uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/system/boot/initrd-openvpn.nix

@@ -0,0 +1,81 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.boot.initrd.network.openvpn;
+
+in
+
+{
+
+  options = {
+
+    boot.initrd.network.openvpn.enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Starts an OpenVPN client during initrd boot. It can be used to e.g.
+        remotely accessing the SSH service controlled by
+        <option>boot.initrd.network.ssh</option> or other network services
+        included. Service is killed when stage-1 boot is finished.
+      '';
+    };
+
+    boot.initrd.network.openvpn.configuration = mkOption {
+      type = types.path; # Same type as boot.initrd.secrets
+      description = ''
+        The configuration file for OpenVPN.
+
+        <warning>
+          <para>
+            Unless your bootloader supports initrd secrets, this configuration
+            is stored insecurely in the global Nix store.
+          </para>
+        </warning>
+      '';
+      example = literalExpression "./configuration.ovpn";
+    };
+
+  };
+
+  config = mkIf (config.boot.initrd.network.enable && cfg.enable) {
+    assertions = [
+      {
+        assertion = cfg.configuration != null;
+        message = "You should specify a configuration for initrd OpenVPN";
+      }
+    ];
+
+    # Add kernel modules needed for OpenVPN
+    boot.initrd.kernelModules = [ "tun" "tap" ];
+
+    # Add openvpn and ip binaries to the initrd
+    # The shared libraries are required for DNS resolution
+    boot.initrd.extraUtilsCommands = ''
+      copy_bin_and_libs ${pkgs.openvpn}/bin/openvpn
+      copy_bin_and_libs ${pkgs.iproute2}/bin/ip
+
+      cp -pv ${pkgs.glibc}/lib/libresolv.so.2 $out/lib
+      cp -pv ${pkgs.glibc}/lib/libnss_dns.so.2 $out/lib
+    '';
+
+    boot.initrd.secrets = {
+      "/etc/initrd.ovpn" = cfg.configuration;
+    };
+
+    # openvpn --version would exit with 1 instead of 0
+    boot.initrd.extraUtilsCommandsTest = ''
+      $out/bin/openvpn --show-gateway
+    '';
+
+    # Add `iproute /bin/ip` to the config, to ensure that openvpn
+    # is able to set the routes
+    boot.initrd.network.postCommands = ''
+      (cat /etc/initrd.ovpn; echo -e '\niproute /bin/ip') | \
+        openvpn /dev/stdin &
+    '';
+  };
+
+}