Fix issue where fib function overflows

utils/consts.go

@@ -2669,6 +2669,15 @@ const (
 	ToNearestTowardZero = "*toNearestTowardZero"
 )
 
+// Go type limits
+const (
+	AbsoluteMaxUint     = ^uint(0)
+	AbsoluteMinUint     = 0
+	AbsoluteMaxInt      = int(AbsoluteMaxUint >> 1)
+	AbsoluteMinInt      = -AbsoluteMaxInt - 1
+	AbsoluteMaxDuration = time.Duration(AbsoluteMaxInt)
+)
+
 func buildCacheInstRevPrefixes() {
 	CachePrefixToInstance = make(map[string]string)
 	for k, v := range CacheInstanceToPrefix {

utils/coreutils.go

@@ -424,11 +424,13 @@ func copyFile(rc io.ReadCloser, path string, fm os.FileMode) (err error) {
 	return
 }
 
-// Fib returns successive Fibonacci numbers
+// Fib returns successive Fibonacci numbers.
 func Fib() func() int {
 	a, b := 0, 1
 	return func() int {
-		a, b = b, a+b
+		if b > 0 {
+			a, b = b, a+b // only increment Fibonacci numbers while b doesn't overflow
+		}
 		return a
 	}
 }
@@ -438,7 +440,12 @@ func Fib() func() int {
 func FibDuration(durationUnit, maxDuration time.Duration) func() time.Duration {
 	fib := Fib()
 	return func() time.Duration {
-		fibNrAsDuration := time.Duration(fib()) * durationUnit
+		fibNrAsDuration := time.Duration(fib())
+		if fibNrAsDuration > (AbsoluteMaxDuration / durationUnit) { // check if the current fibonacci nr. in the sequence would exceed the absolute maximum duration if multiplied by the duration unit value
+			fibNrAsDuration = AbsoluteMaxDuration
+		} else {
+			fibNrAsDuration *= durationUnit
+		}
 		if maxDuration > 0 && maxDuration < fibNrAsDuration {
 			return maxDuration
 		}

utils/coreutils_test.go

@@ -1661,3 +1661,28 @@ func TestAPITPDataGetPaginateOpts(t *testing.T) {
 		t.Errorf("expected: <%+v>, \nreceived: <%+v>", experr, err)
 	}
 }
+
+func TestCoreUtilsFibSeqNrOverflow(t *testing.T) {
+	fib := Fib()
+	for i := 0; i < 92; i++ { // the 93rd fibonacci number in the sequence would normally overflow
+		fib()
+	}
+	exp := fib()
+	for i := 0; i < 100; i++ {
+		if rcv := fib(); rcv != exp {
+			t.Errorf("expected: <%+v>, \nreceived: <%+v>", exp, rcv)
+		}
+	}
+}
+
+func TestCoreUtilsFibDurationSeqNrOverflow(t *testing.T) {
+	fib := FibDuration(time.Second, 0)
+	for i := 0; i < 49; i++ { // the 50th fibonacci number in the sequence would normally overflow when multiplied with time.Second
+		fib()
+	}
+	for i := 0; i < 100; i++ {
+		if rcv := fib(); rcv != AbsoluteMaxDuration {
+			t.Errorf("expected: <%+v>, \nreceived: <%+v>", AbsoluteMaxDuration, rcv)
+		}
+	}
+}