mac80211: add beacon configuration via cfg80211

This patch implements the cfg80211 hooks for configuring beaconing
on an access point interface in mac80211. While doing so, it fixes
a number of races that could badly crash the machine when the
beacon is changed while being requested by the driver.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 40 insertions, 25 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 99590e4ce30b..51c0f00d02d1 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1628,7 +1628,8 @@ void ieee80211_tx_pending(unsigned long data)
 
 static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
                                      struct ieee80211_if_ap *bss,
-                                     struct sk_buff *skb)
+                                     struct sk_buff *skb,
+                                     struct beacon_data *beacon)
 {
         u8 *pos, *tim;
         int aid0 = 0;
@@ -1644,7 +1645,7 @@ static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
                                           IEEE80211_MAX_AID+1);
 
         if (bss->dtim_count == 0)
-                bss->dtim_count = bss->dtim_period - 1;
+                bss->dtim_count = beacon->dtim_period - 1;
         else
                 bss->dtim_count--;
 
@@ -1652,7 +1653,7 @@ static void ieee80211_beacon_add_tim(struct ieee80211_local *local,
         *pos++ = WLAN_EID_TIM;
         *pos++ = 4;
         *pos++ = bss->dtim_count;
-        *pos++ = bss->dtim_period;
+        *pos++ = beacon->dtim_period;
 
         if (bss->dtim_count == 0 && !skb_queue_empty(&bss->ps_bc_buf))
                 aid0 = 1;
@@ -1700,44 +1701,43 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
         struct ieee80211_sub_if_data *sdata = NULL;
         struct ieee80211_if_ap *ap = NULL;
         struct rate_selection rsel;
-        u8 *b_head, *b_tail;
-        int bh_len, bt_len;
+        struct beacon_data *beacon;
+
+        rcu_read_lock();
 
         sdata = vif_to_sdata(vif);
         bdev = sdata->dev;
         ap = &sdata->u.ap;
 
-        if (!ap || sdata->vif.type != IEEE80211_IF_TYPE_AP ||
-            !ap->beacon_head) {
+        beacon = rcu_dereference(ap->beacon);
+
+        if (!ap || sdata->vif.type != IEEE80211_IF_TYPE_AP || !beacon) {
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                 if (net_ratelimit())
                         printk(KERN_DEBUG "no beacon data avail for %s\n",
                                bdev->name);
 #endif /* CONFIG_MAC80211_VERBOSE_DEBUG */
-                return NULL;
+                skb = NULL;
+                goto out;
         }
 
-        /* Assume we are generating the normal beacon locally */
-        b_head = ap->beacon_head;
-        b_tail = ap->beacon_tail;
-        bh_len = ap->beacon_head_len;
-        bt_len = ap->beacon_tail_len;
-
-        skb = dev_alloc_skb(local->tx_headroom +
-                bh_len + bt_len + 256 /* maximum TIM len */);
+        /* headroom, head length, tail length and maximum TIM length */
+        skb = dev_alloc_skb(local->tx_headroom + beacon->head_len +
+                            beacon->tail_len + 256);
         if (!skb)
-                return NULL;
+                goto out;
 
         skb_reserve(skb, local->tx_headroom);
-        memcpy(skb_put(skb, bh_len), b_head, bh_len);
+        memcpy(skb_put(skb, beacon->head_len), beacon->head,
+               beacon->head_len);
 
         ieee80211_include_sequence(sdata, (struct ieee80211_hdr *)skb->data);
 
-        ieee80211_beacon_add_tim(local, ap, skb);
+        ieee80211_beacon_add_tim(local, ap, skb, beacon);
 
-        if (b_tail) {
-                memcpy(skb_put(skb, bt_len), b_tail, bt_len);
-        }
+        if (beacon->tail)
+                memcpy(skb_put(skb, beacon->tail_len), beacon->tail,
+                       beacon->tail_len);
 
         if (control) {
                 rate_control_get_rate(local->mdev, local->oper_hw_mode, skb,
@@ -1749,7 +1749,8 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
                                        wiphy_name(local->hw.wiphy));
                         }
                         dev_kfree_skb(skb);
-                        return NULL;
+                        skb = NULL;
+                        goto out;
                 }
 
                 control->tx_rate =
@@ -1764,6 +1765,9 @@ struct sk_buff *ieee80211_beacon_get(struct ieee80211_hw *hw,
         }
 
         ap->num_beacons++;
+
+ out:
+        rcu_read_unlock();
         return skb;
 }
 EXPORT_SYMBOL(ieee80211_beacon_get);
@@ -1815,13 +1819,24 @@ ieee80211_get_buffered_bc(struct ieee80211_hw *hw,
         struct net_device *bdev;
         struct ieee80211_sub_if_data *sdata;
         struct ieee80211_if_ap *bss = NULL;
+        struct beacon_data *beacon;
 
         sdata = vif_to_sdata(vif);
         bdev = sdata->dev;
 
-        if (!bss || sdata->vif.type != IEEE80211_IF_TYPE_AP ||
-            !bss->beacon_head)
+
+        if (!bss)
+                return NULL;
+
+        rcu_read_lock();
+        beacon = rcu_dereference(bss->beacon);
+
+        if (sdata->vif.type != IEEE80211_IF_TYPE_AP || !beacon ||
+            !beacon->head) {
+                rcu_read_unlock();
                 return NULL;
+        }
+        rcu_read_unlock();
 
         if (bss->dtim_count != 0)
                 return NULL; /* send buffered bc/mc only after DTIM beacon */