{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>

include/linux/nl80211.h

@@ -2112,6 +2112,10 @@ enum nl80211_mntr_flags {
  * @NL80211_MESHCONF_FORWARDING: set Mesh STA as forwarding or non-forwarding
  * or forwarding entity (default is TRUE - forwarding entity)
  *
+ * @NL80211_MESHCONF_RSSI_THRESHOLD: RSSI threshold in dBm. This specifies the
+ * threshold for average signal strength of candidate station to establish
+ * a peer link.
+ *
  * @NL80211_MESHCONF_ATTR_MAX: highest possible mesh configuration attribute
  *
  * @__NL80211_MESHCONF_ATTR_AFTER_LAST: internal use
@@ -2137,6 +2141,7 @@ enum nl80211_meshconf_params {
 	NL80211_MESHCONF_GATE_ANNOUNCEMENTS,
 	NL80211_MESHCONF_HWMP_PERR_MIN_INTERVAL,
 	NL80211_MESHCONF_FORWARDING,
+	NL80211_MESHCONF_RSSI_THRESHOLD,
 
 	/* keep last */
 	__NL80211_MESHCONF_ATTR_AFTER_LAST,

include/net/cfg80211.h

@@ -809,6 +809,7 @@ struct mesh_config {
 	 * Still keeping the same nomenclature to be in sync with the spec. */
 	bool  dot11MeshGateAnnouncementProtocol;
 	bool dot11MeshForwarding;
+	s32 rssi_threshold;
 };
 
 /**

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;
 }
 

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

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();

net/wireless/mesh.c

@@ -23,6 +23,8 @@
 #define MESH_PERR_MIN_INT	100
 #define MESH_DIAM_TRAVERSAL_TIME 50
 
+#define MESH_RSSI_THRESHOLD	0
+
 /*
  * A path will be refreshed if it is used PATH_REFRESH_TIME milliseconds
  * before timing out.  This way it will remain ACTIVE and no data frames
@@ -56,6 +58,7 @@ const struct mesh_config default_mesh_config = {
 	.dot11MeshHWMPRannInterval = MESH_RANN_INTERVAL,
 	.dot11MeshGateAnnouncementProtocol = false,
 	.dot11MeshForwarding = true,
+	.rssi_threshold = MESH_RSSI_THRESHOLD,
 };
 
 const struct mesh_setup default_mesh_setup = {

net/wireless/nl80211.c

@@ -3290,6 +3290,8 @@ static int nl80211_get_mesh_config(struct sk_buff *skb,
 			cur_params.dot11MeshGateAnnouncementProtocol);
 	NLA_PUT_U8(msg, NL80211_MESHCONF_FORWARDING,
 			cur_params.dot11MeshForwarding);
+	NLA_PUT_U32(msg, NL80211_MESHCONF_RSSI_THRESHOLD,
+			cur_params.rssi_threshold);
 	nla_nest_end(msg, pinfoattr);
 	genlmsg_end(msg, hdr);
 	return genlmsg_reply(msg, info);
@@ -3322,6 +3324,7 @@ static const struct nla_policy nl80211_meshconf_params_policy[NL80211_MESHCONF_A
 	[NL80211_MESHCONF_HWMP_RANN_INTERVAL] = { .type = NLA_U16 },
 	[NL80211_MESHCONF_GATE_ANNOUNCEMENTS] = { .type = NLA_U8 },
 	[NL80211_MESHCONF_FORWARDING] = { .type = NLA_U8 },
+	[NL80211_MESHCONF_RSSI_THRESHOLD] = { .type = NLA_U32},
 };
 
 static const struct nla_policy
@@ -3413,6 +3416,8 @@ do {\
 			nla_get_u8);
 	FILL_IN_MESH_PARAM_IF_SET(tb, cfg, dot11MeshForwarding,
 			mask, NL80211_MESHCONF_FORWARDING, nla_get_u8);
+	FILL_IN_MESH_PARAM_IF_SET(tb, cfg, rssi_threshold,
+			mask, NL80211_MESHCONF_RSSI_THRESHOLD, nla_get_u32);
 	if (mask_out)
 		*mask_out = mask;