populate ip address based on hostname and populate the hostfile with other vm ips

nixos/modules/vmNetwork.nix

@@ -0,0 +1,48 @@
+{
+  lib,
+  config,
+  ...
+}: let
+  inherit
+    (lib)
+    mkOption
+    types
+    last
+    init
+    ;
+  inherit
+    (lib.strings)
+    splitString
+    concatStringsSep
+    toInt
+    ;
+  cfg = config.vmNetwork;
+in {
+  imports = [];
+
+  options.vmNetwork = {
+    ipv4 = mkOption {
+      type = types.str;
+      description = "the ipv4 adress of this machine";
+    };
+  };
+
+  config = {
+    networking = {
+      interfaces.enX0.ipv4.addresses = [
+        {
+          address = cfg.ipv4;
+          prefixLength = 16;
+        }
+      ];
+      defaultGateway = let
+        addr = splitString "." cfg.ipv4;
+        addrInit = init addr;
+        addrLastInt = builtins.toString (toInt (last addr) + 127);
+      in
+        concatStringsSep "." (addrInit ++ [addrLastInt]);
+      # https://www.hrz.tu-darmstadt.de/services/it_services/nameserver_dns/index.de.jsp
+      nameservers = ["130.83.22.63" "130.83.22.60" "130.83.56.60"];
+    };
+  };
+}