nixbld: consistent netif variables

nixbld-etc-nixos/configuration.nix

@@ -6,6 +6,8 @@ let
   netifLan = "enp5s0f1";
   netifWifi = "wlp6s0";
   netifSit = "henet0";
+  netifAlt = "alt0";
+  netifAltVlan = "vlan0";
   hydraWwwOutputs = "/var/www/hydra-outputs";
 in
 {
@@ -179,7 +181,7 @@ in
 
         iptables -w -N pccw-sucks
         iptables -A pccw-sucks -o ${netifSit} -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1360
-        iptables -A pccw-sucks -o alt0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1380
+        iptables -A pccw-sucks -o ${netifAlt} -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1380
         iptables -w -A FORWARD -j pccw-sucks
       '';
       extraStopCommands = ''
@@ -202,14 +204,14 @@ in
       addresses = [{ address = "2001:470:18:390::2"; prefixLength = 64; }];
       routes = [{ address = "::"; prefixLength = 0; }];
     };
-    greTunnels.alt0 = {
+    greTunnels."${netifAlt}" = {
       dev = netifWan;
       remote = "103.206.98.1";
       local = "94.190.212.123";
       ttl = 255;
       type = "tun";
     };
-    interfaces.alt0 = {
+    interfaces."${netifAlt}" = {
       ipv4.addresses = [
         {
           address = "103.206.98.227";
@@ -226,12 +228,12 @@ in
       ];
     };
     vlans = {
-      vlan0 = {
+      "${netifAltVlan}" = {
         id = 2;
         interface = netifLan;
       };
     };
-    interfaces.vlan0 = {
+    interfaces."${netifAltVlan}" = {
       ipv4.addresses = [{
         address = "103.206.98.200";
         prefixLength = 29;
@@ -264,7 +266,7 @@ in
       id = "fqdn:igw0.hkg.as150788.net";
       pubkeys = [ "/etc/swanctl/pubkey/igw0.hkg.as150788.net" ];
     };
-    children.alt0 = {
+    children."${netifAlt}" = {
       mode = "transport";
       ah_proposals = [ "sha256-curve25519" ];
       remote_ts = [ "103.206.98.1[gre]" ];
@@ -274,8 +276,8 @@ in
   };
   # prevent race condition similar to https://github.com/NixOS/nixpkgs/issues/27070
   systemd.services.strongswan-swanctl = {
-    after = [ "network-addresses-alt0.service" ];
-    requires = [ "network-addresses-alt0.service" ];
+    after = [ "network-addresses-${netifAlt}.service" ];
+    requires = [ "network-addresses-${netifAlt}.service" ];
   };
 
   systemd.services.network-custom-route-backup = {