From 088da23f9ea4ed95da0f7842689774c0ab1837a3 Mon Sep 17 00:00:00 2001
From: Majiir Paktu <majiir@nabaal.net>
Date: Mon, 2 Oct 2023 21:50:52 -0400
Subject: [PATCH] nixos/test-instrumentation: fix unsetting of defaultGateway

The empty string is coerced to an attrset:

    { address = ""; interface = null; metric = null; }

The new defaultGateway logic (correctly) complains that interface must
be defined when using networkd. We instead clear defaultGateway by
setting it to its actual default value, which is null.
---
 nixos/modules/testing/test-instrumentation.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nixos/modules/testing/test-instrumentation.nix b/nixos/modules/testing/test-instrumentation.nix
index 6dc4091bad17..c91e54f5a4d7 100644
--- a/nixos/modules/testing/test-instrumentation.nix
+++ b/nixos/modules/testing/test-instrumentation.nix
@@ -128,7 +128,7 @@ in
     boot.consoleLogLevel = 7;
 
     # Prevent tests from accessing the Internet.
-    networking.defaultGateway = mkOverride 150 "";
+    networking.defaultGateway = mkOverride 150 null;
     networking.nameservers = mkOverride 150 [ ];
 
     system.requiredKernelConfig = with config.lib.kernelConfig; [