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, 156 insertions, 0 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index d02d9ef6b1ef..5a4c6edd9348 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -10,6 +10,7 @@
 #include <linux/nl80211.h>
 #include <linux/rtnetlink.h>
 #include <net/net_namespace.h>
+#include <linux/rcupdate.h>
 #include <net/cfg80211.h>
 #include "ieee80211_i.h"
 #include "cfg.h"
@@ -294,6 +295,158 @@ static int ieee80211_get_station(struct wiphy *wiphy, struct net_device *dev,
         return 0;
 }
 
+/*
+ * This handles both adding a beacon and setting new beacon info
+ */
+static int ieee80211_config_beacon(struct ieee80211_sub_if_data *sdata,
+                                   struct beacon_parameters *params)
+{
+        struct beacon_data *new, *old;
+        int new_head_len, new_tail_len;
+        int size;
+        int err = -EINVAL;
+
+        old = sdata->u.ap.beacon;
+
+        /* head must not be zero-length */
+        if (params->head && !params->head_len)
+                return -EINVAL;
+
+        /*
+         * This is a kludge. beacon interval should really be part
+         * of the beacon information.
+         */
+        if (params->interval) {
+                sdata->local->hw.conf.beacon_int = params->interval;
+                if (ieee80211_hw_config(sdata->local))
+                        return -EINVAL;
+                /*
+                 * We updated some parameter so if below bails out
+                 * it's not an error.
+                 */
+                err = 0;
+        }
+
+        /* Need to have a beacon head if we don't have one yet */
+        if (!params->head && !old)
+                return err;
+
+        /* sorry, no way to start beaconing without dtim period */
+        if (!params->dtim_period && !old)
+                return err;
+
+        /* new or old head? */
+        if (params->head)
+                new_head_len = params->head_len;
+        else
+                new_head_len = old->head_len;
+
+        /* new or old tail? */
+        if (params->tail || !old)
+                /* params->tail_len will be zero for !params->tail */
+                new_tail_len = params->tail_len;
+        else
+                new_tail_len = old->tail_len;
+
+        size = sizeof(*new) + new_head_len + new_tail_len;
+
+        new = kzalloc(size, GFP_KERNEL);
+        if (!new)
+                return -ENOMEM;
+
+        /* start filling the new info now */
+
+        /* new or old dtim period? */
+        if (params->dtim_period)
+                new->dtim_period = params->dtim_period;
+        else
+                new->dtim_period = old->dtim_period;
+
+        /*
+         * pointers go into the block we allocated,
+         * memory is | beacon_data | head | tail |
+         */
+        new->head = ((u8 *) new) + sizeof(*new);
+        new->tail = new->head + new_head_len;
+        new->head_len = new_head_len;
+        new->tail_len = new_tail_len;
+
+        /* copy in head */
+        if (params->head)
+                memcpy(new->head, params->head, new_head_len);
+        else
+                memcpy(new->head, old->head, new_head_len);
+
+        /* copy in optional tail */
+        if (params->tail)
+                memcpy(new->tail, params->tail, new_tail_len);
+        else
+                if (old)
+                        memcpy(new->tail, old->tail, new_tail_len);
+
+        rcu_assign_pointer(sdata->u.ap.beacon, new);
+
+        synchronize_rcu();
+
+        kfree(old);
+
+        return ieee80211_if_config_beacon(sdata->dev);
+}
+
+static int ieee80211_add_beacon(struct wiphy *wiphy, struct net_device *dev,
+                                struct beacon_parameters *params)
+{
+        struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+        struct beacon_data *old;
+
+        if (sdata->vif.type != IEEE80211_IF_TYPE_AP)
+                return -EINVAL;
+
+        old = sdata->u.ap.beacon;
+
+        if (old)
+                return -EALREADY;
+
+        return ieee80211_config_beacon(sdata, params);
+}
+
+static int ieee80211_set_beacon(struct wiphy *wiphy, struct net_device *dev,
+                                struct beacon_parameters *params)
+{
+        struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+        struct beacon_data *old;
+
+        if (sdata->vif.type != IEEE80211_IF_TYPE_AP)
+                return -EINVAL;
+
+        old = sdata->u.ap.beacon;
+
+        if (!old)
+                return -ENOENT;
+
+        return ieee80211_config_beacon(sdata, params);
+}
+
+static int ieee80211_del_beacon(struct wiphy *wiphy, struct net_device *dev)
+{
+        struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+        struct beacon_data *old;
+
+        if (sdata->vif.type != IEEE80211_IF_TYPE_AP)
+                return -EINVAL;
+
+        old = sdata->u.ap.beacon;
+
+        if (!old)
+                return -ENOENT;
+
+        rcu_assign_pointer(sdata->u.ap.beacon, NULL);
+        synchronize_rcu();
+        kfree(old);
+
+        return ieee80211_if_config_beacon(dev);
+}
+
 struct cfg80211_ops mac80211_config_ops = {
         .add_virtual_intf = ieee80211_add_iface,
         .del_virtual_intf = ieee80211_del_iface,
@@ -302,5 +455,8 @@ struct cfg80211_ops mac80211_config_ops = {
         .del_key = ieee80211_del_key,
         .get_key = ieee80211_get_key,
         .set_default_key = ieee80211_config_default_key,
+        .add_beacon = ieee80211_add_beacon,
+        .set_beacon = ieee80211_set_beacon,
+        .del_beacon = ieee80211_del_beacon,
         .get_station = ieee80211_get_station,
 };