From f1dfb1f9768f061dcdcb9f3aacfa65c17235d697 Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Thu, 31 Aug 2023 18:24:09 +0100
Subject: [PATCH] BRIDGE_VLAN_FILTERING depends on bridge _and_ vlan

I'm half-pleased with this. It demonstrates how we can have complex
conditional kernel config, but the way we detect if vlan exists is
tacky.
---
 modules/bridge/default.nix | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/modules/bridge/default.nix b/modules/bridge/default.nix
index dc1d071a..48fdb125 100644
--- a/modules/bridge/default.nix
+++ b/modules/bridge/default.nix
@@ -41,7 +41,11 @@ in
   };
   config.kernel.config = {
     BRIDGE = "y";
-    BRIDGE_VLAN_FILTERING = "y";
     BRIDGE_IGMP_SNOOPING = "y";
-  };
+  } // lib.optionalAttrs (config.system.service ? vlan) {
+    # depends on bridge _and_ vlan. I would like there to be
+    # a better way to test for the existence of vlan config:
+    # maybe the module should set an `enabled` attribute?
+    BRIDGE_VLAN_FILTERING = "y";
+  };    
 }