From c86976e45dc3e8bb714ad5f8484690d4ad3161eb Mon Sep 17 00:00:00 2001
From: Khue Doan <mail@khuedoan.com>
Date: Mon, 27 Apr 2026 23:34:25 +0700
Subject: [PATCH] fix(nixos): force IPv6 DNS

---
 infra/_modules/nixos/flake.nix | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/infra/_modules/nixos/flake.nix b/infra/_modules/nixos/flake.nix
index 8da8e16..c3433d4 100644
--- a/infra/_modules/nixos/flake.nix
+++ b/infra/_modules/nixos/flake.nix
@@ -35,7 +35,18 @@
             networking.hostName = "kube-1";
             systemd.network.networks."30-wan" = {
               matchConfig.Name = "enp1s0";
-              networkConfig.DHCP = "ipv4";
+              networkConfig = {
+                DHCP = "ipv4";
+                # TODO debug this
+                # CoreDNS runs on the IPv6-only pod network, so it cannot reach
+                # the IPv4 DNS servers advertised by Hetzner DHCP.
+                DNS = [
+                  # https://developers.cloudflare.com/1.1.1.1/ip-addresses
+                  "2606:4700:4700::1112"
+                  "2606:4700:4700::1002"
+                ];
+              };
+              dhcpV4Config.UseDNS = false;
               address = [
                 hosts.kube-1.ipv6_address
               ];
-- 
2.51.2