Do not suspend DPC testing when clocks are not synchronized

If DPC is failing connectivity tests (due to some transient network
issue) and device is powered off for long enough that clocks loose time
(or there is no battery to keep them running), device will not be able
to establish connectivity after power on for a very long time.
This is because we demand that failed DPC is tried again only after
some time elapses (5 minutes) since the last failed connectivity test.
However, when device starts with clocks reset at time "zero"
(i.e. start of the epoch), it will take many decades until the current
time (as reported by clocks) is past the last failure timestamp.
The solution is to detect unsync clocks and allow to test and use DPC
immediately.

Signed-off-by: Milan Lenco <milan@zededa.com>
(cherry picked from commit b3bdbc6)

pkg/pillar/types/zedroutertypes.go

@@ -861,6 +861,14 @@ func (config DevicePortConfig) IsDPCTestable(minTimeSinceFailure time.Duration)
 	if config.LastSucceeded.After(config.LastFailed) {
 		return true
 	}
+	if config.LastFailed.After(time.Now()) {
+		// Clocks are not in sync - most likely they are still around
+		// the start of the epoch.
+		// Network is likely needed to synchronize the clocks using NTP,
+		// and we should attempt to establish network connectivity using
+		// any DPC available.
+		return true
+	}
 	return time.Since(config.LastFailed) >= minTimeSinceFailure
 }
 

pkg/pillar/types/zedroutertypes_test.go

@@ -183,56 +183,75 @@ func TestIsDPCUsable(t *testing.T) {
 }
 
 func TestIsDPCTestable(t *testing.T) {
-	n := time.Now()
 	testMatrix := map[string]struct {
 		devicePortConfig DevicePortConfig
 		expectedValue    bool
 	}{
-		"Difference is exactly 60 seconds": {
+		"DPC always failed test and not enough time passed since the last test": {
 			devicePortConfig: DevicePortConfig{
 				TestResults: TestResults{
-					LastFailed:    n.Add(time.Second * 60),
-					LastSucceeded: n,
+					LastFailed:    time.Now().Add(-2 * time.Minute),
+					LastSucceeded: time.Time{},
 				},
 				Ports: usablePorts,
 			},
 			expectedValue: false,
 		},
-		"Difference is 61 seconds": {
+		"DPC succeeded, then failed and not enough time passed since then": {
 			devicePortConfig: DevicePortConfig{
 				TestResults: TestResults{
-					LastFailed:    n.Add(time.Second * 61),
-					LastSucceeded: n,
+					LastFailed:    time.Now().Add(-2 * time.Minute),
+					LastSucceeded: time.Now().Add(-4 * time.Minute),
 				},
 				Ports: usablePorts,
 			},
 			expectedValue: false,
 		},
-		"Difference is 59 seconds": {
+		"DPC always failed test but enough time passed since the last test": {
 			devicePortConfig: DevicePortConfig{
 				TestResults: TestResults{
-					LastFailed:    n.Add(time.Second * 59),
-					LastSucceeded: n,
+					LastFailed:    time.Now().Add(-6 * time.Minute),
+					LastSucceeded: time.Time{},
 				},
 				Ports: usablePorts,
 			},
-			expectedValue: false,
+			expectedValue: true,
 		},
-		"LastFailed is 0": {
+		"DPC succeeded, then failed but enough time passed since then": {
+			devicePortConfig: DevicePortConfig{
+				TestResults: TestResults{
+					LastFailed:    time.Now().Add(-6 * time.Minute),
+					LastSucceeded: time.Now().Add(-8 * time.Minute),
+				},
+				Ports: usablePorts,
+			},
+			expectedValue: true,
+		},
+		"DPC always succeeded test": {
 			devicePortConfig: DevicePortConfig{
 				TestResults: TestResults{
 					LastFailed:    time.Time{},
-					LastSucceeded: n,
+					LastSucceeded: time.Now().Add(-2 * time.Minute),
 				},
 				Ports: usablePorts,
 			},
 			expectedValue: true,
 		},
-		"Last Succeeded is after Last Failed": {
+		"DPC failed but later succeeded test": {
 			devicePortConfig: DevicePortConfig{
 				TestResults: TestResults{
-					LastFailed:    n,
-					LastSucceeded: n.Add(time.Second * 61),
+					LastFailed:    time.Now().Add(-4 * time.Minute),
+					LastSucceeded: time.Now().Add(-2 * time.Minute),
+				},
+				Ports: usablePorts,
+			},
+			expectedValue: true,
+		},
+		"Clocks are not synchronized": {
+			devicePortConfig: DevicePortConfig{
+				TestResults: TestResults{
+					LastFailed:    time.Now().Add(time.Hour),
+					LastSucceeded: time.Time{},
 				},
 				Ports: usablePorts,
 			},