modules/dhcpcd-prefixdelegation: Add dhcpcd module specifically for prefixdelegation

modules/dhcpcd-prefixdelegation/default.nix

@@ -0,0 +1,144 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.networking.dhcpcd-prefixdelegation;
+
+  downstreamInterfaceConfig = name: opts: "${name}${
+    optionalString (opts.sla_id != null) "/${builtins.toString opts.sla_id}${
+      optionalString (opts.prefix_len != null) "/${builtins.toString opts.prefix_len}${
+        optionalString (opts.suffix != null) "/${opts.suffix}"
+      }"
+    }"
+  }";
+
+  interfaceConfig = name: opts: ''
+    interface ${name}
+      ipv6rs
+      ia_pd ${builtins.toString opts.iaid}${
+        optionalString (opts.prefix != null) "/${opts.prefix}${
+          optionalString (opts.prefix_len != null) "/${builtins.toString opts.prefix_len}"
+        }"
+      } ${concatMapStringsSep " " ({name, value}: downstreamInterfaceConfig name value) (attrsToList opts.interfaces)}
+  '';
+
+
+  dhcpcdConf = pkgs.writeText "dhcpcd.conf" ''
+    duid
+    noipv6rs
+    waitip 6
+    ipv6only
+
+    allowinterfaces ${concatStringsSep " " (builtins.attrNames cfg.interfaces)} ${concatMapStringsSep " " ({name, value}: concatStringsSep "" (builtins.attrNames value.interfaces)) (attrsToList cfg.interfaces)}
+
+    ${concatMapStringsSep "\n" ({name, value}: interfaceConfig name value) (attrsToList cfg.interfaces)}
+  '';
+
+  downstreamInterfaceOpts = { ... }: {
+    options = {
+      sla_id = mkOption {
+        type = with types; nullOr ints.unsigned;
+        default = null;
+      };
+
+      prefix_len = mkOption {
+        type = with types; nullOr ints.unsigned;
+        default = null;
+      };
+
+      suffix = mkOption {
+        type = with types; nullOr str;
+        default = null;
+      };
+    };
+  };
+
+  interfaceOpts = { ... }: {
+    options = {
+      iaid = mkOption {
+        type = with types; ints.unsigned;
+        description = ''
+          Request a delegated prefix with this IAID on this interface
+        '';
+      };
+
+      prefix = mkOption {
+        type = with types; nullOr str;
+        default = null;
+      };
+
+      prefix_len = mkOption {
+        type = with types; nullOr ints.unsigned;
+        default = null;
+      };
+
+      interfaces = mkOption {
+        type = with types; attrsOf (submodule downstreamInterfaceOpts);
+        default = {};
+        description =''
+          Interfaces to assign IPv6 prefixes to
+        '';
+      };
+    };
+  };
+
+in
+
+{
+
+  options = {
+
+    networking.dhcpcd-prefixdelegation = {
+      enable = mkEnableOption "dhcpcd for prefixdelegation";
+
+      interfaces = mkOption {
+        type = with types; attrsOf (submodule interfaceOpts);
+        default = {};
+        description = ''
+          Interfaces to request IPv6 prefixes from
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+
+    environment.etc."dhcpcd.conf".source = dhcpcdConf;
+
+    systemd.services.dhcpcd-prefixdelegation = {
+        description = "DHCP Client for IPv6 Prefix Delegation";
+
+        wantedBy = [ "multi-user.target" ];
+        wants = [ "network.target" ];
+        before = [ "network-online.target" ];
+
+        # Stopping dhcpcd during a reconfiguration is undesirable
+        # because it brings down the network interfaces configured by
+        # dhcpcd.  So do a "systemctl restart" instead.
+        stopIfChanged = false;
+
+        path = [ pkgs.dhcpcd ];
+
+        unitConfig.ConditionCapability = "CAP_NET_ADMIN";
+
+        serviceConfig =
+          { Type = "forking";
+            PIDFile = "/run/dhcpcd/pid";
+            RuntimeDirectory = "dhcpcd";
+            ExecStart = "@${pkgs.dhcpcd}/sbin/dhcpcd dhcpcd --quiet --config ${dhcpcdConf}";
+            ExecReload = "${pkgs.dhcpcd}/sbin/dhcpcd --rebind";
+            Restart = "always";
+          };
+      };
+
+    users.users.dhcpcd = {
+      isSystemUser = true;
+      group = "dhcpcd";
+    };
+    users.groups.dhcpcd = {};
+
+  };
+
+}