Canonicalize the ZONE attribute

library/network/src/modules/NetworkInterfaces.rb

@@ -593,8 +593,8 @@ def ConcealSecrets(devs)
       deep_copy(out)
     end
 
-    # Canonicalize IPADDR and STARTMODE of given config
-    # and nested _aliases
+    # Canonicalize IPADDR, ZONE and STARTMODE of given config
+    # and also the IPADRR of nested _aliases
     #
     # @param [Hash] config a map with netconfig (ifcfg) configuration
     # @return [Hash] ifcfg with canonicalized IP addresses
@@ -606,9 +606,19 @@ def canonicalize_config(config)
       end
 
       config = CanonicalizeIP(config)
+      canonicalize_firewall_zone!(config)
       CanonicalizeStartmode(config)
     end
 
+    # Convenient method to canonicalize the ZONE attribute using the :default
+    # key when ZONE is defined and empty
+    #
+    # @param config [Hash] netconfig (ifcfg) configuration
+    def canonicalize_firewall_zone!(config)
+      config["ZONE"] = :default if config.has_key?("ZONE") && config["ZONE"].to_s.strip.empty?
+      config
+    end
+
     # Variables which could be suffixed and thus duplicated
     LOCALS = [
       "IPADDR",
@@ -866,6 +876,7 @@ def Write(devregex)
             end
           end
           # write all keys to config
+          devmap["ZONE"] = "" if devmap.dig("ZONE") == :default
           Builtins.maplist(
             Convert.convert(
               Map.Keys(devmap),
@@ -982,6 +993,7 @@ def Import(devregex, devices)
           ) do |num, config|
             config = CanonicalizeIP(config)
             config = CanonicalizeStartmode(config)
+            canonicalize_firewall_zone!(config)
             { num => config }
           end
         }