mac80211: mesh: only switch path when new metric is at least 10% better

This helps to reduce frequent path switches when multiple path
candidates have the same or very similar path metrics.
Signed-off-by: Julan Hsu <julanhsu@google.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh_hwmp.c

@@ -447,7 +447,10 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
 			    (mpath->flags & MESH_PATH_SN_VALID)) {
 				if (SN_GT(mpath->sn, orig_sn) ||
 				    (mpath->sn == orig_sn &&
-				     new_metric >= mpath->metric)) {
+				     (rcu_access_pointer(mpath->next_hop) !=
+						      sta ?
+					      mult_frac(new_metric, 10, 9) :
+					      new_metric) >= mpath->metric)) {
 					process = false;
 					fresh_info = false;
 				}
@@ -515,8 +518,10 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
 		if (mpath) {
 			spin_lock_bh(&mpath->state_lock);
 			if ((mpath->flags & MESH_PATH_FIXED) ||
-				((mpath->flags & MESH_PATH_ACTIVE) &&
-					(last_hop_metric > mpath->metric)))
+			    ((mpath->flags & MESH_PATH_ACTIVE) &&
+			     ((rcu_access_pointer(mpath->next_hop) != sta ?
+				       mult_frac(last_hop_metric, 10, 9) :
+				       last_hop_metric) > mpath->metric)))
 				fresh_info = false;
 		} else {
 			mpath = mesh_path_add(sdata, ta);