nix: cleanup guest network config

This makes the guest network config a bit easier (no unnecessary udev
rules anymore). Also, this gets rid of some sporadic errors with
interfaces losing their config. E.g. the second interface of the Cloud
Hypervisor guest (192.168.2.2) would sometimes lose its IP address after
a live migration with the old config. This doesn't happen anymore (or at
least a lot less often).

On-behalf-of: SAP sebastian.eydam@sap.com
Signed-off-by: Sebastian Eydam <sebastian.eydam@cyberus-technology.de>

Author: amphi

images/nixos-image.nix

@@ -89,38 +89,36 @@ nixpkgs.lib.nixosSystem {
         # Please keep in sync with documentation in networks.md!
         networking.firewall.enable = false;
         networking.hostName = "nixos";
-        networking.interfaces.eth1337.ipv4.addresses = [
-          {
-            address = "192.168.1.2";
-            prefixLength = 24;
-          }
-        ];
-        networking.interfaces.eth1337.useDHCP = false;
-        networking.interfaces.eth1338.ipv4.addresses = [
-          {
-            address = "192.168.2.2";
-            prefixLength = 24;
-          }
-        ];
-        networking.interfaces.eth1338.useDHCP = false;
-        networking.interfaces.eth1339.ipv4.addresses = [
-          {
-            address = "192.168.3.2";
-            prefixLength = 24;
-          }
-        ];
-        networking.interfaces.eth1339.useDHCP = false;
-        networking.interfaces.eth1340.ipv4.addresses = [
-          {
-            address = "192.168.4.2";
-            prefixLength = 24;
-          }
-        ];
-        networking.interfaces.eth1340.useDHCP = false;
-
         networking.useDHCP = false;
+        networking.networkmanager.enable = lib.mkForce false;
         networking.useNetworkd = true;
 
+        systemd.network = {
+          enable = true;
+          networks = {
+            eth1337 = {
+              matchConfig.MACAddress = "52:54:00:e5:b8:01";
+              address = [ "192.168.1.2/24" ];
+              linkConfig.RequiredForOnline = "no";
+            };
+            eth1338 = {
+              matchConfig.MACAddress = "52:54:00:e5:b8:02";
+              address = [ "192.168.2.2/24" ];
+              linkConfig.RequiredForOnline = "no";
+            };
+            eth1339 = {
+              matchConfig.MACAddress = "52:54:00:e5:b8:03";
+              address = [ "192.168.3.2/24" ];
+              linkConfig.RequiredForOnline = "no";
+            };
+            eth1340 = {
+              matchConfig.MACAddress = "52:54:00:e5:b8:04";
+              address = [ "192.168.4.2/24" ];
+              linkConfig.RequiredForOnline = "no";
+            };
+          };
+        };
+
         nix.enable = false;
 
         programs = {
@@ -146,35 +144,11 @@ nixpkgs.lib.nixosSystem {
         services.logrotate.enable = false;
         services.resolved.enable = false;
         services.timesyncd.enable = false;
-        services.udev.extraRules = ''
-          # Stable NIC name for the default VM network.
-          ACTION=="add", SUBSYSTEM=="net", \
-            ATTR{address}=="52:54:00:e5:b8:01", \
-            NAME="eth1337"
-
-          # Stable NIC name for hotplugged network (type 'ethernet').
-          ACTION=="add", SUBSYSTEM=="net", \
-            ATTR{address}=="52:54:00:e5:b8:02", \
-            NAME="eth1338"
-
-          # Stable NIC name for hotplugged network #2 (type 'network').
-          ACTION=="add", SUBSYSTEM=="net", \
-            ATTR{address}=="52:54:00:e5:b8:03", \
-            NAME="eth1339"
-
-          # Stable NIC name for hotplugged network #2 (type 'network').
-          ACTION=="add", SUBSYSTEM=="net", \
-            ATTR{address}=="52:54:00:e5:b8:04", \
-            NAME="eth1340"
-        '';
         services.udisks2.enable = false;
 
         system.stateVersion = "25.05";
         system.switch.enable = false;
 
-        systemd.network.wait-online.ignoredInterfaces = [
-          "eth1337"
-        ];
         systemd.services.mount-pstore.enable = false;
         systemd.services.resolvconf.enable = false;
         # We use a dummy key for the test VM to shortcut the boot time.