mac80211: Disallow concurrent IBSS/STA mode interfaces

Disallow having more than one IBSS interface up at any time
because of beacon distribution issues, and for now also disallow
having more than one IBSS/STA interface up at the same time
because we use the master interface's BSS struct which would
be completely corrupted when we have more than one up.

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

1 files changed, 47 insertions, 4 deletions

diff --git a/net/mac80211/ieee80211.c b/net/mac80211/ieee80211.c
index f82ebdd53d48..2133c9fd27a4 100644
--- a/net/mac80211/ieee80211.c
+++ b/net/mac80211/ieee80211.c
@@ -183,8 +183,52 @@ static int ieee80211_open(struct net_device *dev)
         list_for_each_entry(nsdata, &local->interfaces, list) {
                 struct net_device *ndev = nsdata->dev;
 
-                if (ndev != dev && ndev != local->mdev && netif_running(ndev) &&
-                    compare_ether_addr(dev->dev_addr, ndev->dev_addr) == 0) {
+                if (ndev != dev && ndev != local->mdev && netif_running(ndev)) {
+                        /*
+                         * Allow only a single IBSS interface to be up at any
+                         * time. This is restricted because beacon distribution
+                         * cannot work properly if both are in the same IBSS.
+                         *
+                         * To remove this restriction we'd have to disallow them
+                         * from setting the same SSID on different IBSS interfaces
+                         * belonging to the same hardware. Then, however, we're
+                         * faced with having to adopt two different TSF timers...
+                         */
+                        if (sdata->vif.type == IEEE80211_IF_TYPE_IBSS &&
+                            nsdata->vif.type == IEEE80211_IF_TYPE_IBSS)
+                                return -EBUSY;
+
+                        /*
+                         * Disallow multiple IBSS/STA mode interfaces.
+                         *
+                         * This is a technical restriction, it is possible although
+                         * most likely not IEEE 802.11 compliant to have multiple
+                         * STAs with just a single hardware (the TSF timer will not
+                         * be adjusted properly.)
+                         *
+                         * However, because mac80211 uses the master device's BSS
+                         * information for each STA/IBSS interface, doing this will
+                         * currently corrupt that BSS information completely, unless,
+                         * a not very useful case, both STAs are associated to the
+                         * same BSS.
+                         *
+                         * To remove this restriction, the BSS information needs to
+                         * be embedded in the STA/IBSS mode sdata instead of using
+                         * the master device's BSS structure.
+                         */
+                        if ((sdata->vif.type == IEEE80211_IF_TYPE_STA ||
+                             sdata->vif.type == IEEE80211_IF_TYPE_IBSS) &&
+                            (nsdata->vif.type == IEEE80211_IF_TYPE_STA ||
+                             nsdata->vif.type == IEEE80211_IF_TYPE_IBSS))
+                                return -EBUSY;
+
+                        /*
+                         * The remaining checks are only performed for interfaces
+                         * with the same MAC address.
+                         */
+                        if (compare_ether_addr(dev->dev_addr, ndev->dev_addr))
+                                continue;
+
                         /*
                          * check whether it may have the same address
                          */
@@ -196,8 +240,7 @@ static int ieee80211_open(struct net_device *dev)
                          * can only add VLANs to enabled APs
                          */
                         if (sdata->vif.type == IEEE80211_IF_TYPE_VLAN &&
-                            nsdata->vif.type == IEEE80211_IF_TYPE_AP &&
-                            netif_running(nsdata->dev))
+                            nsdata->vif.type == IEEE80211_IF_TYPE_AP)
                                 sdata->u.vlan.ap = nsdata;
                 }
         }