nixos/rsyncd: fix ini format for global section (#385064)

According to the manpage the rsyncd.conf has a global section without a
module header. Settings for listening port or bind address must be put
there and will not work if defined in a global submodule (i.e. below a
"[global]" header).

This commit changes the ini format generator for the rsyncd service to
allow a global section in the config file without a submodule header.

Fixes #304293

Credits to @nydragon

* remove retrocompat, add incompat release notes

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -443,6 +443,10 @@
 - `services.netbird.tunnels` was renamed to [`services.netbird.clients`](#opt-services.netbird.clients),
   hardened (using dedicated less-privileged users) and significantly extended.
 
+- `services.rsyncd.settings` now supports only two attributes `sections` and `globalSection`.
+  As a result, all sections previously defined under `services.rsyncd.settings` must now be put in `services.rsyncd.settings.sections`.
+  Global settings must now be placed in `services.rsyncd.settings.globalSection` instead of `services.rsyncd.settings.global`.
+
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
 ## Other Notable Changes {#sec-release-25.05-notable-changes}

nixos/modules/services/network-filesystems/rsyncd.nix

@@ -6,7 +6,7 @@
 }:
 let
   cfg = config.services.rsyncd;
-  settingsFormat = pkgs.formats.ini { };
+  settingsFormat = pkgs.formats.iniWithGlobalSection { };
   configFile = settingsFormat.generate "rsyncd.conf" cfg.settings;
 in
 {
@@ -25,24 +25,27 @@ in
         inherit (settingsFormat) type;
         default = { };
         example = {
-          global = {
+          globalSection = {
             uid = "nobody";
             gid = "nobody";
             "use chroot" = true;
             "max connections" = 4;
+            address = "0.0.0.0";
           };
-          ftp = {
-            path = "/var/ftp/./pub";
-            comment = "whole ftp area";
-          };
-          cvs = {
-            path = "/data/cvs";
-            comment = "CVS repository (requires authentication)";
-            "auth users" = [
-              "tridge"
-              "susan"
-            ];
-            "secrets file" = "/etc/rsyncd.secrets";
+          sections = {
+            ftp = {
+              path = "/var/ftp/./pub";
+              comment = "whole ftp area";
+            };
+            cvs = {
+              path = "/data/cvs";
+              comment = "CVS repository (requires authentication)";
+              "auth users" = [
+                "tridge"
+                "susan"
+              ];
+              "secrets file" = "/etc/rsyncd.secrets";
+            };
           };
         };
         description = ''
@@ -81,7 +84,7 @@ in
 
   config = lib.mkIf cfg.enable {
 
-    services.rsyncd.settings.global.port = toString cfg.port;
+    services.rsyncd.settings.globalSection.port = toString cfg.port;
 
     systemd =
       let

nixos/tests/rsyncd.nix

@@ -15,13 +15,15 @@ import ./make-test-python.nix (
               enable = true;
               inherit socketActivated;
               settings = {
-                global = {
+                globalSection = {
                   "reverse lookup" = false;
                   "forward lookup" = false;
                 };
-                tmp = {
-                  path = "/nix/store";
-                  comment = "test module";
+                sections = {
+                  tmp = {
+                    path = "/nix/store";
+                    comment = "test module";
+                  };
                 };
               };
             };