[PATCH/RFC] mac80211: fix association with some APs

[Helmut Schaa <hschaa@suse.de>]

Some APs refuse association if the supported rates contained in the association
request do not match its own supported rates. This patch introduces a new
function which builds the intersection between the AP's supported rates and the
client's supported rates to work around such problems. The same approach is
already used in ipw2200 for example.

Signed-off-by: Helmut Schaa <hschaa@suse.de>

---
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index cb01995..8cc5805 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -650,6 +650,26 @@ static void ieee80211_authenticate(struct net_device *dev,
 	mod_timer(&ifsta->timer, jiffies + IEEE80211_AUTH_TIMEOUT);
 }
 
+static int ieee80211_compatible_rates(struct ieee80211_sta_bss *bss,
+				      struct ieee80211_supported_band *sband,
+				      u64 *rates)
+{
+	int i, j, count;
+	*rates = 0;
+	count = 0;
+	for (i = 0; i < bss->supp_rates_len; i++) {
+		int rate = (bss->supp_rates[i] & 0x7F) * 5;
+
+		for (j = 0; j < sband->n_bitrates; j++)
+			if (sband->bitrates[j].bitrate == rate) {
+				*rates |= BIT(j);
+				count++;
+				break;
+			}
+	}
+
+	return count;
+}
 
 static void ieee80211_send_assoc(struct net_device *dev,
 				 struct ieee80211_if_sta *ifsta)
@@ -658,11 +678,12 @@ static void ieee80211_send_assoc(struct net_device *dev,
 	struct sk_buff *skb;
 	struct ieee80211_mgmt *mgmt;
 	u8 *pos, *ies;
-	int i, len;
+	int i, len, count, rates_len, supp_rates_len;
 	u16 capab;
 	struct ieee80211_sta_bss *bss;
 	int wmm = 0;
 	struct ieee80211_supported_band *sband;
+	u64 rates = 0;
 
 	skb = dev_alloc_skb(local->hw.extra_tx_headroom +
 			    sizeof(*mgmt) + 200 + ifsta->extra_ie_len +
@@ -724,24 +745,37 @@ static void ieee80211_send_assoc(struct net_device *dev,
 	*pos++ = ifsta->ssid_len;
 	memcpy(pos, ifsta->ssid, ifsta->ssid_len);
 
+	rates_len = ieee80211_compatible_rates(bss, sband, &rates);
+	supp_rates_len = rates_len;
+	if (supp_rates_len > 8)
+		supp_rates_len = 8;
+
 	len = sband->n_bitrates;
-	if (len > 8)
-		len = 8;
-	pos = skb_put(skb, len + 2);
+	pos = skb_put(skb, supp_rates_len + 2);
 	*pos++ = WLAN_EID_SUPP_RATES;
-	*pos++ = len;
-	for (i = 0; i < len; i++) {
-		int rate = sband->bitrates[i].bitrate;
-		*pos++ = (u8) (rate / 5);
-	}
+	*pos++ = supp_rates_len;
 
-	if (sband->n_bitrates > len) {
-		pos = skb_put(skb, sband->n_bitrates - len + 2);
-		*pos++ = WLAN_EID_EXT_SUPP_RATES;
-		*pos++ = sband->n_bitrates - len;
-		for (i = len; i < sband->n_bitrates; i++) {
+	count = 0;
+	for (i = 0; i < sband->n_bitrates; i++) {
+		if (BIT(i) & rates) {
 			int rate = sband->bitrates[i].bitrate;
 			*pos++ = (u8) (rate / 5);
+			if (++count == 8)
+				break;
+		}
+	}
+
+	if (count == 8)
+	{
+		pos = skb_put(skb, rates_len - count + 2);
+		*pos++ = WLAN_EID_EXT_SUPP_RATES;
+		*pos++ = rates_len - count;
+
+		for (i++; i < sband->n_bitrates; i++) {
+			if (BIT(i) & rates) {
+				int rate = sband->bitrates[i].bitrate;
+				*pos++ = (u8) (rate / 5);
+			}
 		}
 	}