Improve port label validation and diff testing

nomad/structs/diff_test.go

@@ -3507,6 +3507,12 @@ func TestTaskDiff(t *testing.T) {
 								Type: DiffTypeEdited,
 								Name: "Check",
 								Fields: []*FieldDiff{
+									{
+										Type: DiffTypeNone,
+										Name: "AddressMode",
+										Old:  "",
+										New:  "",
+									},
 									{
 										Type: DiffTypeNone,
 										Name: "Command",

nomad/structs/structs.go

@@ -3473,10 +3473,14 @@ func validateServices(t *Task) error {
 		knownServices[service.Name+service.PortLabel] = struct{}{}
 
 		if service.PortLabel != "" {
-			if _, err := strconv.Atoi(service.PortLabel); service.AddressMode == "driver" && err == nil {
-				// Numeric ports are valid when AddressMode=driver
+			if service.AddressMode == "driver" {
+				// Numeric port labels are valid for address_mode=driver
+				_, err := strconv.Atoi(service.PortLabel)
+				if err != nil {
+					// Not a numeric port label, add it to list to check
+					servicePorts[service.PortLabel] = append(servicePorts[service.PortLabel], service.Name)
+				}
 			} else {
-
 				servicePorts[service.PortLabel] = append(servicePorts[service.PortLabel], service.Name)
 			}
 		}