1 files changed, 145 insertions, 0 deletions
diff --git a/nixos/modules/config/resolvconf.nix b/nixos/modules/config/resolvconf.nix
new file mode 100644
index 00000000000..4499481811f
--- /dev/null
+++ b/nixos/modules/config/resolvconf.nix
@@ -0,0 +1,145 @@
+# /etc files related to networking, such as /etc/services.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.networking.resolvconf;
+
+  resolvconfOptions = cfg.extraOptions
+    ++ optional cfg.dnsSingleRequest "single-request"
+    ++ optional cfg.dnsExtensionMechanism "edns0";
+
+  configText =
+    ''
+      # This is the default, but we must set it here to prevent
+      # a collision with an apparently unrelated environment
+      # variable with the same name exported by dhcpcd.
+      interface_order='lo lo[0-9]*'
+    '' + optionalString config.services.nscd.enable ''
+      # Invalidate the nscd cache whenever resolv.conf is
+      # regenerated.
+      libc_restart='/run/current-system/systemd/bin/systemctl try-restart --no-block nscd.service 2> /dev/null'
+    '' + optionalString (length resolvconfOptions > 0) ''
+      # Options as described in resolv.conf(5)
+      resolv_conf_options='${concatStringsSep " " resolvconfOptions}'
+    '' + optionalString cfg.useLocalResolver ''
+      # This hosts runs a full-blown DNS resolver.
+      name_servers='127.0.0.1'
+    '' + cfg.extraConfig;
+
+in
+
+{
+  imports = [
+    (mkRenamedOptionModule [ "networking" "dnsSingleRequest" ] [ "networking" "resolvconf" "dnsSingleRequest" ])
+    (mkRenamedOptionModule [ "networking" "dnsExtensionMechanism" ] [ "networking" "resolvconf" "dnsExtensionMechanism" ])
+    (mkRenamedOptionModule [ "networking" "extraResolvconfConf" ] [ "networking" "resolvconf" "extraConfig" ])
+    (mkRenamedOptionModule [ "networking" "resolvconfOptions" ] [ "networking" "resolvconf" "extraOptions" ])
+    (mkRemovedOptionModule [ "networking" "resolvconf" "useHostResolvConf" ] "This option was never used for anything anyways")
+  ];
+
+  options = {
+
+    networking.resolvconf = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = !(config.environment.etc ? "resolv.conf");
+        defaultText = literalExpression ''!(config.environment.etc ? "resolv.conf")'';
+        description = ''
+          DNS configuration is managed by resolvconf.
+        '';
+      };
+
+      dnsSingleRequest = lib.mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Recent versions of glibc will issue both ipv4 (A) and ipv6 (AAAA)
+          address queries at the same time, from the same port. Sometimes upstream
+          routers will systemically drop the ipv4 queries. The symptom of this problem is
+          that 'getent hosts example.com' only returns ipv6 (or perhaps only ipv4) addresses. The
+          workaround for this is to specify the option 'single-request' in
+          /etc/resolv.conf. This option enables that.
+        '';
+      };
+
+      dnsExtensionMechanism = mkOption {
+        type = types.bool;
+        default = true;
+        description = ''
+          Enable the <code>edns0</code> option in <filename>resolv.conf</filename>. With
+          that option set, <code>glibc</code> supports use of the extension mechanisms for
+          DNS (EDNS) specified in RFC 2671. The most popular user of that feature is DNSSEC,
+          which does not work without it.
+        '';
+      };
+
+      extraConfig = mkOption {
+        type = types.lines;
+        default = "";
+        example = "libc=NO";
+        description = ''
+          Extra configuration to append to <filename>resolvconf.conf</filename>.
+        '';
+      };
+
+      extraOptions = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        example = [ "ndots:1" "rotate" ];
+        description = ''
+          Set the options in <filename>/etc/resolv.conf</filename>.
+        '';
+      };
+
+      useLocalResolver = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Use local DNS server for resolving.
+        '';
+      };
+
+    };
+
+  };
+
+  config = mkMerge [
+    {
+      environment.etc."resolvconf.conf".text =
+        if !cfg.enable then
+          # Force-stop any attempts to use resolvconf
+          ''
+            echo "resolvconf is disabled on this system but was used anyway:" >&2
+            echo "$0 $*" >&2
+            exit 1
+          ''
+        else configText;
+    }
+
+    (mkIf cfg.enable {
+      environment.systemPackages = [ pkgs.openresolv ];
+
+      systemd.services.resolvconf = {
+        description = "resolvconf update";
+
+        before = [ "network-pre.target" ];
+        wants = [ "network-pre.target" ];
+        wantedBy = [ "multi-user.target" ];
+        restartTriggers = [ config.environment.etc."resolvconf.conf".source ];
+
+        serviceConfig = {
+          Type = "oneshot";
+          ExecStart = "${pkgs.openresolv}/bin/resolvconf -u";
+          RemainAfterExit = true;
+        };
+      };
+
+    })
+  ];
+
+}