resolvconf service: init

This is a refactor of how resolvconf is managed on NixOS. We split it
into a separate service which is enabled internally depending on whether
we want /etc/resolv.conf to be managed by it. Various services now take
advantage of those configuration options.

We also now use systemd instead of activation scripts to update
resolv.conf.

NetworkManager now uses the right option for rc-manager DNS
automatically, so the configuration option shouldn't be exposed.

13 files changed, 216 insertions, 145 deletions

diff --git a/nixos/modules/config/networking.nix b/nixos/modules/config/networking.nix
index eab4e73e19a..4b9086022ed 100644
--- a/nixos/modules/config/networking.nix
+++ b/nixos/modules/config/networking.nix
@@ -7,16 +7,6 @@ with lib;
 let
 
   cfg = config.networking;
-  dnsmasqResolve = config.services.dnsmasq.enable &&
-                   config.services.dnsmasq.resolveLocalQueries;
-  hasLocalResolver = config.services.bind.enable ||
-                     config.services.unbound.enable ||
-                     dnsmasqResolve;
-
-  resolvconfOptions = cfg.resolvconfOptions
-    ++ optional cfg.dnsSingleRequest "single-request"
-    ++ optional cfg.dnsExtensionMechanism "edns0";
-
 
   localhostMapped4 = cfg.hosts ? "127.0.0.1" && elem "localhost" cfg.hosts."127.0.0.1";
   localhostMapped6 = cfg.hosts ? "::1"       && elem "localhost" cfg.hosts."::1";
@@ -64,48 +54,6 @@ in
       '';
     };
 
-    networking.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.
-      '';
-    };
-
-    networking.dnsExtensionMechanism = lib.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.
-      '';
-    };
-
-    networking.extraResolvconfConf = lib.mkOption {
-      type = types.lines;
-      default = "";
-      example = "libc=NO";
-      description = ''
-        Extra configuration to append to <filename>resolvconf.conf</filename>.
-      '';
-    };
-
-    networking.resolvconfOptions = lib.mkOption {
-      type = types.listOf types.str;
-      default = [];
-      example = [ "ndots:1" "rotate" ];
-      description = ''
-        Set the options in <filename>/etc/resolv.conf</filename>.
-      '';
-    };
-
     networking.timeServers = mkOption {
       default = [
         "0.nixos.pool.ntp.org"
@@ -240,35 +188,6 @@ in
         # /etc/host.conf: resolver configuration file
         "host.conf".text = cfg.hostConf;
 
-        # /etc/resolvconf.conf: Configuration for openresolv.
-        "resolvconf.conf".text =
-            ''
-              # 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='${pkgs.systemd}/bin/systemctl try-restart --no-block nscd.service 2> /dev/null'
-            '' + optionalString (length resolvconfOptions > 0) ''
-              # Options as described in resolv.conf(5)
-              resolv_conf_options='${concatStringsSep " " resolvconfOptions}'
-            '' + optionalString hasLocalResolver ''
-              # This hosts runs a full-blown DNS resolver.
-              name_servers='127.0.0.1'
-            '' + optionalString dnsmasqResolve ''
-              dnsmasq_conf=/etc/dnsmasq-conf.conf
-              dnsmasq_resolv=/etc/dnsmasq-resolv.conf
-            '' + cfg.extraResolvconfConf + ''
-            '';
-
-      } // optionalAttrs config.services.resolved.enable {
-        # symlink the dynamic stub resolver of resolv.conf as recommended by upstream:
-        # https://www.freedesktop.org/software/systemd/man/systemd-resolved.html#/etc/resolv.conf
-        "resolv.conf".source = "/run/systemd/resolve/stub-resolv.conf";
-      } // optionalAttrs (config.services.resolved.enable && dnsmasqResolve) {
-        "dnsmasq-resolv.conf".source = "/run/systemd/resolve/resolv.conf";
       } // optionalAttrs (pkgs.stdenv.hostPlatform.libc == "glibc") {
         # /etc/rpc: RPC program numbers.
         "rpc".source = pkgs.glibc.out + "/etc/rpc";
@@ -295,29 +214,6 @@ in
     # Install the proxy environment variables
     environment.sessionVariables = cfg.proxy.envVars;
 
-    # This is needed when /etc/resolv.conf is being overriden by networkd
-    # and other configurations. If the file is destroyed by an environment
-    # activation then it must be rebuilt so that applications which interface
-    # with /etc/resolv.conf directly don't break.
-    system.activationScripts.resolvconf = stringAfter [ "etc" "specialfs" "var" ]
-      ''
-        # Systemd resolved controls its own resolv.conf
-        rm -f /run/resolvconf/interfaces/systemd
-        ${optionalString config.services.resolved.enable ''
-          rm -rf /run/resolvconf/interfaces
-          mkdir -p /run/resolvconf/interfaces
-          ln -s /run/systemd/resolve/resolv.conf /run/resolvconf/interfaces/systemd
-        ''}
-
-        # Make sure resolv.conf is up to date if not managed manually, by systemd or
-        # by NetworkManager
-        ${optionalString (!config.environment.etc?"resolv.conf" &&
-                          (cfg.networkmanager.enable ->
-                            cfg.networkmanager.rc-manager == "resolvconf")) ''
-          ${pkgs.openresolv}/bin/resolvconf -u
-        ''}
-      '';
-
   };
 
 }
diff --git a/nixos/modules/config/resolvconf.nix b/nixos/modules/config/resolvconf.nix
new file mode 100644
index 00000000000..406c6a7ac32
--- /dev/null
+++ b/nixos/modules/config/resolvconf.nix
@@ -0,0 +1,149 @@
+# /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='${pkgs.systemd}/bin/systemctl try-restart --no-block nscd.service 2> /dev/null'
+    '' + optionalString (length resolvconfOptions > 0) ''
+      # Options as described in resolv.conf(5)
+      resolv_conf_options='${concatStringsSep " " resolvconfOptions}'
+    '' + optionalString cfg.useLocalResolver ''
+      # This hosts runs a full-blown DNS resolver.
+      name_servers='127.0.0.1'
+    '' + cfg.extraConfig;
+
+in
+
+{
+
+  options = {
+
+    networking.resolvconf = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        internal = true;
+        description = ''
+          DNS configuration is managed by resolvconf.
+        '';
+      };
+
+      useHostResolvConf = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          In containers, whether to use the
+          <filename>resolv.conf</filename> supplied by the host.
+        '';
+      };
+
+      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 [
+    {
+      networking.resolvconf.enable = !(config.environment.etc ? "resolv.conf");
+
+      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;
+        };
+      };
+
+    })
+  ];
+
+}
diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix
index 1d1995eda25..ba9ea9d2824 100644
--- a/nixos/modules/module-list.nix
+++ b/nixos/modules/module-list.nix
@@ -25,6 +25,7 @@
   ./config/nsswitch.nix
   ./config/power-management.nix
   ./config/pulseaudio.nix
+  ./config/resolvconf.nix
   ./config/shells-environment.nix
   ./config/swap.nix
   ./config/sysctl.nix
diff --git a/nixos/modules/rename.nix b/nixos/modules/rename.nix
index 1b77a895d71..ca8db9a1a48 100644
--- a/nixos/modules/rename.nix
+++ b/nixos/modules/rename.nix
@@ -244,6 +244,12 @@ with lib;
     # KSM
     (mkRenamedOptionModule [ "hardware" "enableKSM" ] [ "hardware" "ksm" "enable" ])
 
+    # resolvconf
+    (mkRenamedOptionModule [ "networking" "dnsSingleRequest" ] [ "networking" "resolvconf" "dnsSingleRequest" ])
+    (mkRenamedOptionModule [ "networking" "dnsExtensionMechanism" ] [ "networking" "resolvconf" "dnsExtensionMechanism" ])
+    (mkRenamedOptionModule [ "networking" "extraResolvconfConf" ] [ "networking" "resolvconf" "extraConfig" ])
+    (mkRenamedOptionModule [ "networking" "resolvconfOptions" ] [ "networking" "resolvconf" "extraOptions" ])
+
   ] ++ (flip map [ "blackboxExporter" "collectdExporter" "fritzboxExporter"
                    "jsonExporter" "minioExporter" "nginxExporter" "nodeExporter"
                    "snmpExporter" "unifiExporter" "varnishExporter" ]
diff --git a/nixos/modules/services/networking/bind.nix b/nixos/modules/services/networking/bind.nix
index 7f89cff2232..2097b9a3163 100644
--- a/nixos/modules/services/networking/bind.nix
+++ b/nixos/modules/services/networking/bind.nix
@@ -168,7 +168,9 @@ in
 
   ###### implementation
 
-  config = mkIf config.services.bind.enable {
+  config = mkIf cfg.enable {
+
+    networking.resolvconf.useLocalResolver = mkDefault true;
 
     users.users = singleton
       { name = bindUser;
diff --git a/nixos/modules/services/networking/dnsmasq.nix b/nixos/modules/services/networking/dnsmasq.nix
index 24d16046c63..714a5903bff 100644
--- a/nixos/modules/services/networking/dnsmasq.nix
+++ b/nixos/modules/services/networking/dnsmasq.nix
@@ -79,7 +79,7 @@ in
 
   ###### implementation
 
-  config = mkIf config.services.dnsmasq.enable {
+  config = mkIf cfg.enable {
 
     networking.nameservers =
       optional cfg.resolveLocalQueries "127.0.0.1";
@@ -92,6 +92,15 @@ in
       description = "Dnsmasq daemon user";
     };
 
+    networking.resolvconf = mkIf cfg.resolveLocalQueries {
+      useLocalResolver = mkDefault true;
+
+      extraConfig = ''
+        dnsmasq_conf=/etc/dnsmasq-conf.conf
+        dnsmasq_resolv=/etc/dnsmasq-resolv.conf
+      '';
+    };
+
     systemd.services.dnsmasq = {
         description = "Dnsmasq Daemon";
         after = [ "network.target" "systemd-resolved.service" ];
diff --git a/nixos/modules/services/networking/networkmanager.nix b/nixos/modules/services/networking/networkmanager.nix
index f1f8c9722e0..49d46456c04 100644
--- a/nixos/modules/services/networking/networkmanager.nix
+++ b/nixos/modules/services/networking/networkmanager.nix
@@ -17,7 +17,8 @@ let
     plugins=keyfile
     dhcp=${cfg.dhcp}
     dns=${cfg.dns}
-    rc-manager=${cfg.rc-manager}
+    # If resolvconf is disabled that means that resolv.conf is managed by some other module.
+    rc-manager=${if config.networking.resolvconf.enable then "resolvconf" else "unmanaged"}
 
     [keyfile]
     ${optionalString (cfg.unmanaged != [])
@@ -268,25 +269,6 @@ in {
         '';
       };
 
-      rc-manager = mkOption {
-        type = types.enum [ "symlink" "file" "resolvconf" "netconfig" "unmanaged" "none" ];
-        default = "resolvconf";
-        description = ''
-          Set the <literal>resolv.conf</literal> management mode.
-          </para>
-          <para>
-          A description of these modes can be found in the main section of
-          <link xlink:href="https://developer.gnome.org/NetworkManager/stable/NetworkManager.conf.html">
-            https://developer.gnome.org/NetworkManager/stable/NetworkManager.conf.html
-          </link>
-          or in
-          <citerefentry>
-            <refentrytitle>NetworkManager.conf</refentrytitle>
-            <manvolnum>5</manvolnum>
-          </citerefentry>.
-        '';
-      };
-
       dispatcherScripts = mkOption {
         type = types.listOf (types.submodule {
           options = {
@@ -512,7 +494,7 @@ in {
     networking = {
       useDHCP = false;
       # use mkDefault to trigger the assertion about the conflict above
-      wireless.enable = lib.mkDefault false;
+      wireless.enable = mkDefault false;
     };
 
     security.polkit.extraConfig = polkitConf;
diff --git a/nixos/modules/services/networking/rdnssd.nix b/nixos/modules/services/networking/rdnssd.nix
index 887772f6e5f..bccab805bee 100644
--- a/nixos/modules/services/networking/rdnssd.nix
+++ b/nixos/modules/services/networking/rdnssd.nix
@@ -35,6 +35,11 @@ in
 
   config = mkIf config.services.rdnssd.enable {
 
+    assertions = [{
+      assertion = config.networking.resolvconf.enable;
+      message = "rdnssd needs resolvconf to work (probably something sets up a static resolv.conf)";
+    }];
+
     systemd.services.rdnssd = {
       description = "RDNSS daemon";
       after = [ "network.target" ];
diff --git a/nixos/modules/services/networking/unbound.nix b/nixos/modules/services/networking/unbound.nix
index 1a35979ad44..3cf82e8839b 100644
--- a/nixos/modules/services/networking/unbound.nix
+++ b/nixos/modules/services/networking/unbound.nix
@@ -101,6 +101,8 @@ in
       isSystemUser = true;
     };
 
+    networking.resolvconf.useLocalResolver = mkDefault true;
+
     systemd.services.unbound = {
       description = "Unbound recursive Domain Name Server";
       after = [ "network.target" ];
diff --git a/nixos/modules/system/boot/resolved.nix b/nixos/modules/system/boot/resolved.nix
index 5c66cf4a6e6..3ea96f8e464 100644
--- a/nixos/modules/system/boot/resolved.nix
+++ b/nixos/modules/system/boot/resolved.nix
@@ -3,6 +3,10 @@
 with lib;
 let
   cfg = config.services.resolved;
+
+  dnsmasqResolve = config.services.dnsmasq.enable &&
+                   config.services.dnsmasq.resolveLocalQueries;
+
 in
 {
 
@@ -126,6 +130,12 @@ in
 
   config = mkIf cfg.enable {
 
+    assertions = [
+      { assertion = !config.networking.useHostResolvConf;
+        message = "Using host resolv.conf is not supported with systemd-resolved";
+      }
+    ];
+
     systemd.additionalUpstreamSystemUnits = [
       "systemd-resolved.service"
     ];
@@ -135,21 +145,30 @@ in
       restartTriggers = [ config.environment.etc."systemd/resolved.conf".source ];
     };
 
-    environment.etc."systemd/resolved.conf".text = ''
-      [Resolve]
-      ${optionalString (config.networking.nameservers != [])
-        "DNS=${concatStringsSep " " config.networking.nameservers}"}
-      ${optionalString (cfg.fallbackDns != [])
-        "FallbackDNS=${concatStringsSep " " cfg.fallbackDns}"}
-      ${optionalString (cfg.domains != [])
-        "Domains=${concatStringsSep " " cfg.domains}"}
-      LLMNR=${cfg.llmnr}
-      DNSSEC=${cfg.dnssec}
-      ${config.services.resolved.extraConfig}
-    '';
+    environment.etc = {
+      "systemd/resolved.conf".text = ''
+        [Resolve]
+        ${optionalString (config.networking.nameservers != [])
+          "DNS=${concatStringsSep " " config.networking.nameservers}"}
+        ${optionalString (cfg.fallbackDns != [])
+          "FallbackDNS=${concatStringsSep " " cfg.fallbackDns}"}
+        ${optionalString (cfg.domains != [])
+          "Domains=${concatStringsSep " " cfg.domains}"}
+        LLMNR=${cfg.llmnr}
+        DNSSEC=${cfg.dnssec}
+        ${config.services.resolved.extraConfig}
+      '';
+
+      # symlink the dynamic stub resolver of resolv.conf as recommended by upstream:
+      # https://www.freedesktop.org/software/systemd/man/systemd-resolved.html#/etc/resolv.conf
+      "resolv.conf".source = "/run/systemd/resolve/stub-resolv.conf";
+    } // optionalAttrs dnsmasqResolve {
+      "dnsmasq-resolv.conf".source = "/run/systemd/resolve/resolv.conf";
+    };
 
     # If networkmanager is enabled, ask it to interface with resolved.
     networking.networkmanager.dns = "systemd-resolved";
+
   };
 
 }
diff --git a/nixos/modules/system/boot/stage-2.nix b/nixos/modules/system/boot/stage-2.nix
index 55e6b19c67f..6b0b4722730 100644
--- a/nixos/modules/system/boot/stage-2.nix
+++ b/nixos/modules/system/boot/stage-2.nix
@@ -4,19 +4,20 @@ with lib;
 
 let
 
+  useHostResolvConf = config.networking.resolvconf.enable && config.networking.useHostResolvConf;
+
   bootStage2 = pkgs.substituteAll {
     src = ./stage-2-init.sh;
     shellDebug = "${pkgs.bashInteractive}/bin/bash";
     shell = "${pkgs.bash}/bin/bash";
     isExecutable = true;
     inherit (config.nix) readOnlyStore;
-    inherit (config.networking) useHostResolvConf;
+    inherit useHostResolvConf;
     inherit (config.system.build) earlyMountScript;
-    path = lib.makeBinPath [
+    path = lib.makeBinPath ([
       pkgs.coreutils
       pkgs.utillinux
-      pkgs.openresolv
-    ];
+    ] ++ lib.optional useHostResolvConf pkgs.openresolv);
     fsPackagesPath = lib.makeBinPath config.system.fsPackages;
     postBootCommands = pkgs.writeText "local-cmds"
       ''
diff --git a/nixos/modules/tasks/network-interfaces-scripted.nix b/nixos/modules/tasks/network-interfaces-scripted.nix
index c12ada7a030..2b8a7944dc3 100644
--- a/nixos/modules/tasks/network-interfaces-scripted.nix
+++ b/nixos/modules/tasks/network-interfaces-scripted.nix
@@ -103,7 +103,7 @@ let
 
             script =
               ''
-                ${optionalString (!config.environment.etc?"resolv.conf") ''
+                ${optionalString config.networking.resolvconf.enable ''
                   # Set the static DNS configuration, if given.
                   ${pkgs.openresolv}/sbin/resolvconf -m 1 -a static <<EOF
                   ${optionalString (cfg.nameservers != [] && cfg.domain != null) ''
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index f9b0eb330bf..e903c5ed808 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -1017,7 +1017,6 @@ in
         pkgs.iproute
         pkgs.iputils
         pkgs.nettools
-        pkgs.openresolv
       ]
       ++ optionals config.networking.wireless.enable [
         pkgs.wirelesstools # FIXME: obsolete?