add rudimentary l2tp service module

examples/l2tp.nix

@@ -0,0 +1,83 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}: let
+  secrets = import ./extneder-secrets.nix;
+  rsecrets = import ./rotuer-secrets.nix;
+  inherit (pkgs.liminix.services) oneshot longrun bundle target;
+  inherit (pkgs.pseudofile) dir symlink;
+  inherit (pkgs) writeText dropbear ifwait serviceFns;
+  svc = config.system.service;
+in rec {
+  boot = {
+    tftp = {
+      serverip = "10.0.0.1";
+      ipaddr = "10.0.0.8";
+    };
+  };
+
+  imports = [
+#    ../modules/wlan.nix
+    ../modules/network
+    ../modules/vlan
+    ../modules/ssh
+    ../modules/usb.nix
+    ../modules/watchdog
+    ../modules/mount
+    ../modules/ppp
+  ];
+  hostname = "thing";
+
+  services.dhcpc =
+    let iface = config.hardware.networkInterfaces.lan;
+    in svc.network.dhcp.client.build {
+      interface = iface;
+      dependencies = [ config.services.hostname ];
+    };
+
+  services.sshd = svc.ssh.build { };
+
+  services.resolvconf = oneshot rec {
+    dependencies = [ services.dhcpc ];
+    name = "resolvconf";
+    up = ''
+      . ${serviceFns}
+      ( in_outputs ${name}
+      for i in $(output ${services.dhcpc} dns); do
+        echo "nameserver $i" > resolv.conf
+      done
+      )
+    '';
+  };
+  filesystem = dir {
+    etc = dir {
+      "resolv.conf" = symlink "${services.resolvconf}/.outputs/resolv.conf";
+    };
+    srv = dir {};
+  };
+
+  services.l2tp = svc.l2tp.build {
+    lns = "l2tp.aaisp.net.uk";
+    ppp-options = [
+      "debug" "+ipv6" "noauth"
+      "name" rsecrets.l2tp.name
+      "password" rsecrets.l2tp.password
+    ];
+    dependencies = [ services.defaultroute4 ];
+  };
+
+  services.defaultroute4 = svc.network.route.build {
+    via = "$(output ${services.dhcpc} router)";
+    target = "default";
+    dependencies = [services.dhcpc];
+  };
+
+  users.root = {
+    passwd = lib.mkForce secrets.root.passwd;
+    openssh.authorizedKeys.keys = secrets.root.keys;
+  };
+
+
+}