3912fba..c05f70c 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -351,6 +351,7 @@ struct ieee80211_if_sta {
 	u32 supp_rates_bits[IEEE80211_NUM_BANDS];
 
 	int wmm_last_param_set;
+	unsigned int roam_threshold_count;
 };
 
 struct ieee80211_if_mesh {
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 2e55208..e67fe56 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -45,6 +45,7 @@
 
 #define IEEE80211_IBSS_MAX_STA_ENTRIES 128
 
+#define IEEE80211_ROAMING_QUALITY_THRESHOLD 40
 
 /* utils */
 static int ecw2cw(int ecw)
@@ -1659,6 +1660,27 @@ static void ieee80211_rx_mgmt_probe_resp(struct ieee80211_sub_if_data *sdata,
 	}
 }
 
+static void ieee80211_rx_check_threshold(struct ieee80211_sub_if_data *sdata,
+					 int freq)
+{
+	union iwreq_data wrqu;
+	struct ieee80211_bss *bss;
+	struct ieee80211_if_sta *ifsta = &sdata->u.sta;
+	bss = ieee80211_rx_bss_get(sdata->local, ifsta->bssid, freq,
+				   ifsta->ssid, ifsta->ssid_len);
+
+	if (bss->qual < IEEE80211_ROAMING_QUALITY_THRESHOLD) {
+		if (++(ifsta->roam_threshold_count) > 3) {
+			printk(KERN_DEBUG "%s roaming theshold exceeded\n",
+			       sdata->dev->name);
+			memset(&wrqu, 0, sizeof(wrqu));
+			wireless_send_event(sdata->dev, IWEVROAM, &wrqu, NULL);
+		}
+	} else
+		ifsta->roam_threshold_count = 0;
+
+	ieee80211_rx_bss_put(sdata->local, bss);
+}
 
 static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 				     struct ieee80211_mgmt *mgmt,
@@ -1711,6 +1733,7 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
 					       &bss_info);
 	}
 
+	ieee80211_rx_check_threshold(sdata, rx_status->freq);
 	ieee80211_bss_info_change_notify(sdata, changed);
 }
 
diff --git a/net/wireless/wext.c b/net/wireless/wext.c
index d98ffb7..c2feebb 100644
--- a/net/wireless/wext.c
+++ b/net/wireless/wext.c
@@ -387,6 +387,9 @@ static const struct iw_ioctl_description standard_event[] = {
 		.token_size	= 1,
 		.max_tokens	= sizeof(struct iw_pmkid_cand),
 	},
+	[IWEVROAM	- IWEVFIRST] = {
+		.header_type	= IW_HEADER_TYPE_ADDR,
+	},
 };
 static const unsigned standard_event_num = ARRAY_SIZE(standard_event);