From f50a1bd99de9fff62d09887b81d3e1a00f2e69ee Mon Sep 17 00:00:00 2001
From: "Adam C. Stephens" <adam@valkor.net>
Date: Fri, 22 Nov 2024 12:01:03 -0500
Subject: [PATCH] nixos/lxc/container: fix useDhcp with veth

https://github.com/NixOS/nixpkgs/pull/347283 changed the default to
exclude non-physical network Kind, but that unfortunately also includes
`veth` which LXC uses for its network interfaces. Re-enable that
functionality so users can use networkd with useDHCP.
---
 nixos/modules/virtualisation/lxc-container.nix | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/nixos/modules/virtualisation/lxc-container.nix b/nixos/modules/virtualisation/lxc-container.nix
index 42c323ee4503..ff7a4c11060b 100644
--- a/nixos/modules/virtualisation/lxc-container.nix
+++ b/nixos/modules/virtualisation/lxc-container.nix
@@ -31,6 +31,22 @@
         ${config.nix.package.out}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
       '';
 
+    # supplement 99-ethernet-default-dhcp which excludes veth
+    systemd.network = lib.mkIf config.networking.useDHCP {
+      networks."99-lxc-veth-default-dhcp" = {
+        matchConfig = {
+          Type = "ether";
+          Kind = "veth";
+          Name = [
+            "en*"
+            "eth*"
+          ];
+        };
+        DHCP = "yes";
+        networkConfig.IPv6PrivacyExtensions = "kernel";
+      };
+    };
+
     system.build.tarball = pkgs.callPackage ../../lib/make-system-tarball.nix {
       extraArgs = "--owner=0";