nixos/modules/vlans.nix

{ lib, config, ... }:
let
  types = {
    portList = lib.types.listOf lib.types.int;

    service = lib.types.submodule {
      options = {
        tcp = lib.mkOption {
          type = types.portList;
          default = [ ];
        };
        udp = lib.mkOption {
          type = types.portList;
          default = [ ];
        };
      };
    };

    vlan = lib.types.submodule {
      options = {
        id = lib.mkOption {
          type = lib.types.int;
        };
        staticLeases = lib.mkOption {
          type = lib.types.attrsOf lib.types.str;
          default = { };
        };
        ipv6 = lib.mkEnableOption "ipv6";
        domain = lib.mkOption {
          type = lib.types.str;
          default = "home.arpa";
          description = "Domain name to advertise via DHCP";
        };
      };
    };

    bridge = lib.types.submodule {
      options = {
        enable = lib.mkEnableOption "Enable bridge";

        pvid = lib.mkOption {
          type = lib.types.int;
        };
        bindNetwork = lib.mkOption {
          type = lib.types.str;
        };
        network = lib.mkOption {
          type = lib.types.str;
        };
        netdev = lib.mkOption {
          type = lib.types.str;
        };
      };
    };
  };

  cfg = config.modules.vlans;
  vlans = lib.mapAttrsToList (
    attrName:
    {
      name ? attrName,
      ...
    }@vlan:
    ({ inherit name; } // vlan)
  ) cfg.networks;
  vlanAttrs = lib.listToAttrs (
    lib.map (
      { name, ... }@value:
      {
        inherit name value;
      }
    ) vlans
  );

  buildNetdev =
    name:
    { id, ... }:
    {
      name = "20-${name}";
      value = {
        netdevConfig = {
          Name = name;
          Kind = "vlan";
          MACAddress = "00:0d:b9:49:d2:${toString id}";
        };
        vlanConfig = {
          Id = id;
        };
      };
    };

  buildStaticLease = macAddress: address: ''
    [DHCPServerStaticLease]
    MACAddress=${macAddress}
    Address=${address}
  '';

  buildNetwork =
    name:
    {
      id,
      ipv6,
      staticLeases,
      domain,
      ...
    }:
    {
      name = "30-${name}";
      value = {
        matchConfig = {
          Name = name;
        };
        networkConfig = {
          Address = "10.${toString id}.0.1/23";
          IPMasquerade = "ipv4";
          DHCPServer = true;
          IPv6AcceptRA = false;
          IPv6SendRA = ipv6;
          DHCPPrefixDelegation = ipv6;
        };
        dhcpServerConfig = {
          PoolOffset = 255;
          DNS = "10.${toString id}.0.1";
          EmitDNS = true;
        };
        extraConfig = lib.concatLines (
          (lib.mapAttrsToList buildStaticLease staticLeases)
          ++ [
            ''
              [DHCPServer]
              SendOption=15:string:${domain}
            ''
          ]
        );
      };
    };

  vlanIds = lib.mapAttrsToList (_: { id, ... }: id) vlanAttrs;

  vlanRange = {
    min = lib.foldr lib.min 999 vlanIds;
    max = lib.foldr lib.max 0 vlanIds;
  };

  bridgeVLANConfig = ''
    [BridgeVLAN]
    VLAN=${toString vlanRange.min}-${toString vlanRange.max}
    EgressUntagged=${toString cfg.bridge.pvid}
    PVID=${toString cfg.bridge.pvid}
  '';

  bridgeNetDev =
    if (cfg.bridge.enable) then
      {
        "${cfg.bridge.netdev}".bridgeConfig = {
          VLANFiltering = true;
          DefaultPVID = cfg.bridge.pvid;
        };
      }
    else
      { };

  bridgeBindNetwork =
    if (cfg.bridge.enable) then
      {
        ${cfg.bridge.bindNetwork}.extraConfig = bridgeVLANConfig;
      }
    else
      { };

  bridgeNetwork =
    if (cfg.bridge.enable) then
      {
        "${cfg.bridge.network}" = {
          vlan = lib.map ({ name, ... }: name) vlans;
          bridgeVLANs = lib.map (
            { id, ... }:
            {
              VLAN = id;
            }
          ) vlans;
        };
      }
    else
      { };

  netdevs = lib.mergeAttrsList [
    (lib.mapAttrs' buildNetdev vlanAttrs)
    bridgeNetDev
  ];

  networks = lib.mergeAttrsList [
    (lib.mapAttrs' buildNetwork vlanAttrs)
    bridgeBindNetwork
    bridgeNetwork
  ];
in
{
  options.modules.vlans = {
    enable = lib.mkEnableOption "Enable VLANs";

    networks = lib.mkOption {
      type = lib.types.attrsOf types.vlan;
    };

    bridge = lib.mkOption {
      type = types.bridge;
    };
  };

  config = lib.mkIf cfg.enable {
    systemd.network = {
      enable = lib.mkDefault true;
      inherit netdevs networks;
    };
  };
}