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From:   greearb@candelatech.com
To:     linux-wireless@vger.kernel.org
Cc:     Ben Greear <greearb@candelatech.com>
Subject: [PATCH v3] wifi: mac80211: ethtool: use best available link for default stats.
Date:   Fri, 27 Oct 2023 09:50:35 -0700
Message-Id: <20231027165035.243720-1-greearb@candelatech.com>
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From: Ben Greear <greearb@candelatech.com>

Best link is the link with the highest state (ie, associated)
and if multiple links have same state, the highest
frequency wins.

This makes current ethtool stats more useful.  Per-link
ethtool stats can be added later.

Signed-off-by: Ben Greear <greearb@candelatech.com>
---

v3:  Fix glaring bug in ieee80211_find_best_sta_link that would
have crashed on 2+ links.

Re-work locking slightly in ethtool.c:  Cannot hold rcu_read_lock
while calling sta_set_sinfo.  I'm hoping the wiphy_lock means that
link and/or sta cannot go away while this method is being traversed,
otherwise the rcu read lock/unlock around ieee80211_find_best_sta_link
is probably not sufficient.

 net/mac80211/ethtool.c  | 12 +++++++--
 net/mac80211/link.c     | 56 +++++++++++++++++++++++++++++++++++++++++
 net/mac80211/sta_info.h |  4 +++
 3 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/ethtool.c b/net/mac80211/ethtool.c
index 99f6174a9d69..3d12111996e5 100644
--- a/net/mac80211/ethtool.c
+++ b/net/mac80211/ethtool.c
@@ -83,6 +83,7 @@ static void ieee80211_get_stats(struct net_device *dev,
 	struct ieee80211_local *local = sdata->local;
 	struct station_info sinfo;
 	struct survey_info survey;
+	struct ieee80211_link_data *link = NULL;
 	int i, q;
 #define STA_STATS_SURVEY_LEN 7
 
@@ -112,12 +113,17 @@ static void ieee80211_get_stats(struct net_device *dev,
 	wiphy_lock(local->hw.wiphy);
 
 	if (sdata->vif.type == NL80211_IFTYPE_STATION) {
-		sta = sta_info_get_bss(sdata, sdata->deflink.u.mgd.bssid);
+		rcu_read_lock();
+		sta = ieee80211_find_best_sta_link(sdata, &link);
+		rcu_read_unlock();
 
 		if (!(sta && !WARN_ON(sta->sdata->dev != dev)))
 			goto do_survey;
 
 		memset(&sinfo, 0, sizeof(sinfo));
+		/* sta_set_sinfo cannot hold rcu read lock since it can block
+		 * calling into firmware for stats.
+		 */
 		sta_set_sinfo(sta, &sinfo, false);
 
 		i = 0;
@@ -158,7 +164,9 @@ static void ieee80211_get_stats(struct net_device *dev,
 
 	rcu_read_lock();
 	chanctx_conf = rcu_dereference(sdata->vif.bss_conf.chanctx_conf);
-	if (chanctx_conf)
+	if (link)
+		channel = link->conf->chandef.chan;
+	else if (chanctx_conf)
 		channel = chanctx_conf->def.chan;
 	else
 		channel = NULL;
diff --git a/net/mac80211/link.c b/net/mac80211/link.c
index bf7bd880d062..2dc0f46ee053 100644
--- a/net/mac80211/link.c
+++ b/net/mac80211/link.c
@@ -115,6 +115,62 @@ static void ieee80211_free_links(struct ieee80211_sub_if_data *sdata,
 		kfree(links[link_id]);
 }
 
+/* For cases where we need a link for stats and such, and just want
+ * a 'good' one.
+ */
+struct sta_info *
+ieee80211_find_best_sta_link(struct ieee80211_sub_if_data *sdata,
+			     struct ieee80211_link_data **link)
+{
+	struct ieee80211_link_data *best_link = NULL;
+	struct sta_info *best_sta = NULL;
+	int i;
+
+	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++) {
+		struct ieee80211_link_data *link1;
+		struct sta_info *sta1;
+		bool sta1_better = false;
+
+		link1 = sdata_dereference(sdata->link[i], sdata);
+		if (!link1)
+			continue;
+		if (!best_link) {
+			best_link = link1;
+			best_sta = sta_info_get_bss(sdata, best_link->u.mgd.bssid);
+			continue;
+		}
+
+		sta1 = sta_info_get_bss(sdata, link1->u.mgd.bssid);
+		if (!sta1)
+			continue;
+
+		/* we have two potential best links, find one we like best. */
+		if (!best_sta || sta1->sta_state > best_sta->sta_state) {
+			sta1_better = true;
+		} else if (sta1->sta_state == best_sta->sta_state) {
+			u32 freq_best = 0;
+			u32 freq1 = 0;
+
+			if (best_link->conf->chandef.chan)
+				freq_best = best_link->conf->chandef.chan->center_freq;
+			if (link1->conf->chandef.chan)
+				freq1 = link1->conf->chandef.chan->center_freq;
+			if (freq1 > freq_best)
+				sta1_better = true;
+		}
+
+		if (sta1_better) {
+			best_sta = sta1;
+			best_link = link1;
+		}
+	}
+
+	*link = best_link;
+	if (best_link)
+		return sta_info_get_bss(sdata, best_link->u.mgd.bssid);
+	return sta_info_get_bss(sdata, sdata->deflink.u.mgd.bssid);
+}
+
 static int ieee80211_check_dup_link_addrs(struct ieee80211_sub_if_data *sdata)
 {
 	unsigned int i, j;
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 7acf2223e47a..c57380b622e6 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -929,6 +929,10 @@ void ieee80211_sta_set_max_amsdu_subframes(struct sta_info *sta,
 
 void __ieee80211_sta_recalc_aggregates(struct sta_info *sta, u16 active_links);
 
+struct sta_info *
+ieee80211_find_best_sta_link(struct ieee80211_sub_if_data *sdata,
+			     struct ieee80211_link_data **link);
+
 enum sta_stats_type {
 	STA_STATS_RATE_TYPE_INVALID = 0,
 	STA_STATS_RATE_TYPE_LEGACY,
-- 
2.40.0