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/services/networking/dnscache.nix

@@ -0,0 +1,108 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.dnscache;
+
+  dnscache-root = pkgs.runCommand "dnscache-root" { preferLocalBuild = true; } ''
+    mkdir -p $out/{servers,ip}
+
+    ${concatMapStrings (ip: ''
+      touch "$out/ip/"${lib.escapeShellArg ip}
+    '') cfg.clientIps}
+
+    ${concatStrings (mapAttrsToList (host: ips: ''
+      ${concatMapStrings (ip: ''
+        echo ${lib.escapeShellArg ip} >> "$out/servers/"${lib.escapeShellArg host}
+      '') ips}
+    '') cfg.domainServers)}
+
+    # if a list of root servers was not provided in config, copy it
+    # over. (this is also done by dnscache-conf, but we 'rm -rf
+    # /var/lib/dnscache/root' below & replace it wholesale with this,
+    # so we have to ensure servers/@ exists ourselves.)
+    if [ ! -e $out/servers/@ ]; then
+      # symlink does not work here, due chroot
+      cp ${pkgs.djbdns}/etc/dnsroots.global $out/servers/@;
+    fi
+  '';
+
+in {
+
+  ###### interface
+
+  options = {
+    services.dnscache = {
+
+      enable = mkOption {
+        default = false;
+        type = types.bool;
+        description = "Whether to run the dnscache caching dns server.";
+      };
+
+      ip = mkOption {
+        default = "0.0.0.0";
+        type = types.str;
+        description = "IP address on which to listen for connections.";
+      };
+
+      clientIps = mkOption {
+        default = [ "127.0.0.1" ];
+        type = types.listOf types.str;
+        description = "Client IP addresses (or prefixes) from which to accept connections.";
+        example = ["192.168" "172.23.75.82"];
+      };
+
+      domainServers = mkOption {
+        default = { };
+        type = types.attrsOf (types.listOf types.str);
+        description = ''
+          Table of {hostname: server} pairs to use as authoritative servers for hosts (and subhosts).
+          If entry for @ is not specified predefined list of root servers is used.
+        '';
+        example = literalExpression ''
+          {
+            "@" = ["8.8.8.8" "8.8.4.4"];
+            "example.com" = ["192.168.100.100"];
+          }
+        '';
+      };
+
+      forwardOnly = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Whether to treat root servers (for @) as caching
+          servers, requesting addresses the same way a client does. This is
+          needed if you want to use e.g. Google DNS as your upstream DNS.
+        '';
+      };
+
+    };
+  };
+
+  ###### implementation
+
+  config = mkIf config.services.dnscache.enable {
+    environment.systemPackages = [ pkgs.djbdns ];
+    users.users.dnscache.isSystemUser = true;
+
+    systemd.services.dnscache = {
+      description = "djbdns dnscache server";
+      wantedBy = [ "multi-user.target" ];
+      path = with pkgs; [ bash daemontools djbdns ];
+      preStart = ''
+        rm -rf /var/lib/dnscache
+        dnscache-conf dnscache dnscache /var/lib/dnscache ${config.services.dnscache.ip}
+        rm -rf /var/lib/dnscache/root
+        ln -sf ${dnscache-root} /var/lib/dnscache/root
+      '';
+      script = ''
+        cd /var/lib/dnscache/
+        ${optionalString cfg.forwardOnly "export FORWARDONLY=1"}
+        exec ./run
+      '';
+    };
+  };
+}