fix NIC naming: use udev rules instead of .link files

systemd.network.links didn't generate files; use udev extraRules
to pin NIC names to MACs. Also disable networking.useDHCP catch-all
that silently misconfigured the LAN NIC when it got a wrong name.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hosts/FredOS-Mediaserver.nix

@@ -29,7 +29,7 @@
     ];
 
     # Basic networking
-    networking.useDHCP = lib.mkDefault true;
+    networking.useDHCP = lib.mkForce false;
 
     # Allow fred to act as a remote Nix builder (trusted users can import
     # unsigned store paths sent by the build client).

services/game-servers.nix

@@ -171,6 +171,23 @@
       };
     };
 
+    # Stop 7DTD containers from crash-looping forever — after 5 failures
+    # within 5 minutes, systemd gives up.  Without this, a broken container
+    # spawns a new veth pair every 30 s, flooding systemd-networkd and
+    # potentially interfering with DHCP on the WAN interface.
+    systemd.services."docker-7dtd".serviceConfig = {
+      Restart = lib.mkForce "on-failure";
+      RestartSec = "30s";
+      StartLimitIntervalSec = 300;
+      StartLimitBurst = 5;
+    };
+    systemd.services."docker-7dtd-coop".serviceConfig = {
+      Restart = lib.mkForce "on-failure";
+      RestartSec = "30s";
+      StartLimitIntervalSec = 300;
+      StartLimitBurst = 5;
+    };
+
     networking.firewall.allowedTCPPorts = [ 26900 26910 ];
     networking.firewall.allowedUDPPorts = [ 26900 26901 26902 26910 26911 26912 ];
   };

services/router.nix

@@ -72,9 +72,18 @@ in
       "net.ipv6.conf.all.disable_ipv6" = 1;
     };
 
+    # Pin interface names to MAC addresses so they never swap across boots.
+    # Without this, "eth0" is an unpredictable kernel name that depends on
+    # device probe order — if the NICs swap, the entire LAN/WAN config breaks.
+    services.udev.extraRules = ''
+      SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="6c:0b:84:0c:4c:58", NAME="eth0"
+      SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="6c:0b:84:0c:4c:59", NAME="eno1"
+    '';
+
     # --- Interface configuration ---
     systemd.network = {
       enable = true;
+
       networks = {
         "10-wan" = {
           matchConfig.Name = "eno1";