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
+  '';
+
 }

pkgs/ds-lite-dhcpcd-hook/ds-lite-dhcpcd-hook.sh

@@ -83,7 +83,7 @@ if TUNNEL_INTERFACE_CONFIG="$(ip --json link show "${TUNNEL_INTERFACE_NAME}")";
 	if [[ "${TUNNEL_INTERFACE_ORIGIN_ADDRESS}" != "${WAN_INTERFACE_ADDRESS}" || "${TUNNEL_INTERFACE_REMOTE_ADDRESS}" != "${AFTR_ADDRESS}" || "${TUNNEL_INTERFACE_OPERSTATE}" != "UNKNOWN" ]]; then
 		log_tunnel "Bad configuration, fixing tunnel parameter"
 
-		ip tunnel change "${TUNNEL_INTERFACE_NAME}" mode ipip6 local "${WAN_INTERFACE_ADDRESS}" remote "${AFTR_ADDRESS}"
+		ip tunnel change "${TUNNEL_INTERFACE_NAME}" mode ipip6 local "${WAN_INTERFACE_ADDRESS}" remote "${AFTR_ADDRESS}" encaplimit none
 		ip link set "$TUNNEL_INTERFACE_NAME" up
 	else
 		log_tunnel "Tunnel already configured"
@@ -91,7 +91,7 @@ if TUNNEL_INTERFACE_CONFIG="$(ip --json link show "${TUNNEL_INTERFACE_NAME}")";
 else
 	log_tunnel "Setting up DS-Lite tunnel"
 
-	ip tunnel add "${TUNNEL_INTERFACE_NAME}" mode ipip6 local "${WAN_INTERFACE_ADDRESS}" remote "${AFTR_ADDRESS}"
+	ip tunnel add "${TUNNEL_INTERFACE_NAME}" mode ipip6 local "${WAN_INTERFACE_ADDRESS}" remote "${AFTR_ADDRESS}" encaplimit none
 	ip link set "$TUNNEL_INTERFACE_NAME" up
 fi
 

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 = {