Add OpenSMTPD service option

modules/misc/ids.nix

@@ -76,6 +76,8 @@ in
     nslcd = 58;
     nginx = 60;
     chrony = 61;
+    smtpd = 63;
+    smtpq = 64;    
 
     # When adding a uid, make sure it doesn't match an existing gid.
 
@@ -135,6 +137,8 @@ in
     scanner = 59;
     nginx = 60;
     systemd-journal = 62;
+    smtpd = 63;
+    smtpq = 64;    
 
     # When adding a gid, make sure it doesn't match an existing uid.
 

modules/module-list.nix

@@ -104,6 +104,7 @@
   ./services/mail/dovecot.nix
   ./services/mail/freepops.nix
   ./services/mail/mail.nix
+  ./services/mail/opensmtpd.nix
   ./services/mail/postfix.nix
   ./services/mail/spamassassin.nix
   ./services/misc/autofs.nix

modules/services/mail/opensmtpd.nix

@@ -0,0 +1,83 @@
+{ pkgs, config, ... }:
+
+with pkgs;
+with pkgs.lib;
+
+let
+
+  cfg = config.services.opensmtpd;
+  conf = writeText "smtpd.conf" cfg.serverConfiguration;
+  args = concatStringsSep " " cfg.extraServerArgs;
+
+in {
+
+  ###### interface
+
+  options = {
+
+    services.opensmtpd = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Whether to enable the OpenSMTPD server.";
+      };
+
+      extraServerArgs = mkOption {
+        type = types.listOf types.string;
+        default = [];
+        example = [ "-v" "-P mta" ];
+        description = ''
+          Extra command line arguments provided when the smtpd process
+          is started.
+        '';
+      };
+
+      serverConfiguration = mkOption {
+        type = types.string;
+        default = "";
+        example = ''
+          listen on lo
+          accept for any deliver to lmtp localhost:24
+        ''; 
+        description = ''
+          The contents of the smtpd.conf configuration file. See the
+          OpenSMTPD documentation for syntax information. If this option
+          is left empty, the OpenSMTPD server will not start.
+        '';
+      };
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkIf config.services.opensmtpd.enable {
+    users.extraGroups = {
+      smtpd.gid = config.ids.gids.smtpd;
+      smtpq.gid = config.ids.gids.smtpq;
+    };
+
+    users.extraUsers = {
+      smtpd = {
+        description = "OpenSMTPD process user";
+        uid = config.ids.uids.smtpd;
+        group = "smtpd";
+      };
+      smtpq = {
+        description = "OpenSMTPD queue user";
+        uid = config.ids.uids.smtpq;
+        group = "smtpq";
+      };
+    };
+
+    systemd.services.opensmtpd = {
+      wantedBy = [ "multi-user.target" ];
+      wants = [ "network.target" ];
+      after = [ "network.target" ];
+      preStart = "mkdir -p /var/spool";
+      serviceConfig.ExecStart = "${opensmtpd}/sbin/smtpd -d -f ${conf} ${args}";
+    };
+  };
+}