go to holdover if best GM is worse than 10us

Summary: We should not allow selection of the GM which has a bad clock quality. It's better to just switch to holdover Differential Revision: D53310144
facebook · Feb 1, 2024 · b4eda89 · b4eda89
1 parent 0db5072
commit b4eda89
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Showing 2 changed files with 11 additions and 3 deletions.
diff --git a/ptp/sptp/client/bmca.go b/ptp/sptp/client/bmca.go
@@ -36,7 +36,8 @@ func bmca(msgs []*ptp.Announce, prios map[ptp.ClockIdentity]int) *ptp.Announce {
 			best = b
 		}
 	}
-	if best.AnnounceBody.GrandmasterClockQuality.ClockClass >= ptp.ClockClass13 {
+	// Never select GM in worse than holdover status or with clock quality worse than 10 microseconds
+	if best.AnnounceBody.GrandmasterClockQuality.ClockClass > ptp.ClockClass7 || best.AnnounceBody.GrandmasterClockQuality.ClockAccuracy > ptp.ClockAccuracyMicrosecond10 {
 		return nil
 	}
 	return best

diff --git a/ptp/sptp/client/bmca_test.go b/ptp/sptp/client/bmca_test.go
@@ -37,8 +37,15 @@ func TestBmcaProperlyUsesLocalPriority(t *testing.T) {
 }
 
 func TestBmcaNoMasterForCalibrating(t *testing.T) {
-	best := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 1, GrandmasterClockQuality: ptp.ClockQuality{ClockClass: ptp.ClockClass52}}}
-	worse := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 2, GrandmasterClockQuality: ptp.ClockQuality{ClockClass: ptp.ClockClass13}}}
+	best := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 1, GrandmasterClockQuality: ptp.ClockQuality{ClockClass: ptp.ClockClass13}}}
+	worse := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 2, GrandmasterClockQuality: ptp.ClockQuality{ClockClass: ptp.ClockClass52}}}
+	selected := bmca([]*ptp.Announce{&best, &worse}, map[ptp.ClockIdentity]int{1: 2, 2: 1})
+	require.Empty(t, selected)
+}
+
+func TestBmcaNoMasterForLowAccuracy(t *testing.T) {
+	best := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 1, GrandmasterClockQuality: ptp.ClockQuality{ClockAccuracy: ptp.ClockAccuracyMicrosecond100}}}
+	worse := ptp.Announce{AnnounceBody: ptp.AnnounceBody{GrandmasterIdentity: 2, GrandmasterClockQuality: ptp.ClockQuality{ClockAccuracy: ptp.ClockAccuracySecond10}}}
 	selected := bmca([]*ptp.Announce{&best, &worse}, map[ptp.ClockIdentity]int{1: 2, 2: 1})
 	require.Empty(t, selected)
 }