Date:   Tue, 15 Jan 2019 15:33:03 -0800
Message-Id: <20190115233303.226908-1-julanhsu@google.com>
Mime-Version: 1.0
Subject: [PATCH] mac80211: mesh: only switch path when new metric is at least
 10% better
From:   julanhsu@google.com
To:     johannes@sipsolutions.net
Cc:     linux-wireless@vger.kernel.org, Julan Hsu <julanhsu@google.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

From: Julan Hsu <julanhsu@google.com>

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>
---
 net/mac80211/mesh_hwmp.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 6950cd0bf594..9ce75ef3e249 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -441,7 +441,10 @@ 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;
 				}
@@ -506,8 +509,10 @@ 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);
-- 
2.20.1.97.g81188d93c3-goog