From 5c2e2813d0ccd7103128d312341ce7afb1ab55dd Mon Sep 17 00:00:00 2001
From: Felix Stupp <felix.stupp@banananet.work>
Date: Mon, 26 Aug 2024 00:40:52 +0000
Subject: [PATCH] nixosMod/asserts: add mdns avahi & resolved clash check

---
 nix/nixos-modules/assertions/default.nix |  1 +
 nix/nixos-modules/assertions/mdns.nix    | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)
 create mode 100644 nix/nixos-modules/assertions/mdns.nix

diff --git a/nix/nixos-modules/assertions/default.nix b/nix/nixos-modules/assertions/default.nix
index b8d7294..1d4b0d9 100644
--- a/nix/nixos-modules/assertions/default.nix
+++ b/nix/nixos-modules/assertions/default.nix
@@ -2,6 +2,7 @@
   imports = [
     # files
     ./fileSystems.nix
+    ./mdns.nix
     ./nixos.nix
   ];
 }
diff --git a/nix/nixos-modules/assertions/mdns.nix b/nix/nixos-modules/assertions/mdns.nix
new file mode 100644
index 0000000..1ad09e8
--- /dev/null
+++ b/nix/nixos-modules/assertions/mdns.nix
@@ -0,0 +1,22 @@
+{ config, lib, ... }:
+let
+  cfgAvahi = config.services.avahi;
+  avahiMDNS = cfgAvahi.enable && (cfgAvahi.nssmdns4 || cfgAvahi.nssmdns6);
+  cfgResolved = config.services.resolved;
+  # TODO check settings when cfgResolved.settings exist
+  resolvedMDNS = cfgResolved.enable;
+in
+{
+  config = {
+
+    assertions = [
+      {
+        assertion = !(avahiMDNS && cfgResolved.enable);
+        message = ''
+          systemd-resolved is enabled while Avahi mDNS is enabled, disable one of both!
+        '';
+      }
+    ];
+
+  };
+}