hosts/carbon: Don't send IPv4 to ppp tunnel

hosts/carbon/ppp-ncfttb.nix

@@ -60,4 +60,10 @@
     ip46tables -t mangle -A forward-mangle -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
   '';
 
+  networking.firewall.extraCommands = ''
+    # Reject all IPv4 traffic that tries to enter and leave the PPP tunnel
+    iptables -I INPUT -i ppp-ncfttb -j DROP
+    iptables -I OUTPUT -o ppp-ncfttb -j DROP
+  '';
+
 }

profiles/router/default.nix

@@ -11,8 +11,10 @@ with lib;
   config = mkIf config.profiles.clerie.router.enable {
 
     environment.systemPackages = with pkgs; [
-      wireguard-tools
+      conntrack-tools
+      iptstate # show conntrack table
       tcpdump
+      wireguard-tools
     ];
   
     boot.kernel.sysctl = {