refuse to create a firewall rule with no target tag

Implements #25145
This modification in gce.firewallObject() will return error when trying
to create or update firewall rule if no node tag can be found. Also add
unit test for this modification.

pkg/cloudprovider/providers/gce/gce.go

@@ -938,10 +938,16 @@ func (gce *GCECloud) firewallObject(name, region, desc string, sourceRanges nets
 	for ix := range ports {
 		allowedPorts[ix] = strconv.Itoa(int(ports[ix].Port))
 	}
-	hostTags, err := gce.computeHostTags(hosts)
-	if err != nil {
-		return nil, err
+	// If the node tags to be used for this cluster have been predefined in the
+	// provider config, just use them. Otherwise, invoke computeHostTags method to get the tags.
+	hostTags := gce.nodeTags
+	if len(hostTags) == 0 {
+		var err error
+		if hostTags, err = gce.computeHostTags(hosts); err != nil {
+			return nil, fmt.Errorf("No node tags supplied and also failed to parse the given lists of hosts for tags. Abort creating firewall rule.")
+		}
 	}
+
 	firewall := &compute.Firewall{
 		Name:         makeFirewallName(name),
 		Description:  desc,
@@ -963,17 +969,13 @@ func (gce *GCECloud) firewallObject(name, region, desc string, sourceRanges nets
 	return firewall, nil
 }
 
-// If the node tags to be used for this cluster have been predefined in the
-// provider config, just use them. Otherwise, grab all tags from all relevant
-// instances:
+// ComputeHostTags grabs all tags from all instances being added to the pool.
 // * The longest tag that is a prefix of the instance name is used
-// * If any instance has a prefix tag, all instances must
-// * If no instances have a prefix tag, no tags are used
+// * If any instance has no matching prefix tag, return error
+// Invoking this method to get host tags is risky since it depends on the format
+// of the host names in the cluster. Only use it as a fallback if gce.nodeTags
+// is unspecified
 func (gce *GCECloud) computeHostTags(hosts []*gceInstance) ([]string, error) {
-	if len(gce.nodeTags) > 0 {
-		return gce.nodeTags, nil
-	}
-
 	// TODO: We could store the tags in gceInstance, so we could have already fetched it
 	hostNamesByZone := make(map[string][]string)
 	for _, host := range hosts {
@@ -1012,8 +1014,8 @@ func (gce *GCECloud) computeHostTags(hosts []*gceInstance) ([]string, error) {
 				}
 				if len(longest_tag) > 0 {
 					tags.Insert(longest_tag)
-				} else if len(tags) > 0 {
-					return nil, fmt.Errorf("Some, but not all, instances have prefix tags (%s is missing)", instance.Name)
+				} else {
+					return nil, fmt.Errorf("Could not find any tag that is a prefix of instance name for instance %s", instance.Name)
 				}
 			}
 		}
@@ -1021,11 +1023,9 @@ func (gce *GCECloud) computeHostTags(hosts []*gceInstance) ([]string, error) {
 			glog.Errorf("computeHostTags exceeded maxPages=%d for Instances.List: truncating.", maxPages)
 		}
 	}
-
 	if len(tags) == 0 {
-		glog.V(2).Info("No instances had tags, creating rule without target tags")
+		return nil, fmt.Errorf("No instances found")
 	}
-
 	return tags.List(), nil
 }
 

pkg/cloudprovider/providers/gce/gce_test.go

@@ -152,6 +152,16 @@ func TestScrubDNS(t *testing.T) {
 	}
 }
 
+func TestCreateFirewallFails(t *testing.T) {
+	name := "loadbalancer"
+	region := "us-central1"
+	desc := "description"
+	gce := &GCECloud{}
+	if err := gce.createFirewall(name, region, desc, nil, nil, nil); err == nil {
+		t.Errorf("error expected when creating firewall without any tags found")
+	}
+}
+
 func TestRestrictTargetPool(t *testing.T) {
 	const maxInstances = 5
 	tests := []struct {