Add forward filter module

modules/default.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     ./yate
+    ./forward-filter
     ./fieldpoc
   ];
 }

modules/forward-filter/default.nix

@@ -0,0 +1,162 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.clerie.forward-filter;
+
+  startScript = pkgs.writeScriptBin "forward-filter-start" ''
+    #! ${pkgs.runtimeShell} -e
+
+    ip46tables() {
+      iptables -w "$@"
+      ip6tables -w "$@"
+    }
+
+    ip46tables -D FORWARD -j forward-filter 2> /dev/null || true
+    ip46tables -F forward-filter 2> /dev/null || true
+    ip46tables -X forward-filter 2> /dev/null || true
+
+    ip46tables -N forward-filter
+
+    ip46tables -A forward-filter -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
+
+    ${concatStrings (mapAttrsToList (iface: ifacecfg: ''
+      ${concatMapStrings (rule: if (rule.sourceAddress != null  || rule.destinationAddress != null ) then ''
+          iptables -A forward-filter -o ${iface} ${optionalString (rule.incomingInterface != null) "-i ${rule.incomingInterface}"} ${optionalString (rule.sourceAddress != null) "-s ${rule.sourceAddress}"} ${optionalString (rule.destinationAddress != null) "-d ${rule.destinationAddress}"} ${optionalString (rule.jump != null) "-j ${rule.jump}"}
+        '' else if (rule.sourceAddress6 != null || rule.destinationAddress6 != null ) then ''
+          ip6tables -A forward-filter -o ${iface} ${optionalString (rule.incomingInterface != null) "-i ${rule.incomingInterface}"} ${optionalString (rule.sourceAddress6 != null) "-s ${rule.sourceAddress6}"} ${optionalString (rule.destinationAddress6 != null) "-d ${rule.destinationAddress6}"} ${optionalString (rule.jump != null) "-j ${rule.jump}"}
+        '' else ''
+          ip46tables -A forward-filter -o ${iface} ${optionalString (rule.incomingInterface != null) "-i ${rule.incomingInterface}"} ${optionalString (rule.jump != null) "-j ${rule.jump}"}
+        ''
+      ) ifacecfg.rules}
+      ${optionalString (ifacecfg.default != null) ''
+        ip46tables -A forward-filter -o ${iface} -j ${ifacecfg.default}
+      ''}
+    '') cfg.interfaces)}
+
+    ip46tables -A FORWARD -j forward-filter
+  '';
+
+  stopScript = pkgs.writeScriptBin "forward-filter-stop" ''
+    #! ${pkgs.runtimeShell} -e
+
+    ip46tables() {
+      iptables -w "$@"
+      ip6tables -w "$@"
+    }
+
+    ip46tables -D FORWARD -j forward-filter 2> /dev/null || true
+    ip46tables -F forward-filter 2> /dev/null || true
+    ip46tables -X forward-filter 2> /dev/null || true
+  '';
+
+in
+
+{
+
+  options = {
+
+    clerie.forward-filter = {
+      enable = mkOption {
+        type = types.bool;
+        default = true;
+        description =
+          ''
+            Whether to enable the forward-filter. It gives basic control about
+            blocking and allowing forward between interfaces.
+          '';
+      };
+
+      interfaces = mkOption {
+        default = { };
+        type = with types; attrsOf (submodule {
+          options = {
+            rules = mkOption {
+              type = with types; listOf (submodule {
+                options = {
+                  sourceAddress = mkOption {
+                    type = types.nullOr types.str;
+                    default = null;
+                    example = "192.168.0.0/24";
+                    description = "";
+                  };
+                  sourceAddress6 = mkOption {
+                    type = types.nullOr types.str;
+                    default = null;
+                    example = "fd00::/64";
+                    description = "";
+                  };
+                  destinationAddress = mkOption {
+                    type = types.nullOr types.str;
+                    default = null;
+                    example = "192.168.0.0/24";
+                    description = "";
+                  };
+                  destinationAddress6 = mkOption {
+                    type = types.nullOr types.str;
+                    default = null;
+                    example = "fd00::/64";
+                    description = "";
+                  };
+                  incomingInterface = mkOption {
+                    type = types.nullOr types.str;
+                    default = null;
+                    example = "ens18";
+                    description = "";
+                  };
+                  jump = mkOption {
+                    type = types.nullOr types.str;
+                    default = "ACCEPT";
+                    example = "DROP";
+                    description = "";
+                  };
+                };
+              });
+              description = "List of rules to filter forwarding.";
+            };
+            default = mkOption {
+              type = types.nullOr types.str;
+              default = "DROP";
+              example = "ACCEPT";
+              description = "";
+            };
+          };
+        });
+        description =
+          ''
+            Interface filter options.
+          '';
+      };
+    };
+
+  };
+
+  config = mkIf cfg.enable {
+
+    environment.systemPackages = [ pkgs.iptables ];
+
+    systemd.services.forward-filter = {
+      description = "Forward Filter";
+      wantedBy = [ "sysinit.target" ];
+      wants = [ "network-pre.target" ];
+      before = [ "network-pre.target" ];
+      after = [ "systemd-modules-load.service" ];
+
+      path = [ pkgs.iptables ];
+
+      unitConfig.ConditionCapability = "CAP_NET_ADMIN";
+      unitConfig.DefaultDependencies = false;
+
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        ExecStart = "@${startScript}/bin/forward-filter-start forward-filter-start";
+        ExecStop = "@${stopScript}/bin/forward-filter-stop forward-filter-stop";
+      };
+    };
+
+  };
+
+}