Some work to do with systemd-networkd. Still nowhere near enough to create an actual config.

lib/addressing/default.nix

@@ -331,6 +331,11 @@ let
             {
               ip-address = ip;
               inherit hostname fqdn;
+
+              # New context fields:
+              location = locationName;
+              subnetType = typeName;
+              subnetKey = "${locationName}-${typeName}";
             }
             // optionalAttrs (hostCfg ? hw-address) {
               inherit (hostCfg) hw-address;
@@ -341,7 +346,11 @@ let
             // optionalAttrs (hostCfg ? aliases) {
               inherit (hostCfg) aliases;
             }
-          ))
+            // optionalAttrs (hostCfg ? interface) {
+              inherit (hostCfg) interface;
+            }
+          )
+          )
           hostNames))
         subnets)
       locations;