ops/nixos: start using systemd-resolved

ops/nixos/lib/client.nix

@@ -11,5 +11,11 @@ in
     my.home-manager.imports = lib.mkAfter [ ./home-manager/client.nix ];
     programs.ssh.startAgent = true;
     nix.gc.automatic = false;
+    services.resolved.llmnr = "true";
+    networking.networkmanager.extraConfig = lib.mkAfter ''
+      [connection]
+      # Enable mDNS resolver/responder by default unless otherwise configured.
+      connection.mdns=2
+    '';
   };
 }

ops/nixos/lib/common.nix

@@ -58,6 +58,21 @@ in
       "int.as205479.net"
       "as205479.net"
     ];
+    services.resolved = {
+      enable = true;
+      llmnr = lib.mkDefault "false";  # Re-enabled in client.
+      domains = config.networking.search;
+      fallbackDns = [
+        "8.8.8.8"
+        "8.8.4.4"
+        "2001:4860:4860::8888"
+        "2001:4860:4860::8844"
+        "1.1.1.1"
+        "1.0.0.1"
+        "2606:4700:4700::1111"
+        "2606:4700:4700::1001"
+      ];
+    };
 
     my.rundeck.tags = [ "nixos" ];