{nl,cfg,mac}80211: Implement RSSI threshold for mesh peering

Mesh peer links are established only if average rssi of the peer
candidate satisfies the threshold. This is not in 802.11s specification
but was requested by David Fulgham, an open80211s user. This is a way to avoid
marginal peer links with stations that are barely within range.

This patch adds a new mesh configuration parameter, mesh_rssi_threshold. This
feature is supported only for hardwares that report signal in dBm.

Signed-off-by: Ashok Nagarajan <ashok@cozybit.com>
Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 25 insertions, 1 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 6a77d4c910f9..ab31cc56a2fb 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1314,6 +1314,14 @@ static int ieee80211_update_mesh_config(struct wiphy *wiphy,
         }
         if (_chg_mesh_attr(NL80211_MESHCONF_FORWARDING, mask))
                 conf->dot11MeshForwarding = nconf->dot11MeshForwarding;
+        if (_chg_mesh_attr(NL80211_MESHCONF_RSSI_THRESHOLD, mask)) {
+                /* our RSSI threshold implementation is supported only for
+                 * devices that report signal in dBm.
+                 */
+                if (!(sdata->local->hw.flags & IEEE80211_HW_SIGNAL_DBM))
+                        return -ENOTSUPP;
+                conf->rssi_threshold = nconf->rssi_threshold;
+        }
         return 0;
 }
 
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 510ed1dab3c7..9f484d8905fd 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -443,6 +443,7 @@ IEEE80211_IF_FILE(dot11MeshGateAnnouncementProtocol,
 IEEE80211_IF_FILE(dot11MeshHWMPRannInterval,
                 u.mesh.mshcfg.dot11MeshHWMPRannInterval, DEC);
 IEEE80211_IF_FILE(dot11MeshForwarding, u.mesh.mshcfg.dot11MeshForwarding, DEC);
+IEEE80211_IF_FILE(rssi_threshold, u.mesh.mshcfg.rssi_threshold, DEC);
 #endif
 
 
@@ -581,6 +582,7 @@ static void add_mesh_config(struct ieee80211_sub_if_data *sdata)
         MESHPARAMS_ADD(dot11MeshHWMPRootMode);
         MESHPARAMS_ADD(dot11MeshHWMPRannInterval);
         MESHPARAMS_ADD(dot11MeshGateAnnouncementProtocol);
+        MESHPARAMS_ADD(rssi_threshold);
 #undef MESHPARAMS_ADD
 }
 #endif
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 8806e5ef8ffe..80ce52772538 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -31,6 +31,11 @@
 #define dot11MeshHoldingTimeout(s) (s->u.mesh.mshcfg.dot11MeshHoldingTimeout)
 #define dot11MeshMaxPeerLinks(s) (s->u.mesh.mshcfg.dot11MeshMaxPeerLinks)
 
+#define sta_meets_rssi_threshold(sta, sdata) \
+                (sdata->u.mesh.mshcfg.rssi_threshold == 0 ||\
+                (s8) -ewma_read(&sta->avg_signal) > \
+                sdata->u.mesh.mshcfg.rssi_threshold)
+
 enum plink_event {
         PLINK_UNDEFINED,
         OPN_ACPT,
@@ -301,7 +306,8 @@ void mesh_neighbour_update(u8 *hw_addr, u32 rates,
         if (mesh_peer_accepts_plinks(elems) &&
                         sta->plink_state == NL80211_PLINK_LISTEN &&
                         sdata->u.mesh.accepting_plinks &&
-                        sdata->u.mesh.mshcfg.auto_open_plinks)
+                        sdata->u.mesh.mshcfg.auto_open_plinks &&
+                        sta_meets_rssi_threshold(sta, sdata))
                 mesh_plink_open(sta);
 
         rcu_read_unlock();
@@ -531,6 +537,14 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata, struct ieee80211_m
                 return;
         }
 
+        if (ftype == WLAN_SP_MESH_PEERING_OPEN &&
+            !sta_meets_rssi_threshold(sta, sdata)) {
+                mpl_dbg("Mesh plink: %pM does not meet rssi threshold\n",
+                        sta->sta.addr);
+                rcu_read_unlock();
+                return;
+        }
+
         if (sta && !test_sta_flag(sta, WLAN_STA_AUTH)) {
                 mpl_dbg("Mesh plink: Action frame from non-authed peer\n");
                 rcu_read_unlock();